Classifications

• • 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
• • 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
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
  • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
  • H01M10/0566—Liquid materials
  • H01M10/0568—Liquid materials characterised by the solutes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
  • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
  • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
  • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
  • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates

Definitions

• the present invention relates to a non-aqueous electrolyte and a battery. More specifically, the present invention relates to a nonaqueous electrolyte that can be suitably used as a material for batteries such as lithium ion batteries, and a battery constructed using the same.
• Patent Document 1 discloses a non-aqueous electrolyte for a non-aqueous electrolyte secondary battery that includes a positive electrode and a negative electrode that can occlude and release metal ions, the non-aqueous electrolyte, together with an electrolyte and a non-aqueous solvent, A non-aqueous electrolytic solution containing a compound represented by a predetermined formula is disclosed.
• Patent Document 2 contains a lithium salt, a non-aqueous organic solvent, and a non-aqueous organic electrolyte additive, and the non-aqueous organic electrolyte additive is a non-aqueous organic electrolyte represented by predetermined formulas (I) to (III).
• Non-aqueous organic electrolytes are disclosed that are mixed with additives.
• Patent Document 3 describes an electrolytic solution for lithium ion secondary batteries containing a lithium salt of a sulfonimide and water, which contains orthophosphate ions, pyrophosphate ions, phosphorous acid, or anions produced by dissociation of salts thereof.
• An electrolytic solution for a lithium ion secondary battery is disclosed, which contains at least one type of anion selected from the group consisting of anion formed by dissociation of phosphinic acid, or a salt thereof.
• the present invention has been made in view of the above-mentioned current situation, and an object of the present invention is to provide a non-aqueous electrolyte containing a sulfonylimide compound that has excellent storage stability in a high-temperature environment.
• the present inventor conducted various studies on nonaqueous electrolytes containing sulfonylimide compounds, and found that by combining a sulfonylimide compound with a predetermined structure and a phosphoric acid ester with a predetermined structure, the nonaqueous electrolyte can be heated in a high-temperature environment. We discovered that it has excellent stability even when stored, and came up with the idea that the above problems could be successfully solved, leading to the present invention.
• the present invention includes the following non-aqueous electrolyte and the like.
• the following formula (1) M 1 N(R 1 SO 2 )(R 2 SO 2 )(1)
• M 1 represents an alkali metal atom.
• R 1 and R 2 are the same or different and represent a fluorine atom, an alkyl group having 1 to 6 carbon atoms, or a fluoroalkyl group having 1 to 6 carbon atoms.
• R 3 to R 5 are the same or different and represent a hydrocarbon group having 1 to 14 carbon atoms, a hydrogen atom, or a halogen atom.
• n an integer of 2 to 6.
• a non-aqueous electrolyte containing a compound [2] The above formula (2) in which R 3 to R 5 are the same or different and are an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 14 carbon atoms, a hydrogen atom, or a halogen atom. The non-aqueous electrolyte according to [1]. [3] The non-aqueous electrolyte according to [1] or [2] above, wherein n in formula (2) above is 2.
• the content of the compound represented by formula (2) above is 0.05% by mass or more and less than 5.0% by mass with respect to 100% by mass of the non-aqueous electrolyte, [1] to The non-aqueous electrolyte according to any one of [6].
• M 2 represents an alkali metal atom
• a battery comprising the non-aqueous electrolyte according to any one of [1] to [8] above.
• the non-aqueous electrolyte of the present invention has the above-described structure and has excellent stability when stored in a high-temperature environment, so it can be suitably used as a battery material such as a lithium ion battery.
• the non-aqueous electrolyte of the present invention comprises a sulfonylimide compound represented by the above formula (1) (hereinafter also simply referred to as a sulfonylimide compound) and a phosphate ester represented by the above formula (2). (hereinafter also simply referred to as phosphate ester).
• a sulfonylimide compound represented by the above formula (1) hereinafter also simply referred to as a sulfonylimide compound
• phosphate ester phosphate ester
• DCR direct current resistance
• capacity retention a decrease in capacity retention
• initial interfacial resistance an increase in initial interfacial resistance during repeated charging.
• a battery using an aqueous electrolyte has reduced interfacial resistance and is also excellent in DCR increase rate and capacity retention rate.
• the concentration of the sulfonylimide compound is not particularly limited, but is preferably 0.1 to 6.0 mol/L. Thereby, the effects of the present invention can be more fully exhibited. More preferably 0.2 to 3.0 mol/L, still more preferably 0.4 to 2.0 mol/L, even more preferably 0.6 to 2.0 mol/L, particularly preferably is 0.8 to 2.0 mol/L.
• the concentration of the sulfonylimide compound is preferably 0.1 to 6.0 mol/kg, more preferably 0.2 to 3.0 mol/kg, and still more preferably 0.4 to 2.0 mol/kg. kg, more preferably 0.6 to 2.0 mol/kg, particularly preferably 0.8 to 2.0 mol/kg.
• the content of the phosphate ester is not particularly limited, but it is preferably 0.05% by mass or more and less than 5.0% by mass with respect to 100% by mass of the nonaqueous electrolyte.
• the content of the phosphoric acid ester is more preferably 0.1 to 3.0% by mass, still more preferably 0.2 to 2.0% by mass, and even more preferably 0.5 to 1.5% by mass. and particularly preferably 0.5 to 1.0% by mass. Ru.
• the non-aqueous electrolyte contains the sulfonylimide compound as an alkali metal salt, but may also contain an alkali metal salt other than the sulfonylimide compound.
• the concentration of the alkali metal salt other than the sulfonylimide compound in the nonaqueous electrolyte is not particularly limited, but is preferably 0.1 to 1.5 mol/L. More preferably 0.2 to 1.0 mol/L, still more preferably 0.2 to 0.6 mol/L.
• the concentration of the alkali metal salt other than the sulfonylimide compound is preferably 0.1 to 1.5 mol/kg, more preferably 0.2 to 1.0 mol/kg, and even more preferably 0.2 to 1.0 mol/kg. It is 0.6 mol/kg.
• the non-aqueous electrolyte preferably has a total alkali metal concentration of the sulfonylimide compound and an alkali metal salt other than the sulfonylimide compound from 0.8 to 6.0 mol/L. More preferably 1.0 to 3.0 mol/L, still more preferably 1.2 to 2.0 mol/L.
• the total alkali metal concentration of the sulfonylimide compound and the alkali metal salt other than the sulfonylimide compound is preferably 0.8 to 6.0 mol/kg, more preferably 1.0 to 3.0 mol/kg. and more preferably 1.2 to 2.0 mol/kg.
• the amount of the sulfonylimide compound is preferably 5 to 100 mol% based on 100 mol% of the electrolyte (the sulfonylimide compound and other alkali metal salts) in the nonaqueous electrolyte. Thereby, the effects of the present invention can be more fully exhibited. More preferably 10 to 95 mol%, still more preferably 20 to 90 mol%, even more preferably 30 to 85 mol%, even more preferably 40 to 85 mol%, particularly preferably 50 to 85 mol%. It is 85 mol%, particularly preferably 60 to 85 mol%. In one embodiment, the sulfonylimide compound may be present in an amount of 70 mol% or more, 80 mol% or more, or 90 mol% or more based on 100 mol% of the electrolyte.
• the non-aqueous electrolyte contains a non-aqueous solvent as a solvent, but may contain water at a rate of 10% or less.
• the moisture content is preferably 1% or less. Thereby, the effects of the present invention can be more fully exhibited.
• the water content is more preferably 1000 ppm or less, and still more preferably 100 ppm or less.
• the moisture content can be measured using a Karl Fischer moisture measuring device.
• the proportion of the nonaqueous solvent in the nonaqueous electrolyte is not particularly limited, but is preferably 100 parts by mass to 5000 parts by mass with respect to 100 parts by mass of the electrolyte (the sulfonylimide compound and other alkali metal salts). , more preferably from 150 parts by weight to 2,500 parts by weight, still more preferably from 200 parts by weight to 2,000 parts by weight.
• the nonaqueous electrolyte may contain the sulfonylimide compound, the phosphate ester, an alkali metal salt other than the sulfonylimide compound, and other components other than the solvent.
• the content of other components is not particularly limited, but is preferably 0 to 20% by mass based on 100% by mass of the non-aqueous electrolyte.
• the amount is more preferably 0 to 10% by weight, and even more preferably 0 to 5% by weight.
• the sulfonylimide compound has the following formula (1); M 1 N(R 1 SO 2 )(R 2 SO 2 )(1) (In the formula, M 1 represents an alkali metal atom. R 1 and R 2 are the same or different and represent a fluorine atom, an alkyl group having 1 to 6 carbon atoms, or a fluoroalkyl group having 1 to 6 carbon atoms.) It is a compound represented by
• alkali metal in M1 examples include lithium, sodium, potassium, rubidium, cesium, and francium. Lithium, sodium, and potassium are preferred, and lithium is more preferred.
• alkyl group having 1 to 6 carbon atoms in R 1 examples include straight chain alkyl groups such as methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group (amyl group), and n-hexyl group.
• the number of carbon atoms in the alkyl group in R 1 and R 2 is preferably 1 to 4, more preferably 1 to 3, and still more preferably 1 to 2.
• the fluoroalkyl group having 1 to 6 carbon atoms in R 1 and R 2 above may be one in which at least a portion of the hydrogen atoms bonded to the carbon atoms of the alkyl group having 1 to 6 carbon atoms are substituted with fluorine atoms.
• Specific examples of the alkyl group are as described above.
• Examples of the fluoroalkyl group having 1 to 6 carbon atoms include a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a fluoroethyl group, a difluoroethyl group, a trifluoroethyl group, a pentafluoroethyl group, a fluoropropyl group, and a fluoropropyl group. Examples include pentyl group and fluorohexyl group.
• the number of carbon atoms in the fluoroalkyl group in R 1 and R 2 is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 to 2.
• R 1 and R 2 are preferably a fluorine atom, a trifluoromethyl group, or a pentafluoroethyl group. More preferably, it is a fluorine atom, and it is preferable that at least one of the above R 1 and R 2 is a fluorine atom.
• a form in which R 1 and R 2 are both fluorine atoms is one of the preferred embodiments of the present invention.
• Examples of the sulfonylimide compounds include lithium bis(fluorosulfonyl)imide (hereinafter also referred to as LiFSI), lithium (fluorosulfonyl)(trifluoromethylsulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium sulfonyl)(pentafluoroethylsulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, potassium bis(fluorosulfonyl)imide, potassium(fluorosulfonyl)(trifluoromethylsulfonyl)imide, potassium bis(trifluoromethylsulfonyl)imide , sodium bis(fluorosulfonyl)imide, sodium(fluorosulfonyl)(trifluoromethylsulfonyl)imide, sodium bis(trifluoromethylsulfony
• lithium bis(fluorosulfonyl)imide lithium bis(fluorosulfonyl)imide, lithium (fluorosulfonyl)(trifluoromethylsulfonyl)imide, and lithium(fluorosulfonyl)(pentafluoroethylsulfonyl)imide are preferred, and lithium bis(fluorosulfonyl)imide is more preferred. It is.
• R 3 to R 5 are the same or different and represent a hydrocarbon group having 1 to 14 carbon atoms, a hydrogen atom, or a halogen atom.
• n represents an integer of 2 to 6.
• the hydrocarbon group having 1 to 14 carbon atoms in R 3 to R 5 above includes an aliphatic alkyl group having 1 to 14 carbon atoms, an alicyclic alkyl group having 3 to 14 carbon atoms, and an alkenyl group having 2 to 14 carbon atoms. , an alkynyl group having 2 to 14 carbon atoms, an aryl group having 6 to 14 carbon atoms, and the like.
• Examples of the aliphatic alkyl group having 1 to 14 carbon atoms include methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group (amyl group), n-hexyl group, n-heptyl group.
• n-octyl group n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, i-propyl group, sec-butyl group, i-butyl group , t-butyl group, 1-methylbutyl group, 1-ethylpropyl group, 2-methylbutyl group, i-amyl group, neopentyl group, 1,2-dimethylpropyl group, 1,1-dimethylpropyl group, t-amyl group , 1,3-dimethylbutyl group, 3,3-dimethylbutyl group, 2-ethylbutyl group, 2-ethyl-2-methylpropyl group, 1-methylheptyl group, 2-ethylhexyl group, 1,5-dimethylhexyl group , t-o
• Examples of the alicyclic alkyl group having 3 to 14 carbon atoms include cyclopropyl group, cyclopropylmethyl group, cyclobutyl group, cyclobutylmethyl group, cyclopentyl group, cyclohexyl group, cyclohexylmethyl group, cycloheptyl group, and cyclooctyl group. group, cyclohexylpropyl group, cyclododecyl group, norbornyl group (C7), adamantyl group (C10), cyclopentylethyl group, and the like.
• alkenyl group having 2 to 14 carbon atoms examples include vinyl group, allyl group, 1-butenyl group, 2-butenyl group, pentenyl group, hexenyl group, heptenyl group, octenyl group, nonenyl group, decenyl group, and dodecenyl group. , tetradecenyl group, etc.
• alkynyl group having 2 to 14 carbon atoms examples include ethynyl group, 1-propynyl group, 2-propynyl group, butynyl group, pentynyl group, hexynyl group, heptynyl group, octynyl group, nonynyl group, decynyl group, and dodecynyl group. , tetradecynyl group, etc.
• the number of carbon atoms in the alkyl group is preferably 1 to 10, more preferably 1 to 8, and still more preferably 1 to 4.
• the number of carbon atoms in the alkenyl group and alkynyl group is preferably 2 to 10, more preferably 2 to 8, and still more preferably 2 to 4.
• the number of carbon atoms in the aryl group is preferably 6 to 10, more preferably 6 to 8, and still more preferably 6 to 7.
• halogen atom in R 3 to R 5 examples include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, and the like.
• R 3 to R 5 are preferably an alkyl group having 1 to 14 carbon atoms or an aryl group having 6 to 14 carbon atoms, and more preferably an aryl group having 6 to 14 carbon atoms.
• phosphoric acid esters include tetramethyl pyrophosphate, tetraethyl pyrophosphate, tetrapropyl pyrophosphate, tetrabutyl pyrophosphate, tetravinyl pyrophosphate, tetraallyl pyrophosphate, tetraphenyl pyrophosphate, and tetrabenzyl pyrophosphate. It will be done.
• tetraethyl pyrophosphate preferred are tetraethyl pyrophosphate, tetraphenyl pyrophosphate, and tetrabenzyl pyrophosphate, more preferred are tetraphenyl pyrophosphate and tetrabenzyl pyrophosphate, and particularly preferred is tetrabenzyl pyrophosphate.
• alkali metal salts are preferably M 2 PF 6 , M 2 BF 4 , M 2 PO 2 F 2 or M 2 FSO 3 (M 2 represents an alkali metal atom ); A form containing at least one selected from the group consisting of M 2 BF 4 , M 2 PO 2 F 2 and M 2 FSO 3 is one of the preferred embodiments of the present invention. More preferred as other alkali metal salts is M 2 PF 6 . Specific examples and preferred forms of the alkali metal atom are the same as those of the alkali metal atom in the sulfonylimide compound.
• the solvent in the nonaqueous electrolyte of the present invention is particularly limited as long as it is nonaqueous and can dissolve the electrolyte (sulfonylimide compound and other alkali metal salts), phosphate ester, and other components described below.
• linear carbonates such as dimethyl carbonate, ethylmethyl carbonate, and diethyl carbonate
• cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and chloroethylene carbonate
• tetrahydrofuran 2-methyltetrahydrofuran, 1,4-dioxane, 1 , 1-dimethoxyethane, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-dibutoxyethane, and other ethers
• ⁇ -butyrolactone ⁇ -valerolactone, ⁇ -methyl- ⁇ -butyrolactone, etc.
• Lactones Lactones; chain carboxylic acid esters such as methyl propionate and methyl butyrate; fluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4,4-difluoroethylene carbonate, tetrafluoroethylene carbonate, 4-fluoro-5- Examples include fluorinated cyclic carbonates such as methylethylene carbonate; fluorinated chain carbonates such as trifluorodimethyl carbonate, trifluorodiethyl carbonate, and trifluoroethylmethyl carbonate. These non-aqueous solvents may be used in combination of two or more. Among them, chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethylmethyl carbonate are preferred.
• components in the non-aqueous electrolyte of the present invention are components other than the above-mentioned sulfonylimide compound, the above-mentioned phosphoric acid ester, an alkali metal salt other than the above-mentioned sulfonylimide compound, and a solvent, and are not particularly limited, but include, for example, phenylethylene carbonate.
• carbonate compounds such as erythritane carbonate; 1,3-propanesultone, 1,4-butanesultone, 1,5-pentanesultone, 1,4-hexanesultone, 4,6-heptanesultone, methyl methanesulfonate , sulfonic acid esters such as methyl benzenesulfonate and methyl trifluoromethanesulfonate; sulfone compounds such as sulfolane, 3-methylsulfolane, ethylmethylsulfone, diphenylsulfone, and bis(4-fluorophenyl)sulfone; succinic anhydride, glutaric anhydride acids, carboxylic acid anhydrides such as maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic anhydride, cyclohexanedicarboxylic anhydride, cyclopentanete
• the non-aqueous electrolyte of the present invention has the above-described structure and has excellent stability when stored in a high-temperature environment, so it can be suitably used as a material for batteries such as lithium ion batteries.
• the present invention also provides a battery comprising the non-aqueous electrolyte of the present invention.
• the above battery is preferably a battery comprising a positive electrode and a negative electrode, more preferably a separator impregnated with the non-aqueous electrolyte of the present invention is provided between the positive electrode and the negative electrode, and Preferably, these are housed in an outer case.
• the shape of the battery according to the present invention is not particularly limited, and any conventionally known battery shape such as a cylindrical shape, a square shape, a laminate shape, a coin shape, a large size, etc. can be used. Furthermore, when used as a high voltage power source (several tens of volts to several hundreds of volts) to be installed in an electric vehicle, a hybrid electric vehicle, etc., a battery module can be constructed by connecting individual batteries in series. .
• the battery is preferably an alkali metal battery, and an alkali metal battery comprising the nonaqueous electrolyte of the present invention is also an aspect of the present invention.
• the battery is more preferably a secondary battery, and one preferred embodiment of the present invention is that the battery is a lithium ion secondary battery.
• the positive electrode constituting the battery is not particularly limited, but includes a positive electrode active material composition containing a positive electrode active material, a conductive aid, a binder, a dispersion solvent, etc. supported on a positive electrode current collector, Usually formed into a sheet.
• Examples of methods for manufacturing the positive electrode include coating a positive electrode active material composition on a positive electrode current collector using a doctor blade method, immersing the positive electrode current collector in a positive electrode active material composition, and then drying; A method in which a sheet obtained by kneading, molding, and drying an active material composition is bonded to a positive electrode current collector via a conductive adhesive, followed by pressing and drying; Examples include a method of coating or casting onto an electric body, forming it into a desired shape, removing the liquid lubricant, and then stretching in uniaxial or multiaxial directions.
• the material of the positive electrode current collector is not particularly limited, and for example, conductive metals such as aluminum, aluminum alloy, SUS (stainless steel), and titanium can be used. Among these, aluminum is preferred from the viewpoint of being easy to process into a thin film and being inexpensive.
• the positive electrode active material may be any cathode active material as long as it can absorb and release ions, and conventionally known positive electrode active materials can be used.
• M 3 CoO 2 , M 3 NiO 2 , M 3 MnO 2 , M 3 Ni x Co y Mnz O 2 and M 3 Ni x Co y Al z O 2 (x, y, z are x+y+z 1, 0 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 1, 0 ⁇ z ⁇ 1)
• Composite metal oxides such as ternary oxides
• Olivine structure such as nickel manganic acid
• positive electrode active materials may be used alone or in combination.
• a battery configured with a positive electrode containing such a positive electrode active material is one of the preferred embodiments of the present invention.
• Examples of the conductive aid include acetylene black, carbon black, graphite, metal powder materials, single-walled carbon nanotubes, multi-walled carbon nanotubes, and vapor-grown carbon fibers.
• fluorine resins such as polyvinylidene fluoride and polytetrafluoroethylene
• synthetic rubbers such as styrene-butadiene rubber and nitrile butadiene rubber
• polyamide resins such as polyamideimide
• polyolefin resins such as polyethylene and polypropylene
• poly(meth)acrylic resin polyacrylic acid
• cellulose resin such as carboxymethyl cellulose; and the like.
• these binders may be used alone or in combination. Moreover, these binders may be in a state dissolved in a solvent or in a state dispersed in a solvent at the time of use.
• the blending amounts of the conductive aid and the binder can be appropriately adjusted in consideration of the purpose of use of the battery (emphasis on output, emphasis on energy, etc.), ionic conductivity, and the like.
• examples of the solvent used in the positive electrode active material composition include N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, tetrahydrofuran, acetonitrile, acetone, ethanol, ethyl acetate, water, and the like. These solvents may be used in combination.
• the amount of the solvent used is not particularly limited, and may be appropriately determined depending on the manufacturing method and the materials used.
• the negative electrode constituting the above battery is not particularly limited, but a negative electrode active material composition containing a negative electrode active material, a dispersion solvent, a binder, and if necessary a conductive aid, etc. is supported on a negative electrode current collector. It is usually shaped into a sheet.
• conductive metals such as copper, iron, nickel, silver, and stainless steel (SUS) can be used. Note that copper is preferred from the viewpoint of ease of processing into a thin film.
• negative electrode active material conventionally known negative electrode active materials used in batteries can be used, as long as they are capable of occluding and releasing ions.
• metal alloys such as alkali metals and alkali metal-aluminum alloys, graphite materials such as artificial graphite and natural graphite, mesophase fired bodies made from coal and petroleum pitch, carbon materials such as non-graphitizable carbon, and Si , Si alloy, SiO, and other Si-based negative electrode materials, and Sn-based negative electrode materials such as Sn alloys can be used.
• the negative electrode As a method for manufacturing the negative electrode, a method similar to that for manufacturing the positive electrode can be adopted. Further, the conductive aid, binder, and solvent for material dispersion used in producing the negative electrode are the same as those used in the positive electrode.
• the separator is arranged to separate the positive electrode and the negative electrode.
• the separator constituting the battery is not particularly limited, and commonly used separators can be used.
• Examples of the separator include porous sheets made of polymers that can absorb and retain nonaqueous electrolytes (eg, polyolefin microporous separators, cellulose separators, etc.), nonwoven fabric separators, porous metal bodies, and the like.
• polyolefin-based microporous separators are suitable because they have the property of being chemically stable to organic solvents.
• Examples of the material for the porous sheet include polyethylene, polypropylene, and a laminate having a three-layer structure of polypropylene/polyethylene/polypropylene.
• non-woven fabric separator examples include cotton, rayon, acetate, nylon, polyester, polypropylene, polyethylene, polyimide, aramid, glass, etc., depending on the mechanical strength etc. required for the non-aqueous electrolyte layer.
• the above-mentioned materials can be used alone or in combination.
• the method for evaluating the physical properties of the non-aqueous electrolyte and battery characteristics is as follows. (Measurement of water content of non-aqueous electrolyte) Karl Fischer moisture measuring device AQ-2000 (manufactured by Hiranuma Sangyo Co., Ltd.) was used, Aqualite RS-A (manufactured by Hiranuma Sangyo Co., Ltd.) was used as the generated liquid, and Aqualite CN (manufactured by Hiranuma Sangyo Co., Ltd.) was used as the counter electrode. , the water content of the non-aqueous electrolyte was measured.
• the nonaqueous electrolyte was diluted 100 times with ultrapure water to prepare a measurement solution, and the amount contained in the nonaqueous electrolyte was measured using the ion chromatography system ICS-3000 (manufactured by Nippon Dionex Co., Ltd.) under the following measurement conditions. The concentration of sulfate ions (SO 4 2 ⁇ ) was measured. Measurement conditions Separation mode: Ion exchange eluent: 7-18mM KOH aqueous solution Detector: Electrical conductivity detector Column: Anion analysis column Ion PAC AS-17C (manufactured by Nippon Dionex Co., Ltd.)
• the aged lithium ion secondary battery (cell) was CC charged at 1C (30mA) for 30 minutes at room temperature. After the cell was transferred to a -30° C. constant temperature bath and the temperature was sufficiently controlled, impedance was measured at frequencies from 1 GHz to 1 mHz using an impedance analyzer (manufactured by Bio Logic, product number: VSP-300). The interfacial resistance was determined from the frequency at which the arc of the obtained measured value diverged. Note that the frequency at which the arc diverges is the frequency at which the imaginary axis value reaches a minimum between frequencies of 10 Hz and 0.001 Hz.
• DCR increase rate, capacity maintenance rate (i) DCR
• the aged lithium ion secondary battery (cell) was CCCV charged at 4.2 V and 1 C (30 mA) at room temperature. After 30 minutes, it was discharged at 0.2C (6mA) for 10 seconds, then after being left for 30 minutes, it was discharged at 1C (30mA) for 10 seconds, and after being left for another 30 minutes, it was CC discharged at 3C (90mA) for 10 seconds.
• Each discharge current was plotted on the horizontal axis, and the difference ( ⁇ V) between the closed circuit voltage at the start of discharge and 10 seconds later at each discharge current was plotted on the vertical axis, and the slope of the IV straight line was defined as the DCR of the cell.
• Non-aqueous electrolysis with various salt concentrations can be achieved by dissolving an electrolyte salt, an electrolyte salt with a mixed salt composition containing LiFSI and LiPF 6 (manufactured by Stella Chemifa Co., Ltd.), or an electrolyte salt with a single salt composition containing only LiPF 6 .
• a solution hereinafter also simply referred to as "electrolyte solution" was prepared.
• a phosphoric acid ester was further added to some of the electrolytic solutions at concentrations shown in Tables 1 and 2 to prepare non-aqueous electrolytic solutions.
• ultrapure water (over 18.2 ⁇ cm) was added to the various electrolytic solutions prepared to prepare non-aqueous electrolytic solutions having the water content shown in Tables 1 to 4.
• the phosphoric acid esters used to prepare the above non-aqueous electrolyte are as follows.
• TBP Tribenzyl phosphate
• TEPP Tetraethyl pyrophosphate
• TPPP Tetraphenyl pyrophosphate
• TBPP Tetrabenzyl pyrophosphate
• the water content of the obtained nonaqueous electrolyte was measured, and the stability of the electrolyte after storage at 60° C. for 3 and 6 months was evaluated. The results are shown in Tables 1 to 4.
• (Preparation of lithium ion secondary battery 1) (i) Preparation of positive electrode (NMC111) Ternary positive electrode active materials LiNi 1/3 Co 1/3 Mn 1/3 O 2 (manufactured by Umicore), acetylene black (AB, manufactured by Denka Co., Ltd., product name: Denka Black (registered trademark)), graphite (manufactured by Nippon Graphite Industries Co., Ltd., product number: SP270), and polyvinylidene fluoride (PVdF, manufactured by Kureha Co., Ltd., product number: KF1120) were combined with N-methyl-2-pyrrolidone (NMP).
• NMP N-methyl-2-pyrrolidone
• the obtained positive electrode composite slurry was applied to aluminum foil (positive electrode current collector, manufactured by Nippon Foil Co., Ltd., thickness 15 ⁇ m) so that the coating weight after drying was 19.4 mg/ cm2 . It was coated on one side with an applicator and dried on a hot plate at 110°C for 10 minutes. Furthermore, it was dried for 12 hours in a vacuum drying oven at 110°C. Thereafter, a sheet-shaped positive electrode (thickness: 83 ⁇ m) was obtained by pressure molding using a roll press machine until the density was 3.1 g/cm 3 .
• (iv) Cell aging process The cell obtained in (iii) above was aged using a charge/discharge test device (manufactured by Asuka Electronics Co., Ltd., product number: ACD-01, same hereinafter). Specifically, constant current (CC) charging was performed at 0.1 C (3 mA) for 3 hours at room temperature (25° C., the same applies hereinafter), and the battery was left at room temperature for 48 hours. After standing, the excess laminate was opened and the cell was vacuum-sealed to degas the cell. Further, after constant current constant voltage (CCCV) charging was performed at 4.2 V and 0.5 C (15 mA) at room temperature, CC discharge was performed at 2.75 V and 0.2 C (6 mA).
• CCCV constant current constant voltage
• CC discharge is performed at 2.75V, 1C (30mA)
• CC discharge is performed at 2.75V, 2C (60mA)
• CC discharge was performed at 2.75V and 0.2C (6mA). The above was the cell aging process.
• NMP N-methyl-2-pyrrolidone
• the obtained positive electrode composite slurry was applied to a carbon-coated aluminum foil (positive electrode current collector, manufactured by Nippon Graphite Industries Co., Ltd., thickness 20 ⁇ m) so that the coating weight after drying was 17.6 mg/ cm2 . It was coated on one side with an applicator and dried on a hot plate at 110°C for 10 minutes. Furthermore, it was dried for 12 hours in a vacuum drying oven at 110°C. Thereafter, a sheet-like positive electrode (thickness: 111 ⁇ m) was obtained by pressure molding using a roll press machine until the density was 1.6 g/cm 3 .
• the phosphate ester represented by the above formula (2) has a small DCR increase rate, and the resistance increase during cycle charging and discharging is small. suppressed. Similar to the storage stability of the electrolytic solution, this tendency remains the same even if the type and amount of the compound added is changed as long as the phosphoric ester satisfies formula (2).

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