WO2016052542A1 - 非水系電解液及びそれを用いた非水系電解液二次電池 - Google Patents
非水系電解液及びそれを用いた非水系電解液二次電池 Download PDFInfo
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- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
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- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
- H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
- H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
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- H01M2300/0025—Organic electrolyte
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- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
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- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/134—Electrodes based on metals, Si or alloys
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Definitions
- the present invention relates to a non-aqueous electrolyte and a non-aqueous electrolyte secondary battery using the same.
- non-aqueous electrolyte batteries such as lithium ion secondary batteries having higher energy density than nickel / cadmium batteries and nickel / hydrogen batteries have attracted attention.
- an electrolyte such as LiPF 6 , LiBF 4 , LiN (CF 3 SO 2 ) 2 , LiCF 3 (CF 2 ) 3 SO 3 is used as a high dielectric constant such as ethylene carbonate or propylene carbonate.
- a typical example is a non-aqueous electrolyte solution dissolved in a mixed solvent of a solvent and a low-viscosity solvent such as dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate.
- the negative electrode active material of the lithium ion secondary battery a carbonaceous material that can mainly store and release lithium ions is used. Natural graphite, artificial graphite, amorphous carbon, and the like can be given as representative examples of the carbonaceous material. Furthermore, metal or alloy negative electrodes using silicon, tin, or the like as a negative electrode active material aiming at higher capacity are also known.
- the positive electrode active material a transition metal composite oxide capable of mainly occluding and releasing lithium ions is used as the positive electrode active material. Typical examples of the transition metal in the transition metal composite oxide include cobalt, nickel, manganese, iron and the like.
- the reactivity varies depending on the composition of the non-aqueous electrolyte, so that the battery characteristics vary greatly depending on the non-aqueous electrolyte.
- various studies have been made on non-aqueous solvents and electrolytes.
- Patent Document 1 in a lithium secondary battery including a positive electrode using a lithium transition metal oxide typified by lithium cobaltate as an active material, a negative electrode using graphite, and a nonaqueous electrolytic solution, malonic acid is contained in the electrolytic solution. Studies have been made to improve cycle characteristics by adding an ester compound.
- Patent Document 2 there is a study to increase the reduction resistance of the electrolytic solution by adding a malonic acid ester or a tricarboxylic acid ester compound in the electrolytic solution for the electric double layer capacitor, or a study to suppress the leakage current during constant voltage charging. Has been made.
- Patent Document 3 in a lithium secondary battery including a positive electrode using an amorphous material made of V 2 O 5 and P 2 O 5 as an active material, a negative electrode using metallic lithium, and a nonaqueous electrolytic solution, Studies have been made to improve cycle characteristics by adding a dicarboxylic acid compound therein.
- Patent Document 4 a lithium secondary battery including a positive electrode using a lithium transition metal oxide typified by lithium cobalt oxide as an active material, a negative electrode using artificial graphite, and a non-aqueous electrolyte is specified in the electrolyte. Studies have been made to improve the capacity retention after a high temperature cycle by adding the carboxylic acid ester compound.
- the battery is required to have all the performances such as high-temperature storage characteristics, energy density, output characteristics, life, high-speed charge / discharge characteristics, and low-temperature characteristics at a high level, but has not yet been achieved.
- durability performance such as high-temperature storage characteristics and performance such as capacity, resistance, and output characteristics
- conventional batteries have a good overall balance of all these performances. It is because there is a problem that it is difficult to make it.
- Patent Document 2 The electrolyte that is implemented or described in Patent Document 2 is only a quaternary ammonium salt, and the effect when using an alkali metal salt typified by a lithium salt as the electrolyte salt is not clarified at all. Moreover, the use of the invention is limited to electric double layer capacitors, and Patent Document 2 does not describe that the lithium secondary battery is used.
- the present invention has been made in view of the above-described problems. That is, the present invention provides a non-aqueous electrolyte solution that can improve the high-temperature storage characteristics and load characteristics in a non-aqueous electrolyte secondary battery with a good overall balance in terms of performance such as durability, capacity, resistance, and output characteristics.
- the purpose is to provide.
- Another object of the present invention is to provide a non-aqueous electrolyte battery using such a non-aqueous electrolyte.
- the gist of the present invention is as follows.
- a non-aqueous electrolyte solution for a non-aqueous electrolyte secondary battery comprising a positive electrode and a negative electrode capable of occluding and releasing metal ions, wherein the non-aqueous electrolyte solution together with the electrolyte and the non-aqueous solvent has the following general formula
- R 1 , R 2 and Y each independently represent a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent, and X represents hydrogen or a fluorine atom.
- R 1 , R 2 and Y may be the same or different.
- the amount of the compound represented by the general formula (A) is 0.001% by mass to 10% by mass with respect to the total amount of the non-aqueous electrolyte solution, and any one of (a) to (d) The non-aqueous electrolyte solution described in 1.
- the non-aqueous electrolyte further includes a cyclic carbonate having a carbon-carbon unsaturated bond, a cyclic carbonate having a fluorine atom, a nitrile compound, an isocyanate compound, a compound having an isocyanuric acid skeleton, a fluorinated salt, an acid anhydride (A) to (e) containing at least one additive selected from the group consisting of a physical compound, an acrylate compound, an aromatic compound, a cyclic ether compound, an oxalate salt and a cyclic sulfonate ester Non-aqueous electrolyte.
- a non-aqueous electrolyte secondary battery comprising a positive electrode and a negative electrode capable of inserting and extracting metal ions, and a non-aqueous electrolyte solution, wherein the non-aqueous electrolyte solution is any one of (a) to (g) A non-aqueous electrolyte secondary battery, which is the non-aqueous electrolyte solution described in 1.
- non-aqueous electrolyte secondary battery that is excellent in performance such as high-temperature storage characteristics and load characteristics and has a good balance of overall performance.
- non-aqueous electrolyte secondary battery produced using the non-aqueous electrolyte solution of the present invention is not clear in terms of the action and principle of a secondary battery with a good overall performance balance, it is considered as follows. .
- the present invention is not limited to the operations and principles described below.
- the compound represented by the general formula (A) has an active hydrogen atom or the like on a carbon atom ( ⁇ -position) sandwiched between carbonyl groups. This proton tautomerism of hydrogen gives rise to a tautomer of keto and enol. Further, the compound of the general formula (A) has not only a hydrogen atom but also a hydrocarbon group Y at the ⁇ -position. Since the hydrocarbon group has a higher electron donating property than the hydrogen atom, the acidity of the hydrogen atom is decreased.
- the above-mentioned hydrocarbon group Y is considered to affect not only the reactivity of the ⁇ -position hydrogen atom but also the equilibrium state of the keto body and the enol body.
- the reactivity is lower than that of a compound in which the ⁇ -position is not substituted with a hydrocarbon group
- the compound represented by the general formula (A) is slightly reduced on the negative electrode. This reduction generates a radical anion at the ⁇ -position, and this radical anion is considered to cause keto-enol tautomerism as well as a hydrogen atom. Since an electron-donating hydrocarbon group is bonded to the ⁇ -position, the radical anion at the ⁇ -position is not stable and the equilibrium is considered to be biased toward the enol side.
- the enol body Since the enol body has an anion on the oxygen atom of the carbonyl group, it is considered that the enol body interacts more strongly with the transition metal element of the positive electrode active material. Thereby, it is considered that the activity of the positive electrode surface is reduced, and the decomposition reaction of the nonaqueous electrolytic solution on the surface of the positive electrode active material is suppressed.
- Non-aqueous electrolyte 1-1 Nonaqueous Electrolytic Solution of the Present Invention
- the nonaqueous electrolytic solution of the present invention is characterized by containing a compound represented by the following general formula (A).
- R 1 , R 2 and Y each represent a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent, and X represents a hydrogen atom or a fluorine atom.
- R 1 , R 2 and Y may be the same or different.
- R 1 , R 2 and Y do not combine with each other to form a ring.
- examples of the substituent include a cyano group, an isocyanato group, an acyl group (— (C ⁇ O) —Ra), an acyloxy group (—O (C ⁇ O) —Ra), an alkoxycarbonyl group (— (C ⁇ O) O—Ra), sulfonyl group (—SO 2 —Ra), sulfonyloxy group (—O (SO 2 ) —Ra), alkoxysulfonyl group (— (SO 2 ) —O—Ra), alkoxycarbonyloxy group (—O— (C ⁇ O) —O—Ra), ether group (—O—Ra), acrylic group, methacryl group, halogen (preferably fluorine), trifluoromethyl group and the like can be mentioned.
- Ra represents an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an alkynyl group having 2 to 10 carbon atoms.
- the carbon in these substituents is not counted in the number of carbons in the hydrocarbon group having 1 to 12 carbon atoms of R 1 , R 2 and Y.
- R 1 , R 2 and Y each represent a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent.
- hydrocarbon group examples include an aryl group optionally via an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, or an alkylene group.
- an alkyl group, an alkenyl group, and an alkynyl group are preferable, an alkyl group and an alkenyl group are more preferable, and an alkyl group is particularly preferable.
- R 1 , R 2 and Y are the hydrocarbon groups described above, it is possible to prevent the compound represented by the general formula (A) from reacting with the decomposition product of the non-aqueous electrolyte and increasing the resistance of the electrode. It is done.
- alkyl group examples include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, s-butyl group, i-butyl group, t-butyl group, n-pentyl group, Examples thereof include t-amyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group and the like.
- an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, and a hexyl group are preferable, and an ethyl group, an n-propyl group, and an n-butyl group are more preferable.
- the alkyl group is particularly preferably an ethyl group or an n-butyl group.
- the alkyl group is particularly preferably an ethyl group or an n-butyl group, and most preferably an n-butyl group, from the same viewpoint.
- cycloalkyl group examples include a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantyl group, and the like, and a cyclohexyl group and an adamantyl group are preferable.
- alkenyl group examples include a vinyl group, an allyl group, a methallyl group, a 2-butenyl group, a 3-methyl-2-butenyl group, a 3-butenyl group, and a 4-pentenyl group.
- preferred are vinyl group, allyl group, methallyl group and 2-butenyl group, more preferred are vinyl group, allyl group and methallyl group, and particularly preferred are allyl group and methallyl group.
- An allyl group is preferred.
- the hydrocarbon group is such an alkenyl group, the steric hindrance is appropriate, and it can be adjusted to a suitable degree that the compound of the general formula (A) reacts on the electrode to increase the electrode resistance. is there.
- alkynyl group examples include ethynyl group, 2-propynyl group, 2-butynyl group, 3-butynyl group, 4-pentynyl group, 5-hexynyl group and the like.
- ethynyl group, 2-propynyl group, 2-butynyl group and 3-butynyl group are preferable, 2-propynyl group and 3-butynyl group are more preferable, and 2-propynyl group is particularly preferable.
- the hydrocarbon group is such an alkynyl group, the steric hindrance is appropriate, and it can be adjusted to a suitable extent that the compound of the general formula (A) reacts on the electrode to increase the electrode resistance. is there.
- X represents hydrogen or a fluorine atom. From the viewpoint of the reactivity of the non-aqueous electrolyte and the resistance of the film formed therefrom, X is preferably a hydrogen atom.
- the hydrocarbon group having 1 to 12 carbon atoms which is R 1 , R 2 or Y in the formula is preferably unsubstituted. .
- the reactivity of the compound represented by the general formula (A) on the electrode and the base component such as the reduction product of the nonaqueous electrolytic solution produced on the electrode is lowered.
- non-aqueous electrolyte secondary battery (hereinafter simply referred to as “non-aqueous electrolyte secondary battery” or “non-aqueous electrolyte solution of the present invention” obtained by using the non-aqueous electrolyte solution of the present invention due to a side reaction) Deterioration of the secondary battery may be suppressed.
- Y is preferably an unsubstituted hydrocarbon group.
- Specific examples of the compound represented by the general formula (A) used in the nonaqueous electrolytic solution of the present invention include compounds having the following structure.
- the compound represented by the general formula (A) is preferably a compound having the following structure.
- the compound represented by the general formula (A) is more preferably a compound having the following structure.
- the compound having the following structure is most preferable as represented by the general formula (A).
- the non-aqueous electrolyte solution of the present invention is characterized by containing the compound represented by the general formula (A), but the compound represented by the general formula (A) is not limited to one type, and may be a plurality of types. May be used in combination.
- the total amount of the non-aqueous electrolyte solution of the present invention (Ie, when the mass of the non-aqueous electrolyte is 100), it is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and still more preferably 0.00.
- the non-aqueous electrolyte solution of the present invention contains a carbon-carbon non-aqueous solution in addition to the compound represented by the general formula (A).
- Cyclic carbonate having saturated bond cyclic carbonate having fluorine atom, cyclic carbonate having fluorine atom, nitrile compound, isocyanate compound, compound having isocyanuric acid skeleton, fluorinated salt, acid anhydride compound, acrylate compound, aromatic Compounds, cyclic ether compounds
- a cyclic carbonate having a carbon-carbon unsaturated bond a cyclic carbonate having a fluorine atom, a nitrile compound, and a compound having an isocyanuric acid skeleton are more preferable, and a cyclic carbonate having a carbon-carbon unsaturated bond is preferred. More preferred are carbonates, cyclic carbonates having fluorine atoms, and compounds having an isocyanuric acid skeleton, cyclic carbonates having a carbon-carbon unsaturated bond, cyclic carbonates having fluorine atoms are particularly preferred, and cyclic carbonates having fluorine atoms are most preferred.
- the compound represented by the general formula (A) and the specific additive undergo a reduction reaction on the active material of the electrode to form an anion (nucleophilic species) in the structure. Moreover, since these have a nucleophilic attack accepting site in the molecular structure, they are complex by the compound represented by the general formula (A), the reduction product of the specific additive, and the reduction product of the nonaqueous solvent. It is considered that a thick film is formed.
- these specific additives and the compound represented by the general formula (A) are co-added to the nonaqueous electrolytic solution to react with each other on the active material to form a composite film. For this reason, since the reaction of the non-aqueous electrolyte on the surface of the active material is further suppressed than when each compound is added alone, the battery characteristics are improved.
- the specific additives will be described individually.
- Cyclic carbonate having carbon-carbon unsaturated bond includes a carbon-carbon double bond or a carbon-carbon triple bond. There is no particular limitation as long as it is a cyclic carbonate having a bond. Any unsaturated carbonate can be used as the unsaturated cyclic carbonate.
- the cyclic carbonate having an aromatic ring is also included in the unsaturated cyclic carbonate.
- the unsaturated cyclic carbonate may have a fluorine atom (also referred to as a fluorinated unsaturated carbonate). In that case, the fluorine atom is usually 6 or less, preferably 4 or less, and 1 or 2 Most preferably it is.
- unsaturated cyclic carbonates examples include vinylene carbonates, aromatic carbonates, ethylene carbonates substituted with a substituent having a carbon-carbon double bond or carbon-carbon triple bond, phenyl carbonates, vinyl carbonates, allyl carbonates, Catechol carbonates etc. are mentioned.
- vinylene carbonates Vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, phenyl vinylene carbonate, 4,5-diphenyl vinylene carbonate, vinyl vinylene carbonate, 4,5-divinyl vinylene carbonate, allyl vinylene carbonate, 4,5-diallyl vinylene carbonate 4-fluoro vinylene carbonate, 4-fluoro-5-methyl vinylene carbonate, 4-fluoro-5-phenyl vinylene carbonate, 4-fluoro-5-vinyl vinylene carbonate, 4-allyl-5-fluoro vinylene carbonate, etc. .
- ethylene carbonates substituted with a substituent having the aromatic ring or carbon-carbon double bond or carbon-carbon triple bond include: Vinylethylene carbonate, 4,5-divinylethylene carbonate, 4-methyl-5-vinylethylene carbonate, 4-allyl-5-vinylethylene carbonate, ethynylethylene carbonate, 4,5-diethynylethylene carbonate, 4-methyl-5 -Ethynylethylene carbonate, 4-vinyl-5-ethynylethylene carbonate, 4-allyl-5-ethynylethylene carbonate, phenylethylene carbonate, 4,5-diphenylethylene carbonate, 4-phenyl-5-vinylethylene carbonate, 4-allyl -5-phenylethylene carbonate, allylethylene carbonate, 4,5-diallylethylene carbonate, 4-methyl-5-allylethylene carbonate, 4-fluoro-4-vinylethylene -Bonate, 4-fluoro-4-allylethylene carbonate, 4-fluoro-5-vinylethylene carbonate, 4-flu
- preferred unsaturated cyclic carbonates are: Vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, vinyl vinylene carbonate, 4,5-vinyl vinylene carbonate, allyl vinylene carbonate, 4,5-diallyl vinylene carbonate, vinyl ethylene carbonate, 4,5-divinyl ethylene carbonate 4-methyl-5-vinylethylene carbonate, allylethylene carbonate, 4,5-diallylethylene carbonate, 4-methyl-5-allylethylene carbonate, 4-allyl-5-vinylethylene carbonate, ethynylethylene carbonate, 4,5 -Diethynyl ethylene carbonate, 4-methyl-5-ethynyl ethylene carbonate, 4-vinyl-5-ethynyl ethylene carbonate, 4-fluorovinylene carbonate Bonate, 4-fluoro-5-methyl vinylene carbonate, 4-fluoro-5-vinyl vinylene carbonate, 4-allyl-5-fluorovinylene carbon
- Vinylene carbonate, vinyl ethylene carbonate, and ethynyl ethylene carbonate are particularly preferable because they form a particularly stable interface protective film.
- the molecular weight of the unsaturated cyclic carbonate is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired.
- the molecular weight is preferably 80 or more and 250 or less. If it is this range, it will be easy to ensure the solubility of the unsaturated cyclic carbonate with respect to a non-aqueous electrolyte solution, and the effect of this invention will fully be expressed easily.
- the molecular weight of the unsaturated cyclic carbonate is more preferably 85 or more, and more preferably 150 or less.
- the production method of the unsaturated cyclic carbonate described above is not particularly limited, and can be produced by arbitrarily selecting a known method.
- the unsaturated cyclic carbonate may be used alone or in combination of two or more in any combination and ratio.
- the compounding quantity of unsaturated cyclic carbonate is not restrict
- the blending amount is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and further preferably 0.5% by mass or more in 100% by mass of the non-aqueous electrolyte solution. Particularly preferably, it is 1% by mass or more, and is usually 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less. Within this range, the non-aqueous electrolyte secondary battery is likely to exhibit a sufficient cycle characteristics improvement effect, and the high temperature storage characteristics are reduced, the amount of gas generation is increased, and the discharge capacity maintenance rate is reduced. Easy to avoid the situation.
- Cyclic carbonate having a fluorine atom examples of the cyclic carbonate having a fluorine atom as a specific additive include a fluorinated product of a cyclic carbonate having an alkylene group having 2 to 6 carbon atoms, and derivatives thereof. Examples thereof include fluorinated ethylene carbonate and derivatives thereof. Examples of the derivatives of fluorinated ethylene carbonate include fluorinated ethylene carbonate substituted with an alkyl group (eg, an alkyl group having 1 to 4 carbon atoms). As the cyclic carbonate having a fluorine atom, ethylene carbonate having 1 to 8 fluorine atoms and derivatives thereof are preferable. Regarding the cyclic carbonate having a fluorine atom and an unsaturated bond, the above-mentioned 1-2-1. It is described in.
- At least one selected from the group consisting of monofluoroethylene carbonate, 4,4-difluoroethylene carbonate, and 4,5-difluoroethylene carbonate gives high ionic conductivity, and suitably forms an interface protective film. This is more preferable.
- the cyclic carbonate having a fluorine atom may be used alone or in combination of two or more in any combination and ratio.
- the amount of the cyclic carbonate having a fluorine atom with respect to the entire non-aqueous electrolyte of the present invention is not limited, and is arbitrary as long as the effects of the present invention are not significantly impaired.
- the blending amount is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and further preferably 0.5% by mass or more in 100% by mass of the non-aqueous electrolyte solution. Particularly preferably, it is 1% by mass or more, and is usually 10% by mass or less, preferably 7% by mass or less, more preferably 5% by mass or less, and further preferably 3% by mass or less.
- monofluoroethylene carbonate may be used as a solvent, and in that case, the content is not limited to the above.
- Nitrile compound As the specific additive is not particularly limited as long as it is a compound having a cyano group in the molecule.
- nitrile compounds include, for example, Acetonitrile, propionitrile, butyronitrile, isobutyronitrile, valeronitrile, isovaleronitrile, decane nitrile, lauronitrile, 2-methylbutyronitrile, trimethylacetonitrile, hexanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, acrylonitrile, Methacrylonitrile, crotononitrile, 3-methylcrotononitrile, 2-methyl-2-butenenitryl, 2-pentenenitrile, 2-methyl-2-pentenenitrile, 3-methyl-2-pentenenitrile, 2- Hexenenitrile, fluoroacetonitrile, difluoroacetonitrile, trifluoroacetonitrile, 2-fluoropropionitrile, 3-fluoropropionitrile, 2,2-difluoropropionitri 2,3-difluoropropionitrile
- a nitrile compound may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio. There is no restriction
- the blending amount is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and usually 10% by mass or less, in 100% by mass of the nonaqueous electrolytic solution. Preferably, it is 5 mass% or less, More preferably, it is 3 mass% or less, More preferably, it is 2 mass% or less, Most preferably, it is 1 mass% or less. When the above range is satisfied, effects such as output characteristics, load characteristics, low temperature characteristics, cycle characteristics, and high temperature storage characteristics of the nonaqueous electrolyte secondary battery are further improved.
- the isocyanate compound as a specific additive is not particularly limited as long as it is a compound having an isocyanate group in the molecule.
- isocyanate compound examples include, for example, Hydrocarbon monoisocyanate compounds such as methyl isocyanate, ethyl isocyanate, propyl isocyanate, isopropyl isocyanate, butyl isocyanate, tertiary butyl isocyanate, pentyl isocyanate, hexyl isocyanate, cyclohexyl isocyanate, phenyl isocyanate and fluorophenyl isocyanate; Monoisocyanate compounds having a carbon-carbon unsaturated bond, such as vinyl isocyanate, allyl isocyanate, ethynyl isocyanate, propynyl isocyanate; Monomethylene diisocyanate, dimethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, heptamethylene diisocyanate,
- monoisocyanate compounds having a carbon-carbon unsaturated bond such as vinyl isocyanate, allyl isocyanate, ethynyl isocyanate, propynyl isocyanate; Monomethylene diisocyanate, dimethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, heptamethylene diisocyanate, octamethylene diisocyanate, nonamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, 1,3-bis ( Isocyanatomethyl) cyclohexane, dicyclohexylmethane-4,4′-diisocyanate, bicyclo [2.2.1] heptane-2,5-diylbis (methylisocyanate), bicyclo [2.2.1] heptane-2,6-
- allyl isocyanate hexamethylene diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, diisocyanatosulfone, (ortho-, meta-, para-) toluenesulfonyl isocyanate, and particularly preferred is hexamethylene.
- the isocyanate compound which has a branched chain is preferable.
- the isocyanate compound used in the present invention may be a trimer compound derived from a compound having at least two isocyanate groups in the molecule, or an aliphatic polyisocyanate obtained by adding a polyhydric alcohol thereto.
- aliphatic polyisocyanates include biurets, isocyanurates, adducts, and bifunctional types of modified polysiloxanes represented by the basic structures of the following general formulas (1-2-1) to (1-2-4). Examples thereof include isocyanate and the like (in the following general formulas (1-2-1) to (1-2-4), R and R ′ are each independently any hydrocarbon group).
- compounds having at least two isocyanate groups in the molecule include so-called blocked isocyanates that have been blocked with a blocking agent to enhance storage stability.
- the blocking agent include alcohols, phenols, organic amines, oximes, and lactams. Specific examples thereof include n-butanol, phenol, tributylamine, diethylethanolamine, methyl ethyl ketoxime, ⁇ -caprolactam and the like can be mentioned.
- a metal catalyst such as dibutyltin dilaurate or the like, 1,8-diazabicyclo [5.4.0] undecene It is also preferable to use an amine catalyst such as -7 in combination.
- the isocyanate compounds described above may be used singly or in combination of two or more in any combination and ratio.
- the amount of the isocyanate compound added to the entire non-aqueous electrolyte of the present invention is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and usually 10% by mass or less with respect to the non-aqueous electrolyte solution of the present invention.
- the amount is preferably 5% by mass or less, more preferably 3% by mass or less, further preferably 2% by mass or less, particularly preferably 1% by mass or less, and most preferably 0.5% by mass or less.
- the output characteristics, load characteristics, low temperature characteristics, cycle characteristics, high temperature storage characteristics, etc. of the nonaqueous electrolyte secondary battery are further improved.
- R 1 to R 3 may be the same or different from each other, and may be an organic group having 1 to 20 carbon atoms that may have a substituent. However, at least one of R 1 to R 3 has a carbon-carbon unsaturated bond or a cyano group.
- R 1 to R 3 may be the same or different from each other, and may be an organic group having 1 to 10 carbon atoms which may have a substituent. More preferably, in formula (U), at least one of R 1 to R 3 is an organic group having a carbon-carbon unsaturated bond.
- the organic group represents a functional group composed of an atom selected from the group consisting of a carbon atom, a hydrogen atom, a nitrogen atom, an oxygen atom, a silicon atom, a sulfur atom and a halogen atom.
- organic group which may have a substituent examples include alkyl groups having 1 to 20 carbon atoms, alkenyl groups, alkynyl groups, aryl groups, cyano groups, acryl groups, methacryl groups, vinylsulfonyl groups, vinylsulfo groups. Etc.
- substituent herein examples include a halogen atom and an alkylene group.
- an unsaturated bond or the like may be included in a part of the alkylene group.
- halogen atoms a fluorine atom is preferred.
- Examples thereof include a linear or branched alkyl group, and a cyclic alkyl group such as a cyclopropyl group, a cyclopentyl group, and a cyclohexyl group.
- alkynyl group which may have a substituent include ethynyl group, propargyl group, 1-propynyl group and the like.
- the substituent which may have a substituent described above is an alkyl group, an alkenyl group, an alkynyl group, an acrylic group, a methacryl group or a cyano group which may have a substituent.
- an alkyl group an alkenyl group, an acrylic group, a methacryl group, and a cyano group, which may have a substituent.
- allyl group is preferable from the viewpoint of film forming ability.
- the blending amount is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and usually 10% by mass with respect to the whole non-aqueous electrolyte solution of the present invention.
- it is preferably 5% by mass or less, more preferably 3% by mass or less, further preferably 2% by mass or less, particularly preferably 1% by mass or less, and most preferably 0.5% by mass or less.
- Fluorinated salt There are no particular restrictions on the fluorinated salt that is a specific additive, but it has a highly detachable fluorine atom in the structure, so it is represented, for example, by the general formula (A) Difluorophosphates, fluorosulfonates, fluoroboron salts, and fluoroimide salts are preferred because the compounds can react suitably with anions (nucleophilic species) that are generated through a reduction reaction to form a composite film.
- a fluoroboron salt and a fluorosulfonate are more preferable because the fluorine atom leaving property is particularly high and the reaction with the nucleophilic species suitably proceeds.
- these various salts will be described.
- the counter cation of the difluorophosphate is not particularly limited, but lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, barium, and NR 13 R 14 R 15 R 16 (wherein R 13 to R 16 independently and ammonium represented by.) representing an organic group of a hydrogen atom or a C 1-12 is mentioned as an example.
- the organic group having 1 to 12 carbon atoms represented by R 13 to R 16 of ammonium is not particularly limited.
- the organic group may be substituted with a halogen atom, a halogen atom or an alkyl group.
- examples thereof include an cycloalkyl group which may be substituted, an aryl group which may be substituted with a halogen atom or an alkyl group, and a nitrogen atom-containing heterocyclic group which may have a substituent.
- R 13 to R 16 are preferably each independently a hydrogen atom, an alkyl group, a cycloalkyl group, or a nitrogen atom-containing heterocyclic group.
- difluorophosphate examples include lithium difluorophosphate, sodium difluorophosphate, and potassium difluorophosphate, and lithium difluorophosphate is preferred.
- Difluorophosphate may be used alone or in combination of two or more in any combination and ratio. Moreover, the compounding quantity of a difluorophosphate is not restrict
- the blending amount of difluorophosphate is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and usually 10% by mass in 100% by mass of the non-aqueous electrolyte. % Or less, preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 2% by mass or less, and most preferably 1% by mass or less.
- the non-aqueous electrolyte secondary battery is likely to exhibit a sufficient cycle characteristics improvement effect, and the high temperature storage characteristics are reduced, the amount of gas generation is increased, and the discharge capacity maintenance rate is reduced. Easy to avoid the situation.
- the counter cation of the fluorosulfonate is not particularly limited, but lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, barium, and NR 13 R 14 R 15 R 16 (wherein R 13 to R 16 independently and ammonium represented by.) representing an organic group of a hydrogen atom or a C 1-12 is mentioned as an example.
- the organic group having 1 to 12 carbon atoms represented by R 13 to R 16 of ammonium is not particularly limited.
- the organic group may be substituted with a halogen atom, a halogen atom or an alkyl group.
- examples thereof include an cycloalkyl group which may be substituted, an aryl group which may be substituted with a halogen atom or an alkyl group, and a nitrogen atom-containing heterocyclic group which may have a substituent.
- R 13 to R 16 are preferably each independently a hydrogen atom, an alkyl group, a cycloalkyl group, or a nitrogen atom-containing heterocyclic group.
- fluorosulfonate examples thereof include lithium fluorosulfonate, sodium fluorosulfonate, potassium fluorosulfonate, rubidium fluorosulfonate, cesium fluorosulfonate, and the like, and lithium fluorosulfonate is preferable.
- Fluorosulfonates may be used alone or in combination of two or more in any combination and ratio. Moreover, the compounding quantity of a fluorosulfonate is not restrict
- the blending amount of the fluorosulfonate is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and usually 10% by mass in 100% by mass of the non-aqueous electrolyte. % Or less, preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 2% by mass or less, and most preferably 1% by mass or less.
- the non-aqueous electrolyte secondary battery is likely to exhibit a sufficient cycle characteristics improvement effect, and the high temperature storage characteristics are reduced, the amount of gas generation is increased, and the discharge capacity maintenance rate is reduced. Easy to avoid the situation.
- fluoro boron salt The counter cation of the fluoroboron salt is not particularly limited, but lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, barium, and NR 13 R 14 R 15 R 16 (wherein R 13 to R 16 Each independently represents a hydrogen atom or an organic group having 1 to 12 carbon atoms).
- the organic group having 1 to 12 carbon atoms represented by R 13 to R 16 of ammonium is not particularly limited.
- the organic group may be substituted with a halogen atom, a halogen atom or an alkyl group.
- examples thereof include an cycloalkyl group which may be substituted, an aryl group which may be substituted with a halogen atom or an alkyl group, and a nitrogen atom-containing heterocyclic group which may have a substituent.
- R 13 to R 16 are preferably each independently a hydrogen atom, an alkyl group, a cycloalkyl group, or a nitrogen atom-containing heterocyclic group.
- fluoroboron salts include LiBF 4 , LiB (C i F 2i + 1 ) j (F) 4-j and the like can be mentioned, and LiBF 4 is preferable. Note that i represents an integer of 1 to 10, and j represents an integer of 1 to 4.
- One fluoroboron salt may be used alone, or two or more fluoroboron salts may be used in any combination and ratio.
- the compounding quantity of a fluoro boron salt is not restrict
- the blending amount of the fluoroboron salt is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and usually 3% by mass in 100% by mass of the non-aqueous electrolyte.
- it is preferably 1% by mass or less, more preferably 0.8% by mass or less, further preferably 0.5% by mass or less, and most preferably 0.3% by mass or less.
- the non-aqueous electrolyte secondary battery is likely to exhibit a sufficient cycle characteristics improvement effect, and the high temperature storage characteristics are reduced, the amount of gas generation is increased, and the discharge capacity maintenance rate is reduced. Easy to avoid the situation.
- the counter cation of the fluoroimide salt is not particularly limited, but lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, barium, and NR 13 R 14 R 15 R 16 (wherein R 13 to R 16 Each independently represents a hydrogen atom or an organic group having 1 to 12 carbon atoms).
- the organic group having 1 to 12 carbon atoms represented by R 13 to R 16 of ammonium is not particularly limited.
- the organic group may be substituted with a halogen atom, a halogen atom or an alkyl group.
- examples thereof include an cycloalkyl group which may be substituted, an aryl group which may be substituted with a halogen atom or an alkyl group, and a nitrogen atom-containing heterocyclic group which may have a substituent.
- R 13 to R 16 are preferably each independently a hydrogen atom, an alkyl group, a cycloalkyl group, or a nitrogen atom-containing heterocyclic group.
- LiN (FCO) 2 LiN (FCO) (FSO 2 ), LiN (FSO 2 ) 2 , LiN (FSO 2 ) (CF 3 SO 2 ), LiN (CF 3 SO 2 ) 2 , LiN (C 2 F 5 SO 2 ) 2 , lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropane disulfonylimide, LiN (CF 3 SO 2 ) (C 4 F 9 SO 2 ), and LiN (FSO 2 ) 2 , LiN (CF 3 SO 2 ) 2 , and LiN (C 2 F 5 SO 2 ) 2 are preferable.
- Fluoroimide salts may be used alone or in combination of two or more in any combination and ratio. Moreover, the compounding quantity of a fluoroimide salt is not restrict
- the blending amount of the fluoroimide salt is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and usually 10% by mass in 100% by mass of the non-aqueous electrolyte.
- it is preferably 5% by mass or less, more preferably 3% by mass or less, further preferably 2% by mass or less, and most preferably 1% by mass or less.
- the non-aqueous electrolyte secondary battery is likely to exhibit a sufficient cycle characteristics improvement effect, and the high temperature storage characteristics are reduced, the amount of gas generation is increased, and the discharge capacity maintenance rate is reduced. Easy to avoid the situation.
- Acid anhydride compound The structure of the acid anhydride compound is not particularly limited.
- acid anhydride compounds include carboxylic acid anhydrides, sulfuric acid anhydrides, nitric acid anhydrides, sulfonic acid anhydrides, phosphoric acid anhydrides, phosphorous acid anhydrides, cyclic acid anhydrides, chain acid anhydrides, and the like. Can be mentioned.
- the acid anhydride compound include, for example, Malonic anhydride, succinic anhydride, glutaric anhydride, adipic anhydride, maleic anhydride, citraconic anhydride, 2,3-dimethylmaleic anhydride, glutaconic anhydride, itaconic anhydride, phthalic anhydride, phenylmaleic anhydride 2,3-diphenylmaleic anhydride, cyclohexane-1,2-dicarboxylic anhydride, 4-cyclohexene-1,2-dicarboxylic anhydride, 3,4,5,6-tetrahydrophthalic anhydride, 4 , 4'-oxydiphthalic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, methyl-5-norbornene-2,3-dicarboxylic anhydride, phenylsuccinic anhydride, 2-phenylglutaric anhydride Allyl succinic anhydride, 2-
- Succinic anhydride maleic anhydride, citraconic anhydride, phenylmaleic anhydride, bicyclo [2.2.2] oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 5- (2 , 5-dioxotetrahydrofuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, allyl succinic anhydride, acetic anhydride, methacrylic anhydride, acrylic anhydride, methanesulfonic anhydride preferable.
- An acid anhydride compound may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
- the amount of the acid anhydride compound with respect to the entire non-aqueous electrolyte solution of the present invention is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired.
- the blending amount is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and usually 10% by mass with respect to the whole non-aqueous electrolyte solution of the present invention.
- it is preferably 5% by mass or less, more preferably 3% by mass or less, further preferably 2% by mass or less, particularly preferably 1% by mass or less, and most preferably 0.5% by mass or less.
- the output characteristics, load characteristics, cycle characteristics, high temperature storage characteristics, etc. of the non-aqueous electrolyte secondary battery are further improved.
- acrylate compound is represented by the following general formula (1).
- R 21 to R 23 may be the same or different and each represents hydrogen or a hydrocarbon group having 1 to 6 carbon atoms.
- N represents an integer of 4 to 8.
- A represents carbon.
- It represents an organic group optionally having a heteroelement of 1 to 12.
- R 21 to R 23 may be the same or different and each represents hydrogen or a hydrocarbon group having 1 to 6 carbon atoms.
- the said hydrocarbon group represents the functional group comprised by the atom chosen from the group which consists of a carbon atom and a hydrogen atom.
- R 21 to R 23 are hydrogen or a hydrocarbon group having 1 to 6 carbon atoms, preferably a hydrocarbon group having 4 or less carbon atoms, more preferably a hydrocarbon group having 2 or less carbon atoms. If it is the range, there is little steric hindrance and the film can be stabilized.
- Preferred hydrocarbon groups include hydrogen group, methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group and t-butyl group.
- A is an organic group which may have a heteroelement having 1 to 12 carbon atoms, and the organic group is composed of atoms selected from the group consisting of carbon atoms and hydrogen atoms.
- An organic group that represents a functional group and may have a hetero element is selected from the group consisting of a carbon atom, a hydrogen atom, a nitrogen atom, a phosphorus atom, a boron atom, a sulfur atom, a silicon atom, and an oxygen atom.
- organic group which may have a heteroelement having 1 to 12 carbon atoms represented by A include an alkylene group or a derivative thereof, an alkenylene group or a derivative thereof, a cycloalkylene group or a derivative thereof, an alkynylene group or a derivative thereof Derivatives, cycloalkenylene groups or derivatives thereof, arylene groups or derivatives thereof, carbonyl groups or derivatives thereof, sulfonyl groups or derivatives thereof, sulfinyl groups or derivatives thereof, phosphonyl groups or derivatives thereof, phosphinyl groups or derivatives thereof, amino groups or derivatives thereof Amide group or derivative thereof, imide group or derivative thereof, ether group or derivative thereof, thioether group or derivative thereof, borinic acid group or derivative thereof, borane group or derivative thereof, and the like.
- a derivative represents a functional group substituted with a halogen atom, an alkyl group, an aryl group, an alkenyl group
- an alkylene group or a derivative thereof, an alkenylene group or a derivative thereof, an arylene group or a derivative thereof, an ether group or a derivative thereof is preferable.
- the carbon number of A is 1 or more, preferably 4 or more, and more preferably 5 or more.
- the said carbon number is 12 or less, 11 or less are preferable and 10 or less are more preferable. Within this range, an increase in resistance can be suppressed while maintaining the oxidation resistance of the electrode.
- the lower limit of n is 4, while the upper limit is 8, preferably 7, and more preferably 6.
- a stable negative electrode SEI Solid-electrolyte-interface
- Preferred specific examples of the acrylate compound described above include the following compounds.
- An acrylate compound (a compound represented by the general formula (1)) may be used alone or in combination of two or more in any combination and ratio.
- the blending amount is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and usually 5% by mass with respect to the whole non-aqueous electrolyte solution of the present invention.
- it is preferably 4% by mass or less, more preferably 2% by mass or less.
- Aromatic Compound is an aromatic compound having at least one substituent represented by the following general formula (*).
- the substituent T represents a halogen atom, or an organic group which may have a halogen atom or a hetero atom.
- the organic group which may have a hetero atom is a linear, branched or cyclic saturated hydrocarbon group having 3 to 12 carbon atoms, a group having a carboxylic ester structure, a group having a carbonate structure, or a phosphorus-containing group. Represents a sulfur-containing group and a silicon-containing group.
- each substituent T may be further substituted with a halogen atom, a hydrocarbon group, an aromatic group, a halogen-containing hydrocarbon group, a halogen-containing aromatic group or the like.
- the number of substituents T is 1 or more and 6 or less, and when there are a plurality of substituents, each substituent may be the same or different, and a plurality of substituents are bonded to form a ring. May be. )
- a linear, branched or cyclic saturated hydrocarbon group having 3 to 12 carbon atoms, a group having a carboxylic ester structure, and a group having a carbonate structure are preferable from the viewpoint of battery characteristics. More preferred are a linear, branched or cyclic saturated hydrocarbon group having 3 to 12 carbon atoms and a group having a carbonate structure.
- the substituent T represents a halogen atom, or an organic group that may have a halogen atom or a hetero atom.
- the halogen atom include chlorine, fluorine and the like, preferably fluorine.
- Examples of the organic group having no hetero atom include linear, branched and cyclic saturated hydrocarbon groups having 3 to 12 carbon atoms.
- the linear and branched ones include those having a ring structure. It is.
- Specific examples of the linear, branched or cyclic saturated hydrocarbon group having 3 to 12 carbon atoms include propyl group, isopropyl group, butyl group, isobutyl group, tertiary butyl group, pentyl group, tertiary pentyl group, A cyclopentyl group, a cyclohexyl group, a butylcyclohexyl group, etc. are mentioned.
- the number of carbon atoms of the organic group having no hetero atom is preferably 3 or more and 12 or less, more preferably 3 or more and 10 or less, still more preferably 3 or more and 8 or less, still more preferably 3 or more and 6 or less, and most preferably 3 or more and 5 or less. It is as follows.
- Examples of the hetero atom constituting the organic group having a hetero atom include an oxygen atom, a sulfur atom, a phosphorus atom, and a silicon atom.
- Examples of the group having an oxygen atom include a group having a carboxylic ester structure and a group having a carbonate structure.
- Examples of those having a sulfur atom include groups having a sulfonate structure.
- Examples of those having a phosphorus atom include a group having a phosphate ester structure, a group having a phosphonate ester structure, and the like.
- Examples of the group having a silicon atom include a group having a silicon-carbon structure.
- Examples of the aromatic compound represented by the general formula (*) include the following specific examples.
- T being a halogen atom or an organic group which may have a halogen atom, chlorobenzene, fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, benzotrifluoride, etc.
- examples of the hydrocarbon group having 3 to 12 carbon atoms include 2,2-diphenylpropane, 1,4-diphenylcyclohexane, cyclopentylbenzene, cyclohexylbenzene, cis-1-propyl-4-phenylcyclohexane, trans -1-propyl-4-phenylcyclohexane, cis-1-butyl-4-phenylcyclohexane, trans-1-butyl-4-phenylcyclohexane, 2,2-diphenylbutane, 1,1-diphenylcyclohexane, 1,1- Diphenyl-4-methylcyclohexane, 2,2-di- (p-fluorophenyl) propane, 1,1-di- (p-fluorophenyl) cyclohexane, 2,2-bis- (4-tertiarybutylphenyl) propane 1,3-bis (1-methyl-1-phenyl
- Examples of the group having a carboxylate structure with respect to the substituent T include phenyl acetate, benzyl acetate, 2-phenylethyl acetate, 3-phenylpropyl acetate, 3-phenylpropyl propionate, methyl benzoate, methyl phenylacetate, ⁇ , ⁇ , Dimethyl-phenylacetate methyl, 1-phenyl-cyclopentanoic acid methylphenylacetate, phenylpropionate methyl, phenylbutyrate methyl, phenylphenylvalerate, phenylphenylacetate, ethyl phenylpropionate, phenylphenylbutyrate, phenylyoshi Ethyl herbate, phenyl phenylacetate, phenyl phenylacetate, 2-phenylethyl phenylacetate, phenyl phenylpropionate, benzyl phenylpropionate, 2-phen
- Examples of the group having a carbonate structure with respect to the substituent T include carbonate bodies of bisphenol A, carbonate bodies of bisphenol Z, diphenyl carbonate, methylphenyl carbonate, 2-t-butylphenylmethyl carbonate, 4-t-butylphenylmethyl carbonate.
- Etc Preferably, the carbonate body of bisphenol A, the carbonate body of bisphenol Z, diphenyl carbonate, methylphenyl carbonate, More preferred are diphenyl carbonate and methylphenyl carbonate, More preferred is methylphenyl carbonate.
- Examples of the group having a sulfonate structure with respect to the substituent T include methyl phenyl sulfonate, ethyl phenyl sulfonate, diphenyl sulfonate, 2-t-butylphenyl methyl sulfonate, 4-t-butylphenyl methyl sulfonate, cyclohexyl phenyl methyl sulfonate, and the like.
- methyl phenyl sulfonate, diphenyl sulfonate, 2-t-butylphenyl methyl sulfonate, 4-t-butylphenyl methyl sulfonate, cyclohexyl phenyl methyl sulfonate More preferred are methylphenylsulfonate, 2-t-butylphenylmethylsulfonate, 4-t-butylphenylmethylsulfonate, and cyclohexylphenylmethylsulfonate.
- examples of the group having a silicon-carbon structure include trimethylphenylsilane, diphenylsilane, diphenyltetramethyldisilane, and the like, preferably trimethylphenylsilane.
- examples of groups having a phosphate structure include triphenyl phosphate, tris (2-t-butylphenyl) phosphate, tris (3-t-butylphenyl) phosphate, tris (4-t-butylphenyl).
- triphenyl phosphate tris (2-t-butylphenyl) phosphate, tris (3-t-butylphenyl) phosphate, tris (4-t-butylphenyl) phosphate, tris (2-t-amylphenyl) phosphate, Tris (3-t-amylphenyl) phosphate, tris (4-t-amylphenyl) phosphate, tris (2-cyclohexylphenyl) phosphate, tris (3-cyclohexylphenyl) phosphate, tris (4-cyclohexylphenyl) phosphate , More preferred are tris (2-tert-butylphenyl) phosphate, tris (4-tert-butylphenyl) phosphate, tris (2-cyclohexylphenyl) phosphate, and tris (4-cyclohexylphenyl) phosphate.
- Examples of groups having a phosphonate structure with respect to the substituent T include dimethylphenylphosphonate, diethylphenylphosphonate, methylphenylphenylphosphonate, ethylphenylphenylphosphonate, diphenylphenylphosphonate, dimethyl- (4-fluorophenyl) -phosphonate, dimethyl Benzyl phosphonate, diethyl benzyl phosphonate, methyl phenyl benzyl phosphonate, ethyl phenyl benzyl phosphonate, diphenyl benzyl phosphonate, dimethyl- (4-fluorobenzyl) phosphonate, diethyl- (4-fluorobenzyl) phosphonate, etc.
- the aromatic compound described above may be a fluorinated product.
- the fluorinated product include partially fluorinated products having a hydrocarbon group such as o-cyclohexylfluorobenzene and p-cyclohexylfluorobenzene; 2-fluoro Examples thereof include partially fluorinated compounds having a carboxylic acid ester structure such as phenyl acetate and 4-fluorophenyl acetate.
- the above aromatic compounds may be used alone or in combination of two or more.
- the ratio of the aromatic compound in the whole non-aqueous electrolyte is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and further preferably 0.5% by mass or more. Moreover, it is 10 mass% or less normally, Preferably it is 8 mass% or less, More preferably, it is 5 mass% or less, More preferably, it is 4 mass% or less, Most preferably, it is 3 mass% or less.
- Cyclic ether compound The cyclic ether compound which is a specific additive includes a cyclic ether compound which is an aliphatic compound having an oxygen atom in the molecule and a cyclic ether compound which is an aromatic compound having an oxygen atom in the molecule.
- a cyclic ether compound which is an aliphatic compound having an oxygen atom in the molecule is preferable because the oxidation potential is moderate and the amount of side reaction at room temperature can be reduced.
- cyclic ether compound examples include the following. Ethylene oxide, propylene oxide, butylene oxide, styrene oxide, oxetane, 2-methyloxetane, 3-methyloxetane, tetrahydrofuran, 2-methyltetrahydrofuran, 2-ethyltetrahydrofuran, 3-methyltetrahydrofuran, 3-ethyltetrahydrofuran, 2,2-dimethyl Tetrahydrofuran, 2,3-dimethyltetrahydrofuran, 2-vinyltetrahydrofuran, 3-vinyltetrahydrofuran, 2-ethynyltetrahydrofuran, 3-ethynyltetrahydrofuran, 2-phenyltetrahydrofuran, 3-phenyltetrahydrofuran, tetrahydropyran, 2-methyltetrahydropyran, 2- Ethyltetrahydropyran, 2-methyl
- a cyclic ether compound may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
- the blending amount is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and usually 10% by mass or less, in 100% by mass of the nonaqueous electrolytic solution.
- it is 5 mass% or less, More preferably, it is 3 mass% or less, More preferably, it is 1.5 mass% or less, Most preferably, it is 1.0 mass% or less.
- Oxalate salt There is no particular limitation on the counter cation of the oxalate salt that is a specific additive, but lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, barium, and NR 13 R 14 R 15 R 16 (wherein R 13 to R 16 each independently represents a hydrogen atom or an organic group having 1 to 12 carbon atoms).
- the organic group having 1 to 12 carbon atoms represented by R 13 to R 16 of ammonium is not particularly limited.
- the organic group may be substituted with a halogen atom, a halogen atom or an alkyl group.
- examples thereof include an cycloalkyl group which may be substituted, an aryl group which may be substituted with a halogen atom or an alkyl group, and a nitrogen atom-containing heterocyclic group which may have a substituent.
- R 13 to R 16 are preferably each independently a hydrogen atom, an alkyl group, a cycloalkyl group, or a nitrogen atom-containing heterocyclic group.
- oxalate salts include Lithium difluorooxalatoborate, lithium bis (oxalato) borate, lithium tetrafluorooxalatophosphate, lithium difluorobis (oxalato) phosphate, lithium tris (oxalato) phosphate, etc. Lithium bis (oxalato) borate and lithium difluorobis (oxalato) phosphate are preferred.
- the oxalate salt may be used alone or in combination of two or more in any combination and ratio. Moreover, the compounding quantity of an oxalate salt is not restrict
- the amount of the oxalate salt is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and usually 10% by mass or less in 100% by mass of the non-aqueous electrolyte.
- it is 5 mass% or less, More preferably, it is 3 mass% or less, More preferably, it is 2 mass% or less, Most preferably, it is 1.5 mass% or less.
- the non-aqueous electrolyte secondary battery is likely to exhibit a sufficient cycle characteristics improvement effect, and the high temperature storage characteristics are reduced, the amount of gas generation is increased, and the discharge capacity maintenance rate is reduced. Easy to avoid the situation.
- Cyclic sulfonic acid ester The type of cyclic sulfonic acid ester as a specific additive is not particularly limited.
- cyclic sulfonate ester examples include, for example, 1,3-propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone, 1-methyl-1,3-propane sultone 2-methyl-1,3-propane sultone, 3-methyl-1,3-propane sultone, 1-propene-1,3-sultone, 2-propene-1,3-sultone, 1-fluoro-1-propene -1,3-sultone, 2-fluoro-1-propene-1,3-sultone, 3-fluoro-1-propene-1,3-sultone, 1-fluoro-2-propene-1,3-sultone, 2 -Fluoro-2-propene-1,3-sultone, 3-fluoro-2-propene-1,3-sultone, 1-methyl-1-methyl-1
- 1,3-propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone, 1-propene-1, 3-sultone, 1-fluoro-1-propene-1,3-sultone, 2-fluoro-1-propene-1,3-sultone, 3-fluoro-1-propene-1,3-sultone, 1,4- Butane sultone, methylene methane disulfonate, and ethylene methane disulfonate are preferable from the viewpoint of improving the storage characteristics of the non-aqueous electrolyte, 1,3-propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone, 1-propene-1,3-sultone More preferred.
- the cyclic sulfonic acid ester may be used alone or in combination of two or more in any combination and ratio.
- the blending amount is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and usually 10% by mass or less, in 100% by mass of the nonaqueous electrolytic solution.
- 5% by mass or less is usually 0.001% by mass or less, more preferably 3% by mass or less, particularly preferably 2% by mass or less, and most preferably 1% by mass or less.
- Electrolyte There is no restriction
- an alkali metal salt is usually used, and specific examples thereof include a lithium salt and a sodium salt, and a lithium salt is preferably used.
- the lithium salt is not particularly limited as long as it is known to be used for this purpose, and any lithium salt can be used. Specific examples thereof include the following.
- Inorganic lithium salts such as LiPF 6 , LiBF 4 , LiClO 4 , LiAlF 4 , LiSbF 6 , LiTaF 6 , LiWF 7 ; Lithium tungstates such as LiWOF 5 ; HCO 2 Li, CH 3 CO 2 Li, CH 2 FCO 2 Li, CHF 2 CO 2 Li, CF 3 CO 2 Li, CF 3 CH 2 CO 2 Li, CF 3 CF 2 CO 2 Li, CF 3 CF 2 CF 2 Carboxylic acid lithium salts such as CO 2 Li, CF 3 CF 2 CF 2 CO 2 Li; FSO 3 Li, CH 3 SO 3 Li, CH 2 FSO 3 Li, CHF 2 SO 3 Li, CF 3 SO 3 Li, CF 3 CF 2 SO 3 Li, CF 3 CF 2 SO 3 Li, CF 3 CF 2 SO 3 Li, CF 3 CF 2 Sulfonic acid lithium salts such as CF 2 CF 2 SO 3 Li; LiN (FCO) 2 , LiN (
- lithium salts may be used alone or in combination of two or more.
- a preferable example in the case of using two or more kinds in combination is a combination of LiPF 6 and LiBF 4 , LiPF 6 and LiN (FSO 2 ) 2 , LiPF 6 and FSO 3 Li, or the like. These combinations have the effect of improving the load characteristics and cycle characteristics of the non-aqueous electrolyte secondary battery.
- the amount of LiBF 4 or FSO 3 Li for a non-aqueous electrolyte entire 100 wt% is not, it is not limited unless significantly impairing the effects of the present invention.
- the blending amount is usually 0.01% by mass or more, preferably 0.1% by mass or more, and usually 30% by mass or less, preferably 20% by mass with respect to the whole non-aqueous electrolyte solution of the present invention. It is as follows.
- Another example is the combined use of an inorganic lithium salt and an organic lithium salt.
- the combined use of both has the effect of suppressing deterioration of the non-aqueous electrolyte secondary battery due to high-temperature storage.
- Examples of the organic lithium salt include CF 3 SO 3 Li, LiN (FSO 2 ) 2 , LiN (FSO 2 ) (CF 3 SO 2 ), LiN (CF 3 SO 2 ) 2 , LiN (C 2 F 5 SO 2 ). 2 , lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropane disulfonylimide, LiC (FSO 2 ) 3 , LiC (CF 3 SO 2 ) 3 , LiC (C 2 F 5 SO 2 ) 3 , lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium tetrafluorooxalate phosphate, lithium difluorobisoxalatophosphate, LiBF 3 CF 3 , LiBF 3 C 2 F 5 , LiPF 3 (CF 3 ) 3 , LiPF 3 (C 2 F 5 ) 3 and the like are preferable.
- the ratio of the organic lithium salt to 100% by mass of the entire non-aqueous electrolyte is preferably 0.1% by mass or more, particularly preferably 0.5% by mass or more, and preferably 30% by mass or less. Especially preferably, it is 20 mass% or less.
- the concentration of the electrolyte described above in the nonaqueous electrolytic solution is not particularly limited as long as the effect of the present invention is not impaired.
- the total molar concentration of the electrolyte in the non-aqueous electrolyte is preferably 0.3 mol / L or more, more preferably 0.4 mol from the viewpoint of ensuring the electric conductivity of the electrolyte in a good range and ensuring good battery performance.
- / L or more more preferably 0.5 mol / L or more, particularly preferably 1.0 mol / L or more, preferably 3 mol / L or less, more preferably 2.5 mol / L or less, still more preferably 2. 0 mol / L or less.
- the electric conductivity of the non-aqueous electrolytic solution becomes sufficient, and the decrease in electric conductivity due to the increase in viscosity and the decrease in battery performance due to it can be prevented.
- Nonaqueous solvent there is no restriction
- cyclic carbonate without fluorine atoms examples include cyclic carbonates having an alkylene group having 2 to 4 carbon atoms.
- cyclic carbonate having an alkylene group having 2 to 4 carbon atoms and having no fluorine atom include ethylene carbonate, propylene carbonate, and butylene carbonate.
- ethylene carbonate and propylene carbonate are particularly preferable from the viewpoint of improving battery characteristics resulting from an improvement in the degree of lithium ion dissociation.
- cyclic carbonate having no fluorine atom one kind may be used alone, or two kinds or more may be used in any combination and ratio.
- the compounding amount of the cyclic carbonate having no fluorine atom is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired.
- the blending amount when one kind is used alone is usually 5% by volume or more, more preferably 10% by volume or more, in 100% by volume of the non-aqueous solvent.
- the said compounding quantity is 95 volume% or less normally, More preferably, it is 90 volume% or less, More preferably, it is 85 volume% or less.
- the viscosity of the non-aqueous electrolyte solution is set to an appropriate range, a decrease in ionic conductivity is suppressed, and as a result, the load characteristics of the non-aqueous electrolyte secondary battery are easily set in a favorable range.
- Chain carbonate a chain carbonate having 3 to 7 carbon atoms is preferable, and a dialkyl carbonate having 3 to 7 carbon atoms is more preferable.
- chain carbonate examples include dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, methyl-n-propyl carbonate, n-butyl methyl carbonate, isobutyl methyl.
- Examples thereof include carbonate, t-butyl methyl carbonate, ethyl-n-propyl carbonate, n-butyl ethyl carbonate, isobutyl ethyl carbonate, t-butyl ethyl carbonate and the like.
- dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, and methyl-n-propyl carbonate are preferable, and dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are particularly preferable. is there.
- a chain carbonate having a fluorine atom (hereinafter sometimes referred to as “fluorinated chain carbonate”) can also be suitably used.
- the number of fluorine atoms in the fluorinated chain carbonate is not particularly limited as long as it is 1 or more, but is usually 6 or less, preferably 4 or less.
- the fluorinated chain carbonate has a plurality of fluorine atoms, they may be bonded to the same carbon or may be bonded to different carbons.
- fluorinated chain carbonate examples include fluorinated dimethyl carbonate and derivatives thereof, fluorinated ethyl methyl carbonate and derivatives thereof, and fluorinated diethyl carbonate and derivatives thereof.
- fluorinated dimethyl carbonate and derivatives thereof examples include fluoromethyl methyl carbonate, difluoromethyl methyl carbonate, trifluoromethyl methyl carbonate, bis (fluoromethyl) carbonate, bis (difluoro) methyl carbonate, and bis (trifluoromethyl) carbonate. Can be mentioned.
- fluorinated ethyl methyl carbonate and derivatives thereof examples include 2-fluoroethyl methyl carbonate, ethyl fluoromethyl carbonate, 2,2-difluoroethyl methyl carbonate, 2-fluoroethyl fluoromethyl carbonate, ethyl difluoromethyl carbonate, 2,2, Examples include 2-trifluoroethyl methyl carbonate, 2,2-difluoroethyl fluoromethyl carbonate, 2-fluoroethyl difluoromethyl carbonate, and ethyl trifluoromethyl carbonate.
- fluorinated diethyl carbonate and its derivatives examples include ethyl- (2-fluoroethyl) carbonate, ethyl- (2,2-difluoroethyl) carbonate, bis (2-fluoroethyl) carbonate, ethyl- (2,2,2 -Trifluoroethyl) carbonate, 2,2-difluoroethyl-2'-fluoroethyl carbonate, bis (2,2-difluoroethyl) carbonate, 2,2,2-trifluoroethyl-2'-fluoroethyl carbonate, 2 2,2-trifluoroethyl-2 ′, 2′-difluoroethyl carbonate, bis (2,2,2-trifluoroethyl) carbonate, and the like.
- the chain carbonates described above may be used alone or in combination of two or more in any combination and ratio.
- the blending amount of the chain carbonate is preferably 5% by volume or more, more preferably 10% by volume or more, and further preferably 15% by volume or more in 100% by volume of the non-aqueous solvent.
- the amount of the chain carbonate is preferably 90% by volume or less, more preferably 85% by volume or less, and particularly preferably 80% by volume or less in 100% by volume of the non-aqueous solvent.
- the chain carboxylic acid ester preferably has 3 to 7 carbon atoms.
- chain carboxylic acid ester one kind may be used alone, and two kinds or more may be used in optional combination and ratio.
- the compounding amount of the chain carboxylic acid ester is usually 10% by volume or more, more preferably 15% by volume or more, in 100% by volume of the non-aqueous solvent.
- the blended amount of the chain carboxylic acid ester is preferably 100% by volume or less, more preferably 50% by volume or less, particularly preferably 30% by volume or less, and most preferably 20% by volume or less in 100% by volume of the non-aqueous solvent. It is. By setting the upper limit in this manner, an increase in negative electrode resistance is suppressed, and the large current discharge characteristics and cycle characteristics of the non-aqueous electrolyte secondary battery are easily set in a favorable range.
- the cyclic carboxylic acid ester preferably has 3 to 12 carbon atoms.
- Specific examples thereof include gamma butyrolactone, gamma valerolactone, gamma caprolactone, epsilon caprolactone and the like.
- gamma butyrolactone is particularly preferable from the viewpoint of improving battery characteristics resulting from an improvement in the degree of lithium ion dissociation.
- cyclic carboxylic acid ester one kind may be used alone, and two kinds or more may be used in optional combination and ratio.
- the compounding amount of the cyclic carboxylic acid ester is preferably 5% by volume or more, more preferably 10% by volume or more, in 100% by volume of the non-aqueous solvent. If it is this range, it will become easy to improve the electrical conductivity of a non-aqueous electrolyte solution, and to improve the large current discharge characteristic of a non-aqueous electrolyte secondary battery. Moreover, the compounding quantity of cyclic carboxylic acid ester becomes like this. Preferably it is 50 volume% or less, More preferably, it is 40 volume% or less.
- the viscosity of the non-aqueous electrolyte solution is set to an appropriate range, a decrease in electrical conductivity is avoided, an increase in negative electrode resistance is suppressed, and a large current discharge of the non-aqueous electrolyte secondary battery is performed. It becomes easy to make a characteristic into a favorable range.
- ether compound a chain ether having 3 to 10 carbon atoms in which part of hydrogen may be substituted with fluorine and a cyclic ether having 3 to 6 carbon atoms are preferable.
- chain ether having 3 to 10 carbon atoms examples include Diethyl ether, di (2-fluoroethyl) ether, di (2,2-difluoroethyl) ether, di (2,2,2-trifluoroethyl) ether, ethyl (2-fluoroethyl) ether, ethyl (2, 2,2-trifluoroethyl) ether, ethyl (1,1,2,2-tetrafluoroethyl) ether, (2-fluoroethyl) (2,2,2-trifluoroethyl) ether, (2-fluoroethyl) ) (1,1,2,2-tetrafluoroethyl) ether, (2,2,2-trifluoroethyl) (1,1,2,2-tetrafluoroethyl) ether, (2,2,2-trifluoroethyl) (1,1,2,2-tetrafluoroethyl) ether, (2,
- Examples of the cyclic ether having 3 to 6 carbon atoms include tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 1,3-dioxane, 2-methyl-1,3-dioxane, 4-methyl-1,3-dioxane, Examples thereof include 1,4-dioxane and the like, and fluorinated compounds thereof.
- dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether have high solvating ability to lithium ions.
- Particularly preferred are dimethoxymethane, diethoxymethane, and ethoxymethoxymethane because they have low viscosity and give high ionic conductivity.
- the ether compounds may be used alone or in combination of two or more in any combination and ratio.
- the compounding amount of the ether compound is preferably 5% by volume or more, more preferably 10% by volume or more, further preferably 15% by volume or more, and preferably 70% by volume or less, in 100% by volume of the non-aqueous solvent. Is 60% by volume or less, more preferably 50% by volume or less.
- sulfone compounds As the sulfone compound, a cyclic sulfone having 3 to 6 carbon atoms and a chain sulfone having 2 to 6 carbon atoms are preferable.
- the number of sulfonyl groups in one molecule is preferably 1 or 2.
- Examples of the cyclic sulfone having 3 to 6 carbon atoms include Monosulfone compounds trimethylene sulfones, tetramethylene sulfones, hexamethylene sulfones; Examples include disulfone compounds such as trimethylene disulfones, tetramethylene disulfones, and hexamethylene disulfones.
- tetramethylene sulfones tetramethylene disulfones, hexamethylene sulfones, and hexamethylene disulfones are more preferable from the viewpoint of dielectric constant and viscosity, and tetramethylene sulfones are particularly preferable.
- the tetramethylene sulfones are preferably sulfolane and / or sulfolane derivatives (hereinafter sometimes referred to as “sulfolanes” including sulfolane).
- sulfolanes sulfolane derivatives
- the sulfolane derivative one in which one or more hydrogen atoms bonded to the carbon atom constituting the sulfolane ring are substituted with a fluorine atom or an alkyl group is preferable.
- Examples of the chain sulfone having 2 to 6 carbon atoms include Dimethylsulfone, ethylmethylsulfone, diethylsulfone, n-propylmethylsulfone, n-propylethylsulfone, di-n-propylsulfone, isopropylmethylsulfone, isopropylethylsulfone, diisopropylsulfone, n-butylmethylsulfone, n-butylethyl Sulfone, t-butylmethylsulfone, t-butylethylsulfone, monofluoromethylmethylsulfone, difluoromethylmethylsulfone, trifluoromethylmethylsulfone, monofluoroethylmethylsulfone, difluoroethylmethylsulfone, trifluoroethylmethylsulfone, pentafluoro Ethy
- the sulfone compounds described above may be used alone or in combination of two or more in any combination and ratio.
- the amount of the sulfone compound is preferably 0.3% by volume or more, more preferably 1% by volume or more, still more preferably 5% by volume or more in 100% by volume of the non-aqueous solvent, and preferably 40% by volume. Hereinafter, it is more preferably 35% by volume or less, still more preferably 30% by volume or less.
- the cyclic carbonate having a fluorine atom is used in the nonaqueous electrolytic solution of the present invention, 1-2. As indicated by, it is used as a specific additive, but can also be used as a non-aqueous solvent.
- a cyclic carbonate having a fluorine atom when used as a non-aqueous solvent, one of the non-aqueous solvents exemplified above is combined with a cyclic carbonate having a fluorine atom as a non-aqueous solvent other than the cyclic carbonate having a fluorine atom.
- Two or more kinds may be used in combination with a cyclic carbonate having a fluorine atom.
- one preferred combination of non-aqueous solvents is a combination mainly composed of a cyclic carbonate having a fluorine atom and a chain carbonate.
- the total of the cyclic carbonate having a fluorine atom and the chain carbonate in the non-aqueous solvent is preferably 60% by volume or more, more preferably 80% by volume or more, still more preferably 90% by volume or more
- the ratio of the cyclic carbonate having a fluorine atom to the total of the cyclic carbonate having a fluorine atom and the chain carbonate is 3% by volume or more, preferably 5% by volume or more, more preferably 10% by volume or more, and further preferably 15% by volume or more. It is usually 60% by volume or less, preferably 50% by volume or less, more preferably 40% by volume or less, further preferably 35% by volume or less, particularly preferably 30% by volume or less, and most preferably 20% by volume or less. .
- a cyclic carbonate having a fluorine atom and a chain carbonate Monofluoroethylene carbonate and dimethyl carbonate, Monofluoroethylene carbonate and diethyl carbonate, Monofluoroethylene carbonate and ethyl methyl carbonate, Monofluoroethylene carbonate, dimethyl carbonate and diethyl carbonate, Monofluoroethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, Monofluoroethylene carbonate, diethyl carbonate and ethyl methyl carbonate, Examples thereof include monofluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.
- cyclic carbonates having a fluorine atom and chain carbonates those containing symmetrical chain alkyl carbonates as chain carbonates are more preferred.
- monofluoroethylene carbonate, dimethyl carbonate and ethyl methyl carbonate Monofluoroethylene carbonate, diethyl carbonate and ethyl methyl carbonate
- Non-aqueous solvent containing monofluoroethylene carbonate, symmetric chain carbonates and asymmetric chain carbonates such as monofluoroethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate is a cycle of a non-aqueous electrolyte secondary battery.
- the symmetric chain carbonate is preferably dimethyl carbonate, and the alkyl group of the chain carbonate preferably has 1 to 2 carbon atoms.
- a combination in which a cyclic carbonate having no fluorine atom is further added to the combination of the cyclic carbonate having a fluorine atom and the chain carbonate is also mentioned as a preferable combination.
- the total of the cyclic carbonate having a fluorine atom and the cyclic carbonate having no fluorine atom in the non-aqueous solvent is preferably 10% by volume or more, more preferably 15% by volume or more, and further preferably 20% by volume or more.
- the ratio of the cyclic carbonate having a fluorine atom to the total of the cyclic carbonate having a fluorine atom and the cyclic carbonate having no fluorine atom is usually 1% by volume or more, preferably 3% by volume or more, more preferably 5% by volume. % Or more, more preferably 10% by volume or more, particularly preferably 20% by volume or more, and preferably 95% by volume or less, more preferably 85% by volume or less, still more preferably 75% by volume or less, particularly preferably 60% or less. A combination of not more than volume% is preferred.
- the non-aqueous solvent contains a cyclic carbonate having no fluorine atom in this concentration range, the electric conductivity of the non-aqueous electrolyte can be maintained while forming a stable protective film on the negative electrode.
- a cyclic carbonate having a fluorine atom and a cyclic carbonate having no fluorine atom and a chain carbonate Monofluoroethylene carbonate, ethylene carbonate and dimethyl carbonate, Monofluoroethylene carbonate, ethylene carbonate and diethyl carbonate, Monofluoroethylene carbonate, ethylene carbonate and ethyl methyl carbonate, Monofluoroethylene carbonate, ethylene carbonate, dimethyl carbonate and diethyl carbonate, Monofluoroethylene carbonate, ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, Monofluoroethylene carbonate, ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, Monofluoroethylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate, Monofluoroethylene carbonate, propylene carbonate and dimethyl carbonate, Monofluoroethylene carbonate, Monofluoroethylene carbonate,
- cyclic carbonates having fluorine atoms and cyclic carbonates not having fluorine atoms and chain carbonates those containing asymmetric chain alkyl carbonates as chain carbonates are more preferred, Monofluoroethylene carbonate, ethylene carbonate and ethyl methyl carbonate, Monofluoroethylene carbonate, propylene carbonate and ethyl methyl carbonate, Monofluoroethylene carbonate, ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, Monofluoroethylene carbonate, propylene carbonate, dimethyl carbonate and ethyl methyl carbonate, Monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate and ethyl methyl carbonate, Monofluoroethylene carbonate, ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, Monofluoroethylene carbonate, propylene carbonate, diethyl carbonate and ethyl methyl carbonate, Monofluoroethylene
- a combination in which the asymmetric chain carbonate is ethyl methyl carbonate is preferable, and the alkyl group of the chain carbonate preferably has 1 to 2 carbon atoms.
- the proportion of ethyl methyl carbonate in the total non-aqueous solvent is preferably 10% by volume or more, more preferably 20% by volume or more, and further preferably 25% by volume or more. In particular, it is 30% by volume or more, preferably 95% by volume or less, more preferably 90% by volume or less, still more preferably 85% by volume or less, and particularly preferably 80% by volume or less. If it is contained in this range, the load characteristics of the non-aqueous electrolyte secondary battery may be improved.
- a cyclic carboxylic acid ester in addition to the cyclic carbonate having no fluorine atom, a cyclic carboxylic acid ester, a chain carboxylic acid ester, a cyclic ether, a chain
- solvents such as a chain ether, a sulfur-containing organic solvent, a phosphorus-containing organic solvent, and a fluorine-containing aromatic solvent may be mixed.
- a cyclic carbonate having a fluorine atom is selected from 1-2.
- one kind of the non-aqueous solvent exemplified above other than the cyclic carbonate having a fluorine atom may be used alone, or two or more kinds may be used in any combination and ratio. May be.
- a combination mainly composed of a cyclic carbonate having no fluorine atom and a chain carbonate can be mentioned.
- the total of the cyclic carbonate having no fluorine atom and the chain carbonate in the non-aqueous solvent is preferably 70% by volume or more, more preferably 80% by volume or more, further preferably 90% by volume or more, and
- the ratio of the cyclic carbonate having no fluorine atom to the total of the cyclic carbonate and the chain carbonate is preferably 5% by volume or more, more preferably 10% by volume or more, further preferably 15% by volume or more, and preferably
- the combination is 50% by volume or less, more preferably 35% by volume or less, still more preferably 30% by volume or less, and particularly preferably 25% by volume or less.
- a cyclic carbonate having no fluorine atom and a chain carbonate Ethylene carbonate and dimethyl carbonate, Ethylene carbonate and diethyl carbonate, Ethylene carbonate and ethyl methyl carbonate, Ethylene carbonate, dimethyl carbonate and diethyl carbonate, Ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, Ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, Ethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate, Propylene carbonate and ethyl methyl carbonate, Propylene carbonate, ethyl methyl carbonate and diethyl carbonate, Examples include propylene carbonate, ethyl methyl carbonate, and dimethyl carbonate.
- cyclic carbonates having no fluorine atom and chain carbonates those containing asymmetric chain alkyl carbonates as chain carbonates are more preferable.
- a combination of propylene carbonate, ethyl methyl carbonate, and diethyl carbonate is preferable because it improves the balance between the cycle characteristics and high current discharge characteristics of the non-aqueous electrolyte secondary battery.
- the alkyl group of the chain carbonate preferably has 1 to 2 carbon atoms.
- the proportion of dimethyl carbonate in the total non-aqueous solvent is preferably 10% by volume or more, more preferably 20% by volume or more, and even more preferably 25% by volume or more. It is preferably 30% by volume or more, preferably 90% by volume or less, more preferably 80% by volume or less, still more preferably 75% by volume or less, and particularly preferably 70% by volume or less. If it is contained in this range, the load characteristics of the non-aqueous electrolyte secondary battery may be improved.
- the volume ratio of dimethyl carbonate to ethyl methyl carbonate is 1.1 in terms of improving the electric conductivity of the non-aqueous electrolyte and improving the battery characteristics after storage.
- the above is preferable, 1.5 or more is more preferable, and 2.5 or more is more preferable.
- the volume ratio (dimethyl carbonate / ethyl methyl carbonate) is preferably 40 or less, more preferably 20 or less, still more preferably 10 or less, and particularly preferably 8 or less, from the viewpoint of improving battery characteristics.
- the volume of the non-aqueous solvent is a measured value at 25 ° C., but the measured value at the melting point of a solid at 25 ° C. like ethylene carbonate is regarded as the volume of the non-aqueous solvent.
- an auxiliary agent may be appropriately used depending on the purpose in addition to the compound represented by the general formula (A) and the specific additive.
- the auxiliary agent include compounds having a triple bond shown below and other auxiliary agents.
- Compound having triple bond The type of the compound having triple bond is not particularly limited as long as it is a compound having one or more triple bonds in the molecule.
- the compound having a triple bond include the following compounds.
- Phosphoric acid (methyl) (2-propenyl) (2-propynyl), phosphoric acid (ethyl) (2-propenyl) (2-propynyl), phosphoric acid (2-butenyl) (methyl) (2-propynyl), phosphoric acid (2-butenyl) (ethyl) (2-propynyl), phosphoric acid (1,1-dimethyl-2-propynyl) (methyl) (2-propenyl), phosphoric acid (1,1-dimethyl-2-propynyl) ( Ethyl) (2-propenyl), phosphoric acid (2-butenyl) (1,1-dimethyl-2-propynyl) (methyl), and phosphoric acid (2-butenyl) (ethyl) (1,1-dimethyl-2- Phosphate esters such as propynyl).
- a compound having an alkynyloxy group is preferable because it forms a negative electrode film more stably in a non-aqueous electrolyte solution.
- a compound such as di-2-propynyl oxalate is particularly preferred from the viewpoint of improving storage characteristics.
- the compound having a triple bond may be used alone or in combination of two or more in any combination and ratio.
- the blending amount is usually 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and usually 5% by mass with respect to the whole non-aqueous electrolyte solution of the present invention. Hereinafter, it is preferably 3% by mass or less, more preferably 1% by mass or less.
- auxiliaries As other auxiliaries, known auxiliaries other than the specific additive, the fluorinated unsaturated cyclic carbonate, and the compound having a triple bond can be used.
- auxiliaries Carbonate compounds such as erythritan carbonate, spiro-bis-dimethylene carbonate, methoxyethyl-methyl carbonate; Spiro compounds such as 2,4,8,10-tetraoxaspiro [5.5] undecane, 3,9-divinyl-2,4,8,10-tetraoxaspiro [5.5] undecane; Ethylene sulfite, methyl fluorosulfonate, ethyl fluorosulfonate, methyl methanesulfonate, ethyl methanesulfonate, busulfan, sulfolene, diphenylsulfone, N, N-dimethylmethanesulfonamide, N, N-diethylmethanes
- Nitrogen-containing compounds such as 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone and N-methylsuccinimide; Trimethyl phosphite, triethyl phosphite, triphenyl phosphite, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, dimethyl methylphosphonate, diethyl ethylphosphonate, dimethyl vinylphosphonate, diethyl vinylphosphonate, dimethylphosphine Phosphorus-containing compounds such as methyl acid, ethyl diethylphosphinate, trimethylphosphine oxide, triethylphosphine oxide;
- Hydrocarbon compounds such as heptane, octane, nonane, decane, cycloheptane; Fluorine-containing aromatic compounds such as fluorobenzene, difluorobenzene, hexafluorobenzene and benzotrifluoride; Etc. These may be used alone or in combination of two or more. By adding these auxiliaries to the non-aqueous electrolyte solution, it is possible to improve capacity maintenance characteristics and cycle characteristics of the non-aqueous electrolyte secondary battery after high temperature storage.
- the compounding amount of other auxiliary agents is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired.
- the blending amount of the other auxiliaries is preferably 0.01% by mass or more and usually 5% by mass or less in 100% by mass of the non-aqueous electrolyte solution. If it is this range, the effect of other adjuvants will be fully exhibited easily, and it will be easy to avoid the situation where the characteristics of a nonaqueous electrolyte secondary battery, such as a high load discharge characteristic, will fall.
- non-aqueous electrolyte solution of the present invention includes those existing inside the non-aqueous electrolyte secondary battery of the present invention.
- non-aqueous electrolyte When the non-aqueous electrolyte is present inside the non-aqueous electrolyte secondary battery, specifically, Separately synthesize components of non-aqueous electrolyte such as electrolyte, non-aqueous solvent, specific additives, etc., prepare non-aqueous electrolyte from substantially isolated one, and separately assembled by the method described below In the case of a non-aqueous electrolyte solution in a non-aqueous electrolyte battery obtained by pouring into the battery; When the components of the non-aqueous electrolyte of the present invention are individually placed in a battery and mixed in the battery to obtain the same composition as the non-aqueous electrolyte of the present invention; When the compound constituting the non-aqueous electrolyte solution of the present invention is generated in the non-aqueous electrolyte secondary battery to obtain the same composition as the non-aqueous electrolyte solution of the present invention; And so on.
- the non-aqueous electrolyte solution of the present invention is suitable for use as, for example, an electrolyte solution for a lithium secondary battery among non-aqueous electrolyte secondary batteries.
- an electrolyte solution for a lithium secondary battery among non-aqueous electrolyte secondary batteries for example, an electrolyte solution for a lithium secondary battery among non-aqueous electrolyte secondary batteries.
- a non-aqueous electrolyte secondary battery using the non-aqueous electrolyte of the present invention will be described.
- the non-aqueous electrolyte secondary battery of the present invention can adopt a known structure, and typically includes a negative electrode and a positive electrode capable of inserting and extracting metal ions (for example, lithium ions), and the above-described present invention.
- a non-aqueous electrolyte solution A non-aqueous electrolyte solution.
- the negative electrode, the positive electrode, and other components in the non-aqueous electrolyte secondary battery will be described in this order.
- Negative electrode The negative electrode active material used for the negative electrode is described below.
- the negative electrode active material is not particularly limited as long as it can electrochemically occlude and release metal ions. Specific examples include those having carbon as a constituent element such as a carbonaceous material, alloy materials, and the like. These may be used individually by 1 type, and may be used together combining 2 or more types arbitrarily.
- Negative electrode active material examples include carbonaceous materials and alloy-based materials as described above.
- Examples of the carbonaceous material include (1) natural graphite, (2) artificial graphite, (3) amorphous carbon, (4) carbon-coated graphite, (5) graphite-coated graphite, and (6) resin-coated graphite. It is done.
- Examples of natural graphite include scaly graphite, scaly graphite, soil graphite, and / or graphite particles obtained by subjecting these graphites as raw materials to spheroidization and densification.
- spherical or ellipsoidal graphite subjected to spheroidizing treatment is particularly preferable from the viewpoints of particle filling properties and charge / discharge rate characteristics.
- an apparatus used for the spheronization treatment for example, an apparatus that repeatedly gives mechanical action such as compression, friction, shearing force, etc. including the interaction of particles mainly with impact force to the particles can be used.
- the apparatus which has a mechanism which gives a mechanical action repeatedly by circulating a raw material is preferable.
- the peripheral speed of the rotating rotor is preferably set to 30 to 100 m / sec, more preferably set to 40 to 100 m / sec, and more preferably 50 to 100 m / sec. More preferably, it is set to seconds.
- the spheronization treatment can be performed by simply passing the raw material, but it is preferable to circulate or stay in the apparatus for 30 seconds or more, and to circulate or stay in the apparatus for 1 minute or more. Is more preferable.
- Artificial graphite includes coal tar pitch, coal heavy oil, atmospheric residue, petroleum heavy oil, aromatic hydrocarbon, nitrogen-containing cyclic compound, sulfur-containing cyclic compound, polyphenylene, polyvinyl chloride,
- An organic compound such as polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural polymer, polyphenylene sulfide, polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, imide resin is usually in a range of 2500 ° C. or higher and usually 3200 ° C. or lower. Examples thereof include those produced by graphitization at a temperature and, if necessary, pulverized and / or classified.
- a silicon-containing compound, a boron-containing compound, or the like can also be used as a graphitization catalyst.
- artificial graphite obtained by graphitizing mesocarbon microbeads separated in the heat treatment process of pitch can be mentioned.
- the artificial graphite of the granulated particle which consists of primary particles is also mentioned.
- the resulting graphite particles include a plurality of flat particles and aggregated or bonded so that the orientation planes are non-parallel.
- amorphous carbon an amorphous carbon that has been heat-treated at least once in a temperature range (400 to 2200 ° C.) in which no graphitizable carbon precursor such as tar or pitch is used as a raw material.
- amorphous carbon particles obtained by heat treatment using particles or a non-graphitizable carbon precursor such as a resin as a raw material.
- Examples of the carbon-coated graphite include those obtained as follows. Natural graphite and / or artificial graphite is mixed with a carbon precursor which is an organic compound such as tar, pitch or resin, and heat-treated at least once in the range of 400 to 2300 ° C. The obtained natural graphite and / or artificial graphite is used as nuclear graphite, which is coated with amorphous carbon to obtain a carbon graphite composite. This carbon graphite composite is exemplified as carbon-coated graphite (4).
- the composite form may be a form in which the whole or a part of the surface of the nuclear graphite is coated with amorphous carbon, or a form in which a plurality of primary particles are composited using carbon derived from the carbon precursor as a binder. Good. Also, by reacting natural graphite and / or artificial graphite with hydrocarbon gases such as benzene, toluene, methane, propane, aromatic volatiles at a high temperature, and depositing carbon on the graphite surface (CVD), The carbon graphite composite can be obtained.
- hydrocarbon gases such as benzene, toluene, methane, propane, aromatic volatiles at a high temperature
- Examples of the graphite-coated graphite include those obtained as follows. Natural graphite and / or artificial graphite and a carbon precursor of an easily graphitizable organic compound such as tar, pitch or resin are mixed and heat-treated at least in the range of about 2400 to 3200 ° C. The obtained natural graphite and / or artificial graphite is used as nuclear graphite, and the whole or part of the surface of the nuclear graphite is coated with a graphitized product to obtain graphite-coated graphite (5).
- Resin-coated graphite is, for example, natural graphite and / or artificial graphite mixed with resin and dried at a temperature of less than 400 ° C. It is obtained by coating the nuclear graphite with.
- carbonaceous materials (1) to (6) described above may be used alone or in combination of two or more in any combination and ratio.
- Examples of organic compounds such as tar, pitch and resin used in the carbonaceous materials (2) to (5) above include heavy coal-based oils, direct-current heavy oils, cracked heavy petroleum oils, and aromatic hydrocarbons. , N ring compounds, S ring compounds, polyphenylene, organic synthetic polymers, natural polymers, organic compounds capable of carbonization selected from the group consisting of thermoplastic resins and thermosetting resins.
- the raw material organic compound may be used after being dissolved in a low molecular organic solvent in order to adjust the viscosity at the time of mixing.
- natural graphite and / or artificial graphite used as a raw material for nuclear graphite is preferably natural graphite that has been spheroidized.
- the alloy material used as the negative electrode active material is lithium simple substance, single metal and alloy forming lithium alloy, or oxides, carbides, nitrides, silicas thereof as long as lithium can be occluded / released. Any of compounds such as fluoride, sulfide or phosphide may be used, and it is not particularly limited.
- the single metal and the alloy forming the lithium alloy are preferably materials containing a group 13 and group 14 metal / metalloid element (that is, excluding carbon), More preferably, single metals of aluminum, silicon and tin and alloys or compounds containing these atoms, More preferably, it has silicon or tin as a constituent element, such as a simple metal of silicon and tin and an alloy or compound containing these atoms. These may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.
- the carbonaceous material desirably has the following physical properties.
- the d value (interlayer distance) of the lattice plane (002 plane) obtained by X-ray diffraction by the Gakushin method of carbonaceous materials is usually 0.335 nm or more, usually 0.360 nm or less, and 0.350 nm. The following is preferable, and 0.345 nm or less is more preferable. Further, the crystallite size (Lc) of the carbonaceous material obtained by X-ray diffraction by the Gakushin method is preferably 1.0 nm or more, and more preferably 1.5 nm or more.
- the volume-based average particle diameter of the carbonaceous material is a volume-based average particle diameter (median diameter) determined by a laser diffraction / scattering method, which is usually 1 ⁇ m or more, preferably 3 ⁇ m or more, more preferably 5 ⁇ m or more, It is particularly preferably 7 ⁇ m or more, and is usually 100 ⁇ m or less, preferably 50 ⁇ m or less, more preferably 40 ⁇ m or less, further preferably 30 ⁇ m or less, and particularly preferably 25 ⁇ m or less.
- the volume-based average particle size is below the above range, the irreversible capacity of the non-aqueous electrolyte secondary battery may increase, leading to loss of initial battery capacity.
- the above range is exceeded, when the electrode (the negative electrode active material layer) is produced by coating, it tends to be a non-uniform coating surface, which may be undesirable in the battery production process.
- the volume-based average particle size is measured by dispersing a carbonaceous material in a 0.2% by mass aqueous solution (about 10 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and laser diffraction / scattering type particle size. This is performed using a distribution meter (for example, LA-700 manufactured by Horiba, Ltd.). The median diameter determined by the measurement is defined as the volume-based average particle diameter of the carbonaceous material.
- the Raman R value of the carbonaceous material is a value measured using a laser Raman spectrum method, and is usually 0.01 or more, preferably 0.03 or more, more preferably 0.1 or more, and usually 1. 5 or less, preferably 1.2 or less, more preferably 1.0 or less, and particularly preferably 0.5 or less.
- the Raman R value is below the above range, the crystallinity of the particle surface becomes too high, and there are cases where the number of sites where Li enters between layers decreases with charge / discharge of the non-aqueous electrolyte secondary battery. In other words, the charge acceptance of the battery may be reduced.
- a negative electrode material containing a carbonaceous material is applied to a current collector and then the negative electrode is densified by pressing, crystals tend to be oriented in a direction parallel to the electrode plate, resulting in a decrease in load characteristics of the battery. May be invited.
- the Raman R value calculated by the measurement is defined as the Raman R value of the carbonaceous material.
- said Raman measurement conditions are as follows.
- BET specific surface area of the carbonaceous material is a value of the measured specific surface area using the BET method is usually 0.1 m 2 ⁇ g -1 or more, 0.7 m 2 ⁇ g -1 or more, 1. 0 m 2 ⁇ g -1 or more, and particularly preferably 1.5 m 2 ⁇ g -1 or more, generally not more than 100 m 2 ⁇ g -1, preferably 25 m 2 ⁇ g -1 or less, 15 m 2 ⁇ g ⁇ 1 or less is more preferable, and 10 m 2 ⁇ g ⁇ 1 or less is particularly preferable.
- the acceptability of lithium is likely to deteriorate during charging of the non-aqueous electrolyte secondary battery when such a carbonaceous material is used as the negative electrode material, It becomes easy to precipitate, and there exists a possibility that the stability of a battery may fall.
- the reactivity with the non-aqueous electrolyte increases, gas generation tends to increase, and a preferable battery may be difficult to obtain.
- the specific surface area was measured by the BET method using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Ritsu Okura), and the sample (carbonaceous material) was pre-dried at 350 ° C. for 15 minutes under a nitrogen flow. Thereafter, a nitrogen adsorption BET one-point method using a gas flow method is performed using a nitrogen helium mixed gas that is accurately adjusted so that the value of the relative pressure of nitrogen with respect to atmospheric pressure is 0.3.
- a surface area meter for example, a fully automatic surface area measuring device manufactured by Ritsu Okura
- the circularity is measured as the degree of the sphere of the carbonaceous material, it is preferably within the following range.
- the degree of circularity is desirably closer to 1, more preferably 0.1 or more, preferably 0.5 or more, more preferably 0.8 or more, 0 .85 or more is more preferable, and 0.9 or more is particularly preferable.
- the high current density charge / discharge characteristics of the non-aqueous electrolyte secondary battery improve as the circularity increases. Therefore, if the circularity is less than the above range, the filling property of the negative electrode active material is decreased, the resistance between the particles is increased, and the second short-time high current density charge / discharge characteristics may be decreased.
- the circularity is measured using a flow type particle image analyzer (for example, FPIA manufactured by Sysmex Corporation). About 0.2 g of a sample (carbonaceous material) is dispersed in a 0.2% by mass aqueous solution (about 50 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and an ultrasonic wave of 28 kHz is output at 60 W. After irradiating for 1 minute, the detection range is specified as 0.6 to 400 ⁇ m, and the particle size is measured in the range of 3 to 40 ⁇ m.
- FPIA flow type particle image analyzer
- the method for improving the circularity is not particularly limited, but the carbonaceous material that has been spheroidized to form a sphere has the shape of the interparticle void when it is made into an electrode body. It is preferable to make it.
- spheroidizing treatment include a method of mechanically approaching a sphere by applying a shearing force and a compressive force, a mechanical / physical processing method of granulating a plurality of fine particles by the binder or the adhesive force of the particles themselves, etc. Is mentioned.
- the tap density of the carbonaceous material is usually 0.1 g ⁇ cm ⁇ 3 or more, preferably 0.5 g ⁇ cm ⁇ 3 or more, more preferably 0.7 g ⁇ cm ⁇ 3 or more, and 1 g ⁇ cm ⁇ 3 or more. particularly preferred, and is preferably 2 g ⁇ cm -3 or less, more preferably 1.8 g ⁇ cm -3 or less, 1.6 g ⁇ cm -3 or less are particularly preferred.
- the tap density is lower than the above range, when a negative electrode is produced using the carbonaceous material, the packing density of the negative electrode active material is difficult to increase, and a high-capacity non-aqueous electrolyte secondary battery cannot be obtained. There is a case.
- the above range is exceeded, there are too few voids between particles in the electrode, it is difficult to ensure conductivity between the particles, and it may be difficult to obtain preferable battery characteristics.
- the tap density is measured as follows.
- the sample carbonaceous material
- the sample is dropped into a 20 cm 3 tapping cell through a sieve having a mesh opening of 300 ⁇ m to fill the sample up to the upper end surface of the cell.
- a powder density measuring device for example, a tap denser manufactured by Seishin Enterprise Co., Ltd.
- the cell filled with the sample was tapped 1000 times with a stroke length of 10 mm, and the tap density was determined from the volume and the mass of the sample. Is calculated.
- the orientation ratio of the carbonaceous material is usually 0.005 or more, preferably 0.01 or more, more preferably 0.015 or more, and usually 0.67 or less. When the orientation ratio is below the above range, the high-density charge / discharge characteristics of the non-aqueous electrolyte secondary battery may deteriorate.
- the upper limit of the above range is the theoretical upper limit value of the orientation ratio of the carbonaceous material.
- the orientation ratio is measured by X-ray diffraction after pressure-molding a sample (carbonaceous material). Set the molded body obtained by filling 0.47 g of the sample into a molding machine with a diameter of 17 mm and compressing it with 58.8 MN ⁇ m -2 so that it is flush with the surface of the sample holder for measurement. X-ray diffraction is measured. An orientation ratio represented by (110) diffraction peak intensity / (004) diffraction peak intensity is calculated from the peak intensity of (110) diffraction and (004) diffraction of the obtained carbon.
- the X-ray diffraction measurement conditions are as follows. “2 ⁇ ” indicates a diffraction angle.
- ⁇ Target Cu (K ⁇ ray) graphite monochromator
- Light receiving slit 0.15
- Scattering slit 0.5 degree / measurement range and step angle / measurement time: (110) plane: 75 degrees ⁇ 2 ⁇ ⁇ 80 degrees 1 degree / 60 seconds (004) plane: 52 degrees ⁇ 2 ⁇ ⁇ 57 degrees 1 degree / 60 seconds
- the aspect ratio of the carbonaceous material is usually 1 or more and usually 10 or less, preferably 8 or less, and more preferably 5 or less. If the aspect ratio exceeds the above range, streaking or a uniform coated surface cannot be obtained when forming an electrode plate, and the high current density charge / discharge characteristics of the non-aqueous electrolyte secondary battery may deteriorate.
- the lower limit of the above range is the theoretical lower limit value of the aspect ratio of the carbonaceous material.
- Metal particles that can be alloyed with Li When a single metal and an alloy forming a lithium alloy, or a compound thereof, such as an oxide, carbide, nitride, silicide, sulfide or phosphide, is used as the negative electrode active material, the metal that can be alloyed with Li is: It is in particle form.
- the metal particles are metal particles that can be alloyed with Li, identification of the metal particle phase by X-ray diffraction, observation of the particle structure by electron microscope and elemental analysis, element by fluorescent X-rays Analysis and the like.
- the metal particles that can be alloyed with Li any conventionally known metal particles can be used.
- the metal particles are, for example, Fe, Co. Sb, Bi, Pb, Ni, Ag, Si, Sn, Al, Zr, Cr, P, S, V, Mn, As, Nb, Mo, Cu, Zn, Ge, In, Ti, and W It is preferable that the metal is selected or a compound thereof.
- an alloy composed of two or more kinds of metals may be used, and the metal particles may be alloy particles formed of two or more kinds of metal elements.
- a metal selected from the group consisting of Si, Sn, As, Sb, Al, Zn, and W or a metal compound thereof is preferable.
- metal compound examples include metal oxides, metal nitrides, and metal carbides.
- alloy which consists of 2 or more types of metals.
- Si or Si metal compounds are preferable.
- the Si metal compound is preferably a Si metal oxide.
- Si or Si metal compound is preferable in terms of increasing the capacity of the battery.
- Si or Si metal compounds are collectively referred to as Si compounds.
- Specific examples of the Si compound include SiO x , SiN x , SiC x , and SiZ x O y (Z ⁇ C, N).
- the Si compound is preferably a Si metal oxide, and the Si metal oxide is SiO x in a general formula.
- the general formula SiO x is obtained using Si dioxide (SiO 2 ) and metal Si (Si) as raw materials, and the value of x is usually 0 ⁇ x ⁇ 2.
- SiO x has a larger theoretical capacity than graphite, and amorphous Si or nano-sized Si crystals easily allow alkali ions such as lithium ions to enter and exit, so that a high capacity can be obtained.
- the Si metal oxide is specifically expressed as SiO x , where x is 0 ⁇ x ⁇ 2, more preferably 0.2 or more and 1.8 or less, and still more preferably 0.8. 4 or more and 1.6 or less, particularly preferably 0.6 or more and 1,4 or less. If it is this range, it becomes possible to reduce the irreversible capacity
- the average particle diameter (d50) of the metal particles that can be alloyed with Li is usually 0.01 ⁇ m or more, preferably 0.05 ⁇ m or more, more preferably 0.1 ⁇ m, from the viewpoint of the cycle life of the nonaqueous electrolyte secondary battery. More preferably, it is 0.3 ⁇ m or more, usually 10 ⁇ m or less, preferably 9 ⁇ m or less, more preferably 8 ⁇ m or less.
- the average particle diameter (d50) is determined by a laser diffraction / scattering particle size distribution measuring method or the like.
- the specific surface area of the metal particles that can be alloyed with Li determined by the BET method is usually 0.5 to 60 m 2 / g, and 1 to 40 m 2 / g. It is preferable that It is preferable that the specific surface area by the BET method of the metal particles that can be alloyed with Li is in the above-mentioned range since the charge / discharge efficiency and discharge capacity of the battery are high, lithium can be taken in and out quickly, and the rate characteristics are excellent.
- the oxygen content of metal particles that can be alloyed with Li is not particularly limited, but is usually 0.01 to 8% by mass, and 0.05 to 5% by mass. % Is preferred.
- the oxygen distribution state in the particles may be present near the surface, present inside the particle, or uniformly present within the particle, but is preferably present near the surface.
- the oxygen content of the metal particles that can be alloyed with Li is within the above range, the volume expansion associated with the secondary charge / discharge of the nonaqueous electrolyte solution is suppressed due to the strong bond between the metal particles and O, and the cycle characteristics are excellent. preferable.
- the negative electrode active material may contain metal particles that can be alloyed with Li and graphite particles.
- the negative electrode active material is It may be a mixture in which Li and alloyable metal particles and graphite particles are mixed in the form of independent particles, or Li and alloyable metal particles are present on the surface and / or inside of the graphite particles. It may be a complex.
- the composite of metal particles that can be alloyed with Li and graphite particles is particularly limited as long as the particles include metal particles that can be alloyed with Li and graphite particles. However, it is preferably a particle in which metal particles capable of being alloyed with Li and graphite particles are integrated by physical and / or chemical bonding. As a more preferable form, the solid particles are dispersed in the particles so that the metal particles and graphite particles that can be alloyed with Li are present at least on the surface of the composite particles and in the bulk. In order to integrate them by physical and / or chemical bonding, graphite particles are present.
- a preferable form is a composite material composed of at least metal particles capable of being alloyed with Li and graphite particles, and the graphite particles, preferably, natural graphite has a folded structure with a curved structure.
- the composite material (negative electrode active material) is characterized in that metal particles capable of being alloyed with Li are present in the gaps in the structure.
- the gap may be a gap, or a substance that buffers expansion and contraction of metal particles that can be alloyed with Li, such as amorphous carbon, graphite, and resin, is present in the gap. May be.
- the content ratio of metal particles that can be alloyed with Li with respect to the sum of metal particles that can be alloyed with Li and graphite particles is usually 0.1% by mass or more, preferably 0 0.5% by mass or more, more preferably 1.0% by mass or more, and further preferably 2.0% by mass or more. Also, it is usually 99% by mass or less, preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less, still more preferably 25% by mass or less, still more preferably 20% by mass or less, particularly Preferably it is 15 mass% or less, Most preferably, it is 10 mass% or less. This range is preferable in that a sufficient capacity can be obtained in the non-aqueous electrolyte secondary battery.
- the negative electrode active material of the present invention may be coated with a carbonaceous material or a graphite material.
- a carbonaceous material or a graphite material are preferable from the viewpoint of lithium ion acceptability.
- This coverage is usually 0.5% or more and 30% or less, preferably 1% or more and 25% or less, and more preferably 2% or more and 20% or less.
- this coverage is too large, the amorphous carbon portion of the carbonaceous material increases, and the reversible capacity when the battery is assembled tends to be small. If the coverage is too small, the core carbonaceous material is not evenly coated with amorphous carbon and strong granulation is not performed, and when pulverized after firing, the particle size tends to be too small.
- the coverage (content rate) of the carbide derived from the organic compound of the negative electrode active material finally obtained is the amount of the negative electrode active material, the amount of the organic compound, and the residue measured by a micro method in accordance with JIS K 2270. It can be calculated by the following formula based on the charcoal rate.
- the internal porosity of the negative electrode active material is usually 1% or more, preferably 3% or more, more preferably 5% or more, and further preferably 7% or more. Further, it is usually less than 50%, preferably 40% or less, more preferably 30% or less, and still more preferably 20% or less. If the internal porosity is too small, the amount of liquid in the particles of the negative electrode active material in the non-aqueous electrolyte secondary battery decreases, and the charge / discharge characteristics tend to deteriorate. On the other hand, when the internal porosity is too large, the interparticle gap is small when the electrode is used, and the nonaqueous electrolyte solution tends to be insufficiently diffused. In addition, in this void, a substance that buffers expansion and contraction of metal particles that can be alloyed with Li, such as amorphous carbon, graphite, and resin, is present in the void or filled with the void. May be.
- any known method can be used for the production of the negative electrode as long as the effects of the present invention are not significantly impaired.
- it is formed by adding a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler, etc. to a negative electrode active material to form a slurry, which is applied to a current collector, dried and then pressed. Can do.
- the alloy-based material negative electrode can be manufactured using any known method.
- a manufacturing method of the negative electrode for example, a method in which a negative electrode active material added with a binder or a conductive material is roll-formed as it is to form a sheet electrode, or a compression-molded pellet electrode and The above negative electrode is usually applied to a negative electrode current collector (hereinafter also referred to as “negative electrode current collector”) by a method such as a coating method, a vapor deposition method, a sputtering method, or a plating method.
- a method of forming a thin film layer (negative electrode active material layer) containing an active material is used.
- Examples of the material of the negative electrode current collector include steel, copper, copper alloy, nickel, nickel alloy, and stainless steel. Of these, copper foil is preferred from the viewpoint of easy processing into a thin film and cost.
- the thickness of the negative electrode current collector is usually 1 ⁇ m or more, preferably 5 ⁇ m or more, and is usually 100 ⁇ m or less, preferably 50 ⁇ m or less. If the thickness of the negative electrode current collector is too thick, the capacity of the entire non-aqueous electrolyte secondary battery may decrease too much, and conversely, if it is too thin, handling may be difficult.
- the surface of these negative electrode current collectors is preferably roughened in advance.
- Surface roughening methods include blasting, rolling with a rough surface roll, abrasive cloth paper with abrasive particles fixed, grinding wheel, emery buff, machine that polishes the current collector surface with a wire brush equipped with steel wire, etc. Examples thereof include a mechanical polishing method, an electrolytic polishing method, and a chemical polishing method.
- a perforated negative electrode current collector such as an expanded metal or a punching metal can be used.
- This type of negative electrode current collector can be freely changed in mass by changing its aperture ratio. Further, when a negative electrode active material layer is formed on both surfaces of this type of negative electrode current collector, the negative electrode active material layer is further less likely to peel due to the rivet effect through the hole. However, when the aperture ratio becomes too high, the contact area between the negative electrode active material layer and the negative electrode current collector becomes small, and thus the adhesive strength may be lowered.
- the slurry for forming the negative electrode active material layer is usually prepared by adding a binder, a thickener and the like to the negative electrode material.
- the “negative electrode material” in this specification refers to a material in which a negative electrode active material and a conductive material are combined.
- the content of the negative electrode active material in the negative electrode material is usually 70% by mass or more, particularly 75% by mass or more, and usually 97% by mass or less, and particularly preferably 95% by mass or less.
- the content of the negative electrode active material is too small, the capacity of the secondary battery using the obtained negative electrode tends to be insufficient.
- the content is too large, the content of the conductive material is relatively insufficient, so that It tends to be difficult to ensure conductivity.
- the total amount of the negative electrode active materials may be set to satisfy the above range.
- the conductive material used for the negative electrode examples include metal materials such as copper and nickel; carbon materials such as graphite and carbon black. These may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio. In particular, it is preferable to use a carbon material as the conductive material because the carbon material acts as an active material.
- the content of the conductive material in the negative electrode material is usually 3% by mass or more, preferably 5% by mass or more, and usually 30% by mass or less, and preferably 25% by mass or less. When the content of the conductive material is too small, the conductivity tends to be insufficient. When the content is too large, the content of the negative electrode active material and the like is relatively insufficient, and thus the battery capacity and strength tend to decrease. Note that when two or more conductive materials are used in combination, the total amount of the conductive materials may satisfy the above range.
- any material can be used as long as it is a material that is safe with respect to the solvent and electrolyte used in the production of the electrode.
- examples thereof include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, styrene / butadiene rubber / isoprene rubber, butadiene rubber, ethylene / acrylic acid copolymer, and ethylene / methacrylic acid copolymer. These may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.
- the content of the binder is usually 0.5 parts by mass or more, preferably 1 part by mass or more, and usually 10 parts by mass or less, preferably 8 parts by mass or less, with respect to 100 parts by mass of the negative electrode material. .
- the content of the binder is too small, the strength of the obtained negative electrode tends to be insufficient.
- the content of the negative electrode active material and the like is relatively insufficient, and thus the battery capacity and conductivity tend to be insufficient. It becomes.
- thickener used for the negative electrode examples include carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, and casein. These may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.
- the thickener may be used as necessary, but when used, the thickener content in the negative electrode active material layer is usually in the range of 0.5% by mass or more and 5% by mass or less. Is preferred.
- the slurry for forming the negative electrode active material layer is prepared by mixing a conductive material, a binder, and a thickener as necessary with the negative electrode active material, and using an aqueous solvent or an organic solvent as a dispersion medium.
- aqueous solvent water is usually used, and an organic solvent such as alcohols such as ethanol and cyclic amides such as N-methylpyrrolidone is used in combination within a range of 30% by mass or less based on water. You can also.
- organic solvent examples include cyclic amides such as N-methylpyrrolidone, linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide, and aromatic hydrocarbons such as anisole, toluene and xylene. And alcohols such as butanol and cyclohexanol.
- cyclic amides such as N-methylpyrrolidone
- linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide are preferable. Any one of these may be used alone, or two or more may be used in any combination and ratio.
- the obtained slurry is applied onto the above-described negative electrode current collector, dried, and pressed to form a negative electrode active material layer, thereby obtaining a negative electrode.
- the method of application is not particularly limited, and a method known per se can be used.
- the drying method is not particularly limited, and a known method such as natural drying, heat drying, or reduced pressure drying can be used.
- the electrode structure when the negative electrode active material is made into an electrode is not particularly limited, but the density of the negative electrode active material present on the current collector is preferably 1 g ⁇ cm ⁇ 3 or more, and 1.2 g ⁇ cm ⁇ 3 or more. but more preferably, particularly preferably 1.3 g ⁇ cm -3 or more, preferably 2.2 g ⁇ cm -3 or less, more preferably 2.1 g ⁇ cm -3 or less, 2.0 g ⁇ cm -3 or less More preferred is 1.9 g ⁇ cm ⁇ 3 or less.
- the density of the negative electrode active material present on the current collector exceeds the above range, the negative electrode active material particles are destroyed, and the initial irreversible capacity of the non-aqueous electrolyte secondary battery is increased, or the current collector / negative electrode There is a case where high current density charge / discharge characteristics are deteriorated due to a decrease in permeability of the non-aqueous electrolyte solution near the active material interface.
- the amount is less than the above range, the conductivity between the negative electrode active materials decreases, the battery resistance increases, and the capacity per unit volume may decrease.
- Lithium transition metal compound is a compound having a structure capable of desorbing and inserting Li ions, and examples thereof include sulfides, phosphate compounds, and lithium transition metal composite oxides.
- sulfides include compounds having a two-dimensional layered structure such as TiS 2 and MoS 2 , and solid compounds represented by the general formula Me x Mo 6 S 8 (Me is various transition metals including Pb, Ag, and Cu). Examples thereof include a chevrel compound having a three-dimensional skeleton structure.
- Examples of the phosphate compound include those belonging to the olivine structure, and are generally represented by LiMePO 4 (Me is at least one transition metal), specifically, LiFePO 4 , LiCoPO 4 , LiNiPO 4 , LiMnPO 4 . 4 etc. are mentioned.
- Examples of the lithium transition metal composite oxide include a spinel structure capable of three-dimensional diffusion and a layered structure capable of two-dimensional diffusion of lithium ions. Those having a spinel structure are generally expressed as LiMe 2 O 4 (Me is at least one transition metal), specifically, LiMn 2 O 4 , LiCoMnO 4 , LiNi 0.5 Mn 1.5 O 4. , LiCoVO 4 and the like.
- LiMeO 2 Those having a layered structure are generally expressed as LiMeO 2 (Me is at least one transition metal).
- LiCoO 2 Specifically, LiNiO 2, LiNi 1-x Co x O 2, LiNi 1-x-y Co x Mn y O 2, LiNi 0.5 Mn 0.5 O 2, Li 1.2 Cr 0. 4 Mn 0.4 O 2, Li 1.2 Cr 0.4 Ti 0.4 O 2, LiMnO 2 , and the like.
- composition ⁇ composition> Moreover, as a lithium transition metal type compound, the compound shown by the following compositional formula (F) or (G) is mentioned, for example.
- x is usually 0 or more and 0.5 or less.
- M is an element composed of Ni and Mn or Ni, Mn and Co, and the Mn / Ni molar ratio is usually 0.1 or more and 5 or less.
- the Ni / M molar ratio is usually 0 or more and 0.5 or less.
- the Co / M molar ratio is usually 0 or more and 0.5 or less.
- the rich portion of Li represented by x may be replaced with the transition metal site M.
- composition formula (F) the atomic ratio of the oxygen amount is described as 2 for convenience, but there may be some non-stoichiometry.
- x in the said compositional formula is the preparation composition in the manufacture stage of a lithium transition metal type compound.
- non-aqueous electrolyte secondary batteries on the market are aged after the batteries are assembled. For this reason, the Li amount of the positive electrode may be deficient with charge / discharge.
- x may be measured to be ⁇ 0.65 or more and 1 or less when discharged to 3 V in composition analysis.
- lithium transition metal compounds those obtained by firing at a high temperature in an oxygen-containing gas atmosphere in order to increase the crystallinity of the positive electrode active material are excellent in battery characteristics.
- the lithium transition metal-based compound represented by the composition formula (F) may be a solid solution with Li 2 MO 3 called a 213 layer as shown in the following general formula (F ′).
- ⁇ is a number satisfying 0 ⁇ ⁇ 1.
- M is at least one metal element having an average oxidation number of 4+, specifically, at least one metal element selected from the group consisting of Mn, Zr, Ti, Ru, Re, and Pt. .
- M ′ is at least one metal element having an average oxidation number of 3+, preferably at least one metal element selected from the group consisting of V, Mn, Fe, Co, and Ni, and more preferably Is at least one metal element selected from the group consisting of Mn, Co and Ni.
- Lithium transition metal compound represented by the following composition formula (G) Li [Li a M b Mn 2-ba ] O 4 + ⁇ (G)
- M is an element comprised from at least 1 sort (s) of the transition metals chosen from Ni, Cr, Fe, Co, Cu, Zr, Al, and Mg.
- the value of b is usually 0.4 or more and 0.6 or less. When the value of b is within this range, the energy density per unit weight in the lithium transition metal compound is high.
- a in the above composition formula is a charged composition in the production stage of the lithium transition metal compound.
- batteries on the market are aged after the batteries are assembled. For this reason, the Li amount of the positive electrode may be deficient with charge / discharge. In this case, a may be measured to be ⁇ 0.65 or more and 1 or less when discharged to 3 V in composition analysis.
- the energy density per unit weight in the lithium transition metal compound is not significantly impaired, and good load characteristics can be obtained.
- the value of ⁇ is usually in the range of ⁇ 0.5. If the value of ⁇ is within this range, the stability as a crystal structure is high, and the cycle characteristics and high-temperature storage of a battery having a positive electrode prepared using this lithium transition metal compound are good.
- composition formulas a and b of the lithium transition metal compound are calculated by analyzing each transition metal and lithium with an inductively coupled plasma emission spectrometer (ICP-AES) to obtain the ratio of Li / Ni / Mn. Is done.
- ICP-AES inductively coupled plasma emission spectrometer
- the lithium related to a is substituted for the same transition metal site.
- the average valence of M and manganese becomes larger than 3.5 due to the principle of charge neutrality.
- the lithium transition metal compound may be fluorine-substituted, and such a compound is represented as LiMn 2 O 4-x F 2x .
- lithium transition metal compound having the above composition examples include, for example, Li 1 + x Ni 0.5 Mn 0.5 O 2 , Li 1 + x Ni 0.85 Co 0.10 Al 0.05 O 2 , Li 1 + x Ni 0.33 Mn 0.33 Co 0.33 O 2 , Li 1 + x Ni 0.45 Mn 0.45 Co 0.1 O 2 , Li 1 + x Mn 1.8 Al 0.2 O 4 , Li 1 + x Mn 1.5 Ni 0.5 O 4 and the like.
- These lithium transition metal compounds may be used alone or in a blend of two or more.
- a different element may be introduced into the lithium transition metal compound.
- B Na, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Ru, Rh, Pd, Ag, In, Sb, Te , Ba, Ta, Mo, W, Re, Os, Ir, Pt, Au, Pb, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Bi , N, F, S, Cl, Br, I, As, Ge, P, Pb, Sb, Si and Sn are selected.
- These foreign elements may be incorporated into the crystal structure of the lithium transition metal compound, or may not be incorporated into the crystal structure of the lithium transition metal compound, and may be a single element or compound on the particle surface or grain boundary. May be unevenly distributed.
- a positive electrode for a non-aqueous electrolyte secondary battery is formed by forming a positive electrode active material layer containing a powder of the above-described lithium transition metal compound and a binder on a current collector.
- the positive electrode active material layer is usually formed by mixing a positive electrode material, a binder, and a conductive material and a thickener, which are used if necessary, in a dry form into a sheet shape, and then pressing the positive electrode current collector on the positive electrode current collector.
- these materials are dissolved or dispersed in a liquid medium to form a slurry, which is applied to the positive electrode current collector and dried.
- metal materials such as aluminum, stainless steel, nickel plating, titanium and tantalum, and carbon materials such as carbon cloth and carbon paper are usually used.
- shape in the case of a metal material, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, a foam metal, etc., and in the case of a carbon material, a carbon plate, a carbon thin film, a carbon cylinder Etc.
- the metal thin film may be appropriately formed in a mesh shape.
- the positive electrode current collector When a metal thin film is used as the positive electrode current collector, its thickness is arbitrary, but a range of usually 1 ⁇ m or more and 100 mm or less is suitable. If it is thinner than the above range, the strength required for the current collector may be insufficient. On the other hand, if it is thicker than the above range, the handleability may be impaired.
- the binder used for manufacturing the positive electrode active material layer is not particularly limited, and in the case of a coating method, any material that is stable with respect to the liquid medium used during electrode manufacturing may be used.
- Specific examples thereof include polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, resin polymers such as nitrocellulose, Rubber polymers such as SBR (styrene butadiene rubber), NBR (acrylonitrile butadiene rubber), fluorine rubber, isoprene rubber, butadiene rubber, ethylene propylene rubber, Styrene / butadiene / styrene block copolymer and hydrogenated product thereof, EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene / butadiene / ethylene copolymer, styrene / isoprene styrene block copolymer and the like
- the ratio of the binder in the positive electrode active material layer is usually 0.1% by mass or more and 80% by mass or less. If the proportion of the binder is too low, the positive electrode active material cannot be sufficiently retained and the positive electrode has insufficient mechanical strength, which may deteriorate battery performance such as cycle characteristics. Battery capacity and conductivity may be reduced.
- the positive electrode active material layer usually contains a conductive material in order to increase conductivity.
- a conductive material there are no particular restrictions on the type, but specific examples include metal materials such as copper and nickel, graphite such as natural graphite and artificial graphite, carbon black such as acetylene black, and amorphous carbon such as needle coke.
- the carbon material etc. of this can be mentioned.
- these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
- the proportion of the conductive material in the positive electrode active material layer is usually 0.01% by mass or more and 50% by mass or less. If the proportion of the conductive material is too low, the conductivity may be insufficient, and conversely if it is too high, the battery capacity may be reduced.
- the liquid medium for forming the slurry is a solvent capable of dissolving or dispersing the lithium transition metal compound powder as the positive electrode material, the binder, and the conductive material and thickener used as necessary. If it is, the type is not particularly limited, and either an aqueous solvent or an organic solvent may be used. Examples of the aqueous solvent include water, alcohol, etc.
- organic solvent examples include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N , N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran (THF), toluene, acetone, dimethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, etc. be able to.
- NMP N-methylpyrrolidone
- dimethylformamide dimethylacetamide
- methyl ethyl ketone cyclohexanone
- methyl acetate methyl acrylate
- diethyltriamine N , N-dimethylaminopropylamine
- the solvents described above may be used alone or in combinations of two or more in any combination.
- the content ratio of the lithium transition metal-based compound powder as the positive electrode material in the positive electrode active material layer is usually 10% by mass or more and 99.9% by mass or less. If the proportion of the lithium transition metal compound powder in the positive electrode active material layer is too large, the strength of the positive electrode tends to be insufficient, and if it is too small, the capacity may be insufficient.
- the thickness of the positive electrode active material layer is usually about 10 to 200 ⁇ m.
- the electrode density after pressing of the positive electrode is usually 2.2 g / cm 3 or more and 4.2 g / cm 3 or less.
- the positive electrode active material layer obtained by coating and drying is preferably consolidated by a roller press or the like in order to increase the packing density of the positive electrode active material.
- a positive electrode for a non-aqueous electrolyte secondary battery can be prepared.
- a separator is interposed between the positive electrode and the negative electrode in order to prevent a short circuit.
- the nonaqueous electrolytic solution of the present invention is usually used by impregnating the separator.
- the material and shape of the separator are not particularly limited, and known ones can be arbitrarily adopted as long as the effects of the present invention are not significantly impaired.
- a separator made of a material that is stable with respect to the non-aqueous electrolyte solution of the present invention, made of a resin, glass fiber, inorganic material, etc. is used. It is preferable to use a separator or the like.
- polyolefins such as polyethylene and polypropylene, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, glass filters and the like can be used. Of these, glass filters and polyolefins are preferred, and polyolefins are more preferred. These materials may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
- the thickness of the separator is arbitrary, but is usually 1 ⁇ m or more, preferably 5 ⁇ m or more, more preferably 10 ⁇ m or more, and usually 50 ⁇ m or less, preferably 40 ⁇ m or less, more preferably 30 ⁇ m or less. If the separator is thinner than the above range, the insulation and mechanical strength may be reduced. On the other hand, if the thickness is larger than the above range, not only battery performance such as rate characteristics may be lowered, but also the energy density of the entire non-aqueous electrolyte secondary battery may be lowered.
- the porosity of the separator is arbitrary, but is usually 20% or more, preferably 35% or more, more preferably 45% or more, Further, it is usually 90% or less, preferably 85% or less, and more preferably 75% or less. If the porosity is smaller than the above range, the film resistance tends to increase and the rate characteristics tend to deteriorate. Moreover, when larger than the said range, it exists in the tendency for the mechanical strength of a separator to fall and for insulation to fall.
- the average pore diameter of the separator is also arbitrary, but is usually 0.5 ⁇ m or less, preferably 0.2 ⁇ m or less, and usually 0.05 ⁇ m or more. If the average pore diameter exceeds the above range, a short circuit tends to occur. On the other hand, below the above range, the film resistance may increase and the rate characteristics may deteriorate.
- oxides such as alumina and silicon dioxide
- nitrides such as aluminum nitride and silicon nitride
- sulfates such as barium sulfate and calcium sulfate are used. Used.
- a thin film shape such as a nonwoven fabric, a woven fabric, or a microporous film is used.
- the thin film shape those having a pore diameter of 0.01 to 1 ⁇ m and a thickness of 5 to 50 ⁇ m are preferably used.
- a separator formed by forming a composite porous layer containing inorganic particles on the surface layer of the positive electrode and / or the negative electrode using a resin binder can be used.
- a separator obtained by forming a porous layer by attaching alumina particles having a 90% particle size of less than 1 ⁇ m to both surfaces of the positive electrode using a fluororesin as a binder is mentioned.
- the characteristics of the non-electrolyte secondary battery of the separator can be grasped by the Gurley value.
- Gurley value indicates the difficulty of air passage in the film thickness direction, and is expressed as the number of seconds required for 100 ml of air to pass through the film. It means that it is harder to go through. That is, a smaller value means better communication in the thickness direction of the film, and a larger value means lower communication in the thickness direction of the film. Communication is the degree of connection of holes in the film thickness direction. If the Gurley value of the separator is low, it can be used for various purposes.
- a low Gurley value means that lithium ions can be easily transferred and is preferable because of excellent battery performance.
- the Gurley value of the separator is optional, but is preferably 10 to 1000 seconds / 100 ml, more preferably 15 to 800 seconds / 100 ml, and still more preferably 20 to 500 seconds / 100 ml. If the Gurley value is 1000 seconds / 100 ml or less, the electrical resistance is substantially low, which is preferable as a separator.
- the electrode group has a laminated structure in which the positive electrode plate and the negative electrode plate are interposed through the separator, and a structure in which the positive electrode plate and the negative electrode plate are wound in a spiral shape through the separator. Either is acceptable.
- the ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupation ratio) is usually 40% or more, preferably 50% or more, and usually 90% or less, preferably 80% or less. .
- the battery capacity decreases.
- the above range is exceeded, there are few void spaces, the battery expands, and the internal pressure rises due to the expansion of the vapor pressure of the liquid component of the electrolyte due to the high temperature of the battery.
- various characteristics such as charge / discharge repeatability and high-temperature storage are deteriorated, and further, a gas release valve for releasing the internal pressure to the outside operates.
- the material of the outer case is not particularly limited as long as it is a substance that is stable with respect to the non-aqueous electrolyte used. Specifically, a nickel-plated steel plate, stainless steel, aluminum, an aluminum alloy, a metal such as a magnesium alloy, or a laminated film (laminate film) of a resin and an aluminum foil is used. From the viewpoint of weight reduction, an aluminum or aluminum alloy metal or a laminate film is preferably used.
- an outer case using metals an outer case having a sealed hermetically sealed structure by welding metals together by laser welding, resistance welding, or ultrasonic welding, or a caulking structure using the above metals via a resin gasket And an exterior case.
- the exterior case using the laminate film include an exterior case having a sealed and sealed structure by heat-sealing resin layers.
- a resin different from the resin used for the laminate film may be interposed between the resin layers.
- a resin layer is heat-sealed through a current collecting terminal to form a sealed structure, a metal and a resin are joined, so that a resin having a polar group or a modified group having a polar group introduced as an intervening resin is used.
- Resins are preferably used.
- PTC Positive Temperature Coefficient
- thermal fuse shuts off the current flowing through the circuit due to sudden increase in battery internal pressure or internal temperature during abnormal heat generation
- a valve current cutoff valve or the like
- the protective element it is preferable to select an element that does not operate under normal use at a high current, and it is more preferable that the protective element has a design that does not cause abnormal heat generation or thermal runaway even without the protective element.
- the non-aqueous electrolyte secondary battery of the present invention is usually configured by housing the non-aqueous electrolyte, the negative electrode, the positive electrode, the separator, and the like in an exterior body (exterior case).
- an exterior body exterior body
- the material of the exterior body is not particularly limited as long as it is a stable substance with respect to the non-aqueous electrolyte used. Specifically, a nickel-plated steel plate, stainless steel, aluminum or an aluminum alloy, a magnesium alloy, nickel, titanium, or a metal, or a laminated film (laminate film) of a resin and an aluminum foil is used. From the viewpoint of weight reduction, an aluminum or aluminum alloy metal or a laminate film is preferably used.
- the exterior body made into the structure is mentioned.
- Examples of the exterior body using the laminate film include an exterior body having a hermetically sealed structure by heat-sealing the resin layers. In order to improve sealing performance, a resin different from the resin used for the laminate film may be interposed between the resin layers.
- a resin layer is heat-sealed through a current collecting terminal to form a sealed structure, a metal and a resin are joined, so that a resin having a polar group or a modified group having a polar group introduced as an intervening resin is used.
- Resins are preferably used.
- the shape of the exterior body is also arbitrary, and may be any of a cylindrical shape, a square shape, a laminate shape, a coin shape, a large size, and the like.
- An electrolytic solution in which VC is added to the preliminary solution by 5.0% by mass (in a total of 100% by mass of the solution) (this is referred to as a reference electrolytic solution 2)
- An electrolytic solution in which MFEC was added to the preliminary solution by 5.0% by mass (in a total of 100% by mass of the solution) was prepared (this is referred to as reference electrolytic solution 3).
- Non-aqueous electrolytes were prepared by adding each compound to the reference electrolytes 1 to 3 in the proportions shown in Table 1 below.
- Comparative Example 1-1 is Reference Electrolytic Solution 1
- Comparative Example 1-14 is Reference Electrolytic Solution 2
- Comparative Example 1-15 is Reference Electrolytic Solution 3 itself.
- the “added amount (wt%)” in the table is the concentration in 100% by weight of the non-aqueous electrolyte solution.
- Natural graphite powder as negative electrode active material aqueous dispersion of sodium carboxymethyl cellulose (concentration of 1% by weight of carboxymethyl cellulose sodium) and aqueous dispersion of styrene-butadiene rubber (styrene-butadiene) as thickener and binder, respectively.
- a rubber concentration of 50% by mass was mixed with a disperser to form a slurry. This slurry was uniformly applied to one side of a 12 ⁇ m thick copper foil, dried, and then pressed to obtain a negative electrode.
- non-aqueous electrolyte secondary batteries laminate type
- the positive electrode, the negative electrode, and the polyolefin separator were laminated in the order of the negative electrode, the separator, the positive electrode, the separator, and the negative electrode.
- the battery element thus obtained was wrapped in an aluminum laminate film, and the above-described non-aqueous electrolyte solution was injected, followed by vacuum sealing to produce a sheet-like non-aqueous electrolyte secondary battery.
- Table 1 shows the charge storage gas amount of each Example and Comparative Example normalized by the value of Comparative Example 1-1.
- Example 2-1 and 2-2 Comparative Examples 2-1 and 2-2> With respect to the reference electrolyte solution 1, each compound was added at a ratio shown in Table 2 below to prepare a non-aqueous electrolyte solution. However, Comparative Example 2-1 is the reference electrolyte 1 itself. The “added amount (wt%)” in the table is the concentration in 100% by weight of the non-aqueous electrolyte solution. The same positive electrode, negative electrode, and non-aqueous electrolyte secondary battery as in Example 1 were prepared and tested.
- Table 2 shows the 1.0 C / 0.2 C load after storage of each Example and Comparative Example normalized by the value of Comparative Example 2-1.
- Comparative Example 3-1 [Preparation of non-aqueous electrolyte] With respect to the reference electrolyte solution 3, each compound was added at a ratio shown in Table 3 below to prepare a non-aqueous electrolyte solution. However, Comparative Example 3-1 is the reference electrolyte 3 itself. The “added amount (wt%)” in the table is the concentration in 100% by weight of the non-aqueous electrolyte solution.
- Table 3 shows the 60 ° C. charge storage gas amount of each example and comparative example, normalized by the value of Comparative Example 3-1.
- Example 4-1 to 4-5 Comparative Examples 4-1 to 4-3>
- each compound was added at a ratio shown in Table 4 below to prepare a non-aqueous electrolyte solution.
- Comparative Example 4-1 is the reference electrolyte 1 itself.
- the “added amount (wt%)” in the table is the concentration in 100% by weight of the non-aqueous electrolyte solution.
- the same positive electrode, negative electrode, and non-aqueous electrolyte battery as those of Example 1 were prepared and evaluated.
- Table 4 below shows the continuous charge test gas amounts of each Example and Comparative Example, normalized by the values of Comparative Example 4-1.
- Example 5-1 to 5-2 Comparative Examples 5-1 to 5-2>
- each compound was added at a ratio shown in Table 5 below to prepare a non-aqueous electrolyte solution.
- Comparative Example 5-1 is the reference electrolyte 1 itself.
- the “added amount (wt%)” in the table is the concentration in 100% by weight of the non-aqueous electrolyte solution.
- the same positive electrode, negative electrode, and non-aqueous electrolyte secondary battery as in Example 1 were prepared and tested.
- the non-aqueous electrolyte secondary battery after the initial battery characteristics evaluation was CC-CV charged at 0.05C to 4.4V at 25 ° C (0.05C cut), and then immersed in an ethanol bath.
- the battery volume was determined from the buoyancy, and the change from the initial battery volume was defined as the “initial gas amount” before storage.
- Table 5 below shows the initial gas amounts of the examples and comparative examples normalized by the values of comparative example 5-1.
- Example 5-2 which uses the compound represented by the general formula (A) and the cyclic sulfonic acid ester in combination, suppresses the initial gas amount as compared with the case where each compound is used alone.
- the cyclic sulfonic acid ester is added alone (Comparative Example 5-2)
- the initial gas amount is increased, and thus a synergistic effect by the combined use is shown.
- Table 6 shows the 80 ° C. charge storage gas amount of each Example and Comparative Example, normalized by the values of Comparative Example 6-1.
- Comparative Example 7-1 is the reference electrolyte solution 3 itself
- Comparative Example 7-2 is the reference electrolyte solution 5 itself.
- the “added amount (wt%)” in the table is the concentration in 100% by weight of the non-aqueous electrolyte solution.
- Table 7 shows the recovery 0.2 C capacity of each Example and Comparative Example, normalized by the value of Comparative Example 7-1.
- Example 8-1 and Comparative Example 8-1> Preparation of non-aqueous electrolyte
- a mixture of EC, dimethyl carbonate (DMC), and EMC (volume ratio 3: 3: 4) with LiPF 6 sufficiently dried was 1.0 mol / L (in a non-aqueous electrolyte).
- VC was added in an amount of 1.2% by mass (in a total of 100% by mass of the solution) (this is referred to as a reference electrolyte solution 6).
- Each compound was added to the reference electrolyte solution 6 at a ratio shown in Table 8 below to prepare an electrolyte solution.
- Comparative Example 8-1 is the reference electrolyte 6 itself.
- the “added amount (wt%)” in the table is the concentration in 100% by weight of the non-aqueous electrolyte solution.
- the graphite used has a d50 value of 10.9 ⁇ m, a specific surface area of 3.41 m 2 ⁇ g ⁇ 1 , and a tap density of 0.985 g ⁇ cm -3 .
- the positive electrode, the negative electrode, and the separator were stacked in the order of the negative electrode, the separator, and the positive electrode.
- the separator was made of polypropylene, had a thickness of 20 ⁇ m, and a porosity of 54%.
- the battery element thus obtained was wrapped with a cylindrical aluminum laminate film, and the electrolyte solution was injected, followed by vacuum sealing to produce a sheet-like non-aqueous electrolyte secondary battery. Furthermore, in order to improve the adhesion between the electrodes, the sheet-like battery was sandwiched between glass plates and pressurized.
- the battery was stored at 60 ° C. for 12 hours to stabilize the battery. Thereafter, a charge / discharge cycle of 1/3 C constant current-constant voltage charge up to 3.8 V at 25 ° C., followed by 1/3 C constant current discharge up to 2.5 V was performed. The last discharge capacity at this time was defined as the initial capacity.
- Table 8 below shows the cell swelling after storage of each Example and Comparative Example, normalized by the value of Comparative Example 8-1.
- Comparative Example 9-1 [Preparation of non-aqueous electrolyte] Under a dry argon atmosphere, 1.0 mol / L (as a concentration in the non-aqueous electrolyte) of LiPF 6 sufficiently dried was dissolved in a mixture with EC and DEC (volume ratio 3: 7). VC and MFEC were each added in an amount of 2.0% by mass (in a total of 100% by mass of the solution) (this is referred to as reference electrolyte solution 7). Each compound was added to the reference electrolyte solution 7 at a ratio shown in Table 9 below to prepare an electrolyte solution. However, Comparative Example 9-1 is the reference electrolyte solution 7 itself. The “added amount (wt%)” in the table is the concentration in 100% by weight of the non-aqueous electrolyte solution.
- Lithium / nickel / cobalt / manganese composite oxide Li 1.05 Ni 0.33 Mn 0.33 Co 0.33 O 2 ) 85% by mass as a positive electrode active material and 10% by mass of acetylene black as a conductive material
- 5% by mass of polyvinylidene fluoride (PVdF) was mixed with a disperser in an N-methylpyrrolidone solvent to form a slurry. This was uniformly applied to both sides of a 21 ⁇ m thick aluminum foil, dried, and then pressed to obtain a positive electrode.
- the obtained fired product was further pulverized with a hammer mill, and then subjected to sieving (45 ⁇ m) to prepare a negative electrode active material 1.
- the content of silicon element, average particle diameter d50, tap density, and specific surface area measured by the above measurement methods were 2.0% by mass, 20 ⁇ m, 1.0 g / cm 3, and 7.2 m 2 / g, respectively.
- Negative electrode active materials 2 and 3 having various Si contents shown in Table 9 below were prepared in the same manner as the negative electrode active material 1.
- the Si content is the mass concentration (% by mass) of the Si particles with respect to the total (100% by mass) of the Si particles and the graphite particles.
- Table 10 below shows the storage gas amounts of each Example and Comparative Example, normalized by the value of Comparative Example 9-1.
- Example 10-1 Comparative Example 10-1> [Preparation of non-aqueous electrolyte]
- each compound was added at a ratio shown in Table 11 below with respect to the entire reference electrolyte solution 7 to prepare an electrolyte solution.
- Comparative Example 10-1 is the reference electrolyte 7 itself.
- the “added amount (wt%)” in the table is the concentration in 100% by weight of the non-aqueous electrolyte solution.
- Table 11 shows the 0.5C / 0.2C load after storage of each Example and Comparative Example normalized by the value of Comparative Example 10-1.
- Example 11-1 Comparative Examples 11-1 and 11-2> [Preparation of non-aqueous electrolyte] Under a dry argon atmosphere, 1.0 mol / L (as a concentration in the non-aqueous electrolyte) of LiPF 6 sufficiently dried was dissolved in a mixture with EC, DMC, and EMC (volume ratio 3: 3: 4). Further, MFEC, Compound 26, and Compound 27 were added at 3.0, 1.5, and 1.0% by mass (in a total of 100% by mass of the solution), respectively (this is referred to as reference electrolyte solution 8). Each compound was added to the reference electrolyte solution 8 at a ratio shown in Table 12 below to prepare an electrolyte solution. However, Comparative Example 11-1 is the reference electrolyte 8 itself. The “added amount (wt%)” in the table is the concentration in 100% by weight of the non-aqueous electrolyte solution.
- Lithium / nickel / cobalt / manganese composite oxide (Li 1.05 Ni 0.33 Mn 0.33 Co 0.33 O 2 ) 90% by mass as a positive electrode active material and 7% by mass of acetylene black as a conductive material
- PVdF polyvinylidene fluoride
- High temperature storage test The battery after the initial conditioning was CC-CV charged to 4.3 V at 0.2 C and subjected to a high temperature storage test at 60 ° C. for 30 days. After sufficiently cooling the battery, the volume was measured by immersing in an ethanol bath, and the amount of generated gas was determined from the volume change before and after the storage test, and this was defined as “60 ° C. storage gas amount”.
- Table 12 shows the amount of stored gas at 60 ° C. of each Example and Comparative Example, normalized by the value of Comparative Example 11-1.
- Example 12-1 to 12-2 Comparative Examples 12-1 to 12-2> [Preparation of non-aqueous electrolyte] With respect to the reference electrolyte solution 1, each compound was added at a ratio shown in Table 13 below to prepare a non-aqueous electrolyte solution. However, Comparative Example 12-1 is the reference electrolyte 1 itself. The “added amount (wt%)” in the table is the concentration in 100% by weight of the non-aqueous electrolyte solution.
- non-aqueous electrolyte secondary batteries (coin type)
- the positive electrode was housed in a stainless steel can that also serves as a positive electrode conductor, and the negative electrode was placed on a polypropylene separator impregnated with the non-aqueous electrolyte.
- the can body and a sealing plate serving also as a negative electrode conductor were caulked and sealed through an insulating gasket to produce a non-aqueous electrolyte secondary battery (coin type).
- Table 13 below shows the “high temperature storage capacity remaining rate (%)” of each Example and Comparative Example, normalized by the value of Comparative Example 12-1.
- the discharge storage characteristics and the high-temperature storage characteristics are improved in a well-balanced manner, so that it can be suitably used in all fields such as electronic devices using non-aqueous electrolyte secondary batteries. Moreover, it can utilize suitably also in electrolytic capacitors, such as a lithium ion capacitor using a non-aqueous electrolyte solution.
- non-aqueous electrolyte solution and the non-aqueous electrolyte secondary battery of the present invention is not particularly limited, and can be used for various known applications. Specific examples of applications include laptop computers, electronic book players, mobile phones, mobile faxes, mobile copy, mobile printers, mobile audio players, small video cameras, LCD TVs, handy cleaners, transceivers, electronic notebooks, calculators, and memories. Cards, portable tape recorders, radios, backup power supplies, automobiles, motorcycles, motorbikes, bicycles, lighting equipment, toys, game machines, watches, electric tools, strobes, cameras, etc.
Abstract
Description
(a)金属イオンを吸蔵及び放出可能な正極及び負極を備える非水系電解液二次電池用の非水系電解液であって、該非水系電解液が電解質及び非水系溶媒とともに下記一般式(A)で表される化合物を含有する、非水系電解液:
1-1.本発明の非水系電解液
本発明の非水系電解液は、下記一般式(A)で表される化合物を含有することを特徴としている。
本発明の非水系電解液は、一般式(A)で表される化合物の他に、炭素-炭素不飽和結合を有する環状カーボネート、フッ素原子を有する環状カーボネート、フッ素原子を有する環状カーボネート、ニトリル化合物、イソシアネート化合物、イソシアヌル酸骨格を有する化合物、フッ素化された塩、酸無水物化合物、アクリレート化合物、芳香族化合物、環状エーテル化合物、オキサラート塩及び環状スルホン酸エステルからなる群より選ばれる少なくとも1種の特定添加剤をさらに含有することが、電池特性向上の点から好ましい。
炭素-炭素不飽和結合を有する環状カーボネート(以下、「不飽和環状カーボネート」と記載する場合がある)としては、炭素-炭素二重結合または炭素-炭素三重結合を有する環状カーボネートであれば、特に制限はない。不飽和環状カーボネートとしては、任意の不飽和カーボネートを用いることができる。なお、芳香環を有する環状カーボネートも、不飽和環状カーボネートに包含されることとする。また、不飽和環状カーボネートは、フッ素原子を有していてもよく(フッ素化不飽和カーボネートとも呼ぶ)、その場合、フッ素原子は通常6以下であり、好ましくは4以下であり、1又は2であることが最も好ましい。
ビニレンカーボネート、メチルビニレンカーボネート、4,5-ジメチルビニレンカーボネート、フェニルビニレンカーボネート、4,5-ジフェニルビニレンカーボネート、ビニルビニレンカーボネート、4,5-ジビニルビニレンカーボネート、アリルビニレンカーボネート、4,5-ジアリルビニレンカーボネート、4-フルオロビニレンカーボネート、4-フルオロ-5-メチルビニレンカーボネート、4-フルオロ-5-フェニルビニレンカーボネート、4-フルオロ-5-ビニルビニレンカーボネート、4-アリル-5-フルオロビニレンカーボネート等が挙げられる。
ビニルエチレンカーボネート、4,5-ジビニルエチレンカーボネート、4-メチル-5-ビニルエチレンカーボネート、4-アリル-5-ビニルエチレンカーボネート、エチニルエチレンカーボネート、4,5-ジエチニルエチレンカーボネート、4-メチル-5-エチニルエチレンカーボネート、4-ビニル-5-エチニルエチレンカーボネート、4-アリル-5-エチニルエチレンカーボネート、フェニルエチレンカーボネート、4,5-ジフェニルエチレンカーボネート、4-フェニル-5-ビニルエチレンカーボネート、4-アリル-5-フェニルエチレンカーボネート、アリルエチレンカーボネート、4,5-ジアリルエチレンカーボネート、4-メチル-5-アリルエチレンカーボネート、4-フルオロ-4-ビニルエチレンカーボネート、4-フルオロ-4-アリルエチレンカーボネート、4-フルオロ-5-ビニルエチレンカーボネート、4-フルオロ-5-アリルエチレンカーボネート、4,4-ジフルオロ-4-ビニルエチレンカーボネート、4,4-ジフルオロ-4-アリルエチレンカーボネート、4,5-ジフルオロ-4-ビニルエチレンカーボネート、4,5-ジフルオロ-4-アリルエチレンカーボネート、4-フルオロ-4,5-ジビニルエチレンカーボネート、4-フルオロ-4,5-ジアリルエチレンカーボネート、4,5-ジフルオロ-4,5-ジビニルエチレンカーボネート、4,5-ジフルオロ-4,5-ジアリルエチレンカーボネート、4-フルオロ-4-フェニルエチレンカーボネート、4-フルオロ-5-フェニルエチレンカーボネート、4,4-ジフルオロ-5-フェニルエチレンカーボネート、4,5-ジフルオロ-4-フェニルエチレンカーボネート等が挙げられる。
ビニレンカーボネート、メチルビニレンカーボネート、4,5-ジメチルビニレンカーボネート、ビニルビニレンカーボネート、4,5-ビニルビニレンカーボネート、アリルビニレンカーボネート、4,5-ジアリルビニレンカーボネート、ビニルエチレンカーボネート、4,5-ジビニルエチレンカーボネート、4-メチル-5-ビニルエチレンカーボネート、アリルエチレンカーボネート、4,5-ジアリルエチレンカーボネート、4-メチル-5-アリルエチレンカーボネート、4-アリル-5-ビニルエチレンカーボネート、エチニルエチレンカーボネート、4,5-ジエチニルエチレンカーボネート、4-メチル-5-エチニルエチレンカーボネート、4-ビニル-5-エチニルエチレンカーボネート、4-フルオロビニレンカーボネート、4-フルオロ-5-メチルビニレンカーボネート、4-フルオロ-5-ビニルビニレンカーボネート、4-アリル-5-フルオロビニレンカーボネート、4-フルオロ-4-ビニルエチレンカーボネート、4-フルオロ-4-アリルエチレンカーボネート、4-フルオロ-5-ビニルエチレンカーボネート、4-フルオロ-5-アリルエチレンカーボネート、4,4-ジフルオロ-4-ビニルエチレンカーボネート、4,4-ジフルオロ-4-アリルエチレンカーボネート、4,5-ジフルオロ-4-ビニルエチレンカーボネート、4,5-ジフルオロ-4-アリルエチレンカーボネート、4-フルオロ-4,5-ジビニルエチレンカーボネート、4-フルオロ-4,5-ジアリルエチレンカーボネート、4,5-ジフルオロ-4,5-ジビニルエチレンカーボネート、4,5-ジフルオロ-4,5-ジアリルエチレンカーボネートが挙げられる。
ネートは特に安定な界面保護被膜を形成するので、特に好ましい。
特定添加剤であるフッ素原子を有する環状カーボネートとしては、炭素原子数2~6のアルキレン基を有する環状カーボネートのフッ素化物、及びその誘導体が挙げられる。それらの例としては、エチレンカーボネートのフッ素化物、及びその誘導体が挙げられる。前記エチレンカーボネートのフッ素化物の誘導体としては、例えば、アルキル基(例えば、炭素原子数1~4個のアルキル基)で置換されたエチレンカーボネートのフッ素化物が挙げられる。フッ素原子を有する環状カーボネートとしては、フッ素原子を1~8個有するエチレンカーボネート、及びその誘導体が好ましい。なお、フッ素原子を有し、かつ不飽和結合を有する環状カーボネートについては、上記1-2-1.に記載している。
モノフルオロエチレンカーボネート、4,4-ジフルオロエチレンカーボネート、4,5-ジフルオロエチレンカーボネート、4-フルオロ-4-メチルエチレンカーボネート、4,5-ジフルオロ-4-メチルエチレンカーボネート、4-フルオロ-5-メチルエチレンカーボネート、4,4-ジフルオロ-5-メチルエチレンカーボネート、4-(フルオロメチル)-エチレンカーボネート、4-(ジフルオロメチル)-エチレンカーボネート、4-(トリフルオロメチル)-エチレンカーボネート、4-(フルオロメチル)-4-フルオロエチレンカーボネート、4-(フルオロメチル)-5-フルオロエチレンカーボネート、4-フルオロ-4,5-ジメチルエチレンカーボネート、4,5-ジフルオロ-4,5-ジメチルエチレンカーボネート、4,4-ジフルオロ-5,5-ジメチルエチレンカーボネート等が挙げられる。
特定添加剤であるニトリル化合物は、分子内にシアノ基を有している化合物であれば特にその種類は限定されない。
アセトニトリル、プロピオニトリル、ブチロニトリル、イソブチロニトリル、バレロニトリル、イソバレロニトリル、デカンニトリル、ラウロニトリル、2-メチルブチロニトリル、トリメチルアセトニトリル、ヘキサンニトリル、シクロペンタンカルボニトリル、シクロヘキサンカルボニトリル、アクリロニトリル、メタクリロニトリル、クロトノニトリル、3-メチルクロトノニトリル、2-メチル-2-ブテン二トリル、2-ペンテンニトリル、2-メチル-2-ペンテンニトリル、3-メチル-2-ペンテンニトリル、2-ヘキセンニトリル、フルオロアセトニトリル、ジフルオロアセトニトリル、トリフルオロアセトニトリル、2-フルオロプロピオニトリル、3-フルオロプロピオニトリル、2,2-ジフルオロプロピオニトリル、2,3-ジフルオロプロピオニトリル、3,3-ジフルオロプロピオニトリル、2,2,3-トリフルオロプロピオニトリル、3,3,3-トリフルオロプロピオニトリル、3,3’-オキシジプロピオニトリル、3,3’-チオジプロピオニトリル、1,2,3-プロパントリカルボニトリル、1,3,5-ペンタントリカルボニトリル、ペンタフルオロプロピオニトリル等のニトリル基を1つ有する化合物;
マロノニトリル、スクシノニトリル、グルタロニトリル、アジポニトリル、ピメロニトリル、スベロニトリル、アゼラニトリル、セバコニトリル、ウンデカンジニトリル、ドデカンジニトリル、メチルマロノニトリル、エチルマロノニトリル、イソプロピルマロノニトリル、tert-ブチルマロノニトリル、メチルスクシノニトリル、2,2-ジメチルスクシノニトリル、2,3-ジメチルスクシノニトリル、2,3,3-トリメチルスクシノニトリル、2,2,3,3-テトラメチルスクシノニトリル、2,3-ジエチル-2,3-ジメチルスクシノニトリル、2,2-ジエチル-3,3-ジメチルスクシノニトリル、ビシクロヘキシル-1,1-ジカルボニトリル、ビシクロヘキシル-2,2-ジカルボニトリル、ビシクロヘキシル-3,3-ジカルボニトリル、2,5-ジメチル-2,5-ヘキサンジカルボニトリル、2,3-ジイソブチル-2,3-ジメチルスクシノニトリル、2,2-ジイソブチル-3,3-ジメチルスクシノニトリル、2-メチルグルタロニトリル、2,3-ジメチルグルタロニトリル、2,4-ジメチルグルタロニトリル、2,2,3,3-テトラメチルグルタロニトリル、2,2,4,4-テトラメチルグルタロニトリル、2,2,3,4-テトラメチルグルタロニトリル、2,3,3,4-テトラメチルグルタロニトリル、マレオニトリル、フマロニトリル、1,4-ジシアノペンタン、2,6-ジシアノヘプタン、2,7-ジシアノオクタン、2,8-ジシアノノナン、1,6-ジシアノデカン、1,2-ジジアノベンゼン、1,3-ジシアノベンゼン、1,4-ジシアノベンゼン、3,3’-(エチレンジオキシ)ジプロピオニトリル、3,3’-(エチレンジチオ)ジプロピオニトリル、3,9-ビス(2-シアノエチル)-2,4,8,10-テトラオキサスピロ[5,5]ウンデカン等のニトリル基を2つ有する化合物;
シクロヘキサントリカルボニトリル、トリスシアノエチルアミン、トリスシアノエトキシプロパン、トリシアノエチレン、ペンタントリカルボニトリル、プロパントリカルボニトリル、ヘプタントリカルボニトリル等のシアノ基を3つ有する化合物
等が挙げられる。
特定添加剤であるイソシアネート化合物は、分子内にイソシアネート基を有している化合物であれば特にその種類は限定されない。
メチルイソシアネート、エチルイソシアネート、プロピルイソシアネート、イソプロピルイソシアネート、ブチルイソシアネート、ターシャルブチルイソシアネート、ペンチルイソシアネート、ヘキシルイソシアネート、シクロヘキシルイソシアネート、フェニルイソシアネート、フロロフェニルイソシアネートなどの炭化水素系モノイソシアネート化合物;
ビニルイソシアネート、アリルイソシアネート、エチニルイソシアネート、プロピニルイソシアネートなどの炭素-炭素不飽和結合を有するモノイソシアネート化合物;
モノメチレンジイソシアネート、ジメチレンジイソシアネート、トリメチレンジイソシアネート、テトラメチレンジイソシアネート、ペンタメチレンジイソシアネート、ヘキサメチレンジイソシアネート、ヘプタメチレンジイソシアネート、オクタメチレンジイソシアネート、ノナメチレンジイソシアネート、デカメチレンジイソシアネート、ドデカメチレンジイソシアネート、1,3-ジイソシアナトプロパン、1,4-ジイソシアナト-2-ブテン、1,4-ジイソシアナト-2-フルオロブタン、1,4-ジイソシアナト-2,3-ジフルオロブタン、1,5-ジイソシアナト-2-ペンテン、1,5-ジイソシアナト-2-メチルペンタン、1,6-ジイソシアナト-2-ヘキセン、1,6-ジイソシアナト-3-ヘキセン、1,6-ジイソシアナト-3-フルオロヘキサン、1,6-ジイソシアナト-3,4-ジフルオロヘキサン、トルエンジイソシアネート、キシレンジイソシアネート、トリレンジイソシアネート、1,2-ビス(イソシアナトメチル)シクロヘキサン、1,3-ビス(イソシアナトメチル)シクロヘキサン、1,4-ビス(イソシアナトメチル)シクロヘキサン、1,2-ジイソシアナトシクロヘキサン、1,3-ジイソシアナトシクロヘキサン、1,4-ジイソシアナトシクロヘキサン、ジシクロヘキシルメタン-1,1’-ジイソシアネート、ジシクロヘキシルメタン-2,2’-ジイソシアネート、ジシクロヘキシルメタン-3,3’-ジイソシアネート、ジシクロヘキシルメタン-4,4’-ジイソシアネート、ビシクロ[2.2.1]ヘプタン-2,5-ジイルビス(メチルイソシアネート)、ビシクロ[2.2.1]ヘプタン-2,6-ジイルビス(メチルイソシアネート)、ジイソシアン酸イソホロン、カルボニルジイソシアネート、1,4-ジイソシアナトブタン-1,4-ジオン、1,5-ジイソシアナトペンタン-1,5-ジオン、2,2,4-トリメチルヘキサメチレンジイソシアナート、2,4,4-トリメチルヘキサメチレンジイソシアナートなどの炭化水素系ジイソシアネート化合物;
ジイソシアナトスルホン、(オルト-、メタ-、パラ-)トルエンスルホニルイソシアネート、ベンゼンスルホニルイソシアネート、フルオロスルホニルイソシアネート、フェノキシスルホニルイソシアネート、ペンタフルオロフェノキシスルホニルイソシアネート、メトキシスルホニルイソシアネートなどのイソシアネート化合物;
等が挙げられる。
モノメチレンジイソシアネート、ジメチレンジイソシアネート、トリメチレンジイソシアネート、テトラメチレンジイソシアネート、ペンタメチレンジイソシアネート、ヘキサメチレンジイソシアネート、ヘプタメチレンジイソシアネート、オクタメチレンジイソシアネート、ノナメチレンジイソシアネート、デカメチレンジイソシアネート、ドデカメチレンジイソシアネート、1,3-ビス(イソシアナトメチル)シクロヘキサン、ジシクロヘキシルメタン-4,4’-ジイソシアネート、ビシクロ[2.2.1]ヘプタン-2,5-ジイルビス(メチルイソシアネート)、ビシクロ[2.2.1]ヘプタン-2,6-ジイルビス(メチルイソシアネート)、ジイソシアン酸イソホロン、2,2,4-トリメチルヘキサメチレンジイソシアナート、2,4,4-トリメチルヘキサメチレンジイソシアナート等の炭化水素系ジイソシアネート化合物;
ジイソシアナトスルホン、(オルト-、メタ-、パラ-)トルエンスルホニルイソシアネート、ベンゼンスルホニルイイソシアネート、フルオロスルホニルイソシアネート、フェノキシスルホニルイソシアネート、ペンタフルオロフェノキシスルホニルイソシアネート、メトキシスルホニルイソシアネートなどのイソシアネート化合物;
が、非水系電解液二次電池のサイクル特性・保存特性向上の点から好ましい。
また、本発明に用いるイソシアネート化合物は、分子内に少なくとも2つのイソシアネート基を有する化合物から誘導される三量体化合物、もしくはそれに多価アルコールを付加した脂肪族ポリイソシアネートであってもよい。そのような脂肪族ポリイソシアネートとして、例えば、下記一般式(1-2-1)~(1-2-4)の基本構造で示されるビウレット、イソシアヌレート、アダクト、及び二官能のタイプの変性ポリイソシアネート等が例示できる(下記一般式(1-2-1)~(1-2-4)中、R及びR’はそれぞれ独立して任意の炭化水素基である)。
特定添加剤であるイソシアヌル酸骨格を有する化合物としては、下記一般式(U)で表される化合物が挙げられる。
特定添加剤であるフッ素化された塩に特に制限はないが、構造内に脱離性の高いフッ素原子を有しているため、例えば、一般式(A)で表される化合物が還元反応を受け生成するアニオン(求核種)と好適に反応し、複合的被膜を形成することができることから、ジフルオロリン酸塩、フルオロスルホン酸塩、フルオロホウ素塩及びフルオロイミド塩が好ましい。フッ素原子の脱離性が特に高いこと、求核種との反応が好適に進行することから、フルオロホウ素塩、フルオロスルホン酸塩がより好ましい。以下、これらの各種塩について説明する。
前記ジフルオロリン酸塩のカウンターカチオンとしては特に限定はないが、リチウム、ナトリウム、カリウム、ルビジウム、セシウム、マグネシウム、カルシウム、バリウム、及び、NR13R14R15R16(式中、R13~R16は、各々独立に、水素原子又は炭素数1~12の有機基を表わす。)で表されるアンモニウム等がその例として挙げられる。
ジフルオロリン酸リチウム、ジフルオロリン酸ナトリウム、ジフルオロリン酸カリウム等が挙げられ、ジフルオロリン酸リチウムが好ましい。
前記フルオロスルホン酸塩のカウンターカチオンとしては特に限定はないが、リチウム、ナトリウム、カリウム、ルビジウム、セシウム、マグネシウム、カルシウム、バリウム、及び、NR13R14R15R16(式中、R13~R16は、各々独立に、水素原子又は炭素数1~12の有機基を表わす。)で表されるアンモニウム等がその例として挙げられる。
フルオロスルホン酸リチウム、フルオロスルホン酸ナトリウム、フルオロスルホン酸カリウム、フルオロスルホン酸ルビジウム、フルオロスルホン酸セシウム等が挙げられ、フルオロスルホン酸リチウムが好ましい。
前記フルオロホウ素塩のカウンターカチオンとしては特に限定はないが、リチウム、ナトリウム、カリウム、ルビジウム、セシウム、マグネシウム、カルシウム、バリウム、及び、NR13R14R15R16(式中、R13~R16は、各々独立に、水素原子又は炭素数1~12の有機基を表わす。)で表されるアンモニウム等がその例として挙げられる。
LiBF4、LiB(CiF2i+1)j(F)4-j等が挙げられ、LiBF4が好ましい。なお、iは1~10の整数、jは1~4の整数を表す。
前記フルオロイミド塩のカウンターカチオンとしては特に限定はないが、リチウム、ナトリウム、カリウム、ルビジウム、セシウム、マグネシウム、カルシウム、バリウム、及び、NR13R14R15R16(式中、R13~R16は、各々独立に、水素原子又は炭素数1~12の有機基を表わす。)で表されるアンモニウム等がその例として挙げられる。
LiN(FCO)2、LiN(FCO)(FSO2)、LiN(FSO2)2、LiN(FSO2)(CF3SO2)、LiN(CF3SO2)2、LiN(C2F5SO2)2、リチウム環状1,2-パーフルオロエタンジスルホニルイミド、リチウム環状1,3-パーフルオロプロパンジスルホニルイミド、LiN(CF3SO2)(C4F9SO2)が挙げられ、LiN(FSO2)2、LiN(CF3SO2)2、LiN(C2F5SO2)2が好ましい。
前記酸無水物化合物については、特にその構造は限定されない。酸無水物化合物の例としては、カルボン酸無水物、硫酸無水物、硝酸無水物、スルホン酸無水物、リン酸無水物、亜リン酸無水物、環状酸無水物、鎖状酸無水物等が挙げられる。
無水マロン酸、無水コハク酸、無水グルタル酸、無水アジピン酸、無水マレイン酸、無水シトラコン酸、2、3-ジメチルマレイン酸無水物、無水グルタコン酸、無水イタコン酸、無水フタル酸、無水フェニルマレイン酸、2、3-ジフェニルマレイン酸無水物、シクロヘキサン-1,2-ジカルボン酸無水物、4-シクロヘキセン-1,2-ジカルボン酸無水物、3,4,5,6-テトラヒドロフタル酸無水物、4,4’-オキシジフタル酸無水物、5-ノルボルネン-2,3-ジカルボン酸無水物、メチル-5-ノルボルネン-2,3-ジカルボン酸無水物、フェニルコハク酸無水物、2-フェニルグルタル酸無水物、アリルコハク酸無水物、2-ブテン-11-イルコハク酸無水物、(2-メチル-2-プロペニル)コハク酸無水物、テトラフルオロコハク酸無水物、ジアセチル-酒石酸無水物、ビシクロ[2.2.2]オクト-7-エン-2,3,5,6-テトラカルボン酸二無水物、5-(2,5-ジオキソテトラヒドロフリル)-3-メチル-3-シクロヘキセン-1,2-ジカルボン酸無水物、メタクリル酸無水物、アクリル酸無水物、クロトン酸無水物、メタンスルホン酸無水物、トリフルオロメタンスルホン酸無水物、ノナフルオロブタンスルホン酸無水物、無水酢酸等が挙げられる。
無水コハク酸、無水マレイン酸、無水シトラコン酸、無水フェニルマレイン酸、ビシクロ[2.2.2]オクト-7-エン-2,3,5,6-テトラカルボン酸二無水物、5-(2,5-ジオキソテトラヒドロフリル)-3-メチル-3-シクロヘキセン-1,2-ジカルボン酸無水物、アリルコハク無水物、無水酢酸、メタクリル酸無水物、アクリル酸無水物、メタンスルホン酸無水物が特に好ましい。
前記アクリレート化合物は、下記一般式(1)で表される。
前記芳香族化合物は、下記一般式(※)で表される少なくとも1つの置換基を有する芳香族化合物である。
前記ハロゲン原子として、塩素、フッ素等が挙げられ、好ましくはフッ素である。
酸素原子を有するものとして、カルボン酸エステル構造を有する基、カーボネート構造を有する基等が挙げられる。
硫黄原子を有するものとして、スルホン酸エステル構造を有する基等が挙げられる。
リン原子を有するものとして、リン酸エステル構造を有する基、ホスホン酸エステル構造を有する基等が挙げられる。
ケイ素原子を有するものとして、ケイ素―炭素構造を有する基等が挙げられる。
Tがハロゲン原子又はハロゲン原子を有していてもよい有機基であるものとして、クロロベンゼン、フルオロベンゼン、ジフルオロベンゼン、トリフルオロベンゼン、テトラフルオロベンゼン、ペンタフルオロベンゼン、ヘキサフルオロベンゼン、ベンゾトリフルオライド等が挙げられ、好ましくはフルオロベンゼン、ヘキサフルオロベンゼンである。より好ましくはフルオロベンゼンである。
好ましくは2,2-ジフェニルプロパン、1,4-ジフェニルシクロヘキサン、シクロペンチルベンゼン、シクロヘキシルベンゼン、シス-1-プロピル-4-フェニルシクロヘキサン、トランス-1-プロピル-4-フェニルシクロヘキサン、シス-1-ブチル-4-フェニルシクロヘキサン、トランス-1-ブチル-4-フェニルシクロヘキサン、1,1-ジフェニルシクロヘキサン、1,1-ジフェニル-4-メチルシクロヘキサン、2,2-ジ-(p-フルオロフェニル)プロパン、1,1-ジ-(p-フルオロフェニル)シクロヘキサン、2,2-ビス-(4-ターシャリーブチルフェニル)プロパン、1,3-ビス(1-メチル-1-フェニルエチル)―ベンゼン、1,4-ビス(1-メチル-1-フェニルエチル)―ベンゼン、1-フェニル-1,3,3-トリメチルインダン、2,3-ジヒドロ-1,3-ジメチル-1-(2-メチル-2-フェニルプロピル)-3-フェニル-1H-インダン、ブチルベンゼン、t-ブチルベンゼン、t-アミルベンゼンであり、
より好ましくは2,2-ジフェニルプロパン、ターフェニルの部分水素化体、シクロペンチルベンゼン、シクロヘキシルベンゼン、1,1-ジフェニルシクロヘキサン、1-フェニル-1,3,3-トリメチルインダン、トルエン、t-ブチルベンゼン、t-アミルベンゼンであり、
さらにより好ましくはシクロヘキシルベンゼン、1-フェニル-1,3,3-トリメチルインダン、t-ブチルベンゼン、t-アミルベンゼンであり、
特に好ましくはシクロヘキシルベンゼン、1-フェニル-1,3,3-トリメチルインダンである。
好ましくは、酢酸2-フェニルエチル、酢酸3-フェニルプロピル、プロピオン酸3-フェニルプロピル、フェニル酢酸メチル、α,α,ジメチル-フェニル酢酸メチル、1-フェニル-シクロペンタン酸メチルフェニル酢酸エチル、フェニルプロピオン酸メチル、フェニル酪酸メチル、フェニル酢酸エチル、フェニルプロピオン酸エチル、フェニル酪酸エチル、フェニル酢酸ベンジル、フェニル酢酸2-フェニルエチル、フェニルプロピオン酸ベンジル、フェニルプロピオン酸2-フェニルエチル、ビスフェノールAのアセテート体であり、
より好ましくは酢酸2-フェニルエチル、酢酸3-フェニルプロピル、プロピオン酸3-フェニルプロピル、フェニル酢酸メチル、α,α,ジメチル-フェニル酢酸メチル、1-フェニル-シクロペンタン酸メチルフェニルプロピオン酸メチル、フェニル酪酸メチル、フェニル酢酸ベンジル、フェニル酢酸2-フェニルエチル、フェニルプロピオン酸ベンジル、フェニルプロピオン酸2-フェニルエチル、ビスフェノールAのアセテート体であり、さらに好ましくは酢酸2-フェニルエチル、酢酸3-フェニルプロピル、α,α,ジメチル-フェニル酢酸メチル、1-フェニル-シクロペンタン酸メチルフェニルプロピオン酸メチル、フェニル酢酸2-フェニルエチル、フェニルプロピオン酸ベンジル、フェニルプロピオン酸2-フェニルエチルである。
好ましくはビスフェノールAのカーボネート体、ビスフェノールZのカーボネート体、ジフェニルカーボネート、メチルフェニルカーボネートであり、
より好ましくはジフェニルカーボネート、メチルフェニルカーボネートであり、
さらに好ましくはメチルフェニルカーボネートである。
好ましくはメチルフェニルスルホネート、ジフェニルスルホネート、2-t-ブチルフェニルメチルスルホネート、4-t-ブチルフェニルメチルスルホネート、シクロヘキシルフェニルメチルスルホネートであり、
より好ましくはメチルフェニルスルホネート、2-t-ブチルフェニルメチルスルホネート、4-t-ブチルフェニルメチルスルホネート、シクロヘキシルフェニルメチルスルホネートである。
好ましくはトリフェニルホスフェート、トリス(2-t-ブチルフェニル)ホスフェート、トリス(3-t-ブチルフェニル)ホスフェート、トリス(4-t-ブチルフェニル)ホスフェート、トリス(2-t-アミルフェニル)ホスフェート、トリス(3-t-アミルフェニル)ホスフェート、トリス(4-t-アミルフェニル)ホスフェート、トリス(2-シクロヘキシルフェニル)ホスフェート、トリス(3-シクロヘキシルフェニル)ホスフェート、トリス(4-シクロヘキシルフェニル)ホスフェートであり、
より好ましくはトリス(2-t-ブチルフェニル)ホスフェート、トリス(4-t-ブチルフェニル)ホスフェート、トリス(2-シクロヘキシルフェニル)ホスフェート、トリス(4-シクロヘキシルフェニル)ホスフェートである。
好ましくはジメチルフェニルホスホネート、ジエチルフェニルホスホネート、ジメチル-(4-フルオロフェニル)-ホスホネート、ジメチルベンジルホスホネート、ジエチルベンジルホスホネート、ジメチル-(4-フルオロベンジル)ホスホネート、ジエチル-(4-フルオロベンジル)ホスホネートであり、
より好ましくはジメチルフェニルホスホネート、ジエチルフェニルホスホネート、ジメチルベンジルホスホネート、ジエチルベンジルホスホネート、ジメチル-(4-フルオロベンジル)ホスホネート、ジエチル-(4-フルオロベンジル)ホスホネートである。
好ましくは2-フルオロフェニルアセテート、4-フルオロフェニルアセテート等のカルボン酸エステル構造を有するものの部分フッ素化物等である。
特定添加剤である環状エーテル化合物として、酸素原子を分子内に有する脂肪族化合物である環状エーテル化合物および酸素原子を分子内に有する芳香族化合物である環状エーテル化合物が挙げられる。酸化電位が適度であり、常温での副反応量を少なくできるため、酸素原子を分子内に有する脂肪族化合物である環状エーテル化合物が好ましい。
エチレンオキシド、プロピレンオキシド、ブチレンオキシド、スチレンオキシド、オキセタン、2-メチルオキセタン、3-メチルオキセタン、テトラヒドロフラン、2-メチルテトラヒドロフラン、2-エチルテトラヒドロフラン、3-メチルテトラヒドロフラン、3-エチルテトラヒドロフラン、2,2-ジメチルテトラヒドロフラン、2,3-ジメチルテトラヒドロフラン、2-ビニルテトラヒドロフラン、3-ビニルテトラヒドロフラン、2-エチニルテトラヒドロフラン、3-エチニルテトラヒドロフラン、2-フェニルテトラヒドロフラン、3-フェニルテトラヒドロフラン、テトラヒドロピラン、2-メチルテトラヒドロピラン、2-エチルテトラヒドロピラン、3-メチルテトラヒドロピラン、3-エチルテトラヒドロピラン、4-メチルテトラヒドロピラン、4-エチルテトラヒドロピラン、2、2-ジメチルテトラヒドロピラン、2,3-ジメチルテトラヒドロピラン、2,4-ジメチルテトラヒドロピラン、3,3-ジメチルテトラヒドロピラン、3,4-ジメチルテトラヒドロピラン、4,4-ジメチルテトラヒドロピラン、2-ビニルテトラヒドロピラン、3-ビニルテトラヒドロピラン、4-ビニルテトラヒドロピラン、2-エチニルテトラヒドロピラン、3-エチニルテトラヒドロピラン、4-エチニルテトラヒドロピラン、2-フェニルテトラヒドロピラン、3-フェニルテトラヒドロピラン、4-フェニルテトラヒドロピラン、ヘキサメチレンオキシド、2-メチルヘキサメチレンオキシド、3-メチルヘキサメチレンオキシド、4-エチルヘキサメチレンオキシド2-ビニルヘキサメチレンオキシド、3-エチニルヘキサメチレンオキシド、4-フェニルヘキサメチレンオキシド、ヘプタメチレンオキシド、2-メチルヘプタメチレンオキシド、3-メチルヘプタメチレンオキシド、4-エチルヘプタメチレンオキシド、オクタメチレンオキシド、ノナメチレンオキシド、デカメチレンオキシド、1,3-ジオキソラン、2-メトキシ-1,3-ジオキソラン、2-メチル-1,3-ジオキソラン、2,2-ジメチル-1,3-ジオキソラン、4-メチル-1,3-ジオキソラン、2-エトキシ-1,3-ジオキソラン、2-エチル-1,3-ジオキソラン、2,2-ジエチル-1,3-ジオキソラン、4-エチル-1,3-ジオキソラン、2,2,4-トリメチル-1,3-ジオキソラン、2,2,4-トリエチル-1,3-ジオキソラン、1,3-ジオキサン、4-メチル-1,3-ジオキサン、2,4-ジメチル-1,3-ジオキサン、2,2,4-トリメチル-1,3-ジオキサン、4-エチル-1,3-ジオキサン、2,4-ジエチル-1,3-ジオキサン、2,2,4-トリエチル-1,3-ジオキサン、4-フェニル-1,3-ジオキサン、3-メチル-1,3-ジオキサン、5,5-ジメチル-1,3-ジオキサン、2,5,5-トリメチル-1,3-ジオキサン、4,6-ジメチル-1,3-ジオキサン、2,5-ジメチル-1,3-ジオキサン、1,4-ジオキサン。
プロピレンオキシド、スチレンオキシド、オキセタン、テトラヒドロフラン、2-メチルテトラヒドロフラン、2-エチルテトラヒドロフラン、2,2-ジメチルテトラヒドロフラン、テトラヒドロピラン、2-メチルテトラヒドロピラン、2-エチルテトラヒドロピラン、2,2-ジメチルテトラヒドロピラン、ヘキサメチレンオキシド、1,3-ジオキサン、4-メチル-1,3-ジオキサンが更に好ましく、
オキセタン、テトラヒドロフラン、テトラヒドロピラン、ヘキサメチレンオキシド、1,3-ジオキサン、4-メチル-1,3-ジオキサンが特に好ましく、
テトラヒドロフラン、テトラヒドロピラン、1,3-ジオキサンがより好ましく、
テトラヒドロピランが最も好ましい。
好ましい例で挙げた化合物を用いると、ガス発生の抑制効果が特に大きい為である。
特定添加剤であるオキサラート塩のカウンターカチオンとしては特に限定はないが、リチウム、ナトリウム、カリウム、ルビジウム、セシウム、マグネシウム、カルシウム、バリウム、及び、NR13R14R15R16(式中、R13~R16は、各々独立に、水素原子又は炭素数1~12の有機基を表わす。)で表されるアンモニウム等がその例として挙げられる。
リチウムジフルオロオキサラトボレート、リチウムビス(オキサラト)ボレート、リチウムテトラフルオロオキサラトフォスフェート、リチウムジフルオロビス(オキサラト)フォスフェート、リチウムトリス(オキサラト)フォスフェート等が挙げられ、
リチウムビス(オキサラト)ボレート、リチウムジフルオロビス(オキサラト)フォスフェートが好ましい。
特定添加剤である環状スルホン酸エステルについては、特にその種類は限定されない。
1,3-プロパンスルトン、1-フルオロ-1,3-プロパンスルトン、2-フルオロ-1,3-プロパンスルトン、3-フルオロ-1,3-プロパンスルトン、1-メチル-1, 3-プロパンスルトン、2-メチル-1,3-プロパンスルトン、3-メチル-1 ,3-プロパンスルトン、1-プロペン-1,3-スルトン、2-プロペン-1,3-スルトン、1-フルオロ-1-プロペン-1,3-スルトン、2-フルオロ-1-プロペン-1,3-スルトン、3-フルオロ-1-プロペン-1,3-スルトン、1-フルオロ-2-プロペン-1,3-スルトン、2-フルオロ-2-プロペン-1,3-スルトン、3-フルオロ-2-プロペン-1,3-スルトン、1-メチル-1-プロペン-1,3-スルトン、2-メチル-1-プロペン-1,3-スルトン、3-メチル-1-プロペン-1,3-スルトン、1-メチル-2-プロペン-1,3-スルトン、2-メチル-2-プロペン-1,3-スルトン、3-メチル-2-プロペン-1,3-スルトン、1,4-ブタンスルトン、1-フルオロ-1,4-ブタンスルトン、2-フルオロ-1,4-ブタンスルトン、3-フルオロ-1,4-ブタンスルトン、4-フルオロ-1,4-ブタンスルトン、1-メチル-1,4-ブタンスルトン、2-メチル-1,4-ブタンスルトン、3-メチル-1,4-ブタンスルトン、4-メチル-1,4-ブタンスルトン、1-ブテン-1,4-スルトン、2-ブテン-1,4-スルトン、3-ブテン-1,4-スルトン、1-フルオロ-1-ブテン-1,4-スルトン、2-フルオロ-1-ブテン-1,4-スルトン、3-フルオロ-1-ブテン-1,4-スルトン、4-フルオロ-1-ブテン-1,4-スルトン、1-フルオロ-2-ブテン-1,4-スルトン、2-フルオロ-2-ブテン-1,4-スルトン、3-フルオロ-2-ブテン-1,4-スルトン、4-フルオロ-2-ブテン-1,4-スルトン、1-フルオロ-3-ブテン-1,4-スルトン、2-フルオロ-3-ブテン-1,4-スルトン、3-フルオロ-3-ブテン-1,4-スルトン、4-フルオロ-3-ブテン-1,4-スルトン、1-メチル-1-ブテン-1,4-スルトン、2-メチル-1-ブテン-1,4-スルトン、3-メチル-1-ブテン-1,4-スルトン、4-メチル-1-ブテン-1,4-スルトン、1-メチル-2-ブテン-1,4-スルトン、2-メチル-2-ブテン-1,4-スルトン、3-メチル-2-ブテン-1,4-スルトン、4-メチル-2-ブテン-1,4-スルトン、1-メチル-3-ブテン-1,4-スルトン、2-メチル-3-ブテン-1,4-スルトン、3-メチル-3-ブテン-1,4-スルトン、4-メチル-3-ブテン-1,4-スルトン、1,5-ペンタンスルトン、1-フルオロ-1,5-ペンタンスルトン、2-フルオロ-1,5-ペンタンスルトン、3-フルオロ-1,5-ペンタンスルトン、4-フルオロ-1,5-ペンタンスルトン、5-フルオロ-1,5-ペンタンスルトン、1-メチル-1,5-ペンタンスルトン、2-メチル-1,5-ペンタンスルトン、3-メチル-1,5-ペンタンスルトン、4-メチル-1,5-ペンタンスルトン、5-メチル-1,5-ペンタンスルトン、1-ペンテン-1,5-スルトン、2-ペンテン-1,5-スルトン、3-ペンテン-1,5-スルトン、4-ペンテン-1,5-スルトン、1-フルオロ-1-ペンテン-1,5-スルトン、2-フルオロ-1-ペンテン-1,5-スルトン、3-フルオロ-1-ペンテン-1,5-スルトン、4-フルオロ-1-ペンテン-1,5-スルトン、5-フルオロ-1-ペンテン-1,5-スルトン、1-フルオロ-2-ペンテン-1,5-スルトン、2-フルオロ-2-ペンテン-1,5-スルトン、3-フルオロ-2-ペンテン-1,5-スルトン、4-フルオロ-2-ペンテン-1,5-スルトン、5-フルオロ-2-ペンテン-1,5-スルトン、1-フルオロ-3-ペンテン-1,5-スルトン、2-フルオロ-3-ペンテン-1,5-スルトン、3-フルオロ-3-ペンテン-1,5-スルトン、4-フルオロ-3-ペンテン-1,5-スルトン、5-フルオロ-3-ペンテン-1,5-スルトン、1-フルオロ-4-ペンテン-1,5-スルトン、2-フルオロ-4-ペンテン-1,5-スルトン、3-フルオロ-4-ペンテン-1,5-スルトン、4-フルオロ-4-ペンテン-1,5-スルトン、5-フルオロ-4-ペンテン-1,5-スルトン、1-メチル-1-ペンテン-1,5-スルトン、2-メチル-1-ペンテン-1,5-スルトン、3-メチル-1-ペンテン-1,5-スルトン、4-メチル-1-ペンテン-1,5-スルトン、5-メチル-1-ペンテン-1,5-スルトン、1-メチル-2-ペンテン-1,5-スルトン、2-メチル-2-ペンテン-1,5-スルトン、3-メチル-2-ペンテン-1,5-スルトン、4-メチル-2-ペンテン-1,5-スルトン、5-メチル-2-ペンテン-1,5-スルトン、1-メチル-3-ペンテン-1,5-スルトン、2-メチル-3-ペンテン-1,5-スルトン、3-メチル-3-ペンテン-1,5-スルトン、4-メチル-3-ペンテン-1,5-スルトン、5-メチル-3-ペンテン-1,5-スルトン、1-メチル-4-ペンテン-1,5-スルトン、2-メチル-4-ペンテン-1,5-スルトン、3-メチル-4-ペンテン-1,5-スルトン、4-メチル-4-ペンテン-1,5-スルトン、5-メチル-4-ペンテン-1,5-スルトンなどのスルトン化合物;
メチレンスルフェート、エチレンスルフェート、プロピレンスルフェートなどのスルフェート化合物;
メチレンメタンジスルホネート、エチレンメタンジスルホネートなどのジスルホネート化合物;
1,2,3-オキサチアゾリジン-2,2-ジオキシド、3-メチル-1,2,3-オキサチアゾリジン-2,2-ジオキシド、3H-1,2,3-オキサチアゾール-2,2-ジオキシド、5H-1,2,3-オキサチアゾール-2,2-ジオキシド、1,2,4-オキサチアゾリジン-2,2-ジオキシド、4-メチル-1,2,4-オキサチアゾリジン-2,2-ジオキシド、3H-1,2,4-オキサチアゾール-2,2-ジオキシド、5H-1,2,4-オキサチアゾール-2,2-ジオキシド、1,2,5-オキサチアゾリジン-2,2-ジオキシド、5-メチル-1,2,5-オキサチアゾリジン-2,2-ジオキシド、3H-1,2,5-オキサチアゾール-2,2-ジオキシド、5H-1,2,5-オキサチアゾール-2,2-ジオキシド、1,2,3-オキサチアジナン-2,2-ジオキシド、3-メチル-1,2,3-オキサチアジナン-2,2-ジオキシド、5,6-ジヒドロ-1,2,3-オキサチアジン-2,2-ジオキシド、1,2,4-オキサチアジナン-2,2-ジオキシド、4-メチル-1,2,4-オキサチアジナン-2,2-ジオキシド、5,6-ジヒドロ-1,2,4-オキサチアジン-2,2-ジオキシド、3,6-ジヒドロ-1,2,4-オキサチアジン-2,2-ジオキシド、3,4-ジヒドロ-1,2,4-オキサチアジン-2,2-ジオキシド、1,2,5-オキサチアジナン-2,2-ジオキシド、5-メチル-1,2,5-オキサチアジナン-2,2-ジオキシド、5,6-ジヒドロ-1,2,5-オキサチアジン-2,2-ジオキシド、3,6-ジヒドロ-1,2,5-オキサチアジン-2,2-ジオキシド、3,4-ジヒドロ-1,2,5-オキサチアジン-2,2-ジオキシド、1,2,6-オキサチアジナン-2,2-ジオキシド、6-メチル-1,2,6-オキサチアジナン-2,2-ジオキシド、5,6-ジヒドロ-1,2,6-オキサチアジン-2,2-ジオキシド、3,4-ジヒドロ-1,2,6-オキサチアジン-2,2-ジオキシド、5,6-ジヒドロ-1,2,6-オキサチアジン-2,2-ジオキシドなどの含窒素化合物;
1,2,3-オキサチアホスラン-2,2-ジオキシド、3-メチル-1,2,3-オキサチアホスラン-2,2-ジオキシド、3-メチル-1,2,3-オキサチアホスラン-2,2,3-トリオキシド、3-メトキシ-1,2,3-オキサチアホスラン-2,2,3-トリオキシド、1,2,4-オキサチアホスラン-2,2-ジオキシド、4-メチル-1,2,4-オキサチアホスラン-2,2-ジオキシド、4-メチル-1,2,4-オキサチアホスラン-2,2,4-トリオキシド、4-メトキシ-1,2,4-オキサチアホスラン-2,2,4-トリオキシド、1,2,5-オキサチアホスラン-2,2-ジオキシド、5-メチル-1,2,5-オキサチアホスラン-2,2-ジオキシド、5-メチル-1,2,5-オキサチアホスラン-2,2,5-トリオキシド、5-メトキシ-1,2,5-オキサチアホスラン-2,2,5-トリオキシド、1,2,3-オキサチアホスフィナン-2,2-ジオキシド、3-メチル-1,2,3-オキサチアホスフィナン-2,2-ジオキシド、3-メチル-1,2,3-オキサチアホスフィナン-2,2,3-トリオキシド、3-メトキシ-1,2,3-オキサチアホスフィナン-2,2,3-トリオキシド、1,2,4-オキサチアホスフィナン-2,2-ジオキシド、4-メチル-1,2,4-オキサチアホスフィナン-2,2-ジオキシド、4-メチル-1,2,4-オキサチアホスフィナン-2,2,3-トリオキシド、4-メチル-1,5,2,4-ジオキサチアホスフィナン-2,4-ジオキシド、4-メトキシ-1,5,2,4-ジオキサチアホスフィナン-2,4-ジオキシド、3-メトキシ-1,2,4-オキサチアホスフィナン-2,2,3-トリオキシド、1,2,5-オキサチアホスフィナン-2,2-ジオキシド、5-メチル-1,2,5-オキサチアホスフィナン-2,2-ジオキシド、5-メチル-1,2,5-オキサチアホスフィナン-2,2,3-トリオキシド、5-メトキシ-1,2,5-オキサチアホスフィナン-2,2,3-トリオキシド、1,2,6-オキサチアホスフィナン-2,2-ジオキシド、6-メチル-1,2,6-オキサチアホスフィナン-2,2-ジオキシド、6-メチル-1,2,6-オキサチアホスフィナン-2,2,3-トリオキシド、6-メトキシ-1,2,6-オキサチアホスフィナン-2,2,3-トリオキシドなどの含リン化合物;
が挙げられる。
1,3-プロパンスルトン、1-フルオロ-1,3-プロパンスルトン、2-フルオロ-1,3-プロパンスルトン、3-フルオロ-1,3-プロパンスルトン、1-プロペン-1,3-スルトンがより好ましい。
本発明の非水系電解液に含まれる電解質に特に制限はなく、従来非水系電解液二次電池に使用される各種の電解質が使用可能である。
なお、下記電解質のなかには、上記で説明した特定添加剤と同一の化合物も存在しているが、その使用量によっては、その特定添加剤として記載の化合物を電解質としても使用することができることを意味する。
LiWOF5等のタングステン酸リチウム類;
HCO2Li、CH3CO2Li、CH2FCO2Li、CHF2CO2Li、CF3CO2Li、CF3CH2CO2Li、CF3CF2CO2Li、CF3CF2CF2CO2Li、CF3CF2CF2CF2CO2Li等のカルボン酸リチウム塩類;
FSO3Li、CH3SO3Li、CH2FSO3Li、CHF2SO3Li、CF3SO3Li、CF3CF2SO3Li、CF3CF2CF2SO3Li、CF3CF2CF2CF2SO3Li等のスルホン酸リチウム塩類;
LiN(FCO)2、LiN(FCO)(FSO2)、LiN(FSO2)2、LiN(FSO2)(CF3SO2)、LiN(CF3SO2)2、LiN(C2F5SO2)2、リチウム環状1,2-パーフルオロエタンジスルホニルイミド、リチウム環状1,3-パーフルオロプロパンジスルホニルイミド、LiN(CF3SO2)(C4F9SO2)等のリチウムイミド塩類;
LiC(FSO2)3、LiC(CF3SO2)3、LiC(C2F5SO2)3等のリチウムメチド塩類;
リチウムジフルオロオキサラトボレート、リチウムビス(オキサラト)ボレート等のリチウムオキサラトボレート塩類;
リチウムテトラフルオロオキサラトフォスフェート、リチウムジフルオロビス(オキサラト)フォスフェート、リチウムトリス(オキサラト)フォスフェート等のリチウムオキサラトフォスフェート塩類;
その他、LiPF4(CF3)2、LiPF4(C2F5)2、LiPF4(CF3SO2)2、LiPF4(C2F5SO2)2、LiBF3CF3、LiBF3C2F5、LiBF3C3F7、LiBF2(CF3)2、LiBF2(C2F5)2、LiBF2(CF3SO2)2、LiBF2(C2F5SO2)2等の含フッ素有機リチウム塩類。
本発明の非水系電解液における非水溶媒について特に制限はなく、公知の有機溶媒を用いることが可能である。これらを例示すると、フッ素原子を有さない環状カーボネート、鎖状カーボネート、鎖状カルボン酸エステル、環状カルボン酸エステル、エーテル化合物、スルホン系化合物等が挙げられる。これらの中でも、高温保存特性向上の点から鎖状カルボン酸エステルが好ましい。
上記フッ素原子を有さない環状カーボネートとしては、炭素数2~4のアルキレン基を有する環状カーボネートが挙げられる。
上記鎖状カーボネートとしては、炭素数3~7の鎖状カーボネートが好ましく、炭素数3~7のジアルキルカーボネートがより好ましい。
上記鎖状カルボン酸エステルとしては、炭素数が3~7のものが好ましい。具体的には、
酢酸メチル、酢酸エチル、酢酸-n-プロピル、酢酸イソプロピル、酢酸-n-ブチル、酢酸イソブチル、酢酸-t-ブチル、プロピオン酸メチル、プロピオン酸エチル、プロピオン酸-n-プロピル、プロピオン酸イソプロピル、プロピオン酸-n-ブチル、プロピオン酸イソブチル、プロピオン酸-t-ブチル、酪酸メチル、酪酸エチル、酪酸-n-プロピル、酪酸イソプロピル、イソ酪酸メチル、イソ酪酸エチル、イソ酪酸-n-プロピル、イソ酪酸イソプロピル等が挙げられる。
上記環状カルボン酸エステルとしては、炭素原子数が3~12のものが好ましい。
その具体例としては、ガンマブチロラクトン、ガンマバレロラクトン、ガンマカプロラクトン、イプシロンカプロラクトン等が挙げられる。中でも、ガンマブチロラクトンがリチウムイオン解離度の向上に由来する電池特性向上の点から特に好ましい。
上記エーテル系化合物としては、一部の水素がフッ素にて置換されていてもよい炭素数3~10の鎖状エーテル、及び炭素数3~6の環状エーテルが好ましい。
ジエチルエーテル、ジ(2-フルオロエチル)エーテル、ジ(2,2-ジフルオロエチル)エーテル、ジ(2,2,2-トリフルオロエチル)エーテル、エチル(2-フルオロエチル)エーテル、エチル(2,2,2-トリフルオロエチル)エーテル、エチル(1,1,2,2-テトラフルオロエチル)エーテル、(2-フルオロエチル)(2,2,2-トリフルオロエチル)エーテル、(2-フルオロエチル)(1,1,2,2-テトラフルオロエチル)エーテル、(2,2,2-トリフルオロエチル)(1,1,2,2-テトラフルオロエチル)エーテル、エチル-n-プロピルエーテル、エチル(3-フルオロ-n-プロピル)エーテル、エチル(3,3,3-トリフルオロ-n-プロピル)エーテル、エチル(2,2,3,3-テトラフルオロ-n-プロピル)エーテル、エチル(2,2,3,3,3-ペンタフルオロ-n-プロピル)エーテル、2-フルオロエチル-n-プロピルエーテル、(2-フルオロエチル)(3-フルオロ-n-プロピル)エーテル、(2-フルオロエチル)(3,3,3-トリフルオロ-n-プロピル)エーテル、(2-フルオロエチル)(2,2,3,3-テトラフルオロ-n-プロピル)エーテル、(2-フルオロエチル)(2,2,3,3,3-ペンタフルオロ-n-プロピル)エーテル、2,2,2-トリフルオロエチル-n-プロピルエーテル、(2,2,2-トリフルオロエチル)(3-フルオロ-n-プロピル)エーテル、(2,2,2-トリフルオロエチル)(3,3,3-トリフルオロ-n-プロピル)エーテル、(2,2,2-トリフルオロエチル)(2,2,3,3-テトラフルオロ-n-プロピル)エーテル、(2,2,2-トリフルオロエチル)(2,2,3,3,3-ペンタフルオロ-n-プロピル)エーテル、1,1,2,2-テトラフルオロエチル-n-プロピルエーテル、(1,1,2,2-テトラフルオロエチル)(3-フルオロ-n-プロピル)エーテル、(1,1,2,2-テトラフルオロエチル)(3,3,3-トリフルオロ-n-プロピル)エーテル、(1,1,2,2-テトラフルオロエチル)(2,2,3,3-テトラフルオロ-n-プロピル)エーテル、(1,1,2,2-テトラフルオロエチル)(2,2,3,3,3-ペンタフルオロ-n-プロピル)エーテル、ジ-n-プロピルエーテル、(n-プロピル)(3-フルオロ-n-プロピル)エーテル、(n-プロピル)(3,3,3-トリフルオロ-n-プロピル)エーテル、(n-プロピル)(2,2,3,3-テトラフルオロ-n-プロピル)エーテル、(n-プロピル)(2,2,3,3,3-ペンタフルオロ-n-プロピル)エーテル、ジ(3-フルオロ-n-プロピル)エーテル、(3-フルオロ-n-プロピル)(3,3,3-トリフルオロ-n-プロピル)エーテル、(3-フルオロ-n-プロピル)(2,2,3,3-テトラフルオロ-n-プロピル)エーテル、(3-フルオロ-n-プロピル)(2,2,3,3,3-ペンタフルオロ-n-プロピル)エーテル、ジ(3,3,3-トリフルオロ-n-プロピル)エーテル、(3,3,3-トリフルオロ-n-プロピル)(2,2,3,3-テトラフルオロ-n-プロピル)エーテル、(3,3,3-トリフルオロ-n-プロピル)(2,2,3,3,3-ペンタフルオロ-n-プロピル)エーテル、ジ(2,2,3,3-テトラフルオロ-n-プロピル)エーテル、(2,2,3,3-テトラフルオロ-n-プロピル)(2,2,3,3,3-ペンタフルオロ-n-プロピル)エーテル、ジ(2,2,3,3,3-ペンタフルオロ-n-プロピル)エーテル、ジ-n-ブチルエーテル、ジメトキシメタン、メトキシエトキシメタン、メトキシ(2-フルオロエトキシ)メタン、メトキシ(2,2,2-トリフルオロエトキシ)メタンメトキシ(1,1,2,2-テトラフルオロエトキシ)メタン、ジエトキシメタン、エトキシ(2-フルオロエトキシ)メタン、エトキシ(2,2,2-トリフルオロエトキシ)メタン、エトキシ(1,1,2,2-テトラフルオロエトキシ)メタン、ジ(2-フルオロエトキシ)メタン、(2-フルオロエトキシ)(2,2,2-トリフルオロエトキシ)メタン、(2-フルオロエトキシ)(1,1,2,2-テトラフルオロエトキシ)メタンジ(2,2,2-トリフルオロエトキシ)メタン、(2,2,2-トリフルオロエトキシ)(1,1,2,2-テトラフルオロエトキシ)メタン、ジ(1,1,2,2-テトラフルオロエトキシ)メタン、ジメトキシエタン、メトキシエトキシエタン、メトキシ(2-フルオロエトキシ)エタン、メトキシ(2,2,2-トリフルオロエトキシ)エタン、メトキシ(1,1,2,2-テトラフルオロエトキシ)エタン、ジエトキシエタン、エトキシ(2-フルオロエトキシ)エタン、エトキシ(2,2,2-トリフルオロエトキシ)エタン、エトキシ(1,1,2,2-テトラフルオロエトキシ)エタン、ジ(2-フルオロエトキシ)エタン、(2-フルオロエトキシ)(2,2,2-トリフルオロエトキシ)エタン、(2-フルオロエトキシ)(1,1,2,2-テトラフルオロエトキシ)エタン、ジ(2,2,2-トリフルオロエトキシ)エタン、(2,2,2-トリフルオロエトキシ)(1,1,2,2-テトラフルオロエトキシ)エタン、ジ(1,1,2,2-テトラフルオロエトキシ)エタン、エチレングリコールジ-n-プロピルエーテル、エチレングリコールジ-n-ブチルエーテル、ジエチレングリコールジメチルエーテル等が挙げられる。
上記スルホン系化合物としては、炭素数3~6の環状スルホン、及び炭素数2~6の鎖状スルホンが好ましい。1分子中のスルホニル基の数は、1又は2であることが好ましい。
モノスルホン化合物であるトリメチレンスルホン類、テトラメチレンスルホン類、ヘキサメチレンスルホン類;
ジスルホン化合物であるトリメチレンジスルホン類、テトラメチレンジスルホン類、ヘキサメチレンジスルホン類等が挙げられる。
ジメチルスルホン、エチルメチルスルホン、ジエチルスルホン、n-プロピルメチルスルホン、n-プロピルエチルスルホン、ジ-n-プロピルスルホン、イソプロピルメチルスルホン、イソプロピルエチルスルホン、ジイソプロピルスルホン、n-ブチルメチルスルホン、n-ブチルエチルスルホン、t-ブチルメチルスルホン、t-ブチルエチルスルホン、モノフルオロメチルメチルスルホン、ジフルオロメチルメチルスルホン、トリフルオロメチルメチルスルホン、モノフルオロエチルメチルスルホン、ジフルオロエチルメチルスルホン、トリフルオロエチルメチルスルホン、ペンタフルオロエチルメチルスルホン、エチルモノフルオロメチルスルホン、エチルジフルオロメチルスルホン、エチルトリフルオロメチルスルホン、パーフルオロエチルメチルスルホン、エチルトリフルオロエチルスルホン、エチルペンタフルオロエチルスルホン、ジ(トリフルオロエチル)スルホン、パーフルオロジエチルスルホン、フルオロメチル-n-プロピルスルホン、ジフルオロメチル-n-プロピルスルホン、トリフルオロメチル-n-プロピルスルホン、フルオロメチルイソプロピルスルホン、ジフルオロメチルイソプロピルスルホン、トリフルオロメチルイソプロピルスルホン、トリフルオロエチル-n-プロピルスルホン、トリフルオロエチルイソプロピルスルホン、ペンタフルオロエチル-n-プロピルスルホン、ペンタフルオロエチルイソプロピルスルホン、トリフルオロエチル-n-ブチルスルホン、トリフルオロエチル-t-ブチルスルホン、ペンタフルオロエチル-n-ブチルスルホン、ペンタフルオロエチル-t-ブチルスルホン等が挙げられる。
フッ素原子を有する環状カーボネートは、本発明の非水系電解液において、1-2.で示したとおり、特定添加剤としても用いられるものであるが、非水溶媒としても用いることができる。
フッ素原子を有する環状カーボネートと鎖状カーボネートとの合計に対するフッ素原子を有する環状カーボネートの割合が3体積%以上、好ましくは5体積%以上、より好ましくは10体積%以上、さらに好ましくは15体積%以上であり、また通常60体積%以下、好ましくは50体積%以下、より好ましくは40体積%以下、さらに好ましくは35体積%以下、特に好ましくは30体積%以下、最も好ましくは20体積%以下である。
モノフルオロエチレンカーボネートとジメチルカーボネート、
モノフルオロエチレンカーボネートとジエチルカーボネート、
モノフルオロエチレンカーボネートとエチルメチルカーボネート、
モノフルオロエチレンカーボネートとジメチルカーボネートとジエチルカーボネート、
モノフルオロエチレンカーボネートとジメチルカーボネートとエチルメチルカーボネート、
モノフルオロエチレンカーボネートとジエチルカーボネートとエチルメチルカーボネート、
モノフルオロエチレンカーボネートとジメチルカーボネートとジエチルカーボネートとエチルメチルカーボネート
等が挙げられる。
モノフルオロエチレンカーボネートとジエチルカーボネートとエチルメチルカーボネート、
モノフルオロエチレンカーボネートとジメチルカーボネートとジエチルカーボネートとエチルメチルカーボネート
といった、モノフルオロエチレンカーボネートと対称鎖状カーボネート類と非対称鎖状カーボネート類とを含有する非水溶媒が、非水系電解液二次電池のサイクル特性と大電流放電特性のバランスを良くするので好ましい。中でも、対称鎖状カーボネート類がジメチルカーボネートであることが好ましく、又、鎖状カーボネートのアルキル基の炭素数は1~2が好ましい。
フッ素原子を有する環状カーボネートとフッ素原子を有さない環状カーボネートとの合計に対するフッ素原子を有する環状カーボネートの割合が、通常1体積%以上、好ましくは3体積%以上、より好ましくは5体積%以上、さらに好ましくは10体積%以上、特に好ましくは20体積%以上であり、また、好ましくは95体積%以下、より好ましくは85体積%以下、さらに好ましくは75体積%以下、特に好ましくは60体積%以下の組合せが好ましい。
モノフルオロエチレンカーボネートとエチレンカーボネートとジメチルカーボネート、
モノフルオロエチレンカーボネートとエチレンカーボネートとジエチルカーボネート、
モノフルオロエチレンカーボネートとエチレンカーボネートとエチルメチルカーボネート、
モノフルオロエチレンカーボネートとエチレンカーボネートとジメチルカーボネートとジエチルカーボネート、
モノフルオロエチレンカーボネートとエチレンカーボネートとジメチルカーボネートとエチルメチルカーボネート、
モノフルオロエチレンカーボネートとエチレンカーボネートとジエチルカーボネートとエチルメチルカーボネート、
モノフルオロエチレンカーボネートとエチレンカーボネートとジメチルカーボネートとジエチルカーボネートとエチルメチルカーボネート、
モノフルオロエチレンカーボネートとプロピレンカーボネートとジメチルカーボネート、
モノフルオロエチレンカーボネートとプロピレンカーボネートとジエチルカーボネート、
モノフルオロエチレンカーボネートとプロピレンカーボネートとエチルメチルカーボネート、
モノフルオロエチレンカーボネートとプロピレンカーボネートとジメチルカーボネートとジエチルカーボネート、
モノフルオロエチレンカーボネートとプロピレンカーボネートとジメチルカーボネートとエチルメチルカーボネート、
モノフルオロエチレンカーボネートとプロピレンカーボネートとジエチルカーボネートとエチルメチルカーボネート、
モノフルオロエチレンカーボネートとプロピレンカーボネートとジメチルカーボネートとジエチルカーボネートとエチルメチルカーボネート、
モノフルオロエチレンカーボネートとエチレンカーボネートとプロピレンカーボネートとジメチルカーボネート、
モノフルオロエチレンカーボネートとエチレンカーボネートとプロピレンカーボネートとジエチルカーボネート、
モノフルオロエチレンカーボネートとエチレンカーボネートとプロピレンカーボネートとエチルメチルカーボネート、
モノフルオロエチレンカーボネートとエチレンカーボネートとプロピレンカーボネートとジメチルカーボネートとジエチルカーボネート、
モノフルオロエチレンカーボネートとエチレンカーボネートとプロピレンカーボネートとジメチルカーボネートとエチルメチルカーボネート、
モノフルオロエチレンカーボネートとエチレンカーボネートとプロピレンカーボネートとジエチルカーボネートとエチルメチルカーボネート、
モノフルオロエチレンカーボネートとエチレンカーボネートとプロピレンカーボネートとジメチルカーボネートとジエチルカーボネートとエチルメチルカーボネート
等が挙げられる。
モノフルオロエチレンカーボネートとエチレンカーボネートとエチルメチルカーボネート、
モノフルオロエチレンカーボネートとプロピレンカーボネートとエチルメチルカーボネート、
モノフルオロエチレンカーボネートとエチレンカーボネートとジメチルカーボネートとエチルメチルカーボネート、
モノフルオロエチレンカーボネートとプロピレンカーボネートとジメチルカーボネートとエチルメチルカーボネート、
モノフルオロエチレンカーボネートとエチレンカーボネートとプロピレンカーボネートとジメチルカーボネートとエチルメチルカーボネート、
モノフルオロエチレンカーボネートとエチレンカーボネートとジエチルカーボネートとエチルメチルカーボネート、
モノフルオロエチレンカーボネートとプロピレンカーボネートとジエチルカーボネートとエチルメチルカーボネート、
モノフルオロエチレンカーボネートとエチレンカーボネートとプロピレンカーボネートとジエチルカーボネートとエチルメチルカーボネート、
モノフルオロエチレンカーボネートとエチレンカーボネートとジメチルカーボネートとジエチルカーボネートとエチルメチルカーボネート、
モノフルオロエチレンカーボネートとプロピレンカーボネートとジメチルカーボネートとジエチルカーボネートとエチルメチルカーボネート、
モノフルオロエチレンカーボネートとエチレンカーボネートとプロピレンカーボネートとジメチルカーボネートとジエチルカーボネートとエチルメチルカーボネート
といった、モノフルオロエチレンカーボネートと非対称鎖状カーボネート類を含有するものが、非水系電解液二次電池のサイクル特性と大電流放電特性のバランスを良くするので好ましい。中でも、非対称鎖状カーボネート類がエチルメチルカーボネートである組合せが好ましく、又、鎖状カーボネートのアルキル基の炭素数は1~2が好ましい。
本発明において、フッ素原子を有する環状カーボネートを、1-2.にて説明した通り特定添加剤として用いる場合は、フッ素原子を有する環状カーボネート以外の、上記例示した非水溶媒1種を単独で用いてもよく、2種以上を任意の組み合わせ及び比率で併用してもよい。
環状カーボネートと鎖状カーボネートとの合計に対するフッ素原子を有さない環状カーボネートの割合が好ましくは5体積%以上、より好ましくは10体積%以上、さらに好ましくは15体積%以上であり、また、好ましくは50体積%以下、より好ましくは35体積%以下、さらに好ましくは30体積%以下、特に好ましくは25体積%以下である組合せである。
エチレンカーボネートとジメチルカーボネート、
エチレンカーボネートとジエチルカーボネート、
エチレンカーボネートとエチルメチルカーボネート、
エチレンカーボネートとジメチルカーボネートとジエチルカーボネート、
エチレンカーボネートとジメチルカーボネートとエチルメチルカーボネート、
エチレンカーボネートとジエチルカーボネートとエチルメチルカーボネート、
エチレンカーボネートとジメチルカーボネートとジエチルカーボネートとエチルメチルカーボネート、
プロピレンカーボネートとエチルメチルカーボネート、
プロピレンカーボネートとエチルメチルカーボネートとジエチルカーボネート、
プロピレンカーボネートとエチルメチルカーボネートとジメチルカーボネート
等が挙げられる。
プロピレンカーボネートとエチルメチルカーボネート、
エチレンカーボネートとエチルメチルカーボネートとジメチルカーボネート、
エチレンカーボネートとエチルメチルカーボネートとジエチルカーボネート、
プロピレンカーボネートとエチルメチルカーボネートとジメチルカーボネート、
プロピレンカーボネートとエチルメチルカーボネートとジエチルカーボネート
といった組合せが、非水系電解液二次電池のサイクル特性と大電流放電特性のバランスを良くするので好ましい。
本発明の非水系電解液において、一般式(A)で表される化合物、並びに特定添加剤以外に、目的に応じて適宜助剤を用いてもよい。助剤としては、以下に示される三重結合を有する化合物、その他の助剤等が挙げられる。
前記三重結合を有する化合物については、分子内に三重結合を1つ以上有している化合物であれば特にその種類は限定されない。
1-ペンチン、2-ペンチン、1-ヘキシン、2-ヘキシン、3-ヘキシン、1-ヘプチン、2-ヘプチン、3-ヘプチン、1-オクチン、2-オクチン、3-オクチン、4-オクチン、1-ノニン、2-ノニン、3-ノニン、4-ノニン、1-ドデシン、2-ドデシン、3-ドデシン、4-ドデシン、5-ドデシン、フェニルアセチレン、1-フェニル-1-プロピン、1-フェニル-2-プロピン、1-フェニル-1-ブチン、4-フェニル-1-ブチン、4-フェニル-1-ブチン、1-フェニル-1-ペンチン、5-フェニル-1-ペンチン、1-フェニル-1-ヘキシン、6-フェニル-1-ヘキシン、ジフェニルアセチレン、4-エチニルトルエン、ジシクロヘキシルアセチレン等の炭化水素化合物;
2-ブチン-1,4-ジオール ジメチルジカーボネート、2-ブチン-1,4-ジオール ジエチルジカーボネート、2-ブチン-1,4-ジオール ジプロピルジカーボネート、2-ブチン-1,4-ジオール ジブチルジカーボネート、2-ブチン-1,4-ジオール ジフェニルジカーボネート、2-ブチン-1,4-ジオール ジシクロヘキシルジカーボネート等のジカーボネート;
シュウ酸メチル 2-プロピニル、シュウ酸エチル 2-プロピニル、シュウ酸プロピル 2-プロピニル、シュウ酸2-プロピニル ビニル、シュウ酸アリル 2-プロピニル、シュウ酸ジ-2-プロピニル、シュウ酸2-ブチニル メチル、シュウ酸2-ブチニル エチル、シュウ酸2-ブチニルプロピル、シュウ酸2-ブチニル ビニル、シュウ酸アリル 2-ブチニル、シュウ酸 ジ-2-ブチニル、シュウ酸3-ブチニル メチル、シュウ酸3-ブチニル エチル、シュウ酸3-ブチニルプロピル、シュウ酸3-ブチニル
ビニル、シュウ酸アリル 3-ブチニル、シュウ酸ジ-3-ブチニル等のシュウ酸ジエステル;
2-プロピニルメチルカーボネート、ジ-2-プロピニルカーボネート、2-ブチン-1,4-ジオール ジメチルジカーボネート、酢酸2-プロピニル、2-ブチン-1,4-ジオール ジアセテート、シュウ酸メチル 2-プロピニル、シュウ酸ジ-2-プロピニル
等の化合物が保存特性向上の点から特に好ましい。
その他の助剤としては、上記特定添加剤、フッ素化不飽和環状カーボネート及び三重結合を有する化合物以外の公知の助剤を用いることができる。その他の助剤としては、
エリスリタンカーボネート、スピロ-ビス-ジメチレンカーボネート、メトキシエチル-メチルカーボネート等のカーボネート化合物;
2,4,8,10-テトラオキサスピロ[5.5]ウンデカン、3,9-ジビニル-2,4,8,10-テトラオキサスピロ[5.5]ウンデカン等のスピロ化合物;
エチレンサルファイト、フルオロスルホン酸メチル、フルオロスルホン酸エチル、メタンスルホン酸メチル、メタンスルホン酸エチル、ブスルファン、スルホレン、ジフェニルスルホン、N,N-ジメチルメタンスルホンアミド、N,N-ジエチルメタンスルホンアミド、ビニルスルホン酸メチル、ビニルスルホン酸エチル、ビニルスルホン酸アリル、ビニルスルホン酸プロパルギル、アリルスルホン酸メチル、アリルスルホン酸エチル、アリルスルホン酸アリル、アリルスルホン酸プロパルギル、1,2-ビス(ビニルスルホニロキシ)エタン等の含硫黄化合物;
亜リン酸トリメチル、亜リン酸トリエチル、亜リン酸トリフェニル、リン酸トリメチル、リン酸トリエチル、リン酸トリフェニル、メチルホスホン酸ジメチル、エチルホスホン酸ジエチル、ビニルホスホン酸ジメチル、ビニルホスホン酸ジエチル、ジメチルホスフィン酸メチル、ジエチルホスフィン酸エチル、トリメチルホスフィンオキシド、トリエチルホスフィンオキシド等の含燐化合物;
フルオロベンゼン、ジフルオロベンゼン、ヘキサフルオロベンゼン、ベンゾトリフルオライド等の含フッ素芳香族化合物;
等が挙げられる。これらは1種を単独で用いても、2種以上を併用してもよい。これらの助剤を非水系電解液に添加することにより、非水系電解液二次電池の高温保存後の容量維持特性やサイクル特性を向上させることができる。
電解質や非水溶媒、特定添加剤等の非水系電解液の構成要素を別途合成し、実質的に単離されたものから非水系電解液を調製し、下記に記載する方法にて別途組み立てた電池内に注液して得た非水系電解液電池内の非水系電解液である場合;
本発明の非水系電解液の構成要素を個別に電池内に入れておき、電池内にて混合させることにより本発明の非水系電解液と同じ組成を得る場合;
本発明の非水系電解液を構成する化合物を該非水系電解液二次電池内で発生させて、本発明の非水系電解液と同じ組成を得る場合;
などのことである。
本発明の非水系電解液は、非水系電解液二次電池の中でも、例えばリチウム二次電池用の電解液として用いるのに好適である。以下、本発明の非水系電解液を用いた非水系電解液二次電池について説明する。
以下に負極に使用される負極活物質について述べる。負極活物質としては、電気化学的に金属イオンを吸蔵・放出可能なものであれば、特に制限はない。具体例としては、炭素質材料などの構成元素として炭素を有するもの、合金系材料等が挙げられる。これらは1種を単独で用いてもよく、また2種以上を任意に組み合わせて併用してもよい。
負極活物質としては、前記の通り炭素質材料、合金系材料等が挙げられる。
より好ましくはアルミニウム、ケイ素及びスズの単体金属及びこれら原子を含む合金又は化合物であり、
更に好ましくはケイ素及びスズの単体金属及びこれら原子を含む合金又は化合物などの、ケイ素又はスズを構成元素として有るものである。
これらは、1種を単独で用いてもよく、2種以上を任意の組み合わせ及び比率で併用してもよい。
負極活物質として炭素質材料を用いる場合、当該炭素質材料は、以下の物性を有することが望ましい。
炭素質材料の学振法によるX線回折で求めた格子面(002面)のd値(層間距離)は、通常0.335nm以上であり、また、通常0.360nm以下であり、0.350nm以下が好ましく、0.345nm以下がさらに好ましい。また、学振法によるX線回折で求めた炭素質材料の結晶子サイズ(Lc)は、1.0nm以上であることが好ましく、1.5nm以上であることがさらに好ましい。
炭素質材料の体積基準平均粒径は、レーザー回折・散乱法により求めた体積基準の平均粒径(メジアン径)であり、それは通常1μm以上であり、3μm以上が好ましく、5μm以上がさらに好ましく、7μm以上が特に好ましく、また、通常100μm以下であり、50μm以下が好ましく、40μm以下がより好ましく、30μm以下がさらに好ましく、25μm以下が特に好ましい。
炭素質材料のラマンR値は、レーザーラマンスペクトル法を用いて測定した値であり、通常0.01以上であり、0.03以上が好ましく、0.1以上がさらに好ましく、また、通常1.5以下であり、1.2以下が好ましく、1.0以下がさらに好ましく、0.5以下が特に好ましい。
・レーザー波長 :Arイオンレーザー514.5nm(半導体レーザー532nm)
・測定範囲 :1100cm-1~1730cm-1
・ラマンR値 :バックグラウンド処理、
・スムージング処理 :単純平均、コンボリューション5ポイント
炭素質材料のBET比表面積は、BET法を用いて測定した比表面積の値であり、通常0.1m2・g-1以上であり、0.7m2・g-1以上が好ましく、1.0m2・g-1以上がさらに好ましく、1.5m2・g-1以上が特に好ましく、また、通常100m2・g-1以下であり、25m2・g-1以下が好ましく、15m2・g-1以下がさらに好ましく、10m2・g-1以下が特に好ましい。
炭素質材料の球形の程度として円形度を測定した場合、以下の範囲に収まることが好ましい。なお、円形度は、「円形度=(粒子投影形状と同じ面積を持つ相当円の周囲長)/(粒子投影形状の実際の周囲長)」で定義され、円形度が1のときに理論的真球となる。
炭素質材料のタップ密度は、通常0.1g・cm-3以上であり、0.5g・cm-3以上が好ましく、0.7g・cm-3以上がさらに好ましく、1g・cm-3以上が特に好ましく、また、2g・cm-3以下が好ましく、1.8g・cm-3以下がさらに好ましく、1.6g・cm-3以下が特に好ましい。タップ密度が、上記範囲を下回ると、その炭素質材料を使用して負極を作製した場合に、負極活物質の充填密度が上がり難く、高容量の非水系電解液二次電池を得ることができない場合がある。また、上記範囲を上回ると、電極中の粒子間の空隙が少なくなり過ぎ、粒子間の導電性が確保され難くなり、好ましい電池特性が得られにくい場合がある。
炭素質材料の配向比は、通常0.005以上であり、0.01以上が好ましく、0.015以上がさらに好ましく、また、通常0.67以下である。配向比が、上記範囲を下回ると、非水系電解液二次電池の高密度充放電特性が低下する場合がある。なお、上記範囲の上限は、炭素質材料の配向比の理論上限値である。
・ターゲット:Cu(Kα線)グラファイトモノクロメーター
・スリット :
発散スリット=0.5度
受光スリット=0.15mm
散乱スリット=0.5度
・測定範囲及びステップ角度/計測時間:
(110)面:75度≦2θ≦80度 1度/60秒
(004)面:52度≦2θ≦57度 1度/60秒
炭素質材料のアスペクト比は、通常1以上、また、通常10以下であり、8以下が好ましく、5以下がさらに好ましい。アスペクト比が、上記範囲を上回ると、極板化時にスジ引きや、均一な塗布面が得られず、非水系電解液二次電池の高電流密度充放電特性が低下する場合がある。なお、上記範囲の下限は、炭素質材料のアスペクト比の理論下限値である。
リチウム合金を形成する単体金属及び合金、又はそれらの酸化物、炭化物、窒化物、ケイ化物、硫化物若しくはリン化物等の化合物を負極活物質として使用する場合、Liと合金化可能な金属は、粒子形態である。金属粒子が、Liと合金化可能な金属粒子であることを確認するための手法としては、X線回折による金属粒子相の同定、電子顕微鏡による粒子構造の観察及び元素分析、蛍光X線による元素分析等が挙げられる。
Liと合金化可能な金属粒子の平均粒子径(d50)は、非水系電解液二次電池のサイクル寿命の観点から、通常0.01μm以上、好ましくは0.05μm以上、より好ましくは0.1μm以上、更に好ましくは0.3μm以上であり、通常10μm以下、好ましくは9μm以下、より好ましくは8μm以下である。平均粒子径(d50)が前記範囲内であると、充電池の放電に伴う体積膨張が低減され、充放電容量を維持しつつ、良好なサイクル特性を得ることができる。
なお、平均粒子径(d50)は、レーザー回折・散乱式粒度分布測定方法等で求められる。
Liと合金化可能な金属粒子のBET法により求めた比表面積は、通常0.5~60m2/gであり、1~40m2/gであることが好ましい。Liと合金化可能な金属粒子のBET法による比表面積が前記範囲内であると、電池の充放電効率及び放電容量が高く、高速充放電においてリチウムの出し入れが速く、レート特性に優れるので好ましい。
Liと合金化可能な金属粒子の含有酸素量は、特に制限はないが、通常0.01~8質量%であり、0.05~5質量%であることが好ましい。粒子内の酸素分布状態は、表面近傍に存在、粒子内部に存在、粒子内一様に存在のいずれでもかまわないが、特に表面近傍に存在していることが好ましい。Liと合金化可能な金属粒子の含有酸素量が前記範囲内であると、金属粒子とOの強い結合により、非水系電解液二次充放電に伴う体積膨張が抑制され、サイクル特性に優れるので好ましい。
負極活物質は、Liと合金化可能な金属粒子と黒鉛粒子とを含有するものであってもよい。その負極活物質とは、
Liと合金化可能な金属粒子と黒鉛粒子とが互いに独立した粒子の状態で混合されている混合物でもよいし、Liと合金化可能な金属粒子が黒鉛粒子の表面及び/又は内部に存在している複合体でもよい。
Liと合金化可能な金属粒子と黒鉛粒子の合計に対するLiと合金化可能な金属粒子の含有割合は、通常0.1質量%以上、好ましくは0.5質量%以上、より好ましくは、1.0質量%以上、更に好ましくは2.0質量%以上である。また、通常99質量%以下、好ましくは50質量%以下、より好ましくは40質量%以下、更に好ましくは30質量%以下、より更に好ましくは25質量%以下、より更に好ましくは20質量%以下、特に好ましくは15質量%以下、最も好ましくは10質量%以下である。この範囲であると、非水系電解液二次電池において十分な容量を得ることが可能となる点で好ましい。
本発明の負極活物質は、炭素質物又は黒鉛質物で被覆されていてもよい。この中でも非晶質炭素質物で被覆されていることが、リチウムイオンの受入性の点から好ましい。この被覆率は、通常0.5%以上30%以下、好ましくは1%以上25%以下、より好ましくは、2%以上20%以下である。この被覆率が大きすぎると炭素質材料の非晶質炭素部分が多くなり、電池を組んだ際の可逆容量が小さくなる傾向がある。被覆率が小さすぎると、核となる炭素質材料が非晶質炭素によって均一にコートされないとともに強固な造粒がなされず、焼成後に粉砕した際、粒径が小さくなりすぎる傾向がある。
負極活物質の内部間隙率は通常1%以上、好ましくは3%以上、より好ましく5%以上、更に好ましくは7%以上である。また通常50%未満、好ましくは40%以下、より好ましくは30%以下、更に好ましくは20%以下である。この内部間隙率が小さすぎると、非水系電解液二次電池において負極活物質の粒子内の液量が少なくなり、充放電特性が悪化する傾向がある。一方内部間隙率が大きすぎると、電極にした場合に粒子間間隙が少なく、非水系電解液の拡散が不十分になる傾向がある。また、この空隙には、非晶質炭素や黒鉛質物、樹脂等、Liと合金化可能な金属粒子の膨張、収縮を緩衝するような物質が、空隙中に存在又は空隙がこれらにより満たされていてもよい。
負極の製造は、本発明の効果を著しく損なわない限り、公知のいずれの方法をも用いることができる。例えば、負極活物質に、バインダー、溶媒、必要に応じて、増粘剤、導電材、充填材等を加えてスラリーとし、これを集電体に塗布、乾燥した後にプレスすることによって形成することができる。
負極活物質を電極化した際の電極構造は特に制限されないが、集電体上に存在している負極活物質の密度は、1g・cm-3以上が好ましく、1.2g・cm-3以上がさらに好ましく、1.3g・cm-3以上が特に好ましく、また、2.2g・cm-3以下が好ましく、2.1g・cm-3以下がより好ましく、2.0g・cm-3以下がさらに好ましく、1.9g・cm-3以下が特に好ましい。集電体上に存在している負極活物質の密度が、上記範囲を上回ると、負極活物質粒子が破壊され、非水系電解液二次電池の初期不可逆容量の増加や、集電体/負極活物質界面付近への非水系電解液の浸透性低下による高電流密度充放電特性悪化を招く場合がある。また、上記範囲を下回ると、負極活物質間の導電性が低下し、電池抵抗が増大し、単位容積当たりの容量が低下する場合がある。
<正極活物質>
以下に正極に使用される正極活物質(リチウム遷移金属系化合物)について述べる。
〈リチウム遷移金属系化合物〉
リチウム遷移金属系化合物とは、Liイオンを脱離、挿入することが可能な構造を有する化合物であり、例えば、硫化物やリン酸塩化合物、リチウム遷移金属複合酸化物等が挙げられる。硫化物としては、TiS2やMoS2等の二次元層状構造をもつ化合物や、一般式MexMo6S8(MeはPb,Ag,Cuをはじめとする各種遷移金属)で表される強固な三次元骨格構造を有するシュブレル化合物等が挙げられる。リン酸塩化合物としては、オリビン構造に属するものが挙げられ、一般的にはLiMePO4(Meは少なくとも1種の遷移金属)で表され、具体的にはLiFePO4、LiCoPO4、LiNiPO4、LiMnPO4等が挙げられる。リチウム遷移金属複合酸化物としては、三次元的拡散が可能なスピネル構造や、リチウムイオンの二次元的拡散を可能にする層状構造を有するものが挙げられる。スピネル構造を有するものは、一般的にLiMe2O4(Meは少なくとも1種の遷移金属)と表され、具体的にはLiMn2O4、LiCoMnO4、LiNi0.5Mn1.5O4、LiCoVO4等が挙げられる。層状構造を有するものは、一般的にLiMeO2(Meは少なくとも1種の遷移金属)と表される。具体的にはLiCoO2、LiNiO2、LiNi1-xCoxO2、LiNi1-x-yCoxMnyO2、LiNi0.5Mn0.5O2、Li1.2Cr0.4Mn0.4O2、Li1.2Cr0.4Ti0.4O2、LiMnO2等が挙げられる。
また、リチウム遷移金属系化合物としては、例えば、下記組成式(F)又は(G)で示される化合物が挙げられる。
Li1+xMO2 …(F)
ただし、xは通常0以上、0.5以下である。Mは、Ni及びMn、或いは、Ni、Mn及びCoから構成される元素であり、Mn/Niモル比は通常0.1以上、5以下である。Ni/Mモル比は通常0以上、0.5以下である。Co/Mモル比は通常0以上、0.5以下である。なお、xで表されるLiのリッチ分は、遷移金属サイトMに置換している場合もある。
αLi2MO3・(1-α)LiM’O2・・・(F’)
一般式中、αは、0<α<1を満たす数である。
Li[LiaMbMn2-b-a]O4+δ・・・(G)
ただし、Mは、Ni、Cr、Fe、Co、Cu、Zr、Al及びMgから選ばれる遷移金属のうちの少なくとも1種から構成される元素である。
bの値がこの範囲であれば、リチウム遷移金属系化合物における単位重量当たりのエネルギー密度が高い。
δの値がこの範囲であれば、結晶構造としての安定性が高く、このリチウム遷移金属系化合物を用いて作製した正極を有する電池のサイクル特性や高温保存が良好である。
上記の組成のリチウム遷移金属系化合物の具体例としては、例えば、Li1+xNi0.5Mn0.5O2、Li1+xNi0.85Co0.10Al0.05O2、Li1+xNi0.33Mn0.33Co0.33O2、Li1+xNi0.45Mn0.45Co0.1O2、Li1+xMn1.8Al0.2O4、Li1+xMn1.5Ni0.5O4等が挙げられる。これらのリチウム遷移金属系化合物は、1種を単独で用いてもよく、二種以上をブレンドして用いてもよい。
また、リチウム遷移金属系化合物には、異元素が導入されてもよい。異元素としては、B,Na,Mg,Al,K,Ca,Ti,V,Cr,Fe,Cu,Zn,Sr,Y,Zr,Nb,Ru,Rh,Pd,Ag,In,Sb,Te,Ba,Ta,Mo,W,Re,Os,Ir,Pt,Au,Pb,La,Ce,Pr,Nd,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb,Lu,Bi,N,F,S,Cl,Br,I,As,Ge,P,Pb,Sb,Si及びSnの何れか1種以上が選択される。これらの異元素は、リチウム遷移金属系化合物の結晶構造内に取り込まれていてもよく、あるいは、リチウム遷移金属系化合物の結晶構造内に取り込まれず、その粒子表面や結晶粒界等に単体もしくは化合物として偏在していてもよい。
非水系電解液二次電池用正極は、上述のリチウム遷移金属系化合物の粉体及び結着剤を含有する正極活物質層を集電体上に形成してなるものである。
SBR(スチレン・ブタジエンゴム)、NBR(アクリロニトリル・ブタジエンゴム)、フッ素ゴム、イソプレンゴム、ブタジエンゴム、エチレン・プロピレンゴム等のゴム状高分子、
スチレン・ブタジエン・スチレンブロック共重合体及びその水素添加物、EPDM(エチレン・プロピレン・ジエン三元共重合体)、スチレン・エチレン・ブタジエン・エチレン共重合体、スチレン・イソプレンスチレンブロック共重合体及びその水素添加物等の熱可塑性エラストマー状高分子、
シンジオタクチック-1,2-ポリブタジエン、ポリ酢酸ビニル、エチレン・酢酸ビニル共重合体、プロピレン・α-オレフィン共重合体等の軟質樹脂状高分子、
ポリフッ化ビニリデン、ポリテトラフルオロエチレン、フッ素化ポリフッ化ビニリデン、ポリテトラフルオロエチレン・エチレン共重合体等のフッ素系高分子、
アルカリ金属イオン(特にリチウムイオン)のイオン伝導性を有する高分子組成物
等が挙げられる。なお、これらの物質は、1種を単独で用いてもよく、2種以上を任意の組み合わせ及び比率で併用してもよい。
また、正極活物質層の厚さは、通常10~200μm程度である。
かくして、非水系電解液二次電池用正極が調製できる。
正極と負極との間には、短絡を防止するために、通常はセパレータを介在させる。この場合、本発明の非水系電解液は、通常はこのセパレータに含浸させて用いる。
<電極群>
電極群は、上記の正極板と負極板とを上記のセパレータを介してなる積層構造のもの、及び上記の正極板と負極板とを上記のセパレータを介して渦巻き状に捲回した構造のもののいずれでもよい。電極群の体積が電池内容積に占める割合(以下、電極群占有率と称する)は、通常40%以上であり、50%以上が好ましく、また、通常90%以下であり、80%以下が好ましい。
外装ケースの材質は用いられる非水系電解液に対して安定な物質であれば特に制限されない。具体的には、ニッケルめっき鋼板、ステンレス、アルミニウム又はアルミニウム合金、マグネシウム合金等の金属類、又は、樹脂とアルミ箔との積層フィルム(ラミネートフィルム)が用いられる。軽量化の観点から、アルミニウム又はアルミニウム合金の金属、ラミネートフィルムが好適に用いられる。
保護素子として、異常発熱や過大電流が流れた時に抵抗が増大するPTC(Positive Temperature Coefficient)サーミスター、温度ヒューズ、異常発熱時に電池内部圧力や内部温度の急激な上昇により回路に流れる電流を遮断する弁(電流遮断弁)等を使用することができる。上記保護素子としては高電流の通常使用で作動しない条件のものを選択することが好ましく、保護素子がなくても異常発熱や熱暴走に至らない設計にすることがより好ましい。
本発明の非水系電解液二次電池は、通常、上記の非水系電解液、負極、正極、セパレータ等を外装体(外装ケース)内に収納して構成される。この外装体に制限は無く、本発明の効果を著しく損なわない限り公知のものを任意に採用することができる。
以下に、実施例及び比較例を挙げて本発明をさらに具体的に説明するが、本発明は、これらの実施例に限定されるものではない。
[非水系電解液の調製]
乾燥アルゴン雰囲気下、エチレンカーボネート(EC)、エチルメチルカーボネート(EMC)、及びジエチルカーボネート(DEC)の混合物(体積容量比3:4:3)に、十分に乾燥させたLiPF6を1.2モル/L(非水系電解液中の濃度として)溶解させた(これを予備溶液と呼ぶ)。
前記予備溶液にVCを5.0質量%(溶液の合計100質量%中)添加した電解液(これを基準電解液2と呼ぶ)、
前記予備溶液にMFECを5.0質量%(溶液の合計100質量%中)添加した電解液を調製した(これを基準電解液3と呼ぶ)。
正極活物質としてコバルト酸リチウム(LiCoO2)97質量%と、導電材としてアセチレンブラック1.5質量%と、結着材としてポリフッ化ビニリデン(PVdF)1.5質量%とを、N-メチルピロリドン溶媒中で、ディスパーザーで混合してスラリー化した。これを厚さ21μmのアルミニウム箔の両面に均一に塗布、乾燥した後、プレスして正極とした。
負極活物質としての天然黒鉛粉末に、増粘剤、バインダーとしてそれぞれ、カルボキシメチルセルロースナトリウムの水性ディスパージョン(カルボキシメチルセルロースナトリウムの濃度1質量%)、及び、スチレン-ブタジエンゴムの水性ディスパージョン(スチレン-ブタジエンゴムの濃度50質量%)を、ディスパーザーで混合してスラリー化した。このスラリーを厚さ12μmの銅箔の片面に均一に塗布、乾燥した後、プレスして負極とした。なお、乾燥後の負極において、天然黒鉛:カルボキシメチルセルロースナトリウム:スチレン-ブタジエンゴム=98:1:1の質量比となるように作製した。
上記の正極、負極、及びポリオレフィン製セパレータを、負極、セパレータ、正極、セパレータ、負極の順に積層した。こうして得られた電池要素をアルミニウムラミネートフィルムで包み込み、上述した非水系電解液を注入した後で真空封止し、シート状の非水系電解液二次電池を作製した。
[初期コンディショニング]
25℃の恒温槽中、ラミネート型セルの非水系電解液二次電池を0.05Cに相当する電流で6時間定電流充電した後、0.2Cで3.0Vまで放電した。次に0.2Cで4.1Vまで電池のCC-CV充電を行った。その後、45℃、72時間の条件でエージングを実施した。その後、0.2Cで3.0Vまで放電し、非水系電解液二次電池を安定させた。さらに、0.2Cで4.4Vまで電池のCC-CV充電を行った後、0.2Cで3.0Vまで放電し、電池の初期コンディショニングを行った。
初期コンディショニング後の電池について再度、0.2Cで4.4VまでCC-CV充電を行った後、85℃、24時間の条件で高温保存を行った。電池を十分に冷却させた後、エタノール浴中に浸して体積を測定し、保存試験前後の体積変化から発生ガス量を求め、これを「充電保存ガス量」とした。
基準電解液1に対して、下記表2に記載の割合で各化合物を加えて非水系電解液を調製した。ただし、比較例2-1は基準電解液1そのものである。なお、表中の「添加量(wt%)」は、非水系電解液100重量%中の濃度である。実施例1と同様の正極、負極及び非水系電解液二次電池を作成し、実験を行った。
[初期コンディショニング]
25℃の恒温槽中、ラミネート型セルの非水系電解液二次電池を0.05Cに相当する電流で6時間定電流充電した後、0.2Cで3.0Vまで放電した。次に0.2Cで4.1Vまで電池のCC-CV充電を行った。その後、45℃、72時間の条件でエージングを実施した。その後、0.2Cで3.0Vまで放電し、非水系電解液二次電池を安定させた。さらに、0.2Cで4.4Vまで電池のCC-CV充電を行った後、0.2Cで3.0Vまで放電し、電池の初期コンディショニングを行った。
初期コンディショニング後の電池について再度、0.2Cで4.4VまでCC-CV充電を行った後、85℃、24時間の条件で高温保存を行った。その後、0.2Cで3.0Vまで放電した。続いて0.2Cで4.4Vまで電池をCC-CVした後、0.2C・1.0Cで3.0Vまで放電し、得られた0.2C・1.0C容量の比(1.0C/0.2C)の百分率を「保存後1.0C/0.2C負荷」とした。
[非水系電解液の調製]
基準電解液3に対して、下記表3に記載の割合で各化合物を加えて非水系電解液を調製した。ただし、比較例3-1は基準電解液3そのものである。なお、表中の「添加量(wt%)」は、非水系電解液100重量%中の濃度である。
実施例1と同様の正極を作製し、使用した。
実施例1と同様の負極を作製し、使用した。
実施例1と同様の非水系電解液二次電池を作製し、使用した。
[初期コンディショニング]
25℃の恒温槽中、ラミネート型セルの非水系電解液二次電池を0.05Cに相当する電流で6時間定電流充電した後、0.2Cで3.0Vまで放電した。次に0.2Cで4.1Vまで電池のCC-CV充電を行った。その後、45℃、72時間の条件でエージングを実施した。その後、0.2Cで3.0Vまで放電し、非水系電解液二次電池を安定させた。さらに、0.2Cで4.4Vまで電池のCC-CV充電を行った後、0.2Cで3.0Vまで放電し、電池の初期コンディショニングを行った。
初期コンディショニング後の電池について再度、0.2Cで4.4VまでCC-CV充電を行った後、60℃、168時間の条件で高温保存を行った。電池を十分に冷却させた後、エタノール浴中に浸して体積を測定し、保存試験前後の体積変化から発生ガス量を求め、これを「60℃充電保存ガス量」とした。
基準電解液1に対して、下記表4に記載の割合で各化合物を加えて非水系電解液を調製した。ただし、比較例4-1は基準電解液1そのものである。なお、表中の「添加量(wt%)」は、非水系電解液100重量%中の濃度である。実施例1と同様の正極、負極、及び非水系電解液電池を作成し、評価を行った。
[初期コンディショニング]
25℃の恒温槽中、ラミネート型セルの非水系電解液二次電池を0.05Cに相当する電流で6時間定電流充電した後、0.2Cで3.0Vまで放電した。次に0.2Cで4.1Vまで電池のCC-CV充電を行った。その後、45℃、72時間の条件でエージングを実施した。その後、0.2Cで3.0Vまで放電し、非水系電解液二次電池を安定させた。さらに、0.2Cで4.4Vまで電池のCC-CV充電を行った後、0.2Cで3.0Vまで放電し、電池の初期コンディショニングを行った。
初期コンディショニングを行った後の非水系電解液電池を、60℃において、0.2Cで4.4VまでCC-CV充電(168時間カット)を行うことで、連続充電試験を実施した。試験終了後、電池を十分に冷却させた後、エタノール浴中に浸して体積を測定し、連続充電試験前後の体積変化から発生ガス量を求め、これを「連続充電試験ガス量」とした。
基準電解液1に対して、下記表5に記載の割合で各化合物を加えて非水系電解液を調製した。ただし、比較例5-1は基準電解液1そのものである。なお、表中の「添加量(wt%)」は、非水系電解液100重量%中の濃度である。実施例1と同様の正極、負極、及び非水系電解液二次電池を作成し、実験を行った。
[初期の電池特性評価]
非水系電解液二次電池をエタノール浴中に浸し、そのときの浮力から初期電池体積を求めた(アルキメデスの原理)。その後、ガラス板で挟んで加圧した状態で、25℃において、0.05Cに相当する電流で6時間定電流充電した後、0.2Cで3.0Vまで定電流放電を行った。更に、0.2Cに相当する電流で4.1Vまで定電流―定電圧充電(「CC-CV充電」ともいう)(0.05Cカット)した後、45℃、72時間の条件下で放置した。その後、0.2Cの定電流で3.0Vまで放電した。次いで、0.2Cで4.4VまでCC-CV充電(0.05Cカット)した後、0.2Cで3.0Vまで再度放電し、初期の電池特性を安定させた。
下記表5に、比較例5-1の値で規格化した、各実施例及び比較例の初期ガス量を示す。
[非水系電解液の調製]
乾燥アルゴン雰囲気下、EC、EMC及びDECの混合物(体積容量比3:4:3)に、十分に乾燥させたLiPF6を1.2モル/L(非水系電解液中の濃度として)溶解させ、さらに、VCとMFECと化合物19とを、それぞれ2.0質量%、2.0質量%、1.0質量%ずつ添加した(これを基準電解液4と呼ぶ)。基準電解液4全体に対して、下記表6に記載の割合で各化合物を加えて電解液を調製した。ただし、比較例6-1は基準電解液4そのものである。なお、表中の「添加量(wt%)」は、非水系電解液100重量%中の濃度である。
実施例1と同様の正極を作製し使用した。
実施例1と同様の負極を作製し使用した。
実施例1と同様の非水系電解液二次電池を製造し使用した。
[初期コンディショニング]
25℃の恒温槽中、ラミネート型セルの非水系電解液二次電池を0.05Cに相当する電流で6時間定電流充電した後、0.2Cで3.0Vまで放電した。次に0.2Cで4.1Vまで電池のCC-CV充電を行った。その後、45℃、72時間の条件でエージングを実施した。その後、0.2Cで3.0Vまで放電し、非水系電解液二次電池を安定させた。さらに、0.2Cで4.4Vまで電池のCC-CV充電を行った後、0.2Cで3.0Vまで放電し、電池の初期コンディショニングを行った。
初期コンディショニング後の電池について再度、0.2Cで4.4VまでCC-CV充電を行った後、80℃、72時間の条件で高温保存を行った。電池を十分に冷却させた後、エタノール浴中に浸して体積を測定し、保存試験前後の体積変化から発生ガス量を求め、これを「80℃充電保存ガス量」とした。
[非水系電解液の調製]
乾燥アルゴン雰囲気下、EC、化合物22及びDECの混合物(体積容量比3:4:3)に、十分に乾燥させたLiPF6を1.2モル/L(非水系電解液中の濃度として)溶解させ、さらに、MFECを5.0質量%(溶液の合計100質量%中)添加した(これを基準電解液5と呼ぶ)。基準電解液3又は5全体に対して、下記表7に記載の割合で各化合物を加えて電解液を調製した。ただし、比較例7-1は基準電解液3そのものであり、比較例7-2は基準電解液5そのものである。なお、表中の「添加量(wt%)」は、非水系電解液100重量%中の濃度である。
実施例1と同様の正極を作製し、使用した。
実施例1と同様の負極を作製し、使用した。
実施例1と同様の非水系電解液二次電池を製造し使用した。
[初期コンディショニング]
25℃の恒温槽中、ラミネート型セルの非水系電解液二次電池を0.05Cに相当する電流で6時間定電流充電した後、0.2Cで3.0Vまで放電した。次に0.2Cで4.1Vまで電池のCC-CV充電を行った。その後、45℃、72時間の条件でエージングを実施した。その後、0.2Cで3.0Vまで放電し、非水系電解液二次電池を安定させた。さらに、0.2Cで4.4Vまで電池のCC-CV充電を行った後、0.2Cで3.0Vまで放電し、電池の初期コンディショニングを行った。
初期コンディショニング後の電池について再度、0.2Cで4.4VまでCC-CV充電を行った後、60℃、168時間の条件で高温保存を行った。その後、25℃において0.2Cで3Vまで放電させ、さらに、25℃において0.2Cの定電流で4.40Vまで電池のCC-CV充電(0.05Cカット)をした後、0.2Cで3Vまで再度放電し、これを「回復0.2C容量」とした。
[非水系電解液の調製]
乾燥アルゴン雰囲気下、EC、ジメチルカーボネート(DMC)、EMCとの混合物(体積容量比3:3:4)に、十分に乾燥させたLiPF6を1.0モル/L(非水系電解液中の濃度として)溶解させ、さらに、VCを1.2質量%(溶液の合計100質量%中)添加した(これを基準電解液6と呼ぶ)。基準電解液6全体に対して、下記表8に記載の割合で各化合物を加えて電解液を調製した。ただし、比較例8-1は基準電解液6そのものである。なお、表中の「添加量(wt%)」は、非水系電解液100重量%中の濃度である。
正極活物質としてリン酸鉄リチウム(LiFePO4)83.5質量部を用い、カーボンブラック10質量部とポリフッ化ビニリデン6.5質量部を混合した。この混合物にN-メチル-2-ピロリドンを加えスラリー化し、これを厚さ15μmのアルミニウム箔の両面に均一に13.8mg・cm-2となるように塗布し、乾燥した後、正極活物質層の密度が1.85g・cm-3になるようにプレスして正極とした。
黒鉛に、増粘剤としてカルボキシメチルセルロースナトリウムの水性ディスパージョン(カルボキシメチルセルロースナトリウムの濃度1質量%)と、バインダーとしてスチレン-ブタジエンゴムの水性ディスパージョン(スチレン-ブタジエンゴムの濃度50質量%)を加え、ディスパーザーで混合してスラリー化した。得られたスラリーを厚さ12μmの銅箔の片面に均一に6.0mg・cm-2となるように塗布して乾燥し、その後、負極活物質層の密度が1.36g・cm-3になるようにプレスして負極とした。用いた黒鉛は、d50値が10.9μmであり、比表面積が3.41m2・g-1であり、タップ密度が0.985g・cm-3である。また、スラリーは乾燥後の負極において、黒鉛:カルボキシメチルセルロースナトリウム:スチレン-ブタジエンゴム=97.5:1.5:1の質量比となるように作成した。
上記の正極、負極、及びセパレータを、負極、セパレータ、正極の順に積層した。セパレータにはポリプロピレン製、厚み20μm、空孔率54%のものを用いた。こうして得られた電池要素を筒状のアルミニウムラミネートフィルムで包み込み、前記電解液を注入した後で真空封止し、シート状の非水系電解液二次電池を作製した。更に、電極間の密着性を高めるために、ガラス板でシート状電池を挟んで加圧した。
[初期コンディショニング]
25℃雰囲気下において、シート状の非水系電解液二次電池を0.05Cで10時間充電後、3時間休止させ、その後3.8Vまで0.2Cで定電流充電した。さらに3時間の休止の後に、3.8Vまで0.2Cで定電流-定電圧充電し、次いで1/3Cで2.5Vまで定電流放電した。その後、3.8Vまでの1/3C定電流-定電圧充電と、これに続く2.5Vまでの1/3C定電流放電を1サイクルとする充放電サイクルを2サイクル行った。さらに、3.8Vまで1/3Cで定電流-定電圧充電した後に、電池を60℃で12時間保管することで電池を安定させた。その後、25℃にて3.8Vまでの1/3C定電流-定電圧充電と、これに続く2.5Vまでの1/3C定電流放電の充放電サイクルを2サイクル行った。このときの最後の放電容量を初期容量とした。
初期コンディショニング後の電池を3.8Vに調整し、60℃にて1週間保存した。初期コンディショニング後高温保存前、および、高温保存後の電池をエタノール中に完全に浸漬させ、その時に発生した浮力A(g)、および、浮力B(g)をそれぞれ電子天秤で測定した。浮力Aに対する浮力Bの差分をエタノールの比重(=0.789g・mL-1)で除して得られた値を「保存後セル膨れ」とした。
[非水系電解液の調製]
乾燥アルゴン雰囲気下、EC、DECとの混合物(体積容量比3:7)に、十分に乾燥させたLiPF6を1.0モル/L(非水系電解液中の濃度として)溶解させ、さらに、VC、MFECをそれぞれ2.0質量%(溶液の合計100質量%中)添加した(これを基準電解液7と呼ぶ)。基準電解液7全体に対して、下記表9に記載の割合で各化合物を加えて電解液を調製した。ただし、比較例9-1は基準電解液7そのものである。なお、表中の「添加量(wt%)」は、非水系電解液100重量%中の濃度である。
正極活物質としてリチウム・ニッケル・コバルト・マンガン複合酸化物(Li1.05Ni0.33Mn0.33Co0.33O2)85質量%と、導電材としてアセチレンブラック10質量%と、結着材としてポリフッ化ビニリデン(PVdF)5質量%とを、N-メチルピロリドン溶媒中で、ディスパーザーで混合してスラリー化した。これを厚さ21μmのアルミニウム箔の両面に均一に塗布、乾燥した後、プレスして正極とした。
平均粒子径0.2μmのSi微粒子50gを平均粒径35μmの鱗片状黒鉛2000g中に分散させ、ハイブリダイゼーションシステム(奈良機械製作所製)に投入し、ローター回転数7000rpm、180秒装置内を循環又は滞留させて処理し、Siと黒鉛粒子の複合体を得た。得られた複合体を、焼成後の被覆率が7.5%になるように炭素質物となる有機化合物としてコールタールピッチを混合し、2軸混練機により混練・分散させた。得られた分散物を、焼成炉に導入し、窒素雰囲気下1000℃、3時間焼成した。得られた焼成物は、更にハンマーミルで粉砕後、篩(45μm)を実施し、負極活物質1を作製した。前記測定法で測定した、珪素元素の含有量、平均粒径d50、タップ密度、比表面積はそれぞれ、2.0質量%、20μm、1.0g/cm3、7.2m2/gであった。
負極活物質(天然黒鉛)及び負極活物質1~3の各々に対して、増粘剤、バインダーとしてそれぞれ、カルボキシメチルセルロースナトリウムの水性ディスパージョン(カルボキシメチルセルロースナトリウムの濃度1質量%)、及び、スチレン-ブタジエンゴムの水性ディスパージョン(スチレン-ブタジエンゴムの濃度50質量%)を加え、ディスパーザーで混合してスラリー化した。このスラリーを厚さ10μmの銅箔の片面に均一に塗布、乾燥した後、プレスして、Si含有量が0、2.0、12.0、17.0質量%である活物質を用いた負極を得た。なお、乾燥後の負極において、負極活物質:カルボキシメチルセルロースナトリウム:スチレン-ブタジエンゴム=97.5:1.5:1の質量比となるように作製した。
上記の正極、各Si含有量の負極、及びポリオレフィン製セパレータを、負極、セパレータ、正極の順に積層した。こうして得られた電池要素をアルミニウムラミネートフィルムで包み込み、上記の非水系電解液を注入した後で真空封止し、各Si含有量の負極を有する、シート状の非水系電解液二次電池を作製した。
[初期コンディショニング]
25℃の恒温槽中、上記各Si含有量の負極を有する、ラミネート型セルの非水系電解液二次電池を0.05Cに相当する電流で4.0Vまで定電流-定電圧充電をした。その後、0.05Cで2.5Vまで放電した。続いて0.2Cで4.0Vまで電池をCC-CVした後、0.2Cで2.5Vまで放電した。さらに、0.2Cで4.2Vまで電池をCC-CVした後、0.2Cで2.5Vまで放電し非水系電解液二次電池を安定させた。その後、0.2Cで4.3Vまで電池のCC-CV充電を行った後、0.2Cで2.5Vまで放電させ初期のコンディショニングを行った。
初期コンディショニング後の電池について、再度、0.2Cで4.3VまでCC-CV充電し、60℃、168時間の条件で高温保存を行った。電池を十分に冷却させた後、エタノール浴中に浸して体積を測定し、保存試験前後の体積変化から発生ガス量を求め、これを「保存ガス量」とした。
[非水系電解液の調製]
実施例9と同様にして、基準電解液7全体に対して、下記表11に記載の割合で各化合物を加えて電解液を調製した。ただし、比較例10-1は基準電解液7そのものである。なお、表中の「添加量(wt%)」は、非水系電解液100重量%中の濃度である。
実施例9と同様の正極を作製し、使用した。
負極活物質(黒鉛:SiO(質量比)=100:0、95:5、90:10)に対して、増粘剤、バインダーとしてそれぞれ、カルボキシメチルセルロースナトリウムの水性ディスパージョン(カルボキシメチルセルロースナトリウムの濃度1質量%)、及び、スチレン-ブタジエンゴムの水性ディスパージョン(スチレン-ブタジエンゴムの濃度50質量%)を加え、ディスパーザーで混合してスラリー化した。このスラリーを厚さ10μmの銅箔の片面に均一に塗布、乾燥した後、プレスして負極とした。なお、乾燥後の負極において、負極活物質:カルボキシメチルセルロースナトリウム:スチレンブタジエンゴム=97.5:1.5:1の質量比となるように作製した。
実施例9と同様の非水系電解液二次電池を作製し、使用した。
[初期コンディショニング]
25℃の恒温槽中、ラミネート型セルの非水系電解液二次電池を0.05Cに相当する電流で4.0Vまで定電流-定電圧充電をした。その後、0.05Cで2.5Vまで放電した。続いて0.2Cで4.0VまでCC-CVした後、0.2Cで2.5Vまで放電した。さらに0.2Cで4.2VまでCC-CVした後、0.2Cで2.5Vまで放電し非水系電解液二次電池を安定させた。その後、0.2Cで4.3VまでCC-CV充電を行った後、0.2Cで2.5Vまで放電させ初期のコンディショニングを行った。
初期コンディショニング後の電池について再度、0.2Cで4.3VまでCC-CV充電し、60℃、168時間の条件で高温保存を行った。その後、25℃において0.2Cで4.3VまでCC-CVした後、0.2C・0.5Cで2.5Vまで放電し、得られた0.2C・0.5C容量の比(0.5C/0.2C)を「保存後0.5C/0.2C負荷」とした。
[非水系電解液の調製]
乾燥アルゴン雰囲気下、EC、DMC、EMCとの混合物(体積容量比3:3:4)に、十分に乾燥させたLiPF6を1.0モル/L(非水系電解液中の濃度として)溶解させ、さらに、MFEC、化合物26、化合物27をそれぞれ3.0、1.5、1.0質量%(溶液の合計100質量%中)添加した(これを基準電解液8と呼ぶ)。基準電解液8全体に対して、下記表12に記載の割合で各化合物を加えて電解液を調製した。ただし、比較例11-1は基準電解液8そのものである。なお、表中の「添加量(wt%)」は、非水系電解液100重量%中の濃度である。
正極活物質としてリチウム・ニッケル・コバルト・マンガン複合酸化物(Li1.05Ni0.33Mn0.33Co0.33O2)90質量%と、導電材としてアセチレンブラック7質量%と、結着材としてポリフッ化ビニリデン(PVdF)3質量%とを、N-メチルピロリドン溶媒中で、ディスパーザーで混合してスラリー化した。これを厚さ15μmのアルミニウム箔の両面に均一に塗布、乾燥した後、プレスして正極とした。
黒鉛に、増粘剤としてカルボキシメチルセルロースナトリウムの水性ディスパージョン(カルボキシメチルセルロースナトリウムの濃度1質量%)と、バインダーとしてスチレン-ブタジエンゴムの水性ディスパージョン(スチレン-ブタジエンゴムの濃度50質量%)を加え、ディスパーザーで混合してスラリー化した。得られたスラリーを厚さ12μmの銅箔の片面に均一に塗布、乾燥した後、プレスして負極とした。また、スラリーは乾燥後の負極において、黒鉛:カルボキシメチルセルロースナトリウム:スチレン-ブタジエンゴム=97.5:1.5:1の質量比となるように作成した。
上記の正極、負極、及びポリオレフィン製セパレータを、負極、セパレータ、正極、セパレータ、負極の順に積層した。こうして得られた電池要素をアルミニウムラミネートフィルムで包み込み、後述する電解液を注入した後で真空封止し、シート状の非水系電解液二次電池を作製した。
[初期コンディショニング]
25℃雰囲気下において、シート状の非水系電解液二次電池を0.05Cで10時間充電後、3時間休止させ、その後3.8Vまで0.2Cで定電流充電した。さらに3時間の休止の後に、4.3Vまで0.2Cで定電流-定電圧充電し、次いで1/3Cで3.0Vまで定電流放電した。その後、4.3Vまでの1/3C定電流-定電圧充電と、これに続く3.0Vまでの1/3C定電流放電を1サイクルとする充放電サイクルを2サイクル行い、初期コンディショニングとした。
初期コンディショニング後の電池を、0.2Cで4.3VまでCC-CV充電し、60℃、30日間の条件で高温保存試験を行った。電池を十分に冷却させた後、エタノール浴中に浸して体積を測定し、保存試験前後の体積変化から発生ガス量を求め、これを「60℃保存ガス量」とした。
[非水系電解液の調製]
基準電解液1に対して、下記表13に記載の割合で各化合物を加えて非水系電解液を調製した。ただし、比較例12-1は基準電解液1そのものである。なお、表中の「添加量(wt%)」は、非水系電解液100重量%中の濃度である。
実施例1と同様の正極を作製し使用した。
実施例1と同様の負極を作製し使用した。
正極導電体を兼ねるステンレス鋼製の缶体に上記正極を収容し、その上に上記非水系電解液を含浸させたポリプロピレン製のセパレータを介して上記負極を載置した。この缶体と負極導電体を兼ねる封口板とを、絶縁用のガスケットを介してかしめて密封し、非水系電解液二次電池(コイン型)を作製した。
[初期コンディショニング]
25℃の恒温槽中、ラミネート型セルの非水系電解液二次電池を0.05Cに相当する電流で6時間定電流充電した後、0.2Cで3.0Vまで放電した。次に0.2Cで4.1Vまで電池のCC-CV充電(0.05Cカット)を行った。その後、0.2Cで3.0Vまで放電し、非水系電解液二次電池を安定させた。さらに、0.2Cで4.4Vまで電池のCC-CV充電(0.05Cカット)を行った後、0.2Cで3.0Vまで放電し、初期放電容量を求めた。
初期コンディショニング後の電池について再度、0.2Cで4.4VまでCC-CV充電(0.05Cカット)を行った後、85℃、24時間の条件で高温保存を行った。その後、25℃において0.2Cの定電流で3Vまで放電させ、高温保存試験後の残存容量を測定した。初期容量に対する保存試験後の残存放電容量の割合((保存試験後の残存放電容量/初期容量)×100)を求め、これを「高温保存容量残存率(%)」とした。
Claims (11)
- 前記一般式(A)中、Xが水素原子である、請求項1に記載の非水系電解液。
- 前記一般式(A)中、R1、R2およびYがそれぞれ置換基を有さない炭素数1~12の炭化水素基である、請求項1又は2に記載の非水系電解液。
- 前記一般式(A)中、R1、R2およびYがそれぞれ置換基を有さない炭素数1~12のアルキル基である、請求項1又は2に記載の非水系電解液。
- 前記一般式(A)で表される化合物の添加量が非水系電解液の全量に対して0.001質量%以上10質量%以下である、請求項1乃至4のいずれか一項に記載の非水系電解液。
- 前記非水系電解液が、さらに炭素-炭素不飽和結合を有する環状カーボネート、フッ素原子を有する環状カーボネート、ニトリル化合物、イソシアネート化合物、イソシアヌル酸骨格を有する化合物、フッ素化された塩、酸無水物化合物、アクリレート化合物、芳香族化合物、環状エーテル化合物、オキサラート塩及び環状スルホン酸エステルからなる群より選ばれる少なくとも1種の添加剤を含有する、請求項1乃至5のいずれか一項に記載の非水系電解液。
- 前記非水系溶媒が鎖状カルボン酸エステルを含む、請求項1乃至6のいずれか一項に記載の非水系電解液。
- 金属イオンを吸蔵及び放出可能な正極及び負極と、非水系電解液とを備えた非水系電解液二次電池であって、該非水系電解液が請求項1乃至7のいずれか一項に記載の非水系電解液である、非水系電解液二次電池。
- 前記金属イオンを吸蔵及び放出可能な負極の負極活物質が炭素を構成元素として有する、請求項8に記載の非水系電解液二次電池。
- 前記金属イオンを吸蔵及び放出可能な負極の負極活物質がケイ素(Si)またはスズ(Sn)を構成元素として有する、請求項8に記載の非水系電解液二次電池。
- 前記金属イオンを吸蔵及び放出可能な負極の負極活物質が、Liと合金可能な金属粒子と黒鉛粒子との混合体または複合体である、請求項8に記載の非水系電解液二次電池。
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KR1020177008400A KR102457557B1 (ko) | 2014-09-30 | 2015-09-29 | 비수계 전해액 및 이를 사용한 비수계 전해액 이차 전지 |
EP15846631.8A EP3203569B1 (en) | 2014-09-30 | 2015-09-29 | Nonaqueous electrolyte, and nonaqueous electrolyte secondary battery using same |
CN201580053244.9A CN107078352B (zh) | 2014-09-30 | 2015-09-29 | 非水电解液及使用了该非水电解液的非水电解质二次电池 |
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CN110800150A (zh) * | 2017-03-31 | 2020-02-14 | 株式会社村田制作所 | 包含电解质稳定材料的非水电解质和电解液、包含它们的二次电池及其用途 |
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JPWO2016052542A1 (ja) | 2017-07-13 |
CN107078352A (zh) | 2017-08-18 |
EP3203569A1 (en) | 2017-08-09 |
EP3203569B1 (en) | 2018-10-31 |
EP3203569A4 (en) | 2017-08-09 |
JP6772834B2 (ja) | 2020-10-21 |
US20170200976A1 (en) | 2017-07-13 |
KR102457557B1 (ko) | 2022-10-24 |
KR20170057296A (ko) | 2017-05-24 |
JP2020194782A (ja) | 2020-12-03 |
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US10424812B2 (en) | 2019-09-24 |
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