JP2015065049A - Nonaqueous electrolytic solution, and nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a nonaqueous electrolytic solution which includes, as solvent, acetonitrile superior in the balance of the viscosity and the relative dielectric constant and which is electrochemically stable in a lithium ion secondary battery; and a nonaqueous secondary battery which enables the achievement of a high energy density.SOLUTION: A nonaqueous electrolytic solution comprises: a nonaqueous solvent; and a lithium salt. The nonaqueous solvent includes 40-100 vol.% of acetonitrile to a total volume of the nonaqueous solvent. The lithium salt includes at least one compound selected from a group consisting of compounds expressed by LiN(SOCF)[where m is an integer of 0-1], and a fluorine-containing inorganic lithium salt. The total amount of the compounds expressed by LiN(SOCF)[where m is an integer of 0-1] is 3.1-25 mol to one liter of the acetonitrile in the nonaqueous solvent. A nonaqueous secondary battery is manufactured by use of the nonaqueous electrolytic solution.

Description

  The present invention relates to a non-aqueous electrolyte and a non-aqueous secondary battery.

  Non-aqueous secondary batteries containing non-aqueous electrolytes are characterized by light weight, high energy, and long life, and are portable for notebook computers, mobile phones, smartphones, tablet PCs, digital cameras, video cameras, etc. It is widely used as a power source for electronic equipment. In addition, with the shift to a low environmental impact society, hybrid electric vehicles (Hybrid Electric Vehicles), plug-in HEVs (Plug-in Hybrid Electric Vehicles), and power sources for electric motorcycles, as well as power storage systems for residential power storage systems, etc. It is also attracting attention in the field.

  By the way, it is desirable from a practical point of view to use a non-aqueous electrolyte as an electrolyte for a lithium ion secondary battery operating at room temperature, and a low-viscosity solvent such as a high-permittivity solvent such as a cyclic carbonate and a lower chain carbonate. A combination with a solvent is exemplified as a general solvent. On the other hand, a normal high dielectric constant solvent has a high melting point, and depending on the type of electrolyte salt used in the non-aqueous electrolyte, it may cause deterioration of the low-temperature characteristics of the non-aqueous electrolyte. As one of the solvents for overcoming such a problem, a nitrile solvent excellent in the balance between viscosity and relative dielectric constant has been proposed. Among them, acetonitrile has a high potential as a solvent used for an electrolyte solution of a lithium ion secondary battery. However, since acetonitrile has a fatal defect such as electrochemical reductive decomposition at the negative electrode, practical performance cannot be exhibited, and some improvement measures have been reported.

The main improvement measures proposed so far are classified into the following three.
(1) Method for protecting negative electrode by combination of specific electrolyte salt and additive and suppressing reductive decomposition of acetonitrile For example, in Patent Documents 1 and 2 below, acetonitrile as a solvent is a specific electrolyte salt and additive. There has been reported an electrolyte solution that reduces the influence of reductive decomposition of acetonitrile by combining with the above. In the early days of lithium ion secondary batteries, an electrolyte solution containing a solvent obtained by simply diluting acetonitrile with propylene carbonate or ethylene carbonate has been reported as in Patent Document 3 below. However, in Patent Document 3, since the high-temperature durability performance is determined only by the internal resistance and battery thickness after high-temperature storage, information on whether or not to actually operate as a battery in a high-temperature environment is disclosed. Not. Suppressing reductive decomposition of an electrolyte solution containing an acetonitrile-based solvent simply by diluting with ethylene carbonate or propylene carbonate is actually a difficult task. A method of combining a plurality of electrolyte salts and additives as in Documents 1 and 2 is realistic.

(2) A method for suppressing reductive decomposition of acetonitrile by using a negative electrode active material that occludes lithium ions at a potential nobler than the reduction potential of acetonitrile. For example, Patent Document 4 below discloses a specific metal compound for a negative electrode. It has been reported that a battery avoiding reductive decomposition of acetonitrile can be obtained by using.
(3) Method of maintaining a stable liquid state by dissolving a high concentration electrolyte salt in acetonitrile For example, the following Non-Patent Document 1 includes lithium bis (trifluoromethanesulfonyl) imide (LiN (SO ₂ CF ₃ ) ₂ ) Is prepared using an electrolytic solution in which LiN (SO ₂ CF ₃ ) ₂ is dissolved in acetonitrile so that the concentration becomes 4.2 mol / dm ^−3, and a coin cell having a negative electrode made of lithium metal is prepared. . Non-Patent Document 1 reports that, as a result of charge / discharge measurement on such a coin cell, Li ⁺ insertion / extraction reaction into graphite was observed.

Among these improvements, for applications that place importance on the energy density of lithium ion secondary batteries, it is overwhelmingly advantageous to use a negative electrode active material that occludes lithium ions at a lower potential than the reduction potential of acetonitrile. Therefore, the improvement measure (2) is not covered. Therefore, it is appropriate for those skilled in the art to consider that the conventional knowledge accumulated in the improvement measure (1) is applied to the improvement measure (3) that has just been proposed. Many of imide salts represented by LiN (SO ₂ CF ₃ ) ₂ are known to electrochemically corrode aluminum foils generally used as positive electrode current collectors. The battery configuration described in No. 1 does not necessarily assemble into an optimum state as a battery. In order to satisfy practical performance as a lithium ion secondary battery, for example, as described in Patent Documents 5 and 6 below, measures such as adding a fluorine-containing inorganic lithium salt are essential.

International Publication No. 2012/057311 International Publication No. 2013/062056 JP-A-4-351860 JP 2009-21134 A JP 2004-265849 A JP2013-101900A

“Specific electrochemical properties of organic electrolytes in crystallinity gap”, Proceedings of the 80th Anniversary of the Electrochemical Society of Japan, 2H08, 234 (2013)

  In general, the concentration of the electrolyte salt and the solvent composition are appropriately adjusted by those skilled in the art, and those skilled in the art are able to optimize the electrolyte composition in the crystallinity gap in which crystallization is inhibited and becomes a stable liquid. It can be easily conceived. However, as exemplified by the dimethoxyethane solution in Non-Patent Document 1, the crystallinity gap is a peculiar phenomenon in a narrow concentration range that appears after reaching a saturation concentration and exceeding the state where a solid is precipitated. . For this reason, it is not easy to find the range of such anomalous phenomenon without generating insoluble components in the composite composition of the electrolyte that can be combined infinitely, and to verify the relationship with the electrochemical function. . In addition, it is not necessary for those skilled in the art to limit to the cristallinity gap, which may affect the ionic conductivity, as long as the lithium ion secondary battery operates stably, and further improvements are desired in a more realistic concentration range. It was.

  The present invention has been made in view of the circumstances described above, and achieves a non-aqueous electrolyte solution and high energy density that contain acetonitrile excellent in the balance between viscosity and relative dielectric constant and are also electrochemically stable. An object is to provide a non-aqueous secondary battery.

  As a result of intensive studies in order to solve the above-mentioned problems, the present inventors have dissolved an imide salt with an ultrahigh concentration in acetonitrile in a non-aqueous solvent containing a specific amount of acetonitrile, and further added a fluorine-containing inorganic substance. It has been found that when a lithium salt is dissolved, a nonaqueous electrolytic solution which is electrochemically stable while utilizing the potential of acetonitrile can be obtained, and the present invention has been completed.

That is, the present invention is as follows.
[1] A non-aqueous electrolyte solution containing a non-aqueous solvent and a lithium salt, wherein the non-aqueous solvent contains 40 to 100% by volume of acetonitrile with respect to the total amount of the non-aqueous solvent, [m is an integer of 0-1] _{LiN (SO 2 C m F 2m} + 1) 2 and a one or more compounds and fluorine-containing inorganic lithium salt selected from the group consisting of compounds represented by the LiN (SO ₂ C _m F _{2m + 1} ) ₂ [m is an integer of 0 to 1] The total amount of the compound is 3.1 to 25 mol with respect to 1 liter of the acetonitrile in the non-aqueous solvent, Non-aqueous electrolyte.

[2] The non-aqueous electrolyte according to [1], wherein the fluorine-containing inorganic lithium salt is at least one fluorine-containing inorganic lithium salt selected from the group consisting of LiPF ₆ and LiBF ₄ .
[3] The non-aqueous system according to [1] or [2], wherein the content of the fluorine-containing inorganic lithium salt is 0.05 to 1.0 mol with respect to 1 liter of the non-aqueous solvent. Electrolytic solution.

[4] The above [1], wherein the compound represented by LiN (SO ₂ C _m F _{2m + 1} ) ₂ [m is an integer of 0 to 1] is LiN (SO ₂ F) ₂ . The nonaqueous electrolytic solution according to any one of [3].
[5] A positive electrode using an aluminum foil as a current collector and lithium ion as a negative electrode active material at 0.4 V vs. A non-aqueous secondary, comprising a negative electrode containing a material that occludes at a lower potential than Li / Li ⁺ and the non-aqueous electrolyte according to any one of [1] to [4]. battery.
[6] The nonaqueous secondary battery according to [5], wherein the negative electrode includes graphite as a negative electrode active material.

  According to the present invention, it is possible to provide a nonaqueous secondary battery that includes acetonitrile having an excellent balance between viscosity and relative dielectric constant and that is also electrochemically stable, and achieves a high energy density. it can.

It is sectional drawing which shows roughly an example of the non-aqueous secondary battery of this embodiment.

Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail. In addition, the numerical range described using "-" in this specification includes the numerical value described before and behind that.
The non-aqueous electrolyte solution of the present embodiment (hereinafter also simply referred to as “electrolyte solution”) is an electrolyte solution containing a non-aqueous solvent and a lithium salt, and the non-aqueous solvent contains 40 to 100% by volume of acetonitrile. The lithium salt includes LiN (SO ₂ C _m F _{2m + 1} ) ₂ [m is an integer of 0 to 1] and one or more compounds selected from the group consisting of compounds and a fluorine-containing inorganic lithium salt; The total amount of the compound is 3.1 to 25 mol with respect to 1 liter of acetonitrile in the non-aqueous solvent.

<1. Overall configuration of non-aqueous secondary battery>
As the non-aqueous secondary battery of the present embodiment, for example, a positive electrode containing one or more materials selected from the group consisting of materials capable of inserting and extracting lithium ions as a positive electrode active material, and a negative electrode active material And a negative electrode containing a negative electrode material capable of inserting and extracting lithium ions and a negative electrode containing one or more materials selected from the group consisting of metallic lithium.

Specifically, the non-aqueous secondary battery of the present embodiment may be a lithium ion secondary battery whose cross-sectional view is schematically shown in FIG.
A non-aqueous secondary battery 100 shown in FIG. 1 includes a separator 110, a positive electrode 120 and a negative electrode 130 facing each other with the separator 110 interposed therebetween, an electrolytic solution (not shown), a separator 110, a positive electrode 120, a negative electrode 130, and electrolysis. And a battery exterior 160 that contains the liquid. The laminated body in which the positive electrode 120, the separator 110, and the negative electrode 130 are sequentially laminated is impregnated with a nonaqueous electrolytic solution.

The positive electrode 120 includes a positive electrode active material layer 120A made from a positive electrode mixture and a positive electrode current collector 120B. The negative electrode 130 includes a negative electrode active material layer 130A made from a negative electrode mixture and a negative electrode current collector 130B. The positive electrode 120 and the negative electrode 130 are disposed so that the positive electrode active material layer 120A and the negative electrode active material layer 130A face each other with the separator 110 interposed therebetween.
Hereinafter, the term “electrode” is abbreviated as a general term for the positive electrode and the negative electrode, the term “electrode active material layer” is a generic term for the positive electrode active material layer and the negative electrode active material layer, and the term “electrode mixture” is generically used for the positive electrode mixture and the negative electrode mixture.

  As each of these members, a material provided in a conventional lithium ion secondary battery can be used as long as each requirement in the present embodiment is satisfied. For example, the following materials may be used. Hereinafter, each member of the non-aqueous secondary battery 100 will be described in detail.

<2. Electrolyte>
The electrolytic solution in the present embodiment includes at least a non-aqueous solvent (hereinafter also simply referred to as “solvent”) and a lithium salt. The electrolytic solution in the present embodiment preferably does not contain moisture, but may contain a very small amount of moisture as long as the solution of the problem of the present invention is not hindered. The water content is preferably 0 to 100 ppm with respect to the total amount of the electrolytic solution.

<2-1. Non-aqueous solvent>
The non-aqueous solvent is not particularly limited as long as it contains 40 to 100% by volume of acetonitrile with respect to the total amount of the non-aqueous solvent, and may include other non-aqueous solvents. In addition, the “non-aqueous solvent” referred to in the present embodiment refers to an element obtained by removing a lithium salt from an electrolytic solution. That is, when the electrolytic solution contains an additive to be described later together with a solvent and a lithium salt to be described later, the solvent and the additive are collectively referred to as “non-aqueous solvent”.

Examples of other non-aqueous solvents include alcohols such as methanol and ethanol, and aprotic solvents. Among these, aprotic polar solvents are preferable.
Specific examples of the non-aqueous solvent include, for example, ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, trans-2,3-butylene carbonate, cis-2,3-butylene carbonate, 1,2-pentylene carbonate, Trans-2,3-pentylene carbonate, cis-2,3-pentylene carbonate, trifluoromethylethylene carbonate, fluoroethylene carbonate, cyclic carbonate represented by 1,2-difluoroethylene carbonate; γ-butyrolactone, γ- Lactones typified by valerolactone; sulfur compounds typified by sulfolane and dimethyl sulfoxide; cyclic ethers typified by tetrahydrofuran, 1,4-dioxane and 1,3-dioxane; ethyl methyl carbonate, dimethyl Chain carbonates typified by til carbonate, diethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, methyl butyl carbonate, dibutyl carbonate, ethyl propyl carbonate, methyl trifluoroethyl carbonate; propionitrile, butyronitrile, valeronitrile , Benzonitrile, acrylonitrile and other mononitriles; methoxyacetonitrile, alkoxy-substituted nitriles typified by 3-methoxypropionitrile; chain carboxylic acid esters typified by methylpropionate; chain typified by dimethoxyethane Ether; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone are listed. Moreover, the halide represented by these fluorides is also mentioned. These are used singly or in combination of two or more.

Since acetonitrile is easily electrochemically reductively decomposed, it is preferable to mix with another solvent and / or add an additive for forming a protective film on the electrode.
In order to increase the ionization degree of the lithium salt that contributes to charging / discharging of the non-aqueous secondary battery, the non-aqueous solvent preferably contains one or more cyclic aprotic polar solvents, and contains one or more cyclic carbonates. More preferably.

Moreover, in order to make all the functions of lithium salt solubility, conductivity and ionization good, it is preferable to use a mixed solvent in which two or more kinds of non-aqueous solvents are mixed. Examples of the non-aqueous solvent that is a component of the mixed solvent include the above-described non-aqueous solvents, and examples of the mixed solvent include a mixed solvent of a cyclic carbonate and acetonitrile.
The content of acetonitrile is 40 to 100% by volume with respect to the total amount of the non-aqueous solvent, more preferably 45 to 95% by volume, and still more preferably 50 to 85% by volume. When the content of acetonitrile is 40% by volume or more, ionic conductivity tends to increase and high output characteristics tend to be exhibited, and further, dissolution of the lithium salt can be promoted. When the content of acetonitrile in the non-aqueous solvent is within the above range, the long-term cycle performance and other battery characteristics tend to be improved while maintaining the excellent performance of acetonitrile. It is in.

<2-2. Lithium salt>
The lithium salt in the present embodiment is one or more compounds selected from the group consisting of compounds represented by LiN (SO ₂ C _m F _{2m + 1} ) ₂ [m is an integer of 0 to 1], a fluorine-containing inorganic lithium salt, including. Here, the “fluorine-containing inorganic lithium salt” refers to a lithium salt that does not contain a carbon atom in an anion but contains a fluorine atom in an anion and is soluble in acetonitrile.

Specific examples of the compound represented by LiN (SO ₂ C _m F _{2m + 1} ) ₂ [m is an integer of 0 to 1] include LiN (SO ₂ F) ₂ and LiN (SO ₂ CF ₃ ) _2. It is done. These compounds are generally referred to as imide salts. Hereinafter, a compound represented by LiN (SO ₂ C _m F _{2m + 1} ) ₂ [m is an integer of 0 to 1] is also referred to as an imide salt. As the imide salt, LiN (SO ₂ F) ₂ is particularly desirable. The “fluorine-containing inorganic lithium salt” does not include a compound represented by LiN (SO ₂ C _m F _{2m + 1} ) ₂ [m is an integer of 0 to 1].

Traditionally, imide salts, when small amounts are added to a solution containing LiPF _6, it is known that an effect of suppressing thermal decomposition and hydrolysis due to LiPF _6. On the other hand, in the present invention, an imide salt is not used as an additive having an effect of suppressing thermal decomposition and hydrolysis. In the present embodiment, attention is paid to the effect of stabilizing the acetonitrile itself by dissolving an imide salt having an extremely high concentration in acetonitrile as a main lithium salt.

The total amount of the imide salt is 3.1 to 25 mol with respect to 1 liter of acetonitrile in the non-aqueous solvent. When the imide salt is in this range, it is possible to effectively suppress the reductive decomposition of acetonitrile in the negative electrode regardless of whether or not it is within the crystallinity gap (see Non-Patent Document 1).
The fluorine-containing inorganic lithium salt in the present embodiment forms a passive film on the surface of the metal foil that is the positive electrode current collector, and is represented by LiN (SO ₂ C _m F _{2m + 1} ) ₂ [m is an integer of 0 to 1]. Suppresses the corrosion of the positive electrode current collector by the generated compound. For this reason, the fluorine-containing inorganic lithium salt must be added as a lithium salt. Specific examples of the fluorine-containing inorganic lithium salt include, for example, LiPF ₆ , LiBF ₄ , LiAsF ₆ , Li ₂ SiF ₆ , LiSbF ₆ , Li ₂ B ₁₂ F _b H _12-b [b is an integer of 0 to 3], etc. Is mentioned.

These fluorine-containing inorganic lithium salts are used singly or in combination of two or more. As the fluorine-containing inorganic lithium salt, a compound that is a double salt of LiF and Lewis acid is desirable. Among them, the use of a fluorine-containing inorganic lithium salt having a phosphorus atom is more preferable because it easily releases a free fluorine atom. ₆ is particularly preferred. Further, when a fluorine-containing inorganic lithium salt having a boron atom is used as the fluorine-containing inorganic lithium salt, it is preferable because an excessive free acid component that may cause battery deterioration is easily captured. From such a viewpoint, LiBF ₄ is particularly preferred.

  The content of the fluorine-containing inorganic lithium salt in the electrolytic solution of the present embodiment is preferably 0.05 to 1.0 mol, and preferably 0.1 to 0.7 mol with respect to 1 liter of the non-aqueous solvent. More preferably, it is 0.2-0.5 mol. When the content of the fluorine-containing inorganic lithium salt is within the above range, the fluorine-containing inorganic lithium salt acts as an additive rather than as the main lithium salt. For this reason, the electrolytic solution of the present embodiment is not affected by thermal decomposition or hydrolysis of the fluorine-containing inorganic lithium salt itself, and the electrolytic solution is kept in a higher electrical conductivity, and at the same time a non-aqueous secondary The charge / discharge efficiency of the battery tends to be kept higher. Moreover, the electrolyte solution of this embodiment exists in the tendency which can function preferentially the high acetonitrile stabilization ability of an ultra high concentration imide salt. When an aluminum current collector is used for the positive electrode and acetonitrile contains 50% by volume or more of the solvent, it is desirable to dissolve 0.2 to 0.8 mol of the fluorine-containing inorganic lithium salt with respect to 1 liter of acetonitrile. It is more desirable to dissolve 3 to 0.6 mol. Thereby, even if the ratio of acetonitrile is high, corrosion of the positive electrode current collector can be suppressed.

<2-3. Additives>
The electrolytic solution in the present embodiment may contain an additive for protecting the electrode. In addition, as above-mentioned, when an additive is included, content of acetonitrile should just contain 40-100 volume% with respect to the total amount of a non-aqueous solvent and an additive.
The additive is not particularly limited as long as it does not inhibit the solution of the problem according to the present invention, and may substantially overlap with a substance that plays a role as a solvent for dissolving a lithium salt, that is, the above-described solvent. The additive is preferably a substance that contributes to improving the performance of the electrolytic solution and the non-aqueous secondary battery in the present embodiment, but also includes a substance that does not directly participate in the electrochemical reaction. Are used alone or in combination of two or more.

  Specific examples of the additive include, for example, 4-fluoro-1,3-dioxolan-2-one, 4,4-difluoro-1,3-dioxolan-2-one, cis-4,5-difluoro-1, 3-dioxolan-2-one, trans-4,5-difluoro-1,3-dioxolan-2-one, 4,4,5-trifluoro-1,3-dioxolan-2-one, 4,4,5 , 5-tetrafluoro-1,3-dioxolan-2-one, fluoroethylene carbonate represented by 4,4,5-trifluoro-5-methyl-1,3-dioxolan-2-one; vinylene carbonate, 4 , 5-Dimethyl vinylene carbonate, cyclic carbonate containing unsaturated bond typified by vinyl ethylene carbonate; γ-butyrolactone, γ-valerolactone, γ-caprolacto , Δ-valerolactone, δ-caprolactone, lactone typified by ε-caprolactone; cyclic ether typified by 1,4-dioxane; ethylene sulfite, propylene sulfite, butylene sulfite, pentene sulfite, sulfolane, 3 -Cyclic sulfur compounds represented by methyl sulfolane, 1,3-propane sultone, 1,4-butane sultone and tetramethylene sulfoxide. These are used singly or in combination of two or more.

  Although there is no restriction | limiting in particular about content of the additive in the electrolyte solution in this embodiment, It is preferable that content of the additive with respect to the whole quantity of a non-aqueous solvent is 0.1-30 volume%, 2-20 It is more preferable that it is volume%, and it is still more preferable that it is 5-15 volume%. In this embodiment, the additive contributes to the development of high cycle performance, but on the other hand, the contribution to high output performance in a low temperature environment has not been confirmed. The higher the additive content, the more the deterioration of the electrolyte solution can be suppressed. However, the lower the additive content, the higher the high output characteristics of the non-aqueous secondary battery in a low temperature environment. Therefore, by adjusting the content of the additive within the above-mentioned range, the superior performance based on the high ionic conductivity of the electrolytic solution can be more sufficiently obtained without impairing the basic function as a non-aqueous secondary battery. There is a tendency to be able to demonstrate. By preparing the electrolytic solution with such a composition, all of the cycle performance of the non-aqueous secondary battery, the high output performance under a low temperature environment, and other battery characteristics tend to be further improved.

<3. Positive electrode>
The positive electrode 120 includes a positive electrode active material layer 120A made from a positive electrode mixture and a positive electrode current collector 120B. The positive electrode 120 is not particularly limited as long as it functions as a positive electrode of a non-aqueous secondary battery, and may be a known one.

  The positive electrode active material layer 120A preferably contains one or more materials selected from the group consisting of materials capable of inserting and extracting lithium ions as the positive electrode active material. Moreover, it is preferable that the positive electrode active material layer 120A contains a conductive additive and a binder as necessary together with the positive electrode active material. The use of such a material is preferable because a high voltage and a high energy density tend to be obtained.

Examples of the positive electrode active material include lithium-containing compounds represented by the following general formulas (1a) and (1b), and metal oxides and metal chalcogenides having a tunnel structure and a layered structure. The chalcogenide refers to sulfide, selenide, and telluride.
Li _x MO ₂ (1a)
Li _y M ₂ O ₄ (1b)
Here, in the formula, M represents one or more metal elements including at least one transition metal element, x represents a number from 0 to 1.1, and y represents a number from 0 to 2.

Examples of lithium-containing compounds represented by the general formulas (1a) and (1b) include lithium cobalt oxides typified by LiCoO ₂ ; LiMnO ₂ , LiMn ₂ O ₄ , and Li ₂ Mn ₂ O _4. Lithium manganese oxide; lithium nickel oxide typified by LiNiO ₂ ; Li _z MO ₂ (M contains at least one transition metal element selected from Ni, Mn, and Co, and Ni, Mn, Co, 2 or more kinds of metal elements selected from the group consisting of Al and Mg, and z represents a number greater than 0.9 and less than 1.2).

The lithium-containing compound other than the lithium-containing compound represented by the general formulas (1a) and (1b) is not particularly limited as long as it contains lithium. Examples of such a lithium-containing compound include a composite oxide containing lithium and a transition metal element, a metal phosphate compound containing lithium and a transition metal element, and a metal silicate compound containing lithium and a transition metal element ( For example, Li _t M _u SiO ₄ , M is synonymous with the general formula (1a), t is a number from 0 to 1, and u is a number from 0 to 2. From the viewpoint of obtaining a higher voltage, lithium-containing compounds include lithium, cobalt (Co), nickel (Ni), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), chromium ( A composite oxide containing at least one transition metal element selected from the group consisting of Cr), vanadium (V) and titanium (Ti), and a metal phosphate compound are preferred.

More specifically, the lithium-containing compound is preferably a metal oxide having lithium or a metal chalcogenide having lithium and a metal phosphate compound having lithium. For example, in the following general formulas (2a) and (2b), And the compounds represented. Among these, a metal oxide having lithium and a metal chalcogenide having lithium are more preferable.
^{_{Li v M I D 2 (2a}} )
Li _w M ^II PO ₄ (2b)
Here, in the formula, D represents oxygen or a chalcogen element, M ^I and M ^II each represent one or more transition metal elements, and the values of v and w vary depending on the charge / discharge state of the battery. 0.05 to 1.10, w represents a number from 0.05 to 1.10.

  The lithium-containing compound represented by the above general formula (2a) generally has a layered structure, and the compound represented by the above general formula (2b) generally has an olivine structure. For the purpose of stabilizing the structure, these lithium-containing compounds are obtained by substituting a part of the transition metal element with Al, Mg, other transition metal elements or included in the crystal grain boundary, or oxygen atoms. A part of may be substituted with a fluorine atom or the like. Further, the lithium-containing compound may be one in which at least a part of the surface of the positive electrode active material is coated with another positive electrode active material.

Examples of the metal oxide or metal chalcogenide having a tunnel structure and a layered structure include, for example, MnO ₂ , FeO ₂ , FeS ₂ , V ₂ O ₅ , V ₆ O ₁₃ , TiO ₂ , TiS ₂ , MoS ₂ and NbSe. ₂ includes oxides, sulfides, and selenides of metals other than lithium.
Examples of other positive electrode active materials include sulfur and conductive polymers represented by polyaniline, polythiophene, polyacetylene, and polypyrrole.

The positive electrode active materials described above are used singly or in combination of two or more.
Examples of the conductive aid include carbon black typified by graphite, acetylene black and ketjen black, and carbon fiber.
Examples of the binder include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid, styrene butadiene rubber, and fluorine rubber.

  In addition, the positive electrode active material layer 120A is obtained by applying, to the positive electrode current collector 120B, a positive electrode mixture-containing slurry in which a positive electrode mixture obtained by mixing a positive electrode active material and, if necessary, a conductive additive and a binder is dispersed in a solvent. It is formed by. There is no restriction | limiting in particular as such a solvent, A conventionally well-known thing can be used, For example, N-methyl- 2-pyrrolidone, a dimethylformamide, a dimethylacetamide, and water are mentioned.

  The positive electrode current collector 120B is made of, for example, a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil. Further, the positive electrode current collector 120B may have a surface coated with carbon or processed into a mesh shape. The thickness of the positive electrode current collector 120B is preferably 5 to 40 μm, more preferably 7 to 35 μm, and still more preferably 9 to 30 μm.

<4. Negative electrode>
The negative electrode 130 includes a negative electrode active material layer 130A made from a negative electrode mixture and a negative electrode current collector 130B. The negative electrode 130 is not particularly limited as long as it functions as a negative electrode of a non-aqueous secondary battery, and may be a known one.

From the viewpoint that the negative electrode active material layer 130A can increase the battery voltage, 0.4 V vs. lithium ion is used as the negative electrode active material. It is preferable to contain a material that can be occluded at a lower potential than Li / Li ⁺ . Moreover, it is preferable that the negative electrode active material layer 130A contains a conductive additive and a binder as necessary together with the negative electrode active material.
Examples of the negative electrode active material include amorphous carbon (hard carbon), artificial graphite, natural graphite, graphite, pyrolytic carbon, coke, glassy carbon, organic polymer compound fired body, mesocarbon microbeads, carbon fiber, activated carbon In addition to carbon materials represented by graphite, carbon colloid and carbon black, metal lithium, metal oxide, metal nitride, lithium alloy, tin alloy, silicon alloy, intermetallic compound, organic compound, inorganic compound, metal complex, An organic polymer compound is mentioned.

A negative electrode active material is used individually by 1 type or in combination of 2 or more types.
Examples of the conductive aid include carbon black typified by graphite, acetylene black and ketjen black, and carbon fiber.
Examples of the binder include PVDF, PTFE, polyacrylic acid, styrene butadiene rubber, and fluorine rubber.

  In addition, the negative electrode active material layer 130A is obtained by applying a negative electrode mixture-containing slurry in which a negative electrode mixture obtained by mixing a negative electrode active material and, if necessary, a conductive additive and a binder in a solvent is applied to the negative electrode current collector 130B. It is formed by. There is no restriction | limiting in particular as such a solvent, A conventionally well-known thing can be used, For example, N-methyl- 2-pyrrolidone, a dimethylformamide, a dimethylacetamide, water etc. are mentioned.

  The negative electrode current collector 130B is made of, for example, a metal foil such as a copper foil, a nickel foil, or a stainless steel foil. Further, the negative electrode current collector 130B may have a surface coated with carbon or processed into a mesh. The thickness of the negative electrode current collector 130B is preferably 5 to 40 μm, more preferably 6 to 35 μm, and still more preferably 7 to 30 μm.

<5. Separator>
The nonaqueous secondary battery 100 in this embodiment preferably includes a separator 110 between the positive electrode 120 and the negative electrode 130 from the viewpoint of providing safety such as prevention of short circuit between the positive electrode 120 and the negative electrode 130 and shutdown. The separator 110 may be the same as that provided in a known non-aqueous secondary battery, and is preferably an insulating thin film having high ion permeability and excellent mechanical strength. Examples of the separator 110 include a woven fabric, a nonwoven fabric, and a synthetic resin microporous membrane. Among these, a synthetic resin microporous membrane is preferable.

As the synthetic resin microporous membrane, for example, a microporous membrane containing polyethylene or polypropylene as a main component or a polyolefin microporous membrane such as a microporous membrane containing both of these polyolefins is preferably used. Examples of the non-woven fabric include porous films made of heat-resistant resin such as glass, ceramic, polyolefin, polyester, polyamide, liquid crystal polyester, and aramid.
The separator 110 may have a configuration in which one type of microporous membrane is laminated or a plurality of microporous membranes may be laminated, or two or more types of microporous membranes may be laminated. In addition, the separator 110 may have a configuration in which a single layer or a plurality of layers are stacked using a mixed resin material obtained by melting and kneading two or more kinds of resin materials.

<6. Battery exterior>
Although the structure of the battery exterior 160 of the non-aqueous secondary battery 100 in this embodiment is not specifically limited, The battery exterior of either a battery can or a laminate film exterior body can be used. As the battery can, for example, a metal can made of steel or aluminum can be used. As the laminate film outer package, for example, a laminate film having a three-layer structure of hot melt resin / metal film / resin can be used.

  The laminate film exterior body is overlapped with the heat-melting resin side facing inward, or folded so that the heat-melting resin side faces inward, and the end portion is sealed with a heat seal. It can be used as an exterior body in a state. In addition, when using a laminate film exterior body, a positive electrode terminal (or a lead tab connected to the positive electrode terminal and the positive electrode terminal) is connected to the positive electrode current collector 120B, and a negative electrode terminal (or a negative electrode terminal and a negative electrode terminal) is connected to the negative electrode current collector 130B. A lead tab to be connected) may be connected. In this case, the laminate film outer package may be sealed with the ends of the positive electrode terminal and the negative electrode terminal (or the lead tab connected to each of the positive electrode terminal and the negative electrode terminal) pulled out of the outer package.

<7. Manufacturing method of battery>
The non-aqueous secondary battery 100 in the present embodiment is manufactured by a known method using the above-described non-aqueous electrolyte solution, the positive electrode 120, the negative electrode 130, the battery casing 160, and the separator 110 as necessary.

  For example, the long positive electrode 120 and the negative electrode 130 can be wound in a stacked state in which a long separator is interposed between the positive electrode 120 and the negative electrode 130 to form a wound structure. In addition, a laminate having a laminated structure in which a positive electrode sheet and a negative electrode sheet obtained by cutting the positive electrode 120 and the negative electrode 130 into a plurality of sheets having a certain area and shape are alternately laminated via a separator sheet is formed. can do. In addition, it is possible to form a laminate having a laminated structure in which long separators are folded in a zigzag manner, and positive electrode sheets and negative electrode sheets are alternately inserted between the zipped separators.

Next, by housing the above-described laminate in the battery exterior 160 (battery case), injecting the electrolyte solution according to the present embodiment into the battery case, immersing the laminate in the electrolyte solution and sealing it, The nonaqueous secondary battery in this embodiment can be produced.
Alternatively, an electrolyte solution in a gel state is prepared in advance by impregnating a base material made of a polymer material with an electrolytic solution, and a sheet-like positive electrode 120, a negative electrode 130, an electrolyte membrane, and, if necessary, a separator 110 are used. Then, after forming a laminated body having a laminated structure, the non-aqueous secondary battery 100 can be manufactured by being housed in the battery exterior 160.

The shape of the non-aqueous secondary battery 100 in the present embodiment is not particularly limited, and for example, a cylindrical shape, an elliptical shape, a rectangular tube shape, a button shape, a coin shape, a flat shape, a laminate shape, and the like are suitably employed. .
The non-aqueous secondary battery 100 in the present embodiment can function as a battery by the initial charge, but is stabilized when a part of the electrolytic solution is decomposed during the initial charge. Although there is no restriction | limiting in particular about the method of initial charge, It is preferable that initial charge is performed at 0.001-0.3C, It is more preferable to be performed at 0.002-0.25C, 0.003-0.2C More preferably, In addition, it is also preferable that the initial charging is performed via the constant voltage charging in the middle. In addition, the constant current which discharges rated capacity in 1 hour is 1C. By setting a long voltage range in which lithium salt is involved in the electrochemical reaction, SEI (Solid Electrolyte Interface) is formed on the electrode surface, and the effect of suppressing the increase in internal resistance including positive electrode 120 There is. In addition, the reaction product is not firmly fixed only on the negative electrode 130, and a good effect is given to members other than the negative electrode 130 such as the positive electrode 120 and the separator 110 in some form. For this reason, it is very effective to perform the initial charge in consideration of the electrochemical reaction of the lithium salt dissolved in the non-aqueous electrolyte.

The nonaqueous secondary battery 100 in this embodiment can also be used as a battery pack in which a plurality of nonaqueous secondary batteries 100 are connected in series or in parallel. In addition, from the viewpoint of managing the charge / discharge state of the battery pack, the operating voltage range per unit is preferably 2 to 5 V, more preferably 2.5 to 5 V, and 2.75 V to 5 V. It is particularly preferred.
As mentioned above, although the form for implementing this invention was demonstrated, this invention is not limited to the above-mentioned embodiment. The present invention can be variously modified without departing from the gist thereof.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples. Various evaluations were performed as follows.
(1) Lithium foil immersion test In an inert atmosphere, a nonaqueous electrolyte solution (5 mL) visually confirmed to be completely dissolved in a lithium salt was transferred to a polypropylene container, and a lithium foil having a thickness of 200 μm cut to 5 mm × 5 mm. Was immersed and allowed to stand at 25 ° C. for 1 day. “○” when the non-aqueous electrolyte solution remains colorless and transparent, and no deterioration of the lithium foil is observed, and when the electrolyte solution discoloration or lithium foil deterioration is observed even if the lithium foil remains Was judged as “C”, and the case where the lithium foil was completely dissolved was judged as “x”. The lithium foil determined to be “◯” after standing at 25 ° C. for 1 day was then left again at 50 ° C. for 1 day, and again judged according to the same criteria as when left at 25 ° C. for 1 day.

(2) Battery Production (2-1) Production of Positive Electrode (P1) Composite oxide of lithium, nickel, manganese and cobalt having a number average particle diameter of 11 μm as a positive electrode active material (Ni / Mn / Co = 1/1/1) (Element ratio), LiNi _1/3 Mn _1/3 Co _1/3 O ₂ ; density 4.70 g / cm ³ ) and graphite carbon powder (density 2.26 g) having a number average particle size of 6.5 μm as a conductive aid. / cm ³⁾ and acetylene black powder having an average particle diameter of 48 nm (density 1.95 g / cm ^3), polyvinylidene fluoride (PVdF as a binder; and density of ^{1.75g / cm 3), 100:} 4.2: The mixture was mixed at a mass ratio of 1.8: 4.6 to obtain a positive electrode mixture. N-methyl-2-pyrrolidone as a solvent was added to the obtained positive electrode mixture so as to have a solid content of 68% by mass and further mixed to prepare a positive electrode mixture-containing slurry. The positive electrode mixture-containing slurry was applied to one side of an aluminum foil having a thickness of 20 μm and a width of 200 mm to be a positive electrode current collector by a doctor blade method while adjusting the basis weight to be 24.0 mg / cm ^2. Was removed by drying. Then, it rolled by the roll press so that an actual electrode density might be 2.90 g / cm < ³ >, and the positive electrode (P1) which consists of a positive electrode active material layer and a positive electrode electrical power collector was obtained.

(2-2) Production of negative electrode (N1) Graphite carbon powder having a number average particle diameter of 12.7 μm (density 2.23 g / cm ³ ) and graphite carbon powder having a number average particle diameter of 6.5 μm (density 2) as a negative electrode active material .27 g / cm ³ ), a carboxymethyl cellulose (density 1.60 g / cm ³ ) solution (solid content concentration 1.83 mass%) as a binder, and a styrene butadiene latex (glass transition temperature: −5 ° C., number during drying) Average particle diameter: 120 nm, density 1.00 g / cm ³ , dispersion medium: water, solid content concentration 40 mass%) at a solid content mass ratio of 87.2: 9.7: 1.4: 1.7. By mixing, a negative electrode mixture was obtained. Water was added to the obtained negative electrode mixture as a solvent so as to have a solid content of 45% by mass, and further mixed to prepare a negative electrode mixture-containing slurry. This negative electrode mixture-containing slurry was applied to one side of a copper foil having a thickness of 10 μm and a width of 200 mm to be a negative electrode current collector while adjusting the basis weight to be 10.6 mg / cm ² by a doctor blade method. Removed dry. Then, it rolled by the roll press so that an actual electrode density might be 1.50 g / cm < ³ >, and the negative electrode (N1) which consists of a negative electrode active material layer and a negative electrode collector was obtained.

(2-3) Production of coin-type non-aqueous secondary battery A positive electrode obtained by punching the positive electrode obtained as described above in the center of a CR2032-type battery case (SUS304 / Al clad) into a disk shape having a diameter of 16 mm is used as the positive electrode. The active material layer was set upward. A polyethylene microporous membrane (film thickness 20 μm) and a polypropylene gasket were set from above, and 150 μL of electrolyte was injected. Thereafter, the negative electrode obtained as described above was punched into a disk shape having a diameter of 16 mm and set with the negative electrode active material layer facing downward. After setting the spacer and spring, the battery cap was fitted and crimped with a caulking machine. The electrolyte that overflowed from the battery case was wiped clean with a waste cloth. The battery case containing the laminate and the non-aqueous electrolyte was held for 24 hours in a 25 ° C. environment, and the laminate was sufficiently impregnated with the electrolyte to obtain a coin-type non-aqueous secondary battery.

(3) Battery Evaluation Regarding the battery for evaluation obtained as described above (hereinafter also simply referred to as “battery”), first, the initial charge process and the initial charge / discharge capacity are performed according to the following procedure (3-1). Measurements were made. Next, each battery was evaluated according to the following (3-2) and (3-3). In addition, charging / discharging was performed using charge / discharge apparatus ACD-01 (trade name) manufactured by Asuka Electronics Co., Ltd. and a thermostat PLM-63S (trade name) manufactured by Futaba Kagaku.
Here, 1C means a current value at which a fully charged battery is discharged at a constant current and is expected to be discharged in 1 hour. It means a current value expected to be discharged from a fully charged state of 4.2 V to 3.0 V at a constant current and finished in 1 hour.

(3-1) Initial charge / discharge treatment of coin-type non-aqueous secondary battery The battery temperature is set to 4.2 V by setting the ambient temperature of the battery to 25 ° C. and charging with a constant current of 0.6 mA corresponding to 0.1 C. Then, the battery was charged at a constant voltage of 4.2 V for a total of 15 hours. Thereafter, the battery was discharged to 3.0 V at a constant current of 1.8 mA corresponding to 0.3 C, and the initial efficiency was calculated. The discharge capacity at this time was defined as the initial capacity.
(3-2) Measurement of discharge capacity at high output of coin-type non-aqueous secondary battery (output test)
After charging with a constant current of 6 mA corresponding to 1 C and charging until the battery voltage reaches 4.2 V using the battery that has been subjected to the initial charge / discharge treatment by the method described in (3-1) above The battery was charged at a constant voltage of 4.2 V for a total of 3 hours. Thereafter, the battery was discharged to a battery voltage of 3.0 V with a constant current of 6 mA corresponding to 1C. The discharge capacity at this time was A. Next, the battery was charged with a constant current of 6 mA corresponding to 1 C and charged until the battery voltage reached 4.2 V, and then charged with a constant voltage of 4.2 V for a total of 3 hours. Thereafter, the battery was discharged to a battery voltage of 3.0 V with a constant current of 30 mA corresponding to 5C. The discharge capacity at this time was B. The following values were calculated as output test measurement values.
Capacity maintenance rate = 100 × B / A [%]

(3-3) 85 ° C. Full-Charge Storage Test of Coin Type Non-Aqueous Secondary Battery Durability at the time of 85 ° C. full-charge storage for the battery subjected to the initial charge / discharge treatment by the method described in (3-1) above. Evaluated. First, the ambient temperature of the battery was set to 25 ° C., the battery was charged with a constant current of 6 mA corresponding to 1 C, and the battery voltage reached 4.2 V. Then, the battery was charged with a constant voltage of 4.2 V for a total of 3 hours. . Next, this battery was stored in a constant temperature bath at 85 ° C. for 4 hours. Thereafter, the ambient temperature of the battery was returned to 25 ° C. and discharged to a battery voltage of 3.0 V with a constant current of 1.8 mA corresponding to 0.3 C. The discharge capacity at this time was defined as the remaining capacity. Next, after charging at a constant current of 6 mA corresponding to 1 C and the battery voltage reached 4.2 V, charging was performed for a total of 3 hours at a constant voltage of 4.2 V, and a current of 1.8 mA corresponding to 0.3 C was charged. The battery was discharged at a constant current to 3.0V. The discharge capacity at this time was 0.3 C recovery capacity. From these results, the following values were calculated.
Maintenance rate = 100 × remaining capacity / initial capacity [%]
Recovery rate = 100 × 0.3C recovery capacity / initial capacity [%]

[Reference Example 1] to [Reference Example 5]
In an inert atmosphere, 3.0 mol, 9.5 mol, 10.2 mol, 13.0 mol, 20.0 mol of LiN (SO ₂ CF ₃ ) ₂ was dissolved in 1 L of acetonitrile, respectively, and an electrolytic solution (S1) To (S5). About these electrolyte solution (S1)-(S5), the lithium foil immersion test was done by the method as described in the above-mentioned (1).

  The evaluation results of Reference Examples 1 to 5 are shown in Table 1 below.

From the above results, in the high concentration region (Reference Example 2, Reference Example 3, Reference Example 4 and Reference Example 5) in which the imide salt described in the non-patent document 1 is considered to be near the crystallinity gap at a high concentration, lithium is used. The foil was retained and the reduction resistance of the non-aqueous electrolyte was demonstrated.
[Reference Example 6] to [Reference Example 10]
Under an inert atmosphere, 1.5 mol, 2.3 mol, 3.0 mol, 3.7 mol, 4.0 mol of LiN (SO ₂ F) ₂ was dissolved in 1 L of acetonitrile, respectively, and the electrolytic solution (S6) to (S10) was obtained. About these electrolyte solutions, the lithium foil immersion test was done by the method as described in said (1).
The evaluation results of Reference Example 6 to Reference Example 10 are shown in Table 2 below.

From the above results, the reduction resistance of the non-aqueous electrolyte in the high concentration region (Reference Example 9 and Reference Example 10) was also demonstrated for LiN (SO ₂ F) ₂ .
[Example 1]
Under an inert atmosphere, 4.0 mol of LiN (SO ₂ CF ₃ ) ₂ was dissolved in 1 L of acetonitrile. Next, ethylene carbonate and vinylene carbonate were added to and mixed with the acetonitrile used first so that the volume ratio of acetonitrile, ethylene carbonate, and vinylene carbonate was 69: 23: 8. Additionally, non-aqueous solvent (acetonitrile, ethylene carbonate and vinylene carbonate) of the mixed solution by dissolving LiPF ₆ so as to be 0.3mol against 1L, to give electrolyte solution (S11). About the obtained electrolyte solution (S11), it was confirmed visually that all the lithium salts (LiN (SO ₂ CF ₃ ) ₂ and LiPF ₆ ) were dissolved. This electrolyte solution (S11) was subjected to a lithium foil immersion test by the method described in (1) above.

[Comparative Example 1]
An electrolyte solution (S12) was obtained in the same manner as in Example 1 except that LiPF ₆ was not dissolved. About the obtained electrolyte solution (S12), it was confirmed visually that all the lithium salts (LiN (SO ₂ CF ₃ ) ₂ ) were dissolved. This electrolyte solution (S12) was subjected to a lithium foil immersion test by the method described in (1) above.
[Example 2]
An electrolytic solution (S13) was obtained in the same manner as in Example 1 except that 0.3 mol of LiBF ₄ was dissolved instead of LiPF ₆ . The obtained electrolyte solution (S13), it was confirmed that the lithium salt _{(LiN (SO 2 CF 3)} 2 and LiBF ₄₎ are all dissolved visually. This electrolyte solution (S13) was subjected to a lithium foil immersion test by the method described in (1) above.

[Example 3]
Under an inert atmosphere, 4.0 mol of LiN (SO ₂ F) ₂ was dissolved in 1 L of acetonitrile. Next, ethylene carbonate and vinylene carbonate were added and mixed with the acetonitrile used first so that the volume ratio of acetonitrile, ethylene carbonate, and vinylene carbonate was 57: 36: 7. Furthermore, LiPF ₆ was dissolved so as to be 0.3 mol per liter of the non-aqueous solvent (acetonitrile, ethylene carbonate, and vinylene carbonate) in the mixed solution to obtain an electrolytic solution (S14). About the obtained electrolyte solution (S14), it was confirmed visually that all the lithium salts (LiN (SO ₂ F) ₂ and LiPF ₆ ) were dissolved. This electrolyte solution (S14) was subjected to a lithium foil immersion test by the method described in (1) above.

[Comparative Example 2]
An electrolyte solution (S15) was obtained in the same manner as in Example 1 except that 2.9 mol of LiN (SO ₂ CF ₃ ) ₂ was dissolved in 1 L of acetonitrile, and LiPF ₆ was not dissolved. The obtained electrolyte solution (S15), it was confirmed that the lithium salt _{(LiN (SO 2 CF 3)} 2) is dissolved all visually. This electrolyte solution (S15) was subjected to a lithium foil immersion test by the method described in (1) above.
[Comparative Example 3]
An electrolyte solution (S16) was obtained in the same manner as in Example 1 except that 4.3 mol of LiN (SO ₂ CF ₃ ) ₂ was dissolved in 1 L of acetonitrile and LiPF ₆ was not dissolved. About the obtained electrolyte solution (S16), it was confirmed visually that all the lithium salts (LiN (SO ₂ CF ₃ ) ₂ ) were dissolved. This electrolyte solution (S16) was subjected to a lithium foil immersion test by the method described in (1) above.

[Comparative Example 4]
An electrolyte solution (S17) was obtained in the same manner as in Example 1 except that 5.1 mol of LiN (SO ₂ CF ₃ ) ₂ was dissolved in 1 L of acetonitrile, and LiPF ₆ was not dissolved. About the obtained electrolyte solution (S17), it was confirmed visually that all the lithium salts (LiN (SO ₂ CF ₃ ) ₂ ) were dissolved. This electrolyte solution (S17) was subjected to a lithium foil immersion test by the method described in (1) above.
The evaluation results of Examples 1 to 3 and Comparative Examples 1 to 4 are shown in Table 3 below.

  In the electrolytic solution containing a specific amount of acetonitrile, in Comparative Examples 1 to 4 that did not contain the fluorine-containing inorganic lithium salt, discoloration of the non-aqueous electrolytic solution and alteration of the lithium foil were observed. On the other hand, in Examples 1 to 3 containing a fluorine-containing inorganic lithium salt in an electrolyte containing a specific amount of acetonitrile, no discoloration of the non-aqueous electrolyte and no alteration of the lithium foil were observed. From these results, it was revealed that the fluorine-containing inorganic lithium salt strongly acts on the reduction resistance in the electrolytic solution containing a specific amount of acetonitrile.

[Example 4]
A positive electrode (P1), a negative electrode (N1), and an electrolytic solution (S11) were combined to produce a coin-type non-aqueous secondary battery according to the method described in (2-3) above. This coin-type non-aqueous secondary battery is subjected to the initial charge / discharge treatment by the method described in (3-1) above, and the discharge capacity measurement and the method described in (3-2) and (3-3) above are performed. A storage test was conducted.
[Example 5]
A coin-type non-aqueous secondary battery was produced in the same manner as in Example 4 except that the electrolytic solution (S14) was used. This coin-type non-aqueous secondary battery is subjected to the initial charge / discharge treatment by the method described in (3-1) above, and the discharge capacity measurement and the method described in (3-2) and (3-3) above are performed. A storage test was conducted.

[Comparative Example 5]
Under an inert atmosphere, 8.0 mol of LiN (SO ₂ CF ₃ ) ₂ was dissolved in 1 L of acetonitrile. Next, ethylene carbonate and vinylene carbonate were added and mixed with the acetonitrile used first so that the volume ratio of acetonitrile, ethylene carbonate, and vinylene carbonate was 35: 57: 8. Furthermore, LiPF ₆ was dissolved so that it might become 0.3 mol with respect to 1L of non-aqueous solvents (acetonitrile, ethylene carbonate, and vinylene carbonate) in this liquid mixture, and electrolyte solution (S18) was obtained.

  A coin-type non-aqueous secondary battery was produced in the same manner as in Example 4 except that the electrolytic solution (S18) was used. This coin-type non-aqueous secondary battery is subjected to the initial charge / discharge treatment by the method described in (3-1) above, and the discharge capacity measurement and the method described in (3-2) and (3-3) above are performed. A storage test was conducted.

[Comparative Example 6]
Under an inert atmosphere, 6.0 mol of LiN (SO ₂ CF ₃ ) ₂ was dissolved in 1 L of acetonitrile. Next, ethylene carbonate and vinylene carbonate were added and mixed with the acetonitrile used first so that the volume ratio of acetonitrile, ethylene carbonate, and vinylene carbonate was 35: 57: 8. Additionally, non-aqueous solvent (acetonitrile, ethylene carbonate and vinylene carbonate) in this mixture was dissolved LiPF ₆ to be 1.0mol against 1L, to give electrolyte solution (S19).
A coin-type non-aqueous secondary battery was produced in the same manner as in Example 4 except that the electrolytic solution (S19) was used. The battery was first charged / discharged by the method described in (3-1) above, and the discharge capacity measurement and storage test were performed by the methods described in (3-2) and (3-3) above.

[Comparative Example 7]
A coin-type non-aqueous secondary battery was produced in the same manner as in Example 4 except that the electrolytic solution (S3) was used. This battery was subjected to the initial charge / discharge treatment by the method described in (3-1) above, but since the initial capacity was low, the subsequent evaluation was not performed.
[Comparative Example 8]
Under an inert atmosphere, ethylene carbonate, vinylene carbonate and diethyl carbonate are mixed so that the volume ratio is 19.7: 1.5: 78.8, and this non-aqueous solvent (ethylene carbonate, vinylene carbonate and diethyl carbonate) 1 L LiPF ₆ was dissolved in an amount of 1.18 mol to obtain an electrolytic solution (S20).
A coin-type non-aqueous secondary battery was produced in the same manner as in Example 4 except that the electrolytic solution (S20) was used. The battery was first charged / discharged by the method described in (3-1) above, and the discharge capacity measurement and storage test were performed by the methods described in (3-2) and (3-3) above.

[Comparative Example 9]
Under an inert atmosphere, acetonitrile, ethylene carbonate, and vinylene carbonate are mixed so that the volume ratio is 49: 46: 5, and becomes 1.2 mol with respect to 1 L of this non-aqueous solvent (acetonitrile, ethylene carbonate, and vinylene carbonate). LiPF ₆ was dissolved to obtain an electrolytic solution (S21).
A coin-type non-aqueous secondary battery was produced in the same manner as in Example 4 except that the electrolytic solution (S21) was used. The battery was first charged / discharged by the method described in (3-1) above, and the discharge capacity measurement and storage test were performed by the methods described in (3-2) and (3-3) above.
The evaluation results of Examples 4 to 5 and Comparative Examples 5 to 9 are shown in Table 4 below.

In Table 4, “AN” represents acetonitrile, “EC” represents ethylene carbonate, “VC” represents vinylene carbonate, and “DEC” represents diethyl carbonate.
From the results of Example 4 and Example 5 and Comparative Example 5 and Comparative Example 6, when the content of acetonitrile in the non-aqueous solvent was 40% by volume or more, the content of acetonitrile was less than 40% by volume. It was confirmed that the capacity retention rate in the output test was improved as compared with the case where

From the results of Example 4 and Comparative Example 7, when the electrolytic solution containing the fluorine-containing inorganic lithium salt was used, the initial efficiency was significantly improved as compared with the case of using the electrolytic solution not containing the fluorine-containing inorganic lithium salt. Confirmed to do.
From the results of Example 4 and Comparative Example 8, when the electrolytic solution containing acetonitrile and imide salt was used, the capacity retention rate in the output test was remarkable compared to the case where the electrolytic solution not containing acetonitrile and imide salt was used. It was confirmed that it improved.

From the results of Example 4 and Comparative Example 9, when the content of acetonitrile in the non-aqueous solvent was 40% by volume or more and an electrolyte containing an imide salt was used, the content of acetonitrile was 40% by volume or more. Even if it exists, it was confirmed that the capacity | capacitance maintenance rate in an output test, and the maintenance factor and recovery rate after a storage test improve notably compared with the case where the electrolyte solution which does not contain an imide salt is used.
From the above results, it can be seen that the non-aqueous secondary battery using the electrolytic solution of the present embodiment has high output characteristics and high temperature durability performance similar to that of the existing electrolytic solution.

  The non-aqueous secondary battery of the present invention includes, for example, mobile devices such as a mobile phone, a portable audio device, a personal computer, and an IC (Integrated Circuit) tag, as well as a vehicle such as a hybrid vehicle, a plug-in hybrid vehicle, and an electric vehicle. It is also expected to be used as a battery and as a residential power storage system.

  DESCRIPTION OF SYMBOLS 100 ... Lithium ion secondary battery, 110 ... Separator, 120 ... Positive electrode, 120A ... Positive electrode active material layer, 120B ... Positive electrode collector, 130 ... Negative electrode, 130A ... Negative electrode active material layer, 130B ... Negative electrode collector, 160 ... Battery exterior

Claims (6)

A non-aqueous electrolyte solution containing a non-aqueous solvent and a lithium salt,
The non-aqueous solvent contains 40 to 100% by volume of acetonitrile with respect to the total amount of the non-aqueous solvent,
The lithium salt includes one or more compounds selected from the group consisting of compounds represented by LiN (SO ₂ C _m F _{2m + 1} ) ₂ [m is an integer of 0 to 1] and a fluorine-containing inorganic lithium salt,
The total amount of the compound represented by LiN (SO ₂ C _m F _{2m + 1} ) ₂ [m is an integer of 0 to 1] is 3.1 to 25 mol with respect to 1 liter of the acetonitrile in the non-aqueous solvent. A non-aqueous electrolyte characterized by The non-aqueous electrolyte solution according to claim 1, wherein the fluorine-containing inorganic lithium salt is at least one fluorine-containing inorganic lithium salt selected from the group consisting of LiPF ₆ and LiBF ₄ . The nonaqueous electrolytic solution according to claim 1 or 2, wherein the content of the fluorine-containing inorganic lithium salt is 0.05 to 1.0 mol with respect to 1 liter of the nonaqueous solvent. 4. The compound represented by LiN (SO ₂ C _m F _{2m + 1} ) ₂ [m is an integer of 0 to 1] is LiN (SO ₂ F) _2. The non-aqueous electrolyte solution according to item. A positive electrode using an aluminum foil as a current collector;
Lithium ion as a negative electrode active material was 0.4 V vs. A negative electrode containing a material that occludes at a lower potential than Li / Li ⁺ ;
A non-aqueous secondary battery comprising: the non-aqueous electrolyte solution according to claim 1. The non-aqueous secondary battery according to claim 5, wherein the negative electrode includes graphite as a negative electrode active material.

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