WO2012035821A1 - 非水系電解液及び非水系電解液二次電池 - Google Patents
非水系電解液及び非水系電解液二次電池 Download PDFInfo
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- WO2012035821A1 WO2012035821A1 PCT/JP2011/060926 JP2011060926W WO2012035821A1 WO 2012035821 A1 WO2012035821 A1 WO 2012035821A1 JP 2011060926 W JP2011060926 W JP 2011060926W WO 2012035821 A1 WO2012035821 A1 WO 2012035821A1
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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
- H01M10/0567—Liquid materials characterised by the additives
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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
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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
- 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
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or 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 a non-aqueous electrolyte and a non-aqueous electrolyte secondary battery, and more specifically, a specific cyclic compound having a carbon-carbon triple bond, a compound having a cyano group, a cyclic ester compound containing a sulfur atom, and an isocyanate.
- the present invention relates to a non-aqueous electrolyte solution containing any one or more of a group-containing compound and a non-aqueous electrolyte battery.
- Non-aqueous electrolyte secondary batteries such as lithium secondary batteries are widely used as power sources for so-called portable electronic devices such as mobile phones and notebook computers, to in-vehicle power sources for automobiles and large power sources for stationary applications. It is being put into practical use.
- the demand for applied secondary batteries is increasing, and the high performance of the battery characteristics of secondary batteries is increasing. For example, it is required to achieve high levels of improvement in capacity, high temperature storage characteristics, cycle characteristics, and the like.
- Non-aqueous electrolyte The electrolyte used for the lithium secondary battery is usually composed mainly of an electrolyte and a non-aqueous solvent.
- Main components of the non-aqueous solvent include cyclic carbonates such as ethylene carbonate and propylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; cyclic carboxylic acid esters such as ⁇ -butyrolactone and ⁇ -valerolactone. It is used.
- the oxidative decomposition of unsaturated cyclic carbonate on the positive electrode causes a problem of generation of a solid decomposition product in addition to the generation of carbon dioxide gas.
- Generation of such a solid decomposition product causes clogging of the electrode layer and the separator to inhibit the movement of lithium ions, or the solid decomposition product remains on the surface of the electrode active material and causes the lithium ion insertion / release reaction. May interfere.
- the charge / discharge capacity may gradually decrease during the continuous charge / discharge cycle, the charge / discharge capacity may decrease from the initial stage after storage at a high temperature of the battery or after the continuous charge / discharge cycle, or the load characteristics may deteriorate.
- the oxidative decomposition of unsaturated cyclic carbonate on these positive electrodes is a particularly serious problem under the recent high performance secondary battery design. That is, this oxidative decomposition tends to become prominent when the potential at which the positive electrode active material inserts and desorbs lithium rises above the redox potential of lithium. For example, when an attempt is made to operate at a higher voltage than a battery of 4.2 V that is a battery voltage at the time of full charge of a secondary battery that is currently commercially available, these oxidation reactions are particularly prominent.
- the non-aqueous electrolyte battery using the electrolyte described in Patent Documents 1 and 2 has a problem in that charge / discharge characteristics at a high current density are deteriorated because the resistance of the negative electrode film is generally large.
- the additives described in Patent Documents 3 and 4 are contained in the nonaqueous electrolyte, there is a problem that deterioration due to side reaction on the electrode occurs, and the storage characteristics and cycle characteristics of the battery are insufficient. .
- An object of the present invention is to provide a non-aqueous electrolyte battery having improved characteristics.
- the non-aqueous electrolyte used in the non-aqueous electrolyte battery contains a compound represented by the following general formula (1) and a cyano group.
- a non-aqueous electrolyte battery with improved durability and load characteristics such as cycle and storage can be realized by containing at least one of a compound having a cyclic ester compound containing a sulfur atom and a compound having an isocyanate group. As a result, the present invention has been completed.
- the gist of the present invention is as follows. a) A non-aqueous electrolyte solution containing a lithium salt and a non-aqueous solvent for dissolving the lithium salt, the non-aqueous electrolyte solution containing a compound represented by the following general formula (1), and further having a cyano group A nonaqueous electrolytic solution comprising at least one selected from the group consisting of a compound having a cyclic ester compound containing a sulfur atom, and a compound having an isocyanate group.
- X and Z represent CR 1 2 , C ⁇ O, C ⁇ N—R 1 , C ⁇ PR 1 , O, S, N—R 1 , PR 1 .
- Y may represent CR 1 2 , C ⁇ O, S ⁇ O, S ( ⁇ O) 2 , P ( ⁇ O) —R 2 , P ( ⁇ O) —OR 3 .
- R and R 1 are hydrogen, halogen, or a hydrocarbon group having 1 to 20 carbon atoms which may have a functional group, and may be the same or different from each other.
- R 2 is a hydrocarbon group having 1 to 20 carbon atoms which may have a functional group
- R 3 is a hydrocarbon group having 1 to 20 carbon atoms which may have Li, NR 4 4 or a functional group
- R 4 is a hydrocarbon group having 1 to 20 carbon atoms which may have a functional group, and may be the same or different from each other, and n and m each represents an integer of 0 or more.
- R 3 is a hydrocarbon group having 1 to 20 carbon atoms
- R 3 is Li, NR 4 4 , or a hydrocarbon group having 1 to 20 carbon atoms which may have a functional group
- R 4 is a functional group.
- U represents V having 1 to 10 carbon atoms composed of an atom selected from the group consisting of carbon atom, hydrogen atom, nitrogen atom, oxygen atom, sulfur atom, phosphorus atom and halogen atom.
- V is an integer of 1 or more.
- d) The nonaqueous electrolytic solution according to c), wherein the compound having a cyano group is a compound represented by NC— (CH 2 ) n —CN (n 2 to 6).
- e The nonaqueous electrolytic solution according to any one of a) to d), wherein the cyclic ester containing a sulfur atom is a compound represented by the following general formula (4).
- R 5 and R 6 are each independently composed of an atom selected from the group consisting of carbon atom, hydrogen atom, nitrogen atom, oxygen atom, sulfur atom, phosphorus atom and halogen atom. Represents an organic group having 1 to 10 carbon atoms, and R 5 and R 6 may contain an unsaturated bond together with —O—SO 2 —.
- the nonaqueous electrolytic solution according to any one of a) to e), wherein the compound having an isocyanate group is a compound represented by the following general formula (5).
- A represents a C 1-20 organic group composed of an atom selected from the group consisting of a hydrogen atom, a carbon atom, a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom, and a halogen atom; n ′ is an integer of 2 or more.
- the nonaqueous electrolyte solution contains at least one selected from the group consisting of a cyclic carbonate having a carbon-carbon double bond and a cyclic carbonate having a fluorine atom. Aqueous electrolyte.
- a non-aqueous electrolyte battery comprising a negative electrode and a positive electrode capable of inserting and extracting lithium ions, and a non-aqueous electrolyte solution, wherein the non-aqueous electrolyte solution is a non-aqueous electrolyte according to any one of a) to g).
- the present invention relates to a compound in which a carbon-carbon triple bond is bonded to a ring structure with a single bond without any other functional group or heteroelement, a compound having a cyano group, a cyclic ester compound containing a sulfur atom, and an isocyanate group.
- One of the characteristics is that any one or more of the compounds having the above are used in a non-aqueous electrolyte battery.
- Patent Documents 1 and 2 many of the materials that protect the electrode surface and improve battery durability such as storage characteristics and cycle characteristics are compounds of a cyclic structure, and further have multiple bonding sites. Have.
- the present inventors paid attention to this point, and examined in detail the bonding sites of functional groups and heteroelements in the ring structure, the sites where multiple bonds are bonded to the ring structure, and the hybrid state of the electron orbits of the multiple bonds.
- a compound in which multiple bonds are bonded to a ring structure is superior to a compound in which a part of the ring skeleton constituting the cyclic compound is a multiple bond.
- an effect superior to the durability property is obtained as compared with the carbon-carbon double bond, and knowledge that the above problems can be solved has been obtained.
- the use of a compound having a cyano group, a cyclic ester compound containing a sulfur atom, or a compound having an isocyanate group alone improves battery characteristics, but also causes electrode deterioration due to side reactions. Even if the non-aqueous electrolyte is used as an additive, there is a problem that the storage characteristics and cycle characteristics of the battery are insufficient.
- the present inventors pay attention to this point, and non-aqueous electrolysis of any one or more of a compound having a cyano group, a cyclic ester compound containing a sulfur atom and a compound having an isocyanate group, and the above carbon-carbon triple bond compound.
- the non-aqueous electrolyte solution has improved battery load characteristics, durability characteristics such as cycle and storage, especially in the design of lithium secondary batteries with higher voltages and higher capacities.
- a battery and a non-aqueous electrolyte used for the non-aqueous electrolyte are provided.
- Non-aqueous electrolyte 1-1 Electrolyte ⁇ Lithium salt> As the electrolyte, a lithium salt is usually used.
- the lithium salt is not particularly limited as long as it is known to be used for this purpose, and any lithium salt can be used. Specific examples include the following.
- lithium salts may be used alone or in combination of two or more.
- a preferable example in the case of using two or more kinds in combination is LiPF 6 and LiBF 4 , LiPF 6 and FSO 3 Li, LiPF 6 and LiPO 2 F 2 , LiPF 6 and LiN (FSO 2 ) 2 , LiPF 6 and LiN (CF 3 SO 2 ) 2 , LiPF 6 and lithium bisoxalatoborate, LiPF 6 and lithium difluorooxalatoborate, LiPF 6 and lithium tetrafluorooxalate phosphate, LiPF 6 and lithium difluorobis (oxalato) phosphate, LiPF 6 and lithium tris (Oxalato) phosphate, LiPF 6 and FSO 3 Li and LiPO 2 F 2 , LiPF 6 and FSO 3 Li and lithium bis (oxalato) borate, LiPF 6 and FSO 3 Li and lithium tetrafluorooxalato phosphate, LiPF 6 and FSO 3 Li
- LiPF 6 and LiBF 4 LiPO 2 F 2 , FSO 3 Li, LiN (FSO 2 ) 2 , LiN (CF 3 SO 2 ) 2 , lithium bis (oxalato) borate, lithium difluorooxalatoborate, lithium tetrafluorooxalatophosphate , Lithium difluorobis (oxalato) phosphate, lithium tris (oxalato) phosphate, etc.
- LiBF 4 LiPO 2 F 2 , FSO 3 Li, LiN (FSO 2 ) 2 , LiN with respect to 100% by mass of the entire non-aqueous electrolyte solution (CF 3 SO 2) 2, lithium bis (oxalato) borate, lithium difluoro oxalatoborate, lithium tetrafluoro-oxa Lato phosphate, lithium difluoro (oxalato) phosphate, lithium tris (oxalato) phosphate
- CF 3 SO 2
- the upper limit is usually 12% by mass or less, preferably 10% by mass or less. Within this range, effects such as output characteristics, load characteristics, low temperature characteristics, cycle characteristics, and high temperature characteristics are improved. On the other hand, if it is too much, it may be deposited at low temperature to deteriorate the battery characteristics, and if it is too little, the effect of improving the low temperature characteristics, cycle characteristics, high temperature storage characteristics, etc. may be reduced.
- the active material prepared in the electrolyte solution in the case of incorporating the LiPO 2 F 2 in the electrolyte solution and a method of adding a LiPO 2 F 2 which is separately synthesized by a known method in an electrolytic solution containing LiPF 6, to be described later
- the method for measuring the content of LiPO 2 F 2 in the non-aqueous electrolyte and the non-aqueous electrolyte battery is not particularly limited, and any known method can be used. Examples include ion chromatography and F nuclear magnetic resonance spectroscopy (hereinafter sometimes abbreviated as NMR).
- the concentration of these lithium salts in the non-aqueous electrolyte solution is not particularly limited as long as the effects of the present invention are not impaired, but the electric conductivity of the electrolyte solution is in a good range, and good battery performance is ensured. Therefore, the total molar concentration of the lithium salt in the nonaqueous electrolytic solution is preferably 0.3 mol / L or more, more preferably 0.4 mol / L or more, and further preferably 0.5 mol / L or more. , Preferably 3 mol / L or less, more preferably 2.5 mol / L or less, and even more preferably 2.0 mol / L or less. If the total molar concentration of lithium is too low, the electrical conductivity of the electrolyte may be insufficient. On the other hand, if the concentration is too high, the electrical conductivity may decrease due to an increase in viscosity, resulting in decreased battery performance. There is a case.
- Non-aqueous solvent a saturated cyclic carbonate, a cyclic carbonate having a fluorine atom, a chain carbonate, a cyclic or chain carboxylic acid ester, an ether compound, a sulfone compound, or the like can be used. These nonaqueous solvents may be used in any combination.
- saturated cyclic carbonate examples include those having an alkylene group having 2 to 4 carbon atoms.
- saturated cyclic carbonate having 2 to 4 carbon atoms examples include ethylene carbonate, propylene carbonate, butylene carbonate and the like.
- 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.
- Saturated cyclic carbonates may be used alone or in combination of two or more 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 one kind is used alone is 5% in 100% by volume of the non-aqueous solvent. Volume% or more, more preferably 10 volume% or more. By setting this range, the decrease in electrical conductivity resulting from the decrease in the dielectric constant of the non-aqueous electrolyte is avoided, and the large current discharge characteristics, negative electrode stability, and cycle characteristics of the non-aqueous electrolyte secondary battery are good. It becomes easy to be in a range.
- an upper limit is 95 volume% or less, More preferably, it is 90 volume% or less, More preferably, it is 85 volume% or less.
- the viscosity of the non-aqueous electrolyte solution is set to an appropriate range, a decrease in ionic conductivity is suppressed, and as a result, the load characteristics of the non-aqueous electrolyte secondary battery are easily set in a favorable range.
- the cyclic carbonate having a fluorine atom (hereinafter also referred to as fluorinated cyclic carbonate) is not particularly limited as long as it is a cyclic carbonate having a fluorine atom.
- the fluorinated cyclic carbonate include cyclic carbonate derivatives having an alkylene group having 2 to 6 carbon atoms, such as ethylene carbonate derivatives.
- the ethylene carbonate derivative include ethylene carbonate or a fluorinated product of ethylene carbonate substituted with an alkyl group (for example, an alkyl group having 1 to 4 carbon atoms), and particularly those having 1 to 8 fluorine atoms. Is preferred.
- At least one selected from the group consisting of monofluoroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, and 4,5-difluoro-4,5-dimethylethylene carbonate has high ionic conductivity. It is more preferable in terms of imparting properties and suitably forming an interface protective film.
- a fluorinated cyclic carbonate may be used individually by 1 type, and may have 2 or more types together by arbitrary combinations and ratios.
- 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 in 100% by volume of the non-aqueous solvent, preferably 0.01% by volume or more, more preferably 0.8%. It is 1 volume% or more, More preferably, it is 0.2 volume% or more, Preferably it is 90 volume% or less, More preferably, it is 70 volume% or less, More preferably, it is 60 volume% or less.
- the fluorinated cyclic carbonate exhibits an effective function not only as a solvent but also as an “auxiliary” described in 1-5 below.
- the blending amount is preferably 5% by volume or more, more preferably 7% by volume or more, still more preferably 8% by volume or more, preferably 100% by volume, in 100% by volume of the non-aqueous solvent.
- Volume% or less More preferably, it is 70 volume% or less, More preferably, it is 60 volume% or less.
- the blending amount is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and still more preferably 0.1% by mass in 100% by mass of the non-aqueous electrolyte. It is 2% by mass or more, preferably 5% by mass or less, more preferably 4% by mass or less, and further preferably 3% by mass or less. Within this range, the durability can be improved without excessively increasing the charge transfer resistance, so that the charge / discharge durability at a high current density can be improved.
- the role of the fluorinated cyclic carbonate as a solvent and an auxiliary agent has been described above, there is no clear boundary in the amount of the solvent or auxiliary agent, and a nonaqueous electrolytic solution can be prepared at an arbitrary ratio.
- the chain carbonate is preferably one having 3 to 7 carbon atoms.
- the chain carbonate having 3 to 7 carbon atoms dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, methyl-n-propyl carbonate, Examples thereof include n-butyl methyl carbonate, isobutyl methyl carbonate, t-butyl methyl carbonate, ethyl-n-propyl carbonate, n-butyl ethyl carbonate, isobutyl ethyl carbonate, t-butyl ethyl carbonate and the like.
- dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, and methyl n-propyl carbonate are preferable, and dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are particularly preferable. is there.
- chain carbonate one kind may be used alone, and two kinds or more may be used in optional combination and ratio.
- the blending amount of the chain carbonate is preferably 5% by volume or more, more preferably 8% by volume or more, and further preferably 10% 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, the decrease in ionic conductivity is suppressed, and the large current discharge characteristics of the non-aqueous electrolyte secondary 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 nonaqueous solvent.
- chain carbonates having a fluorine atom (hereinafter also referred to as fluorinated chain carbonate) can be suitably used.
- 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, 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).
- Ethyl) carbonate 2,2-difluoroethyl-2′-fluoroethyl carbonate, bis (2,2-difluoroethyl) carbonate, 2,2,2-trifluoroethyl-2′-fluoroethyl carbonate, 2,2, Examples include 2-trifluoroethyl-2 ′, 2′-difluoroethyl carbonate, bis (2,2,2-trifluoroethyl) carbonate, and the like.
- chain carbonate one kind may be used alone, and two kinds or more may be used in optional combination and ratio.
- the blending amount of the fluorinated chain carbonate is not particularly limited and may be arbitrary as long as the effects of the present invention are not significantly impaired. However, in 100% by volume of the non-aqueous solvent, preferably 0.01% by volume or more, more preferably 0. .1% by volume or more, more preferably 0.2% by volume or more, preferably 95% by volume or less, more preferably 90% by volume or less, and still more preferably 85% by volume or less.
- the fluorinated chain carbonate exhibits an effective function not only as a solvent but also as an “auxiliary” described in 1-5 below.
- the blending amount thereof is preferably 5% by volume or more, more preferably 7% by volume or more, further preferably 8% by volume or more, preferably in 100% by volume of the non-aqueous solvent. It is 95 volume% or less, More preferably, it is 90 volume% or less, More preferably, it is 85 volume% or less. Within this range, when the battery is operated at a high voltage, the secondary decomposition reaction of the non-aqueous electrolyte can be suppressed, the battery durability can be improved, and the electrical conductivity of the non-aqueous electrolyte can be drastically reduced. Can be prevented.
- the blending amount is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and still more preferably 0.1% by mass in 100% by mass of the non-aqueous electrolyte. It is 2% by mass or more, preferably 5% by mass or less, more preferably 4% by mass or less, and further preferably 3% by mass or less. Within this range, the durability can be improved without excessively increasing the charge transfer resistance, so that the charge / discharge durability at a high current density can be improved.
- ⁇ 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, epsilon 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.
- cyclic carboxylic acid ester may be used individually by 1 type, and may have 2 or more types together by arbitrary combinations and ratios.
- 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.
- the compounding quantity of cyclic carboxylic acid ester becomes like this. Preferably it is 50 volume% or less, More preferably, it is 40 volume% or less.
- the viscosity of the non-aqueous electrolyte solution is set to an appropriate range, a decrease in electrical conductivity is avoided, an increase in negative electrode resistance is suppressed, and a large current discharge of the non-aqueous electrolyte secondary battery is performed. It becomes easy to make a characteristic into a favorable range.
- Examples of the chain carboxylic acid ester 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, isopropyl butyrate, methyl isobutyrate, ethyl isobutyrate, isobutyric acid-n- Examples include propyl and isopropyl isobutyrate.
- strand-shaped carboxylic acid ester may be used individually by 1 type, and may have 2 or more types together by arbitrary combinations and ratios.
- 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 60 volume% or less preferably in 100 volume% of nonaqueous solvents, More preferably, it is 50 volume% or less.
- ether compound a chain ether having 3 to 10 carbon atoms in which part of hydrogen may be substituted with fluorine and a cyclic ether having 3 to 6 carbon atoms are preferable.
- chain ether having 3 to 10 carbon atoms include diethyl ether, di (2-fluoroethyl) ether, di (2,2-difluoroethyl) ether, di (2,2,2-trifluoroethyl) ether, ethyl (2-fluoroethyl) ether, ethyl (2,2,2-trifluoroethyl) ether, ethyl (1,1,2,2-tetrafluoroethyl) ether, (2-fluoroethyl) (2,2,2 -Trifluoroethyl) ether, (2-fluoroethyl) (1,1,2,2-tetrafluoroethyl) ether, (2,2,2-trifluoroethyl) ether,
- Examples of the cyclic ether having 3 to 6 carbon atoms include tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 1,3-dioxane, 2-methyl-1,3-dioxane, 4-methyl-1,3-dioxane, 1 , 4-dioxane and the like, and fluorinated compounds thereof.
- dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether have high solvating ability to lithium ions and improve ion dissociation.
- dimethoxymethane, diethoxymethane, and ethoxymethoxymethane are preferable because they have low viscosity and give high ionic conductivity.
- ether compounds may be used alone or in combination of two or more in any combination and ratio.
- the compounding amount of the ether compound is usually in 100% by volume of the non-aqueous solvent, preferably 5% by volume or more, more preferably 10% by volume or more, further preferably 15% by volume or more, and preferably 70% by volume or less. More 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 co-insertion.
- sulfone compounds As the sulfone compound, a cyclic sulfone having 3 to 6 carbon atoms and a chain sulfone having 2 to 6 carbon atoms are preferable.
- the number of sulfonyl groups in one molecule is preferably 1 or 2.
- cyclic sulfone examples include trimethylene sulfones, tetramethylene sulfones, and hexamethylene sulfones that are monosulfone compounds; trimethylene disulfones, tetramethylene disulfones, and hexamethylene disulfones that are disulfone compounds.
- trimethylene sulfones, tetramethylene disulfones, and hexamethylene disulfones that are disulfone compounds examples include trimethylene sulfones, tetramethylene sulfones, and hexamethylene sulfones that are monosulfone compounds; trimethylene disulfones, tetramethylene disulfones, and hexamethylene disulfones that are disulfone compounds.
- sulfolanes As sulfolanes, sulfolane and / or sulfolane derivatives (hereinafter also referred to as sulfolanes including sulfolane) are preferable.
- sulfolane derivative one in which one or more hydrogen atoms bonded to the carbon atom constituting the sulfolane ring are substituted with a fluorine atom or an alkyl group is preferable.
- chain sulfone dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, n-propyl methyl sulfone, n-propyl ethyl sulfone, di-n-propyl sulfone, isopropyl methyl sulfone, isopropyl ethyl sulfone, diisopropyl sulfone, n- Butyl methyl sulfone, n-butyl ethyl sulfone, t-butyl methyl sulfone, t-butyl ethyl sulfone, monofluoromethyl methyl sulfone, difluoromethyl methyl sulfone, trifluoromethyl methyl sulfone, monofluoroethyl methyl sulfone, difluoroethyl methyl sulfone
- sulfone compounds may be used alone or in combination of two or more in any combination and ratio.
- the compounding amount of the sulfone compound is usually 0.3% by volume or more, more preferably 0.5% by volume or more, and further preferably 1% by volume or more in 100% by volume of the nonaqueous solvent. Is 40% by volume or less, more preferably 35% by volume or less, and still more preferably 30% by volume or less. Within this range, durability improvement effects such as cycle characteristics and storage characteristics can be easily obtained, and the viscosity of the non-aqueous electrolyte can be set to an appropriate range to avoid a decrease in electrical conductivity. When charging / discharging an aqueous electrolyte secondary battery at a high current density, it is easy to avoid a situation in which the charge / discharge capacity retention rate decreases.
- X and Z represent CR 1 2 , C ⁇ O, C ⁇ N—R 1 , C ⁇ PR 1 , O, S, N—R 1 , PR 1 , They may be the same or different.
- Y represents CR 1 2 , C ⁇ O, S ⁇ O, S ( ⁇ O) 2 , P ( ⁇ O) —R 2 , P ( ⁇ O) —OR 3 .
- R and R 1 are hydrogen, halogen, or a hydrocarbon group having 1 to 20 carbon atoms which may have a functional group, and may be the same or different from each other.
- R 2 is a hydrocarbon group having 1 to 20 carbon atoms which may have a functional group.
- R 3 is Li, NR 4 4 or a hydrocarbon group having 1 to 20 carbon atoms which may have a functional group.
- R 4 is a hydrocarbon group having 1 to 20 carbon atoms which may have a functional group, and may be the same or different.
- n and m represent an integer of 0 or more.
- W is a range having the same meaning as R, and W may be the same as or different from R.
- X and Z are not particularly limited as long as they are within the range defined in the formula, but CR 1 2 , O, S, and N—R 1 are more preferable.
- R and R 1 are not particularly limited as long as they are within the range defined in the formula, but preferably, hydrogen, fluorine, a saturated aliphatic hydrocarbon group which may have a substituent, or a substituent.
- R 2 and R 4 are not particularly limited as long as they are within the range defined in the formula, but are preferably a saturated aliphatic hydrocarbon group which may have a substituent or an unsaturated group which may have a substituent.
- examples thereof include an aliphatic hydrocarbon and an aromatic hydrocarbon / aromatic heterocycle which may have a substituent.
- R 3 is not particularly limited as long as it is within the range defined in the formula, but preferably Li, a saturated aliphatic hydrocarbon which may have a substituent, or an unsaturated aliphatic which may have a substituent Examples thereof include hydrocarbons and optionally substituted aromatic hydrocarbons / aromatic heterocycles.
- an unsaturated aliphatic hydrocarbon which may have a substituent As a saturated aliphatic hydrocarbon which may have a substituent, an unsaturated aliphatic hydrocarbon which may have a substituent, a substituent of an aromatic hydrocarbon / aromatic heterocycle which may have a substituent Is not particularly limited, but preferably has a saturated aliphatic hydrocarbon group, which may have a substituent such as halogen, carboxylic acid, carbonic acid, sulfonic acid, phosphoric acid, phosphorous acid, etc. And an unsaturated aliphatic hydrocarbon group which may be substituted, an ester of an aromatic hydrocarbon group which may have a substituent, and the like, more preferably halogen, and most preferably fluorine.
- Preferable saturated aliphatic hydrocarbons are specifically methyl group, ethyl group, fluoromethyl group, difluoromethyl group, trifluoromethyl group, 1-fluoroethyl group, 2-fluoroethyl group, 1,1-difluoroethyl.
- Preferable unsaturated aliphatic hydrocarbons include ethenyl group, 1-fluoroethenyl group, 2-fluoroethenyl group, 1-methylethenyl group, 2-propenyl group, 2-fluoro-2-propenyl group 3-fluoro-2-propenyl group, ethynyl group, 2-fluoroethynyl group, 2-propynyl group, and 3-fluoro-2-propynyl group.
- Preferred aromatic hydrocarbons include phenyl group, 2-fluorophenyl group, 3-fluorophenyl group, 2,4-difluorophenyl group, 2,6-difluorophenyl group, 3,5-difluorophenyl group, 2, 4 , 6-trifluorophenyl group.
- Preferred aromatic heterocycles include 2-furanyl group, 3-furanyl group, 2-thiophenyl group, 3-thiophenyl group, 1-methyl-2-pyrrolyl group, 1-methyl-3-pyrrolyl group.
- a methyl group, an ethyl group, a fluoromethyl group, a trifluoromethyl group, a 2-fluoroethyl group, a 2,2,2-trifluoroethyl group, an ethenyl group, an ethynyl group, and a phenyl group are more preferable. More preferred are a methyl group, an ethyl group, and an ethynyl group.
- the molecular weight is preferably 50 or more. Moreover, Preferably, it is 500 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. Specific examples of these preferable compounds are shown below.
- R is preferably a hydrogen, fluorine or ethynyl group from the viewpoint of both reactivity and stability.
- R is preferably a hydrogen, fluorine or ethynyl group from the viewpoint of both reactivity and stability.
- the reactivity is lowered, and the expected properties may be lowered.
- it is halogen other than fluorine, there is a possibility that the reactivity is too high and the side reaction increases.
- X and Z are more preferably CR 1 2 or O. In cases other than these, the reactivity may be too high and side reactions may increase.
- the molecular weight is more preferably 100 or more, and more preferably 200 or less. If it is this range, it will be easy to ensure further the solubility of General formula (1) with respect to a non-aqueous electrolyte solution, and the effect of this invention will be fully further easily expressed.
- R is all hydrogen.
- the side reaction is most likely to be suppressed while maintaining the expected characteristics.
- Y is C ⁇ O or S ⁇ O
- one of X and Z is O, indicating that Y is S ( ⁇ O) 2 , P ⁇ O—R 2 , P ⁇ O—OR 3.
- both X and Z are O or CH 2
- one of X and Z is O and the other is CH 2 .
- a compound represented by the following general formula (2) is preferable from the viewpoint of ease of industrial production.
- Y represents C ⁇ O, S ⁇ O, S ( ⁇ O) 2 , P ⁇ O—R 2 , and P ⁇ O—OR 3 .
- R 2 is a hydrocarbon group having 1 to 20 carbon atoms which may have a functional group.
- R 3 is Li, NR 4 4 , or a hydrocarbon group having 1 to 20 carbon atoms which may have a functional group.
- R 4 is a hydrocarbon group having 1 to 20 carbon atoms which may have a functional group, and may be the same or different.
- the compounds represented by the general formula (1) may be used alone or in combination of two or more in any combination and ratio. Moreover, the compounding quantity of the compound represented by General formula (1) is not restrict
- the compounding amount of the compound represented by the general formula (1) is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and further preferably 0.1% by mass in 100% by mass of the non-aqueous electrolyte solution. % Or more, preferably 30% by mass or less, more preferably 10% by mass or less, still more preferably 5% by mass or less, and particularly preferably 3% by mass or less.
- the non-aqueous electrolyte secondary battery is likely to exhibit a sufficient cycle characteristics improvement effect, and the high-temperature storage characteristics are reduced, the amount of gas generated is increased, and the discharge capacity maintenance rate is reduced. Easy to avoid. On the other hand, if the amount is too small, the effects of the present invention may not be sufficiently exerted. If the amount is too large, the resistance may increase and the output and load characteristics may decrease.
- the compound represented by General formula (1) may use what was synthesize
- the nonaqueous electrolyte solution of this invention contains the compound and sulfur atom which have a cyano group with the compound represented by General formula (1). It contains at least one kind of a cyclic ester compound and a compound having an isocyanate group.
- the compound having a cyano group is not particularly limited as long as it has a cyano group in the molecule, but a compound represented by the following general formula (3) is more preferable.
- U is a V-valent having 1 to 10 carbon atoms composed of an atom selected from the group consisting of carbon atom, hydrogen atom, nitrogen atom, oxygen atom, sulfur atom, phosphorus atom and halogen atom.
- Organic group. V is an integer of 1 or more.
- a V-valent organic group having 1 to 10 carbon atoms composed of an atom selected from the group consisting of a carbon atom, a hydrogen atom, a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom and a halogen atom is a carbon atom and a hydrogen atom
- the organic group which may contain the nitrogen atom, the oxygen atom, the sulfur atom, the phosphorus atom, or the halogen atom other than the organic group comprised from these is meant.
- the organic group which may contain a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom or a halogen atom is an organic group in which a part of the carbon atoms of the skeleton is substituted with these atoms, or is composed of these atoms It is meant to include an organic group having a substituted group.
- the molecular weight of the compound having a cyano group 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, more preferably 80 or more, still more preferably 100 or more, and 200 or less. If it is this range, it will be easy to ensure the solubility of the compound which has a cyano group with respect to nonaqueous electrolyte solution, and the effect of this invention will be easy to be expressed.
- the production method of the compound having a cyano group is not particularly limited, and can be produced by arbitrarily selecting a known method.
- Specific examples of the compound represented by the general formula (3) include, for example, Acetonitrile, propionitrile, butyronitrile, isobutyronitrile, valeronitrile, isovaleronitrile, lauronitrile, 2-methylbutyronitrile, trimethylacetonitrile, hexanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, acrylonitrile, methacrylonitrile Crotononitrile, 3-methylcrotononitrile, 2-methyl-2-butenenitryl, 2-pentenenitrile, 2-methyl-2-pentenenitrile, 3-methyl-2-pentenenitrile, 2-hexenenitrile, Fluoroacetonitrile, difluoroacetonitrile, trifluoroacetonitrile, 2-fluoropropionitrile, 3-fluoropropionitrile, 2,2-difluoropropionitrile, 2,3-diflu Lopropionitrile, 3,3-di
- cyano groups such as 1,2,3-tris (2-cyanoethoxy) propane and tris (2-cyanoethyl) amine; Cyanate compounds such as methyl cyanate, ethyl cyanate, propyl cyanate, butyl cyanate, pentyl cyanate, hexyl cyanate, heptyl cyanate;
- a compound having a cyano group may be used alone or in combination of two or more in any combination and ratio.
- the compounding amount of the compound having a cyano group with respect to the entire non-aqueous electrolyte solution of the present invention is not limited, and is arbitrary as long as the effects of the present invention are not significantly impaired. 001% by mass or more, preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and usually 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less.
- R 5 and R 6 are each independently carbon composed of an atom selected from the group consisting of a carbon atom, a hydrogen atom, a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom and a halogen atom. Represents an organic group of formula 1 to 10, and R 5 and R 6 may each contain —O—SO 2 — and an unsaturated bond.
- the organic group having 1 to 10 carbon atoms composed of an atom selected from the group consisting of carbon atom, hydrogen atom, nitrogen atom, oxygen atom, sulfur atom, phosphorus atom and halogen atom is composed of carbon atom and hydrogen atom.
- it means an organic group which may contain a nitrogen atom, oxygen atom, sulfur atom, phosphorus atom, or halogen atom.
- the organic group which may contain a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom or a halogen atom is an organic group in which a part of the carbon atoms of the skeleton is substituted with these atoms, or is composed of these atoms It is meant to include an organic group having a substituted group.
- the molecular weight of the cyclic ester compound containing a sulfur atom 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 100 or more and 250 or less. If it is this range, it will be easy to ensure the solubility of the cyclic ester compound containing the sulfur atom with respect to a non-aqueous electrolyte solution, and the effect of this invention will be easy to be expressed.
- the production method of the cyclic ester compound containing a sulfur atom is not particularly limited, and can be produced by arbitrarily selecting a known method.
- Specific examples of the compound represented by the general formula (4) include, for example, 1,3-propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone, 1-methyl-1,3-propane sultone 2-methyl-1,3-propane sultone, 3-methyl-1,3-propane sultone, 1-propene-1,3-sultone, 2-propene-1,3-sultone, 1-fluoro-1-propene -1,3-sultone, 2-fluoro-1-propene-1,3-sultone, 3-fluoro-1-propene-1,3-sultone, 1-fluoro-2-propene-1,3-sultone, 2 -Fluoro-2-propene-1,3-sultone, 3-fluoro-2-propene-1,3-sultone, 1-methyl-1-propen
- 1,3-propane sultone 1-fluoro-1,3-propane Sultone, 2-fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone, 1- Ropen 1,3 sultone, ethylene glycol sulfuric ester, 1,3-propanediol ester sulfate, methylene methane disulfonate more preferable.
- the cyclic ester compound containing a sulfur atom may be used alone or in combination of two or more in any combination and ratio. There is no limit to the amount of the cyclic ester compound containing a sulfur atom with respect to the entire non-aqueous electrolyte of the present invention, and it is optional as long as the effects of the present invention are not significantly impaired. 0.001% by mass or more, preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and usually 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less. To contain. When the above range is satisfied, effects such as output characteristics, load characteristics, low temperature characteristics, cycle characteristics, and high temperature storage characteristics are further improved.
- the compound having an isocyanate group is not particularly limited as long as it is a compound having an isocyanate group in the molecule.
- the compound represented by the general formula (5) is preferable in order to form a good protective film.
- A represents a C 1-20 organic group composed of an atom selected from the group consisting of a hydrogen atom, a carbon atom, a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom, and a halogen atom; n ′ is an integer of 2 or more.
- the organic group having 1 to 20 carbon atoms composed of an atom selected from the group consisting of a hydrogen atom, a carbon atom, a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom, and a halogen atom is composed of a carbon atom and a hydrogen atom.
- the organic group which may contain a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom, or a halogen atom in addition to the organic group to be formed is meant.
- An organic group which may contain a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom, or a halogen atom is an organic group in which a part of the carbon atoms of the skeleton is substituted with these atoms, or these atoms. It is meant to include an organic group having a configured substituent.
- the molecular weight of the compound represented by the general formula (5) is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired.
- the molecular weight is preferably 80 or more, more preferably 115 or more, still more preferably 180 or more, and is 400 or less, more preferably 270 or less. If it is this range, it will be easy to ensure the solubility of the compound represented by General formula (5) with respect to a non-aqueous electrolyte solution, and the effect of this invention will be easy to be expressed.
- the production method of the compound represented by the general formula (5) is not particularly limited, and can be produced by arbitrarily selecting a known method.
- a in the general formula (5) for example, Alkylene group or derivative thereof, alkenylene group or derivative thereof, cycloalkylene group or derivative thereof, alkynylene group or derivative thereof, cycloalkenylene group or derivative thereof, arylene group or derivative thereof, carbonyl group or derivative thereof, sulfonyl group or derivative thereof, Sulfinyl group or derivative thereof, phosphonyl group or derivative thereof, phosphinyl group or derivative thereof, amide group or derivative thereof, imide group or derivative thereof, ether group or derivative thereof, thioether group or derivative thereof, borinic acid group or derivative thereof, borane Group or a derivative thereof.
- an alkylene group or a derivative thereof an alkenylene group or a derivative thereof, a cycloalkylene group or a derivative thereof, an alkynylene group or a derivative thereof, an arylene group or a derivative thereof is preferable. More preferably, A is an organic group having 2 to 14 carbon atoms which may have a substituent.
- Specific examples of the compound represented by the general formula (5) include, for example, monomethylene diisocyanate, dimethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, heptamethylene diisocyanate, octamethylene diisocyanate, Nonamethylene diisocyanate, decamethylene diisocyanate, 1,3-diisocyanatopropane, 1,4-diisocyanato-2-butene, 1,4-diisocyanato-2-fluorobutane, 1,4-diisocyanato-2,3-difluorobutane 1,5-diisocyanato-2-pentene, 1,5-diisocyanato-2-methylpentane, 1,6-diisocyanato-2-hexene, 1,6-diisocyanato 3-hexene, 1,6
- trimethylene diisocyanate trimethylene diisocyanate, hexamethylene diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, dicyclohexylmethane-4,4′-diisocyanate, basic structures of formulas (5-1) to (5-4)
- the biurets, isocyanurates, adducts, and bifunctional types of modified polyisocyanates shown are preferred because they form more stable films.
- the compound represented by the general formula (5) may be used alone or in combination of two or more in any combination and ratio.
- the compounding amount of the compound represented by the general formula (5) with respect to the entire non-aqueous electrolyte of the present invention is not limited, and is arbitrary as long as the effects of the present invention are not significantly impaired. In general, it is 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and usually 5% by mass or less, preferably 4% by mass or less, more preferably 2% by mass. It is contained at the following concentrations. When the above range is satisfied, effects such as output characteristics, load characteristics, low temperature characteristics, cycle characteristics, and high temperature storage characteristics are further improved.
- auxiliary agents include cyclic carbonates having unsaturated bonds, chain carbonates having unsaturated bonds, cyclic carbonates having fluorine atoms, unsaturated cyclic carbonates having fluorine atoms, overcharge inhibitors, and other assistants as shown below. Agents and the like.
- ⁇ Cyclic carbonate having an unsaturated bond> in addition to the compound of the formula (1), a compound of the formula (1) is used in order to form a film on the negative electrode surface of the non-aqueous electrolyte battery and achieve a long battery life.
- a cyclic carbonate having an unsaturated bond removed from hereinafter also referred to as an unsaturated cyclic carbonate
- the unsaturated cyclic carbonate is not particularly limited as long as it is a cyclic carbonate having a carbon-carbon double bond, and any unsaturated carbonate can be used.
- the cyclic carbonate having a substituent having an aromatic ring is also included in the unsaturated cyclic carbonate.
- the unsaturated cyclic carbonate include vinylene carbonates, ethylene carbonates substituted with a substituent having an aromatic ring or a carbon-carbon double bond, phenyl carbonates, vinyl carbonates, and allyl carbonates.
- the vinylene carbonates include vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, phenyl vinylene carbonate, 4,5-diphenyl vinylene carbonate, vinyl vinylene carbonate, 4,5-vinyl vinylene carbonate, allyl vinylene carbonate, 4 , 5-diallyl vinylene carbonate.
- ethylene carbonate substituted with a substituent having an aromatic ring or a carbon-carbon double bond examples include vinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, 4-methyl-5-vinyl ethylene carbonate, 4- Allyl-5-vinylethylene carbonate, phenylethylene carbonate, 4,5-diphenylethylene carbonate, 4-phenyl-5-vinylethylene carbonate, 4-allyl-5-phenylethylene carbonate, allylethylene carbonate, 4,5-diallylethylene Examples thereof include carbonate and 4-methyl-5-allylethylene carbonate.
- unsaturated cyclic carbonates particularly preferable for use in combination with the compound of formula (1) include vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, vinyl vinylene carbonate, 4,5-vinyl vinylene carbonate, allyl.
- Vinylene carbonate, 4,5-diallyl vinylene carbonate, vinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, 4-methyl-5-vinyl ethylene carbonate, allyl ethylene carbonate, 4,5-diallyl ethylene carbonate, 4-methyl-5 -Allylethylene carbonate and 4-allyl-5-vinylethylene carbonate are more preferably used because they form a stable interface protective film.
- the molecular weight of the unsaturated cyclic carbonate is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired.
- the molecular weight is preferably 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.
- the production method of the unsaturated cyclic carbonate is not particularly limited, and can be produced by arbitrarily selecting a known method.
- the unsaturated cyclic carbonate may be used alone or in combination of two or more in any combination and ratio. Moreover, the compounding quantity of unsaturated cyclic carbonate is not restrict
- the amount of the unsaturated cyclic carbonate is 100% by mass in the non-aqueous 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, 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 secondary battery is likely to exhibit a sufficient cycle characteristics improvement effect, and the high-temperature storage characteristics are reduced, the amount of gas generated is increased, and the discharge capacity maintenance rate is reduced. Easy to avoid. On the other hand, if the amount is too small, the effects of the present invention may not be sufficiently exerted. If the amount is too large, the resistance may increase and the output and load characteristics may decrease.
- the compound of formula (1) in order to form a film on the negative electrode surface of the non-aqueous electrolyte battery and to extend the life of the battery, in addition to the compound of formula (1), the compound of formula (1) A linear carbonate having an unsaturated bond (hereinafter also referred to as an unsaturated cyclic carbonate) can be used.
- Examples of the unsaturated chain carbonate include chain carbonates having a carbon-carbon unsaturated bond, chain carbonates substituted with a substituent having an aromatic ring, and the like.
- chain carbonates having a chain hydrocarbon having a carbon-carbon unsaturated bond Methyl vinyl carbonate, ethyl vinyl carbonate, divinyl carbonate, methyl-1-propenyl carbonate, ethyl-1-propenyl carbonate, di-1-propenyl carbonate, methyl (1-methylvinyl) carbonate, ethyl (1-methylvinyl) carbonate, Di (1-methylvinyl) carbonate, methyl-2-propenyl carbonate, ethyl-2-propenyl carbonate, di (2-propenyl) carbonate, 1-butenylmethyl carbonate, 1-butenylethyl carbonate, di (1-butenyl) ) Carbonate, methyl (1-methyl-1-propenyl) carbonate, ethyl (1-methyl-1-propenyl) carbonate, di (1-methyl-1-propenyl) carbonate, methyl-1-ethylvinyl -Bonate, ethyl vinyl
- chain carbonates substituted with a substituent having an aromatic ring Methyl phenyl carbonate, ethyl phenyl carbonate, phenyl vinyl carbonate, allyl phenyl carbonate, enethyl phenyl carbonate, 2-propenyl phenyl carbonate, diphenyl carbonate, methyl (2-methylphenyl) carbonate, ethyl (2-methylphenyl) carbonate, (2 -Methylphenyl) vinyl carbonate, allyl (2-methylphenyl) carbonate, enethyl (2-methylphenyl) carbonate, 2-propenyl (2-methylphenyl) carbonate, di (2-methylphenyl) carbonate, methyl (3-methyl) Phenyl) carbonate, ethyl (3-methylphenyl) carbonate, (3-methylphenyl) vinyl carbonate, allyl (3-methylphenyl) carbonate Enethyl (3-methylphenyl) carbonate, 2-
- fluorinated unsaturated cyclic carbonate it is also preferable to use a cyclic carbonate having an unsaturated bond and a fluorine atom (hereinafter also referred to as a fluorinated unsaturated cyclic carbonate).
- 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-fluoro-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-Diff Oro-4,5-diallylethylene carbonate, 4-fluoro-4-phenylethylene carbonate, 4-fluoro-5-phenylethylene carbonate, 4,4-difluoro-5-phenyl
- fluorinated unsaturated cyclic carbonates for use in combination with the compound of the formula (1) include 4-fluoro vinylene carbonate, 4-fluoro-5-methyl vinylene carbonate, 4-fluoro-5-vinyl vinylene carbonate, 4-allyl-5-fluorovinylene carbonate, 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- Fluo -4,5-divinylethylene carbonate, 4-fluoro-4,5-diallylethylene carbonate, 4,5-difluoro-4,5-divinylethylene carbonate, 4,5-difluoro-
- 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 250 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.
- the production method of the fluorinated unsaturated cyclic carbonate is not particularly limited, and can be produced by arbitrarily selecting a known method.
- the molecular weight is more preferably 80 or more, and more preferably 150 or less.
- Fluorinated unsaturated cyclic carbonates may be used alone or in combination of two or more in any combination and 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 non-aqueous electrolyte solution, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and further preferably 0.2% by mass. Further, it is preferably 5% by mass or less, more preferably 4% by mass or less, and further preferably 3% by mass or less.
- the non-aqueous electrolyte secondary battery is likely to exhibit a sufficient cycle characteristics improvement effect, and the high-temperature storage characteristics are reduced, the amount of gas generated is increased, and the discharge capacity maintenance rate is reduced. Easy to avoid. On the other hand, if the amount is too small, the effects of the present invention may not be sufficiently exerted. If the amount is too large, the resistance may increase and the output and load characteristics may decrease.
- an overcharge inhibitor can be used to effectively suppress battery rupture / ignition when the non-aqueous electrolyte secondary battery is in an overcharged state or the like.
- aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran; 2-fluorobiphenyl, Partially fluorinated products of the above aromatic compounds such as o-cyclohexylfluorobenzene and p-cyclohexylfluorobenzene; 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, 3,5-difluoroanisole and the like And a fluorine-containing anisole compound.
- aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene
- 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, a partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene,
- aromatic compounds not containing oxygen such as t-amylbenzene
- oxygen-containing aromatic compounds such as diphenyl ether, dibenzofuran, and the like
- the blending 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 inhibitor is preferably 0.1% by mass or more and 5% by mass or less in 100% by mass of the non-aqueous electrolyte 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 battery characteristics, 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.
- auxiliaries include carbonate compounds such as erythritan carbonate, spiro-bis-dimethylene carbonate, methoxyethyl-methyl carbonate; succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, anhydrous Carboxylic anhydrides such as itaconic acid, diglycolic anhydride, cyclohexanedicarboxylic anhydride, cyclopentanetetracarboxylic dianhydride and phenylsuccinic anhydride; 2,4,8,10-tetraoxaspiro [5.5 ] Spiro compounds such as undecane, 3,9-divinyl-2,4,8,10-tetraoxaspiro [5.5] undecane; ethylene sulfite, methyl fluorosulf
- the compounding amount of other auxiliary agents is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired.
- the other auxiliary agent is preferably 0.01% by mass or more and 5% by mass or less in 100% by mass of the non-aqueous electrolyte solution. Within this range, the effects of other auxiliaries can be sufficiently exhibited, and it is easy to avoid a situation in which battery characteristics such as high-load discharge characteristics deteriorate.
- the blending amount of other auxiliaries is more preferably 0.1% by mass or more, further preferably 0.2% by mass or more, more preferably 3% by mass or less, and further preferably 1% by mass or less. .
- the non-aqueous electrolyte solution described above includes those existing inside the non-aqueous electrolyte battery according to the present invention. Specifically, the components of the non-aqueous electrolyte solution such as lithium salt, solvent, and auxiliary agent are separately synthesized, and the non-aqueous electrolyte solution is prepared from what is substantially isolated by the method described below.
- nonaqueous electrolyte solution in a nonaqueous electrolyte battery obtained by pouring into a separately assembled battery the components of the nonaqueous electrolyte solution of the present invention are individually placed in the battery, In order to obtain the same composition as the non-aqueous electrolyte solution of the present invention by mixing in a non-aqueous electrolyte battery, the compound constituting the non-aqueous electrolyte solution of the present invention is further generated in the non-aqueous electrolyte battery. The case where the same composition as the aqueous electrolyte is obtained is also included.
- the non-aqueous electrolyte battery of the present invention is suitable for use as an electrolyte for a secondary battery, for example, a lithium secondary battery, among non-aqueous electrolyte batteries.
- a non-aqueous electrolyte battery using the non-aqueous electrolyte of the present invention will be described.
- the non-aqueous electrolyte secondary battery of the present invention can adopt a known structure.
- the negative electrode and the positive electrode capable of occluding and releasing ions for example, lithium ions
- An aqueous electrolyte solution An aqueous electrolyte solution.
- Negative electrode The negative electrode active material used for the negative electrode is described below.
- the negative electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions. Specific examples include carbonaceous materials, alloy materials, lithium-containing metal composite oxide materials, and the like. These may be used alone or in combination of two or more.
- the negative electrode active material examples include carbonaceous materials, alloy materials, lithium-containing metal composite oxide materials, and the like.
- a carbonaceous material used as a negative electrode active material (1) natural graphite, (2) a carbonaceous material obtained by heat-treating an artificial carbonaceous material and an artificial graphite material at least once in the range of 400 to 3200 ° C; (3) a carbonaceous material in which the negative electrode active material layer is made of carbonaceous materials having at least two or more different crystallinities and / or has an interface in contact with the different crystalline carbonaceous materials, (4) A carbonaceous material in which the negative electrode active material layer is made of carbonaceous materials having at least two or more different orientations and / or has an interface in contact with the carbonaceous materials having different orientations, Is preferably a good balance between initial irreversible capacity and high current density charge / discharge characteristics.
- the carbonaceous materials (1) to (4) may be used alone or in combination of two or more in any combination and ratio
- Examples of the artificial carbonaceous material and artificial graphite material of (2) above include natural graphite, coal-based coke, petroleum-based coke, coal-based pitch, petroleum-based pitch, those obtained by oxidizing these pitches, needle coke, pitch coke and Carbon materials that are partially graphitized, furnace black, acetylene black, organic pyrolysis products such as pitch-based carbon fibers, carbonizable organic materials and their carbides, or carbonizable organic materials are benzene, toluene, xylene, quinoline And a solution dissolved in a low-molecular organic solvent such as n-hexane, and carbides thereof.
- the single metal and alloy forming the lithium alloy are preferably materials containing group 13 and group 14 metal / metalloid elements (that is, excluding carbon), more preferably aluminum, silicon and tin (hereinafter referred to as “ Simple metals) and alloys or compounds containing these atoms (sometimes abbreviated as “specific metal elements”). 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.
- compounds in which these complex compounds are complexly bonded to several elements such as simple metals, alloys or non-metallic elements are also included.
- silicon and tin an alloy of these elements and a metal that does not operate as a negative electrode can be used.
- tin 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.
- any one simple metal of a specific metal element, an alloy of two or more specific metal elements, oxidation of a specific metal element In particular, silicon and / or tin metal simple substance, alloy, oxide, carbide, nitride and the like are preferable from the viewpoint of capacity per unit mass and environmental load.
- 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 sometimes abbreviated as “lithium titanium composite oxide”). 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 secondary battery because the output resistance is greatly reduced.
- lithium or titanium of the lithium titanium composite oxide is at least selected from the group consisting of other metal elements such as Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, and Nb. Those substituted with one element are also preferred.
- the metal oxide is a lithium titanium composite oxide represented by the general formula (A). In the general formula (A), 0.7 ⁇ x ⁇ 1.5, 1.5 ⁇ y ⁇ 2.3, It is preferable that 0 ⁇ z ⁇ 1.6 because the structure upon doping and dedoping of lithium ions is stable.
- 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.
- 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.
- (A) 1.2 ⁇ x ⁇ 1.4, 1.5 ⁇ y ⁇ 1.7, z 0
- This structure is particularly preferable because of a good balance of battery performance.
- Particularly preferred representative compositions of the above compounds are Li 4/3 Ti 5/3 O 4 in (a), Li 1 Ti 2 O 4 in (b), Li 4/5 Ti 11/5 O in (c). 4 .
- the rhombohedral crystal ratio can be determined from the ratio of the rhombohedral structure graphite layer (ABC stacking layer) and the hexagonal structure graphite layer (AB stacking layer) by the X-ray wide angle diffraction method (XRD) using the following formula.
- Rhombohedral crystal ratio (%) integrated intensity of ABC (101) peak of XRD ⁇ XRD AB (101) peak integrated intensity ⁇ 100
- the rhombohedral crystal ratio of the carbonaceous material that can be used in the present invention is usually 0% or more, preferably 3% or more, more preferably 5% or more, and particularly preferably 12% or more as a lower limit. is there.
- an upper limit Preferably it is 35% or less, More preferably, it is 27% or less, More preferably, it is 24% or less, Most preferably, it is the range of 20% or less.
- the rhombohedral crystal ratio of 0% indicates that no XRD peak derived from the ABC stacking layer is detected.
- “greater than 0%” means that even a slight XRD peak derived from the ABC stacking layer is detected.
- the rhombohedral crystal ratio is within the above range, for example, there are few defects in the crystal structure of the carbonaceous material, the reactivity with the electrolytic solution is small, the consumption of the electrolytic solution during the cycle is small, and the cycle characteristics are excellent.
- the XRD measurement method for determining the rhombohedral crystal ratio is as follows: a 0.2 mm sample plate is filled so that the graphite powder is not oriented, and an X-ray diffractometer (for example, CuK ⁇ ray by X'Pert Pro MPD manufactured by PANalytical) is used. And an output of 45 kV and 40 mA). Using the obtained diffraction pattern, the peak integrated intensity is calculated by profile fitting using an asymmetric Pearson VII function using analysis software JADE 5.0, and the rhombohedral crystal ratio is obtained from the above formula.
- the X-ray diffraction measurement conditions are as follows. “2 ⁇ ” indicates a diffraction angle.
- ⁇ Target Cu (K ⁇ ray) graphite monochromator
- ⁇ Slit Solar slit 0.04 degree divergence slit 0.5 degree side divergence mask 15mm Anti-scattering slit 1 degree
- Measurement range and step angle / measurement time (101) plane: 41 ° ⁇ 2 ⁇ ⁇ 47.5 ° 0.3 ° / 60 seconds
- Background correction Connect 42.7 to 45.5 degrees with a straight line and subtract as background.
- -Peak of rhombohedral-structure graphite particle layer refers to a peak around 43.4 degrees.
- -Peak of hexagonal structure graphite particle layer It indicates a peak around 44.5 degrees.
- a method for obtaining graphite particles having a rhombohedral crystal ratio in the above range can employ a method of manufacturing using conventional techniques, and is not particularly limited, but the graphite particles are heat-treated at a temperature of 500 ° C. or higher. It is preferable to manufacture by this. In particular, mechanical effects such as compression, friction, shearing force, etc. including the interaction of particles are given to graphite particles mainly by impact force.
- the rhombohedral crystal ratio defined in the present invention can also be adjusted by changing the strength of mechanical action, processing time, presence / absence of repetition, and the like.
- a rotor with a large number of blades installed inside the casing, and when the rotor rotates at high speed, mechanical action such as impact compression, friction, shearing force, etc. is applied to the carbon material introduced inside.
- An apparatus that provides a surface treatment is preferable.
- a preferable apparatus there can be mentioned a hybridization system manufactured by Nara Machinery Co., Ltd.
- heat treatment after the mechanical action is applied. Further, it is particularly preferable that after applying the mechanical action, it is combined with a carbon precursor and subjected to heat treatment at a temperature of 700 ° C. or higher.
- the d value (interlayer distance) of the lattice plane (002 plane) determined by X-ray diffraction by the Gakushin method of carbonaceous material is preferably 0.335 nm or more, and is usually 0.360 nm or less. 350 nm or less is preferable, and 0.345 nm or less is more preferable. Further, the crystallite size (Lc) of the carbonaceous material obtained by X-ray diffraction by the Gakushin method is preferably 1.0 nm or more, and more preferably 1.5 nm or more.
- the volume-based average particle diameter of the carbonaceous material is a volume-based average particle diameter (median diameter) obtained by a laser diffraction / scattering method, and is usually 1 ⁇ m or more, preferably 3 ⁇ m or more, more preferably 5 ⁇ m or more, and 7 ⁇ m.
- the above is particularly preferable, and is usually 100 ⁇ m or less, preferably 50 ⁇ m or less, more preferably 40 ⁇ m or less, further preferably 30 ⁇ m or less, and particularly preferably 25 ⁇ m or less.
- the volume-based average particle size is measured by dispersing the carbon powder in a 0.2% by mass aqueous solution (about 10 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and laser diffraction / scattering particle size distribution. This is carried out using a total (LA-700 manufactured by Horiba Ltd.). The median diameter determined by the measurement is defined as the volume-based average particle diameter of the carbonaceous material of the present invention.
- the Raman R value of the carbonaceous material is a value measured using an argon ion laser Raman spectrum method, and is usually 0.01 or more, preferably 0.03 or more, more preferably 0.1 or more, and usually 1.5 or less, preferably 1.2 or less, more preferably 1 or less, and particularly preferably 0.5 or less.
- the Raman R value is lower than the above range, the crystallinity of the particle surface becomes too high, and there are cases where the sites where Li enters between layers are reduced along with charge / discharge. That is, charge acceptance may be reduced.
- the negative electrode is densified by applying it to the current collector and then pressing it, the crystals are likely to be oriented in a direction parallel to the electrode plate, which may lead to a decrease in load characteristics.
- the film forms a good network on the negative electrode surface and has a suitable film density. And cycle characteristics and load characteristics can be dramatically improved.
- the Raman half-width in the vicinity of 1580 cm ⁇ 1 of the carbonaceous material is not particularly limited, but is usually 10 cm ⁇ 1 or more, preferably 15 cm ⁇ 1 or more, and usually 100 cm ⁇ 1 or less, and 80 cm ⁇ 1 or less. Preferably, it is more preferably 60 cm ⁇ 1 or less, particularly preferably 40 cm ⁇ 1 or less.
- the Raman half-width is less than the above range, the crystallinity of the particle surface becomes too high, and there are cases where the number of sites where Li enters between layers decreases with charge and discharge. That is, charge acceptance may be reduced.
- the negative electrode is densified by applying it to the current collector and then pressing it, the crystals are likely to be oriented in a direction parallel to the electrode plate, which may lead to a decrease in load characteristics.
- it exceeds the above range the crystallinity of the particle surface is lowered, the reactivity with the non-aqueous electrolyte is increased, and the efficiency may be lowered and the gas generation may be increased.
- the measurement of the Raman spectrum using a Raman spectrometer (manufactured by JASCO Corporation Raman spectrometer), the sample is naturally dropped into the measurement cell and filled, and while irradiating the sample surface in the cell with argon ion laser light, This is done by rotating the cell in a plane perpendicular to the laser beam.
- the resulting Raman spectrum, the intensity I A of the peak P A in the vicinity of 1580 cm -1, and measuring the intensity I B of a peak P B in the vicinity of 1360 cm -1, the intensity ratio R (R I B / I A) Is calculated.
- the Raman R value calculated by the measurement is defined as the Raman R value of the carbonaceous material of the present invention.
- the half width of the peak P A in the vicinity of 1580 cm -1 of the resulting Raman spectrum was measured, which is defined as the Raman half-value width of the carbonaceous material of the present invention.
- said Raman measurement conditions are as follows. Argon ion laser wavelength: 514.5nm ⁇ Laser power on the sample: 15-25mW ⁇ Resolution: 10-20cm -1 Measurement range: 1100 cm -1 to 1730 cm -1 ⁇ Raman R value, Raman half width analysis: background processing, -Smoothing processing: Simple average, 5 points of convolution
- the orientation ratio of the carbonaceous material is usually 0.005 or more, preferably 0.01 or more, more preferably 0.015 or more, and usually 0.67 or less. When the orientation ratio is below the above range, the high-density charge / discharge characteristics may deteriorate.
- the upper limit of the above range is the theoretical upper limit value of the orientation ratio of the carbonaceous material.
- the orientation ratio is measured by X-ray diffraction after pressure-molding the sample.
- Set the molded body obtained by filling 0.47 g of the sample into a molding machine with a diameter of 17 mm and compressing it with 58.8 MN ⁇ m -2 so that it is flush with the surface of the sample holder for measurement.
- X-ray diffraction is measured.
- From the (110) diffraction and (004) diffraction peak intensities of the obtained carbon a ratio represented by (110) diffraction peak intensity / (004) diffraction peak intensity is calculated.
- the orientation ratio calculated by the measurement is defined as the orientation ratio of the carbonaceous material of the present invention.
- the X-ray diffraction measurement conditions are as follows. “2 ⁇ ” indicates a diffraction angle.
- ⁇ Target Cu (K ⁇ ray) graphite monochromator
- Light receiving slit 0.15
- Scattering slit 0.5 degree / measurement range and step angle / measurement time: (110) plane: 75 degrees ⁇ 2 ⁇ ⁇ 80 degrees 1 degree / 60 seconds (004) plane: 52 degrees ⁇ 2 ⁇ ⁇ 57 degrees 1 degree / 60 seconds
- the aspect ratio of the carbonaceous material is usually 1 or more and usually 10 or less, preferably 8 or less, and more preferably 5 or less. If the aspect ratio exceeds the above range, streaking or a uniform coated surface cannot be obtained when forming an electrode plate, and the high current density charge / discharge characteristics may deteriorate.
- the lower limit of the above range is the theoretical lower limit value of the aspect ratio of the carbonaceous material.
- the aspect ratio by magnifying the carbonaceous material particles with a scanning electron microscope. Carbonaceous material particles when three-dimensional observation is performed by selecting arbitrary 50 graphite particles fixed to the end face of a metal having a thickness of 50 ⁇ m or less and rotating and tilting the stage on which the sample is fixed. The longest diameter a and the shortest diameter b orthogonal to it are measured, and the average value of a / b is obtained.
- the aspect ratio (a / b) obtained by the measurement is defined as the aspect ratio of the carbonaceous material of the present invention.
- any known method can be used for producing the electrode as long as the effects of the present invention are not significantly impaired. For example, it is formed by adding a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler, etc. to a negative electrode active material to form a slurry, which is applied to a current collector, dried and then pressed. Can do.
- a method of forming a thin film layer (negative electrode active material layer) containing the above-described negative electrode active material by a technique such as vapor deposition, sputtering, or plating is also used.
- the current collector for holding the negative electrode active material As the current collector for holding the negative electrode active material, a known material can be arbitrarily used. Examples of the current collector for the negative electrode include metal materials such as aluminum, copper, nickel, stainless steel, and nickel-plated steel. Copper is particularly preferable from the viewpoint of ease of processing and cost.
- 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, etc. when the current collector is a metal material.
- a metal thin film is preferable, a copper foil is more preferable, and a rolled copper foil by a rolling method and an electrolytic copper foil by an electrolytic method are more preferable.
- 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. This is because if the thickness of the negative electrode current collector is too thick, the capacity of the entire battery may be too low, and conversely if it is too thin, handling may be difficult.
- the binder for binding the negative electrode active material is not particularly limited as long as it is a material that is stable with respect to the non-aqueous electrolyte solution and the solvent used in manufacturing the electrode.
- resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, polyimide, cellulose, nitrocellulose; SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluororubber, 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 copoly
- the ratio of the binder to 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% by mass. The following is more preferable, 10% by mass or less is further preferable, and 8% by mass or less is particularly 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.
- a thickener is normally used in order to adjust the viscosity of the slurry at the time of producing a negative electrode active material layer.
- 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 electrode structure when the negative electrode active material is converted 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 Further 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 negative electrode active material layer obtained by subtracting the thickness of the metal foil (current collector) from the negative electrode plate is usually 15 ⁇ m.
- the thickness of the negative electrode active material layer obtained by subtracting the thickness of the metal foil (current collector) from the negative electrode plate is usually 15 ⁇ m.
- 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.
- Positive electrode ⁇ positive electrode active material> The positive electrode active material used for the positive electrode is described below.
- composition 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 transition metal of the lithium transition metal composite oxide is preferably V, Ti, Cr, Mn, Fe, Co, Ni, Cu or the like, and specific examples include lithium-cobalt composite oxide such as LiCoO 2 , LiMnO 2 , LiMn. Examples thereof include lithium / manganese composite oxides such as 2 O 4 and Li 2 MnO 4 and lithium / nickel composite oxides such as LiNiO 2 . Further, some of the transition metal atoms that are the main components of these lithium transition metal composite oxides are Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, and Si.
- lithium-nickel-cobalt-aluminum composite oxides lithium-cobalt-nickel composite oxides, lithium-cobalt-manganese composite oxides, lithium- Nickel / manganese composite oxide, lithium / nickel / cobalt / manganese composite oxide, and the like can be given.
- lithium / nickel / manganese composite oxide and lithium / nickel / cobalt / manganese composite oxide are preferable because of good battery characteristics.
- substituted ones include, for example, Li 1 + a Ni 0.5 Mn 0.5 O 2 , Li 1 + a Ni 0.8 Co 0.2 O 2 , Li 1 + a Ni 0.85 Co 0.10 Al 0.05 O 2 , Li 1 + a Ni 0.33 Co 0.33 Mn 0.33 O 2 , Li 1 + a Ni 0.45 Mn 0.45 Co 0.1 O 2 , Li 1 + a Ni 0.475 Mn 0.475 Co 0.05 O 2 , Li 1 + a Mn 1.8 Al 0.2 O 4 , Li 1 + a Mn 2 O 4 , Li 1 + a Mn 1.5 Ni 0.5 O 4 , xLi 2 MnO 3.
- LiFePO 4 Li 3 Fe 2 (PO 4) 3, LiFeP 2 O 7 , etc.
- lithium transition metal phosphate compounds are Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Examples include those substituted with other metals such as Nb and Si.
- iron phosphates such as LiFePO 4 , Li 3 Fe 2 (PO 4 ) 3 , and LiFeP 2 O 7 are preferably used because they are less likely to cause metal elution at high temperatures and charged states and are inexpensive. It is done.
- the above-mentioned “with Li x MPO 4 as the basic composition” means not only the composition represented by the composition formula but also a part of the site such as Fe in the crystal structure substituted with another element. Is also included. Furthermore, it means that not only a stoichiometric composition but also a non-stoichiometric composition in which some elements are deficient or the like is included.
- Other elements to be substituted are preferably elements such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, and Si. In the case of performing the substitution of other elements, the content is preferably 0.1 mol% or more and 5 mol% or less, more preferably 0.2 mol% or more and 2.5 mol% or less.
- the said positive electrode active material may be used independently and may use 2 or more types together.
- foreign elements may be introduced into the lithium transition metal-based compound powder of the present invention. Different elements include B, Na, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Ru, Rh, Pd, Ag, In, Sn, Sb. Te, Ba, Ta, Mo, W, Re, Os, Ir, Pt, Au, Pb, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu , Bi, N, F, Cl, Br, or I. These foreign elements may be incorporated into the crystal structure of the lithium transition metal compound, or may not be incorporated into the crystal structure of the lithium transition metal compound, and may be a single element or compound on the particle surface or grain boundary. May be unevenly distributed.
- 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 by mass with respect to the positive electrode active material, preferably 0.1 ppm or more, more preferably 1 ppm or more, still more 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. In the case where it is too high, the resistance may increase in order to inhibit the entry and exit of lithium ions, so this composition range is preferable.
- a material in which a material having a different composition is attached to the surface of the positive electrode active material is also referred to as “positive electrode active material”.
- the 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, which are conventionally used. It is preferable that the secondary particles have a spherical shape or an elliptical shape.
- an electrochemical element expands and contracts as the active material in the electrode expands and contracts as it is charged and discharged. Therefore, the active material is easily damaged due to the stress or the conductive path is broken. Therefore, it is preferable that the primary particles are aggregated to form secondary particles, rather than a single particle active material having only primary particles, in order to relieve expansion and contraction stress and prevent deterioration.
- spherical or oval spherical particles are less oriented during molding of the electrode than plate-like equiaxed particles, so that the expansion and contraction of the electrode during charging and discharging is small, and the electrode is produced.
- the mixing with the conductive material is also preferable because it is easy to mix uniformly.
- the median diameter d 50 of the positive electrode active material particles is preferably 0.1 ⁇ m or more, more preferably 0.5 ⁇ m or more,
- the upper limit is preferably 20 ⁇ m or less, more preferably 18 ⁇ m or less, still more preferably 16 ⁇ m or less, and most preferably 15 ⁇ m or less. If the lower limit is not reached, a high tap density product may not be obtained. If the upper limit is exceeded, it takes time for the diffusion of lithium in the particles. When 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 filling property at the time of forming the positive electrode can be further improved.
- the median diameter d 50 is measured by a known laser diffraction / scattering particle size distribution measuring apparatus.
- 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 0.03 ⁇ m or more, more preferably 0.05 ⁇ 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
- 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 active material, a binder, and, if necessary, a conductive material and a thickener mixed in a dry form into a sheet form are pressure-bonded to the positive electrode current collector, or these materials are liquid media
- 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 95 mass% or less, More preferably, it is 93 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 , further preferably 2.2 g / cm 3 or more, and preferably 4.0 g as an upper limit. / cm 3 or less, more preferably 3.8 g / cm 3 or less, more preferably 3.6 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 for manufacturing the positive electrode active material layer is not particularly limited, and in the case of a coating method, any material that can be dissolved or dispersed in a liquid medium used during electrode manufacturing 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 3% by mass or more, and the upper limit is usually 80% by mass or less, preferably 60%. It is not more than mass%, more preferably not more than 40 mass%, most preferably not more than 10 mass%. If the ratio of the binder is too low, the positive electrode active material cannot be sufficiently retained, and the mechanical strength of the positive electrode is insufficient, 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.
- a thickener can be used normally in order to adjust the viscosity of the slurry used for manufacture of a positive electrode active material layer.
- an aqueous medium it is preferably slurried using a thickener and a latex such as styrene-butadiene rubber (SBR).
- SBR styrene-butadiene rubber
- 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 0.5% by mass or more, more preferably 0.6% 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 from the viewpoint of reducing the electronic contact resistance between the current collector and the positive electrode active material layer.
- the conductive assistant include noble metals such as carbon, gold, platinum, and silver.
- 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 positive electrode active material layer obtained by subtracting the thickness of the metal foil (current collector) from the positive electrode plate is set on one side of the current collector.
- the lower limit is preferably 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.
- a separator is interposed between the positive electrode and the negative electrode in order to prevent a short circuit.
- the nonaqueous electrolytic solution of the present invention is usually used by impregnating the separator.
- the material and shape of the separator are not particularly limited, and known ones can be arbitrarily adopted as long as the effects of the present invention are not significantly impaired.
- a resin, glass fiber, inorganic material, etc. formed of a material that is stable with respect to the non-aqueous electrolyte solution of the present invention is used, and a porous sheet or a nonwoven fabric-like material having excellent liquid retention properties is used. Is preferred.
- polyolefins such as polyethylene and polypropylene, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, glass filters and the like can be used. Of these, glass filters and polyolefins are preferred, and polyolefins are more preferred. These materials may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
- the thickness of the separator is arbitrary, but is usually 1 ⁇ m or more, preferably 5 ⁇ m or more, more preferably 10 ⁇ m or more, and usually 50 ⁇ m or less, preferably 40 ⁇ m or less, more preferably 30 ⁇ m or less. If the separator is 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 the battery performance such as the rate characteristic may be lowered, but also the energy density of the whole non-aqueous electrolyte secondary battery may be lowered.
- the porosity of the separator is arbitrary, but is usually 20% or more, preferably 35% or more, more preferably 45% or more, Further, it is usually 90% or less, preferably 85% or less, and more preferably 75% or less. If the porosity is 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.
- inorganic materials for example, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate are used. Used.
- a thin film shape such as a nonwoven fabric, a woven fabric, or a microporous film is used.
- the thin film shape those having a pore diameter of 0.01 to 1 ⁇ m and a thickness of 5 to 50 ⁇ m are preferably used.
- a separator formed by forming a composite porous layer containing 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 characteristics of the non-electrolyte secondary battery of the separator can be grasped by the Gurley value.
- Gurley value indicates the difficulty of air passage in the film thickness direction, and is expressed as the number of seconds required for 100 ml of air to pass through the film. It means that it is harder to go through. That is, a smaller value means better communication in the thickness direction of the film, and a larger value means lower communication in the thickness direction of the film. Communication is the degree of connection of holes in the film thickness direction. If the Gurley value of the separator of the present invention is low, it can be used for various purposes.
- a low Gurley value means that lithium ions can be easily transferred and is preferable because of excellent battery performance.
- the Gurley value of the separator is optional, but is preferably 10 to 1000 seconds / 100 ml, more preferably 15 to 800 seconds / 100 ml, and still more preferably 20 to 500 seconds / 100 ml. If the Gurley value is 1000 seconds / 100 ml or less, the electrical resistance is substantially low, which is preferable as a separator.
- the electrode group has a laminated structure in which the positive electrode plate and the negative electrode plate are interposed through the separator, and a structure in which the positive electrode plate and the negative electrode plate are wound in a spiral shape through the separator. Either is acceptable.
- the ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupation ratio) is usually 40% or more, preferably 50% or more, and usually 90% or less, preferably 80% or less. .
- the battery capacity decreases. 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 material of the outer case is not particularly limited as long as it is a substance that is stable with respect to the non-aqueous electrolyte used. Specifically, a nickel-plated steel plate, stainless steel, aluminum, an aluminum alloy, a metal such as a magnesium alloy, or a laminated film (laminate film) of a resin and an aluminum foil is used. From the viewpoint of weight reduction, an aluminum or aluminum alloy metal or a laminate film is preferably used.
- 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.
- Protection elements such as PTC (Positive Temperature Coefficient), thermal fuse, thermistor, which increases resistance when abnormal heat is generated or excessive current flows, shuts off current flowing through the circuit due to sudden increase in battery internal pressure or internal temperature during abnormal heat generation
- a valve current cutoff valve or the like can be used. It is preferable to select a protective element that does not operate under normal use at a high current, and it is more preferable that the protective element is designed so as not to cause abnormal heat generation or thermal runaway even without the protective element.
- the non-aqueous electrolyte secondary battery of the present invention is usually configured by housing the non-aqueous electrolyte, the negative electrode, the positive electrode, the separator, and the like in an exterior body.
- This exterior body is not particularly limited, and any known one can be arbitrarily adopted as long as the effects of the present invention are not significantly impaired.
- the material of the exterior body is arbitrary, but usually, for example, nickel-plated iron, stainless steel, aluminum or an alloy thereof, nickel, titanium, or the like is used.
- the shape of the exterior body is also arbitrary, and may be any of a cylindrical shape, a square shape, a laminate shape, a coin shape, a large size, and the like.
- the compound of the general formula (1) used in this example was synthesized by the following method.
- Example A [Production of negative electrode] 98 parts by mass of carbonaceous material, 100 parts by mass of an aqueous dispersion of sodium carboxymethylcellulose (concentration of 1% by mass of carboxymethylcellulose sodium) and an aqueous dispersion of styrene-butadiene rubber (styrene-butadiene, respectively) as a thickener and binder 1 part by mass of rubber concentration 50 mass%) was added and mixed with a disperser to form a slurry. The obtained slurry was applied to a copper foil having a thickness of 10 ⁇ m, dried, and rolled with a press. The active material layer was 30 mm wide, 40 mm long, 5 mm wide, and 9 mm long uncoated. A negative electrode used in Examples 1 to 7, Comparative Examples 1 to 5, and Reference Example 1 was cut into a shape having a portion.
- a slurry is prepared by mixing 90% by mass of LiCoO 2 as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride as a binder in an N-methylpyrrolidone solvent. did.
- the obtained slurry was applied to an aluminum foil having a thickness of 15 ⁇ m, dried, and rolled with a press.
- the active material layer was 30 mm in width, 40 mm in length, 5 mm in width, and 9 mm in length.
- a positive electrode used in Examples 1 to 7, Comparative Examples 1 to 5, and Reference Example 1 was cut into a shape having a work part.
- the positive electrode, the negative electrode, and the 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 each of the electrolyte solutions shown in Table 1 was placed in the bag. Then, a sheet-like battery was manufactured and used as Examples 1 to 7, Comparative Examples 1 to 5, and Reference Example 1.
- a non-aqueous electrolyte secondary battery is charged while being sandwiched between glass plates and pressurized at 25 ° C. to 4.1 V at a current corresponding to 0.2 C, and then 3 V at a constant current of 0.2 C.
- CCCV charge constant current-constant voltage charge
- 0.05C cut a constant current-constant voltage charge
- 3V 3V at 0.2C
- 1C represents a current value for discharging the reference capacity of the battery in one hour
- 0.2C represents a current value of 1/5 thereof.
- the batteries using the non-aqueous electrolyte according to the present invention are the batteries using the non-aqueous electrolyte other than the non-aqueous electrolyte according to the present invention (Comparative Example). Compared with 1 to 5 and Reference Example 1), it can be seen that the amount of gas generated during high-temperature storage is low and the remaining capacity after high-temperature storage is excellent.
- the compound represented by the general formula (1) alone has the function of protecting the electrode surface and improving the battery durability (Reference Example 1), but together with the compound represented by the general formula (1), cyano
- the electrode protective layer formed by the compound represented by the general formula (1) incorporates at least one selected from a compound having a cyano group, a cyclic ester compound containing a sulfur atom, and a compound having an isocyanate group.
- a basic electrolyte was prepared by dissolving LiPF 6 dried in a mixture of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate (volume ratio 30:30:40) to a ratio of 1 mol / L. .
- the basic electrolyte solution was mixed with the compounds shown in Table 3 to obtain electrolyte solutions used in Examples 8 to 10, Comparative Examples 6 to 11, and Reference Example 2.
- a sheet-like battery was produced in the same manner as in Example ⁇ A> except that the positive electrode and the electrolytic solution were used.
- a non-aqueous electrolyte secondary battery is charged while being sandwiched between glass plates and pressurized at 25 ° C. to 4.1 V at a current corresponding to 0.2 C, and then 3 V at a constant current of 0.2 C.
- the cycle was discharged twice until CCCV charge (0.05 C cut) to 4.4 V at a current corresponding to 0.2 C, and then the battery was stabilized by discharging to 0.2 V at 3 C. Subsequently, after CCCV charge (0.05C cut) to 4.4V at 0.2C, it was discharged again to 3V at 0.2C, and the initial discharge capacity was obtained.
- the batteries using the non-aqueous electrolyte solution according to the present invention are the batteries using the non-aqueous electrolyte solution that is not the non-aqueous electrolyte solution according to the present invention (Comparative Example).
- the high temperature storage capacity retention rate, the high temperature cycle capacity retention rate, and the discharge capacity after the high temperature cycle are excellent.
- a cyclic carbonate compound having a carbon-carbon double bond or a chain carbonate having a carbon-carbon triple bond is combined with a cyclic ester containing a sulfur atom (Comparative Examples 7 and 9)
- the compound represented by the general formula (1) alone has a function of protecting the electrode surface and improving the battery durability (Reference Example 2)
- the compound represented by the general formula (1) together with the sulfur atom By introducing a cyclic ester compound containing, it is possible to provide a more excellent high-temperature storage capacity retention rate, high-temperature cycle capacity retention rate, and discharge capacity after a high-temperature cycle. This is because the electrode protective layer formed by the compound of the general formula (1) incorporates a compound containing a sulfur atom, and the electrode surface durability is remarkably improved. Is presumed to be caused.
- the initial charge capacity and input / output characteristics of the non-aqueous electrolyte secondary battery can be improved.
- the non-aqueous electrolyte secondary battery using the non-aqueous electrolyte 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. It has excellent output characteristics and is useful. Therefore, the non-aqueous electrolyte solution of the present invention and the non-non-aqueous electrolyte secondary battery using the same can be used for various known applications.
- 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
このような背景の下、特許文献1、2に記載されている電解液を用いた非水電解液電池では、充電状態の電池を高温で放置したり、連続充放電サイクルを行うと、正極上で不飽和環状カーボネートまたはその誘導体が酸化分解して炭酸ガスを発生するという問題があった。このような使用環境下で炭酸ガスが発生すると、例えば、電池の安全弁が作動したり、電池が膨張する等により電池自体が使用不能になる場合がある。
さらに、特許文献3、4に記載の添加剤を非水電解質に含有させても、電極上での副反応による劣化がおき、電池の保存特性及びサイクル特性が不十分であるという問題があった。
a)リチウム塩とこれを溶解する非水系溶媒を含有してなる非水系電解液であって、該非水系電解液が、下記一般式(1)で表される化合物を含有し、さらにシアノ基を有する化合物、硫黄原子を含む環状エステル化合物、イソシアネート基を有する化合物からなる群のうち少なくとも1種以上を含有することを特徴とする非水系電解液。
b)前記一般式(1)で表される化合物が、下記一般式(2)で表される化合物であることを特徴とする、a)に記載の非水系電解液。
c)前記シアノ基を有する化合物が、下記一般式(3)で表される化合物である、a)またはb)に記載の非水系電解液。
d)前記シアノ基を有する化合物が、NC-(CH2)n-CN(n=2~6)で表される化合物である、c)に記載の非水系電解液。
e)前記硫黄原子を含む環状エステルが、下記一般式(4)で表される化合物である、a)~d)の何れかに記載の非水系電解液。
f)前記イソシアネート基を有する化合物が、下記一般式(5)で表される化合物である、a)~e)の何れかに記載の非水系電解液。
g)前記非水系電解液が、炭素-炭素二重結合を有する環状カーボネート及びフッ素原子を有する環状カーボネートから選ばれる群の中から少なくとも1種以上を含有する、a)~f)に記載の非水系電解液。
1-1.電解質
<リチウム塩>
電解質としては、通常、リチウム塩が用いられる。リチウム塩としては、この用途に用いることが知られているものであれば特に制限がなく、任意のものを用いることができ、具体的には以下のものが挙げられる。
Li2PO3F、LiPO2F2等のフルオロリン酸リチウム類;
LiWOF5等のタングステン酸リチウム類;
HCO2Li、CH3CO2Li、CH2FCO2Li、CHF2CO2Li、CF3CO2Li、CF3CH2CO2Li、CF3CF2CO2Li、CF3CF2CF2CO2Li、CF3CF2CF2CF2CO2Li等のカルボン酸リチウム塩類;
FSO3Li、CH3SO3Li、CH2FSO3Li、CHF2SO3Li、CF3SO3Li、CF3CF2SO3Li、CF3CF2CF2SO3Li、CF3CF2CF2CF2SO3Li等のスルホン酸リチウム塩類;
LiN(FCO)2、LiN(FCO)(FSO2)、LiN(FSO2)2、LiN(FSO2)(CF3SO2)、LiN(CF3SO2)2、LiN(C2F5SO2)2、リチウム環状1,2-パーフルオロエタンジスルホニルイミド、リチウム環状1,3-パーフルオロプロパンジスルホニルイミド、LiN(CF3SO2)(C4F9SO2)等のリチウムイミド塩類;
LiC(FSO2)3、LiC(CF3SO2)3、LiC(C2F5SO2)3等のリチウムメチド塩類;
リチウムジフルオロオキサラトボレート、リチウムビス(オキサラト)ボレート等のリチウムオキサラトボレート塩類;
リチウムテトラフルオロオキサラトホスフェート、リチウムジフルオロビス(オキサラト)ホスフェート、リチウムトリス(オキサラト)ホスフェート等のリチウムオキサラトホスフェート塩類;
その他、LiPF4(CF3)2、LiPF4(C2F5)2、LiPF4(CF3SO2)2、LiPF4(C2F5SO2)2、LiBF3CF3、LiBF3C2F5、LiBF3C3F7、LiBF2(CF3)2、LiBF2(C2F5)2、LiBF2(CF3SO2)2、LiBF2(C2F5SO2)2等の含フッ素有機リチウム塩類;
等が挙げられる。
非水溶媒としては、飽和環状カーボネート、フッ素原子を有する環状カーボネート、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可能である。また、これら非水溶媒は、任意に組み合わせて使用してもよい。
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る。具体的には、炭素数2~4の飽和環状カーボネートとしては、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。中でも、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。
フッ素原子を有する環状カーボネート(以下、フッ素化環状カーボネートともいう)としては、フッ素原子を有する環状カーボネートであれば、特に制限はない。
フッ素化環状カーボネートとしては、炭素原子数2~6のアルキレン基を有する環状カーボネートの誘導体が挙げられ、例えばエチレンカーボネート誘導体である。エチレンカーボネート誘導体としては、例えば、エチレンカーボネート又はアルキル基(例えば、炭素原子数1~4個のアルキル基)で置換されたエチレンカーボネートのフッ素化物が挙げられ、中でもフッ素原子が1~8個のものが好ましい。
尚、フッ素化環状カーボネートの溶媒および助剤としての役割について上述したが、溶媒あるいは助剤の配合量に明確な境界は存在せず、任意の割合で非水系電解液を調製できるものとする。
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、ジエチルカーボネート、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、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。
また、フッ素原子を有する鎖状カーボネート類(以下、フッ素化鎖状カーボネートともいう)も好適に用いることができる。フッ素化鎖状カーボネートが有するフッ素原子の数は、1以上であれば特に制限されないが、通常6以下であり、好ましくは4以下である。フッ素化鎖状カーボネートが複数のフッ素原子を有する場合、それらは互いに同一の炭素に結合していてもよく、異なる炭素に結合していてもよい。フッ素化鎖状カーボネートとしては、フッ素化ジメチルカーボネート誘導体、フッ素化エチルメチルカーボネート誘導体、フッ素化ジエチルカーボネート誘導体等が挙げられる。
尚、フッ素化鎖状カーボネートの溶媒および助剤としての役割について上述したが、溶媒あるいは助剤の配合量に明確な境界は存在せず、任意の割合で非水系電解液を調製できるものとする。
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。
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。
エーテル系化合物としては、一部の水素がフッ素にて置換されていてもよい炭素数3~10の鎖状エーテル、及び炭素数3~6の環状エーテルが好ましい。
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(2-フルオロエチル)エーテル、ジ(2,2-ジフルオロエチル)エーテル、ジ(2,2,2-トリフルオロエチル)エーテル、エチル(2-フルオロエチル)エーテル、エチル(2,2,2-トリフルオロエチル)エーテル、エチル(1,1,2,2-テトラフルオロエチル)エーテル、(2-フルオロエチル)(2,2,2-トリフルオロエチル)エーテル、(2-フルオロエチル)(1,1,2,2-テトラフルオロエチル)エーテル、(2,2,2-トリフルオロエチル)(1,1,2,2-テトラフルオロエチル)エーテル、エチル-n-プロピルエーテル、エチル(3-フルオロ-n-プロピル)エーテル、エチル(3,3,3-トリフルオロ-n-プロピル)エーテル、エチル(2,2,3,3-テトラフルオロ-n-プロピル)エーテル、エチル(2,2,3,3,3-ペンタフルオロ-n-プロピル)エーテル、2-フルオロエチル-n-プロピルエーテル、(2-フルオロエチル)(3-フルオロ-n-プロピル)エーテル、(2-フルオロエチル)(3,3,3-トリフルオロ-n-プロピル)エーテル、(2-フルオロエチル)(2,2,3,3-テトラフルオロ-n-プロピル)エーテル、(2-フルオロエチル)(2,2,3,3,3-ペンタフルオロ-n-プロピル)エーテル、2,2,2-トリフルオロエチル-n-プロピルエーテル、(2,2,2-トリフルオロエチル)(3-フルオロ-n-プロピル)エーテル、(2,2,2-トリフルオロエチル)(3,3,3-トリフルオロ-n-プロピル)エーテル、(2,2,2-トリフルオロエチル)(2,2,3,3-テトラフルオロ-n-プロピル)エーテル、(2,2,2-トリフルオロエチル)(2,2,3,3,3-ペンタフルオロ-n-プロピル)エーテル、1,1,2,2-テトラフルオロエチル-n-プロピルエーテル、(1,1,2,2-テトラフルオロエチル)(3-フルオロ-n-プロピル)エーテル、(1,1,2,2-テトラフルオロエチル)(3,3,3-トリフルオロ-n-プロピル)エーテル、(1,1,2,2-テトラフルオロエチル)(2,2,3,3-テトラフルオロ-n-プロピル)エーテル、(1,1,2,2-テトラフルオロエチル)(2,2,3,3,3-ペンタフルオロ-n-プロピル)エーテル、ジ-n-プロピルエーテル、(n-プロピル)(3-フルオロ-n-プロピル)エーテル、(n-プロピル)(3,3,3-トリフルオロ-n-プロピル)エーテル、(n-プロピル)(2,2,3,3-テトラフルオロ-n-プロピル)エーテル、(n-プロピル)(2,2,3,3,3-ペンタフルオロ-n-プロピル)エーテル、ジ(3-フルオロ-n-プロピル)エーテル、(3-フルオロ-n-プロピル)(3,3,3-トリフルオロ-n-プロピル)エーテル、(3-フルオロ-n-プロピル)(2,2,3,3-テトラフルオロ-n-プロピル)エーテル、(3-フルオロ-n-プロピル)(2,2,3,3,3-ペンタフルオロ-n-プロピル)エーテル、ジ(3,3,3-トリフルオロ-n-プロピル)エーテル、(3,3,3-トリフルオロ-n-プロピル)(2,2,3,3-テトラフルオロ-n-プロピル)エーテル、(3,3,3-トリフルオロ-n-プロピル)(2,2,3,3,3-ペンタフルオロ-n-プロピル)エーテル、ジ(2,2,3,3-テトラフルオロ-n-プロピル)エーテル、(2,2,3,3-テトラフルオロ-n-プロピル)(2,2,3,3,3-ペンタフルオロ-n-プロピル)エーテル、ジ(2,2,3,3,3-ペンタフルオロ-n-プロピル)エーテル、ジ-n-ブチルエーテル、ジメトキシメタン、メトキシエトキシメタン、メトキシ(2-フルオロエトキシ)メタン、メトキシ(2,2,2-トリフルオロエトキシ)メタンメトキシ(1,1,2,2-テトラフルオロエトキシ)メタン、ジエトキシメタン、エトキシ(2-フルオロエトキシ)メタン、エトキシ(2,2,2-トリフルオロエトキシ)メタン、エトキシ(1,1,2,2-テトラフルオロエトキシ)メタン、ジ(2-フルオロエトキシ)メタン、(2-フルオロエトキシ)(2,2,2-トリフルオロエトキシ)メタン、(2-フルオロエトキシ)(1,1,2,2-テトラフルオロエトキシ)メタンジ(2,2,2-トリフルオロエトキシ)メタン、(2,2,2-トリフルオロエトキシ)(1,1,2,2-テトラフルオロエトキシ)メタン、ジ(1,1,2,2-テトラフルオロエトキシ)メタン、ジメトキシエタン、メトキシエトキシエタン、メトキシ(2-フルオロエトキシ)エタン、メトキシ(2,2,2-トリフルオロエトキシ)エタン、メトキシ(1,1,2,2-テトラフルオロエトキシ)エタン、ジエトキシエタン、エトキシ(2-フルオロエトキシ)エタン、エトキシ(2,2,2-トリフルオロエトキシ)エタン、エトキシ(1,1,2,2-テトラフルオロエトキシ)エタン、ジ(2-フルオロエトキシ)エタン、(2-フルオロエトキシ)(2,2,2-トリフルオロエトキシ)エタン、(2-フルオロエトキシ)(1,1,2,2-テトラフルオロエトキシ)エタン、ジ(2,2,2-トリフルオロエトキシ)エタン、(2,2,2-トリフルオロエトキシ)(1,1,2,2-テトラフルオロエトキシ)エタン、ジ(1,1,2,2-テトラフルオロエトキシ)エタン、エチレングリコールジ-n-プロピルエーテル、エチレングリコールジ-n-ブチルエーテル、ジエチレングリコールジメチルエーテル等が挙げられる。
スルホン系化合物としては、炭素数3~6の環状スルホン、及び炭素数2~6の鎖状スルホンが好ましい。1分子中のスルホニル基の数は、1又は2であることが好ましい。
RとR1は、式中で定められた範囲であれば特に限定されないが、好ましくは、水素、フッ素、置換基を有してもよい飽和脂肪族炭化水素基、置換基を有してもよい不飽和脂肪族炭化水素基、置換基を有してもよい芳香族炭化水素基があげられる。
R2およびR4は、式中で定められた範囲であれば特に限定されないが、好ましくは、置換基を有してもよい飽和脂肪族炭化水素基、置換基を有してもよい不飽和脂肪族炭化水素、置換基を有してもよい芳香族炭化水素・芳香族ヘテロ環があげられる。
R3は、式中で定められた範囲であれば特に限定されないが、好ましくは、Li、置換基を有してもよい飽和脂肪族炭化水素、置換基を有してもよい不飽和脂肪族炭化水素、置換基を有してもよい芳香族炭化水素・芳香族ヘテロ環があげられる。
好ましい芳香族炭化水素としては、フェニル基、2-フルオロフェニル基、3-フルオロフェニル基、2、4-ジフルオロフェニル基、2、6-ジフルオロフェニル基、3、5-ジフルオロフェニル基、2、4、6-トリフルオロフェニル基、があげられる。
また、これらの中でも、n=1、m=0が好ましい。双方が0である場合、環のひずみから安定性が悪化し、反応性が高くなりすぎて副反応が増加する恐れが有る。また、n=2以上、またはn=1であっても、m=1以上で有る場合、環状より鎖状である方が安定となる恐れがあり、初期の特性を示さない恐れが有る。
また、分子量は、より好ましくは100以上であり、また、より好ましくは200以下である。この範囲であれば、非水系電解液に対する一般式(1)の溶解性をさらに確保しやすく、本発明の効果が十分にさらに発現されやすい。
これら、好ましい条件を持つ化合物を以下に示す。
本発明の非水系電解液は、一般式(1)で表される化合物とともに、シアノ基を有する化合物、硫黄原子を含む環状エステル化合物及びイソシアネート基を有する化合物の少なくとも1種類以上含有することを特徴とする。これらの化合物を併用することによって、電極上での副反応を抑制するとともに、二次電池の保存特性を改善することができる。
アセトニトリル、プロピオニトリル、ブチロニトリル、イソブチロニトリル、バレロニトリル、イソバレロニトリル、ラウロニトリル、2-メチルブチロニトリル、トリメチルアセトニトリル、ヘキサンニトリル、シクロペンタンカルボニトリル、シクロヘキサンカルボニトリル、アクリロニトリル、メタクリロニトリル、クロトノニトリル、3-メチルクロトノニトリル、2-メチル-2-ブテン二トリル、2-ペンテンニトリル、2-メチル-2-ペンテンニトリル、3-メチル-2-ペンテンニトリル、2-ヘキセンニトリル、フルオロアセトニトリル、ジフルオロアセトニトリル、トリフルオロアセトニトリル、2-フルオロプロピオニトリル、3-フルオロプロピオニトリル、2,2-ジフルオロプロピオニトリル、2,3-ジフルオロプロピオニトリル、3,3-ジフルオロプロピオニトリル、2,2,3-トリフルオロプロピオニトリル、3,3,3-トリフルオロプロピオニトリル、3,3'-オキシジプロピオニトリル、3,3'-チオジプロピオニトリル、1,2,3-プロパントリカルボニトリル、1,3,5-ペンタントリカルボニトリル、ペンタフルオロプロピオニトリル等のシアノ基を1つ有する化合物;
メチルシアネート、エチルシアネート、プロピルシアネート、ブチルシアネート、ペンチルシアネート、ヘキシルシアネート、ヘプチルシアネートなどのシアネート化合物;
ジメチル亜ホスフィン酸シアニド、シアノホスホン酸ジメチル、シアノ亜ホスホン酸ジメチル、メチルホスホン酸シアノメチル、メチル亜ホスホン酸シアノメチル、リン酸シアノジメチル、亜リン酸シアノジメチルなどの含リン化合物;
等が挙げられる。
1,3-プロパンスルトン、1-フルオロ-1,3-プロパンスルトン、2-フルオロ-1,3-プロパンスルトン、3-フルオロ-1,3-プロパンスルトン、1-メチル-1,3-プロパンスルトン、2-メチル-1,3-プロパンスルトン、3-メチル-1,3-プロパンスルトン、1-プロペン-1,3-スルトン、2-プロペン-1,3-スルトン、1-フルオロ-1-プロペン-1,3-スルトン、2-フルオロ-1-プロペン-1,3-スルトン、3-フルオロ-1-プロペン-1,3-スルトン、1-フルオロ-2-プロペン-1,3-スルトン、2-フルオロ-2-プロペン-1,3-スルトン、3-フルオロ-2-プロペン-1,3-スルトン、1-メチル-1-プロペン-1,3-スルトン、2-メチル-1-プロペン-1,3-スルトン、3-メチル-1-プロペン-1,3-スルトン、1-メチル-2-プロペン-1,3-スルトン、2-メチル-2-プロペン-1,3-スルトン、3-メチル-2-プロペン-1,3-スルトン、1,4-ブタンスルトン、1-フルオロ-1,4-ブタンスルトン、2-フルオロ-1,4-ブタンスルトン、3-フルオロ-1,4-ブタンスルトン、4-フルオロ-1,4-ブタンスルトン、1-メチル-1,4-ブタンスルトン、2-メチル-1,4-ブタンスルトン、3-メチル-1,4-ブタンスルトン、4-メチル-1,4-ブタンスルトン、1-ブテン-1,4-スルトン、2-ブテン-1,4-スルトン、3-ブテン-1,4-スルトン、1-フルオロ-1-ブテン-1,4-スルトン、2-フルオロ-1-ブテン-1,4-スルトン、3-フルオロ-1-ブテン-1,4-スルトン、4-フルオロ-1-ブテン-1,4-スルトン、1-フルオロ-2-ブテン-1,4-スルトン、2-フルオロ-2-ブテン-1,4-スルトン、3-フルオロ-2-ブテン-1,4-スルトン、4-フルオロ-2-ブテン-1,4-スルトン、1-フルオロ-3-ブテン-1,4-スルトン、2-フルオロ-3-ブテン-1,4-スルトン、3-フルオロ-3-ブテン-1,4-スルトン、4-フルオロ-3-ブテン-1,4-スルトン、1-メチル-1-ブテン-1,4-スルトン、2-メチル-1-ブテン-1,4-スルトン、3-メチル-1-ブテン-1,4-スルトン、4-メチル-1-ブテン-1,4-スルトン、1-メチル-2-ブテン-1,4-スルトン、2-メチル-2-ブテン-1,4-スルトン、3-メチル-2-ブテン-1,4-スルトン、4-メチル-2-ブテン-1,4-スルトン、1-メチル-3-ブテン-1,4-スルトン、2-メチル-3-ブテン-1,4-スルトン、3-メチル-3-ブテン-1,4-スルトン、4-メチル-3-ブテン-1,4-スルトン、1,5-ペンタンスルトン、1-フルオロ-1,5-ペンタンスルトン、2-フルオロ-1,5-ペンタンスルトン、3-フルオロ-1,5-ペンタンスルトン、4-フルオロ-1,5-ペンタンスルトン、5-フルオロ-1,5-ペンタンスルトン、1-メチル-1,5-ペンタンスルトン、2-メチル-1,5-ペンタンスルトン、3-メチル-1,5-ペンタンスルトン、4-メチル-1,5-ペンタンスルトン、5-メチル-1,5-ペンタンスルトン、1-ペンテン-1,5-スルトン、2-ペンテン-1,5-スルトン、3-ペンテン-1,5-スルトン、4-ペンテン-1,5-スルトン、1-フルオロ-1-ペンテン-1,5-スルトン、2-フルオロ-1-ペンテン-1,5-スルトン、3-フルオロ-1-ペンテン-1,5-スルトン、4-フルオロ-1-ペンテン-1,5-スルトン、5-フルオロ-1-ペンテン-1,5-スルトン、1-フルオロ-2-ペンテン-1,5-スルトン、2-フルオロ-2-ペンテン-1,5-スルトン、3-フルオロ-2-ペンテン-1,5-スルトン、4-フルオロ-2-ペンテン-1,5-スルトン、5-フルオロ-2-ペンテン-1,5-スルトン、1-フルオロ-3-ペンテン-1,5-スルトン、2-フルオロ-3-ペンテン-1,5-スルトン、3-フルオロ-3-ペンテン-1,5-スルトン、4-フルオロ-3-ペンテン-1,5-スルトン、5-フルオロ-3-ペンテン-1,5-スルトン、1-フルオロ-4-ペンテン-1,5-スルトン、2-フルオロ-4-ペンテン-1,5-スルトン、3-フルオロ-4-ペンテン-1,5-スルトン、4-フルオロ-4-ペンテン-1,5-スルトン、5-フルオロ-4-ペンテン-1,5-スルトン、1-メチル-1-ペンテン-1,5-スルトン、2-メチル-1-ペンテン-1,5-スルトン、3-メチル-1-ペンテン-1,5-スルトン、4-メチル-1-ペンテン-1,5-スルトン、5-メチル-1-ペンテン-1,5-スルトン、1-メチル-2-ペンテン-1,5-スルトン、2-メチル-2-ペンテン-1,5-スルトン、3-メチル-2-ペンテン-1,5-スルトン、4-メチル-2-ペンテン-1,5-スルトン、5-メチル-2-ペンテン-1,5-スルトン、1-メチル-3-ペンテン-1,5-スルトン、2-メチル-3-ペンテン-1,5-スルトン、3-メチル-3-ペンテン-1,5-スルトン、4-メチル-3-ペンテン-1,5-スルトン、5-メチル-3-ペンテン-1,5-スルトン、1-メチル-4-ペンテン-1,5-スルトン、2-メチル-4-ペンテン-1,5-スルトン、3-メチル-4-ペンテン-1,5-スルトン、4-メチル-4-ペンテン-1,5-スルトン、5-メチル-4-ペンテン-1,5-スルトンなどのスルトン化合物;
エチレングリコール硫酸エステル、1,2-プロパンジオール硫酸エステル、1,3-プロパンジオール硫酸エステル、1,2-ブタンジオール硫酸エステル、1,3-ブタンジオール硫酸エステル、2,3-ブタンジオール硫酸エステル、1,4-ブタンジオール硫酸エステル、フェニルエチレングリコール硫酸エステルなどの硫酸エステル化合物;
メチレンメタンジスルホネート、エチレンメタンジスルホネートなどのジスルホネート化合物;
1,2,3-オキサチアゾリジン-2,2-ジオキシド、3-メチル-1,2,3-オキサチアゾリジン-2,2-ジオキシド、3H-1,2,3-オキサチアゾール-2,2-ジオキシド、5H-1,2,3-オキサチアゾール-2,2-ジオキシド、1,2,4-オキサチアゾリジン-2,2-ジオキシド、4-メチル-1,2,4-オキサチアゾリジン-2,2-ジオキシド、3H-1,2,4-オキサチアゾール-2,2-ジオキシド、5H-1,2,4-オキサチアゾール-2,2-ジオキシド、1,2,5-オキサチアゾリジン-2,2-ジオキシド、5-メチル-1,2,5-オキサチアゾリジン-2,2-ジオキシド、3H-1,2,5-オキサチアゾール-2,2-ジオキシド、5H-1,2,5-オキサチアゾール-2,2-ジオキシド、1,2,3-オキサチアジナン-2,2-ジオキシド、3-メチル-1,2,3-オキサチアジナン-2,2-ジオキシド、5,6-ジヒドロ-1,2,3-オキサチアジン-2,2-ジオキシド、1,2,4-オキサチアジナン-2,2-ジオキシド、4-メチル-1,2,4-オキサチアジナン-2,2-ジオキシド、5,6-ジヒドロ-1,2,4-オキサチアジン-2,2-ジオキシド、3,6-ジヒドロ-1,2,4-オキサチアジン-2,2-ジオキシド、3,4-ジヒドロ-1,2,4-オキサチアジン-2,2-ジオキシド、1,2,5-オキサチアジナン-2,2-ジオキシド、5-メチル-1,2,5-オキサチアジナン-2,2-ジオキシド、5,6-ジヒドロ-1,2,5-オキサチアジン-2,2-ジオキシド、3,6-ジヒドロ-1,2,5-オキサチアジン-2,2-ジオキシド、3,4-ジヒドロ-1,2,5-オキサチアジン-2,2-ジオキシド、1,2,6-オキサチアジナン-2,2-ジオキシド、6-メチル-1,2,6-オキサチアジナン-2,2-ジオキシド、5,6-ジヒドロ-1,2,6-オキサチアジン-2,2-ジオキシド、3,4-ジヒドロ-1,2,6-オキサチアジン-2,2-ジオキシド、5,6-ジヒドロ-1,2,6-オキサチアジン-2,2-ジオキシドなどの含窒素化合物;
1,2,3-オキサチアホスラン-2,2-ジオキシド、3-メチル-1,2,3-オキサチアホスラン-2,2-ジオキシド、3-メチル-1,2,3-オキサチアホスラン-2,2,3-トリオキシド、3-メトキシ-1,2,3-オキサチアホスラン-2,2,3-トリオキシド、1,2,4-オキサチアホスラン-2,2-ジオキシド、4-メチル-1,2,4-オキサチアホスラン-2,2-ジオキシド、4-メチル-1,2,4-オキサチアホスラン-2,2,4-トリオキシド、4-メトキシ-1,2,4-オキサチアホスラン-2,2,4-トリオキシド、1,2,5-オキサチアホスラン-2,2-ジオキシド、5-メチル-1,2,5-オキサチアホスラン-2,2-ジオキシド、5-メチル-1,2,5-オキサチアホスラン-2,2,5-トリオキシド、5-メトキシ-1,2,5-オキサチアホスラン-2,2,5-トリオキシド、1,2,3-オキサチアホスフィナン-2,2-ジオキシド、3-メチル-1,2,3-オキサチアホスフィナン-2,2-ジオキシド、3-メチル-1,2,3-オキサチアホスフィナン-2,2,3-トリオキシド、3-メトキシ-1,2,3-オキサチアホスフィナン-2,2,3-トリオキシド、1,2,4-オキサチアホスフィナン-2,2-ジオキシド、4-メチル-1,2,4-オキサチアホスフィナン-2,2-ジオキシド、4-メチル-1,2,4-オキサチアホスフィナン-2,2,3-トリオキシド、4-メチル-1,5,2,4-ジオキサチアホスフィナン-2,4-ジオキシド、4-メトキシ-1,5,2,4-ジオキサチアホスフィナン-2,4-ジオキシド、3-メトキシ-1,2,4-オキサチアホスフィナン-2,2,3-トリオキシド、1,2,5-オキサチアホスフィナン-2,2-ジオキシド、5-メチル-1,2,5-オキサチアホスフィナン-2,2-ジオキシド、5-メチル-1,2,5-オキサチアホスフィナン-2,2,3-トリオキシド、5-メトキシ-1,2,5-オキサチアホスフィナン-2,2,3-トリオキシド、1,2,6-オキサチアホスフィナン-2,2-ジオキシド、6-メチル-1,2,6-オキサチアホスフィナン-2,2-ジオキシド、6-メチル-1,2,6-オキサチアホスフィナン-2,2,3-トリオキシド、6-メトキシ-1,2,6-オキサチアホスフィナン-2,2,3-トリオキシドどの含リン化合物が挙げられる。
イソシアネート基を有する化合物としては、分子内にイソシアネート基を有している化合物であれば特にその種類は限定されないが、具体例としては、
イソシアナトメタン、1-イソシアナトエタン、1-イソシアナト-2-メトキシエタン、3-イソシアナト-1-プロペン、イソシアナトシクロプロパン、2-イソシアナトプロパン、1-イソシアナトプロパン、1-イソシアナト-3-メトキシプロパン、1-イソシアナト-3-エトキシプロパン、2-イソシアナト-2-メチルプロパン、1-イソシアナトブタン、2-イソシアナトブタン、1-イソシアナト-4-メトキシブタン、1-イソシアナト-4-エトキシブタン、メチルイソシナトフォルメート、イソアナトシクロペンタン、1-イソシアナトペンタン、1-イソシアナト-5-メトキシペンタン、1-イソシアナト-5-エトキシペンタン、2-(イソシアナトメチル)フラン、イソシアナトシクロヘキサン、1-イソシアナトヘキサン、1-イソシアナト-6-メトキシヘキサン、1-イソシアナト-6-エトキシヘキサン、エチルイソシアナトアセテート、イソシアナトシクロペンタン、イソシアナトメチル(シクロヘキサン)、モノメチレンジイソシアネート、ジメチレンジイソシアネート、トリメチレンジイソシアネート、テトラメチレンジイソシアネート、ペンタメチレンジイソシアネート、ヘキサメチレンジイソシアネート、ヘプタメチレンジイソシアネート、オクタメチレンジイソシアネート、ノナメチレンジイソシアネート、デカメチレンジイソシアネート、1,3-ジイソシアナトプロパン、1,4-ジイソシアナト-2-ブテン、1,4-ジイソシアナト-2-フルオロブタン、1,4-ジイソシアナト-2,3-ジフルオロブタン、1,5-ジイソシアナト-2-ペンテン、1,5-ジイソシアナト-2-メチルペンタン、1,6-ジイソシアナト-2-ヘキセン、1,6-ジイソシアナト-3-ヘキセン、1,6-ジイソシアナト-3-フルオロヘキサン、1,6-ジイソシアナト-3,4-ジフルオロヘキサン、トルエンジイソシアネート、キシレンジイソシアネート、トリレンジイソシアネート、1,2-ビス(イソシアナトメチル)シクロヘキサン、1,3-ビス(イソシアナトメチル)シクロヘキサン、1,4-ビス(イソシアナトメチル)シクロヘキサン、1,2-ジイソシアナトシクロヘキサン、1,3-ジイソシアナトシクロヘキサン、1,4-ジイソシアナトシクロヘキサン、ジシクロヘキシルメタン-1,1'-ジイソシアネート、ジシクロヘキシルメタン-2,2'-ジイソシアネート、ジシクロヘキシルメタン-3,3'-ジイソシアネート、ジシクロヘキシルメタン-4,4'-ジイソシアネート、イソホロンジイソシアネート、また、それぞれ式(5-1)~(5-4)の基本構造で示されるビウレット、イソシアヌレート、アダクト、及び二官能のタイプの変性ポリイソシアネート等が挙げられる(式中、R7及びR8はそれぞれ任意の炭化水素基である)。
アルキレン基またはその誘導体、アルケニレン基またはその誘導体、シクロアルキレン基またはその誘導体、アルキニレン基またはその誘導体、シクロアルケニレン基またはその誘導体、アリーレン基またはその誘導体、カルボニル基またはその誘導体、スルホニル基またはその誘導体、スルフィニル基またはその誘導体、ホスホニル基またはその誘導体、ホスフィニル基またはその誘導体、アミド基またはその誘導体、イミド基またはその誘導体、エーテル基またはその誘導体、チオエーテル基またはその誘導体、ボリン酸基またはその誘導体、ボラン基またはその誘導体等が挙げられる。
本発明の非水系電解液電池において、一般式(1)の化合物等以外に、目的に応じて適宜助剤を用いてもよい。助剤としては、以下に示される不飽和結合を有する環状カーボネート、不飽和結合を有する鎖状カーボネート、フッ素原子を有する環状カーボネート、フッ素原子を有する不飽和環状カーボネート、過充電防止剤、その他の助剤、等が挙げられる。
本発明の非水系電解液において、非水系電解液電池の負極表面に皮膜を形成し、電池の長寿命化を達成するために、式(1)の化合物に加えて、式(1)の化合物の除いた不飽和結合を有する環状カーボネート(以下、不飽和環状カーボネートともいう)を用いることができる。
本発明の非水系電解液において、非水系電解液電池の負極表面に皮膜を形成し、電池の長寿命化を達成するために、式(1)の化合物に加えて、式(1)の化合物の除いた不飽和結合を有する鎖状カーボネート(以下、不飽和環状カーボネートともいう)を用いることができる。
メチルビニルカーボネート、エチルビニルカーボネート、ジビニルカーボネート、メチル-1-プロペニルカーボネート、エチル-1-プロペニルカーボネート、ジ-1-プロペニルカーボネート、メチル(1-メチルビニル)カーボネート、エチル(1-メチルビニル)カーボネート、ジ(1-メチルビニル)カーボネート、メチル-2-プロペニルカーボネート、エチル-2-プロペニルカーボネート、ジ(2-プロペニル)カーボネート、1-ブテニルメチルカーボネート、1-ブテニルエチルカーボネート、ジ(1-ブテニル)カーボネート、メチル(1-メチル-1-プロペニル)カーボネート、エチル(1-メチル-1-プロペニル)カーボネート、ジ(1-メチル-1-プロペニル)カーボネート、メチル-1-エチルビニルカーボネート、エチル-1-エチルビニルカーボネート、ジ-1-エチルビニルカーボネート、メチル(2-メチル-1-プロペニル)カーボネート、エチル(2-メチル-1-プロペニル)カーボネート、ジ(2-メチル-1-プロペニル)カーボネート、2-ブテニルメチルカーボネート、2-ブテニルエチルカーボネート、ジ-2-ブテニルカーボネート、メチル(1-メチル-2-プロペニル)カーボネート、エチル(1-メチル-2-プロペニル)カーボネート、ジ(1-メチル-2-プロペニル)カーボネート、メチル(2-メチル-2-プロペニル)カーボネート、エチル(2-メチル-2-プロペニル)カーボネート、ジ(2-メチル-2-プロペニル)カーボネート、メチル(1,2-ジメチル-1-プロペニル)カーボネート、エチル(1,2-ジメチル-1-プロペニル)カーボネート、ジ(1,2-ジメチル-1-プロペニル)カーボネート、エチニルメチルカーボネート、エチルエチニルカーボネート、ジエチニルカーボネート、メチル-1-プロピニルカーボネート、エチル-1-プロピニルカーボネート、ジ-1-プロピニルカーボネート、メチル-2-プロピニルカーボネート、エチル-2-プロピニルカーボネート、ジ-2-プロピニルカーボネート、1-ブチニルメチルカーボネート、1-ブチニルエチルカーボネート、ジ-1-ブチニルカーボネート、2-ブチニルメチルカーボネート、2-ブチニルエチルカーボネート、ジ-2-ブチニルカーボネート、メチル(1-メチル-2-プロピニル)カーボネート、エチル(1-メチル-2-プロピニル)カーボネート、ジ(1-メチル-2-プロピニル)カーボネート、3-ブチニルメチルカーボネート、3-ブチニルエチルカーボネート、ジ-3-ブチニルカーボネート、メチル(1,1-ジメチル-2-プロピニル)カーボネート、エチル(1,1-ジメチル-2-プロピニル)カーボネート、ジチル(1,1-ジメチル-2-プロピニル)カーボネート、メチル(1,3-ジメチル-2-プロピニル)カーボネート、エチル(1,3-ジメチル-2-プロピニル)カーボネート、ジチル(1,3-ジメチル-2-プロピニル)カーボネート、メチル(1,2,3-トリメチル-2-プロピニル)カーボネート、エチル(1,2,3-トリメチル-2-プロピニル)カーボネート、ジチル(1,2,3-トリメチル-2-プロピニル)カーボネート、等が挙げられる。
メチルフェニルカーボネート、エチルフェニルカーボネート、フェニルビニルカーボネート、アリルフェニルカーボネート、エニチルフェニルカーボネート、2-プロペニルフェニルカーボネート、ジフェニルカーボネート、メチル(2-メチルフェニル)カーボネート、エチル(2-メチルフェニル)カーボネート、(2-メチルフェニル)ビニルカーボネート、アリル(2-メチルフェニル)カーボネート、エニチル(2-メチルフェニル)カーボネート、2-プロペニル(2-メチルフェニル)カーボネート、ジ(2-メチルフェニル)カーボネート、メチル(3-メチルフェニル)カーボネート、エチル(3-メチルフェニル)カーボネート、(3-メチルフェニル)ビニルカーボネート、アリル(3-メチルフェニル)カーボネート、エニチル(3-メチルフェニル)カーボネート、2-プロペニル(3-メチルフェニル)カーボネート、ジ(3-メチルフェニル)カーボネート、メチル(4-メチルフェニル)カーボネート、エチル(4-メチルフェニル)カーボネート、(4-メチルフェニル)ビニルカーボネート、アリル(4-メチルフェニル)カーボネート、エニチル(4-メチルフェニル)カーボネート、2-プロペニル(4-メチルフェニル)カーボネート、ジ(4-メチルフェニル)カーボネート、ベンジルメチルカーボネート、ベンジルエチルカーボネート、ベンジルフェニルカーボネート、ベンジルビニルカーボネート、べンジル-2-プロペニルカーボネート、ベンジルエチニルカーボネート、ベンジル-2-プロピニルカーボネート、ジベンジルカーボネート、メチル(2-シクロヘキシルフェニル)カーボネート、メチル(3-シクロヘキシルフェニル)カーボネート、メチル(4-シクロヘキシルフェニル)カーボネート、エチル(2-シクロヘキシルフェニル)カーボネート、ジ(2-シクロヘキシルフェニル)カーボネート、等が挙げられる。
また、不飽和鎖状カーボネートは、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有してもよい。
フッ素化環状カーボネートとして、不飽和結合とフッ素原子とを有する環状カーボネート(以下、フッ素化不飽和環状カーボネートともいう)を用いることも好ましい。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以上であれば、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-フルオロ-5-メチルビニレンカーボネート、4-フルオロ-5-フェニルビニレンカーボネート、4-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。
本発明の非水系電解液において、非水系電解液二次電池が過充電等の状態になった際に電池の破裂・発火を効果的に抑制するために、過充電防止剤を用いることができる。
過充電防止剤としては、ビフェニル、アルキルビフェニル、ターフェニル、ターフェニルの部分水素化体、シクロヘキシルベンゼン、t-ブチルベンゼン、t-アミルベンゼン、ジフェニルエーテル、ジベンゾフラン等の芳香族化合物;2-フルオロビフェニル、o-シクロヘキシルフルオロベンゼン、p-シクロヘキシルフルオロベンゼン等の上記芳香族化合物の部分フッ素化物;2,4-ジフルオロアニソール、2,5-ジフルオロアニソール、2,6-ジフルオロアニソール、3,5-ジフルオロアニソール等の含フッ素アニソール化合物等が挙げられる。中でも、ビフェニル、アルキルビフェニル、ターフェニル、ターフェニルの部分水素化体、シクロヘキシルベンゼン、t-ブチルベンゼン、t-アミルベンゼン、ジフェニルエーテル、ジベンゾフラン等の芳香族化合物が好ましい。これらは1種を単独で用いても、2種以上を併用してもよい。2種以上併用する場合は、特に、シクロヘキシルベンゼンとt-ブチルベンゼン又はt-アミルベンゼンとの組み合わせ、ビフェニル、アルキルビフェニル、ターフェニル、ターフェニルの部分水素化体、シクロヘキシルベンゼン、t-ブチルベンゼン、t-アミルベンゼン等の酸素を含有しない芳香族化合物から選ばれる少なくとも1種と、ジフェニルエーテル、ジベンゾフラン等の含酸素芳香族化合物から選ばれる少なくとも1種を併用するのが過充電防止特性と高温保存特性のバランスの点から好ましい。
本発明の非水系電解液には、公知のその他の助剤を用いることができる。その他の助剤としては、エリスリタンカーボネート、スピロ-ビス-ジメチレンカーボネート、メトキシエチル-メチルカーボネート等のカーボネート化合物;無水コハク酸、無水グルタル酸、無水マレイン酸、無水シトラコン酸、無水グルタコン酸、無水イタコン酸、無水ジグリコール酸、シクロヘキサンジカルボン酸無水物、シクロペンタンテトラカルボン酸二無水物及びフェニルコハク酸無水物等のカルボン酸無水物;2,4,8,10-テトラオキサスピロ[5.5]ウンデカン、3,9-ジビニル-2,4,8,10-テトラオキサスピロ[5.5]ウンデカン等のスピロ化合物;エチレンサルファイト、フルオロスルホン酸メチル、フルオロスルホン酸エチル、メタンスルホン酸メチル、メタンスルホン酸エチル、ブスルファン、スルホレン、ジフェニルスルホン、N,N-ジメチルメタンスルホンアミド、N,N-ジエチルメタンスルホンアミド等の含硫黄化合物;1-メチル-2-ピロリジノン、1-メチル-2-ピペリドン、3-メチル-2-オキサゾリジノン、1,3-ジメチル-2-イミダゾリジノン及びN-メチルスクシンイミド等の含窒素化合物;ヘプタン、オクタン、ノナン、デカン、シクロヘプタン等の炭化水素化合物、フルオロベンゼン、ジフルオロベンゼン、ヘキサフルオロベンゼン、ベンゾトリフルオライド等の含フッ素芳香族化合物等が挙げられる。これらは1種を単独で用いても、2種以上を併用してもよい。これらの助剤を添加することにより、高温保存後の容量維持特性やサイクル特性を向上させることができる。
本発明の非水系電解液電池は、非水系電解液電池の中でも二次電池用、例えばリチウム二次電池用の電解液として用いるのに好適である。以下、本発明の非水系電解液を用いた非水系電解液電池について説明する。
本発明の非水系電解液二次電池は、公知の構造を採ることができ、典型的には、イオン(例えば、リチウムイオン)を吸蔵・放出可能な負極及び正極と、上記の本発明の非水系電解液とを備える。
以下に負極に使用される負極活物質について述べる。負極活物質としては、電気化学的に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、合金系材料、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。
負極活物質としては、炭素質材料、合金系材料、リチウム含有金属複合酸化物材料等が挙げられる。
負極活物質として用いられる炭素質材料としては、
(1)天然黒鉛、
(2)人造炭素質物質並びに人造黒鉛質物質を400~3200℃の範囲で1回以上熱処理した炭素質材料、
(3)負極活物質層が少なくとも2種以上の異なる結晶性を有する炭素質からなり、かつ/又はその異なる結晶性の炭素質が接する界面を有している炭素質材料、
(4)負極活物質層が少なくとも2種以上の異なる配向性を有する炭素質からなり、かつ/又はその異なる配向性の炭素質が接する界面を有している炭素質材料、
から選ばれるものが、初期不可逆容量、高電流密度充放電特性のバランスがよく好ましい。また、(1)~(4)の炭素質材料は、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。
上記金属酸化物が、一般式(A)で表されるリチウムチタン複合酸化物であり、一般式(A)中、0.7≦x≦1.5、1.5≦y≦2.3、0≦z≦1.6であることが、リチウムイオンのドープ・脱ドープの際の構造が安定であることから好ましい。
[一般式(1)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。]
上記の一般式(A)で表される組成の中でも、
(a)1.2≦x≦1.4、1.5≦y≦1.7、z=0
(b)0.9≦x≦1.1、1.9≦y≦2.1、z=0
(c)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。
負極活物質として炭素質材料を用いる場合、以下の物性を有するものであることが望ましい。
(菱面体晶率)
菱面体晶率は、X線広角回折法(XRD)による菱面体晶構造黒鉛層(ABCスタッキング層)と六方晶構造黒鉛層(ABスタッキング層)の割合から次式を用いて求めることができる。
菱面体晶率(%)=XRDのABC(101)ピークの積分強度÷
XRDのAB(101)ピーク積分強度×100
ここで、本発明で用いることができる炭素質材料の菱面体晶率は、下限値としては、通常0%以上、好ましくは3%以上、更に好ましくは5%以上、特に好ましくは12%以上である。また、上限値としては、好ましくは35%以下、より好ましくは27%以下、更に好ましくは24%以下、特に好ましくは20%以下の範囲である。ここで、菱面体晶率が0%とは、ABCスタッキング層に由来するXRDピークが全く検出されないことを指す。また0%より大きいとは、ABCスタッキング層に由来するXRDピークが僅かでも検出されていることを指す。
・ターゲット:Cu(Kα線)グラファイトモノクロメーター
・ スリット:
ソーラースリット 0.04度
発散スリット 0.5度
横発散マスク 15mm
散乱防止スリット 1度
・測定範囲及びステップ角度/計測時間:
(101)面:41度≦2θ≦47.5度 0.3度/60秒
・バックグラウンド補正:
42.7から45.5度の間を直線で結び、バックグラウンドとし差し引く。
・菱面体晶構造黒鉛粒子層のピーク:43.4度付近のピークのことを指す。
・六方晶構造黒鉛粒子層のピーク:44.5度付近のピークのことを指す。
更に前記機械的作用を与えた後に炭素前駆体と複合化し700℃以上の温度で熱処理を加えることが特に好ましい。
炭素質材料の学振法によるX線回折で求めた格子面(002面)のd値(層間距離)が、0.335nm以上であることが好ましく、また、通常0.360nm以下であり、0.350nm以下が好ましく、0.345nm以下がさらに好ましい。また、学振法によるX線回折で求めた炭素質材料の結晶子サイズ(Lc)は、1.0nm以上であることが好ましく、中でも1.5nm以上であることがさらに好ましい。
炭素質材料の体積基準平均粒径は、レーザー回折・散乱法により求めた体積基準の平均粒径(メジアン径)であり、通常1μm以上であり、3μm以上が好ましく、5μm以上がさらに好ましく、7μm以上が特に好ましく、また、通常100μm以下であり、50μm以下が好ましく、40μm以下がより好ましく、30μm以下がさらに好ましく、25μm以下が特に好ましい。
体積基準平均粒径の測定は、界面活性剤であるポリオキシエチレン(20)ソルビタンモノラウレートの0.2質量%水溶液(約10mL)に炭素粉末を分散させて、レーザー回折・散乱式粒度分布計(堀場製作所社製LA-700)を用いて行なう。該測定で求められるメジアン径を、本発明の炭素質材料の体積基準平均粒径と定義する。
炭素質材料のラマンR値は、アルゴンイオンレーザーラマンスペクトル法を用いて測定した値であり、通常0.01以上であり、0.03以上が好ましく、0.1以上がさらに好ましく、また、通常1.5以下であり、1.2以下が好ましく、1以下がさらに好ましく、0.5以下が特に好ましい。
また、炭素質材料の1580cm-1付近のラマン半値幅は特に制限されないが、通常10cm-1以上であり、15cm-1以上が好ましく、また、通常100cm-1以下であり、80cm-1以下が好ましく、60cm-1以下がさらに好ましく、40cm-1以下が特に好ましい。
・アルゴンイオンレーザー波長 :514.5nm
・試料上のレーザーパワー :15~25mW
・分解能 :10~20cm-1
・測定範囲 :1100cm-1~1730cm-1
・ラマンR値、ラマン半値幅解析:バックグラウンド処理、
・スムージング処理 :単純平均、コンボリューション5ポイント
炭素質材料の配向比は、通常0.005以上であり、0.01以上が好ましく、0.015以上がさらに好ましく、また、通常0.67以下である。配向比が、上記範囲を下回ると、高密度充放電特性が低下する場合がある。なお、上記範囲の上限は、炭素質材料の配向比の理論上限値である。
・ターゲット:Cu(Kα線)グラファイトモノクロメーター
・スリット :
発散スリット=0.5度
受光スリット=0.15mm
散乱スリット=0.5度
・測定範囲及びステップ角度/計測時間:
(110)面:75度≦2θ≦80度 1度/60秒
(004)面:52度≦2θ≦57度 1度/60秒
炭素質材料のアスペクト比は、通常1以上、また、通常10以下であり、8以下が好ましく、5以下がさらに好ましい。アスペクト比が、上記範囲を上回ると、極板化時にスジ引きや、均一な塗布面が得られず、高電流密度充放電特性が低下する場合がある。なお、上記範囲の下限は、炭素質材料のアスペクト比の理論下限値である。
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、導電材、充填材等を加えてスラリーとし、これを集電体に塗布、乾燥した後にプレスすることによって形成することができる。
負極活物質を保持させる集電体としては、公知のものを任意に用いることができる。負極の集電体としては、例えば、アルミニウム、銅、ニッケル、ステンレス鋼、ニッケルメッキ鋼等の金属材料が挙げられるが、加工し易さとコストの点から特に銅が好ましい。
負極活物質を結着するバインダーとしては、非水系電解液や電極製造時に用いる溶媒に対して安定な材料であれば、特に制限されない。
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-オレフィン共重合体等の軟質樹脂状高分子;ポリフッ化ビニリデン、ポリテトラフルオロエチレン、フッ素化ポリフッ化ビニリデン、ポリテトラフルオロエチレン・エチレン共重合体等のフッ素系高分子;アルカリ金属イオン(特にリチウムイオン)のイオン伝導性を有する高分子組成物等が挙げられる。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。
増粘剤は、通常、負極活物質層を作製する際のスラリーの粘度を調整するために使用される。増粘剤としては、特に制限されないが、具体的には、カルボキシメチルセルロース、メチルセルロース、ヒドロキシメチルセルロース、エチルセルロース、ポリビニルアルコール、酸化スターチ、リン酸化スターチ、カゼイン及びこれらの塩等が挙げられる。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。
負極活物質を電極化した際の電極構造は特に制限されないが、集電体上に存在している負極活物質の密度は、1g・cm-3以上が好ましく、1.2g・cm-3以上がさらに好ましく、1.3g・cm-3以上が特に好ましく、また、2.2g・cm-3以下が好ましく、2.1g・cm-3以下がより好ましく、2.0g・cm-3以下がさらに好ましく、1.9g・cm-3以下が特に好ましい。集電体上に存在している負極活物質の密度が、上記範囲を上回ると、負極活物質粒子が破壊され、初期不可逆容量の増加や、集電体/負極活物質界面付近への非水系電解液の浸透性低下による高電流密度充放電特性悪化を招く場合がある。また、上記範囲を下回ると、負極活物質間の導電性が低下し、電池抵抗が増大し、単位容積当たりの容量が低下する場合がある。
負極板の厚さは用いられる正極板に合わせて設計されるものであり、特に制限されないが、負極板から金属箔(集電体)厚さを差し引いた負極活物質層の厚さは通常15μm以上、好ましくは20μm以上、より好ましくは30μm以上、また、通常300μm以下、好ましくは280μm以下、より好ましくは250μm以下が望ましい。
また、上記負極板の表面に、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。
(組成)
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。
これらの中でも、LiFePO4、Li3Fe2(PO4)3、LiFeP2O7等のリン酸鉄類が、高温・充電状態での金属溶出が起こりにくく、また安価であるために好適に用いられる。
また、本発明のリチウム遷移金属系化合物粉体は、異元素が導入されてもよい。異元素としては、B、Na、Mg、Al、K、Ca、Ti、V、Cr、Fe、Cu、Zn、Sr、Y、Zr、Nb、Ru、Rh、Pd、Ag、In、Sn、Sb、Te、Ba、Ta、Mo、W、Re、Os、Ir、Pt、Au、Pb、La、Ce、Pr、Nd、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm、Yb、Lu、Bi、N、F、Cl、Br、Iの何れか1種以上の中から選択される。これらの異元素は、リチウム遷移金属系化合物の結晶構造内に取り込まれていてもよく、あるいは、リチウム遷移金属系化合物の結晶構造内に取り込まれず、その粒子表面や結晶粒界などに単体もしくは化合物として偏在していてもよい。
また、上記正極活物質の表面に、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。
本発明においては、正極活物質の表面に、これとは異なる組成の物質が付着したものをも「正極活物質」という。
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が、中でも一次粒子が凝集して、二次粒子を形成して成り、その二次粒子の形状が球状ないし楕円球状であるものが好ましい。通常、電気化学素子はその充放電に伴い、電極中の活物質が膨張収縮をするため、そのストレスによる活物質の破壊や導電パス切れ等の劣化がおきやすい。そのため一次粒子のみの単一粒子活物質であるよりも、一次粒子が凝集して、二次粒子を形成したものである方が膨張収縮のストレスを緩和して、劣化を防ぐため好ましい。また、板状等軸配向性の粒子であるよりも球状ないし楕円球状の粒子の方が、電極の成形時の配向が少ないため、充放電時の電極の膨張収縮も少なく、また電極を作成する際の導電材との混合においても、均一に混合されやすいため好ましい。
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0.1μm以上、より好ましくは0.5μm以上、さらに好ましくは1.0μm以上、最も好ましくは2μm以上であり、上限は、好ましくは20μm以下、より好ましくは18μm以下、さらに好ましくは16μm以下、最も好ましくは15μm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、電池性能の低下を招いたり、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をもつ該正極活物質を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、該正極活物質の平均一次粒子径としては、好ましくは0.03μm以上、より好ましくは0.05μm以上、さらに好ましくは0.08μm以上であり、特に好ましくは0.1μm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。
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、正極活物質と結着材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、正極活物質と結着材、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材としては、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。
増粘剤は、通常、正極活物質層の製造に用いるスラリーの粘度を調製するために使用することができる。特に水系媒体を用いる場合、増粘剤と、スチレン-ブタジエンゴム(SBR)等のラテックスを用いてスラリー化するのが好ましい。増粘剤としては、特に制限はないが、具体的には、カルボキシメチルセルロース、メチルセルロース、ヒドロキシメチルセルロース、エチルセルロース、ポリビニルアルコール、酸化スターチ、リン酸化スターチ、カゼイン及びこれらの塩等が挙げられる。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。さらに増粘剤を添加する場合には、活物質に対する増粘剤の割合は、0.1質量%以上、好ましくは0.5質量%以上、より好ましくは0.6質量%以上であり、また、上限としては5質量%以下、好ましくは3質量%以下、より好ましくは2質量%以下の範囲である。この範囲を下回ると、著しく塗布性が低下する場合がある。上回ると、正極活物質層に占める活物質の割合が低下し、電池の容量が低下する問題や正極活物質間の抵抗が増大する問題が生じる場合がある。
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。
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、正極板から金属箔(集電体)厚さを差し引いた正極活物質層の厚さは、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。
正極と負極との間には、短絡を防止するために、通常はセパレータを介在させる。この場合、本発明の非水系電解液は、通常はこのセパレータに含浸させて用いる。
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。中でも、本発明の非水系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。
一方、無機物の材料としては、例えば、アルミナや二酸化ケイ素等の酸化物、窒化アルミや窒化ケイ素等の窒化物、硫酸バリウムや硫酸カルシウム等の硫酸塩が用いられ、粒子形状もしくは繊維形状のものが用いられる。
<電極群>
電極群は、上記の正極板と負極板とを上記のセパレータを介してなる積層構造のもの、及び上記の正極板と負極板とを上記のセパレータを介して渦巻き状に捲回した構造のもののいずれでもよい。電極群の体積が電池内容積に占める割合(以下、電極群占有率と称する)は、通常40%以上であり、50%以上が好ましく、また、通常90%以下であり、80%以下が好ましい。
外装ケースの材質は用いられる非水系電解液に対して安定な物質であれば特に制限されない。具体的には、ニッケルめっき鋼板、ステンレス、アルミニウム又はアルミニウム合金、マグネシウム合金等の金属類、又は、樹脂とアルミ箔との積層フィルム(ラミネートフィルム)が用いられる。軽量化の観点から、アルミニウム又はアルミニウム合金の金属、ラミネートフィルムが好適に用いられる。
保護素子として、異常発熱や過大電流が流れた時に抵抗が増大するPTC(Positive Temperature Coefficient)、温度ヒューズ、サーミスター、異常発熱時に電池内部圧力や内部温度の急激な上昇により回路に流れる電流を遮断する弁(電流遮断弁)等を使用することができる。上記保護素子は高電流の通常使用で作動しない条件のものを選択することが好ましく、保護素子がなくても異常発熱や熱暴走に至らない設計にすることがより好ましい。
本発明の非水系電解液二次電池は、通常、上記の非水系電解液、負極、正極、セパレータ等を外装体内に収納して構成される。この外装体は、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。具体的に、外装体の材質は任意であるが、通常は、例えばニッケルメッキを施した鉄、ステンレス、アルミウム又はその合金、ニッケル、チタン等が用いられる。
また、外装体の形状も任意であり、例えば円筒型、角形、ラミネート型、コイン型、大型等のいずれであってもよい。
原料1)は、非特許文献(JOC 56(3),1083-8,1991)の方法に従って合成を行った。次に原料1)を用い、Eur.J.O.C.2009(20),2836-2844に準じる方法により、化合物Iを得た。
[負極の作製]
炭素質材料98質量部に、増粘剤及びバインダーとして、それぞれ、カルボキシメチルセルロースナトリウムの水性ディスパージョン(カルボキシメチルセルロースナトリウムの濃度1質量%)100質量部及びスチレン-ブタジエンゴムの水性ディスパージョン(スチレン-ブタジエンゴムの濃度50質量%)1質量部を加え、ディスパーザーで混合してスラリー化した。得られたスラリーを厚さ10μmの銅箔に塗布して乾燥し、プレス機で圧延したものを、活物質層のサイズとして幅30mm、長さ40mm、及び幅5mm、長さ9mmの未塗工部を有する形状に切り出し、実施例1~7、比較例1~5、参考例1に用いる負極とした。
正極活物質としてLiCoO2を90質量%と、導電材としてのアセチレンブラック5質量%と、結着材としてのポリフッ化ビニリデン5質量%とを、N-メチルピロリドン溶媒中で混合して、スラリー化した。得られたスラリーを、厚さ15μmのアルミ箔に塗布して乾燥し、プレス機で圧延したものを、活物質層のサイズとして幅30mm、長さ40mm、及び幅5mm、長さ9mmの未塗工部を有する形状に切り出し、実施例1~7、比較例1~5、参考例1に用いる正極とした。
乾燥アルゴン雰囲気下、モノフルオロエチレンカーボネートとジメチルカーボネートとの混合物(体積比30:70)に乾燥したLiPF6を1mol/Lの割合となるように溶解して基本電解液を調製した。この基本電解液に、表2に記載の割合で化合物を混合し、実施例1~7、比較例1~5、参考例1に用いる電解液とした。
上記の正極、負極、及びポリエチレン製のセパレータを、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、表1に記載の電解液をそれぞれ袋内に注入し、真空封止を行い、シート状電池を作製し、実施例1~7、比較例1~5、参考例1に用いる電池とした。
非水系電解液二次電池を、ガラス板で挟んで加圧した状態で、25℃において、0.2Cに相当する電流で4.1Vまで定電流充電した後、0.2Cの定電流で3Vまで放電し、さらに0.2Cに相当する電流で4.33Vまで定電流-定電圧充電(以下適宜、「CCCV充電」という)(0.05Cカット)した後、0.2Cで3Vまで放電して電池を安定させた。次いで、0.2Cで4.3VまでCCCV充電(0.05Cカット)した後、0.2Cで3Vまで再度放電し、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し、例えば、0.2Cとはその1/5の電流値を表す。
初期放電容量評価の終了した電池を、再度、4.3VまでCCCV充電(0.05Cカット)を行った後、85℃、24時間の条件で高温保存を行った。電池を十分に冷却させた後、エタノール浴中に浸して体積を測定し、保存前後の体積変化から発生したガス量を求めた。次に、25℃において0.2Cで3Vまで放電させ、高温保存特性試験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、これを高温保存後の残存容量(%)とした。
この理由は、一般式(1)で表される化合物が形成する電極保護層に、シアノ基を有する化合物、硫黄原子を含む環状エステル化合物、イソシアネート基を有する化合物から選ばれる少なくとも1種が取り込まれることにより、電極表面耐久性が著しく向上し、結果として上記のような特筆すべき電池耐久性能の向上が引き起こされるものと推測される。
正極活物質としてLi(Ni1/3Mn1/3Co1/3)O2を90質量%と、導電材としてのアセチレンブラック5質量%と、結着剤としてのポリフッ化ビニリデン5質量%とを、N-メチルピロリドン溶媒中で混合して、スラリー化した。得られたスラリーを、予め導電助剤を塗布した厚さ15μmのアルミ箔に塗布して乾燥し、プレス機で圧延したものを、活物質層のサイズとして幅30mm、長さ40mm、及び幅5mm、長さ9mmの未塗工部を有する形状に切り出し、実施例8~10、比較例6~11、及び参考例2正極とした。
乾燥アルゴン雰囲気下、エチレンカーボネートとジメチルカーボネートとエチルメチルカーボネートとの混合物(体積比30:30:40)に乾燥したLiPF6を1mol/Lの割合となるように溶解して基本電解液を調製した。この基本電解液に、表3に記載の割合で化合物を混合し、実施例8~10、比較例6~11、及び参考例2に用いる電解液とした。
上記正極並びに上記電解液を使用した以外、上記実施例<A>と同様にしてシート状電池を作製した。
非水系電解液二次電池を、ガラス板で挟んで加圧した状態で、25℃において、0.2Cに相当する電流で4.1Vまで定電流充電した後、0.2Cの定電流で3Vまで放電するサイクルを2回繰返し、さらに0.2Cに相当する電流で4.4VまでCCCV充電(0.05Cカット)した後、0.2Cで3Vまで放電して電池を安定させた。次いで、0.2Cで4.4VまでCCCV充電(0.05Cカット)した後、0.2Cで3Vまで再度放電し、初期放電容量を求めた。
初期放電容量評価の終了した電池を、再度、4.4VまでCCCV充電(0.05Cカット)を行った後、75℃、5日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、高温保存特性試験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、これを高温保存後の残存容量(%)とした。
初期放電容量評価の終了した電池を、60℃において、4.4Vまで2Cの定電流で充電後、3.0Vまで2Cの定電流で放電する過程を1サイクルとして、300サイクル実施した。(300サイクル目の放電容量)÷(1サイクル目の放電容量)×100の計算式から、放電容量維持率を求めた。
高温サイクル特性評価の終了した電池を、25℃において、4.4Vまで0.2CのCCCV充電(0.05Cカット)を行った後、25℃にて3.0Vまで1Cの定電流で放電し、放電容量を求めた。
特に、炭素-炭素二重結合を有する環状カーボネート化合物や炭素-炭素三重結合を有する鎖状カーボネートと、硫黄原子を含む環状エステルと組み合わせても(比較例7及び9)、本発明のように特筆すべき電池性能の向上は確認されなかった。このことから、一般式(1)で表される化合物と併用しなければ本発明の優れた効果は発現されないことが分かる。また、上限充電電圧を4.3Vとした<実施例A>と比較して、<実施例B>の結果から明らかなように、上限電池電圧を4.4Vのように高めても、本発明の顕著な効果は発揮される。
一般式(1)で表される化合物はそれ単独でも電極表面を保護して電池耐久性を向上させる機能を有するが(参考例2)、一般式(1)で表される化合物はと共に硫黄原子を含む環状エステル化合物を導入することで、より優れた高温保存容量維持率、高温サイクル容量維持率並びに高温サイクル後の放電容量を提供することができる。
この理由は、一般式(1)の化合物が形成する電極保護層に硫黄原子を含む化合物が取り込まれ、電極表面耐久性が著しく向上し、結果として上記のような特筆すべき電池耐久性能の向上が引き起こされるものと推測される。
Claims (8)
- リチウム塩とこれを溶解する非水系溶媒を含有してなる非水系電解液であって、該非水系電解液が、下記一般式(1)で表される化合物を含有し、さらにシアノ基を有する化合物、硫黄原子を含む環状エステル化合物、イソシアネート基を有する化合物からなる群のうち少なくとも1種以上を含有することを特徴とする非水系電解液。
- 前記シアノ基を有する化合物が、NC-(CH2)n-CN(n=2~6)で表される化合物である、請求項3に記載の非水系電解液。
- 前記非水系電解液が、二重結合を有する環状カーボネート及びフッ素原子を有する環状カーボネートから選ばれる群の中から少なくとも1種以上を含有する、請求項1乃至6の何れか1項に記載の非水系電解液。
- リチウムイオンを吸蔵・放出可能な負極及び正極、並びに非水系電解液を含む非水系電解液電池であって、前記非水系電解液が請求項1乃至7の何れか1項に記載の非水系電解液であることを特徴とする非水系電解液電池。
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CN2011800438576A CN103109410A (zh) | 2010-09-16 | 2011-05-12 | 非水系电解液及非水系电解液二次电池 |
EP11824833.5A EP2618418A4 (en) | 2010-09-16 | 2011-05-12 | NON-WATER ELECTROLYTE AND BATTERY WITH NON-WATER ELECTROLYTE |
KR1020137006082A KR20130108286A (ko) | 2010-09-16 | 2011-05-12 | 비수계 전해액 및 비수계 전해액 2차 전지 |
US13/842,473 US9553333B2 (en) | 2010-09-16 | 2013-03-15 | Nonaqueous electrolytic solution and nonaqueous electrolyte secondary battery |
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JP2011-095370 | 2011-04-21 | ||
JP2011095370A JP5857434B2 (ja) | 2011-04-21 | 2011-04-21 | 非水系電解液及びそれを用いた非水系電解液電池 |
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CN104205471A (zh) * | 2012-03-23 | 2014-12-10 | 宇部兴产株式会社 | 非水电解液及使用了该非水电解液的蓄电设备 |
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WO2014125946A1 (ja) * | 2013-02-12 | 2014-08-21 | 昭和電工株式会社 | 二次電池用非水電解液および非水電解液二次電池 |
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CN103109410A (zh) | 2013-05-15 |
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EP2618418A1 (en) | 2013-07-24 |
US20130216919A1 (en) | 2013-08-22 |
KR20130108286A (ko) | 2013-10-02 |
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