WO2014050873A1 - 電解液、電気化学デバイス、リチウム電池、及び、モジュール - Google Patents
電解液、電気化学デバイス、リチウム電池、及び、モジュール Download PDFInfo
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- WO2014050873A1 WO2014050873A1 PCT/JP2013/075879 JP2013075879W WO2014050873A1 WO 2014050873 A1 WO2014050873 A1 WO 2014050873A1 JP 2013075879 W JP2013075879 W JP 2013075879W WO 2014050873 A1 WO2014050873 A1 WO 2014050873A1
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- 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
- H01M10/0566—Liquid materials
- H01M10/0567—Liquid materials characterised by the additives
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- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- 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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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- 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
- H01M10/0566—Liquid materials
- H01M10/0568—Liquid materials characterised by the solutes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- 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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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- 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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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- 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
- H01M10/0566—Liquid materials
- H01M10/0569—Liquid materials characterised by the solvents
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0025—Organic electrolyte
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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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- 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 an electrolytic solution, an electrochemical device, a lithium battery, and a module.
- Non-aqueous electrolyte batteries such as non-aqueous electrolyte batteries have been put to practical use as a wide range of power sources ranging from power supplies for portable electronic devices such as mobile phones and notebook computers to automobile power supplies for automobiles and large power supplies for stationary applications. It is being done.
- the demand for applied secondary batteries is increasing, and the high performance of the battery characteristics of secondary batteries is increasing.
- characteristics such as higher capacity, high temperature storage characteristics, cycle characteristics, and the like.
- the electrolyte used for a non-aqueous electrolyte battery is usually mainly composed of an electrolyte and a non-aqueous solvent.
- the main components of the non-aqueous solvent include cyclic carbonates that are high dielectric solvents such as ethylene carbonate and propylene carbonate, chain carbonates that are low viscosity solvents such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, and ⁇ -butyrolactone. Cyclic carboxylic acid esters such as ⁇ -valerolactone are used.
- Non-aqueous solvents, electrolytes, auxiliaries, and the like have been proposed in order to improve battery characteristics such as load characteristics, cycle characteristics, storage characteristics, and low-temperature characteristics of batteries using these non-aqueous electrolytes.
- a non-aqueous electrolyte using a carbon material for the negative electrode by using vinylene carbonate and its derivatives or vinyl ethylene carbonate derivatives, a cyclic carbonate having a double bond reacts preferentially with the negative electrode on the negative electrode surface.
- Patent Documents 1 and 2 disclose that a high-quality film is formed, which improves battery storage characteristics and cycle characteristics.
- Patent Document 10 proposes an electrolytic solution containing a fluorine-containing cyclic carbonate having a fluorine-containing ether group or a fluorinated alkyl group having 2 or more carbon atoms and an electrolyte salt.
- Non-Patent Documents 1 to 3 describe electrochemical behavior and thermal properties in lithium ion batteries for organic fluorine compounds containing a fluorinated ether carbonate or a fluorinated cyclic carbonate having a fluorinated alkyl group having 2 or more carbon atoms. Stability and electrochemical properties are described.
- the present invention is intended to solve these problems, and provides a lithium battery having a high remaining capacity after high-temperature storage even when used at a high voltage, and an electrolyte used therefor.
- the present inventors use a non-aqueous solvent containing a specific amount of a compound represented by the following general formula (1) and an electrolyte solution containing an electrolyte salt. It has been found that a lithium battery with a high remaining capacity can be realized.
- the present invention is an electrolytic solution containing a non-aqueous solvent and an electrolyte salt, wherein the compound represented by the general formula (1) contains 10% by volume or more in 100% by volume of the non-aqueous solvent. It is a liquid.
- R 1 , R 2 and R 3 may be the same or different, and each represents a hydrogen atom, a fluorine atom, an alkyl group having 1 to 20 carbon atoms, or a fluorinated alkyl having 1 to 20 carbon atoms) Except that R 1 , R 2 and R 3 are all hydrogen atoms and fluorine atoms.
- the electrolyte salt is LiPF 6 and the content of the electrolyte salt is preferably 0.2 mol / liter or more.
- the present invention is also an electrochemical device comprising the above-described electrolytic solution.
- the present invention also provides a lithium battery comprising a negative electrode and a positive electrode capable of inserting or extracting lithium ions, a separator, and the above-described electrolytic solution.
- the negative electrode capable of inserting or extracting lithium ions preferably includes at least one negative electrode active material selected from the group consisting of a carbonaceous material and a metal material.
- the potential of the positive electrode is 4.3 V or more based on metallic lithium.
- the present invention is also a module including the above-described lithium secondary battery.
- a nonaqueous electrolytic solution battery having improved durability characteristics such as high-temperature storage and load characteristics of the battery is provided.
- the present invention is an electrolytic solution containing a non-aqueous solvent and an electrolyte salt, and containing the compound represented by the general formula (1).
- R 1 , R 2 and R 3 may be the same or different, and each represents a hydrogen atom, a fluorine atom, an alkyl group having 1 to 20 carbon atoms, or a fluorinated alkyl having 1 to 20 carbon atoms) Except that R 1 , R 2 and R 3 are all hydrogen atoms and fluorine atoms.
- the electrolytic solution of the present invention contains a compound represented by the general formula (1).
- R 1 , R 2 and R 3 may be the same or different, and each is a hydrogen atom, a fluorine atom, an alkyl group having 1 to 20 carbon atoms, or a carbon atom having 1 to 20 carbon atoms.
- a fluorinated alkyl group is an alkyl group in which part or all of the hydrogen atoms of the alkyl group are substituted with fluorine atoms.
- the alkyl group and the fluorinated alkyl group have a molecular weight of 1 to 20 and a viscosity of 1 to 10 because the molecular weight increases, the viscosity increases, and the resistance increases when the carbon number exceeds 20. Is preferable, and 1 is more preferable.
- At least one of R 1 , R 2 and R 3 is preferably a fluorine atom or a fluorinated alkyl group, more preferably at least one is a fluorine atom, and at least a fluorine atom and CF 3 is more preferable.
- R 1 , R 2 and R 3 in the formula are hydrogen atoms and fluorine atoms.
- the following compounds are preferable as a compound shown by General formula (1) at the point which has the more excellent electrical property.
- Content of the compound shown by General formula (1) is 10 volume% or more in 100 volume% of non-aqueous solvents.
- the content of the compound represented by the general formula (1) is 10% by volume or more in 100% by volume of the non-aqueous solvent, an electrolyte solution having excellent battery characteristics such as high-temperature storage characteristics, discharge capacity retention ratio, and load characteristics can do.
- the content of the compound represented by the general formula (1) is preferably 15% by volume or more in 100% by volume of the non-aqueous solvent.
- 90 volume% or less is preferable and 85 volume% or less is more preferable.
- the non-aqueous electrolyte battery tends to exhibit a sufficient cycle characteristics improvement effect, and the discharge capacity maintenance rate is reduced due to a decrease in load characteristics due to an increase in resistance, a decrease in high-temperature storage characteristics, and an increase in gas generation. It is easy to avoid the drop.
- the electrolytic solution of the present invention further contains a non-aqueous solvent and an electrolyte salt.
- a non-aqueous solvent saturated cyclic carbonate, chain carbonate, cyclic and chain carboxylic acid ester, ether compound, sulfone compound and the like can be used.
- saturated cyclic carbonate examples include those having an alkylene group having 2 to 4 carbon atoms, and specific examples include ethylene carbonate, propylene carbonate, butylene carbonate and the like. Among these, 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. Two or more of these saturated cyclic carbonates may be used in any combination and ratio.
- the blending amount of the saturated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired.
- the lower limit of the blending amount when used alone is preferably in 100% by volume of the non-aqueous solvent. Is 5% by volume or more, more preferably 10% by volume or more. Within this range, a decrease in electrical conductivity due to a decrease in the dielectric constant of the non-aqueous electrolyte solution is avoided, and the high-current discharge characteristics, stability to the negative electrode, and cycle characteristics of the non-aqueous electrolyte battery are in a favorable range. It becomes easy. Moreover, an upper limit becomes like this.
- the viscosity of the non-aqueous electrolyte is set to an appropriate range, a decrease in ionic conductivity is suppressed, and battery characteristics such as load characteristics are easily set in a favorable range.
- the fluorinated cyclic carbonate is a cyclic carbonate compound different from the compound represented by the above general formula (1), and does not include the compound represented by the general formula (1).
- the fluorinated cyclic carbonate the following general formula (A):
- X 1 to X 4 are the same or different and each represents —H, —F, a fluorinated alkyl group that may have an ether bond, or a fluorinated alkoxy group that may have an ether bond. Provided that at least one of X 1 to X 4 is —F, a fluorinated alkyl group that may have an ether bond, or a fluorinated alkoxy group that may have an ether bond). Fluorinated cyclic carbonate (A).
- the fluorinated cyclic carbonate (A) when the fluorinated cyclic carbonate (A) is included, when the electrolytic solution of the present invention is applied to a lithium battery or the like, a stable film can be formed on the negative electrode, and the side reaction of the electrolytic solution at the negative electrode is sufficiently performed. Can be suppressed. As a result, extremely stable and excellent charge / discharge characteristics can be obtained.
- the “ether bond” is a bond represented by —O—.
- X 1 to X 4 are —H, —F, fluorinated alkyl, since it is expected to lower the viscosity at low temperature, increase the flash point, and further improve the solubility of the electrolyte salt.
- the group (a), a fluorinated alkyl group (b) having an ether bond, or a fluorinated alkoxy group (c) is preferred.
- X 1 to X 4 are —H, —F, fluorinated alkyl, since it is expected to lower the viscosity at low temperature, increase the flash point, and further improve the solubility of the electrolyte salt.
- the group (a), a fluorinated alkyl group (b) having an ether bond, or a fluorinated alkoxy group (c) is preferred.
- At least one or two of X 1 to X 4 are —F, a fluorinated alkyl group optionally having an ether bond, or In addition, a fluorinated alkoxy group which may have an ether bond is preferable.
- the fluorinated alkyl group (a) is obtained by substituting at least one hydrogen atom of the alkyl group with a fluorine atom.
- the number of carbon atoms in the fluorinated alkyl group (a) is preferably 1-20, more preferably 2-17, still more preferably 2-7, and particularly preferably 2-5. If the carbon number is too large, the low-temperature characteristics may be lowered or the solubility of the electrolyte salt may be lowered. If the carbon number is too small, the solubility of the electrolyte salt is lowered, the discharge efficiency is lowered, and further, An increase in viscosity may be observed.
- fluorinated alkyl groups (a) those having 1 carbon atom include CFH 2 —, CF 2 H—, and CF 3 —.
- fluorinated alkyl groups those having 2 or more carbon atoms are represented by the following general formula (a-1): R 1 -R 2- (a-1) (Wherein R 1 is an alkyl group having 1 or more carbon atoms which may have a fluorine atom; R 2 is an alkylene group having 1 to 3 carbon atoms which may have a fluorine atom; provided that R 1 and A fluorinated alkyl group represented by (at least one of R 2 has a fluorine atom) can be preferably exemplified from the viewpoint of good solubility of the electrolyte salt. R 1 and R 2 may further have other atoms other than the carbon atom, the hydrogen atom, and the fluorine atom.
- R 1 is an alkyl group having 1 or more carbon atoms which may have a fluorine atom.
- R 1 is preferably a linear or branched alkyl group having 1 to 16 carbon atoms.
- the number of carbon atoms of R 1 is more preferably 1 to 6, and further preferably 1 to 3.
- R 1 specifically, as a linear or branched alkyl group, CH 3 —, CH 3 CH 2 —, CH 3 CH 2 CH 2 —, CH 3 CH 2 CH 2 CH 2 —,
- R 1 is a linear alkyl group having a fluorine atom, CF 3 —, CF 3 CH 2 —, CF 3 CF 2 —, CF 3 CH 2 CH 2 —, CF 3 CF 2 CH 2 — CF 3 CF 2 CF 2- , CF 3 CH 2 CF 2- , CF 3 CH 2 CH 2 CH 2- , CF 3 CF 2 CH 2 CH 2- , CF 3 CH 2 CF 2 CH 2- , CF 3 CH 2 CF 2 CH 2- , CF 3 CF 2 CF 2 CH 2 —, CF 3 CF 2 CF 2 CH 2 —, CF 3 CF 2 CH 2 CF 2 —, CF 3 CH 2 CH 2 CF 2 —, CF 3 CH 2 CH 2 CH 2 —, CF 3 CF 2 CH 2 CH 2 —, CF 3 CF 2 CH 2 CH 2 CH 2 —, CF 3 CF 2 CH 2 CH 2 —, CF 3 CF 2 CF 2 CH 2 CH 2 —,
- R 1 is a branched alkyl group having a fluorine atom
- Etc. are preferable. However, since the viscosity tends to be high if there is a branch of —CH 3 or —CF 3 , the number is preferably small (one) or zero.
- R 2 is an alkylene group having 1 to 3 carbon atoms which may have a fluorine atom.
- R 2 may be linear or branched.
- An example of the minimum structural unit constituting such a linear or branched alkylene group is shown below.
- R 2 is composed of these alone or in combination.
- the base is composed of a constitutional unit that does not contain Cl, because de-HCl reaction with a base does not occur and is more stable.
- R 2 is linear, it is composed of only the above-mentioned linear minimum structural unit, and —CH 2 —, —CH 2 CH 2 — or CF 2 — is particularly preferable. From the viewpoint of further improving the solubility of the electrolyte salt, —CH 2 — or —CH 2 CH 2 — is more preferable.
- R 2 When R 2 is branched, it comprises at least one of the aforementioned branched minimum structural units, and R 2 is represented by the general formula — (CX a X b ) — (X a is H, F CH 3 or CF 3 ; X b is CH 3 or CF 3, provided that when X b is CF 3 , X a is H or CH 3 .
- the solubility of the electrolyte salt can be further improved.
- Preferred fluorinated alkyl groups (a) include, for example, CF 3 CF 2 —, HCF 2 CF 2 —, H 2 CFCF 2 —, CH 3 CF 2 —, CF 3 CF 2 CF 2 —, HCF 2 CF 2 CF 2 -, H 2 CFCF 2 CF 2- , CH 3 CF 2 CF 2- ,
- the fluorinated alkyl group (b) having an ether bond is obtained by substituting at least one hydrogen atom of the alkyl group having an ether bond with a fluorine atom.
- the fluorinated alkyl group (b) having an ether bond preferably has 2 to 17 carbon atoms.
- the solubility of the electrolyte salt decreases due to the decrease in the dielectric constant, and the phase with other solvents. A decrease in solubility may be observed.
- the fluorinated alkyl group (b) having an ether bond preferably has 2 to 10 carbon atoms, and more preferably 2 to 7 carbon atoms.
- the alkylene group constituting the ether portion of the fluorinated alkyl group (b) having an ether bond may be a linear or branched alkylene group.
- An example of the minimum structural unit constituting such a linear or branched alkylene group is shown below.
- the alkylene group may be composed of these minimum structural units alone, and may be linear (i), branched (ii), or linear (i) and branched (ii). You may comprise by the combination. Preferred specific examples will be described later.
- the base is composed of a constitutional unit that does not contain Cl, because de-HCl reaction with a base does not occur and is more stable.
- fluorinated alkyl group (b) having an ether bond include a compound represented by the general formula (b-1): R 3- (OR 4 ) n1- (b-1) (Wherein R 3 may have a fluorine atom, preferably an alkyl group having 1 to 6 carbon atoms; R 4 may have a fluorine atom, preferably an alkylene having 1 to 4 carbon atoms) N1 is an integer of 1 to 3; provided that at least one of R 3 and R 4 has a fluorine atom).
- R 3 and R 4 include the following, and these can be combined as appropriate to form a fluorinated alkyl group (b) having an ether bond represented by the general formula (b-1). However, it is not limited to these.
- R 3 the general formula: X c 3 C— (R 5 ) n2 — (the three X c are the same or different and each is H or F; R 5 represents a fluorine atom having 1 to 5 carbon atoms)
- R 3 includes CH 3 —, CF 3 —, HCF 2 —, and H 2 CF—.
- R 3 is linear, CF 3 CH 2 —, CF 3 CF 2 —, CF 3 CH 2 CH 2 —, CF 3 CF 2 CH 2 —, CF 3 CF 2 CF 2 —, CF 3 CH 2 CF 2 —, CF 3 CH 2 CH 2 CH 2 —, CF 3 CH 2 CF 2 CH 2 —, CF 3 CH 2 CF 2 CH 2 —, CF 3 CH 2 CF 2 CH 2 —, CF 3 CH 2 CF 2 CH 2 —, CF 3 CF 2 CF 2 CH 2- , CF 3 CF 2 CH 2 CF 2- , CF 3 CH 2 CH 2 CH 2- , CF 3 CH 2 CF 2 CH 2 CH 2 —, CF 3 CH 2 CF 2 CH 2 CH 2 —, CF 3 CH 2 CF 2 CH 2 CH 2 —, CF 3 CH 2 CF 2 CH 2 CH 2 —, CF 3 CH 2 CF 2 CH 2 CH 2 —, CF 3 CH 2 CF 2 CH 2 CH 2
- n2 is 1, and as R 3 is branched, the
- R 3 is more preferably linear.
- n1 is an integer of 1 to 3, preferably 1 or 2.
- R 4 may be the same or different.
- R 4 include the following linear or branched ones.
- the fluorinated alkoxy group (c) is obtained by substituting at least one hydrogen atom of the alkoxy group with a fluorine atom.
- the fluorinated alkoxy group (c) preferably has 1 to 17 carbon atoms. More preferably, it has 1 to 6 carbon atoms.
- the fluorinated alkoxy group (c) is represented by the general formula: X d 3 C— (R 6 ) n3 —O— (the three X d are the same or different, and all are H or F; R 6 is preferably carbon number)
- fluorinated alkoxy group (c) examples include a fluorinated alkoxy group in which an oxygen atom is bonded to the terminal of the alkyl group exemplified as R 1 in the general formula (a-1).
- the fluorine content of the fluorinated alkyl group (a), the fluorinated alkyl group (b) having an ether bond, and the fluorinated alkoxy group (c) in the fluorinated cyclic carbonate (A) is preferably 10% by mass or more. If the fluorine content is too low, the effect of lowering the viscosity at low temperatures and the effect of increasing the flash point may not be sufficiently obtained. From this viewpoint, the fluorine content is more preferably 12% by mass or more, and further preferably 15% by mass or more. The upper limit is usually 76% by mass.
- the fluorine content of the fluorinated alkyl group (a), the fluorinated alkyl group (b) having an ether bond, and the fluorinated alkoxy group (c) is determined based on the structural formula of each group ⁇ (fluorine atom Number ⁇ 19) / formula amount of each group ⁇ ⁇ 100 (%).
- the fluorine content of the entire fluorinated cyclic carbonate (A) is preferably 10% by mass or more, and more preferably 15% by mass or more.
- the upper limit is usually 76% by mass.
- the fluorine content of the fluorinated cyclic carbonate (A) is determined based on the structural formula of the fluorinated cyclic carbonate (A): ⁇ (number of fluorine atoms ⁇ 19) / molecular weight of the fluorinated cyclic carbonate (A) ⁇ ⁇ 100 It is a value calculated by (%).
- Etc. can be used.
- At least one of X 1 to X 4 is a fluorinated alkyl group (a), and the rest are all —H.
- At least one of X 1 to X 4 is a fluorinated alkyl group (b) or a fluorinated alkoxy group (c) having an ether bond, and the rest are all —H.
- fluorinated cyclic carbonate (A) As a specific example of the fluorinated cyclic carbonate (A),
- the fluorinated cyclic carbonate (A) is not limited to the specific examples described above.
- the said fluorinated cyclic carbonate (A) may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
- the blending amount of the fluorinated cyclic carbonate is not particularly limited and may be arbitrary as long as the effects of the present invention are not significantly impaired, but is preferably 0.01% by volume or more in 100% by volume of the non-aqueous solvent. 1 volume% or more is more preferable, and 0.2 volume% or more is further more preferable. Moreover, it is preferable that the said content is 95 volume% or less, and it is more preferable that it is 90 volume% or less. If it is this range, a non-aqueous electrolyte battery is easy to express sufficient cycle characteristic improvement effect, and it is easy to avoid that a discharge capacity maintenance factor falls by the fall of a high temperature storage characteristic or the increase in the amount of gas generation.
- the chain carbonate is preferably one having 3 to 7 carbon atoms. Specifically, as the chain carbonate having 3 to 7 carbon atoms, dimethyl carbonate (DMC), diethyl carbonate (DEC), di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate (EMC) ), Methyl-n-propyl carbonate, n-butylmethyl carbonate, isobutylmethyl carbonate, t-butylmethyl carbonate, ethyl-n-propyl carbonate, n-butylethyl carbonate, isobutylethyl carbonate, t-butylethyl carbonate, etc. It is done.
- DMC dimethyl carbonate
- DEC diethyl carbonate
- EMC ethyl methyl carbonate
- Methyl-n-propyl carbonate n-butylmethyl carbonate
- dimethyl carbonate (DMC), diethyl carbonate (DEC), di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate (EMC), and methyl-n-propyl carbonate are particularly preferable.
- fluorinated chain carbonates can also be suitably used as the chain carbonate.
- the number of fluorine atoms contained in the fluorinated chain carbonate is not particularly limited as long as it is 1 or more, but is usually 6 or less and 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.
- the fluorinated chain carbonate include a fluorinated dimethyl carbonate derivative, a fluorinated ethyl methyl carbonate derivative, and a fluorinated diethyl carbonate derivative.
- fluorinated dimethyl carbonate derivative examples include fluoromethyl methyl carbonate, difluoromethyl methyl carbonate, trifluoromethyl methyl carbonate, bis (fluoromethyl) carbonate, bis (difluoro) methyl carbonate, bis (trifluoromethyl) carbonate, and the like.
- Fluorinated ethyl methyl carbonate derivatives include 2-fluoroethyl methyl carbonate, ethyl fluoromethyl carbonate, 2,2-difluoroethyl methyl carbonate, 2-fluoroethyl fluoromethyl carbonate, ethyl difluoromethyl carbonate, 2,2,2-trimethyl Examples include fluoroethyl methyl carbonate, 2,2-difluoroethyl fluoromethyl carbonate, 2-fluoroethyl difluoromethyl carbonate, and ethyl trifluoromethyl carbonate.
- Fluorinated diethyl carbonate derivatives include ethyl- (2-fluoroethyl) carbonate, ethyl- (2,2-difluoroethyl) carbonate, bis (2-fluoroethyl) carbonate, ethyl- (2,2,2-trifluoro).
- a chain carbonate and a fluorinated chain carbonate 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 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 viscosity of the non-aqueous electrolyte solution is set to an appropriate range, a decrease in ionic conductivity is suppressed, and the large current discharge characteristics of the non-aqueous electrolyte battery are easily set to a favorable range.
- the chain carbonate is preferably 90% by volume or less, more preferably 85% by volume or less, in 100% by volume of the non-aqueous solvent.
- a decrease in electrical conductivity resulting from a decrease in the dielectric constant of the nonaqueous electrolyte solution can be avoided, and the large current discharge characteristics and the like of the nonaqueous electrolyte solution battery can be easily set in a favorable range.
- the battery performance can be remarkably improved by combining ethylene carbonate at a specific blending amount with respect to the specific chain carbonate.
- the blending amount of ethylene carbonate is 10% by volume or more and 80% by volume or less, and the blending amount of DMC, EMC, or DEC is 20% by volume. As mentioned above, it is preferable that it is 90 volume% or less.
- the blending amount of ethylene carbonate is 10% by volume or more and 60% by volume or less
- the blending amount of DMC is 10% by volume or more and 70% by volume or less
- the blending of EMC The amount of 10% by volume or more and 80% by volume or less is particularly preferable.
- the blending amount of ethylene carbonate is 10% by volume or more and 60% by volume or less
- the blending amount of DMC is 10% by volume or more and 70% by volume or less
- DEC The compounding amount of 10% by volume or more and 70% by volume or less is particularly preferable.
- the blending amount of ethylene carbonate is 10% by volume or more and 60% by volume or less
- the blending amount of EMC is 10% by volume or more and 80% by volume or less
- DEC is particularly preferable.
- cyclic carboxylic acid ester examples include those having 3 to 12 total carbon atoms in the structural formula. Specific examples include gamma butyrolactone, gamma valerolactone, gamma caprolactone, isopsilon caprolactone, and the like. Among these, gamma butyrolactone is particularly preferable from the viewpoint of improving battery characteristics resulting from an improvement in the degree of lithium ion dissociation.
- the compounding amount of the cyclic carboxylic acid ester is usually 5% by volume or more, more preferably 10% by volume or more, in 100% by volume of the non-aqueous solvent. Within this range, the electrical conductivity of the non-aqueous electrolyte solution is improved, and the high-current discharge characteristics of the non-aqueous electrolyte battery are easily improved. 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, the decrease in electrical conductivity is avoided, the increase in negative electrode resistance is suppressed, and the large current discharge characteristics of the non-aqueous electrolyte battery are improved. Make it easy to achieve a good range.
- fluorinated cyclic carboxylic acid ester (fluorine-containing lactone) can also be suitably used.
- fluorine-containing lactone examples include the following formula (C):
- X 15 to X 20 are the same or different and all are —H, —F, —Cl, —CH 3 or a fluorinated alkyl group; provided that at least one of X 15 to X 20 is a fluorinated alkyl
- Examples of the fluorinated alkyl group for X 15 to X 20 include —CFH 2 , —CF 2 H, —CF 3 , —CH 2 CF 3 , —CF 2 CF 3 , —CH 2 CF 2 CF 3 , —CF (CF 3 ) 2 and the like are mentioned, and —CH 2 CF 3 and —CH 2 CF 2 CF 3 are preferable from the viewpoint of high oxidation resistance and an effect of improving safety.
- X 15 to X 20 is a fluorinated alkyl group, —H, —F, —Cl, —CH 3 or the fluorinated alkyl group is substituted at only one position of X 15 to X 20.
- a plurality of locations may be substituted.
- it is 1 to 3 sites, more preferably 1 to 2 sites from the viewpoint of good solubility of the electrolyte salt.
- the substitution position of the fluorinated alkyl group is not particularly limited. However, since the synthesis yield is good, X 17 and / or X 18 is particularly preferably X 17 or X 18 is a fluorinated alkyl group, particularly —CH 2 CF 3. , —CH 2 CF 2 CF 3 is preferable. X 15 to X 20 other than the fluorinated alkyl group are —H, —F, —Cl or CH 3 , and —H is particularly preferable from the viewpoint of good solubility of the electrolyte salt.
- one of A and B is CX 26 X 27 (X 26 and X 27 are the same or different, and each of them is —H, —F, —Cl, —CF 3 , —CH 3 or a hydrogen atom)
- Rf 12 is a fluorinated alkyl group or a fluorinated group which may have an ether bond
- X 21 and X 22 are the same or different; all are —H, —F, —Cl, —CF 3 or CH 3 ;
- Chain carboxylic acid esters include those having 3 to 7 carbon atoms in the structural formula. Specifically, methyl acetate, ethyl acetate, acetate n-propyl, isopropyl acetate, n-butyl acetate, isobutyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, Isopropyl propionate, n-butyl propionate, isobutyl propionate, t-butyl propionate, methyl butyrate, ethyl butyrate, n-propyl butyrate, n-propyl butyrate, isopropyl butyrate, methyl isobutyrate, ethyl isobutyrate , Isobutyric acid-n-propyl, isobutyric acid isopropyl and
- methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate, etc. are ions due to viscosity reduction. It is preferable from the viewpoint of improvement of conductivity.
- 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.
- strand-shaped carboxylic acid ester is preferably 60 volume% or less in 100 volume% of non-aqueous solvents, More preferably, it is 50 volume% or less.
- fluorinated chain carboxylic acid ester can also be used suitably.
- the fluorine-containing ester the following formula (H): Rf 10 COORf 11 (H) (Wherein Rf 10 is a fluorinated alkyl group having 1 to 2 carbon atoms, Rf 11 is a fluorinated alkyl group having 1 to 4 carbon atoms), and the flame retardant property is high, And it is preferable from the viewpoint of good compatibility with other solvents and oxidation resistance.
- Rf 10 examples include CF 3- , CF 3 CF 2- , HCF 2 CF 2- , HCF 2- , CH 3 CF 2- , CF 3 CH 2- and the like, among which CF 3- , CF 3 CF 2 -is particularly preferable from the viewpoint of good rate characteristics.
- Rf 11 examples include CF 3 , —CF 2 CF 3 , —CH (CF 3 ) 2 , —CH 2 CF 3 , —CH 2 CH 2 CF 3 , —CH 2 CF 2 CFHCF 3 , —CH 2 C 2
- fluorinated chain carboxylic acid ester examples include, for example, CF 3 C ( ⁇ O) OCH 2 CF 3 , CF 3 C ( ⁇ O) OCH 2 CH 2 CF 3 , and CF 3 C ( ⁇ O) OCH 2 C.
- CF 3 C ( ⁇ O) OCH 2 CF 3 CF 3 C ( ⁇ O) OCH 2 CH 2 CF 3
- CF 3 C ( ⁇ O) OCH 2 C One or more of 2 F 5 , CF 3 C ( ⁇ O) OCH 2 CF 2 CF 2 H, CF 3 C ( ⁇ O) OCH (CF 3 ) 2, etc.
- ether compound a chain ether having 3 to 10 carbon atoms and a cyclic ether having 3 to 6 carbon atoms are preferable.
- chain ether having 3 to 10 carbon atoms include diethyl ether, di-n-butyl ether, dimethoxymethane, methoxyethoxymethane, diethoxymethane, dimethoxyethane, methoxyethoxyethane, diethoxyethane, and ethylene glycol di-n-propyl.
- examples include ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether and the like.
- fluorinated ether can also be used suitably.
- the fluorinated ether include the following general formula (I): Rf 1 -O-Rf 2 (I) (In the formula, Rf 1 and Rf 2 are the same or different and are an alkyl group having 1 to 10 carbon atoms or a fluorinated alkyl group having 1 to 10 carbon atoms, provided that at least one of Rf 1 and Rf 2 is fluorine.
- a fluorinated ether (I) represented by formula (1).
- Rf 1 and Rf 2 may be a fluorinated alkyl group having 1 to 10 carbon atoms.
- both Rf 1 and Rf 2 are preferably fluorinated alkyl groups having 1 to 10 carbon atoms.
- Rf 1 and Rf 2 may be the same or different from each other. Among them, Rf 1 and Rf 2 are the same or different, Rf 1 is a fluorinated alkyl group having 3 to 6 carbon atoms, and Rf 2 is a fluorinated alkyl group having 2 to 6 carbon atoms. It is preferable.
- the fluorinated ether (I) preferably has a fluorine content of 40 to 75% by mass. When it has a fluorine content in this range, it is particularly excellent in the balance between incombustibility and compatibility. Moreover, it is preferable also from a point with favorable oxidation resistance and safety
- the lower limit of the fluorine content is more preferably 45% by mass, still more preferably 50% by mass, and particularly preferably 55% by mass.
- the upper limit is more preferably 75% by mass, still more preferably 70% by mass, and particularly preferably 66% by mass.
- the fluorine content is calculated from ⁇ (number of fluorine atoms ⁇ 19) / molecular weight of fluorinated ether (I) ⁇ ⁇ 100 (%) based on the structural formula of fluorinated ether (I). It is the value.
- Rf 1 examples include CF 3 CF 2 CH 2 —, CF 3 CFHCF 2 —, HCF 2 CF 2 CF 2 —, HCF 2 CF 2 CH 2 —, CF 3 CF 2 CH 2 CH 2 —, CF 3 CFHCF 2 CH 2 —, HCF 2 CF 2 CF 2 —, HCF 2 CF 2 CH 2 CH 2 —, HCF 2 CF (CF 3 ) CH 2 — and the like can be mentioned.
- Rf 2 examples include —CH 2 CF 2 CF 3 , —CF 2 CFHCF 3 , —CF 2 CF 2 CF 2 H, —CH 2 CF 2 CF 2 H, —CH 2 CH 2 CF 2 CF 3 , —CH 2 CF 2 CFHCF 3 , —CF 2 CF 2 CF 2 CF 2 H, —CH 2 CF 2 CF 2 H, —CH 2 CH 2 CF 2 CF 2 H, —CH 2 CF (CF 3 ) CF 2 H, —CF 2 CF 2 H, —CH 2 CF 2 H, —CF 2 CH 3 and the like can be mentioned.
- fluorinated ether (I) include, for example, HCF 2 CF 2 CH 2 OCF 2 CF 2 H, CF 3 CF 2 CH 2 OCF 2 CF 2 H, HCF 2 CF 2 CH 2 OCF 2 CFHCF 3 , CF 3 CF 2 CH 2 OCF 2 CFHCF 3 , C 6 F 13 OCH 3 , C 6 F 13 OC 2 H 5 , C 8 F 17 OCH 3 , C 8 F 17 OC 2 H 5 , CF 3 CFHCF 2 CH (CH 3 ) OCF 2 CFHCF 3 , HCF 2 CF 2 OCH (C 2 H 5 ) 2 , HCF 2 CF 2 OC 4 H 9 , HCF 2 CF 2 OCH 2 CH (C 2 H 5 ) 2 , HCF 2 CF 2 OCH 2 CH (CH 3) 2 or the like can be mentioned.
- fluorinated ether (I) having a high boiling point.
- the boiling point of the fluorinated ether (I) is preferably 67 to 120 ° C. More preferably, it is 80 degreeC or more, More preferably, it is 100 degreeC or more.
- fluorinated ether (I) examples include CF 3 CH 2 OCF 2 CFHCF 3 , CF 3 CF 2 CH 2 OCF 2 CFHCF 3 , HCF 2 CF 2 CH 2 OCF 2 CFHCF 3 , and HCF 2 CF 2 CH 2 OCH 2 CF 2 CF 2 H , CF 3 CFHCF 2 CH 2 OCF 2 CFHCF 3, HCF 2 CF 2 CH 2 OCF 2 CF 2 H, CF 3 CF 2 CH 2 OCF 2 CF 2 1 type of H, etc. or two The above is mentioned.
- HCF 2 CF 2 CH 2 OCF 2 CFHCF 3 (boiling point 106 ° C.), CF 3 CF 2 CH is advantageous because of its high boiling point, compatibility with other solvents, and good solubility of the electrolyte salt.
- 2 OCF 2 CFHCF 3 (boiling point 82 ° C.), HCF 2 CF 2 CH 2 OCF 2 CF 2 H (boiling point 88 ° C.) and CF 3 CF 2 CH 2 OCF 2 CF 2 H (boiling point 68 ° C.).
- HCF 2 CF 2 CH 2 OCF 2 CFHCF 3 (boiling point 106 ° C.)
- HCF 2 CF 2 CH 2 OCF 2 CF 2 H (boiling point 88 ° C.)
- One type is more preferable.
- Examples of the cyclic ether having 3 to 6 carbon atoms include 1,3-dioxane, 2-methyl-1,3-dioxane, 4-methyl-1,3-dioxane, 1,4-dioxane, and fluorinated compounds thereof. Is mentioned. Among them, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether have high solvating ability to lithium ions and improve the degree of ion dissociation. Dimethoxymethane, diethoxymethane, and ethoxymethoxymethane are particularly preferable because they have low viscosity and give high ionic conductivity.
- the compounding amount of the ether compound is usually 5% by volume or more, preferably 10% by volume or more, more preferably 15% by volume or more, and preferably 70% by volume or less, in 100% by volume of the non-aqueous solvent. Preferably it is 60 volume% or less, More preferably, it is 50 volume% or less. If it is this range, it is easy to ensure the improvement effect of the lithium ion dissociation degree of chain ether, and the improvement of the ionic conductivity derived from a viscosity fall, and when a negative electrode active material is a carbonaceous material, a chain ether with lithium ion It is easy to avoid a situation where the capacity is reduced due to insertion.
- the electrolyte solution of the present invention may contain other components in addition to the above solvent depending on the purpose.
- other components include unsaturated cyclic carbonates, nitrogen-containing compounds, boron-containing compounds, organosilicon-containing compounds, and overcharge inhibitors.
- An unsaturated cyclic carbonate is a cyclic carbonate having at least one carbon-carbon unsaturated bond in the molecule.
- an unsaturated cyclic carbonate can be contained in order to form a film on the negative electrode surface of the non-aqueous electrolytic battery and to extend the life of the battery.
- unsaturated cyclic carbonates examples include vinylene carbonate (VC), methyl vinylene carbonate, ethyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, 4,5-diethyl vinylene carbonate, and the like; 4-vinylethylene carbonate (VEC) 4-methyl-4-vinylethylene carbonate, 4-ethyl-4-vinylethylene carbonate, 4-n-propyl-4-vinylene ethylene carbonate, 5-methyl-4-vinylethylene carbonate, 4,4-divinylethylene carbonate Vinyl ethylene carbonate compounds such as 4,5-divinylethylene carbonate, 4,4-dimethyl-5-methylene ethylene carbonate, 4,4-diethyl-5-methylene ethylene carbonate, etc.
- vinylene carbonate 4-vinylethylene carbonate, 4-methyl-4-vinylethylene carbonate or 4,5-divinylethylene carbonate is preferable, and vinylene carbonate or 4-vinylethylene carbonate is particularly preferable.
- 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 50 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 80 or more, and more preferably 150 or less.
- An unsaturated cyclic carbonate may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio. Moreover, the compounding quantity of unsaturated cyclic carbonate is not restrict
- the blending amount of the unsaturated cyclic carbonate is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and further preferably 0.2% by mass or more, in 100% by mass of the non-aqueous electrolyte solution. Preferably, it is 5 mass% or less, More preferably, it is 4 mass% or less, More preferably, it is 3 mass% or less.
- the non-aqueous electrolyte battery is likely to exhibit a sufficient cycle characteristics improvement effect, and the high-temperature storage characteristics are deteriorated, the amount of gas generation is increased, and the discharge capacity maintenance ratio may not be sufficiently exhibited. If the amount is too large, the resistance may increase and the output and load characteristics may decrease.
- a fluorinated unsaturated cyclic carbonate can also be used suitably.
- the number of fluorine atoms contained in the fluorinated unsaturated cyclic carbonate is not particularly limited as long as it is 1 or more. Among them, the number of fluorine atoms is usually 6 or less, preferably 4 or less, and most preferably 1 or 2 fluorine atoms.
- fluorinated unsaturated cyclic carbonate examples include a fluorinated vinylene carbonate derivative, a fluorinated ethylene carbonate derivative substituted with an aromatic ring or a substituent having a carbon-carbon double bond.
- Fluorinated vinylene carbonate derivatives include 4-fluoro vinylene carbonate, 4-fluor-5-methyl vinylene carbonate, 4-fluoro-5-phenyl vinylene carbonate, 4-allyl-5-fluoro vinylene carbonate, 4-fluoro-5- And vinyl vinylene carbonate.
- fluorinated ethylene carbonate derivative substituted with a substituent having an aromatic ring or a carbon-carbon double bond examples include 4-fluoro-4-vinylethylene carbonate, 4-fluoro-4-allylethylene carbonate, 4-fluoro-5 -Vinylethylene carbonate, 4-fluoro-5-allylethylene carbonate, 4,4-difluoro-4-vinylethylene carbonate, 4,4-difluoro-4-allylethylene carbonate, 4,5-difluoro-4-vinylethylene carbonate 4,5-difluoro-4-allylethylene carbonate, 4-fluoro-4,5-divinylethylene carbonate, 4-fluoro-4,5-diallylethylene carbonate, 4,5-difluoro-4,5-divinylethylene carbonate , 4,5-diflu B-4,5-diallylethylene carbonate, 4-fluoro-4-phenylethylene carbonate, 4-fluoro-5-phenylethylene carbonate, 4,4-difluoro-5-phenyl
- the molecular weight of the fluorinated 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 50 or more and 500 or less. If it is this range, it will be easy to ensure the solubility of the fluorinated cyclic carbonate with respect to a non-aqueous electrolyte solution, and the effect of this invention will be easy to be expressed.
- a fluorinated unsaturated cyclic carbonate may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio. Moreover, the compounding quantity of a fluorinated unsaturated cyclic carbonate is not restrict
- the blending amount of the fluorinated unsaturated cyclic carbonate is usually in 100% by mass of the electrolyte solution, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and further preferably 0.2% by mass or more. Moreover, it is preferably 10% by mass or less, more preferably 8% by mass or less, and further preferably 6% by mass or less. Within this range, the non-aqueous electrolyte battery can easily exhibit a sufficient cycle characteristics improvement effect, avoid high-temperature storage characteristics, increase the amount of gas generated, and reduce the discharge capacity maintenance rate. It's easy to do.
- nitrogen-containing compounds include 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxaziridinone, 1,3-dimethyl-2-imidazolidinone, and N-methylsuccinimide.
- nitrogen-containing compounds include 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxaziridinone, 1,3-dimethyl-2-imidazolidinone, and N-methylsuccinimide.
- nitrogen-containing compounds include 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxaziridinone, 1,3-dimethyl-2-imidazolidinone, and N-methylsuccinimide.
- examples include nitrile, fluorine-containing nitrile, carboxylic acid amide, fluorine-containing carboxylic acid amide, sulfonic acid amide, and fluorine-containing sulfonic acid amide.
- boron-containing compound examples include boric acid esters such as trimethyl borate and triethyl borate, boric ether, and alkyl borate.
- organosilicon-containing compound examples include (CH 3 ) 4 —Si, (CH 3 ) 3 —Si—Si (CH 3 ) 3, and the like.
- the overcharge preventing agent is preferably an overcharge preventing agent having an aromatic ring in that the battery can be prevented from being ruptured or ignited during overcharging or the like.
- Specific examples of the overcharge preventing agent having an aromatic ring include, for example, cyclohexylbenzene, dichloroaniline, toluene, biphenyl, alkylbiphenyl, terphenyl, terphenyl partial hydride, t-butylbenzene, t-amyl.
- Aromatic compounds such as benzene, diphenyl ether, benzofuran and dibenzofuran; fluorides of aromatic compounds such as hexafluorobenzene, fluorobenzene, 2-fluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene; 2,4-difluoro Examples thereof include fluorine-containing anisole compounds such as anisole, 2,5-difluoroanisole, 2,6-difluoroanisole, and 3,5-difluoroanisole.
- aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, terphenyl partially hydrogenated, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran are preferable. These may be used alone or in combination of two or more.
- a combination of cyclohexylbenzene and t-butylbenzene or t-amylbenzene biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene,
- aromatic compounds not containing oxygen such as t-amylbenzene
- oxygen-containing aromatic compounds such as diphenyl ether, dibenzofuran, etc.
- the amount of the overcharge inhibitor is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired.
- the overcharge preventing agent is preferably 0.1% by mass or more and 5% by mass or less in 100% by mass of the electrolytic solution. If it is this range, it will be easy to fully express the effect of an overcharge inhibiting agent, and it will be easy to avoid the situation where the characteristics of batteries, such as a high temperature storage characteristic, fall.
- the overcharge inhibitor is more preferably 0.2% by mass or more, further preferably 0.3% by mass or more, particularly preferably 0.5% by mass or more, and more preferably 3% by mass or less, still more preferably. Is 2% by mass or less.
- the non-aqueous solvent also contains other known auxiliary agents such as non-flammable (flame retardant) agents, surfactants, high dielectric additives, cycle characteristics and rate characteristic improvers. May be.
- auxiliary agents such as non-flammable (flame retardant) agents, surfactants, high dielectric additives, cycle characteristics and rate characteristic improvers. May be.
- non-flammable (flame retardant) agents include phosphate esters and phosphazene compounds such as (CH 3 O) 3 P ⁇ O and (CF 3 CH 2 O) 3 P ⁇ O.
- any of a cationic surfactant, an anionic surfactant, a nonionic surfactant, and an amphoteric surfactant may be used, but the fluorine-containing surfactant has good cycle characteristics and rate characteristics. It is preferable from the point. By including the surfactant, capacity characteristics and rate characteristics can be improved.
- high dielectric additive examples include sulfolane, methyl sulfolane, ⁇ -butyrolactone, ⁇ -valerolactone, acetonitrile, propionitrile and the like.
- cycle characteristic and rate characteristic improving agent examples include methyl acetate, ethyl acetate, tetrahydrofuran, 1,4-dioxane and the like.
- auxiliary agents include carbonate compounds such as erythritan carbonate, spiro-bis-dimethylene carbonate, methoxyethyl-methyl carbonate; succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, Carboxylic anhydrides such as glutaconic anhydride, itaconic anhydride, diglycolic anhydride, cyclohexanedicarboxylic anhydride, cyclopentanetetracarboxylic dianhydride and phenylsuccinic anhydride; 2,4,8,10-tetraoxa Spiro compounds such as spiro [5,5] undecane, 3,9-divinyl-2,4,8,10-tetraoxaspiro [5,5] undecane; ethylene sulfite, 1,3-propane sultone, 1-fluoro -1,3-propane sultone, 2-fluoro-1,3-propyl-
- the electrolytic solution of the present invention further contains an electrolyte salt.
- electrolyte salt examples include conventionally known metal salts, liquid salts (ionic liquids), inorganic polymer type salts, organic polymer type salts, and the like.
- electrolyte salts suitable known compounds can be appropriately used depending on the purpose of use of the electrolytic solution, and among them, lithium salts are preferable.
- lithium salt examples include inorganic lithium salts such as LiPF 6 and LiBF 4 ; LiCF 3 SO 3 , LiC (CF 3 SO 2 ) 3 , LiPF 4 (CF 3 ) 2 , LiPF 4 (C 2 F 5 ) 2 , LiPF 4 (CF 3 SO 2 ) 2 , LiPF 4 (C 2 F 5 SO 2 ) 2 , LiBF 2 (CF 3 ) 2 , LiBF 2 (C 2 F 5 ) 2 , LiBF 2 (CF 3 SO 2) ) 2 , LiBF 2 (C 2 F 5 SO 2 ) 2 , lithium difluoro (oxalate) borate, lithium bis (oxalate) borate, LiPO 2 F, LiFSI and the formula: LiPF a (C n F 2n + 1 ) 6-a ( In the formula, a is an integer of 0 to 5, and n is an integer of 1 to 6).
- LiPF 6 LiPF 6 because it has an effect of improving output characteristics, high-rate charge / discharge characteristics, high-temperature storage characteristics, cycle characteristics, and the like.
- LiPF a (C n F 2n + 1 ) 6-a examples include LiPF 3 (CF 3 ) 3 , LiPF 3 (C 2 F 5) 3 , LiPF 3 (C 3 F 7 ) 3 LiPF 3 (C 4 F 9 ) 3 , LiPF 4 (CF 3 ) 2 , LiPF 4 (C 2 F 5 ) 2 , LiPF 4 (C 3 F 7 ) 2 , LiPF 4 (C 4 F 9 ) 2
- the alkyl group represented by C 3 F 7 or C 4 F 9 in the formula may be either a straight chain or a branched structure.
- the concentration of the electrolyte salt varies depending on the required current density, application, type of electrolyte salt, and the like, but is preferably 0.2 mol / liter or more in the electrolytic solution. More preferably, it is 0.5 mol / liter or more, and still more preferably 0.7 mol / liter or more. If the concentration of the electrolyte salt is too low, the electric conductivity of the electrolytic solution may be insufficient.
- the concentration of the electrolyte salt is also preferably 3.0 mol / liter or less, more preferably 2.0 mol / liter or less in the electrolytic solution. If the concentration is too high, the electrical conductivity may decrease due to an increase in viscosity, and the battery performance may decrease. If it is said range, effects, such as a low temperature characteristic, cycling characteristics, and a high temperature characteristic, will improve.
- electrolytic solution of the present invention may be further combined with a polymer material to form a gel (plasticized) gel electrolytic solution.
- Examples of such a polymer material include conventionally known polyethylene oxide and polypropylene oxide, modified products thereof (JP-A-8-222270 and JP-A-2002-1000040); polyacrylate polymers, polyacrylonitrile, and polyvinylidene fluoride.
- Fluorine resins such as vinylidene fluoride-hexafluoropropylene copolymer (JP-A-4-506726, JP-A-8-507407, JP-A-10-294131); Examples include composites with resins (Japanese Patent Laid-Open Nos. 11-35765 and 11-86630).
- the electrolytic solution of the present invention may also contain an ion conductive compound described in Japanese Patent Application No. 2004-301934.
- This ion conductive compound has the formula (1-1): A- (D) -B (1-1) [Wherein D represents the formula (2-1): -(D1) n- (FAE) m- (AE) p- (Y) q- (2-1) (In the formula, D1 represents the formula (2a):
- Rf is a fluorine-containing ether group which may have a crosslinkable functional group; the R 10 group or a bond that binds the Rf main chain
- ether having a fluorine-containing ether group in the side chain represented by unit FAE is represented by formula (2b):
- Rfa is hydrogen atom, a crosslinkable functional group which may have a fluorinated alkyl group; R 11 is a group or a bond that binds the Rfa main chain) fluorinated alkyl group in the side chain represented by Ether units having: AE is the formula (2c):
- R 13 has a hydrogen atom, an alkyl group which may have a crosslinkable functional group, an aliphatic cyclic hydrocarbon group which may have a crosslinkable functional group, or a crosslinkable functional group.
- An aromatic hydrocarbon group which may be present R 12 is an ether unit represented by R 13 and a group or a bond which bonds the main chain;
- Y represents the formulas (2d-1) to (2d-3):
- a and B are the same or different and are a hydrogen atom, a fluorine atom and / or an alkyl group which may contain a crosslinkable functional group, a fluorine atom and / or a phenyl group which may contain a crosslinkable functional group, —COOH A group, —OR (wherein R is a hydrogen atom or a fluorine atom and / or an alkyl group which may contain a crosslinkable functional group), an ester group or a carbonate group (provided that when D is terminated with an oxygen atom, a —COOH group;
- electrochemical devices such as non-aqueous electrolyte batteries
- present invention also includes an electrochemical device that is suitable as an electrolyte solution and includes the electrolyte solution of the present invention.
- Electrochemical devices include lithium ion secondary batteries, capacitors (electrolytic double layer capacitors), radical batteries, solar cells (especially dye-sensitized solar cells), fuel cells, various electrochemical sensors, electrochromic devices, and electrochemical switching. Examples include an element, an aluminum electrolytic capacitor, and a tantalum electrolytic capacitor. Among these, a lithium ion secondary battery is preferable.
- the electrolyte solution of the present invention is suitable for use as an electrolyte solution for lithium batteries among non-aqueous electrolyte batteries.
- a lithium battery provided with a positive electrode, a negative electrode, a separator and an electrolytic solution of the present invention capable of inserting or extracting lithium ions.
- a lithium battery including a negative electrode and a positive electrode capable of inserting or extracting lithium ions, a separator, and the above-described electrolyte is also one aspect of the present invention.
- 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 lithium ions. Specific examples include carbonaceous materials, metal materials, lithium-containing metal composite oxide materials, and the like. These may be used individually by 1 type, and may be used together combining 2 or more types arbitrarily.
- the negative electrode active is improved in terms of improving battery characteristics such as high-temperature storage characteristics, discharge capacity retention rate, load characteristics, energy density, and the like.
- the substance is preferably at least one selected from the group consisting of a carbonaceous material and a metal material, and more preferably a metal material.
- the lithium battery of the present invention includes an electrolytic solution containing a specific compound and a negative electrode containing a specific negative electrode active material, and thus has excellent high-temperature storage characteristics, discharge capacity retention ratio, load characteristics, and the like. , Have good battery characteristics.
- Examples of the carbonaceous material used as the negative electrode active material include natural graphite, artificial graphite, artificial carbonaceous material, and a carbonaceous material obtained by heat treating an artificial graphite material at least once in the range of 400 to 3200 ° C., and a negative electrode active material layer.
- a carbonaceous material comprising at least two kinds of carbonaceous materials having different crystallinity and / or having an interface in contact with the different crystalline carbonaceous materials, and at least two kinds of different orientations of the negative electrode active material layer
- a carbonaceous material having an interface with which the carbonaceous material is in contact is preferable because of a good balance between initial irreversible capacity and high current density charge / discharge characteristics.
- these carbon materials may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
- Examples of the carbonaceous material obtained by heat treating the artificial carbonaceous material and the artificial graphite material at least once in the range of 400 to 3200 ° C. include natural graphite, coal-based coke, petroleum-based coke, coal-based pitch, petroleum-based pitch, and these Oxidized pitch, needle coke, pitch coke and carbon agents partially graphitized from these, pyrolytic products of organic materials such as furnace black, acetylene black, pitch-based carbon fiber, carbonizable organic materials and their carbides, Alternatively, a solution obtained by dissolving an organic substance that can be carbonized in a low molecular organic solvent such as benzene, toluene, xylene, quinoline, n-hexane, and a carbide thereof.
- a low molecular organic solvent such as benzene, toluene, xylene, quinoline, n-hexane, and a carbide thereof.
- the metal material used as the negative electrode active material excluding lithium-titanium composite oxide
- simple lithium, simple metal and alloy forming lithium alloy or oxidation thereof
- Any of compounds such as oxides, carbides, nitrides, silicides, sulfides or phosphides may be used, and there is no particular limitation.
- the single metal and alloy forming the lithium alloy are preferably materials containing group 13 and group 14 metal / metalloid elements, more preferably aluminum, silicon and tin (hereinafter abbreviated as “specific metal elements”). ) Simple metals and alloys or compounds 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.
- a negative electrode active material having at least one kind of atom selected from a specific metal element, a metal simple substance of any one specific metal element, an alloy composed of two or more specific metal elements, one type or two or more specific types Alloys comprising metal elements and one or more other metal elements, as well as compounds containing one or more specific metal elements, and oxides, carbides, nitrides and silicides of the compounds And composite compounds such as sulfides or phosphides.
- these simple metals, alloys or metal compounds as the negative electrode active material, the capacity of the battery can be increased.
- a compound in which these complex compounds are complexly bonded to several kinds of elements such as a simple metal, an alloy, or a nonmetallic element is also included.
- a simple metal, an alloy, or a nonmetallic element such as silicon and tin
- an alloy of these elements and a metal that does not operate as a negative electrode can be used.
- a complex compound containing 5 to 6 kinds of elements in combination with a metal that acts as a negative electrode other than tin and silicon, a metal that does not operate as a negative electrode, and a nonmetallic element may be used. it can.
- the second constituent element is, for example, at least one of cobalt, iron, magnesium, titanium, vanadium, chromium, manganese, nickel, copper, zinc, gallium, and zirconium.
- the third constituent element is at least one of boron, carbon, aluminum, and phosphorus.
- the metal material silicon or tin alone (which may contain a small amount of impurities), SiOv (0 ⁇ v ⁇ 2), SnOw (0 ⁇ w) ⁇ 2), Si—Co—C composite material, Si—Ni—C composite material, Sn—Co—C composite material, and Sn—Ni—C composite material are preferable.
- the lithium-containing metal composite oxide material used as the negative electrode active material is not particularly limited as long as it can occlude and release lithium, but a material containing titanium and lithium is preferable from the viewpoint of high current density charge / discharge characteristics, A lithium-containing composite metal oxide material containing titanium is more preferable, and a composite oxide of lithium and titanium (hereinafter abbreviated as “lithium titanium composite oxide”) is more preferable. That is, it is particularly preferable to use a lithium titanium composite oxide having a spinel structure in a negative electrode active material for a non-aqueous electrolyte battery because the output resistance is greatly reduced.
- lithium titanium complex oxide As said lithium titanium complex oxide, general formula (J): Li x Ti y M z O 4 (J) [In General Formula (J), M represents at least one element selected from the group consisting of Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, and Nb. ] It is preferable that it is a compound represented by these.
- This structure is particularly preferable because of a good balance of battery performance.
- compositions of the above compounds are Li 4/3 Ti 5/3 O 4 in (i), Li 1 Ti 2 O 4 in (ii), and Li 4/5 Ti 11/5 O in (iii). 4 .
- structure of Z ⁇ 0, for example, Li 4/3 Ti 4/3 Al 1/3 O 4 is preferable.
- any known method can be used for producing the electrode as long as the effects of the present invention are not significantly impaired.
- it may be formed by adding a binder, a solvent, and, if necessary, a thickener, a conductive agent, a filler, etc. to the negative electrode active material to form a slurry, which is applied to a current collector, dried and then pressed. it can.
- a method of forming the above-described thin film layer (negative electrode active material layer) containing the negative electrode active material by a technique such as vapor deposition, sputtering, or plating is also used.
- the shape of the current collector may be, for example, 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, or the like when the current collector is a metal material.
- a metal thin film more preferably a copper foil, more preferably a rolled copper foil by a rolling method and an electrolytic copper foil by an electrolytic method, both of which can be used as a current collector.
- the thickness of the 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 battery may be reduced too much, and conversely if it is too thin, handling may be difficult.
- the binder for binding the negative electrode active material As the binder for binding the negative electrode active material, the binder for binding the negative electrode active material to the solvent used at the time of manufacturing the non-aqueous electrolyte and the electrode is stable against the solvent used at the time of manufacturing the non-aqueous electrolyte and the electrode. If it is material, it will not restrict
- resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, polyimide, cellulose, and nitrocellulose; SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluorine rubber, Rubber polymers such as NBR (acrylonitrile / butadiene rubber) and ethylene / propylene rubber; styrene / butadiene / styrene block copolymer or hydrogenated product thereof; EPDM (ethylene / propylene / diene terpolymer), styrene / Thermoplastic elastomeric polymers such as ethylene / butadiene / styrene copolymers, styrene / isoprene / styrene block copolymers or hydrogenated products thereof; syndiotactic-1,2-polybutadiene,
- the ratio of the binder for binding the negative electrode active material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, particularly preferably 0.6% by mass or more, and preferably 20% by mass or less, 15 mass% or less is more preferable, 10 mass% or less is more preferable, and 8 mass% or less is especially preferable.
- the ratio of the binder with respect to a negative electrode active material exceeds the said range, the binder ratio from which the amount of binders does not contribute to battery capacity may increase, and the fall of battery capacity may be caused.
- the strength of the negative electrode may be reduced.
- the ratio of the binder to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, and 0 .6% by mass or more is more preferable, and is usually 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less.
- the main component contains a fluorine-based polymer typified by polyvinylidene fluoride
- the ratio to the negative electrode active material is usually 1% by mass or more, preferably 2% by mass or more, and more preferably 3% by mass or more. It is preferably 15% by mass or less, preferably 10% by mass or less, and more preferably 8% by mass or less.
- the solvent for forming the slurry is not particularly limited as long as it is a solvent capable of dissolving or dispersing the negative electrode active material, the binder, and the thickener and conductive material used as necessary.
- a solvent capable of dissolving or dispersing the negative electrode active material, the binder, and the thickener and conductive material used as necessary Alternatively, either an aqueous solvent or an organic solvent may be used. Examples of the aqueous solvent include water and alcohol.
- organic solvent examples include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N, N- Examples include dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, and the like.
- NMP N-methylpyrrolidone
- dimethylformamide dimethylacetamide
- methyl ethyl ketone cyclohexanone
- methyl acetate methyl acrylate
- diethyltriamine N
- N- Examples include dimethylaminopropylamine, tetrahydr
- aqueous solvent when used, it is preferable to add a dispersant or the like in addition to the thickener and slurry it using a latex such as SBR.
- these solvents may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio.
- a thickener is usually used to adjust the viscosity of the slurry.
- the thickener is not particularly limited, and specific examples include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.
- the ratio of the thickener to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, Moreover, it is 5 mass% or less normally, 3 mass% or less is preferable, and 2 mass% or less is more preferable.
- the ratio of the thickener to the negative electrode active material is less than the above range, applicability may be significantly reduced.
- it exceeds the said range the ratio of the negative electrode active material which occupies for a negative electrode active material layer will fall, and the problem that the capacity
- 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 existing on the current collector exceeds the above range, the negative electrode active material particles are destroyed, and the initial irreversible capacity increases or non-aqueous system near the current collector / negative electrode active material interface. There is a case where high current density charge / discharge characteristics are deteriorated due to a decrease in permeability of the electrolytic solution.
- 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.
- the thickness of the negative electrode plate is designed according to the positive electrode plate to be used, and is not particularly limited.
- the thickness of the composite layer obtained by subtracting the thickness of the metal foil of the core is usually 15 ⁇ m or more, preferably 20 ⁇ m or more. More preferably, it is 30 ⁇ m or more, and usually 300 ⁇ m or less, preferably 280 ⁇ m or less, more preferably 250 ⁇ m or less.
- Surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate And sulfates such as aluminum sulfate and carbonates such as lithium carbonate, calcium carbonate and magnesium carbonate.
- the positive electrode active material used for the positive electrode is described below.
- the positive electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions.
- a material containing lithium and at least one transition metal is preferable.
- Specific examples include lithium transition metal composite oxides and lithium-containing transition metal phosphate compounds.
- the positive electrode active material is preferably a lithium transition metal composite oxide.
- V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc. are preferable as the transition metal of the lithium transition metal composite oxide.
- Specific examples include lithium-cobalt composite oxides such as LiCoO 2 and LiNiO 2 .
- Lithium / nickel composite oxide, LiMnO 2 , LiMn 2 O 4 , Li 2 MnO 4 and other lithium / manganese composite oxides, part of transition metal atoms that are the main components of these lithium transition metal composite oxides are Na , B, F, Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, W, etc. And the like.
- substituted ones for example, LiNi 0.5 Mn 0.5 O 2 , LiNi 0.85 Co 0.10 Al 0.05 O 2 , LiNi 0.33 Co 0.33 Mn 0.33 O 2 , LiNi 0.45 Co 0.10 Al 0.45 O 2 , LiMn 1.8 Al 0.2 O 4 , LiMn 1.5 Ni 0.5 O 4 and the like.
- transition metal of the lithium-containing transition metal phosphate compound V, Ti, Cr, Mn, Fe, Co, Ni, Cu and the like are preferable, and specific examples include, for example, LiFePO 4 , Li 3 Fe 2 (PO 4 ). 3 , iron phosphates such as LiFeP 2 O 7 , cobalt phosphates such as LiCoPO 4 , and some of the transition metal atoms that are the main components of these lithium transition metal phosphate compounds are Al, Ti, V, Cr, Mn , Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si and the like substituted with other elements.
- lithium phosphate in the positive electrode active material because continuous charge characteristics are improved.
- the lower limit of the amount of lithium phosphate to be used is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and further preferably 0.5% by mass with respect to the total of the positive electrode active material and lithium phosphate. %, And the upper limit is preferably 10% by mass or less, more preferably 8% by mass or less, and further preferably 5% by mass or less.
- Surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate And sulfates such as aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate, and carbon.
- these surface adhering substances are dissolved or suspended in a solvent, impregnated and added to the positive electrode active material, and dried.
- the surface adhering substance precursor is dissolved or suspended in a solvent and impregnated and added to the positive electrode active material, It can be made to adhere to the surface of the positive electrode active material by a method of reacting by heating or the like, a method of adding to the positive electrode active material precursor and firing simultaneously.
- the method of making carbonaceous adhere mechanically later in the form of activated carbon etc. can also be used, for example.
- the amount of the surface adhering substance is, in terms of mass with respect to the positive electrode active material, preferably 0.1 ppm or more, more preferably 1 ppm or more, further preferably 10 ppm or more, and the upper limit, preferably 20% or less, more preferably as the lower limit. Is used at 10% or less, more preferably 5% or less.
- the surface adhering substance can suppress the oxidation reaction of the electrolyte solution on the surface of the positive electrode active material and can improve the battery life. However, when the amount of the adhering quantity is too small, the effect is not sufficiently manifested. If it is too high, the resistance may increase in order to inhibit the entry and exit of lithium ions.
- a material in which a material having a different composition is attached to the surface of the positive electrode active material is referred to as a “positive electrode active material”.
- shape of the positive electrode active material particles examples include a lump shape, a polyhedron shape, a sphere shape, an oval sphere shape, a plate shape, a needle shape, and a column shape as conventionally used.
- primary particles may aggregate to form secondary particles.
- the tap density of the positive electrode active material is preferably 0.5 g / cm 3 or more, more preferably 0.8 g / cm 3 or more, and further preferably 1.0 g / cm 3 or more. If the tap density of the positive electrode active material is lower than the lower limit, the amount of the required dispersion medium increases when the positive electrode active material layer is formed, and the necessary amount of conductive material and binder increases, so that the positive electrode to the positive electrode active material layer The filling rate of the active material is restricted, and the battery capacity may be restricted. By using a complex oxide powder having a high tap density, a high-density positive electrode active material layer can be formed.
- the tap density is preferably as large as possible, and there is no particular upper limit, but if it is too large, diffusion of lithium ions using the electrolytic solution in the positive electrode active material layer as a medium is rate-limiting, and load characteristics may be easily reduced.
- the upper limit is preferably 4.0 g / cm 3 or less, more preferably 3.7 g / cm 3 or less, and still more preferably 3.5 g / cm 3 or less.
- the tap density is defined as the powder packing density (tap density) g / cc when 5 to 10 g of the positive electrode active material powder is put in a 10 ml glass graduated cylinder and tapped 200 times with a stroke of about 20 mm. Ask.
- the median diameter d50 of the positive electrode active material particles is preferably 0.3 ⁇ m or more, more preferably 0.5 ⁇ m or more, and even more preferably. Is 0.8 ⁇ m or more, most preferably 1.0 ⁇ m or more, and the upper limit is preferably 30 ⁇ m or less, more preferably 27 ⁇ m or less, still more preferably 25 ⁇ m or less, and most preferably 22 ⁇ m or less. If the lower limit is not reached, a high tap density product may not be obtained.
- the positive electrode of the battery that is, the active material
- a conductive material, a binder, or the like is slurried with a solvent and applied as a thin film, problems such as streaking may occur.
- the positive electrode active materials having different median diameters d50, it is possible to further improve the filling property at the time of forming the positive electrode.
- the median diameter d50 is measured by a known laser diffraction / scattering particle size distribution measuring device.
- LA-920 manufactured by HORIBA is used as a particle size distribution meter
- a 0.1% by mass sodium hexametaphosphate aqueous solution is used as a dispersion medium for measurement, and a measurement refractive index of 1.24 is set after ultrasonic dispersion for 5 minutes. Measured.
- the average primary particle diameter of the positive electrode active material is preferably 0.05 ⁇ m or more, more preferably 0.1 ⁇ m or more, and still more preferably 0.8.
- the upper limit is preferably 5 ⁇ m or less, more preferably 4 ⁇ m or less, still more preferably 3 ⁇ m or less, and most preferably 2 ⁇ m or less. If the above upper limit is exceeded, it is difficult to form spherical secondary particles, which adversely affects the powder filling property, or the specific surface area is greatly reduced, so that there is a high possibility that battery performance such as output characteristics will deteriorate. is there. On the other hand, when the value falls below the lower limit, there is a case where problems such as inferior reversibility of charge / discharge are usually caused because crystals are not developed.
- the primary particle diameter is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph at a magnification of 10000 times, the longest value of the intercept by the left and right boundary lines of the primary particles with respect to the horizontal straight line is obtained for any 50 primary particles and obtained by taking the average value. It is done.
- SEM scanning electron microscope
- BET specific surface area of the positive electrode active material is preferably 0.1 m 2 / g or more, more preferably 0.2 m 2 / g or more, still more preferably 0.3 m 2 / g or more, and the upper limit is preferably 50 m 2 / g or less, more preferably 40 m 2 / g or less, and further preferably 30 m 2 / g or less. If the BET specific surface area is smaller than this range, the battery performance tends to be lowered. If the BET specific surface area is larger, the tap density is difficult to increase, and a problem may occur in applicability when forming the positive electrode active material layer.
- the BET specific surface area is determined by using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken), preliminarily drying the sample at 150 ° C. for 30 minutes under nitrogen flow, and then atmospheric pressure.
- a surface area meter for example, a fully automatic surface area measuring device manufactured by Okura Riken
- This is defined as a value measured by a nitrogen adsorption BET one-point method using a gas flow method, using a nitrogen-helium mixed gas accurately adjusted so that the value of the relative pressure of nitrogen to 0.3 is 0.3.
- Method for producing positive electrode active material As a manufacturing method of the positive electrode active material, a general method is used as a manufacturing method of the inorganic compound. In particular, various methods are conceivable for preparing a spherical or elliptical active material. For example, a transition metal source material is dissolved or pulverized and dispersed in a solvent such as water, and the pH is adjusted while stirring. And a spherical precursor is prepared and recovered, and dried as necessary. Then, a Li source such as LiOH, Li 2 CO 3 , LiNO 3 is added, and the active material is obtained by baking at a high temperature. .
- the positive electrode active material may be used alone, or one or more of different compositions may be used in any combination or ratio.
- a preferable combination in this case is a combination of LiCoO 2 and LiMn 2 O 4 such as LiNi 0.33 Co 0.33 Mn 0.33 O 2 or a part of this Mn substituted with another transition metal or the like. Or a combination with LiCoO 2 or a part of this Co substituted with another transition metal or the like.
- the positive electrode can be produced by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current collector. Manufacture of the positive electrode using a positive electrode active material can be performed by a conventional method.
- a positive electrode can be obtained by forming a positive electrode active material layer on the current collector by applying it to a positive electrode current collector and drying it as a slurry by dissolving or dispersing in a slurry.
- the content of the positive electrode active material in the positive electrode active material layer is preferably 80% by mass or more, more preferably 82% by mass or more, and particularly preferably 84% by mass or more. Moreover, an upper limit becomes like this. Preferably it is 99 mass% or less, More preferably, it is 98 mass% or less. If the content of the positive electrode active material in the positive electrode active material layer is low, the electric capacity may be insufficient. Conversely, if the content is too high, the strength of the positive electrode may be insufficient.
- the positive electrode active material layer obtained by coating and drying is preferably consolidated by a hand press, a roller press or the like in order to increase the packing density of the positive electrode active material.
- the density of the positive electrode active material layer is preferably 1.5 g / cm 3 or more as a lower limit, more preferably 2 g / cm 3 or more, still more preferably 2.2 g / cm 3 or more, and the upper limit is preferably 5 g / cm 3. It is cm 3 or less, more preferably 4.5 g / cm 3 or less, and still more preferably 4 g / cm 3 or less.
- a known conductive material can be arbitrarily used as the conductive material. Specific examples include metal materials such as copper and nickel; graphite such as natural graphite and artificial graphite (graphite); carbon black such as acetylene black; and carbon materials such as amorphous carbon such as needle coke. In addition, these may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.
- the conductive material is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 1% by mass or more in the positive electrode active material layer, and the upper limit is usually 50% by mass or less, preferably It is used so as to contain 30% by mass or less, more preferably 15% by mass or less. If the content is lower than this range, the conductivity may be insufficient. Conversely, if the content is higher than this range, the battery capacity may decrease.
- the binder used in the production of the positive electrode active material layer is not particularly limited, and in the case of the coating method, any material that can be dissolved or dispersed in the liquid medium used during electrode production may be used.
- Resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, nitrocellulose; SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluorine rubber, isoprene rubber , Rubber polymers such as butadiene rubber and ethylene-propylene rubber; styrene / butadiene / styrene block copolymer or hydrogenated product thereof, EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene / butadiene / Ethylene copolymer, styrene Thermoplastic elastomeric
- the ratio of the binder in the positive electrode active material layer is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 1.5% by mass or more, and the upper limit is usually 80% by mass or less, preferably Is 60% by mass or less, more preferably 40% by mass or less, and most preferably 10% by mass or less.
- the ratio 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. On the other hand, if it is too high, battery capacity and conductivity may be reduced.
- the solvent for forming the slurry As the solvent for forming the slurry, the positive electrode active material, the conductive material, the binder, and a solvent capable of dissolving or dispersing the thickener used as necessary may be used. There is no restriction, and either an aqueous solvent or an organic solvent may be used. Examples of the aqueous medium include water, a mixed medium of alcohol and water, and the like.
- organic medium examples include aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone.
- Esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N, N-dimethylaminopropylamine; ethers such as diethyl ether, propylene oxide and tetrahydrofuran (THF); N-methylpyrrolidone (NMP) Amides such as dimethylformamide and dimethylacetamide; and aprotic polar solvents such as hexamethylphosphalamide and dimethylsulfoxide.
- amines such as diethylenetriamine and N, N-dimethylaminopropylamine
- ethers such as diethyl ether, propylene oxide and tetrahydrofuran (THF)
- NMP N-methylpyrrolidone
- Amides such as dimethylformamide and dimethylacetamide
- aprotic polar solvents such as hexamethylphosphalamide and dimethylsulfoxide.
- an aqueous medium when used, it is preferably slurried using a thickener and a latex such as styrene-butadiene rubber (SBR).
- a thickener is usually used to adjust the viscosity of the slurry.
- the thickener is not particularly limited, and specific examples include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.
- the ratio of the thickener to the active material is 0.1% by mass or more, preferably 0.2% by mass or more, more preferably 0.3% by mass or more.
- the upper limit is 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. Below this range, applicability may be significantly reduced. If it exceeds, the ratio of the active material in the positive electrode active material layer may decrease, and there may be a problem that the capacity of the battery decreases and a problem that the resistance between the positive electrode active materials increases.
- the material of the positive electrode current collector is not particularly limited, and a known material can be arbitrarily used. Specific examples include metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; and carbon materials such as carbon cloth and carbon paper. Of these, metal materials, particularly aluminum, are preferred.
- the shape of the current collector examples include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, and foam metal in the case of a metal material.
- a thin film, a carbon cylinder, etc. are mentioned. Of these, metal thin films are preferred.
- the thickness of the thin film is arbitrary, it is usually 1 ⁇ m or more, preferably 3 ⁇ m or more, more preferably 5 ⁇ m or more, and the upper limit is usually 1 mm or less, preferably 100 ⁇ m or less, more preferably 50 ⁇ m or less. If the thin film is thinner than this range, the strength required for the current collector may be insufficient. Conversely, if the thin film is thicker than this range, the handleability may be impaired.
- a conductive additive is applied to the surface of the current collector.
- the conductive assistant include noble metals such as carbon, gold, platinum, and silver.
- the ratio of the thickness of the current collector to the positive electrode active material layer is not particularly limited, but the value of (thickness of the positive electrode active material layer on one side immediately before electrolyte injection) / (thickness of the current collector) is 20
- the lower limit is preferably 15 or less, most preferably 10 or less, and the lower limit is preferably 0.5 or more, more preferably 0.8 or more, and most preferably 1 or more. Above this range, the current collector may generate heat due to Joule heat during high current density charge / discharge. Below this range, the volume ratio of the current collector to the positive electrode active material increases and the battery capacity may decrease.
- the area of the positive electrode active material layer is larger than the outer surface area of the battery outer case from the viewpoint of increasing the stability at high output and high temperature.
- the sum of the electrode areas of the positive electrode with respect to the surface area of the exterior of the secondary battery is preferably 15 times or more, and more preferably 40 times or more.
- the outer surface area of the battery outer case in the case of a square shape with a bottom, is the total area calculated from the vertical, horizontal, and thickness dimensions of the case part filled with the power generation element excluding the protruding part of the terminal.
- the geometric surface area approximates the case portion filled with the power generation element excluding the protruding portion of the terminal as a cylinder.
- the total electrode area of the positive electrode is the geometric surface area of the positive electrode mixture layer facing the mixture layer containing the negative electrode active material, and in the structure in which the positive electrode mixture layer is formed on both sides via the current collector foil. , The sum of the areas where each surface is calculated separately.
- the thickness of the positive electrode plate is not particularly limited, but from the viewpoint of high capacity and high output, the thickness of the composite layer obtained by subtracting the metal foil thickness of the core material is preferably as a lower limit with respect to one side of the current collector. Is 10 ⁇ m or more, more preferably 20 ⁇ m or more, and the upper limit is preferably 500 ⁇ m or less, more preferably 450 ⁇ m or less.
- Electrode surface coating (Positive electrode surface coating) Moreover, you may use what adhered the substance of the composition different from this to the surface of the said positive electrode plate.
- Surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate And sulfates such as aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate, and carbon.
- the material and shape of the separator that can be used in the present invention 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 resin, glass fiber, inorganic material, etc., formed of a material that is stable with respect to the electrolytic solution of the present invention is used, and a porous sheet or a nonwoven fabric-like material having excellent liquid retention properties is used. preferable.
- polyolefins such as polyethylene and polypropylene, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, glass filters and the like can be used.
- These materials such as a polypropylene / polyethylene two-layer film and a polypropylene / polyethylene / polypropylene three-layer film, may be used alone or in combination of two or more in any combination and ratio.
- the thickness of the separator is arbitrary, but is usually 1 ⁇ m or more, preferably 5 ⁇ m or more, more preferably 8 ⁇ m or more, and usually 50 ⁇ m or less, preferably 40 ⁇ m or less, more preferably 30 ⁇ m or less. If the separator is too thin than the above range, the insulating properties and mechanical strength may decrease. On the other hand, if it is thicker 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 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 too smaller than the above range, the membrane 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 a separator is also arbitrary, it is 0.5 micrometer or less normally, 0.2 micrometer or less is preferable, and it is 0.05 micrometer or more normally. 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 non-woven 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 the inorganic particles on the surface layer of the positive electrode and / or the negative electrode using a resin binder can be used.
- a porous layer may be formed by using alumina particles having a 90% particle size of less than 1 ⁇ m on both surfaces of the positive electrode and using a fluororesin as a binder.
- 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. Also, if the above range is exceeded, the void space is small, the battery expands, and the member expands or the vapor pressure of the electrolyte liquid component increases and the internal pressure rises. In some cases, the gas release valve that lowers various characteristics such as storage at high temperature and the like, or releases the internal pressure to the outside is activated.
- the current collecting structure is not particularly limited, but in order to more effectively realize the high current density charge / discharge characteristics by the electrolytic solution of the present invention, it is necessary to make the structure that reduces the resistance of the wiring part and the joint part. preferable. Thus, when internal resistance is reduced, the effect using the electrolyte solution of this invention is exhibited especially favorable.
- the electrode group has the above laminated structure
- a structure formed by bundling the metal core portions of the electrode layers and welding them to the terminals is preferably used.
- the internal resistance increases. Therefore, it is also preferable to provide a plurality of terminals in the electrode to reduce the resistance.
- the electrode group has the winding structure described above, the internal resistance can be lowered by providing a plurality of lead structures for the positive electrode and the negative electrode, respectively, and bundling the terminals.
- the material of the outer case is not particularly limited as long as it is a material that is stable with respect to the electrolytic solution 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.
- the metal is welded together by laser welding, resistance welding, or ultrasonic welding to form a sealed sealed structure, or a caulking structure using the above metals via a resin gasket. Things.
- the outer case using the laminate film include a case where a resin-sealed structure is formed 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.
- the shape of the lithium battery (lithium ion secondary battery) of the present invention is arbitrary, and examples thereof include a cylindrical shape, a square shape, a laminate shape, a coin shape, and a large shape.
- the shape and structure of a positive electrode, a negative electrode, and a separator can be changed and used according to the shape of each battery.
- the potential of the positive electrode is preferably 4.3 V or more based on metallic lithium.
- a module comprising the lithium secondary battery (lithium ion secondary battery) of the present invention is also one aspect of the present invention.
- Positive electrode in which LiNi 1/3 Mn 1/3 Co 1/3 O 2 as a positive electrode active material, acetylene black as a conductive material, and polyvinylidene fluoride (PVdF) as a binder are mixed in 92/3/5 (mass% ratio).
- a positive electrode mixture slurry was prepared by dispersing the material in N-methyl-2-pyrrolidone to form a slurry.
- the obtained positive electrode mixture slurry was uniformly applied onto an aluminum foil current collector having a thickness of 21 ⁇ m, dried to form a positive electrode mixture layer, and then compression molded by a press to obtain a positive electrode.
- the negative electrode A manufactured in Production Example 1, the positive electrode, and a polyethylene separator were laminated in the order of the negative electrode, the separator, and the positive electrode to prepare a battery element.
- the battery element was inserted into a bag made of a laminate film in which both surfaces of aluminum (thickness: 40 ⁇ m) were coated with a resin layer while projecting positive and negative terminals, and then the electrolytes of Examples and Comparative Examples were respectively It inject
- the secondary battery A is expressed as constant current-constant voltage charge (hereinafter referred to as (CC / CV charge)) up to 4.35 V at a current corresponding to 0.2 C at 25 ° C. in a state of being sandwiched between plates and pressurized. ) (0.1 C cut), and then discharged to 3 V at a constant current of 0.2 C. This was taken as one cycle, and the initial discharge capacity was determined from the discharge capacity at the third cycle.
- 1C represents a current value for discharging the reference capacity of the battery in one hour, and, for example, 0.2C represents a current value of 1/5 thereof.
- the non-aqueous electrolyte battery obtained using the electrolytic solution of the present invention has a high capacity retention rate and excellent input / output performance even after endurance tests such as a high-temperature storage test and a cycle test, and input / output characteristics at low temperatures. It is also excellent and useful. Therefore, the electrolytic solution of the present invention and the non-aqueous electrolytic battery using the same can be used for various known applications. Specific examples include notebook computers, pen input computers, mobile computers, electronic book players, mobile phones, mobile faxes, mobile copy, mobile printers, headphone stereos, video movies, LCD TVs, handy cleaners, portable CDs, minidiscs, etc.
- Walkie Talkie Electronic Notebook, Calculator, Memory Card, Portable Tape Recorder, Radio, Backup Power Supply, Motor, Automobile, Motorcycle, Motorbike, Bicycle, Lighting Equipment, Toy, Game Equipment, Clock, Electric Tool, Strobe, Camera, Load Examples include leveling power sources and natural energy storage power sources.
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Abstract
Description
上記電解質塩はLiPF6であり、上記電解質塩の含有量が0.2モル/リットル以上であることが好ましい。
本発明はまた、上述の電解液を備えることを特徴とする電気化学デバイスでもある。
本発明はまた、リチウムイオンを吸蔵又は放出可能な負極及び正極、セパレータ、ならびに、上述の電解液を備えることを特徴とするリチウム電池である。
上記リチウムイオンを吸蔵又は放出可能な正極は、一般式(2):
Li1+WMnxNiyCoZO2 (2)
(式中、w、x、y及びzは、0≦w<0.4、0.3<x<1、0≦y<0.4、0≦z<0.4、0<y+z、及び、w+x+y+z=1を満たす。)
で表されるリチウム遷移金属酸化物からなる正極活物質を含むことが好ましい。
上記リチウムイオンを吸蔵又は放出可能な負極は、炭素質材料及び金属材料からなる群より選択される少なくとも1種の負極活物質を含むことが好ましい。
上記リチウム電池において、正極の電位が、金属リチウム基準で4.3V以上であることが好ましい。
本発明はまた、上述のリチウム二次電池を備えることを特徴とするモジュールでもある。
一般式(1)において、R1、R2及びR3は、同じか又は異なっていてもよく、それぞれ水素原子、フッ素原子、炭素数1~20のアルキル基、又は、炭素数1~20のフッ素化アルキル基である。
ただし、R1、R2及びR3のすべてが水素原子である場合及びはフッ素原子である場合を除くものである。
本明細書において、「フッ素化アルキル基」とは、アルキル基の水素原子の一部または全部がフッ素原子で置換されたアルキル基である。
一般式(1)で示される化合物の含有量が、非水系溶媒100体積%中10体積%以上であると、高温保存特性、放電容量維持率、負荷特性等の電池特性が優れた電解液とすることができる。
一般式(1)で示される化合物の含有量は、非水系溶媒100体積%中15体積%以上が好ましい。また、90体積%以下が好ましく、85体積%以下がより好ましい。この範囲であれば、非水系電解液電池が十分なサイクル特性向上効果を発現しやすく、抵抗の増加による負荷特性の低下や、高温保存特性の低下、ガス発生量の増加により、放電容量維持率が低下することを回避しやすい。
上記非水系溶媒としては、飽和環状カーボネート、鎖状カーボネート、環状及び鎖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を使用することができる。
飽和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ものが挙げられ、具体的には、エチレンカーボネート、プロピレンカーボネート、ブチレンカーボネート等が挙げられる。なかでも、エチレンカーボネートとプロピレンカーボネート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。
これら飽和環状カーボネートは、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。
上記フッ素化環状カーボネートとしては、下記一般式(A):
上記フッ素化環状カーボネート(A)を含むと、本発明の電解液をリチウム電池等に適用した場合に、負極に安定な被膜を形成することができ、負極での電解液の副反応を充分に抑制することができる。その結果、極めて安定で優れた充放電特性が得られる。
なお、本明細書中で「エーテル結合」は、-O-で表される結合である。
炭素数が大きくなりすぎると低温特性が低下したり、電解質塩の溶解性が低下したりするおそれがあり、炭素数が少な過ぎると、電解質塩の溶解性の低下、放電効率の低下、更には粘性の増大等がみられることがある。
R1-R2- (a-1)
(式中、R1はフッ素原子を有していてもよい炭素数1以上のアルキル基;R2はフッ素原子を有していてもよい炭素数1~3のアルキレン基;ただし、R1及びR2の少なくとも一方はフッ素原子を有している)で示されるフッ素化アルキル基が、電解質塩の溶解性が良好な点から好ましく例示できる。
なお、R1及びR2は、更に、炭素原子、水素原子及びフッ素原子以外の、その他の原子を有していてもよい。
-CH2-、-CHF-、-CF2-、-CHCl-、-CFCl-、-CCl2-
-CH2-、-CHF-、-CF2-、-CHCl-、-CFCl-、-CCl2-
R3-(OR4)n1- (b-1)
(式中、R3はフッ素原子を有していてもよい、好ましくは炭素数1~6のアルキル基;R4はフッ素原子を有していてもよい、好ましくは炭素数1~4のアルキレン基;n1は1~3の整数;ただし、R3及びR4の少なくとも1つはフッ素原子を有している)で示されるものが挙げられる。
鎖状カーボネートとしては、炭素数3~7のものが好ましい。
具体的には、炭素数3~7の鎖状カーボネートとしては、ジメチルカーボネート(DMC)、ジエチルカーボネート(DEC)、ジ-n-プロピルカーボネート、ジイソプロピルカーボネート、n-プロピルイソプロピルカーボネート、エチルメチルカーボネート(EMC)、メチル-n-プロピルカーボネート、n-ブチルメチルカーボネート、イソブチルメチルカーボネート、t-ブチルメチルカーボネート、エチル-n-プロピルカーボネート、n-ブチルエチルカーボネート、イソブチルエチルカーボネート、t-ブチルエチルカーボネート等が挙げられる。
フッ素化エチルメチルカーボネート誘導体としては、2-フルオロエチルメチルカーボネート、エチルフルオロメチルカーボネート、2,2-ジフルオロエチルメチルカーボネート、2-フルオロエチルフルオロメチルカーボネート、エチルジフルオロメチルカーボネート、2,2,2-トリフルオロエチルメチルカーボネート、2,2-ジフルオロエチルフルオロメチルカーボネート、2-フルオロエチルジフルオロメチルカーボネート、エチルトリフルオロメチルカーボネート等が挙げられる。
CF3CH2OCOOCH2CF3、CF3CF2CH2OCOOCH2CF2CF3、CF3CF2CH2OCOOCH3、CF3CH2OCOOCH3、CF3CF2CH2OCOOCH3、HCF2CF2CH2OCOOCH3、CF3OCOOCH3、HCF2CF2CH2OCOOC2H5、HCF2CF2CH2OCOOC2H5
鎖状カーボネートの配合量は、非水系溶媒100体積%中、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%以上である。この範囲であると、非水系電解液の粘度を適切な範囲とし、イオン伝導度の低下を抑制し、非水系電解液電池の大電流放電特性等を良好な範囲としやすくなる。また、鎖状カーボネートは、非水系溶媒100体積%中、90体積%以下、より好ましくは85体積%以下であることが好ましい。この範囲であると、非水系電解液の誘電率の低下に由来する電気伝導率の低下を回避し、非水系電解液電池の大電流放電特性等を良好な範囲としやすくなる。
環状カルボン酸エステルとしては、その構造式中の全炭素原子数が3~12のものが挙げられる。具体的には、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、イソ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。
フッ素化環状カルボン酸エステルを含有させることにより、イオン伝導度の向上、安全性の向上、高温時の安定性向上といった効果が得られる。
鎖状カルボン酸エステルとしては、その構造式中の全炭素数が3~7のものが挙げられる。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-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。
Rf10COORf11 (H)
(式中、Rf10は炭素数1~2のフッ素化アルキル基、Rf11は炭素数1~4のフッ素化アルキル基)で示されるフッ素化鎖状カルボン酸エステルが、難燃性が高く、かつ他溶媒との相溶性や耐酸化性が良好な点から好ましい。
エーテル化合物としては、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。
炭素数3~10の鎖状エーテルとしては、ジエチルエーテル、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、ジエトキシメタン、ジメトキシエタン、メトキシエトキシエタン、ジエトキシエタン、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。
上記フッ素化エーテルとしては、下記一般式(I):
Rf1-O-Rf2 (I)
(式中、Rf1及びRf2は同じか又は異なり、炭素数1~10のアルキル基又は炭素数1~10のフッ素化アルキル基である。ただし、Rf1及びRf2の少なくとも一方は、フッ素化アルキル基である。)で表されるフッ素化エーテル(I)が挙げられる。フッ素化エーテル(I)を含有させることにより、電解液の難燃性が向上するとともに、高温高電圧での安定性、安全性が向上する。
なかでも、Rf1及びRf2が、同じか又は異なり、Rf1が炭素数3~6のフッ素化アルキル基であり、かつ、Rf2が炭素数2~6のフッ素化アルキル基であるであることが好ましい。
上記フッ素含有率の下限は、45質量%がより好ましく、50質量%が更に好ましく、55質量%が特に好ましい。上限は75質量%がより好ましく、70質量%が更に好ましく、66質量%が特に好ましい。
なお、本発明において、フッ素含有率は、フッ素化エーテル(I)の構造式に基づいて、{(フッ素原子の個数×19)/フッ素化エーテル(I)の分子量}×100(%)により算出した値である。
なかでも、高沸点、他の溶媒との相溶性や電解質塩の溶解性が良好な点で有利なことから、HCF2CF2CH2OCF2CFHCF3(沸点106℃)、CF3CF2CH2OCF2CFHCF3(沸点82℃)、HCF2CF2CH2OCF2CF2H(沸点88℃)及びCF3CF2CH2OCF2CF2H(沸点68℃)からなる群より選択される少なくとも1種であることが好ましく、HCF2CF2CH2OCF2CFHCF3(沸点106℃)及びHCF2CF2CH2OCF2CF2H(沸点88℃)からなる群より選択される少なくとも1種であることがより好ましい。
フッ素化不飽和環状カーボネートが有するフッ素原子の数は1以上があれば、特に制限されない。中でもフッ素原子が通常6以下、好ましくは4以下であり、1個又は2個のものが最も好ましい。
フッ素化ビニレンカーボネート誘導体としては、4-フルオロビニレンカーボネート、4-フルオ-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-アリル-5-フルオロ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等が挙げられる。
界面活性剤を含むことにより、容量特性、レート特性の改善を図ることができる。
上記電解質塩としては、従来公知の金属塩、液体状の塩(イオン性液体)、無機高分子型の塩、有機高分子型の塩等が挙げられる。
ただし、出力特性やハイレート充放電特性、高温保存特性、サイクル特性等を向上させる効果がある点で、少なくとも1種のリチウム塩がLiPF6であることが好ましい。
A-(D)-B (1-1)
[式中、Dは式(2-1):
-(D1)n-(FAE)m-(AE)p-(Y)q- (2-1)
(式中、D1は、式(2a):
FAEは、式(2b):
AEは、式(2c):
Yは、式(2d-1)~(2d-3):
nは0~200の整数;mは0~200の整数;pは0~10000の整数;qは1~100の整数;ただしn+mは0ではなく、D1、FAE、AE及びYの結合順序は特定されない);
A及びBは同じか又は異なり、水素原子、フッ素原子及び/又は架橋性官能基を含んでいてもよいアルキル基、フッ素原子及び/又は架橋性官能基を含んでいてもよいフェニル基、-COOH基、-OR(Rは水素原子又はフッ素原子及び/又は架橋性官能基を含んでいてもよいアルキル基)、エステル基又はカーボネート基(ただし、Dの末端が酸素原子の場合は-COOH基、-OR、エステル基及びカーボネート基ではない)]で表される側鎖に含フッ素基を有する非晶性含フッ素ポリエーテル化合物である。
そのなかでも、リチウムイオンを吸蔵又は放出可能な正極、負極、セパレータ及び本発明の電解液を備えるリチウム電池用として使用することが好適である。
リチウムイオンを吸蔵又は放出可能な負極および正極、セパレータ、ならびに、上述した電解液を備えることを特徴とするリチウム電池もまた、本発明の一つである。
(負極活物質)
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、電気化学的にリチウムイオンを吸蔵・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、金属材料、リチウム含有金属複合酸化物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。
なかでも、特に一般式(1)の化合物を含有する本発明の電解液と併用する場合に、高温保存特性、放電容量維持率、負荷特性、エネルギー密度等の電池特性向上の点から、負極活物質は、炭素質材料及び金属材料からなる群より選択される少なくとも1種であることが好ましく、金属材料であることがより好ましい。
このように、本発明のリチウム電池は、特定の化合物を含む電解液と、特定の負極活物質を含む負極とを備えるものであるため、高温保存特性、放電容量維持率、負荷特性等に優れ、良好な電池特性を有する。
また、SiまたはSnを第一の構成元素とし、それに加えて第2、第3の構成元素を含む複合材料が挙げられる。第2の構成元素は、例えば、コバルト、鉄、マグネシウム、チタン、バナジウム、クロム、マンガン、ニッケル、銅、亜鉛、ガリウム及びジルコニウムのうち少なくとも1種である。第3の構成元素は、例えば、ホウ素、炭素、アルミニウム及びリンのうち少なくとも1種である。
特に、高い電池容量および優れた電池特性が得られることから、上記金属材料として、ケイ素またはスズの単体(微量の不純物を含んでよい)、SiOv(0<v≦2)、SnOw(0≦w≦2)、Si-Co-C複合材料、Si-Ni-C複合材料、Sn-Co-C複合材料、Sn-Ni-C複合材料が好ましい。
LixTiyMzO4 (J)
[一般式(J)中、Mは、Na、K、Co、Al、Fe、Ti、Mg、Cr、Ga、Cu、Zn及びNbからなる群より選ばれる少なくとも1種の元素を表わす。]
で表される化合物であることが好ましい。
上記の一般式(J)で表わされる組成の中でも、
(i)1.2≦x≦1.4、1.5≦y≦1.7、z=0
(ii)0.9≦x≦1.1、1.9≦y≦2.1、z=0
(iii)0.7≦x≦0.9、2.1≦y≦2.3、z=0
の構造が、電池性能のバランスが良好なため特に好ましい。
電極の製造は、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、導電剤、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。
具体例としては、ポリエチレン、ポリプロピレン、ポリエチレンテレフタレート、ポリメチルメタクリレート、芳香族ポリアミド、ポリイミド、セルロース、ニトロセルロース等の樹脂系高分子;SBR(スチレン・ブタジエンゴム)、イソプレンゴム、ブタジエンゴム、フッ素ゴム、NBR(アクリロニトリル・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又はその水素添加物;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・スチレン共重合体、スチレン・イソプレン・スチレンブロック共重合体又は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-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。これらは、1種を単独で用いても、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。
水系溶媒としては、水、アルコール等が挙げられ、有機系溶媒としてはN-メチルピロリドン(NMP)、ジメチルホルムアミド、ジメチルアセトアミド、メチルエチルケトン、シクロヘキサノン、酢酸メチル、アクリル酸メチル、ジエチルトリアミン、N,N-ジメチルアミノプロピルアミン、テトラヒドロフラン(THF)、トルエン、アセトン、ジエチルエーテル、ジメチルアセトアミド、ヘキサメチルホスファルアミド、ジメチルスルホキシド、ベンゼン、キシレン、キノリン、ピリジン、メチルナフタレン、ヘキサン等が挙げられる。
(正極活物質)
以下に正極に使用される正極活物質について述べる。
正極活物質としては、電気化学的にリチウムイオンを吸蔵・放出可能なものであれば特に制限されないが、例えば、リチウムと少なくとも1種の遷移金属を含有する物質が好ましい。具体例としては、リチウム遷移金属複合酸化物、リチウム含有遷移金属リン酸化合物が挙げられる。なかでも、正極活物質としては、リチウム遷移金属複合酸化物であることが好ましい。
Li1+WMnxNiyCoZO2 (2)
(式中、w、x、y及びzは、0≦w<0.4、0.3<x<1、0≦y<0.4、0≦z<0.4、0<y+z、及び、w+x+y+z=1を満たす。)
で表されるリチウム遷移金属酸化物であることが好ましい。
正極活物質の粒子の形状は、従来用いられるような、塊状、多面体状、球状、楕円球状、板状、針状、柱状等が挙げられる。また、一次粒子が凝集して、二次粒子を形成していてもよい。
正極活物質のタップ密度は、好ましくは0.5g/cm3以上、より好ましくは0.8g/cm3以上、さらに好ましくは1.0g/cm3以上である。該正極活物質のタップ密度が上記下限を下回ると正極活物質層形成時に、必要な分散媒量が増加すると共に、導電材や結着剤の必要量が増加し、正極活物質層への正極活物質の充填率が制約され、電池容量が制約される場合がある。タップ密度の高い複合酸化物粉体を用いることにより、高密度の正極活物質層を形成することができる。タップ密度は一般に大きいほど好ましく、特に上限はないが、大きすぎると、正極活物質層内における電解液を媒体としたリチウムイオンの拡散が律速となり、負荷特性が低下しやすくなる場合があるため、上限は、好ましくは4.0g/cm3以下、より好ましくは3.7g/cm3以下、さらに好ましくは3.5g/cm3以下である。
なお、本発明では、タップ密度は、正極活物質粉体5~10gを10mlのガラス製メスシリンダーに入れ、ストローク約20mmで200回タップした時の粉体充填密度(タップ密度)g/ccとして求める。
正極活物質の粒子のメジアン径d50(一次粒子が凝集して二次粒子を形成している場合には二次粒子径)は好ましくは0.3μm以上、より好ましくは0.5μm以上、さらに好ましくは0.8μm以上、最も好ましくは1.0μm以上であり、上限は、好ましくは30μm以下、より好ましくは27μm以下、さらに好ましくは25μm以下、最も好ましくは22μm以下である。上記下限を下回ると、高タップ密度品が得られなくなる場合があり、上限を超えると粒子内のリチウムの拡散に時間がかかるため、電池性能の低下をきたしたり、電池の正極作成、即ち活物質と導電材やバインダー等を溶媒でスラリー化し、薄膜状に塗布する際に、スジを引く等の問題を生ずる場合がある。ここで、異なるメジアン径d50をもつ上記正極活物質を2種類以上混合することで、正極作成時の充填性をさらに向上させることができる。
一次粒子が凝集して二次粒子を形成している場合には、上記正極活物質の平均一次粒子径としては、好ましくは0.05μm以上、より好ましくは0.1μm以上、さらに好ましくは0.2μm以上であり、上限は、好ましくは5μm以下、より好ましくは4μm以下、さらに好ましくは3μm以下、最も好ましくは2μm以下である。上記上限を超えると球状の二次粒子を形成し難く、粉体充填性に悪影響を及ぼしたり、比表面積が大きく低下するために、出力特性等の電池性能が低下する可能性が高くなる場合がある。逆に、上記下限を下回ると、通常、結晶が未発達であるために充放電の可逆性が劣る等の問題を生ずる場合がある。
正極活物質のBET比表面積は、好ましくは0.1m2/g以上、より好ましくは0.2m2/g以上、さらに好ましくは0.3m2/g以上であり、上限は好ましくは50m2/g以下、より好ましくは40m2/g以下、さらに好ましくは30m2/g以下である。BET比表面積がこの範囲よりも小さいと電池性能が低下しやすく、大きいとタップ密度が上がりにくくなり、正極活物質層形成時の塗布性に問題が発生しやすい場合がある。
正極活物質の製造法としては、無機化合物の製造法として一般的な方法が用いられる。特に球状ないし楕円球状の活物質を作成するには種々の方法が考えられるが、例えば、遷移金属の原料物質を水等の溶媒中に溶解ないし粉砕分散して、攪拌をしながらpHを調節して球状の前駆体を作成回収し、これを必要に応じて乾燥した後、LiOH、Li2CO3、LiNO3等のLi源を加えて高温で焼成して活物質を得る方法等が挙げられる。
以下に、正極の構成について述べる。本発明において、正極は、正極活物質と結着剤とを含有する正極活物質層を、集電体上に形成して作製することができる。正極活物質を用いる正極の製造は、常法により行うことができる。即ち、正極活物質と結着剤、並びに必要に応じて導電材及び増粘剤等を乾式で混合してシート状にしたものを正極集電体に圧着するか、又はこれらの材料を液体媒体に溶解又は分散させてスラリーとして、これを正極集電体に塗布し、乾燥することにより、正極活物質層を集電体上に形成されることにより正極を得ることができる。
導電材としては、公知の導電材を任意に用いることができる。具体例としては、銅、ニッケル等の金属材料;天然黒鉛、人造黒鉛等の黒鉛(グラファイト);アセチレンブラック等のカーボンブラック;ニードルコークス等の無定形炭素等の炭素材料等が挙げられる。なお、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。導電材は、正極活物質層中に、通常0.01質量%以上、好ましくは0.1質量%以上、より好ましくは1質量%以上であり、また上限は、通常50質量%以下、好ましくは30質量%以下、より好ましくは15質量%以下含有するように用いられる。含有量がこの範囲よりも低いと導電性が不十分となる場合がある。逆に、含有量がこの範囲よりも高いと電池容量が低下する場合がある。
正極活物質層の製造に用いる結着剤としては、特に限定されず、塗布法の場合は、電極製造時に用いる液体媒体に対して溶解又は分散される材料であればよいが、具体例としては、ポリエチレン、ポリプロピレン、ポリエチレンテレフタレート、ポリメチルメタクリレート、ポリイミド、芳香族ポリアミド、セルロース、ニトロセルロース等の樹脂系高分子;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又はその水素添加物、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又は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(PVdF)、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。
スラリーを形成するための溶媒としては、正極活物質、導電材、結着剤、並びに必要に応じて使用される増粘剤を溶解又は分散することが可能な溶媒であれば、その種類に特に制限はなく、水系溶媒と有機系溶媒のどちらを用いてもよい。水系媒体としては、例えば、水、アルコールと水との混合媒等が挙げられる。有機系媒体としては、例えば、ヘキサン等の脂肪族炭化水素類;ベンゼン、トルエン、キシレン、メチルナフタレン等の芳香族炭化水素類;キノリン、ピリジン等の複素環化合物;アセトン、メチルエチルケトン、シクロヘキサノン等のケトン類;酢酸メチル、アクリル酸メチル等のエステル類;ジエチレントリアミン、N,N-ジメチルアミノプロピルアミン等のアミン類;ジエチルエーテル、プロピレンオキシド、テトラヒドロフラン(THF)等のエーテル類;N-メチルピロリドン(NMP)、ジメチルホルムアミド、ジメチルアセトアミド等のアミド類;ヘキサメチルホスファルアミド、ジメチルスルホキシド等の非プロトン性極性溶媒等が挙げられる。
正極集電体の材質としては特に制限されず、公知のものを任意に用いることができる。
具体例としては、アルミニウム、ステンレス鋼、ニッケルメッキ、チタン、タンタル等の金属材料;カーボンクロス、カーボンペーパー等の炭素材料が挙げられる。中でも金属材料、特にアルミニウムが好ましい。
集電体と正極活物質層の厚さの比は特には限定されないが、(電解液注液直前の片面の正極活物質層の厚さ)/(集電体の厚さ)の値が20以下であることが好ましく、より好ましくは15以下、最も好ましくは10以下であり、下限は、0.5以上が好ましく、より好ましくは0.8以上、最も好ましくは1以上の範囲である。この範囲を上回ると、高電流密度充放電時に集電体がジュール熱による発熱を生じる場合がある。この範囲を下回ると、正極活物質に対する集電体の体積比が増加し、電池の容量が減少する場合がある。
本発明の電解液を用いる場合、高出力かつ高温時の安定性を高める観点から、正極活物質層の面積は、電池外装ケースの外表面積に対して大きくすることが好ましい。具体的には、二次電池の外装の表面積に対する正極の電極面積の総和が面積比で15倍以上とすることが好ましく、さらに40倍以上とすることがより好ましい。電池外装ケースの外表面積とは、有底角型形状の場合には、端子の突起部分を除いた発電要素が充填されたケース部分の縦と横と厚さの寸法から計算で求める総面積をいう。有底円筒形状の場合には、端子の突起部分を除いた発電要素が充填されたケース部分を円筒として近似する幾何表面積である。正極の電極面積の総和とは、負極活物質を含む合材層に対向する正極合材層の幾何表面積であり、集電体箔を介して両面に正極合材層を形成してなる構造では、それぞれの面を別々に算出する面積の総和をいう。
正極板の厚さは特に限定されないが、高容量かつ高出力の観点から、芯材の金属箔厚さを差し引いた合材層の厚さは、集電体の片面に対して下限として、好ましくは10μm以上、より好ましくは20μm以上で、上限としては、好ましくは500μm以下、より好ましくは450μm以下である。
また、上記正極板の表面に、これとは異なる組成の物質が付着したものを用いてもよい。表面付着物質としては酸化アルミニウム、酸化ケイ素、酸化チタン、酸化ジルコニウム、酸化マグネシウム、酸化カルシウム、酸化ホウ素、酸化アンチモン、酸化ビスマス等の酸化物、硫酸リチウム、硫酸ナトリウム、硫酸カリウム、硫酸マグネシウム、硫酸カルシウム、硫酸アルミニウム等の硫酸塩、炭酸リチウム、炭酸カルシウム、炭酸マグネシウム等の炭酸塩、炭素等が挙げられる。
本発明に使用できるセパレータの材料や形状については特に制限されず、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。なかでも、本発明の電解液に対し安定な材料で形成された、樹脂、ガラス繊維、無機物等が用いられ、保液性に優れた多孔性シート又は不織布状の形態の物等を用いるのが好ましい。
(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。
集電構造は、特に制限されないが、本発明の電解液による高電流密度の充放電特性の向上をより効果的に実現するには、配線部分や接合部分の抵抗を低減する構造にすることが好ましい。この様に内部抵抗を低減させた場合、本発明の電解液を使用した効果は特に良好に発揮される。
外装ケースの材質は用いられる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。
また、本発明のリチウム二次電池(リチウムイオン二次電池)を備えることを特徴とするモジュールも本発明の一つである。
表1~2に示す割合となるように、乾燥アルゴン雰囲気下、下記に示す成分(I)、成分(II-a)、成分(III-a)、成分(III-b)の混合物に、乾燥したLiPF6を溶解し、電解液を調製した。
成分(I)
成分(I-a):
成分(III-b):フルオロエチレンカーボネート(FEC)
成分(IV):LiPF6
製造例1 負極Aの製造
負極活物質として人造黒鉛粉末、増粘剤としてカルボキシル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%)、結着剤としてスチレン-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97.6/1.2/1.2(質量%比)にて水溶媒中で、混合してスラリー状とした負極合剤スラリーを準備した。厚さ20μmの銅箔に均一に塗布、乾燥した後、プレス機により圧縮形成して、負極Aとした。
正極活物質としてLiNi1/3Mn1/3Co1/3O2、導電材としてアセチレンブラック、結着剤としてポリフッ化ビニリデン(PVdF)を92/3/5(質量%比)で混合した正極材料をN-メチル-2-ピロリドンに分散してスラリー状とした正極合剤スラリーを準備した。厚さ21μmのアルミ箔集電体上に、得られた正極合剤スラリーを均一に塗布し、乾燥して正極合剤層を形成し、その後、プレス機により圧縮成形して、正極とした。
製造例1で製造した負極A、正極及びポリエチレン製セパレータを負極、セパレータ、正極の順に積層して、電池要素を作製した。
この電池要素を、アルミニウム(厚さ40μm)の両面を樹脂層で被覆したラミネートフィルムからなる袋内に正極と負極の端子を突設させながら挿入した後、実施例及び比較例の電解液をそれぞれ袋内に注入し、真空封止を行い、シート状のリチウムイオン二次電池Aを作製した。
二次電池Aを、板で挟み加圧した状態で、25℃において、0.2Cに相当する電流で4.35Vまで定電流-定電圧充電(以下、(CC/CV充電)と表記する。)(0.1Cカット)した後、0.2Cの定電流で3Vまで放電し、これを1サイクルとして、3サイクル目の放電容量から初期放電容量を求めた。ここで、1Cとは電池の基準容量を1時間で放電する電流値を表わし、例えば、0.2Cとはその1/5の電流値を表わす。
初期放電容量評価後、4.35VまでCC/CV充電(0.1Cカット)を行った後、85℃12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、25℃において0.2Cで3Vまで放電させ、高温保存後の残存容量を測定し、初期放電容量に対する残存容量の割合を求め、これを保存容量維持率(%)とした((残存容量)÷(初期放電容量)×100=保存容量維持率(%))。
Claims (8)
- 電解質塩はLiPF6であり、前記電解質塩の含有量が0.2モル/リットル以上である請求項1記載の電解液。
- 請求項1又は2記載の電解液を備えることを特徴とする電気化学デバイス。
- リチウムイオンを吸蔵又は放出可能な負極及び正極、セパレータ、ならびに、請求項1又は2記載の電解液を備えることを特徴とするリチウム電池。
- リチウムイオンを吸蔵又は放出可能な正極は、一般式(2):
Li1+WMnxNiyCoZO2 (2)
(式中、w、x、y及びzは、0≦w<0.4、0.3<x<1、0≦y<0.4、0≦z<0.4、0<y+z、及び、w+x+y+z=1を満たす。)
で表されるリチウム遷移金属酸化物からなる正極活物質を含む請求項4記載のリチウム電池。 - リチウムイオンを吸蔵又は放出可能な負極は、炭素質材料及び金属材料からなる群より選択される少なくとも1種の負極活物質を含む請求項4又は5記載のリチウム電池。
- 正極の電位が、金属リチウム基準で4.3V以上である請求項4、5又は6記載のリチウム電池。
- 請求項4、5、6又は7記載のリチウム二次電池を備えることを特徴とするモジュール。
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