Lithium-ion battery

Abstract

To suppress the elution of aluminum from an aluminum-containing current collector into an electrolyte in a lithium-ion battery.SOLUTION: A lithium-ion battery includes 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 aluminum-containing current collector is in contact with the electrolyte. The electrolyte includes a cyclic carbonate and a lithium amide salt dissolved in the cyclic carbonate. The lithium amide salt includes a chain-type lithium amide salt and a cyclic lithium amide salt. The molar ratio of the chain-type lithium amide salt to the cyclic carbonate is greater than 0.25 and less than or equal to 0.33, and the molar ratio of the cyclic lithium amide salt to the cyclic carbonate is greater than 0 and less than or equal to 0.07.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] This application discloses a lithium ion battery. [Background technology]

[0002] Patent Document 1 discloses a lithium ion conductive material that includes a cyclic carbonate as a solvent and a lithium amide salt dissolved in the cyclic carbonate, and the molar ratio of the lithium amide salt to the cyclic carbonate is greater than 0.25 and less than or equal to 0.33. The lithium ion conductive material disclosed in Patent Document 1 can be used, for example, as an electrolyte for a lithium ion battery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-138137 A Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional lithium ion batteries have room for improvement in terms of suppressing the elution of aluminum from aluminum-containing current collectors into the electrolyte. [Means for solving the problem]

[0005] The present application discloses the following aspects as means for solving the above problems. <Aspect 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 solution is Cyclic carbonates, and a lithium amide salt dissolved in said cyclic carbonate; Including, The lithium amide salt is A chain lithium amide salt, and Cyclic lithium amide salts, Including, a molar ratio of the chain lithium amide salt to the cyclic carbonate is greater than 0.25 and less than or equal to 0.33; The molar ratio of the cyclic lithium amide salt to the cyclic carbonate is greater than 0 and less than or equal to 0.07. Lithium-ion battery. <Aspect 2> 2. The lithium ion battery of embodiment 1, At least the positive electrode has the aluminum-containing current collector. Lithium-ion battery. <Aspect 3> 3. The lithium ion battery of embodiment 1 or 2, The cyclic carbonate is one or both of propylene carbonate and ethylene carbonate; Lithium-ion battery. <Aspect 4> The lithium ion battery according to any one of aspects 1 to 3, The chain lithium amide salt is one or both of lithium bisfluorosulfonylamide and lithium bistrifluoromethanesulfonylamide. Lithium-ion battery. <Aspect 5> The lithium ion battery according to any one of aspects 1 to 4, The cyclic lithium amide salt is represented by the following formula (1): Lithium-ion battery. [ka] In the formula (1), n ​​is an integer of 2 to 5. Effect of the Invention

[0006] The lithium ion battery of the present disclosure can suppress the elution of aluminum from the aluminum-containing current collector into the electrolyte, as compared to conventional lithium ion batteries. [Brief description of the drawings]

[0007] [Figure 1] 1 shows a schematic configuration of a lithium-ion battery. [Diagram 2] The results of Al corrosion evaluation are shown. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, one embodiment of the lithium ion battery etc. of the present disclosure will be described, however, the lithium ion battery etc. of the present disclosure is not limited to the embodiment described below.

[0009] 1. Lithium-ion battery As shown in FIG. 1, a lithium ion battery 100 according to an embodiment includes 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 include an aluminum-containing current collector. The electrolyte 30 includes a cyclic carbonate and a lithium amide salt dissolved in the cyclic carbonate. The lithium amide salt includes a chain lithium amide salt and a cyclic lithium amide salt. The molar ratio of the chain lithium amide salt to the cyclic carbonate is greater than 0.25 and is equal to or less than 0.33. The molar ratio of the cyclic lithium amide salt to the cyclic carbonate is greater than 0 and is equal to or less than 0.07.

[0010] 1.1 Positive electrode As shown in FIG. 1, a positive electrode 10 according to an embodiment may include a positive electrode active material layer 11 and a positive electrode current collector 12. When a negative electrode current collector 22 described later is an aluminum-containing current collector, the positive electrode current collector 12 may or may not be an aluminum-containing current collector. When a negative electrode current collector 22 described later is not an aluminum-containing current collector, the positive electrode current collector 12 is an aluminum-containing current collector. In particular, the elution of aluminum from an aluminum-containing current collector into the electrolyte is likely to occur when the aluminum-containing current collector is at a high potential. However, according to the technology of the present disclosure, even when at least the positive electrode 10 has an aluminum-containing current collector, the elution of aluminum into the electrolyte 30 can be suppressed.

[0011] 1.1.1 Cathode active material layer The positive electrode active material layer 11 includes a positive electrode active material, and may further include an electrolyte, a conductive assistant, a binder, and various additives. The content of each of the positive electrode active material, electrolyte, conductive assistant, binder, and the like in the positive electrode active material layer 11 may be appropriately determined according to the target battery performance. For example, the content of the positive electrode active material may be 40 mass% or more, 50 mass% or more, or 60 mass% or more, or less than 100 mass% or 90 mass% or less, with the entire positive electrode active material layer 11 (total solid content) being 100 mass%. The shape of the positive electrode active material layer 11 is not particularly limited, and may be, for example, a sheet shape having a substantially flat surface. The thickness of the positive electrode active material layer 11 is not particularly limited, and may be, for example, 0.1 μm or more, 1 μm or more, 10 μm or more, or 30 μm or more, and may be 2 mm or less, 1 mm or less, 500 μm or less, or 100 μm or less.

[0012] The positive electrode active material may be a known positive electrode active material for a lithium ion battery. Among known active materials, a material whose potential (charge / discharge potential) for absorbing and releasing lithium ions is higher than that of the negative electrode active material described below may be used as the positive electrode active material. For example, various lithium-containing composite oxides such as lithium cobalt oxide, lithium nickel oxide, lithium manganate, lithium manganese nickel cobalt oxide, and spinel-based lithium compounds may be used as the positive electrode active material. Only one type of positive electrode active material may be used alone, or two or more types may be used in combination. The positive electrode active material may be, for example, particulate, and the size is not particularly limited. The particles of the positive electrode active material may be solid particles or hollow particles. The particles of the positive electrode active material may be primary particles or secondary particles formed by agglomeration of a plurality of primary particles. The average particle diameter (D50) of the particles of the positive electrode active material 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. The average particle diameter (D50) is the particle diameter (D50, median diameter) at an integrated value of 50% in a volume-based particle size distribution by a laser diffraction / scattering method.

[0013] 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 positive electrode active material and a protective layer provided on the surface thereof. Examples of the lithium ion conductive oxide include Li3BO3, LiBO2, Li2CO3, LiAlO2, Li4SiO4, Li2SiO3, Li3PO4, Li2SO4, Li2TiO3, Li4Ti5O 12 , Li2Ti2O5, Li2ZrO3, LiNbO3, Li2MoO4, and 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 more, and may be 100 nm or less, or 20 nm or less.

[0014] The positive electrode active material layer 11 may contain an electrolyte solution 30 described later. The positive electrode active material layer 11 may contain other electrolytes in addition to the electrolyte solution 30. The other electrolytes may be solid electrolytes, electrolyte solutions other than the electrolyte solution 30, or combinations thereof. The solid electrolyte may be a known solid electrolyte for lithium ion batteries. The solid electrolyte may be an inorganic solid electrolyte or an organic polymer electrolyte. In particular, the inorganic solid electrolyte has excellent ion conductivity and heat resistance. Examples of the inorganic solid electrolyte include a sulfide solid electrolyte and an oxide solid electrolyte. In particular, the sulfide solid electrolyte, particularly the sulfide solid electrolyte containing at least Li, S, and P as constituent elements, has high performance, and the sulfide solid electrolyte based on the Li3PS4 skeleton and containing at least one or more types of halogen also has high performance. The solid electrolyte may be amorphous or crystalline. The solid electrolyte may be, for example, particulate. Only one type of solid electrolyte may be used alone, or two or more types may be used in combination. The electrolyte solution other than the electrolyte solution 30 (other electrolyte solution) may contain, for example, lithium ions as carrier ions. The other electrolyte solution may be, for example, a non-aqueous electrolyte solution. For example, the other electrolyte solution may be a solution in which a lithium salt is dissolved at a predetermined concentration in a carbonate-based solvent.

[0015] Examples of the conductive assistant that may be included in the positive electrode active material layer 11 include 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. The conductive assistant may be, for example, particulate or fibrous, and the size is not particularly limited. Only one type of conductive assistant may be used alone, or two or more types may be used in combination.

[0016] Examples of binders that can be included in the positive electrode active material layer 11 include 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. Only one type of binder may be used alone, or two or more types may be used in combination.

[0017] 1.1.2 Positive electrode current collector As shown in FIG. 1, 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 of those commonly used as positive electrode collectors for lithium ion batteries. The positive electrode collector 12 may be in the form of a foil, a plate, a mesh, a punched metal, a foam, or the like. The positive electrode collector 12 may be made of a metal foil or a metal mesh. In particular, the metal foil is excellent in terms of ease of handling. The positive electrode collector 12 may be made of a plurality of foils. Examples of metals constituting the positive electrode collector 12 include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, and the like. 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 which case oxidation resistance and the like are easily ensured. The positive electrode current collector 12 may have some kind of coating layer on its surface for the purpose of adjusting the resistance, etc. Also, the positive electrode current collector 12 may be a metal foil or a base material on which the above metal is plated or vapor-deposited. Also, when the positive electrode current collector 12 is made of a plurality of metal foils, some kind of layer may be present 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 more, and may be 1 mm or less or 100 μm or less.

[0018] In addition to the above configuration, the positive electrode 10 may have a general configuration as a positive electrode of a lithium ion battery. For example, a tab, a terminal, etc. The positive electrode 10 can be manufactured by applying a known method. For example, the positive electrode active material layer 11 can be easily formed by forming a positive electrode mixture containing the above various components in a dry or wet manner. The positive electrode active material layer 11 may be formed together with the positive electrode current collector 12, or may be formed separately from the positive electrode current collector 12.

[0019] 1.2 Negative electrode 1, the negative electrode 20 according to one embodiment may include a negative electrode active material layer 21 and a negative electrode current collector 22. When the above-mentioned positive electrode current collector 12 is an aluminum-containing current collector, the negative electrode current collector 22 may or may not be an aluminum-containing current collector. When the above-mentioned positive electrode current collector 12 is not an aluminum-containing current collector, the negative electrode current collector 22 is an aluminum-containing current collector.

[0020] 1.2.1 Negative electrode active material layer The negative electrode active material layer 21 includes a negative electrode active material, and may further include an electrolyte, a conductive assistant, a binder, various additives, and the like. The contents of the negative electrode active material, electrolyte, conductive assistant, binder, and the like in the negative electrode active material layer 21 may be appropriately determined according to the target battery performance. For example, the content of the negative electrode active material may be 40 mass% or more, 50 mass% or more, or 60 mass% or more, or less than 100 mass% or 90 mass% or less, with the entire negative electrode active material layer 21 (total solid content) being 100 mass%. The shape of the negative electrode active material layer 21 is not particularly limited, and may be, for example, a sheet shape having a substantially flat surface. The thickness of the negative electrode active material layer 21 is not particularly limited, and may be, for example, 0.1 μm or more, 1 μm or more, 10 μm or more, or 30 μm or more, and may be 2 mm or less, 1 mm or less, 500 μm or less, or 100 μm or less.

[0021] The negative electrode active material may be any known material for a lithium ion battery. Of the known active materials, any material that has a potential (charge / discharge potential) for absorbing and releasing lithium ions that is lower than that of the positive electrode active material may be used as the negative electrode active material. For example, 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, and the like may be used as the negative electrode active material. Only one type of negative electrode active material may be used alone, or two or more types may be used in combination. The negative electrode active material may be, for example, particulate, and the size is not particularly limited. The particles of the negative electrode active material may be solid particles or hollow particles. The particles of the negative electrode active material may be primary particles, or may be secondary particles formed by agglomeration of a plurality of primary particles. The average particle diameter (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 a sheet form (foil form, film form) such as lithium foil. That is, the negative electrode active material layer 21 may be made of a sheet of the negative electrode active material.

[0022] The negative electrode active material layer 21 may contain an electrolyte solution 30 described later. The negative electrode active material layer 21 may contain other electrolytes in addition to the electrolyte solution 30. Examples of other electrolytes include the above-mentioned solid electrolyte, the electrolyte solution, or a combination of these. The conductive assistant that may be contained in the negative electrode active material layer 21 may be appropriately selected from, for example, those exemplified as the conductive assistant that may be contained in the above-mentioned positive electrode active material layer 11. The binder that may be contained in the negative electrode active material layer 21 may be appropriately selected from, for example, those exemplified as the binder that may be contained in the above-mentioned positive electrode active material layer 11. Each of the electrolyte, the conductive assistant, and the binder may be used alone or in combination of two or more kinds.

[0023] 1.2.2 Negative electrode current collector As shown in FIG. 1, the negative electrode 20 may include a negative electrode current collector 22 in contact with the negative electrode active material layer 21 and the electrolyte solution 30. The negative electrode current collector 22 may be any of those commonly used as a negative electrode current collector for a battery. The negative electrode current collector 22 may be in the form of a foil, a plate, a mesh, a punched metal, a foam, or the like. The negative electrode current collector 22 may be a metal foil or a metal mesh, or may be a carbon sheet. In particular, a metal foil is excellent in terms of ease of handling. The negative electrode current collector 22 may be made of a plurality of foils or sheets. Examples of metals constituting the negative electrode current collector 22 include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, and the like. From the viewpoint of ensuring reduction resistance and being difficult to alloy with lithium, the negative electrode current collector 22 may contain at least one metal selected from Cu, Ni, and stainless steel. Alternatively, as described above, the negative electrode 20 may include, as the negative electrode collector 22, an aluminum-containing current collector in contact with the negative electrode active material layer 21 and the electrolyte solution 30. The negative electrode collector 22 may have some kind of coating layer on its surface for the purpose of adjusting the resistance or the like. The negative electrode collector 22 may also be a metal foil or a base material on which the above metal is plated or vapor-deposited. When the negative electrode collector 22 is made of a plurality of metal foils, some kind of layer may be present between the plurality of metal foils. The thickness of the negative electrode collector 22 is not particularly limited. For example, it may be 0.1 μm or more or 1 μm or more, and may be 1 mm or less or 100 μm or less.

[0024] In addition to the above configuration, the negative electrode 20 may have a general configuration as a negative electrode of a lithium ion battery. For example, a tab, a terminal, etc. The negative electrode 20 can be manufactured by applying a known method. For example, the negative electrode active material layer 21 can be easily formed by forming a negative electrode mixture containing the above various components in a dry or wet manner. The negative electrode active material layer 21 may be formed together with the negative electrode current collector 22 or may be formed separately from the negative electrode current collector 22.

[0025] 1.3 Electrolyte The electrolyte 30 includes a cyclic carbonate and a lithium amide salt dissolved in the cyclic carbonate.

[0026] 1.3.1 Cyclic carbonates The electrolyte solution 30 contains a cyclic carbonate as a solvent. The cyclic carbonate has a higher dielectric constant than the chain carbonate and is more likely to coordinate lithium ions. In other words, in the electrolyte solution 30, the cyclic carbonate is less likely to be in a free state, and as a result, the thermal stability is more likely to be increased. In particular, when a lithium amide salt is dissolved in the cyclic carbonate at a predetermined concentration, almost all of the cyclic carbonate can be solvated with lithium ions, and as a result, the thermal stability can be further improved. In addition, due to a small amount of lithium ions that are not solvated with the cyclic carbonate, the transport number of lithium ions is increased even under high viscosity, and excellent lithium ion conductivity is easily ensured.

[0027] The cyclic carbonate may be any one that has a cyclic structure as a chemical structure, is liquid at a temperature at which lithium ion conductivity is desired to be exhibited, and can dissolve lithium amide salt at a predetermined concentration. Specific examples of the cyclic carbonate include propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), vinylene carbonate (VC), or derivatives thereof (e.g., halides, etc.). In particular, when 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. The cyclic carbonate may be used alone or in combination of two or more.

[0028] 1.3.2 Solvents other than cyclic carbonates (co-solvents) The solvent constituting the electrolytic solution 30 may be made of the above-mentioned cyclic carbonate, or may contain a solvent (sub-solvent) other than the cyclic carbonate in addition to the above-mentioned cyclic carbonate. Examples of the sub-solvent other than the cyclic carbonate include chain carbonate. Examples of the chain carbonate include dimethyl carbonate (DMC), diethyl carbonate (DEC) or derivatives thereof (e.g., halides, particularly those having a perfluoroalkyl group). However, chain carbonates have a lower dielectric constant than cyclic carbonates, and lithium ions tend not to be easily coordinated. Therefore, chain carbonates tend to be in a state of being isolated alone in the lithium ion conductive material, and are easily volatilized. In this regard, when the amount of the sub-solvent other than the cyclic carbonate is small, the electrolytic solution 30 is likely to have high thermal stability. In the electrolytic solution 30, the molar ratio of the sub-solvent to the cyclic carbonate ([sub-solvent (mol)] / [cyclic carbonate (mol)]) may be 0.10 or less, 0.05 or less, or 0.03 or less. The lower limit of the molar ratio of the sub-solvent to the cyclic carbonate is 0.

[0029] 1.3.3 Lithium amide salts The electrolyte solution 30 contains a lithium amide salt dissolved in the above-mentioned cyclic carbonate. The lithium amide salt may be dissolved in the cyclic carbonate and ionized into a cation and an anion, or may form some kind of association with the cyclic carbonate or the like. The electrolyte solution 30 contains both a chain lithium amide salt and a cyclic lithium amide salt as the lithium amide salt. The term "amide salt" is a concept that also includes "imide salt".

[0030] 1.3.3.1 Linear lithium amide salts Specific examples of the chain lithium amide salt include sulfonylamide salts such as lithium bisfluorosulfonylamide (LiFSA, LiN(SO2F)2), lithium bistrifluoromethanesulfonylamide (LiTFSA, Li[N(CF3SO2)2]), lithium bisperfluoroethylsulfonylamide (Li[N(C2F5SO2)2]), lithium bisperfluorobutylsulfonylamide (Li[N(C4F9SO2)2]), and lithium fluorosulfonyltrifluoromethanesulfonylamide (Li[N(FSO2)(C2F5SO2)]). Alternatively, a silylamide salt having Si instead of S may be used. In particular, when the chain lithium amide salt is one or both of lithium bisfluorosulfonylamide (LiFSA, LiN(SO2F)2) and lithium bistrifluoromethanesulfonylamide (LiTFSA, Li[N(CF3SO2)2]), it is easy to ensure even better lithium ion conductivity and thermal stability. The chain lithium amide salt may be used alone or in combination of two or more kinds.

[0031] The molar ratio of the chain lithium amide salt to the cyclic carbonate ([chain lithium amide salt (mol)] / [cyclic carbonate (mol)]) is greater than 0.25 and less than 0.33. In other words, the chain lithium amide salt is dissolved at a concentration of 0.25 mol or more and 0.33 mol or less per 1 mol of the cyclic carbonate. When the concentration of the chain lithium amide salt in the cyclic carbonate is within this range, the thermal stability and lithium ion conductivity are likely to be significantly improved. If the concentration of the chain lithium amide salt to the cyclic carbonate is too low, the thermal stability and lithium ion conductivity are difficult to improve. On the other hand, if the concentration of the chain lithium amide salt to the cyclic carbonate is excessive, the viscosity becomes too high, and there is a risk of the lithium ion conductivity decreasing. The molar ratio may be 0.26 or more, 0.27 or more, or 0.28 or more, and may be 0.32 or less, 0.31 or less, or 0.30 or less. The molar ratio of the chain lithium amide salt to the cyclic carbonate can be determined by analyzing the ions, elements, etc. contained in the cyclic carbonate.

[0032] 1.3.3.2 Cyclic lithium amide salts According to the inventor's new findings, when the electrolyte of a lithium ion battery contains only a chain lithium amide salt together with the carbonate solvent, aluminum is likely to dissolve from the aluminum-containing current collector into the electrolyte. The inventor has conducted intensive research to solve this problem, and has found that dissolution of aluminum from the aluminum-containing current collector into the electrolyte can be suppressed by dissolving a cyclic lithium amide salt together with the chain lithium amide salt in the electrolyte 30 of the lithium ion battery 100. Specifically, when a cyclic lithium amide salt is dissolved together with the chain lithium amide salt in the electrolyte 30, a coating derived from the cyclic lithium amide salt is formed on the surface of the aluminum-containing current collector in contact with the electrolyte 30. The coating functions as a protective film that suppresses dissolution of aluminum from the aluminum-containing current collector into the electrolyte 30.

[0033] Specific examples of the cyclic lithium amide salt include those in which the sulfonylamide groups or silylamide groups in the above-mentioned sulfonylamide salts or silylamide salts form a ring via a perfluoroalkylene group, etc. In particular, according to the new findings of the present inventors, when the cyclic lithium amide salt is one represented by the following formula (1), the elution of aluminum can be more significantly suppressed. [ka] In the formula (1), n ​​is an integer of 2 to 5. n may be an integer of 2 to 4, or may be 3.

[0034] The molar ratio of the cyclic lithium amide salt to the cyclic carbonate ([cyclic lithium amide salt (mol)] / [cyclic carbonate (mol)]) is greater than 0 and less than or equal to 0.07. In other words, the cyclic lithium amide salt is dissolved at a concentration of more than 0 mol and less than or equal to 0.07 mol per 1 mol of the cyclic carbonate. When the concentration of the cyclic lithium amide salt in the cyclic carbonate is within this range, excellent thermal stability and lithium ion conductivity can be ensured along with the aluminum elution suppression effect. The molar ratio may be 0.01 or more, 0.02 or more, or 0.03 or more, and may be 0.06 or less, 0.05 or less, or 0.04 or less. The molar ratio of the cyclic lithium amide salt to the cyclic carbonate can be determined by analyzing the ions and elements contained in the cyclic carbonate.

[0035] 1.3.4 Lithium salts other than lithium amide salts In the electrolytic solution 30, the lithium salt dissolved in the solvent may be the lithium amide salt described above, or may be a combination of the lithium amide salt described above and a lithium salt other than the lithium amide salt (other lithium salt). In any case, by dissolving the chain lithium amide salt and the cyclic lithium amide salt in the cyclic carbonate at a predetermined concentration, excellent thermal stability and ionic conductivity are ensured, and the elution of aluminum from the aluminum current collector into the electrolytic solution 30 can be suppressed. In the electrolytic solution 30, the proportion of the lithium amide salt in the lithium salt dissolved in the solvent is preferably high, and specifically, the proportion of the lithium amide salt in the total lithium 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.

[0036] 1.3.5 Other optional ingredients The electrolyte solution 30 may contain various additives in addition to the above-mentioned solvent and lithium amide salt to the extent that the above-mentioned problems can be solved. The type of additive may be appropriately selected according to the desired performance. The electrolyte solution 30 may also be combined with a solid material (e.g., a solid electrolyte).

[0037] 1.4 Other matters 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 held in the separator 40. The separator 40 may be a separator known as a separator for the lithium ion battery 100. The lithium ion battery 100 may be one in which each of the above-mentioned components is housed inside an exterior body. Any known exterior body for a battery may be used as the exterior body. A plurality of lithium ion batteries 100 may be electrically connected and stacked in any manner to form an assembled battery. In this case, the assembled battery may be housed inside a known battery case. The lithium ion battery 100 may also have other obvious configurations such as necessary terminals. Examples of the shape of the lithium ion battery 100 include a coin type, a laminate type, a cylindrical type, and a square type. 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 follows. However, the method for manufacturing the lithium ion battery 100 is not limited to the following method, and each layer may be formed by, for example, dry molding or the like. (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 a positive electrode current collector using a doctor blade or the like, and then dried to form a positive electrode active material layer on the surface of the positive electrode current collector, thereby forming a positive electrode. (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 current collector using a doctor blade or the like, and then dried to form a negative electrode active material layer on the surface of the negative electrode current collector, thereby forming a negative electrode. (3) The layers are laminated so that the electrolyte layer (separator) is sandwiched between the negative electrode and the positive electrode to obtain a laminate having the negative electrode current collector, the negative electrode active material layer, the electrolyte layer, the positive electrode active material layer, and the positive electrode current collector in this order. Other members such as terminals are attached to the laminate as necessary. (4) The laminate is housed in a battery case, and the laminate is immersed in an electrolyte solution and sealed in the battery case to produce a lithium ion battery. Note that the electrolyte solution may be impregnated into the negative electrode active material layer, the separator, and the positive electrode active material layer in the above step (3).

[0038] 2. Lithium ion conductive materials The technology of the present disclosure has an aspect as a lithium ion conductive material. That is, the lithium ion conductive material of the present disclosure includes a cyclic carbonate and a lithium amide salt dissolved in the cyclic carbonate, the lithium amide salt includes a chain lithium amide salt and a cyclic lithium amide salt, the molar ratio of the chain lithium amide salt to the cyclic carbonate is greater than 0.25 and is 0.33 or less, and the molar ratio of the cyclic lithium amide salt to the cyclic carbonate is greater than 0 and is 0.07 or less. Details of each component constituting the lithium ion conductive material are as described above.

[0039] 3. Vehicles The lithium ion battery of the present disclosure can be suitably used in at least one vehicle selected from, for example, a hybrid vehicle (HEV), a plug-in hybrid vehicle (PHEV), and an electric vehicle (BEV). That is, the technology of the present disclosure also has an aspect of a vehicle equipped with a lithium ion battery, the lithium ion battery having a positive electrode, a negative electrode, and an electrolyte, one or both of the positive electrode and the negative electrode having an aluminum-containing current collector, the electrolyte containing a cyclic carbonate and a lithium amide salt dissolved in the cyclic carbonate, the lithium amide salt containing a chain lithium amide salt and a cyclic lithium amide salt, the molar ratio of the chain lithium amide salt to the cyclic carbonate being greater than 0.25 and less than 0.33, and the molar ratio of the cyclic lithium amide salt to the cyclic carbonate being greater than 0 and less than 0.07. EXAMPLES

[0040] The technology of the present disclosure will be described in more detail below with reference to examples, but the technology of the present disclosure is not limited to the following examples.

[0041] 1. Preparation of Electrolyte 1.1 Comparative Example 1 The electrolyte solution of Comparative Example 1 was obtained by weighing, mixing, and stirring each component so that the molar ratio of propylene carbonate (PC) as a solvent and lithium bisfluorosulfonylamide (LiFSA) as a chain lithium amide salt was 0.33 (PC:LiFSA=3:1).

[0042] 1.2 Example 1 The electrolyte solution of Example 1 was obtained by weighing, mixing, and stirring each component so that the molar ratio of LiFSA to PC was 0.33 (PC:LiFSA=3:1) and the molar ratio of lithium 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonimide (LiCFSA, formula (1a) below) as a cyclic lithium amide salt to PC was 0.033 (PC:LiCFSA=3:0.1). [ka]

[0043] 1.3 Example 2 The electrolyte solution of Example 2 was obtained by weighing, mixing, and stirring each component so that the molar ratio of LiFSA to PC was 0.30 (PC:LiFSA=3.3:1) and the molar ratio of LiCFSA as a cyclic lithium amide salt to PC was 0.030 (PC:LiCFSA=3.3:0.1).

[0044] 1.4 Example 3 The electrolyte solution of Example 3 was obtained by weighing, mixing, and stirring each component 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).

[0045] 1.5 Comparative Example 2 The electrolyte solution of Comparative Example 2 was obtained by weighing, mixing, and stirring each component so that the molar ratio of lithium bis(trifluoromethane)sulfonylamide (LiTFSA) as a chain lithium amide salt to PC was 0.33 (PC:LiTFSA=3:1).

[0046] 1.6 Example 4 The electrolyte solution of Example 4 was obtained by weighing, mixing, and stirring each component 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).

[0047] 2. Evaluation of ionic conductivity The resistance value was measured at 25°C by the AC impedance method in a two-electrode symmetrical cell with a fixed electrode distance using Li metal for the electrodes. The ionic conductivity was calculated from the obtained resistance value and the cell shape (electrode area, electrode distance). The specific measurement conditions are as follows: Measurement conditions: Temperature 25℃, Amplitude 10mV, Frequency 1M~10mHz

[0048] 3. Aluminum corrosion evaluation A half cell was prepared using Al foil as the working electrode, Li metal as the counter electrode, and each of the electrolyte solutions according to the above-mentioned Examples and Comparative Examples, and the presence or absence of Al dissolution into the electrolyte solution (Al corrosivity) was evaluated by linear sweep voltammetry (LSV measurement). The specific measurement conditions are as follows. Measurement conditions: Sweep speed 10mV / s, from OCV to 6V

[0049] 4. Evaluation Results The following Table 1 shows the composition and ion conductivity of each of the electrolytes according to Examples 1 to 4 and Comparative Examples 1 and 2, as well as the presence or absence of Al corrosion behavior. Also, FIG. 2 shows the results of LSV measurement according to each of Examples 1 to 4 and Comparative Examples 1 and 2.

[0050] [Table 1]

[0051] As is clear from the results shown in Table 1, the electrolyte solutions according to Examples 1 to 4 and Comparative Examples 1 to 2 had high ionic conductivity. In addition, as is clear from the results shown in FIG. 2, when the LSV measurements were performed using the electrolyte solutions according to Comparative Examples 1 and 2, an increase in current due to the dissolution of Al was confirmed. In contrast, when the LSV measurements were performed using the electrolyte solutions according to Examples 1 to 4, the increase in current due to the dissolution of Al was suppressed. In Examples 1 to 4, a coating derived from LiCFSA was formed on the surface of the Al foil, and it is believed that this functioned as a protective film that suppressed the dissolution of Al.

[0052] 5. Summary From the above results, it can be said that when a lithium ion battery is constructed using an electrolyte solution having the following configurations (1) to (4), the elution of aluminum from an aluminum-containing current collector into the electrolyte solution can be suppressed. (1) The electrolyte solution contains a cyclic carbonate and a lithium amide salt dissolved in the cyclic carbonate. (2) The lithium amide salt includes a chain lithium amide salt and a cyclic lithium amide salt. (3) The molar ratio of the chain lithium amide salt to the cyclic carbonate is greater than 0.25 and is not greater than 0.33. (4) The molar ratio of the cyclic lithium amide salt to the cyclic carbonate is greater than 0 and is 0.07 or less. [Explanation of symbols]

[0053] 10 positive electrode 11 Cathode active material layer 12 Positive electrode current collector 20 negative electrode 21 Negative electrode active material layer 22 Negative electrode current collector 30 Electrolyte 40 Separator 100 Lithium-ion batteries

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 solution is Cyclic carbonates, and a lithium amide salt dissolved in said cyclic carbonate; Including, The lithium amide salt is A chain lithium amide salt, and Cyclic lithium amide salts, Including, a molar ratio of the chain lithium amide salt to the cyclic carbonate is greater than 0.25 and less than or equal to 0.33; the molar ratio of the cyclic lithium amide salt to the cyclic carbonate is greater than 0 and less than or equal to 0.07; Lithium-ion battery.

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

3. 2. The lithium ion battery of claim 1, The cyclic carbonate is one or both of propylene carbonate and ethylene carbonate; Lithium-ion battery.

4. 2. The lithium ion battery of claim 1, The chain lithium amide salt is one or both of lithium bisfluorosulfonylamide and lithium bistrifluoromethanesulfonylamide. Lithium-ion battery.

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

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