JP6252200B2 - Non-aqueous electrolyte and power storage device using the same - Google Patents

Description

  The present invention relates to a nonaqueous electrolytic solution capable of improving electrochemical characteristics when an electricity storage device is used at a high voltage, and an electricity storage device using the same.

  In recent years, power storage devices, particularly lithium secondary batteries, have been widely used as power sources for electronic devices such as mobile phones and laptop computers, or for electric vehicles and power storage. In particular, thin-type electronic devices such as tablet terminals and ultrabooks often use laminate-type batteries or square-type batteries that use a laminate film such as an aluminum laminate film as the exterior member. The problem of being easily deformed due to the expansion of the exterior member is that the effect of the deformation on the electronic device is very large.

A lithium secondary battery is mainly composed of a positive electrode and a negative electrode containing a material capable of occluding and releasing lithium, and a non-aqueous electrolyte composed of a lithium salt and a non-aqueous solvent. Examples of the non-aqueous solvent include ethylene carbonate (EC) and propylene. Carbonates such as carbonate (PC) are used.
As negative electrodes of lithium secondary batteries, lithium metal, metal compounds capable of inserting and extracting lithium (metal simple substance, oxide, alloy with lithium, etc.) and carbon materials are known. In particular, non-aqueous electrolyte secondary batteries using carbon materials that can occlude and release lithium, such as coke and graphite (artificial graphite, natural graphite), are widely used. The above negative electrode materials store and release lithium and electrons at an extremely low potential equivalent to that of lithium metal, so many solvents may undergo reductive decomposition, regardless of the type of negative electrode material. Some of the solvent in the electrolyte solution is reductively decomposed on the negative electrode, and the migration of lithium ions is hindered by the deposition of decomposition products, gas generation, and electrode swelling, especially when the battery is used at high temperature and high voltage. There have been problems such as deterioration of battery characteristics such as cycle characteristics and deformation of the battery due to swelling of the electrodes. Furthermore, lithium secondary batteries using lithium metal, alloys thereof, simple metals such as tin or silicon, and oxides as negative electrode materials have high initial capacities, but fine powders progress during the cycle. In comparison, reductive decomposition of a nonaqueous solvent occurs at an accelerated rate, and battery performance such as battery capacity and cycle characteristics is greatly reduced, and problems such as battery deformation due to electrode swelling are known.

On the other hand, materials capable of occluding and releasing lithium, such as LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , and LiFePO ₄ used as positive electrode materials, store and release lithium and electrons at a precious voltage of 3.5 V or more on the basis of lithium. Therefore, in particular, when a battery is used at a high temperature and a high voltage, many solvents have a possibility of undergoing oxidative decomposition, and the solvent in the electrolytic solution on the positive electrode does not depend on the type of the positive electrode material. There is a problem that a part is oxidized and decomposed to increase resistance due to deposition of decomposition products, or gas is generated due to decomposition of the solvent and the battery is swollen.
Under such circumstances, in electronic devices equipped with lithium secondary batteries, power consumption is increasing and capacity is increasing. The environment is becoming more prone to decomposition for electrolytes, such as battery temperature rise due to heat generated from electronic devices and higher battery charge setting voltage. Gas generation causes battery expansion, current interruption, etc. There was a problem that the safety mechanism of the battery operated and the battery could not be used.

  In spite of the above situation, electronic devices equipped with lithium secondary batteries are becoming more and more multifunctional and power consumption is increasing. As a result, the capacity of lithium secondary batteries has been increasing, and the volume occupied by non-aqueous electrolyte in the battery has become smaller, such as increasing the electrode density and reducing the useless space volume in the battery. . Therefore, the battery performance when the battery is used at a high temperature and a high voltage is likely to deteriorate with a slight decomposition of the non-aqueous electrolyte.

  Patent Document 1 shows that the addition of a dialkyl squarate to the electrolyte improves the electrochemical characteristics of the battery, particularly the cycle capacity retention rate at 23 ° C. Patent Document 2 shows that the cycle capacity retention rate at 25 ° C. is improved when an electrolytic solution containing lithium N, N′-bis (nonafuryl) squalamide is used.

JP 2008-262900 A JP 2012-109089 A

  The present invention improves the electrochemical characteristics when the electricity storage device is used at a high temperature and a high voltage, and further can suppress not only the capacity retention rate after storage at a high voltage and a high temperature, but also the gas generation, and An object is to provide an electricity storage device using the same.

As a result of examining the performance of the above-described conventional non-aqueous electrolyte in detail, the non-aqueous electrolyte secondary batteries of Patent Documents 1 and 2 show that the storage device is used at a high temperature and a high voltage. The actual situation is that the effect of suppressing the generation of gas accompanying charging / discharging can hardly be exhibited.
Therefore, as a result of intensive studies to solve the above problems, the present inventors have added a specific compound to increase the capacity retention rate after storage when the power storage device is used at high temperature and high voltage. The present invention has been completed by finding that it can be improved and gas generation can be suppressed.

  That is, the present invention provides the following (1) to (2).

(1) A nonaqueous electrolytic solution in which an electrolyte salt is dissolved in a nonaqueous solvent, containing at least one lithium salt represented by the following general formula (I):

(In the formula, M represents a boron atom or a phosphorus atom, X represents a halogen atom, Rf represents a fluoroalkyl group having 1 to 4 carbon atoms, n represents an integer of 1 to 3, p and q represent Represents an integer of 0 to 4. When M is a boron atom, m represents 1 or 2, and 2m + p + q = 4 When M is a phosphorus atom, m represents an integer of 1 to 2 and 2m + p + q = 6 .)

(2) An electricity storage device including a nonaqueous electrolyte solution in which an electrolyte salt is dissolved in a positive electrode, a negative electrode, and a nonaqueous solvent, wherein the nonaqueous electrolyte solution is a lithium salt represented by the general formula (I) An electricity storage device comprising at least one kind.

  According to the present invention, it is possible to improve the capacity retention rate after storage when the power storage device is used at a high temperature and high voltage, and to suppress the generation of gas, such as a non-aqueous electrolyte and a lithium battery using the nonaqueous electrolyte An electricity storage device can be provided.

  The present invention relates to a non-aqueous electrolyte and an electricity storage device using the same.

[Non-aqueous electrolyte]
The nonaqueous electrolytic solution of the present invention is a nonaqueous electrolytic solution in which an electrolyte salt is dissolved in a nonaqueous solvent, and contains the lithium salt represented by the general formula (I) in the nonaqueous electrolytic solution. And

The reason why the nonaqueous electrolytic solution of the present invention can greatly improve the electrochemical characteristics when the electricity storage device is used at high temperature and high voltage is not clear, but is considered as follows.
The compound used in the present invention is a complex salt having an oxocarbonic acid and further having a metal atom such as a boron atom or a phosphorus atom. Because of this, it is highly reactive, reacts quickly at the active sites of both the positive electrode and the negative electrode, and forms a stronger film by including metal atoms such as boron atoms and phosphorus atoms in the film. It is considered that voltage storage characteristics are improved and gas generation due to decomposition of the solvent is suppressed.

  The lithium salt contained in the nonaqueous electrolytic solution of the present invention is represented by the following general formula (I).

(In the formula, M represents a boron atom or a phosphorus atom, X represents a halogen atom, Rf represents a fluoroalkyl group having 1 to 4 carbon atoms, n represents an integer of 1 to 3, p and q represent Represents an integer of 0 to 4. When M is a boron atom, m represents 1 or 2, and 2m + p + q = 4 When M is a phosphorus atom, m represents an integer of 1 to 2 and 2m + p + q = 6 .)

  In the general formula (I), in the formula, n represents an integer of 1 to 3, and when n is 2, it is particularly preferable. M represents a boron atom or a phosphorus atom. When M is a boron atom, m is an integer of 1 or 2, p and q are integers of 0 to 2, and it is particularly preferable when m is 1 and p is 2. When M is a phosphorus atom, m is an integer of 1 to 3, p and q are integers of 0 to 4, and when m is 1 and p is 4, or when m is 2 and p is 2, preferable. X represents a halogen atom, preferably a fluorine atom. Rf represents a C1-C4 fluoroalkyl group, preferably a C1-C2 fluoroalkyl group.

  Specific examples of Rf include a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a 2-fluoroethyl group, a 2,2-difluoroethyl group, a 2,2,2-trifluoroethyl group, and a 3-fluoropropyl group. 3,3-difluoropropyl group, 3,3,3-trifluoropropyl group, 2,2,3,3-tetrafluoropropyl group, 2,2,3,3,3-pentafluoropropyl group, etc. Preferred examples include a halogenated alkyl group. Among them, a trifluoromethyl group, a 2,2,2-trifluoroethyl group, and a 2,2,3,3-tetrafluoropropyl group are preferable, and a trifluoromethyl group is more preferable. preferable.

  Specific examples of the general formula (I) include the following lithium salts.

  Among the lithium salts, lithium salts having a structural formula of 5, 8, 9, 15-18, or 20 are more preferable, and 5, 8, 15, or 16 is particularly preferable.

  In the nonaqueous electrolytic solution of the present invention, the content of the lithium salt represented by the following general formula (I) is preferably 0.001 to 10% by mass in the nonaqueous electrolytic solution. If the content is 10% by mass or less, a coating film is excessively formed on the electrode, and there is little risk of deterioration of storage characteristics when the battery is used at high temperature and high voltage, and 0.001% by mass or more. If the battery is used at a high temperature and a high voltage, the effect of improving the storage characteristics is enhanced. The content is preferably 0.01% by mass or more, and more preferably 0.3% by mass or more in the nonaqueous electrolytic solution. Moreover, the upper limit is preferably 8% by mass or less, more preferably 5% by mass or less, and particularly preferably 3% by mass or less.

[Nonaqueous solvent]
As the nonaqueous solvent used in the nonaqueous electrolytic solution of the present invention, one or more selected from cyclic carbonates, chain esters, lactones, ethers, and amides are preferably exemplified. Since electrochemical properties are synergistically improved at high temperatures, it is preferable that a chain ester is included, more preferably a chain carbonate is included, and most preferably both a cyclic carbonate and a chain carbonate are included. .

  The term “chain ester” is used as a concept including a chain carbonate and a chain carboxylic acid ester.

  Examples of the cyclic carbonate include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 4-fluoro-1,3-dioxolan-2-one (FEC), trans or Cis-4,5-difluoro-1,3-dioxolan-2-one (hereinafter collectively referred to as “DFEC”), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), and 4-ethynyl-1 , 3-dioxolan-2-one (EEC) or two or more selected from ethylene carbonate, propylene carbonate, 4-fluoro-1,3-dioxolan-2-one, vinylene carbonate, and 4-ethynyl Selected from -1,3-dioxolan-2-one (EEC) That one or two or more is more preferable.

  In addition, it is preferable to use at least one of unsaturated bonds such as carbon-carbon double bonds or carbon-carbon triple bonds or cyclic carbonates having a fluorine atom, since the electrochemical properties at high temperatures are further improved. More preferably, both a cyclic carbonate containing an unsaturated bond such as a carbon double bond or a carbon-carbon triple bond and a cyclic carbonate having a fluorine atom are included. As the cyclic carbonate having an unsaturated bond such as a carbon-carbon double bond or carbon-carbon triple bond, VC, VEC, or EEC is more preferable, and as the cyclic carbonate having a fluorine atom, FEC or DFEC is more preferable.

  The content of the cyclic carbonate having an unsaturated bond such as a carbon-carbon double bond or a carbon-carbon triple bond is preferably 0.07% by volume or more, more preferably 0.8%, based on the total volume of the nonaqueous solvent. 2 vol% or more, more preferably 0.7 vol% or more, and the upper limit thereof is preferably 7 vol% or less, more preferably 4 vol% or less, further preferably 2.5 vol% or less. And, it is preferable because the stability of the coating at a high temperature can be further increased without impairing the Li ion permeability.

  The content of the cyclic carbonate having a fluorine atom is preferably 0.07% by volume or more, more preferably 4% by volume or more, still more preferably 7% by volume or more, based on the total volume of the nonaqueous solvent. The upper limit is preferably 35% by volume or less, more preferably 25% by volume or less, and further 15% by volume or less, because the stability of the coating at high temperatures can be further increased without impairing Li ion permeability. preferable.

  When the non-aqueous solvent contains both a cyclic carbonate having an unsaturated bond such as a carbon-carbon double bond or a carbon-carbon triple bond and a cyclic carbonate having a fluorine atom, the carbon to the content of the cyclic carbonate having a fluorine atom The content of the cyclic carbonate having an unsaturated bond such as a carbon double bond or a carbon-carbon triple bond is preferably 0.2% by volume or more, more preferably 3% by volume or more, and further preferably 7% by volume or more. The upper limit is preferably 40% by volume or less, more preferably 30% by volume or less, and further 15% by volume or less, which may further increase the stability of the coating at high temperatures without impairing Li ion permeability. This is particularly preferable because it can be performed.

  Further, when the non-aqueous solvent contains both ethylene carbonate and a cyclic carbonate having an unsaturated bond such as a carbon-carbon double bond or a carbon-carbon triple bond, the stability of the coating film formed on the electrode at high temperature is improved. Preferably, the content of cyclic carbonate having an unsaturated bond such as ethylene carbonate and a carbon-carbon double bond or a carbon-carbon triple bond is preferably 3% by volume or more based on the total volume of the nonaqueous solvent. Preferably it is 5 volume% or more, More preferably, it is 7 volume% or more, Moreover, as the upper limit, Preferably it is 45 volume% or less, More preferably, it is 35 volume% or less, More preferably, it is 25 volume% or less.

  These solvents may be used alone, and when two or more types are used in combination, the electrochemical properties at high temperatures are further improved, and it is particularly preferable to use a combination of three or more types. preferable. Preferred combinations of these cyclic carbonates include EC and PC, EC and VC, PC and VC, VC and FEC, EC and FEC, PC and FEC, FEC and DFEC, EC and DFEC, PC and DFEC, VC and DFEC , VEC and DFEC, VC and EEC, EC and EEC, EC and PC and VC, EC and PC and FEC, EC and VC and FEC, EC and VC and VEC, EC and VC and EEC, EC and EEC and FEC, PC And VC and FEC, EC and VC and DFEC, PC and VC and DFEC, EC and PC and VC and FEC, or EC and PC, VC and DFEC are preferable. Of the above combinations, EC and VC, EC and FEC, PC and FEC, EC and PC and VC, EC and PC and FEC, EC and VC and FEC, EC and VC and EEC, EC and EEC and FEC, PC and A combination of VC and FEC, or EC, PC, VC and FEC is more preferable.

  As the chain ester, one or more asymmetric chain carbonates selected from methyl ethyl carbonate (MEC), methyl propyl carbonate (MPC), methyl isopropyl carbonate (MIPC), methyl butyl carbonate, and ethyl propyl carbonate, One or more symmetrical linear carbonates selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, and dibutyl carbonate, pivalate esters such as methyl pivalate, ethyl pivalate, and propyl pivalate Preferable examples include one or two or more chain carboxylic acid esters selected from methyl propionate, ethyl propionate, methyl acetate, and ethyl acetate.

  Among the chain esters, chain esters having a methyl group selected from dimethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, methyl butyl carbonate, methyl propionate, methyl acetate, and ethyl acetate are preferable, particularly methyl. A chain carbonate having a group is preferred.

  Moreover, when using chain carbonate, it is preferable to use 2 or more types. Further, it is more preferable that both a symmetric chain carbonate and an asymmetric chain carbonate are contained, and it is further more preferable that the content of the symmetric chain carbonate is more than that of the asymmetric chain carbonate.

  The content of the chain ester is not particularly limited, but it is preferably used in the range of 60 to 90% by volume with respect to the total volume of the nonaqueous solvent. If the content is 60% by volume or more, the viscosity of the non-aqueous electrolyte does not become too high, and if it is 90% by volume or less, the electrical conductivity of the non-aqueous electrolyte decreases and the electrochemical properties at high temperature are low. Since there is little possibility of a fall, it is preferable that it is the said range.

  The volume ratio of the symmetric chain carbonate in the chain carbonate is preferably 51% by volume or more, and more preferably 55% by volume or more. The upper limit is more preferably 95% by volume or less, and still more preferably 85% by volume or less. It is particularly preferred that the symmetric chain carbonate contains dimethyl carbonate. The asymmetric chain carbonate preferably has a methyl group, and methyl ethyl carbonate is particularly preferable. The above case is preferable because the electrochemical characteristics at a higher temperature are further improved.

  The ratio between the cyclic carbonate and the chain ester is preferably 10:90 to 45:55, and 15:85 to 40:60, from the viewpoint of improving electrochemical properties at high temperatures. Is more preferable, and 20:80 to 35:65 is particularly preferable.

  Other nonaqueous solvents include cyclic ethers such as tetrahydrofuran, 2-methyltetrahydrofuran, and 1,4-dioxane, chains such as 1,2-dimethoxyethane, 1,2-diethoxyethane, and 1,2-dibutoxyethane. Preferable examples include one or more selected from amides such as cyclic ethers, amides such as dimethylformamide, sulfones such as sulfolane, and lactones such as γ-butyrolactone, γ-valerolactone, and α-angelicalactone.

  The above non-aqueous solvents are usually used as a mixture in order to achieve appropriate physical properties. The combination includes, for example, a combination of a cyclic carbonate and a chain carbonate, a combination of a cyclic carbonate and a chain carboxylic acid ester, a combination of a cyclic carbonate, a chain carbonate and a lactone, and a combination of a cyclic carbonate, a chain carbonate and an ether. A combination or a combination of a cyclic carbonate, a chain carbonate, and a chain carboxylic acid ester is preferable.

In order to further improve the stability of the coating film at a higher temperature, it is preferable to add other additives to the non-aqueous electrolyte.
Specific examples of other additives include the following compounds (A) to (I).

(A) One or more nitriles selected from acetonitrile, propionitrile, succinonitrile, glutaronitrile, adiponitrile, pimeonitrile, suberonitrile, and sebacononitrile.

(B) cyclohexylbenzene, fluorocyclohexylbenzene compound (1-fluoro-2-cyclohexylbenzene, 1-fluoro-3-cyclohexylbenzene, 1-fluoro-4-cyclohexylbenzene), tert-butylbenzene, tert-amylbenzene, 1 Aromatic compounds having a branched alkyl group such as fluoro-4-tert-butylbenzene, biphenyl, terphenyl (o-, m-, p-isomer), diphenyl ether, fluorobenzene, difluorobenzene (o-, m -, P-form), anisole, 2,4-difluoroanisole, terphenyl partially hydride (1,2-dicyclohexylbenzene, 2-phenylbicyclohexyl, 1,2-diphenylcyclohexane, o-cyclohexylbiphenyl), etc. Aroma Compound.

(C) Selected from methyl isocyanate, ethyl isocyanate, butyl isocyanate, phenyl isocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, octamethylene diisocyanate, 1,4-phenylene diisocyanate, 2-isocyanatoethyl acrylate, and 2-isocyanatoethyl methacrylate One or more isocyanate compounds.

(D) 2-propynyl methyl carbonate, 2-propynyl acetate, 2-propynyl formate, 2-propynyl methacrylate, 2-propynyl methanesulfonate, 2-propynyl vinylsulfonate, 2- (methanesulfonyloxy) propionate 2- Propynyl, di (2-propynyl) oxalate, methyl 2-propynyl oxalate, ethyl 2-propynyl oxalate, di (2-propynyl) glutarate, 2-butyne-1,4-diyl dimethanesulfonate, 2- One or more triple bond-containing compounds selected from butyne-1,4-diyl diformate and 2,4-hexadiyne-1,6-diyl dimethanesulfonate.

(E) 1,3-propane sultone, 1,3-butane sultone, 2,4-butane sultone, 1,4-butane sultone, 1,3-propene sultone, 2,2-dioxide-1,2-oxathiolan-4-yl Acetate, or sultone such as 5,5-dimethyl-1,2-oxathiolane-4-one 2,2-dioxide, ethylene sulfite, hexahydrobenzo [1,3,2] dioxathiolane-2-oxide (1,2 -Cyclohexanediol cyclic sulfite), or cyclic sulfites such as 5-vinyl-hexahydro-1,3,2-benzodioxathiol-2-oxide, butane-2,3-diyl dimethanesulfonate, butane -1,4-diyl dimethanesulfonate, or methylenemethane disulfonate Phosphate esters, divinyl sulfone, 1,2-bis (vinylsulfonyl) ethane, or bis (2-vinylsulfonylethyl) one or two or more of the S = O group containing compound selected from vinyl sulfone compounds such as ethers.

(F) Cyclic acetal compounds such as 1,3-dioxolane, 1,3-dioxane and 1,3,5-trioxane.

(G) trimethyl phosphate, tributyl phosphate, and trioctyl phosphate,
Tris (2,2,2-trifluoroethyl) phosphate, bis (2,2,2-trifluoroethyl) methyl phosphate, bis (2,2,2-trifluoroethyl) ethyl phosphate, bisphosphate (2,2,2-trifluoroethyl) 2,2-difluoroethyl, bis (2,2,2-trifluoroethyl) phosphate 2,2,3,3-tetrafluoropropyl, bis (2, 2-difluoroethyl) 2,2,2-trifluoroethyl, bis (2,2,3,3-tetrafluoropropyl) phosphate, 2,2,2-trifluoroethyl phosphate and phosphoric acid (2,2,2- Trifluoroethyl) (2,2,3,3-tetrafluoropropyl) methyl, tris (1,1,1,3,3,3-hexafluoropropan-2-yl) phosphate, methyl methylenebisphosphonate, methylene bi Ethyl phosphonate, methyl ethylene bisphosphonate, ethyl ethylene bisphosphonate, methyl butylene bisphosphonate, ethyl butylene bisphosphonate, methyl 2- (dimethylphosphoryl) acetate, ethyl 2- (dimethylphosphoryl) acetate, methyl 2- (diethylphosphoryl) acetate Ethyl 2- (diethylphosphoryl) acetate, 2-propynyl 2- (dimethylphosphoryl) acetate, 2-propynyl 2- (diethylphosphoryl) acetate, methyl 2- (dimethoxyphosphoryl) acetate, ethyl 2- (dimethoxyphosphoryl) acetate, Methyl 2- (diethoxyphosphoryl) acetate, ethyl 2- (diethoxyphosphoryl) acetate, 2-propynyl 2- (dimethoxyphosphoryl) acetate, 2 —Propinyl 2- (diethoxyphosphoryl) acetate, and one or more phosphorus-containing compounds selected from methyl pyrophosphate and ethyl pyrophosphate.

(H) Chain carboxylic anhydrides such as acetic anhydride and propionic anhydride, succinic anhydride, maleic anhydride, 3-allyl succinic anhydride, glutaric anhydride, itaconic anhydride, or 3-sulfo-propionic anhydride Cyclic acid anhydrides such as products.

(I) Cyclic phosphazene compounds such as methoxypentafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, phenoxypentafluorocyclotriphosphazene, or ethoxyheptafluorocyclotetraphosphazene.

  Among these, it is preferable to include at least one selected from (A) nitrile, (B) aromatic compound, and (C) isocyanate compound, since the electrochemical characteristics in a wider temperature range are further improved.

  Among (A) nitriles, one or more selected from succinonitrile, glutaronitrile, adiponitrile, and pimelonitrile are more preferable.

  (B) Among aromatic compounds, one or more selected from biphenyl, terphenyl (o-, m-, p-isomer), fluorobenzene, cyclohexylbenzene, tert-butylbenzene, and tert-amylbenzene Are more preferable, and one or more selected from biphenyl, o-terphenyl, fluorobenzene, cyclohexylbenzene, and tert-amylbenzene are particularly preferable.

  Among (C) isocyanate compounds, one or more selected from hexamethylene diisocyanate, octamethylene diisocyanate, 2-isocyanatoethyl acrylate, and 2-isocyanatoethyl methacrylate are more preferable.

  The content of the compounds (A) to (C) is preferably 0.01 to 7% by mass in the non-aqueous electrolyte. In this range, the coating film is sufficiently formed without becoming too thick, and the stability of the coating film at a higher temperature is further increased. The content is more preferably 0.05% by mass or more, more preferably 0.1% by mass or more in the non-aqueous electrolyte, and the upper limit thereof is more preferably 5% by mass or less, further preferably 3% by mass or less. .

  (D) Triple bond-containing compound, (E) Sultone, cyclic sulfite, sulfonic acid ester, cyclic S = O group-containing compound selected from vinyl sulfone, (F) cyclic acetal compound, (G) Including a phosphorus-containing compound, (H) a cyclic acid anhydride, and (I) a cyclic phosphazene compound is preferable because the stability of the coating film at a higher temperature is further improved.

  (D) As a triple bond containing compound, 2-propynyl methyl carbonate, 2-propynyl methacrylate, 2-propynyl methanesulfonate, 2-propynyl vinylsulfonate, 2-propynyl 2- (methanesulfonyloxy) propionate, di One or more selected from (2-propynyl) oxalate, methyl 2-propynyl oxalate, ethyl 2-propynyl oxalate, and 2-butyne-1,4-diyl dimethanesulfonate, 2-propynyl methanesulfonate, One or more selected from 2-propynyl vinyl sulfonate, 2-propynyl 2- (methanesulfonyloxy) propionate, di (2-propynyl) oxalate, and 2-butyne-1,4-diyl dimethanesulfonate Preferred.

  (E) A cyclic or chain-containing S═O group-containing compound selected from sultone, cyclic sulfite, sulfonic acid ester, and vinyl sulfone (provided that the triple bond-containing compound and any of the above general formulas are specified) It is preferable to use a lithium salt.

  Examples of the cyclic S═O group-containing compound include 1,3-propane sultone, 1,3-butane sultone, 1,4-butane sultone, 2,4-butane sultone, 1,3-propene sultone, 2,2-dioxide- 1,2-oxathiolan-4-yl acetate, 5,5-dimethyl-1,2-oxathiolan-4-one 2,2-dioxide, methylene methane disulfonate, ethylene sulfite, and 4- (methylsulfonylmethyl)- One, two or more selected from 1,3,2-dioxathiolane 2-oxide are preferred.

  Examples of the chain-like S═O group-containing compound include butane-2,3-diyl dimethanesulfonate, butane-1,4-diyl dimethanesulfonate, dimethylmethane disulfonate, pentafluorophenyl methanesulfonate, divinylsulfone, And one or more selected from bis (2-vinylsulfonylethyl) ether are preferred.

  Among the cyclic or chain-containing S═O group-containing compounds, 1,3-propane sultone, 1,4-butane sultone, 2,4-butane sultone, 2,2-dioxide-1,2-oxathiolan-4-yl acetate , And 5,5-dimethyl-1,2-oxathiolane-4-one 2,2-dioxide, butane-2,3-diyl dimethanesulfonate, pentafluorophenyl methanesulfonate, and divinylsulfone The above is more preferable.

  (F) As the cyclic acetal compound, 1,3-dioxolane or 1,3-dioxane is preferable, and 1,3-dioxane is more preferable.

  (G) Phosphorus-containing compounds include tris phosphate (2,2,2-trifluoroethyl), tris phosphate (1,1,1,3,3,3-hexafluoropropan-2-yl), methyl 2- (dimethylphosphoryl) acetate, ethyl 2- (dimethylphosphoryl) acetate, methyl 2- (diethylphosphoryl) acetate, ethyl 2- (diethylphosphoryl) acetate, 2-propynyl 2- (dimethylphosphoryl) acetate, 2-propynyl 2 -(Diethylphosphoryl) acetate, methyl 2- (dimethoxyphosphoryl) acetate, ethyl 2- (dimethoxyphosphoryl) acetate, methyl 2- (diethoxyphosphoryl) acetate, ethyl 2- (diethoxyphosphoryl) acetate, 2-propynyl 2- (Dimethoxyphospho Ryl) acetate or 2-propynyl 2- (diethoxyphosphoryl) acetate is preferred, and tris phosphate (2,2,2-trifluoroethyl), tris phosphate (1,1,1,3,3,3- Hexafluoropropan-2-yl), ethyl 2- (diethylphosphoryl) acetate, 2-propynyl 2- (dimethylphosphoryl) acetate, 2-propynyl 2- (diethylphosphoryl) acetate, ethyl 2- (diethoxyphosphoryl) acetate, 2-propynyl 2- (dimethoxyphosphoryl) acetate or 2-propynyl 2- (diethoxyphosphoryl) acetate is more preferred.

  (H) As the cyclic acid anhydride, succinic anhydride, maleic anhydride, or 3-allyl succinic anhydride is preferable, and succinic anhydride or 3-allyl succinic anhydride is more preferable.

  (I) As the cyclic phosphazene compound, a cyclic phosphazene compound such as methoxypentafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, or phenoxypentafluorocyclotriphosphazene is preferable, and methoxypentafluorocyclotriphosphazene or ethoxypentafluorocyclo More preferred is triphosphazene.

  The content of the compounds (D) to (I) is preferably 0.001 to 5% by mass in the non-aqueous electrolyte. In this range, the coating film is sufficiently formed without becoming too thick, and the stability of the coating film at a higher temperature is further increased. The content is more preferably 0.01% by mass or more, more preferably 0.1% by mass or more in the non-aqueous electrolyte, and the upper limit thereof is more preferably 3% by mass or less, and further preferably 2% by mass or less. .

Further, for the purpose of further improving the stability of the coating film at a high temperature, among non-aqueous electrolytes, among lithium salts having an oxalic acid skeleton, lithium salts having a phosphoric acid skeleton, and lithium salts having an S═O group It is preferable that 1 or more types of lithium salt chosen from these are included.
Specific examples of lithium salts include lithium bis (oxalato) borate (LiBOB), lithium difluoro (oxalato) borate (LiDFOB), lithium tetrafluoro (oxalato) phosphate (LiTFOP), and lithium difluorobis (oxalato) phosphate (LiDFOP). Lithium salt having at least one oxalic acid skeleton selected from Lithium salt having phosphoric acid skeleton such as LiPO ₂ F ₂ and Li ₂ PO ₃ F, lithium trifluoro ((methanesulfonyl) oxy) borate (LiTFMSB), lithium Pentafluoro ((methanesulfonyl) oxy) phosphate (LiPFMSP), lithium methyl sulfate (LMS), lithium ethyl sulfate (LES), lithium 2,2,2-tri Le Oro ethylsulfate (LFES), and lithium salt preferably include having one or more S = O group selected from _{FSO 3 Li, LiBOB, LiDFOB,} LiTFOP, LiDFOP, LiPO 2 F 2, LiTFMSB, LMS, LES More preferably, it contains a lithium salt selected from LFES, LFES, and FSO ₃ Li.

  The total content of one or more lithium salts selected from the lithium salt having an oxalic acid skeleton, the lithium salt having a phosphoric acid skeleton, and the lithium salt having an S═O group is 0.001 in the non-aqueous electrolyte. 001-10 mass% is preferable. If the content is 10% by mass or less, a film is excessively formed on the electrode and is less likely to deteriorate the storage characteristics. If the content is 0.001% by mass or more, formation of the film is sufficient, The effect of improving the characteristics when used at a high voltage is increased. The content is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, still more preferably 0.3% by mass or more, and the upper limit is preferably 5% by mass or less in the non-aqueous electrolyte. 3 mass% or less is more preferable, and 2 mass% or less is still more preferable.

(Lithium salt)
Preferred examples of the electrolyte salt used in the present invention include the following lithium salts.
Examples of the lithium salt include inorganic lithium salts such as LiPF ₆ , LiBF ₄ , and LiClO ₄ , LiN (SO ₂ F) ₂ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiCF ₃ SO ₃ , LiC (SO ₂ CF ₃ ) ₃ , LiPF ₄ (CF ₃ ) ₂ , LiPF ₃ (C ₂ F ₅ ) ₃ , LiPF ₃ (CF ₃ ) ₃ , LiPF ₃ (iso-C ₃ F ₇ ) ₃ , LiPF ₅ (iso-C ₃ F ₇ ) and other lithium salts containing a chain-like fluorinated alkyl group, (CF ₂ ) ₂ (SO ₂ ) ₂ NLi, (CF ₂ ) ₃ (SO ₂ ) ₂ NLi, etc. Preferred examples include lithium salts having a cyclic fluorinated alkylene chain, and preferred examples include at least one lithium salt selected from these, and one or more of these may be used in combination. Can be used.
Among these, LiPF ₆ , LiBF ₄ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , and one or more selected from LiN (SO ₂ F) ₂ are preferable, and LiPF Most preferably, ₆ is used. The concentration of the lithium salt is usually preferably 0.3 M or more, more preferably 0.7 M or more, and further preferably 1.1 M or more with respect to the non-aqueous solvent. Moreover, the upper limit is preferably 2.5M or less, more preferably 2.0M or less, and still more preferably 1.6M or less.
Further, suitable combinations of these lithium salts include LiPF _6, further _{LiBF 4, LiN (SO 2 CF} 3) 2, and LiN _(SO 2 _F) at least one lithium salt non selected from ₂ The case where it is contained in the water electrolyte is preferable, and the proportion of the lithium salt other than LiPF _{6 in the} non-aqueous solvent is 0.001M or more, which improves the electrochemical characteristics when the battery is used at a high temperature. The effect is easily exhibited, and it is preferably 0.005 M or less because there is little concern that the effect of improving electrochemical characteristics when the battery is used at high temperature is reduced. Preferably it is 0.01M or more, Especially preferably, it is 0.03M or more, Most preferably, it is 0.04M or more. The upper limit is preferably 0.4M or less, particularly preferably 0.2M or less.

[Production of non-aqueous electrolyte]
In the nonaqueous electrolytic solution of the present invention, for example, the nonaqueous solvent is mixed, and the lithium salt represented by the general formula (I) is added to the electrolyte salt and the nonaqueous electrolytic solution. Can be obtained.
At this time, it is preferable that the compound added to the non-aqueous solvent and the non-aqueous electrolyte to be used is one that is purified in advance and has as few impurities as possible within a range that does not significantly reduce the productivity.

  The nonaqueous electrolytic solution of the present invention can be used in the following first to fourth power storage devices, and not only a liquid but also a gelled one can be used as the nonaqueous electrolyte. Furthermore, the non-aqueous electrolyte of the present invention can be used for a solid polymer electrolyte. In particular, it is preferably used for the first electricity storage device (that is, for a lithium battery) or the fourth electricity storage device (that is, for a lithium ion capacitor) that uses a lithium salt as an electrolyte salt, and is used for a lithium battery. More preferably, it is more preferably used for a lithium secondary battery.

[First power storage device (lithium battery)]
In this specification, the lithium battery is a general term for a lithium primary battery and a lithium secondary battery. In this specification, the term lithium secondary battery is used as a concept including a so-called lithium ion secondary battery. The lithium battery of the present invention comprises the nonaqueous electrolyte solution in which an electrolyte salt is dissolved in a positive electrode, a negative electrode, and a nonaqueous solvent. Components other than the non-aqueous electrolyte, such as a positive electrode and a negative electrode, can be used without particular limitation.

  For example, as the positive electrode active material for a lithium secondary battery, a composite metal oxide with lithium containing one or more selected from cobalt, manganese, and nickel is used. These positive electrode active materials can be used individually by 1 type or in combination of 2 or more types.

Examples of such a lithium composite metal oxide include LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiCo _1-x Ni _x O ₂ (0.01 <x <1), LiCo _1/3 Ni _1/3. One type or two or more types selected from Mn _1/3 O ₂ , LiNi _1/2 Mn _3/2 O ₄ , and LiCo _0.98 Mg _0.02 O ₂ may be mentioned. Moreover, LiCoO ₂ and LiMn ₂ O _4, LiCoO ₂ and LiNiO _2, may be used in combination as LiMn ₂ O ₄ and LiNiO _2.

  In addition, in order to improve safety and cycle characteristics during overcharge, or to enable use at a charging potential of 4.3 V or higher, a part of the lithium composite metal oxide may be substituted with another element. . For example, a part of cobalt, manganese, nickel is replaced with at least one element of Sn, Mg, Fe, Ti, Al, Zr, Cr, V, Ga, Zn, Cu, Bi, Mo, or La. , A part of O may be substituted with S or F, or a compound containing these other elements may be coated.

Among these, lithium composite metal oxides such as LiCoO ₂ , LiMn ₂ O ₄ , and LiNiO ₂ that can be used at a charged potential of the positive electrode in a fully charged state of 4.3 V or more on the basis of Li are preferable, and LiCo _1-x M _x O ₂ (where M is one or more elements selected from Sn, Mg, Fe, Ti, Al, Zr, Cr, V, Ga, Zn, and Cu, 0.001 ≦ x ≦ 0) .05), LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , LiNi _1/2 Mn _3/2 O ₄ , Li ₂ MnO ₃ and LiMO ₂ (M is Co, Ni, Mn, Fe, etc.) More preferable is a lithium composite metal oxide that can be used at 4.4 V or higher, such as a solid solution with a transition metal. When a lithium composite metal oxide that operates at a high charging voltage is used, the electrochemical characteristics when used in a wide temperature range are liable to deteriorate due to a reaction with the electrolyte during charging, but the lithium secondary battery according to the present invention Then, the deterioration of these electrochemical characteristics can be suppressed. In particular, in the case of a positive electrode containing Mn, the resistance of the battery tends to increase with the elution of Mn ions from the positive electrode, so that the electrochemical characteristics when used in a wide temperature range tend to be lowered. The lithium secondary battery according to the invention is preferable because it can suppress a decrease in these electrochemical characteristics.

Furthermore, lithium-containing olivine-type phosphate can also be used as the positive electrode active material. In particular, a lithium-containing olivine-type phosphate containing one or more selected from iron, cobalt, nickel, and manganese is preferable. Specific examples thereof include one or more selected from LiFePO ₄ , LiCoPO ₄ , LiNiPO ₄ , and LiMnPO ₄ . Some of these lithium-containing olivine-type phosphates may be substituted with other elements, and some of iron, cobalt, nickel, and manganese are replaced with Co, Mn, Ni, Mg, Al, B, Ti, V, and Nb. , Cu, Zn, Mo, Ca, Sr, W, and Zr can be substituted with one or more elements selected from, or coated with a compound or carbon material containing these other elements . Among these, LiFePO ₄ or LiMnPO ₄ is preferable. Moreover, lithium containing olivine type | mold phosphate can also be mixed with the said positive electrode active material, for example, and can be used.

As positive electrodes for lithium primary batteries, CuO, Cu ₂ O, Ag ₂ O, Ag ₂ CrO ₄ , CuS, CuSO ₄ , TiO ₂ , TiS ₂ , SiO ₂ , SnO, V ₂ O ₅ , V ₆ O ₁₂ , VO _{x, Nb 2 O 5, Bi} 2 O 3, Bi 2 Pb 2 O 5, Sb 2 O 3, CrO 3, Cr 2 O 3, MoO 3, WO 3, SeO 2, MnO 2, Mn 2 O 3, Fe ₂ O ₃ , FeO, Fe ₃ O ₄ , Ni ₂ O ₃ , NiO, CoO ₃ , or an oxide of one or more metal elements such as CoO or a chalcogen compound, sulfur such as SO ₂ and SOCl ₂ Examples thereof include a compound and fluorocarbon (fluorinated graphite) represented by the general formula (CF _x ) _n . Among _{these, MnO 2, V 2 O 5} , fluorinated graphite and the like are preferable.

When the pH of the supernatant liquid when 10.0 g of the positive electrode active material is dispersed in 100 ml of distilled water is 10.0 to 12.5, the effect of improving the electrochemical characteristics in a wider temperature range can be easily obtained. The case of 10.5 to 12.0 is more preferable.
Further, when Ni is contained as an element in the positive electrode, since impurities such as LiOH in the positive electrode active material tend to increase, an effect of improving electrochemical characteristics in a wider temperature range is easily obtained, which is preferable. The case where the atomic concentration of Ni in the substance is 5 to 25 atomic% is more preferable, and the case where it is 8 to 21 atomic% is particularly preferable.

  The conductive agent for the positive electrode is not particularly limited as long as it is an electron conductive material that does not cause a chemical change. For example, graphite such as natural graphite (flaky graphite, etc.), graphite such as artificial graphite, acetylene black, ketjen black, channel black, furnace black, lamp black, and one or more carbon blacks selected from thermal black, etc. Can be mentioned. Further, graphite and carbon black may be appropriately mixed and used. 1-10 mass% is preferable and, as for the addition amount to the positive mix of a electrically conductive agent, 2-5 mass% is especially preferable.

  The positive electrode is composed of a conductive agent such as acetylene black and carbon black, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), a copolymer of styrene and butadiene (SBR), acrylonitrile and butadiene. This is mixed with a binder such as copolymer (NBR), carboxymethyl cellulose (CMC), or ethylene propylene diene terpolymer, and a high boiling point solvent such as 1-methyl-2-pyrrolidone is added thereto and kneaded. After forming this agent, this positive electrode mixture is applied to an aluminum foil as a current collector or a stainless steel lath plate, etc., dried and pressure-molded, and then vacuumed at a temperature of about 50 ° C. to 250 ° C. for about 2 hours. It can produce by heat-processing with.

The density of the part except the collector of the positive electrode is usually at 1.5 g / cm ³ or more, for further increasing the capacity of the battery, it is preferably 2 g / cm ³ or more, more preferably, 3 g / cm ³ It is above, More preferably, it is 3.6 g / cm ³ or more. The upper limit is preferably 4 g / cm ³ or less.

Examples of the negative electrode active material for a lithium secondary battery include lithium metal, lithium alloy, and a carbon material capable of occluding and releasing lithium (easily graphitized carbon and a (002) plane spacing of 0.37 nm or more). Non-graphitizable carbon, graphite with (002) plane spacing of 0.34 nm or less, etc.], tin (simple substance), tin compound, silicon (simple substance), silicon compound, or titanic acid such as Li ₄ Ti ₅ O ₁₂ A lithium compound can be used individually by 1 type or in combination of 2 or more types.

Among the negative electrode active materials, it is more preferable to use a highly crystalline carbon material such as artificial graphite or natural graphite in terms of the ability to occlude and release lithium ions, and the spacing (d ₀₀₂ ) between lattice planes ( ₀₀₂ ). It is more preferable to use a carbon material having a graphite-type crystal structure having a thickness of 0.340 nm (nanometer) or less, particularly 0.335 to 0.337 nm. In particular, artificial graphite particles having a massive structure in which a plurality of flat graphite fine particles are assembled or bonded non-parallel to each other, and mechanical actions such as compressive force, frictional force, shearing force, etc. are repeatedly applied, and scaly natural graphite is spherical. It is preferable to use particles that have been treated.

The peak intensity I (110) of the (110) plane of the graphite crystal obtained from the X-ray diffraction measurement of the negative electrode sheet when the density of the portion excluding the current collector of the negative electrode is pressed to a density of 1.5 g / cm ³ or more. ) And the (004) plane peak intensity I (004) ratio I (110) / I (004) is preferably 0.01 or more because the electrochemical characteristics in a wider temperature range are further improved. More preferably, it is more preferably 0.1 or more. In addition, since the crystallinity may be lowered due to excessive treatment and the discharge capacity of the battery may be lowered, the upper limit of the peak intensity ratio I (110) / I (004) is preferably 0.5 or less. 3 or less is more preferable.

In addition, it is preferable that the highly crystalline carbon material (core material) is coated with a carbon material having lower crystallinity than the core material because electrochemical characteristics in a wide temperature range are further improved. The crystallinity of the carbon material of the coating can be confirmed by TEM.
When a highly crystalline carbon material is used, it reacts with the non-aqueous electrolyte during charging and tends to lower the electrochemical characteristics at low or high temperatures due to an increase in interface resistance. However, in the lithium secondary battery according to the present invention, Excellent electrochemical characteristics over a wide temperature range.

  Examples of metal compounds capable of inserting and extracting lithium as the negative electrode active material include Si, Ge, Sn, Pb, P, Sb, Bi, Al, Ga, In, Ti, Mn, Fe, Co, Ni, Cu, and Zn. Preferred examples include compounds containing at least one metal element such as Ag, Mg, Sr, or Ba. These metal compounds may be used in any form such as simple substance, alloy, oxide, nitride, sulfide, boride, or alloy with lithium. Any one is preferable because the capacity can be increased. Among these, those containing at least one element selected from Si, Ge, and Sn are preferable, and those containing at least one element selected from Si and Sn are more preferable because the capacity of the battery can be increased.

  The negative electrode is kneaded using the same conductive agent, binder, and high-boiling solvent as in the production of the positive electrode, and then the negative electrode mixture is applied to the copper foil of the current collector. After being dried and pressure-molded, it can be produced by heat treatment under vacuum at a temperature of about 50 ° C. to 250 ° C. for about 2 hours.

The density of the portion excluding the current collector of the negative electrode is usually 1.1 g / cm ³ or more, and is preferably 1.5 g / cm ³ or more, more preferably 1.7 g in order to further increase the battery capacity. / Cm ³ or more. The upper limit is preferably 2 g / cm ³ or less.

  Examples of the negative electrode active material for the lithium primary battery include lithium metal and lithium alloy.

  There is no particular limitation on the structure of the lithium battery, and a coin-type battery, a cylindrical battery, a square battery, a laminated battery, or the like having a single-layer or multi-layer separator can be applied.

  The battery separator is not particularly limited, and a single layer or laminated microporous film, woven fabric, nonwoven fabric or the like of polyolefin such as polypropylene or polyethylene can be used.

  The lithium secondary battery according to the present invention has excellent electrochemical characteristics in a wide temperature range even when the end-of-charge voltage is 4.2 V or more, particularly 4.3 V or more, and the characteristics are also good at 4.4 V or more. is there. The end-of-discharge voltage is usually 2.8 V or more, and further 2.5 V or more, but the lithium secondary battery in the present invention can be 2.0 V or more. Although it does not specifically limit about an electric current value, Usually, it uses in the range of 0.1-30C. Moreover, the lithium battery in this invention can be charged / discharged at -40-100 degreeC, Preferably it is -10-80 degreeC.

  In the present invention, as a countermeasure against an increase in the internal pressure of the lithium battery, a method of providing a safety valve on the battery lid or cutting a member such as a battery can or a gasket can be employed. Further, as a safety measure for preventing overcharge, the battery lid can be provided with a current interruption mechanism that senses the internal pressure of the battery and interrupts the current.

[Second power storage device (electric double layer capacitor)]
The 2nd electrical storage device of this invention is an electrical storage device which stores the energy using the electric double layer capacity | capacitance of electrolyte solution and an electrode interface including the non-aqueous electrolyte of this invention. An example of the present invention is an electric double layer capacitor. The most typical electrode active material used for this electricity storage device is activated carbon. Double layer capacity increases roughly in proportion to surface area.

[Third power storage device]
The 3rd electrical storage device of this invention is an electrical storage device which stores the energy using the dope / dedope reaction of an electrode including the non-aqueous electrolyte of this invention. Examples of the electrode active material used in this power storage device include metal oxides such as ruthenium oxide, iridium oxide, tungsten oxide, molybdenum oxide, and copper oxide, and π-conjugated polymers such as polyacene and polythiophene derivatives. Capacitors using these electrode active materials can store energy associated with electrode doping / dedoping reactions.

[Fourth storage device (lithium ion capacitor)]
The 4th electrical storage device of this invention is an electrical storage device which stores the energy using the intercalation of the lithium ion to carbon materials, such as a graphite which is a negative electrode, containing the nonaqueous electrolyte solution of this invention. It is called a lithium ion capacitor (LIC). Examples of the positive electrode include those using an electric double layer between an activated carbon electrode and an electrolytic solution, and those using a π-conjugated polymer electrode doping / dedoping reaction. The electrolytic solution contains at least a lithium salt such as LiPF ₆ .

  Examples of the electrolytic solution of the present invention are shown below, but the present invention is not limited to these examples.

Examples 1-16, 18 , 20-23 , Comparative Examples 1-3 , A, B
[Production of lithium ion secondary battery]
LiCoO ₂ ; 94% by mass, acetylene black (conducting agent); 3% by mass were mixed, and a solution in which polyvinylidene fluoride (binder); 3% by mass was previously dissolved in 1-methyl-2-pyrrolidone was mixed. In addition, the mixture was mixed to prepare a positive electrode mixture paste. This positive electrode mixture paste was applied to one side of an aluminum foil (current collector), dried and pressurized, and cut into a predetermined size to produce a belt-like positive electrode sheet. The density of the portion excluding the current collector of the positive electrode was 3.6 g / cm ³ . Further, silicon (simple substance): 10% by mass, artificial graphite (d ₀₀₂ = 0.335 nm, negative electrode active material); 80% by mass, acetylene black (conductive agent); Adhesive); 5% by mass was added to and mixed with the solution in which 1-methyl-2-pyrrolidone was dissolved to prepare a negative electrode mixture paste. This negative electrode mixture paste was applied to one side of a copper foil (current collector), dried and pressurized, and cut into a predetermined size to produce a negative electrode sheet. The density of the portion excluding the current collector of the negative electrode was 1.5 g / cm ³ . As a result of X-ray diffraction measurement using this electrode sheet, the ratio of the peak intensity I (110) of the (110) plane of the graphite crystal to the peak intensity I (004) of the (004) plane [I (110) / I (004)] was 0.1. Then, a positive electrode sheet, a separator made of a microporous polyethylene film, and a negative electrode sheet were laminated in this order, and a non-aqueous electrolyte solution having the composition described in Tables 1 and 2 was added to prepare a laminate type battery.

[Discharge capacity maintenance ratio after storage at high temperature]
<Initial discharge capacity>
Using the laminated battery produced by the above method, in a constant temperature bath at 25 ° C., it is charged with a constant current and a constant voltage of 1 C for 3 hours to a final voltage of 4.4 V, and reaches a final voltage of 2.75 V under a constant current of 1 C. After discharging, the initial discharge capacity was determined.
<High-temperature charge storage test>
Next, this laminate battery was charged in a constant temperature bath at 45 ° C. with a constant current and a constant voltage of 1 C for 3 hours to a final voltage of 4.4 V, and stored for 5 days while being held at 4.4 V. Then, it put into the thermostat of 25 degreeC, and discharged once to the final voltage 2.75V under the constant current of 1C.
<Discharge capacity after storage at high temperature>
Thereafter, the discharge capacity after storage at high temperature charge was determined in the same manner as the measurement of the initial discharge capacity.
<Capacity maintenance rate after storage at high temperature>
The capacity retention rate after storage at high temperature was determined by the following formula.
Discharge capacity retention rate after storage at high temperature (%) = (discharge capacity after storage at high temperature / initial discharge capacity) × 100
[Evaluation of gas generation after storage at high temperature]
The amount of gas generated after storage at high temperature was measured by the Archimedes method. The relative amount of gas generated was examined on the basis of the amount of gas generated in Comparative Example 1 as 100%.
In addition, Tables 1 to 3 show battery manufacturing conditions and battery characteristics.

Examples 24 and 25 and Comparative Example 4
A positive electrode sheet was produced using LiNi _1/2 Mn _3/2 O ₄ (positive electrode active material) instead of the positive electrode active material used in Example 1 and Comparative Example 1. LiNi _1/2 Mn _3/2 O ₄ ; 94% by mass, acetylene black (conductive agent); 3% by mass are mixed in advance, and polyvinylidene fluoride (binder); 3% by mass is added to 1-methyl-2-pyrrolidone. The positive electrode mixture paste was prepared by adding to and mixing with the solution previously dissolved in the mixture. This positive electrode mixture paste was applied to one side of an aluminum foil (current collector), dried, pressurized and cut into a predetermined size to produce a positive electrode sheet, and the end-of-charge voltage during battery evaluation A laminate type battery was prepared and evaluated in the same manner as in Example 1 and Comparative Example 1 except that 4.9 V was set to 4.9 V and the final discharge voltage was set to 2.7 V. The results are shown in Table 4.

Examples 26 and 27 and Comparative Example 5
Instead of the negative electrode active material used in Example 1 and Comparative Example 1, a negative electrode sheet was prepared using lithium titanate Li ₄ Ti ₅ O ₁₂ (negative electrode active material). Lithium titanate Li ₄ Ti ₅ O ₁₂ ; 80% by mass, acetylene black (conductive agent); 15% by mass are mixed in advance, and polyvinylidene fluoride (binder); 5% by mass in 1-methyl-2-pyrrolidone A negative electrode mixture paste was prepared by adding to the dissolved solution and mixing. This negative electrode mixture paste was applied to one side of a copper foil (current collector), dried, pressurized and cut into a predetermined size to produce a negative electrode sheet, and a charge termination voltage during battery evaluation. A laminated battery was prepared in the same manner as in Example 1 and Comparative Example 1 except that the discharge end voltage was 1.2 V and the composition of the non-aqueous electrolyte was changed to a predetermined one. The battery was evaluated. The results are shown in Table 5.

Any of the lithium secondary batteries of Examples 1 to 23 described in Comparative Example 1, Patent Document 1 and Patent Document 2 in the case where the lithium salt represented by Compound (I) is not added to the nonaqueous electrolytic solution of the present invention. Compared with the lithium secondary batteries of Comparative Examples 2 and 3 when the above compound is added, the high temperature and high voltage storage characteristics are improved and the amount of gas generated is suppressed. From the above, it has been found that the effect when the power storage device of the present invention is used at a high voltage is a characteristic effect when the lithium salt (I) is contained in the non-aqueous electrolyte.
Also, from the comparison between Examples 24 and 25 and Comparative Example 4, the case where lithium nickel manganate (LiNi _1/2 Mn _3/2 O ₄ ) was used for the positive electrode or the comparison between Examples 26 and 27 and Comparative Example 5 were used. Therefore, the same effect can be seen when lithium titanate (Li ₄ Ti ₅ O ₁₂ ) is used for the negative electrode. Therefore, it is clear that the effect of the present invention is not an effect dependent on a specific positive electrode or negative electrode.

  Furthermore, the nonaqueous electrolytic solution of the present invention also has an effect of improving discharge characteristics when a lithium primary battery is used at a high voltage.

  The electricity storage device using the non-aqueous electrolyte of the present invention is useful as an electricity storage device such as a lithium secondary battery having excellent electrochemical characteristics when the battery is used at a high voltage.

Claims (2)

A nonaqueous electrolytic solution in which an electrolyte salt is dissolved in a nonaqueous solvent, containing one or more lithium salts represented by the following general formula (I):
(In the formula, M represents a boron atom or a phosphorus atom, X represents a halogen atom, Rf represents a fluoroalkyl group having 1 to 4 carbon atoms, n represents 2 , p and q represent 0 to 4) An integer is shown. When M is a boron atom, m is 1 or 2, and 2m + p + q = 4. When M is a phosphorus atom, m is an integer of 1 to 3, and 2m + p + q = 6.)
  An electricity storage device comprising a non-aqueous electrolyte in which an electrolyte salt is dissolved in a positive electrode, a negative electrode, and a non-aqueous solvent, wherein the non-aqueous electrolyte comprises at least one lithium salt represented by the general formula (I) An electricity storage device comprising: