JP5817001B2 - Non-aqueous secondary battery - Google Patents

Description

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

  For example, a lithium ion secondary battery is a secondary battery having a high charge / discharge capacity and capable of high input / 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.

  Lithium ion secondary batteries have 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.

  As a negative electrode active material for lithium ion secondary batteries, carbon materials such as graphite are widely used. 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 solvents such as ethylene carbonate and propylene carbonate have a large reaction resistance, and a drastic electrolyte solution composition for improving rate capacity characteristics. Review is required.

T. Abe et al., J. Electrochem. Soc., 151, A1120-A1123 (2004). T. Abe et al., J. Electrochem. Soc., 152, A2151-A2154 (2005). Y. Yamada et al., Langmuir, 25, 12766-12770 (2009).

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

A feature of the non-aqueous secondary battery of the present invention that solves the above problems includes a salt having a cation of alkali metal, alkaline earth metal or aluminum and an organic solvent having a hetero element, and the organic solvent in a vibrational spectroscopic spectrum When the intensity of the peak derived from the organic solvent is I _o and the intensity of the peak shifted from the peak is I _s , the electrolyte solution with I _s > I _o and G- and a negative electrode having a negative electrode active material layer containing graphite having a G / D ratio of 3.5 or more, which is a ratio of a band and a D-band peak. 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, particularly It means that the height ratio of the peak is 3.5 or more. Hereinafter, the electrolytic solution in the above-described non-aqueous secondary battery of the present invention may be referred to as “the electrolytic solution of the present invention”.

  According to the non-aqueous secondary battery of the present invention, the electrolytic solution of the present invention comprising a salt having an alkali metal, alkaline earth metal or aluminum cation as a cation and an organic solvent having a heteroatom, and G-band in Raman spectrum And a negative electrode having a negative electrode active material layer containing graphite having a G / D ratio of 3.5 or more, which is a D-band peak intensity ratio. When graphite having a G / D ratio of less than 3.5 is used as the negative electrode active material, the improvement in rate capacity characteristics is slight even when the same electrolytic solution of the present invention is used, but graphite having a G / D ratio of 3.5 or more. By using, the rate capacity characteristics are improved and the cycle characteristics are also improved.

3 is an IR spectrum of the electrolytic solution of the present invention used in the lithium ion secondary battery according to Example 1 of the present invention. 2 is an IR spectrum of an organic solvent (acetonitrile) contained in an electrolyte solution of the present invention used for a lithium ion secondary battery according to Example 1 of the present invention. 2 is an IR spectrum of a supporting salt (LiFSA) contained in the electrolyte solution of the present invention used in the lithium ion secondary battery according to Example 1 of the present invention. 3 is an IR spectrum of an electrolytic solution according to Comparative Example 1. 1 shows a cyclic voltamentary (CV) of a lithium secondary battery according to Example 1. 2 shows a cyclic voltamentary (CV) of a lithium secondary battery according to Example 2. FIG. 3 shows a cyclic voltamentary (CV) of a lithium secondary battery according to Example 3. FIG. 7 shows a cyclic voltamentary (CV) of a lithium secondary battery according to Comparative Example 2. 5 shows a cyclic voltamentary (CV) of a lithium secondary battery according to Comparative Example 3. 7 shows a cyclic voltamentary (CV) of a lithium secondary battery according to Comparative Example 4. 7 shows a cyclic voltamentary (CV) of a lithium secondary battery according to Comparative Example 5. 7 shows a cyclic voltamentary (CV) of a lithium secondary battery according to Comparative Example 6. 7 shows a cyclic voltamentary (CV) of a lithium secondary battery according to Comparative Example 7. 7 shows a cyclic voltamentary (CV) of a lithium secondary battery according to Comparative Example 8. 2 shows DSC charts of lithium ion secondary batteries according to Example 5 and Comparative Example 9. FIG. 2 shows DSC charts of lithium ion secondary batteries according to Example 6 and Comparative Example 9. FIG. The relationship between the number of cycles and the current capacity ratio of the lithium secondary batteries according to Example 1 and Comparative Example 2 is shown. It is IR spectrum of electrolyte solution E3. It is IR spectrum of electrolyte solution E4. It is IR spectrum of electrolyte solution E7. It is IR spectrum of electrolyte solution E8. It is IR spectrum of electrolyte solution E10. It is IR spectrum of electrolyte solution C2. It is IR spectrum of 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 (2100-2400 cm ⁻¹ ). It is IR spectrum of the electrolyte solution E11. It is IR spectrum of electrolyte solution E12. It is IR spectrum of the electrolyte solution E13. It is IR spectrum of electrolyte solution E14. It is IR spectrum of electrolyte solution E15. It is IR spectrum of electrolyte solution E16. It is IR spectrum of electrolyte solution E17. It is IR spectrum of electrolyte solution E18. It is IR spectrum of electrolyte solution E19. It is IR spectrum of electrolyte solution E20. It is IR spectrum of the electrolyte solution E21. It is IR spectrum of electrolyte solution C6. It is IR spectrum of electrolyte solution C7. It is IR spectrum of 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 ). 10 shows a charge / discharge curve of the lithium secondary battery of Example 8. FIG. 10 shows a charge / discharge curve of the lithium secondary battery of Example 9. 10 shows a charge / discharge curve of the lithium secondary battery of Example 10. FIG. 10 shows a charge / discharge curve of the lithium secondary battery of Example 11. FIG. 10 shows a charge / discharge curve of the lithium secondary battery of Comparative Example 10. It is a Raman spectrum of the electrolytic solution E8. It is a Raman spectrum of the electrolytic solution E9. It is a Raman spectrum of the electrolytic solution C4. It is a Raman spectrum of the electrolytic solution E11. It is a Raman spectrum of the electrolytic solution E13. It is a Raman spectrum of the electrolytic solution E15. It is a Raman spectrum of the electrolytic solution C6. 10 is a graph showing a relationship between a current rate and a voltage curve in the lithium secondary battery of Example 12. 10 is a graph showing a relationship between a current rate and a voltage curve in a lithium secondary battery of Comparative Example 5. It is a result of the cycle characteristic of the evaluation example 24.

  Below, the form for implementing this invention is demonstrated. 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 secondary battery of the present invention includes the electrolytic solution of the present invention and a negative electrode having a negative electrode active material layer containing graphite having a G / D ratio of 3.5 or more.

<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, per peak intensity derived from the organic solvent in the vibration spectrum, the intensity of the original peak organic solvent and I _o, if the intensity of a peak inherent peak organic solvent was wavenumber shift was I _s, is I _s> I _o .

In the conventional electrolyte, the relationship between I _s and I _o is I _s <I _o .

[Metal salt]
The metal salt may be a compound used as an electrolyte, such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiAlCl ₄ , etc., usually 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 anions 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, I can be mentioned.

  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 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, Select from 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, and OCN Is done.
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, and Si = O.
X ² is selected from SO ₂ , C = O, C = S, R ^c P = O, R ^d P = S, S = O, and Si = O.
R ^a , R ^b , R ^c and R ^d are each independently substituted with hydrogen, halogen, an alkyl group which may be substituted with a substituent, a cycloalkyl group which 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, SO 2, C = O,} C = S, R e P = O, R f P = S, S = O, is selected from 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 an alkyl 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 optionally substituted alkoxy group, an unsaturated alkoxy group optionally substituted with a substituent, a thioalkoxy group optionally substituted with a substituent, an unsaturated thioalkoxy group optionally substituted with a substituent, OH , SH, CN, SCN, 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 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 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 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, and OCN The
R ⁶ is hydrogen, halogen, an alkyl group that may be substituted with a substituent, a cycloalkyl group that may be substituted with a substituent, an unsaturated alkyl group that 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 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, and 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, and Si = O.
X ⁶ is selected from SO ₂ , C = O, C = S, R ^k P = O, R ^l P = S, S = O, Si = O.
R ^g , R ^h , R ⁱ , R ^j , R ^k , 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 structures represented by the general formulas (1) to (3) will be described. For example, in the case of “an alkyl group that may be substituted with a substituent”, an alkyl group in which one or more of the hydrogens of the alkyl group are substituted with a substituent, or an alkyl group that does not have a particular substituent Means.

  Examples of the substituent in the phrase “may be substituted with a substituent” include an alkyl group, alkenyl group, alkynyl group, cycloalkyl group, unsaturated cycloalkyl group, aromatic group, heterocyclic group, halogen, 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, hydroxamic acid group, Rufino 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, 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, and Si = O.
R ^m , R ⁿ , R ^o and R ^p are each independently substituted with hydrogen, halogen, an alkyl group which may be substituted with a substituent, a cycloalkyl group which 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 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 optionally substituted alkoxy group, an unsaturated alkoxy group optionally substituted with a substituent, a thioalkoxy group optionally substituted with a substituent, an unsaturated thioalkoxy group optionally substituted with a substituent, OH , SH, CN, SCN, 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 is 2n = a + b + c + d + e + f + g + Satisfy h. Further, three of R ¹⁰ , R ¹¹ and R ¹² may combine to form a ring, in which case two of the three groups are 2n = a + b + c + d + e + f + g + Satisfy h, and one group satisfies 2n-1 = a + b + c + d + e + f + g + h.
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 , 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. )

  In the chemical structures represented by the general formulas (4) to (6), the meaning of the phrase “may be substituted with a substituent” 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 above 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 anion of the salt 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, 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. R ¹⁶ , R ¹⁷ and R ¹⁸ may combine to form a ring, in which case two of the three groups satisfy 2n = a + b + c + d + e, The group satisfies 2n-1 = a + b + c + d + e. )

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 structure 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 include (CF ₃ SO ₂ ) ₂ NLi (hereinafter sometimes referred to as “LiTFSA”), (FSO 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 is particularly preferred.

  What was sufficient is just to employ | adopt what combined the cation and anion which were demonstrated above in an appropriate number, respectively. 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 ethyl methyl carbonate, amides such as formamide, N, N-dimethylformamide, N, N-dimethylacetamide, and N-methylpyrrolidone , Isopropyl isocyanate, n-propyl isocyanate , Isocyanates such as chloromethyl isocyanate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, methyl formate, ethyl formate, vinyl acetate, methyl acrylate, methyl methacrylate, esters, glycidyl methyl ether, epoxy butane, Epoxys such as 2-ethyloxirane, oxazoles such as oxazole, 2-ethyloxazole, oxazoline, 2-methyl-2-oxazoline, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, acetic anhydride, propionic anhydride, etc. Acid anhydrides, sulfones such as dimethyl sulfone and sulfolane, sulfoxides such as dimethyl sulfoxide, nitros such as 1-nitropropane and 2-nitropropane, furans such as furan and furfural, γ-butyrolactone, γ-butyl Cyclic esters such as lolactone and δ-valerolactone, aromatic heterocycles such as thiophene and pyridine, heterocycles such as tetrahydro-4-pyrone, 1-methylpyrrolidine and N-methylmorpholine, trimethyl phosphate, phosphorus And phosphoric acid esters such as triethyl acid.

  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 each independently represent 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 0 or an integer, 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 , 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 sometimes referred to as “DME”) is preferred.

  These organic solvents may be used alone in the electrolytic solution, or a plurality of them may be used in combination.

Peak electrolytic solution of the present invention, in the vibration spectrum, per peak intensity derived from the organic solvent contained in the electrolytic solution of the present invention, the intensity of the original peak organic solvent and I _o, the original peak organic solvent was shifted (Hereinafter, it may be referred to as “shift peak”.) When the intensity is I _s , the characteristic is I _s > I _o . That is, in the vibrational spectral spectrum chart obtained by subjecting the electrolytic solution of the present invention to vibrational spectral measurement, the relationship between the two peak intensities is I _s > _Io .

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

In the vibration spectrum of the electrolyte solution of the present invention, when a peak inherent peak organic solvent is shifted there are a plurality, if it is determined the relationship based on the likely peak determines the relationship of the most I _s and I _o Good. Further, when an organic solvent having a hetero element in the electrolytic solution of the present invention using a plurality of kinds, the most I _s and I relationship easy determination of _o (the difference between the most I _s and I _o is noticeable) organic solvent And the relationship between _Is and _Io may be determined based on the peak intensity. Also, small amount of shift of the peak, if the overlap peak shift back and forth look like a gentle mountain performs peak separation using known means may determine the relationship between I _s and I _o .

  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 the 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 60% or more. Preferably, 80% or more is particularly preferable. Further, in an 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 I _s > 2 × I _o , more preferably satisfies the condition of I _s > 3 × I _o , and satisfies the condition of I _s > 5 × I _o . It is particularly preferable to satisfy it. Most preferably, in the vibration spectrum of the electrolyte solution of the present invention, the intensity I _o of the original peak organic solvent is not observed, an electrolytic solution strength of the shift peak I _s is observed. 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 (state where I _o = 0).

  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 considered to form a stable cluster. From the results of the 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 to one molecule of a metal salt. The In consideration of 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, and 1.5 mol or more and 3.1 mol. The following is more preferable, and 1.6 mol or more and 3 mol or less is more preferable.

  In the electrolytic solution of the present invention, it is presumed that clusters are 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.

  The concentration (mol / L) of the electrolytic solution of the present invention is individually exemplified in Table 1.

  An organic solvent that forms a cluster and an 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 that is 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.

Examples of the vibrational spectrum include an IR spectrum and a Raman spectrum. 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. About one to select the IR spectrum or the Raman spectrum, the vibrational spectrum of the electrolyte solution of the present invention may be selected towards the spectrum tends to determine the relationship between I _s and I _o. 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 acetonitrile solvent at a concentration of 1 mol / L to obtain an electrolyte 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, acetonitrile molecules solvated with LiTFSA and acetonitrile molecules not solvated with LiTFSA are different in the environment where the acetonitrile molecules are placed. Is done. More specifically, the peak of acetonitrile that is not solvated with LiTFSA is observed at the same position (wave number) as when IR measurement was performed with only acetonitrile, but the peak of acetonitrile that was solvated with LiTFSA Is observed with the peak position (wave number) shifted to the high wave number side.

And, in the concentration of the conventional electrolyte, there are many acetonitriles that are not solvated with LiTFSA, so in the vibrational spectrum of the conventional electrolyte, the peak intensity I _o of the original acetonitrile and the original acetonitrile The relationship between the peak intensity I _s and the peak shift is I _s <I _o .

On the other hand, the electrolytic solution of the present invention has a higher concentration of LiTFSA than the conventional electrolytic solution, and the number of acetonitrile molecules solvated with LiTFSA in the electrolytic solution (forms clusters) is different from that of LiTFSA. More than the number of unsolvated acetonitrile molecules. Then, the relationship between the intensity I _o of the original peak of acetonitrile and the intensity I _{s of} the peak shifted from the original peak of acetonitrile in the vibrational spectroscopic spectrum of the electrolytic solution of the present invention is I _s > I _o .

Table 2, in the vibration spectrum of the electrolyte solution of the present invention are illustrated and the wave number of organic solvents that may be useful in calculating the I _o and I _s, the attribution. 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.

Known data may be referred to for the wave number of the organic solvent and its attribution. As references, the Spectroscopical Society of Japan Series 17 Raman Spectroscopy, Hiroo Higuchi, Atsuko Hirakawa, Academic Publishing Center, pages 231-249. Further, even calculation using the computer, it is possible to predict the wave number of organic solvents that may be useful in calculating the I _o and I _s, the wave number shift of the case where the organic solvent and the metal salt is coordinated. For example, Gaussian09 (registered trademark, Gaussian) may be used to calculate the density functional as B3LYP and the basis function as 6-311G ++ (d, p). Those skilled in the art, described in Table 2, the known data, by reference to calculation results of the computer, select the peak of the organic solvent, it is possible to calculate the I _o and I _s.

  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. (If lithium is lithium, the lithium transport number is improved), the reaction rate between the electrode and the electrolyte is improved, the uneven salt concentration of the electrolyte during high-rate charge / discharge of the battery is reduced, and the electric double layer capacity is 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 electrolytic solution of the present invention has a higher viscosity than the conventional electrolytic solution of a battery. 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 for this is that due to the Li concentration unevenness that occurs 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 is 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 by the physical properties of the electrolytic solution of the present invention with high viscosity. In addition, due to the physical properties of the electrolytic solution of the present invention with high viscosity, the liquid retaining property of the electrolytic solution at the electrode interface was improved, and the state where the electrolytic solution was insufficient at the electrode interface (so-called liquid withdrawn state) could be suppressed. The reason is considered.

  By the way, the electrolytic solution of the present invention contains a high concentration of metal salt cations. For this reason, in the electrolytic solution of the present invention, the distance between adjacent cations is extremely short. When a cation such as lithium ion moves between the positive electrode and the negative electrode during charge / discharge of the nonaqueous secondary battery, the cation closest to the destination electrode is 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 correspondingly. Due to this, the reaction rate of the nonaqueous secondary battery of the present invention having the electrolytic solution of the present invention is considered to be high.

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

  The higher the ionic conductivity of the electrolytic solution, the more suitable ions can be transferred, and an excellent electrolytic solution for a battery can be obtained. The ion conductivity σ (mS / cm) of the electrolytic solution of the present invention is preferably 1 ≦ σ. Regarding the ionic conductivity σ (mS / cm) of the electrolytic solution of the present invention, when it shows a suitable range including the upper limit, a range of 2 <σ <200 is preferable, and a range of 3 <σ <100 is more preferable. 4 <σ <50 is more preferable, and 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 in the range of 1.2 ≦ d ≦ 2.2, and more preferably in the range of 1.24 ≦ d ≦ 2.0. Preferably, the range of 1.26 ≦ d ≦ 1.8 is more preferable, and the 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 a density at 20 ° C. D / c described below is a value obtained by dividing the above d by the salt concentration c (mol / L).

  D / c in the electrolytic solution of the present invention is 0.15 ≦ d / c ≦ 0.71, preferably in the range of 0.15 ≦ d / c ≦ 0.56, more preferably in the range of 0.25 ≦ d / c ≦ 0.56, and 0.26 ≦ d A range of /c≦0.50 is more preferable, and a range of 0.27 ≦ d / c ≦ 0.47 is particularly preferable.

  The d / c in the electrolytic solution of the present invention can be defined even when the metal salt and the 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 more preferably within the range of 0.44 ≦ d / c ≦ 0.52. 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 more preferably in the range of 0.36 ≦ d / c ≦ 0.39. 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 more preferably in the range of 0.34 ≦ d / c ≦ 0.42. 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, more preferably in the range of 0.25 ≦ d / c ≦ 0.38, and 0.25 ≦ d / A range of c ≦ 0.31 is more preferable, and a 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 more preferably in the range of 0.34 ≦ d / c ≦ 0.42. 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 more preferably in the range of 0.37 ≦ d / c ≦ 0.45. 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 more preferably in the range of 0.39 ≦ d / c ≦ 0.48.

  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, so that the metal ion transport rate in the electrolyte solution is improved (especially when the metal is lithium). , 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.

  The manufacturing method of the electrolyte solution of this invention is demonstrated. Since the electrolytic solution of the present invention has a higher metal salt content than the conventional electrolytic solution, the production method of adding an organic solvent to a solid (powder) metal salt results in the formation of an agglomerate. 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 under 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” means 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 including the conventional metal salt concentration, and then the thermodynamically unstable liquid state. It becomes a third electrolyte solution in a new liquid state that passes through the two electrolyte solutions and is thermodynamically stable, that is, the electrolyte 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 organic solvents 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 dissolving step is a step of preparing a first electrolytic solution by mixing an organic solvent having a hetero atom and a metal salt, and dissolving the metal salt.

  In order to mix the organic solvent having a hetero atom and the metal salt, the metal salt may be added to the organic solvent having a hetero atom, or the organic solvent having a hetero atom 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 carried out continuously, or the first electrolytic solution obtained in the first dissolution step is temporarily stored (standing), and after a certain time has elapsed, the second 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.

  In order to prepare the second electrolyte solution in a supersaturated state that is thermodynamically unstable, it is essential that the second dissolution step be performed under stirring and / or heating conditions. By performing the second dissolution step with a stirrer with a stirrer such as a mixer, it may be under stirring conditions, or the second dissolution step may be performed using a stirrer and a device that operates the stirrer (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, when the added metal salt is not sufficiently dissolved, an increase in stirring speed and / or further heating is performed. 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.

  Once the second electrolytic solution obtained in the second dissolution step is allowed to stand, crystal of the metal salt will precipitate, so it is preferable to carry out the second dissolution step and the third dissolution step 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, so that 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 dissolution step, the second dissolution step, and the third dissolution step is about 2: 1, the production of the third electrolytic solution (the electrolytic solution of the present invention) can be performed. 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 assumed to be composed of, for example, two molecules of an organic solvent with respect to one molecule of a lithium salt, and 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 type of the metal salt and the organic solvent, the first to third dissolving steps described above may be performed at the treatment temperature in each dissolving step even though the supersaturated state is not passed. The electrolytic solution of the present invention can be appropriately produced using the specific dissolution means described in 1.

  Moreover, in the manufacturing method of the electrolyte solution of this invention, it is preferable to have a vibrational spectroscopic measurement process which performs vibrational spectroscopic measurement of the electrolyte solution in the middle of manufacture. 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 subjecting it to vibration spectroscopic measurement, or a method of performing vibration spectroscopic measurement of each electrolytic solution in situ (in situ) But it ’s okay. As a method for in-vitro vibrational spectroscopic measurement of an electrolytic solution, a method of performing vibrational spectroscopic measurement by introducing an electrolytic solution in the middle of production into a transparent flow cell, or a method of performing Raman measurement from outside the container using a transparent manufacturing container Can be mentioned.

By including the electrolyte vibrational spectroscopy measurement step to the manufacturing method of the present invention, it is possible to check during the manufacturing of the relationship between I _s and I _o in the electrolytic solution, the electrolytic solution in the process of production is reach 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 be grasped.

  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 electrolyte solution of the present invention is mixed with a polymer or an inorganic filler to form a mixture, the mixture contains the electrolyte 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 said polymer, the polymer used for batteries, such as a lithium ion secondary battery, and the general chemically crosslinked polymer are employable. 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, polymethyl methacrylate, polyethylene oxide, polypropylene oxide, polyacrylonitrile, polyvinylidene fluoride, polyethylene glycol dimethacrylate, polyethylene glycol acrylate, polyglycidol, polytetrafluoroethylene, polyhexafluoropropylene, Polycarboxylic acid such as polysiloxane, polyvinyl acetate, polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, polyitaconic acid, polyfumaric acid, polycrotonic acid, polyangelic acid, carboxymethylcellulose, styrene-butadiene rubber, nitrile-butadiene rubber, polystyrene , Polycarbonate, unsaturated polyester copolymerized with maleic anhydride and glycols, substituted It can be exemplified polyethylene oxide derivative, a copolymer of vinylidene fluoride and hexafluoropropylene having. 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, The agar containing polysaccharides, such as agarose, can be illustrated as the said material.

  As said inorganic filler, inorganic ceramics, such as an oxide and nitride, are preferable.

  Inorganic ceramics have hydrophilic and hydrophobic functional groups on their surfaces. 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. In addition, the inorganic ceramic itself may have lithium conductivity, specifically, Li ₃ N, LiI, LiI-Li ₃ N-LiOH, LiI-Li ₂ SP ₂ O ₅ , LiI-Li ₂ SP ₂ S ₅ , LiI-Li ₂ SB ₂ S ₃ , Li ₂ OB ₂ S ₃ , Li ₂ OV ₂ O ₃ -SiO ₂ , Li ₂ OB ₂ O ₃ -P ₂ O ₅ , Li ₂ OB ₂ O ₃ -ZnO, Li Examples include ₂ O—Al ₂ O ₃ —TiO ₂ —SiO ₂ —P ₂ O ₅ , LiTi ₂ (PO ₄ ) ₃ , Li-βAl ₂ O ₃ , and LiTaO ₃ .

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 a compound represented by xLi ₂ S- (1-x) P ₂ S ₅ , a compound obtained by substituting a part of S of the compound with another element, and a 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, a nonaqueous electrolyte secondary battery using the electrolytic solution of the present invention will be described.

  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 discharging or charging of a non-aqueous 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, etc. 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.

The negative electrode active material contains graphite having a G / D ratio of 3.5 or more, which is the ratio of G-band to 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 is sometimes referred to as high crystalline graphite, and graphite having a G / D ratio of less than 3.5 is sometimes 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.

  If the negative electrode active material is mainly high crystalline graphite having a G / D ratio of 3.5 or more, it can also contain low crystalline graphite or amorphous carbon.

In the non-aqueous secondary battery of the present invention, in addition to the high crystal graphite, a material that can occlude and release charge carriers can be used. For example, in the case of a lithium ion secondary battery, there is no particular limitation as long as it is a simple substance, alloy, or compound that can occlude and release lithium ions. For example, as a negative electrode active material, Li, group 14 elements such as carbon, silicon, germanium and tin, group 13 elements such as aluminum and indium, group 12 elements such as zinc and cadmium, group 15 elements such as antimony and bismuth, magnesium , Alkaline earth metals such as calcium, and group 11 elements such as silver and gold may be used alone. When silicon or the like is used for the negative electrode active material, a silicon single atom reacts with a plurality of lithiums, so that it becomes a high-capacity active material, but there is a problem that the expansion and contraction of the volume accompanying the insertion and extraction of lithium becomes significant. In order to reduce the fear, it is also preferable to employ an alloy or compound in which another element such as a transition metal is combined with a simple substance such as silicon as the negative electrode active material. Specific examples of the alloy or compound include tin-based materials such as Ag-Sn alloy, Cu-Sn alloy, 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 a combination of a silicon-based material and a carbon-based material. Further, as the negative electrode active material, oxides such as Nb ₂ O ₅ , TiO ₂ , Li ₄ Ti ₅ O ₄ , WO ₂ , MoO ₂ , Fe ₂ O ₃ , or Li _3-x M _x N (M = Co Nitride represented by Ni, Cu) may be employed. One or more of these materials can be used as the negative electrode active material.

  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 blending 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 as needed in the negative electrode active material layer 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 Grown) 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 blending 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 aid is too small, an efficient conductive path cannot be formed, and if the amount of the conductive aid 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 for a non-aqueous secondary battery, a negative electrode active material powder, a conductive additive such as carbon powder, a binder, and an appropriate amount of solvent are mixed and mixed to form a slurry, which is a roll coat method, dip It can be produced by applying onto a current collector by a method such as a 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 secondary battery has a positive electrode active material capable of inserting and extracting charge carriers such as lithium ions. 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. When the non-aqueous secondary battery of the present invention is a lithium ion secondary battery and the potential of the positive electrode is 4 V or higher with respect to lithium, it is preferable to employ an aluminum current collector.

  The electrolytic solution of the present invention hardly corrodes an aluminum current collector. That is, it is considered that a non-aqueous secondary battery using the electrolytic solution of the present invention and using an 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, it is preferable to use a positive electrode current collector 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.
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 series alloys (Al-Fe series).

  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, a layered compound _{Li a Ni b Co c Mn d} D e O f (0.2 ≦ a ≦ 1.2, b + c + d + e = 1,0 ≦ e <1, D is Li, Fe, At least one element selected from Cr, 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 can be mentioned. Further, as the 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 (for example, 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 contained in the basic composition may be substituted with another metal element.

In addition, a positive electrode active material that does not include a charge carrier that contributes to charge and discharge can also be used as the positive electrode active material. For example, in the case of a lithium ion secondary battery, sulfur alone (S), a compound composed of sulfur and carbon, 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 secondary battery as in the case of 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, an active material layer-forming composition 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 the collection is performed. 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 in the non-aqueous secondary battery 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, polyaramide (Aromatic polyamide), 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 connected to 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 system. A secondary battery may be used. Moreover, the non-aqueous 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.

  The shape of the nonaqueous 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 secondary battery of the present invention may be mounted on a vehicle. The vehicle may be a vehicle that uses electric energy from a non-aqueous 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 secondary battery is mounted on a vehicle, a plurality of non-aqueous secondary batteries may be connected in series to form an assembled battery. Examples of devices equipped with non-aqueous secondary batteries include various home appliances driven by batteries such as personal computers and portable communication devices, office equipment, and industrial equipment, in addition to vehicles. Further, the non-aqueous 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 of ships and / or power supply sources of auxiliary machinery, aircraft, Power supply for spacecraft and / or auxiliary equipment, auxiliary power supply for vehicles that do not use electricity as a power source, power supply for mobile home robots, power supply for system backup, power supply for uninterruptible power supply, You may use for the electrical storage apparatus which stores temporarily the electric power required for charge in the charging station for electric vehicles.

  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. Hereinafter, unless otherwise specified, “parts” means parts by mass, and “%” means mass%.

Example 1
<Preparation of the electrolytic solution of the present invention>
About 5 mL of acetonitrile, which is an organic solvent, was placed in a flask equipped with a stir bar. Under stirring conditions, (FSO ₂ ) ₂ NLi (hereinafter referred to as LiFSA), which is a lithium salt, was gradually added to and dissolved in acetonitrile in the flask. When 16.83 g of LiFSA 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. The production was performed in a glove box under an inert gas atmosphere. The concentration of LiFSA in the obtained electrolytic solution of the present invention is 4.5 mol / L, and 2.4 molecules of acetonitrile are contained per molecule of LiFSA.

The obtained electrolyte solution of the present invention, acetonitrile, and LiFSA were subjected to IR measurement under the following conditions. IR spectra in the range of 2100 to 2400 cm ⁻¹ are shown in FIGS. 1 to 3, respectively. The horizontal axis of the figure is the wave number (cm ⁻¹ ), and the vertical axis is the absorbance (reflection absorbance).

(Evaluation Example 1: IR measurement)
<IR measurement conditions>
Equipment: FT-IR (Bruker Optics)
Measurement conditions: ATR method (with diamond)
Measurement atmosphere: Inert gas atmosphere

In the vicinity of 2250 cm ⁻¹ of the IR spectrum of acetonitrile shown in FIG. 2, a characteristic peak derived from the stretching vibration of the triple bond between C and N of acetonitrile was observed. No special peak was observed in the vicinity of 2250 cm ^{−1 in} the IR spectrum of LiFSA shown in FIG.

In the IR spectrum of the electrolyte solution of the present invention shown in FIG. 1, 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 (I _o = 0.00997). It was done. More IR spectrum of Figure 1, characteristic peaks peaks derived from stretching vibration triple bond between C and N acetonitrile near 2280 cm ^-1 shifted from the vicinity of 2250 cm ^-1 to the high frequency side intensity I _s = Observed at 0.08288. The relationship between the peak intensities of I _s and I _o was I _s > I _o , and I _s = 11 × I _o .

[Comparative Example 1]
An electrolytic solution of Comparative Example 1 having a LiFSA concentration of 1.0 mol / L was produced in the same manner as in Example 1 using 3.74 g of LiFSA. In the electrolyte solution of Comparative Example 1, 17 molecules of acetonitrile are contained per molecule of LiFSA.

In the IR spectrum of the electrolyte solution of Comparative Example 1 shown in FIG. 4, 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 as in FIG. Observed at _o = 0.04975. More IR spectrum of Figure 4, characteristic peaks peak due to stretching vibration of the triple bond between C and N acetonitrile near 2280 cm ^-1 shifted from the vicinity of 2250 cm ^-1 to the high frequency side intensity I _s = Observed at 0.03804. The relationship between the peak intensities of I _s and I _o was I _s <I _o .

(Evaluation Example 2: Viscosity)
Using a falling ball viscometer (Lovis 2000 M manufactured by Anton Paar GmbH (Anton Paar GmbH)), an electrolytic solution was sealed in a test cell under an Ar atmosphere, and the viscosity was measured at 30 ° C.

  The viscosity of the electrolytic solution of the present invention according to Example 1 is higher than that of the electrolytic solution according to Comparative Example 1, and can be said to be high. Therefore, the battery using the electrolytic solution of the present invention according to Example 1 suppresses leakage of the electrolytic solution even if the battery is damaged.

(Evaluation Example 3: Ionic conductivity)
In an Ar atmosphere, an electrolyte was sealed in a glass cell with a platinum electrode and a known cell constant, and the impedance was measured at 30 ° C. and 1 kHz. The ion conductivity was calculated from the impedance measurement result. As a measuring instrument, Solartron 147055BEC (Solartron) was used.

  When the ionic conductivity of the electrolytic solution of the present invention according to Example 1 was measured under the above conditions, it was 9.7 mS / cm, indicating excellent ionic conductivity. Therefore, it can be understood that the electrolytic solution of the present invention according to Example 1 can function as an electrolytic solution for various batteries.

(Evaluation Example 4: Volatility)
The volatility of the electrolytic solution of the present invention according to Example 1 and the electrolytic solution according to Comparative Example 1 was measured by the following method.

  About 10 mg of the electrolytic solution was put in an aluminum pan and placed in a thermogravimetric measuring apparatus (TA Instruments, SDT600), and the change in weight 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 4.

  The maximum volatilization rate of the electrolytic solution according to Example 1 was significantly smaller than the maximum volatilization rate of the electrolytic solution according to Comparative Example 1. 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: Li transportation rate)
The Li transport number of the electrolyte solutions of Example 1 and Comparative Example 1 was measured under the following conditions. The results are shown in Table 5.

The NMR tube containing the electrolyte solution of Example 1 or Comparative Example 1 was subjected to a PFG-NMR apparatus (ECA-500, JEOL), and under conditions of 500 MHz and a magnetic field gradient of 1.26 T / m, for 7Li, 19F, Using the spin echo method, the diffusion coefficient of Li ions and anions in each electrolyte was measured while changing the magnetic field pulse width. Li transport number was calculated by the following formula.
Li transport number = (Li ion diffusion coefficient) / (Li ion diffusion coefficient + anion diffusion coefficient)

  The Li transport number of the electrolyte solution of the present invention of Example 1 was significantly higher than that of the electrolyte solution of Comparative Example 1. 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. Then, it can be said that the electrolyte solution of the present invention has a higher lithium ion (cation) transport rate than the conventional electrolyte solution exhibiting the same ionic conductivity.

<Production of lithium secondary battery>
Adds SNO grade graphite (average particle size 15μm) 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 a device, 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 to form a negative electrode active material layer 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 .

  A lithium secondary battery (half cell) was produced using the produced negative electrode as an evaluation electrode. 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 of the present invention according to Example 1 produced as described above was injected, and the battery case was sealed to obtain a lithium secondary battery. Details of the lithium battery of Example 1 and the nonaqueous electrolyte secondary batteries of the following Examples and Comparative Examples are shown in Table 21 at the end of the column of Examples.

(Example 2)
The negative electrode was prepared in the same manner as in Example 1 except that SNO grade graphite (average particle size 10 μm) graphite (hereinafter sometimes referred to as graphite (B)) was used instead of graphite (A). Other than that, a lithium secondary battery was obtained in the same manner as in Example 1. The graphite (B) used was subjected to Raman spectrum analysis in the same manner as in Example 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 3)
A negative electrode was produced in the same manner as in Example 1 except that graphite (C) having an average particle size of 10 μm was used instead of graphite (A), and a lithium secondary battery was obtained in the same manner as in Example 1. . The graphite (C) used was subjected to Raman spectrum analysis in the same manner as in Example 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 4
About 5 mL of dimethyl carbonate, 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. The above production was carried out in a glove box under an inert gas atmosphere. The concentration of (FSO ₂ ) ₂ NLi in the obtained electrolytic solution was 3.9 mol / L. Further, in this electrolytic solution, _two molecules of dimethyl carbonate are contained with respect to one molecule of (FSO ₂ ) ₂ NLi.
A lithium secondary battery was obtained in the same manner as in Example 3 except that the above electrolytic solution was used as the electrolytic solution.

[Comparative Example 2]
Example 1 was used except that graphite (A) was replaced with graphite of the product name SG-BH (average particle diameter 20 μm) of Ito Graphite Industries Co., Ltd. (hereinafter sometimes referred to as graphite (D)). A lithium secondary battery was obtained in the same manner as in Example 1 except that a negative electrode was produced. The graphite (D) used was subjected to Raman spectrum analysis in the same manner as in Example 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 3]
Example 1 except that graphite with the product name SG-BH8 (average particle size 8 μm) (hereinafter sometimes referred to as graphite (E)) of Ito Graphite Industries Co., Ltd. was used instead of graphite (A). A lithium secondary battery was obtained in the same manner as in Example 1 except that a negative electrode was produced. The graphite (E) used was subjected to Raman spectrum analysis in the same manner as in Example 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 4]
Other than using an electrolytic solution in which LiPF ₆ was dissolved at a concentration of 1M in a mixed solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at 3: 7 (volume ratio) instead of the electrolytic solution of the present invention. Obtained a lithium secondary battery in the same manner as in Example 1.

[Comparative Example 5]
Other than using an electrolytic solution in which LiPF ₆ was dissolved at a concentration of 1M in a mixed solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at 3: 7 (volume ratio) instead of the electrolytic solution of the present invention. Obtained a lithium secondary battery in the same manner as in Example 2.

[Comparative Example 6]
Other than using an electrolytic solution in which LiPF ₆ was dissolved at a concentration of 1M in a mixed solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at 3: 7 (volume ratio) instead of the electrolytic solution of the present invention. Obtained a lithium secondary battery in the same manner as in Example 3.

[Comparative Example 7]
Comparative Example 1 was used except that an electrolytic solution in which LiPF ₆ was dissolved at a concentration of 1M was used in a mixed solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a ratio of 3: 7 (volume ratio). A lithium secondary battery was obtained.

[Comparative Example 8]
Other than using an electrolytic solution in which LiPF ₆ was dissolved at a concentration of 1M in a mixed solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at 3: 7 (volume ratio) instead of the electrolytic solution of the present invention. Obtained a lithium secondary battery in the same manner as in Comparative Example 2.

<Test and evaluation>
Table 6 shows the configurations of the lithium secondary batteries according to Examples 1 to 4 and Comparative Examples 2 to 8.

(Evaluation Example 6: Cyclic voltammetry)
For the lithium secondary batteries according to Examples 1 to 4 and Comparative Examples 2 to 8, the conditions were (temperature: 25 ° C., sweep rate: 0.1 mV / sec., Voltage range: 0.01 V-2 V, 1 to 5 cycles). Then, cyclic voltammetry (CV) measurement was performed. The results are shown in FIGS. In the lithium secondary batteries according to Examples 1 to 4, reversible oxidation / reduction reactions are confirmed in the same manner as the conventionally used lithium secondary batteries according to Comparative Examples 2 to 8. In addition, a reversible oxidation / reduction reaction can be confirmed even when graphite having a G / D ratio of less than 3.5 is used as in the lithium secondary batteries according to Comparative Examples 2 and 3. That is, it can be understood that the electrolytic solution of the present invention can be used as a lithium secondary battery if graphite is used as the negative electrode active material regardless of the G / D ratio.

(Example 5)
The same negative electrode as in Example 1 was used.

Li [Ni _0.5 Co _0.2 Mn _0.3 ] O ₂ , acetylene black (AB), polyvinylidene fluoride (PVdF), and N-methyl-2-pyrrolidone (NMP) were added and mixed as a positive electrode active material, A positive electrode mixture was prepared. 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.

  Using the positive electrode, the negative electrode, and the electrolytic solution of Example 1, a laminate type lithium ion 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 6)
An electrolytic solution of the present invention was prepared in the same manner as in Example 1 except that “LiTFSA” was used instead of “LiFSA” so as to have a concentration of 4.2 M (4.2 mol / L). A lithium ion secondary battery was produced in the same manner as in Example 5 except that the same negative electrode as in Example 1 and the same positive electrode as in Example 5 were used and the electrolytic solution of the present invention was used.

For this electrolytic solution of the present invention, IR measurement was performed in the same manner as in Example 1. The IR spectrum, 2250 cm ^-1 near the derived acetonitrile peak (I _o) is not almost observed, triple bond between C and N acetonitrile near 2280 cm ^-1 shifted from the vicinity of 2250 cm ^-1 to the high frequency side characteristic peak derived from stretching vibration was observed at a peak intensity I _s = 0.05234. The relationship between the peak intensities of I _s and I _o was I _s > I _o .

  The viscosity measured in the same manner as in Example 1 was 138 mPa · s, and the ionic conductivity measured in the same manner as in Example 1 was 0.98 mS / cm.

[Comparative Example 9]
Other than using an electrolytic solution in which LiPF ₆ was dissolved at a concentration of 1M in a mixed solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at 3: 7 (volume ratio) instead of the electrolytic solution of the present invention. Obtained a lithium ion secondary battery in the same manner as in Example 5.

<Test and evaluation>
(Evaluation Example 7: Thermal stability)
The lithium ion secondary batteries of Examples 5 and 6 and Comparative Example 9 were fully charged under a potential difference of 4.2 V and a constant current and constant voltage condition. The fully charged lithium ion 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 hermetic pan, differential scanning calorimetry was performed under a nitrogen atmosphere under a temperature increase rate of 20 ° C./min., And a DSC curve was observed. FIG. 15 shows a DSC chart of the lithium ion secondary batteries of Example 5 and Comparative Example 9, and FIG. 16 shows a DSC chart of the lithium ion secondary batteries of Example 6 and Comparative Example 9.

  In a lithium ion secondary battery using graphite as a negative electrode active material, when it is heated to a fully charged state using a general electrolytic solution, a plurality of exothermic reactions are caused at 300 ° C. or lower as in Comparative Example 9. However, in Examples 5 and 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 are excellent. I understand that.

<Test and evaluation>
(Evaluation Example 8: Rate characteristics)
Using the lithium secondary batteries of Example 1 and Comparative Example 2, 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: 2V → 0.01V (vsLi / 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 the current value required to fully charge or discharge the battery in 1 hour at a constant current.

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

<Test and evaluation>
(Evaluation Example 9: Rate characteristics, cycle durability)
Using the lithium secondary batteries of Examples 1 to 3 and Comparative Examples 2 to 4 and 8, rate capacity characteristics and cycle capacity retention rates 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) Measurement 3 times for each rate (24 cycles in total)
(5) Temperature is room temperature

  The current capacities at 0.1C rate and 2C rate were measured under the above conditions, and the ratio of the current capacity at 2C rate to the current capacity at 0.1C rate was defined as the rate capacity characteristic. In addition, charge / discharge of 25 cycles was repeated at 0.2 C, and the ratio of the current capacity at the 25th cycle to the initial current capacity was defined as a cycle capacity maintenance rate. The results are shown in Table 7.

  As in Comparative Examples 2 and 3, when 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 are combined, the cycle capacity retention rate is lowered. Further, as in Comparative Examples 4 and 8, when a conventional electrolytic solution is used, the rate capacity characteristics are lowered regardless of the G / D ratio of graphite. However, it can be seen that the rate capacity characteristics and the cycle capacity retention ratio are compatible 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. Further, from the comparison between the examples, it is recognized that the higher the G / D ratio, the more the rate capacity characteristics and the cycle capacity maintenance ratio tend to improve, and the G / D ratio is more preferably 10 or more. In addition, it can be seen from this result that the rate capacity characteristics and the cycle capacity retention ratio are improved both when AN is used as the organic solvent for the electrolyte and when DMC is used.

(Example 7)
<Preparation of the electrolytic solution of the present invention>
About 5 mL of acetonitrile, which is an organic solvent, was placed in a flask equipped with a stir bar. Under stirring conditions, (FSO ₂ ) ₂ NLi (hereinafter referred to as LiFSA), which is a lithium salt, was gradually added to and dissolved in acetonitrile in the flask. When 16.88 g of LiFSA 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. The production was performed in a glove box under an inert gas atmosphere. The concentration of LiFSA in the obtained electrolytic solution of the present invention is 4.5 mol / L, and 2.4 molecules of acetonitrile are contained per molecule of LiFSA.

<Production of negative electrode>
As the negative electrode active material, SEC Carbon Co., Ltd. SNO grade graphite (average particle size: 15 μm) graphite (hereinafter sometimes referred to as graphite (A)) 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 a device, 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.

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

<Preparation of 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 polyvinylidene fluoride (PVDF). The conductive auxiliary agent is made of acetylene black (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, LiNi _0.5 Co _0.2 Mn _0.3 O ₂ , PVDF and AB are mixed so as to have the above mass ratio, and N-methyl-2-pyrrolidone (NMP) as a solvent is added to form a paste The 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 with the positive electrode active material layer formed on the surface was compressed using a roll press machine, and the aluminum foil and the positive electrode active material layer were firmly bonded. The joined product was heated with a vacuum dryer at 120 ° C. for 6 hours, cut into a predetermined shape, and a positive electrode was obtained.

<Production of lithium secondary battery>
The laminated lithium ion secondary of Example 7 was used in the same manner as in Example 5 except that the above-described positive electrode, negative electrode, and electrolytic solution of the present invention of Example 7 were used and a cellulose nonwoven fabric (thickness 20 μm) was used as the separator. I made a battery.

[Comparative Example 10]
Other than using an electrolytic solution in which LiPF ₆ was dissolved at a concentration of 1M in a mixed solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at 3: 7 (volume ratio) instead of the electrolytic solution of the present invention. Obtained a lithium secondary battery in the same manner as in Example 7.

<Test and evaluation>
(Evaluation Example 10: Input characteristics)
Using the lithium ion batteries of Example 7 and Comparative Example 10, the input (charging) characteristics were evaluated under the following conditions.
(1) Working voltage range: 3V-4.2V
(2) Capacity: 13.5mAh
(3) SOC80%
(4) Temperature: 0 ℃, 25 ℃
(5) Number of measurements: 3 times each

  The evaluation conditions are a state of charge (SOC) 80%, 0 ° C., 25 ° C., operating voltage range 3V-4.2V, and capacity 13.5 mAh. SOC 80%, 0 ° C. is an area in which input characteristics are difficult to be obtained, for example, when used in a refrigerator room. The input characteristics of Example 4 and Comparative Example 9 were evaluated three times for 2-second input and 5-second input, respectively. Tables 8 and 9 show the evaluation results of the input characteristics. “2-second input” in the table means an input 2 seconds after the start of charging, and “5-second input” means an input 5 seconds after the start of charging.

  The results are shown in Table 8 and Table 9. In the table, the electrolytic solution of the present invention used in Example 7 is abbreviated as “FSA”, and the electrolytic solution used in Comparative Example 10 is abbreviated as “ECPF”.

  At both 0 ° C. and 25 ° C., the input (charge) characteristics of Example 7 are improved compared to Comparative Example 10. This is an effect of using graphite having a GD ratio of 3.5 or more and the electrolytic solution of the present invention, and particularly shows high input (charging) characteristics even at 0 ° C. It is shown that the movement proceeds smoothly.

  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, which is 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 stagnated temporarily, so 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, and when 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 whole 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 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)
In the same manner as in 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. When predetermined (CF ₃ SO ₂ ) ₂ NLi was added, 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 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)
In the same manner as the electrolytic solution C, an electrolytic solution D having a (CF ₃ SO ₂ ) ₂ NLi concentration 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. Manufactured.

(Electrolyte F)
Except for using dimethyl sulfoxide as the organic solvent, in the same manner as electrolyte C, the concentration of (CF ₃ SO ₂ ) ₂ NLi is 3.2 mol / L, and the density is 1.49 g / cm ^3. F was produced.

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

(Electrolyte H)
By a method similar to that for the electrolytic solution G, an electrolytic solution H having a (FSO ₂ ) ₂ NLi concentration of 3.6 mol / L and a density of 1.29 g / cm ³ was produced.

(Electrolyte I)
By a method similar to that for the electrolytic solution G, an electrolytic solution I having a (FSO ₂ ) ₂ NLi concentration 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 10 shows a list of the electrolyte solutions.

(Electrolyte E1)
The electrolytic solution of the present invention was produced as follows.

About 5 mL of 1,2-dimethoxyethane, which is 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 stagnated temporarily, so 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, and when 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 whole 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 of 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 electrolytic solution E1. The electrolytic solution E2 contains 2.1 molecules of 1,2-dimethoxyethane with respect to (CF ₃ SO ₂ ) ₂ NLi1 molecules.

(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 per 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 (CF ₃ SO ₂ ) ₂ NLi concentration 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)
Except for using 13.47 g of (FSO ₂ ) ₂ NLi as the lithium salt and 1,2-dimethoxyethane as the organic solvent, the concentration of (FSO ₂ ) ₂ NLi was 3.6 mol in the same manner as in the electrolytic solution E3. Electrolyte E5 that is / L was produced. In the electrolytic solution E5, 1.9 molecules of 1,2-dimethoxyethane are contained per (FSO ₂ ) ₂ NLi1 molecule.

(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 (FSO ₂ ) ₂ NLi concentration of 4.2 mol / L 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 per 1 molecule of (FSO ₂ ) ₂ NLi.

(Electrolyte E8)
Using 16.83 g of (FSO ₂ ) ₂ NLi, 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. In the electrolytic solution E8, 2.4 molecules of acetonitrile are contained per (FSO ₂ ) ₂ NLi1 molecule.

(Electrolytic solution E9)
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 electrolyte solution E9, 2.1 molecules of acetonitrile are contained per (FSO ₂ ) ₂ NLi1 molecule.

(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 electrolytic solution E10, _two molecules of acetonitrile are contained with respect to one molecule of (FSO ₂ ) ₂ NLi.

(Electrolytic solution E11)
About 5 mL of dimethyl carbonate, 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 electrolyte solution E13, three molecules of dimethyl carbonate are contained with respect to one molecule of (FSO ₂ ) ₂ NLi.

(Electrolytic solution E14)
Dilution was performed by adding dimethyl carbonate to the electrolytic solution E11 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)
Dilution was performed by adding dimethyl carbonate to the electrolytic solution E11 to obtain an electrolytic solution E15 having a concentration of (FSO ₂ ) ₂ NLi of 2.0 mol / L. In the electrolytic solution E15, 5 molecules of dimethyl carbonate are contained per 1 molecule of (FSO ₂ ) ₂ NLi.

(Electrolytic solution E16)
About 5 mL of ethyl methyl carbonate, 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 resulting electrolyte was transferred to a 20 mL volumetric flask and ethyl methyl carbonate was added until the volume was 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 (FSO ₂ ) ₂ NLi concentration of 2.2 mol / L. In the electrolytic solution E18, 3.5 molecules of ethyl methyl carbonate are contained per 1 molecule of (FSO ₂ ) ₂ NLi.

(Electrolytic solution E19)
About 5 mL of diethyl carbonate, 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 diethyl carbonate in the flask. When 11.37 g of 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 concentration of (FSO ₂ ) ₂ NLi of 2.6 mol / L. In the electrolytic solution E20, 2.5 molecules of diethyl carbonate are contained per 1 molecule of (FSO ₂ ) ₂ NLi.

(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)
Except that 5.74 g of (CF ₃ SO ₂ ) ₂ NLi was used and 1,2-dimethoxyethane was used as the organic solvent, the concentration of (CF ₃ SO ₂ ) ₂ NLi was 1.0 in the same manner as the electrolytic solution E3. An electrolytic solution C1 having a mol / L was produced. 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 molecules.

(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 (FSO ₂ ) ₂ NLi1 molecule.

(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 electrolytic solution C4, 17 molecules of acetonitrile are contained per 1 molecule of (FSO ₂ ) ₂ NLi.

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

(Electrolytic solution C6)
Diluted dimethyl carbonate was added to the electrolytic solution E11 to prepare 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 per 1 molecule of (FSO ₂ ) ₂ NLi.

(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 11 shows a list of electrolyte solutions.

(Evaluation Example 11: 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, The IR measurement was performed under the following conditions. IR spectra in the range of 2100 to 2400 cm ⁻¹ are shown in FIGS. 18 to 27, respectively. Furthermore, IR measurement was performed on the following conditions for the electrolytic solutions E11 to E21, the electrolytic solutions C6 to C8, and dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate. IR spectra in the range of 1900 to 1600 cm ⁻¹ are shown in FIGS. 28 to 44, respectively. In addition, FIG. 45 shows an IR spectrum in the range of 1900 to 1600 cm ⁻¹ for (FSO ₂ ) ₂ NLi. The horizontal axis of 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 of the IR spectrum of acetonitrile shown in FIG. 25, a characteristic peak derived from the stretching vibration of the triple bond between C and N of acetonitrile was observed. It should be noted 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. 26 and the IR spectrum of (FSO ₂ ) ₂ NLi shown in FIG.

In the IR spectrum of the electrolytic solution E3 shown in FIG. 18, a characteristic peak derived from the stretching vibration of the triple bond between C and N of acetonitrile was observed in the vicinity of 2250 cm ⁻¹ (I _o = 0.00699). . More IR spectrum of Figure 18, characteristic peaks peak due to stretching vibration of the triple bond between C and N acetonitrile near 2280 cm ^-1 shifted from the vicinity of 2250 cm ^-1 to the high frequency side intensity I _s = Observed at 0.05828. The relationship between the peak intensities of I _s and I _o was I _s > I _o and I _s = 8 × I _o .

The IR spectrum of the electrolyte E4 shown in FIG. 19, 2250 cm ^-1 peak derived from acetonitrile was not observed in the vicinity, between 2250 cm from the vicinity ^-1 shifted acetonitrile 2280cm around ^-1 to the high frequency side C and N characteristic peak derived from stretching vibration of the triple bond was observed at a peak intensity I _s = 0.05234 in. The relationship between the peak intensities of I _s and I _o was I _s > I _o .

In the IR spectrum of the electrolyte solution E7 shown in FIG. 20, a characteristic peak derived from the stretching vibration of the triple bond between C and N of acetonitrile was observed in the vicinity of 2250 cm ⁻¹ (I _o = 0.00997). . More IR spectrum of Figure 20, characteristic peaks peak due to stretching vibration of the triple bond between C and N acetonitrile near 2280 cm ^-1 shifted from the vicinity of 2250 cm ^-1 to the high frequency side intensity I _s = Observed at 0.08288. The relationship between the peak intensities of I _s and I _o was I _s > I _o and I _s = 8 × I _o . Also in the IR spectrum of the electrolytic solution E8 shown in FIG. 21, the same intensity peak as in the IR chart of FIG. 20 was observed at the same wave number. The relationship between the peak intensities of I _s and I _o was I _s > I _o and I _s = 11 × I _o .

The IR spectrum of the electrolyte E10 shown in FIG. 22, 2250 cm ^-1 peak derived from acetonitrile was not observed in the vicinity, between 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 of was observed at a peak intensity I _s = 0.07350. The relationship between the peak intensities of I _s and I _o was I _s > I _o .

The IR spectrum of the electrolyte C2 shown in Figure 23, similarly to FIG. 25, characteristic peaks peak due to stretching vibration of the triple bond between C and N acetonitrile near 2250 cm ^-1 intensity I _s = .04441 Was observed. More IR spectrum of Figure 23, characteristic peaks peak due to stretching vibration of the triple bond between C and N acetonitrile near 2280 cm ^-1 shifted from the vicinity of 2250 cm ^-1 to the high frequency side intensity I _s = Observed at 0.03018. The relationship between the peak intensities of I _s and I _o was I _s <I _o .

In the IR spectrum of the electrolytic solution C4 shown in FIG. 24, as in FIG. 25, a characteristic peak derived from the stretching vibration of the triple bond between C and N of acetonitrile in the vicinity of 2250 cm ⁻¹ has a peak intensity Io = 0.04975. Observed. More IR spectrum of Figure 24, characteristic peaks peak due to stretching vibration of the triple bond between C and N acetonitrile near 2280 cm ^-1 shifted from the vicinity of 2250 cm ^-1 to the high frequency side intensity I _s = Observed at 0.03804. The relationship between the peak intensities of I _s and I _o was I _s <I _o .

In the vicinity of 1750 cm ⁻¹ of the IR spectrum of dimethyl carbonate shown in FIG. 42, 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 of the IR spectrum of (FSO ₂ ) ₂ NLi shown in FIG.

In the IR spectrum of the electrolyte solution E11 shown in FIG. 28, a characteristic peak derived from the stretching vibration of the double bond between C and O of dimethyl carbonate is slightly observed at around 1750 cm ⁻¹ (I _o = 0.16628). It was done. Further, in the IR spectrum of FIG. 28, a characteristic peak derived from the stretching vibration of the double bond between C and O of dimethyl carbonate is observed in the vicinity of 1717 cm ⁻¹ shifted from the vicinity of 1750 cm ⁻¹ to the low wavenumber side. Observed at _s = 0.48032. The relationship between the peak intensities of I _s and I _o was I _s > I _o and I _s = 2.89 × I _o .

In the IR spectrum of the electrolytic solution E12 shown in FIG. 29, a characteristic peak derived from the stretching vibration of the double bond between C and O of dimethyl carbonate is observed slightly in the vicinity of 1750 cm ⁻¹ (I _o = 0.18129). It was done. More IR spectrum of FIG. 29, 1750 cm from the vicinity of ^-1 in the vicinity of 1717 cm ^-1 shifted to a lower wavenumber side of dimethyl carbonate C and O between the double bonds of the stretch from vibration characteristic peaks peak intensity I Observed at _s = 0.52005. The relationship between the peak intensities of I _s and I _o was I _s > I _o and I _s = 2.87 × I _o .

In the IR spectrum of the electrolytic solution E13 shown in FIG. 30, a characteristic peak derived from the stretching vibration of the double bond between C and O of dimethyl carbonate is observed slightly (I _o = 0.20293) in the vicinity of 1750 cm ^−1. It was done. More IR spectrum of FIG. 30, 1750 cm from the vicinity of ^-1 in the vicinity of 1717 cm ^-1 shifted to a lower wavenumber side of dimethyl carbonate C and O between the double bonds of the stretch from vibration characteristic peaks peak intensity I Observed at _s = 0.53091. The relationship between the peak intensities of I _s and I _o was I _s > I _o and I _s = 2.62 × I _o .

In the IR spectrum of the electrolyte solution E14 shown in FIG. 31, a characteristic peak derived from the stretching vibration of the double bond between C and O of dimethyl carbonate is observed slightly (I _o = 0.23891) in the vicinity of 1750 cm ^−1. It was done. More IR spectrum of FIG. 31, 1750 cm from the vicinity of ^-1 in the vicinity of 1717 cm ^-1 shifted to a lower wavenumber side of dimethyl carbonate C and O between the double bonds of the stretch from vibration characteristic peaks peak intensity I Observed at _s = 0.53098. The relationship between the peak intensities of I _s and I _o was I _s > I _o and I _s = 2.22 × I _o .

In the IR spectrum of the electrolytic solution E15 shown in FIG. 32, a characteristic peak derived from the stretching vibration of the double bond between C and O of dimethyl carbonate is slightly observed at around 1750 cm ⁻¹ (I _o = 0.33054). It was done. More IR spectrum of Figure 32, 1750 cm from near ^-1 around 1717 cm ^-1 shifted to a lower wavenumber side of dimethyl carbonate C and O between the double bonds of the stretch from vibration characteristic peaks peak intensity I Observed at _s = 0.50223. The relationship between the peak intensities of I _s and I _o was I _s > I _o , and I _s = 1.65 × I _o .

In the IR spectrum of the electrolytic solution C6 shown in FIG. 39, a characteristic peak (I _o = 0.48204) derived from the stretching vibration of the double bond between C and O of dimethyl carbonate was observed near 1750 cm ⁻¹ . . More IR spectrum of FIG. 39, 1750 cm from the vicinity of ^-1 in the vicinity of 1717 cm ^-1 shifted to a lower wavenumber side of dimethyl carbonate C and O between the double bonds of the stretch from vibration characteristic peaks peak intensity I Observed at _s = 0.39244. The relationship between the peak intensities of I _s and I _o was I _s <I _o .

In the vicinity of 1745 cm ⁻¹ of the IR spectrum of ethyl methyl carbonate shown in FIG. 43, 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. 33, a characteristic peak derived from the stretching vibration of the double bond between C and O of ethylmethyl carbonate is slightly present in the vicinity of 1745 cm ^-1 (I _o = 0.13582). Observed. Furthermore, in the IR spectrum of FIG. 33, 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 I _s = 0.45888. The relationship between the peak intensities of I _s and I _o was I _s > I _o and I _s = 3.38 × I _o .

In the IR spectrum of the electrolytic solution E17 shown in FIG. 34, there is a slight characteristic peak (I _o = 0.15151) 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. 34, a characteristic peak derived from the stretching vibration of the double bond between C and O of ethylmethyl carbonate is observed at 1711 cm ^-1 shifted from the vicinity of 1745 cm ^-1 to the lower wavenumber side. Observed at I _s = 0.48779. The relationship between the peak intensities of I _s and I _o was I _s > I _o and I _s = 3.22 × I _o .

In the IR spectrum of the electrolytic solution E18 shown in FIG. 35, there is a slight characteristic peak (I _o = 0.20191) derived from stretching vibration of double bond between C and O of ethylmethyl carbonate in the vicinity of 1745 cm ^−1. Observed. Furthermore, in the IR spectrum of FIG. 35, 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 near 1745 cm ^-1 to the lower wavenumber side. Observed at I _s = 0.48407. The relationship between the peak intensities of I _s and I _o was I _s > I _o and I _s = 2.40 × I _o .

In the IR spectrum of the electrolytic solution C7 shown in FIG. 40, a characteristic peak (I _o = 0.41907) derived from the stretching vibration of the double bond between C and O of ethylmethyl carbonate is observed around 1745 cm ^−1. It was. Furthermore, in the IR spectrum of FIG. 40, a characteristic peak derived from the stretching vibration of the double bond between C and O of ethyl methyl carbonate is observed near 1711 cm ^-1 shifted from the vicinity of 1745 cm ^-1 to the lower wavenumber side. Observed at I _s = 0.33929. The relationship between the peak intensities of I _s and I _o was I _s <I _o .

In the vicinity of 1742 cm ⁻¹ of the IR spectrum of diethyl carbonate shown in FIG. 44, 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 electrolyte E19 shown in FIG. 36, a characteristic peak derived from the stretching vibration of the double bond between diethyl carbonate C and O was observed slightly (I _o = 0.11202) in the vicinity of 1742 cm ^−1. It was done. Further, in the IR spectrum of FIG. 36, a characteristic peak derived from the stretching vibration of the double bond between C and O of diethyl carbonate is observed in the vicinity of 1706 cm ^-1 shifted from the vicinity of 1742 cm ^-1 to the low wavenumber side. Observed at _s = 0.42925. The relationship between the peak intensities of I _s and I _o was I _s > I _o and I _s = 3.83 × I _o .

In the IR spectrum of the electrolyte E20 shown in FIG. 37, a characteristic peak derived from the stretching vibration of the double bond between diethyl carbonate C and O was observed slightly (I _o = 0.15231) in the vicinity of 1742 cm ^−1. It was done. Further, in the IR spectrum of FIG. 37, a characteristic peak derived from the stretching vibration of the double bond between C and O of diethyl carbonate is observed in the vicinity of 1706 cm ^-1 shifted from the vicinity of 1742 cm ^-1 to the lower wavenumber side. Observed at _s = 0.45679. The relationship between the peak intensities of I _s and I _o was I _s > I _o and I _s = 3.00 × I _o .

In the IR spectrum of the electrolyte solution E21 shown in FIG. 38, a characteristic peak derived from the stretching vibration of the double bond between C and O of diethyl carbonate is slightly observed (I _o = 0.20337) in the vicinity of 1742 cm ^−1. It was done. Further, in the IR spectrum of FIG. 38, 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 near 1742 cm ^-1 to the lower wavenumber side. Observed at _s = 0.43841. The relationship between the peak intensities of I _s and I _o was I _s > I _o and I _s = 2.16 × I _o .

In the IR spectrum of the electrolytic solution C8 shown in FIG. 41, a characteristic peak (I _o = 0.39636) derived from the stretching vibration of the double bond between C and O of diethyl carbonate was observed near 1742 cm ⁻¹ . . More IR spectrum of FIG. 41, 1742 cm from the vicinity ^-1 low wavenumber diethyl carbonate in the vicinity of 1709 cm ^-1 shifted to the side C and O between the double bonds of the stretch from vibration characteristic peaks peak intensity I Observed at _s = 0.31129. The relationship between the peak intensities of I _s and I _o was I _s <I _o .

(Evaluation Example 12: Ionic conductivity)
The ionic conductivities of the electrolytic solutions E1, E2, electrolytic solutions E4 to E6, electrolytic solution E8, electrolytic solution E11, electrolytic solution E16, and electrolytic solution E19 were measured under the following conditions. The results are shown in Table 12.

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

  Electrolytic solutions E1, E2, electrolytic solutions E4 to E6, electrolytic solution E8, electrolytic solution E11, electrolytic solution E16, and electrolytic solution 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 13: Viscosity)
Electrolytic solution E1, electrolytic solution E2, electrolytic solutions E4 to E6, electrolytic solution E8, electrolytic solution E11, electrolytic solution E16, electrolytic solution E19 and electrolytic solutions C1 to C4 and electrolytic solutions C6 to C8 were measured under the following conditions: . The results are shown in Table 13.

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

  Electrolyte E1, Electrolyte E2, Electrolytes E4 to E6, Electrolyte E8, Electrolyte E11, Electrolyte E16, Electrolyte E19 have viscosities compared to those of Electrolytes C1 to C4 and Electrolytes C6 to C8 It was remarkably high. 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 14: Volatility)
The volatility of the electrolytic solutions E2, E4, E8, E11, E13 and the electrolytic solutions C1, C2, C4, C6 was measured by the following method.

  About 10 mg of the electrolytic solution was placed in an aluminum pan and placed in a thermogravimetric measurement 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 14.

  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 15: Combustibility)
The combustibility of the electrolytic solution E4 and the electrolytic solution C2 was tested by the following method.

  Three drops of the electrolytic solution were dropped onto 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 16: Low temperature test)
Electrolytes E11, E13, E16, and E19 were put 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.

(Example 8)
A half cell using the above-described electrolytic solution E11 was produced as follows.

  90 parts by mass of natural graphite having an average particle size of 10 μm as an active material and 10 parts by mass of polyvinylidene fluoride as a binder were mixed. This mixture was dispersed in an appropriate amount of N-methyl-2-pyrrolidone 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 natural graphite used had a G / D ratio of 4.4 in the Raman spectrum, which is the intensity ratio of the G-band and D-band peaks.

The copper foil coated with the slurry was dried to remove N-methyl-2-pyrrolidone, 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. The mass of the active material on the 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 polyvinylidene fluoride before pressing was 0.68 g / cm ³ , and the density of the active material layer after pressing was 1.025 g / cm ³ .

  The counter electrode was metallic Li.

  The working electrode, the counter electrode, and the electrolyte solution of Example 8 were accommodated in a battery case (CR2032 type coin cell case manufactured by Hosen Co., Ltd.) having a diameter of 13.82 mm to form a half cell. This was designated as the half cell of Example 8.

Example 9
A half cell of Example 9 was produced in the same manner as in Example 8, except that the above-described electrolytic solution E8 was used instead of the electrolytic solution E11.

(Example 10)
A half cell of Example 10 was produced in the same manner as in Example 8, except that the above-described electrolytic solution E16 was used instead of the electrolytic solution E11.

(Example 11)
A half cell of Example 11 was produced in the same manner as in Example 8, except that the above-described electrolytic solution E19 was used instead of the electrolytic solution E11.

[Comparative Example 11]
In place of the electrolytic solution E11, an electrolytic solution in which LiPF ₆ was dissolved at a concentration of 1M in a mixed solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at 3: 7 (volume ratio) was used. A half cell of Comparative Example 11 was produced in the same manner as Example 8.

<Test and evaluation>
(Evaluation Example 17: Reversibility of reaction)
For each of the lithium secondary batteries of Examples 8 to 11 and Comparative Example 11, a charge / discharge test was performed three times under the conditions shown in Table 15. The charge / discharge curves at that time are shown in FIGS.

  It can be seen that the lithium secondary batteries of Examples 8 to 11 are reversibly charged and discharged similarly to the general lithium secondary battery of Comparative Example 11.

(Evaluation Example 18: Rate characteristics)
The rate characteristics of the half cells of Examples 8 to 11 and Comparative Example 11 were tested by the following method. After charging a half cell at a rate of 0.1C, 0.2C, 0.5C, 1C, 2C (1C means the current value required to fully charge or discharge the battery in 1 hour at a constant current) Discharge was performed, and the capacity (discharge capacity) of the working electrode at each speed was measured. In this description, the counter electrode is regarded as a negative electrode and the working electrode is regarded as a positive electrode. The ratio (rate characteristic) of the capacity at other rates to the capacity of the working electrode at the 0.1 C rate was calculated. The results are shown in Table 16.

  In the half cells of Examples 8 to 11 at a rate of 0.2C, 0.5C, and 1C, further, Examples 8 and 9 are suppressed in capacity at a rate of 2C as compared with the half cell of Comparative Example 11, It was confirmed that it shows excellent rate characteristics.

(Evaluation Example 19: Capacity maintenance rate)
The capacity retention rates of the half cells of Examples 8 to 11 and Comparative Example 11 were tested by the following method.

For each half-cell, charge / discharge cycle of 2.0V-0.01V, CC charge (constant current charge) to 25 ° C, voltage 2.0V and CC discharge (constant current discharge) to voltage 0.01V, charge / discharge rate 0.1C Then, 3 cycles were performed for each charge / discharge rate in the order of 0.2C, 0.5C, 1C, 2C, 5C, and 10C, and finally 3 cycles of charge / discharge were performed at 0.1C. The capacity retention rate (%) of each half cell was determined by the following formula.
Capacity maintenance rate (%) = B / A x 100
A: Discharge capacity of the second working electrode in the first 0.1C charge / discharge cycle
B: Discharge capacity of the second working electrode in the last 0.1C charge / discharge cycle

  The results are shown in Table 17. In this description, the counter electrode is regarded as a negative electrode and the working electrode is regarded as a positive electrode.

  All of the half cells performed a charge / discharge reaction satisfactorily and exhibited a suitable capacity retention rate. In particular, the capacity retention ratios of the half cells of Examples 9, 10, and 11 were remarkably excellent.

(Evaluation Example 20: Raman spectrum measurement)
Raman spectra were measured for the electrolytic solutions E8, E9, C4 and E11, E13, E15, C6 under the following conditions. FIGS. 51 to 57 show Raman spectra in which peaks derived from the anion portion of the metal salt of each electrolytic solution were observed. The horizontal axis of the figure is the wave number (cm ⁻¹ ), and the vertical axis is the scattering intensity.

Raman spectrum measurement conditions Equipment: Laser Raman spectrophotometer (NRS series, JASCO Corporation)
Laser wavelength: 532nm
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 electrolytes E8, E9, and C4 shown in FIGS. . Here, it can be seen from FIGS. 51 to 53 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 are 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. 54 to 57 that the peak shifts to the higher wavenumber side as the LiFSA concentration increases. As discussed in the previous paragraph, this phenomenon is caused by the fact that (FSO ₂ ) ₂ N corresponding to the anion of the salt interacts with a plurality of Li by increasing the concentration of the electrolyte. It is inferred that the result is reflected.

(Evaluation Example 21: Li transportation rate)
The Li transport numbers of the electrolytic solutions E2 and C5 were measured under the following conditions. The results are shown in Table 18. Table 18 also shows the results of the electrolytic solution (E8) used in Example 1 and the electrolytic solution (C4) used in Comparative Example 1. The conditions for measuring the Li transport number are the same as those when the Li transport number of the electrolyte solutions of Example 1 and Comparative Example 1 was measured.

The Li transport numbers of the electrolytic solutions E2 and E8 were significantly higher than those of the electrolytic solutions C4 and C5. That is, also from this result, it can be said that the electrolytic solution of the present invention has a higher lithium ion (cation) transport rate than the conventional electrolytic solution exhibiting the same ionic conductivity.
Further, for the electrolytic solution E8, the Li transport number when the temperature was changed was measured according to the above Li transport number measurement conditions. The results are shown in Table 19.

  From the results in Table 19, 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.

(Example 12)
A lithium secondary battery (half cell) of Example 12 was produced in the same manner as Example 2 except that the electrolytic solution E9 was used.

<Test and evaluation>
(Evaluation Example 22: Rate characteristics at low temperature)
Using the lithium secondary batteries of Example 12 and Comparative Example 5, the rate characteristics at −20 ° C. were evaluated as follows. The results are shown in FIGS. 58 and 59.
(1) Current is passed in the direction in which lithium occlusion proceeds to the negative electrode (evaluation electrode).
(2) Voltage range: 2V → 0.01V (vsLi / 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.

  58 and 59, it can be seen that the voltage curve of the lithium secondary battery of Example 12 at each current rate is higher than that of the lithium secondary battery of Comparative Example 5. 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 23: Rate characteristics)
The rate characteristics of the lithium secondary batteries of Example 2 and Comparative Example 5 were tested by the following method.
For each lithium secondary battery, 0.1 C, 0.2 C, 0.5 C, 1 C, 2 C rate (1 C means a current value required to fully charge or discharge the battery in one hour at a constant current. ) And then discharging, and the capacity (discharge capacity) of the working electrode at each speed was measured. In this description, the counter electrode is regarded as a negative electrode and the working electrode is regarded as a positive electrode. The ratio (rate characteristic) of the capacity at other rates to the capacity of the working electrode at the 0.1 C rate was calculated. The results are shown in Table 20.

  As for the lithium secondary battery of Example 2, the capacity | capacitance fall is suppressed compared with the lithium secondary battery of the comparative example 5 in any rate of 0.2C, 0.5C, 1C, 2C, Excellent rate characteristics. It was confirmed that the secondary battery using the electrolytic solution of the present invention exhibits excellent rate characteristics.

(Evaluation Example 24: Responsiveness to repeated rapid charge / discharge)
With respect to the lithium secondary batteries of Example 2 and Comparative Example 5, 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 lithium secondary battery of Comparative Example 5 has a tendency to increase the polarization when a current is passed at a rate of 1 C as charging and discharging are repeated, and the capacity obtained before reaching 2 V to 0.01 V decreases rapidly. did. On the other hand, the lithium secondary battery of Example 2 maintained its capacity suitably with little increase or decrease in polarization as can be confirmed from the overlapping of the three curves in FIG. The reason why the polarization increased in the lithium secondary battery of Comparative Example 5 was that a sufficient amount of Li was electrolyzed at the reaction interface with the electrode due to the uneven Li concentration generated in the electrolyte when charging and discharging were rapidly repeated. It can be considered that the liquid cannot be supplied, that is, the Li concentration of the electrolytic solution is unevenly distributed. In the lithium secondary battery of Example 2, it is considered that the uneven distribution of Li concentration in the electrolytic solution could be suppressed by using the electrolytic solution of the present invention having a high Li concentration. It was confirmed that the secondary battery using the electrolytic solution of the present invention exhibits excellent responsiveness to rapid charge / discharge.

  The non-aqueous 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 secondary battery for motor drive of electric vehicles and hybrid vehicles, personal computers, portable communication devices, home appliances, office equipment, industrial equipment, etc. It can be optimally used for driving motors of electric vehicles and hybrid vehicles.

Claims (13)

Including a negative electrode and an electrolyte,
The electrolytic solution includes a salt having lithium as a cation, and an organic solvent having a hetero element,
The chemical structure of the anion of the salt is represented by the following general formula (7):
(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 be bonded to each other to form a ring, in which case 2n = a + b + c + d + e is satisfied.
n is an integer from 0 to 6. When R ¹³ and R ¹⁴ are combined to form a ring, n is an integer of 1 to 8. )
For 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 has a negative active material layer containing graphite having a G / D ratio of 3.5 or more, which is a ratio of G-band to D-band peaks in a Raman spectrum, wherein the non-aqueous secondary battery (however, The electrolytic solution excludes LiN (SO ₂ CF ₃ ) ₂ as the salt and 1,2-dialkoxyethane as the organic solvent .   2. The nonaqueous secondary battery according to claim 1, wherein the relationship between Is and Io is Is> 2 × Io. Including a negative electrode and an electrolyte,
The electrolytic solution includes a salt having lithium as a cation, and an organic solvent having a hetero element,
The chemical structure of the anion of the salt is represented by the following general formula (7):
(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 be bonded to each other to form a ring, in which case 2n = a + b + c + d + e is satisfied.
n is an integer from 0 to 6. When R ¹³ and R ¹⁴ are combined to form a ring, n is an integer of 1 to 8. )
The density d (g / cm ³ ) of the electrolytic solution is 1.2 ≦ d ≦ 2.2,
D / c obtained by dividing the density d (g / cm ³ ) of the electrolytic solution by the salt concentration c (mol / L) of the electrolytic solution is in the range of 0.15 ≦ d / c ≦ 0.71.
The negative electrode has a negative active material layer containing graphite having a G / D ratio of 3.5 or more, which is a ratio of G-band to D-band peaks in a Raman spectrum, wherein the non-aqueous secondary battery (however, The electrolytic solution excludes LiN (SO ₂ CF ₃ ) ₂ as the salt and 1,2-dialkoxyethane as the organic solvent . In the electrolyte solution, the organic solvent is nitriles, carbonates, amides, isocyanates, esters, epoxies, oxazoles, ketones, acid anhydrides, sulfones, sulfoxides, nitros, furans, cyclic 4. The nonaqueous secondary battery according to claim 1 , wherein the nonaqueous secondary battery is an ester, an aromatic heterocycle, a heterocycle, or a phosphate ester.   The non-aqueous secondary battery according to claim 1, wherein the G / D ratio is 10 or more.   6. The nonaqueous secondary battery according to claim 1, wherein the electrolyte solution has c, d, and e of 0. In the electrolytic solution, n is an integer of 0 to 4. When R ¹³ and R ¹⁴ are combined to form a ring, n is an integer of 1 to 7.
The nonaqueous secondary battery according to any one of claims 1 to 6. In the electrolytic solution, n is an integer of 0 to 2. When R ¹³ and R ¹⁴ are bonded to form a ring, n is an integer of 1 to 3.
The nonaqueous secondary battery according to any one of claims 1 to 7. In the electrolyte 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, (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 The nonaqueous secondary battery according to claim 1, which is ₅ SO ₂ ) NLi. In the electrolyte 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 nonaqueous secondary battery according to any one of claims 1-9 or _{(SO 2 CF 2 CF 2 CF} 2 SO 2) is NLi,. Nonaqueous secondary battery according to any one of claim 1 to 10, wherein the organic solvent is acetonitrile. The electrolyte, a nonaqueous secondary battery according to any one of claims 1 to 10, wherein said organic solvent is selected from linear carbonates represented by the following general formula (10).
R ¹⁹ OCOOR ²⁰ general formula (10)
(R ¹⁹ and R ²⁰ each independently represent 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. _j , n, a, b, c, d, e, m, f, g, h, i, j are each independently an integer of 0 or more, and 2n + 1 = a + b + c + d + e, 2m = f + g + h + i + j.) Nonaqueous secondary battery according to any one of claims 1-10, according to claim 12, wherein the organic solvent is dimethyl carbonate, is selected from ethyl methyl carbonate or diethyl carbonate.