Method for manufacturing solid-state battery

Abstract

To provide a method for manufacturing a solid-state battery that can suppress the occurrence of abnormal electrodeposition and has favorable battery performance.SOLUTION: In a method for manufacturing a solid-state battery having an electrode stack in which an anode layer, an intermediate layer, a solid electrolyte layer, and a cathode layer are stacked in this order, the solid electrolyte layer includes a first solid electrolyte layer disposed on the anode layer side, a second solid electrolyte layer disposed adjacent to the first solid electrolyte layer, and a third solid electrolyte layer disposed on the cathode layer side, and the method includes Step 1, Step 2A, Step 3, and Step 4A.SELECTED DRAWING: Figure 2B

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a solid-state battery. [Background technology]

[0002] In recent years, research and development into secondary batteries that contribute to energy efficiency has been conducted to ensure that more people have access to affordable, reliable, sustainable and advanced energy.

[0003] Known examples of such secondary batteries include solid-state batteries such as lithium metal batteries and lithium ion secondary batteries, in which a solid electrolyte layer is disposed between a positive electrode layer and a negative electrode layer.

[0004] Known technology relating to solid-state batteries includes technology relating to all-solid-state batteries having a first solid electrolyte layer adjacent to a negative electrode and a second solid electrolyte layer located between the first solid electrolyte layer and a positive electrode, where the first solid electrolyte layer has a smaller Young's modulus than the second solid electrolyte layer (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-108202 Summary of the Invention [Problem to be solved by the invention]

[0006] The technology disclosed in Patent Document 1 aims to suppress deterioration of the interfacial contact between the solid electrolyte layer and the positive and negative electrode layers, and to suppress voltage drop during self-discharge. One method for reducing the Young's modulus of the first solid electrolyte layer is to relatively increase the binder content of the first solid electrolyte layer. However, because the binder acts as a resistor during the operation of the solid-state battery, it is not desirable to increase the binder content of the solid electrolyte layer.

[0007] One method for fabricating such a solid-state battery is to press the positive electrode layer and the negative electrode layer separately, and then sandwich the solid electrolyte layer between them and press them together to integrate them. However, if the pressing pressure during integration is too high, each layer may be damaged, so there is a practical upper limit to the pressing pressure during integration. As a result, the solid electrolyte layer may not be sufficiently densified at the interface between the negative electrode layer and the solid electrolyte layer. Furthermore, the negative electrode layer and the solid electrolyte layer may not be sufficiently adhered to each other. If the degree of densification and adhesion is insufficient, abnormal electrodeposition occurs, resulting in the problem of not being able to achieve the required battery performance.

[0008] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method for manufacturing a solid-state battery that can suppress the occurrence of abnormal electrodeposition and has favorable battery performance. [Means for solving the problem]

[0009] (1) The present invention provides a method for manufacturing a solid-state battery having an electrode laminate in which an anode layer, an intermediate layer, a solid electrolyte layer, and a cathode layer are laminated in this order, the solid electrolyte layer having a first solid electrolyte layer disposed on the anode layer side, a second solid electrolyte layer disposed adjacent to the first solid electrolyte layer, and a third solid electrolyte layer disposed on the cathode layer side, the method comprising: a first step of press-bonding the anode layer and the intermediate layer to obtain an intermediate layer-anode layer laminate; and a second step of press-bonding the first solid electrolyte layer to a surface of the intermediate layer in the intermediate layer-anode layer laminate. The present invention relates to a method for manufacturing a solid-state battery, the method comprising: a second step A of arranging and press-bonding materials constituting an electrolyte layer to obtain a solid electrolyte layer-intermediate layer-anode layer laminate; a third step B of arranging and press-bonding materials constituting the third solid electrolyte layer on the lamination surface of the cathode layer to obtain a solid electrolyte layer-cathode layer laminate; and a fourth step A of arranging and press-bonding the second solid electrolyte layer between the solid electrolyte layer-intermediate layer-anode layer laminate and the solid electrolyte layer-cathode layer laminate so as to face each solid electrolyte layer, to obtain an electrode laminate.

[0010] According to the invention (1), it is possible to provide a method for producing a solid-state battery that can suppress the occurrence of abnormal electrodeposition and has favorable battery performance.

[0011] (2) The method for producing a solid-state battery according to (1), wherein the pressing pressure in the step 2A is higher than the pressing pressure in the step 4A.

[0012] According to the invention (2), the first solid electrolyte layer can be densified, and each layer can be prevented from being damaged or excessively deformed.

[0013] (3) The method for producing a solid-state battery according to (1) or (2), wherein the pressing pressure in the step 2A is more than 500 MPa and not more than 700 MPa.

[0014] According to the invention (3), the first solid electrolyte layer can be reliably densified.

[0015] (4) The method for producing a solid state battery according to any one of (1) to (3), wherein the pressing pressure in the step 4A is 300 MPa or more and 500 MPa or less.

[0016] According to the invention (4), damage and excessive deformation of each layer can be reliably prevented.

[0017] (5) The method for producing a solid state battery according to any one of (1) to (4), wherein the pressing pressure in the third step is higher than the pressing pressure in the fourth step.

[0018] According to the fifth aspect of the present invention, the third solid electrolyte layer can be made denser, thereby improving the battery performance. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a conceptual cross-sectional view showing the configuration of a solid-state battery according to an embodiment of the present invention. [Figure 2A] 2A to 2C are diagrams illustrating some of the steps in a method for manufacturing a solid state battery according to a first embodiment of the present invention. [Figure 2B]2A to 2C are diagrams illustrating some of the steps in a method for manufacturing a solid state battery according to a first embodiment of the present invention. [Figure 2C] 1A to 1C are diagrams illustrating some steps in a method for manufacturing a solid-state battery according to each embodiment of the present invention. [Figure 2D] 2A to 2C are diagrams illustrating some of the steps in a method for manufacturing a solid state battery according to a first embodiment of the present invention. [Figure 3A] 1 is a graph showing charge / discharge curves of a solid-state battery according to an example of the present invention. [Figure 3B] 1 is a graph showing charge / discharge curves of a solid-state battery according to an example of the present invention. [Figure 4] 1 is a graph showing charge / discharge curves of a solid-state battery according to a comparative example of the present invention. [Figure 5] 1 is a graph showing the cross-sectional porosity of a solid electrolyte layer of a solid battery according to an example of the present invention. [Figure 6] 1 is a graph showing the average cross-sectional void size of the solid electrolyte layer of the solid state battery according to the example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] [Solid battery] As shown in Fig. 1, a solid state battery 1 manufactured by the manufacturing method according to the present invention has an electrode laminate in which an anode layer 2, a solid electrolyte layer 4, and a cathode layer 3 are laminated in this order. In this embodiment, the structure in which the anode layer 2, the solid electrolyte layer 4, the cathode layer 3, the solid electrolyte layer 4, and the anode layer 2 are laminated in this order as shown in Fig. 1 will be described as the laminate structure of the solid state battery 1. However, the structure of the solid state battery 1 is not limited to the above, and it is sufficient if the solid state battery 1 has a structure in which the solid electrolyte layer 4 is laminated between the anode layer 2 and the cathode layer 3.

[0021] The solid electrolyte layer 4 in the solid battery 1 has at least a first solid electrolyte layer 41 disposed on the anode layer 2 side, a second solid electrolyte layer 42 disposed adjacent to the first solid electrolyte layer 41, and a third solid electrolyte layer disposed on the cathode layer side. An intermediate layer 5 is disposed between the anode layer 2 and the solid electrolyte layer 4.

[0022] The solid state battery 1 is not particularly limited, but may be a lithium ion solid state secondary battery or a lithium metal secondary battery.

[0023] (negative electrode layer) The anode layer 2 has an anode active material layer 21 and an anode current collector layer 22. The anode active material layer 21 is not particularly limited and can be made of a material that can be used as an anode active material for a solid-state battery. The anode active material layer 21 is preferably a lithium metal layer in which the anode active material is lithium metal. This is because, in the solid-state battery 1 according to the present invention, even if the anode active material layer 21 is made of a hard metal, it can adhere to the solid electrolyte layer 4 with high adhesion. The lithium metal includes not only elemental lithium metal but also lithium alloys, etc. The anode active material layer 21 can also be made of silicon-based active materials such as Si and Si alloys, lithium titanate (Li4Ti5O 12 The electrode may be composed of lithium transition metal oxides such as TiO2, Nb2O3 and WO3, metal sulfides, metal nitrides, carbon materials such as graphite, soft carbon and hard carbon, metallic indium, etc.

[0024] The negative electrode active material layer 21 may contain materials that can be contained in a negative electrode active material layer of a solid-state battery in addition to the above. Examples of such materials include a solid electrolyte, a conductive additive, and a binder. Examples of the solid electrolyte include the same solid electrolyte contained in the solid electrolyte layer 4 described below. Examples of the conductive additive include carbon black, natural graphite, carbon fiber, and carbon nanotubes. Examples of the binder include a fluorine-based polymer, a nitrile-based polymer, a polyester-based polymer, an acrylic acid-based polymer, a cellulose-based polymer, a styrene-based polymer, a styrene-butadiene-based polymer, a vinyl acetate-based polymer, a urethane-based polymer, and a fluoroethylene-based polymer.

[0025] The negative electrode current collector layer 22 is not particularly limited, but may be made of copper, nickel, stainless steel, or the like. Examples of the shape of the negative electrode current collector layer 22 include foil, plate, mesh, nonwoven fabric, and foam. A portion of the negative electrode current collector layer 22 extends in a predetermined direction to form a negative electrode current collector tab 22a.

[0026] (Solid electrolyte layer) The solid electrolyte layer 4 is formed between the anode layer 2 and the cathode layer 3. In this embodiment, the solid electrolyte layer 4 has a structure in which a first solid electrolyte layer 41 disposed on the anode layer side, a second solid electrolyte layer 42, and a third solid electrolyte layer 43 disposed on the cathode side are stacked in this order.

[0027] The first solid electrolyte layer 41 is disposed on the anode layer side. The first solid electrolyte layer 41 may be disposed adjacent to the anode layer 2. When the solid battery 1 has an intermediate layer 5 as shown in FIG. 1, the first solid electrolyte layer 41 may be disposed adjacent to the intermediate layer 5. The first solid electrolyte layer 41 has a higher density than the second solid electrolyte layer 42 and is densified. During the densification process, the first solid electrolyte layer 41 adheres closely to the intermediate layer 5 or the anode layer 2. The densification of the first solid electrolyte layer 41 and its adhesion to the intermediate layer 5 or the anode layer 2 can suppress the occurrence of abnormal electrodeposition. Furthermore, favorable battery performance can be obtained.

[0028] The density of the first solid electrolyte layer 41 is 1.65 g / cm 3 It is preferable that the value is 1.80 / cm or more. 3 The density of the first solid electrolyte layer 41 is not particularly limited, but is preferably 2.00 / cm 3 or more. 3 It may be the following:

[0029] The solid electrolyte material constituting the first solid electrolyte layer 41 is not particularly limited, and may be any material that can be used as an electrolyte in a solid-state battery. Examples include inorganic solid electrolytes such as sulfide solid electrolyte materials, oxide solid electrolyte materials, halide solid electrolytes, and lithium-containing salts, and polymer solid electrolytes such as polyethylene oxide. The above solid electrolytes may be used alone or in combination of two or more.

[0030] The solid electrolyte material constituting the first solid electrolyte layer 41 is preferably in a particulate form. The particle size (D50, median diameter) of the solid electrolyte material constituting the first solid electrolyte layer 41 is preferably 1 μm or less. This allows the first solid electrolyte layer 41 to be easily densified. The particle size of the solid electrolyte material is more preferably 0.7 μm or less. The particle size of the solid electrolyte material is not particularly limited, but may be 50 nm or more.

[0031] The first solid electrolyte layer 41 may contain, in addition to the solid electrolyte material, a material that can be used in a solid electrolyte layer of a solid-state battery. For example, the first solid electrolyte layer 41 may contain a binder. The binder may be the same material as the binder that can be contained in the negative electrode active material layer 21. When the first solid electrolyte layer 41 contains a binder, the upper limit of the binder content is 25 mass % with respect to the total mass of the first solid electrolyte layer 41. The content of the binder is preferably 10 mass % or less, and more preferably 1.3 mass % or less. This allows the first solid electrolyte layer 41 to be easily densified and the energy density of the solid-state battery 1 to be improved. The content of the binder may be 0 mass %.

[0032] The thickness of the first solid electrolyte layer 41 (the length of each layer in the stacking direction) is preferably 7 μm or less. This allows the first solid electrolyte layer 41 to be easily densified. The thickness of the first solid electrolyte layer 41 is more preferably 3 μm or less. The thickness of the first solid electrolyte layer 41 is not particularly limited, but may be 1 μm or more.

[0033] The porosity of the first solid electrolyte layer 41 is preferably 7% or less. This can be said to increase the density of the first solid electrolyte layer 41. Furthermore, the efficiency of charge transfer within the first solid electrolyte layer 41 is improved. The porosity of the first solid electrolyte layer 41 is more preferably 4% or less. The porosity of the first solid electrolyte layer 41 is not particularly limited, but may be 1% or more.

[0034] The second solid electrolyte layer 42 is disposed adjacent to the first solid electrolyte layer 41. The second solid electrolyte layer 42 has a lower density than the first solid electrolyte layer 41. The solid electrolyte material constituting the second solid electrolyte layer 42 is not particularly limited and may be the same as the solid electrolyte material constituting the first solid electrolyte layer 41. The particle size of the solid electrolyte material constituting the second solid electrolyte layer 42 may be the same as or larger than that of the solid electrolyte material constituting the first solid electrolyte layer 41. Alternatively, a solid electrolyte material having the same particle size as that of the solid electrolyte material constituting the first solid electrolyte layer 41 may be combined with a solid electrolyte material having the larger particle size. This allows the second solid electrolyte layer 42 to be densified.

[0035] Like the first solid electrolyte layer 41, the second solid electrolyte layer 42 may contain a binder or the like in addition to the solid electrolyte material. The second solid electrolyte layer 42 may also contain a support. The support may be a three-dimensional structure such as a mesh, a woven fabric, a nonwoven fabric, an embossed body, a punched body, an expanded body, or a foamed body. The second solid electrolyte layer 42 may not contain the support.

[0036] The thickness of the second solid electrolyte layer 42 (the length of each layer in the stacking direction) is not particularly limited, but can be, for example, 5 to 50 μm.

[0037] The third solid electrolyte layer 43 is disposed on the positive electrode layer side. In this embodiment, the third solid electrolyte layer 43 is disposed adjacent to the positive electrode active material layer 31 in the positive electrode layer 3. The third solid electrolyte layer 43 is disposed adjacent to the second solid electrolyte layer 42. That is, in this embodiment, the third solid electrolyte layer 43 is disposed between the positive electrode active material layer 31 and the second solid electrolyte layer 42.

[0038] The configuration of the third solid electrolyte layer 43 can be the same as the configuration of the first solid electrolyte layer 41. The third solid electrolyte layer 43 is densified and adheres closely to the positive electrode active material layer 31, thereby achieving favorable battery performance. For example, low resistance is an example of favorable battery performance.

[0039] (positive electrode layer) The positive electrode layer 3 has a positive electrode active material layer 31 and a positive electrode current collector layer 32. In this embodiment, the positive electrode layer 3 has a configuration in which two positive electrode active material layers 31 are stacked on both sides of one positive electrode current collector layer 32. However, the configuration of the positive electrode layer 3 is not limited to the above, and the positive electrode layer 3 may have a configuration in which one positive electrode active material layer 31 is stacked on one side of one positive electrode current collector layer 32.

[0040] The positive electrode active material layer 31 is not particularly limited and can be made of a material that can be used as a positive electrode active material for a solid-state battery. Examples of the positive electrode active material that makes up the positive electrode active material layer 31 include LiCoO2, LiNiO2, LiCo x Ni y Mn z O2 (x+y+z=1), LiVO2, LiCrO2, etc., layered positive electrode active material particles, LiMn2O4, Li(Ni 0.25 Mn 0.75Examples of such positive electrode active materials include spinel-type positive electrode active materials such as LiCoPO, LiMnPO, and LiFePO; solid solution oxides (LiMnO-LiMO (M=Co, Ni, etc.)); conductive polymers such as polyaniline and polypyrrole; sulfides such as LiS, CuS, Li-Cu-S compounds, TiS, FeS, MoS, and Li-Mo-S compounds; and mixtures of sulfur and carbon. The positive electrode active material may be one of the above materials, or may be composed of two or more of the above materials.

[0041] An insulating frame 6 may be provided around the outer periphery of the positive electrode active material layer 31. The insulating frame 6 can prevent short circuits in the solid state battery 1 and improve its strength. In this embodiment, the insulating frame 6 is disposed so as to cover the side surfaces of the two positive electrode active material layers 31 formed on both sides of the positive electrode current collector layer 32. The insulating frame 6 also abuts against a portion of the stacking surface of the positive electrode current collector layer 32, and has a gap through which a positive electrode current collector tab 32a (described later) extends. The material for the insulating frame 6 is not particularly limited, but examples thereof include insulating oxides such as alumina, resins such as polyvinylidene fluoride (PVDF), and rubbers such as styrene-butadiene rubber (SBR).

[0042] The positive electrode current collector layer 32 is not particularly limited, and can be made of, for example, aluminum, stainless steel, conductive carbon (graphite, carbon nanotubes, etc.), etc. Examples of the shape of the positive electrode current collector layer 32 include foil, plate, mesh, nonwoven fabric, and foam. A portion of the positive electrode current collector layer 32 extends in a predetermined direction to form a positive electrode current collector tab 32a.

[0043] (middle class) The intermediate layer 5 is disposed between the anode layer 2 and the solid electrolyte layer 4. For example, when the solid battery 1 is a lithium metal battery, the intermediate layer 5 has the function of uniformly depositing lithium metal. Therefore, the interface between the intermediate layer 5 and the first solid electrolyte layer 41 is stabilized. When the solid battery 1 is a lithium metal secondary battery having the intermediate layer 5, the solid battery 1 may be an anode-free battery in which the anode active material layer 21 is not present during the initial charge. In this case, a lithium metal layer is formed as the anode active material layer 21 after the initial charge / discharge.

[0044] The material constituting the intermediate layer 5 is not particularly limited, and examples thereof include metals capable of forming an alloy with lithium and amorphous carbon. Examples of metals capable of forming an alloy with lithium include tin (Sn), silicon (Si), zinc (Zn), magnesium (Mg), gold (Au), platinum (Pt), palladium (Pd), silver (Ag), aluminum (Al), bismuth (Bi), and antimony (Sb). The metal capable of forming an alloy with lithium may be nanoparticles. Examples of amorphous carbon include carbon blacks such as acetylene black, furnace black, and ketjen black, coke, and activated carbon. The amorphous carbon may be graphitizable carbon (soft carbon), non-graphitizable carbon (hard carbon), CNT (carbon nanotube), fullerene, or graphene. The intermediate layer may contain a binder in addition to the above materials.

[0045] [Solid-state battery manufacturing method] First Embodiment A method for manufacturing a solid-state battery according to this embodiment will be described below with reference to FIGS. 2A to 2D. The method for manufacturing a solid-state battery according to this embodiment is a method for manufacturing a solid-state battery having an electrode laminate La in which an anode layer, an intermediate layer, a solid electrolyte layer, and a cathode layer are laminated in this order. The method for manufacturing a solid-state battery according to this embodiment includes the following steps 1, 2A, 3, and 4A. The steps can be performed in any order except that step 2A is performed after step 1, and step 4A is performed after steps 2A and 3.

[0046] 2A, the first step is a step of press-bonding the negative electrode layer 2 and the intermediate layer 5 to obtain an intermediate layer-negative electrode layer laminate L1. A specific method for disposing the intermediate layer 5 on the surface of the negative electrode layer 2 on the negative electrode active material layer 21 side, which is the lamination surface, is a method of transferring the intermediate layer using an intermediate layer transfer sheet. The intermediate layer transfer sheet can be obtained, for example, by dispersing the material constituting the intermediate layer 5 in a solvent, applying the resulting slurry to a support sheet, and drying the resulting slurry.

[0047] The pressure for pressing the negative electrode layer 2 and the intermediate layer 5 together in the first step is not particularly limited as long as the pressure does not excessively deform the negative electrode layer 2 and the intermediate layer 5 and allows them to be bonded together without peeling in a subsequent step. The pressing pressure in the first step is, for example, in the range of 300 MPa or more and 600 MPa or less.

[0048] As shown in FIG. 2B , step 2A is a step of placing a material constituting the first solid electrolyte layer 41 on the lamination surface of the intermediate layer 5 in the intermediate layer-anode layer laminate L1 and press-bonding them to obtain a solid electrolyte layer-intermediate layer-anode layer laminate L2. The first solid electrolyte layer 41 may be placed on the lamination surface of the intermediate layer 5 by using a solid electrolyte layer transfer sheet, or by using a solid electrolyte sheet formed in advance into a sheet shape. The solid electrolyte layer transfer sheet has the same configuration as the intermediate layer transfer sheet.

[0049] The pressure used to press the intermediate layer-negative electrode layer laminate L1 and the first solid electrolyte layer 41 in step 2A is preferably higher than the pressure used in step 4A to integrate the layers. This allows the first solid electrolyte layer 41 to be densified. The pressure used in step 2A is, for example, in the range of more than 500 MPa and not more than 700 MPa. The pressure is preferably in the range of not less than 600 MPa and not more than 700 MPa.

[0050] As shown in FIG. 2C , the third step is a step of placing a material constituting a third solid electrolyte layer 43 on the stacking surface of the positive electrode layer 3 and press-bonding them to obtain a solid electrolyte layer-positive electrode layer stack L3. In this embodiment, the positive electrode layer 3 has positive electrode active material layers 31 formed on both sides of the positive electrode current collector layer 32, and the third solid electrolyte layer 43 is placed on both positive electrode active material layers 31. If the positive electrode layer 3 has a positive electrode active material layer 31 formed on only one side of the positive electrode current collector layer 32, the third solid electrolyte layer 43 can be placed on a single positive electrode active material layer 31. The method of placing the third solid electrolyte layer 43 can be the same as in step 2A.

[0051] The pressure used to press the positive electrode layer 3 and the third solid electrolyte layer 43 in the third step is preferably higher than the pressure used in step 4A to integrate the layers. This increases the density of the third solid electrolyte layer 43. The pressure used in the third step is, for example, in the range of 700 MPa to 1200 MPa.

[0052] As shown in FIG. 2D , in step 4A, a second solid electrolyte layer 42 is disposed between the solid electrolyte layer-intermediate layer-anode layer laminate L2 and the solid electrolyte layer-cathode layer laminate L3 so as to face each solid electrolyte layer, and then press-bonded to obtain an electrode laminate La. The second solid electrolyte layer 42 may be, for example, a pre-formed sheet. In this embodiment, the solid electrolyte layer-cathode layer laminate L3 has a third solid electrolyte layer 43 on both sides. Therefore, two second solid electrolyte layers 42 are disposed so as to face both sides of the solid electrolyte layer-cathode layer laminate L3, and each layer is disposed so as to be sandwiched between two solid electrolyte layer-intermediate layer-anode layer laminates L2. For example, if the solid electrolyte layer-cathode layer laminate L3 has a third solid electrolyte layer 43 on only one side, one second solid electrolyte layer 42 can be disposed so as to face the third solid electrolyte layer 43, and one solid electrolyte layer-intermediate layer-anode layer laminate L2 can be disposed.

[0053] Since Step 4A is a step of integrating the layers, it is preferable to apply a pressing pressure that does not excessively deform the layers. The pressing pressure in Step 4A is, for example, in the range of 300 MPa or more and 500 MPa or less. Even if the pressing pressure in Step 4A is within the above range, the first solid electrolyte layer 41 is already sufficiently densified by Step 2A. Therefore, abnormal electrodeposition can be suppressed, and favorable battery performance can be obtained.

[0054] In each of the above steps, the press bonding apparatus is not particularly limited, and a roll press apparatus or a flat plate press apparatus can be used. When press bonding is performed using a roll press apparatus, the conveying direction of the objects to be press bonded to the roll press apparatus may be the same direction or different directions. For example, the conveying direction of the objects to the roll press apparatus in steps 2A and 3 may be different from or perpendicular to the conveying direction of the objects to the roll press apparatus in step 4A. This allows the layer with a low Young's modulus in each layer to extend in one direction, which stretches the solid electrolyte layer 4, making it less likely that defects will occur in the solid electrolyte layer 4.

[0055] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. The solid state battery 1 may have a configuration that can be used in a solid state battery, such as an exterior body, in addition to the electrode laminate shown in FIG. 1. The method for manufacturing the solid state battery according to the first embodiment may include any other steps in addition to those described above.

[0056] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the contents of the following examples. [Example]

[0057] Example 1 An electrode stack in which a negative electrode layer, an intermediate layer, a solid electrolyte layer, and a positive electrode layer were stacked in this order was produced by the following procedure.

[0058] [Preparation of positive electrode layer] A 12.0 μm thick aluminum foil was prepared as a positive electrode current collector. 60.0 parts by mass of lithium nickel cobalt manganese composite oxide (NCM622) was used as the positive electrode active material, 35.8 parts by mass of a sulfide solid electrolyte was used as the solid electrolyte, 2.9 parts by mass of acetylene black (DENKA BLACK Li-100, manufactured by Denka Co., Ltd.) was used as the conductive additive, and 1.3 parts by mass of an SBR (styrene butadiene rubber) binder were mixed together. The resulting mixture was dispersed in a solvent to prepare a positive electrode active material slurry. The resulting positive electrode active material slurry was applied to both sides of the positive electrode current collector so that the basis weight after drying was 27.4 mg / cm. 2 The solution was applied using a bar coater so as to form a positive electrode layer, and then dried.

[0059] [Preparation of intermediate layer transfer sheet] Sn particles (median diameter: 0.07 μm) were used as the metal nanoparticles, and acetylene black (median diameter: 0.05 μm) was used as the amorphous carbon. A total of 95 parts by mass of the above mixture was mixed with 5 parts by mass of a PVDF binder. The resulting mixture was dispersed in a solvent to prepare an intermediate layer slurry. The resulting intermediate layer slurry was applied to a support sheet and dried to produce an intermediate layer transfer sheet with a final thickness of 4 to 10 μm.

[0060] [Preparation of solid electrolyte transfer sheets for the first and third solid electrolyte layers] A dispersion of a sulfide solid electrolyte (median diameter: 0.7 μm) was applied to a support sheet and dried to prepare a solid electrolyte transfer sheet.

[0061] [Fabrication of the second solid electrolyte layer] The sulfide solid electrolytes used were a mixture of one with a median diameter of 3 μm (A) and one with a median diameter of 0.7 μm (B) in a ratio of 8:2. An SBR (styrene butadiene rubber) binder was used. The solid electrolyte and binder were mixed in a ratio of 94.5 parts by mass and 5.5 parts by mass, respectively. The resulting mixture was dispersed in a solvent to prepare a solid electrolyte slurry. The resulting solid electrolyte slurry was impregnated into a nonwoven fabric substrate and dried to produce a second solid electrolyte layer.

[0062] [Creating the negative electrode layer] A copper foil with a thickness of 10 μm was prepared as a negative electrode current collector, and a metallic lithium foil with a thickness of 6.5 μm was laminated on the surface of the copper foil to prepare a negative electrode layer.

[0063] [Fabrication of electrode stack] An intermediate layer from an intermediate layer transfer sheet was transferred to the surface of the metallic lithium foil of the negative electrode layer to form an intermediate layer, and the resulting mixture was press-bonded at 25°C under a bonding pressure of 400 MPa to produce an intermediate layer-negative electrode layer laminate. Next, a solid electrolyte from a solid electrolyte transfer sheet was transferred to the surface of the intermediate layer of the intermediate layer-negative electrode layer laminate to form a first solid electrolyte layer. The intermediate layer-negative electrode layer laminate and the first solid electrolyte layer were then press-bonded at 25°C under a bonding pressure of 600 MPa to produce a solid electrolyte layer-intermediate layer-negative electrode layer laminate. Furthermore, a solid electrolyte from a solid electrolyte transfer sheet was transferred to the surfaces of two positive electrode active material layers of the positive electrode layer to form a third solid electrolyte layer. The positive electrode layer and the third solid electrolyte layer were then press-bonded at 25°C under a bonding pressure of 800 MPa to produce a solid electrolyte layer-positive electrode layer laminate. Next, two second solid electrolyte layers were placed so as to sandwich the solid electrolyte layer-cathode layer laminate from both sides, and two more solid electrolyte layer-intermediate layer-anode layer laminates were placed on the outside, and these three laminates were press-bonded at 25°C with a bonding pressure of 500 MPa. A roll press was used for the pressing method. In this way, the electrode laminate of Example 1 was produced.

[0064] <Example 2> An electrode laminate according to Example 2 was produced in the same manner as in Example 1, except that only acetylene black was used as the intermediate layer transfer sheet.

[0065] <Comparative Example 1> An electrode laminate according to Comparative Example 1 was produced in the same manner as in Example 1, except that a first solid electrolyte layer was not formed. That is, instead of producing a solid electrolyte layer-intermediate layer-negative electrode layer laminate, two second solid electrolyte layers were arranged to sandwich the solid electrolyte layer-cathode layer laminate from both sides, and two intermediate layer-negative electrode layer laminates were further arranged on the outside, and these three laminates were press-bonded at 25°C with a bonding pressure of 500 MPa. A roll press was used as the pressing method. In this way, an electrode laminate according to Comparative Example 1 was produced.

[0066] FIG. 3A shows the results of a charge-discharge test of the solid-state battery according to Example 2. Similarly, FIG. 3B shows the results of a charge-discharge test of the solid-state battery according to Example 1. The test conditions are the same as those shown in FIG. 3A. Example 1 was performed with N=2, and the respective results are shown as Example 1a and Example 1b. The charge-discharge efficiencies calculated from FIGS. 3A and 3B were 100.4% for Example 1a, 97.2% for Example 1b, and 98.5% for Example 2, which clearly shows that favorable charge-discharge efficiencies were obtained.

[0067] Fig. 4 shows the results of a charge-discharge test of the solid-state battery according to Comparative Example 1. The test conditions are the same as those in Fig. 3A. As shown in Fig. 4, the voltage during charging does not increase relative to the discharge capacity, and it is clear that an overcharged state has occurred.

[0068] [Cross-sectional porosity measurement] FIG. 5 is a graph comparing the cross-sectional porosity near the interface between the intermediate layer and the solid electrolyte layer of electrode laminates according to Comparative Example 1, Example 1, and Reference Example. The porosity (%) was measured as follows: First, an SEM cross-sectional photograph of the target solid-state battery was obtained, and voids were extracted by image processing within the relevant area (the solid electrolyte layer near the interface between the intermediate layer and the solid electrolyte of the electrode laminate). Next, the total area of ​​the calculated void portions was calculated and divided by the total area of ​​the relevant area to obtain the porosity (%). Note that the Reference Example is an example in which an electrode laminate was produced in the same manner as Example 1, except that a water-insulating press (WIP) machine was used instead of a roll press machine. As shown in FIG. 5, the cross-sectional porosity of the electrode laminate according to Example 1 was lower than that of the electrode laminate according to Comparative Example 1, although not as high as that of the Reference Example, and it is clear that the first solid electrolyte layer is densified.

[0069] [Average cross-sectional void size measurement] 6 is a graph comparing the average cross-sectional void size near the interface between the intermediate layer and the solid electrolyte layer of the electrode laminates according to Comparative Example 1, Example 1, and Reference Example. The average cross-sectional void size was calculated by aggregating the size of the void portion calculated when calculating the porosity (%). As shown in FIG. 6, the average cross-sectional void size of the electrode laminate according to Example 1 is lower than the average cross-sectional void size of the electrode laminates according to Reference Example and Comparative Example 1, clearly indicating that the first solid electrolyte layer is densified. [Explanation of symbols]

[0070] 1 solid state battery 2. Negative electrode layer 3 Positive electrode layer 4 Solid electrolyte layer 41 First solid electrolyte layer 42 Second solid electrolyte layer 43 Third solid electrolyte layer 5. Middle class L1 Intermediate layer-negative electrode layer laminate L2 Solid electrolyte layer-intermediate layer-negative electrode layer stack L3 Solid electrolyte layer-positive electrode layer laminate La electrode laminate

Claims

1. A method for manufacturing a solid-state battery having an electrode stack in which an anode layer, an intermediate layer, a solid electrolyte layer, and a cathode layer are stacked in this order, comprising: the solid electrolyte layer includes a first solid electrolyte layer disposed on the negative electrode layer side, a second solid electrolyte layer disposed adjacent to the first solid electrolyte layer, and a third solid electrolyte layer disposed on the positive electrode layer side; a first step of press-bonding the negative electrode layer and the intermediate layer to obtain an intermediate layer-negative electrode layer laminate; a second step A of arranging a material constituting the first solid electrolyte layer on a lamination surface of the intermediate layer in the intermediate layer-negative electrode layer laminate and press-bonding the material to obtain a solid electrolyte layer-intermediate layer-negative electrode layer laminate; a third step of arranging a material constituting the third solid electrolyte layer on the lamination surface of the positive electrode layer and press-bonding the material to obtain a solid electrolyte layer-positive electrode layer laminate; and a fourth step A of placing the second solid electrolyte layer between the solid electrolyte layer-intermediate layer-anode layer stack and the solid electrolyte layer-cathode layer stack so as to face each solid electrolyte layer, and press-bonding them to obtain an electrode stack.

2. The method for manufacturing a solid-state battery according to claim 1 , wherein the pressing pressure in the second A step is higher than the pressing pressure in the fourth A step.

3. The method for producing a solid-state battery according to claim 2 , wherein the pressing pressure in the second A step is more than 500 MPa and not more than 700 MPa.

4. 4. The method for manufacturing a solid-state battery according to claim 2, wherein the pressing pressure in the step 4A is 300 MPa or more and 500 MPa or less.

5. The method for manufacturing a solid-state battery according to claim 1 , wherein the pressing pressure in the third step is higher than the pressing pressure in the fourth step.

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