JP5998013B2 - Electric storage device and electrolyte - Google Patents

Description

  The present invention relates to an electricity storage device and an electrolytic solution used therefor.

  Electric storage devices such as electrolytic capacitors, electric double layer capacitors, lithium ion capacitors, and lithium ion secondary batteries are used in a wide range of fields such as power supplies for mobile phones, personal computers, and automobile power supplies. In addition, in these electricity storage devices, various studies have been conducted with the aim of ensuring safety and improving various characteristics such as cycle characteristics and electric capacity.

For example, in a lithium ion secondary battery, a carbon material such as a positive electrode, graphite, and the like using lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), or lithium manganate (LiMn ₂ O ₄ ) as an active material. And an electrolytic solution using ethylene carbonate or propylene carbonate as a solvent. In the lithium ion secondary battery having such a configuration, it is known that a part of the solvent is decomposed in the positive electrode and / or the negative electrode during charging, resulting in a decrease in battery performance. It is also known that when the negative electrode current collector is made of copper and overdischarge occurs, the copper current collector dissolves and the battery performance decreases.

  In order to solve the above problem, it has been proposed to add an additive to the electrolytic solution (Patent Documents 1 to 8). Examples of the additive include a disulfide derivative having an aromatic ring (Patent Documents 1 to 3), Disulfide ether compound having ether bond and disulfide bond in the same molecule (Patent Document 4), ethylene glycol derivative (Patent Document 5), ether derivative (Patent Document 6), chain saturated hydrocarbon dinitrile compound, chain ether nitrile A compound (Patent Document 7), a thiodialkylnitrile compound (Patent Document 8) and the like are disclosed.

JP 2001-52735 A JP 2001-307766 A JP 2001-307767 A Japanese Patent No. 4304570 Japanese Patent No. 2939468 Japanese Patent No. 2983205 JP 2010-165653 A JP 2006-73513 A

  Although the above-mentioned technology has improved the characteristics of power storage devices to some extent, today, the application to power sources for portable electronic devices, automobile power supplies, household and industrial power storage devices is further advanced, and further improvements in power storage device characteristics Is required.

  The present invention has been made paying attention to the circumstances as described above, and its purpose is to prevent deterioration of characteristics such as discharge capacity over time and to improve the cycle characteristics, and to be used for the same. It is to provide an electrolyte solution.

The electricity storage device of the present invention that can achieve the above object has a gist in that it includes a thioether nitrile compound represented by the following general formula (1).
(NC) _m1 − (R ¹ XR ² ) _n − (CN) _m2 (1)
(In the formula, m1 and m2 are 0 or an integer of 1 or more, m1 + m2 is 1 or more, n is an integer of 1 or more, and R ¹ and R ² are the same or different and have a hetero atom or a substituent. An optionally substituted hydrocarbon group having 1 or more carbon atoms, X represents O or S, and at least one X is S.)

  When the thioether nitrile compound is contained in the electricity storage device, there is no clear reason why the deterioration of the electricity storage device characteristics over time is suppressed, but the thioether nitrile compound includes a thioether nitrile contained in the electricity storage device. The effect of deactivating active sites on the electrode that cause irreversible capacity by adsorbing to the electrode surface; by forming a film on the electrode surface due to the reaction of the thioether nitrile compound during the operation of the electricity storage device, the electrolyte The effect of increasing the affinity between the film interface and the electrode; the presence of a thioether nitrile compound excellent in lithium ion coordination ability on the electrode surface; the effect of suppressing the decomposition of the electrode and electrolyte in the electricity storage device; etc. The present inventors believe that the synergistic effects of these characteristics We believe that the time degradation can be suppressed. The effects derived from the thioether nitrile compound according to the present invention are not limited to the effects exemplified above.

  In the present invention, the electrolyte solution preferably contains the thioether nitrile compound.

  The thioether nitrile compound preferably has a cyano group bonded to an aliphatic group. The thioether nitrile compound preferably does not contain an aromatic group. Furthermore, it is preferable that the thioether nitrile compound has at least one ether bond.

  The electricity storage device of the present invention is preferably a lithium ion secondary battery.

The present invention also includes an electrolytic solution that is used in the above electricity storage device and includes a thioether nitrile compound represented by the following general formula (1).
(NC) _m1 − (R ¹ XR ² ) _n − (CN) _m2 (1)
(In the formula, m1 and m2 are 0 or an integer of 1 or more, m1 + m2 is 1 or more, n is an integer of 1 or more, and R ¹ and R ² are the same or different and have a hetero atom or a substituent. An optionally substituted hydrocarbon group having 1 or more carbon atoms, X represents O or S, and at least one X is S.)

  According to the present invention, by including the thioether nitrile compound represented by the above general formula (1), it is possible to expect an electricity storage device that is unlikely to deteriorate over time and that can be driven stably.

FIG. 1 is a graph showing the results of a cycle test (relationship between the number of cycles and the discharge capacity) in Examples and Comparative Examples. FIG. 2 is a graph showing the results of cycle tests in the examples and comparative examples (relationship between the number of cycles and the discharge capacity retention rate).

The electricity storage device of the present invention is characterized in that it contains a thioether nitrile compound represented by the following general formula (1).
(NC) _m1 − (R ¹ XR ² ) _n − (CN) _m2 (1)
(In the formula, m1 and m2 are 0 or an integer of 1 or more, m1 + m2 is 1 or more, n is an integer of 1 or more, and R ¹ and R ² are the same or different and have a hetero atom or a substituent. An optionally substituted hydrocarbon group having 1 or more carbon atoms, X represents O or S, and at least one X is S.)

  The present inventors have found that when the electricity storage device contains the thioether nitrile compound represented by the general formula (1), the discharge capacity and capacity retention rate of the electricity storage device are improved, and the present invention has been completed. First, the thioether nitrile compound according to the present invention will be described.

1. Thioether nitrile compound The thioether nitrile compound according to the present invention has the above general formula (1); (NC) _m1- (R ¹ XR ² ) _n- (CN) _m2 (wherein m1 and m2 are integers of 0 or 1 or more) M1 + m2 is 1 or more, n is an integer of 1 or more, R ¹ and R ² are the same or different, and a hetero atom, a hydrocarbon group having 1 or more carbon atoms which may have a substituent, X represents O or S, and at least one X is S.). That is, the thioether nitrile compound according to the present invention has at least one cyano group (—CN) and at least one sulfide bond (—S—) in its molecular structure.

  In the general formula (1), m1 and m2 are 0 or an integer of 1 or more, m1 + m2 is 1 or more, and m1 + m2 is preferably 7 or less. m1 + m2 is more preferably 2 to 5, and further preferably 2 to 3. n is an integer greater than or equal to 1, Preferably it is 7 or less, n becomes like this. More preferably, it is 1-5, More preferably, it is 1-4.

In general formula (1), R ¹ and R ² are the same or different and represent a hydrocarbon group having 1 or more carbon atoms. When n is 2 or more, two or more R ^{1 s} may be the same or different (same for R ² ), and R ¹ and R ² may form a ring containing X Good. The hydrocarbon group may be either saturated or unsaturated, and may be linear, branched or cyclic. Further, the hydrocarbon group may have a hetero atom (O, N, S, etc.) or a substituent, and even if a part or all of the hydrogen atoms bonded to the carbon atom are substituted with a halogen atom. Good. The halogen atom is preferably a fluorine atom or a bromine atom, more preferably a fluorine atom. The number of carbon atoms constituting the hydrocarbon group is preferably 1-20, more preferably 2-16, and even more preferably 4-12. Specific examples of the hydrocarbon group include a monovalent group such as an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, and an aralkyl group, which may have a substituent, and a substituent. Divalent groups such as an alkylene group, an alkenylene group, an alkynylene group, an arylene group, and an aralkylene group may be mentioned. Examples of the substituent include a carboxy group, a cyano group, an N-substituted amino group, a nitro group, an alkyl group having 1 to 20 carbon atoms, a fluoroalkyl group, an alkoxy group, an alkoxycarbonyl group, an acyl group, a cyanoalkyl group, and a cyanoalkoxy group. Is mentioned.

  In the general formula (1), X represents O or S, and at least one X is S. By using a thioether nitrile compound containing S in the molecular structure, the cycle characteristics of the electricity storage device can be improved. In addition, the ratio O / S of O atoms to S atoms contained in the thioether nitrile compound is not particularly limited, but for example, O / S (molar ratio) is preferably 0 to 5, and more preferably. It is 0-4, More preferably, it is 0-3.

  Specific examples of the thioether nitrile compound include compounds represented by the following formulas (1-1) to (1-52). The thioether nitrile compound according to the present invention is not limited to these.

  A thioether nitrile compound may be used individually by 1 type, and may be used in combination of 2 or more type.

  Of the thioether nitrile compounds, those having a cyano group bonded to an aliphatic group are preferred, and those having no aromatic group in their molecular structure are preferred. Among the compounds exemplified above, 3-((2- (2-cyanoethoxy) ethyl) thio) propionitrile (formula 1-19), 3,3 ′-(ethylenedithio) dipropionitrile (formula 1-22) ), 3,3 ′-(thiobisethylenebisoxy) bispropionitrile (formula 1-41), 3,3 ′-(oxybisethylenebisthio) bispropionitrile (formula 1-42), 3, 3 ′-((thiobis (ethane-2,1-diyl)) bis (sulfanediyl)) dipropionitrile (3,3 ′-(thiobisethylenebisthio) bispropionitrile) (formula 1-43) 4,13-dioxa-7,10-dithiahexadecane-1,16-dinitrile (Formula 1-50) is more preferred. From the viewpoint of further improving the cycle characteristics of the electricity storage device, a thioether nitrile compound having an ether bond (—O—) in the molecular structure is suitable.

  From the viewpoint of ensuring the safety of the electricity storage device, it is recommended to use a thioether nitrile compound having a high boiling point. For example, it is preferable to use a thioether nitrile compound having a boiling point of 120 ° C. or higher, more preferably a compound having a boiling point of 150 ° C. or higher, and still more preferably a compound having a boiling point of 200 ° C. or higher. The upper limit of the boiling point is not particularly limited, but is preferably about 300 ° C.

  As the thioether nitrile compound, those having a molecular weight of 150 or more are preferably used. As for the molecular weight of a thioether nitrile compound, it is more preferable that it is 150-500, More preferably, it is 170-400. If the molecular weight is too large, the viscosity of the electrolyte solution containing the thioether nitrile compound may be high, and it may be difficult to obtain the desired conductivity, or the storage device may be difficult to manufacture due to the viscosity of the thioether nitrile compound. On the other hand, if the molecular weight is too low, an odor problem may occur, which is not preferable from the viewpoint of ensuring the safety of the electricity storage device. In addition, although the molecular weight of a thioether nitrile compound can be measured with a mass spectrometer etc., you may refer to a manufacturer's nominal value.

2. Presence aspect of thioether nitrile compound The electrical storage device of this invention should just contain the thioether nitrile compound represented by the said General formula (1), and is not specifically limited. Moreover, the presence aspect of the said thioether nitrile compound is not limited, For example, what is necessary is just to be contained as a constituent material of an electrical storage device. Specifically, (i) a mode in which a thioether nitrile compound is contained in the electrolyte solution of the electricity storage device; (ii) a thioether nitrile compound is contained in the electricity storage device constituent material (electrode, separator, exterior, etc.) other than the electrolyte solution (Iii) an embodiment in which the above (i) and (ii) are combined; and the like.

(I) A mode in which a thioether nitrile compound is contained in the electrolytic solution of the electricity storage device In aspect (i), a thioether nitrile compound may be used as a constituent component of the electrolytic solution provided in the electricity storage device, and the preparation of the electrolytic solution is easy. Therefore, it is preferable (mixing a thioether nitrile compound and other components such as an electrolyte or a medium, or adding a thioether nitrile compound to a previously prepared electrolyte).

  The blending amount of the thioether nitrile compound is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more with respect to 100 parts by mass of the electrolytic solution (total of electrolyte, medium and thioether nitrile compound). The amount of the thioether nitrile compound is more preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and still more preferably 3 parts by mass or less. If the blending amount of the thioether nitrile compound is too small, it may be difficult to obtain the effect of suppressing deterioration of the electrode or decomposition of the electrolytic solution, while it is difficult to obtain an effect proportional to the amount used even if used in a large amount. In addition, the viscosity of the electrolytic solution increases, and it may be difficult to obtain the desired conductivity.

(Ii) A mode in which the constituent material of the electricity storage device other than the electrolytic solution contains a thioether nitrile compound The thioether nitrile compound may be contained in the constituent material of the electricity storage device other than the electrolytic solution, such as an electrode, a separator, or an exterior. . A thioether nitrile compound is preferably contained in the electrode because the concentration of the thioether nitrile compound in the vicinity of the electrode can be easily improved, and a film can be formed on the electrode surface quickly and continuously.

  In this case, the electrode preferably contains 0.01 part by mass or more of the thioether nitrile compound with respect to 100 parts by mass of the electrode active material, more preferably 0.05 part by mass or more, and further preferably 0.1 part by mass. The content of the thioether nitrile compound is more preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and further preferably 5 parts by mass or less. If the content of the thioether nitrile compound is too small, it may be difficult to obtain the effect of inhibiting electrode corrosion and solvent decomposition, while it is difficult to obtain an effect proportional to the amount of use even if it is used in a large amount. There is a possibility that the ratio of the thioether nitrile compound in the constituent material becomes large and it becomes difficult to manufacture the electrode.

  The method for supporting (holding) the thioether nitrile compound on the electrode is not particularly limited. For example, if a thioether nitrile compound is used as a part of the electrode constituent material and the electrode is produced by a conventionally known production method, an electrode carrying the thioether nitrile compound can be obtained. Specifically, an electrode material composition is prepared by mixing a thioether nitrile compound with an electrode material such as an electrode active material to be described later, a conductive additive, and a binder, and this is applied to a current collector and dried. Method: A method in which a sheet obtained by kneading, molding and drying an electrode material composition containing a thioether nitrile compound is bonded to a current collector through a conductive adhesive, pressed, and dried; the electrode material composition is collected into a current collector A method of applying or spraying a solution containing a thioether nitrile compound on a sheet-like electrode obtained by coating and drying, and drying; a liquid or slurry electrode material composition (thioether nitrile compound added with a liquid lubricant) Are applied or cast on a positive electrode current collector to form a desired shape, and then the liquid lubricant is removed, and then the film is stretched in a uniaxial or multiaxial direction.

3. Power Storage Device The power storage device of the present invention is not particularly limited as long as it contains the thioether nitrile compound represented by the above general formula (1). Examples of the capacitor include an electric double layer capacitor, a lithium ion capacitor, a lithium ion secondary battery, a sodium ion battery, and a potassium ion battery. Further, there is no particular limitation on the configuration of these power storage devices, and a configuration of a conventionally known power storage device such as an electrolytic solution, an electrode, and a separator can be employed in the present invention.

  An electrolyte solution having a configuration common to the power storage device will be described.

3-1. Electrolytic Solution The electrolytic solution used for the electricity storage device usually includes an electrolyte and a medium. The electrolyte solution according to the present invention preferably contains a thioether nitrile compound (the above embodiments (i) and (iii)).

3-1-1. Electrolyte In the present invention, a conventionally known electrolyte can be used. As the electrolyte, those having a large dissociation constant in the electrolytic solution and having an anion that is difficult to solvate with a non-aqueous solvent described later are preferable. Specific examples of the electrolyte include alkali metal salts and alkaline earth metal salts of trifluoromethanesulfonic acid such as LiCF ₃ SO ₃ , NaCF ₃ SO ₃ , KCF ₃ SO ₃ ; LiC (CF ₃ SO ₂ ) ₃ , LiN ( Perfluoroalkanesulfonic acid imide such as CF ₃ CF ₂ SO ₂ ) ₂ , LiN (FSO ₂ ) ₂ or alkali metal salt or alkaline earth metal salt of fluorosulfonyl imide; hexafluoro such as LiPF ₆ , NaPF ₆ , KPF ₆ Alkali metal salts and alkaline earth metal salts of phosphoric acid; alkali metal salts and alkaline earth metal salts of perchloric acid such as LiClO ₄ , NaClO ₄ and KClO ₄ ; tetrafluoroborate salts such as LiBF ₄ , NaBF ₄ and KBF ₄ Cyanoboric acid such as lithium tetracyanoborate, sodium tetracyanoborate and potassium tetracyanoborate Alkali metal salts such as LiAsF ₆ , LiI, LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ , LiCl, NaI, NaAsF ₆ , KI and the like; quaternary ammonium salts of perchloric acid such as tetraethylammonium perchlorate; _{(C 2 H 5) 4 NBF} 4, (C 2 H 5) 3 (CH 3) NBF 4 quaternary ammonium salts of tetrafluoroboric acid such as; tetraethylammonium tetracyanoborate, 1-ethyl-3-methylimidazolium Ammonium salts of cyanoboric acid such as tetracyanoborate; Quaternary ammonium salts such as (C ₂ H ₅ ) ₄ NPF ₆ ; (CH ₃ ) ₄ P · BF ₄ , (C ₂ H ₅ ) ₄ P · BF ₄ etc. And the like. These electrolytes may be used individually by 1 type, and may be used in combination of 2 or more type.

Among the electrolytes, alkali metal salts and / or alkaline earth metal salts are preferable. Further, from the viewpoint of solubility in a non-aqueous solvent and ion conductivity, LiPF ₆ , LiBF ₄ , LiAsF ₆ , alkali metal salts or alkaline earth metal salts of perfluoroalkanesulfonic acid imide, chain quaternary quaternary Ammonium salts are preferred, and chain quaternary ammonium salts are preferred from the viewpoint of reduction resistance. As the alkali metal salt, a lithium salt, a sodium salt, and a potassium salt are preferable, and as the alkaline earth metal salt, a calcium salt and a magnesium salt are preferable. More preferred is a lithium salt.

  The concentration of the electrolyte is preferably 0.5 mol / L or more in the electrolytic solution according to the present invention, more preferably 0.7 mol / L or more, still more preferably 0.9 mol / L or more, preferably Is not more than a saturated concentration, more preferably not more than 2.0 mol / L, still more preferably not more than 1.8 mol / L. If the electrolytic mass is too small, it may be difficult to obtain a desired conductivity. On the other hand, if the electrolytic mass is too large, ion migration may be hindered.

3-1-2. Medium The medium is not particularly limited as long as it can dissolve the thioether nitrile compound and the electrolyte, and any conventionally known medium used for an electricity storage device such as a non-aqueous solvent, a polymer, or a polymer gel can be used.

  As the non-aqueous solvent, a solvent having a large dielectric constant, high solubility of the thioether nitrile compound, a boiling point of 60 ° C. or higher, and a wide electrochemical stability range is preferable. More preferably, it is an organic solvent (non-aqueous solvent) having a low water content. Examples of such organic solvents include ethylene glycol dimethyl ether (1,2-dimethoxyethane), ethylene glycol diethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, 2,6-dimethyltetrahydrofuran, tetrahydropyran, crown ether, triethylene glycol dimethyl ether, Ethers such as tetraethylene glycol dimethyl ether, 1,4-dioxane, 1,3-dioxolane; dimethyl carbonate, ethyl methyl carbonate (methyl ethyl carbonate), diethyl carbonate (diethyl carbonate), diphenyl carbonate, methyl phenyl carbonate, etc. Chain carbonates of ethylene carbonate (ethylene carbonate), propylene carbonate (propylene carbonate), 2,3-dimethylethylene carbonate, butyrate , Cyclic carbonates such as vinylene carbonate and 2-vinylethylene carbonate; fluorinated cyclic carbonates such as fluoroethylene carbonate, trans-difluoroethylene carbonate, cis-difluoroethylene carbonate; methyl formate, methyl acetate, propionic acid, propionic acid Aliphatic carboxylic acid esters such as methyl, ethyl acetate, propyl acetate, butyl acetate and amyl acetate; Aromatic carboxylic acid esters such as methyl benzoate and ethyl benzoate; γ-butyrolactone, γ-valerolactone, δ-valero Lactones such as lactones; phosphate esters such as trimethyl phosphate, ethyldimethyl phosphate, diethylmethyl phosphate, triethyl phosphate; acetonitrile, propionitrile, methoxypropionitrile, glutaronitrile, adipone , Nitriles such as 2-methylglutaronitrile, valeronitrile, butyronitrile, isobutylnitrile; N-methylformamide, N-ethylformamide, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidinone, Amides such as N-vinylpyrrolidone; sulfur compounds such as dimethylsulfone, ethylmethylsulfone, diethylsulfone, sulfolane, 3-methylsulfolane, 2,4-dimethylsulfolane: ethylene glycol, propylene glycol, ethylene glycol monomethyl ether, ethylene Alcohols such as glycol monoethyl ether; Sulfoxides such as dimethyl sulfoxide, methyl ethyl sulfoxide, and diethyl sulfoxide; Aromatic nitrites such as benzonitrile and tolunitrile Nitromethane, 1,3-dimethyl-2-imidazolidinone, 1,3-dimethyl-3,4,5,6-tetrahydro-2 (1H) -pyrimidinone, 3-methyl-2-oxazolidinone, etc. be able to.

  Among these, chain carbonic acid esters, cyclic carbonic acid esters, aliphatic carboxylic acid esters, lactones, ethers are preferable, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, γ-butyrolactone, γ-valerolactone and the like are more preferable. The said non-aqueous solvent may be used individually by 1 type, and may be used in combination of 2 or more type.

  Polymers used as the medium include polyether polymers such as polyethylene oxide (PEO) and polypropylene oxide, which are homopolymers or copolymers of epoxy compounds (ethylene oxide, propylene oxide, butylene oxide, allyl glycidyl ether, etc.) Methacrylic polymers such as methyl methacrylate (PMMA), nitrile polymers such as polyacrylonitrile (PAN), fluoropolymers such as polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene, and copolymers thereof Is mentioned. In addition, a polymer gel obtained by mixing these polymers with another organic solvent can also be used as the medium according to the present invention. Examples of the other organic solvent include the non-aqueous solvents described above.

  When the polymer gel is used as a medium, a solution obtained by dissolving a thioether nitrile compound in the above non-aqueous solvent is dropped into a polymer formed by a conventionally known method, and the thioether nitrile compound and the non-aqueous solvent are impregnated. Method of supporting; melting and mixing the polymer and thioether nitrile compound at a temperature equal to or higher than the melting point of the polymer, forming a film, and impregnating it with a non-aqueous solvent (the gel electrolyte); dissolving in an organic solvent in advance After mixing the thioether nitrile compound solution and the polymer, this is formed by casting or coating, and the organic solvent is volatilized; the polymer and thioether nitrile compound are melted and mixed at a temperature above the melting point of the polymer. And the like (intrinsic polymer electrolyte);

3-1-3. Additive The electrolytic solution according to the present invention may contain an additive for the purpose of improving various characteristics of the electricity storage device.

  As additives, cyclic carbonates having unsaturated bonds such as vinylene carbonate (VC), vinyl ethylene carbonate (VEC), methyl vinylene carbonate (MVC), ethyl vinylene carbonate (EVC); fluoroethylene carbonate, trifluoropropylene carbonate, Carbonate compounds such as phenylethylene carbonate and erythritan carbonate; succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic anhydride, cyclohexanedicarboxylic anhydride, cyclopentanetetra Carboxylic anhydrides such as carboxylic dianhydride and phenyl succinic anhydride; ethylene sulfite, 1,3-propane sultone, 1,4-butane sultone, methane sulfone Sulfur-containing compounds such as methyl, busulfan, sulfolane, sulfolene, dimethyl sulfone, tetramethylthiuram monosulfide; 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3- Nitrogen-containing compounds such as dimethyl-2-imidazolidinone and N-methylsuccinimide; phosphates such as monofluorophosphate and difluorophosphate; hydrocarbon compounds such as heptane, octane and cycloheptane.

  The additive is preferably used in a concentration of 0.1% by mass to 10% by mass in the electrolytic solution of the present invention (more preferably 0.2% by mass to 8% by mass, and still more preferably 0.3% by mass). Mass% to 5 mass%). If the amount of the additive used is too small, it may be difficult to obtain the effect derived from the additive.On the other hand, even if another additive is used in a large amount, it is difficult to obtain an effect commensurate with the added amount. There is a possibility that the viscosity of the electrolytic solution increases and the conductivity decreases.

4). Lithium Ion Secondary Battery Among the above-exemplified power storage devices, the lithium ion secondary battery will be described in more detail. The lithium ion secondary battery has a positive electrode, a negative electrode, and an electrolytic solution. More specifically, a separator is provided between the positive electrode and the negative electrode, In a state of being impregnated in the separator, it is housed in an outer case together with a positive electrode, a negative electrode, and the like.

  The lithium ion secondary battery of the present invention includes a thioether nitrile compound, and preferably includes a thioether nitrile compound in the electrolytic solution and / or the electrode (the above embodiments (i) to (iii)).

  The shape of the lithium ion secondary battery according to the present invention is not particularly limited, and any conventionally known shape can be used as the shape of the lithium ion secondary battery, such as a cylindrical shape, a square shape, a laminate shape, a coin shape, and a large size. Can do. Further, when used as a high voltage power source (several tens of volts to several hundreds of volts) for mounting on an electric vehicle, a hybrid electric vehicle or the like, a battery module configured by connecting individual batteries in series can also be used. .

4-1. The positive electrode is a positive electrode active material composition containing a positive electrode active material, a conductive additive, a binder, a dispersion solvent and the like supported on a positive electrode current collector, and is usually formed into a sheet shape. .

  As a method for producing the positive electrode, for example, a method in which the positive electrode active material composition is applied to the positive electrode current collector by the doctor blade method or the like and dried after being immersed; the positive electrode active material composition is kneaded and dried. A method in which the obtained sheet is bonded to the positive electrode current collector via a conductive adhesive, pressed, and dried; a positive electrode active material composition to which a liquid lubricant is added is applied or cast on the positive electrode current collector; Examples include a method in which after forming into a desired shape, the liquid lubricant is removed, and then the film is stretched in a uniaxial or multiaxial direction. When it is desired to support the thioether nitrile compound on the positive electrode (the above embodiments (ii) and (iii)), the thioether nitrile compound may be used as a material constituting the positive electrode active material composition.

4-1-1. Positive electrode current collector The material of the positive electrode current collector is not particularly limited, and for example, conductive metals such as aluminum, aluminum alloy, SUS (stainless steel), and titanium can be used. Among these, aluminum is preferable because it is easy to process into a thin film and is inexpensive.

4-1-2. Positive Electrode Active Material As the positive electrode active material, any known positive electrode active material used in lithium secondary batteries may be used as long as it can occlude and release lithium ions.

Specifically, lithium cobalt acid, lithium nickel acid, lithium manganese _{acid, LiNi 1-xy Co x Mn} y O 2 or _{LiNi 1-xy Co x Al y} O 2 (0 ≦ x ≦ 1,0 ≦ y ≦ 1 ) Transition metal oxides such as ternary oxides, compounds having an olivine structure such as LiAPO ₄ (A = Fe, Mn, Ni, Co), and solid solution materials incorporating a plurality of transition metals (electrochemistry) Inactive layered Li ₂ MnO ₃ and electrochemically active layered LiM ″ O [M ″ = transition metal such as Co and Ni]) can be exemplified as the positive electrode active material. . These positive electrode active materials may be used individually by 1 type, or may be used in combination of multiple.

4-1-3. Conductive aid Examples of the conductive aid include acetylene black, carbon black, graphite, metal powder material, single-walled carbon nanotube, multi-walled carbon nanotube, and vapor grown carbon fiber.

4-1-4. Binders As binders, fluorine resins such as polyvinylidene fluoride and polytetrafluoroethylene; synthetic rubbers such as styrene-butadiene rubber and nitrile butadiene rubber; polyamide resins such as polyamideimide; polyethylene, polypropylene and the like Polyolefin resin; poly (meth) acrylic resin; polyacrylic acid; cellulose resin such as carboxymethylcellulose; A binder may be used individually by 1 type, and multiple types may be mixed and used for it. Further, the binder may be in a state dissolved in a solvent during use or in a state dispersed in a solvent.

  The blending amounts of the conductive auxiliary agent and the binder can be appropriately adjusted in consideration of the intended use of the battery (emphasis on output, importance on energy, etc.), ion conductivity and the like.

  In the production of the positive electrode, examples of the solvent used in the positive electrode active material composition include N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, tetrahydrofuran, acetone, ethanol, ethyl acetate, and water. These solvents may be used in combination. The amount of the solvent used is not particularly limited, and may be appropriately determined according to the production method and the material to be used.

4-2. Negative electrode A negative electrode is a negative electrode active material composition containing a negative electrode active material, a dispersing solvent, a binder and, if necessary, a conductive additive, etc. supported on a negative electrode current collector. Molded.

4-2-1. Negative Electrode Current Collector As a material for the negative electrode current collector, a conductive metal such as copper, iron, nickel, silver, stainless steel (SUS) can be used. From the viewpoint of easy processing into a thin film, copper is preferable.

4-2-2. Negative electrode active material As the negative electrode active material, a conventionally known negative electrode active material used in lithium ion secondary batteries can be used as long as it can occlude and release lithium ions. Specifically, graphite materials such as artificial graphite and natural graphite, mesophase fired bodies made from coal / petroleum pitch, carbon materials such as non-graphitizable carbon, Si, Si alloys, Si-based negative electrode materials such as SiO, Sn Sn-based negative electrode materials such as alloys, lithium alloys such as lithium metal and lithium-aluminum alloys, and titanium-based compounds such as lithium titanate can be used.

  As a manufacturing method of the negative electrode, a method similar to the manufacturing method of the positive electrode can be employed. In addition, the same conductive auxiliary agent, binder, and material dispersing solvent as used in the positive electrode are used in the production of the negative electrode. When it is desired to support the thioether nitrile compound on the negative electrode (the above embodiments (ii) and (iii)), a thioether nitrile compound may be used as a material constituting the negative electrode active material composition.

4-3. Separator The separator is disposed so as to separate the positive electrode and the negative electrode. There is no restriction | limiting in particular in a separator, In this invention, all the conventionally well-known separators can be used. Specific examples of the separator include a porous sheet made of a polymer that absorbs and retains a nonaqueous electrolytic solution (for example, a polyolefin microporous separator or a cellulose separator), a nonwoven fabric separator, a porous metal body, and the like. It is done. Among these, a polyolefin-based microporous separator is preferable because it has a property of being chemically stable to an organic solvent.

  Examples of the material for the porous sheet include polyethylene, polypropylene, and a laminate having a three-layer structure of polypropylene / polyethylene / polypropylene.

  Examples of the material of the nonwoven fabric separator include cotton, rayon, acetate, nylon, polyester, polypropylene, polyethylene, polyimide, aramid, glass, etc., depending on the mechanical strength required for the non-aqueous electrolyte layer, etc. The above-exemplified materials can be used alone or in combination.

4-4. Battery Exterior Material A battery element including a positive electrode, a negative electrode, a separator, an electrolytic solution, and the like is accommodated in a battery exterior material in order to protect the battery element from external impact, environmental degradation, and the like when using a lithium ion secondary battery. In the present invention, the material of the battery exterior material is not particularly limited, and any conventionally known exterior material can be used.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

Example 1
Lithium hexafluorophosphate (Kishida Chemical Co., Ltd.) in a non-aqueous solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed at 3: 7 (volume ratio) so that the concentration becomes 1.0 mol / L. Non-aqueous electrolyte (1) was prepared by dissolving. Next, 0.04 g of 3,3 ′-(thiobisethylenebisoxy) bispropionitrile is added to 1.96 g of this non-aqueous electrolyte (1) so that the concentration in the non-aqueous electrolyte is 2% by mass. (Formula 1-41 below) was added to prepare a non-aqueous electrolyte (2).

[Battery characteristics evaluation]
(Production of battery)
Commercially available positive electrode sheet having a positive electrode active material layer area of φ12 mm (manufactured by Piotrek Co., Ltd., active material: lithium cobaltate), graphite negative electrode sheet having a negative electrode area of φ14 mm (manufactured by Piotrek Co., Ltd.), and CR2032 coin-type battery A coin-type lithium battery was produced using the parts for use (made by Hosen Co., Ltd.). Specifically, a negative electrode cap equipped with a gasket, a wave washer, a spacer, a negative electrode, and a polyethylene separator were stacked in this order, and then the separator was impregnated with 70 μL of the non-aqueous electrolyte (2). Next, the positive electrode is placed so that the positive electrode active material layer forming surface faces the negative electrode active material layer forming surface, and a positive electrode case is further stacked thereon, and the coin type lithium battery (1) is then crimped by a caulking machine. Produced.

(Cycle test)
About the obtained coin-type lithium battery (1), a charge / discharge test apparatus ("ACD-01", manufactured by Asuka Electronics Co., Ltd.) was used, and a charge / discharge rate of 0.2 C (constant current mode), 3.0 V to Under the condition of 4.2 V, a cycle test was conducted with a charge / discharge pause time of 10 minutes during each charge / discharge. Table 1 shows the discharge capacity retention ratio when the discharge capacity in each cycle and the discharge capacity in the first cycle are 100%.

Example 2
The same operation as in Example 1 was carried out except that 3,3 ′-(oxybisethylenebisthio) bispropionitrile represented by the following formula (1-42) was used as the thionitrile ether compound. A water electrolyte (3) was prepared. Moreover, except having used nonaqueous electrolyte (3) as nonaqueous electrolyte, operation similar to Example 1 was performed and the coin-type lithium battery (2) was produced, and the cycle test was implemented. The results are shown in Table 1.

Comparative Example 1
Using the non-aqueous electrolyte (1) prepared in Example 1, the same operation as in Example 1 was performed to produce a coin-type lithium battery (3) in which the electrolyte did not contain a thioether nitrile compound, and a cycle test Carried out. The results are shown in Table 1.

Comparative Example 2
Example 1 except that 3,3 ′-[oxybis (2,1-ethanediyloxy)] bispropanenitrile (ether nitrile compound) represented by the following general formula (2) was used as the ether nitrile compound. The same operation was performed to prepare a nonaqueous electrolytic solution (4). Moreover, except having used nonaqueous electrolyte (4) as nonaqueous electrolyte, operation similar to Example 1 was performed and the coin-type lithium battery (4) was produced, and the cycle test was implemented. The results are shown in Table 1.

  From Table 1, in Example 1 and Example 2 using a thioether nitrile compound containing a sulfide bond in the molecular structure, compared with Comparative Example 1 not containing a thioether nitrile compound, the decrease in discharge capacity was suppressed, and the discharge It was found that the capacity maintenance rate improved significantly.

  In addition, in Comparative Example 2 using an ether nitrile compound that does not contain a sulfide bond in the molecular structure as an additive, the discharge capacity is significantly lower than that in Comparative Example 1, and the discharge capacity retention rate is significantly deteriorated. Turned out to be. This result shows that cycle characteristics can be improved by using a thioether nitrile compound containing a sulfide bond in the molecular structure.

  As described above, according to the present invention, by including the thioether nitrile compound represented by the general formula (1), it is difficult to cause deterioration of characteristics over time, and an electric storage device capable of stable driving is expected. it can.

Claims (5)

A power storage device represented by the following general formula (1), comprising a thioether nitrile compound having a cyano group bonded to an aliphatic group and at least one ether bond .
(NC) _m1 − (R ¹ XR ² ) _n − (CN) _m2 (1)
(In the formula, m1 and m2 are 0 or an integer of 1 or more, m1 + m2 is 1 or more, n is an integer of 1 or more, and R ¹ and R ² are the same or different and have a hetero atom or a substituent. An optionally substituted hydrocarbon group having 1 or more carbon atoms, X represents O or S, and at least one X is S.)   The electrical storage device of Claim 1 which contains the said thioether nitrile compound in electrolyte solution. The thioether nitrile compound, the electric storage device according to claim 1 or 2 do not contain aromatic groups. It is a lithium ion secondary battery, The electrical storage device in any one of Claims 1-3 . A electrolyte used in the device according to any of claims 1-4, represented by the following general formula (1), a cyano group attached to an aliphatic group, a thioether having at least one ether bond An electrolytic solution comprising a nitrile compound.
(NC) _m1 − (R ¹ XR ² ) _n − (CN) _m2 (1)
(In the formula, m1 and m2 are 0 or an integer of 1 or more, m1 + m2 is 1 or more, n is an integer of 1 or more, and R ¹ and R ² are the same or different and have a hetero atom or a substituent. An optionally substituted hydrocarbon group having 1 or more carbon atoms, X represents O or S, and at least one X is S.)