WO2015045387A1

WO2015045387A1 - Non-aqueous electrolyte secondary battery

Info

Publication number: WO2015045387A1
Application number: PCT/JP2014/004911
Authority: WO
Inventors: 山田　淳夫; 裕貴山田; 佳浩中垣; 智之河合; 雄紀長谷川; 浩平間瀬; 合田　信弘
Original assignee: 国立大学法人東京大学
Priority date: 2013-09-25
Filing date: 2014-09-25
Publication date: 2015-04-02

Abstract

The invention addresses the problem of improving battery characteristics by the optimum combination of an electrolyte and a negative electrode active material. In a non-aqueous electrolyte secondary battery, an electrolyte is used that contains a metal salt and an organic solvent having a heteroatom and satisfies the relationship Is > Io, where, for peak intensities derived from the organic solvent in a vibrational spectroscopy spectrum, Io is the intensity of a peak inherent in the organic solvent and Is is the intensity of a peak to which the peak inherent in the organic solvent shifts. As a negative electrode, any of the followings (1) to (5) is used: (1) Graphite having a G/D ratio of 3.5 or more, said G/D ratio being the ratio of the peak of the G-band and the peak of the D-band in a raman spectrum (2) Carbon material having a crystallite size of 20 nm or less, said crystallite size being calculated from the half width of a peak appearing at 2θ = 20° to 30° in an x-ray diffraction profile measured by an x-ray diffraction method (3) Silicon element and/or tin element (4) Metal oxide that can absorb and release lithium ions (5) Graphite having a major axis to minor axis ratio (major axis/minor axis) of 1 to 5

Description

Nonaqueous electrolyte secondary battery

The present invention relates to a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery.

For example, a lithium ion secondary battery is a secondary battery with high charge / discharge capacity and high output. Currently, there is a demand for smaller and lighter secondary batteries that are mainly used as power sources for portable electronic devices, notebook computers, and electric vehicles. In particular, in automobile applications, it is necessary to charge and discharge with a large current, and development of a secondary battery having high rate characteristics capable of high-speed charging and discharging is required.

The lithium ion secondary battery has active materials capable of inserting and extracting lithium (Li) in the positive electrode and the negative electrode, respectively. Then, the lithium ion moves through the electrolytic solution sealed between the two electrodes. In order to increase the rate, it is necessary to improve the active material and binder used in the positive electrode and / or the negative electrode, and improve the electrolytic solution.

Carbon materials such as graphite are widely used as negative electrode active materials for lithium ion secondary batteries. In order to enable reversible insertion / extraction of lithium ions to / from such a negative electrode active material, a non-aqueous carbonate solvent such as a cyclic ester or a chain ester is used for the electrolytic solution. However, when using a carbonate-based solvent, it has been difficult to significantly improve the rate characteristics. That is, as described in Non-Patent Documents 1 to 3 below, carbonate-based solvents such as ethylene carbonate and propylene carbonate have a large activation barrier for electrode reaction. Review of the solvent composition is required.

The present invention has been made in view of the above-described circumstances, and a main problem to be solved is to improve battery characteristics by an optimal combination of an electrolytic solution and a negative electrode active material.

Hereinafter, if necessary, “the organic solvent contains a salt having alkali metal, alkaline earth metal or aluminum as a cation and an organic solvent having a hetero element, and the peak intensity derived from the organic solvent in a vibrational spectroscopic spectrum. When the original peak intensity is Io and the peak shifted intensity is Is, the “electrolytic solution with Is> Io” may be referred to as the “electrolytic solution of the present invention”.

The feature of the nonaqueous electrolyte secondary battery (1) of the present invention that solves the above problems is that the electrolyte solution of the present invention described above and the G / D ratio, which is the ratio of the peak of G-band and D-band in the Raman spectrum. And a negative electrode having a negative electrode active material layer containing graphite of 3.5 or more. The “G / D ratio is 3.5 or more” in the present invention means that either the area ratio or the height ratio of the G-band and D-band peaks in the Raman spectrum is 3.5 or more. In particular, the height ratio of the peak is 3.5 or more.

The feature of the non-aqueous electrolyte secondary battery (2) of the present invention that solves the above-described problems is that the above-described electrolytic solution of the present invention and 2θ = 20 degrees to 30 degrees in an X-ray diffraction profile measured by an X-ray diffraction method. A negative electrode having a negative electrode active material layer containing a carbon material having a crystallite size of 20 nm or less calculated from the half width of the peak appearing in FIG.

A feature of the nonaqueous electrolyte secondary battery (3) of the present invention that solves the above problems is that it comprises the above-described electrolytic solution of the present invention and a negative electrode containing a silicon element and / or a tin element in the negative electrode active material. It is in.

The characteristics of the nonaqueous electrolyte secondary battery (4) of the present invention that solves the above problems are the above-described electrolytic solution of the present invention, a negative electrode containing a metal oxide capable of inserting and extracting lithium ions as a negative electrode active material, It is in having.

The feature of the non-aqueous electrolyte secondary battery (5) of the present invention that solves the above problems is that the above-described electrolytic solution of the present invention and the ratio of the major axis to the minor axis (major axis / minor axis) are 1 to 5. And a negative electrode having a negative electrode active material layer containing graphite.

According to the nonaqueous electrolyte secondary battery of the present invention, battery characteristics are improved.

It is IR spectrum of the electrolyte solution E3. It is IR spectrum of the electrolyte solution E4. It is IR spectrum of the electrolyte solution E7. It is IR spectrum of the electrolyte solution E8. It is IR spectrum of the electrolyte solution E10. It is IR spectrum of the electrolyte solution C2. It is IR spectrum of the electrolyte solution C4. It is IR spectrum of acetonitrile. It is an IR spectrum of (CF ₃ SO ₂ ) ₂ NLi. It is an IR spectrum of (FSO ₂ ) ₂ NLi (2100 to 2400 cm ⁻¹ ). It is IR spectrum of the electrolyte solution E11. It is IR spectrum of the electrolyte solution E12. It is IR spectrum of the electrolyte solution E13. It is IR spectrum of the electrolyte solution E14. It is IR spectrum of the electrolyte solution E15. It is IR spectrum of the electrolyte solution E16. It is IR spectrum of the electrolyte solution E17. It is IR spectrum of the electrolyte solution E18. It is IR spectrum of the electrolyte solution E19. It is IR spectrum of the electrolyte solution E20. It is IR spectrum of the electrolyte solution E21. It is IR spectrum of the electrolyte solution C6. It is IR spectrum of the electrolyte solution C7. It is IR spectrum of the electrolyte solution C8. It is IR spectrum of dimethyl carbonate. It is IR spectrum of ethyl methyl carbonate. It is IR spectrum of diethyl carbonate. It is an IR spectrum of (FSO ₂ ) ₂ NLi (1900-1600 cm ⁻¹ ). It is a Raman spectrum of the electrolyte solution E8. It is a Raman spectrum of the electrolyte solution E9. It is a Raman spectrum of the electrolyte solution C4. It is a Raman spectrum of the electrolyte solution E11. It is a Raman spectrum of the electrolyte solution E13. It is a Raman spectrum of the electrolyte solution E15. It is a Raman spectrum of the electrolyte solution C6. 3 is a graph showing a cyclic voltamentary (CV) of the nonaqueous electrolyte secondary battery of Example 1-1. 3 is a graph showing a cyclic voltamentary (CV) of the nonaqueous electrolyte secondary battery of Example 1-2. 4 is a graph showing a cyclic voltamentary (CV) of the nonaqueous electrolyte secondary battery of Example 1-3. 6 is a graph showing a cyclic voltamentary (CV) of the nonaqueous electrolyte secondary battery of Comparative Example 1-1. 6 is a graph showing a cyclic voltamentary (CV) of the nonaqueous electrolyte secondary battery of Comparative Example 1-2. 6 is a graph showing a cyclic voltamentary (CV) of the nonaqueous electrolyte secondary battery of Comparative Example 1-3. 6 is a graph showing a cyclic voltamentary (CV) of the nonaqueous electrolyte secondary battery of Comparative Example 1-4. 6 is a graph showing a cyclic voltamentary (CV) of the nonaqueous electrolyte secondary battery of Comparative Example 1-5. 7 is a graph showing a cyclic voltamentary (CV) of the nonaqueous electrolyte secondary battery of Comparative Example 1-6. 7 is a graph showing a cyclic voltamentary (CV) of the nonaqueous electrolyte secondary battery of Comparative Example 1-7. 6 is a DSC chart of the nonaqueous electrolyte secondary battery of Example 1-5 and the nonaqueous electrolyte secondary battery of Comparative Example 1-8. 6 is a DSC chart of the nonaqueous electrolyte secondary battery of Example 1-6 and the nonaqueous electrolyte secondary battery of Comparative Example 1-8. 6 is a graph showing the relationship between the number of cycles and the current capacity ratio of the nonaqueous electrolyte secondary battery of Example 1-1 and the nonaqueous electrolyte secondary battery of Comparative Example 1-1. 6 is a charge / discharge curve of the nonaqueous electrolyte secondary battery in Example 1-8. FIG. 6 is a charge / discharge curve of the nonaqueous electrolyte secondary battery of Example 1-9. FIG. 3 is a charge / discharge curve of the nonaqueous electrolyte secondary battery in Example 1-10. 3 is a charge / discharge curve of the nonaqueous electrolyte secondary battery in Example 1-11. 10 is a charge / discharge curve of a nonaqueous electrolyte secondary battery in Comparative Example 1-9. 10 is a graph showing a relationship between a current rate and a voltage curve in the nonaqueous electrolyte secondary battery of Example 1-12. 6 is a graph showing a relationship between a current rate and a voltage curve in the nonaqueous electrolyte secondary battery of Comparative Example 1-4. It is a result of the cycle characteristic of the evaluation example 19. The initial charge / discharge curves of the nonaqueous electrolyte secondary battery of Example 2-1 and the nonaqueous electrolyte secondary battery of Comparative Example 2-1 are shown. 6 is a graph showing the relationship between the number of cycles and the current capacity ratio of the nonaqueous electrolyte secondary battery of Example 2-1 and the nonaqueous electrolyte secondary battery of Comparative Example 2-1. 3 is a charge / discharge curve of the nonaqueous electrolyte secondary battery of Example 3-2 and Comparative Example 3-2. 3 is a charge / discharge curve of the nonaqueous electrolyte secondary battery of Example 3-3. It is a charging / discharging curve of the nonaqueous electrolyte secondary battery of Example 4-1. It is a charging / discharging curve of the nonaqueous electrolyte secondary battery of Comparative Example 4-1. It is a charging / discharging curve of the nonaqueous electrolyte secondary battery of Example 4-2. It is a charging / discharging curve of the nonaqueous electrolyte secondary battery of Example 4-3. It is a graph which shows the relationship between the square root of the cycle number at the time of a cycle test, and a discharge capacity maintenance factor. It is an XPS analysis result about the carbon element of the negative electrode S and O containing film | membrane of EB1, EB2, and CB1 in the evaluation example 26. It is an XPS analysis result about the fluorine element of the negative electrode S, O containing film | membrane of EB1, EB2, and CB1 in the evaluation example 26. It is an XPS analysis result about the nitrogen element of the negative electrode S, O containing film | membrane of EB1, EB2, and CB1 in the evaluation example 26. It is an XPS analysis result about the oxygen element of the negative electrode S and O containing film | membrane of EB1, EB2, and CB1 in the evaluation example 26. It is an XPS analysis result about the sulfur element of the negative electrode S and O containing film | membrane of EB1, EB2, and CB1 in the evaluation example 26. It is a XPS analysis result of the negative electrode S and O containing film | membrane of EB1 in the evaluation example 26. It is a XPS analysis result of the negative electrode S and O containing film | membrane of EB2 in the evaluation example 26. 27 is a BF-STEM image of a negative electrode S, O-containing film of EB1 in Evaluation Example 26. FIG. It is a STEM analysis result about C of the negative electrode S and O containing film | membrane of EB1 in the evaluation example 26. It is a STEM analysis result about O of the negative electrode S and O containing film | membrane of EB1 in the evaluation example 26. It is a STEM analysis result about S of negative electrode S and O containing film | membrane of EB1 in the evaluation example 26. It is a XPS analysis result about O of the positive electrode S of EB1, and the film containing O in Evaluation Example 26. It is an XPS analysis result about S of the positive electrode S and O containing film | membrane of EB1 in the evaluation example 26. It is an XPS analysis result about S of the positive electrode S and O containing film | membrane of EB4 in the evaluation example 26. It is an XPS analysis result about O of the positive electrode S of EB4 and the coating containing O in Evaluation Example 26. It is an XPS analysis result about S of the positive electrode S and O containing film | membrane of EB4, EB5, and CB2 in the evaluation example 26. It is an XPS analysis result about S of the positive electrode S and O containing film | membrane of EB6, EB7, and CB3 in the evaluation example 26. It is an XPS analysis result about O of the positive electrode S, O containing film | membrane of EB4, EB5, and CB2 in the evaluation example 26. It is the analysis result about O of the positive electrode S and O containing film | membrane of EB6, EB7, and CB3 in the evaluation example 26. It is an analysis result about S of the negative electrode S and O containing film | membrane of EB4, EB5, and CB2 in the evaluation example 26. It is an analysis result about S of the negative electrode S and O containing film | membrane of EB6, EB7, and CB3 in the evaluation example 26. It is the analysis result about O of the negative electrode S and O containing film | membrane of EB4, EB5, and CB2 in the evaluation example 26. It is an analysis result about O of the negative electrode S and O containing film | membrane of EB6, EB7, and CB3 in the evaluation example 26. It is a complex impedance plane plot of the battery obtained by measuring the alternating current impedance after the first charge / discharge and after 100 cycles using EB8, EB9, EB10 and CB4. It is a graph which shows the relationship between the electric current of EB12 in evaluation example 36, and electrode potential. 44 is a graph showing a relationship between a potential (3.1 to 4.6 V) with respect to EB 12 and a response current in Evaluation Example 37. 44 is a graph showing a relationship between a potential (3.1 to 5.1 V) with respect to EB 12 and a response current in Evaluation Example 37. 44 is a graph showing a relationship between a potential (3.1 to 4.6 V) with respect to EB 13 and a response current in Evaluation Example 37. 40 is a graph showing a relationship between a potential (3.1 to 5.1 V) with respect to EB 13 and a response current in Evaluation Example 37. 44 is a graph showing a relationship between a potential (3.1 to 4.6 V) with respect to EB 14 and a response current in Evaluation Example 37. 44 is a graph showing a relationship between a potential (3.1 to 5.1 V) with respect to EB 14 and a response current in Evaluation Example 37. 44 is a graph showing a relationship between a potential (3.1 to 4.6 V) with respect to EB 15 and a response current in Evaluation Example 37. 44 is a graph showing a relationship between a potential (3.1 to 5.1 V) with respect to EB 15 and a response current in Evaluation Example 37. 44 is a graph showing a relationship between a potential (3.1 to 4.6 V) with respect to CB6 and a response current in Evaluation Example 37. 44 is a graph showing a relationship between a potential (3.0 to 4.5 V) with respect to EB 13 and a response current in Evaluation Example 37. In FIG. 100, the scale of the vertical axis in FIG. 93 is changed. 42 is a graph showing a relationship between a potential (3.0 to 5.0 V) with respect to EB 13 and a response current in Evaluation Example 37. In FIG. 101, the scale of the vertical axis in FIG. 94 is changed. 44 is a graph showing a relationship between a potential (3.0 to 4.5 V) with respect to EB16 and a response current in Evaluation Example 37. 44 is a graph showing a relationship between a potential (3.0 to 5.0 V) with respect to EB16 and a response current in Evaluation Example 37. 44 is a graph showing a relationship between a potential (3.0 to 4.5 V) with respect to CB7 and a response current in Evaluation Example 37. 44 is a graph showing a relationship between a potential (3.0 to 5.0 V) and a response current with respect to CB7 in Evaluation Example 37. 42 is a DSC chart of EB19 in Evaluation Example 39. 42 is a DSC chart of CB10 in Evaluation Example 39.

Hereinafter, modes for carrying out the present invention will be described. Unless otherwise specified, the numerical range “a to b” described in this specification includes the lower limit “a” and the upper limit “b”. The numerical range can be configured by arbitrarily combining these upper limit value and lower limit value and the numerical values listed in the examples. Furthermore, numerical values arbitrarily selected from the numerical value range can be used as upper and lower numerical values.

The non-aqueous electrolyte secondary battery of the present invention is intended to improve battery characteristics by an optimal combination of an electrolytic solution and a negative electrode active material. Therefore, there are no particular limitations on other battery components, such as the positive electrode. Moreover, the charge carrier in the nonaqueous electrolyte secondary battery of the present invention is not particularly limited. For example, the nonaqueous electrolyte secondary battery of the present invention may be a nonaqueous electrolyte secondary battery using lithium as a charge carrier (for example, a lithium secondary battery or a lithium ion secondary battery), or sodium as a charge carrier. It may be a non-aqueous electrolyte secondary battery (for example, a sodium secondary battery or a sodium ion secondary battery).
The non-aqueous electrolyte secondary battery (1) of the present invention is a main problem that should be solved by improving the rate capacity characteristics and improving the cycle characteristics by an optimal combination of the electrolytic solution and the negative electrode active material. It is. The nonaqueous electrolyte secondary battery (1) of the present invention includes the electrolyte of the present invention and graphite having a G / D ratio of 3.5 or more, which is a ratio of G-band and D-band peaks in the Raman spectrum. A negative electrode having a negative electrode active material layer. Such a nonaqueous electrolyte secondary battery (1) of the present invention is a nonaqueous electrolyte secondary battery having improved rate capacity characteristics and cycle characteristics. When graphite having a G / D ratio of less than 3.5 is used as the negative electrode active material, there is a problem that it is difficult to achieve both rate capacity and cycle characteristics even when the same electrolytic solution of the present invention is used. However, by using graphite having a G / D ratio of 3.5 or more as the negative electrode active material, the rate capacity characteristics are improved and the cycle characteristics are also improved.

The nonaqueous electrolyte secondary battery (2) of the present invention is a main problem that should be solved to improve the rate capacity characteristics by an optimal combination of an electrolytic solution and a negative electrode active material. The nonaqueous electrolyte secondary battery (2) of the present invention includes the electrolytic solution of the present invention and a negative electrode having a negative electrode active material layer containing a carbon material having a crystallite size of 20 nm or less. Such a nonaqueous electrolyte secondary battery (2) of the present invention includes a carbon material of 2θ = 20 degrees to 30 degrees as a negative electrode active material, so that a nonaqueous electrolyte secondary battery using a general electrolytic solution is used. The rate can be increased compared to the above.

The nonaqueous electrolyte secondary battery (3) of the present invention uses silicon (Si) or tin (Sn) as the negative electrode active material for the nonaqueous electrolyte secondary battery, and improves the battery characteristics of the nonaqueous electrolyte secondary battery. This is the main problem to be solved. The nonaqueous electrolyte secondary battery (3) of the present invention comprises the electrolytic solution of the present invention and a negative electrode containing a silicon element and / or a tin element in the negative electrode active material. Such a non-aqueous electrolyte secondary battery (3) of the present invention has an effect derived from the negative electrode active material by using a negative electrode active material containing silicon and / or tin and carbon together with the electrolytic solution of the present invention. Excellent battery characteristics are achieved through cooperation with the effects derived from the electrolyte.

The non-aqueous electrolyte secondary battery (4) of the present invention is a main problem to be solved by providing a non-aqueous electrolyte secondary battery having a metal oxide as a negative electrode active material and excellent in energy density and charge / discharge efficiency. is there. For example, as disclosed in JP 2012-160345 A, a technique using a metal oxide capable of inserting and extracting lithium ions as a negative electrode active material for a non-aqueous electrolyte secondary battery is known. As this kind of metal oxide, for example, lithium titanate is known. In a non-aqueous electrolyte secondary battery using lithium titanate as a negative electrode, it is considered that lithium occlusion and release reactions are performed stably, and as a result, deterioration of the active material is also suppressed. That is, it is known that a non-aqueous electrolyte secondary battery using this type of metal oxide as a negative electrode active material is excellent in cycle characteristics. On the other hand, non-aqueous electrolyte secondary batteries using this type of metal oxide as the negative electrode active material have a lower energy density at the negative electrode than non-aqueous electrolyte secondary batteries using carbon-based negative electrode active materials such as graphite. It has been known. Accordingly, it has been desired to develop a non-aqueous electrolyte secondary battery that uses a metal oxide as a negative electrode active material and has further improved battery characteristics. The nonaqueous electrolyte secondary battery (4) of the present invention uses a metal oxide as a negative electrode active material and is excellent in battery characteristics.

The nonaqueous electrolyte secondary battery (5) of the present invention has the negative electrode active material layer containing the electrolyte of the present invention and graphite having a major axis / minor axis ratio (major axis / minor axis) of 1 to 5. A negative electrode. Such a nonaqueous electrolyte secondary battery (5) of the present invention is a nonaqueous electrolyte secondary battery having further improved input / output characteristics. That is, when the electrolytic solution of the present invention is used, the input / output characteristics of the nonaqueous electrolyte secondary battery are improved. In addition to the electrolyte solution of the present invention, graphite having a major axis / minor axis ratio (major axis / minor axis) of 1 to 5 is used as the negative electrode active material, so that the non-aqueous electrolyte secondary battery can be inserted. It is possible to further improve the output characteristics.

<Electrolyte>
The electrolytic solution of the present invention includes a salt having alkali metal, alkaline earth metal or aluminum as a cation (hereinafter sometimes referred to as “metal salt” or simply “salt”) and an organic solvent having a hetero atom, With respect to the peak intensity derived from the organic solvent in the vibrational spectrum, if the intensity of the peak inherent to the organic solvent is Io and the intensity of the peak obtained by wave number shifting of the peak inherent to the organic solvent is Is, Is> Io.

In the conventional electrolytic solution, the relationship between Is and Io is Is <Io.

[Metal salt]
The metal salt may be a compound that is usually used as an electrolyte, such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiAlCl ₄ , etc. contained in the battery electrolyte. Examples of the cation of the metal salt include alkali metals such as lithium, sodium and potassium, alkaline earth metals such as beryllium, magnesium, calcium, strontium and barium, and aluminum. The cation of the metal salt is preferably the same metal ion as the charge carrier of the battery using the electrolytic solution. For example, if the electrolytic solution of the present invention is used as an electrolytic solution for a lithium ion secondary battery, the metal salt cation is preferably lithium.

The chemical structure of the anion of the salt may include at least one element selected from halogen, boron, nitrogen, oxygen, sulfur or carbon. Specific examples of the chemical structure of an anion containing halogen or boron include ClO ₄ , PF ₆ , AsF ₆ , SbF ₆ , TaF ₆ , BF ₄ , SiF ₆ , B (C ₆ H ₅ ) ₄ , and B (oxalate). ₂ , Cl, Br, and I.

The chemical structure of an anion containing nitrogen, oxygen, sulfur or carbon will be specifically described below.

The chemical structure of the anion of the salt is preferably a chemical structure represented by the following general formula (1), general formula (2), or general formula (3).

(R ¹ X ¹ ) (R ² X ² ) N... General formula (1)
(R ¹ is hydrogen, halogen, an alkyl group which may be substituted with a substituent, a cycloalkyl group which may be substituted with a substituent, an unsaturated alkyl group which may be substituted with a substituent, or a substituent. An unsaturated cycloalkyl group which may be substituted with, an aromatic group which may be substituted with a substituent, a heterocyclic group which may be substituted with a substituent, or an alkoxy group which may be substituted with a substituent , An unsaturated alkoxy group that may be substituted with a substituent, a thioalkoxy group that may be substituted with a substituent, an unsaturated thioalkoxy group that may be substituted with a substituent, CN, SCN, or OCN Is done.
R ² represents hydrogen, halogen, an alkyl group which may be substituted with a substituent, a cycloalkyl group which may be substituted with a substituent, an unsaturated alkyl group which may be substituted with a substituent, or a substituent. An unsaturated cycloalkyl group which may be substituted, an aromatic group which may be substituted with a substituent, a heterocyclic group which may be substituted with a substituent, an alkoxy group which may be substituted with a substituent, Selected from an unsaturated alkoxy group which may be substituted with a substituent, a thioalkoxy group which may be substituted with a substituent, an unsaturated thioalkoxy group which may be substituted with a substituent, CN, SCN, OCN The
R ¹ and R ² may be bonded to each other to form a ring.
X ¹ is selected from SO ₂ , C = O, C = S, R ^a P = O, R ^b P = S, S = O, Si = O.
X ² _{^{is, SO 2, C = O,}} C = S, R c P = O, R d P = S, S = O, is selected from Si = O.
R ^a , R ^b , R ^c , and R ^d are each independently hydrogen, halogen, an alkyl group that may be substituted with a substituent, a cycloalkyl group that may be substituted with a substituent, or a substituent. An unsaturated alkyl group which may be substituted, an unsaturated cycloalkyl group which may be substituted with a substituent, an aromatic group which may be substituted with a substituent, or a heterocyclic group which may be substituted with a substituent , An alkoxy group that may be substituted with a substituent, an unsaturated alkoxy group that may be substituted with a substituent, a thioalkoxy group that may be substituted with a substituent, and a non-optionally substituted substituent. Selected from saturated thioalkoxy groups, OH, SH, CN, SCN, OCN.
R ^a , R ^b , R ^c , and R ^d may combine with R ¹ or R ² to form a ring. )

R ³ X ³ Y: General formula (2)
(R ³ is hydrogen, halogen, an alkyl group which may be substituted with a substituent, a cycloalkyl group which may be substituted with a substituent, an unsaturated alkyl group which may be substituted with a substituent, or a substituent. An unsaturated cycloalkyl group which may be substituted with, an aromatic group which may be substituted with a substituent, a heterocyclic group which may be substituted with a substituent, or an alkoxy group which may be substituted with a substituent , An unsaturated alkoxy group that may be substituted with a substituent, a thioalkoxy group that may be substituted with a substituent, an unsaturated thioalkoxy group that may be substituted with a substituent, CN, SCN, or OCN Is done.
X ³ is selected from SO ₂ , C = O, C = S, R ^e P = O, R ^f P = S, S = O, and Si = O.
R ^e and R ^f are each independently hydrogen, halogen, an alkyl group that may be substituted with a substituent, a cycloalkyl group that may be substituted with a substituent, or a group that may be substituted with a substituent. A saturated alkyl group, an unsaturated cycloalkyl group that may be substituted with a substituent, an aromatic group that may be substituted with a substituent, a heterocyclic group that may be substituted with a substituent, and a substituent An alkoxy group which may be substituted, an unsaturated alkoxy group which may be substituted with a substituent, a thioalkoxy group which may be substituted with a substituent, an unsaturated thioalkoxy group which may be substituted with a substituent, OH , SH, CN, SCN, and OCN.
R ^e and R ^f may combine with R ³ to form a ring.
Y is selected from O and S. )

(R ⁴ X ⁴ ) (R ⁵ X ⁵ ) (R ⁶ X ⁶ ) C ... General formula (3)
(R ⁴ is hydrogen, halogen, an alkyl group which may be substituted with a substituent, a cycloalkyl group which may be substituted with a substituent, an unsaturated alkyl group which may be substituted with a substituent, or a substituent. An unsaturated cycloalkyl group which may be substituted with, an aromatic group which may be substituted with a substituent, a heterocyclic group which may be substituted with a substituent, or an alkoxy group which may be substituted with a substituent , An unsaturated alkoxy group that may be substituted with a substituent, a thioalkoxy group that may be substituted with a substituent, an unsaturated thioalkoxy group that may be substituted with a substituent, CN, SCN, or OCN Is done.
R ⁵ represents hydrogen, halogen, an alkyl group which may be substituted with a substituent, a cycloalkyl group which may be substituted with a substituent, an unsaturated alkyl group which may be substituted with a substituent, or a substituent. An unsaturated cycloalkyl group which may be substituted, an aromatic group which may be substituted with a substituent, a heterocyclic group which may be substituted with a substituent, an alkoxy group which may be substituted with a substituent, Selected from an unsaturated alkoxy group which may be substituted with a substituent, a thioalkoxy group which may be substituted with a substituent, an unsaturated thioalkoxy group which may be substituted with a substituent, CN, SCN, OCN The
R ⁶ is hydrogen, halogen, an alkyl group which may be substituted with a substituent, a cycloalkyl group which may be substituted with a substituent, an unsaturated alkyl group which may be substituted with a substituent, or a substituent. An unsaturated cycloalkyl group which may be substituted, an aromatic group which may be substituted with a substituent, a heterocyclic group which may be substituted with a substituent, an alkoxy group which may be substituted with a substituent, Selected from an unsaturated alkoxy group which may be substituted with a substituent, a thioalkoxy group which may be substituted with a substituent, an unsaturated thioalkoxy group which may be substituted with a substituent, CN, SCN, OCN The
Further, any two or three of R ⁴ , R ⁵ and R ⁶ may be bonded to form a ring.
X ⁴ _{^{is, SO 2, C = O,}} C = S, R g P = O, R h P = S, S = O, is selected from Si = O.
X ⁵ is selected from SO ₂ , C = O, C = S, R ⁱ P = O, R ^j P = S, S = O, Si = O.
X ⁶ is selected from SO ₂ , C = O, C = S, R ^k P = O, R ¹ P = S, S = O, Si = O.
R ^g , R ^h , R ⁱ , R ^j , R ^k , and R ^l are each independently hydrogen, halogen, an alkyl group that may be substituted with a substituent, or a cycloalkyl that may be substituted with a substituent. Group, an unsaturated alkyl group that may be substituted with a substituent, an unsaturated cycloalkyl group that may be substituted with a substituent, an aromatic group that may be substituted with a substituent, or a substituent that is substituted with a substituent A heterocyclic group which may be substituted, an alkoxy group which may be substituted with a substituent, an unsaturated alkoxy group which may be substituted with a substituent, a thioalkoxy group which may be substituted with a substituent, and a substituent It is selected from an unsaturated thioalkoxy group which may be substituted, OH, SH, CN, SCN, OCN.
R ^g , R ^h , R ⁱ , R ^j , R ^k , and R ^l may combine with R ⁴ , R ^5, or R ⁶ to form a ring. )

The term “may be substituted with a substituent” in the chemical structure represented by the general formulas (1) to (3) will be described. For example, in the case of “an alkyl group which may be substituted with a substituent”, an alkyl group in which one or more of hydrogens of the alkyl group are substituted with a substituent, or an alkyl group having no particular substituent Means.

Examples of the substituent in the phrase “may be substituted with a substituent” include an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, an unsaturated cycloalkyl group, an aromatic group, a heterocyclic group, a halogen, and OH. SH, CN, SCN, OCN, nitro group, alkoxy group, unsaturated alkoxy group, amino group, alkylamino group, dialkylamino group, aryloxy group, acyl group, alkoxycarbonyl group, acyloxy group, aryloxycarbonyl group, Acyloxy group, acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, alkylthio group, arylthio group, sulfonyl group, sulfinyl group, ureido group, phosphoric acid amide group, sulfo group, Carboxyl group, Dorokisamu acid group, a sulfino group, a hydrazino group, an imino group, and a silyl group. These substituents may be further substituted. When there are two or more substituents, the substituents may be the same or different.

The chemical structure of the salt anion is more preferably a chemical structure represented by the following general formula (4), general formula (5), or general formula (6).

(R ⁷ X ⁷ ) (R ⁸ X ⁸ ) N ... General formula (4)
(R ⁷ and R ⁸ are each independently C _n H _a F _b Cl _c Br _d I _e (CN) _f (SCN) _g (OCN) _h .
n, a, b, c, d, e, f, g, and h are each independently an integer of 0 or more, and satisfy 2n + 1 = a + b + c + d + e + f + g + h.
R ⁷ and R ⁸ may combine with each other to form a ring, in which case 2n = a + b + c + d + e + f + g + h is satisfied.
X ⁷ _{^{is, SO 2, C = O,}} C = S, R m P = O, R n P = S, S = O, is selected from Si = O.
X ⁸ is selected from SO ₂ , C = O, C = S, R ^o P = O, R ^p P = S, S = O, Si = O.
R ^m , R ⁿ , R ^o , and R ^p are each independently substituted with hydrogen, halogen, an alkyl group that may be substituted with a substituent, a cycloalkyl group that may be substituted with a substituent, or a substituent. An unsaturated alkyl group which may be substituted, an unsaturated cycloalkyl group which may be substituted with a substituent, an aromatic group which may be substituted with a substituent, or a heterocyclic group which may be substituted with a substituent , An alkoxy group that may be substituted with a substituent, an unsaturated alkoxy group that may be substituted with a substituent, a thioalkoxy group that may be substituted with a substituent, and a non-optionally substituted substituent. Selected from saturated thioalkoxy groups, OH, SH, CN, SCN, OCN.
R ^m , R ⁿ , R ^o , and R ^p may combine with R ⁷ or R ⁸ to form a ring. )

R ⁹ X ⁹ Y: General formula (5)
^{(R 9} _is a _{_{_{_{C n H a F b Cl c}}}} Br d I e (CN) f (SCN) g (OCN) h.
n, a, b, c, d, e, f, g, and h are each independently an integer of 0 or more, and satisfy 2n + 1 = a + b + c + d + e + f + g + h.
X ⁹ _{^{is, SO 2, C = O,}} C = S, R q P = O, R r P = S, S = O, is selected from Si = O.
R ^q and R ^r are each independently hydrogen, halogen, an alkyl group that may be substituted with a substituent, a cycloalkyl group that may be substituted with a substituent, or a group that may be substituted with a substituent. A saturated alkyl group, an unsaturated cycloalkyl group that may be substituted with a substituent, an aromatic group that may be substituted with a substituent, a heterocyclic group that may be substituted with a substituent, and a substituent An alkoxy group which may be substituted, an unsaturated alkoxy group which may be substituted with a substituent, a thioalkoxy group which may be substituted with a substituent, an unsaturated thioalkoxy group which may be substituted with a substituent, OH , SH, CN, SCN, and OCN.
R ^q and R ^r may combine with R ⁹ to form a ring.
Y is selected from O and S. )

(R ¹⁰ X ¹⁰ ) (R ¹¹ X ¹¹ ) (R ¹² X ¹² ) C ... General formula (6)
(R ¹⁰ , R ¹¹ , and R ¹² are each independently C _n H _a F _b Cl _c Br _d I _e (CN) _f (SCN) _g (OCN) _h .
n, a, b, c, d, e, f, g, and h are each independently an integer of 0 or more, and satisfy 2n + 1 = a + b + c + d + e + f + g + h.
Any two of R ¹⁰ , R ¹¹ , and R ¹² may combine to form a ring, in which case the group forming the ring satisfies 2n = a + b + c + d + e + f + g + h. Three of R ¹⁰ , R ¹¹ and R ¹² may combine to form a ring, in which case two of the three satisfy 2n = a + b + c + d + e + f + g + h, and one group satisfies 2n−1 = a + b + c + d + e + f + g + h. Fulfill.
X ¹⁰ _{^{is, SO 2, C = O,}} C = S, R s P = O, R t P = S, S = O, is selected from Si = O.
X ¹¹ _{^{is, SO 2, C = O,}} C = S, R u P = O, R v P = S, S = O, is selected from Si = O.
X ¹² _{^{is, SO 2, C = O,}} C = S, R w P = O, R x P = S, S = O, is selected from Si = O.
R ^s , R ^t , R ^u , R ^v , R ^w , and R ^x are each independently hydrogen, halogen, an alkyl group that may be substituted with a substituent, or a cycloalkyl that may be substituted with a substituent. Group, an unsaturated alkyl group that may be substituted with a substituent, an unsaturated cycloalkyl group that may be substituted with a substituent, an aromatic group that may be substituted with a substituent, or a substituent that is substituted with a substituent A heterocyclic group which may be substituted, an alkoxy group which may be substituted with a substituent, an unsaturated alkoxy group which may be substituted with a substituent, a thioalkoxy group which may be substituted with a substituent, and a substituent It is selected from an unsaturated thioalkoxy group which may be substituted, OH, SH, CN, SCN, OCN.
R ^s , R ^t , R ^u , R ^v , R ^w , and R ^x may combine with R ¹⁰ , R ^11, or R ¹² to form a ring. )

The meaning of the phrase “may be substituted with a substituent” in the chemical structures represented by the general formulas (4) to (6) has been explained in the general formulas (1) to (3). It is synonymous with.

In the chemical structures represented by the general formulas (4) to (6), n is preferably an integer of 0 to 6, more preferably an integer of 0 to 4, and particularly preferably an integer of 0 to 2. In the chemical structures represented by the general formulas (4) to (6), when R ⁷ and R ⁸ are bonded, or R ¹⁰ , R ¹¹ , and R ¹² are bonded to form a ring. In the formula, n is preferably an integer of 1 to 8, more preferably an integer of 1 to 7, and particularly preferably an integer of 1 to 3.

The chemical structure of the salt anion is more preferably represented by the following general formula (7), general formula (8) or general formula (9).

(R ¹³ SO ₂ ) (R ¹⁴ SO ₂ ) N... General formula (7)
(R ¹³ and R ¹⁴ are each independently C _n H _a F _b Cl _c Br _d I _e .
n, a, b, c, d, and e are each independently an integer of 0 or more, and satisfy 2n + 1 = a + b + c + d + e.
R ¹³ and R ¹⁴ may combine with each other to form a ring, in which case 2n = a + b + c + d + e is satisfied. )

R ¹⁵ SO ₃ ... General formula (8)
^{(R 15} _is a _{_{_{C n H a F b Cl c}}} Br d I e.
n, a, b, c, d, and e are each independently an integer of 0 or more, and satisfy 2n + 1 = a + b + c + d + e. )

(R ¹⁶ SO ₂ ) (R ¹⁷ SO ₂ ) (R ¹⁸ SO ₂ ) C General formula (9)
(R ¹⁶ , R ¹⁷ , and R ¹⁸ are each independently C _n H _a F _b Cl _c Br _d I _e .
n, a, b, c, d, and e are each independently an integer of 0 or more, and satisfy 2n + 1 = a + b + c + d + e.
Any two of R ¹⁶ , R ¹⁷ and R ¹⁸ may combine to form a ring, in which case the group forming the ring satisfies 2n = a + b + c + d + e. Three of R ¹⁶ , R ¹⁷ and R ¹⁸ may combine to form a ring, in which case two of the three satisfy 2n = a + b + c + d + e, and one group satisfies 2n−1 = a + b + c + d + e. Fulfill. )

In the chemical structures represented by the general formulas (7) to (9), n is preferably an integer of 0 to 6, more preferably an integer of 0 to 4, and particularly preferably an integer of 0 to 2. In the chemical structures represented by the above general formulas (7) to (9), when R ¹³ and R ¹⁴ are bonded, or R ¹⁶ , R ¹⁷ and R ¹⁸ are bonded to form a ring. In the formula, n is preferably an integer of 1 to 8, more preferably an integer of 1 to 7, and particularly preferably an integer of 1 to 3.

In the chemical structures represented by the general formulas (7) to (9), those in which a, c, d, and e are 0 are preferable.

Metal _{_{_{salts, (CF 3 SO 2) 2}}} NLi ( hereinafter sometimes referred to as _{_{_{"LiTFSA".), (F S O 2}}} ) 2 NLi ( hereinafter sometimes referred to as "LiFSA".), (C ₂ F ₅ SO ₂ ) ₂ NLi, FSO ₂ (CF ₃ SO ₂ ) NLi, (SO ₂ CF ₂ CF ₂ SO ₂ ) NLi, (SO ₂ CF ₂ CF ₂ CF ₂ SO ₂ ) NLi, FSO ₂ (CH ₃ SO ₂ ) NLi, FSO ₂ (C ₂ F ₅ SO ₂ ) NLi, or FSO ₂ (C ₂ H ₅ SO ₂ ) NLi are particularly preferred.

The metal salt may be a combination of an appropriate number of cations and anions described above. One kind of metal salt may be adopted, or a plurality of kinds may be used in combination.

[Organic solvent]
As the organic solvent having a hetero element, an organic solvent in which the hetero element is at least one selected from nitrogen, oxygen, sulfur and halogen is preferable, and an organic solvent in which the hetero element is at least one selected from nitrogen or oxygen Is more preferable. As the organic solvent having a hetero element, an aprotic solvent having no proton donating group such as NH group, NH ₂ group, OH group, and SH group is preferable.

Specific examples of the organic solvent having a hetero element (hereinafter sometimes simply referred to as “organic solvent”) include nitriles such as acetonitrile, propionitrile, acrylonitrile, malononitrile, 1,2-dimethoxyethane, 1, 2-diethoxyethane, tetrahydrofuran, 1,2-dioxane, 1,3-dioxane, 1,4-dioxane, 2,2-dimethyl-1,3-dioxolane, 2-methyltetrahydropyran, 2-methyltetrahydrofuran, crown Ethers such as ether, carbonates such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethylmethyl carbonate, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolide Amides such as isopropyl isocyanate, n-propyl isocyanate, chloromethyl isocyanate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, methyl formate, ethyl formate, vinyl acetate, methyl acrylate, methyl methacrylate, etc. Esters, glycidyl methyl ether, epoxy butane, epoxy such as 2-ethyloxirane, oxazole, 2-ethyloxazole, oxazoline, oxazole such as 2-methyl-2-oxazoline, ketone such as acetone, methyl ethyl ketone, methyl isobutyl ketone Acid anhydrides such as acetic anhydride and propionic anhydride, sulfones such as dimethyl sulfone and sulfolane, sulfoxides such as dimethyl sulfoxide, 1-nitropropane and 2-nitrate Nitros such as propane, furans such as furan and furfural, cyclic esters such as γ-butyrolactone, γ-valerolactone and δ-valerolactone, aromatic heterocycles such as thiophene and pyridine, tetrahydro-4-pyrone, Examples thereof include heterocyclic rings such as 1-methylpyrrolidine and N-methylmorpholine, and phosphate esters such as trimethyl phosphate and triethyl phosphate.

Examples of the organic solvent having a hetero element include a chain carbonate represented by the following general formula (10).

R ¹⁹ OCOOR ²⁰ ··· General formula (10)
(R ¹⁹ and R ²⁰ are each independently C _n H _a F _b Cl _c Br _d I _e which is a chain alkyl, or C _m H _f F _g Cl _h Br _i I containing a cyclic alkyl in the chemical structure. .n selected from any of _{j, a, b, c,} d, e, m, f, g, h, i, j are each independently an integer of 0 or more, 2n + 1 = a + b + c + d + e, 2m = f + g + h + i + j Meet)

In the chain carbonate represented by the general formula (10), n is preferably an integer of 1 to 6, more preferably an integer of 1 to 4, and particularly preferably an integer of 1 to 2. m is preferably an integer of 3 to 8, more preferably an integer of 4 to 7, and particularly preferably an integer of 5 to 6. Among the chain carbonates represented by the general formula (10), dimethyl carbonate (hereinafter sometimes referred to as “DMC”), diethyl carbonate (hereinafter sometimes referred to as “DEC”), ethylmethyl Carbonate (hereinafter sometimes referred to as “EMC”) is particularly preferred.

As the organic solvent having a hetero element, a solvent having a relative dielectric constant of 20 or more or a donor ether oxygen is preferable. Examples of such an organic solvent include nitriles such as acetonitrile, propionitrile, acrylonitrile, and malononitrile, 2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,2-dioxane, 1,3-dioxane, 1,4-dioxane, 2,2-dimethyl-1,3-dioxolane, 2-methyltetrahydropyran And ethers such as 2-methyltetrahydrofuran and crown ether, N, N-dimethylformamide, acetone, dimethyl sulfoxide, and sulfolane. In particular, acetonitrile (hereinafter sometimes referred to as “AN”), 1, 2-dimethoxyethane (hereinafter referred to as “D There is the fact that E ".) Is preferred.

These organic solvents may be used alone or in combination as an electrolyte.

The electrolyte solution of the present invention has a peak in which the original peak of the organic solvent is shifted to Io with respect to the peak intensity derived from the organic solvent contained in the electrolyte solution of the present invention in the vibrational spectrum. Hereinafter, the intensity of the “shift peak” may be Is, where Is> Io. That is, in the vibrational spectroscopic spectrum chart obtained by subjecting the electrolytic solution of the present invention to vibrational spectroscopic measurement, the relationship between the two peak intensities is Is> Io.

Here, “the original peak of the organic solvent” means a peak observed at the peak position (wave number) when vibration spectroscopy measurement is performed only on the organic solvent. The value of the intensity Io of the original peak of the organic solvent and the value of the intensity Is of the shift peak are the height or area from the baseline of each peak in the vibrational spectrum.

In the vibrational spectroscopic spectrum of the electrolytic solution of the present invention, when there are a plurality of peaks in which the original peak of the organic solvent is shifted, the relationship may be determined based on the peak for which the relationship between Is and Io is most easily determined. In addition, when a plurality of organic solvents having heteroelements are used in the electrolytic solution of the present invention, an organic solvent that can determine the relationship between Is and Io most easily (the difference between Is and Io is most pronounced) is selected, The relationship between Is and Io may be determined based on the peak intensity. Further, when the peak shift amount is small and the peaks before and after the shift appear to be a gentle mountain, peak separation may be performed using known means to determine the relationship between Is and Io.

Note that in the vibrational spectroscopic spectrum of an electrolytic solution using a plurality of organic solvents having a hetero element, the peak of an organic solvent that is most easily coordinated with a cation (hereinafter sometimes referred to as “preferred coordination solvent”) is another. Shift in preference to. In an electrolytic solution using a plurality of organic solvents having a hetero element, the mass% of the preferential coordination solvent with respect to the entire organic solvent having a hetero element is preferably 40% or more, more preferably 50% or more, and further preferably 60% or more. 80% or more is particularly preferable. Further, in the electrolytic solution using a plurality of organic solvents having a hetero element, the volume% of the preferential coordination solvent with respect to the entire organic solvent having a hetero element is preferably 40% or more, more preferably 50% or more, and 60% or more. Is more preferable, and 80% or more is particularly preferable.

The relationship between the two peak intensities preferably satisfies the condition of Is> 2 × Io, more preferably satisfies the condition of Is> 3 × Io, and particularly preferably satisfies the condition of Is> 5 × Io. Most preferred is an electrolytic solution in which the intensity Io of the peak inherent in the organic solvent is not observed and the intensity Is of the shift peak is observed in the vibrational spectrum of the electrolytic solution of the present invention. In the electrolytic solution, it means that all the molecules of the organic solvent contained in the electrolytic solution are completely solvated with the metal salt. The electrolyte solution of the present invention is most preferably in a state where all the molecules of the organic solvent contained in the electrolyte solution are completely solvated with the metal salt (Io = 0 state).

In the electrolytic solution of the present invention, it is presumed that the metal salt and the organic solvent (or preferential coordination solvent) having a hetero element have an interaction. Specifically, a metal salt and a hetero element of an organic solvent (or preferential coordination solvent) having a hetero element form a coordination bond, and the organic solvent (or preferential coordinating solvent) having a metal salt and a hetero element ) Is estimated to form a stable cluster. From the results of Examples described later, this cluster is presumed to be formed by coordination of two molecules of an organic solvent (or preferential coordination solvent) having a hetero element with one molecule of a metal salt. The Considering this point, the molar range of the organic solvent having a hetero element (or preferential coordination solvent) with respect to 1 mol of the metal salt in the electrolytic solution of the present invention is preferably 1.4 mol or more and less than 3.5 mol. More preferably, it is 0.5 mol or more and 3.1 mol or less, and 1.6 mol or more and 3 mol or less are still more preferable.

The viscosity η (mPa · s) of the electrolytic solution of the present invention is preferably in the range of 10 <η <500, more preferably in the range of 12 <η <400, further preferably in the range of 15 <η <300, and 18 <η. A range of <150 is particularly preferred, and a range of 20 <η <140 is most preferred.

The electrolytic solution of the present invention exhibits excellent ionic conductivity. For this reason, the nonaqueous electrolyte secondary battery of this invention is excellent in a battery characteristic. The ionic conductivity σ (mS / cm) of the electrolytic solution of the present invention is preferably 1 ≦ σ.

The higher the ionic conductivity σ (mS / cm) of the electrolytic solution of the present invention, the more suitable ions can be transferred, and an excellent battery electrolytic solution can be obtained. Regarding the ionic conductivity σ (mS / cm) of the electrolytic solution of the present invention, when a suitable range including the upper limit is shown, a range of 2 <σ <200 is preferable, and a range of 3 <σ <100 is more preferable. The range of 4 <σ <50 is more preferable, and the range of 5 <σ <35 is particularly preferable.

The density d (g / cm ³ ) in the electrolytic solution of the present invention is preferably d ≧ 1.2 or d ≦ 2.2, more preferably 1.2 ≦ d ≦ 2.2. A range of 24 ≦ d ≦ 2.0 is more preferable, a range of 1.26 ≦ d ≦ 1.8 is more preferable, and a range of 1.27 ≦ d ≦ 1.6 is particularly preferable. The density d (g / cm ³ ) in the electrolytic solution of the present invention means the density at 20 ° C. D / c described below is a value obtained by dividing the above d by the salt concentration c (mol / L).
In the electrolytic solution of the present invention, d / c is 0.15 ≦ d / c ≦ 0.71, preferably 0.15 ≦ d / c ≦ 0.56, and 0.25 ≦ d / c ≦ 0. Within the range of .56, more preferably within the range of 0.26 ≦ d / c ≦ 0.50, and particularly preferably within the range of 0.27 ≦ d / c ≦ 0.47.

D / c in the electrolytic solution of the present invention can be defined even when a metal salt and an organic solvent are specified. For example, when LiTFSA is selected as the metal salt and DME is selected as the organic solvent, d / c is preferably within the range of 0.42 ≦ d / c ≦ 0.56, and 0.44 ≦ d / c ≦ 0.52 The range of is more preferable. When LiTFSA is selected as the metal salt and AN is selected as the organic solvent, d / c is preferably in the range of 0.35 ≦ d / c ≦ 0.41, and 0.36 ≦ d / c ≦ 0.39. The inside is more preferable. When LiFSA is selected as the metal salt and DME is selected as the organic solvent, d / c is preferably in the range of 0.32 ≦ d / c ≦ 0.46, and in the range of 0.34 ≦ d / c ≦ 0.42. The inside is more preferable. When LiFSA is selected as the metal salt and AN is selected as the organic solvent, d / c is preferably in the range of 0.25 ≦ d / c ≦ 0.48, and in the range of 0.25 ≦ d / c ≦ 0.38. Is more preferable, the range of 0.25 ≦ d / c ≦ 0.31 is still more preferable, and the range of 0.26 ≦ d / c ≦ 0.29 is still more preferable. When LiFSA is selected as the metal salt and DMC is selected as the organic solvent, d / c is preferably in the range of 0.32 ≦ d / c ≦ 0.46, and in the range of 0.34 ≦ d / c ≦ 0.42. The inside is more preferable. When LiFSA is selected as the metal salt and EMC is selected as the organic solvent, d / c is preferably in the range of 0.34 ≦ d / c ≦ 0.50, and in the range of 0.37 ≦ d / c ≦ 0.45. The inside is more preferable. When LiFSA is selected as the metal salt and DEC is selected as the organic solvent, d / c is preferably in the range of 0.36 ≦ d / c ≦ 0.54, and in the range of 0.39 ≦ d / c ≦ 0.48. The inside is more preferable.

Compared with conventional electrolytes, the electrolyte solution of the present invention is different in the environment in which the metal salt and the organic solvent are present, and has a high density. , Improvement in lithium transport number), improvement in the reaction rate between the electrode and the electrolyte solution, relaxation of uneven distribution of the salt concentration of the electrolyte that occurs during high-rate charge / discharge of the battery, and increase in the electric double layer capacity can be expected. Furthermore, in the electrolytic solution of the present invention, since the density is high, the vapor pressure of the organic solvent contained in the electrolytic solution is lowered. As a result, volatilization of the organic solvent from the electrolytic solution of the present invention can be reduced.

In the electrolytic solution of the present invention, it is presumed that a cluster is formed by coordination of two molecules of an organic solvent (or a preferential coordination solvent) having a hetero element with one molecule of a metal salt. The concentration (mol / L) of the electrolytic solution of the invention depends on the molecular weight of each of the metal salt and the organic solvent and the density when the solution is used. Therefore, it is not appropriate to prescribe the concentration of the electrolytic solution of the present invention.

Table 1 individually illustrates the concentration (mol / L) of the electrolytic solution of the present invention.

The organic solvent that forms the cluster and the organic solvent that is not involved in the formation of the cluster have different environments. Therefore, in vibrational spectroscopy measurement, the peak derived from the organic solvent forming the cluster is higher than the observed wave number of the peak derived from the organic solvent not involved in the cluster formation (original peak of the organic solvent). Or it is observed shifted to the low wavenumber side. That is, the shift peak corresponds to the peak of the organic solvent forming the cluster.

As the vibrational spectrum, an IR spectrum or a Raman spectrum can be exemplified. Examples of the measurement method for IR measurement include transmission measurement methods such as Nujol method and liquid film method, and reflection measurement methods such as ATR method. As to whether to select the IR spectrum or the Raman spectrum, it is only necessary to select a spectrum in which the relationship between Is and Io can be easily determined in the vibrational spectrum of the electrolytic solution of the present invention. The vibrational spectroscopic measurement is preferably performed under conditions that can reduce or ignore the influence of moisture in the atmosphere. For example, IR measurement may be performed under low or no humidity conditions such as a dry room or a glove box, or Raman measurement may be performed with the electrolytic solution of the present invention in a sealed container.

Here, the peak in the electrolytic solution of the present invention containing LiTFSA as the metal salt and acetonitrile as the organic solvent will be specifically described.

When only acetonitrile is measured by IR, a peak derived from stretching vibration of a triple bond between C and N is usually observed in the vicinity of 2100 to 2400 cm ⁻¹ .

Here, it is assumed that LiTFSA is dissolved in an acetonitrile solvent at a concentration of 1 mol / L to obtain an electrolytic solution according to conventional technical common sense. Since 1 L of acetonitrile corresponds to about 19 mol, 1 L of conventional electrolyte includes 1 mol of LiTFSA and 19 mol of acetonitrile. Then, in the conventional electrolyte, there are many acetonitriles that are not solvated with LiTFSA (not coordinated with Li) simultaneously with acetonitrile that is solvated with LiTFSA (coordinated with Li). . Now, since the acetonitrile molecule is different between the LiTFSA solvated acetonitrile molecule and the LiTFSA non-solvated acetonitrile molecule, in the IR spectrum, the acetonitrile peaks of both are distinguished and observed. Is done. More specifically, the peak of acetonitrile that is not solvated with LiTFSA is observed at the same position (wave number) as in the case of IR measurement of only acetonitrile, but the peak of acetonitrile that is solvated with LiTFSA. Is observed with the peak position (wave number) shifted to the high wave number side.

Since there are many acetonitriles that are not solvated with LiTFSA in the concentration of the conventional electrolyte, in the vibrational spectrum of the conventional electrolyte, the peak intensity Io of the original acetonitrile and the peak of the original acetonitrile The relationship with the intensity Is of the peak shifted is Is <Io.

On the other hand, the electrolytic solution of the present invention has a higher LiTFSA concentration than the conventional electrolytic solution, and the number of acetonitrile molecules solvated with LiTFSA (forming clusters) in the electrolytic solution is different from that of LiTFSA. More than the number of unsolvated acetonitrile molecules. Then, the relation between the intensity Io of the original peak of the acetonitrile and the intensity Is of the peak obtained by shifting the original peak of acetonitrile in the vibrational spectrum of the electrolytic solution of the present invention is Is> Io.

Table 2 exemplifies the wave numbers of organic solvents that are considered useful for the calculation of Io and Is and their attribution in the vibrational spectrum of the electrolytic solution of the present invention. It should be added that the wave number of the observed peak may be different from the following wave numbers depending on the measurement apparatus, measurement environment, and measurement conditions of the vibrational spectrum.

It is also possible to refer to known data regarding the wave number of organic solvents and their attribution. As references, the Spectroscopical Society of Japan Measurement Series 17, Raman Spectroscopy, Hiroo Higuchi, Atsuko Hirakawa, Academic Publishing Center, pages 231 to 249 are listed. In addition, the calculation using a computer can also predict the wave number of an organic solvent that is considered useful for the calculation of Io and Is and the wave number shift when the organic solvent and the metal salt are coordinated. For example, Gaussian 09 (registered trademark, Gaussian) may be used, and the density functional may be calculated as B3LYP and the basis function as 6-311G ++ (d, p). A person skilled in the art can calculate the Io and Is by selecting the peak of the organic solvent with reference to the description in Table 2, known data, and the calculation result in the computer.

The electrolytic solution of the present invention is different from the conventional electrolytic solution in that the presence environment of the metal salt and the organic solvent is different and the concentration of the metal salt is high, so that the metal ion transport rate in the electrolytic solution is improved (especially metal When Li is lithium, the lithium transport number is improved), the reaction rate between the electrode and the electrolyte solution is improved, the uneven distribution of the salt concentration of the electrolyte solution that occurs during high-rate charge / discharge of the battery, and the electric double layer capacity can be expected to increase . Furthermore, in the electrolytic solution of the present invention, since most of the organic solvent having a hetero element forms a cluster with a metal salt, the vapor pressure of the organic solvent contained in the electrolytic solution is lowered. As a result, volatilization of the organic solvent from the electrolytic solution of the present invention can be reduced.

The electrolyte of the present invention has a higher viscosity than the conventional battery electrolyte. For example, the preferable Li concentration of the electrolytic solution of the present invention is about 2 to 5 times the Li concentration of a general electrolytic solution. Therefore, if it is a battery using the electrolyte solution of this invention, even if a battery is damaged, electrolyte solution leakage is suppressed. Moreover, the capacity | capacitance reduction of the secondary battery using the conventional electrolyte solution was remarkable at a high-speed charging / discharging cycle. The reason is that due to the uneven Li concentration generated in the electrolyte when rapidly charging and discharging, the electrolyte cannot supply a sufficient amount of Li to the reaction interface with the electrode. The uneven distribution of Li concentration in the liquid can be considered. However, it has become clear that the capacity of the secondary battery using the electrolytic solution of the present invention is suitably maintained during high-speed charge / discharge. It is considered that the uneven distribution of Li concentration in the electrolytic solution could be suppressed due to the physical properties of the electrolytic solution of the present invention with high viscosity. In addition, due to the high viscosity of the electrolyte solution of the present invention, the liquid retention of the electrolyte solution at the electrode interface has been improved, and the state where the electrolyte solution is insufficient at the electrode interface (so-called liquid withdrawn state) has been suppressed. The reason is considered.

Incidentally, the electrolytic solution of the present invention contains a metal salt cation in a high concentration. For this reason, in the electrolytic solution of the present invention, the distance between adjacent cations is extremely short. When cations such as lithium ions move between the positive electrode and the negative electrode during charge / discharge of the nonaqueous electrolyte secondary battery, the cations closest to the destination electrode are first supplied to the electrode. And the other cation adjacent to the said cation moves to the place with the said supplied cation. In other words, in the electrolytic solution of the present invention, it is expected that a domino-like phenomenon occurs in which adjacent cations change one by one toward the electrode to be supplied one by one. For this reason, the movement distance of the cation at the time of charging / discharging is short, and it is thought that the movement speed | rate of a cation is high by that much. Due to this, the reaction rate of the nonaqueous electrolyte secondary battery of the present invention having the electrolytic solution of the present invention is considered to be high. Further, as will be described later, the nonaqueous electrolyte secondary battery of the present invention has an S, O-containing film on the electrode (that is, the negative electrode and / or the positive electrode), and the S, O-containing film has an S═O structure. It is thought to contain many cations. It is considered that cations contained in the S, O-containing film are preferentially supplied to the electrode. Therefore, in the nonaqueous electrolyte secondary battery of the present invention, it is considered that the cation transport rate is further improved by having an abundant cation source (that is, an S, O-containing film) in the vicinity of the electrode. Therefore, in the nonaqueous electrolyte secondary battery of the present invention, it is considered that excellent battery characteristics are exhibited by the cooperation of the electrolytic solution of the present invention and the S, O-containing film.

The method for producing the electrolytic solution of the present invention will be described. Since the electrolytic solution of the present invention has a higher metal salt content than the conventional electrolytic solution, the production method in which an organic solvent is added to a solid (powder) metal salt results in the formation of aggregates. It is difficult to produce an electrolytic solution. Therefore, in the manufacturing method of the electrolyte solution of this invention, it is preferable to manufacture, adding a metal salt gradually with respect to an organic solvent, and maintaining the solution state of electrolyte solution.

Depending on the type of metal salt and organic solvent, the electrolytic solution of the present invention includes a liquid in which the metal salt is dissolved in the organic solvent beyond the conventionally considered saturation solubility. Such a method for producing an electrolytic solution of the present invention includes a first dissolving step of preparing a first electrolytic solution by mixing an organic solvent having a hetero element and a metal salt, dissolving the metal salt, stirring and / or Alternatively, under heating conditions, the metal salt is added to the first electrolyte solution, the metal salt is dissolved, and a second electrolyte solution in a supersaturated state is prepared; and stirring and / or heating conditions, A third dissolving step of adding the metal salt to the second electrolytic solution, dissolving the metal salt, and preparing a third electrolytic solution;

Here, the “supersaturated state” refers to a state in which metal salt crystals are precipitated from the electrolyte when the stirring and / or heating conditions are canceled or when crystal nucleation energy such as vibration is applied. Means. The second electrolytic solution is “supersaturated”, and the first electrolytic solution and the third electrolytic solution are not “supersaturated”.

In other words, the above-described method for producing the electrolytic solution of the present invention is a thermodynamically stable liquid state, and passes through the first electrolytic solution containing the conventional metal salt concentration, and then the thermodynamically unstable liquid state. The second electrolytic solution passes through the two electrolytic solutions and becomes a thermodynamically stable new electrolytic third solution, that is, the electrolytic solution of the present invention.

Since the stable third electrolyte solution in a liquid state maintains a liquid state under normal conditions, the third electrolyte solution is composed of, for example, two molecules of an organic solvent for one lithium salt molecule, and a strong distribution between these molecules. It is presumed that the cluster stabilized by the coordinate bond inhibits the crystallization of the lithium salt.

The first dissolution step is a step of preparing a first electrolytic solution by mixing an organic solvent having a hetero atom and a metal salt to dissolve the metal salt.

In order to mix an organic solvent having a heteroatom and a metal salt, a metal salt may be added to the organic solvent having a heteroatom, or an organic solvent having a heteroatom may be added to the metal salt.

The first dissolution step is preferably performed under stirring and / or heating conditions. What is necessary is just to set suitably about stirring speed. About heating conditions, it is preferable to control suitably with thermostats, such as a water bath or an oil bath. Since heat of dissolution is generated when the metal salt is dissolved, it is preferable to strictly control the temperature condition when using a metal salt that is unstable to heat. In addition, the organic solvent may be cooled in advance, or the first dissolution step may be performed under cooling conditions.

The first dissolution step and the second dissolution step may be performed continuously, or the first electrolytic solution obtained in the first dissolution step is temporarily stored (standing), and after a certain time has passed, You may implement a melt | dissolution process.

The second dissolution step is a step of preparing a supersaturated second electrolyte solution by adding a metal salt to the first electrolyte solution under stirring and / or heating conditions to dissolve the metal salt.

It is essential to perform the second dissolution step under stirring and / or warming conditions in order to prepare a supersaturated second electrolyte solution that is thermodynamically unstable. By performing the second dissolution step with a stirrer with a stirrer such as a mixer, the stirring condition may be achieved, or the second dissolution step is performed using a stirrer and a device (stirrer) that operates the stirrer. Thus, the stirring condition may be used. About heating conditions, it is preferable to control suitably with thermostats, such as a water bath or an oil bath. Of course, it is particularly preferable to perform the second dissolution step using an apparatus or system having both a stirring function and a heating function. In addition, heating here refers to warming a target object to temperature more than normal temperature (25 degreeC). The heating temperature is more preferably 30 ° C. or higher, and further preferably 35 ° C. or higher. Further, the heating temperature is preferably lower than the boiling point of the organic solvent.

In the second dissolution step, if the added metal salt is not sufficiently dissolved, increase the stirring speed and / or further heating. In this case, a small amount of an organic solvent having a hetero atom may be added to the electrolytic solution in the second dissolution step.

Since the crystal of the metal salt is deposited once the second electrolyte obtained in the second dissolution step is allowed to stand, the second dissolution step and the third dissolution step are preferably carried out continuously.

The third dissolution step is a step of preparing a third electrolyte solution by adding a metal salt to the second electrolyte solution under stirring and / or heating conditions to dissolve the metal salt. In the third dissolution step, it is necessary to add a metal salt to the supersaturated second electrolytic solution and dissolve it. Therefore, it is essential to perform the stirring and / or heating conditions as in the second dissolution step. Specific stirring and / or heating conditions are the same as those in the second dissolution step.

If the molar ratio of the organic solvent and the metal salt added through the first dissolving step, the second dissolving step, and the third dissolving step is about 2: 1, the production of the third electrolytic solution (the electrolytic solution of the present invention) is completed. finish. Even when the stirring and / or heating conditions are canceled, the metal salt crystals are not precipitated from the electrolytic solution of the present invention. In view of these circumstances, the electrolytic solution of the present invention is composed of, for example, two molecules of an organic solvent for one molecule of a lithium salt, and is presumed to form a cluster stabilized by a strong coordinate bond between these molecules. Is done.

In producing the electrolytic solution of the present invention, depending on the types of metal salt and organic solvent, the first to third dissolving steps can be performed even if the supersaturated state is not passed at the treatment temperature in each dissolving step. The electrolytic solution of the present invention can be appropriately produced using the specific dissolution means described in 1.

In addition, in the method for producing an electrolytic solution of the present invention, it is preferable to have a vibrational spectroscopic measurement step of performing vibrational spectroscopic measurement of the electrolytic solution being manufactured. As a specific vibration spectroscopic measurement step, for example, a method of sampling a part of each electrolytic solution in the middle of production and using it for vibration spectroscopic measurement, or a method of performing spectroscopic spectroscopic measurement of each electrolytic solution in situ (situ) But it ’s okay. As a method for in-vitro vibrational spectroscopic measurement of an electrolytic solution, a method of introducing an electrolytic solution in the middle of production into a transparent flow cell and performing vibrational spectroscopic measurement, or a method of performing Raman measurement from outside the container using a transparent production vessel Can be mentioned.

Since the relationship between Is and Io in the electrolytic solution can be confirmed during the production by including the vibrational spectroscopic measurement step in the method for producing the electrolytic solution of the present invention, whether the electrolytic solution during the production reaches the electrolytic solution of the present invention. It is possible to determine whether or not the amount of metal salt added to reach the electrolytic solution of the present invention when the electrolytic solution being manufactured does not reach the electrolytic solution of the present invention. can do.

In the electrolyte solution of the present invention, in addition to the organic solvent having a hetero element, the solvent has a low polarity (low dielectric constant) or a low donor number and does not exhibit a special interaction with a metal salt, that is, the present invention. A solvent that does not affect the formation and maintenance of the clusters in the electrolyte can be added. By adding such a solvent to the electrolytic solution of the present invention, an effect of lowering the viscosity of the electrolytic solution of the present invention can be expected while maintaining the formation of the cluster of the electrolytic solution of the present invention.

Specific examples of the solvent that does not exhibit a special interaction with the metal salt include benzene, toluene, ethylbenzene, o-xylene, m-xylene, p-xylene, 1-methylnaphthalene, hexane, heptane, and cyclohexane. it can.

In addition to the organic solvent having a hetero element, a flame retardant solvent can be added to the electrolytic solution of the present invention. By adding a flame retardant solvent to the electrolytic solution of the present invention, the safety of the electrolytic solution of the present invention can be further increased. Examples of the flame retardant solvent include halogen solvents such as carbon tetrachloride, tetrachloroethane, and hydrofluoroether, and phosphoric acid derivatives such as trimethyl phosphate and triethyl phosphate.

Furthermore, when the electrolytic solution of the present invention is mixed with a polymer or an inorganic filler to form a mixture, the mixture contains the electrolytic solution and becomes a pseudo solid electrolyte. By using the pseudo-solid electrolyte as the battery electrolyte, leakage of the electrolyte in the battery can be suppressed.

As the polymer, a polymer used for a battery such as a lithium ion secondary battery or a general chemically crosslinked polymer can be employed. In particular, a polymer that can absorb an electrolyte such as polyvinylidene fluoride and polyhexafluoropropylene and gel can be used, and a polymer such as polyethylene oxide in which an ion conductive group is introduced.

Specific polymers include polymethyl acrylate, polymethacrylate, polymethyl methacrylate, polyethylene oxide, polypropylene oxide, polyacrylonitrile, polyvinylidene fluoride, polyethylene glycol dimethacrylate, polyethylene glycol acrylate, polyglycidol, polytetrafluoroethylene, polyhexa Fluoropropylene, polysiloxane, polyvinyl acetate, polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, polyitaconic acid, polyfumaric acid, polycrotonic acid, polyangelic acid, polycarboxylic acids such as carboxymethylcellulose, styrene-butadiene rubber, nitrile-butadiene Rubber, polystyrene, polycarbonate, maleic anhydride and glycols copolymerized Sum polyesters, polyethylene oxide derivative having a substituent, a copolymer of vinylidene fluoride and hexafluoropropylene can be exemplified. Further, as the polymer, a copolymer obtained by copolymerizing two or more monomers constituting the specific polymer may be selected.

Polysaccharides are also suitable as the polymer. Specific examples of the polysaccharide include glycogen, cellulose, chitin, agarose, carrageenan, heparin, hyaluronic acid, pectin, amylopectin, xyloglucan, and amylose. Moreover, you may employ | adopt the material containing these polysaccharides as said polymer, and the agar containing polysaccharides, such as agarose, can be illustrated as the said material.

The inorganic filler is preferably an inorganic ceramic such as oxide or nitride.

Inorganic ceramics have hydrophilic and hydrophobic functional groups on the surface. Therefore, when the functional group attracts the electrolytic solution, a conductive path can be formed in the inorganic ceramic. Furthermore, the inorganic ceramics dispersed in the electrolytic solution can form a network between the inorganic ceramics by the functional groups and serve to contain the electrolytic solution. With such a function of the inorganic ceramics, it is possible to more suitably suppress the leakage of the electrolytic solution in the battery. In order to suitably exhibit the above functions of the inorganic ceramics, the inorganic ceramics preferably have a particle shape, and particularly preferably have a particle size of nano level.

Examples of the inorganic ceramics include general alumina, silica, titania, zirconia, and lithium phosphate. Further, the inorganic ceramic itself may be lithium conductive, and specifically, Li ₃ N, LiI, LiI—Li ₃ N—LiOH, LiI—Li ₂ S—P ₂ O ₅ , LiI—Li ₂ S —P ₂ S ₅ , LiI—Li ₂ S—B ₂ S ₃ , Li ₂ O—B ₂ S ₃ , Li ₂ O—V ₂ O ₃ —SiO ₂ , Li ₂ O—B ₂ O ₃ —P ₂ O ₅ , Li ₂ O—B ₂ O ₃ —ZnO, Li ₂ O—Al ₂ O ₃ —TiO ₂ —SiO ₂ —P ₂ O ₅ , LiTi ₂ (PO ₄ ) ₃ , Li—βAl ₂ O ₃ , LiTaO ₃ Can be illustrated.

Glass ceramics may be employed as the inorganic filler. Since glass ceramics can contain an ionic liquid, the same effect can be expected for the electrolytic solution of the present invention. Glass ceramics include compounds represented by xLi ₂ S- (1-x) P ₂ S ₅ , those obtained by substituting part of S of the compound with other elements, and compounds of P of the compound. An example in which the part is replaced with germanium can be exemplified.

Since the electrolytic solution of the present invention described above exhibits excellent ionic conductivity, it is suitably used as an electrolytic solution for power storage devices such as batteries. In particular, it is preferably used as an electrolyte solution for a secondary battery, and particularly preferably used as an electrolyte solution for a lithium ion secondary battery.

Hereinafter, the nonaqueous electrolyte secondary battery of the present invention using the electrolytic solution of the present invention will be described. Unless otherwise specified, it is considered that the nonaqueous electrolyte secondary batteries (1) to (5) of the present invention described above are all explained.

The nonaqueous electrolyte secondary battery includes a negative electrode having a negative electrode active material capable of occluding and releasing charge carriers such as lithium ions, a positive electrode having a positive electrode active material capable of occluding and releasing the charge carriers, and the electrolytic solution of the present invention With. Since the electrolytic solution of the present invention employs a lithium salt as a metal salt, it is particularly suitable as an electrolytic solution for a lithium ion secondary battery.

<Negative electrode>
The negative electrode has a current collector and a negative electrode active material layer bound to the current collector surface.

[Current collector]
The current collector refers to a chemically inert electronic high conductor that keeps a current flowing through an electrode during discharge or charging of a nonaqueous electrolyte secondary battery. As the current collector, at least one selected from silver, copper, gold, aluminum, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, molybdenum, and stainless steel Metal materials can be exemplified. The current collector may be covered with a known protective layer. What collected the surface of the electrical power collector by the well-known method may be used as an electrical power collector.

The current collector can take the form of a foil, a sheet, a film, a linear shape, a rod shape, a mesh, or the like. Therefore, metal foils, such as copper foil, nickel foil, stainless steel foil, can be used suitably as a collector, for example. When the current collector is in the form of foil, sheet or film, the thickness is preferably in the range of 1 μm to 100 μm.

[Negative electrode active material layer]
The negative electrode active material layer includes a negative electrode active material and generally a binder. Furthermore, you may contain a conductive support agent as needed.

<Nonaqueous electrolyte secondary battery (1)>
The negative electrode active material in the nonaqueous electrolyte secondary battery (1) contains graphite having a G / D ratio of 3.5 or more. As described above, the G / D ratio is the ratio of the G-band and D-band peaks in the Raman spectrum. In the Raman spectrum of graphite, each peak appears in the G-band (1590cm ^-1 vicinity) and D-band (1350cm around ^-1), G-band 'is derived from the graphite structure, D-band' is to be attributed to a defect . Therefore, the higher the G / D ratio, which is the ratio of G-band to D-band, means that the graphite has fewer defects and higher crystallinity. Hereinafter, graphite having a G / D ratio of 3.5 or more may be referred to as high crystalline graphite, and graphite having a G / D ratio of less than 3.5 may be referred to as low crystalline graphite.

As such highly crystalline graphite, either natural graphite or artificial graphite can be used. In the classification method by shape, scaly graphite, spherical graphite, massive graphite, earthy graphite, and the like can be used. Also, coated graphite whose surface is coated with a carbon material or the like can be used.

The negative electrode active material may be mainly high crystalline graphite having a G / D ratio of 3.5 or more, and may contain low crystalline graphite or amorphous carbon.

<Nonaqueous electrolyte secondary battery (2)>
The negative electrode active material in the nonaqueous electrolyte secondary battery (2) includes a carbon material having a crystallite size of 20 nm or less. As described above, the crystallite size is calculated from the half width of the peak appearing at 2θ = 20 degrees to 30 degrees in the X-ray diffraction profile measured by the X-ray diffraction method. A larger crystallite size means that the atoms are arranged periodically and accurately according to a certain rule. On the other hand, it can be said that a carbon material having a crystallite size of 20 nm or less has poor periodicity and accuracy. For example, if the carbon material is graphite, the size of the graphite crystal is 20 nm or less, or due to the influence of strain, defects, impurities, etc., the regularity of the arrangement of the atoms constituting the graphite becomes poor. The size is 20 nm or less. In the nonaqueous electrolyte secondary battery (2) of the present invention, it is particularly preferable to use a carbon material having a crystallite size of 5 nm or less.

The carbon material having a crystallite size of 20 nm or less is typically hard carbon or soft carbon, but the “carbon material having a crystallite size of 20 nm or less” in the nonaqueous electrolyte secondary battery (2) of the present invention is It is not limited to.

In order to measure the crystallite size of the carbon material, an X-ray diffraction method using CuKα rays as an X-ray source may be used. With the X-ray diffraction method, the crystallite size can be calculated using the following Scherrer equation based on the half-value width and diffraction angle of a diffraction peak detected at a diffraction angle 2θ = 20 degrees to 30 degrees.

L = 0.94λ / (βcosθ)
here,
L: Crystallite size λ: Incident X-ray wavelength (1.54 mm)
β: half width of peak (radian)
θ: Diffraction angle

<Nonaqueous electrolyte secondary battery (3)>
The negative electrode active material in the nonaqueous electrolyte secondary battery (3) contains a silicon element and / or a tin element. Silicon and tin are known to be negative electrode active materials that can greatly improve the capacity of the nonaqueous electrolyte secondary battery. Silicon and tin belong to group 14 elements. Since these simple substances can occlude and release a large number of charge carriers (lithium ions, etc.) per unit volume (mass), they become high-capacity negative electrode active materials. However, on the other hand, non-aqueous electrolyte secondary batteries using these as negative electrode active materials have relatively poor rate characteristics.
In contrast, a non-aqueous electrolyte secondary battery using carbon as a negative electrode active material has excellent rate characteristics. Therefore, by using both of them as the negative electrode active material, the nonaqueous electrolyte secondary battery can have a high capacity, and excellent rate characteristics can be imparted to the nonaqueous electrolyte secondary battery.

Silicon has a large theoretical capacity when used as a negative electrode active material, but has a large volume change during charge and discharge. Therefore, as the negative electrode active material containing silicon element, it is particularly preferable to use SiO _x (0.3 ≦ x ≦ 1.6) disproportionated into two phases of a Si phase and a silicon oxide phase. The Si phase in SiO _x can occlude and release lithium ions. This Si phase undergoes volume change (that is, expansion and contraction) as lithium ions are occluded and released. Silicon oxide phase consists of SiO ₂ or the like, the volume change due to charging and discharging as compared with Si phase is small. That is, SiO _x as the negative electrode active material realizes a high capacity by the Si phase and suppresses the volume change of the entire negative electrode active material (or the negative electrode) by having the silicon oxide phase. If x is less than the lower limit, the Si ratio becomes excessive, so that the volume change at the time of charging / discharging becomes too large and the cycle characteristics deteriorate. On the other hand, when x exceeds the upper limit value, the Si ratio becomes too small and the energy density decreases. The range of x is more preferably 0.5 ≦ x ≦ 1.5, and further preferably 0.7 ≦ x ≦ 1.2.
In the SiO _x as described above, the alloying reaction by the silicon element contained in the lithium element and Si phase is believed to occur during charge and discharge of a nonaqueous electrolyte secondary battery. And it is thought that this alloying reaction contributes to charging / discharging of a nonaqueous electrolyte secondary battery (in this case, a lithium ion secondary battery). Similarly, it is considered that a negative electrode active material containing a tin element described later can be charged and discharged by an alloying reaction between a tin element and a lithium element.

Examples of the negative electrode active material containing tin element include Sn alone, tin alloy (Cu—Sn alloy, Co—Sn alloy), amorphous tin oxide, tin silicon oxide, and the like. Among them, the amorphous tin oxide _SnB 0.4 _P 0.6 _{O 3.1} is exemplified. The Suzukei containing oxide SnSiO ₃ is illustrated.

The negative electrode active material containing silicon element and the negative electrode active material containing tin element can be combined with a material containing carbon element (carbon material). By using these in combination rather than individually, the structure of silicon and / or tin is particularly stabilized, and the durability of the negative electrode is improved. Specifically, a carbon material such as graphite is a material with less volume change at the time of charging / discharging as compared with a silicon simple substance or a tin simple substance. Therefore, by combining a negative electrode active material containing silicon element and a negative electrode active material containing tin element with such a carbon material, damage of the negative electrode due to volume change during charging and discharging can be suppressed. Durability is improved. As a result, the cycle characteristics of the nonaqueous electrolyte secondary battery are improved. The composite of the negative electrode active material containing silicon element and / or the negative electrode active material containing tin element and the carbon material may be performed by a known method.

As the carbon material to be combined with the negative electrode active material containing silicon element and / or the negative electrode active material containing tin element, graphite, hard carbon (non-graphitizable carbon), soft carbon (graphitizable carbon), etc. are preferable. Can be used. The particle diameter of graphite is not particularly limited, whether natural or artificial.

<Nonaqueous electrolyte secondary battery (4)>
The negative electrode active material in the nonaqueous electrolyte secondary battery (4) contains a metal oxide that can occlude and release lithium ions. For example, titanium oxide such as TiO ₂ , lithium titanium oxide, tungsten oxide such as WO ₃ , amorphous tin oxide, tin silicon oxide, and the like.

Specifically, lithium titanium oxide includes spinel lithium titanate (for example, Li _{4 + x} Ti _{5 + y} O ₁₂ (x is −1 ≦ x ≦ 4, y is −1 ≦ y ≦ 1)), ramsdellite structure. Examples thereof include lithium titanate (for example, Li ₂ Ti ₃ O ₇ ). An example of the amorphous tin oxide is SnB _0.4 P _0.6 O _3.1 . The Suzukei containing oxide SnSiO ₃ is illustrated. Among these, it is particularly preferable to use spinel lithium titanate. More specifically, Li ₄ Ti ₅ O ₁₂ is used. In such a lithium ion secondary battery using lithium titanate as a negative electrode, it is considered that the lithium occlusion and release reactions are performed stably, and as a result, the deterioration of the active material is also suppressed. . That is, it is known that a lithium ion secondary battery using such a metal compound as a negative electrode active material is excellent in cycle characteristics. By using the metal oxide in combination with the non-aqueous electrolyte secondary battery of the present invention using the electrolytic solution of the present invention, the excellent battery characteristics derived from the electrolytic solution of the present invention and the excellent cycle characteristics are compatible. A water electrolyte secondary battery can be obtained.

<Nonaqueous electrolyte secondary battery (5)>
The negative electrode active material in the nonaqueous electrolyte secondary battery (5) includes graphite having a major axis / minor axis ratio (major axis / minor axis) of 1 to 5. Typical graphite having a major axis / minor axis ratio (major axis / minor axis) of 1 to 5 includes spherical graphite, MCMB (mesocarbon microbeads), and the like. Spherical graphite is a carbon material such as artificial graphite, natural graphite, graphitizable carbon, and non-graphitizable carbon, and has a spherical shape or a substantially spherical shape.

The spherical graphite particles are obtained by collecting the flakes and compressing them into a spherical shape while pulverizing the raw graphite with an impact pulverizer having a relatively small crushing force. For example, a hammer mill or a pin mill can be used as the impact pulverizer. The outer peripheral linear velocity of the rotating hammer or pin is preferably about 50 to 200 m / sec. Moreover, it is preferable to perform supply and discharge | emission of graphite with respect to these grinders by making it accompany airflow, such as air.

The degree of spheroidization of graphite particles can be expressed by the ratio of the major axis to the minor axis of the particle (major axis / minor axis: hereinafter referred to as aspect ratio). That is, in an arbitrary cross section of the graphite particles, when the axis having the maximum aspect ratio is selected from the axes orthogonal to the center of gravity, the closer the aspect ratio is to 1, the closer to the true sphere. By the spheroidization treatment, the aspect ratio can be easily reduced to 5 or less (1 to 5). Further, if the spheroidization treatment is sufficiently performed, the aspect ratio can be made 3 or less (1 to 3). The graphite used in the present invention has a particle aspect ratio of 1 to 5. It is preferably 1 to 3. By setting the aspect ratio to 5 or less, the diffusion path of the electrolytic solution in the negative electrode active material layer is shortened, so that the resistance component due to the electrolytic solution can be reduced, so that the input / output can be improved. When the aspect ratio is 1, the graphite has a shape closest to a true sphere, and the electrolyte solution diffusion path can be shortened to the shortest.

By the way, graphite tends to be flat because it is derived from its crystal structure and easily breaks at the basal plane. Therefore, when flat graphite is arranged in the negative electrode active material layer, the ratio of the orientation of the basal plane of the graphite crystal parallel to the current collector surface increases, and I (002) or the like derived from the basal plane in the XRD analysis. The diffraction intensity becomes relatively strong.

By utilizing this feature, the ratio [I (110) / I (004)] of diffraction intensity derived from a crystal plane different from the basal plane such as I (110) is included, and how much flat graphite is included. Information such as Therefore, the graphite used in the present invention is preferably in a range where I (110) / I (004) is 0.03 to 1. By using such graphite, the arrangement of the flat particles is reduced, and the diffusion path of the electrolytic solution in the negative electrode active material layer is shortened, so that the input / output characteristics are improved.

The graphite particles preferably have a BET specific surface area in the range of 0.5 to 15 m ³ / g. If the BET specific surface area exceeds 15 m ³ / g, the side reaction with the electrolytic solution tends to accelerate, and if it is less than 0.5 m ³ / g, the reaction resistance increases and the input / output may decrease.

If the negative electrode active material is mainly graphite having an aspect ratio of 1 to 5, it can also contain graphite or amorphous carbon having an aspect ratio outside this range.

The nonaqueous electrolyte secondary battery (1) to the nonaqueous electrolyte secondary battery (5) of the present invention occlude charge carriers in addition to the characteristic negative electrode active material that can be used for each nonaqueous electrolyte secondary battery described above. And other negative electrode active materials that can be released. Hereinafter, the other negative electrode active material is referred to as a sub negative electrode active material as necessary. The characteristic negative electrode active material in each of the nonaqueous electrolyte secondary batteries of the present invention is referred to as a main negative electrode active material. For example, if the non-aqueous electrolyte secondary battery of the present invention is a lithium ion secondary battery, the secondary negative electrode active material may be capable of occluding and releasing charge carriers, that is, lithium ions. There is no particular limitation. Examples of elemental elements that can be used as the secondary negative electrode active material include group 14 elements such as Li, carbon, silicon, germanium, and tin, group 13 elements such as aluminum and indium, group 12 elements such as zinc and cadmium, antimony, A group 15 element such as bismuth, an alkaline earth metal such as magnesium or calcium, and a group 11 element such as silver or gold may be employed alone.

Note that when silicon or the like is employed as the sub-negative electrode active material, one silicon atom reacts with a plurality of lithiums, so that a high-capacity active material is obtained. However, volume expansion and contraction due to insertion and extraction of lithium become significant. Such a problem may occur. In order to reduce the fear, it is also preferable to employ an alloy or a compound in which another element such as a transition metal is combined with a simple substance such as silicon as the sub-negative electrode active material. Specific examples of the alloy or compound include tin-based materials such as Ag—Sn alloy, Cu—Sn alloy and Co—Sn alloy, carbon-based materials such as various graphites, SiO _x (disproportionated to silicon simple substance and silicon dioxide). Examples thereof include silicon-based materials such as 0.3 ≦ x ≦ 1.6), silicon alone, or composites obtained by combining silicon-based materials and carbon-based materials. Further, as the secondary negative electrode active material, oxides such as Nb ₂ O ₅ , TiO ₂ , Li ₄ Ti ₅ O ₁₂ , WO ₂ , MoO ₂ , FE ₂ O ₃ , or Li _3-x M _x N (M = A nitride represented by (Co, Ni, Cu) may be employed. One or more of these materials can be used as the sub negative electrode active material.

By using the various sub-negative electrode active materials described above in combination with the main negative electrode active material, further excellent battery characteristics can be imparted to the non-aqueous electrolyte secondary battery. For example, in the non-aqueous electrolyte secondary battery (4), any one of the above-described sub-negative electrode active materials is used in combination with the metal oxide as the main negative electrode active material, so that non-metal oxide is used in comparison with the case where the metal oxide is used alone. The capacity of the water electrolyte secondary battery can be further increased. Even when the main negative electrode active material and the sub negative electrode active material are used in combination, the main component of the negative electrode active material may be the main negative electrode active material. Specifically, the main negative electrode active material preferably occupies 50% by mass or more of the entire negative electrode active material, and more preferably 80% by mass or more. The same applies to negative electrode active materials in other nonaqueous electrolyte secondary batteries.
In the non-aqueous electrolyte secondary battery (4), the metal oxide negative electrode active material described above is selected from titanium oxide, lithium titanium oxide, tungsten oxide, amorphous tin oxide, and tin silicon oxide. At least one kind is a main component. In addition, a main component here means that the applicable component is contained 50 mass% or more of the reference population. Specifically, when the total amount of metal oxide that can function as a negative electrode active material is 100% by mass, the main components (that is, titanium oxide, lithium titanium oxide, tungsten oxide, amorphous tin oxide, tin silicon oxide) 50% by mass or more) is contained. The negative electrode can contain other inevitable ingredients. Inevitable inclusions include, for example, Li, Fe, Cr, Cu, Zn, Ca, Mg, S, Si, Na, K, Al, Zr, Ti, P, Ga, Ge, V, Mo, Nb, W, La The at least 1 element chosen from can be illustrated.

The binder plays a role of connecting the active material and the conductive additive to the surface of the current collector.

Examples of the binder include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, alkoxysilyl group-containing resins, polyacrylic acid ( Examples thereof include polymers having hydrophilic groups such as PAA) and carboxymethylcellulose (CMC). The mixing ratio of the binder in the negative electrode active material layer is preferably negative electrode active material: binder = 1: 0.005 to 1: 0.3 in terms of mass ratio. This is because when the amount of the binder is too small, the moldability of the electrode is lowered, and when the amount of the binder is too large, the energy density of the electrode is lowered.

A conductive additive contained in the negative electrode active material layer as necessary is added to increase the conductivity of the electrode. Therefore, the conductive auxiliary agent may be added arbitrarily when the electrode conductivity is insufficient, and may not be added when the electrode conductivity is sufficiently excellent. The conductive auxiliary agent may be any chemically inert electronic high conductor, such as carbon black, graphite, acetylene black, ketjen black (registered trademark), vapor grown carbon fiber (Vapor Growth), which are carbonaceous fine particles. Carbon Fiber (VGCF) is exemplified. These conductive assistants can be added to the active material layer alone or in combination of two or more. The mixing ratio of the conductive additive in the negative electrode active material layer is not particularly limited, but is preferably negative electrode active material: conductive additive = 1: 0.01 to 1: 0.5 in terms of mass ratio. This is because if the amount of the conductive auxiliary is too small, an efficient conductive path cannot be formed, and if the amount of the conductive auxiliary is too large, the formability of the negative electrode active material layer is deteriorated and the energy density of the electrode is lowered.

In order to produce a negative electrode of a non-aqueous electrolyte secondary battery, a negative electrode active material powder, a conductive auxiliary agent such as carbon powder, a binder, and an appropriate amount of solvent mixed to form a slurry, a roll coating method, It can be produced by applying on a current collector by a method such as a dip coating method, a doctor blade method, a spray coating method, or a curtain coating method, and drying or curing the binder. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. In order to increase the electrode density, the dried product may be compressed.

<Positive electrode>
A positive electrode used for a non-aqueous electrolyte secondary battery has a positive electrode active material that can occlude and release charge carriers. The positive electrode has a current collector and a positive electrode active material layer bound to the surface of the current collector. The positive electrode active material layer includes a positive electrode active material and, if necessary, a binder and / or a conductive aid. The positive electrode current collector is not particularly limited as long as it is a metal that can withstand a voltage suitable for the active material to be used. For example, silver, copper, gold, aluminum, tungsten, cobalt, zinc, nickel, iron, platinum, tin , Indium, titanium, ruthenium, tantalum, chromium, molybdenum, and metal materials such as stainless steel. In addition, when the non-aqueous electrolyte secondary battery of the present invention is a lithium ion secondary battery and the potential of the positive electrode is set to 4 V or more with respect to lithium, it is preferable to employ an aluminum current collector.

The electrolyte of the present invention hardly corrodes the aluminum current collector. That is, it is considered that the non-aqueous electrolyte secondary battery using the electrolytic solution of the present invention and using the aluminum current collector for the positive electrode hardly causes elution of Al even at a high potential. Although it is not clear why the elution of Al is unlikely to occur, the electrolytic solution of the present invention differs from the conventional electrolytic solution in the types of metal salt and organic solvent, the existing environment, and the metal salt concentration. For this reason, it is estimated that the solubility of Al in the electrolytic solution of the present invention may be lower than that of the conventional electrolytic solution.

Specifically, the positive electrode current collector is preferably made of aluminum or an aluminum alloy. Here, aluminum refers to pure aluminum, and aluminum having a purity of 99.0% or more is referred to as pure aluminum. An alloy obtained by adding various elements to pure aluminum is referred to as an aluminum alloy. Examples of the aluminum alloy include Al—Cu, Al—Mn, Al—Fe, Al—Si, Al—Mg, Al—Mg—Si, and Al—Zn—Mg.

Further, as aluminum or aluminum alloy, specifically, for example, A1000 series alloys (pure aluminum series) such as JIS A1085 and A1N30, A3000 series alloys (Al-Mn series) such as JIS A3003 and A3004, JIS A8079, A8021, etc. A8000-based alloy (Al-Fe-based).

The current collector may be covered with a known protective layer. What collected the surface of the electrical power collector by the well-known method may be used as an electrical power collector.

The current collector can take the form of a foil, a sheet, a film, a linear shape, a rod shape, a mesh, or the like. Therefore, for example, a metal foil such as a copper foil, a nickel foil, an aluminum foil, and a stainless steel foil can be suitably used as the current collector. When the current collector is in the form of foil, sheet or film, the thickness is preferably in the range of 1 μm to 100 μm.

The binder for the positive electrode and the conductive additive are the same as those described for the negative electrode.

As the positive electrode active material, the layered compound Li _a Ni _b Co _c Mn _d _De O _f (0.2 ≦ a ≦ 1.2, b + c + d + e = 1, 0 ≦ e <1, D is Li, Fe, Cr, At least one element selected from Cu, Zn, Ca, Mg, S, Si, Na, K, Al, Zr, Ti, P, Ga, Ge, V, Mo, Nb, W, La, 1.7 ≦ f ≦ 2.1) and Li ₂ MnO ₃ . Further, as a positive electrode active material, a solid solution composed of a spinel such as LiMn ₂ O ₄ and a mixture of a spinel and a layered compound, LiMPO ₄ , LiMVO ₄ or Li ₂ MSiO ₄ (wherein M is Co, Ni, Mn, And a polyanionic compound represented by (selected from at least one of Fe).

Furthermore, as the positive electrode active material, tavorite compound (the M a transition metal) LiMPO ₄ F, such as LiFePO ₄ F represented by, Limbo ₃ such LiFeBO ₃ (M is a transition metal) include borate-based compound represented by be able to. Any metal oxide used as the positive electrode active material may have the above composition formula as a basic composition, and a metal element included in the basic composition may be substituted with another metal element.

Further, as the positive electrode active material, a positive electrode active material that does not include a charge carrier that contributes to charge / discharge can also be used. For example, in the case of a lithium ion secondary battery, sulfur alone (S), a compound in which sulfur and carbon are combined, metal sulfides such as TiS ₂ , oxides such as V ₂ O ₅ and MnO ₂ , polyaniline and anthraquinone, and these A compound containing an aromatic in the chemical structure, a conjugated material such as a conjugated diacetate-based organic substance, or other known materials can be used as the positive electrode active material. Further, a compound having a stable radical such as nitroxide, nitronyl nitroxide, galvinoxyl, phenoxyl, etc. may be adopted as the positive electrode active material.

When using a positive electrode active material that does not contain a charge carrier such as lithium, it is necessary to add a charge carrier to the positive electrode and / or the negative electrode in advance by a known method. Specifically, the charge carrier may be added in an ionic state, or may be added in a nonionic state such as a metal or a compound. For example, a lithium foil or the like may be integrated by sticking to a positive electrode and / or a negative electrode. The positive electrode may contain a conductive additive, a binder, and the like, similarly to the negative electrode. The conductive auxiliary agent and the binder are not particularly limited as long as they can be used for the non-aqueous electrolyte secondary battery like the negative electrode described above.

In order to form an active material layer on the surface of the current collector, a current collecting method such as a roll coating method, a die coating method, a dip coating method, a doctor blade method, a spray coating method, or a curtain coating method can be used. An active material may be applied to the surface of the body. Specifically, a composition for forming an active material layer containing an active material and, if necessary, a binder and a conductive aid is prepared, and an appropriate solvent is added to the composition to make a paste, and then collected. After applying to the surface of the electric body, it is dried. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. In order to increase the electrode density, the dried product may be compressed.

A separator is used for non-aqueous electrolyte secondary batteries as necessary. The separator separates the positive electrode and the negative electrode and allows lithium ions to pass while preventing a short circuit of current due to contact between the two electrodes. As separators, natural resins such as polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamide, polyaramid (Aromatic polymer), polyester, polyacrylonitrile, etc., polysaccharides such as cellulose, amylose, fibroin, keratin, lignin, suberin, etc. Examples thereof include porous bodies, nonwoven fabrics, and woven fabrics using one or more electrically insulating materials such as polymers and ceramics. The separator may have a multilayer structure. Since the electrolytic solution of the present invention has a slightly high viscosity and a high polarity, a membrane in which a polar solvent such as water can easily penetrate is preferable. Specifically, a film in which a polar solvent such as water soaks into 90% or more of the existing voids is more preferable.

A separator is sandwiched between the positive electrode and the negative electrode as necessary to form an electrode body. The electrode body may be either a stacked type in which the positive electrode, the separator and the negative electrode are stacked, or a wound type in which the positive electrode, the separator and the negative electrode are sandwiched. After connecting between the positive electrode current collector and the negative electrode current collector to the positive electrode terminal and the negative electrode terminal that communicate with the outside using a current collecting lead, the electrolyte solution of the present invention is added to the electrode body to make a non-aqueous solution. It is preferable to use an electrolyte secondary battery. Moreover, the non-aqueous electrolyte secondary battery of this invention should just be charged / discharged in the voltage range suitable for the kind of active material contained in an electrode.

In the non-aqueous electrolyte secondary battery of the present invention containing the electrolytic solution of the present invention, a special structure SEI film derived from the electrolytic solution of the present invention is formed on the negative electrode surface and / or the positive electrode surface. As will be described later, the SEI film includes S and O, and has an S═O structure. Therefore, the electrolytic solution of the present invention for producing the SEI film particularly contains sulfur element and oxygen element in the chemical structure of the anion of the salt. Hereinafter, the SEI film having the special structure is referred to as an S, O-containing film as necessary. The S, O-containing coating contributes to improvement of battery characteristics (improvement of battery life, improvement of input / output characteristics, etc.) of the non-aqueous electrolyte secondary battery through cooperation with the electrolytic solution of the present invention.

The shape of the nonaqueous electrolyte secondary battery of the present invention is not particularly limited, and various shapes such as a cylindrical shape, a square shape, a coin shape, and a laminate shape can be adopted.

The non-aqueous electrolyte secondary battery of the present invention may be mounted on a vehicle. The vehicle may be a vehicle that uses electric energy from the non-aqueous electrolyte secondary battery for all or a part of its power source. For example, the vehicle may be an electric vehicle or a hybrid vehicle. When a non-aqueous electrolyte secondary battery is mounted on a vehicle, a plurality of non-aqueous electrolyte secondary batteries may be connected in series to form an assembled battery. In addition to vehicles, devices equipped with non-aqueous electrolyte secondary batteries include personal computers, portable communication devices, and various household electrical appliances driven by batteries, office equipment, industrial equipment, and the like. Further, the non-aqueous electrolyte secondary battery of the present invention includes wind power generation, solar power generation, hydroelectric power generation and other power system power storage devices and power smoothing devices, power for power sources such as ships, and / or power supply sources for auxiliary machinery, aircraft Power supplies for spacecrafts and / or auxiliary equipment, auxiliary power sources for vehicles that do not use electricity as power sources, mobile home robot power sources, system backup power sources, uninterruptible power supply power sources In addition, it may be used for a power storage device that temporarily stores electric power required for charging in an electric vehicle charging station or the like.

As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. The present invention can be implemented in various forms without departing from the gist of the present invention, with modifications and improvements that can be made by those skilled in the art.

Hereinafter, embodiments of the present invention will be specifically described with reference to examples and comparative examples. In addition, this invention is not limited by these Examples. In the following, unless otherwise specified, “part” means part by mass, and “%” means mass%.

(Electrolytic solution of the present invention)

(Electrolytic solution E1)
The electrolytic solution of the present invention was produced as follows.
About 5 mL of 1,2-dimethoxyethane, an organic solvent, was placed in a flask equipped with a stir bar and a thermometer. Under stirring conditions, (CF ₃ SO ₂ ) ₂ NLi, which is a lithium salt, was gradually added to 1,2-dimethoxyethane in the flask so as to keep the solution temperature at 40 ° C. or lower and dissolved. When about 13 g of (CF ₃ SO ₂ ) ₂ NLi was added, the dissolution of (CF ₃ SO ₂ ) ₂ NLi temporarily stagnated. Therefore, the flask was put into a thermostat, and the solution temperature in the flask was 50 ° C. (CF ₃ SO ₂ ) ₂ NLi was dissolved. When about 15 g of (CF ₃ SO ₂ ) ₂ NLi was added, the dissolution of (CF ₃ SO ₂ ) ₂ NLi stagnated again, so 1 drop of 1,2-dimethoxyethane was added with a pipette (CF ₃ SO ₂ ) ₂ NLi dissolved. Further, (CF ₃ SO ₂ ) ₂ NLi was gradually added, and the entire amount of predetermined (CF ₃ SO ₂ ) ₂ NLi was added. The resulting electrolyte was transferred to a 20 mL volumetric flask and 1,2-dimethoxyethane was added until the volume was 20 mL. This was designated as an electrolytic solution E1. The obtained electrolytic solution had a volume of 20 mL, and (CF ₃ SO ₂ ) ₂ NLi contained in this electrolytic solution was 18.38 g. The concentration of (CF ₃ SO ₂ ) ₂ NLi in the electrolytic solution E1 was 3.2 mol / L. In the electrolytic solution E1, 1.6 molecules of 1,2-dimethoxyethane are contained with respect to (CF ₃ SO ₂ ) ₂ NLi1 molecules.
The production was performed in a glove box under an inert gas atmosphere.

(Electrolytic solution E2)
Using 16.08 g of (CF ₃ SO ₂ ) ₂ NLi, an electrolytic solution E2 having a concentration of (CF ₃ SO ₂ ) ₂ NLi of 2.8 mol / L was produced in the same manner as the electrolytic solution E1. In the electrolytic solution E2, 2.1 molecules of 1,2-dimethoxyethane are contained per molecule of (CF ₃ SO ₂ ) ₂ NLi.

(Electrolytic solution E3)
About 5 mL of acetonitrile, which is an organic solvent, was placed in a flask equipped with a stir bar. Under stirring conditions, (CF ₃ SO ₂ ) ₂ NLi, which is a lithium salt, was gradually added to and dissolved in acetonitrile in the flask. When 19.52 g of (CF ₃ SO ₂ ) ₂ NLi was added in total, the mixture was stirred overnight. The resulting electrolyte was transferred to a 20 mL volumetric flask and acetonitrile was added until the volume was 20 mL. This was designated as an electrolytic solution E3. The production was performed in a glove box under an inert gas atmosphere.
The concentration of (CF ₃ SO ₂ ) ₂ NLi in the electrolytic solution E3 was 3.4 mol / L. In the electrolytic solution E3, 3 molecules of acetonitrile are contained with respect to 1 molecule of (CF ₃ SO ₂ ) ₂ NLi.

(Electrolytic solution E4)
Using 24.11 g of (CF ₃ SO ₂ ) ₂ NLi, an electrolytic solution E4 having a concentration of (CF ₃ SO ₂ ) ₂ NLi of 4.2 mol / L was produced in the same manner as the electrolytic solution E3. In the electrolytic solution E4, 1.9 molecules of acetonitrile are contained with respect to (CF ₃ SO ₂ ) ₂ NLi1 molecules.

(Electrolytic solution E5)
Using _(FSO _{2) 2} NLi of 13.47g lithium salt, except for using 1,2-dimethoxyethane as the organic solvent, in the same manner as the electrolyte solution _{E3, (FSO} ₂₎ concentration of 2 NLi 3 An electrolytic solution E5 having a concentration of 6 mol / L was produced. In the electrolytic solution E5, 1.9 molecules of 1,2-dimethoxyethane are contained per 1 molecule of (FSO ₂ ) ₂ NLi.

(Electrolytic solution E6)
Using 14.97 g of (FSO ₂ ) ₂ NLi, an electrolytic solution E6 having a concentration of (FSO ₂ ) ₂ NLi of 4.0 mol / L was produced in the same manner as the electrolytic solution E5. In the electrolytic solution E6, 1.5 molecules of 1,2-dimethoxyethane are contained per 1 molecule of (FSO ₂ ) ₂ NLi.

(Electrolytic solution E7)
An electrolytic solution E7 having a concentration of 4.2 mol / L of (FSO ₂ ) ₂ NLi was produced in the same manner as the electrolytic solution E3 except that 15.72 g of (FSO ₂ ) ₂ NLi was used as the lithium salt. . In the electrolytic solution E7, 3 molecules of acetonitrile are contained with respect to 1 molecule of (FSO ₂ ) ₂ NLi.

(Electrolyte E8)
An electrolytic solution E8 having a concentration of (FSO ₂ ) ₂ NLi of 4.5 mol / L was produced in the same manner as the electrolytic solution E7 using 16.83 g of (FSO ₂ ) ₂ NLi. In the electrolytic solution E8, 2.4 molecules of acetonitrile are contained with respect to (FSO ₂ ) ₂ NLi1 molecules.

(Electrolytic solution E9)
By using 18.71 g of (FSO ₂ ) ₂ NLii, an electrolytic solution E9 having a concentration of (FSO ₂ ) ₂ NLi of 5.0 mol / L was produced in the same manner as the electrolytic solution E7. In the electrolytic solution E9, 2.1 molecules of acetonitrile are contained with respect to (FSO ₂ ) ₂ NLi1 molecules.

(Electrolytic solution E10)
Using 20.21 g of (FSO ₂ ) ₂ NLi, an electrolytic solution E10 having a concentration of (FSO ₂ ) ₂ NLi of 5.4 mol / L was produced in the same manner as the electrolytic solution E7. In the electrolyte solution E10, ₂ molecules of acetonitrile are contained with respect to 1 molecule of (FSO ₂ ) ₂ NLi.

(Electrolytic solution E11)
About 5 mL of dimethyl carbonate, which is an organic solvent, was placed in a flask equipped with a stir bar. Under stirring conditions, (FSO ₂ ) ₂ NLi, which is a lithium salt, was gradually added to dimethyl carbonate in the flask and dissolved. When (FSO ₂ ) ₂ NLi was added in a total amount of 14.64 g, the mixture was stirred overnight. The resulting electrolyte was transferred to a 20 mL volumetric flask and dimethyl carbonate was added until the volume was 20 mL. This was designated as an electrolytic solution E11. The production was performed in a glove box under an inert gas atmosphere.
The concentration of (FSO ₂ ) ₂ NLi in the electrolytic solution E11 was 3.9 mol / L. In the electrolytic solution E11, _two molecules of dimethyl carbonate are contained with respect to one molecule of (FSO ₂ ) ₂ NLi.

(Electrolytic solution E12)
Dimethyl carbonate was added to the electrolytic solution E11 for dilution to obtain an electrolytic solution E12 having a (FSO ₂ ) ₂ NLi concentration of 3.4 mol / L. In the electrolytic solution E12, 2.5 molecules of dimethyl carbonate are contained with respect to (FSO ₂ ) ₂ NLi1 molecules.

(Electrolytic solution E13)
Dimethyl carbonate was added to the electrolytic solution E11 for dilution to obtain an electrolytic solution E13 having a (FSO ₂ ) ₂ NLi concentration of 2.9 mol / L. In the electrolytic solution E13, three molecules of dimethyl carbonate are contained with respect to one molecule of (FSO ₂ ) ₂ NLi.

(Electrolytic solution E14)
Dimethyl carbonate was added to the electrolytic solution E11 for dilution to obtain an electrolytic solution E14 having a concentration of (FSO ₂ ) ₂ NLi of 2.6 mol / L. In the electrolytic solution E14, 3.5 molecules of dimethyl carbonate are contained with respect to (FSO ₂ ) ₂ NLi1 molecules.

(Electrolytic solution E15)
Dimethyl carbonate was added to the electrolytic solution E11 for dilution to obtain an electrolytic solution E15 having a (FSO ₂ ) ₂ NLi concentration of 2.0 mol / L. In the electrolytic solution E15, five molecules of dimethyl carbonate are contained with respect to one molecule of (FSO ₂ ) ₂ NLi.

(Electrolytic solution E16)
About 5 mL of ethyl methyl carbonate, which is an organic solvent, was placed in a flask equipped with a stir bar. Under stirring conditions, (FSO ₂ ) ₂ NLi, which is a lithium salt, was gradually added to and dissolved in ethyl methyl carbonate in the flask. When 12.81 g of (FSO ₂ ) ₂ NLi was added in total, the mixture was stirred overnight. The obtained electrolytic solution was transferred to a 20 mL volumetric flask, and ethyl methyl carbonate was added until the volume became 20 mL. This was designated as an electrolytic solution E16. The production was performed in a glove box under an inert gas atmosphere.
The concentration of (FSO ₂ ) ₂ NLi in the electrolytic solution E16 was 3.4 mol / L. In the electrolytic solution E16, _two molecules of ethyl methyl carbonate are contained with respect to one molecule of (FSO ₂ ) ₂ NLi.

(Electrolytic solution E17)
The electrolyte solution E16 was diluted by adding ethyl methyl carbonate to obtain an electrolyte solution E17 having a (FSO ₂ ) ₂ NLi concentration of 2.9 mol / L. In the electrolytic solution E17, 2.5 molecules of ethyl methyl carbonate are contained per 1 molecule of (FSO ₂ ) ₂ NLi.

(Electrolytic solution E18)
The electrolyte solution E16 was diluted by adding ethyl methyl carbonate to obtain an electrolyte solution E18 having a concentration of (FSO ₂ ) ₂ NLi of 2.2 mol / L. In the electrolytic solution E18, 3.5 molecules of ethyl methyl carbonate are contained with respect to (FSO ₂ ) ₂ NLi1 molecules.

(Electrolytic solution E19)
About 5 mL of diethyl carbonate, which is an organic solvent, was placed in a flask equipped with a stirring bar. Under stirring conditions, (FSO ₂ ) ₂ NLi, which is a lithium salt, was gradually added to and dissolved in diethyl carbonate in the flask. When 11.37 g of the total amount of (FSO ₂ ) ₂ NLi was added, the mixture was stirred overnight. The resulting electrolyte was transferred to a 20 mL volumetric flask and diethyl carbonate was added until the volume was 20 mL. This was designated as an electrolytic solution E19. The production was performed in a glove box under an inert gas atmosphere.
The concentration of (FSO ₂ ) ₂ NLi in the electrolytic solution E19 was 3.0 mol / L. In the electrolytic solution E19, _two molecules of diethyl carbonate are contained with respect to one molecule of (FSO ₂ ) ₂ NLi.

(Electrolytic solution E20)
Diethyl carbonate was added to the electrolytic solution E19 for dilution to obtain an electrolytic solution E20 having a (FSO ₂ ) ₂ NLi concentration of 2.6 mol / L. In the electrolytic solution E20, 2.5 molecules of diethyl carbonate are contained with respect to (FSO ₂ ) ₂ NLi1 molecules.

(Electrolytic solution E21)
Diethyl carbonate was added to the electrolytic solution E19 for dilution to obtain an electrolytic solution E21 having a (FSO ₂ ) ₂ NLi concentration of 2.0 mol / L. In the electrolytic solution E21, 3.5 molecules of diethyl carbonate are contained with respect to (FSO ₂ ) ₂ NLi1 molecules.

(Electrolytic solution C1)
Using _(CF ₃ SO ₂₎ 2 NLi of 5.74 g, as except for using 1,2-dimethoxyethane organic solvents, in the same manner as the electrolyte solution _E3, is (CF ₃ SO ₂₎ concentration of 2 NLi Electrolyte C1 which is 1.0 mol / L was manufactured. In the electrolytic solution C1, 8.3 molecules of 1,2-dimethoxyethane are contained with respect to (CF ₃ SO ₂ ) ₂ NLi1 molecules.

(Electrolytic solution C2)
Using 5.74 g of (CF ₃ SO ₂ ) ₂ NLi, an electrolytic solution C2 having a concentration of (CF ₃ SO ₂ ) ₂ NLi of 1.0 mol / L was produced in the same manner as the electrolytic solution E3. In the electrolytic solution C2, 16 molecules of acetonitrile are contained with respect to (CF ₃ SO ₂ ) ₂ NLi1 molecule.

(Electrolytic solution C3)
Using 3.74 g of (FSO ₂ ) ₂ NLi, an electrolytic solution C3 having a concentration of (FSO ₂ ) ₂ NLi of 1.0 mol / L was produced in the same manner as the electrolytic solution E5. In the electrolytic solution C3, 8.8 molecules of 1,2-dimethoxyethane are contained per molecule of (FSO ₂ ) ₂ NLi.

(Electrolytic solution C4)
Using 3.74 g of (FSO ₂ ) ₂ NLi, an electrolytic solution C4 having a concentration of (FSO ₂ ) ₂ NLi of 1.0 mol / L was produced in the same manner as the electrolytic solution E7. In the electrolyte solution C4, 17 molecules of acetonitrile are contained with respect to (FSO ₂ ) ₂ NLi1 molecule.

(Electrolytic solution C5)
Except that a mixed solvent of ethylene carbonate and diethyl carbonate (volume ratio 3: 7, hereinafter referred to as “EC / DEC”) was used as the organic solvent, and 3.04 g of LiPF ₆ was used as the lithium salt. An electrolytic solution C5 having a LiPF ₆ concentration of 1.0 mol / L was produced in the same manner as in the liquid E3.

(Electrolytic solution C6)
Dimethyl carbonate was added to the electrolytic solution E11 for dilution to obtain an electrolytic solution C6 having a (FSO ₂ ) ₂ NLi concentration of 1.1 mol / L. In the electrolytic solution C6, 10 molecules of dimethyl carbonate are contained per 1 molecule of (FSO ₂ ) ₂ NLi.

(Electrolytic solution C7)
The electrolyte solution E16 was diluted by adding ethyl methyl carbonate to obtain an electrolyte solution C7 having a (FSO ₂ ) ₂ NLi concentration of 1.1 mol / L. In the electrolytic solution C7, 8 molecules of ethyl methyl carbonate are contained with respect to (FSO ₂ ) ₂ NLi1 molecule.

(Electrolytic solution C8)
Diethyl carbonate was added to the electrolytic solution E19 for dilution to obtain an electrolytic solution C8 having a (FSO ₂ ) ₂ NLi concentration of 1.1 mol / L. In the electrolytic solution C8, 7 molecules of diethyl carbonate are contained per 1 molecule of (FSO ₂ ) ₂ NLi.

Table 3 shows a list of the electrolytic solutions E1 to E21 and the electrolytic solutions C1 to C8.

(Evaluation Example 1: IR measurement)
Electrolytic solution E3, electrolytic solution E4, electrolytic solution E7, electrolytic solution E8, electrolytic solution E10, electrolytic solution C2, electrolytic solution C4, and acetonitrile, (CF ₃ SO ₂ ) ₂ NLi, (FSO ₂ ) ₂ NLi are as follows: The IR measurement was performed under the following conditions. IR spectra in the range of 2100 to 2400 cm ⁻¹ are shown in FIGS. 1 to 10, respectively. Further, IR measurement was performed on the electrolytic solutions E11 to E21, the electrolytic solutions C6 to C8, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate under the following conditions. IR spectra in the range of 1900 to 1600 cm ⁻¹ are shown in FIGS. 11 to 27, respectively. In addition, FIG. 28 shows an IR spectrum in the range of 1900 to 1600 cm ⁻¹ for (FSO ₂ ) ₂ NLi. The horizontal axis in the figure is the wave number (cm ⁻¹ ), and the vertical axis is the absorbance (reflection absorbance).

IR measurement conditions Device: FT-IR (Bruker Optics)
Measurement conditions: ATR method (using diamond)
Measurement atmosphere: Inert gas atmosphere

In the vicinity of 2250 cm ^{−1 in} the IR spectrum of acetonitrile shown in FIG. 8, a characteristic peak derived from the stretching vibration of the triple bond between C and N of acetonitrile was observed. Note that no special peak was observed in the vicinity of 2250 cm ⁻¹ of the IR spectrum of (CF ₃ SO ₂ ) ₂ NLi shown in FIG. 9 and the IR spectrum of (FSO ₂ ) ₂ NLi shown in FIG.

In the IR spectrum of the electrolyte solution E3 shown in FIG. 1, a characteristic peak derived from the stretching vibration of the triple bond between C and N of acetonitrile is slightly observed (Io = 0.00699) in the vicinity of 2250 cm ^−1. It was. More IR spectrum of FIG. 1, 2250 cm characteristic peaks peak intensity derived from the stretching vibration of the triple bond between the vicinity of ^-1 acetonitrile near 2280 cm ^-1 shifted to the high frequency side C and N Is = 0 .05828. The relationship between the peak intensities of Is and Io was Is> Io, and Is = 8 × Io.

The IR spectrum of the electrolyte E4 shown in FIG. 2, 2250 cm ^-1 peak derived from acetonitrile was not observed in the vicinity, between 2250 cm from the vicinity ^-1 acetonitrile near 2280 cm ^-1 shifted to the high frequency side C and N A characteristic peak derived from the stretching vibration of the triple bond was observed at a peak intensity Is = 0.05234. The relationship between the peak intensities of Is and Io was Is> Io.

In the IR spectrum of the electrolytic solution E7 shown in FIG. 3, a characteristic peak derived from the stretching vibration of the triple bond between C and N of acetonitrile is slightly observed (Io = 0.00997) in the vicinity of 2250 cm ^−1. It was. More IR spectrum of FIG. 3, 2250 cm characteristic peaks peak intensity derived from the stretching vibration of the triple bond between the vicinity of ^-1 acetonitrile near 2280 cm ^-1 shifted to the high frequency side C and N Is = 0 .08288. The relationship between the peak intensities of Is and Io was Is> Io, and Is = 8 × Io. Also in the IR spectrum of the electrolytic solution E8 shown in FIG. 4, the same intensity peak as that in the IR chart of FIG. 3 was observed at the same wave number. The relationship between the peak intensities of Is and Io was Is> Io, and Is = 11 × Io.

FIG The IR spectrum of the electrolyte E10 represented by 5, is not a peak derived from acetonitrile observed around 2250 cm ^-1, inter 2250 cm from the vicinity ^-1 shifted acetonitrile 2280cm around ^-1 to the high frequency side C and N A characteristic peak derived from the stretching vibration of the triple bond was observed at a peak intensity Is = 0.07350. The relationship between the peak intensities of Is and Io was Is> Io.

In the IR spectrum of the electrolytic solution C2 shown in FIG. 6, a characteristic peak derived from the stretching vibration of the triple bond between C and N of acetonitrile is observed in the vicinity of 2250 cm ^{−1 in} the IR spectrum of FIG. Observed at 04441. More IR spectrum of FIG. 6, 2250 cm characteristic peaks peak intensity derived from the stretching vibration of the triple bond between the vicinity of ^-1 acetonitrile near 2280 cm ^-1 shifted to the high frequency side C and N Is = 0 .03018. The relationship between the peak intensities of Is and Io was Is <Io.

In the IR spectrum of the electrolytic solution C4 shown in FIG. 7, a characteristic peak derived from the stretching vibration of the triple bond between C and N of acetonitrile is observed in the vicinity of 2250 cm ^{−1 in} the IR spectrum of FIG. Observed at 04975. More IR spectrum of Figure 7, 2250 cm characteristic peaks peak intensity derived from the stretching vibration of the triple bond between the vicinity of ^-1 acetonitrile near 2280 cm ^-1 shifted to the high frequency side C and N Is = 0 .03804. The relationship between the peak intensities of Is and Io was Is <Io.

In the vicinity of 1750 cm ⁻¹ of the IR spectrum of dimethyl carbonate shown in FIG. 25, a characteristic peak derived from the stretching vibration of the double bond between C and O of dimethyl carbonate was observed. Note that no special peak was observed in the vicinity of 1750 cm ^{−1 in} the IR spectrum of (FSO ₂ ) ₂ NLi shown in FIG.

In the IR spectrum of the electrolytic solution E11 shown in FIG. 11, a characteristic peak derived from the stretching vibration of the double bond between C and O of dimethyl carbonate is slightly present at around 1750 cm ⁻¹ (Io = 0.166628). Observed. More IR spectrum of Figure 11, characteristic peaks peak intensity Is derived from stretching vibration of double bonds between C and O of dimethyl carbonate in the vicinity of 1717 cm ^-1 shifted from the vicinity of 1750 cm ^-1 to a lower wavenumber side = 0.48032. The relationship between the peak intensities of Is and Io was Is> Io, and Is = 2.89 × Io.

In the IR spectrum of the electrolytic solution E12 shown in FIG. 12, a characteristic peak derived from stretching vibration of a double bond between C and O of dimethyl carbonate is slightly present (Io = 0.18129) in the vicinity of 1750 cm ^−1. Observed. More IR spectrum of Figure 12, characteristic peaks peak intensity Is derived from stretching vibration of double bonds between C and O of dimethyl carbonate in the vicinity of 1717 cm ^-1 shifted from the vicinity of 1750 cm ^-1 to a lower wavenumber side = 0.52005 was observed. The relationship between the peak intensities of Is and Io was Is> Io, and Is = 2.87 × Io.

In the IR spectrum of the electrolytic solution E13 shown in FIG. 13, a characteristic peak derived from the stretching vibration of the double bond between C and O of dimethyl carbonate is slightly present in the vicinity of 1750 cm ⁻¹ (Io = 0.20293). Observed. More IR spectrum of Figure 13, characteristic peaks peak intensity Is derived from stretching vibration of double bonds between C and O of dimethyl carbonate in the vicinity of 1717 cm ^-1 shifted from the vicinity of 1750 cm ^-1 to a lower wavenumber side = 0.53091. The relationship between the peak intensities of Is and Io was Is> Io, and Is = 2.62 × Io.

In the IR spectrum of the electrolytic solution E14 shown in FIG. 14, there is a slight characteristic peak (Io = 0.38991) derived from the stretching vibration of the double bond between C and O of dimethyl carbonate in the vicinity of 1750 cm ^−1. Observed. More IR spectrum of Figure 14, characteristic peaks peak intensity Is derived from stretching vibration of double bonds between C and O of dimethyl carbonate in the vicinity of 1717 cm ^-1 shifted from the vicinity of 1750 cm ^-1 to a lower wavenumber side = 0.53098. The relationship between the peak intensities of Is and Io was Is> Io, and Is = 2.22 × Io.

In the IR spectrum of the electrolytic solution E15 shown in FIG. 15, a characteristic peak derived from the stretching vibration of the double bond between C and O of dimethyl carbonate is slightly present at around 1750 cm ⁻¹ (Io = 0.050514). Observed. More IR spectrum of Figure 15, characteristic peaks peak intensity Is derived from stretching vibration of double bonds between C and O of dimethyl carbonate in the vicinity of 1717 cm ^-1 shifted from the vicinity of 1750 cm ^-1 to a lower wavenumber side = 0.50223. The relationship between the peak intensities of Is and Io was Is> Io, and Is = 1.65 × Io.

In the IR spectrum of the electrolytic solution C6 shown in FIG. 22, a characteristic peak (Io = 0.48204) derived from stretching vibration of a double bond between C and O of dimethyl carbonate is observed around 1750 cm ^−1. It was. More IR spectrum of Figure 22, characteristic peaks peak intensity Is derived from stretching vibration of double bonds between C and O of dimethyl carbonate in the vicinity of 1717 cm ^-1 shifted from the vicinity of 1750 cm ^-1 to a lower wavenumber side = 0.39244. The relationship between peak intensities of Is and Io was Is <Io.

In the vicinity of 1745 cm ⁻¹ of the IR spectrum of ethyl methyl carbonate shown in FIG. 26, a characteristic peak derived from the stretching vibration of the double bond between C and O of ethyl methyl carbonate was observed.

In the IR spectrum of the electrolytic solution E16 shown in FIG. 16, a characteristic peak derived from the stretching vibration of the double bond between C and O of ethylmethyl carbonate is slightly observed at around 1745 cm ⁻¹ (Io = 0.13582). ) Observed. Further, in the IR spectrum of FIG. 16, a characteristic peak derived from the stretching vibration of the double bond between C and O of ethylmethyl carbonate is observed near 1711 cm ⁻¹ shifted from the vicinity of 1745 cm ⁻¹ to the lower wavenumber side. Observed at Is = 0.45888. The relationship between the peak intensities of Is and Io was Is> Io, and Is = 3.38 × Io.

In the IR spectrum of the electrolytic solution E17 shown in FIG. 17, there is a slight characteristic peak (Io = 0.151151) derived from the stretching vibration of the double bond between C and O of ethylmethyl carbonate in the vicinity of 1745 cm ^−1. ) Observed. Further, in the IR spectrum of FIG. 17, a characteristic peak derived from the stretching vibration of the double bond between C and O of ethylmethyl carbonate is observed near 1711 cm ⁻¹ shifted from the vicinity of 1745 cm ⁻¹ to the lower wavenumber side. Observed at Is = 0.48779. The relationship between the peak intensities of Is and Io was Is> Io, and Is = 3.22 × Io.

In the IR spectrum of the electrolytic solution E18 shown in FIG. 18, there is a slight characteristic peak (Io = 0.20191) derived from the stretching vibration of the double bond between C and O of ethylmethyl carbonate in the vicinity of 1745 cm ^−1. ) Observed. Further, in the IR spectrum of FIG. 18, a characteristic peak derived from the stretching vibration of the double bond between C and O of ethylmethyl carbonate is observed near 1711 cm ⁻¹ shifted from the vicinity of 1745 cm ⁻¹ to the lower wavenumber side. Observed at Is = 0.408407. The relationship between the peak intensities of Is and Io was Is> Io, and Is = 2.40 × Io.

In the IR spectrum of the electrolytic solution C7 shown in FIG. 23, a characteristic peak (Io = 0.41907) derived from stretching vibration of a double bond between C and O of ethylmethyl carbonate was observed in the vicinity of 1745 cm ^−1. It was done. Further, in the IR spectrum of FIG. 23, a characteristic peak derived from the stretching vibration of the double bond between C and O of ethylmethyl carbonate is observed near 1711 cm ⁻¹ shifted from the vicinity of 1745 cm ⁻¹ to the lower wavenumber side. Observed at Is = 0.33929. The relationship between the peak intensities of Is and Io was Is <Io.

In the vicinity of 1742 cm ⁻¹ of the IR spectrum of diethyl carbonate shown in FIG. 27, a characteristic peak derived from the stretching vibration of the double bond between C and O of diethyl carbonate was observed.

In the IR spectrum of the electrolytic solution E19 shown in FIG. 19, there is a slight characteristic peak (Io = 0.12002) derived from the stretching vibration of the double bond between C and O of diethyl carbonate in the vicinity of 1742 cm ^−1. Observed. Furthermore, in the IR spectrum of FIG. 19, a characteristic peak derived from the stretching vibration of the double bond between C and O of diethyl carbonate is observed near 1706 cm ⁻¹ shifted from the vicinity of 1742 cm ⁻¹ to the low wavenumber side. = 0.42925. The relationship between the peak intensities of Is and Io was Is> Io, and Is = 3.83 × Io.

In the IR spectrum of the electrolytic solution E20 shown in FIG. 20, a characteristic peak derived from the stretching vibration of a double bond between C and O of diethyl carbonate is slightly present in the vicinity of 1742 cm ⁻¹ (Io = 0.153231). Observed. Further, in the IR spectrum of FIG. 20, a characteristic peak derived from the stretching vibration of the double bond between C and O of diethyl carbonate is observed near 1706 cm ⁻¹ shifted from the vicinity of 1742 cm ⁻¹ to the low wavenumber side. = 0.45679. The relationship between the peak intensities of Is and Io was Is> Io, and Is = 3.00 × Io.

In the IR spectrum of the electrolytic solution E21 shown in FIG. 21, there is a slight characteristic peak (Io = 0.20337) derived from stretching vibration of the double bond between C and O of diethyl carbonate in the vicinity of 1742 cm ^−1. Observed. Furthermore, in the IR spectrum of FIG. 21, a characteristic peak derived from the stretching vibration of the double bond between C and O of diethyl carbonate is observed near 1706 cm ⁻¹ shifted from the vicinity of 1742 cm ⁻¹ to the lower wavenumber side. = 0.43841. The relationship between the peak intensities of Is and Io was Is> Io, and Is = 2.16 × Io.

In the IR spectrum of the electrolytic solution C8 shown in FIG. 24, a characteristic peak (Io = 0.396636) derived from stretching vibration of a double bond between C and O of diethyl carbonate is observed near 1742 cm ^−1. It was. More IR spectrum of Figure 24, characteristic peaks peak intensity Is derived from stretching vibration of double bonds between C and O in diethyl carbonate in the vicinity of 1709 cm ^-1 shifted from the vicinity of 1742 cm ^-1 to a lower wavenumber side = 0.31129. The relationship between peak intensities of Is and Io was Is <Io.

(Evaluation Example 2: Ionic conductivity)
The ionic conductivities of the electrolytic solutions E1 and E2, and the electrolytic solutions E4 to E6, E8, E11, E16, and E19 were measured under the following conditions. The results are shown in Table 4.

Ionic conductivity measurement conditions In an Ar atmosphere, an electrolytic solution was sealed in a glass cell with a platinum constant and a known cell constant, and impedance at 30 ° C. and 1 kHz was measured. The ion conductivity was calculated from the impedance measurement result. As the measuring instrument, Solartron 147055BEC (Solartron) was used.

Electrolytic solutions E1 and E2, electrolytic solutions E4 to E6, E8, E11, E16, and E19 all exhibited ion conductivity. Therefore, it can be understood that the electrolytic solution of the present invention can function as an electrolytic solution for various batteries.

(Evaluation Example 3: Viscosity)
The viscosities of the electrolytic solutions E1, E2, the electrolytic solutions E4 to E6, E8, E11, E16, and E19, the electrolytic solutions C1 to C4, and the electrolytic solutions C6 to C8 were measured under the following conditions. The results are shown in Table 5.

Viscosity measurement conditions Using a falling ball viscometer (Lovis 2000 M manufactured by Anton Paar GmbH (Anton Paar)), an electrolytic solution was sealed in a test cell under an Ar atmosphere, and the viscosity was measured at 30 ° C.

The viscosities of electrolytic solutions E1, E2, E4 to E6, E8, E11, E16, and E19 were significantly higher than those of electrolytic solutions C1 to C4 and electrolytic solutions C6 to C8. Therefore, if the battery uses the electrolytic solution of the present invention, leakage of the electrolytic solution is suppressed even if the battery is damaged.

(Evaluation Example 4: Volatility)
The volatility of the electrolytic solutions E2, E4, E8, E11, E13, C1, C2, C4 and C6 was measured by the following method.

About 10 mg of the electrolytic solution was put in an aluminum pan and placed in a thermogravimetric apparatus (TA Instruments, SDT600), and the weight change of the electrolytic solution at room temperature was measured. The volatilization rate was calculated by differentiating the weight change (mass%) with time. The maximum volatilization rate was selected and shown in Table 6.

The maximum volatilization rates of the electrolytic solutions E2, E4, E8, E11, and E13 were significantly smaller than the maximum volatilization rates of the electrolytic solutions C1, C2, C4, and C6. Therefore, even if the battery using the electrolytic solution of the present invention is damaged, the volatilization rate of the electrolytic solution is small, so that rapid volatilization of the organic solvent to the outside of the battery is suppressed.

(Evaluation Example 5: Combustibility)
The combustibility of the electrolytic solution E4 and the electrolytic solution C2 was tested by the following method.

3 drops of the electrolytic solution was dropped on the glass filter with a pipette, and the electrolytic solution was held on the glass filter. The glass filter was held with tweezers, and the glass filter was brought into contact with flame.

Electrolyte E4 did not ignite even after 15 seconds of indirect flame. On the other hand, the electrolytic solution C2 burned out in about 5 seconds. It was confirmed that the electrolytic solution of the present invention is difficult to burn.

(Evaluation Example 6: Low temperature test)
Electrolytes E11, E13, E16, and E19 were placed in containers, filled with an inert gas, and sealed. These were stored in a freezer at −30 ° C. for 2 days. Each electrolyte was observed after storage. None of the electrolytes were solidified and maintained in a liquid state, and no salt deposition was observed.
(Evaluation Example 7: Raman spectrum measurement)
For the electrolytes E8, E9, C4, and E11, E13, E15, C6, Raman spectrum measurement was performed under the following conditions. FIGS. 29 to 35 show Raman spectra in which peaks derived from the anion portion of the metal salt of each electrolytic solution were observed. In the figure, the horizontal axis represents the wave number (cm ⁻¹ ), and the vertical axis represents the scattering intensity.
Raman spectrum measurement conditions Equipment: Laser Raman spectrophotometer (NRS series, JASCO Corporation)
Laser wavelength: 532 nm
The electrolyte was sealed in a quartz cell under an inert gas atmosphere and used for measurement.
A characteristic peak derived from (FSO ₂ ) ₂ N of LiFSA dissolved in acetonitrile was observed in 700 to 800 cm ⁻¹ of the Raman spectra of the electrolytic solutions E8, E9, and C4 shown in FIGS. . Here, it can be seen from FIGS. 29 to 31 that the peak shifts to the higher wavenumber side as the LiFSA concentration increases. As the electrolyte concentration increases, (FSO ₂ ) ₂ N corresponding to the anion of the salt interacts with Li. In other words, when the concentration is low, Li and the anion become SSIP (Solvent-separated ion pairs). ) State is mainly formed, and it is assumed that a CIP (Contact ion pairs) state and an AGG (aggregate) state are mainly formed as the concentration is increased. It can be considered that such a state was observed as a peak shift of the Raman spectrum.
A characteristic peak derived from (FSO ₂ ) ₂ N of LiFSA dissolved in dimethyl carbonate is observed in 700 to 800 cm ⁻¹ of the Raman spectra of the electrolytic solutions E11, E13, E15, and C6 shown in FIGS. Observed. Here, it can be seen from FIGS. 32 to 35 that the peak shifts to the higher wavenumber side as the concentration of LiFSA increases. This phenomenon is similar to that discussed in the previous paragraph. When the concentration of the electrolyte is increased, the state in which (FSO ₂ ) ₂ N corresponding to the anion of the salt interacts with a plurality of Li is shown in the spectrum. It is inferred that the result is reflected.

(Evaluation Example 8: Li transportation rate)
The Li transport numbers of the electrolytic solutions E2, E8, C4 and C5 were measured under the following conditions.
The NMR tube containing each electrolyte solution was supplied to a PFG-NMR apparatus (ECA-500, JEOL), and the spin echo method was used for 7Li and 19F under conditions of 500 MHz and a magnetic field gradient of 1.26 T / m. The diffusion coefficient of Li ions and anions in each electrolyte was measured while changing the magnetic field pulse width. The Li transport number was calculated by the following formula.
Li transport number = (Li ion diffusion coefficient) / (Li ion diffusion coefficient + anion diffusion coefficient)
Table 7 shows the measurement results of the Li transport number.

The Li transport number of the electrolytic solutions E2 and E8 was significantly higher than the Li transport number of the electrolytic solutions C4 and C5. Here, the Li ion conductivity of the electrolytic solution can be calculated by multiplying the ionic conductivity (total ionic conductivity) contained in the electrolytic solution by the Li transport number. If it does so, it can be said that the electrolyte solution of this invention has the high transport rate of lithium ion (cation) compared with the conventional electrolyte solution which shows comparable ionic conductivity.
Moreover, about electrolyte solution E8, the Li transport number at the time of changing temperature was measured according to the said Li transport number measurement conditions. The results are shown in Table 8.

From the results in Table 8, it can be seen that the electrolytic solution of the present invention maintains a suitable Li transport number regardless of the temperature. It can be said that the electrolytic solution of the present invention maintains a liquid state even at a low temperature.

Specific examples of the electrolytic solution of the present invention include the following electrolytic solutions. The following electrolytes include those already described.
(Electrolytic solution A)
The electrolytic solution of the present invention was produced as follows.

About 5 mL of 1,2-dimethoxyethane, an organic solvent, was placed in a flask equipped with a stir bar and a thermometer. Under stirring conditions, (CF ₃ SO ₂ ) ₂ NLi, which is a lithium salt, was gradually added to 1,2-dimethoxyethane in the flask so as to keep the solution temperature at 40 ° C. or lower and dissolved. When about 13 g of (CF ₃ SO ₂ ) ₂ NLi was added, the dissolution of (CF ₃ SO ₂ ) ₂ NLi temporarily stagnated. Therefore, the flask was put into a thermostat, and the solution temperature in the flask was 50 ° C. (CF ₃ SO ₂ ) ₂ NLi was dissolved. When about 15 g of (CF ₃ SO ₂ ) ₂ NLi was added, the dissolution of (CF ₃ SO ₂ ) ₂ NLi stagnated again, so 1 drop of 1,2-dimethoxyethane was added with a pipette (CF ₃ SO ₂ ) ₂ NLi dissolved. Further, (CF ₃ SO ₂ ) ₂ NLi was gradually added, and the entire amount of predetermined (CF ₃ SO ₂ ) ₂ NLi was added. The resulting electrolyte was transferred to a 20 mL volumetric flask and 1,2-dimethoxyethane was added until the volume was 20 mL. The obtained electrolytic solution had a volume of 20 mL, and (CF ₃ SO ₂ ) ₂ NLi contained in this electrolytic solution was 18.38 g. This was designated as an electrolytic solution A. The concentration of (CF ₃ SO ₂ ) ₂ NLi in the electrolytic solution A was 3.2 mol / L, and the density was 1.39 g / cm ³ . The density was measured at 20 ° C.
The production was performed in a glove box under an inert gas atmosphere.

(Electrolytic solution B)
By a method similar to that for the electrolytic solution A, an electrolytic solution B having a (CF ₃ SO ₂ ) ₂ NLi concentration of 2.8 mol / L and a density of 1.36 g / cm ³ was produced.

(Electrolytic solution C)
About 5 mL of acetonitrile, which is an organic solvent, was placed in a flask equipped with a stir bar. Under stirring conditions, (CF ₃ SO ₂ ) ₂ NLi, which is a lithium salt, was gradually added to and dissolved in acetonitrile in the flask. The mixture was stirred overnight when the prescribed (CF ₃ SO ₂ ) ₂ NLi was added. The resulting electrolyte was transferred to a 20 mL volumetric flask and acetonitrile was added until the volume was 20 mL. This was designated as an electrolytic solution C. The production was performed in a glove box under an inert gas atmosphere.
The electrolytic solution C had a (CF ₃ SO ₂ ) ₂ NLi concentration of 4.2 mol / L and a density of 1.52 g / cm ³ .

(Electrolyte D)
By a method similar to that of the electrolytic solution C, an electrolytic solution D having a concentration of (CF ₃ SO ₂ ) ₂ NLi of 3.0 mol / L and a density of 1.31 g / cm ³ was produced.

(Electrolyte E)
Except for using sulfolane as the organic solvent, in the same manner as the electrolytic solution C, the concentration of (CF ₃ SO ₂ ) ₂ NLi is 3.0 mol / L and the density is 1.57 g / cm ^3. Liquid E was produced.

(Electrolyte F)
The concentration of (CF ₃ SO ₂ ) ₂ NLi is 3.2 mol / L and the density is 1.49 g / cm ³ except that dimethyl sulfoxide is used as the organic solvent. Electrolytic solution F was produced.

(Electrolyte G)
The concentration of (FSO ₂ ) ₂ NLi is 4.0 mol / L in the same manner as in the electrolytic solution C, except that (FSO ₂ ) ₂ NLi is used as the lithium salt and 1,2-dimethoxyethane is used as the organic solvent. An electrolyte solution G having a density of 1.33 g / cm ³ was produced.

(Electrolyte H)
In the same manner as the electrolytic solution G, an electrolytic solution H having a concentration of (FSO ₂ ) ₂ NLi of 3.6 mol / L and a density of 1.29 g / cm ³ was produced.

(Electrolyte I)
In the same manner as the electrolytic solution G, an electrolytic solution I having a concentration of (FSO ₂ ) ₂ NLi of 2.4 mol / L and a density of 1.18 g / cm ³ was produced.

(Electrolytic solution J)
Except that acetonitrile was used as the organic solvent, an electrolytic solution J having a concentration of (FSO ₂ ) ₂ NLi of 5.0 mol / L and a density of 1.40 g / cm ³ in the same manner as the electrolytic solution G Manufactured.

(Electrolytic solution K)
In the same manner as the electrolytic solution J, an electrolytic solution K having a concentration of (FSO ₂ ) ₂ NLi of 4.5 mol / L and a density of 1.34 g / cm ³ was produced.

(Electrolytic solution L)
About 5 mL of dimethyl carbonate, which is an organic solvent, was placed in a flask equipped with a stir bar. Under stirring conditions, (FSO ₂ ) ₂ NLi, which is a lithium salt, was gradually added to dimethyl carbonate in the flask and dissolved. When (FSO ₂ ) ₂ NLi was added in a total amount of 14.64 g, the mixture was stirred overnight. The resulting electrolyte was transferred to a 20 mL volumetric flask and dimethyl carbonate was added until the volume was 20 mL. This was designated as an electrolytic solution L. The production was performed in a glove box under an inert gas atmosphere.
The concentration of (FSO ₂ ) ₂ NLi in the electrolytic solution L was 3.9 mol / L, and the density of the electrolytic solution L was 1.44 g / cm ³ .

(Electrolyte M)
In the same manner as the electrolytic solution L, an electrolytic solution M having a (FSO ₂ ) ₂ NLi concentration of 2.9 mol / L and a density of 1.36 g / cm ³ was produced.

(Electrolytic solution N)
About 5 mL of ethyl methyl carbonate, which is an organic solvent, was placed in a flask equipped with a stir bar. Under stirring conditions, (FSO ₂ ) ₂ NLi, which is a lithium salt, was gradually added to and dissolved in ethyl methyl carbonate in the flask. When 12.81 g of (FSO ₂ ) ₂ NLi was added in total, the mixture was stirred overnight. The obtained electrolytic solution was transferred to a 20 mL volumetric flask, and ethyl methyl carbonate was added until the volume became 20 mL. This was designated as an electrolytic solution N. The production was performed in a glove box under an inert gas atmosphere.
The concentration of (FSO ₂ ) ₂ NLi in the electrolytic solution N was 3.4 mol / L, and the density of the electrolytic solution N was 1.35 g / cm ³ .

(Electrolytic solution O)
About 5 mL of diethyl carbonate, which is an organic solvent, was placed in a flask equipped with a stirring bar. Under stirring conditions, (FSO ₂ ) ₂ NLi, which is a lithium salt, was gradually added to and dissolved in diethyl carbonate in the flask. When 11.37 g of the total amount of (FSO ₂ ) ₂ NLi was added, the mixture was stirred overnight. The resulting electrolyte was transferred to a 20 mL volumetric flask and diethyl carbonate was added until the volume was 20 mL. This was designated as an electrolytic solution O. The production was performed in a glove box under an inert gas atmosphere.
The concentration of (FSO ₂ ) ₂ NLi in the electrolytic solution O was 3.0 mol / L, and the density of the electrolytic solution O was 1.29 g / cm ³ .
Table 9 shows a list of the electrolyte solutions.

(Non-aqueous electrolyte secondary battery)
The nonaqueous electrolyte secondary battery (1) to the nonaqueous electrolyte secondary battery (5) will be specifically described below. In the following embodiments, items are described separately for convenience, and therefore may be duplicated. The following examples and EB and CB described later may correspond to a plurality of examples of the nonaqueous electrolyte secondary battery (1) to the nonaqueous electrolyte secondary battery (5).
<Nonaqueous electrolyte secondary battery (1)>
Example 1-1

A nonaqueous electrolyte secondary battery of Example 1-1 was produced using the electrolytic solution E8.
<Negative electrode>
Adds SNO grade graphite (average particle size 15 μm) graphite (hereinafter sometimes referred to as graphite (A)), polyvinylidene fluoride (PVdF), and N-methyl-2-pyrrolidone (NMP) from SEC Carbon Co., Ltd. By mixing, a slurry-like negative electrode mixture was prepared. The composition ratio of each component (solid content) in the slurry is graphite: PVdF = 90: 10 (mass ratio).

The graphite (A) powder used was subjected to Raman spectrum analysis. As the apparatus, RAMAN-11 (excitation wavelength λ = 532 nm, grating: 600 gr / mm, laser power: 0.02 mW) manufactured by Nanophoton Co., Ltd. was used. In the Raman spectrum, the G / D ratio, which is the intensity ratio of the G-band and D-band peaks, was 12.2.

This slurry was applied to the surface of an electrolytic copper foil (current collector) having a thickness of 20 μm using a doctor blade, and a negative electrode active material layer was formed on the copper foil.

Then, it dried at 80 degreeC for 20 minute (s), and the organic solvent was volatilized and removed from the negative electrode active material layer. After drying, the current collector and the negative electrode active material layer were firmly and closely joined with a roll press. This was vacuum-dried at 120 ° C. for 6 hours to form a negative electrode having a negative electrode active material layer thickness of about 30 μm.
In this negative electrode, the basis weight of the negative electrode active material layer was 2.3 mg / cm ² and the density was 0.86 g / cm ³ .

<Nonaqueous electrolyte secondary battery>
A non-aqueous electrolyte secondary battery was produced using the produced negative electrode as an evaluation electrode. The counter electrode was a metal lithium foil (thickness 500 μm). This nonaqueous electrolyte secondary battery is a nonaqueous electrolyte secondary battery for evaluation, a so-called half cell.

The counter electrode was cut to φ13 mm, the evaluation electrode was cut to φ11 mm, and a separator (Whatman glass fiber filter paper) having a thickness of 400 μm was sandwiched between them to form an electrode body battery. This electrode body battery was accommodated in a battery case (CR2032 coin cell manufactured by Hosen Co., Ltd.). Then, electrolyte solution E8 was injected, and the battery case was sealed to obtain a nonaqueous electrolyte secondary battery of Example 1-1. Details of the lithium battery of Example 1-1 and the nonaqueous electrolyte secondary batteries of the following examples and comparative examples are shown in Table 41 at the end of the column of Examples.

Example 1-2
Example 1-1 was used except that SNO grade graphite (average particle size 10 μm) graphite (hereinafter sometimes referred to as graphite (B)) from SEC Carbon Co. was used instead of graphite (A). A negative electrode was produced, and the nonaqueous electrolyte secondary battery of Example 1-2 was obtained in the same manner as in Example 1-1. The graphite (B) used was subjected to Raman spectrum analysis in the same manner as in Example 1-1. As a result, the G / D ratio, which is the intensity ratio of the G-band and D-band peaks, was 4.4.

(Example 1-3)
A negative electrode was prepared in the same manner as in Example 1-1 except that graphite (C) having an average particle diameter of 10 μm was used in place of graphite (A), and the other examples were the same as in Example 1-1. -3 non-aqueous electrolyte secondary battery was obtained. The graphite (C) used was subjected to Raman spectrum analysis in the same manner as in Example 1-1. As a result, the G / D ratio, which is the intensity ratio of the G-band and D-band peaks, was 16.0.

(Example 1-4)
A nonaqueous electrolyte secondary battery of Example 1-4 was obtained in the same manner as Example 1-3 except that the electrolytic solution E11 was used.

(Comparative Example 1-1)
Example 1-1 was used except that graphite of the product name SG-BH (average particle size 20 μm) (hereinafter sometimes referred to as graphite (D)) of Ito Graphite Industries Co., Ltd. was used instead of graphite (A). A negative electrode was produced in the same manner, and the nonaqueous electrolyte secondary battery of Comparative Example 1-1 was obtained in the same manner as in Example 1-1. The graphite (D) used was subjected to Raman spectrum analysis in the same manner as in Example 1-1. As a result, the G / D ratio, which is the intensity ratio of the G-band and D-band peaks, was 3.4.

(Comparative Example 1-2)
Example 1-1 was used except that instead of graphite (A), graphite with the product name SG-BH8 (average particle size: 8 μm) of Ito Graphite Industries Co., Ltd. (hereinafter sometimes referred to as graphite (E)) was used. A negative electrode was produced in the same manner, and the nonaqueous electrolyte secondary battery of Comparative Example 1-2 was obtained in the same manner as in Example 1-1. The graphite (E) used was subjected to Raman spectrum analysis in the same manner as in Example 1-1. As a result, the G / D ratio, which is the intensity ratio of the G-band and D-band peaks, was 3.2.

(Comparative Example 1-3)
A nonaqueous electrolyte secondary battery of Comparative Example 1-3 was obtained in the same manner as Example 1-1 except that the electrolytic solution C5 was used instead of the electrolytic solution of the present invention.

(Comparative Example 1-4)
A nonaqueous electrolyte secondary battery of Comparative Example 1-4 was obtained in the same manner as Example 1-2 except that the electrolytic solution C5 was used instead of the electrolytic solution of the present invention.

(Comparative Example 1-5)
A nonaqueous electrolyte secondary battery of Comparative Example 1-5 was obtained in the same manner as Example 1-3 except that the electrolytic solution C5 was used instead of the electrolytic solution of the present invention.

(Comparative Example 1-6)
A nonaqueous electrolyte secondary battery of Comparative Example 1-6 was obtained in the same manner as Comparative Example 1-1 except that the electrolytic solution C5 was used instead of the electrolytic solution of the present invention.

(Comparative Example 1-7)
A nonaqueous electrolyte secondary battery of Comparative Example 1-7 was obtained in the same manner as Comparative Example 1-2 except that the electrolytic solution C5 was used instead of the electrolytic solution of the present invention.

Table 6 shows the configurations of the nonaqueous electrolyte secondary batteries of Examples 1-1 to 1-4 and Comparative Examples 1-1 to 1-7.

(Evaluation example 9: cyclic voltammetry)
For the nonaqueous electrolyte secondary batteries of Examples 1-1 to 1-4 and Comparative Examples 1-1 to 1-7, the temperature was 25 ° C., the sweep rate was 0.1 mV / sec. Cyclic voltammetry (so-called CV) measurement was performed under the conditions of voltage range: 0.01V-2V, 1 to 5 cycles. The results are shown in FIGS. The nonaqueous electrolyte secondary batteries of Examples 1-1 to 1-4 are reversible in the same manner as the nonaqueous electrolyte secondary batteries of Comparative Examples 1-1 to 1-7 (ie, conventional nonaqueous electrolyte secondary batteries). A typical redox reaction is confirmed. In addition, a reversible redox reaction is confirmed even when graphite having a G / D ratio of less than 3.5 is used, as in the nonaqueous electrolyte secondary batteries of Comparative Examples 1-1 and 1-2. That is, it can be understood that the electrolytic solution of the present invention can be used for a non-aqueous electrolyte secondary battery if graphite is used as a negative electrode active material regardless of the G / D ratio.

(Example 1-5)
In the non-aqueous electrolyte secondary battery of Example 1-5, the same negative electrode as in Example 1-1 was used.

<Positive electrode>
Li [Ni _0.5 Co _0.2 Mn _0.3 ] O ₂ , acetylene black (AB), PVdF, and NMP were added and mixed as a positive electrode active material to prepare a slurry-like positive electrode mixture. The composition ratio of each component (solid content) in the slurry is active material: AB: PVdF = 94: 3: 3 (mass ratio). This slurry was applied to the surface of an aluminum foil (current collector) using a doctor blade and dried to produce a positive electrode having a positive electrode active material layer having a thickness of about 25 μm. Hereinafter, Li [Ni _0.5 Co _0.2 Mn _0.3 ] O ₂ is referred to as NCM 523 as necessary.

<Nonaqueous electrolyte secondary battery>
Using the positive electrode, the negative electrode, and the electrolytic solution E8, a laminated lithium ion secondary battery, which is a kind of non-aqueous electrolyte secondary battery, was manufactured. Specifically, an experimental filter paper having a thickness of 260 μm was sandwiched between the positive electrode and the negative electrode to form an electrode plate group. The electrode plate group was covered with a set of two laminated films, and the three sides were sealed. Then, the electrolyte solution of the present invention was injected into the bag-like laminated film. Thereafter, the remaining one side was sealed to obtain a laminate type lithium ion secondary battery in which the four sides were hermetically sealed and the electrode plate group and the electrolyte were sealed. Note that the positive electrode and the negative electrode have a tab that can be electrically connected to the outside, and a part of the tab extends to the outside of the laminated lithium ion secondary battery.

(Example 1-6)
A nonaqueous electrolyte secondary battery of Example 1-6 was produced in the same manner as Example 1-5 except that the electrolytic solution E4 was used.

(Comparative Example 1-8)
A nonaqueous electrolyte secondary battery of Comparative Example 1-8 was obtained in the same manner as Example 1-5 except that the electrolytic solution C5 was used instead of the electrolytic solution of the present invention.

(Evaluation Example 10: Thermal stability)
The nonaqueous electrolyte secondary batteries of Examples 1-5 and 1-6 and Comparative Example 1-8 were fully charged under a potential difference of 4.2 V and a constant current and constant voltage condition. The fully charged nonaqueous electrolyte secondary battery was disassembled and the negative electrode was taken out. 2.8 mg of the negative electrode and 1.68 μL of the electrolytic solution were placed in a stainless steel pan, and the pan was sealed. Using a sealed pan, under a nitrogen atmosphere, the heating rate was 20 ° C./min. The differential scanning calorimetry was performed under the conditions described above, and the DSC curve was observed. 46 shows a DSC chart of the nonaqueous electrolyte secondary batteries of Example 1-5 and Comparative Example 1-8, and FIG. 47 shows a DSC chart of the nonaqueous electrolyte secondary batteries of Example 1-6 and Comparative Example 1-8. Respectively.

In a non-aqueous electrolyte secondary battery using graphite as a negative electrode active material, when heated in a fully charged state using a general electrolytic solution, multiple exothermic reactions are caused at 300 ° C. or lower as in Comparative Example 1-8. However, in Examples 1-5 and 1-6 using the electrolytic solution of the present invention, the exothermic peak generated at the position of the arrow in the figure disappears, and the reactivity between the graphite negative electrode and the electrolytic solution of the present invention is low, and the thermophysical properties. It turns out that it is excellent in.

(Evaluation Example 11: Rate characteristics)
Using the nonaqueous electrolyte secondary batteries of Example 1-1 and Comparative Example 1-1, the rate capacity characteristics were evaluated under the following conditions. The results are shown in FIG.
(1) Current is passed in the direction in which lithium occlusion proceeds to the negative electrode.
(2) Voltage range: 2 V → 0.01 V (vs. Li ^/ Li ⁺ )
(3) Rate: 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, 10C, 0.1C (current is stopped after reaching 0.01V)
(4) Measurement 3 times for each rate (total 24 cycles) 1C indicates a current value required to fully charge or discharge the battery in one hour at a constant current.

It can be seen that the nonaqueous electrolyte secondary battery of Example 1-1 has a current capacity approximately twice that of Comparative Example 1-1 in the range of 0.5 C to 2 C, and can be charged at high speed.

(Evaluation Example 12: Rate characteristics, cycle durability)
Using the nonaqueous electrolyte secondary batteries of Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-3 and 1-7, the rate capacity characteristics and the cycle capacity retention rate were evaluated.
(1) Current is passed in the direction in which lithium occlusion proceeds to the negative electrode.
(2) Voltage range: 0.01V-2V (vs. Li)
(3) Rate: 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, 10C, 0.1C (current is stopped after reaching 0.01V)
(4) 3 times for each rate (24 cycles in total) (5) Temperature is room temperature

The current capacities at 0.1 C rate and 2 C rate were measured under the above conditions, and the ratio of the current capacity at 2 C rate to the current capacity at 0.1 C rate was defined as the rate capacity characteristic. In addition, charge / discharge was repeated for 25 cycles at 0.2 C, and the ratio between the 25th cycle and the initial current capacity was defined as the cycle capacity retention rate. The results are shown in Table 11.

As in Comparative Examples 1-1 and 1-2, it is difficult to improve the cycle capacity retention rate only by combining a negative electrode using graphite having a G / D ratio of less than 4 as a negative electrode active material and the electrolytic solution of the present invention. Further, as in Comparative Examples 1-3 and 1-7, when a conventional electrolyte is used, it is difficult to improve the rate capacity characteristics regardless of the G / D ratio of graphite. However, as in Examples 1-1 to 1-3, by combining the electrolytic solution of the present invention with a negative electrode using graphite having a G / D ratio of 3.5 or more as a negative electrode active material, Both the cycle capacity maintenance rate can be improved. Further, from the comparison between the examples, the higher the G / D ratio, the more the rate capacity characteristics and the cycle capacity retention rate tend to be improved, and it is considered that the G / D ratio is more preferably 10 or more. Also, from this result, both when using AN as the organic solvent for the electrolytic solution and when using DMC, the electrolytic solution is the electrolytic solution of the present invention, and the G / D ratio is 3.5 or more. It can be understood that the rate capacity characteristics and the cycle capacity retention ratio are improved by using the graphite together.

(Example 1-7)
<Negative electrode>
As the negative electrode active material, SNO grade graphite (average particle size: 15 μm) graphite (hereinafter sometimes referred to as graphite (A)) manufactured by SEC Carbon Co., Ltd. was used. 98 parts by mass of graphite (A) as a negative electrode active material, 1 part by mass of styrene butadiene rubber as a binder, and 1 part by mass of carboxymethyl cellulose were mixed. This mixture was dispersed in an appropriate amount of ion-exchanged water to prepare a slurry-like negative electrode mixture. Hereinafter, styrene butadiene rubber is abbreviated as SBR and carboxymethyl cellulose is abbreviated as CMC as necessary.

The graphite (A) powder used was subjected to Raman spectrum analysis. As the apparatus, RAMAN-11 (excitation wavelength λ = 532 nm, grating: 1800 gr / mm, laser power mW) manufactured by Nanophoton Co., Ltd. was used. In the Raman spectrum, the G / D ratio, which is the intensity ratio of the G-band and D-band peaks, was 12.2.

Then, it dried at 80 degreeC for 20 minute (s), and the organic solvent was volatilized and removed from the negative electrode active material layer. After drying, the current collector and the negative electrode active material layer were firmly and closely joined with a roll press. This was vacuum-dried at 100 ° C. for 6 hours to form a negative electrode having a negative electrode active material layer weight of about 8.5 mg / cm ² .

<Positive electrode>
The positive electrode includes a positive electrode active material layer and a current collector covered with the positive electrode active material layer. The positive electrode active material layer has a positive electrode active material, a binder, and a conductive additive. The positive electrode active material is made of LiNi _0.5 Co _0.2 Mn _0.3 O ₂ . The binder is made of PVDF, and the conductive additive is made of AB. The current collector is made of an aluminum foil having a thickness of 20 μm. When the positive electrode active material layer is 100 parts by mass, the mass ratio of the positive electrode active material, the binder, and the conductive additive is 94: 3: 3.

In order to produce a positive electrode, NCM523, PVDF and AB are mixed so as to have the above mass ratio, and NMP as a solvent is added to obtain a paste-like positive electrode material. The paste-like positive electrode material was applied to the surface of the current collector using a doctor blade to form a positive electrode active material layer. The positive electrode active material layer was dried at 80 ° C. for 20 minutes to remove NMP by volatilization. The aluminum foil having the positive electrode active material layer formed on the surface thereof was compressed using a roll press, and the aluminum foil and the positive electrode active material layer were firmly bonded. The joined product was heated in a vacuum dryer at 120 ° C. for 6 hours, cut into a predetermined shape, and a positive electrode was obtained.

<Nonaqueous electrolyte secondary battery>
A nonaqueous electrolyte secondary battery of Example 1-7 was obtained in the same manner as Example 1-5, except that the above positive electrode, negative electrode, and electrolytic solution E8 were used, and a cellulose nonwoven fabric (thickness 20 μm) was used as the separator. It was.

(Comparative Example 1-9)
A nonaqueous electrolyte secondary battery of Comparative Example 1-9 was obtained in the same manner as Example 1-7, except that electrolytic solution C5 was used instead of the electrolytic solution of the present invention.

(Evaluation example 13: Input characteristics)
Using the lithium ion batteries of Example 1-7 and Comparative Example 1-9, the input (charging) characteristics were evaluated under the following conditions.
(1) Working voltage range: 3V-4.2V
(2) Capacity: 13.5mAh
(3) SOC 80%
(4) Temperature: 0 ° C, 25 ° C
(5) Number of measurements: 3 times each

Evaluation conditions are 80% charged state (SOC), 0 ° C., 25 ° C., operating voltage range 3V-4.2V, and capacity 13.5 mAh. SOC 80%, 0 ° C. is a region in which input characteristics are difficult to be obtained, for example, when used in a refrigerator room. The input characteristics of Example 1-7 and Comparative Example 1-9 were evaluated three times for 2-second input and 5-second input, respectively. Tables 12 and 13 show the evaluation results of the input characteristics. “2-second input” in the table means an input after 2 seconds from the start of charging, and “5-second input” means an input after 5 seconds from the start of charging.

In Tables 12 and 13, the electrolytic solution of the present invention used in Example 1-7 is abbreviated as “FSA”, and the electrolytic solution used in Comparative Example 1-9 is abbreviated as “ECPF”.

At both 0 ° C. and 25 ° C., the input (charging) characteristics of Example 1-7 are improved compared to Comparative Example 1-9. This is an effect obtained by using graphite having a GD ratio of 3.5 or more and the electrolytic solution of the present invention. In particular, since it exhibits a high input (charge) characteristic even at 0 ° C., lithium in the electrolytic solution even at a low temperature. It is shown that the movement of ions proceeds smoothly.

(Example 1-8)
A nonaqueous electrolyte secondary battery of Example 1-8 using the electrolytic solution E11 was produced as follows.

<Negative electrode>
90 parts by mass of natural graphite having an average particle diameter of 10 μm as an active material and 10 parts by mass of PVdF as a binder were mixed. This mixture was dispersed in an appropriate amount of NMP to prepare a slurry. A copper foil having a thickness of 20 μm was prepared as a current collector. 2.46 mg of the slurry was applied to the surface of the copper foil in the form of a film using a doctor blade. The G / D ratio of natural graphite used in Example 1-8 was 4.4.

The copper foil coated with the slurry was dried to remove NMP, and then the copper foil was pressed to obtain a bonded product. The obtained joined product was heat-dried at 120 ° C. for 6 hours with a vacuum dryer to obtain a copper foil on which an active material layer was formed. This was the working electrode. In addition, the mass of the active material on copper foil was 2.214 mg, and the mass of the active material per 1 cm <2> of copper foil was 1.48 mg. The density of natural graphite and PVdF before pressing was 0.68 g / cm ³ , and the density of the active material layer after pressing was 1.025 g / cm ³ .

<Nonaqueous electrolyte secondary battery>
The counter electrode was metal Li.

The working electrode, the counter electrode, and the electrolytic solution E11 were accommodated in a battery case (CR2032 type coin cell case manufactured by Hosen Co., Ltd.) having a diameter of 13.82 mm to obtain a nonaqueous electrolyte secondary battery of Example 1-8.

(Example 1-9)
A nonaqueous electrolyte secondary battery of Example 1-9 was obtained in the same manner as in Example 1-8, except that electrolytic solution E8 was used instead of electrolytic solution E11.

(Example 1-10)
A nonaqueous electrolyte secondary battery of Example 1-10 was obtained in the same manner as in Example 1-8, except that electrolytic solution E16 was used instead of electrolytic solution E11.

(Example 1-11)
A nonaqueous electrolyte secondary battery of Example 1-11 was obtained in the same manner as in Example 1-8, except that electrolytic solution E19 was used instead of electrolytic solution E11.

(Comparative Example 1-10)
A nonaqueous electrolyte secondary battery of Comparative Example 1-10 was obtained in the same manner as Example 1-8 except that the electrolytic solution C5 was used instead of the electrolytic solution E11.

(Evaluation Example 14: Reversibility of reaction)
Each of the nonaqueous electrolyte secondary batteries of Examples 1-8 to 1-11 and Comparative Example 1-10 was subjected to a charge / discharge test three times under the conditions shown in Table 14. The charge / discharge curves at that time are shown in FIGS.

It can be seen that the nonaqueous electrolyte secondary batteries of Examples 1-8 to 1-11 are reversibly charged and discharged in the same manner as the general nonaqueous electrolyte secondary battery of Comparative Example 1-10.

(Evaluation Example 15: Rate characteristics)
The rate characteristics of the nonaqueous electrolyte secondary batteries of Examples 1-8 to 1-11 and Comparative Example 1-10 were tested by the following method. Each non-aqueous electrolyte secondary battery was charged at a rate of 0.1 C, 0.2 C, 0.5 C, 1 C, and 2 C, and then discharged, and the discharge capacity of the working electrode at each speed was measured. 1C means a current value required to fully charge or discharge the battery in one hour at a constant current. In the description here, the counter electrode is regarded as a negative electrode, and the working electrode is regarded as a positive electrode. The ratio of the capacity at other rates to the capacity of the working electrode at the 0.1 C rate, that is, the rate characteristic was calculated. The results are shown in Table 15.

The nonaqueous electrolyte secondary batteries of Examples 1-8 to 1-11 had a capacity reduction at rates of 0.2 C, 0.5 C, and 1 C compared to the nonaqueous electrolyte secondary battery of Comparative Example 1-10. It is suppressed. From these results, it was confirmed that the nonaqueous electrolyte secondary battery of each example, that is, the nonaqueous electrolyte secondary battery of the present invention showed excellent rate characteristics. Furthermore, the nonaqueous electrolyte secondary batteries of Examples 1-8 and 1-9 are suppressed in capacity reduction even at the rate of 2C compared to the nonaqueous electrolyte secondary battery of Comparative Example 1-10. That is, the nonaqueous electrolyte secondary batteries of Examples 1-8 and 1-9 show particularly excellent rate characteristics.

(Evaluation Example 16: Capacity maintenance rate)
The capacity retention rates of the nonaqueous electrolyte secondary batteries of Examples 1-8 to 1-11 and Comparative Example 1-10 were tested by the following method.

Each non-aqueous electrolyte secondary battery is CC charged (constant current charge) to 25 ° C. and a voltage of 2.0 V, and is subjected to CC discharge (constant current discharge) to a voltage of 0.01 V. A discharge cycle was performed. Specifically, first, charge / discharge is performed for 3 cycles at a charge / discharge rate of 0.1C, and then charge / discharge is performed for each charge / discharge rate in 3 cycles in the order of 0.2C, 0.5C, 1C, 2C, 5C, Finally, 3 cycles of charge and discharge were performed at 0.1 C. The capacity retention rate (%) of each non-aqueous electrolyte secondary battery was determined by the following formula.
Capacity maintenance rate (%) = B / A × 100
A: Discharge capacity of the second working electrode in the first 0.1 C charge / discharge cycle B: Discharge capacity of the second working electrode in the last 0.1 C charge / discharge cycle

The results are shown in Table 16. In this description, the counter electrode is regarded as a negative electrode and the working electrode is regarded as a positive electrode.

Any of the nonaqueous electrolyte secondary batteries performed a charge / discharge reaction satisfactorily and exhibited a suitable capacity retention rate. In particular, the capacity retention rates of the half cells of Examples 1-9, 1-10, and 1-11 were remarkably excellent.

(Example 1-12)
A nonaqueous electrolyte secondary battery of Example 1-12 was obtained in the same manner as Example 1-2 except that the electrolytic solution E9 was used.

(Evaluation Example 17: Rate characteristics at low temperature)
Using the nonaqueous electrolyte secondary batteries of Example 1-12 and Comparative Example 1-4, the rate characteristics at −20 ° C. were evaluated as follows. The results are shown in FIGS. 54 and 55.
(1) A current is passed in the direction in which lithium occlusion proceeds to the negative electrode (evaluation electrode).
(2) Voltage range: 2V → 0.01V (vs Li / Li +)
(3) Rate: 0.02C, 0.05C, 0.1C, 0.2C, 0.5C (current stopped after reaching 0.01V)
1C represents a current value required to fully charge or discharge the battery in one hour at a constant current.

54 and 55, the voltage curve of the nonaqueous electrolyte secondary battery of Example 1-12 at each current rate is higher than the voltage curve of the nonaqueous electrolyte secondary battery of Comparative Example 1-4. You can see that. From this result, it was confirmed that the nonaqueous electrolyte secondary battery of the present invention exhibits excellent rate characteristics even in a low temperature environment.

(Evaluation Example 18: Rate characteristics)
The rate characteristics of the nonaqueous electrolyte secondary batteries of Example 1-2 and Comparative Example 1-4 were tested by the following method.
Each non-aqueous electrolyte secondary battery was charged at a rate of 0.1C, 0.2C, 0.5C, 1C, 2C, then discharged, and the capacity (discharge capacity) of the working electrode at each speed was measured. The rate characteristics were calculated in the same manner as described above, assuming that the counter electrode was a negative electrode and the working electrode was a positive electrode. The results are shown in Table 17.

The nonaqueous electrolyte secondary battery of Example 1-2 has a capacity higher than that of the nonaqueous electrolyte secondary battery of Comparative Example 1-4 at any rate of 0.2C, 0.5C, 1C, and 2C. The decline of the was suppressed. That is, the non-aqueous electrolyte secondary battery of Example 1-2 exhibited excellent rate characteristics. This result also confirmed that the non-aqueous electrolyte secondary battery of the present invention using the electrolytic solution of the present invention exhibits excellent rate characteristics.

(Evaluation Example 19: Responsiveness to repeated rapid charge / discharge)
For the nonaqueous electrolyte secondary batteries of Example 1-2 and Comparative Example 1-4, changes in capacity and voltage were observed when charging and discharging were repeated three times at a 1C rate. The results are shown in FIG.

The nonaqueous electrolyte secondary battery of Comparative Example 1-4 has a tendency to increase the polarization when a current is passed at a rate of 1 C with repeated charge and discharge, and the capacity obtained from reaching 2 V to 0.01 V Fell rapidly. On the other hand, in the nonaqueous electrolyte secondary battery of Example 1-2, there was almost no increase or decrease in polarization even after repeated charge and discharge, and the capacity was suitably maintained. This can also be confirmed from the fact that the three curves overlap in FIG.

The reason why the polarization increased in the nonaqueous electrolyte secondary battery of Comparative Example 1-4 is that the amount sufficient for the reaction interface with the electrode due to the uneven Li concentration generated in the electrolyte when rapidly charging and discharging was repeated. It can be considered that the electrolyte solution can no longer supply Li, that is, the Li concentration of the electrolyte solution is unevenly distributed. In the non-aqueous electrolyte secondary battery of Example 1-2, it is considered that the uneven distribution of the Li concentration of the electrolytic solution could be suppressed by using the electrolytic solution of the present invention having a high Li concentration. Also from this result, it was confirmed that the nonaqueous electrolyte secondary battery of the present invention using the electrolytic solution of the present invention exhibits excellent responsiveness to rapid charge / discharge.
<Nonaqueous electrolyte secondary battery (2)>
Example 2-1
<Negative electrode>
A hard carbon having a crystallite size (L) of 1.1 nm, polyvinylidene fluoride (PVdF), and N-methyl-2-pyrrolidone (NMP) were added and mixed to prepare a slurry-like negative electrode mixture. The composition ratio of each component (solid content) in the slurry is hard carbon: PVdF = 9: 1 (mass ratio).

The crystallite size is measured by the X-ray diffraction method using CuKα ray as an X-ray source, using the Scherrer equation from the half-value width and diffraction angle of the diffraction peak detected at a diffraction angle 2θ = 20 ° to 30 °. did. The measuring device was manufactured by Rigaku [SmartLab], and the optical system was a concentration method.

Thereafter, drying was performed at 80 ° C. for 20 minutes, and the organic solvent was volatilized and removed from the negative electrode active material layer. After drying, the current collector and the negative electrode active material layer were firmly and closely joined with a roll press. This was heated and dried at 120 ° C. for 6 hours in a vacuum atmosphere to form a negative electrode having a negative electrode active material layer thickness of about 30 μm.

<Nonaqueous electrolyte secondary battery>
Using the negative electrode produced above as an evaluation electrode, a non-aqueous electrolyte secondary battery was produced. The counter electrode was a metal lithium foil (thickness 500 μm).

The counter electrode was cut to φ13 mm, the evaluation electrode was cut to φ11 mm, and a separator (Whatman glass fiber filter paper) having a thickness of 400 μm was sandwiched between them to form an electrode body battery. This electrode body battery was accommodated in a battery case (CR2032 coin cell manufactured by Hosen Co., Ltd.). Then, the electrolyte solution E8 was injected, the battery case was sealed, and the nonaqueous electrolyte secondary battery of Example 2-1 was obtained. Details of the nonaqueous electrolyte secondary battery of Example 2-1 and the nonaqueous electrolyte secondary batteries of the following examples and comparative examples are shown in Table 42 at the end of the column of Examples.

(Comparative Example 2-1)
A nonaqueous electrolyte secondary battery of Comparative Example 2-1 was obtained in the same manner as in Example 2-1, except that the electrolytic solution C5 was used instead of the electrolytic solution E8.

(Evaluation Example 20: Reversibility of charge / discharge)
The rate capacity characteristics of the nonaqueous electrolyte secondary battery of Example 2-1 and the nonaqueous electrolyte secondary battery of Comparative Example 2-1 were evaluated under the following conditions. The initial charge / discharge curve is shown in FIG. 57, and the rate capacity test results are shown in FIG.
(1) Current is passed in the direction in which lithium occlusion proceeds to the negative electrode.
(2) Voltage range: 2 V → 0.01 V (vs. Li ^/ Li ⁺ )
(3) Rate: 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, 10C, 0.1C (current is stopped after reaching 0.01V)
(4) Measurement 3 times for each rate (total 24 cycles) 1C indicates a current value required to fully charge or discharge the battery in one hour at a constant current.

FIG. 57 clearly shows that the nonaqueous electrolyte secondary battery of Example 2-1 can be charged and discharged. Also, from FIG. 58, the nonaqueous electrolyte secondary battery of Example 2-1 has better rate capacity characteristics than the nonaqueous electrolyte secondary battery of Comparative Example 2-1, and functions as a battery for high-speed charging and high input / output. I understand that

(Example 2-2)
A negative electrode was produced in the same manner as in Example 1-1 except that soft carbon having a crystallite size (L) of 4.2 nm was selected and this soft carbon was used. A nonaqueous electrolyte secondary battery of Example 2-2 was obtained in the same manner as Example 1-1 except that this negative electrode was used.

(Example 2-3)
A nonaqueous electrolyte secondary battery of Example 2-3 was obtained in the same manner as Example 2-1, except that the electrolytic solution E11 was used.

(Example 2-4)
A nonaqueous electrolyte secondary battery of Example 2-4 was obtained in the same manner as Example 2-2, except that the same electrolytic solution E11 as in Example 2-3 was used.

(Comparative Example 2-2)
A negative electrode was produced in the same manner as in Example 2-1, except that graphite having a crystallite size (L) of 28 nm was selected and this graphite was used. A nonaqueous electrolyte secondary battery of Comparative Example 2-2 was obtained in the same manner as in Example 2-1, except that this negative electrode was used.

(Comparative Example 2-3)
A negative electrode was produced in the same manner as in Example 2-1, except that graphite having a crystallite size (L) of 42 nm was selected and this graphite was used. A nonaqueous electrolyte secondary battery of Comparative Example 2-3 was obtained in the same manner as Example 2-1, except that this negative electrode was used.

(Comparative Example 2-4)
Using the same hard carbon as in Example 2-1, a negative electrode was produced in the same manner as in Example 2-1. A nonaqueous electrolyte secondary battery of Comparative Example 2-4 was obtained in the same manner as in Example 2-1, except that this negative electrode was used and the electrolytic solution C5 was used instead of the electrolytic solution of the present invention.

(Comparative Example 2-5)
Using the same soft carbon as in Example 2-2, a negative electrode was produced in the same manner as in Example 2-1. A nonaqueous electrolyte secondary battery of Comparative Example 2-5 was obtained in the same manner as in Example 2-1, except that this negative electrode was used and the electrolytic solution C5 was used instead of the electrolytic solution of the present invention.

(Comparative Example 2-6)
A negative electrode was produced in the same manner as in Comparative Example 2-2. A nonaqueous electrolyte secondary battery of Comparative Example 2-6 was obtained in the same manner as in Example 2-1, except that this negative electrode was used and the electrolytic solution C5 was used instead of the electrolytic solution of the present invention.

(Comparative Example 2-7)
A negative electrode was produced in the same manner as in Comparative Example 2-3. A nonaqueous electrolyte secondary battery of Comparative Example 2-7 was obtained in the same manner as in Example 2-1, except that this negative electrode was used and the electrolytic solution C5 was used instead of the electrolytic solution of the present invention.

(Evaluation Example 21: Rate characteristics)
Regarding the non-aqueous electrolyte secondary batteries of Example 2-1, Example 2-2, and Comparative Examples 2-2 to 2-7, the same conditions as in the above (Evaluation Example 20: Reversibility of charge / discharge) are used. The rate capacity characteristics were evaluated. The ratio of the 5C rate current capacity to the 0.1C rate current capacity was defined as the rate capacity characteristic. The results are shown in Table 18.

As in Comparative Example 2-2 and Comparative Example 2-3, a combination of a carbon material having a crystallite size (L) exceeding 20 nm and the electrolytic solution of the present invention cannot provide a sufficiently large rate capacity characteristic. On the other hand, by using a carbon material having a crystallite size (L) of less than 20 nm as in Example 2-1 and Example 2-2, even when using the electrolytic solution of the present invention, Comparative Examples 2-4 to Excellent rate capacity characteristics equivalent to or better than those of Example 2-7 are exhibited. Moreover, the tendency for the rate capacity characteristics to improve as the crystallite size (L) decreases is observed, and the crystallite size (L) is more preferably 5 nm or less.
Similarly, when DMC, which is a chain carbonate, is used as the organic solvent for the electrolytic solution as in Example 2-3 and Example 2-4, it is similarly compared with Comparative Example 2-2 and Comparative Example 2-3. Excellent rate capacity characteristics.

<Nonaqueous electrolyte secondary battery (3)>
Example 3-1
A nonaqueous electrolyte secondary battery of Example 3-1 was manufactured using the above-described electrolytic solution E8 and a negative electrode active material made of silicon-carbon composite powder.
<Negative electrode>
The silicon-carbon composite powder is obtained by mixing Si powder having a particle diameter of 50 nm and acetylene black at a mass ratio of 6: 4 and using a planetary ball mill to form a composite.

90 parts by mass of silicon-carbon composite powder as a negative electrode active material and 10 parts by mass of polyamideimide (PAI) as a binder were mixed. This mixture was dispersed in an appropriate amount of NMP to prepare a slurry-like negative electrode mixture. This slurry was applied to the negative electrode current collector in a film form using a doctor blade. As the negative electrode current collector, a copper foil having a thickness of 20 μm was used. The negative electrode current collector coated with the slurry-like negative electrode mixture was dried at 80 ° C. for 20 minutes and then pressed using a roller press. The bonded product after pressing was heated in a vacuum dryer at 200 ° C. for 2 hours, and cut into a predetermined shape to obtain a negative electrode.

As the counter electrode, lithium foil (metallic lithium) was used, and as the electrolytic solution, electrolytic solution E8 was used.

A non-aqueous electrolyte secondary battery was manufactured using the above negative electrode, positive electrode and electrolyte. Specifically, a Whatman glass fiber filter paper having a thickness of 400 μm was sandwiched between the positive electrode and the negative electrode to form an electrode plate group. This electrode group was accommodated in a battery case (CR2032 coin cell manufactured by Hosen Co., Ltd.). An electrolytic solution was further injected into the battery case. After injecting the electrolyte, the battery case was sealed to obtain the nonaqueous electrolyte secondary battery of Example 3-1. Details of the nonaqueous electrolyte secondary battery of Example 4-1 and each of the following batteries are shown in Table 43 at the end of the column of the example.

(Example 3-2)
The nonaqueous electrolyte secondary battery of Example 3-2 is the same as the nonaqueous electrolyte secondary battery of Example 3-1, except for the composition of the negative electrode mixture. The negative electrode mixture in the non-aqueous electrolyte secondary battery of Example 3-2 was 75 parts by mass of silicon-carbon composite powder as the negative electrode active material, 15 parts by mass of graphite as the negative electrode active material, and as the binder. And 10 parts by mass of polyamideimide (PAI).

(Example 3-3)
The nonaqueous electrolyte secondary battery of Example 3-3 is the same as the nonaqueous electrolyte secondary battery of Example 3-2 except that the electrolytic solution E11 is used.

(Comparative Example 3-1)
The non-aqueous electrolyte secondary battery of Comparative Example 3-1 is the same as the non-aqueous electrolyte secondary battery of Example 3-1 except that the electrolytic solution C5 was used.

(Comparative Example 3-2)
The nonaqueous electrolyte secondary battery of Comparative Example 3-2 is the same as the nonaqueous electrolyte secondary battery of Example 3-2 except that the same electrolytic solution C5 as Comparative Example 3-1 was used.

(Evaluation Example 22: Charge / Discharge Characteristics)
The charge / discharge characteristics of the nonaqueous electrolyte secondary batteries of Example 3-1 to Example 3-3, Comparative Example 3-1 and Comparative Example 3-2 were evaluated by the following methods.

The constant current (CC) charge / discharge was performed with respect to each nonaqueous electrolyte secondary battery. The voltage range was 2V to 0.01V, and the C rate was 0.1C. Table 19 shows the discharge capacity of each non-aqueous electrolyte secondary battery. The charge / discharge curves of the nonaqueous electrolyte secondary batteries of Example 3-2 and Comparative Example 3-2 are shown in FIG. A charge / discharge curve of the nonaqueous electrolyte secondary battery of Example 3-3 is shown in FIG.

As shown in Table 19, Example 3-1 and Comparative Example 3-1 use the same negative electrode mixture, and Example 3-2 and Comparative Example 3-2 use the same negative electrode mixture. . The non-aqueous electrolyte secondary battery of Example 3-1 using the same negative electrode mixture was compared with the non-aqueous electrolyte secondary battery of Comparative Example 3-1, and Example 3-2 using the same negative electrode mixture When comparing the non-aqueous electrolyte secondary battery of Example 3-2 with the non-aqueous electrolyte secondary battery of Comparative Example 3-2, the discharge capacity of the non-aqueous electrolyte secondary battery is improved by using the electrolyte solution of the present invention as the electrolyte solution. I understand that This result shows that the discharge capacity of a nonaqueous electrolyte secondary battery can be improved by combining the composite material of silicon and carbon and the electrolytic solution of the present invention. The reason is not clear, but in the electrolyte solution of the present invention, the coordinating environment of the solvent and anion is different from that of a general electrolyte solution. The

Further, as in the nonaqueous electrolyte secondary battery of Example 3-3, the nonaqueous electrolyte secondary battery using DMC as the organic solvent for the electrolytic solution is similar to the nonaqueous electrolyte secondary battery of the example. It turns out that it fully charges / discharges. From this result, it can be seen that the electrolytic solution of the present invention using a chain carbonate as an organic solvent is also useful for combining with a composite material of silicon and carbon.

<Nonaqueous electrolyte secondary battery (4)>
Example 4-1
A nonaqueous electrolyte secondary battery of Example 4-1 was manufactured using the above-described electrolytic solution E8.

<Negative electrode>
The negative electrode in the nonaqueous electrolyte secondary battery of Example 4-1 includes a negative electrode active material, a binder, and a conductive additive. 90 parts by mass of lithium titanate (Li ₄ Ti ₅ O ₁₂ , so-called LTO) as a negative electrode active material, 2 parts by mass of SBR as a binder, 2 parts by mass of CMC as a binder, and ketjen black (as a conductive additive) 6 parts by weight of KB) was taken and mixed. This mixture was dispersed in an appropriate amount of ion-exchanged water to prepare a slurry-like negative electrode mixture. This negative electrode mixture was applied to the negative electrode current collector in a film form using a doctor blade. As the negative electrode current collector, a copper foil having a thickness of 20 μm was used. The composite of the negative electrode mixture and the negative electrode current collector was dried and then pressed using a roller press to obtain a bonded product. The bonded product after pressing was heated in a vacuum dryer at 100 ° C. for 6 hours, and cut into a predetermined shape to obtain a negative electrode.

As the positive electrode in the nonaqueous electrolyte secondary battery of Example 4-1, lithium foil (metallic lithium) was used. That is, the nonaqueous electrolyte secondary battery of Example 4-1 is a half cell for evaluation. By charging and discharging the half cell, the effect of the negative electrode and the electrolyte on the battery characteristics of the nonaqueous electrolyte secondary battery can be evaluated.

A non-aqueous electrolyte secondary battery was manufactured using the above negative electrode, positive electrode, and electrolytic solution E8. Specifically, a Whatman glass fiber filter paper having a thickness of 400 μm was sandwiched between the positive electrode and the negative electrode to form an electrode plate group. This electrode group was accommodated in a battery case (CR2032 coin cell manufactured by Hosen Co., Ltd.). An electrolytic solution was further injected into the battery case. After injecting the electrolytic solution, the battery case was sealed to obtain the nonaqueous electrolyte secondary battery of Example 4-1. Details of the nonaqueous electrolyte secondary battery of Example 4-1 and each of the following batteries are shown in Table 44 at the end of the column of the example.

(Example 4-2)
The nonaqueous electrolyte secondary battery of Example 4-2 was manufactured in the same manner as Example 4-1, except that the electrolytic solution E11 was used instead of the electrolytic solution E8.
(Example 4-3)
The nonaqueous electrolyte secondary battery of Example 4-3 was manufactured in the same manner as Example 4-1, except that the electrolytic solution E13 was used instead of the electrolytic solution E8.

(Comparative Example 4-1)
The nonaqueous electrolyte secondary battery of Comparative Example 1 is different from Example 4-1 in the components of the electrolytic solution. In the nonaqueous electrolyte secondary battery of Comparative Example 4-1, the electrolytic solution C5 was used. Other configurations are the same as those of the embodiment 4-1.

(Evaluation Example 23: Energy density and charge / discharge efficiency)
The energy density and charge / discharge efficiency of the nonaqueous electrolyte secondary batteries of Example 4-1 and Comparative Example 4-1 were evaluated by the following methods.

Each non-aqueous electrolyte secondary battery was charged at a rate of 0.1 C and then discharged, and the working electrode capacity (charge capacity and discharge capacity) was measured. FIG. 61 shows the charge / discharge curve (second cycle) of the nonaqueous electrolyte secondary battery of Example 4-1, and FIG. 62 shows the charge / discharge curve (second cycle) of the half cell of Comparative Example 4-1. Based on the charge / discharge curves shown in FIG. 61 and FIG. 62, assuming that a positive electrode having an average voltage of 4 V was used as the counter electrode, discharge of the nonaqueous electrolyte secondary batteries of Example 4-1 and Comparative Example 4-1 The energy density at the time (mWh / g) and the charge / discharge efficiency (%) were calculated. The energy density is a density per 1 g of the negative electrode active material layer (that is, solid mass of LTO, binder, etc.). Furthermore, the charge / discharge efficiency was calculated based on (energy density during discharge / energy density during charge) × 100 (%).

Table 20 shows the energy density and charge / discharge efficiency of the nonaqueous electrolyte secondary batteries of Example 4-1 and Comparative Example 4-1. Charge / discharge efficiency can also be rephrased as energy efficiency.

The non-aqueous electrolyte secondary batteries of Example 4-1 and Comparative Example 4-1 using lithium titanium oxide (LTO) as the negative electrode active material differ only in the electrolyte solution. As shown in Table 20, the energy density and the charge / discharge efficiency vary greatly depending on the electrolyte. Specifically, the non-aqueous electrolyte secondary battery of Example 4-1 using the electrolytic solution of the present invention has a higher energy than the non-aqueous electrolyte secondary battery of Comparative Example 4-1 using a normal electrolytic solution. High density and excellent charge / discharge efficiency. As shown in FIGS. 61 and 62, when the current is passed at the same rate, the magnitude of polarization in the nonaqueous electrolyte secondary battery of Example 4-1 is the same as that of the nonaqueous electrolyte 2 of Comparative Example 4-1. It is smaller than the magnitude of polarization in the secondary battery. Therefore, it is considered that the nonaqueous electrolyte secondary battery of Example 4-1 is superior in energy density and charge / discharge efficiency as compared with the nonaqueous electrolyte secondary battery of Comparative Example 4-1. In addition, the electrolyte solution of the present invention used in the nonaqueous electrolyte secondary battery of Example 4-1 contains a large amount of cation of the supporting salt. In the nonaqueous electrolyte secondary battery of Example 4-1, It is presumed that since the cation is sufficiently supplied to the negative electrode, the reaction resistance is lowered and the polarization is suppressed.

Note that the non-aqueous electrolyte secondary battery of Example 4-1 uses lithium titanium oxide as the negative electrode active material. For this reason, the non-aqueous electrolyte secondary battery of Example 4-1 is provided with excellent cycle characteristics derived from lithium titanium oxide.

Further, with respect to the non-aqueous electrolyte secondary battery of Example 4-2 and the non-aqueous electrolyte secondary battery of Example 4-3, the working voltage range was 1.3 V to 2.5 V (Li standard), and the C rate was 0.1 C. CC charging / discharging was repeated 3 cycles. The charge / discharge curve of the nonaqueous electrolyte secondary battery of Example 4-2 is shown in FIG. 63, and the charge / discharge curve of the nonaqueous electrolyte secondary battery of Example 4-3 is shown in FIG. As shown in FIGS. 63 and 64, when a negative electrode using LTO as a negative electrode active material is combined with the electrolytic solution of the present invention using a chain carbonate, that is, DMC, a reversible charge / discharge reaction is obtained. It was. That is, from this result, it can be seen that the combination of the negative electrode active material and the electrolytic solution can be applied to the nonaqueous electrolyte secondary battery of the present invention.

<Nonaqueous electrolyte secondary battery (5)>
Example 5-1
A nonaqueous electrolyte secondary battery of Example 5-1 was produced using the electrolytic solution E8.

<Negative electrode>
98 parts by mass of Ito Graphite Industries Co., Ltd. product name SG-BH8 (average particle size 8 μm), and 1 part by mass of SBR and 1 part by mass of CMC as a binder were mixed. This mixture was dispersed in an appropriate amount of ion-exchanged water to prepare a slurry. The graphite particles used had an aspect ratio of 2.1, and I (110) / I (004) measured by X-ray diffraction was 0.035.

The aspect ratio was calculated by measuring the major axis and the minor axis of the active material section using a scanning electron microscope (SEM) after preparing an electrode section observation sample using a JEOL cross section polisher. X-ray diffraction was measured by Rigaku [SmartLab], using an optical system using a concentration method, and I (110) / I (004) was calculated from the ratio of integrated intensities of I (110) and I (004). .

The slurry was applied in the form of a film using a doctor blade on the surface of an electrolytic copper foil (current collector) having a thickness of 20 μm. The copper foil coated with the slurry was dried to remove water, and then the copper foil was pressed to obtain a bonded product.

The obtained joined product was dried by heating at 100 ° C. for 6 hours with a vacuum dryer to obtain a copper foil on which a negative electrode active material layer was formed. This was used as a negative electrode. The basis weight of the negative electrode active material layer in this negative electrode was about 8.5 mg / cm ² .

<Positive electrode>
The positive electrode includes a positive electrode active material layer and a current collector covered with the positive electrode active material layer. The positive electrode active material layer has a positive electrode active material, a binder, and a conductive additive. The positive electrode active material is NCM523. The binder is made of PVdF. The conductive auxiliary agent is made of AB. The current collector is made of an aluminum foil having a thickness of 20 μm. When the positive electrode active material layer is 100 parts by mass, the mass ratio of the positive electrode active material, the binder, and the conductive additive is 94: 3: 3.

<Nonaqueous electrolyte secondary battery>
Using the positive electrode, the negative electrode, and the electrolytic solution E8, a laminated lithium ion secondary battery, which is a kind of non-aqueous electrolyte secondary battery, was manufactured. Specifically, a cellulose nonwoven fabric (thickness 20 μm) was sandwiched as a separator between the positive electrode and the negative electrode to form an electrode plate group. The electrode plate group was covered with a set of two laminated films, and the three sides were sealed, and then the electrolyte solution was poured into the bag-like laminated film. Thereafter, the remaining one side was sealed to obtain a laminate type lithium ion secondary battery in which the four sides were hermetically sealed and the electrode plate group and the electrolyte were sealed. Note that the positive electrode and the negative electrode have a tab that can be electrically connected to the outside, and a part of the tab extends to the outside of the laminated lithium ion secondary battery. Hereinafter, for convenience, this lithium ion secondary battery is referred to as the nonaqueous electrolyte secondary battery of Example 5-1. Details of the non-aqueous electrolyte secondary battery of Example 5-1 and each of the following batteries are shown in Table 45 at the end of the column of the example.

(Comparative Example 5-1)
A negative electrode was produced in the same manner as in Example 5-1, except that graphite having an aspect ratio of 6.5 (SNO grade (average particle size: 10 μm) from SEC Carbon Co., Ltd.) was used as the active material. A negative electrode having the same basis weight as in Example 5-1 was formed. Other than that, a nonaqueous electrolyte secondary battery of Comparative Example 5-1 was obtained in the same manner as Example 5-1. I (110) / I (004) measured by X-ray diffraction was 0.027.

(Comparative Example 5-2)
A nonaqueous electrolyte secondary battery of Comparative Example 5-2 was obtained in the same manner as in Example 5-1, except that the electrolytic solution C5 was used instead of the electrolytic solution E8.

(Evaluation Example 24: Input characteristics)
Using the nonaqueous electrolyte secondary batteries of Example 5-1, Comparative Example 5-1, and Comparative Example 5-2, the input (charging) characteristics were evaluated under the following conditions.
(1) Working voltage range: 3V-4.2V
(2) Capacity: 13.5mAh
(3) SOC 80%
(4) Temperature: 0 ° C, 25 ° C
(5) Number of measurements: 3 times each

Evaluation conditions are 80% charged state (SOC), 0 ° C., 25 ° C., operating voltage range 3V-4.2V, and capacity 13.5 mAh. SOC 80%, 0 ° C. is a region in which input characteristics are difficult to be obtained, for example, when used in a refrigerator room. The input characteristics of Example 5-1 and Comparative Examples 5-1 and 5-2 were evaluated three times for 2-second input and 5-second input, respectively. Tables 21 and 22 show the evaluation results of the input characteristics. “2-second input” in the table means an input after 2 seconds from the start of charging, and “5-second input” means an input after 5 seconds from the start of charging.

In Table 21 and Table 22, the electrolytic solution of the present invention used in Example 5-1 and Comparative Example 5-1 is abbreviated as “FSA”, and the electrolytic solution used in Comparative Example 5-2 is designated as “ECPF”. Abbreviated.

At both 0 ° C. and 25 ° C., the input / output characteristics of Example 5-1 are improved compared to Comparative Example 5-1 and Comparative Example 5-2. This is an effect obtained by using graphite having a predetermined aspect ratio and the electrolytic solution of the present invention. In particular, since it exhibits high input / output characteristics even at 0 ° C., the migration of lithium ions in the electrolytic solution can be achieved even at low temperatures. It has been shown to proceed smoothly.

(Example 5-2)
<Positive electrode>
The positive electrode includes a positive electrode active material layer and a current collector covered with the positive electrode active material layer. The positive electrode active material layer has a positive electrode active material, a binder, and a conductive additive. The positive electrode active material is NCM523. The binder is made of PVdF. The conductive auxiliary agent is made of AB. The current collector is made of an aluminum foil having a thickness of 20 μm. When the positive electrode active material layer is 100 parts by mass, the mass ratio of the positive electrode active material, the binder, and the conductive additive is 94: 3: 3.

In order to produce a positive electrode, NCM523, PVdF and AB were mixed at the above mass ratio, and NMP as a solvent was added to obtain a paste-like positive electrode mixture. The paste-like positive electrode mixture was applied to the surface of the current collector using a doctor blade to form a positive electrode active material layer. The positive electrode active material layer was dried at 80 ° C. for 20 minutes to remove NMP by volatilization. The aluminum foil having the positive electrode active material layer formed on the surface thereof was compressed using a roll press, and the aluminum foil and the positive electrode active material layer were firmly bonded. The joined product was heated in a vacuum dryer at 120 ° C. for 6 hours, cut into a predetermined shape, and a positive electrode was obtained.

<Negative electrode>
The negative electrode includes a negative electrode active material layer and a current collector covered with the negative electrode active material layer. The negative electrode active material layer has a negative electrode active material and a binder. In order to produce a negative electrode, 98 parts by mass of graphite as a negative electrode active material and 1 part by mass of SBR and 1 part by mass of CMC were mixed as a binder. This mixture was dispersed in an appropriate amount of ion-exchanged water to prepare a slurry-like negative electrode mixture. The slurry-like negative electrode mixture was applied to a copper foil having a thickness of 20 μm, which is a negative electrode current collector, so as to form a film using a doctor blade to form a negative electrode active material layer. The composite material of the negative electrode active material layer and the current collector was dried and pressed, and the bonded product after pressing was heated in a vacuum dryer at 100 ° C. for 6 hours, cut into a predetermined shape, and used as a negative electrode.

The graphite particles used had an aspect ratio of 2.1.

<Nonaqueous electrolyte secondary battery>
A nonaqueous electrolyte secondary battery of Example 5-2 was obtained in the same manner as in Example 5-1, except that the above positive electrode and negative electrode were used and the above-described electrolytic solution E11 was used as the electrolytic solution.

(Comparative Example 5-3)
A nonaqueous electrolyte secondary battery of Comparative Example 5-3 was obtained in the same manner as in Example 5-2 except that the electrolytic solution C5 was used instead of the electrolytic solution E11.

(Evaluation Example 25: Cycle durability)
Using the non-aqueous electrolyte secondary batteries of Example 5-2 and Comparative Example 5-3, the battery was charged to 4.1 V under the conditions of CC charging at a temperature of 25 ° C. and 1 C, and after resting for 1 minute, the CC of 1 C A cycle test was conducted by repeating 500 cycles of discharging to 3.0 V and resting for 1 minute. The discharge capacity retention ratio at the 500th cycle was measured, and the results are shown in Table 23. The discharge capacity retention ratio is a value obtained as a percentage of the value obtained by dividing the discharge capacity at the 500th cycle by the initial discharge capacity ((discharge capacity at the 500th cycle) / (initial discharge capacity) × 100). FIG. 65 shows the change in the discharge capacity retention rate during the cycle test.

In addition, at the initial stage and the 200th cycle, after adjusting the voltage to 3.5 V with a CCCV of 25 ° C. and 0.5 C, the amount of voltage change when the CC discharge was performed for 10 seconds at 3 C (the voltage before discharge and the discharge for 10 seconds) The DC resistance (discharge) was measured from the difference between the post-voltage and the current value according to Ohm's law.

Furthermore, at the initial stage and the 200th cycle, after adjusting the voltage to 3.5 V with a CCCV of 25 ° C. and 0.5 C, the amount of voltage change when the CC charge is performed for 10 seconds at 3 C (the pre-charge voltage and the charge 10 seconds) The DC resistance (charging) was measured from Ohm's law from the difference between the post-voltage and the current value. The results are shown in Table 23.

It can be seen that the non-aqueous electrolyte secondary battery of Example 5-2 has a low resistance even after cycling. In addition, it can be said that the nonaqueous electrolyte secondary battery of Example 5-2 has a high capacity retention rate and is hardly deteriorated.

(Other aspects I)
Hereinafter, other embodiments that the nonaqueous electrolyte secondary battery of the present invention can take will be described in more detail with reference to test examples and reference test examples. Hereinafter, the non-aqueous electrolyte secondary battery of the test example is EB, and the non-aqueous electrolyte secondary battery of the reference test example is CB. The difference between EB and CB lies in the electrolytic solution, and EB uses the electrolytic solution of the present invention.
As described above, a film (S, O-containing film) is formed on the negative electrode of the nonaqueous electrolyte secondary battery using the electrolytic solution of the present invention. For reference, the analysis results of the S, O-containing coating are listed below. The following nonaqueous electrolyte secondary batteries include those described above.

(EB1)
A nonaqueous electrolyte secondary battery EB1 using the electrolytic solution E8 was produced as follows. The positive electrode was produced in the same manner as the positive electrode of the non-aqueous electrolyte secondary battery in Example 5-1, and the negative electrode was produced in the same manner as the negative electrode in the non-aqueous electrolyte secondary battery in Example 5-2. In addition, a nonaqueous electrolyte secondary battery EB1 was obtained in the same manner as in Example 5-1, except that experimental filter paper (Toyo Filter Paper Co., Ltd., cellulose, thickness: 260 μm) was used as the separator.

(EB2)
The nonaqueous electrolyte secondary battery EB2 is the same as EB1 except that the electrolytic solution E4 is used.

(EB3)
The nonaqueous electrolyte secondary battery EB3 is the same as EB1 except that the electrolytic solution E11 is used.

(EB4)
The nonaqueous electrolyte secondary battery EB4 is the same as EB1 except that the electrolytic solution E11 is used, the mixing ratio of the positive electrode active material, the conductive additive and the binder, and the separator. About the positive electrode, it was set as NCM523: AB: PVdF = 90: 8: 2. The basis weight of the active material layer in the positive electrode was 5.5 mg / cm ² and the density was 2.5 g / cm ³ . The same applies to the following EB5 to EB7, CB2 and CB3.
The negative electrode was natural graphite: SBR: CMC = 98: 1: 1. The basis weight of the active material layer in the negative electrode was 3.8 mg / cm ² , and the density was 1.1 g / cm ³ . The same applies to the following EB5 to EB7, CB2 and CB3. A cellulose nonwoven fabric with a thickness of 20 μm was used as the separator.

(EB5)
The nonaqueous electrolyte secondary battery EB5 is the same as EB4 except that the electrolytic solution E8 is used.

(EB6)
In the nonaqueous electrolyte secondary battery EB6, the type of the binder for the negative electrode and the mixing ratio of the negative electrode active material and the binder are the same as those of EB4. The negative electrode was natural graphite: polyacrylic acid (PAA) = 90: 10.

(EB7)
The nonaqueous electrolyte secondary battery EB7 is the same as EB6 except that the electrolytic solution E8 is used.

(CB1)
The nonaqueous electrolyte secondary battery CB1 is the same as EB1 except that the electrolytic solution C5 is used.

(CB2)
The nonaqueous electrolyte secondary battery CB2 is the same as EB4 except that the electrolytic solution C5 is used.

(CB3)
The nonaqueous electrolyte secondary battery CB3 is the same as EB6 except that the electrolytic solution C5 is used.

(Evaluation Example 26: Analysis of S, O-containing film)
Hereinafter, the film formed on the negative electrode surface of EB1 to EB7 is abbreviated as the negative electrode S, O-containing film of EB1 to EB7, and the film formed on the negative electrode surface of CB1 to CB3 is referred to as CB1 to CB3. Abbreviated as CB3 negative electrode film. Similarly, the film formed on the surface of the positive electrode in EB1 to EB7 is abbreviated as the film containing the positive electrode S, O of EB1 to EB7, and the film formed on the surface of the positive electrode in CB1 to CB3 is made of CB1 to CB3. Abbreviated as positive electrode film.

(Analysis of negative electrode S, O-containing film and negative electrode film)
For EB1, EB2, and CB1, after repeating 100 cycles of charge and discharge, analysis of the S, O-containing film or film surface was performed by X-ray photoelectron spectroscopy (XPS) in a discharge state of voltage 3.0V. went. The following processing was performed as preprocessing. First, each non-aqueous electrolyte secondary battery was disassembled, the negative electrode was taken out, this negative electrode was washed and dried, and a negative electrode to be analyzed was obtained. Washing was performed 3 times using DMC (dimethyl carbonate). In addition, all steps from disassembling the cell to conveying the negative electrode as the analysis target to the analyzer were performed in an Ar gas atmosphere without exposing the negative electrode to the atmosphere. The following pretreatment was performed for each of EB1, EB2, and CB1, and the obtained negative electrode specimen was subjected to XPS analysis. As the apparatus, ULVAC-PHI PHI5000 VersaProbeII was used. The X-ray source was monochromatic AlKα radiation (15 kV, 10 mA). The analysis results of the negative electrode S, O-containing film of EB1 and EB2 and the negative electrode film of CB1 measured by XPS are shown in FIGS. Specifically, FIG. 66 shows the analysis result for carbon element, FIG. 67 shows the analysis result for fluorine element, FIG. 68 shows the analysis result for nitrogen element, and FIG. 69 shows the analysis result for oxygen element. FIG. 70 shows the result of analysis for elemental sulfur.

The electrolytic solution in EB1 and the electrolytic solution in EB2 contain sulfur element (S), oxygen element and nitrogen element (N) in the salt. On the other hand, the electrolyte solution in CB1 does not contain these in the salt. Furthermore, the electrolyte solutions in EB1, EB2, and CB1 all contain a fluorine element (F), a carbon element (C), and an oxygen element (O) in the salt.

As shown in FIGS. 66 to 70, as a result of analyzing the negative electrode S, O-containing film of EB1 and the negative electrode S, O-containing film of EB2, a peak indicating the presence of S (FIG. 70) and a peak indicating the presence of N ( FIG. 68) was observed. That is, the negative electrode S, O-containing film of EB1 and the negative electrode S, O-containing film of EB2 contained S and N. However, these peaks were not confirmed in the analysis results of the negative electrode film of CB1. That is, the negative electrode film of CB1 did not contain an amount exceeding the detection limit for both S and N. Note that peaks indicating the presence of F, C, and O were observed in all analysis results of the negative electrode S, O-containing films of EB1 and EB2 and the negative electrode film of CB1. That is, the negative electrode S, O-containing film of EB1 and EB2 and the negative electrode film of CB1 all contained F, C, and O.

These elements are all components derived from the electrolytic solution. In particular, S, O and F are components contained in the metal salt of the electrolytic solution, specifically, components contained in the chemical structure of the anion of the metal salt. Therefore, it can be seen from these results that each of the negative electrode S, O-containing film and the negative electrode film contains a component derived from the chemical structure of the anion of the metal salt (that is, the supporting salt).
The analysis result of elemental sulfur (S) shown in FIG. 70 was analyzed in more detail. About the analysis result of EB1 and EB2, peak separation was performed using the Gauss / Lorentz mixed function. 71 shows the analysis result of EB1, and FIG. 72 shows the analysis result of EB2.

As shown in FIGS. 71 and 72, as a result of analyzing the negative electrode S, O-containing films of EB1 and EB2, a relatively large peak (waveform) was observed in the vicinity of 165 to 175 eV. As shown in FIGS. 71 and 72, the peak (waveform) near 170 eV was separated into four peaks. One of them is a peak around 170 eV indicating the presence of SO ₂ (S═O structure). From this result, it can be said that the S, O-containing film formed on the negative electrode surface in the nonaqueous electrolyte secondary battery of the present invention has an S = O structure. In consideration of this result and the above XPS analysis result, it is presumed that S contained in the S═O structure of the S, O-containing coating is S contained in the chemical structure of the metal salt, that is, the anion of the supporting salt.

(S element ratio of negative electrode S, O-containing coating)
Based on the XPS analysis results of the negative electrode S and O-containing coating described above, the ratio of the S element during discharge in the negative electrode S and O-containing coating of EB1 and EB2 and the negative electrode coating of CB1 was calculated. Specifically, for each negative electrode S, O-containing film and negative electrode film, the element ratio of S was calculated when the sum of the peak intensities of S, N, F, C, and O was 100%. The results are shown in Table 24.

As described above, the negative electrode film of CB1 did not contain S exceeding the detection limit, but S was detected from the negative electrode S, O-containing film of EB1 and the negative electrode S, O-containing film of EB2. Further, the negative electrode S, O-containing film of EB1 contained more S than the negative electrode S, O-containing film of EB2. Since S was not detected from the negative electrode S, O-containing film of CB1, S contained in the negative electrode S, O-containing film of each test example was derived from inevitable impurities and other additives contained in the positive electrode active material. It can be said that it originates from the metal salt in the electrolyte solution.

Further, since the S element ratio in the negative electrode S, O-containing film of EB1 is 10.4 atomic% and the S element ratio in the negative electrode S, O-containing film of EB2 is 3.7 atomic%, In the water electrolyte secondary battery, the S element ratio in the negative electrode S, O-containing film is 2.0 atomic% or more, preferably 2.5 atomic% or more, more preferably 3.0 atomic% or more, More preferably, it is 3.5 atomic% or more. The elemental ratio (atomic%) of S indicates the peak intensity ratio of S when the sum of the peak intensities of S, N, F, C, and O is 100% as described above. The upper limit value of the element ratio of S is not particularly defined, but to be strong, it should be 25 atomic% or less.

(Thickness of negative electrode S, O-containing film)
About EB1, the thing which was made into the discharge state of voltage 3.0V after repeating 100 cycles charging / discharging, and the thing made into the charge state of voltage 4.1V after repeating 100 cycles charging / discharging are prepared, and said XPS analysis A negative electrode specimen to be analyzed was obtained in the same manner as in the pretreatment. The obtained negative electrode specimen was processed by FIB (Focused Ion Beam) to obtain a specimen for STEM analysis having a thickness of about 100 nm. In addition, Pt was vapor-deposited on the negative electrode as a pretreatment for FIB processing. The above steps were performed without exposing the negative electrode to the atmosphere.

Each STEM analysis specimen was analyzed by STEM (Scanning Transmission Electron Microscope) with an EDX (Energy Dispersive X-ray spectroscopy) apparatus. The results are shown in FIGS. 73 is a BF (Bright-field) -STEM image, and FIGS. 74 to 76 are element distribution images by STEM-EDX in the same observation region as FIG. 74 shows the analysis result for C, FIG. 75 shows the analysis result for O, and FIG. 76 shows the analysis result for S. 74 to 76 show the analysis results of the negative electrode in the discharged nonaqueous electrolyte secondary battery.

As shown in FIG. 73, there is a black portion in the upper left part of the STEM image. This black part is derived from Pt deposited in the pretreatment of FIB processing. In each STEM image, a portion above the Pt-derived portion (referred to as a Pt portion) can be regarded as a contaminated portion after Pt deposition. Therefore, in FIGS. 74 to 76, only the portion below the Pt portion was examined.

As shown in FIG. 74, C was layered below the Pt portion. This is considered to be a layered structure of graphite as a negative electrode active material. In FIG. 75, O exists in the part corresponding to the outer periphery and interlayer of graphite. Also in FIG. 76, S exists in the part corresponding to the outer periphery and interlayer of graphite. From these results, it is surmised that the negative electrode S, O-containing film containing S and O, such as the S═O structure, is formed between the surface and the interlayer of graphite.

Ten negative electrode S, O-containing films formed on the surface of graphite were randomly selected, the thickness of the negative electrode S, O-containing film was measured, and the average value of the measured values was calculated. The negative electrode in the charged nonaqueous electrolyte secondary battery was analyzed in the same manner, and the average value of the thicknesses of the negative electrode S and O-containing coating formed on the surface of the graphite was calculated based on each analysis result. The results are shown in Table 25.

As shown in Table 25, the thickness of the negative electrode S, O-containing film increases after charging. From this result, it is presumed that the negative electrode S, O-containing film has a fixing portion that stably exists with respect to charging and discharging and an adsorption portion that increases and decreases with charging and discharging. And it is estimated that the thickness of the negative electrode S, O-containing film increased or decreased during charging / discharging due to the presence of the adsorbing portion.

(Analysis of positive electrode film)
For EB1, after 3 cycles of charge / discharge, a voltage of 3.0V was discharged, after 3 cycles of charge / discharge was repeated, a voltage of 4.1V was charged, after 100 cycles of charge / discharge was repeated Four were prepared: a 3.0V discharge state and a 100V charge state after repeated charge and discharge for 100 cycles. Using the same method as described above for each of the four EB1, positive electrodes to be analyzed were obtained. Then, each obtained positive electrode was analyzed by XPS. The results are shown in FIGS. 77 and 78. Note that FIG. 77 shows the analysis results for the oxygen element, and FIG. 78 shows the analysis results for the sulfur element.

77 and 78, it can be seen that the positive electrode S, O-containing film of EB1 also contains S and O. In addition, since a peak near 170 eV is recognized in FIG. 78, the positive electrode S, O-containing film of EB1 also has an S═O structure derived from the electrolytic solution of the present invention, like the negative electrode S, O-containing film of EB1. I understand that.

By the way, as shown in FIG. 77, the height of the peak existing in the vicinity of 529 eV decreases after the cycle. This peak is considered to indicate the presence of O derived from the positive electrode active material. Specifically, in XPS analysis, photoelectrons excited by O atoms in the positive electrode active material pass through the S, O-containing coating and are detected. It is thought that it was done. Since this peak decreased after the cycle, it is considered that the thickness of the S, O-containing film formed on the positive electrode surface increased with the cycle.

In addition, as shown in FIGS. 77 and 78, O and S in the positive electrode S and O-containing film increased during discharging and decreased during charging. From this result, it is considered that O and S enter and leave the positive electrode S and O-containing film with charge and discharge. From this fact, the concentration of S and O in the positive electrode S and O-containing coating is increased or decreased during charging or discharging, or the presence of an adsorbing portion in the positive electrode S and O-containing coating as well as the negative electrode S and O-containing coating. It is estimated that the thickness increases or decreases.

Further, for EB4, the positive electrode S, O-containing coating and the negative electrode S, O-containing coating were analyzed by XPS.
EB4 was set to 25 ° C. and a working voltage range of 3.0 V to 4.1 V, and CC charge / discharge was repeated 500 cycles at a rate of 1C. After 500 cycles, the XPS spectrum of the positive electrode S, O-containing film was measured in a discharge state of 3.0 V and a charge state of 4.0 V. Further, the negative electrode S, O-containing coating in the 3.0V discharge state before the cycle test (that is, after the first charge / discharge) and the negative electrode S, O-containing coating in the 3.0V discharge state after 500 cycles are measured by XPS. Elemental analysis was performed, and the S element ratio contained in the negative electrode S, O-containing film was calculated. FIG. 79 and FIG. 80 show the analysis results of the positive electrode S, O-containing film of EB4 measured by XPS. Specifically, FIG. 79 shows the analysis result for sulfur element, and FIG. 80 shows the analysis result for oxygen element. Table 26 shows the S element ratio (atomic%) of the negative electrode S, O-containing coating. The S element ratio was calculated in the same manner as the above-mentioned item “S element ratio of negative electrode S, O-containing film”.

As shown in FIGS. 79 and 80, a peak indicating the presence of S and a peak indicating the presence of O were also detected from the positive electrode S, O-containing film in EB4. In addition, both the S peak and the O peak increased during discharging and decreased during charging. This result also confirms that the positive electrode S, O-containing film has an S = O structure, and O and S in the positive electrode S, O-containing film enter and exit the positive electrode S, O-containing film with charge and discharge. .

As shown in Table 26, the negative electrode S, O-containing film of EB4 contained 2.0 atomic% or more of S even after the first charge / discharge and after 500 cycles. From this result, it can be seen that the negative electrode S, O-containing film in the nonaqueous electrolyte secondary battery of the present invention contains 2.0 atomic% or more of S before or after the cycle.

EB4 to EB7 and CB2 and CB3 were subjected to a high temperature storage test that was stored at 60 ° C. for 1 week. After the high temperature storage test, the positive electrode S, O-containing film and negative electrode S, O-containing film of EB4 to EB7, and CB2, CB3 The positive electrode film and the negative electrode film were analyzed. Before starting the high temperature storage test, CC-CV charging was performed at a rate of 0.33 C from 3.0 V to 4.1 V. The charge capacity at this time was set as a standard (SOC100), 20% of the standard was CC discharged and adjusted to SOC80, and then a high-temperature storage test was started. After the high temperature storage test, CC-CV discharge was performed to 3.0V at 1C. And the XPS spectrum of the positive electrode S, O containing film | membrane and negative electrode S, O containing film | membrane after a discharge and a positive electrode film | membrane and a negative electrode film | membrane was measured. 81 to 84 show the analysis results of the positive electrode S, O-containing films of EB4 to EB7 and the positive electrode films of CB2 and CB3 measured by XPS. 85 to 88 show the analysis results of the EB4 to EB7 negative electrode S, O-containing films and the CB2 and CB3 negative electrode films measured by XPS.

Specifically, FIG. 81 shows the analysis results for the elemental sulfur in the positive electrode S, O-containing coatings of EB4 and EB5 and the positive electrode coating of CB2. FIG. 82 shows the analysis results of the elemental sulfur of the positive electrode S, O-containing film of EB6 and EB7 and the positive electrode film of CB3. FIG. 83 shows the analysis results of oxygen elements in the positive electrode S, O-containing film of EB4 and EB5 and the positive electrode film of CB2. FIG. 84 shows analysis results of oxygen elements in the positive electrode S, O-containing films of EB6 and EB7 and the positive electrode film of CB3. FIG. 85 shows the analysis results of sulfur elements in the negative electrode S, O-containing films of EB4 and EB5 and the negative electrode film of CB2. FIG. 86 shows the analysis results of sulfur elements in the negative electrode S, O-containing films of EB6 and EB7 and the negative electrode film of CB3. FIG. 87 shows the results of analysis of oxygen elements in the negative electrode S, O-containing films of EB4 and EB5 and the negative electrode film of CB2. FIG. 88 shows the analysis results of oxygen elements in the negative electrode S, O-containing films of EB6 and EB7 and the negative electrode film of CB3.

As shown in FIGS. 81 and 82, CB2 and CB3 using the conventional electrolytic solution do not contain S in the positive electrode film, whereas EB4 to EB7 using the electrolytic solution of the present invention contain positive electrodes S and O. The film contained S. Further, as shown in FIGS. 83 and 84, EB4 to EB7 all contained O in the positive electrode S, O-containing coating. Further, as shown in FIGS. 81 and 82, a peak around 170 eV indicating the presence of SO ₂ (S═O structure) was detected from the positive electrode S, O-containing films in EB4 to EB7. From these results, in the non-aqueous electrolyte secondary battery of the present invention, a stable positive electrode S containing S and O is used both when AN is used as the organic solvent for the electrolytic solution and when DMC is used. It can be seen that an O-containing film is formed. Moreover, since this positive electrode S, O containing film is not influenced by the kind of negative electrode binder, it is thought that O in the positive electrode S, O containing film does not originate in CMC. Further, as shown in FIGS. 83 and 84, when DMC was used as the organic solvent for the electrolyte, an O peak derived from the positive electrode active material was detected in the vicinity of 530 eV. For this reason, when DMC is used as the organic solvent for the electrolytic solution, it is considered that the thickness of the positive electrode S, O-containing film is thinner than when AN is used.

Similarly, as shown in FIGS. 85 to 88, CB2 and CB3 using the conventional electrolytic solution do not contain S in the negative electrode film, whereas EB4 to EB7 using the electrolytic solution of the present invention are negative electrode S. The O-containing film contained S and O. As shown in FIGS. 85 and 86, a peak around 170 eV indicating the presence of SO ₂ (S═O structure) was detected from the negative electrode S, O-containing films in EB4 to EB7. From these results, in the non-aqueous electrolyte secondary battery of the present invention, a stable negative electrode S containing S and O, both when AN is used as the organic solvent for the electrolytic solution and when DMC is used. It can be seen that an O-containing film is formed.

For EB4, EB5, and CB2, the XPS spectra of the negative electrode S, O-containing film and the negative electrode film after the above high-temperature storage test and discharge were measured, and the discharge in the negative electrode S, O-containing film of EB4, EB5 and the negative electrode film of CB2 The ratio of S element at the time was calculated. Specifically, for each negative electrode S, O-containing film or negative electrode film, the element ratio of S was calculated when the sum of the peak intensities of S, N, F, C, and O was 100%. The results are shown in Table 27.

As shown in Table 27, the negative electrode film of CB2 did not contain S exceeding the detection limit, but S was detected from the negative electrode S, O-containing films of EB4 and EB5. Further, the negative electrode S, O-containing film of EB5 contained more S than the negative electrode S, O-containing film of EB4. Further, from this result, it is understood that the S element ratio in the negative electrode S, O-containing film is 2.0 atomic% or more even after high temperature storage.

(EB8)
EB8 uses the electrolytic solution E11. EB8 is the same as the nonaqueous electrolyte secondary battery of Example 5-1, except for the composition of the negative electrode mixture, the mixing ratio of the negative electrode active material and the conductive additive, the separator, and the electrolytic solution. About the positive electrode, it was set as NCM523: AB: PVdF = 90: 8: 2.

(EB9)
EB9 uses the electrolytic solution E13. EB9 is the same as EB8 except for the electrolytic solution.

(EB10)
EB10 is the same as EB8 except that electrolytic solution E8 is used.

(CB4)
CB4 is the same as EB8 except that electrolytic solution C5 is used.

(Evaluation Example 27: Internal resistance of battery)
Using EB8, EB9, EB10 and CB4, the internal resistance of the battery was evaluated.

For each non-aqueous electrolyte secondary battery, CC charging / discharging (that is, constant current charging / discharging) was repeated at room temperature in the range of 3.0 V to 4.1 V (vs. Li standard). Then, the AC impedance after the first charge / discharge and the AC impedance after 100 cycles were measured. Based on the obtained complex impedance plane plot, the reaction resistances of the electrolytic solution, the negative electrode, and the positive electrode were each analyzed. As shown in FIG. 89, two circular arcs were seen in the complex impedance plane plot. The arc on the left side of the figure (that is, the side where the real part of the complex impedance is small) is called the first arc. The arc on the right side in the figure is called the second arc. The reaction resistance of the negative electrode was analyzed based on the size of the first arc, and the reaction resistance of the positive electrode was analyzed based on the size of the second arc. The resistance of the electrolytic solution was analyzed based on the leftmost plot in FIG. 89 continuous with the first arc. The analysis results are shown in Table 28 and Table 29. Table 28 shows the resistance (so-called solution resistance) of the electrolytic solution after the first charge / discharge, the reaction resistance of the negative electrode, and the reaction resistance of the positive electrode, and Table 29 shows each resistance after 100 cycles.

As shown in Table 28 and Table 29, in each non-aqueous electrolyte secondary battery, the negative electrode reaction resistance and the positive electrode reaction resistance after 100 cycles tend to be lower than the respective resistances after the first charge / discharge.

Further, each non-aqueous electrolyte secondary battery has a difference in durability even though the same polymer (CMC-SBR) having a hydrophilic group is used as a binder for the negative electrode. That is, after 100 cycles shown in Table 29, the negative electrode reaction resistance and the positive electrode reaction resistance of the nonaqueous electrolyte secondary batteries of EB8, EB9, and EB10 are the negative electrode reaction resistance and the positive electrode reaction resistance of the nonaqueous electrolyte secondary battery of CB4. Low compared to This is because the non-aqueous electrolyte secondary battery of CB4 did not use the electrolytic solution of the present invention, whereas the non-aqueous electrolyte secondary batteries of EB8, EB9, and EB10 used the electrolytic solution of the present invention. It is thought to be caused by. That is, it can be said that the nonaqueous electrolyte secondary battery of the present invention using the electrolytic solution of the present invention is excellent in durability because the reaction resistance is reduced after the cycle.

Furthermore, EB8, EB9, and EB10 use the electrolytic solution of the present invention, and S and O-containing films derived from the electrolytic solution of the present invention are formed on the surfaces of the negative electrode and the positive electrode. On the other hand, in CB4 which does not use the electrolytic solution of the present invention, the S, O-containing film is not formed on the surfaces of the negative electrode and the positive electrode. And as shown in Table 29, the negative electrode reaction resistance and the positive electrode reaction resistance of EB8, EB9, and EB10 are lower than CB4. From this, in each test example, it is guessed that the negative electrode reaction resistance and the positive electrode reaction resistance were reduced due to the presence of the S, O-containing film derived from the electrolytic solution of the present invention.

In addition, the solution resistance of the electrolyte solution in EB10 and CB4 is substantially the same, and the solution resistance of the electrolyte solution in EB8 and EB9 is higher than that of EB10 and CB4. The solution resistance of each electrolyte solution in each non-aqueous electrolyte secondary battery is substantially the same after the first charge / discharge and after 100 cycles. For this reason, it is considered that durability deterioration of each electrolyte solution does not occur, and the difference between the negative electrode reaction resistance and the positive electrode reaction resistance generated in the above reference test examples and test examples is not related to the durability deterioration of the electrolyte solution. It is thought that this occurs in the electrode itself.

The internal resistance of the non-aqueous electrolyte secondary battery can be comprehensively determined from the solution resistance of the electrolytic solution, the reaction resistance of the negative electrode, and the reaction resistance of the positive electrode. Based on the results of Table 28 and Table 29, it can be said that EB8 and EB9 are particularly excellent in durability, and then EB10 is excellent in durability from the viewpoint of suppressing the increase in internal resistance of the nonaqueous electrolyte secondary battery. .

(Evaluation Example 28: Battery cycle durability)
For EB8, EB9, EB10, and CB4, CC charge / discharge was repeated at room temperature in the range of 3.0 V to 4.1 V (vs. Li standard), the discharge capacity at the first charge / discharge, the discharge capacity at 100 cycles, and 500 The discharge capacity during the cycle was measured. And the capacity | capacitance maintenance factor (%) of each nonaqueous electrolyte secondary battery at the time of 100 cycles and 500 cycles was computed by making the capacity | capacitance of each nonaqueous electrolyte secondary battery at the time of initial charge / discharge into 100%. The results are shown in Table 30.

As shown in Table 30, EB8, EB9, and EB10 showed a capacity retention rate equivalent to CB4 even after 100 cycles. That is, the nonaqueous electrolyte secondary battery of each test example was excellent in cycle durability like CB4.

It is considered that the SEI film on the electrode surface is involved in improving the cycle durability. EC in the electrolytic solution is considered to be a material for the SEI film. In general, in order to form a SEI film and improve cycle durability, EC is blended in the electrolytic solution.
However, although EB8, EB9, and EB10 did not include EC as a material for SEI, they exhibited a capacity retention rate equivalent to that of CB4 including EC. This is thought to be because the S and O-containing coating derived from the electrolytic solution of the present invention is present on the positive electrode and the negative electrode in the nonaqueous electrolyte secondary battery of each test example. And for EB8, it showed a very high capacity retention rate even after 500 cycles, and was particularly excellent in durability. Therefore, when DMC was selected as the organic solvent, it was more durable than when AN was selected. It can be said that the property is improved.

(Evaluation Example 29: High temperature storage resistance of battery)
EB8, EB10 and CB4 were subjected to a high-temperature storage test in which they were stored at 60 ° C. for 1 week. Before starting the high-temperature storage test, CC-CV (constant current constant voltage) charging was performed from 3.0 V to 4.1 V. The charge capacity at this time was set as a standard (SOC100), 20% of the standard was CC discharged and adjusted to SOC80, and then a high-temperature storage test was started. After the high temperature storage test, CC-CV discharge was performed to 3.0V at 1C. From the ratio of the discharge capacity at this time and the SOC 80 capacity before storage, the remaining capacity was calculated as follows. The results are shown in Table 31.
Remaining capacity = 100 × (CC-CV discharge capacity after storage) / (SOC 80 capacity before storage)

The remaining capacity of EB8 and EB10 is larger than the remaining capacity of CB4. From this result, it can be said that the S, O-containing coating derived from the electrolytic solution of the present invention and formed on the positive electrode and the negative electrode contributes to an increase in the remaining capacity.

(EB11)
Nonaqueous electrolyte secondary battery EB11 was produced in the same manner as EB1 except for the basis weight of the positive electrode and the negative electrode. The basis weight of the active material layer in the positive electrode was 5.5 mg / cm ² , and the basis weight of the active material layer in the negative electrode was 4.0 mg / cm ² . The basis weight of the active material layer here refers to the basis weight after roll press and drying. In EB1, the basis weight of the active material layer in the positive electrode was 11.0 mg / cm ² , and the basis weight of the active material layer in the negative electrode was 8.0 mg / cm ² .

(CB5)
Nonaqueous electrolyte secondary battery CB5 was produced in the same manner as CB1 except for the weights of the positive electrode and the negative electrode. The basis weight of the active material layer in the positive electrode was 5.5 mg / cm ² as in EB11, and the basis weight of the active material layer in the negative electrode was also 4.0 mg / cm ² as in EB11. Note that the basis weight of the active material layer in the positive electrodes of EB11 and CB5 and the basis weight of the active material layer in the negative electrode were half of EB1 and CB1. In addition, the basis weight of the positive electrode and the negative electrode in the nonaqueous electrolyte secondary battery of Comparative Example 5-2 was the same as that of the nonaqueous electrolyte secondary battery of Example 5-1.

(Evaluation Example 30: Battery input / output characteristics)
The output characteristics of EB11 and CB5 described above were evaluated.
The operating voltage range at the time of evaluation is 3V-4.2V, and the capacity is 13.5 mAh. For each battery, the state of charge (SOC) is 30% and -30 ° C, the SOC is 30% and -10 ° C, the SOC is 80% and 25 ° C. Three levels were evaluated. The evaluation was performed three times for each of the 2 second output and the 5 second output. Table 32 shows the evaluation results of the output characteristics. Hereinafter, “output in 2 seconds” means output after 2 seconds from the start of discharge, and “input in 5 seconds” means input after 5 seconds from the start of discharge.

As shown in Table 32, even when the basis weight is about half that of EB1, EB11 using the electrolytic solution of the present invention has input / output characteristics compared to CB5 not using the electrolytic solution of the present invention. Excellent.

(Evaluation Example 31: Rate capacity characteristics)
The rate capacity characteristics of EB1 and CB1 were evaluated by the following methods. The capacity of each battery was adjusted to 160 mAh / g. The evaluation condition was that each non-aqueous electrolyte secondary battery was charged at a rate of 0.1 C, 0.2 C, 0.5 C, 1 C, 2 C, and then discharged, and the capacity of the working electrode at each rate (discharge) Capacity). Table 33 shows the discharge capacity after 0.1 C discharge and after 1 C discharge. The discharge capacity shown in Table 33 is the capacity calculated per mass (g) of the positive electrode active material.

As shown in Table 33, when the discharge rate is slow (0.1 C), there is almost no difference in discharge capacity between EB1 and CB1. However, when the discharge rate is fast (1.0 C), the discharge capacity of EB1 is larger than the discharge capacity of CB1. This result supports that the nonaqueous electrolyte secondary battery of the present invention is excellent in rate capacity characteristics. As described above, this is because the electrolyte in the non-aqueous electrolyte secondary battery of the present invention is different from the conventional one, and S, O formed on the negative electrode and / or the positive electrode of the non-aqueous electrolyte secondary battery of the present invention. It is thought that the contained film is also different from the conventional film.

(Evaluation Example 32: Output characteristic evaluation at 0 °, SOC 20%)
The output characteristics of EB1 and CB1 described above were evaluated. The evaluation conditions are a state of charge (SOC) 20%, 0 ° C., a working voltage range 3V-4.2V, and a capacity 13.5 mAh. SOC 20%, 0 ° C. is a region where output characteristics are difficult to be obtained, for example, when used in a refrigerator room. Evaluation of the output characteristics of EB1 and CB1 was performed three times for each of the 2-second output and the 5-second output. The evaluation results of the output characteristics are shown in Table 34.

As shown in Table 34, the output of EB1 at 0 ° C. and SOC 20% was 1.2 to 1.3 times higher than the output of CB1.

(Evaluation Example 33: Output characteristic evaluation at 25 ° C. and SOC 20%)
The output characteristics of EB1 and CB1 were evaluated under the conditions of a state of charge (SOC) of 20%, 25 ° C., a working voltage range of 3 V to 4.2 V, and a capacity of 13.5 mAh. Evaluation of the output characteristics of EB1 and CB1 was performed three times for each of the 2-second output and the 5-second output. The evaluation results are shown in Table 35.

As shown in Table 35, the output of EB1 at 25 ° C. and SOC 20% was 1.2 to 1.3 times higher than the output of CB1.

(Evaluation Example 34: Effect of temperature on output characteristics)
Moreover, the influence of the temperature at the time of measurement on the output characteristics of EB1 and CB1 was examined. Measurement was performed at 0 ° C. and 25 ° C. In any measurement, the evaluation conditions were a state of charge (SOC) of 20%, a working voltage range of 3 V to 4.2 V, and a capacity of 13.5 mAh. The ratio of the output at 0 ° C. to the output at 25 ° C. (0 ° C. output / 25 ° C. output) was determined. The results are shown in Table 36.

As shown in Table 36, the ratio of the output at 0 ° C. to the output at 25 ° C. (0 ° C. output / 25 ° C. output) at the output of 2 seconds and 5 seconds is about the same as CB1, and EB1 Was found to be able to suppress a decrease in output at a low temperature to the same extent as CB1.

(Evaluation Example 35: Analysis of coating film containing positive electrode S and O)
Using TOF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry), the structural information of each molecule contained in the positive electrode S, O-containing coating of EB4 was analyzed.

EB4 was charged and discharged at 25 ° C. for 3 cycles, then disassembled in a 3V discharge state, and the positive electrode was taken out. Separately, EB4 was charged and discharged at 25 ° C. for 500 cycles, then disassembled in a 3V discharge state, and the positive electrode was taken out. Separately from this, EB4 was charged and discharged at 25 ° C. for 3 cycles, then left at 60 ° C. for one month, disassembled in a 3V discharge state, and the positive electrode was taken out. Each positive electrode was washed with DMC three times to obtain a positive electrode for analysis. In addition, the positive electrode S and O containing film was formed in the said positive electrode, and the structural information of the molecule | numerator contained in the positive electrode S and O containing film was analyzed in the following analysis.

Each positive electrode for analysis was analyzed by TOF-SIMS. A time-of-flight secondary ion mass spectrometer was used as a mass spectrometer, and positive secondary ions and negative secondary ions were measured. Bi was used as the primary ion source, and the primary acceleration voltage was 25 kV. Ar-GCIB (Ar1500) was used as the sputter ion source. The measurement results are shown in Tables 37 to 39. In Table 38, the positive ion intensity (relative value) of each fragment is a relative value with the total positive ion intensity of all detected fragments as 100%. Similarly, the negative ionic strength (relative value) of each fragment described in Table 39 is a relative value where the sum of the negative ionic strengths of all the detected fragments is 100%.

As shown in Table 37, the fragments presumed to be derived from the solvent of the electrolytic solution were only C ₃ H ₃ and C ₄ H ₃ detected as positive secondary ions. In addition, a fragment presumed to be derived from a salt of the electrolytic solution is mainly detected as a negative secondary ion, and has a higher ionic strength than the above-described fragment derived from a solvent. Furthermore, fragments containing Li are mainly detected as positive secondary ions, and the ionic strength of the fragments containing Li accounts for a large proportion of positive secondary ions and negative secondary ions.

From the above, it is presumed that the main component of the S, O-containing film is a component derived from the metal salt contained in the electrolytic solution, and that the S, O-containing film contains a large amount of Li.

Furthermore, as shown in Table 37, SNO ₂ , SFO ₂ , S ₂ F ₂ NO _{4, and the} like have also been detected as fragments estimated to be derived from salts. Each of these has an S═O structure, and N or F is bonded to S. That is, in the S, O-containing film, S is not only double-bonded with O, but can also have a structure bonded to other elements such as SNO ₂ , SFO ₂ , S ₂ F ₂ NO _4, etc. . Therefore, it is sufficient that the S, O-containing film has at least the S═O structure, and it can be said that S contained in the S═O structure may be bonded to other elements. Needless to say, the S, O-containing film may contain S and O which do not take the S = O structure.

By the way, in the conventional electrolyte solution introduced in, for example, JP-A-2013-145732, that is, a conventional electrolyte solution containing EC as an organic solvent, LiPF ₆ as a metal salt, and LiFSA as an additive, S is taken into the decomposition product of the organic solvent. For this reason, S is considered to exist as ions such as C _p H _q S (p and q are independent integers) in the negative electrode film and / or the positive electrode film. On the other hand, as shown in Tables 37 to 39, the fragment containing S detected from the S, O-containing film is mainly a fragment reflecting the anion structure, not the C _p H _q S fragment. This also reveals that the S, O-containing coating is fundamentally different from the coating formed on the conventional nonaqueous electrolyte secondary battery.

(EB12)
A nonaqueous electrolyte secondary battery using the electrolytic solution E8 was produced as follows.
An aluminum foil (JIS A1000 series) having a diameter of 13.82 mm, an area of 1.5 cm ² and a thickness of 20 μm was used as a working electrode, and the counter electrode was metal Li. As the separator, Whatman glass fiber filter paper having a thickness of 400 μm: No. 1825-055 was used.
A working electrode, a counter electrode, a separator, and an electrolyte solution of E8 were housed in a battery case (CR2032-type coin cell case manufactured by Hosen Co., Ltd.) to obtain a nonaqueous electrolyte secondary battery EB12.

(Evaluation example 36: Confirmation of elution of Al)
Changes in current and electrode potential when linear sweep voltammetry measurement (so-called LSV) is repeated 10 times in a range of 3.1 V to 4.6 V (vs. Li reference) at a speed of 1 mV / s with respect to EB12. Observed. A graph showing the relationship between the first and second, third and third currents and the electrode potential of EB12 is shown in FIG.

From FIG. 90, in EB12 in which the working electrode is Al, almost no current is confirmed at 4.0V,
The current once increased slightly at 4.3 V, but no significant increase was observed up to 4.6 V thereafter. In addition, the amount of current decreased due to repeated charging and discharging, and it became a steady state.
From the above results, it is considered that the nonaqueous electrolyte secondary battery using the electrolytic solution of the present invention and using the aluminum current collector for the positive electrode hardly causes elution of Al even at a high potential. Although it is not clear why the elution of Al is unlikely to occur, the electrolytic solution of the present invention differs from the conventional electrolytic solution in the types of metal salt and organic solvent, the existing environment and the metal salt concentration. In comparison with this, it is presumed that the solubility of Al in the electrolytic solution of the present invention is low.

(EB13)
A nonaqueous electrolyte secondary battery EB13 was obtained in the same manner as EB12 except that the electrolytic solution E11 was used instead of the electrolytic solution E8.

(EB14)
A nonaqueous electrolyte secondary battery EB14 was obtained in the same manner as EB12 except that the electrolytic solution E16 was used instead of the electrolytic solution E8.

(EB15)
A nonaqueous electrolyte secondary battery EB15 was obtained in the same manner as EB12 except that the electrolytic solution E19 was used instead of the electrolytic solution E8.

(EB16)
A nonaqueous electrolyte secondary battery EB16 was obtained in the same manner as EB12 except that the electrolytic solution E13 was used instead of the electrolytic solution E8.

(CB6)
A nonaqueous electrolyte secondary battery CB6 was obtained in the same manner as EB12 except that the electrolytic solution C5 was used instead of the electrolytic solution E8.

(CB7)
A nonaqueous electrolyte secondary battery CB7 was obtained in the same manner as EB12 except that the electrolytic solution C6 was used instead of the electrolytic solution E8.

(Evaluation Example 37: Cyclic voltammetry evaluation with working electrode Al)
For EB12 to EB15 and CB6, cyclic voltammetry evaluation was performed for 5 cycles under conditions of 3.1 V to 4.6 V and 1 mV / s, and thereafter, 5 conditions were applied under conditions of 3.1 V to 5.1 V and 1 mV / s. Cyclic voltammetric evaluation of the cycle was performed.

In addition, for EB13, EB16 and CB7, 10 cycles of cyclic voltammetry was evaluated under the conditions of 3.0 V to 4.5 V and 1 mV / s, and then 3.0 V to 5.0 V and 1 mV / s. Under conditions, 10 cycles of cyclic voltammetry evaluation was performed.

91 to 99 are graphs showing the relationship between the potential and response current for EB12 to EB15 and CB6. Further, graphs showing the relationship between the potential and response current with respect to EB13, EB16, and CB7 are shown in FIGS.

From FIG. 99, it can be seen that in CB6, the current flows from 3.1 V to 4.6 V after the second cycle, and the current increases as the potential increases. In FIGS. 104 and 105, similarly, in CB7, the current flows from 3.0 V to 4.5 V in the second and subsequent cycles, and the current increases as the potential increases. This current is presumed to be the oxidation current of Al due to the corrosion of the working electrode aluminum.

On the other hand, it can be seen from FIGS. 91 to 98 that in EB12 to EB15, almost no current flows from 3.1 V to 4.6 V after two cycles. Although a slight increase in current was observed as the potential increased at 4.3 V or higher, the amount of current decreased as the cycle was repeated, and the steady state was reached. In particular, in EB13 to EB15, no significant increase in current was observed up to 5.1 V, which is a high potential, and a decrease in the amount of current was observed as the cycle was repeated.

Also, from FIG. 100 to FIG. 103, it can be seen that in EB13 and EB16 as well, almost no current flows from 3.0 V to 4.5 V after two cycles. In particular, after the third cycle, there is almost no increase in current up to 4.5V. In EB16, an increase in current is observed after 4.5V, which is a high potential, which is much smaller than the current value after 4.5V in CB7. For EB13, there was almost no increase in current from 4.5V to 5.0V, and a decrease in the amount of current was observed as the cycle was repeated, as in EB13 to EB15.

From the results of cyclic voltammetry evaluation, it can be said that the corrosiveness of the electrolytes E8, E11, E16, and E19 to aluminum is low even under high potential conditions exceeding 5V. That is, the electrolytes E8, E11, E16, and E19 can be said to be suitable electrolytes for batteries using aluminum as a current collector or the like.

(EB17)
A nonaqueous electrolyte secondary battery EB17 using the electrolytic solution E8 was produced as follows.
94 parts by mass of NCM523 as a positive electrode active material, 3 parts by mass of AB as a conductive additive, and 3 parts by mass of PVdF as a binder were mixed. This mixture was dispersed in an appropriate amount of NMP to obtain a slurry-like positive electrode mixture. An aluminum foil (JIS A1000 series) having a thickness of 20 μm was prepared as a positive electrode current collector. The surface of the positive electrode current collector was applied using a doctor blade so that the positive electrode mixture was in the form of a film. NMP was removed by volatilization by drying the positive electrode current collector coated with the positive electrode mixture at 80 ° C. for 20 minutes. Thereafter, the composite of the positive electrode mixture and the positive electrode current collector was pressed to obtain a bonded product. The obtained joined product was heat-dried at 120 ° C. for 6 hours with a vacuum dryer to obtain a positive electrode in which a positive electrode active material layer was formed on the positive electrode current collector.
98 parts by mass of natural graphite as a negative electrode active material and 1 part by mass of SBR and CMC as binders were taken and mixed. This mixture was dispersed in an appropriate amount of ion-exchanged water to obtain a slurry-like negative electrode mixture. A copper foil having a thickness of 20 μm was prepared as a negative electrode current collector. The negative electrode mixture was applied to the surface of the negative electrode current collector in the form of a film using a doctor blade. The negative electrode current collector coated with the negative electrode mixture was dried to remove water, and then a composite of the negative electrode mixture and the negative electrode current collector was pressed to obtain a bonded product. The obtained joined product was heat-dried at 100 ° C. for 6 hours with a vacuum dryer to obtain a negative electrode in which a negative electrode active material layer was formed on the negative electrode current collector.
A cellulose nonwoven fabric having a thickness of 20 μm was prepared as a separator.
A separator was sandwiched between the positive electrode and the negative electrode to form an electrode plate group. The electrode plate group was covered with a set of two laminated films, and the three sides were sealed, and then the electrolyte solution E8 was injected into the laminated film in a bag shape. Thereafter, the remaining one side was sealed to obtain a nonaqueous electrolyte secondary battery EB17 in which the four sides were hermetically sealed, and the electrode plate group and the electrolyte were sealed.

(EB18)
A nonaqueous electrolyte secondary battery EB18 using the electrolytic solution E8 was produced as follows.
The positive electrode was manufactured in the same manner as the positive electrode of EB17.
90 parts by mass of natural graphite as a negative electrode active material and 10 parts by mass of PVdF as a binder were mixed. This mixture was dispersed in an appropriate amount of ion-exchanged water to obtain a slurry-like negative electrode mixture. A copper foil having a thickness of 20 μm was prepared as a negative electrode current collector. The negative electrode mixture was applied to the surface of the copper foil in the form of a film using a doctor blade. The composite of the negative electrode mixture and the negative electrode current collector was dried to remove water, and then pressed to obtain a bonded product. The obtained joined product was heat-dried at 120 ° C. for 6 hours with a vacuum dryer to obtain a negative electrode in which a negative electrode active material layer was formed on the negative electrode current collector. Using this negative electrode, a nonaqueous electrolyte secondary battery EB18 was obtained in the same manner as EB17.

(CB8)
A nonaqueous electrolyte secondary battery CB8 was obtained in the same manner as EB17 except that the electrolytic solution C5 was used.

(CB9)
A nonaqueous electrolyte secondary battery CB9 was obtained in the same manner as EB18 except that the electrolytic solution C5 was used.

(Evaluation Example 38: Input / Output Characteristics of Nonaqueous Electrolyte Secondary Battery)
The output characteristics of EB17, EB18, CB8, and CB9 were evaluated under the following conditions.
(1) Evaluation of input characteristics at 0 ° C. or 25 ° C. and SOC 80% Evaluation conditions were 80% charge state (SOC), 0 ° C. or 25 ° C., operating voltage range 3V-4.2V, and capacity 13.5 mAh. The input characteristics were evaluated three times for each battery for a 2-second input and a 5-second input.
Moreover, based on the volume of each battery, the battery output density (W / L) in 25 degreeC and 2 second input was computed.
Table 40 shows the evaluation results of the input characteristics. In Table 40, “2 second input” means an input after 2 seconds from the start of charging, and “5 seconds input” means an input after 5 seconds from the start of charging.
As shown in Table 40, the input of EB17 was significantly higher than the input of CB8 regardless of the difference in temperature. Similarly, the EB18 input was significantly higher than the CB9 input.
The battery input density of EB17 was significantly higher than that of CB8. Similarly, the battery input density of EB18 was significantly higher than the battery input density of CB9.

(2) Evaluation of output characteristics at 0 ° C. or 25 ° C. and SOC 20% The evaluation conditions were the state of charge (SOC) 20%, 0 ° C. or 25 ° C., operating voltage range 3V-4.2V, and capacity 13.5 mAh. SOC 20%, 0 ° C. is a region where output characteristics are difficult to be obtained, for example, when used in a refrigerator room. The output characteristics were evaluated three times for each battery for the 2-second output and 5-second output.
Moreover, based on the volume of each battery, the battery output density (W / L) in 25 degreeC and a 2-second output was computed.
Table 40 shows the evaluation results of the output characteristics. In Table 40, “2 seconds output” means an output 2 seconds after the start of discharge, and “5 seconds output” means an output 5 seconds after the start of discharge.
As shown in Table 40, the output of EB17 was significantly higher than the output of CB8 regardless of the difference in temperature. Similarly, the output of EB18 was significantly higher than that of CB9.
In addition, the battery output density of EB17 was significantly higher than that of CB8. Similarly, the battery output density of EB18 was significantly higher than that of CB9.

(EB19)
A nonaqueous electrolyte secondary battery EB19 using the electrolytic solution E8 was produced as follows. The positive electrode was manufactured in the same manner as the positive electrode of EB17.
98 parts by mass of natural graphite, which is a negative electrode active material, and 1 part by mass of SBR and 1 part by mass of CMC, which are binders, were mixed. This mixture was dispersed in an appropriate amount of ion-exchanged water to obtain a slurry-like negative electrode mixture. Using this negative electrode mixture, a negative electrode was obtained in the same manner as in EB17. As a separator, experimental filter paper (Toyo Filter Paper Co., Ltd., cellulose, thickness 260 μm) was prepared. Using the above positive electrode, negative electrode and separator, a nonaqueous electrolyte secondary battery EB19 was obtained in the same manner as EB17.

(CB10)
A nonaqueous electrolyte secondary battery CB10 was obtained in the same manner as EB19 except that the electrolytic solution C5 was used.

(Evaluation Example 39: Thermal stability of battery)
The thermal stability of the electrolyte solution with respect to the charged positive electrodes of EB19 and CB10 was evaluated by the following method.
Each nonaqueous electrolyte secondary battery was fully charged under a charge end voltage of 4.2 V and a constant current and constant voltage condition. The fully charged nonaqueous electrolyte secondary battery was disassembled and the positive electrode was taken out. 3 mg of the positive electrode active material layer obtained from the positive electrode and 1.8 μL of the electrolytic solution were placed in a stainless steel pan, and the pan was sealed. Using a sealed pan, under a nitrogen atmosphere, the heating rate was 20 ° C./min. The differential scanning calorimetry was performed under the conditions described above, and the DSC curve was observed. A Rigaku DSC8230 was used as a differential scanning calorimeter. FIG. 106 shows a DSC chart when the positive electrode active material layer in the charged state of EB19 and the electrolyte coexist. In addition, FIG. 107 shows DSC charts when the positive electrode active material layer in the charged state of CB10 and the electrolyte coexist, respectively.

As is apparent from the results of FIGS. 106 and 107, the DSC curve in the case where the positive electrode in the charged state and the electrolyte in EB19 coexist hardly showed an endothermic peak, whereas the positive electrode in the charged state of CB10. An exothermic peak was observed at around 300 ° C. in the DSC curve in the case of coexisting with electrolyte. This exothermic peak is presumed to have occurred as a result of the reaction between the positive electrode active material and the electrolytic solution.
From these results, the non-aqueous electrolyte secondary battery using the electrolytic solution of the present invention is more reactive with the positive electrode active material and the electrolytic solution than the non-aqueous electrolyte secondary battery using the conventional electrolytic solution. It can be seen that it is low and has excellent thermal stability.

The nonaqueous electrolyte secondary battery of the present invention can be used for secondary batteries, electric double layer capacitors, lithium ion capacitors, and the like. It is also useful as a non-aqueous electrolyte secondary battery for motor drive of electric vehicles and hybrid vehicles, personal computers, portable communication devices, home appliances, office equipment, industrial equipment, etc. Especially, large capacity and high output are required. It can be optimally used for driving a motor of a simple electric vehicle or hybrid vehicle.

Claims

Including a negative electrode and an electrolyte,
The electrolytic solution includes a salt having an alkali metal, an alkaline earth metal or aluminum as a cation, and an organic solvent having a hetero element,
Regarding the peak intensity derived from the organic solvent in the vibrational spectrum of the electrolyte solution, when the intensity of the original peak of the organic solvent is Io and the intensity of the peak shifted from the peak is Is, Is> Io,
The negative electrode is a non-aqueous electrolyte secondary battery in which a negative electrode active material includes graphite having a G / D ratio of 3.5 or more, which is a ratio of G-band and D-band peaks in a Raman spectrum.
The non-aqueous electrolyte secondary battery according to claim 1, wherein the G / D ratio is 10 or more.
Including a negative electrode and an electrolyte,
The electrolytic solution includes a salt having an alkali metal, an alkaline earth metal or aluminum as a cation, and an organic solvent having a hetero element,
Regarding the peak intensity derived from the organic solvent in the vibrational spectrum of the electrolyte solution, when the intensity of the original peak of the organic solvent is Io and the intensity of the peak shifted from the peak is Is, Is> Io,
The negative electrode includes, in the negative electrode active material, a carbon material having a crystallite size of 20 nm or less calculated from a half width of a peak appearing at 2θ = 20 degrees to 30 degrees in an X-ray diffraction profile measured by an X-ray diffraction method. Non-aqueous electrolyte secondary battery.
The non-aqueous electrolyte secondary battery according to claim 3, wherein the crystallite size is 5 nm or less.
Including a negative electrode and an electrolyte,
The electrolytic solution includes a salt having an alkali metal, an alkaline earth metal or aluminum as a cation, and an organic solvent having a hetero element,
Regarding the peak intensity derived from the organic solvent in the vibrational spectrum of the electrolyte solution, when the intensity of the original peak of the organic solvent is Io and the intensity of the peak shifted from the peak is Is, Is> Io,
The negative electrode is a non-aqueous electrolyte secondary battery in which a negative electrode active material contains a silicon element and / or a tin element.
The non-aqueous electrolyte secondary battery according to claim 5, wherein the negative electrode active material contains silicon element.
The non-aqueous electrolyte secondary battery according to claim 5 or 6, wherein the negative electrode active material includes a silicon element, an oxygen element and / or a carbon element.
Including a negative electrode and an electrolyte,
The electrolytic solution includes a salt having an alkali metal, an alkaline earth metal or aluminum as a cation, and an organic solvent having a hetero element,
Regarding the peak intensity derived from the organic solvent in the vibrational spectrum of the electrolyte solution, when the intensity of the original peak of the organic solvent is Io and the intensity of the peak shifted from the peak is Is, Is> Io,
The negative electrode is a non-aqueous electrolyte secondary battery including a metal oxide capable of inserting and extracting lithium ions as a negative electrode active material.
The non-aqueous electrolyte secondary battery according to claim 8, wherein the metal oxide is mainly composed of at least one selected from titanium oxide, lithium titanium oxide, tungsten oxide, amorphous tin oxide, and tin silicon oxide. .
The metal oxide mainly comprises lithium titanium oxide represented by Li 4 + x Ti 5 + y O 12 (x is -1≤x≤4, y is -1≤y≤1). 9. The nonaqueous electrolyte secondary battery according to 9.
Including a negative electrode and an electrolyte,
The electrolytic solution includes a salt having an alkali metal, an alkaline earth metal or aluminum as a cation, and an organic solvent having a hetero element,
Regarding the peak intensity derived from the organic solvent in the vibrational spectrum of the electrolyte solution, when the intensity of the original peak of the organic solvent is Io and the intensity of the peak shifted from the peak is Is, Is> Io,
The negative electrode is a non-aqueous electrolyte secondary battery in which a negative electrode active material includes graphite having a major axis / minor axis ratio (major axis / minor axis) of 1 to 5.
The nonaqueous electrolyte secondary battery according to claim 11, wherein the graphite particles have an I (110) / I (004) measured by X-ray diffraction in a range of 0.03 to 1.
The nonaqueous electrolyte secondary battery according to any one of claims 1 to 12, wherein in the electrolytic solution, a cation of the salt is lithium.
The non-aqueous solution according to any one of claims 1 to 13, wherein the electrolytic solution contains at least one element selected from halogen, boron, nitrogen, oxygen, sulfur or carbon, in the chemical structure of the anion of the salt. Electrolyte secondary battery.
The non-aqueous electrolyte according to any one of claims 1 to 14, wherein the electrolyte has a chemical structure of the anion of the salt represented by the following general formula (1), general formula (2), or general formula (3). Electrolyte secondary battery.
(R 1 X 1 ) (R 2 X 2 ) N... General formula (1)
(R 1 is hydrogen, halogen, an alkyl group which may be substituted with a substituent, a cycloalkyl group which may be substituted with a substituent, an unsaturated alkyl group which may be substituted with a substituent, or a substituent. An unsaturated cycloalkyl group which may be substituted with, an aromatic group which may be substituted with a substituent, a heterocyclic group which may be substituted with a substituent, or an alkoxy group which may be substituted with a substituent , An unsaturated alkoxy group that may be substituted with a substituent, a thioalkoxy group that may be substituted with a substituent, an unsaturated thioalkoxy group that may be substituted with a substituent, CN, SCN, or OCN Is done.
R 2 represents hydrogen, halogen, an alkyl group which may be substituted with a substituent, a cycloalkyl group which may be substituted with a substituent, an unsaturated alkyl group which may be substituted with a substituent, or a substituent. An unsaturated cycloalkyl group which may be substituted, an aromatic group which may be substituted with a substituent, a heterocyclic group which may be substituted with a substituent, an alkoxy group which may be substituted with a substituent, Selected from an unsaturated alkoxy group which may be substituted with a substituent, a thioalkoxy group which may be substituted with a substituent, an unsaturated thioalkoxy group which may be substituted with a substituent, CN, SCN, OCN The
R 1 and R 2 may be bonded to each other to form a ring.
X 1 is selected from SO 2 , C = O, C = S, R a P = O, R b P = S, S = O, Si = O.
X 2 is, SO 2, C = O, C = S, R c P = O, R d P = S, S = O, is selected from Si = O.
R a , R b , R c , and R d are each independently hydrogen, halogen, an alkyl group that may be substituted with a substituent, a cycloalkyl group that may be substituted with a substituent, or a substituent. An unsaturated alkyl group which may be substituted, an unsaturated cycloalkyl group which may be substituted with a substituent, an aromatic group which may be substituted with a substituent, or a heterocyclic group which may be substituted with a substituent , An alkoxy group that may be substituted with a substituent, an unsaturated alkoxy group that may be substituted with a substituent, a thioalkoxy group that may be substituted with a substituent, and a non-optionally substituted substituent. Selected from saturated thioalkoxy groups, OH, SH, CN, SCN, OCN.
R a , R b , R c , and R d may combine with R 1 or R 2 to form a ring. )
R 3 X 3 Y: General formula (2)
(R 3 is hydrogen, halogen, an alkyl group which may be substituted with a substituent, a cycloalkyl group which may be substituted with a substituent, an unsaturated alkyl group which may be substituted with a substituent, or a substituent. An unsaturated cycloalkyl group which may be substituted with, an aromatic group which may be substituted with a substituent, a heterocyclic group which may be substituted with a substituent, or an alkoxy group which may be substituted with a substituent , An unsaturated alkoxy group that may be substituted with a substituent, a thioalkoxy group that may be substituted with a substituent, an unsaturated thioalkoxy group that may be substituted with a substituent, CN, SCN, or OCN Is done.
X 3 is selected from SO 2 , C = O, C = S, R e P = O, R f P = S, S = O, and Si = O.
R e and R f are each independently hydrogen, halogen, an alkyl group that may be substituted with a substituent, a cycloalkyl group that may be substituted with a substituent, or a group that may be substituted with a substituent. A saturated alkyl group, an unsaturated cycloalkyl group that may be substituted with a substituent, an aromatic group that may be substituted with a substituent, a heterocyclic group that may be substituted with a substituent, and a substituent An alkoxy group which may be substituted, an unsaturated alkoxy group which may be substituted with a substituent, a thioalkoxy group which may be substituted with a substituent, an unsaturated thioalkoxy group which may be substituted with a substituent, OH , SH, CN, SCN, and OCN.
R e and R f may combine with R 3 to form a ring.
Y is selected from O and S. )
(R 4 X 4 ) (R 5 X 5 ) (R 6 X 6 ) C ... General formula (3)
(R 4 is hydrogen, halogen, an alkyl group which may be substituted with a substituent, a cycloalkyl group which may be substituted with a substituent, an unsaturated alkyl group which may be substituted with a substituent, or a substituent. An unsaturated cycloalkyl group which may be substituted with, an aromatic group which may be substituted with a substituent, a heterocyclic group which may be substituted with a substituent, or an alkoxy group which may be substituted with a substituent , An unsaturated alkoxy group that may be substituted with a substituent, a thioalkoxy group that may be substituted with a substituent, an unsaturated thioalkoxy group that may be substituted with a substituent, CN, SCN, or OCN Is done.
R 5 represents hydrogen, halogen, an alkyl group which may be substituted with a substituent, a cycloalkyl group which may be substituted with a substituent, an unsaturated alkyl group which may be substituted with a substituent, or a substituent. An unsaturated cycloalkyl group which may be substituted, an aromatic group which may be substituted with a substituent, a heterocyclic group which may be substituted with a substituent, an alkoxy group which may be substituted with a substituent, Selected from an unsaturated alkoxy group which may be substituted with a substituent, a thioalkoxy group which may be substituted with a substituent, an unsaturated thioalkoxy group which may be substituted with a substituent, CN, SCN, OCN The
R 6 is hydrogen, halogen, an alkyl group which may be substituted with a substituent, a cycloalkyl group which may be substituted with a substituent, an unsaturated alkyl group which may be substituted with a substituent, or a substituent. An unsaturated cycloalkyl group which may be substituted, an aromatic group which may be substituted with a substituent, a heterocyclic group which may be substituted with a substituent, an alkoxy group which may be substituted with a substituent, Selected from an unsaturated alkoxy group which may be substituted with a substituent, a thioalkoxy group which may be substituted with a substituent, an unsaturated thioalkoxy group which may be substituted with a substituent, CN, SCN, OCN The
Further, any two or three of R 4 , R 5 and R 6 may be bonded to form a ring.
X 4 is, SO 2, C = O, C = S, R g P = O, R h P = S, S = O, is selected from Si = O.
X 5 is selected from SO 2 , C = O, C = S, R i P = O, R j P = S, S = O, Si = O.
X 6 is selected from SO 2 , C = O, C = S, R k P = O, R 1 P = S, S = O, Si = O.
R g , R h , R i , R j , R k , and R l are each independently hydrogen, halogen, an alkyl group that may be substituted with a substituent, or a cycloalkyl that may be substituted with a substituent. Group, an unsaturated alkyl group that may be substituted with a substituent, an unsaturated cycloalkyl group that may be substituted with a substituent, an aromatic group that may be substituted with a substituent, or a substituent that is substituted with a substituent A heterocyclic group which may be substituted, an alkoxy group which may be substituted with a substituent, an unsaturated alkoxy group which may be substituted with a substituent, a thioalkoxy group which may be substituted with a substituent, and a substituent It is selected from an unsaturated thioalkoxy group which may be substituted, OH, SH, CN, SCN, OCN.
R g , R h , R i , R j , R k , and R l may combine with R 4 , R 5, or R 6 to form a ring. )
The non-aqueous electrolyte according to any one of claims 1 to 15, wherein the electrolyte has a chemical structure of the anion of the salt represented by the following general formula (4), general formula (5), or general formula (6). Electrolyte secondary battery.
(R 7 X 7 ) (R 8 X 8 ) N ... General formula (4)
(R 7 and R 8 are each independently C n H a F b Cl c Br d I e (CN) f (SCN) g (OCN) h .
n, a, b, c, d, e, f, g, and h are each independently an integer of 0 or more, and satisfy 2n + 1 = a + b + c + d + e + f + g + h.
R 7 and R 8 may combine with each other to form a ring, in which case 2n = a + b + c + d + e + f + g + h is satisfied.
X 7 is, SO 2, C = O, C = S, R m P = O, R n P = S, S = O, is selected from Si = O.
X 8 is selected from SO 2 , C = O, C = S, R o P = O, R p P = S, S = O, Si = O.
R m , R n , R o , and R p are each independently substituted with hydrogen, halogen, an alkyl group that may be substituted with a substituent, a cycloalkyl group that may be substituted with a substituent, or a substituent. An unsaturated alkyl group which may be substituted, an unsaturated cycloalkyl group which may be substituted with a substituent, an aromatic group which may be substituted with a substituent, or a heterocyclic group which may be substituted with a substituent , An alkoxy group that may be substituted with a substituent, an unsaturated alkoxy group that may be substituted with a substituent, a thioalkoxy group that may be substituted with a substituent, and a non-optionally substituted substituent. Selected from saturated thioalkoxy groups, OH, SH, CN, SCN, OCN.
R m , R n , R o , and R p may combine with R 7 or R 8 to form a ring. )
R 9 X 9 Y: General formula (5)
(R 9 is a C n H a F b Cl c Br d I e (CN) f (SCN) g (OCN) h.
n, a, b, c, d, e, f, g, and h are each independently an integer of 0 or more, and satisfy 2n + 1 = a + b + c + d + e + f + g + h.
X 9 is, SO 2, C = O, C = S, R q P = O, R r P = S, S = O, is selected from Si = O.
R q and R r are each independently hydrogen, halogen, an alkyl group that may be substituted with a substituent, a cycloalkyl group that may be substituted with a substituent, or a group that may be substituted with a substituent. A saturated alkyl group, an unsaturated cycloalkyl group that may be substituted with a substituent, an aromatic group that may be substituted with a substituent, a heterocyclic group that may be substituted with a substituent, and a substituent An alkoxy group which may be substituted, an unsaturated alkoxy group which may be substituted with a substituent, a thioalkoxy group which may be substituted with a substituent, an unsaturated thioalkoxy group which may be substituted with a substituent, OH , SH, CN, SCN, and OCN.
R q and R r may combine with R 9 to form a ring.
Y is selected from O and S. )
(R 10 X 10) (R 11 X 11) (R 12 X 12) C ··· formula (6)
(R 10 , R 11 , R 12 are each independently C n H a F b Cl c Br d I e (CN) f (SCN) g (OCN) h . N, a, b, c, d, e, f, g, and h are each independently an integer of 0 or more, and satisfy 2n + 1 = a + b + c + d + e + f + g + h.
Any two of R 10 , R 11 , and R 12 may combine to form a ring, in which case the group forming the ring satisfies 2n = a + b + c + d + e + f + g + h. Three of R 10 , R 11 and R 12 may combine to form a ring, in which case two of the three satisfy 2n = a + b + c + d + e + f + g + h, and one group satisfies 2n−1 = a + b + c + d + e + f + g + h. Fulfill.
X 10 is, SO 2, C = O, C = S, R s P = O, R t P = S, S = O, is selected from Si = O.
X 11 is, SO 2, C = O, C = S, R u P = O, R v P = S, S = O, is selected from Si = O.
X 12 is, SO 2, C = O, C = S, R w P = O, R x P = S, S = O, is selected from Si = O.
R s , R t , R u , R v , R w , and R x are each independently hydrogen, halogen, an alkyl group that may be substituted with a substituent, or a cycloalkyl that may be substituted with a substituent. Group, an unsaturated alkyl group that may be substituted with a substituent, an unsaturated cycloalkyl group that may be substituted with a substituent, an aromatic group that may be substituted with a substituent, or a substituent that is substituted with a substituent A heterocyclic group which may be substituted, an alkoxy group which may be substituted with a substituent, an unsaturated alkoxy group which may be substituted with a substituent, a thioalkoxy group which may be substituted with a substituent, and a substituent It is selected from an unsaturated thioalkoxy group which may be substituted, OH, SH, CN, SCN, OCN.
R s , R t , R u , R v , R w , and R x may combine with R 10 , R 11, or R 12 to form a ring. )
The non-aqueous electrolyte according to any one of claims 1 to 16, wherein the electrolyte has a chemical structure of the salt anion represented by the following general formula (7), general formula (8), or general formula (9). Electrolyte secondary battery.
(R 13 SO 2 ) (R 14 SO 2 ) N... General formula (7)
(R 13 and R 14 are each independently C n H a F b Cl c Br d I e .
n, a, b, c, d, and e are each independently an integer of 0 or more, and satisfy 2n + 1 = a + b + c + d + e.
R 13 and R 14 may combine with each other to form a ring, in which case 2n = a + b + c + d + e is satisfied. )
R 15 SO 3 ... General formula (8)
(R 15 is a C n H a F b Cl c Br d I e.
n, a, b, c, d, and e are each independently an integer of 0 or more, and satisfy 2n + 1 = a + b + c + d + e. )
(R 16 SO 2 ) (R 17 SO 2 ) (R 18 SO 2 ) C. General formula (9)
(R 16 , R 17 , and R 18 are each independently C n H a F b Cl c Br d I e .
n, a, b, c, d, and e are each independently an integer of 0 or more, and satisfy 2n + 1 = a + b + c + d + e.
Any two of R 16 , R 17 and R 18 may combine to form a ring, in which case the group forming the ring satisfies 2n = a + b + c + d + e. Three of R 16 , R 17 and R 18 may combine to form a ring, in which case two of the three satisfy 2n = a + b + c + d + e, and one group satisfies 2n−1 = a + b + c + d + e. Fulfill. )
In the electrolytic solution, the salt is (CF 3 SO 2 ) 2 NLi, (FSO 2 ) 2 NLi, (C 2 F 5 SO 2 ) 2 NLi, FSO 2 (CF 3 SO 2 ) NLi, (SO 2 CF 2 CF 2 SO 2) NLi or (SO 2 CF 2 CF 2 CF 2 SO 2) non-aqueous electrolyte secondary battery according to any one of claims 1 to 17 which is a NLi,.
The nonaqueous electrolyte secondary battery according to any one of claims 1 to 18, wherein the electrolytic solution is at least one selected from nitrogen, oxygen, sulfur, and halogen as a hetero element of the organic solvent.
The nonaqueous electrolyte secondary battery according to any one of claims 1 to 19, wherein in the electrolytic solution, the organic solvent is an aprotic solvent.
The non-aqueous electrolyte secondary battery according to any one of claims 1 to 20, wherein the organic solvent is selected from acetonitrile or 1,2-dimethoxyethane.
The nonaqueous electrolyte secondary battery according to any one of claims 1 to 20, wherein the organic solvent is selected from chain carbonates represented by the following general formula (10).
R 19 OCOOR 20 ··· General formula (10)
(R 19 and R 20 are each independently C n H a F b Cl c Br d I e which is a chain alkyl, or C m H f F g Cl h Br i I containing a cyclic alkyl in the chemical structure. .n selected from any of j, a, b, c, d, e, m, f, g, h, i, j are each independently an integer of 0 or more, 2n + 1 = a + b + c + d + e, 2m = f + g + h + i + j Meet)
The nonaqueous electrolyte secondary battery according to any one of claims 1 to 20 and 22, wherein the organic solvent is selected from dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate.