Solid electrolyte, electrode mixture, battery, and method for producing battery

Abstract

A main object of the present disclosure is to provide a solid electrolyte capable of suppressing an increase in battery resistance.SOLUTION: The breaking energy of a pellet having a length of 5mm in the X-axis direction, a length of 20mm in the Y-axis direction, and a length of 1mm in the Z-axis direction is 6.0 * 103kJ / m3 or more and 21.4 * 103kJ / m3 or less at a packing ratio of 100%.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a solid electrolyte, an electrode mixture, a battery, and a method for manufacturing the battery. [Background technology]

[0002] A battery typically includes 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. For example, Patent Document 1 discloses the production of an all-solid-state lithium battery using a negative electrode slurry containing a silicon-based active material, a sulfide solid electrolyte, styrene-butadiene rubber, and a dispersion solvent. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-125468 Summary of the Invention [Problem to be solved by the invention]

[0004] In batteries, the electrode active material layer may expand and contract during charging and discharging. Repeated charging and discharging may cause cracks in the electrode active material layer and the solid electrolyte layer, or peeling of the electrode active material layer and the solid electrolyte layer. Cracking and peeling can disrupt the ionic and electronic conduction paths, increasing battery resistance. Therefore, from the perspective of improving battery performance, it is necessary to suppress cracking and peeling and thus suppress increases in battery resistance.

[0005] The present disclosure has been made in view of the above circumstances, and has as its main object to provide a solid electrolyte that can suppress an increase in battery resistance. [Means for solving the problem]

[0006] [1] When molded into pellets with a length of 5 mm in the X-axis direction, 20 mm in the Y-axis direction, and 1 mm in the Z-axis direction, the fracture energy is 6.0 x 10 at a filling rate of 100%. 3 kJ / m 3 That's 21.4 x 10 3 kJ / m 3 The following is a solid electrolyte:

[0007] [2] When molded into pellets with a length of 5 mm in the X-axis direction, 20 mm in the Y-axis direction, and 1 mm in the Z-axis direction, the fracture energy is 6.0 x 10 at a filling rate of 100%. 3 kJ / m 3 That's all, It is used in an electrode mixture containing an electrode active material, The electrode active material is a solid electrolyte whose volume expansion rate upon charging and discharging is four times or less.

[0008] [3] The solid electrolyte according to [2], wherein the electrode active material is a positive electrode active material.

[0009] [4] The solid electrolyte according to any one of [1] to [3], wherein the solid electrolyte is a sulfide solid electrolyte.

[0010] [5] The sulfide solid electrolyte according to [4], which contains Li element, A element (A is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In), and S element.

[0011] [6] The sulfide solid electrolyte according to [4] or [5], wherein the sulfide solid electrolyte contains Li, P, and S elements.

[0012] [7] The sulfide solid electrolyte according to any one of [4] to [6], wherein the sulfide solid electrolyte contains a halogen element.

[0013] [8] An electrode mixture containing an electrode active material and a solid electrolyte, The solid electrolyte is the solid electrolyte according to any one of [1] to [7].

[0014] [9] A battery having a positive electrode active material layer, a negative electrode active material layer, and an electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer, A battery in which at least one of the positive electrode active material layer and the negative electrode active material layer contains the electrode mixture according to [8].

[0015]

[10] A battery having a positive electrode active material layer, a negative electrode active material layer, and an electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer, the positive electrode active material layer contains a positive electrode active material having a volume expansion rate due to charge and discharge of 4 times or less, and a first solid electrolyte; the negative electrode active material layer contains a negative electrode active material having a volume expansion rate of more than four times due to charge and discharge, and a second solid electrolyte; The first solid electrolyte has a fracture energy of 6.0×10 when molded into a pellet having a length of 5 mm in the X-axis direction, a length of 20 mm in the Y-axis direction, and a length of 1 mm in the Z-axis direction at a filling rate of 100%. 3 kJ / m 3 That's all, The battery, wherein the second solid electrolyte has a greater breaking energy when formed into the pellet than the first solid electrolyte.

[0016]

[11] A method for manufacturing a battery having a positive electrode active material layer, a negative electrode active material layer, and an electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer, the method comprising: a preparation step of preparing a laminate having the positive electrode active material layer, the negative electrode active material layer, and the electrolyte layer; a densification step of densifying the laminate by pressing; and at least one of the positive electrode active material layer and the negative electrode active material layer contains a solid electrolyte; The above solid electrolyte has a fracture energy of 6.0 × 10 when molded into a pellet with a length of 5 mm in the X-axis direction, a length of 20 mm in the Y-axis direction, and a length of 1 mm in the Z-axis direction at a filling rate of 100%. 3 kJ / m 3 That's all, In the densification step, the pressing is performed at a temperature of less than 135°C. [Effects of the Invention]

[0017] The present disclosure has the effect of suppressing an increase in battery resistance. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic perspective view illustrating a pellet according to the present disclosure. [Figure 2] FIG. 1 is a schematic cross-sectional view illustrating a battery according to the present disclosure. [Figure 3] 1 is a graph showing the relationship between breaking energy and battery resistance in Examples, Comparative Examples, and Reference Examples. DETAILED DESCRIPTION OF THE INVENTION

[0019] The solid electrolyte, electrode mixture, battery, and battery manufacturing method according to the present disclosure will be described in detail below.

[0020] A. Solid electrolyte As shown in FIG. 1, the solid electrolyte of the present disclosure has a fracture energy of 6.0×10 when molded into a pellet having a length of 5 mm in the X-axis direction, a length of 20 mm in the Y-axis direction, and a length of 1 mm in the Z-axis direction at a filling rate of 100%. 3 kJ / m 3 As an example of an embodiment of the solid electrolyte in the present disclosure, the breaking energy of the solid electrolyte is 21.4 × 10 3 kJ / m 3In another example of an embodiment of the solid electrolyte according to the present disclosure, the solid electrolyte may be used in an electrode mixture containing an electrode active material. Furthermore, the electrode active material may have a volume expansion rate of 4 times or less upon charge and discharge.

[0021] According to the present disclosure, the fracture energy when pelletized to a predetermined size is within a predetermined range, and the solid electrolyte has high adhesion (bonding strength), so it is believed that even if the electrode active material layer expands and contracts due to charging and discharging of the battery, cracking or peeling of the electrode active material layer and the solid electrolyte layer can be suppressed. As a result, good ion conduction paths and electron conduction paths can be maintained, and an increase in battery resistance can be suppressed.

[0022] The fracture energy is 6.3 × 10 at a filling rate (filling rate of solid electrolyte in the pellet) of 100%. 3 kJ / m 3 It may be 8.0 x 10 or more. 3 kJ / m 3 It may be 10.0 x 10 or more. 3 kJ / m 3 On the other hand, the breaking energy may be, for example, 75.0×10 3 kJ / m 3 is less than or equal to 67.9 x 10 3 kJ / m 3 The breaking energy may be 11.9×10 or less. 3 kJ / m 3 The breaking energy may be less than 100 wt %, and the breaking energy may be measured by the method described in the Examples. The breaking energy may be adjusted, for example, by the composition of the solid electrolyte, the degree of crystallinity of the solid electrolyte, and the particle size of the solid electrolyte.

[0023] The crystallinity of the solid electrolyte is, for example, 80% or less, or may be 70% or less, or may be 60% or less, or may be 50% or less. The lower the crystallinity of the solid electrolyte, the higher the breaking energy tends to be. On the other hand, the crystallinity is, for example, 5% or more, or may be 10% or more, or may be 30% or more. The crystallinity may be a value obtained by X-ray diffraction. Alternatively, the crystallinity may be a value obtained by differential scanning calorimetry (DSC).

[0024] The solid electrolyte preferably has high Li-ion conductivity. The Li-ion conductivity of the solid electrolyte at 25° C. is, for example, 1×10 -4 S / cm or more, 1×10 -3 The solid electrolyte preferably has high insulating properties. The electronic conductivity of the solid electrolyte at 25° C. is, for example, 10 -6 S / cm or less, 10 -8 S / cm or less, -10 The average particle diameter (D 50 ) is, for example, 0.1 μm or more and 50 μm or less. 50 ) refers to the cumulative 50% particle size in the volume-based particle size distribution measured by a laser diffraction particle size analyzer.

[0025] Examples of solid electrolytes include inorganic solid electrolytes such as sulfide solid electrolytes, oxide solid electrolytes, and nitride solid electrolytes, as well as organic solid electrolytes such as polymer electrolytes. Among these, sulfide solid electrolytes are preferred because of their high Li-ion conductivity.

[0026] The sulfide solid electrolyte preferably contains sulfur (S) as the main anion element, the oxide solid electrolyte preferably contains oxygen (O) as the main anion element, and the nitride solid electrolyte preferably contains nitrogen (N) as the main anion element.

[0027] The sulfide solid electrolyte preferably contains, for example, Li, A (A is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In), and S. The sulfide solid electrolyte may further contain at least one of O and a halogen element. Examples of halogen elements include F, Cl, Br, and I.

[0028] Sulfide solid electrolytes have an anion structure with an ortho-composition (e.g., PS4 3- Structure, SiS4 4- Structure, GeS4 4- Structure, AlS3 3- Structure or BS3 3- It is preferable that the anion structure has an ortho-composition (ortho-structure) as the main component of the anion structure, because this has high chemical stability. The proportion of the anion structure with an ortho-composition is, for example, 70 mol % or more, and may be 90 mol % or more, based on the total anion structures in the sulfide solid electrolyte.

[0029] The sulfide solid electrolyte may have a crystalline phase, such as a Thio-LISICON-type crystalline phase, an LGPS-type crystalline phase, or an Argyrodite-type crystalline phase.

[0030] The composition of the sulfide solid electrolyte is not particularly limited, but examples include xLiS·(100-x)P2S5 (70≦x≦80), yLiI·zLiBr·(100-yz)(xLiS·(1-x)P2S5) (0.7≦x≦0.8, 0≦y≦30, 0≦z≦30).

[0031] The sulfide solid electrolyte has the general formula: Li 4-x Ge 1-x P xIt may have a composition represented by S4(0 < x < 1). In the above general formula, at least a part of Ge may be substituted with 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 may be substituted with 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 may be substituted with at least one of Na, K, Mg, Ca, and Zn. In the above general formula, a part of S may be substituted with a halogen (at least one of F, Cl, Br, and I).

[0032] The sulfide solid electrolyte is, for example, 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 or more to 2 or less). a may be 0, or may be greater than 0. In the latter case, a may be 0.1 or more, may be 0.5 or more, or may be 1 or more. Also, a may be 1.8 or less, or may be 1.5 or less.

[0033] Examples of the oxide solid electrolyte include perovskite-type solid electrolytes such as (Li,La)TiO3. Examples of the nitride solid electrolyte include, for example, Li3N, Li3N-LiI-LiOH. Also, examples of the polymer electrolyte include polyethylene oxide (PEO) and polypropylene oxide (PPO).

[0034] The solid electrolyte in the present disclosure may be used in an electrode mixture containing an electrode active material. The electrode mixture may be a positive electrode active material or a negative electrode active material. Details of the electrode mixture will be described in "B. Electrode Mixture" described later. On the other hand, the solid electrolyte in the present disclosure may be used in the electrolyte layer of a battery. The electrolyte layer will be described in "C. Battery" described later.

[0035] B. Electrode Mixture The electrode mixture in the present disclosure contains an electrode active material and the above-described solid electrolyte.

[0036] According to the present disclosure, by using the above-described solid electrolyte, an electrode mixture that can suppress an increase in battery resistance is obtained.

[0037] The electrode active material may have a volume expansion rate upon charging and discharging of 4 times or less. For example, oxide active materials (e.g., NCM, NCA) useful as positive electrode active materials have a volume expansion rate of less than 1.1 times upon charging and discharging, graphite useful as negative electrode active materials has a volume expansion rate of about 1.1 times upon charging and discharging, and silicon useful as negative electrode active materials has a volume expansion rate of more than 4 times upon charging. The volume expansion rate upon charging and discharging can be determined by space-group-independent evaluation, as described in "Simon Schweidler et al., 'Volume Changes of Graphite Anodes Revisited: A Combined Operando X-ray Diffraction and In Situ Pressure Analysis Study,' J. Phys. Chem. C 2018, 122, 16, 8829-8835." The electrode active material may have a volume expansion rate due to charging and discharging of 3 times or less, a volume expansion rate due to charging and discharging of 2 times or less, a volume expansion rate due to charging and discharging of 1.5 times or less, or a volume expansion rate due to charging of 1.2 times or less. Note that the positive electrode active material typically contracts in volume during charging and expands in volume during discharging. On the other hand, the negative electrode active material typically expands in volume during charging and contracts in volume during discharging.

[0038] The electrode mixture in the present disclosure may be a positive electrode mixture containing a positive electrode active material as the electrode active material, or may be a negative electrode mixture containing a negative electrode active material as the electrode active material.

[0039] The positive electrode active material may be, for example, an oxide active material. Examples of the oxide active material include a rock salt layered active material, a spinel active material, and an olivine active material. An example of the rock salt layered active material is an active material containing Li, Ni, Co, Mn, and O elements (NCM-based active material). Examples of the NCM-based active material include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2. Other examples of rock salt layered active materials include active materials containing Li, Ni, Co, Al and O elements (NCA-based active materials). Examples of NCA-based active materials include LiNi 0.8 Co 0.15 Mn 0.05 Examples of the positive electrode active material include LiMn2O4, LiFePO4, and sulfur (S).

[0040] Examples of negative electrode active materials include Li-based active materials such as metallic lithium and lithium alloys; carbon-based active materials such as graphite, hard carbon, and soft carbon; oxide-based active materials such as lithium titanate; and Si-based active materials.

[0041] The electrode active material may be in the form of particles, for example. 50 ) is, for example, 10 nm or more, and may be 100 nm or more. On the other hand, the average particle diameter (D 50 ) is, for example, 50 μm or less, and may be 20 μm or less.

[0042] The solid content of the electrode active material in the electrode mixture is, for example, 50% by volume or more, or alternatively, 60% by volume or more, or 70% by volume or more, while the solid content of the electrode active material in the electrode mixture is, for example, 90% by volume or less.

[0043] The electrode mixture contains a solid electrolyte. The solid electrolyte is as described in "A. Solid Electrolyte." The solid content of the solid electrolyte in the electrode mixture is, for example, 20% by mass or more, or may be 30% by volume or more, or may be 40% by volume or more. On the other hand, the solid content of the solid electrolyte in the electrode mixture is, for example, 50% by volume or less.

[0044] The electrode mixture may contain at least one of a conductive additive and a binder, as necessary. Examples of the conductive additive include carbon materials. Examples of the carbon materials include particulate carbon materials such as acetylene black (AB) and ketjen black (KB), and fibrous carbon materials such as carbon fiber, carbon nanotubes (CNT), and carbon nanofibers (CNF).

[0045] Examples of binders include rubber-based binders such as butadiene rubber (BR), acrylate butadiene rubber (ABR), and styrene butadiene rubber (SBR), as well as fluorine-containing binders such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).

[0046] The electrode mixture may contain a liquid electrolyte (electrolytic solution) as an electrolyte. When the electrode mixture contains an electrolytic solution, the proportion of the electrolytic solution relative to the total electrolyte is, for example, 10 mass % or less. Examples of the electrolytic solution include conventionally known electrolytic solutions that can be used in lithium ion batteries.

[0047] C.Battery Fig. 2 is a schematic cross-sectional view illustrating a battery according to the present disclosure. The battery 10 shown in Fig. 2 has a positive electrode active material layer 1, a negative electrode active material layer 2, and an electrolyte layer 3 disposed between the positive electrode active material layer 1 and the negative electrode active material layer 2. At least one of the positive electrode active material layer 1 and the negative electrode active material layer 2 contains the above-described electrode mixture. As shown in Fig. 2, the battery 10 typically has a positive electrode current collector 4 that collects electrons from the positive electrode active material layer 1 and a negative electrode current collector 5 that collects electrons from the negative electrode active material layer 2.

[0048] According to the present disclosure, by using the above-described electrode mixture, a battery can be obtained that can suppress an increase in resistance.

[0049] 1.Cathode active material layer The positive electrode active material layer contains at least a positive electrode active material. The positive electrode active material layer may contain at least one of a conductive additive, a binder, and an electrolyte, as necessary. In particular, the positive electrode active material layer preferably contains the electrode mixture described above in "B. Electrode Mixture." The thickness of the positive electrode active material layer is not particularly limited, but is, for example, 0.1 μm or more and 1000 μm or less.

[0050] 2.Negative electrode active material layer The negative electrode active material layer contains at least a negative electrode active material. The negative electrode active material layer may contain at least one of a conductive additive, a binder, and an electrolyte, as necessary. In particular, the negative electrode active material layer preferably contains the electrode mixture described above in "B. Electrode Mixture." The thickness of the negative electrode active material layer is not particularly limited, but is, for example, 0.1 μm or more and 1000 μm or less.

[0051] 3. Electrolyte layer The electrolyte layer contains at least an electrolyte. The electrolyte layer may contain a solid electrolyte. The type of solid electrolyte is not particularly limited, and for example, the solid electrolytes described above in "A. Solid Electrolyte" can be used. The electrolyte layer may contain a binder as needed. The binder is as described above. On the other hand, the electrolyte layer may contain a liquid electrolyte (electrolytic solution) as the electrolyte. Furthermore, the electrolyte layer may contain only a solid electrolyte, or may contain both a solid electrolyte and a liquid electrolyte, or may contain only a liquid electrolyte. Furthermore, the thickness of the electrolyte layer is not particularly limited, and is, for example, 0.1 μm or more and 1000 μm or less.

[0052] The present disclosure can also provide a battery having a positive electrode active material layer, a negative electrode active material layer, and an electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer, wherein the positive electrode active material layer electrolyte layer contains the solid electrolyte described above in "A. Solid Electrolyte".

[0053] 4. Positive and negative electrode current collectors Examples of materials for the positive electrode current collector include metals such as aluminum, SUS, nickel, etc. Examples of materials for the negative electrode current collector include metals such as copper, SUS, nickel, etc. Examples of shapes for the positive electrode current collector and the negative electrode current collector include foil and mesh shapes.

[0054] 5.Battery The battery according to the present disclosure may include an exterior body that houses the above-mentioned components. Examples of the exterior body include a laminate-type exterior body and a case-type exterior body. The battery according to the present disclosure may also include a restraining jig that applies a restraining pressure in the thickness direction to the above-mentioned components. A known jig can be used as the restraining jig. The restraining pressure may be, for example, 0.1 MPa or more and 50 MPa or less, or 1 MPa or more and 20 MPa or less.

[0055] The type of battery in the present disclosure is not particularly limited, but is typically a lithium-ion secondary battery. The use of the battery is not particularly limited, but examples include power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), electric vehicles (BEVs), gasoline-powered vehicles, and diesel-powered vehicles. In particular, it is preferable to use the battery as a driving power source for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or electric vehicles (BEVs). The battery in the present disclosure may also be used as a power source for mobile objects other than vehicles (e.g., railways, ships, and aircraft), or as a power source for electrical appliances such as information processing devices.

[0056] The present disclosure provides a battery having a positive electrode active material layer, a negative electrode active material layer, and an electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer, wherein the positive electrode active material layer contains a positive electrode active material having a volume expansion rate due to charge and discharge of 4 times or less, and a first solid electrolyte, and the negative electrode active material layer contains a negative electrode active material having a volume expansion rate due to charge and discharge of more than 4 times, and a second solid electrolyte, and the first solid electrolyte has a breaking energy of 6.0 × 10 when molded into a pellet having a length of 5 mm in the X-axis direction, a length of 20 mm in the Y-axis direction, and a length of 1 mm in the Z-axis direction at a packing ratio of 100%. 3 kJ / m 3 As described above, a battery can be provided in which the second solid electrolyte has a greater breaking energy when molded into the pellet than the first solid electrolyte.

[0057] Details of the first solid electrolyte and the second solid electrolyte are the same as those described above in "A. Solid Electrolytes." The ratio of the fracture energy of the second solid electrolyte to the fracture energy of the first solid electrolyte is, for example, 1.2 times or more, or may be 1.5 times or more, or 2.0 times or more, or may be 3.0 times or more. The fracture energy of the second solid electrolyte is 34.2 × 10 3 kJ / m 3 It may be 51.3 x 10 or more. 3 kJ / m 3 It may be more than that.

[0058] D. Battery manufacturing method The method for manufacturing a battery according to the present disclosure includes a positive electrode active material layer, a negative electrode active material layer, and an electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer, and includes a preparation step of preparing a laminate including the positive electrode active material layer, the negative electrode active material layer, and the electrolyte layer, and a densification step of densifying the laminate by pressing. The method further includes a step of forming a pellet having a length of 5 mm in the X-axis direction, a length of 20 mm in the Y-axis direction, and a length of 1 mm in the Z-axis direction, and the breakage energy of the pellet is 6.0×10 at a packing density of 100%. 3 kJ / m 3 In the densification step, pressing is carried out at a temperature of less than 135°C.

[0059] According to the present disclosure, by using the above-described solid electrolyte, a battery can be obtained that can suppress an increase in resistance even when densified at a low temperature.

[0060] 1. Preparation process The preparation step in the present disclosure is a step of preparing a laminate having a positive electrode active material layer, a negative electrode active material layer, and an electrolyte layer.

[0061] At least one of the positive electrode active material layer and the negative electrode active material layer contains a solid electrolyte. The solid electrolyte has a breaking energy of 6.0×10 when molded into a pellet having a length of 5 mm in the X-axis direction, a length of 20 mm in the Y-axis direction, and a length of 1 mm in the Z-axis direction at a packing ratio of 100%. 3 kJ / m 3 The details of the solid electrolyte are the same as those described in "A. Solid Electrolyte."

[0062] The method for preparing the laminate is not particularly limited, but examples include a method in which a positive electrode having a positive electrode current collector and a positive electrode active material layer, a negative electrode having a negative electrode current collector and a negative electrode active material layer, and an electrolyte layer containing a solid electrolyte are prepared, and the electrolyte layer is disposed between the positive electrode and the negative electrode. Examples of methods for preparing the positive electrode include a method in which a positive electrode composite containing a dispersion medium is applied to a positive electrode current collector and then dried. Examples of methods for preparing the negative electrode include a method in which a negative electrode composite containing a dispersion medium is applied to a negative electrode current collector and then dried. Examples of methods for preparing the electrolyte layer include a method in which a composite for the electrolyte layer containing a dispersion medium is applied to a substrate and then dried.

[0063] 2. Densification process The densification step in the present disclosure is a step of densifying the laminate by pressing. In the densification step, pressing is performed at a temperature of less than 135°C.

[0064] The temperature during pressing may be 130°C or lower, 110°C or lower, 100°C or lower, 50°C or lower, or 40°C or lower. Alternatively, pressing may be performed at room temperature without heating. On the other hand, when heating is performed during pressing, the heating method is not particularly limited, and examples include a method of heating the press.

[0065] Examples of pressing methods include roll pressing and plate pressing. The pressure during pressing is not particularly limited, but when applying a linear pressure, it may be, for example, 1.0 ton / cm or more and 10.0 ton / cm or less, or 1.5 ton / cm or more and 6.0 ton / cm or less. When applying a surface pressure, the pressure during pressing is, for example, 800 MPa or more and 2000 MPa or less.

[0066] 3.Battery The battery is the same as described in "C. Battery." The present disclosure also provides a method for manufacturing a battery having a positive electrode active material layer, a negative electrode active material layer, and an electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer, the method comprising: a preparation step of preparing a laminate having the positive electrode active material layer, the negative electrode active material layer, and the electrolyte layer; and a densification step of densifying the laminate by pressing, the electrolyte layer containing a solid electrolyte, and the solid electrolyte having a breaking energy of 6.0 × 10 when molded into a pellet having a length of 5 mm in the X-axis direction, a length of 20 mm in the Y-axis direction, and a length of 1 mm in the Z-axis direction at a packing ratio of 100%. 3 kJ / m 3 As described above, a battery manufacturing method can also be provided in which, in the densification step, the pressing is performed at a temperature of less than 135° C. Details of the solid electrolyte and the pressing conditions are as described above.

[0067] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea described in the claims of the present disclosure and that provides similar effects is included within the technical scope of the present disclosure. [Example]

[0068] [Preparation of sulfide solid electrolyte A] A raw material composition was obtained by mixing Li2S, P2S5, LiI, and LiBr. This raw material composition and tetrahydrofuran in a mass ratio of 20 times that of the raw material composition were placed in a glass container and stirred at 25°C for 72 hours. The precipitate was then recovered as a precursor of a sulfide solid electrolyte. The recovered precursor was dried at 25°C under an argon atmosphere and then fired at 100°C for 1 hour under atmospheric pressure. The resulting fired body was vacuum-sealed in a quartz tube, which was then placed in a muffle furnace and fired at 140°C for 5 hours. This yielded sulfide solid electrolyte A (a LiBr-LiI-Li3PS4-based sulfide solid electrolyte).

[0069] [Preparation of sulfide solid electrolytes B to E] Sulfide solid electrolytes B to E were produced in the same manner as sulfide solid electrolyte A, except that the firing temperature in the muffle furnace was changed as shown in Table 1.

[0070] [Preparation of sulfide solid electrolyte F] A raw material composition was obtained by mixing Li2S, P2S5, LiBr, and LiCl. This raw material composition and tetrahydrofuran in a mass ratio of 20 times that of the raw material composition were placed in a glass container and stirred at 25°C for 72 hours. The precipitate was then recovered as a precursor of a sulfide solid electrolyte. The recovered precursor was dried at 25°C under an argon atmosphere and then fired at 100°C for 1 hour under atmospheric pressure. The resulting fired body was vacuum-sealed in a quartz tube, which was then placed in a muffle furnace and fired at 550°C for 5 hours. This resulted in a sulfide solid electrolyte F (a sulfide solid electrolyte having an argyrodite-type crystal phase).

[0071] [Preparation of sulfide solid electrolyte G] Sulfide solid electrolyte G was prepared in the same manner as sulfide solid electrolyte F, except that the firing temperature in the muffle furnace was changed as shown in Table 1. [Measurement of breaking energy] The fracture energy of sulfide solid electrolytes A to G was measured. Specifically, 0.2 g of sulfide solid electrolyte was sampled and pressed at 5 kN, 20 kN, and 35 kN using a press jig to form pellets as shown in Figure 1. The three pellets obtained were subjected to a bending test using a TENSIRON (manufactured by A&D Co., Ltd.). The bending test was performed in TENSIRON compression mode at 0.05 mm / min. The fracture energy was calculated by integrating the stress-strain curve created based on the stress (bending stress) and strain (bending strain) obtained from the bending test. The results are shown in Table 1. The stress was calculated using the following formula (1), and the strain was calculated using the following formula (2).

[0072]

number

[0073]

number

[0074] The fracture energy shown in Table 1 is the fracture energy for a pellet with a sulfide solid electrolyte filling rate of 100%, obtained based on a calibration curve. The calibration curves for the filling rate and fracture energy were created by producing the three pellets described above and performing the bending test on the three pellets.

[0075] [Table 1]

[0076] [Example 1] An all-solid-state battery was fabricated as follows using sulfide solid electrolyte A in the positive electrode active material layer: The design capacity of the all-solid-state battery was 0.3 Ah.

[0077] Cathode active material (LiNi 1 / 3 Co 1 / 3 Mn 1 / 380.0 g of O2), 9.51 g of sulfide solid electrolyte A, and 2.5 g of conductive additive (VGCF) were placed in a FILMICS container. Then, a solution containing styrene butadiene rubber as a binder (the binder concentration in the solution was 5% by mass relative to the total solution) and 32.21 g of solvent (tetralin) were added to the FILMICS container. This resulted in a positive electrode raw material composition with a solids concentration of 69% by mass. The raw material composition was kneaded using a kneading device (FILMICS) to obtain an electrode composition for the positive electrode. The electrode composition was applied in the form of a film to the surface of a positive electrode current collector (aluminum foil) using a blade coating method with an applicator, and the film-like electrode composition was heated at 100°C for 30 minutes. This resulted in a positive electrode having a positive electrode current collector and a positive electrode active material layer.

[0078] 18.6 g of negative electrode active material (simple Si), 8.69 g of Li2S-P2S5-based sulfide solid electrolyte, a solution containing styrene butadiene rubber as a binder (the binder concentration in the solution was 5% by mass relative to the total solution), and a solvent (diisobutyl ketone) were added to a Filmix container. This resulted in a negative electrode raw material composition with a solids concentration of 43% by mass. The raw material composition was kneaded using a kneading device (Filmix) to obtain an electrode composition for the negative electrode. A high-shear PC wheel was used for the Filmix. The electrode composition was applied in the form of a film to the surface of a negative electrode current collector (nickel foil) using a blade coating method with an applicator, and the film-like electrode composition was heated at 100°C for 30 minutes. This resulted in a negative electrode having a negative electrode current collector and a negative electrode active material layer.

[0079] 40 g of a Li2S-P2S5-based sulfide solid electrolyte, 8.00 g of a solution containing acrylate butadiene rubber and hexane (the concentration of the acrylate butadiene rubber in the solution was 5% by mass relative to the total solution), 25.62 g of heptane, and 8.00 g of dibutyl ether were mixed and kneaded using an ultrasonic homogenizer. This yielded a solid electrolyte layer composition. The solid electrolyte layer composition was applied to the surface of aluminum foil in the form of a film using a blade coating method with an applicator, and the film-like solid electrolyte layer composition was heated at 100°C for 30 minutes. This yielded a transfer member having a substrate (aluminum foil) and a solid electrolyte layer.

[0080] The negative electrode and the transfer member were stacked so that the negative electrode active material layer and the solid electrolyte layer faced each other, and pressed at 20 kN. The aluminum foil was then peeled off, and the solid electrolyte layer was transferred onto the negative electrode active material layer. The positive electrode was then stacked so that the solid electrolyte layer and the positive electrode active material layer faced each other, and pressed at 20 kN. This resulted in a laminate having a negative electrode, a solid electrolyte layer, and a positive electrode in this order. This laminate was densified at 25°C and 2.5 ton / cm, and then sealed with a laminate to produce an all-solid-state battery. The produced battery was constrained at 5 MPa using a restraining jig.

[0081] [Examples 2 to 5 and Comparative Examples 1 and 2] All-solid-state batteries were fabricated in the same manner as in Example 1, except that the sulfide solid electrolyte A used in the positive electrode active material layer was changed to sulfide solid electrolytes B to G as shown in Table 2.

[0082] [Example 6] An all-solid-state battery was fabricated in the same manner as in Example 1, except that the densification conditions were changed to 100°C and 2.5 ton / cm.

[0083] [Examples 7 to 10 and Comparative Examples 3 and 4] All-solid-state batteries were fabricated in the same manner as in Example 6, except that the sulfide solid electrolyte A used in the positive electrode active material layer was changed to sulfide solid electrolytes B to G as shown in Table 2.

[0084] [Reference example 1] An all-solid-state battery was fabricated in the same manner as in Example 1, except that the densification conditions were changed to 135°C and 2.5 ton / cm.

[0085] [Reference examples 2~7] All-solid-state batteries were fabricated in the same manner as in Reference Example 1, except that the sulfide solid electrolyte A used in the positive electrode active material layer was changed to sulfide solid electrolytes B to G as shown in Table 3.

[0086] [Reference example 8] An all-solid-state battery was fabricated in the same manner as in Example 1, except that the densification conditions were changed to 170°C and 2.5 ton / cm.

[0087] [Reference examples 9-14] All-solid-state batteries were fabricated in the same manner as in Reference Example 8, except that the sulfide solid electrolyte A used in the positive electrode active material layer was changed to sulfide solid electrolytes B to G as shown in Table 3.

[0088] [evaluation] A charge-discharge test was conducted on each of the obtained all-solid-state batteries. The test conditions were CCCV charge-discharge with an upper limit voltage of 4.05 V and a lower limit voltage of 2.5 V, 0.1 C, and 4 cycles. The battery resistance after 4 cycles was measured. The results are shown in Tables 2 and 3. The relationship between the fracture energy and battery resistance is also shown in Figure 3.

[0089] [Table 2]

[0090] [Table 3]

[0091] As shown in Table 2 and FIG. 3, Examples 1 to 5 had lower battery resistance than Comparative Examples 1 and 2. Furthermore, in Examples 1 to 5, the greater the fracture energy of the sulfide solid electrolyte, the more improved the adhesion (bonding strength) of the sulfide solid electrolyte, the more suppressed the occurrence of cracks in the positive electrode active material layer, and the lower the battery resistance. Similarly, as shown in Table 3 and FIG. 3, Examples 6 to 10 had lower battery resistance than Comparative Examples 3 and 4. Furthermore, in Examples 6 to 10, the greater the fracture energy of the sulfide solid electrolyte, the more improved the adhesion (bonding strength) of the sulfide solid electrolyte, the more suppressed the occurrence of cracks in the positive electrode active material layer, and the lower the battery resistance.

[0092] On the other hand, similar battery resistances were obtained regardless of the fracture energy of the sulfide solid electrolyte in Reference Examples 1 to 14. In contrast, Examples 1 to 5 and 6 to 10 were able to reduce the battery resistance compared to Reference Examples 1 to 14, despite the fact that the densification temperature was lower.

[0093] [Preparation of sulfide solid electrolytes H to K] Sulfide solid electrolytes H to K were prepared in the same manner as sulfide solid electrolyte A, except that the firing temperature in the muffle furnace was changed as shown in Table 4. The fracture energy of the prepared sulfide solid electrolytes H to K was measured in the same manner as above. The results are shown in Table 4.

[0094] [Reference example 15] An all-solid-state battery was fabricated as follows using sulfide solid electrolyte H as the negative electrode active material layer. The design capacity of the all-solid-state battery was 0.3 Ah.

[0095] 18.6 g of negative electrode active material (simple Si), 8.69 g of sulfide solid electrolyte H, a solution containing styrene butadiene rubber as a binder (the binder concentration in the solution was 5% by mass relative to the total solution), and a solvent (diisobutyl ketone) were added to a Filmix container. This resulted in a negative electrode raw material composition with a solids concentration of 43% by mass. The raw material composition was kneaded using a kneading device (Filmix) to obtain an electrode composition for the negative electrode. A high-shear PC wheel was used for the Filmix. The electrode composition was applied in the form of a film to the surface of a negative electrode current collector (nickel foil) using a blade coating method with an applicator, and the film-like electrode composition was heated at 100°C for 30 minutes. This resulted in a negative electrode having a negative electrode current collector and a negative electrode active material layer.

[0096] Cathode active material (LiNi 1 / 3 Co 1 / 3 Mn 1 / 380.0 g of O2), 9.51 g of a Li2S-P2S5-based sulfide solid electrolyte, and 2.5 g of a conductive additive (VGCF) were placed in a FILMICS container. Then, a solution containing styrene-butadiene rubber as a binder (the binder concentration in the solution was 5% by mass relative to the total solution) and 32.21 g of a solvent (tetralin) were added to the FILMICS container. This resulted in a positive electrode raw material composition with a solids concentration of 69% by mass. The raw material composition was kneaded using a kneading device (FILMICS) to obtain an electrode composition for the positive electrode. The electrode composition was applied in the form of a film to the surface of a positive electrode current collector (aluminum foil) using a blade coating method with an applicator, and the film-like electrode composition was heated at 100°C for 30 minutes. This resulted in a positive electrode having a positive electrode current collector and a positive electrode active material layer.

[0097] 40 g of a Li2S-P2S5-based sulfide solid electrolyte, 8.00 g of a solution containing acrylate butadiene rubber and hexane (the concentration of the acrylate butadiene rubber in the solution was 5% by mass relative to the total solution), 25.62 g of heptane, and 8.00 g of dibutyl ether were mixed and kneaded using an ultrasonic homogenizer. This yielded a solid electrolyte layer composition. The solid electrolyte layer composition was applied to the surface of aluminum foil in the form of a film using a blade coating method with an applicator, and the film-like solid electrolyte layer composition was heated at 100°C for 30 minutes. This yielded a transfer member having a substrate (aluminum foil) and a solid electrolyte layer.

[0098] The negative electrode and transfer member were placed together so that the negative electrode active material layer and the solid electrolyte layer faced each other, and pressed at 20 kN. The aluminum foil was then peeled off, and the solid electrolyte layer was transferred onto the negative electrode active material layer. The positive electrode was then placed together so that the solid electrolyte layer and the positive electrode active material layer faced each other, and pressed at 20 kN. This resulted in a laminate having a negative electrode, a solid electrolyte layer, and a positive electrode in this order. This laminate was densified at 170°C and 4 ton / cm, and then sealed with a laminate to produce an all-solid-state battery. The produced battery was constrained at 5 MPa using a restraining jig.

[0099] [Reference examples 16-18] All-solid-state batteries were fabricated in the same manner as in Reference Example 15, except that the sulfide solid electrolyte H used in the negative electrode active material layer was changed to one of the sulfide solid electrolytes I to K as shown in Table 4.

[0100] [evaluation] A charge-discharge test was performed on each of the obtained all-solid-state batteries. The conditions for the charge-discharge test were CCCV charge-discharge with an upper limit voltage of 4.55 V and a lower limit voltage of 2.5 V, 0.1 C, and 1000 cycles. The battery resistance after 1000 cycles was measured. The results are shown in Table 4.

[0101] [Table 4]

[0102] As shown in Reference Examples 15 to 18, even when a battery using Si, which undergoes a large volume change due to charge and discharge, as the negative electrode active material was subjected to 1000 charge and discharge cycles, the battery resistance could be maintained low. [Explanation of symbols]

[0103] 1...Cathode active material layer 2...Negative electrode active material layer 3...electrolyte layer 4...Positive electrode current collector 5...Negative electrode current collector 10...battery

Claims

1. When molded into pellets with a length of 5 mm in the X-axis direction, a length of 20 mm in the Y-axis direction, and a length of 1 mm in the Z-axis direction, the fracture energy is 6.0 × 10 at a filling rate of 100%. ３ kJ / m ３ That's it, 21.4 x 10 ３ kJ / m ３ The following is a solid electrolyte:

2. When molded into pellets with a length of 5 mm in the X-axis direction, a length of 20 mm in the Y-axis direction, and a length of 1 mm in the Z-axis direction, the fracture energy is 6.0 × 10 at a filling rate of 100%. ３ kJ / m ３ That's all, It is used in an electrode mixture containing an electrode active material, The electrode active material is a solid electrolyte whose volume expansion rate upon charging and discharging is 4 times or less.

3. The solid electrolyte according to claim 2 , wherein the electrode active material is a positive electrode active material.

4. 3. The solid electrolyte according to claim 1, wherein the solid electrolyte is a sulfide solid electrolyte.

5. 5. The solid electrolyte according to claim 4, wherein the sulfide solid electrolyte contains a Li element, an A element (A is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In), and an S element.

6. The solid electrolyte according to claim 4 , wherein the sulfide solid electrolyte contains Li, P, and S elements.

7. The solid electrolyte according to claim 6 , wherein the sulfide solid electrolyte contains a halogen element.

8. An electrode mixture containing an electrode active material and a solid electrolyte, An electrode mixture, wherein the solid electrolyte is the solid electrolyte according to claim 1 or 2.

9. A battery having a positive electrode active material layer, a negative electrode active material layer, and an electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer, A battery, wherein at least one of the positive electrode active material layer and the negative electrode active material layer contains the electrode mixture according to claim 8 .

10. A battery having a positive electrode active material layer, a negative electrode active material layer, and an electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer, the positive electrode active material layer contains a positive electrode active material having a volume expansion rate due to charge and discharge of 4 times or less and a first solid electrolyte; the negative electrode active material layer contains a negative electrode active material having a volume expansion rate of more than four times due to charge and discharge, and a second solid electrolyte; The first solid electrolyte has a fracture energy of 6.0×10 when molded into a pellet having a length of 5 mm in the X-axis direction, a length of 20 mm in the Y-axis direction, and a length of 1 mm in the Z-axis direction at a packing rate of 100%. ３ kJ / m ３ That's all, The second solid electrolyte has a greater breaking energy when formed into the pellet than the first solid electrolyte.

11. A method for manufacturing a battery having a positive electrode active material layer, a negative electrode active material layer, and an electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer, the method comprising: a preparation step of preparing a laminate including the positive electrode active material layer, the negative electrode active material layer, and the electrolyte layer; a densification step of densifying the laminate by pressing; and at least one of the positive electrode active material layer and the negative electrode active material layer contains a solid electrolyte; The solid electrolyte has a breaking energy of 6.0 × 10 when molded into a pellet having a length of 5 mm in the X-axis direction, a length of 20 mm in the Y-axis direction, and a length of 1 mm in the Z-axis direction at a packing rate of 100%. ３ kJ / m ３ That's all, The method for manufacturing a battery, wherein the pressing is performed at a temperature of less than 135°C in the densification step.

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