Lithium ion battery

Abstract

The invention provides a lithium ion battery. The purpose of the present invention is to suppress elution of aluminum from an aluminum-containing current collector into an electrolyte solution in a lithium ion battery. This lithium ion battery has a positive electrode, a negative electrode, and an electrolyte solution, and is characterized in that the positive electrode and / or the negative electrode has an aluminum-containing current collector, the aluminum-containing current collector is in contact with the electrolyte solution, and the electrolyte solution contains a cyclic carbonate and an amide lithium salt dissolved in the cyclic carbonate. The amide lithium salt comprises a chain amide lithium salt and a cyclic amide lithium salt, the molar ratio of the chain amide lithium salt to the cyclic carbonate is greater than 0.25 and 0.33 or less, and the molar ratio of the cyclic amide lithium salt to the cyclic carbonate is greater than 0 and 0.07 or less.

Description

Technical Field

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

[0002] Patent document 1 discloses a lithium ion conductive material, comprising a cyclic carbonate as a solvent and an amide lithium salt dissolved in the cyclic carbonate, wherein the molar ratio of the amide lithium salt to the cyclic carbonate is greater than 0.25 and less than 0.33. The lithium ion conductive material disclosed in Patent document 1 can be used as an electrolyte of a lithium ion battery, for example.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2023-138137 Summary of the invention

[0006] There is still room for improvement in existing lithium-ion batteries in terms of suppressing the dissolution of aluminum from aluminum-containing current collectors into the electrolyte.

[0007] The present application discloses the following plural aspects as means for solving the above-mentioned problems.

[0008] <Method 1>

[0009] A lithium ion battery comprises a positive electrode, a negative electrode and an electrolyte.

[0010] One or both of the positive electrode and the negative electrode has an aluminum-containing current collector,

[0011] The electrolyte comprises a cyclic carbonate and an amide lithium salt dissolved in the cyclic carbonate.

[0012] The above-mentioned amide lithium salt includes chain amide lithium salt and cyclic amide lithium salt.

[0013] The molar ratio of the chain amide lithium salt to the cyclic carbonate is greater than 0.25 and less than 0.33,

[0014] The molar ratio of the cyclic amide lithium salt to the cyclic carbonate is greater than 0 and less than 0.07.

[0015] <Method 2>

[0016] The lithium ion battery according to aspect 1, wherein at least the positive electrode has the aluminum-containing current collector.

[0017] <Method 3>

[0018] The lithium ion battery according to aspect 1 or 2, wherein the cyclic carbonate is one or both of propylene carbonate and ethylene carbonate.

[0019] <Method 4>

[0020] The lithium ion battery according to any one of aspects 1 to 3, wherein the chain amide lithium salt is one or both of bisfluorosulfonamide lithium and bistrifluoromethanesulfonamide lithium.

[0021] <Method 5>

[0022] The lithium ion battery according to any one of aspects 1 to 4, wherein the cyclic amide lithium salt is represented by the following formula (1).

[0023]

[0024] In formula (1), n ​​is an integer of 2-5.

[0025] The lithium ion battery disclosed herein can suppress the dissolution of aluminum from the aluminum-containing current collector into the electrolyte solution, compared with conventional lithium ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The structure of a lithium-ion battery is schematically shown.

[0027] Figure 2 Indicates the results of aluminum corrosion evaluation.

[0028] Explanation of symbols

[0029] 10 Positive electrode

[0030] 11 Positive electrode active material layer

[0031] 12Positive electrode collector

[0032] 20 negative electrode

[0033] 21 Negative electrode active material layer

[0034] 22 Negative electrode collector

[0035] 30 electrolyte

[0036] 40 Isolators

[0037] 100 Lithium-ion Batteries DETAILED DESCRIPTION

[0038] An embodiment of the lithium ion battery and the like of the present disclosure will be described below, but the lithium ion battery and the like of the present disclosure are not limited to the embodiment described below.

[0039] 1. Lithium-ion battery

[0040] like Figure 1As shown, a lithium ion battery 100 according to one embodiment has a positive electrode 10, a negative electrode 20 and an electrolyte 30. One or both of the positive electrode 10 and the negative electrode 20 have an aluminum-containing current collector. The electrolyte 30 includes a cyclic carbonate and an amide lithium salt dissolved in the cyclic carbonate. The amide lithium salt includes a chain amide lithium salt and a cyclic amide lithium salt. The molar ratio of the chain amide lithium salt to the cyclic carbonate is greater than 0.25 and is less than 0.33. The molar ratio of the cyclic amide lithium salt to the cyclic carbonate is greater than 0 and is less than 0.07.

[0041] 1.1 Positive electrode

[0042] like Figure 1 As shown, the positive electrode 10 involved in one embodiment may include a positive electrode active material layer 11 and a positive electrode collector 12. When 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. When 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, the dissolution of aluminum from the aluminum-containing collector into the electrolyte is easy to occur when the aluminum-containing collector is at a high potential. According to the technology disclosed in the present invention, even if at least the positive electrode 10 has an aluminum-containing collector, the dissolution of aluminum into the electrolyte 30 can be suppressed.

[0043] 1.1.1 Positive electrode active material layer

[0044] The positive electrode active material layer 11 contains a positive electrode active material, and may also arbitrarily contain an electrolyte, a conductive aid, a binder, and various additives. The respective contents of the positive electrode active material, electrolyte, conductive aid, and binder in the positive electrode active material layer 11 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%. The shape of the positive electrode active material layer 11 is not particularly limited, for example, it can be a sheet with a roughly flat surface. The thickness of the positive electrode active material layer 11 is not particularly limited, 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.

[0045] The positive electrode active material can be a substance known as a positive electrode active material for a lithium ion battery. Among the known active materials, a material having a 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 cobaltate, lithium nickelate, lithium manganate, lithium manganese nickel cobaltate, and spinel lithium compounds can be used as the positive electrode active material. The positive electrode active material can be used alone or in combination of two or more. The positive electrode active material can be, for example, in the form of particles, and its size is not particularly limited. 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 size (D50) of the particles of the positive electrode active material can be, for example, 1 nm or more, 5 nm or more, or 10 nm or more, and can also be 500 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less. The average particle size (D50) refers to a particle size at which the cumulative value is 50% in a volume-based particle size distribution measured by a laser diffraction / scattering method (D50, median particle size).

[0046] 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 contain 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 can be, for example, 70% or more, 80% or more, or 90% or more. The thickness of the protective layer can be, for example, 0.1nm or more or 1nm or more, or 100nm or less or 20nm or less.

[0047] The positive electrode active material layer 11 may include the electrolyte 30 described later. In addition, the positive electrode active material layer 11 may include other electrolytes in addition to the electrolyte 30. Other electrolytes may be solid electrolytes, electrolytes other than the electrolyte 30, or combinations thereof. The solid electrolyte may use substances known as solid electrolytes for lithium ion batteries. The solid electrolyte may be an inorganic solid electrolyte or an organic polymer electrolyte. In particular, inorganic solid electrolytes have excellent ion conductivity and heat resistance. As inorganic solid electrolytes, sulfide solid electrolytes and oxide solid electrolytes may be exemplified. In particular, among 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 a Li3PS4 skeleton and 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 than the electrolyte solution 30 (other electrolyte solution) may contain lithium ions as carrier ions, for example. The other electrolyte solution may be a non-aqueous electrolyte solution, for example, an electrolyte solution in which a lithium salt is dissolved in a carbonate-based solvent at a predetermined concentration may be used as the other electrolyte solution.

[0048] As the conductive aid that can be contained 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); metal materials such as nickel, aluminum, and stainless steel can be cited. 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.

[0049] As the binder that can be contained 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 cited. Only one type of binder can be used alone, or two or more types can be used in combination.

[0050] 1.1.2 Positive electrode collector

[0051] like Figure 1As shown, 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. The positive electrode collector 12 may be any collector commonly used as a positive electrode collector for a lithium ion battery. In addition, the positive electrode collector 12 may be in the form of a foil, a plate, a mesh, a perforated metal, a foam, etc. The positive electrode collector 12 may be composed 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 cited. As described above, the positive electrode 10 may include an aluminum-containing collector in contact with the positive electrode active material layer 11 and the electrolyte 30 as the positive electrode collector 12. In this case, it is easy to ensure oxidation resistance, etc. For purposes such as adjusting resistance, the positive electrode collector 12 may have a coating on its surface. In addition, the positive electrode current collector 12 may be a current collector formed 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, a certain layer may be provided between the plurality of metal foils. The thickness of the positive electrode current collector 12 is not particularly limited. For example, it may be 0.1 μm or more or 1 μm or less, and may be 1 mm or less or 100 μm or less.

[0052] In addition to the above-mentioned structure, the positive electrode 10 may also have a structure commonly used as a positive electrode of a lithium ion battery. For example, a connector or a terminal. The positive electrode 10 can be manufactured by a known method. For example, by forming the positive electrode mixture containing the above-mentioned various components by a dry method or a wet method, the positive electrode active material layer 11 can be easily formed. The positive electrode active material layer 11 can be formed together with the positive electrode collector 12, or it can be formed separately from the positive electrode collector 12.

[0053] 1.2 Negative electrode

[0054] like Figure 1 As shown, 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.

[0055] 1.2.1 Negative electrode active material layer

[0056] The negative electrode active material layer 21 contains a negative electrode active material, and may also arbitrarily contain an electrolyte, a conductive aid, a binder, and various additives. The respective contents of the negative electrode active material, electrolyte, conductive aid, and binder in the negative electrode active material layer 21 can be appropriately determined 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 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%. The shape of the negative electrode active material layer 21 is not particularly limited, for example, it can be a sheet with a roughly flat surface. The thickness of the negative electrode active material layer 21 is not particularly limited, 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.

[0057] The negative electrode active material can be a substance known as a negative electrode active material for a lithium ion battery. Among the known active materials, a substance having a potential (charge and discharge potential) for absorbing and releasing lithium ions lower than the potential 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 the size thereof is not particularly limited. 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 can be, for example, 1 nm or more, 5 nm or more, or 10 nm or more, and can also be 500 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less. Alternatively, the negative electrode active material can be in the form of a sheet (foil, film) such as lithium foil. That is, the negative electrode active material layer 21 can be composed of a sheet of the negative electrode active material.

[0058] The negative electrode active material layer 21 may contain the electrolyte 30 described later. In addition, the negative electrode active material layer 21 may contain other electrolytes in addition to the electrolyte 30. As other electrolytes, the above-mentioned solid electrolytes, electrolytes or combinations thereof can be cited. The conductive aid that can be contained in the negative electrode active material layer 21 can be appropriately selected from the substances exemplified as the conductive aid that can be contained in the above-mentioned positive electrode active material layer 11. The binder that can be contained in the negative electrode active material layer 21 can be appropriately selected from the substances exemplified as the binder that can be contained in the above-mentioned positive electrode active material layer 11. The electrolyte, the conductive aid, and the binder can be used alone or in combination of two or more.

[0059] 1.2.2 Negative electrode collector

[0060] like Figure 1 As shown, 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. The negative electrode collector 22 may be any current collector commonly used as a negative electrode collector for a battery. In addition, the negative electrode collector 22 may be in the form of a foil, a plate, a mesh, a perforated 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 or 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 cited. From the viewpoint of ensuring reduction resistance and the viewpoint of not being easily alloyed with lithium, the negative electrode collector 22 may contain at least one metal selected from Cu, Ni, and stainless steel. Alternatively, as described above, the negative electrode 20 may have an aluminum-containing collector in contact with the negative electrode active material layer 21 and the electrolyte 30 as the negative electrode collector 22. For the purpose of adjusting resistance, etc., the negative electrode collector 22 may have a coating on its surface. In addition, the negative electrode collector 22 may be a collector formed by plating or vapor-depositing the above-mentioned metal on a metal foil or a substrate. In addition, when the negative electrode collector 22 is composed of a plurality of metal foils, a certain layer may be provided between the plurality of metal foils. The thickness of the negative electrode collector 22 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.

[0061] In addition to the above-mentioned structure, the negative electrode 20 may also have a structure commonly used as a negative electrode of a lithium ion battery. For example, a connector or a terminal. The negative electrode 20 can be manufactured by a known method. For example, by forming the negative electrode mixture containing the above-mentioned various components by a dry method or a wet method, the negative electrode active material layer 21 can be easily formed. The negative electrode active material layer 21 can be formed together with the negative electrode collector 22, or it can be formed separately from the negative electrode collector 22.

[0062] 1.3 Electrolyte

[0063] The electrolyte solution 30 contains a cyclic carbonate and an amide lithium salt dissolved in the cyclic carbonate.

[0064] 1.3.1 Cyclic carbonates

[0065] Electrolyte 30 comprises cyclic carbonate as solvent. Cyclic carbonate has high dielectric constant and is easy to coordinate lithium ion compared with chain carbonate. In other words, in electrolyte 30, cyclic carbonate is difficult to become free state, and the result easily improves thermal stability. Especially, when amide lithium salt is dissolved in cyclic carbonate with specified concentration, almost all cyclic carbonate and lithium ion solvation can be made, and the result can further improve thermal stability. In addition, by a small amount of lithium ion etc. that is not solvated with cyclic carbonate, even if the migration number of lithium ion is also high under high viscosity, excellent lithium ion conductivity can be easily ensured.

[0066] As long as cyclic carbonate has a cyclic structure as a chemical structure, and is liquid at a temperature where lithium ion conductivity is desired to be presented, and can dissolve amide lithium salts with a specified concentration. As a specific example of cyclic carbonate, propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), vinylene carbonate (VC) or their derivatives (for example, halides, etc.) etc. can be cited. When particularly cyclic carbonate is at least one of propylene carbonate and ethylene carbonate, it is easy to ensure more excellent lithium ion conductivity and thermal stability. Cyclic carbonate can only be used alone 1 kind, and can also be used in combination of more than 2 kinds.

[0067] 1.3.2 Solvents other than cyclic carbonates (sub-solvents)

[0068] The solvent constituting the electrolyte 30 may be composed of the above-mentioned cyclic carbonate, or may contain a solvent (sub-solvent) other than the cyclic carbonate on the basis of the above-mentioned cyclic carbonate. As a sub-solvent other than the cyclic carbonate, for example, a chain carbonate may be cited. As a chain carbonate, for example, dimethyl carbonate (DMC), diethyl carbonate (DEC) or their derivatives (such as halides, especially substances with perfluoroalkyl groups) may be cited. However, compared with cyclic carbonates, chain carbonates have a low dielectric constant and a tendency to be difficult to coordinate lithium ions. Therefore, chain carbonates are prone to being freed alone in lithium ion conductive materials and are prone to volatilization. In this regard, when the sub-solvent other than the cyclic carbonate in the electrolyte 30 is a small amount, it is easy to ensure high thermal stability. In the electrolyte 30, the molar ratio of the sub-solvent to the cyclic carbonate ([sub-solvent (mol)] / [cyclic carbonate (mol)]) may be less than 0.10, less than 0.05 or less than 0.03. The lower limit of the molar ratio of the sub-solvent to the cyclic carbonate is 0.

[0069] 1.3.3 Lithium amide salt

[0070] The electrolyte 30 contains an amide lithium salt dissolved in the above-mentioned cyclic carbonate. The amide lithium salt can be dissolved in the cyclic carbonate and ionized into a state of cations and anions, or can form a certain association body together with the cyclic carbonate, etc. The electrolyte 30 contains both a chain amide lithium salt and a cyclic amide lithium salt as the amide lithium salt. It should be noted that "amide salt" refers to a concept that also includes "imide salt".

[0071] 1.3.3.1 Chain amide lithium salt

[0072] Specific examples of chain amide lithium salts include sulfonamide salts such as lithium bisfluorosulfonamide (LiFSA, LiN(SO2F)2), lithium bistrifluoromethanesulfonamide (LiTFSA, Li[N(CF3SO2)2]), lithium bisperfluoroethanesulfonamide (Li[N(C2F5SO2)2]), lithium bisperfluorobutanesulfonamide (Li[N(C4F9SO2)2]), and lithium fluorosulfonyltrifluoromethanesulfonamide (Li[N(FSO2)(C2F5SO2)]). Alternatively, a silylamide salt having Si instead of S can be used. In particular, when the chain amide lithium salt is one or both of lithium bisfluorosulfonamide (LiFSA, LiN(SO2F)2) and lithium bistrifluoromethanesulfonamide (LiTFSA, Li[N(CF3SO2)2]), it is easy to ensure better lithium ion conductivity and thermal stability. The chain amide lithium salt can be used alone or in combination of two or more.

[0073] The molar ratio of the chain amide lithium salt to the cyclic carbonate ([chain amide lithium salt (mol)] / [cyclic carbonate (mol)]) is greater than 0.25 and less than 0.33. In other words, the chain amide lithium salt is dissolved in a concentration of 0.25 mol to 0.33 mol per mole of cyclic carbonate. When the concentration of the chain amide lithium salt in the cyclic carbonate is in this range, thermal stability and lithium ion conductivity are easily significantly improved. If the concentration of the chain amide lithium salt relative to the cyclic carbonate is too low, it is difficult to improve thermal stability and lithium ion conductivity. On the other hand, if the concentration of the chain amide lithium salt relative to the cyclic carbonate is too high, the viscosity becomes too high and the lithium ion conductivity may decrease. The molar ratio can be greater than 0.26, greater than 0.27 or greater than 0.28, and can be less than 0.32, less than 0.31 or less than 0.30. The molar ratio of the chain amide lithium salt to the cyclic carbonate can be determined by analyzing the ions or elements contained in the cyclic carbonate.

[0074] 1.3.3.2 Cyclic amide lithium salt

[0075] According to the new discovery of the inventors, in the electrolyte of the lithium ion battery, when only the chain amide lithium salt is included together with the above-mentioned carbonate solvent, aluminum is easily dissolved from the aluminum-containing collector into the electrolyte. The inventors have conducted in-depth research to solve this problem, and found that by dissolving the cyclic amide lithium salt together with the chain amide lithium salt in the electrolyte 30 of the lithium ion battery 100, the dissolution of aluminum from the aluminum-containing collector into the electrolyte can be suppressed. Specifically, in the electrolyte 30, when the cyclic amide lithium salt is dissolved together with the above-mentioned chain amide lithium salt, a film from the cyclic amide lithium salt can be formed on the surface of the above-mentioned aluminum-containing collector in contact with the electrolyte 30. The film functions as a protective film that suppresses the dissolution of aluminum from the aluminum-containing collector into the electrolyte 30.

[0076] Specific examples of cyclic amide lithium salts include cyclic amide lithium salts in which sulfonamide groups or silylamide groups in the above-mentioned sulfonamide salts or silylamide salts form a ring via a perfluoroalkylene group, etc. In particular, according to the new discovery of the present inventors, when the cyclic amide lithium salt is represented by the following formula (1), the dissolution of aluminum can be more significantly suppressed.

[0077]

[0078] In formula (1), n ​​is an integer of 2 to 5. n may be an integer of 2 to 4, and may be 3.

[0079] The molar ratio of the cyclic amide lithium salt to the cyclic carbonate ([cyclic amide lithium salt (mol)] / [cyclic carbonate (mol)]) is greater than 0 and less than 0.07. In other words, the cyclic amide lithium salt is dissolved in each mole of the cyclic carbonate at a concentration greater than 0 mol and less than 0.07 mol. When the concentration of the cyclic amide lithium salt in the cyclic carbonate is within this range, the aluminum dissolution inhibition effect and excellent thermal stability and lithium ion conductivity can be ensured. The molar ratio can be greater than 0.01, greater than 0.02 or greater than 0.03, and can be less than 0.06, less than 0.05 or less than 0.04. The molar ratio of the cyclic amide lithium salt to the cyclic carbonate can be determined by analyzing the ions or elements contained in the cyclic carbonate.

[0080] 1.3.4 Lithium salts other than lithium amide salts

[0081] In the electrolyte 30, the lithium salt dissolved in the solvent may be composed of the above-mentioned amide lithium salt, or may be a combination of the above-mentioned amide lithium salt and a lithium salt other than the amide lithium salt (other lithium salt). In either case, by dissolving the above-mentioned chain amide lithium salt and cyclic amide lithium salt in the cyclic carbonate at a specified concentration, respectively, it is possible to ensure excellent thermal stability and ion conductivity, and inhibit the dissolution of aluminum from the aluminum collector into the electrolyte 30. In the electrolyte 30, the higher the proportion of amide lithium salt in the lithium salt dissolved in the solvent, the better. Specifically, the proportion of amide lithium salt in the overall lithium salt (100 mol%) 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, or 99 mol% or more.

[0082] 1.3.5 Other optional ingredients

[0083] In addition to the above-mentioned solvent and lithium amide salt, the electrolyte 30 may also contain various additives 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).

[0084] 1.4 Other matters

[0085] 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 maintained in the separator 40. The separator 40 may adopt a known structure as a separator of the lithium ion battery 100. In addition, the lithium ion battery 100 may be a battery in which the above-mentioned structures are housed inside an outer body. The outer body may adopt all outer bodies known as outer bodies of batteries. In addition, a plurality of lithium ion batteries 100 may be electrically connected arbitrarily, or overlapped arbitrarily to form a battery pack. In this case, the battery pack may be housed inside a known battery casing. In addition, 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 type, a cylindrical type, and a square type may be cited. The lithium ion battery 100 may be a secondary battery. The lithium ion battery 100 may be manufactured by applying a known method. For example, it may be manufactured as follows. However, the manufacturing method of the lithium ion battery 100 is not limited to the following method, for example, each layer may be formed by dry molding, etc.

[0086] (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.

[0087] (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.

[0088] (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 may be installed in the laminate as needed.

[0089] (4) The stack is housed in a battery case and sealed in the battery case so that the stack is immersed in an electrolyte to prepare a lithium ion battery. It should be noted that in the above step (3), the negative electrode active material layer, the separator, and the positive electrode active material layer may contain an electrolyte.

[0090] 2. Lithium ion conductive materials

[0091] 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 is characterized in that it contains a cyclic carbonate and an amide lithium salt dissolved in the above-mentioned cyclic carbonate, the above-mentioned amide lithium salt contains a chain amide lithium salt and a cyclic amide lithium salt, the molar ratio of the above-mentioned chain amide lithium salt to the above-mentioned cyclic carbonate is greater than 0.25 and is less than 0.33, and the molar ratio of the above-mentioned cyclic amide lithium salt to the above-mentioned cyclic carbonate is greater than 0 and is less than 0.07. The details of each component constituting the lithium ion conductive material are as described above.

[0092] 3. Vehicles

[0093] The lithium ion battery disclosed in the present invention can be applied to at least one vehicle selected from, for example, a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV) and an electric vehicle (BEV). That is, the technology disclosed in the present invention also relates to an aspect of a vehicle equipped with a lithium ion battery, wherein the lithium ion battery has a positive electrode, a negative electrode and an electrolyte, one or both of the positive electrode and the negative electrode have an aluminum-containing current collector, the electrolyte comprises a cyclic carbonate and an amide lithium salt dissolved in the cyclic carbonate, the amide lithium salt comprises a chain amide lithium salt and a cyclic amide lithium salt, the molar ratio of the chain amide lithium salt to the cyclic carbonate is greater than 0.25 and is less than 0.33, and the molar ratio of the cyclic amide lithium salt to the cyclic carbonate is greater than 0 and is less than 0.07.

[0094] Example

[0095] The technology of the present disclosure will be described in further detail below with reference to examples, but the technology of the present disclosure is not limited to the following examples.

[0096] 1. Preparation of electrolyte

[0097] 1.1 Comparative Example 1

[0098] Lithium bisfluorosulfonamide (LiFSA) as a chain amide lithium salt and propylene carbonate (PC) as a solvent were weighed, mixed and stirred so that the molar ratio was 0.33 (PC:LiFSA=3:1), thereby obtaining an electrolyte solution according to Comparative Example 1.

[0099] 1.2 Example 1

[0100] The electrolyte solution of Example 1 was obtained by weighing, mixing and stirring the two components in such a manner that the molar ratio of LiFSA to PC was 0.33 (PC:LiFSA=3:1) and the molar ratio of 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonylimide lithium (LiCFSA, the following formula (1a)) as a cyclic amide lithium salt to PC was 0.033 (PC:LiCFSA=3:0.1).

[0101]

[0102] 1.3 Example 2

[0103] The electrolyte solution according to Example 2 was obtained by weighing, mixing and stirring the components such that the molar ratio of LiFSA to PC was 0.30 (PC:LiFSA=3.3:1) and the molar ratio of LiCFSA as the cyclic amide lithium salt to PC was 0.030 (PC:LiCFSA=3.3:0.1).

[0104] 1.4 Example 3

[0105] The electrolyte solution according to Example 3 was obtained by weighing, mixing and stirring the components so that the molar ratio of LiFSA to PC was 0.25 (PC:LiFSA=4:1) and the molar ratio of LiCFSA to PC was 0.025 (PC:LiCFSA=4:0.1).

[0106] 1.5 Comparative Example 2

[0107] The electrolyte solution according to Comparative Example 2 was obtained by weighing lithium bis(trifluoromethane)sulfonamide (LiTFSA) as a chain amide lithium salt and PC so that the molar ratio was 0.33 (PC:LiTFSA=3:1), mixing and stirring.

[0108] 1.6 Example 4

[0109] The electrolyte solution according to Example 4 was obtained by weighing, mixing and stirring the components so that the molar ratio of LiTFSA to PC was 0.33 (PC:LiTFSA=3:1) and the molar ratio of LiCFSA to PC was 0.033 (PC:LiCFSA=3:0.1).

[0110] 2. Evaluation of ion conductivity

[0111] For a bipolar symmetrical battery using Li metal as the electrode and with a fixed inter-electrode distance, the resistance value was measured by the AC impedance method at 25° C. The ion conductivity was calculated from the obtained resistance value and the battery shape (electrode area, inter-electrode distance). The specific measurement conditions are as follows.

[0112] Measurement conditions: temperature 25°C, amplitude 10mV, frequency 1M~10mHz

[0113] 3. Evaluation of aluminum corrosion

[0114] A half-cell was prepared using aluminum 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 of aluminum dissolution into the electrolyte solution (aluminum corrosion) was evaluated by linear sweep voltammetry (LSV measurement). Specific measurement conditions are as follows.

[0115] Measurement conditions: Scanning speed 10mV / s, from OCV to 6V

[0116] 4. Evaluation results

[0117] Table 1 below shows the composition and ion conductivity of each electrolyte solution involved in Examples 1 to 4 and Comparative Examples 1 to 2, as well as the presence or absence of aluminum corrosion behavior. Figure 2 The LSV measurement results of Examples 1 to 4 and Comparative Examples 1 and 2 are shown in FIG.

[0118] [Table 1]

[0119]

[0120] From the results shown in Table 1, it can be seen that the electrolyte solutions of Examples 1 to 4 and Comparative Examples 1 to 2 have high ion conductivity. Figure 2 The results shown show that when the LSV measurement was performed using the electrolyte solutions involved in Comparative Examples 1 and 2, an increase in current due to the dissolution of aluminum was confirmed. In contrast, when the LSV measurement was performed using the electrolyte solutions involved in Examples 1 to 4, an increase in current due to the dissolution of aluminum was suppressed. It is believed that in Examples 1 to 4, a film derived from LiCFSA was formed on the surface of the aluminum foil, which functioned as a protective film that suppressed the dissolution of aluminum.

[0121] 5. Summary

[0122] From the above results, it can be said that when a lithium ion battery is constructed using an electrolyte solution having the following structures (1) to (4), the elution of aluminum from the aluminum-containing current collector into the electrolyte solution can be suppressed.

[0123] (1) The electrolyte solution contains a cyclic carbonate and an amide lithium salt dissolved in the cyclic carbonate.

[0124] (2) The above-mentioned amide lithium salt includes a chain amide lithium salt and a cyclic amide lithium salt.

[0125] (3) The molar ratio of the linear amide lithium salt to the cyclic carbonate is greater than 0.25 and less than 0.33.

[0126] (4) The molar ratio of the cyclic amide lithium salt to the cyclic carbonate is greater than 0 and is not more than 0.07.

Claims

1. A lithium ion battery having a positive electrode, a negative electrode and an electrolyte, One or both of the positive electrode and the negative electrode has an aluminum-containing current collector, The electrolyte comprises a cyclic carbonate and an amide lithium salt dissolved in the cyclic carbonate, The amide lithium salt comprises a chain amide lithium salt and a cyclic amide lithium salt, The molar ratio of the chain amide lithium salt to the cyclic carbonate is greater than 0.25 and less than 0.33, The molar ratio of the cyclic amide lithium salt to the cyclic carbonate is greater than 0 and is less than or equal to 0.

07.

2. The lithium ion battery according to claim 1, wherein At least the positive electrode has the aluminum-containing current collector.

3. The lithium ion battery according to claim 1 or 2, wherein: The cyclic carbonate is one or both of propylene carbonate and ethylene carbonate.

4. The lithium ion battery according to any one of claims 1 to 3, wherein The chain amide lithium salt is one or both of bisfluorosulfonamide lithium and bistrifluoromethanesulfonamide lithium.

5. The lithium ion battery according to any one of claims 1 to 4, wherein The cyclic amide lithium salt is represented by the following formula (1): In formula (1), n ​​is an integer of 2-5.

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