Lithium ion battery

Abstract

In a lithium ion battery, elution of aluminum from an aluminum-containing current collector into an electrolyte solution can be suppressed. This lithium ion battery has a positive electrode, a negative electrode, and an electrolyte solution, the electrolyte solution containing an organic solvent and a lithium amide salt dissolved in the organic solvent, the lithium amide salt containing LiCFSA, one or both of the positive electrode and the negative electrode having an aluminum-containing current collector, and the aluminum-containing current collector having a coating film on a contact surface with the electrolyte solution, the coating film contains Al (CFSA) x.

Description

Technical Field

[0001] The present application discloses a lithium-ion battery. Background Art

[0002] Patent document 1 discloses an electrolyte for a storage device, which contains a cyclic lithium sulfonyl imide salt, a hydrofluoroether, and a carbonate-based solvent. In addition, in Patent document 1, a lithium ion secondary battery is exemplified as the storage device. Patent document 2 discloses a non-aqueous electrolyte containing a carboxylic acid ester. Patent document 3 discloses an electrolyte for a lithium ion secondary battery, which contains: a lithium imide salt; a solvent of at least one of carbonate (salt), ester, ether, and room temperature molten salt; and at least one of a Group 1 element and a Group 2 element.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2010 / 110388

[0006] Patent Document 2: Japanese Patent Application Publication No. 2009-129719

[0007] Patent Document 3: Japanese Patent Application Publication No. 2019-096463 Summary of the invention

[0008] Problems to be solved by the invention

[0009] In order to effectively use an aluminum-containing current collector in a lithium-ion battery, it is necessary to suppress the elution of aluminum from the aluminum-containing current collector into an electrolyte. The present application discloses a technology capable of suppressing the elution of aluminum from an aluminum-containing current collector into an electrolyte in a lithium-ion battery.

[0010] Means for solving problems

[0011] This application discloses the following multiple solutions as means for solving the above-mentioned problems.

[0012] <Option 1>

[0013] A lithium-ion battery having a positive electrode, a negative electrode and an electrolyte.

[0014] The electrolyte solution comprises an organic solvent and a lithium amide salt dissolved in the organic solvent.

[0015] The lithium amide salt includes LiCFSA represented by the following formula (1), one or both of the positive electrode and the negative electrode have an aluminum-containing current collector,

[0016] The aluminum-containing current collector has a coating on the surface in contact with the electrolyte.

[0017] The above film contains Al(CFSA) x ,

[0018]

Chemistry 1

[0019]

[0020] <Option 2>

[0021] The lithium ion battery according to Embodiment 1, wherein the electrolyte solution contains sulfolane as the organic solvent.

[0022] <Option 3>

[0023] The lithium ion battery according to embodiment 1 or 2, wherein the electrolyte solution contains a carboxylic acid ester as the organic solvent.

[0024] <Option 4>

[0025] The lithium ion battery according to any one of aspects 1 to 3, wherein the coating comprises aluminum fluoride.

[0026] <Option 5>

[0027] The lithium ion battery according to any one of aspects 1 to 4, wherein at least the positive electrode has the aluminum-containing current collector.

[0028] Effects of the Invention

[0029] According to the lithium ion battery of the present disclosure, the dissolution of aluminum from the aluminum-containing current collector into the electrolyte can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 An example of the structure of a lithium ion battery is schematically shown.

[0031] Figure 2 The results of Al corrosion evaluation on Comparative Example 1 are shown.

[0032] Figure 3 The results of Al corrosion evaluation on Comparative Example 2 are shown.

[0033] Figure 4 The results of Al corrosion evaluation on Comparative Example 3 are shown.

[0034] Figure 5 The results of Al corrosion evaluation on Comparative Example 4 are shown.

[0035] Figure 6 The results of Al corrosion evaluation on Comparative Example 5 are shown.

[0036] Figure 7 The results of Al corrosion evaluation on Example 1 are shown.

[0037] Figure 8 The results of Al corrosion evaluation on Example 2 are shown.

[0038] Fig. 9 The results of Al corrosion evaluation on Example 3 are shown.

[0039] Fig.10 The XPS analysis results of a film formed on the surface of an aluminum-containing current collector at 4 V (XPS spectrum for Al2p) are shown.

[0040] Fig.11 The XPS analysis results of a film formed on the surface of an aluminum-containing current collector at 4 V (XPS spectrum for F1s) are shown.

[0041] Fig.12 The XPS analysis results of a film formed on the surface of an aluminum-containing current collector at 4 V (XPS spectrum for S2p) are shown.

[0042] Fig.13 The XPS analysis results of a film formed on the surface of an aluminum-containing current collector at 6 V (XPS spectrum for Al2p) are shown.

[0043] Fig.14 The XPS analysis results of a film formed on the surface of an aluminum-containing current collector at 6 V (XPS spectrum for F1s) are shown.

[0044] Fig.15 The XPS analysis results of a film formed on the surface of an aluminum-containing current collector at 6 V (XPS spectrum for S2p) are shown.

[0045] Description of Reference Numerals

[0046] 10 Positive electrode

[0047] 11 Positive electrode active material layer

[0048] 12. Positive electrode collector

[0049] 20 Negative electrode

[0050] 21 Negative electrode active material layer

[0051] 22 Negative electrode collector

[0052] 30 electrolyte

[0053] 40 Spacer

[0054] 50 membrane

[0055] 100 Lithium-ion battery DETAILED DESCRIPTION

[0056] Hereinafter, an embodiment of the lithium ion battery and the like of the present disclosure will be described, but the lithium ion battery and the like of the present disclosure are not limited to the embodiment described below.

[0057] 1. Lithium-ion battery

[0058] like Figure 1 As shown in , a lithium ion battery 100 according to one embodiment includes a positive electrode 10, a negative electrode 20, and an electrolyte 30. The electrolyte 30 includes an organic solvent and a lithium amide salt dissolved in the organic solvent. The lithium amide salt includes LiCFSA represented by the following formula (1). One or both of the positive electrode 10 and the negative electrode 20 include an aluminum-containing collector. The aluminum collector includes a film 50 on the contact surface with the electrolyte 30. The film 50 includes Al(CFSA) x .

[0059]

Chemistry 2

[0060]

[0061] 1.1 Positive electrode

[0062] like Figure 1 As shown in , the positive electrode 10 involved in one embodiment may include a positive electrode active material layer 11 and a positive electrode collector 12. In the case where the negative electrode collector 22 described later is an aluminum-containing collector, the positive electrode collector 12 may be an aluminum-containing collector or may not be an aluminum-containing collector. In the case where the negative electrode collector 22 described later is not an aluminum-containing collector, the positive electrode collector 12 is an aluminum-containing collector. In particular, with respect to the dissolution of aluminum from the aluminum-containing collector into the electrolyte, it is easy to occur when the aluminum-containing collector becomes a high potential. As a result, according to the technology disclosed in the present invention, even when at least the positive electrode 10 has an aluminum-containing collector, the dissolution into the aluminum electrolyte 30 can be suppressed.

[0063] 1.1.1 Positive electrode active material layer

[0064] The positive electrode active material layer 11 contains a positive electrode active material, and further, may optionally contain an electrolyte, a conductive aid, a binder, and various additives. As for the respective contents of the positive electrode active material, electrolyte, conductive aid, and binder in the positive electrode active material layer 11, they can be appropriately determined according to the target battery performance. For example, the entire positive electrode active material layer 11 (the entire solid component) is set to 100 mass%, and the content of the positive electrode active material can be 40 mass% or more, 50 mass% or more, or 60 mass% or more, and can be less than 100 mass% or less than 90 mass%. There is no particular limitation on the shape of the positive electrode active material layer 11, for example, it can be a sheet with a roughly flat surface. There is no particular limitation on the thickness of the positive electrode active material layer 11, for example, it can be 0.1 μm or more, 1 μm or more, 10 μm or more, or 30 μm or more, and can be less than 2 mm, less than 1 mm, less than 500 μm, or less than 100 μm.

[0065] The positive electrode active material can be a positive electrode active material known as a positive electrode active material for a lithium ion battery. Among the known active materials, a material that can make the potential (charge and discharge potential) of absorbing and releasing lithium ions higher than the potential of the negative electrode active material described later can be used as the positive electrode active material. For example, various lithium-containing composite oxides such as lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium manganese nickel cobalt oxide, and spinel lithium compounds can be used as the positive electrode active material. Only one type of positive electrode active material can be used alone, or two or more types can be used in combination. The positive electrode active material can be, for example, in the form of particles, and there is no particular limitation on its size. The particles of the positive electrode active material can be solid particles or hollow particles. The particles of the positive electrode active material can be primary particles or secondary particles formed by the aggregation of multiple primary particles. The average particle diameter (D50) of the particles of the positive electrode active material can be, for example, more than 1 nm, more than 5 nm, or more than 10 nm, and can be less than 500 μm, less than 100 μm, less than 50 μm, or less than 30 μm. It is explained that the so-called average particle diameter (D50) is the particle diameter (D50, median particle diameter) at the cumulative value 50% in the particle size distribution of the volume basis obtained by the laser diffraction scattering method.

[0066] The surface of the positive electrode active material may be covered with a protective layer containing a lithium ion conductive oxide. That is, the positive electrode active material layer 11 may include: a composite having the above-mentioned positive electrode active material and a protective layer provided on the surface thereof. Examples of lithium ion conductive oxides include Li3BO3, LiBO2, Li2CO3, LiAlO2, Li4SiO4, Li2SiO3, Li3PO4, Li2SO4, Li2TiO3, Li4Ti5O 12, Li2Ti2O5, Li2ZrO3, LiNbO3, Li2MoO4, Li2WO4. The coverage (area ratio) of the protective layer may be, for example, 70% or more, 80% or more, or 90% or more. The thickness of the protective layer may be, for example, 0.1 nm or more or 1 nm or less, 100 nm or less, or 20 nm or less.

[0067] The positive electrode active material layer 11 may include the electrolyte 30 described later. In addition, in addition to the electrolyte 30, other electrolytes may be included in the positive electrode active material layer 11. Other electrolytes may be solid electrolytes, electrolytes other than the electrolyte 30, or combinations thereof. Solid electrolytes may be solid electrolytes known as solid electrolytes for lithium ion batteries. Solid electrolytes may be inorganic solid electrolytes or organic polymer electrolytes. In particular, inorganic solid electrolytes have excellent ion conductivity and heat resistance. As inorganic solid electrolytes, sulfide solid electrolytes and oxide solid electrolytes can be exemplified. In particular, sulfide solid electrolytes, sulfide solid electrolytes containing at least Li, S and P as constituent elements, have high performance, and sulfide solid electrolytes based on Li3PS4 skeletons containing at least one or more halogens also have high performance. The solid electrolyte may be amorphous or crystalline. The solid electrolyte may be, for example, in the form of particles. The solid electrolyte may be used alone or in combination of two or more. The electrolyte solution (other electrolyte solution) other than the electrolyte solution 30 may contain, for example, lithium ions as carrier ions. The other electrolyte solution may be, for example, a non-aqueous electrolyte solution. For example, as the other electrolyte solution, a product obtained by dissolving a lithium salt at a predetermined concentration in a carbonate-based solvent may be used.

[0068] As the conductive aid that can be included in the positive electrode active material layer 11, for example, carbon materials such as vapor grown carbon fiber (VGCF), acetylene black (AB), Ketjen black (KB), carbon nanotubes (CNT), and carbon nanofibers (CNF); and metal materials such as nickel, aluminum, and stainless steel can be listed. The conductive aid can be, for example, in the form of particles or fibers, and its size is not particularly limited. The conductive aid can be used alone or in combination of two or more.

[0069] As the binder that can be included in the positive electrode active material layer 11, for example, butadiene rubber (BR)-based binders, butylene rubber (IIR)-based binders, acrylate butadiene rubber (ABR)-based binders, styrene butadiene rubber (SBR)-based binders, polyvinylidene fluoride (PVdF)-based binders, polytetrafluoroethylene (PTFE)-based binders, polyimide (PI)-based binders, polyacrylic acid-based binders, etc. can be listed. Only one type of binder can be used alone, or two or more types can be used in combination.

[0070] 1.1.2 Positive electrode collector

[0071] like Figure 1 As described in, the positive electrode 10 may include a positive electrode collector 12 in contact with the positive electrode active material layer 11 and the electrolyte 30. As for the positive electrode collector 12, any general positive electrode collector as a positive electrode collector of a lithium ion battery can be used. In addition, the positive electrode collector 12 may be in the form of a foil, a plate, a mesh, a punched metal, a foam, etc. The positive electrode collector 12 may be formed of a metal foil or a metal mesh. In particular, the metal foil has excellent handling properties. The positive electrode collector 12 may be composed of a plurality of foils. As metals constituting the positive electrode collector 12, Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, etc. may be listed. As described above, as for the positive electrode 10, an aluminum-containing collector in contact with the positive electrode active material layer 11 and the electrolyte 30 may be provided as the positive electrode collector 12. In this case, it is easy to ensure oxidation resistance, etc. The positive electrode current collector 12 may have some coating on its surface for the purpose of adjusting resistance, etc. In addition, the positive electrode current collector 12 may be a product obtained by plating or vapor-depositing the above-mentioned metal on a metal foil or a substrate. In addition, when the positive electrode current collector 12 is composed of a plurality of metal foils, there may be some layers between the plurality of metal foils. The thickness of the positive electrode current collector 12 is not particularly limited. For example, it may be greater than 0.1 μm or greater than 1 μm, and may be less than 1 mm or less than 100 μm.

[0072] The positive electrode 10 may have a general structure as a positive electrode of a lithium ion battery in addition to the above-mentioned structure. For example, it may be a pole piece, a terminal, etc. The positive electrode 10 can be manufactured by applying a known method. For example, by forming the positive electrode mixture containing the above-mentioned various components by dry or wet molding, the positive electrode active material layer 11 can be easily formed. The positive electrode active material layer 11 may be formed together with the positive electrode collector 12, or may be formed separately from the positive electrode collector 12.

[0073] 1.2 Negative electrode

[0074] like Figure 1 As shown in , the negative electrode 20 involved in one embodiment may include a negative electrode active material layer 21 and a negative electrode collector 22. When the positive electrode collector 12 is an aluminum-containing collector, the negative electrode collector 22 may be an aluminum-containing collector or may not be an aluminum-containing collector. When the positive electrode collector 12 is not an aluminum-containing collector, the negative electrode collector 22 is an aluminum-containing collector.

[0075] 1.2.1 Negative electrode active material layer

[0076] The negative electrode active material layer 21 contains a negative electrode active material, and further, may optionally contain an electrolyte, a conductive aid, a binder, and various additives. As for the respective contents of the negative electrode active material, electrolyte, conductive aid, and binder in the negative electrode active material layer 21, it is sufficient to appropriately determine them according to the target battery performance. For example, the entire negative electrode active material layer 21 (the entire solid component) is set to 100 mass%, and the content of the negative electrode active material may be 40 mass% or more, 50 mass% or more, or 60 mass% or more, and may be less than 100 mass% or less than 90 mass%. There is no particular limitation on the shape of the negative electrode active material layer 21, for example, it may be a sheet with a substantially flat surface. There is no particular limitation on the thickness of the negative electrode active material layer 21, for example, it may be 0.1 μm or more, 1 μm or more, 10 μm or more, or 30 μm or more, and may be less than 2 mm, less than 1 mm, less than 500 μm, or less than 100 μm.

[0077] As for the negative electrode active material, any material known as the negative electrode active material of the lithium ion battery can be used. Among the known active materials, a material whose potential for absorbing and releasing lithium ions (charge and discharge potential) is lower than that of the above-mentioned positive electrode active material can be used as the negative electrode active material. For example, as the negative electrode active material, silicon-based active materials such as Si, Si alloys, and silicon oxide; carbon-based active materials such as graphite and hard carbon; various oxide-based active materials such as lithium titanate; metallic lithium, lithium alloys, etc. can be used. The negative electrode active material can be used alone or in combination of two or more. The negative electrode active material can be, for example, in the form of particles, and there is no particular limitation on its size. The particles of the negative electrode active material can be solid particles or hollow particles. The particles of the negative electrode active material can be primary particles or secondary particles formed by the aggregation of multiple primary particles. The average particle size (D50) of the negative electrode active material particles may be, for example, 1 nm or more, 5 nm or more, or 10 nm or more, and may be 500 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less. Alternatively, the negative electrode active material may be in the form of a sheet (foil, film) such as lithium foil. That is, the negative electrode active material layer 21 may be composed of a sheet of the negative electrode active material.

[0078] The negative electrode active material layer 21 may contain the electrolyte 30 described later. In addition, in addition to the electrolyte 30, other electrolytes may be contained in the negative electrode active material layer 21. As other electrolytes, the above-mentioned solid electrolytes, electrolytes or combinations thereof can be listed. As for the conductive aid that can be contained in the negative electrode active material layer 21, for example, it is sufficient to appropriately select from the conductive aids exemplified as the conductive aids that can be contained in the above-mentioned positive electrode active material layer 11. As for the binder that can be contained in the negative electrode active material layer 21, for example, it is sufficient to appropriately select from the binders exemplified as the binders that can be contained in the above-mentioned positive electrode active material layer 11. The electrolyte, the conductive aid, and the binder may be used alone or in combination of two or more.

[0079] 1.2.2 Negative electrode collector

[0080] like Figure 1 As described in, the negative electrode 20 may include a negative electrode collector 22 in contact with the negative electrode active material layer 21 and the electrolyte 30. As for the negative electrode collector 22, any general negative electrode collector as a negative electrode collector of a battery can be used. In addition, the negative electrode collector 22 may be in the form of a foil, a plate, a mesh, a punched metal, a foam, etc. The negative electrode collector 22 may be a metal foil or a metal mesh, or may be a carbon sheet. In particular, the metal foil has excellent handling properties. The negative electrode collector 22 may be composed of a plurality of foils and sheets. As metals constituting the negative electrode collector 22, Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, etc. may be listed. From the viewpoint of ensuring reduction resistance and the viewpoint of being difficult to alloy with lithium, the negative electrode collector 22 may contain at least one metal selected from Cu, Ni and stainless steel. Alternatively, as described above, as for the negative electrode 20, as the negative electrode current collector 22, an aluminum-containing current collector in contact with the negative electrode active material layer 21 and the electrolyte 30 may be provided. As for the negative electrode current collector 22, on its surface, for the purpose of adjusting resistance, etc., some coating may be provided. In addition, the negative electrode current collector 22 may be a product obtained by plating or vapor-depositing the above-mentioned metal on a metal foil or a substrate. In addition, when the negative electrode current collector 22 is composed of a plurality of metal foils, some layers may be provided between the plurality of metal foils. There is no particular limitation on the thickness of the negative electrode current collector 22. For example, it may be greater than 0.1 μm or greater than 1 μm, and may be less than 1 mm or less than 100 μm.

[0081] The negative electrode 20 may have a general structure as a negative electrode of a lithium ion battery in addition to the above-mentioned structure. For example, it may be a pole piece, a terminal, etc. The negative electrode 20 can be manufactured by applying a known method. For example, by forming the negative electrode mixture containing the above-mentioned various components by dry or wet molding, the negative electrode active material layer 21 can be easily formed. The negative electrode active material layer 21 may be formed together with the negative electrode collector 22, or may be formed separately from the negative electrode collector 22.

[0082] 1.3 Electrolyte

[0083] The electrolyte solution 30 includes an organic solvent and a lithium amide salt dissolved in the organic solvent.

[0084] 1.3.1 Organic solvents

[0085] The electrolyte 30 contains an organic solvent. As for the organic solvent, any known organic solvent used in the electrolyte of a lithium ion battery can be used. Even when any organic solvent is used, a film 50 is formed on the surface of the aluminum-containing current collector by the lithium amide salt described later, and the dissolution of aluminum from the aluminum-containing current collector into the electrolyte 30 can be suppressed. As for the organic solvent, for example, it can be sulfones, carbonates, carboxylates, or a combination thereof.

[0086] Sulfones have a sulfonyl group (-S(=O)2-). Sulfones may be cyclic sulfones or chain sulfones. As for sulfones, it is sufficient that they are liquid at the temperature at which lithium ion conductivity is desired to be exhibited and that lithium amide salts can be dissolved. In the case where the electrolyte 30 contains sulfones as an organic solvent, it is believed that the mobility of lithium ions is improved by a hopping conduction mechanism via the O site of the sulfonyl group. In addition, it is believed that, together with the lithium amide salt described later, sulfones contribute to the formation of the film 50 and improve the stability of the film 50. In particular, in the case where the electrolyte 30 contains cyclic sulfones as the above-mentioned organic solvent, in the case of containing cyclopentane sulfone, the mobility is easily further improved. As the organic solvent, only one sulfone may be used alone or two or more may be used in combination. Regarding the amount of sulfones as organic solvents contained in the electrolyte 30, the total amount of the organic solvent is set to 100 mol%, and can be 50 mol% or more, 60 mol% or more, 70 mol% or more, 80 mol% or more, 90 mol% or more, 95 mol% or more, 97 mol% or more, or 99 mol% or more.

[0087] Carbonates have a carbonate group (-O-(C=O)-O-). Carbonates may be cyclic carbonates or chain carbonates. As for carbonates, as long as they are liquid at the temperature at which lithium ion conductivity is desired to be exhibited and lithium amide salts can be dissolved. In particular, cyclic carbonates have a higher dielectric constant than chain carbonates and are easily coordinated with lithium ions. In other words, in the case where the electrolyte 30 contains cyclic carbonates as an organic solvent, the cyclic carbonates are difficult to become free, and as a result, thermal stability is easily improved. Specific examples of cyclic carbonates include propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), vinylene carbonate (VC) or their derivatives (such as halides, etc.). In particular, in the case where the cyclic carbonate is at least one of propylene carbonate and ethylene carbonate, it is easy to ensure better lithium ion conductivity and thermal stability. With regard to linear carbonate, for example, can enumerate dimethyl carbonate (DMC), diethyl carbonate (DEC) or their derivative (for example halides, particularly derivatives with perfluoroalkyl) etc.But, with regard to linear carbonate, compared with cyclic carbonate, dielectric constant is low, tends to be difficult to coordination of lithium ion.Carbonates as organic solvent can only use 1 kind separately, also can use with more than 2 kinds of combinations.With regard to the amount of carbonates as organic solvent contained in the electrolyte 30, the whole of this organic solvent is made as 100 mole %, can be more than 50 mole %, more than 60 mole %, more than 70 mole %, more than 80 mole %, more than 90 mole %, more than 95 mole %, more than 97 mole % or more than 99 mole %.

[0088] Carboxylic acid ester has an ester group (-(C=O)-O-). In the case of carboxylic acid ester as an organic solvent, the function of dissociating lithium ions from the lithium amide salt described later can be achieved through the action of the ester group. In addition, carboxylic acid ester as an organic solvent can have the function of reducing the viscosity of the electrolyte 30. Therefore, in the case where the electrolyte 30 contains carboxylic acid ester as an organic solvent, the ion conductivity of the electrolyte 30 is easily improved. Carboxylic acid ester may be a monocarboxylic acid ester or a polycarboxylic acid ester such as a dicarboxylic acid ester or a tricarboxylic acid ester. In particular, in the case where the electrolyte 30 contains a monocarboxylic acid ester as an organic solvent, the ion conductivity of the electrolyte 30 is easily improved more significantly. In addition, carboxylic acid ester may be an aliphatic carboxylic acid ester or an aromatic carboxylic acid ester. In particular, in the case where the electrolyte 30 contains an aliphatic carboxylic acid ester as an organic solvent, the ion conductivity of the electrolyte 30 is easily improved more significantly. In particular, when the electrolytic solution 30 contains a carboxylic acid ester represented by the following formula (1) as an organic solvent, the ion conductivity of the electrolytic solution 30 tends to be particularly significantly improved.

[0089] R 1 -(C=O)-OR 2· ·· (1)

[0090] R 1 : A hydrocarbon group having 1 to 4 carbon atoms, such as an alkyl group having 1 to 4 carbon atoms

[0091] R 2 : A hydrocarbon group having 1 to 4 carbon atoms, such as an alkyl group having 1 to 4 carbon atoms

[0092] In the above formula (1), R 1 When the alkyl group is an alkyl group having 1 to 3 carbon atoms, particularly an alkyl group having 2 to 3 carbon atoms, the ion conductivity of the electrolyte 30 is likely to be significantly improved. 2 When it is an alkyl group having 1 to 3 carbon atoms, especially an alkyl group having 1 to 2 carbon atoms, the ion conductivity of the electrolyte 30 tends to be significantly improved. 1 The carbon number and R 2 The total number of carbon atoms may be, for example, 2 or more and 6 or less, 3 or more and 5 or less, or 3 or 4. Specific examples of carboxylic acid esters include ethyl formate, methyl isobutyrate, methyl acetate, methyl propionate, and the like. In particular, when the electrolyte 30 includes methyl propionate as an organic solvent, the ion conductivity of the electrolyte 30 is likely to be significantly improved.

[0093] Electrolyte 30 can comprise above-mentioned carbonate and carboxylate.In this case, the ionic conductivity of electrolyte 30 is easy to improve more significantly.For example, electrolyte 30 comprises carbonate as organic solvent and carboxylate as organic solvent, the ratio of carbonate shared in all organic solvents contained in electrolyte 30 is more than 5 volume % and below 95 volume %, more than 5 volume % and below 50 volume % or more than 10 volume % and below 20 volume %, the ratio of carboxylate shared in all organic solvents contained in electrolyte 30 is more than 5 volume % and below 95 volume %, more than 50 volume % and below 95 volume % or more than 80 volume % and below 90 volume %, the ratio of the total of carbonate shared in all organic solvents contained in electrolyte 30 and carboxylate can be more than 50 volume % and below 100 volume %, more than 75 volume % and below 100 volume % or more than 90 volume % and below 100 volume %.

[0094] The electrolyte 30 may contain other organic solvents. As other organic solvents, for example, ethers may be cited. The amount of ethers as organic solvents contained in the electrolyte 30 may be 5 mol% or less, 3 mol% or less, or 1 mol% or less, based on the total amount of the organic solvent as 100 mol%. Alternatively, the electrolyte 30 may not contain ethers.

[0095] 1.3.2 Lithium amide salt

[0096] The electrolyte 30 contains a lithium amide salt dissolved in the above-mentioned organic solvent. In the electrolyte 30, the lithium amide salt may be dissolved in the above-mentioned organic solvent and ionized into cations and anions, or may form some associations. It should be noted that in this application, "amide salt" is a concept that includes "imide salt".

[0097] 1.3.2.1LiCFSA

[0098] The lithium amide salt includes LiCFSA (1,1,2,2,3,3-hexafluoropropane-1,3-disulfonylimide lithium) represented by the above formula (1). According to the new knowledge of the present inventors, if a lithium ion battery 100 is constructed using an electrolyte 30 in which LiCFSA is dissolved and the lithium ion battery 100 is charged and discharged, a coating 50 derived from LiCFSA can be formed on the surface of an aluminum-containing current collector. For example, until the potential of the aluminum-containing current collector reaches about 4.0 V (vs. Li / Li+), CFSA anions are adsorbed on the surface of the aluminum-containing current collector to form a coating 50 derived from CFSA anions. In the case where CFSA anions are adsorbed on the surface of the aluminum-containing current collector to form a coating 50 derived from CFSA anions, the coating 50 includes Al(CFSA) x Among them, the so-called "Al(CFSA) x ", means that Al from the aluminum-containing collector and CFSA anions from LiCFSA are adsorbed and combined with each other. The value of x is not particularly limited. A layer containing Al(CFSA) is formed on the surface of the aluminum-containing collector. x In the case of the film 50, the film 50 functions as a protective film, and even when the aluminum-containing current collector reaches a high potential, it is possible to suppress the dissolution of aluminum from the aluminum-containing current collector into the electrolyte 30. In addition, whether the film formed on the surface of the aluminum-containing current collector contains Al(CFSA) x For example, it can be confirmed by X-ray photoelectron spectroscopy (XPS: X-ray Photoelectron Spectroscopy).

[0099] As an electrolyte for lithium-ion batteries, a product obtained by dissolving LiPF6 as a lithium salt in an organic solvent is known. The present inventors have confirmed that LiPF6 decomposes at a high potential, thereby forming a film composed of fluoride on the surface of the current collector. Among them, according to the new knowledge and insights of the present inventors, when a film from LiPF6 is formed on the surface of the current collector, there is a problem of simultaneous decomposition of the electrolyte and generation of gas. In contrast, in the lithium-ion battery 100 disclosed in the present invention, LiCFSA is dissolved in the electrolyte 30 until the potential of the aluminum current collector reaches 4.0 V (vs. Li / Li +) or so, the CFSA anions can be adsorbed on the surface of the aluminum-containing current collector to form a film 50. However, until the potential of the aluminum current collector reaches 4.0 V (vs. Li / Li + ), the electrolyte 30 is unlikely to decompose. That is, in the lithium ion battery 100 of the present disclosure, it can be said that the coating 50 can be formed on the surface of the aluminum-containing current collector while suppressing the decomposition of the electrolyte 30 and suppressing the generation of gas.

[0100] The concentration of LiCFSA in the electrolyte 30 is not particularly limited. Regardless of whether it is a low concentration or a high concentration, the above-mentioned film 50 is formed on the surface of the aluminum-containing collector, exerting an aluminum dissolution inhibition effect. As for the molar ratio of LiCFSA to the organic solvent ([LiCFSA (mol)] / [organic solvent (mol)]), for example, it can be 0.01 or more and 0.50 or less, 0.05 or more and 0.40 or less, or 0.10 or more and 0.33 or less. In other words, LiCFSA can be dissolved at a concentration of 0.01 mol or more and 0.50 mol or less, 0.05 mol or more and 0.40 mol or less, or 0.10 mol or more and 0.33 mol or less per 1 mol of the organic solvent. When the concentration of LiCFSA dissolved in the organic solvent is within this range, the above-mentioned aluminum dissolution inhibition effect is further improved, and it is easy to become an electrolyte 30 with excellent ion conductivity. The molar ratio of LiCFSA to the organic solvent can be determined by analyzing ions, elements, and the like contained in the organic solvent.

[0101] 1.3.2.2 Other lithium amide salts

[0102] As for the electrolyte 30, as long as the above-mentioned LiCFSA is dissolved, a lithium amide salt other than LiCFSA may be included while containing the above-mentioned LiCFSA. The lithium amide salt other than LiCFSA may be a chain lithium amide salt or a cyclic lithium amide salt other than LiCFSA. As specific examples of chain lithium amide salts, sulfonamide salts such as bisfluorosulfonamide lithium (LiFSA, LiN(SO2F)2), bistrifluoromethanesulfonamide lithium (LiTFSA, Li[N(CF3SO2)2]), bisperfluoroethanesulfonamide lithium (Li[N(C2F5SO2)2]), bisperfluorobutanesulfonamide lithium (Li[N(C4F9 SO2)2]), and fluorosulfonyltrifluoromethanesulfonamide lithium (Li[N(FSO2)(C2F5 SO2)]) may be listed. Alternatively, a silylamide salt having Si instead of S may be used. The chain lithium amide salt may be used alone or in combination of two or more. As specific examples of cyclic lithium amide salts other than LiCFSA, products in which the above-mentioned sulfonamide salts, sulfonamide groups in silylamine salts, and silylamine groups form a ring via a perfluoroalkylene group or the like can be listed. The concentration of other lithium amide salts in the electrolyte 30 is not particularly limited, and may be a low concentration or a high concentration. In the electrolyte 30, the proportion of LiCFSA in the lithium amide salt dissolved in the solvent may be high, and specifically, the proportion of LiCFSA in the entire lithium amide salt (100 mol%) may be 50 mol% or more, 60 mol% or more, 70 mol% or more, 80 mol% or more, 90 mol% or more, 95 mol% or more, or 99 mol% or more. Alternatively, in the electrolyte 30, the proportion of LiCFSA in the lithium amide salt dissolved in the solvent may be low, specifically, the proportion of LiCFSA in the entire lithium amide salt (100 mol %) may be less than 50 mol %, less than 40 mol %, less than 30 mol %, or less than 20 mol %.

[0103] 1.3.3 Lithium salts other than lithium amide salts

[0104] In the electrolyte 30, the lithium salt dissolved in the organic solvent may be composed of the above-mentioned lithium amide salt, or may be a combination of the above-mentioned lithium amide salt and a lithium salt other than the lithium amide salt (other lithium salt). In the electrolyte 30, the proportion of the lithium amide salt in the lithium salt dissolved in the solvent may be high, specifically, the proportion of the lithium amide salt in the lithium salt as a whole (100 mol%) may be 50 mol% or more, 60 mol% or more, 70 mol% or more, 80 mol% or more, 90 mol% or more, 95 mol% or more, or 99 mol% or more. Alternatively, in the electrolyte 30, the proportion of the lithium amide salt in the lithium salt dissolved in the solvent may be low, specifically, the proportion of the lithium amide salt in the lithium salt as a whole (100 mol%) may be 50 mol% or less, 40 mol% or less, 30 mol% or less, or 20 mol% or less.

[0105] 1.3.4 Other optional ingredients

[0106] The electrolyte 30 may contain various additives in addition to the organic solvent and the lithium amide salt, within the scope of being able to solve the above-mentioned problems. The type of additive may be appropriately selected according to the target performance. In addition, the electrolyte 30 may be combined with a solid material (eg, a solid electrolyte).

[0107] 1.4 Coating

[0108] As described above, in the lithium ion battery 100, one or both of the positive electrode 10 and the negative electrode 20 have an aluminum-containing current collector, and the aluminum-containing current collector has a surface containing Al(CFSA) on the contact surface with the electrolyte 30. x As described above, the film 50 can be formed by heating the aluminum-containing current collector to a potential of 4.0 V (vs. Li / Li + ) or so, the CFSA anions are adsorbed on the surface of the aluminum-containing current collector. In addition, according to the new knowledge of the present inventors, in the lithium-ion battery 100, until the potential of the aluminum-containing current collector reaches 6.0 V (vs. Li / Li + ) or so, a layer containing Al(CFSA) can be formed on the surface of the aluminum-containing current collector. x , and a film 50 containing aluminum fluoride. That is, the film 50 may contain aluminum fluoride. Thus, by containing Al(CFSA) x The film 50 containing aluminum fluoride can also suppress the dissolution of aluminum from the aluminum-containing current collector into the electrolyte 30. Alternatively, the film 50 contains Al(CFSA) x On the other hand, aluminum fluoride may not be contained. As described above, even if the film 50 contains Al(CFSA) x , and the dissolution of aluminum from the aluminum-containing current collector into the electrolyte 30 can also be suppressed. In addition, whether the film formed on the surface of the aluminum-containing current collector contains Al(CFSA)x 、Aluminum fluoride (AlF x ), for example, it can be confirmed by X-ray photoelectron spectroscopy (XPS: X-ray Photoelectron Spectroscopy).

[0109] As for the film 50, Figure 1 As described in, the film 50 may be formed on the surface of the aluminum-containing collector serving as the positive electrode collector 12. Alternatively, the film 50 may be formed on the surface of the aluminum-containing collector serving as the negative electrode collector 22. Alternatively, the film 50 may be formed on the surfaces of both the aluminum-containing collector serving as the positive electrode collector 12 and the aluminum-containing collector serving as the negative electrode collector 22. In particular, when the film 50 is formed at least on the surface of the aluminum-containing collector serving as the positive electrode collector 12, a higher effect can be easily obtained. There is no particular limitation on the thickness of the film 50. The thickness of the film 50 may be, for example, greater than 0 μm and less than 10 μm. Alternatively, the thickness of the film 50 may be, for example, greater than 10 μm. In particular, when the thickness of the film 50 is greater than 0 μm and less than 10 μm, the above-mentioned aluminum dissolution inhibition effect is ensured, and at the same time, the balance of other performances of the battery is easily improved. The coating 50 may be formed on the entire contact surface between the aluminum-containing current collector and the electrolyte 30 or may be formed on a portion of the contact surface.

[0110] 1.4 Other matters

[0111] The lithium ion battery 100 may have a separator 40 between the positive electrode 10 and the negative electrode 20, and the above-mentioned electrolyte 30 may be retained in the separator 40. The separator 40 may be a separator known as a separator of the lithium ion battery 100. In addition, as far as the lithium ion battery 100 is concerned, each of the above-mentioned structures is accommodated inside the outer casing. As far as the outer casing is concerned, any outer casing known as the outer casing of the battery can be used. In addition, a plurality of lithium ion batteries 100 are electrically connected arbitrarily, and can be overlapped arbitrarily to form a battery pack. In this case, the battery pack can be accommodated inside a known battery casing. The lithium ion battery 100 may also have obvious structures such as necessary terminals. As the shape of the lithium ion battery 100, for example, a coin type, a laminated body type, a cylindrical type, and a square type can be listed. The lithium ion battery 100 may be a secondary battery. The lithium ion battery 100 can be manufactured by applying a known method. For example, it can be manufactured as described below. However, the method for manufacturing the lithium ion battery 100 is not limited to the following method, and for example, each layer may be formed by dry molding or the like.

[0112] (1) The positive electrode active material constituting the positive electrode active material layer is dispersed in a solvent to obtain a positive electrode slurry. The solvent used in this case is not particularly limited, and water or various organic solvents can be used. The positive electrode slurry is applied to the surface of the positive electrode collector using a scraper or the like, and then dried to form a positive electrode active material layer on the surface of the positive electrode collector to prepare a positive electrode.

[0113] (2) The negative electrode active material constituting the negative electrode active material layer is dispersed in a solvent to obtain a negative electrode slurry. The solvent used in this case is not particularly limited, and water or various organic solvents can be used. The negative electrode slurry is applied to the surface of the negative electrode collector using a scraper or the like, and then dried to form a negative electrode active material layer on the surface of the negative electrode collector to prepare a negative electrode.

[0114] (3) The layers are stacked in such a way that the electrolyte layer (separator) is sandwiched between the negative electrode and the positive electrode to obtain a laminate having a negative electrode collector, a negative electrode active material layer, an electrolyte layer, a positive electrode active material layer, and a positive electrode collector in this order. Other components such as terminals are attached to the laminate as needed.

[0115] (4) The stack is placed in a battery case, immersed in an electrolyte, and sealed in the battery case to produce a lithium ion battery. In the above step (3), the negative electrode active material layer, the separator, and the positive electrode active material layer may contain an electrolyte.

[0116] 2. Lithium ion conductive materials

[0117] The technology disclosed in the present invention has an aspect as a lithium ion conductive material. That is, the lithium ion conductive material disclosed in the present invention includes an organic solvent and a lithium amide salt dissolved in the organic solvent, and the lithium amide salt is characterized in that it includes LiCFSA represented by the above formula (1). The details of each component constituting the lithium ion conductive material are as described above.

[0118] 3. Vehicles

[0119] The lithium ion battery of the present disclosure can be preferably used in at least one vehicle selected from a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV) and an electric vehicle (BEV). That is, the technology of the present disclosure also has the following aspects: a vehicle, which is a vehicle having a lithium ion battery, wherein the lithium ion battery has a positive electrode, a negative electrode and an electrolyte, wherein the electrolyte comprises an organic solvent and a lithium amide salt dissolved in the organic solvent, wherein the lithium amide salt comprises LiCFSA represented by the above formula (1), wherein one or both of the positive electrode and the negative electrode comprises an aluminum-containing collector, wherein the aluminum-containing collector has a coating on a surface in contact with the electrolyte, wherein the coating comprises Al(CFSA) x .

[0120] Example

[0121] The following examples are provided to explain the technology of the present disclosure in more detail, but the technology of the present disclosure is not limited to the following examples. It should be noted that all the following experiments were conducted in an Ar atmosphere with a dew point of less than -80°C and an oxygen concentration of less than 3 ppm, in a glove box or in an atmosphere non-exposed environment based thereon.

[0122] 1. Preparation of electrolyte

[0123] 1.1 Comparative Example 1

[0124] As the electrolyte solution involved in Comparative Example 1, LBG electrolyte solution manufactured by Kishida Chemical Co., Ltd. was prepared. The electrolyte solution involved in Comparative Example 1 was prepared by dissolving LiPF6 at a concentration of 1 M in a mixed organic solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC).

[0125] 1.2 Comparative Example 2

[0126] The electrolyte solution according to Comparative Example 2 was obtained by weighing, mixing and stirring lithium bis(fluorosulfonyl)amide (LiFSA) as a lithium amide salt to propylene carbonate (PC) as an organic solvent so that the molar ratio was 0.33 (PC:LiFSA=3:1).

[0127] 1.3 Comparative Example 3

[0128] The electrolyte solution according to Comparative Example 3 was obtained by weighing, mixing and stirring lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) as a lithium amide salt to PC so that the molar ratio was 0.33 (PC:LiTFSA=3:1).

[0129] 1.4 Comparative Example 4

[0130] The electrolyte solution according to Comparative Example 4 was obtained by weighing, mixing and stirring the organic solvent such that the molar ratio of LiFSA to sulfolane (SL, melting point 27.8° C.) was 0.10 (SL:LiFSA=10:1).

[0131] 1.5 Comparative Example 5

[0132] The electrolyte solution according to Comparative Example 5 was obtained by weighing, mixing and stirring the respective components so that the molar ratio of LiFSA to SL was 0.33 (SL:LiFSA=3:1).

[0133] 1.6 Example 1

[0134] The electrolyte solution according to Example 1 was obtained by weighing, mixing and stirring lithium 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonylimide (LiCFSA) as a lithium amide salt to SL so that the molar ratio was 0.10 (SL:LiCFSA=10:1).

[0135] 1.7 Example 2

[0136] The electrolyte of Example 2 was obtained by weighing, mixing and stirring each other so that the molar ratio of LiCFSA to SL was 0.33 (SL:LiCFSA=3:1). The electrolyte of Example 3 was solid at room temperature (25°C), but liquid at 60°C and could be used as an electrolytic solution.

[0137] 1.8 Example 3

[0138] The electrolyte solution according to Example 3 was obtained by weighing, mixing and stirring each other so that the molar ratio of LiCFSA to PC was 0.10 (PC:LiCFSA=10:1).

[0139] 2. Evaluation of ion conductivity and mobility

[0140] For the electrode, Li metal was used, and as the electrolyte, the above-mentioned various electrolytes were used to make a two-electrode symmetrical battery with fixed electrode area and inter-electrode distance, and the resistance value was measured by AC impedance method at 25°C. The ion conductivity was calculated from the obtained resistance value and battery shape (electrode area, inter-electrode distance). In addition, the Bruce method combining DC polarization and impedance method was used to calculate the mobility. The impedance measurement conditions and DC polarization conditions are as follows.

[0141] Impedance measurement conditions: temperature 25°C, amplitude 10mV, frequency 1M~10mHz

[0142] DC polarization conditions: temperature 25°C, applied voltage 10mV, holding time 10 hours

[0143] 3. Evaluation of Al corrosion

[0144] A half-cell was prepared using Al foil as a working electrode, Li metal as a counter electrode, and each electrolyte solution involved in the above Examples and Comparative Examples, and the presence or absence of Al dissolution into the electrolyte solution (Al corrosion) was evaluated by cyclic voltammetry (CV measurement). Specific measurement conditions are as follows.

[0145] Measurement conditions: Scan rate 10mV / s, OCV→(6V→3V), Cycle number: 5 cycles

[0146] 4. Analysis of the film on Al foil using XPS

[0147] 4.1 For the film after 4V maintenance

[0148] A half-cell was made using Al foil as a working electrode, Li metal as a counter electrode, and the electrolyte solutions of Examples 1 to 3 and Comparative Example 1. After the half-cell was maintained at 4 V, the Al foil was recovered from the half-cell, washed with dimethyl ether (DME), and the surface of the Al foil was analyzed using XPS.

[0149] 4.2 For the film after 6V maintenance

[0150] A half-cell was made using Al foil as a working electrode, Li metal as a counter electrode, and the electrolyte solutions of Examples 1 and 3. After the half-cell was maintained at 6 V, the Al foil was recovered from the half-cell, washed with dimethyl ether (DME), and the surface of the Al foil was analyzed using XPS.

[0151] 5. Evaluation results

[0152] Table 1 below shows the composition of each electrolyte solution involved in Examples 1 to 3 and Comparative Examples 1 to 5, the ion conductivity and mobility, the presence or absence of Al corrosion behavior, and the components contained in the film formed on the surface of the Al foil. Figures 2 to 9 In the figure, the CV measurement results of each of Comparative Examples 1 to 5 and Examples 1 to 3 are shown. Figures 10-12 In the figure, for each of Comparative Example 1 and Examples 1 to 3, the analysis results using XPS of the film formed on the surface of the Al foil after holding at 4 V are shown. Figures 13-15 Detailed Description of the Invention In each of Examples 1 and 3, the analysis results using XPS of the film formed on the surface of the Al foil after holding at 6 V are shown.

[0153]

Table 1

[0154]

[0155] From Table 1 and Figures 2 to 12 The results shown in show the following.

[0156] like Figures 3 to 6 As shown in , for Comparative Examples 2 to 5, in the CV measurement, the current value increased when the potential was scanned in the negative direction (negative direction) after the 6 V return compared to when the potential was scanned in the positive direction (positive direction) to 6 V. This means that the Al foil corroded and Al was eluted into the electrolyte.

[0157] like Figure 2 and Figures 7 to 9As shown in , for Comparative Example 1 and Examples 1 to 3, in CV measurement, the current value is smaller when scanning to a lower negative potential after 6 V return than when scanning to a positive potential of 6 V. This means that the dissolution of Al into the electrolyte is suppressed.

[0158] like Figure 2 As shown in , for Comparative Example 1 using LiPF6, in the CV measurement, a current rise from around 3V was confirmed in the first cycle, with a peak at around 3.7V. Figures 10-12 The XPS analysis results of the film on the Al foil shown in the figure indicate that the peak near 3.7 V corresponds to the decomposition current of LiPF6. It is known that due to the decomposition of LiPF6, a layer of aluminum fluoride (AlF x ) film. In Comparative Example 1, gas is generated due to the decomposition of LiPF6 during film formation, and a process and mechanism for discharging the gas from the battery are required. If the gas is retained in the battery, the performance of the battery may deteriorate due to the reduction of the conduction path and the reaction area.

[0159] like Figures 7 to 9 As shown in , in Examples 1 to 3 using LiCFSA, no current increase was observed until around 3.7 V in the CV measurement. Figures 10-12 The analysis results of the film on the Al foil by XPS shown in FIG. 1 show that no AlF x On the other hand, the membrane derived from the adsorption of CFSA anions was confirmed. Specifically, Fig.10 As shown in Examples 1 to 3, a layer containing Al(CFSA) is formed on the surface of the Al foil. x Among them, Fig.10 In the experiment, Al2O3 was also detected on the surface of the Al foil (under the film), indicating that Al(CFSA) x The film is a thin film of less than 10 μm. Fig.11 As shown in , in Examples 1 to 3, the film on the surface of the Al foil has CF2 bonds. This is derived from the above-mentioned CFSA anions. Fig.12 It is also known that in Examples 1 to 3, a film derived from CFSA anions is formed on the surface of the Al foil. That is, when the electrolyte solutions involved in Examples 1 to 3 are used to construct a lithium ion battery, the electrolyte solution (solvent and lithium salt) is basically not decomposed up to 4V, and a film derived from the adsorption of CFSA anions (including Al(CFSA)) can be formed on the surface of the Al foil. x Thus, it can be said that Al corrosion can be suppressed. That is, for Examples 1 to 3, in the case of the Al(CFSA) xSince no decomposition reaction of the electrolyte occurs during film formation, it can be said that the generation of gas during film formation, which was a problem in Comparative Example 1, can be suppressed.

[0160] From Table 1 and Figures 13-15 The results shown in the figure show the following. That is, for Examples 1 to 3, at 6 V, a layer of Al(CFSA) was formed on the surface of the Al foil. x It also contains aluminum fluoride (AlF x As described above, when only LiFSA and LiTFSA were used as in Comparative Examples 2 to 5, Al corrosion occurred. In contrast, by using LiCFSA as in Examples 1 to 3, it can be said that the dissolution of Al through the film was suppressed even at a high potential of 6 V.

[0161] From the results shown in Table 1, it is understood that when sulfones (eg, sulfolane) are used as the organic solvent, a more excellent mobility can be secured compared to the case where carbonates are used.

[0162] 6. Summary

[0163] From the above results, it can be said that according to the lithium ion battery having the following structures (1) to (3), the film on the surface of the aluminum-containing collector can suppress the dissolution of aluminum from the aluminum-containing collector into the electrolyte. In addition, it can be said that when the film is formed on the surface of the aluminum collector, the decomposition of the electrolyte can be suppressed and the generation of gas can be suppressed.

[0164] (1) A lithium-ion battery has a positive electrode, a negative electrode, and an electrolyte.

[0165] (2) The electrolyte solution includes an organic solvent and a lithium amide salt dissolved in the organic solvent, and the lithium amide salt includes LiCFSA represented by the above formula (1).

[0166] (3) One or both of the positive electrode and the negative electrode have an aluminum-containing current collector, and the aluminum-containing current collector has a coating on the surface in contact with the electrolyte, and the coating contains Al(CFSA) x .

[0167] 7. Further research on organic solvents constituting electrolytes

[0168] 7.1 Preparation of electrolyte

[0169] 7.1.1 Comparative Example A

[0170] Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) were mixed in a volume ratio of 3:3:4 to obtain a mixed solvent. LiPF6 as a lithium salt was mixed and stirred in a concentration of 1.15M to obtain an electrolyte solution according to Comparative Example A.

[0171] 7.1.2 Comparative Example B

[0172] Ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio of 1:1 to obtain a mixed solvent. Lithium bis(fluorosulfonyl)amide (LiFSA) as a lithium amide salt was mixed and stirred with the mixed solvent to a concentration of 1 M to obtain an electrolyte solution according to Comparative Example B.

[0173] 7.1.3 Example A

[0174] Ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1 to obtain a mixed solvent. For the mixed solvent, lithium bis(fluorosulfonyl)amide (LiFSA) and lithium 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonylimide (LiCFSA) as lithium amide salts were mixed and stirred in a molar ratio of 0.8:0.2 and a total concentration of 1M to obtain the electrolyte solution involved in Example A.

[0175] 7.1.4 Example B

[0176] Ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1 to obtain a mixed solvent. 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonylimide lithium (LiCFSA) as a lithium amide salt was mixed and stirred in a concentration of 1 M to obtain the electrolyte solution involved in Example B.

[0177] 7.1.5 Comparative Example C

[0178] Ethylene carbonate (EC) and methyl propionate (MP) were mixed at a volume ratio of 15:85 to obtain a mixed solvent. Lithium bis(fluorosulfonyl)amide (LiFSA) as a lithium amide salt was mixed and stirred with the mixed solvent to a concentration of 1 M to obtain an electrolyte solution according to Comparative Example C.

[0179] 7.1.6 Example C

[0180] Ethylene carbonate (EC) and methyl propionate (MP) were mixed in a volume ratio of 15:85 to obtain a mixed solvent. In the mixed solvent, lithium bis(fluorosulfonyl)amide (LiFSA) and lithium 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonylimide (LiCFSA) as lithium amide salts were mixed and stirred in a molar ratio of 0.8:0.2 and a total concentration of 1 M to obtain an electrolyte solution according to Example C.

[0181] 7.1.7 Example D

[0182] Ethylene carbonate (EC) and methyl propionate (MP) were mixed in a volume ratio of 15:85 to obtain a mixed solvent. 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonylimide lithium (LiCFSA) as a lithium amide salt was mixed and stirred in a concentration of 1 M to obtain the electrolyte solution involved in Example D.

[0183] 7.1.8 Example E

[0184] Ethylene carbonate (EC) and methyl propionate (MP) were mixed in a volume ratio of 15:85 to obtain a mixed solvent. For the mixed solvent, lithium bis(fluorosulfonyl)amide (LiFSA) and 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonylimide lithium (LiCFSA) as lithium amide salts were mixed and stirred in a molar ratio of 1.0:0.4 and a total concentration of 1.4 M to obtain the electrolyte solution involved in Example E.

[0185] 7.2Al Corrosion Evaluation

[0186] A half-cell was prepared using Al foil as a working electrode, Li metal as a counter electrode, and the electrolyte solutions of Examples A to E and Comparative Examples A to C, and the presence or absence of Al dissolution into the electrolyte solution (Al corrosion) was evaluated by cyclic voltammetry (CV measurement). The specific measurement conditions were the same as those described above.

[0187] 7.3 Evaluation of ionic conductivity

[0188] For the electrode, Li metal was used as the electrolyte. The electrolytes involved in the above-mentioned Examples A to E and Comparative Examples A to C were used to prepare a two-electrode symmetrical battery with fixed electrode area and distance between electrodes, and the resistance value was measured by AC impedance method at 25°C. The ion conductivity was calculated from the obtained resistance value and battery shape (electrode area, distance between electrodes). A two-electrode symmetrical battery with fixed electrode area and distance between electrodes was constructed, and the resistance value was measured by AC impedance method at 25°. The ion conductivity of the electrolyte was calculated from the obtained resistance value and battery shape (electrode area and distance between electrodes). The impedance measurement conditions are the same as those described above.

[0189] 7.4 Evaluation results

[0190] Table 2 below shows the presence or absence of Al corrosion behavior and the results of measuring ion conductivity for each of the electrolyte solutions according to Examples A to E and Comparative Examples A to C.

[0191]

Table 2

[0192]

[0193] From the results shown in Table 2, it is known that the Al corrosion inhibition effect produced by the inclusion of LiCFSA in the electrolyte is exerted independently of the type of organic solvent constituting the electrolyte. On the other hand, it is also known that the ion conductivity of the electrolyte changes depending on the type of organic solvent. From the results shown in Table 2, it is known that when the electrolyte contains carboxylic acid ester as an organic solvent, the ion conductivity of the electrolyte is significantly improved.

Claims

1. A lithium-ion battery having a positive electrode, a negative electrode and an electrolyte, The electrolyte solution includes an organic solvent and a lithium amide salt dissolved in the organic solvent. The lithium amide salt comprises LiCFSA represented by the following formula (1): One or both of the positive electrode and the negative electrode have a current collector containing aluminum, The aluminum-containing current collector has a coating on a surface in contact with the electrolyte. The film comprises Al(CFSA) x , 2. The lithium ion battery according to claim 1, wherein The electrolyte solution contains sulfolane as the organic solvent.

3. The lithium ion battery according to claim 1 or 2, wherein: The electrolyte solution contains a carboxylic acid ester as the organic solvent.

4. The lithium ion battery according to any one of claims 1 to 3, wherein The film contains aluminum fluoride.

5. The lithium ion battery according to any one of claims 1 to 4, wherein At least the positive electrode has the aluminum-containing current collector.

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