Solid-state battery and method for producing solid-state battery

Abstract

To provide a solid-state battery in which an increase in battery resistance caused by peeling of an electrode layer is suppressed.SOLUTION: In the present disclosure, there is provided a solid-state battery including: a cathode current collector; a first cathode active material layer, a first solid electrolyte layer, a first anode active material layer and a first anode current collector which are laminated in this order from a first surface of the cathode current collector; and a second cathode active material layer, a second solid electrolyte layer, a second anode active material layer and a second anode current collector which are laminated in this order from a second surface opposed to the first surface of the cathode current collector. Each of the cathode current collector, the first anode current collector and the second anode current collector is a metal current collector, and a resin layer is disposed at least either between the first anode active material layer and the first anode current collector or between the second anode active material layer and the second anode current collector.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to solid-state batteries and methods for manufacturing solid-state batteries. [Background technology]

[0002] In recent years, with the rapid spread of electronic devices such as personal computers and mobile phones, the development of batteries to be used as their power sources is progressing. In addition, the automotive industry is also developing batteries for use in hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and battery electric vehicles (BEVs).

[0003] For example, Patent Document 1 discloses a current collector for a bipolar secondary battery that has a structure composed of a layer made of a crystalline resin having a melting point of 120°C or higher and a conductive material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-170833 Summary of the Invention [Problem to be solved by the invention]

[0005] Batteries that use a solid electrolyte as the electrolyte are generally called solid-state batteries. In solid-state batteries, the electrode layers (positive electrode active material layer and negative electrode active material layer) expand and contract as the battery is charged and discharged, which can cause the electrode layers to peel off from the current collector, resulting in an increase in battery resistance.

[0006] The present disclosure has been made in view of the above circumstances, and has as its main object to provide a solid-state battery in which an increase in battery resistance due to peeling of the electrode layer is suppressed. [Means for solving the problem]

[0007] [1] a positive electrode current collector; a first positive electrode active material layer, a first solid electrolyte layer, a first negative electrode active material layer, and a first negative electrode current collector, which are stacked in this order from the first surface of the positive electrode current collector; a second positive electrode active material layer, a second solid electrolyte layer, a second negative electrode active material layer, and a second negative electrode current collector, which are laminated in this order from a second surface of the positive electrode current collector that faces the first surface, the positive electrode current collector, the first negative electrode current collector, and the second negative electrode current collector are metal current collectors; a resin layer disposed at least either between the first negative electrode active material layer and the first negative electrode current collector or between the second negative electrode active material layer and the second negative electrode current collector;

[0008] [2] a preparation step of preparing a laminate having a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer, and a current collecting member having a metal current collector and a resin layer; a first pressing step of pressing the laminate to densify it; a second pressing step, after the first pressing step, of overlapping the laminate and the current collecting member and hot pressing them to attach the resin layer to at least one of the positive electrode active material layer and the negative electrode active material layer; The method for manufacturing a solid-state battery, wherein the pressing pressure in the second pressing step is lower than the pressing pressure in the first pressing step.

[0009] [3] the pressing pressure (linear pressure) in the first pressing step is 40 kN / cm or more; The method for producing a solid state battery according to [2], wherein the pressing pressure (linear pressure) in the second pressing step is 5 kN / cm or less.

[0010] [4] the resin layer contains a thermoplastic resin and a conductive material, The method for producing a solid state battery according to [2] or [3], wherein the softening temperature of the thermoplastic resin is 170°C or lower.

[0011] [5] The laminate is a positive electrode current collector; a first positive electrode active material layer, a first solid electrolyte layer, and a first negative electrode active material layer stacked in this order on a first surface of the positive electrode current collector; a second positive electrode active material layer, a second solid electrolyte layer, and a second negative electrode active material layer stacked in this order on a second surface of the positive electrode current collector opposite to the first surface, the metal current collector in the current collecting member is a negative electrode current collector, The method for producing a solid state battery according to any one of [2] to [4], wherein in the second pressing step, the resin layer is attached to the first negative electrode active material layer and the second negative electrode active material layer. [Effects of the Invention]

[0012] The present disclosure has an effect of providing a solid-state battery in which an increase in battery resistance due to peeling of the electrode layer is suppressed. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating a solid-state battery according to the present disclosure. [Figure 2] 3 is a schematic cross-sectional view illustrating a laminate prepared in a preparation step. FIG. [Figure 3] 3 is a schematic cross-sectional view illustrating a laminate prepared in a preparation step. FIG. [Figure 4] 5A and 5B are schematic cross-sectional views illustrating current collecting members prepared in a preparation step. [Figure 5] 1 is a flow chart illustrating a method for manufacturing a solid-state battery in Reference Example 1. FIG. [Figure 6] 10 is a flow diagram illustrating a method for manufacturing a solid-state battery in Reference Example 2. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] The solid-state battery and the method for manufacturing the solid-state battery according to the present disclosure will be described in detail below. The following drawings are schematic illustrations, and the size and shape of each part are appropriately exaggerated for ease of understanding. Herein, in this specification, for example, when simply referring to a positive electrode active material layer, it refers to both the first positive electrode active material layer and the second positive electrode active material layer. The same applies to the negative electrode active material layer, the solid electrolyte layer, and the negative electrode current collector.

[0015] A. Solid state battery Fig. 1 is a schematic cross-sectional view illustrating a solid-state battery according to the present disclosure. The solid-state battery 10 shown in Fig. 1 includes a positive electrode current collector 1, a first positive electrode active material layer 2A, a first solid electrolyte layer 3A, a first negative electrode active material layer 4A, and a first negative electrode current collector 5A, which are stacked in this order on a first surface A of the positive electrode current collector 1, and a second positive electrode active material layer 2B, a second solid electrolyte layer 3B, a second negative electrode active material layer 4B, and a second negative electrode current collector 5B, which are stacked in this order on a second surface B of the positive electrode current collector 1 opposite the first surface A. In the solid-state battery 10, the positive electrode current collector 1, the first negative electrode current collector 5A, and the second negative electrode current collector 5B are metal current collectors. Furthermore, in the solid state battery 10, a resin layer 6 is disposed between the first negative electrode active material layer 4A and the first negative electrode current collector 5A, and between the second negative electrode active material layer 4B and the second negative electrode current collector 5B.

[0016] In the solid-state battery of the present disclosure, a resin layer is disposed at least one between the first negative electrode active material layer and the first negative electrode current collector and between the second negative electrode active material layer and the second negative electrode current collector. The resin contained in the resin layer is believed to improve adhesion between the negative electrode active material layer and the negative electrode current collector. In other words, the resin layer is believed to function as an adhesive layer. As a result, an increase in battery resistance due to peeling of the negative electrode active material layer is believed to be suppressed.

[0017] 1. Resin layer The resin layer is a layer disposed at least either between a first negative electrode active material layer and a first negative electrode current collector, or between a second negative electrode active material layer and a second negative electrode current collector, which will be described later. The resin layer may be disposed only between the first negative electrode active material layer and the first negative electrode current collector, only between the second negative electrode active material layer and the second negative electrode current collector, or both.

[0018] The resin layer typically contains a resin. Examples of the resin include thermoplastic resins such as polypropylene, polyethylene, polyvinyl chloride, polystyrene, acrylonitrile butadiene styrene (ABS) resin, methacrylic resin, polyamide, polyester, polycarbonate, and polyacetal. The softening temperature (softening point) of the resin is not particularly limited, but may be, for example, 170°C or lower, 150°C or lower, 130°C or lower, or 100°C or lower. On the other hand, the softening point of the resin is, for example, 60°C or higher.

[0019] The proportion of the resin in the resin layer is, for example, 50% by weight or more and 95% by weight or less.

[0020] Furthermore, the resin layer generally contains a conductive material to provide conductivity. Examples of the conductive material include carbon materials. Examples of the carbon material 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). The proportion of the conductive material in the resin layer is, for example, 5% by weight or more and 50% by weight or less.

[0021] The resin layer may also contain a filler such as an inorganic filler. Examples of inorganic fillers include metal oxides such as alumina, zirconia, and silica, and metal nitrides such as silicon nitride. By containing a filler in the resin layer, deformation of the resin layer can be suppressed. The proportion of the filler in the resin layer is, for example, 5% by weight or more and 50% by weight or less.

[0022] The thickness of the resin layer is not particularly limited, but is, for example, 1 μm or more and 500 μm or less.

[0023] 2. Positive electrode current collector The positive electrode current collector is a member that collects electrons from the positive electrode active material layers (first positive electrode active material layer and second positive electrode active material layer) described below. The positive electrode current collector in the present disclosure is a metal current collector.

[0024] Examples of materials for the positive electrode current collector (metal current collector) include SUS, aluminum, nickel, and carbon. Examples of the shape of the positive electrode current collector include foil. The thickness of the positive electrode current collector is, for example, 1 μm or more and 500 μm or less.

[0025] As shown in FIG. 1, the positive electrode current collector 1 is T The optical fiber 10 has a first surface A and a second surface B opposite to the first surface A.

[0026] 3. First Positive Electrode Active Material Layer and Second Positive Electrode Active Material Layer The first positive electrode active material layer is a member disposed on a first surface of the positive electrode current collector, and the second positive electrode active material layer is a member disposed on a second surface of the positive electrode current collector.

[0027] The positive electrode active material layer contains at least a positive electrode active material. Examples of the positive electrode active material include oxide active materials. Examples of oxide active materials include LiCoO2 and LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc., rock salt layered active materials, LiMn2O4, Li4Ti5O 12 and olivine type active materials such as LiFePO4. The positive electrode active material is, for example, in the form of particles.

[0028] The positive electrode active material layer may further contain at least one of a conductive material, a binder, and an electrolyte, as necessary. The conductive material is the same as that described in "1. Resin Layer." Examples of binders include rubber-based binders such as butylene rubber (BR) and styrene butadiene rubber (SBR), and fluoride-based binders such as polyvinylidene fluoride (PVDF). The electrolyte is the same as that described in "4. First Solid Electrolyte Layer and Second Solid Electrolyte Layer." The thickness of the positive electrode active material layer is, for example, 0.1 μm or more and 1000 μm or less.

[0029] 4. First solid electrolyte layer and second solid electrolyte layer The first solid electrolyte layer and the second solid electrolyte layer contain at least a solid electrolyte, and are members disposed on the first surface side and the second surface side of the positive electrode current collector, respectively.

[0030] Examples of solid electrolytes include inorganic solid electrolytes such as sulfide solid electrolytes, oxide solid electrolytes, and halide solid electrolytes. 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. The halide solid electrolyte preferably contains halogen as the main anion element. Among these, the sulfide solid electrolyte is preferred.

[0031] Other examples of the solid electrolyte include organic solid electrolytes such as polymer electrolytes and gel electrolytes. The solid electrolyte layer may contain a liquid electrolyte (electrolytic solution) as the electrolyte. The thickness of the solid electrolyte layer is, for example, 1 μm or more and 500 μm or less.

[0032] 5. First negative electrode active material layer and second negative electrode active material layer The first negative electrode active material layer and the second negative electrode active material layer contain at least a negative electrode active material, and are members disposed on the first surface side and the second surface side of the positive electrode current collector, respectively.

[0033] Examples of the negative electrode active material include metal active materials such as Li and Sn, Si-based active materials, carbon active materials such as graphite, and Li4Ti5O 12 Among these, Si-based active materials are preferred because they can increase the capacity of the battery.

[0034] The negative electrode active material layer may further contain at least one of a conductive material, a binder, and an electrolyte, as necessary. These are the same as those described in "3. First Positive Electrode Active Material Layer and Second Positive Electrode Active Material Layer." The thickness of the negative electrode active material layer is, for example, 0.1 μm or more and 1000 μm or less.

[0035] 6. First negative electrode current collector and second negative electrode current collector The first and second negative electrode current collectors are members that collect electrons from the first and second negative electrode active material layers, respectively. In addition, the first and second negative electrode current collectors in the present disclosure are metal current collectors.

[0036] Examples of materials for the negative electrode current collector (metal current collector) include SUS, copper, and nickel. Examples of the shape of the negative electrode current collector include foil. The thickness of the negative electrode current collector is, for example, 1 μm or more and 500 μm or less.

[0037] 7. Solid state battery The solid-state battery according to the present disclosure may have an exterior housing that houses the above-described components. Examples of the exterior housing include a case-type exterior housing and a laminate-type exterior housing. The solid-state battery may also include a restraining jig that applies a restraining pressure in the thickness direction to the above-described 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.

[0038] The above-mentioned solid-state battery has two sets (power generation units) of a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer, and is a so-called monopolar battery. The solid-state battery in the present disclosure is typically a lithium-ion secondary battery. The solid-state battery in the present disclosure may be a semi-solid-state battery or an all-solid-state battery. Generally, a solid-state battery in which the entire electrolyte constituting the solid electrolyte layer is made of an inorganic solid electrolyte is called an all-solid-state battery.

[0039] The use of the solid-state battery in the present disclosure is not particularly limited, and examples thereof 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 that the solid-state battery be used as a driving power source for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or electric vehicles (BEVs). The solid-state battery may also be used as a power source for mobile objects other than vehicles (e.g., railways, ships, and aircraft), and may also be used as a power source for electrical appliances such as information processing devices.

[0040] The solid-state battery according to the present disclosure is preferably manufactured by, for example, the method described below in "B. Manufacturing method of solid-state battery."

[0041] B. Manufacturing methods for solid-state batteries 2 and 3 are schematic cross-sectional views illustrating an example of a laminate prepared in the method for manufacturing a solid-state battery according to the present disclosure. FIG. 4 is a schematic cross-sectional view illustrating an example of a current collecting member prepared in the method for manufacturing a solid-state battery according to the present disclosure. In the method for manufacturing a solid-state battery according to the present disclosure, a laminate L having a positive electrode active material layer 2 (2A, 2B), a solid electrolyte layer 3 (3A, 3B), and a negative electrode active material layer 4 (4A, 4B) as shown in FIGS. 2 and 3, and a current collecting member C having a metal current collector M and a resin layer 6 as shown in FIG. 4 are prepared (preparation step). Next, the laminate L is pressed to densify it (first pressing step). After the first pressing step, the laminate L and the current collecting member C are stacked and hot-pressed to attach the resin layer 6 to at least one of the positive electrode active material layer 2 and the negative electrode active material layer 4 (second pressing step). In particular, in the method for manufacturing a solid-state battery according to the present disclosure, the pressing pressure in the second pressing step is lower than the pressing pressure in the first pressing step.

[0042] The method for manufacturing a solid-state battery according to the present disclosure makes it possible to manufacture a solid-state battery including a resin layer as described above.

[0043] Here, when manufacturing a solid-state battery, it is assumed that a pressing pressure is applied to densify each layer constituting the solid-state battery. Furthermore, it is assumed that a relatively large pressing pressure is applied to achieve densification. On the other hand, the resin layer is easily deformed and stretched by the pressing pressure. Furthermore, if the electrode layer deforms following the stretching of the resin layer, cracks may occur in the electrode layer. In contrast, in the manufacturing method of a solid-state battery according to the present disclosure, a laminate without a resin layer is pressed to densify the positive electrode active material layer and the like, and then the resin layer is attached, so that a large pressing pressure is not applied to the resin layer. As a result, it is possible to suppress deformation (stretching) of the resin layer during the manufacturing process of the solid-state battery, and it is possible to manufacture a solid-state battery (a solid-state battery having a resin layer) with suppressed cracks in the electrode layer.

[0044] 1. Preparation process The preparation step in the present disclosure is a step of preparing a predetermined laminate and current collecting member.

[0045] (1) Laminate The laminate has a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer. Details of the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer are the same as those described in "A. Solid-state battery."

[0046] The positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer can each be formed by a coating method using a slurry. Examples of the coating method include the methods described in the Reference Examples below. Examples of the method for laminating each layer include, for example, a method using a transfer member, as described in the Reference Examples below.

[0047] As shown in FIGS. 2(a) and (b), the laminate L may have either a positive electrode current collector 1 or a negative electrode current collector 5. In this case, a resin layer (described later) is attached to the electrode layer (negative electrode active material layer 4 or positive electrode active material layer 2) that does not have a current collector. When the layers are laminated using a transfer member, the laminate L has a thickness direction D as shown in FIGS. 2(c), (d), and (e). T In the above structure, the substrate P may be provided on at least one surface of the electrode layers (positive electrode active material layer 2, negative electrode active material layer 4) located at the ends.

[0048] In the laminate, the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer may be disposed on only one surface of the current collector in the thickness direction (FIG. 2) or on both surfaces (FIG. 3). For example, the laminate L in FIG. 3 includes a positive electrode current collector 1, a first positive electrode active material layer 2A, a first solid electrolyte layer 3A, and a first negative electrode active material layer 4A, which are laminated in this order from a first surface A of the positive electrode current collector 1, and a second positive electrode active material layer 2B, a second solid electrolyte layer 3B, and a second negative electrode active material layer 4B, which are laminated in this order from a second surface B of the positive electrode current collector 1 opposite to the first surface A. In such a laminate L, the thickness direction D T In this case, a substrate P may be disposed on at least one surface of the electrode layer (negative electrode active material layer 4) located at the end. Here, the laminate L shown in Fig. 3 is a so-called monopolar type, but it may also be a bipolar type.

[0049] (2) Current collecting member As shown in FIG. 4, the current collecting member C has a metal current collector M and a resin layer 6. The resin layer is the same as that described in "A. Solid-state battery." The current collecting member may be a positive electrode side member or a negative electrode side member. In other words, the metal current collector may be a positive electrode current collector or a negative electrode current collector. The positive electrode current collector and the negative electrode current collector are the same as those described in "A. Solid-state battery."

[0050] The current collecting member can be prepared by applying a resin slurry containing at least a resin to a metal current collector and drying it. The current collecting member may be prepared before the first pressing step described below, or after the first pressing step and before the second pressing step.

[0051] 2. First pressing process The first pressing step is a step of pressing the laminate to densify it.

[0052] The pressing method in the first pressing step is not particularly limited, and examples thereof include roll pressing and plate pressing. The pressing pressure (linear pressure, surface pressure) in the first pressing step is not particularly limited as long as it can densify the laminate and is greater than the pressing pressure in the second pressing step described below. The linear pressure is, for example, 40 kN / cm or more, and may be 50 kN / cm or more. On the other hand, the linear pressure is, for example, 100 kN / cm or less, and may be 80 kN / cm or less. The surface pressure in the plate pressing is, for example, 10 kN / cm. 2 or more, 30kN / cm 2 On the other hand, the surface pressure may be, for example, 70 kN / cm 2 less than 50kN / cm 2 The pressing may be carried out at room temperature (for example, 25°C) or while heating the laminate. The heating temperature is, for example, 60°C or higher and 170°C or lower.

[0053] 3. Second pressing process The second pressing step is a step of attaching the resin layer to at least one of the positive electrode active material layer and the negative electrode active material layer by overlapping the laminate and the current collecting member and hot pressing them after the first pressing step. In particular, the pressing pressure in the second pressing step is smaller than the pressing pressure in the first pressing step. Note that if the laminate has a substrate, the substrate is removed before the second pressing step.

[0054] In the second pressing step, a resin layer may be attached to the positive electrode active material layer, or a resin layer may be attached to the negative electrode active material layer. When the laminate has negative electrode active material layers at both ends in the thickness direction, a resin layer may be attached to one of the layers, or to both layers.

[0055] The pressing method in the second pressing step is not particularly limited as long as it is a hot press, and examples thereof include roll pressing and flat plate pressing. The pressing pressure (linear pressure, surface pressure) in the second pressing step is not particularly limited as long as it can attach the resin layer to the electrode layer and is smaller than the pressing pressure in the first pressing step. The linear pressure is, for example, 5.0 kN / cm or less, and may be 4.0 kN / cm or less, or 2.5 kN / cm or less. On the other hand, the linear pressure is, for example, 1.0 kN / cm or more. The surface pressure is, for example, 8 kN / cm. 2 Below, 1kN / cm 2 That's all.

[0056] The heating temperature in the heat press is preferably equal to or higher than the softening point of the resin in the resin layer, as this can improve the adhesiveness of the resin layer. The heating temperature is, for example, 60°C or higher, or may be 80°C or higher, or may be 100°C or higher. On the other hand, the heating temperature is, for example, 170°C or lower, or may be 150°C or lower, or may be 130°C or lower.

[0057] 4. Solid state battery The solid-state battery manufactured by the above-described steps may be a battery having two power generation units. In this case, the solid-state battery may be a monopolar battery as shown in "A. Solid-state battery" or a bipolar battery. The solid-state battery manufactured may also be a battery having one of the above-described power generation units.

[0058] Other details regarding the components and uses of solid-state batteries are the same as those described in "A. Solid-state batteries."

[0059] 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]

[0060] [Reference example 1] As shown in FIG. 5, a laminate L having no resin layer was subjected to densification pressing (first pressing step), and then a current collecting member was attached (second pressing step) to fabricate a solid state battery.

[0061] (Preparation of current collecting material) A current collecting member C having a metal current collector (negative electrode current collector 5) and a resin layer 6 disposed on one surface of the metal current collector in the thickness direction was prepared as follows. First, a vinyl resin (thermoplastic resin) and carbon (conductive material) were mixed in a weight ratio of 80:20 to prepare a resin slurry. The softening point of the vinyl resin used was 68°C. The resin slurry was applied to a nickel foil (negative electrode current collector) by the blade method and dried on a hot plate at 80°C for 30 minutes. Then, it was further dried on a hot plate at 170°C for 30 minutes. This prepared a current collecting member.

[0062] (Laminate preparation) Cathode active material (NCA: LiNi 0.8 Co 0.15 Al 0.05A positive electrode slurry was obtained by stirring a slurry containing NCA, a sulfide-based solid electrolyte (SE:Li2S-P2S5), vapor-grown carbon fiber (VGCF), a polyvinylidene fluoride (PVdF)-based binder, and butyl butyrate using an ultrasonic disperser. The weight ratio of NCA, SE, VGCF, and PVdF-based binder was 78.3:18.8:1.6:1.4. This positive electrode slurry was applied to an Al foil (positive electrode current collector) using a blade method and dried on a hot plate at 50°C for 30 minutes. It was then further dried on a hot plate at 170°C for 30 minutes. This resulted in a positive electrode having a positive electrode active material layer 2 and a positive electrode current collector 1.

[0063] Next, a slurry containing a sulfide-based solid electrolyte (SE: Li2S-P2S5), an acrylonitrile butadiene rubber (ABR) binder, heptane, and butyl butyrate was stirred using an ultrasonic disperser to obtain an SE slurry. The weight ratio of SE to ABR binder was 99.4:0.6. This SE slurry was applied to the positive electrode active material layer using a blade method and dried on a hot plate at 50°C for 1 minute. This was then further dried on a hot plate at 150°C for 30 minutes to obtain a solid electrolyte layer (SE layer). Another SE layer was formed on the SE layer using the same procedure. This resulted in a positive electrode member having a positive electrode current collector 1, a positive electrode active material layer 2, and a solid electrolyte layer 3.

[0064] Next, a negative electrode slurry was obtained by stirring a negative electrode active material (silicon: Si), a sulfide-based solid electrolyte (SE: Li2S-P2S5), vapor-grown carbon fiber (VGCF), a polyvinylidene fluoride (PVdF)-based binder, and butyl butyrate using an ultrasonic disperser. The weight ratio of Si, SE, VGCF, and PVdF-based binder was adjusted to 49.3:41.5:6.4:2.8. This negative electrode slurry was applied to a substrate (stainless steel (SUS) foil) using a blade method and dried on a hot plate at 50 °C for 30 minutes. It was then further dried on a hot plate at 170 °C for 30 minutes. This resulted in a transfer member having a negative electrode active material layer 4 and a substrate P.

[0065] The positive electrode member and the transfer member were stacked so that the solid electrolyte layer and the negative electrode active material layer faced each other, thereby obtaining a laminate L having a positive electrode current collector 1, a positive electrode active material layer 2, a solid electrolyte layer 3, a negative electrode active material layer 4, and a substrate P.

[0066] (Fabrication of all-solid-state batteries) The laminate L was roll-pressed at 165°C and 50 kN / cm, and the substrate (SUS foil) was peeled off (first press step). Then, the laminate L and the current collector C were arranged so that the negative electrode active material layer 4 and the resin layer 6 faced each other, and roll-pressed at 165°C and 2.5 kN / cm (second press step). This resulted in an all-solid-state battery 10 in which the resin layer 6 was disposed between the negative electrode active material layer 4 and the negative electrode current collector 5.

[0067] [Reference example 2] As shown in FIG. 6, the laminate L having the resin layer 6 was subjected to densification pressing multiple times to fabricate a solid-state battery.

[0068] First, a current collecting member C having a resin layer 6 and a metal current collector (negative electrode current collector 5) was prepared in the same manner as in Reference Example 1. Next, a slurry containing a negative electrode active material (silicon: Si), a sulfide-based solid electrolyte (SE: Li2S-P2S5), vapor-grown carbon fiber (VGCF), a polyvinylidene fluoride (PVdF)-based binder, and butyl butyrate was stirred using an ultrasonic disperser to obtain a negative electrode slurry. Here, the weight ratio of Si, SE, VGCF, and PVdF-based binder was 49.3:41.5:6.4:2.8. This negative electrode slurry was applied to the resin layer of the current collecting member by a blade method and dried on a hot plate at 50 °C for 30 minutes. Then, it was further dried on a hot plate at 170 °C for 30 minutes. This resulted in a negative electrode having a negative electrode active material layer 4, a resin layer 6, and a negative electrode current collector 5.

[0069] In addition, an SE slurry was prepared in the same manner as in Reference Example 1. This SE slurry was applied to a substrate (Al foil) by a blade method and dried, thereby preparing a transfer member having a solid electrolyte layer 3 and a substrate P.

[0070] 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, sandwiched between SUS foil, and roll-pressed at 25°C and 30 kN / cm. The Al foil was then peeled off. This yielded an intermediate member having the negative electrode current collector 5, the resin layer 6, the negative electrode active material layer 4, and the solid electrolyte layer 3.

[0071] Next, a transfer member having a solid electrolyte layer 3 (SE layer for bonding) and a substrate P was prepared in the same manner as above, except that the substrate was changed to SUS foil. In addition, a positive electrode side member was produced in the same manner as in Reference Example 1, except that the number of solid electrolyte layers was changed to one layer.

[0072] The intermediate member and the transfer member were stacked so that the solid electrolyte layers faced each other, and subjected to a temperature of 25°C and 19 kN / cm 2 The negative electrode member and the positive electrode member were then stacked so that the solid electrolyte layers faced each other, and pressed at 160°C and 50 kN / cm 2 The resultant was uniaxially pressed under the conditions shown below. This resulted in an all-solid-state battery.

[0073] [evaluation] The negative electrode active material layers of the all-solid-state batteries produced in Reference Examples 1 and 2 were visually inspected for the presence or absence of cracks. The results are shown in Table 1. As shown in Table 1, no cracks occurred in the electrode in Reference Example 1.

[0074] [Table 1]

[0075] In both of the all-solid-state batteries fabricated in Reference Examples 1 and 2, a resin layer was disposed between the negative electrode active material layer and the negative electrode current collector, which is believed to have suppressed peeling of the negative electrode active material layer from the negative electrode current collector and thus suppressed an increase in battery resistance due to peeling of the negative electrode active material layer. On the other hand, it was suggested that the method for manufacturing a solid-state battery according to the present disclosure, as shown in Reference Example 1, was able to suppress cracking of the electrode layer during manufacturing, and that the battery resistance itself of the solid-state battery could be reduced. [Explanation of symbols]

[0076] 1 ...positive electrode current collector 2A…1st positive electrode active material layer 2B...Second positive electrode active material layer 3A…1st solid electrolyte layer 3B...Second solid electrolyte layer 4A ...1st negative electrode active material layer 4B...Second negative electrode active material layer 5A…1st negative electrode current collector 5B...Second negative electrode current collector 6 ...resin layer 10 …Solid-state batteries

Claims

1. a positive electrode current collector; a first positive electrode active material layer, a first solid electrolyte layer, a first negative electrode active material layer, and a first negative electrode current collector, which are stacked in this order from a first surface of the positive electrode current collector; a second positive electrode active material layer, a second solid electrolyte layer, a second negative electrode active material layer, and a second negative electrode current collector, which are stacked in this order on a second surface of the positive electrode current collector that faces the first surface, the positive electrode current collector, the first negative electrode current collector, and the second negative electrode current collector are metal current collectors, a resin layer disposed at least either between the first negative electrode active material layer and the first negative electrode current collector or between the second negative electrode active material layer and the second negative electrode current collector.

2. a preparation step of preparing a laminate having a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer, and a current collecting member having a metal current collector and a resin layer; a first pressing step of pressing the laminate to densify it; a second pressing step of, after the first pressing step, overlapping the laminate and the current collecting member and hot pressing them to attach the resin layer to at least one of the positive electrode active material layer and the negative electrode active material layer, a pressing pressure in the second pressing step being lower than a pressing pressure in the first pressing step.

3. The pressing pressure (linear pressure) in the first pressing step is 40 kN / cm or more, The method for manufacturing a solid-state battery according to claim 2 , wherein the pressing pressure (linear pressure) in the second pressing step is 5 kN / cm or less.

4. the resin layer contains a thermoplastic resin and a conductive material, The method for manufacturing a solid state battery according to claim 2 , wherein the softening temperature of the thermoplastic resin is 170° C. or lower.

5. The laminate is a positive electrode current collector; a first positive electrode active material layer, a first solid electrolyte layer, and a first negative electrode active material layer stacked in this order on a first surface of the positive electrode current collector; a second positive electrode active material layer, a second solid electrolyte layer, and a second negative electrode active material layer stacked in this order on a second surface of the positive electrode current collector opposite to the first surface, the metal current collector in the current collecting member is a negative electrode current collector, The method for manufacturing a solid-state battery according to claim 2 , wherein the resin layer is attached to the first negative electrode active material layer and the second negative electrode active material layer in the second pressing step.

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