Electrode for lithium ion battery and lithium ion battery

Abstract

The present invention provides an electrode for a lithium ion battery, which contains a sulfonic acid compound that contains a sulfonic acid anion represented by formula (1) and an Mn cation, R-SO3-(1) (wherein R represents a hydrogen atom or a hydrogen atom). R represents an alkyl group which is optionally substituted by a fluorine atom and has 1-5 carbon atoms, an alkenyl group which is optionally substituted by a fluorine atom and has 2-5 carbon atoms, an alkynyl group which is optionally substituted by a fluorine atom and has 2-5 carbon atoms or an aryl group which is optionally substituted by a fluorine atom.

Description

Technical Field

[0001] The invention relates to an electrode for a lithium ion battery and a lithium ion battery. Background Art

[0002] In lithium-ion batteries, when repeatedly charged and discharged, lithium loss occurs due to the decomposition of the electrolyte on the electrode surface, and as a result, there is a tendency for the battery capacity to decrease. Therefore, as a method for preventing the decomposition of the electrolyte on the electrode surface, a method for forming a coating on the electrode surface is being studied. For example, in Patent Document 1, it is recorded that in order to improve the cycle characteristics and storage characteristics, a specific lithium sulfonate salt is added to the negative electrode slurry and dispersed, the slurry is applied and dried, so that the lithium sulfonate salt is attached to the surface of the negative electrode active material. In addition, in Patent Document 2, it is recorded that in order to reduce the battery resistance after storage, a battery containing LiPF6 and lithium bis(fluorosulfonyl)imide (LiFSI) as electrolytes and a non-aqueous electrolyte of lithium trifluoromethylsulfonate as an additive is used.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2014 / 119375

[0006] Patent Document 2: International Publication No. 2020 / 026853 Summary of the invention

[0007] 1. Technical issues to be resolved

[0008] The present invention relates to an electrode for a lithium ion battery capable of maintaining a higher discharge capacity after the lithium ion battery is repeatedly charged and discharged at a high temperature.

[0009] (II) Technical solution

[0010] One aspect of the present invention relates to an electrode for a lithium ion battery, comprising a sulfonic acid compound comprising a sulfonic acid anion represented by the following formula (1) and a Mn cation.

[0011] R-SO3 - (1)

[0012] In formula (1), R represents an alkyl group having 1 to 5 carbon atoms which is optionally substituted by a fluorine atom, an alkenyl group having 2 to 5 carbon atoms which is optionally substituted by a fluorine atom, an alkynyl group having 2 to 5 carbon atoms which is optionally substituted by a fluorine atom, or an aryl group which is optionally substituted by a fluorine atom.

[0013] Another aspect of the present invention relates to a lithium ion battery comprising a positive electrode and a negative electrode disposed opposite to each other and an electrolyte, wherein at least one of the positive electrode or the negative electrode comprises a sulfonic acid compound comprising a sulfonic acid anion represented by the following formula (1) and a Mn cation.

[0014] R-SO3 - (1)

[0015] In formula (1), R represents an alkyl group having 1 to 5 carbon atoms which is optionally substituted by a fluorine atom, an alkenyl group having 2 to 5 carbon atoms which is optionally substituted by a fluorine atom, an alkynyl group having 2 to 5 carbon atoms which is optionally substituted by a fluorine atom, or an aryl group which is optionally substituted by a fluorine atom.

[0016] (III) Beneficial effects

[0017] One aspect of the present invention provides an electrode for a lithium ion battery capable of maintaining a higher discharge capacity after the lithium ion battery is repeatedly charged and discharged at a high temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a cross-sectional view showing an example of an electrode for a lithium ion battery.

[0019] Figure 2 is a cross-sectional view showing an example of a lithium ion battery. DETAILED DESCRIPTION

[0020] Several embodiments of the present invention are described in detail. The present invention is not limited to the following examples.

[0021] Figure 1 This is a cross-sectional view schematically showing an example of an electrode for a lithium ion battery. Figure 1 The lithium ion battery electrode 10 shown in FIG. 1 includes a current collector 11 and an active material layer 12. Figure 1 As shown, active material layer 12 may be provided on one surface of current collector 11 or on both surfaces of current collector 11 .

[0022] One example of the lithium ion battery electrode 10 includes a sulfonic acid compound including a sulfonic acid anion represented by the following formula (1) and a Mn cation.

[0023] R-SO3 - (1)

[0024] In formula (1), R represents an alkyl group having 1 to 5 carbon atoms which is optionally substituted by a fluorine atom, an alkenyl group having 2 to 5 carbon atoms which is optionally substituted by a fluorine atom, an alkynyl group having 2 to 5 carbon atoms which is optionally substituted by a fluorine atom, or an aryl group which is optionally substituted by a fluorine atom.

[0025] When the lithium ion battery electrode 10 contains a sulfonic acid compound containing a sulfonic acid anion represented by formula (1) and a Mn cation, decomposition of the electrolyte on the surface of the lithium ion battery electrode 10 can be suppressed in a lithium ion battery produced using the lithium ion battery electrode 10, compared to a case where the sulfonic acid compound is not contained. It is believed that this makes it possible to maintain a higher discharge capacity after repeated charge and discharge of the lithium ion battery.

[0026] The alkyl group, alkenyl group, alkynyl group and aryl group as R may be unsubstituted, or one or more hydrogen atoms may be substituted by fluorine atoms.

[0027] The number of carbon atoms of the alkyl group with 1 to 5 carbon atoms optionally substituted by fluorine atoms is 1, 2, 3, 4 or 5. The alkyl group with 1 to 5 carbon atoms optionally substituted by fluorine atoms can be straight-chain or branched. As examples of alkyl groups with 1 to 5 carbon atoms optionally substituted by fluorine atoms, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl and trifluoromethyl can be cited. From the perspective of reducing battery resistance, the alkyl group with 1 to 5 carbon atoms optionally substituted by fluorine atoms can be methyl, ethyl or tert-butyl. When the alkyl group with 1 to 5 carbon atoms optionally substituted by fluorine atoms is a methyl group optionally substituted by fluorine atoms, the battery resistance can be further reduced.

[0028] The number of carbon atoms of the alkenyl group with 2 to 5 carbon atoms optionally substituted by fluorine atoms is 2, 3, 4 or 5. The alkenyl group with 2 to 5 carbon atoms optionally substituted by fluorine atoms can be straight-chain or branched. As examples of alkenyl groups with 2 to 5 carbon atoms optionally substituted by fluorine atoms, vinyl, allyl, isopropenyl, 1-butenyl, 2-butenyl, 3-butenyl, isobutenyl and 1,1-difluoro-1-propenyl can be cited. The alkenyl group with 2 to 5 carbon atoms optionally substituted by fluorine atoms can be vinyl groups optionally substituted by fluorine atoms.

[0029] The number of carbon atoms of the alkynyl group with 2 to 5 carbon atoms optionally substituted by fluorine atoms can be 2, 3, 4 or 5. The alkynyl group with 2 to 5 carbon atoms optionally substituted by fluorine atoms can be straight chain or branched. As examples of the alkynyl group with 2 to 5 carbon atoms optionally substituted by fluorine atoms, 1-propynyl, 2-propynyl, 1-butynyl, 2-butynyl and 3-butynyl can be mentioned. The alkynyl group with 2 to 5 carbon atoms optionally substituted by fluorine atoms can be 2-propynyl group optionally substituted by fluorine atoms.

[0030] Examples of the aryl group which may be substituted with a fluorine atom include a phenyl group, a tolyl group, a pentafluorophenyl group, a xylyl group and a naphthyl group.

[0031] The Mn cation may be a divalent, trivalent, tetravalent, pentavalent or heptavalent Mn cation. From the perspective of maintaining a higher discharge capacity after repeated charge and discharge of the lithium ion battery, the Mn cation may be a divalent Mn cation.

[0032] The sulfonic acid compound may be a compound represented by the following formula (2).

[0033] (R-SO3 - )2[Mn] 2+ (2)

[0034] R in formula (2) has the same meaning as R in the above formula (1).

[0035] Examples of the compound represented by the above formula (2) include manganese (II) methanesulfonate, manganese (II) trifluoromethanesulfonate, manganese (II) ethanesulfonate, manganese (II) propanesulfonate, manganese (II) pentanesulfonate, manganese (II) vinylsulfonate, manganese (II) allylsulfonate, manganese (II) propynylsulfonate, manganese (II) benzenesulfonate and manganese (II) pentafluorobenzenesulfonate.

[0036] The sulfonic acid compound may be attached to the surface of the lithium ion battery electrode 10 . More specifically, the sulfonic acid compound may be attached to the surface of the active material layer 12 .

[0037] As a method for attaching the sulfonic acid compound to the surface of the active material layer 12, for example, a method including a step of immersing the electrode for a lithium ion battery in a solution containing the above-mentioned sulfonic acid compound can be cited. The immersion time can be, for example, less than 48 hours or less than 24 hours, and can be more than 1 hour. In addition, the temperature of the solution for immersing the electrode can be, for example, room temperature (25° C.) to 40° C. The solution containing the sulfonic acid compound can be an electrolyte in a lithium ion battery.

[0038] It is known that in lithium-ion batteries, an electrochemical reaction occurs on the electrode surface during initial charge and discharge, and a coating called a solid electrolyte interface (SEI) (hereinafter also referred to as "SEI coating") is formed on the surface of the active material layer, etc. The lithium-ion battery electrode 10 may have an SEI coating, and more specifically, may have an SEI coating formed on the surface of the active material layer 12. In this case, the sulfonic acid compound may be contained in the SEI coating.

[0039] The lithium ion battery electrode 10 is an electrode used in a lithium ion battery, and can be a positive electrode or a negative electrode. When the lithium ion battery electrode 10 is a positive electrode for a lithium ion battery, the collector 11 is a positive electrode collector, and the active material layer 12 is a positive electrode active material layer. In addition, when the lithium ion battery electrode 10 is a negative electrode for a lithium ion battery, the collector 11 is a negative electrode collector, and the active material layer 12 is a negative electrode active material layer.

[0040] The positive electrode collector may include a material having electronic conductivity. As examples of materials having electronic conductivity, conductive materials such as carbon, titanium, chromium, molybdenum, ruthenium, rhodium, tantalum, tungsten, osmium, iridium, platinum, gold, aluminum, and alloys containing two or more conductive materials (e.g., stainless steel) can be cited. From the perspective of high electronic conductivity, stability in the electrolyte and excellent oxidation resistance, the material of the positive electrode collector may be carbon, aluminum or stainless steel, and from the perspective of cost, may be aluminum.

[0041] The positive electrode current collector may be a foil (foil-shaped). When the positive electrode current collector is a foil, the positive electrode current collector may have a primer layer on its surface in order to further increase the capacity.

[0042] The positive electrode active material layer contains a positive electrode active material. The positive electrode active material may be a composite oxide containing lithium. Examples of composite oxides containing lithium include LiMnO2, LiFeO2, LiMn2O4, Li2FeSiO4, LiNi 1 / 3 Co 1 / 3Mn 1 / 3 O2、LiNi 0.5 Co 0.2 Mn 0.3 O2、LiNi 0.6 Co 0.2 Mn 0.2 O2、LiNi 0.8 Co 0.1 Mn 0.1 O2、Li z Ni (1-x-y) Co x M y O2 (wherein 0≤x≤0.40, 0≤y≤0.40 and 0.90≤z≤1.20, M is at least one element selected from the group consisting of Mn, V, Mg, Mo, Nb and Al.), LiFePO4, and Li z Co (1-x) M x O2 (wherein 0≤x≤0.1 and 0.97≤z≤1.20, M is at least one element selected from the group consisting of Mn, Ni, V, Mg, Mo, Nb and Al.) From the perspective of further realizing a high capacity of the battery, the positive electrode active material may be LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2、LiNi 0.5 Co 0.2 Mn 0.3 O2、LiNi 0.6 Co 0.2 Mn0.2 O2、LiNi 0.8 Co 0.1 Mn 0.1 O2 or Li z Ni (1-x-y) Co x M y O2 (wherein 0≤x≤0.40, 0≤y≤0.40 and 0.90≤z≤1.20, and M is at least one element selected from the group consisting of Mn, V, Mg, Mo, Nb and Al.).

[0043] The negative electrode current collector may include metals such as aluminum, copper, nickel, and stainless steel. From the perspective of ease of processing and cost, the negative electrode current collector may include copper. The negative electrode current collector may be a foil (foil-shaped). The surface of the negative electrode current collector may be roughened.

[0044] The negative electrode active material layer contains a negative electrode active material. The negative electrode active material is, for example, a material that can embed and deintercalate lithium. Examples of negative electrode active materials include carbon materials such as graphite and amorphous carbon, and oxide materials such as indium oxide, silicon oxide, tin oxide, lithium titanate, zinc oxide, and lithium oxide. In addition, the negative electrode active material can be lithium metal or a metal material that can form an alloy with lithium. Examples of metals that can form an alloy with lithium include Cu, Sn, Si, Co, Mn, Fe, Sb, and Ag. The negative electrode active material is an alloy containing these metals and lithium, and may also contain an alloy containing two or three metals. These exemplified negative electrode active materials can be used alone or in combination of two or more.

[0045] From the perspective of high energy density, the negative electrode active material can include carbon materials such as graphite and amorphous carbon and Si-based active materials selected from Si, Si alloys and Si oxides. In this case, the mass of the Si-based active material relative to the total mass of the carbon material and the Si-based active material can be 0.5% by mass or more, 1% by mass or more, or 2% by mass or more, or 95% by mass or less, 50% by mass or less, or 40% by mass or less. The mass of the Si-based active material relative to the total mass of the carbon material and the Si-based active material can be 0.5% by mass or more and 95% by mass or less, 50% by mass or less, or 40% by mass or less, or 1% by mass or more and 95% by mass or less, 50% by mass or less, or 40% by mass or more, or 2% by mass or more and 95% by mass or less, 50% by mass or less, or 40% by mass or less.

[0046] The positive electrode active material layer and the negative electrode active material layer may further include a binder. As examples of binders, polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, styrene-butadiene copolymer rubber (SBR), carboxymethyl cellulose (CMC), polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamide-imide, polyacrylic acid, polyvinyl alcohol, acrylic acid-polyacrylonitrile, polyacrylamide, polymethacrylic acid and their copolymers can be cited. The positive electrode active material layer and the negative electrode active material layer may include binders that are the same or different from each other. When the positive electrode active material layer includes a binder, the binder included in the positive electrode active material layer may be polyvinylidene fluoride (PVDF). When the negative electrode active material layer includes a binder, from the perspective of better cycle characteristics, the binder included in the negative electrode active material layer may be SBR, CMC, polyacrylic acid or a copolymer containing them.

[0047] An example of a lithium ion battery comprises a positive electrode and a negative electrode disposed opposite to each other and an electrolyte, wherein at least one of the positive electrode or the negative electrode contains the above-mentioned sulfonic acid compound. The positive electrode and the negative electrode may be the above-mentioned electrodes for lithium ion batteries.

[0048] Figure 2 is a cross-sectional view schematically showing an example of a lithium ion battery. Figure 2 The lithium ion battery 1 shown in FIG. 1 includes negative electrodes 4 and positive electrodes 9 alternately stacked, an electrolyte 5 disposed between the negative electrodes 4 and the positive electrodes 9, and a separator 6 disposed in the electrolyte 5. The lithium ion battery 1 includes 7 layers of negative electrodes 4 and 6 layers of positive electrodes 9. Figure 2 , a part of the repeated structure is omitted. The negative electrode 4 has a negative electrode collector 3 and a negative electrode active material layer 2 provided on both sides of the negative electrode collector 3. The positive electrode 9 has a positive electrode collector 8 and a positive electrode active material layer 7 provided on both sides of the positive electrode collector 8. The positive electrode 9 is a positive electrode for a lithium ion battery having the above-mentioned positive electrode collector and the positive electrode active material layer. In addition, the negative electrode 4 is a negative electrode for a lithium ion battery having the above-mentioned negative electrode collector and the negative electrode active material layer.

[0049] The electrolyte 5 specifically contains a non-aqueous solvent and an electrolyte. The electrolyte 5 may be a non-aqueous electrolyte.

[0050] From the perspective of suppressing the viscosity of the electrolyte 5 to be lower, the nonaqueous solvent can be an aprotic solvent. The aprotic solvent can be at least one selected from the group consisting of cyclic carbonate, linear carbonate, aliphatic carboxylic acid ester, lactone, lactam, cyclic ether, linear ether, sulfone, nitrile and their halogen derivatives. The aprotic solvent can comprise cyclic carbonate or linear carbonate, and can also comprise the combination of cyclic carbonate and linear carbonate.

[0051] Examples of cyclic carbonates include ethylene carbonate, propylene carbonate, butylene carbonate, and fluoroethylene carbonate. Examples of chain carbonates include dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Examples of aliphatic carboxylic acid esters include methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, and methyl trimethylacetate. Examples of lactones include γ-butyrolactone. Examples of lactams include ε-caprolactam and N-methylpyrrolidone. Examples of cyclic ethers include tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, and 1,3-dioxolane. Examples of chain ethers include 1,2-diethoxyethane and ethoxymethoxyethane. Examples of sulfones include sulfolane. Examples of nitrites include acetonitrile. Examples of halogen derivatives include 4-fluoro-1,3-dioxolane-2-one, 4-chloro-1,3-dioxolane-2-one, and 4,5-difluoro-1,3-dioxolane-2-one. The nonaqueous solvent may contain one or more compounds selected from the above compounds.

[0052] The content of the nonaqueous solvent in the electrolyte solution 5 is, for example, 70 to 99% by mass based on the total mass of the electrolyte solution 5 .

[0053] The electrolyte may be a lithium salt that is an ion source of lithium ions. The electrolyte may include at least one lithium salt (first lithium salt) selected from the group consisting of LiAlCl4, LiBF4, LiPF6, LiClO4, LiTFSI (lithium bistrifluoromethanesulfonyl imide), LiFSI (lithium bisfluorosulfonyl imide), LiAsF6 and LiSbF6. From the perspective of having a high degree of dissociation and being able to improve the ion conductivity of the electrolyte and further having the effect of inhibiting the performance degradation of the storage device caused by long-term use through anti-oxidation-reduction characteristics, the electrolyte may include LiBF4, LiPF6 or a combination thereof.

[0054] When the electrolyte is LiBF4, LiPF6 or a combination thereof, the nonaqueous solvent may include cyclic carbonates and chain carbonates. LiBF4 and / or LiPF6 may be combined with ethylene carbonate and diethyl carbonate.

[0055] The concentration of the electrolyte in the electrolyte 5 can be 0.1 mol / L or more and 2.0 mol / L or less, based on the total volume of the electrolyte 5. When the concentration of the electrolyte based on the total volume of the electrolyte 5 is 0.1 mol / L or more, it is easy to obtain good conductivity of the electrolyte 5, and when it is 2.0 mol / L or less, it is particularly easy to ensure the mobility of ions by suppressing the increase in the viscosity of the electrolyte 5. From the same perspective, the concentration of the electrolyte can be 0.5 mol / L or more and 1.5 mol / L or less, based on the total volume of the electrolyte 5.

[0056] The electrolyte 5 may include the above-mentioned lithium salt (first lithium salt) and one or more second lithium salts different from the first lithium salt. Examples of the second lithium salt include lithium difluorophosphate, lithium bis(oxalato)borate (LiBOB), lithium tetrafluoro(oxalate)phosphate (LiTFOP), lithium difluorooxalatoborate (LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFOP), lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, and Li2PO3F, which have a phosphate skeleton, and lithium trifluoro((methylsulfonyl)oxy)borate, lithium pentafluoro((methylsulfonyl)oxy)phosphate, lithium methyl sulfate, lithium ethyl sulfate, 2,2,2-trifluoroethyl lithium sulfate, and lithium fluorosulfonate, which have a S(=O) group. The second lithium salt may include one or more lithium salts selected from the group consisting of lithium difluorophosphate, lithium bisoxalatoborate, lithium tetrafluoro(oxalate)phosphate, lithium difluorooxalatoborate, lithium difluorobisoxalatophosphate, lithium methyl sulfate, lithium ethyl sulfate, and lithium fluorosulfonate.

[0057] The concentration of the second lithium salt in the electrolyte 5 may be 1.0 mol / L or less, based on the total volume of the electrolyte 5. When the concentration of the second lithium salt is 1.0 mol / L or less, the mobility of ions can be fully ensured because the viscosity of the electrolyte 5 is not easily increased. From the same perspective, the concentration of the second lithium salt may be 0.8 mol / L or less or 0.5 mol / L or less.

[0058] The electrolyte 5 may contain the above-mentioned sulfonic acid compound as an additive. When the electrolyte 5 contains the sulfonic acid compound, the sulfonic acid compound can be attached to the surface of the positive electrode active material layer 7 of the positive electrode 9 and / or the negative electrode active material layer 2 of the negative electrode 4 by immersing the positive electrode 9 and / or the negative electrode 4 (electrode for lithium ion battery) in the electrolyte 5. And, after the sulfonic acid compound is attached to the surface of the positive electrode active material layer 7 and / or the negative electrode active material layer 2, the lithium ion battery 1 is charged and discharged, and when the SEI film is formed on the surface of the positive electrode active material layer 7 and / or the negative electrode active material layer 2, the formed SEI film can contain the sulfonic acid compound. The sulfonic acid compound can be attached only to the surface of either the positive electrode active material layer 7 or the negative electrode active material layer 2, but from the perspective of further reducing the resistance, it can also be attached to the surface of the positive electrode active material layer 7 and the negative electrode active material layer 2.

[0059] The concentration of the sulfonic acid compound in the electrolyte 5 may be 0.05 mmol / L or more or 0.1 mmol / L or more based on the total amount of the electrolyte 5. Furthermore, the concentration of the sulfonic acid compound in the electrolyte 5 may be 0.05 mmol / L or more or 0.1 mmol / L or more and 1.0 mol / L or less based on the total amount of the electrolyte 5.

[0060] The electrolyte 5 may contain a compound having a sulfonyl group (>S(=O)2) as an additive and different from the sulfonic acid compound of formula (1). Examples of the compound having a sulfonyl group include 1,3-propane sultone, 1-propenyl-1,3-sultone, 1,3,2-dioxazolidinone-2,2-dioxide, 1,3,2-dioxathiophene-2,2-dioxide, 2-(methylsulfonyl)ethyl methanesulfonate, 2-(methylsulfonyl)ethyl ethanesulfonate, 2-(methylsulfonyl)ethyl vinylsulfonate, 2-(methylsulfonyl)ethylbenzenesulfonate, 3-trifluoromethylsulfonyltetrahydrothiophene-1,1-dioxide, 3-methylsulfonyltetrahydrothiophene-1,1-dioxide, 3-vinylsulfonyltetrahydrothiophene-1,1-dioxide, 3-methylene ... Propylsulfonyltetrahydrothiophene-1,1-dioxide, benzenesulfonyltetrahydrothiophene-1,1-dioxide, 3-methylsulfonyltetrahydrothiophene-1,1-dioxide-2-ene, 4-methylsulfonyltetrahydrothiophene-1,1-dioxide, 3-methylsulfonyloxytetrahydrothiophene-1,1-dioxide, 3-vinylsulfonyloxytetrahydrothiophene-1,1-dioxide, 3-methylallylsulfonyloxytetrahydrothiophene-1,1-dioxide, benzenesulfonyloxytetrahydrothiophene-1,1-dioxide, 3-methylsulfonyloxytetrahydrothiophene-1,1-dioxide-2-ene, 4-methylsulfonyloxytetrahydrothiophene-1,1-dioxide, and methylene methanedisulfonate. These compounds may be used alone or in combination of two or more. When the electrolyte 5 contains a compound having a sulfonyl group, if the lithium ion battery 1 is charged and discharged, as a result of the electrochemical reaction on the surface of the positive electrode active material layer 7 and / or the negative electrode active material layer 2, the above-mentioned sulfonic acid compound containing sulfonic acid anions and Mn cations from the compound having a sulfonyl group is sometimes generated. At this time, an SEI film containing a sulfonic acid compound can be formed. The sulfonic acid compound may be attached only to the surface of either the positive electrode active material layer 7 or the negative electrode active material layer 2, but from the perspective of further reducing the resistance, it may also be attached to the surface of the positive electrode active material layer 7 and the negative electrode active material layer 2.

[0061] The concentration of the compound having a sulfonyl group in the electrolyte 5 is not particularly limited, but from an economical point of view, it may be 0.005 mass % or more or 0.01 mass % or more based on the total mass of the electrolyte 5. The concentration of the compound having a sulfonyl group may be 0.005 mass % or more and 10 mass % or less or 0.005 mass % or more and 5 mass % or less.

[0062] The electrolyte 5 may contain other additives different from the above-mentioned sulfonic acid compound and the compound having a sulfonyl group. As examples of other additives, compounds containing sulfur atoms other than the above-mentioned sulfonic acid compound and the compound having a sulfonyl group, negative electrode protective agents, positive electrode protective agents, flame retardants, overcharge inhibitors, cyclic carbonate compounds, nitrile compounds, isocyanate compounds, compounds having acetylene-1,2-diyl (-C≡C-), phosphate compounds, acid anhydrides, cyclic phosphazene compounds, compounds containing boron atoms, and compounds containing silicon atoms can be cited.

[0063] Examples of the compound containing a sulfur atom other than the sulfonic acid compound and the compound having a sulfonyl group include 1,3,2-dioxazolidinone-2-oxide and 1,3,2-dioxathiinane-2-oxide.

[0064] Examples of cyclic carbonate compounds include 4-fluoro-1,3-dioxolane-2-one (FEC), trans- or cis-4,5-difluoro-1,3-dioxolane-2-one (DFEC), vinylene carbonate (VC), vinylethylene carbonate (VEC), and 4-ethynyl-1,3-dioxolane-2-one (EEC). The cyclic carbonate compound may be VC, FEC, VEC, or a combination thereof.

[0065] Examples of nitrile compounds include mononitrile compounds such as acetonitrile and propionitrile, and dinitrile compounds such as succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, and sebaconitrile. The nitrile compound may be succinonitrile, adiponitrile, or a combination thereof.

[0066] Examples of the isocyanate compound include methyl isocyanate, ethyl isocyanate, butyl isocyanate, phenyl isocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, octane methylene diisocyanate, 1,4-phenylene diisocyanate, 2-isocyanatoethyl acrylate, and 2-isocyanatoethyl methacrylate.

[0067] Examples of compounds having an acetylene-1,2-diyl group (-C≡C-) include 2-propynyl methyl carbonate, 2-propynyl acetate, 2-propynyl formate, 2-propynyl methacrylate, di(2-propynyl) oxalate, methyl-2-propynyl oxalate, ethyl-2-propynyl oxalate, di(2-propynyl) glutarate, and dimethyl 2-butyne-1,4-dicarboxylate.

[0068] Examples of the phosphate ester compound include trimethyl phosphate, tributyl phosphate, trioctyl phosphate, tris(2,2,2-trifluoroethyl) phosphate, bis(2,2,2-trifluoroethyl) methyl phosphate, bis(2,2,2-trifluoroethyl) ethyl phosphate, bis(2,2,2-trifluoroethyl) 2,2-difluoroethyl phosphate, bis(2,2,2-trifluoroethyl) 2,2,3,3-tetrafluoropropyl phosphate, bis(2,2-difluoroethyl) 2,2,2-trifluoroethyl phosphate, bis(2,2,3,3-tetrafluoropropyl) 2,2,2-trifluoroethyl phosphate, (2,2,2-trifluoroethyl) (2,2,3,3-tetrafluoropropyl) methyl phosphate, tris(1,1,1,3,3,3-hexafluoropropane-2-yl) phosphate, methyl methylenebisphosphonate, Ethyl methylenebisphosphonate, methyl ethylenebisphosphonate, ethyl ethylenebisphosphonate, methyl butylenebisphosphonate, ethyl butylenebisphosphonate, methyl 2-(dimethylphosphoryl)acetate, ethyl 2-(dimethylphosphoryl)acetate, methyl 2-(diethylphosphoryl)acetate, ethyl 2-(diethylphosphoryl)acetate, 2-propynyl 2-(dimethylphosphoryl)acetate, 2-propynyl 2-(diethylphosphoryl)acetate, methyl 2-(dimethoxyphosphoryl)acetate, ethyl 2-(dimethoxyphosphoryl)acetate, methyl 2-(diethoxyphosphoryl)acetate, ethyl 2-(diethoxyphosphoryl)acetate, 2-propynyl 2-(dimethoxyphosphoryl)acetate, 2-propynyl 2-(diethoxyphosphoryl)acetate, methyl pyrophosphate and ethyl pyrophosphate.

[0069] Examples of the acid anhydride include acetic anhydride, propionic anhydride, succinic anhydride, maleic anhydride, 3-allylsuccinic anhydride, glutaric anhydride, and itaconic anhydride.

[0070] Examples of the cyclic phosphazene compound include methoxypentafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, phenoxypentafluorocyclotriphosphazene, and ethoxyheptafluorocyclotetraphosphazene.

[0071] Examples of compounds containing a boron atom include boroxine, trimethylboroxine, trimethoxyboroxine, triethylboroxine, triethoxyboroxine, triisopropylboroxine, triisopropoxyboroxine, tri-n-propylboroxine, tri-n-propoxyboroxine, tri-n-butylboroxine, tri-n-butoxyboroxine, triphenylboroxine, triphenoxyboroxine, tricyclohexylboroxine and tricyclohexyloxyboroxine.

[0072] Examples of the compound containing a silicon atom include hexamethylcyclotrisiloxane, hexaethylcyclotrisiloxane, hexaphenylcyclotrisiloxane, 1,3,5-trimethyl-1,3,5-trivinylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, trimethylfluorosiloxane, triethylfluorosiloxane, tripropylfluorosiloxane, phenyldimethylfluorosiloxane, triphenylfluorosiloxane, vinyldimethylfluorosiloxane, vinyldiethylfluorosiloxane, vinyldiphenylfluorosiloxane, trimethoxyfluorosiloxane, triethoxyfluorosiloxane, dimethyldifluorosiloxane, diethyldifluorosiloxane, divinyldifluorosiloxane, ethylvinyldifluorosiloxane, methyltrifluorosiloxane, and ethyltrifluorosiloxane. trimethylsilyl phosphate, and trimethylsilyl phosphite.

[0073] The separator 6 may be, for example, a porous film or a nonwoven fabric. The separator 6 may include a resin selected from polyethylene, polypropylene, and fluororesins, or may include a polymer electrolyte. The separator 6 may be a single layer or may have multiple layers.

[0074] The specific configurations of the shapes and thicknesses of the components constituting the lithium-ion battery can be appropriately set by those skilled in the art. Figure 2 The implementation scheme can be modified appropriately.

[0075] Example

[0076] The present invention will be described in further detail below with reference to examples, but the present invention is not limited to these examples.

[0077] 1. Production of lithium-ion batteries

[0078] <Example 1>

[0079] Coin-type battery manufacturing

[0080] A positive electrode sheet (manufactured by Hachiyama Co., Ltd.) containing a lithium-containing composite oxide and a negative electrode sheet (manufactured by Hachiyama Co., Ltd.) containing graphite were prepared. The positive electrode sheet had an aluminum foil (thickness of 20 μm) as a positive electrode current collector and a positive electrode active material layer formed on both sides thereof. The positive electrode active material layer contained a lithium-containing composite oxide (LiNi 0.5 Co 0.2 Mn 0.3 O2), carbon black (CB) and carbon (KS) as conductivity imparting agents, and polyvinylidene fluoride (PVDF) as a binder. The mass ratio of these components is: lithium-containing composite oxide: CB: KS: PVDF = 92: 2.5: 2.5: 3. The negative electrode sheet has a copper foil (thickness of 10 μm) as a negative electrode collector and a negative electrode active material layer formed on both sides thereof. The negative electrode active material layer contains graphite (Gr) as a negative electrode active material and carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR) as a binder. The mass ratio of these components is Gr: CMC: SBR = 98: 1: 1. A coin-type battery (CR2032) is made using a positive electrode sheet and a negative electrode sheet as electrodes and a glass filter paper ("GA-100" manufactured by ADVANTEC CO., LTD.) as a separator.

[0081] Preparation of non-aqueous electrolyte

[0082] LiPF6 as an electrolyte was dissolved in a mixed non-aqueous solvent (manufactured by KISHIDA CHEMICAL Co., Ltd.) containing ethylene carbonate (EC) and diethyl carbonate (EMC) in a volume composition ratio of EC:EMC=30:70 to obtain a LiPF6 solution with a concentration of 1 mol / L. Manganese (II) trifluoromethanesulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.) was added to the LiPF6 solution to prepare a non-aqueous electrolyte. Based on the total amount of the non-aqueous electrolyte, the concentration of manganese (II) trifluoromethanesulfonate was 0.12 mmol / L.

[0083] Lithium-ion battery manufacturing

[0084] The non-aqueous electrolyte prepared by the above method is injected into the coin-type battery prepared by the above method, and the battery is left to stand at room temperature (27°C) for 5 hours to immerse the electrode in the non-aqueous electrolyte, thereby obtaining a lithium-ion battery having an electrode (positive electrode sheet and negative electrode sheet) comprising a positive electrode active material layer or a negative electrode active material layer to which manganese (II) trifluoromethanesulfonate is attached.

[0085] <Comparative Example 1>

[0086] A nonaqueous electrolyte was prepared in the same manner as in Example 1, except that manganese (II) trifluoromethanesulfonate was not added, to obtain a lithium ion battery.

[0087] 2. Evaluation

[0088] After charging the lithium ion batteries obtained in the embodiments and comparative examples at 25°C for 1 hour with a current equivalent to 0.1C, they were kept at 25°C for 10 hours. Then, charging was performed at a current equivalent to 0.1C for 5 hours and kept at 45°C for 24 hours. Then, at 25°C, after discharging to 3V with a current equivalent to 0.1C, degassing was performed. Then, the battery was stabilized by sequentially performing: charging to 4.2V with a current equivalent to 0.2C and discharging to 3V with a current equivalent to 0.2C for 3 cycles, charging to 4.2V with a current equivalent to 0.5C and discharging to 3.0V with a current equivalent to 0.5C for 3 cycles, and charging to 4.2V with a current equivalent to 1C and discharging to 3.0V with a current equivalent to 1C for 3 cycles. Then, as the initial charge and discharge, charge and discharge were performed with a current equivalent to 2.0C. The discharge capacity observed in the initial charge and discharge is set as the "initial capacity".

[0089] Furthermore, the lithium-ion battery after the initial charge and discharge was charged to 50% of the initial capacity, and then discharged at a current equivalent to 0.2C to observe the change in battery voltage. Then, after a 10-minute rest, the current (discharge rate) during discharge was changed to 0.5C, 1.0C, and 2.0C, and charging and discharging were repeated.

[0090] (Determination of capacity after cycling)

[0091] Next, for the lithium ion batteries of the embodiments and comparative examples that were subjected to the above-mentioned charge and discharge, a charge and discharge cycle test was performed at 45°C, in which the charge and discharge cycle was repeated for 100 cycles, and the charge rate was set to 2C, the discharge rate was set to 2C, the charge end voltage was set to 4.2V, and the discharge end voltage was set to 3.0V. The discharge capacity after 100 cycles was set to "discharge capacity after 100 cycles". The results are shown in Table 1.

[0092] [Table 1]

[0093]

[0094] Description of Reference Numerals

[0095] 10: Electrode for lithium-ion battery, 11: Current collector, 12: Active material layer, 1: Lithium-ion battery, 2: Negative electrode active material layer, 3: Negative electrode current collector, 4: Negative electrode, 5: Electrolyte, 6: Separator, 7: Positive electrode active material layer, 8: Positive electrode current collector, 9: Positive electrode.

Claims

1. A lithium ion battery electrode comprising a sulfonic acid compound, wherein the sulfonic acid compound comprises a sulfonic acid anion represented by the following formula (1) and a Mn cation, <h2 style=";text-align:left;direction:ltr">R-SO3<h2 style=";text-align:left;direction:ltr"> - <h2 style=";text-align:left;direction:ltr"> (1) In formula (1), R represents an alkyl group having 1 to 5 carbon atoms which is optionally substituted by a fluorine atom, an alkenyl group having 2 to 5 carbon atoms which is optionally substituted by a fluorine atom, an alkynyl group having 2 to 5 carbon atoms which is optionally substituted by a fluorine atom, or an aryl group which is optionally substituted by a fluorine atom.

2. The lithium ion battery electrode according to claim 1, wherein The sulfonic acid compound is a compound represented by the following formula (2): <h2 style=";text-align:left;direction:ltr">(R-SO3<h2 style=";text-align:left;direction:ltr"> - <h2 style=";text-align:left;direction:ltr"> )2[Mn]<h2 style=";text-align:left;direction:ltr"> 2+ <h2 style=";text-align:left;direction:ltr"> (2) In formula (2), R represents an alkyl group having 1 to 5 carbon atoms which is optionally substituted by a fluorine atom, an alkenyl group having 2 to 5 carbon atoms which is optionally substituted by a fluorine atom, an alkynyl group having 2 to 5 carbon atoms which is optionally substituted by a fluorine atom, or an aryl group which is optionally substituted by a fluorine atom.

3. The lithium ion battery electrode according to claim 1 or 2, wherein R is an alkyl group having 1 to 5 carbon atoms which may be substituted with a fluorine atom.

4. A lithium ion battery comprising a positive electrode and a negative electrode arranged opposite to each other and an electrolyte, At least one of the positive electrode or the negative electrode contains a sulfonic acid compound, the sulfonic acid compound containing a sulfonic acid anion represented by the following formula (1) and a Mn cation, <h2 style=";text-align:left;direction:ltr">R-SO3<h2 style=";text-align:left;direction:ltr"> - <h2 style=";text-align:left;direction:ltr"> (1) In formula (1), R represents an alkyl group having 1 to 5 carbon atoms which is optionally substituted by a fluorine atom, an alkenyl group having 2 to 5 carbon atoms which is optionally substituted by a fluorine atom, an alkynyl group having 2 to 5 carbon atoms which is optionally substituted by a fluorine atom, or an aryl group which is optionally substituted by a fluorine atom.

5. The lithium ion battery according to claim 4, wherein: The sulfonic acid compound is a compound represented by the following formula (2): <h2 style=";text-align:left;direction:ltr">(R-SO3<h2 style=";text-align:left;direction:ltr"> - <h2 style=";text-align:left;direction:ltr"> )2[Mn]<h2 style=";text-align:left;direction:ltr"> 2+ <h2 style=";text-align:left;direction:ltr"> (2) In formula (2), R represents an alkyl group having 1 to 5 carbon atoms which is optionally substituted by a fluorine atom, an alkenyl group having 2 to 5 carbon atoms which is optionally substituted by a fluorine atom, an alkynyl group having 2 to 5 carbon atoms which is optionally substituted by a fluorine atom, or an aryl group which is optionally substituted by a fluorine atom.

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