Lithium ion conducting material, lithium ion secondary battery, and method for producing lithium ion conducting material

Abstract

Disclosed is a lithium ion conducting material having excellent lithium ion input / output characteristics. Lithium ion conducting materials of the present disclosure include a complex of a polymer and an electrolyte. The electrolyte solution contains a cyclic carbonate as a solvent, and an amide lithium salt dissolved in the cyclic carbonate. The molar ratio of the amide lithium salt to the cyclic carbonate is greater than 0.25 and less than or equal to 0.33.

Description

Technical Field

[0001] The present application discloses a lithium ion conductive material, a lithium ion secondary battery, and a method for manufacturing the lithium ion conductive material. Background Art

[0002] Patent Document 1 discloses an electrolyte for a lithium-ion secondary battery, comprising a non-aqueous solvent and a lithium salt, wherein the amount of the non-aqueous solvent is 3 mol or less relative to 1 mol of the lithium salt. Patent Document 2 discloses an electrolyte for a lithium-ion secondary battery, comprising a prescribed solvent, an imide lithium salt, and at least one of a Group I element and a Group II element, wherein the molar ratio of the imide lithium salt to the solvent is 1:0.8 to 1:2.0. Patent Document 3 discloses an electrolyte comprising a chain carbonate, an unsaturated cyclic carbonate, and a lithium salt, wherein the lithium salt is contained at a concentration of 1.1 to 3.8 mol / L.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2016-122657

[0006] Patent Document 2: Japanese Patent Application Publication No. 2019-096463

[0007] Patent Document 3: International Publication No. 2017 / 179682 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] There is room for improvement in the input and output characteristics of existing lithium ion conductive materials.

[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 conductive material comprises a composite of an electrolyte and a polymer, wherein the electrolyte comprises 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 is not more than 0.33.

[0014] Option 2

[0015] The lithium ion conductive material according to claim 1, wherein the polymer is a fluoride-based polymer.

[0016] Option 3

[0017] The lithium ion conductive material according to embodiment 1 or 2 comprises the composite and a sulfide solid electrolyte.

[0018] Option 4

[0019] The lithium ion conductive material according to any one of aspects 1 to 3, wherein the cyclic carbonate is at least one of propylene carbonate and ethylene carbonate.

[0020] Option 5

[0021] The lithium ion conductive material according to any one of aspects 1 to 4, wherein the lithium amide salt is at least one of lithium bisfluorosulfonamide and lithium bistrifluoromethanesulfonamide.

[0022] Option 6

[0023] A lithium ion secondary battery comprising a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer, wherein at least one of the positive electrode active material layer, the electrolyte layer, and the negative electrode active material layer comprises the lithium ion conductive material according to any one of aspects 1 to 5.

[0024] <Option 7>

[0025] The lithium ion secondary battery according to claim 6, wherein at least the negative electrode active material layer contains the lithium ion conductive material.

[0026] <Option 8>

[0027] The lithium ion secondary battery according to aspect 6 or 7, wherein the negative electrode active material layer contains Si as a negative electrode active material.

[0028] <Option 9>

[0029] A method for producing a lithium ion conductive material comprises compounding an electrolyte solution with a polymer, wherein the electrolyte solution comprises 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.

[0030] <Option 10>

[0031] The production method according to claim 9 comprises: mixing a diluent with the electrolyte solution and the polymer to obtain a solution; and removing the diluent from the solution to form a composite of the electrolyte solution and the polymer.

[0032] Effects of the Invention

[0033] The lithium ion conductive material disclosed herein has excellent lithium ion input and output characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 An example of the structure of a lithium-ion secondary battery is schematically shown.

[0035] Figure 2 The results of evaluating the thermal stability of the lithium ion conductive material are shown.

[0036] Figure 3 The evaluation results of the lithium ion transfer rates of the lithium ion conductive materials are shown.

[0037] Figure 4 The evaluation results of the lithium ion conductivity of the lithium ion conductive material are shown.

[0038] Figure 5 X-ray diffraction peaks of the sulfide solid electrolyte before and after immersion in the lithium ion conductive material are shown.

[0039] Figure 6 CV test results are shown.

[0040] Figure 7 The charge-discharge cycle dependence of the Si interface resistance is shown.

[0041] Figure 8 Shown are the XPS measurement results of the Si electrode after 10 cycles of charge and discharge. DETAILED DESCRIPTION

[0042] 1. Lithium ion conductive materials

[0043] The lithium ion conductive material disclosed herein comprises a composite of an electrolyte and a polymer. The electrolyte comprises a cyclic carbonate as a solvent and an amide lithium salt dissolved in the cyclic carbonate. The molar ratio of the amide lithium salt to the cyclic carbonate is greater than 0.25 and is less than 0.33.

[0044] 1.1 Electrolyte

[0045] The electrolyte solution constituting the composite of the present disclosure contains a cyclic carbonate as a solvent and an amide lithium salt dissolved in the cyclic carbonate.

[0046] 1.1.1 Solvent

[0047] The electrolyte solution contains a cyclic carbonate as a solvent. In one embodiment, the solvent may be composed of the cyclic carbonate. In one embodiment, the solvent may be a mixed solvent of the cyclic carbonate and a solvent other than the cyclic carbonate.

[0048] 1.1.1.1 Cyclic carbonates

[0049] According to the understanding of the inventors, cyclic carbonate has a high dielectric constant compared with linear carbonate, and is easily coordinated with lithium ion. In other words, in the complex disclosed herein, cyclic carbonate is difficult to become free state, and as a result, thermal stability is easily improved. Especially, for cyclic carbonate, when amide lithium salt is dissolved with a prescribed concentration, cyclic carbonate can be made to be almost entirely solvated by lithium ion, and as a result, thermal stability can be further improved. In addition, by utilizing the lithium ion etc. that is not solvated with cyclic carbonate, the transmission rate of lithium ion improves, and easily ensures excellent lithium ion conductivity.

[0050] Cyclic carbonate has the cyclic structure as chemical structure, as long as it is liquid at the temperature that wants to manifest lithium ion conductivity, and amide lithium salt can be dissolved with the concentration of regulation.As the specific example of cyclic carbonate, can list out at least one selected from propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), vinylene carbonate (VC) and their derivatives (such as halides etc.) etc. In particular, when 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 a kind of, also can be used in combination of two or more.

[0051] 1.1.1.2 Solvents other than cyclic carbonates (sub-solvents)

[0052] The solvent (sub-solvent) other than the cyclic carbonate can be, for example, a chain carbonate. As the chain carbonate, for example, at least one selected from dimethyl carbonate (DMC), diethyl carbonate (DEC) and their derivatives (such as halides, particularly derivatives with perfluoroalkyl groups) can be listed. However, compared with the cyclic carbonate, the chain carbonate has a low dielectric constant, and lithium ions tend to be difficult to coordinate. Therefore, the chain carbonate is easily free in the electrolyte, easily volatilizes, and is easily highly reactive to the sulfide solid electrolyte described later. In this regard, in the electrolyte, when the sub-solvent other than the cyclic carbonate is in a small amount, it is easy to ensure high thermal stability, and it is easy to improve ionic conductivity under the state of suppressing the reactivity with the sulfide solid electrolyte. In the electrolyte, the molar ratio ([sub-solvent (mol)] / [cyclic carbonate (mol)]) of the sub-solvent and the cyclic carbonate can be more than 0 and less than 0.10, more than 0 and less than 0.05, or more than 0 and less than 0.03.

[0053] 1.1.2 Lithium Salts

[0054] The electrolyte solution includes a lithium salt dissolved in the aforementioned solvent. In one embodiment, the lithium salt dissolved in the aforementioned solvent may be composed of an amide lithium salt. In one embodiment, the lithium salt dissolved in the aforementioned solvent may be a combination of an amide lithium salt and a lithium salt other than an amide lithium salt.

[0055] 1.1.2.1 Lithium amide salts

[0056] The electrolyte contains an amide lithium salt dissolved in the above-mentioned cyclic carbonate. That is, the amide lithium salt dissolves in the cyclic carbonate and may be in a state of ionization into cations and anions, and may form a certain association with the cyclic carbonate, etc. The molar ratio of the amide lithium salt to the cyclic carbonate ([amide lithium salt (mol)] / [cyclic carbonate (mol)]) is greater than 0.25 and is less than 0.33. In other words, the amide lithium salt is dissolved in the cyclic carbonate at a concentration of 0.25 mol or more and 0.33 mol or less per 1 mol of the cyclic carbonate.

[0057] As amide lithium salts, various amide salts can be used. In the composite disclosed herein, it is believed that it is independent of the type of amide lithium salt and that lithium ions can be coordinated to the active site of the cyclic carbonate, thereby ensuring excellent thermal stability and lithium ion conductivity. As specific examples of amide lithium salts, at least one sulfonamide salt selected from 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]), lithium fluorosulfonyltrifluoromethanesulfonamide (Li[N(FSO2)(C2F5SO2)]) and the like can be cited. Alternatively, a silylamide salt having Si instead of S can be used. In particular, when the lithium amide salt is at least one of lithium bisfluorosulfonamide (LiFSA, LiN(SO2F)2) and lithium bistrifluoromethanesulfonamide (LiTFSA, Li[N(CF3SO2)2]), it is easy to ensure more excellent lithium ion conductivity and thermal stability, and further reduce the reactivity with the sulfide solid electrolyte described later. The lithium amide salt can be used alone or in combination of two or more. In this application, the term "amide salt" also includes "imide salt".

[0058] As mentioned above, the molar ratio of the amide lithium salt to the cyclic carbonate is greater than 0.25 and is less than 0.33. When the concentration of the amide lithium salt in the cyclic carbonate is within this range, thermal stability and lithium ion conductivity are easily significantly improved. In addition, the reaction between the active site of the cyclic carbonate and the sulfide solid electrolyte described later is suppressed, and the deterioration of the sulfide solid electrolyte is easily suppressed. If the concentration of the amide lithium salt relative to the cyclic carbonate is too small, thermal stability and lithium ion conductivity are difficult to improve. On the other hand, if the concentration of the amide lithium salt for the cyclic carbonate is excessive, lithium ion conductivity is likely to decrease. This molar ratio can be more than 0.26, more than 0.27 or more than 0.28, and can be less than 0.32, less than 0.31 or less than 0.30. The molar ratio of the amide lithium salt to the cyclic carbonate in the complex can be determined by analyzing the ions, elements, etc. that constitute the complex.

[0059] 1.1.2.2 Lithium salts other than lithium amide salts

[0060] In the electrolyte, 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 any case, by dissolving the above-mentioned amide lithium salt at a prescribed concentration relative to the cyclic carbonate, it is easy to ensure excellent thermal stability and ion conductivity. However, according to the knowledge of the present inventors, among the lithium salts other than the amide lithium salt, there are lithium salts that are reactive to the sulfide solid electrolyte described later. For example, when the molecular weight of the anion constituting the lithium salt is too small, the charge density is excessively increased (the electron donation is excessively increased), depriving the Li of the sulfide solid electrolyte, etc., and it is possible to degrade the sulfide solid electrolyte. If it is an amide lithium salt, such a problem is unlikely to occur. In this regard, in the electrolyte, the higher the proportion of the amide lithium salt in the lithium salt dissolved in the solvent, the better. Specifically, the proportion of the 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.

[0061] 1.1.3 Any component in the electrolyte

[0062] In addition to the above-mentioned cyclic carbonate and amide lithium salt, the electrolyte solution may contain other components. Examples of other components include the above-mentioned secondary solvents and other lithium salts. In addition, the electrolyte solution may contain various additives.

[0063] 1.2 Polymer

[0064] According to the inventors' findings, by compounding the above-mentioned electrolyte with a polymer, excellent lithium ion conductivity is ensured, and the input and output characteristics of lithium ions can be improved. For example, by combining the composite disclosed herein with an active material to form a battery, even if the battery is repeatedly charged and discharged, the SEI that hinders the deintercalation / intercalation of lithium ions is difficult to form on the surface of the active material, and the interface between the composite and the active material is in a good state, which easily leads to excellent input and output characteristics of lithium ions. If the electrolyte is not compounded with the polymer and the electrolyte itself is applied to the battery as it is, it is difficult to obtain such an effect.

[0065] 1.2.1 Types of polymers

[0066] There is no particular limitation on the type of polymer that constitutes the composite disclosed herein; any polymer that can be composited with the aforementioned electrolyte can be used. In the composite according to one embodiment, the polymer can be a fluoride-based polymer or a non-fluoride-based polymer. Fluoride-based polymers have the advantage of low reactivity with the sulfide solid electrolyte described later. On the other hand, non-fluoride-based polymers have the advantage of easily increasing their affinity with the aforementioned electrolyte compared to fluoride-based polymers.

[0067] Fluoride-based polymers can be at least one selected from polyvinylidene fluoride (PVdF) based polymers, polytetrafluoroethylene (PTFE) based polymers etc. These fluoride-based polymers can be homopolymers obtained by polymerizing one monomer alone, or copolymers comprising polymerized units from other monomers such as hexafluoropropylene. More than 50 mol % and less than 100 mol %, more than 60 mol % and less than 100 mol %, more than 70 mol % and less than 100 mol %, more than 80 mol % and less than 100 mol %, more than 90 mol % and less than 100 mol % or more than 95 mol % and less than 100 mol % of all polymerized units of fluoride-based polymers can be from fluoride-based monomers.

[0068] The non-fluorinated polymer can be an ether polymer or a non-ether polymer. The ether polymer can be at least one selected from polyethylene oxide, polypropylene oxide, etc. The non-ether polymer can be at least one selected from butadiene rubber (BR), butylene rubber (IIR), acrylate butadiene rubber, or styrene butadiene rubber (SBR), polyimide (PI), polyacrylic acid, etc. These non-fluorinated polymers can be homopolymers obtained by polymerizing one monomer alone, or copolymers comprising polymerized units from other monomers. More than 50 mol % and less than 100 mol %, more than 60 mol % and less than 100 mol %, more than 70 mol % and less than 100 mol %, more than 80 mol % and less than 100 mol %, more than 90 mol % and less than 100 mol %, or more than 95 mol % and less than 100 mol % of all polymerized units of the non-fluorinated polymer are from non-fluorinated monomers.

[0069] 1.2.2 Molecular weight of polymer

[0070] When the polymer constituting the composite of the present invention has a molecular weight above a certain level, the composite tends to be in a state of having no fluidity as a whole (viscosity at 25°C is 10,000 mPa·s or more). From this point of view, the weight average molecular weight of the polymer can be, for example, 30,000 or more and 3,000,000 or less. The weight average molecular weight of the polymer can be 100,000 or more or 500,000 or more, or 2,000,000 or less or 1,000,000 or less. The weight average molecular weight of the polymer is a value based on gel permeation chromatography (GPC: Gel Permeation Chromatography).

[0071] 1.3 Complex

[0072] The composite disclosed in the present invention is a composite of the above-mentioned electrolyte and a polymer. The composite involved in one embodiment may be a composite that uses the above-mentioned polymer to maintain the above-mentioned electrolyte. The composite involved in one embodiment may be a composite that uses the above-mentioned polymer to increase the viscosity of the above-mentioned electrolyte. The composite involved in one embodiment may be a composite in which the above-mentioned polymer and the above-mentioned electrolyte are integrated with each other and do not have fluidity as a whole (viscosity at 25°C is 10,000 mPa·s or more). The composite involved in one embodiment is a composite in which, when the composite is used, there is basically no electrolyte free from the composite to the outside of the composite (the electrolyte free to the outside of the composite is less than 0.1% by mass of the total electrolyte contained in the composite). The composite involved in one embodiment may be solid at 25°C.

[0073] 1.3.1 Electrolyte and polymer ratio (mass ratio)

[0074] In the composite of the present invention, there is no particular limitation on the mixing ratio (mass ratio) of the above-mentioned electrolyte and polymer. When the above-mentioned polymer and the above-mentioned electrolyte are to be integrated with each other and to be in a state where the composite as a whole does not have fluidity (viscosity at 25°C is 10,000 mPa·s or more), for example, the ratio M2 / (M1+M2) of the mass M2 of the polymer relative to the total M1+M2 of the mass M1 of the electrolyte and the mass M2 of the polymer constituting the composite may be 0.10 or more and 0.50 or less. The ratio M2 / (M1+M2) may be 0.15 or more or 0.20 or more, and may be 0.40 or less or 0.30 or less. The mass ratio of the electrolyte to the polymer in the composite can be determined by analyzing the components, ions, elements, etc. constituting the composite.

[0075] 1.3.2 Viscosity

[0076] The viscosity of the composite of the present disclosure at 25°C may be 10,000 mPa·s or more, 50,000 mPa·s or more, or 100,000 mPa·s or more. There is no particular upper limit to the viscosity. The composite of the present disclosure may be solid at 25°C. The viscosity of the composite can be measured at 25°C using a rheometer (manufactured by Thermo Scientific).

[0077] 1.3.3 Complex Existence

[0078] As described above, the composite of the present invention may be a composite that does not have fluidity as a whole, that is, it may be a composite that has a fixed shape. The composite of the present invention may be, for example, in the form of a sheet or a powder. Alternatively, the composite of the present invention may be integrated with a material different from the composite. The composite involved in one embodiment may be integrated with a solid electrolyte, for example. More specifically, for example, at least a portion of the surface of the solid electrolyte particles may be covered with the composite of the present invention. The composite involved in one embodiment may be integrated with an active material. More specifically, at least a portion of the surface of the active material particles may be covered with the composite of the present invention. The solid electrolyte and the active material will be described later.

[0079] 1.4 Other ingredients

[0080] The lithium ion conductive material of the present disclosure includes at least the above-mentioned composite. The lithium ion conductive material according to one embodiment may be composed of the above-mentioned composite. The lithium ion conductive material according to one embodiment may be a combination of the above-mentioned composite and a material other than the composite.

[0081] 1.4.1 Sulfide Solid Electrolyte

[0082] The lithium ion conductive material disclosed herein may comprise the aforementioned composite and a sulfide solid electrolyte. Depending on the combination of the composite and the sulfide solid electrolyte, for example, the composite can fill gaps between sulfide solid electrolytes. In other words, ion conductive pathways can also be formed in the gaps between sulfide solid electrolytes. Furthermore, depending on the combination of the composite and the sulfide solid electrolyte, for example, the composite can function as a binder, bonding sulfide solid electrolytes to each other or to other materials.

[0083] On the other hand, when the above-mentioned composite is combined with a sulfide solid electrolyte, it is preferable to suppress the reaction between the composite and the sulfide solid electrolyte as described above. Specifically, when the lithium ion conductive material of the present disclosure comprises the above-mentioned composite and a sulfide solid electrolyte, it can satisfy at least one of the following (1) to (3), can satisfy two or more of (1) to (3), or can satisfy all of (1) to (3).

[0084] (1) The electrolyte solution contains only a cyclic carbonate as a solvent, or contains a cyclic carbonate and a solvent other than the cyclic carbonate (sub-solvent), and the molar ratio of the sub-solvent to the cyclic carbonate ([sub-solvent (mol)] / [cyclic carbonate (mol)]) is 0.10 or less, 0.05 or less, or 0.03 or less.

[0085] (2) In the electrolyte, the proportion of the amide lithium salt in the total lithium salt dissolved in the solvent (100 mol%) is 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, and the amide lithium salt is at least one of lithium bisfluorosulfonamide (LiFSA) and lithium bistrifluoromethanesulfonamide (LiTFSA).

[0086] (3) The polymer is a fluoride-based polymer.

[0087] The sulfide solid electrolyte may be a glass-based sulfide solid electrolyte (sulfide glass), a glass-ceramic sulfide solid electrolyte, or a crystalline sulfide solid electrolyte. Sulfide glass is amorphous. Sulfide glass may have a glass transition temperature (Tg). When the sulfide solid electrolyte has a crystalline phase, examples of the crystalline phase include a Thio-Lisicon phase, an LGPS phase, and an Argentite phase.

[0088] The sulfide solid electrolyte may contain, for example, Li, X (X is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In), and S. Furthermore, the sulfide solid electrolyte may further contain at least one of O and a halogen element. Furthermore, the sulfide solid electrolyte may contain S as the main component of the anion element.

[0089] The sulfide solid electrolyte can be, for example, selected from Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-GeS2, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-P2S5-LiI-LiBr, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-ZmSn (wherein m and n are positive numbers. Z is any one of Ge, Zn, and Ga.), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (wherein x and y are positive numbers. M is any one of P, Si, Ge, B, Al, Ga, and In.)

[0090] There is no particular limitation on the composition of the sulfide solid electrolyte, and examples thereof include xLi2S·(100-x)P2S5(70≤x≤80), yLiI·zLiBr·(100-yz)(xLi2S·(1-x)P2S5)(0.7≤x≤0.8, 0≤y≤30, 0≤z≤30), etc. Alternatively, the sulfide solid electrolyte may have a general formula: Li 4-x Ge 1-x P x The composition represented by S4 (0<x<1). In the above general formula, at least a part of Ge can be replaced by at least one of Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V and Nb. In the above general formula, at least a part of P can be replaced by at least one of Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V and Nb. In the above general formula, a part of Li can be replaced by at least one of Na, K, Mg, Ca and Zn. In the above general formula, a part of S can be replaced by halogen (at least one of F, Cl, Br and I). Alternatively, the sulfide solid electrolyte may have a structure consisting of Li 7-a PS 6-a X a(X is at least one of Cl, Br, and I, and a is a number from 0 to 2.) a may be 0 or greater. In the latter case, a may be 0.1 or greater, 0.5 or greater, or 1 or greater. In addition, a may be 1.8 or less, or 1.5 or less.

[0091] The sulfide solid electrolyte may be in particulate form. The average particle size (D50) of the sulfide solid electrolyte may be, for example, 10 nm or more and 100 μm or less. The average particle size D50 referred to in this application is the particle size (median diameter) at the 50th percentile of the cumulative value in a volume-based particle size distribution determined using a laser diffraction scattering method.

[0092] 1.4.2 Various additives

[0093] The lithium ion conductive material of the present disclosure may contain various additives in addition to the above. The type of additive can be selected according to the application of the lithium ion conductive material.

[0094] 2. Lithium-ion secondary batteries

[0095] The lithium ion conductive material disclosed herein is used as an electrolyte material for a lithium ion secondary battery. Hereinafter, a lithium ion secondary battery having the lithium ion conductive material disclosed herein will be described. Figure 1 As shown, a lithium ion secondary battery 100 according to one embodiment includes a positive electrode active material layer 20, an electrolyte layer 30, and a negative electrode active material layer 40. Here, at least one of the positive electrode active material layer 20, the electrolyte layer 30, and the negative electrode active material layer 40 includes the lithium ion conductive material of the present disclosure. Figure 1 As shown, the secondary battery 100 may include a positive electrode current collector 10 in contact with a positive electrode active material layer 20. Figure 1 As shown, the secondary battery 100 may include a negative electrode collector 50 in contact with the negative electrode active material layer 40 .

[0096] As described above, the lithium ion conductive material of the present invention has excellent thermal stability and lithium ion conductivity, and also has excellent lithium ion input and output characteristics. In this regard, by containing the lithium ion conductive material of the present invention in at least one of the positive electrode active material layer 20, the electrolyte layer 30, and the negative electrode active material layer 40 of the secondary battery 100, the performance of the secondary battery 100 can be easily improved. For example, when the secondary battery 100 is repeatedly charged and discharged, it is easy to maintain the resistance of the interface between the active material and the lithium ion conductive material low. In particular, when at least the negative electrode active material layer 40 contains the lithium ion conductive material of the present invention, the performance of the secondary battery 100 can be easily further improved. In addition, when the negative electrode active material layer 40 contains Si as the negative electrode active material, it is also easy to further improve the performance of the secondary battery 10.

[0097] 2.1 Positive electrode collector

[0098] The secondary battery 100 may include a positive electrode collector 10 in contact with the positive electrode active material layer 20. Any common positive electrode collector for a secondary battery can be used as the positive electrode collector 10. Furthermore, the positive electrode collector 10 may have at least one shape selected from the group consisting of foil, plate, mesh, punched metal, and foam. The positive electrode collector 10 may be made of metal foil or metal mesh. Metal foil is particularly advantageous in terms of handling properties. The positive electrode collector 10 may be made of multiple sheets of foil. Examples of metals that constitute the positive electrode collector 10 include at least one selected from the group consisting of Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, V, Mg, Pb, Ge, In, Sn, Zr, and stainless steel. In particular, the positive electrode collector 10 may contain Al to ensure oxidation resistance. The positive electrode current collector 10 may have some coating on its surface for purposes such as adjusting resistance. For example, the positive electrode current collector 10 may have a carbon coating. Furthermore, the positive electrode current collector 10 may be formed by plating or vapor-depositing the aforementioned metal onto a metal foil or substrate. Furthermore, when the positive electrode current collector 10 is composed of multiple metal foils, there may be some layers between the multiple metal foils. The thickness of the positive electrode current collector 10 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.

[0099] 2.2 Positive electrode active material layer

[0100] The secondary battery 100 includes a positive electrode active material layer 20. The positive electrode active material layer 20 contains at least a positive electrode active material. Furthermore, the positive electrode active material layer 20 may optionally contain an electrolyte, a conductive additive, a binder, and various additives. When the positive electrode active material layer 20 contains the lithium ion conductive material disclosed above, in addition to the positive electrode active material and the lithium ion conductive material, the positive electrode active material layer 20 may further optionally contain other electrolytes, conductive additives, binders, and various additives. The content of each component in the positive electrode active material layer 20 can be appropriately determined based on the target battery performance. For example, assuming the solid content of the positive electrode active material layer 20 as a whole is 100 mass%, the content of the positive electrode active material may be 40 mass% or more, 50 mass% or more, 60 mass% or more, or 70 mass% or more, or may be 100 mass% or less, less than 100 mass%, 95 mass% or less, or 90 mass% or less. Alternatively, the positive electrode active material layer 20 as a whole is set to 100 volume%, and the positive electrode active material and the optional electrolyte, conductive additive, and binder can contain a total of 85 volume% or more, 90 volume% or more, or 95 volume% or more. The remainder can be voids or other components. There is no particular limitation on the shape of the positive electrode active material layer 20, and for example, it can be a sheet with a substantially flat surface. There is no particular limitation on the thickness of the positive electrode active material layer 20, and 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 2 mm or less, 1 mm or less, 500 μm or less, or 100 μm or less.

[0101] 2.2.1 Positive electrode active material

[0102] As for the positive electrode active material, any positive electrode active material known as a positive electrode active material for a secondary battery can be used. Among the known active materials, a material with a higher potential (charge and discharge potential) for absorbing and releasing lithium ions can be used as a positive electrode active material, and a lower potential can be used as a negative electrode active material described later. The positive electrode active material can be, for example, at least one selected from various lithium-containing compounds, elemental sulfur, and sulfur compounds. The lithium-containing compound as a positive electrode active material can be a lithium-containing oxide containing at least one element M, Li, and O. Element M can be, for example, at least one selected from Mn, Ni, Co, Al, Mg, Ca, Sc, V, Cr, Cu, Zn, Ga, Ge, Y, Zr, Sn, Sb, W, Pb, Bi, Fe, and Ti, and can be at least one selected from Mn, Ni, Co, Al, Fe, and Ti. More specifically, the lithium-containing oxide can be selected from lithium cobaltate, lithium nickelate, lithium manganate, lithium nickel cobaltate, lithium nickel manganate, lithium cobalt manganate, lithium nickel cobalt manganate (Li 1±α Ni x Co y Mn z O 2±δ(e.g. 0<x<1, 0<y<1, 0<z<1, x+y+z=1)), spinel lithium compounds (composed of Li 1+x Mn 2-x-y M y O4 (M is one or more selected from Al, Mg, Co, Fe, Ni and Zn) represented by the composition of the heterogeneous element substitution Li-Mn spinel, etc.), lithium nickel cobalt aluminum oxide (such as Li 1±α Ni p Co q Al r O 2±δ (e.g., p+q+r=1)), lithium titanate, lithium metal phosphate (LiMPO4, etc., M is one or more selected from Fe, Mn, Co and Ni), etc. In particular, when the positive electrode active material comprises an oxide containing lithium containing at least one of Ni, Co and Mn, Li, and O as constituent elements, the performance of the secondary battery is likely to be further improved. Alternatively, when the positive electrode active material comprises an oxide containing lithium containing at least one of Ni, Co and Al, Li, and O as constituent elements, the performance of the secondary battery is likely to be further improved. The positive electrode active material may be used alone or in combination of two or more.

[0103] As for the shape of the positive electrode active material, any general shape of the positive electrode active material for a secondary battery can be used. The positive electrode active material can be, for example, in the form of particles. The positive electrode active material can have voids, for example, can be porous or hollow. The positive electrode active material can be a primary particle, or a secondary particle formed by the aggregation of multiple primary particles. The average particle size D50 of the positive electrode active material can be, for example, greater than 1 nm, greater than 5 nm, or greater than 10 nm, and can be less than 500 μm, less than 100 μm, less than 50 μm, or less than 30 μm. It should be noted that the average particle size D50 of the positive electrode active material is the particle size (median diameter) at the cumulative value of 50% in the volume-based particle size distribution determined by a laser diffraction scattering method.

[0104] 2.2.2 Protective layer

[0105] An ion-conductive protective layer may be formed on the surface of the positive electrode active material. That is, the positive electrode active material layer 20 may include a composite of a positive electrode active material and a protective layer, in which at least a portion of the surface of the positive electrode active material may be covered by the protective layer. This makes it easier to suppress, for example, reactions between the positive electrode active material and other battery materials (such as the sulfide solid electrolyte described later). The ion-conductive protective layer may include various ion-conductive compounds. For example, the ion-conductive compound may be at least one selected from an ion-conductive oxide and an ion-conductive halide.

[0106] The ion conductive oxide may contain, for example, at least one element selected from B, C, Al, Si, P, S, Ti, La, Zr, Nb, Mo, Zn, and W, Li, and O. The ion conductive oxide may be an oxynitride containing N. More specifically, the ion conductive oxide may be selected from Li3BO3, LiBO2, Li2CO3, LiAlO2, Li4SiO4, Li2SiO3, Li3PO4, Li2SO4, Li2TiO3, Li4Ti5O 12 , Li2Ti2O5, Li2ZrO3, LiNbO3, Li2MoO4, Li2WO4, LiPON, Li2O-LaO2, Li2O-ZnO2, etc. The ion conductive oxide may be partially replaced by various doping elements.

[0107] The ion-conductive halide may be, for example, at least one of the various compounds exemplified as halide solid electrolytes described below. For example, the ion-conductive halide may contain: at least one element selected from Mg, Ca, Sr, Ba, Zn, Sn, Al, Sc, Ga, Bi, Sb, Zr, Hf, Ti, Ta, Nb, W, Y, Gd, Tb, and Sm; at least one halogen element selected from Cl, Br, I, and F; and Li. The ion-conductive halide may contain: at least one element selected from Ti, Al, Gd, Ca, Zr, and Y; at least one selected from Cl, Br, I, and F; and Li. Furthermore, the ion-conductive halide may contain: at least one element selected from Ti and Al; at least one element selected from Cl, Br, I, and F; and Li. Furthermore, the ion-conductive halide may be, for example, a complex halide of Li, Ti, Al, and F.

[0108] The coverage (area ratio) of the protective layer relative to the surface of the positive electrode active material can be, for example, 70% or more, 80% or more, or 90% or more. The thickness of the protective layer can be, for example, 0.1 nm or more or 1 nm or more, and 100 nm or less or 20 nm or less.

[0109] 2.2.3 Electrolytes

[0110] The positive electrode active material layer 20 may include an electrolyte. The electrolyte included in the positive electrode active material layer 20 may be the lithium ion conductive material disclosed above, a solid electrolyte, a liquid electrolyte, or a combination thereof.

[0111] 2.2.3.1 Solid Electrolyte

[0112] As the solid electrolyte, a solid electrolyte known as a solid electrolyte for secondary batteries can be used. The solid electrolyte other than the lithium ion conductive material disclosed in the present invention may be an inorganic solid electrolyte or an organic polymer electrolyte. In particular, the ion conductivity and heat resistance of the inorganic solid electrolyte are excellent. As inorganic solid electrolytes, for example, oxide solid electrolytes, sulfide solid electrolytes, and ion-bound inorganic solid electrolytes can be listed. Among inorganic solid electrolytes, sulfide solid electrolytes, and further sulfide solid electrolytes containing at least Li, S and P as constituent elements, have high performance. Alternatively, among inorganic solid electrolytes, ion-bound solid electrolytes, and further solid electrolytes containing at least Li, Y and halogen (at least one of Cl, Br, I and F) as constituent elements, have high performance. The solid electrolyte may be amorphous or crystalline. The solid electrolyte may be in particulate form. The average particle size (D50) of the solid electrolyte may be, for example, greater than 10 nm and less than 10 μm. The ion conductivity of the solid electrolyte at 25°C may be, for example, 1×10 -5 S / cm or more, 1×10 -4 S / cm or above, or 1×10 -3 S / cm or more. The solid electrolyte may be used alone or in combination of two or more.

[0113] The oxide solid electrolyte can be selected from lithium lanthanum zirconate, LiPON, Li 1+X Al X Ge 2-X One or more of (PO4)3, Li-SiO-based glass, Li-Al-SO-based glass, etc. In addition, when an oxide solid electrolyte is combined with a liquid electrolyte, ion conductivity can be improved.

[0114] The sulfide solid electrolyte is as described above.

[0115] The ion-bound solid electrolyte may, for example, contain at least one element selected from Mg, Ca, Sr, Ba, Zn, Sn, Al, Sc, Ga, Bi, Sb, Zr, Hf, Ti, Ta, Nb, W, Y, Gd, Tb and Sm. These elements can generate cations in water. In addition, the ion-bound solid electrolyte material may further contain at least one halogen element selected from Cl, Br, I and F. These elements can generate anions in water. The ion-bound solid electrolyte may contain: at least one selected from Gd, Ca, Zr and Y, at least one selected from Cl, Br, I and F, and Li. In addition, the ion-bound solid electrolyte contains Li and Y, and may contain at least one selected from Cl, Br, I and F. More specifically, the ion-bound solid electrolyte may contain Li, Y, Cl and Br, may contain Li, Ca, Y, Gd, Cl and Br, or may contain Li, Zr, Y and Cl. More specifically, the ion-bound solid electrolyte may be Li3YBr2Cl4, Li 2.8 Ca 0.1 Y 0.5 Gd 0.5 Br2Cl4, and Li 2.5 Y 0.5 Zr 0.5 At least one of Cl6.

[0116] The ion-binding solid electrolyte may be a halide solid electrolyte. Halide solid electrolytes have excellent ion conductivity. For example, the halide solid electrolyte may have a composition represented by formula (A).

[0117] Li α M β X γ ···(A)

[0118] Here, α, β, and γ are each independently greater than 0, M is at least one selected from metal elements and semi-metal elements other than Li, and X is at least one selected from Cl, Br, and I. Furthermore, the "semi-metal element" may be at least one selected from B, Si, Ge, As, Sb, and Te. Furthermore, the "metal element" may include (i) all elements contained in Groups 1 to 12 of the periodic table (excluding hydrogen) and (ii) all elements contained in Groups 13 to 16 of the periodic table (excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se). Metal elements form inorganic compounds together with halide ions and can become cations.

[0119] In formula (A), M may include Y (ie, yttrium). The halide solid electrolyte including Y may have a a Me b Yc A composition represented by X6 (wherein a+mb+3c=6, c>0, Me is at least one metal element and semimetal element selected from Li and Y, and m is the valence of Me). Me can be, for example, at least one selected from Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb.

[0120] The halide solid electrolyte may have a structure represented by formula (A1): Li 6-3d Y d The composition represented by X6. In formula (A1), X is one or more elements selected from Cl, Br and I. d may satisfy 0<d<2, and may be d=1. The halide solid electrolyte may have a structure represented by formula (A2): Li 3-3δ Y 1+δ The composition represented by Cl6. In formula (A2), 0<δ≤0.15. The halide solid electrolyte may have a composition represented by formula (A3): Li 3-3δ Y 1+δ The composition represented by Br6. In formula (A3), 0 < δ ≤ 0.25. The halide solid electrolyte may have a composition represented by formula (A4): Li 3-3δ+a Y 1+δ-a Me a Cl 6-x-y Br x I y In formula (A4), Me may be at least one selected from Mg, Ca, Sr, Ba and Zn. In formula (A4), for example, -1<δ<2, 0<a<3, 0<(3-3δ+a), 0<(1+δ-a), 0≤x≤6, 0≤y≤6 and (x+y)≤6 are satisfied. The halide solid electrolyte may have a structure represented by formula (A5): Li 3-3δ Y 1+δ-a Me a Cl 6-x-y Br x I y In formula (A5), Me may be at least one selected from Al, Sc, Ga, and Bi. In formula (A5), -1<δ<1, 0<a<2, 0<(1+δ-a), 0≤x≤6, 0≤y≤6, and (x+y)≤6. The halide solid electrolyte may have a composition represented by formula (A6): Li 3-3δ- a Y 1+δ-a Me a Cl 6-x-y Br x I yIn formula (A6), Me may be at least one selected from Zr, Hf, and Ti. In formula (A6), -1<δ<1, 0<a<1.5, 0<(3-3δ-a), 0<(1+δ-a), 0≤x≤6, 0≤y≤6, and (x+y)≤6. The halide solid electrolyte may have a composition represented by formula (A7): Li 3-3δ-2a Y 1+δ-a Me a Cl 6-x-y Br x I y In formula (A7), Me may be at least one selected from Ta and Nb. In formula (A7), -1<δ<1, 0<a<1.2, 0<(3-3δ-2a), 0<(1+δ-a), 0≤x≤6, 0≤y≤6, and (x+y)≤6.

[0121] The ion-bound solid electrolyte may be a complex hydride solid electrolyte. The complex hydride solid electrolyte may be composed of Li ions and complex ions containing H. The complex ions containing H may, for example, have an element M containing at least one of a non-metallic element, a semi-metallic element, and a metal element, and H bound to the element M. In addition, in the case of complex ions containing H, the element M as the central element and the H surrounding the element M may be bound to each other via covalent bonds. In addition, the complex ions containing H may be composed of (M m H n ) α- In this case, m is an arbitrary positive number, and n and α can be any positive numbers according to m, the valence of the element M, etc. The element M can be a non-metallic element or a metal element that can form a complex ion. For example, the element M can contain at least one of B, C and N as a non-metallic element, and can contain B. In addition, for example, the element M can contain at least one of Al, Ni and Fe as a metal element. In particular, when the complex ion contains B, or contains C and B, it is easy to ensure higher ion conductivity. As a specific example of a complex ion containing H, (CB9H 10 ) - 、(CB 11 H 12 ) - 、(B 10 H 10 ) 2- 、(B 12 H 12 ) 2- 、(BH4) - NH2 - 、(AlH4) - , and combinations thereof. In particular, when using (CB9H 10 ) - 、(CB11 H 12 ) - , or a combination thereof, it is easy to ensure higher ion conductivity. That is, the complex hydride solid electrolyte can contain Li, C, B and H.

[0122] 2.2.3.2 Liquid Electrolyte

[0123] The liquid electrolyte (electrolyte) is a liquid containing lithium ions as carrier ions. The electrolyte can be an aqueous electrolyte or a non-aqueous electrolyte. As for the composition of the electrolyte, it is sufficient as long as it is the same as the composition of the electrolyte known as the electrolyte of a lithium ion secondary battery. The electrolyte can dissolve the lithium salt in water or a non-aqueous solvent. As non-aqueous solvents, for example, the various carbonate solvents mentioned above can be listed. As lithium salts, for example, the amide lithium salts mentioned above, LiPF6, etc. can be listed. The electrolyte may be the same as or different from the electrolyte constituting the composite of the present disclosure.

[0124] 2.2.4 Conductive additives

[0125] Examples of conductive additives that may be included in the positive electrode active material layer 20 include carbon materials such as vapor-grown carbon fiber (VGCF), acetylene black (AB), Ketjen black (KB), carbon nanotubes (CNTs), and carbon nanofibers (CNFs); and metal materials such as nickel, titanium, aluminum, and stainless steel. The conductive additive may be in the form of particles or fibers, and its size is not particularly limited. One conductive additive may be used alone, or two or more may be used in combination.

[0126] 2.2.5 Adhesives

[0127] Examples of the binder that may be contained in the positive electrode active material layer 20 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, and polyimide (PI)-based binders. The binders may be used alone or in combination of two or more.

[0128] 2.2.6 Others

[0129] The positive electrode active material layer 20 may contain various additives in addition to the above-mentioned components, such as a dispersant and a lubricant.

[0130] The positive electrode active material layer 20 can be manufactured by applying known methods. For example, the positive electrode mixture containing the various components described above can be dry-molded or wet-molded to easily form the positive electrode active material layer 20. The positive electrode active material layer 20 can be molded together with the positive electrode current collector 10 or independently of the positive electrode current collector 10.

[0131] 2.3 Electrolyte layer

[0132] The secondary battery 100 includes an electrolyte layer 30. The electrolyte layer 30 is arranged between the positive electrode active material layer 20 and the negative electrode active material layer 40. The electrolyte layer 30 contains at least an electrolyte. The electrolyte layer 30 may contain at least one of a solid electrolyte and an electrolyte solution, and may further optionally contain a binder, etc. In the case where the electrolyte layer 30 contains the lithium ion conductive material disclosed above, the electrolyte layer 30 may further contain other electrolytes, binders, and various additives in addition to the lithium ion conductive material. There is no particular limitation on the content of the electrolyte and binder, etc. in the electrolyte layer 30. Alternatively, the electrolyte layer 30 may have a separator, etc. for retaining the electrolyte solution and preventing contact between the positive electrode active material layer 20 and the negative electrode active material layer 40. There is no particular limitation on the thickness of the electrolyte layer 30, and for example, it may be greater than 0.1 μm or greater than 1 μm, and may be less than 2 mm or less than 1 mm.

[0133] The electrolyte layer 30 may be composed of a single layer or a plurality of layers. For example, the electrolyte layer 30 may include a first layer disposed on the positive electrode active material layer 20 side and a second layer disposed on the negative electrode active material layer 40 side. The first layer may contain a first electrolyte, and the second layer may contain a second electrolyte. The first electrolyte and the second electrolyte may be of different types. The first electrolyte and the second electrolyte may each be at least one selected from the above-mentioned oxide solid electrolyte, sulfide solid electrolyte, and ionically bound solid electrolyte. For example, the first layer may contain an ionically bound solid electrolyte, and the second layer may contain at least one of an ionically bound solid electrolyte and a sulfide solid electrolyte.

[0134] The electrolyte contained in the electrolyte layer 30 can be appropriately selected from the lithium ion conductive material disclosed above and the electrolyte (solid electrolyte and / or liquid electrolyte) exemplified as the electrolyte that can be contained in the above-mentioned positive electrode active material layer. In addition, the binder that can be contained in the electrolyte layer 30 can be appropriately selected from the binders exemplified as the binders that can be contained in the above-mentioned positive electrode active material layer. Only one type of electrolyte and binder can be used alone, or two or more types can be used in combination. The separator can be any separator commonly used in lithium ion secondary batteries, for example, separators composed of resins such as polyethylene (PE), polypropylene (PP), polyester and polyamide. The separator can be a single-layer structure or a multi-layer structure. As a separator of a multi-layer structure, for example, a separator of a two-layer structure of PE / PP, or a separator of a three-layer structure of PP / PE / PP or PE / PP / PE can be listed. The separator can be composed of non-woven fabrics such as cellulose non-woven fabrics, resin non-woven fabrics, and glass fiber non-woven fabrics.

[0135] 2.4 Negative electrode active material layer

[0136] The secondary battery 100 includes a negative electrode active material layer 40. The negative electrode active material layer 40 contains at least a negative electrode active material. Additionally, the negative electrode active material layer 40 may optionally contain an electrolyte, a conductive additive, a binder, and various additives. When the negative electrode active material layer 40 contains the lithium ion conductive material disclosed above, in addition to the negative electrode active material and the lithium ion conductive material, the negative electrode active material layer 40 may further optionally contain other electrolytes, conductive additives, binders, and various additives. The content of each component in the negative electrode active material layer 40 can be appropriately determined based on the target battery performance. For example, assuming the solid content of the negative electrode active material layer 40 as a whole is 100 mass%, the content of the negative electrode active material may be 40 mass% or more, 50 mass% or more, 60 mass% or more, or 70 mass% or more, or may be 100 mass% or less, less than 100 mass%, 95 mass% or less, or 90 mass% or less. Alternatively, the negative electrode active material layer 40, when taken as 100% by volume, may comprise at least 85% by volume, at least 90% by volume, or at least 95% by volume of the negative electrode active material, and optionally, an electrolyte, a conductive additive, and a binder. The remainder may be voids or other components. The shape of the negative electrode active material layer 40 is not particularly limited; for example, it may be a substantially flat sheet. The thickness of the negative electrode active material layer 31 is not particularly limited; for example, it may be at least 0.1 μm, at least 1 μm, at least 10 μm, or at least 30 μm, and may be less than 2 mm, less than 1 mm, less than 500 μm, or less than 100 μm.

[0137] 2.4.1 Negative electrode active material

[0138] As for the negative electrode active material, any negative electrode active material known as a negative electrode active material for a secondary battery can be used. Among the known active materials, various materials whose potential for absorbing and releasing lithium ions (charge and discharge potential) is lower than that of the above-mentioned positive electrode active materials can be used. 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, etc. can be used. Among them, when the negative electrode active material layer 40 contains Si as a negative electrode active material, the performance of the secondary battery 100 is easily improved. Only one negative electrode active material can be used alone, or two or more negative electrode active materials can be used in combination. The shape of the negative electrode active material can be any shape that is generally used as a negative electrode active material for a secondary battery. For example, the negative electrode active material can be in the form of particles. The negative electrode active material particles 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 a sheet form (foil or film) such as lithium foil. That is, the negative electrode active material layer 31 can be composed of a sheet of negative electrode active material.

[0139] 2.4.2 Others

[0140] Examples of the electrolyte that may be contained in the negative electrode active material layer 40 include the lithium ion conductive material disclosed herein, the solid electrolyte described above, an electrolyte solution, or a combination thereof. The conductive aid that may be contained in the negative electrode active material layer 40 may be appropriately selected from the conductive aids listed above as examples of the conductive aids that may be contained in the positive electrode active material layer. The binder that may be contained in the negative electrode active material layer 40 may be appropriately selected from the binders listed above as examples of the binders that may be contained in the positive electrode active material layer. One of each of the electrolyte, conductive aid, and binder may be used alone, or two or more of them may be used in combination.

[0141] The negative electrode active material layer 40 can be manufactured by applying known methods. For example, the negative electrode mixture containing the various components described above can be dry-molded or wet-molded to easily form the negative electrode active material layer 40. The negative electrode active material layer 40 can be molded together with the negative electrode current collector 50 or independently of the negative electrode current collector 50.

[0142] 2.5 Negative electrode collector

[0143] The secondary battery 100 may include a negative electrode current collector 50 in contact with the negative electrode active material layer 40. Any common negative electrode current collector for a secondary battery can be used for the negative electrode current collector 50. Furthermore, the negative electrode current collector 50 may be in the form of a foil, plate, mesh, punched metal, or foam. The negative electrode current collector 50 may be a metal foil or metal mesh, or a carbon sheet. Metal foil is particularly advantageous in terms of handling properties. The negative electrode current collector 50 may be composed of multiple foils or sheets. Examples of metals comprising the negative electrode current collector 50 include at least one selected from the group consisting of Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, V, Mg, Pb, Ge, In, Sn, Zr, and stainless steel. In particular, to ensure reduction resistance and resist alloying with lithium, the negative electrode current collector 50 may be composed of at least one metal selected from the group consisting of Cu, Ni, and stainless steel. The negative electrode current collector 50 may have some coating on its surface for the purpose of adjusting resistance, etc. For example, the negative electrode current collector 50 may have a carbon coating. The negative electrode current collector 50 may be an aluminum foil with a carbon coating. In addition, the negative electrode current collector 50 may be formed by plating or vapor-depositing the above-mentioned metal on a metal foil or a substrate. In addition, when the negative electrode current collector 50 is composed of multiple metal foils, there may be some layers between the multiple metal foils. There is no particular limitation on the thickness of the negative electrode current collector 50. 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.

[0144] 2.6 Other components

[0145] In addition to the above-mentioned structures, the secondary battery 100 may include structures generally used in secondary batteries. For example, tabs, terminals, etc. As for the secondary battery 100, the above-mentioned structures can be housed inside the outer packaging body. As for the outer packaging body, any outer packaging body known as the outer packaging body of a battery can be used. In addition, a plurality of secondary batteries 100 can be electrically connected arbitrarily, and can be stacked arbitrarily to form a battery pack. In this case, the battery pack can be housed inside a known battery case. In addition, the secondary battery 100 may include obvious structures such as necessary terminals. Examples of the shape of the secondary battery 100 include a coin shape, a stacked body shape, a cylindrical shape, and a square shape.

[0146] 3. Method for manufacturing lithium ion conductive materials

[0147] The lithium ion conductive material disclosed herein can be manufactured, for example, using the following method. Specifically, the method for manufacturing the lithium ion conductive material disclosed herein comprises forming a composite of an electrolyte and a polymer. The electrolyte comprises 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. Details of the electrolyte and polymer are as described above.

[0148] According to the inventors' findings, simply mixing an electrolyte with a polymer does not yield sufficient affinity between the electrolyte and the polymer, resulting in mutual incompatibility and separation of the electrolyte and the polymer. Therefore, further effort is required to composite the electrolyte and the polymer. As one solution to this problem, for example, a diluent is sometimes used when mixing the electrolyte with the polymer to improve the affinity between the electrolyte and the polymer. Specifically, the method for producing a lithium ion conductive material disclosed herein may include: mixing a diluent with the electrolyte and the polymer to obtain a solution; and composite the electrolyte with the polymer by removing the diluent from the solution. The diluent is preferably a substance that can dissolve both the electrolyte and the polymer. The diluent may also be referred to as a compatibilizer for improving the compatibility between the electrolyte and the polymer. Furthermore, when the boiling point of the diluent is lower than that of the solvent (cyclic carbonate) constituting the electrolyte, it is believed that the diluent can be more easily removed by heating. The diluent may be, for example, a chain carbonate. Specifically, the diluent may be dimethyl carbonate. There is no particular limitation on the mixing ratio of the electrolyte, polymer, and diluent. When the electrolyte, polymer, and diluent are mixed, heating may or may not be performed.

[0149] 4. Composite solid electrolytes and composite active materials

[0150] As described above, the lithium ion conductive material of the present disclosure can be integrated with a solid electrolyte or with an active material. For example, a solution of the above-mentioned electrolyte, polymer, and diluent is prepared, and after applying the solution to the surface of the solid electrolyte and the active material, the diluent is removed, so that at least a portion of the surface of the solid electrolyte and the active material can be covered with the lithium ion conductive material of the present disclosure. Thus, it is believed that a composite solid electrolyte and a composite active material can be manufactured. More specifically, the composite solid electrolyte of the present disclosure is characterized in that it comprises a lithium ion conductive material and a solid electrolyte, wherein the lithium ion conductive material comprises a complex of an electrolyte and a polymer, wherein the electrolyte comprises 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 is less than 0.33, and the solid electrolyte is at least one selected from an oxide solid electrolyte, a sulfide solid electrolyte, and an ion-bound solid electrolyte, and at least a portion of the surface of the solid electrolyte is covered with the lithium ion conductive material. Alternatively, the composite active material disclosed herein is characterized in that it comprises a lithium ion conductive material and an active material, wherein the lithium ion conductive material comprises a complex of an electrolyte and a polymer, wherein the electrolyte comprises 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 is less than 0.33, and at least a portion of the surface of the active material is coated with the lithium ion conductive material. The solid electrolyte and the active material are as described above, and may be, for example, in a particulate form. The active material may be a positive electrode active material or a negative electrode active material.

[0151] 5. Method for manufacturing lithium-ion secondary batteries

[0152] The lithium-ion secondary battery 100 can be manufactured by applying a known method. For example, it can be manufactured as follows. However, the manufacturing method of the secondary battery 100 is not limited to the following method. For example, each layer can be formed by dry molding or the like.

[0153] (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 current 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 current collector to produce a positive electrode.

[0154] (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 scraper or the like, and then dried to form a negative electrode active material layer on the surface of the negative electrode current collector, thereby producing a negative electrode.

[0155] (3) The layers are stacked so that the electrolyte layer (solid electrolyte layer or separator) is sandwiched between the negative electrode and the positive electrode to obtain a laminate having, in this order, a negative electrode current collector, a negative electrode active material layer, an electrolyte layer, a positive electrode active material layer, and a positive electrode current collector. Other components such as terminals are attached to the laminate as needed.

[0156] (4) The stacked body is housed in a battery case. In the case of an electrolyte battery, the battery case is filled with an electrolyte, the stacked body is immersed in the electrolyte, and the stacked body is sealed in the battery case to produce a secondary battery. In the case of a battery containing an electrolyte, the electrolyte can be contained in the negative electrode active material layer, the separator, and the positive electrode active material layer in the above-mentioned stage (3).

[0157] 6. Method for improving lithium ion input and output characteristics in lithium ion secondary batteries

[0158] The disclosed technology also has aspects as a method for improving the input and output characteristics of lithium ions in lithium-ion secondary batteries. Specifically, the disclosed method is characterized by improving the input and output characteristics of lithium ions by employing the disclosed lithium-ion conductive material described above in at least one of the positive electrode active material layer, electrolyte layer, and negative electrode active material layer of the lithium-ion secondary battery. The details of the lithium-ion conductive material and the lithium-ion secondary battery are as described above.

[0159] 7. Vehicles

[0160] As described above, the lithium ion secondary battery of the present disclosure has excellent input and output characteristics of lithium ions. For example, it is easy to maintain low resistance at the interface between the active material and the lithium ion conductive material even in the case of repeated charge and discharge. Such a secondary battery can be preferably used in a vehicle selected from at least one of hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV) and electric vehicles (BEV). That is, the technology of the present disclosure also has the following aspects, which are vehicles with lithium ion secondary batteries, wherein the lithium ion secondary battery includes a positive electrode active material layer, an electrolyte layer and a negative electrode active material layer, and at least one of the positive electrode active material layer, the electrolyte layer and the negative electrode active material layer includes the above-mentioned lithium ion conductive material of the present disclosure. The details of the structure of the lithium ion secondary battery are as described above.

[0161] Example

[0162] The following examples illustrate the technology of the present disclosure in more detail, but the technology of the present disclosure is not limited to the following examples. All experiments were conducted in an Ar atmosphere with a dew point below -80°C and an oxygen concentration of less than 3 ppm, either in a glove box or in an environment not exposed to the atmosphere.

[0163] 1. Evaluation of electrolyte

[0164] The electrolyte solution constituting the lithium ion conductive material of the present disclosure was evaluated.

[0165] 1.1 Preparation of electrolyte

[0166] 1.1.1 Example 1

[0167] Lithium bisfluorosulfonamide (LiFSA, manufactured by Kishida Chemical Co., Ltd.) as a lithium salt and propylene carbonate (PC, manufactured by Kishida Chemical Co., Ltd.) as a solvent were weighed, mixed, and stirred so that the molar ratio was 0.33 (PC:LiFSA = 3:1) to obtain an electrolyte solution for evaluation.

[0168] 1.1.2 Example 2

[0169] The components were weighed, mixed, and stirred so that the molar ratio of LiFSA to PC became 0.29 (PC:LiFSA=3.5:1), thereby obtaining an electrolyte solution for evaluation.

[0170] 1.1.3 Example 3

[0171] The components were weighed, mixed, and stirred so that the molar ratio of LiFSA to PC became 0.26 (PC:LiFSA=3.8:1), thereby obtaining an electrolyte solution for evaluation.

[0172] 1.1.4 Example 4

[0173] An electrolytic solution for evaluation was obtained in the same manner as in Example 1 except that lithium bistrifluoromethanesulfonamide (LiTFSA, manufactured by Kishida Chemical Co., Ltd.) was used instead of LiFSA.

[0174] 1.1.5 Example 5

[0175] An electrolytic solution for evaluation was obtained in the same manner as in Example 2 except that LiTFSA was used instead of LiFSA.

[0176] 1.1.6 Example 6

[0177] An electrolytic solution for evaluation was obtained in the same manner as in Example 3 except that LiTFSA was used instead of LiFSA.

[0178] 1.1.7 Example 7

[0179] An electrolyte solution for evaluation was obtained in the same manner as in Example 1 except that a mixed solvent of PC and ethylene carbonate (EC, manufactured by Kishida Chemical Co., Ltd.) (mixed so that the molar ratio of PC to EC was PC:EC=1:2) was used instead of the PC single solvent.

[0180] 1.1.8 Comparative Example 1

[0181] The components were weighed, mixed, and stirred so that the molar ratio of LiFSA to PC became 0.08 (PC:LiFSA=11.8:1), thereby obtaining an electrolyte solution for evaluation.

[0182] 1.1.9 Comparative Example 2

[0183] The components were weighed, mixed, and stirred so that the molar ratio of LiFSA to PC became 0.25 (PC:LiFSA=4:1), thereby obtaining an electrolyte solution for evaluation.

[0184] 1.1.10 Comparative Example 3

[0185] An electrolytic solution for evaluation was obtained in the same manner as in Comparative Example 1 except that LiTFSA was used instead of LiFSA.

[0186] 1.1.11 Comparative Example 4

[0187] An electrolytic solution for evaluation was obtained in the same manner as in Comparative Example 2 except that LiTFSA was used instead of LiFSA.

[0188] 1.1.12 Comparative Example 5

[0189] An electrolytic solution for evaluation was obtained in the same manner as in Example 1 except that dimethyl carbonate (DMC, manufactured by Kishida Chemical Co., Ltd.) was used instead of PC.

[0190] 1.1.13 Comparative Example 6

[0191] An evaluation electrolyte solution was obtained in the same manner as in Example 1, except that a mixed solvent of DMC and EC (mixed at a molar ratio of DMC:EC = 1:2) was used instead of the PC single solvent. In the electrolyte solution of Comparative Example 6, the molar ratio of LiFSA to EC was 0.50 (EC:LiFSA = 2:1).

[0192] 1.1.14 Comparative Example 7

[0193] An electrolytic solution for evaluation was obtained in the same manner as in Example 1 except that lithium hexafluorophosphate (LiPF 6 , manufactured by Kishida Chemical Co., Ltd.) was used instead of LiFSA.

[0194] 1.1.15 Comparative Example 8

[0195] LiTFSA and tetraglyme (G4, manufactured by Kishida Chemical Co., Ltd.) as a solvent were weighed so that the molar ratio was 1.25 (G4:LiTFSA=8:10), mixed, and stirred to obtain an electrolyte solution for evaluation.

[0196] 1.2 Evaluation method of electrolyte

[0197] 1.2.1 Evaluation of heat resistance

[0198] For each electrolyte solution, a TG-DTA test was performed at a heating rate of 10°C / min, and the 0.5 wt% weight loss temperature (T -0.5wt％ The higher the temperature, the better the heat resistance (thermal stability). Figure 2 .

[0199] 1.2.2 Ionic conductivity and lithium ion transport rate (tLi + )'s evaluation

[0200] Li metal was used as the electrode, and a two-pole target cell with a fixed distance between the electrodes was used. The ion conductivity was determined by the complex impedance method at 25°C, and the lithium ion transmission rate was determined by the Bruce method (Bruce et al. Solid State Ionics 28-30, 1987, 918-922), which combines DC polarization and impedance methods. The results of the lithium ion transmission rate are shown in Figure 3 .

[0201] 1.2.3 Evaluation of lithium ion conductivity

[0202] The lithium ion conductivity was evaluated by multiplying the lithium ion transfer rate obtained by the above electrochemical method by the ion conductivity. Figure 4 .

[0203] 1.2.4 Reactivity Evaluation of Sulfide Solid Electrolytes

[0204] A sulfide solid electrolyte having a composition of 75(75Li2S·25P2S5)·10LiI·15LiBr (numbers are in mol%) was immersed in each electrolyte for 2 months. X-ray diffraction measurements were performed on the sulfide solid electrolyte before and after immersion to confirm changes in the X-ray diffraction spectrum. The results are shown in Figure 5.

[0205] 1.3 Evaluation results of electrolyte

[0206] 1.3.1 About heat resistance

[0207] Depend on Figure 2 The results shown reveal the following: When the molar ratio of lithium salt to solvent is less than 0.1, as in Comparative Example 1, the heat resistance is comparable to that of a case without lithium salt. In other words, dissolving the lithium salt in the solvent does not improve heat resistance. Furthermore, when the molar ratio is 0.25, as in Comparative Examples 2 and 4, heat resistance improves somewhat. Furthermore, when the molar ratio exceeds 0.25, as in Examples 1 and 4, heat resistance significantly improves.

[0208] 1.3.2 Lithium Ion Conductivity

[0209] 1.3.2.1 Lithium Ion Transfer Rate

[0210] Depend on Figure 3 The results shown reveal the following. Compared to the case where the molar ratio of the lithium salt to the solvent is 0.25 or less, as in Comparative Examples 1 to 4, when the molar ratio exceeds 0.25, as in Examples 1 to 6, the lithium ion transmission rate is significantly improved. On the other hand, the inventors have confirmed that if the molar ratio of the lithium salt to the solvent is excessive, the viscosity increases excessively (for example, becoming solid at room temperature), and the lithium ion conductivity tends to decrease. If the molar ratio of the lithium salt to the solvent is greater than 0.25 and is 0.33 or less, as in Examples 1 to 6, this problem does not occur.

[0211] 1.3.2.2 Lithium Ion Conductivity

[0212] Depend on Figure 4 The results shown here reveal the following: Generally, as the concentration of lithium salt in the solvent increases, there is a concern that the viscosity will increase, leading to a decrease in ion conductivity. However, in Examples 1 to 6, even with increased viscosity, high lithium ion conductivity can be easily maintained due to the increased lithium ion transport rate described above.

[0213] As mentioned above, the molar ratio of amide lithium salt to cyclic carbonate is greater than 0.25 and is an electrolyte solution (Examples 1 to 6) below 0.33 compared with the electrolyte solution (Comparative Examples 1 to 4) below 0.25 of this molar ratio, and it can be said that the balance of heat resistance and lithium ion conductivity is excellent. Furthermore, according to the present inventors, as in Comparative Example 6, due to the presence of a large amount of solvent (such as chain carbonate) other than the cyclic carbonate, the cyclic carbonate amount is relatively reduced, and as a result, when the concentration of the Li salt relative to the cyclic carbonate is relatively excessive, the heat resistance of the electrolyte tends to decrease.

[0214] 1.3.3 Reactivity with Sulfide Solid Electrolytes

[0215] Depend on Figure 5 The results shown show the following. Figure 5 In Examples 1, 4, and 7, the X-ray diffraction peak patterns of the sulfide solid electrolytes after immersion in the electrolyte showed little change relative to the X-ray diffraction peak patterns of the sulfide solid electrolytes before immersion (reference example). In contrast, the X-ray diffraction peak patterns of the sulfide solid electrolytes after immersion in the electrolyte for Comparative Examples 5 to 8 showed significant changes relative to the X-ray diffraction peak patterns of the sulfide solid electrolytes before immersion (reference example). This suggests that the reactivity between the electrolyte and the sulfide solid electrolyte varies depending on the type and polarity of the solvent constituting the electrolyte, the type of anion in the lithium salt, and other factors. For example, when a cyclic carbonate is not used as a solvent but a chain carbonate is used as a solvent as in Comparative Example 5, or when a large amount of chain carbonate is used as a solvent together with a cyclic carbonate as in Comparative Example 6 (where the molar ratio of the lithium salt to the cyclic carbonate is excessive), it is believed that the chain carbonate easily exists freely, and the active site of the chain carbonate reacts with the sulfide solid electrolyte, causing the sulfide solid electrolyte to deteriorate and degrade. The same is true when G4 is used as a solvent as in Comparative Example 8. In addition, when LiPF6 is used as a lithium salt instead of an amide lithium salt as in Comparative Example 7, it is believed that the PF6 anion reacts with the sulfide solid electrolyte, causing the sulfide solid electrolyte to deteriorate and degrade.

[0216] 1.4. Summary

[0217] From the above results, it can be said that the electrolyte solution having the following structures (1) and (2) has excellent thermal stability and lithium ion conductivity.

[0218] (1) A method comprising a cyclic carbonate as a solvent and an amide lithium salt dissolved in the cyclic carbonate.

[0219] (2) The molar ratio of the amide lithium salt to the cyclic carbonate is greater than 0.25 and is 0.33 or less.

[0220] Furthermore, the electrolyte solution having the above-mentioned structures (1) and (2) can also be used in combination with a sulfide solid electrolyte. In particular, the electrolyte solution having the following structure (3) can suppress the degradation of the sulfide solid electrolyte while having the above-mentioned effects.

[0221] (3) The amide lithium salt is at least one of lithium bisfluorosulfonamide and lithium bistrifluoromethanesulfonamide.

[0222] 2. Evaluation of lithium ion conductive materials (complexes of electrolyte and polymer)

[0223] The effect of forming a composite of an electrolyte solution and a polymer was confirmed.

[0224] 2.1 Preparation of evaluation samples

[0225] 2.1.1 Example 1

[0226] Using propylene carbonate (PC, cyclic carbonate, manufactured by Kishida Chemical), lithium bisfluorosulfonamide (LiFSA, amide lithium salt, manufactured by Kishida Chemical), fluoride-based polymer (copolymer of polyvinylidene fluoride and hexafluoropropylene, manufactured by Kureha, weight average molecular weight: 670,000), and dimethyl carbonate (DMC, manufactured by Kishida Chemical) as a diluent, the mixture was weighed and mixed in such a way that the molar ratio of LiFSA to PC was 0.33, the proportion of polymer in the total of PC, LiFSA and polymer was 25% by mass, and the diluent was 8 times the weight of the polymer, and heated and stirred to obtain a uniform solution. After the obtained solution was cast into a film at 60°C, the diluent was dried and volatilized to obtain a sheet-like lithium ion conductive material (a complex of electrolyte and polymer) as an evaluation sample. The lithium ion conductive material is solid at 25°C and has no fluidity. In addition, no release of the electrolyte from the lithium ion conductive material was confirmed.

[0227] 2.1.2 Comparative Example 1

[0228] The electrolyte solution (weighed and mixed so that the molar ratio of LiFSA to PC became 0.33) was not composited with the polymer and was used as an evaluation sample as it was.

[0229] 2.1.3 Comparative Example II

[0230] The same procedure as in Comparative Example 1 was followed, except that the concentration of LiFSA in the electrolyte solution was changed to 1 M. The electrolyte solution was not composited with the polymer and was used as an evaluation sample as it was.

[0231] 2.2 Cyclic voltammetry (CV) test and charge-discharge test

[0232] The Si wafer is used as the working electrode and the Li metal is used as the counter electrode and reference electrode to form a bipolar battery cell. In this bipolar battery cell, the above-mentioned evaluation sample was arranged between the working electrode and the counter electrode, and the evaluation was carried out at 25°C. The CV test was carried out at a scan rate of 1mV / s. The charge and discharge test was carried out at 0.1V for 10 hours and at 0.5V for 10 hours, and this was carried out for 10 cycles. After each cycle of charge and discharge, impedance measurement was carried out to measure the electrode interface resistance. For the Li metal interface resistance, the Li metal target battery cell was evaluated in advance, and the Li metal interface resistance was subtracted from the electrode interface resistance to obtain the Si interface resistance.

[0233] exist Figure 6 The results of the CV test are shown in FIG. Figure 6 As shown, in Example 1, impurities on the Si surface are removed by repeated cycles, and it is found that Li alloying / dealloying of Si proceeds around 0.3 to 0.4 V. Furthermore, in Comparative Example 1, where the electrolyte solution was used alone without being composited with a polymer, the activity was low, while in Example 1 composited with a polymer, the redox current increased, confirming a significant improvement in reaction activity. The reaction activity of Example 1 was higher than that of Comparative Example II, which had a typical electrolyte concentration, confirming that composited electrolyte solution with a polymer produces a significant and unique effect.

[0234] exist Figure 7 The results of the resistance change at the Si interface during the charge and discharge cycle are shown in FIG. In Comparative Example II, it is generally known that the resistance increase of the growth of the SEI film as the electrolyte decomposes depends on the increase in the number of cycles and is confirmed. On the other hand, Comparative Example I with a high concentration of amide lithium salt failed to confirm the resistance increase associated with SEI growth, and maintained a high resistance state from the initial stage. On the other hand, in Example I in which the concentration of amide lithium salt in the electrolyte is high and the electrolyte is composited with a polymer, although the resistance increases due to poor adhesion to the electrode at the initial stage of the cycle, after the third cycle, as the number of cycles increases, a significant decrease in the Si interface resistance is confirmed, and it is known that the interface resistance becomes smaller than that of an electrolyte with a general lithium salt concentration. From this result, it can be seen that in a lithium ion secondary battery, if a composite of a specified electrolyte and a polymer is used as a lithium ion conductive material, for example, the growth of SEI at the interface of the active material and the lithium ion conductive material is suppressed, the input and output characteristics of lithium ions are improved.

[0235] 2.3 Evaluation using XPS

[0236] In order to confirm the validity of the investigation of the CV test results and the charge-discharge test results, the surface of each Si electrode after 10 cycles of charge-discharge was observed by XPS. Figure 8 .like Figure 8 As shown, components derived from anions and decomposition products were detected in both Comparative Examples I and II. Components believed to be derived from anions and decomposition products were not detected in Example I, confirming that SEI did not grow on the Si electrode surface.

[0237] 2.4 Supplement

[0238] It should be noted that in the above embodiment, PC is used as a cyclic carbonate constituting the electrolyte, LiFSA is used as an amide lithium salt constituting the electrolyte, and a predetermined fluoride-based polymer is used as a polymer composited with the electrolyte. However, the technology disclosed herein is not limited to this form. Even when cyclic carbonates, amide lithium salts, and polymers other than these are used, the same effect can be expected.

[0239] Furthermore, while the lithium ion input / output characteristics of Si were evaluated in the aforementioned examples, the lithium ion conductive material disclosed herein is believed to exhibit similarly excellent lithium ion input / output characteristics for other materials. Specifically, by forming a composite of a predetermined electrolyte with a polymer, the electrolyte's release is suppressed, which is believed to inhibit reactions between the electrolyte and the battery material, thereby suppressing SEI growth.

[0240] 2.5 Summary

[0241] The above results indicate that the lithium ion conductive material having the following structures (A) to (C) has excellent lithium ion input and output characteristics. In addition, as described above, it can be said that the lithium ion conductivity and thermal stability are also excellent.

[0242] (A) A composite comprising an electrolyte solution and a polymer.

[0243] (B) The electrolyte solution contains a cyclic carbonate as a solvent and an amide lithium salt dissolved in the cyclic carbonate.

[0244] (C) The molar ratio of the amide lithium salt to the cyclic carbonate is greater than 0.25 and is 0.33 or less.

[0245] Furthermore, lithium-ion conductive materials having the aforementioned configurations (A) to (C) can also be used in combination with a sulfide solid electrolyte. In particular, lithium-ion conductive materials having one or both of the following configurations (D) and (E) can be said to be able to suppress degradation of the sulfide solid electrolyte while exhibiting the aforementioned effects.

[0246] (D) The polymer is a fluoride-based polymer.

[0247] (E) The amide lithium salt is at least one of lithium bisfluorosulfonamide and lithium bistrifluoromethanesulfonamide.

[0248] Description of Reference Numerals

[0249] 10Positive electrode collector

[0250] 20 positive electrode active material layer

[0251] 30 electrolyte layer

[0252] 40 negative electrode active material layer

[0253] 50 negative electrode collector

[0254] 100 lithium-ion secondary batteries

Claims

1. A lithium ion conductive material comprising a composite of an electrolyte and a polymer, wherein the electrolyte comprises 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 not more than 0.

33.

2. The lithium ion conductive material according to claim 1, wherein The polymer is a fluoride-based polymer. The lithium ion conductive material according to claim 1 or 2, comprising the composite and a sulfide solid electrolyte.

4. The lithium ion conductive material according to any one of claims 1 to 3, wherein The cyclic carbonate is at least one of propylene carbonate and ethylene carbonate.

5. The lithium ion conductive material according to any one of claims 1 to 4, wherein The amide lithium salt is at least one of lithium bisfluorosulfonamide and lithium bistrifluoromethanesulfonamide.

6. A lithium ion secondary battery comprising a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer, wherein at least one of the positive electrode active material layer, the electrolyte layer, and the negative electrode active material layer comprises the lithium ion conductive material according to any one of claims 1 to 5.

7. The lithium ion secondary battery according to claim 6, wherein At least the negative electrode active material layer contains the lithium ion conductive material.

8. The lithium ion secondary battery according to claim 6 or 7, wherein The negative electrode active material layer contains Si as a negative electrode active material.

9. A method for producing a lithium ion conductive material, comprising compounding an electrolyte with a polymer, wherein the electrolyte comprises 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 is less than 0.

33.

10. The manufacturing method according to claim 9, comprising: A diluent is mixed with the electrolyte and the polymer to obtain a solution, and the electrolyte and the polymer are composited by removing the diluent from the solution.

Images