JP5121127B2 - Non-aqueous electrolyte composition and non-aqueous electrolyte secondary battery using the composition - Google Patents

Description

  The present invention relates to a non-aqueous electrolyte composition and a non-aqueous electrolyte secondary battery using the non-aqueous electrolyte composition. Specifically, in a non-aqueous electrolyte composition obtained by dissolving an electrolyte salt in an organic solvent, The organic solvent is ethylene carbonate (a) 20 to 35% by volume, ethyl methyl carbonate (b) 35 to 45% by volume, dimethyl carbonate (c) 15 to 35% by volume, and diethyl carbonate or propylene carbonate (d) 3 A non-aqueous electrolyte composition that is a mixed organic solvent containing 15% by volume, and a non-aqueous electrolyte secondary excellent in battery characteristics at room temperature and low temperature after cycling by using the non-aqueous electrolyte composition It relates to batteries.

  In recent years, non-aqueous electrolyte secondary batteries that use lithium metal, lithium alloy, or a material capable of inserting and extracting lithium ions as a negative electrode active material have attracted attention because of their features such as high energy density and low self-discharge. ing. However, the non-aqueous electrolyte secondary battery has drawbacks such as high voltage, the electrolyte is easily decomposed in both positive and negative electrodes, poor storage stability, and it is difficult to ensure a long cycle life. It was.

  For this reason, the development of a non-aqueous electrolyte excellent in storage characteristics or cycle characteristics has become the most important issue in putting a non-aqueous electrolyte secondary battery into practical use. The non-aqueous electrolyte is a solute electrolyte dissolved in an organic solvent. The required properties of the solvent are a large dielectric constant, a large amount of solute electrolyte, and a low viscosity. It has excellent low-temperature characteristics, is stable against oxidation and reduction, does not decompose, and has low volatility and high safety in use.

  Conventionally, low-boiling solvents such as 1,2-dimethoxyethane and 1,3-dioxolane have been used as solvents used in non-aqueous electrolyte secondary batteries, but these low-boiling solvents have a dielectric constant. Not only is it small, but when used alone, lithium, which is a negative electrode material, reacts with the solvent and elutes into the electrolyte solution to deteriorate the storage characteristics, or the ionic conductivity of the lithium oxide film formed by the reaction decreases. Since it is not good, the internal resistance of the battery is increased and the high rate discharge characteristics are deteriorated.

  For this reason, as a solvent used for a nonaqueous electrolyte secondary battery, a mixed solvent of a cyclic carbonate having a high dielectric constant such as ethylene carbonate or propylene carbonate and a low boiling point solvent such as 1,2-dimethoxyethane or tetrahydrofuran is used. Is used. This type of solvent is intended to reduce the viscosity of the electrolyte by using a low-boiling solvent while forming a lithium carbonate film having excellent ionic conductivity on the negative electrode surface by reaction between the cyclic carbonate and lithium. This is intended to prevent a decrease in the ionic conductivity of the electrolyte and to improve the high rate discharge characteristics.

  However, low boiling solvents such as 1,2-dimethoxyethane and tetrahydrofuran tend to decompose at the contact interface with the high potential positive electrode due to their low redox potential. Although the formed lithium carbonate film is gradually decomposed and changed to an insulating lithium oxide film, the initial high-rate discharge characteristics can be improved to some extent, but the high-rate discharge characteristics after storage are sufficiently satisfactory. It wasn't something to get.

  For this reason, the improvement regarding electrolyte solution solvent is calculated | required strongly, for example, patent document 1, patent document 2, patent document 3, patent document 4, patent document 5 and patent document 6 include ethylene carbonate, propylene carbonate, 1 It has been proposed to use a mixed solvent of a cyclic carbonate compound such as 1,2-butylene carbonate or vinylene carbonate and a chain carbonate compound such as dimethyl carbonate, diethyl carbonate or dipropyl carbonate.

  Patent Document 7 discloses a mixture containing dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate in an equilibrium state by forcibly transesterifying a mixture of dimethyl carbonate and diethyl carbonate using a catalyst. A composition of an electrolytic solution in which ethylene carbonate is added to this is proposed.

JP-A-6-84542 JP 2003-323915 A Japanese Patent No. 3157209 Japanese Patent No. 3311104 Japanese Patent No. 3428750 JP 2000-67914 A JP 2002-117898 A

  By using a chain carbonate compound in place of 1,2-dimethoxyethane, tetrahydrofuran, etc., high-rate discharge characteristics after initial and storage are improved to some extent, but an electrolyte having sufficiently excellent low-temperature characteristics can be obtained. It wasn't.

  The problem to be solved is that, as described above, an electrolytic solution that exhibits good low-temperature characteristics has not been obtained so far.

  Accordingly, an object of the present invention is to provide a non-aqueous electrolyte secondary battery excellent in storage characteristics or cycle characteristics by using an electrolytic solution composition excellent in low temperature characteristics.

  As a result of repeating various studies in view of the present situation, the present inventors have used a specific carbonate compound at a specific ratio to maintain a good low-temperature characteristic even after repeated cycles. It was found that a product was obtained.

The present invention has been made based on the above knowledge, and in a non-aqueous electrolyte composition obtained by dissolving an electrolyte salt in an organic solvent, the organic solvent contains 20 to 35% by volume of ethylene carbonate (a), ethyl methyl carbonate. (b) 35 to 45% by volume of dimethyl carbonate (c) 15 to 35 vol%, and Ri mixed organic solvent der which comprises 3 to 15% by volume of diethyl carbonate or propylene carbonate (d), further described below general It contains at least one selected from the silicon compound represented by the formula (1) and the silicon compound represented by the following general formula (2), and the content of the silicon compound is 100 parts by mass of the mixed organic solvent. there is provided a nonaqueous electrolyte composition comprising 0.05 to 5 parts by der Rukoto respect.
Further, the present invention provides a nonaqueous electrolyte solution comprising the nonaqueous electrolyte solution as the nonaqueous electrolyte solution in a nonaqueous electrolyte secondary battery having a nonaqueous electrolyte solution, a positive electrode, and a negative electrode. A secondary battery is provided.

  According to the present invention, by using a non-aqueous electrolyte composition characterized by containing a specific carbonate compound in a specific ratio, a non-aqueous electrolyte solution having excellent electrical characteristics at room temperature and low temperature after cycling is used. Next battery can be provided.

  Hereinafter, the non-aqueous electrolyte composition of the present invention and the non-aqueous electrolyte secondary battery of the present invention using the non-aqueous electrolyte composition will be described in detail based on preferred embodiments thereof.

  The non-aqueous electrolyte composition of the present invention is a non-aqueous electrolyte composition in which an electrolyte salt is dissolved in an organic solvent. The organic solvent contains 20 to 35% by volume of ethylene carbonate (a), ethyl methyl carbonate (b ) A mixed organic solvent containing 35 to 45% by volume, 15 to 35% by volume of dimethyl carbonate (c), and 3 to 15% by volume of diethyl carbonate or propylene carbonate (d). The non-aqueous electrolyte composition of the present invention may be composed of only four components (a) to (d), and if necessary, other cyclic carbonate compounds, other chain carbonate compounds, and other organic compounds. A solvent may be contained.

  As a composition of the said organic solvent used for the non-aqueous electrolyte composition of this invention, ethylene carbonate (a) 25-35 volume%, ethyl methyl carbonate (b) 35-45 volume%, dimethyl carbonate (c) 18-32 The composition of 3% by volume and diethyl carbonate or propylene carbonate (d) is preferable because the performance at low temperature can be sufficiently secured.

  As a first specific example of a preferable composition of the organic solvent, ethylene carbonate (a) 30% by volume, ethyl methyl carbonate (b) 40% by volume, dimethyl carbonate (c) 20% by volume and diethyl carbonate (d) 10% by volume. It is preferable to use an organic solvent having this composition because sufficient performance at low temperatures can be secured.

  As a 2nd specific example of the preferable composition of the said organic solvent, ethylene carbonate (a) 25 volume%, ethyl methyl carbonate (b) 40 volume%, dimethyl carbonate (c) 30 volume%, and diethyl carbonate (d) 5 volume% It is preferable to use an organic solvent having this composition because sufficient performance at low temperatures can be secured.

  As a third specific example of a preferable composition of the organic solvent, ethylene carbonate (a) 25% by volume, ethyl methyl carbonate (b) 40% by volume, dimethyl carbonate (c) 25% by volume and diethyl carbonate (d) 10% by volume. It is preferable to use an organic solvent having this composition because sufficient performance at low temperatures can be secured.

  As a fourth specific example of the preferred composition of the organic solvent, ethylene carbonate (a) 25% by volume, ethyl methyl carbonate (b) 40% by volume, dimethyl carbonate (c) 30% by volume and propylene carbonate (d) 5% by volume. It is preferable to use an organic solvent having this composition because sufficient performance at low temperatures can be secured.

  Other cyclic carbonate compounds that can be used in the non-aqueous electrolyte composition of the present invention include vinylene carbonate, 1,2-butylene carbonate, 2-methyl-1,2-butylene carbonate, and 1,1-dimethyl. Examples thereof include ethylene carbonate, 2-methyl-1,3-propylene carbonate, and 3-methyl-1,3-propylene carbonate. Examples of the other chain carbonate compounds include ethyl-n-butyl carbonate, methyl-t-butyl-carbonate, di-i-propyl carbonate, t-butyl-i-propyl carbonate, and the like. 1,2-bis (methoxycarbonyloxy) ethane, 1,2-bis (ethoxycarbonyloxy) ethane and 1,2-bis (ethoxycarbonyloxy) propane, which are alkylene biscarbonate compounds classified as chain carbonate compounds And so on.

  Examples of the other organic solvents include cyclic ester compounds such as γ-butyrolactone and γ-valerolactone, sulfolanes such as sulfolane, sulfolene, tetramethylsulfolane, diphenylsulfone, dimethylsulfone and dimethylsulfoxide, and N- Amide compounds such as methylpyrrolidone, dimethylformamide, dimethylacetamide and the like can be mentioned.

  Furthermore, as the other organic solvent, a linear or cyclic ether compound that can increase the performance of the electrolyte solution at low temperature and low temperature may be used. Examples of the linear or cyclic ether compound include tetrahydrofuran, Examples include dioxolane and dioxane. Furthermore, as the other organic solvent, a chain ester compound can be used. Examples of the chain ester compound include methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, sec-butyl acetate, and butyl acetate. , Methyl propionate, ethyl propionate and the like. In addition, acetonitrile, propionitrile, nitromethane, and derivatives thereof can also be used.

  Moreover, you may use the glycol diether compound classified into chain ether as said other organic solvent. Examples of the glycol diether compound include ethylene glycol bis (trifluoroethyl) ether, i-propylene glycol (trifluoroethyl) ether, ethylene glycol bis (trifluoromethyl) ether, diethylene glycol bis (trifluoroethyl) ether, and the like. In these compounds, since the terminal group is substituted with a fluorine atom, the compound exhibits a surfactant-like action at the electrode interface and can increase the affinity of the non-aqueous electrolyte composition to the electrode. It is possible to reduce the initial internal resistance of the battery and increase the mobility of lithium ions.

  The total content of the components (a) to (d) according to the present invention is preferably 70 to 100% by volume, particularly preferably 90 to 100% by volume in all organic solvents, and is further blended as necessary. The blending amount of the organic solvent other than the components (a) to (d) is preferably 0 to 30% by volume in the total organic solvent because the dielectric constant of the electrolytic solution and the performance at low temperature can be sufficiently secured.

The non-aqueous electrolyte composition of the present invention further includes a silicon compound represented by the following general formula (1) and a silicon compound represented by the following general formula (2) in order to impart more excellent cycle characteristics. Ru is contained at least one selected from among.

(Wherein, R ₁ to R ₆ are each shown to .n alkyl or alkenyl group having 2 to 8 carbon atoms having 1 to 12 carbon atoms independently indicates 1, X is a direct bond or oxygen showing the atom. However, exhibit at least two unsaturated bond-containing group of R ₁ ~ R _6.)

(In the formula, R ₇ represents an alkenyl group having 2 to 10 carbon atoms, R ₈ and R ₉ each independently represents an alkyl group having 1 to 10 carbon atoms, and X represents a halogen.)

In the general formula (1), preferred examples of the alkyl group and alkoxy group represented by R _{1 to} R ₆ include methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, pentyl, hexyl, Examples thereof include alkyl groups having 1 to 12 carbon atoms such as heptyl, octyl, isooctyl, 2-ethylhexyl, nonyl, decyl, undecyl and dodecyl, and alkoxy groups derived from these groups, and alkenyl groups and alkenyloxy groups are preferred. Examples include alkenyl groups having 2 to 8 carbon atoms such as vinyl, allyl, 1-propenyl, isopropenyl, 2-butenyl, 1,3-butadienyl, 2-pentenyl, 2-octenyl, and the like. Alkenyloxy groups are preferred, and alkynyl and alkynyloxy groups are preferred. Examples include alkynyl groups having 2 to 8 carbon atoms such as ethynyl, 2-propynyl, 1,1-dimethyl-2-propynyl, and alkynyloxy groups derived from these groups. Preferable examples of the group include aryl groups having 6 to 12 carbon atoms such as phenyl, tolyl, xylyl, tert-butylphenyl, and aryloxy groups derived from these groups. Preferred examples of the alkylene group and alkylenedioxy group represented by X include 1 to 8 carbon atoms such as methylene, ethylene, trimethylene, 2,2-dimethyltrimethylene, tetramethylene, pentamethylene and hexamethylene. And preferable examples of the alkenylene group and the alkenylene dioxy group are those having 2 to 2 carbon atoms such as vinylene, propenylene, isopropenylene, butenylene, and pentenylene. 8 alkenylene groups and alkenylene dioxy groups derived from these groups. Preferred examples of the alkynylene and alkynylene dioxy groups include ethynylene, propynylene, butynylene, pentynylene, 1,1,4,4- Carbon such as tetramethylbutenylene Examples thereof include alkynylene groups having 2 to 8 alkynylene groups and alkynylene dioxy groups derived from these groups. Preferred examples of arylene groups and arylene dioxy groups include phenylene, methylphenylene, dimethylphenylene, and tertiary butylphenylene. An arylene group having 6 to 12 carbon atoms, such as, and an aryleneoxy group derived from these groups.

  Specific examples of the silicon compound represented by the general formula (1) include the following compound Nos. 1-No. 7 is mentioned. However, this invention is not restrict | limited at all by the following illustrations.

  The silicon compound having an unsaturated bond represented by the general formula (1) is a known compound, and its synthesis method is not particularly limited. 1 can be obtained by dehydrogenation coupling reaction of a hydrogen-containing silicon compound and a hydroxyl group-containing silicon compound.

In the general formula (2), examples of the alkenyl group represented by R _{7 to} R ₉ include vinyl, allyl, 1-propenyl, isopropenyl, 2-butenyl, 1,3-butadienyl, 2-pentenyl, 2 -Octenyl and the like. Examples of the alkyl group, alkoxy group and alkenyl group represented by R ₈ and R ₉ include methyl, ethyl, propyl, butyl, sec-butyl, butyl acid pentyl, hexyl, heptyl, octyl 2-ethyl-hexyl. , Nonyl, decyl and the like, alkoxy groups derived from these alkyl groups, and alkenyl groups corresponding to these alkyl groups. Examples of the halogen represented by Y, R ₈ and R ₉ include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

  Specific examples of the silicon compound represented by the general formula (2) include the following compound Nos. 8-No. 13 is mentioned. However, this invention is not restrict | limited at all by the following illustrations.

Although the mechanism by which the silicon compound exhibits its effect is not clear, it is considered that a film that maintains high lithium ion conductivity even at low temperatures is formed by polymerization or reaction at the electrode interface at the beginning of the cycle. Moreover, in order to express this effect, the said silicon compound is contained with the addition amount of 0.05-5 mass parts with respect to 100 mass parts of all the organic solvents , and 0.1-3 mass parts is more desirable. . If it is less than 0.05 parts by mass, the effect is hardly recognized, and even if it is contained in excess of 5 parts by mass, the effect is not manifested any more, so it is not only useless, but adversely affects the properties of the electrolyte. Since it may affect, it is not preferable.

  In the non-aqueous electrolyte composition of the present invention, one kind selected from the silicon compound represented by the general formula (1) and the silicon compound represented by the general formula (2) is contained alone. In addition, two or more selected from these silicon compounds may be contained in combination, and further, an organic tin compound or an organic germanium compound may be contained in combination.

  In addition, in order to impart flame retardancy to the non-aqueous electrolyte composition of the present invention, halogen-based, phosphorus-based, and other flame retardants can be added as appropriate. Examples of the phosphoric flame retardant include phosphoric esters such as trimethyl phosphate and triethyl phosphate, melamine polyphosphate, ammonium polyphosphate, ethylenediamine polyphosphate, hexamethylenediamine polyphosphate, piperazine polyphosphate, and the like.

  5-100 mass parts is preferable with respect to 100 mass parts of all the organic solvents which comprise a non-aqueous electrolyte composition, and, as for the usage-amount of flame retardants, such as the said phosphorus flame retardant, 10-50 mass parts is especially preferable. If it is less than 5 parts by mass, a sufficient flame retarding effect cannot be obtained.

Further, as the electrolyte salt in the non-aqueous electrolyte composition of the present invention, conventionally known electrolyte salts can be used. For example, LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiN (CF ₃ SO _{2 ) 2, LiC (CF 3 SO} 2) 3, LiSbF 6, LiSiF 5, LiAlF 4, like _{LiSCN, LiClO 4, LiCl, LiF} , LiBr, LiI, LiAlF 4, LiAlCl 4, NaClO 4, NaBF 4, NaI and the like Among these, the inorganic salts LiPF ₆ , LiBF ₄ , LiAsF ₆ and LiClO ₄ , and the organic salts LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ and LiC (CF ₃ SO ₂ ) ₃ , And combinations of one or two or more salts selected from the group consisting of these and derivatives thereof are preferred because of their excellent electrical properties.

  The electrolyte salt is dissolved in the organic solvent so that the concentration in the non-aqueous electrolyte composition is 0.1 to 3.0 mol / liter, particularly 0.5 to 2.0 mol / liter. Is preferred. If the concentration of the electrolyte salt in the non-aqueous electrolyte composition is less than 0.1 mol / liter, a sufficient current density may not be obtained. If the concentration is greater than 3.0 mol / liter, the stability of the electrolyte solution may be reduced. There is a risk of damage.

  The non-aqueous electrolyte secondary battery of the present invention uses the non-aqueous electrolyte composition of the present invention as the non-aqueous electrolyte. The positive electrode, negative electrode and separator used in the non-aqueous electrolyte secondary battery of the present invention are not particularly limited, and various materials conventionally used in non-aqueous electrolyte secondary batteries should be used as they are. Can do.

Examples of the electrode material used in the nonaqueous electrolyte secondary battery of the present invention include a positive electrode and a negative electrode.
As the positive electrode, a material obtained by applying a slurry of a positive electrode active material, a binder and a conductive material to a current collector and drying it into a sheet can be used. Examples of the positive electrode active material include TiS ₂ , TiS ₃ , MoS ₃ , FeS ₂ , Li _(1-x) MnO ₂ , Li _(1-x) Mn ₂ O ₄ , Li _(1-x) CoO ₂ , Li _{( 1-x) NiO 2, LiV} 2 O 3, V 2 O 5 and the like. In addition, X in the illustration of this positive electrode active material shows the number of 0-1. Of these positive electrode active materials, composite oxides of lithium and transition metals are preferable, and specific examples thereof include LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiMnO ₂ , and LiV ₂ O ₃ . Examples of the binder for the positive electrode active material include, but are not limited to, polyvinylidene fluoride, polytetrafluoroethylene, EPDM, SBR, NBR, and fluororubber.

  Examples of the conductive material for the positive electrode include graphite fine particles, carbon black such as acetylene black, and amorphous carbon fine particles such as needle coke, but are not limited thereto. As the solvent used for slurrying, an organic solvent that dissolves the binder is usually used. Specific examples include N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, and methyl acrylate. , Diethyltriamine, NN-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran and the like, but are not limited thereto. Moreover, a dispersing agent, a thickener, etc. are added to water, and an active material may be slurried with latex, such as SBR.

  As the negative electrode, a negative electrode active material and a binder slurryed with a solvent is applied to a current collector and dried to form a sheet. Examples of the negative electrode active material include lithium, lithium alloys, tin compounds and other inorganic compounds, carbonaceous materials, conductive polymers, and the like. In particular, carbonaceous materials that can occlude and release highly safe lithium ions are preferable. . This carbonaceous material is not particularly limited, but graphite, petroleum coke, coal coke, petroleum pitch carbide, coal pitch carbide, resin carbide such as phenol resin / crystalline cellulose, and the like And carbon materials partially carbonized, furnace black, acetylene black, pitch-based carbon fibers, PAN-based carbon fibers, and the like. Moreover, what was illustrated as a binder and a solvent which can be used for the said positive electrode can respectively be used as the said binder and said solvent used for a negative electrode.

  Copper, nickel, stainless steel, nickel-plated steel or the like is usually used for the current collector of the negative electrode, and aluminum, stainless steel, nickel-plated steel or the like is usually used for the current collector of the positive electrode.

  In the nonaqueous electrolyte secondary battery of the present invention, a separator is used between the positive electrode and the negative electrode, and the separator is particularly limited to a microporous film of a polymer compound usually used in a nonaqueous electrolyte secondary battery. For example, polyethylene, polypropylene, polyvinylidene fluoride, polyvinylidene chloride, polyacrylonitrile, polyacrylamide, polytetrafluoroethylene, polysulfone, polyethersulfone, polycarbonate, polyamide, polyimide, polyethylene oxide, polypropylene oxide, etc. Polyethers, various celluloses such as carboxymethylcellulose and hydroxypropylcellulose, high molecular compounds and derivatives thereof such as poly (meth) acrylic acid and various esters thereof, copolymers thereof, Films and the like comprising a compound. Moreover, these films may be used independently and may be used as a multilayer film which laminated | stacked the several film. Furthermore, various additives may be used for these films, and the type and content thereof are not particularly limited. Among these microporous films, polyethylene, polypropylene, polyvinylidene fluoride, and polysulfone are preferably used for the nonaqueous electrolyte secondary battery of the present invention.

  The film used as the separator is microporous so that the non-aqueous electrolyte is soaked and ions are easily transmitted. As a method for microporosity, the above polymer compound and a solvent solution are formed into a film while microphase separation is performed, and the solvent is extracted and removed to make the film porous. Extrusion film formation with a high draft, followed by heat treatment, crystals are arranged in one direction, and further, a “stretching method” in which gaps are formed between the crystals by stretching to achieve porosity, etc., depending on the polymer film used Selected.

  A phenolic antioxidant, a phosphorus antioxidant, a thioether antioxidant, and a hindered amine compound are added to the non-aqueous electrolyte composition of the present invention, the electrode material and the separator for the purpose of improving safety. May be.

  Examples of the phenol-based antioxidant include 1,6-hexamethylene bis [(3-tert-butyl-5-methyl-4-hydroxyphenyl) propionic acid amide], 4,4′-thiobis (6-tert. Tributyl-m-cresol), 4,4′-butylidenebis (6-tert-butyl-m-cresol), 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane 1,3,5-tris (2,6-dimethyl-3-hydroxy-4-tert-butylbenzyl) isocyanurate, 1,3,5-tris (3,5-ditert-butyl-4-hydroxybenzyl) ) Isocyanurate, 1,3,5-tris (3,5-ditert-butyl-4-hydroxybenzyl) -2,4,6-trimethylbenzene, tetrakis [3- (3,5-ditert-butyl- 4- Droxyphenyl) methyl propionate] methane, thiodiethylene glycol bis [(3,5-ditert-butyl-4-hydroxyphenyl) propionate], 1,6-hexamethylenebis [(3,5-ditert-butyl- 4-hydroxyphenyl) propionate], bis [3,3-bis (4-hydroxy-3-tert-butylphenyl) butyric acid] glycol ester, bis [2-tert-butyl-4-methyl-6- (2 -Hydroxy-3-tert-butyl-5-methylbenzyl) phenyl] terephthalate, 1,3,5-tris [(3,5-ditert-butyl-4-hydroxyphenyl) propionyloxyethyl] isocyanurate, 3, 9-bis [1,1-dimethyl-2-{(3-tert-butyl-4-hydroxy-5-methylphenyl) propiyl Nyloxy} ethyl] -2,4,8,10-tetraoxaspiro [5,5] undecane, triethylene glycol bis [(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate] and the like. .

  Examples of the phosphorus antioxidant include trisnonylphenyl phosphite, tris [2-tert-butyl-4- (3-tert-butyl-4-hydroxy-5-methylphenylthio) -5-methylphenyl]. Phosphite, tridecyl phosphite, octyl diphenyl phosphite, di (decyl) monophenyl phosphite, di (tridecyl) pentaerythritol diphosphite, di (nonylphenyl) pentaerythritol diphosphite, bis (2,4-di Tert-butylphenyl) pentaerythritol diphosphite, bis (2,6-ditert-butyl-4-methylphenyl) pentaerythritol diphosphite, bis (2,4,6-tritert-butylphenyl) pentaerythritol diphosphite Phosphite, bis (2,4-dicumylphenyl) pen Erythritol diphosphite, tetra (tridecyl) isopropylidene diphenol diphosphite, tetra (tridecyl) -4,4′-n-butylidenebis (2-tert-butyl-5-methylphenol) diphosphite, hexa (tridecyl) -1 , 1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane triphosphite, tetrakis (2,4-ditert-butylphenyl) biphenylene diphosphonite, 9,10-dihydro-9 -Oxa-10-phosphaphenanthrene-10-oxide, 2,2'-methylenebis (4,6-tert-butylphenyl) -2-ethylhexyl phosphite, 2,2'-methylenebis (4,6- Tributylphenyl) -octadecyl phosphite, 2,2′-ethylidenebis (4 6-ditert-butylphenyl) fluorophosphite, tris (2-[(2,4,8,10-tetrakis tert-butyldibenzo [d, f] [1,3,2] dioxaphosphine-6 -Yl) oxy] ethyl) amine, phosphite of 2-ethyl-2-butylpropylene glycol and 2,4,6-tritert-butylphenol, and the like.

  Examples of the thioether-based antioxidant include dialkylthiodipropionates such as dilauryl thiodipropionate, dimyristyl thiodipropionate, and distearyl thiodipropionate, and pentaerythritol tetra (β-alkylmercaptopropionate esters). Is mentioned.

  Examples of the hindered amine compound include 2,2,6,6-tetramethyl-4-piperidyl stearate, 1,2,2,6,6-pentamethyl-4-piperidyl stearate, 2,2,6,6. -Tetramethyl-4-piperidylbenzoate, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1-octoxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, tetrakis (2,2,6,6-tetramethyl-4-piperidyl) -1,2,3,4-butanetetra Carboxylate, tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate, bis (2,2,6, 6-tetramethyl-4-piperidyl) di (tridecyl) -1,2,3,4-butanetetracarboxylate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) di (tridecyl) ) -1,2,3,4-butanetetracarboxylate, bis (1,2,2,4,4-pentamethyl-4-piperidyl) -2-butyl-2- (3,5-ditert-butyl- 4-hydroxybenzyl) malonate, 1- (2-hydroxyethyl) -2,2,6,6-tetramethyl-4-piperidinol / diethyl succinate polycondensate, 1,6-bis (2,2, 6,6-tetramethyl-4-piperidylamino) hexane / 2,4-dichloro-6-morpholino-s-triazine polycondensate, 1,6-bis (2,2,6,6-tetramethyl-4- Piperidylamino) hex 2,4-dichloro-6-tert-octylamino-s-triazine polycondensate, 1,5,8,12-tetrakis [2,4-bis (N-butyl-N- (2,2,6 , 6-tetramethyl-4-piperidyl) amino) -s-triazin-6-yl] -1,5,8,12-tetraazadodecane, 1,5,8,12-tetrakis [2,4-bis ( N-butyl-N- (1,2,2,6,6-pentamethyl-4-piperidyl) amino) -s-triazin-6-yl] -1,5,8-12-tetraazadodecane, 1,6 , 11-tris [2,4-bis (N-butyl-N- (2,2,6,6-tetramethyl-4-piperidyl) amino) -s-triazin-6-yl] aminoundecane, 1,6 , 11-tris [2,4-bis (N-butyl-N- (1,2,2,6 6-pentamethyl-4-piperidyl) amino) -s-triazin-6-yl] aminoundecanoic like.

  The non-aqueous electrolyte secondary battery of the present invention having the above-described configuration is not particularly limited in its shape, and can be a battery of various shapes such as a flat type (button type), a cylindrical type, and a square type. . Representative examples of the non-aqueous electrolyte secondary battery of the present invention include lithium secondary batteries using a negative electrode active material such as lithium or a lithium alloy or a material capable of inserting and extracting lithium ions, but are not limited thereto. It is also possible to adopt a configuration whose structure is appropriately changed within a range not impairing the effects of the present invention. FIG. 1 is a perspective view showing a cross section of the internal structure of an example of a non-aqueous electrolyte secondary battery of the present invention that is a cylindrical battery, and FIG. 2 is a non-aqueous electrolyte composition using the non-aqueous electrolyte composition of the present invention. It is the schematic which shows the basic composition of a water electrolyte secondary battery.

  A lithium secondary battery, which is the non-aqueous electrolyte secondary battery 10 shown in FIG. 2, includes a negative electrode 1 and a negative electrode current collector 2 each having at least lithium, a lithium alloy, or a substance capable of inserting and extracting lithium ions as an active material. The positive electrode terminal 7 and the negative electrode terminal 8 are included. In FIG. 2, 3 is a positive electrode, 4 is a positive electrode current collector, 5 is an electrolytic solution, and 6 is a separator. Further, in the cylindrical battery 10 shown in FIG. 1, 1 ′ is a negative electrode plate, 1 ″ is a negative electrode lead, 3 ′ is a positive electrode plate, 3 ″ is a positive electrode lead, 6 is a separator, 7 is a positive electrode terminal, and 8 is a non-polar terminal. , 11 is a case, 12 is an insulating plate, 13 is a gasket, 14 is a safety valve, and 15 is a PTC element. In addition, constituent materials other than those usually used for non-aqueous electrolytic secondary batteries can be used for the lithium secondary battery, if necessary.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples. Of the following Examples 1 and 2, Example 2 is an example of the present invention, and Example 1 is a reference example.

[Example 1 and Comparative Example 1]
A lithium secondary battery was produced according to the following procedure.

(Preparation of positive electrode)
85 parts by weight of the positive electrode active material LiNiO _2, 10 parts by weight of acetylene black as a conductive agent, and 5 parts by weight of polyvinylidene fluoride (PVDF) as a binder were mixed to obtain a positive electrode material. This positive electrode material was dispersed in N-methyl-2-pyrrolidone (NMP) to form a slurry. This slurry was applied to both sides of a positive electrode current collector made of aluminum, dried and press-molded to obtain a positive electrode plate. Then, this positive electrode plate was cut into a predetermined size, and a sheet-like positive electrode was produced by scraping off the electrode mixture at a portion that became a lead tab weld for extracting current.

(Preparation of negative electrode)
7.5 parts by weight of PVDF was mixed with 92.5 parts by weight of the carbon material powder to obtain a negative electrode material. This negative electrode material was dispersed in NMP to form a slurry. This slurry was applied to both sides of a copper negative electrode current collector, dried and press-molded to obtain a negative electrode plate. Then, this negative electrode plate was cut into a predetermined size, and a sheet-like negative electrode was produced by scraping off the electrode mixture at a portion to be a lead tab weld for extracting current.

(Preparation of non-aqueous electrolyte)
LiPF ₆ was dissolved at a concentration of 1.5 mol / liter in a mixed organic solvent having the composition (volume%) shown in Tables 1 and 2 to obtain a non-aqueous electrolyte. In Tables 1 and 2, EC represents ethylene carbonate, EMC represents ethyl methyl carbonate, DMC represents dimethyl carbonate, DEC represents diethyl carbonate, and PC represents propylene carbonate.

(Assembly of lithium secondary battery)
The sheet-like positive electrode and the sheet-like negative electrode obtained above were wound through a microporous polyethylene film having a thickness of 25 μm to form a wound electrode body. The obtained wound electrode body was inserted into the case and held in the case. At this time, the current collecting lead having one end welded to the lead tab weld portion of the sheet-like positive electrode and the sheet-like negative electrode was joined to the positive electrode terminal or the negative electrode terminal of the case. Thereafter, the non-aqueous electrolyte was injected into the case holding the wound electrode body, and the case was sealed and sealed. By the above procedure, a cylindrical lithium secondary battery having a diameter of 18 mm and an axial length of 65 mm was manufactured.

  The characteristics (initial output, output after 500 cycles, and discharge capacity retention after 500 cycles) of the manufactured lithium secondary battery were measured by the following measuring method. These measurements were performed at 20 ° C. and −30 ° C., respectively. The results are shown in Tables 1 and 2. However, the initial output indicated the measured value in Comparative Example 1-1 as 100.

(Initial output measurement method)
First, the battery was charged at a constant current at room temperature, and the state of charge (SOC) of the battery was adjusted to 60%. Then, the operating voltage range of the battery is set to a range from 4.1 V to 3 V, the discharge current of the battery is changed, each discharge is performed for 10 seconds, a current-voltage line at the 10th second is obtained, and the lower limit voltage is 3 V. The value of the output characteristic was calculated by multiplying the current value by the lower limit voltage of 3V.

(Output measurement method after 500 cycles)
A lithium secondary battery, placed in an ambient temperature 60 ° C. in a constant temperature bath, and constant current charging to 4.1V at a charging current 2.2 mA / cm ^2, a constant current discharge at a discharge current of 2.2 mA / cm ² to 3V The cycle to be performed was repeated 500 times. For this lithium secondary battery, the value of the output characteristic was calculated according to the above (initial output measurement method).

(Measurement method of discharge capacity maintenance rate after 500 cycles)
First, constant current and constant voltage charging was performed up to 4.1 V at a charging current of 0.25 mA / cm ² , and constant current discharging was performed up to 3.0 V at a discharging current of 0.33 mA / cm ² . Then, the charging current 1.1mA / cm ² with a constant current constant voltage charge to 4.1 V, after 4 times the constant current discharge at a discharge current of 1.1mA / cm ² to 3.0 V, charging current 1.1mA / cm ² with a constant current constant voltage charge to 4.1 V, the discharge current 0.33 mA / cm ² up to 3.0V constant current discharge, the discharge capacity at this time was a battery initial capacity. The initial battery capacity was measured in an atmosphere at 20 ° C.
A lithium secondary battery, placed in an ambient temperature 60 ° C. in a constant temperature bath, and constant current charging to 4.1V at a charging current 2.2 mA / cm ^2, a constant current discharge at a discharge current of 2.2 mA / cm ² to 3V The cycle to be performed was repeated 500 times. After that, the ambient temperature is set to the measurement temperature (20 ° C. or −30 ° C.), the charging current is 1.1 mA / cm ² and the constant current is constant voltage charging up to 4.1 V, and the discharging current is 0.33 mA / cm ² and the voltage is fixed to 3.0 V. The current was discharged, and the ratio of the discharge capacity to the initial battery capacity at this time was defined as the discharge capacity retention rate (%) after 500 cycles.

[Example 2 and Comparative Example 2]
A lithium secondary battery was produced in the same manner as in Example 1 except that the non-aqueous electrolyte was prepared as follows, and the characteristics of the lithium secondary battery were measured. The results are shown in Tables 3 and 4. However, the initial output indicated the measured value in Comparative Example 1-1 as 100.
(Preparation of non-aqueous electrolyte)
LiPF ₆ was added in an amount of 1.5 mol to the compound (added by volume) of 100 parts by weight of the mixed organic solvent shown in Tables 3 and 4 and the amount of the added sample compound shown in Tables 3 and 4 (parts by weight) was blended. A non-aqueous electrolyte was obtained by dissolving at a concentration of 1 liter.

  As is clear from the results in Tables 1 to 4 above, the non-aqueous electrolytes of the examples containing the specific cyclic carbonate compound and the chain carbonate compound of the present invention have battery characteristics at room temperature and low temperature after the cycle. It was confirmed that the battery characteristics were excellent, particularly at low temperatures. In comparison with this, it was confirmed that there was a problem in the low-temperature characteristics after the cycle when the non-aqueous electrolyte of the comparative example was used.

It is a perspective view which shows the internal structure of the lithium secondary battery (cylindrical type) as a nonaqueous electrolyte secondary battery of this invention as a cross section. It is the schematic which shows the basic composition of the lithium secondary battery as a nonaqueous secondary battery of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Negative electrode 1 'Negative electrode plate 1 "Negative electrode lead 2 Negative electrode collector 3 Positive electrode 3' Positive electrode plate 3" Positive electrode lead 4 Positive electrode collector 5 Electrolyte 6 Separator 7 Positive electrode terminal 8 Negative electrode terminal 10 Non-aqueous electrolyte secondary battery 11 Case 12 Insulating plate 13 Gasket 14 Safety valve 15 PTC element

Claims (14)

In a non-aqueous electrolyte composition obtained by dissolving an electrolyte salt in an organic solvent, the organic solvent contains 20 to 35% by volume of ethylene carbonate (a), 35 to 45% by volume of ethyl methyl carbonate (b), and dimethyl carbonate (c). A mixed organic solvent containing 15 to 35% by volume and diethyl carbonate or propylene carbonate (d) 3 to 15% by volume;
Furthermore, it contains at least one selected from the silicon compound represented by the following general formula (1) and the silicon compound represented by the following general formula (2), and the content of the silicon compound is the above mixed organic solvent 100. A non-aqueous electrolyte composition, which is 0.05 to 5 parts by mass with respect to parts by mass.
(Wherein, R ₁ to R ₆ are each shown to .n alkyl or alkenyl group having 2 to 8 carbon atoms having 1 to 12 carbon atoms independently indicates 1, X is a direct bond or oxygen showing the atom. However, exhibit at least two unsaturated bond-containing group of R ₁ ~ R _6.)
(In the formula, R ₇ represents an alkenyl group having 2 to 10 carbon atoms, R ₈ and R ₉ each independently represents an alkyl group having 1 to 10 carbon atoms, and X represents a halogen.)   The organic solvent is ethylene carbonate (a) 25-35% by volume, ethyl methyl carbonate (b) 35-45% by volume, dimethyl carbonate (c) 18-32% by volume, and diethyl carbonate or propylene carbonate (d) 3-3. The non-aqueous electrolyte composition according to claim 1, which is a mixed organic solvent containing 10 vol%.   The organic solvent is a mixed organic solvent comprising 30% by volume of ethylene carbonate (a), 40% by volume of ethyl methyl carbonate (b), 20% by volume of dimethyl carbonate (c) and 10% by volume of diethyl carbonate (d). 3. The non-aqueous electrolyte composition according to 1 or 2.   The organic solvent is a mixed organic solvent composed of 25% by volume of ethylene carbonate (a), 40% by volume of ethyl methyl carbonate (b), 30% by volume of dimethyl carbonate (c) and 5% by volume of diethyl carbonate (d). 3. The non-aqueous electrolyte composition according to 1 or 2.   The organic solvent is a mixed organic solvent composed of 25% by volume of ethylene carbonate (a), 40% by volume of ethyl methyl carbonate (b), 25% by volume of dimethyl carbonate (c) and 10% by volume of diethyl carbonate (d). 3. The non-aqueous electrolyte composition according to 1 or 2.   The organic solvent is a mixed organic solvent composed of 25% by volume of ethylene carbonate (a), 40% by volume of ethyl methyl carbonate (b), 30% by volume of dimethyl carbonate (c) and 5% by volume of propylene carbonate (d). 3. The non-aqueous electrolyte composition according to 1 or 2. The electrolyte _{salt, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiCF 3 SO 3, LiN derivative of (CF ₃ SO _{2) 2} and LiC (CF ₃ SO _{2) 3} and LiCF ₃ SO _3, LiN (CF ₃ SO _{2) 2} derivative, and LiC (CF ₃ SO _{2) 3} at least one kind of claim 1, 2 or 3 non-aqueous electrolyte composition according selected from the derivatives. The electrolyte _{salt, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiCF 3 SO 3, LiN derivative of (CF ₃ SO _{2) 2} and LiC (CF ₃ SO _{2) 3} and LiCF ₃ SO _3, LiN (CF ₃ SO _{2) 2} derivative, and LiC (CF ₃ SO _{2) 3} at least one kind of claim 1, 2 or 4 non-aqueous electrolyte composition according selected from the derivatives. The electrolyte _{salt, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiCF 3 SO 3, LiN derivative of (CF ₃ SO _{2) 2} and LiC (CF ₃ SO _{2) 3} and LiCF ₃ SO _3, LiN (CF ₃ SO _{2) 2} derivative, and LiC (CF ₃ SO ₂₎ at least one kind of claim 1, 2 or 5 non-aqueous electrolyte composition according selected from among ₃ derivatives. The electrolyte _{salt, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiCF 3 SO 3, LiN derivative of (CF ₃ SO _{2) 2} and LiC (CF ₃ SO _{2) 3} and LiCF ₃ SO _3, LiN (CF ₃ SO _{2) 2} derivative, and LiC (CF ₃ SO ₂₎ at least one kind of claim 1, 2 or 6 non-aqueous electrolyte composition according selected from among ₃ derivatives.   A non-aqueous electrolyte secondary battery having a non-aqueous electrolyte, a positive electrode, and a negative electrode, wherein the non-aqueous electrolyte composition according to claim 1, 2, 3, or 7 is used as the non-aqueous electrolyte. Non-aqueous electrolyte secondary battery.   A non-aqueous electrolyte secondary battery having a non-aqueous electrolyte, a positive electrode, and a negative electrode, wherein the non-aqueous electrolyte composition according to claim 1, 2, 4, or 8 is used as the non-aqueous electrolyte. Non-aqueous electrolyte secondary battery.   A non-aqueous electrolyte secondary battery having a non-aqueous electrolyte, a positive electrode, and a negative electrode, wherein the non-aqueous electrolyte composition according to claim 1, 2, 5, or 9 is used as the non-aqueous electrolyte. Non-aqueous electrolyte secondary battery.   A non-aqueous electrolyte secondary battery having a non-aqueous electrolyte, a positive electrode, and a negative electrode, wherein the non-aqueous electrolyte composition according to claim 1, 2, 6, or 10 is used as the non-aqueous electrolyte. Non-aqueous electrolyte secondary battery.