All-solid-state battery manufacturing method and all-solid-state battery

Abstract

To provide a manufacturing method for an all-solid battery that exhibits excellent uniformity in the degree of compression in the in-plane direction of a cell stack, and an all-solid battery.SOLUTION: A manufacturing method for an all-solid battery 100 includes preparing a structure 60 including a first exterior material 10, a first resin layer 20, a cell stack 30, a second resin layer 40, and a second exterior material 50, in this order, and applying pressure to the structure 60 in the thickness direction at a temperature at which the first resin layer 10 and the second resin layer 20 melt or soften.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing an all-solid-state battery and an all-solid-state battery. [Background technology]

[0002] All-solid-state batteries, a type of lithium-ion secondary battery, have advantages over lithium-ion secondary batteries that use an electrolyte dissolved in an organic solvent, such as higher safety, a wider operating temperature range, and ease of increasing energy density, and research and development is underway to promote their widespread use.

[0003] An all-solid-state battery includes a cell stack composed of an anode layer, a cathode layer, and a solid electrolyte layer, and charging and discharging are performed by the movement of lithium ions between the layers that make up the cell stack. For this reason, all-solid-state batteries are generally subjected to a compression process in which pressure is applied in the thickness direction of the cell stack to increase the lithium ion movement efficiency and prevent peeling between the layers.

[0004] Each layer constituting the cell stack of an all-solid-state battery is produced through a process in which a material containing an active material or a solid electrolyte is applied to a substrate. Therefore, some degree of variation in the thickness of the cell stack is unavoidable. When a cell stack with varying thickness is compressed using a flat plate or roll, the degree of compression in the in-plane direction of the cell stack varies. Variations in the degree of compression of the cell stack may affect the performance and durability of the all-solid-state battery. As a measure to reduce variations in pressure applied to the cell stack, for example, Patent Document 1 proposes placing a buffer layer between the cell stacks. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-177448 Summary of the Invention [Problem to be solved by the invention]

[0006] The method described in Patent Document 1 has problems such as an increase in the volume of the all-solid-state battery due to the placement of a buffer layer between the cell stacks. In view of the above circumstances, an object of one embodiment of the present disclosure is to provide a method for manufacturing an all-solid-state battery and an all-solid-state battery that have excellent uniformity in the degree of compression in the in-plane direction of a cell stack. [Means for solving the problem]

[0007] The means for solving the above problems include the following embodiments. <1> preparing a structure including a first exterior material, a first resin layer, a cell stack, a second resin layer, and a second exterior material in this order; and applying pressure to the structure in a thickness direction at a temperature at which the first resin layer and the second resin layer melt or soften. <2> The pressure is applied using a member having a flat surface facing the structure. <1> A method for producing the all-solid-state battery described in <3> further comprising the step of applying an isostatic pressure to the structure. <1> or <2> A method for producing the all-solid-state battery described in <4> a structure including a first exterior material, a first resin layer, a cell stack, a second resin layer, and a second exterior material in this order; At least one of the first resin layer and the second resin layer is adhered to the cell laminate. <5> The first resin layer and the second resin layer are each bonded to the cell stack. <4> The all-solid-state battery described in <6> a structure including a first exterior material, a first resin layer, a cell stack, a second resin layer, and a second exterior material in this order; an all-solid-state battery, wherein the variation in thickness of the entire structure in an in-plane direction is smaller than the variation in thickness of the cell laminate in the in-plane direction. <7> The first resin layer and the second resin layer each contain a thermoplastic resin. <4> ~ <6> 10. The all-solid-state battery according to claim 1, [Effects of the Invention]

[0008] According to one embodiment of the present disclosure, a method for manufacturing an all-solid-state battery and an all-solid-state battery are provided, which have excellent uniformity in the degree of compression in the in-plane direction of the cell stack. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view schematically illustrating an example of the configuration of an all-solid-state battery according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] In the present disclosure, a numerical range indicated using "to" means a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. In the numerical ranges described in this disclosure, the upper or lower limit value described in a certain numerical range may be replaced with the value shown in the examples. In the present disclosure, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved. In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In the present disclosure, when there are multiple substances corresponding to each component, the amount of each component means the total amount of the multiple substances unless otherwise specified. When embodiments of the present disclosure are described with reference to the drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. Furthermore, the sizes of the components in each drawing are conceptual, and the relative size relationships between the components are not limited to these.

[0011] <Manufacturing method for all-solid-state batteries> The method for producing an all-solid-state battery according to the present disclosure includes: preparing a structure including a first exterior material, a first resin layer, a cell stack, a second resin layer, and a second exterior material in this order; and applying pressure to the structure in the thickness direction at a temperature at which the first resin layer and the second resin layer melt or soften.

[0012] Hereinafter, the first and second exterior materials included in the structure may be collectively referred to as "exterior materials," and the first and second resin layers may be collectively referred to as "resin layers."

[0013] In the method disclosed herein, pressure is applied to the structure at a temperature at which the resin layer melts or softens. This deforms the resin layer to conform to the undulations on the surface of the cell stack and adheres the resin layer to the cell stack. As a result, an all-solid-state battery with excellent uniformity in the degree of compression in the in-plane direction of the cell stack can be manufactured.

[0014] From the viewpoint of equalizing the degree of compression in the in-plane direction of the cell stack, it is preferable to apply pressure to the structure using a member whose surface facing the structure is flat. By applying pressure using a member whose surface facing the structure is flat, the first resin layer and the second resin layer can be effectively deformed. Examples of the member having a flat surface that comes into contact with the structure include a flat plate, a roll, and a table with a flat surface.

[0015] In the method of the present disclosure, the conditions for applying pressure to the structure (hereinafter also referred to as the pressurizing step) are not particularly limited, and can be set depending on the application, performance, etc. of the all-solid-state battery to be manufactured. From the viewpoint of sufficiently deforming the resin layer, the pressure in the pressing step is preferably 0.0001 MPa or more, more preferably 0.001 MPa or more, and even more preferably 0.01 MPa or more. From the viewpoint of preventing damage to the cell stack, the pressure in the pressurizing step is preferably 100 MPa or less, more preferably 10 MPa or less, and even more preferably 1 MPa or less.

[0016] In the method of the present disclosure, the number of times that pressure is applied to the structure (hereinafter also referred to as the pressurizing step) may be one or more. For example, a second pressurizing step may be carried out in addition to a pressurizing step (hereinafter also referred to as a first pressurizing step) carried out at a temperature at which the resin layer melts or softens. By carrying out the second pressurizing step in addition to the first pressurizing step, it is possible to increase the uniformity of the degree of compression in the in-plane direction of the cell stack and adjust the compression ratio. The second pressurizing step may be carried out before or after the first pressurizing step. The second pressurizing step may be performed in the same manner as the first pressurizing step, or in a different manner. From the viewpoint of uniformly compressing the cell stack, the second pressurizing step is preferably performed by applying isotropic pressure to the structure. The method for applying isostatic pressure to the structure is not particularly limited, and can be, for example, a known method using a fluid such as a liquid, gas, or powder as a pressure medium.

[0017] The method of the present disclosure may include steps other than the pressurizing step, if necessary. For example, the method may include a step of bonding the peripheral edges of the first and second exterior materials together to enclose the cell stack inside the exterior materials. The bonding of the peripheral edges may be carried out simultaneously with the pressurizing step.

[0018] For details and preferred embodiments of the all-solid-state battery produced by the method of the present disclosure, reference can be made to the details and preferred embodiments of the all-solid-state battery described below.

[0019] <All-Solid-State Battery (First Embodiment)> The all-solid-state battery according to the first embodiment of the present disclosure is a structure including a first exterior material, a first resin layer, a cell stack, a second resin layer, and a second exterior material in this order; At least one of the first resin layer and the second resin layer is bonded to the cell stack. The first resin layer and the second resin layer may each be bonded to the cell stack.

[0020] <All-Solid-State Battery (Second Embodiment)> The all-solid-state battery according to the second embodiment of the present disclosure is a structure including a first exterior material, a first resin layer, a cell stack, a second resin layer, and a second exterior material in this order; The thickness variation in the in-plane direction of the entire structure is smaller than the thickness variation in the in-plane direction of the cell stack.

[0021] Hereinafter, the all-solid-state battery of the first embodiment and the all-solid-state battery of the second embodiment may be collectively referred to as the "all-solid-state battery of the present disclosure." The all-solid-state battery of the present disclosure includes a resin layer disposed between the cell stack and the exterior material. The resin layer functions to absorb variations in thickness of the cell stack in the in-plane direction. As a result, when pressure is applied to the all-solid-state battery in the thickness direction, variations in the degree of compression of the all-solid-state battery in the in-plane direction are suppressed.

[0022] FIG. 1 shows a schematic diagram of an example of the configuration of an all-solid-state battery according to the present disclosure. The all-solid-state battery 100 shown in FIG. 1 has a structure 60 including a first exterior material 10, a first resin layer 20, a cell laminate 30, a second resin layer 40, and a second exterior material 50 in this order. The cell stack 30 of the all-solid-state battery 100 has thickness variations in the in-plane direction (direction indicated by arrow X). The surfaces of the first resin layer 10 and the second resin layer 40 facing the cell stack 30 are deformed along the undulations of the surface of the cell stack 30. That is, the thickness variations of the cell stack 30 are absorbed by the first resin layer 10 and the second resin layer 40. Therefore, when pressure is applied in the thickness direction of the all-solid-state battery 100 (direction indicated by arrow Y), the difference between the pressure applied to the thicker parts of the cell stack 30 and the pressure applied to the thinner parts of the cell stack 30 is reduced. As a result, the degree of compression of the cell stack 30 in the in-plane direction is less likely to vary.

[0023] In the all-solid-state battery 100 shown in FIG. 1, the structure 60 is composed only of the first exterior material 10, the first resin layer 20, the cell stack 30, the second resin layer 40, and the second exterior material 50, but the all-solid-state battery of the present disclosure is not limited to this and may include other layers. The all-solid-state battery 100 shown in FIG. 1 may include members such as tab leads (not shown).

[0024] The first exterior material 10 and the second exterior material 50 shown in Fig. 1 may each be made up of a plurality of components, for example, a base material layer and a barrier layer.

[0025] Unlike the all-solid-state battery shown in Figure 1, if there is no resin layer between the cell stack and the exterior material, or if the resin layer is not deformed along the undulations on the surface of the cell stack, when pressure is applied in the thickness direction of the all-solid-state battery, the pressure applied to the thicker parts of the cell stack will be greater than the pressure applied to the thinner parts of the cell stack. As a result, the degree of compression in the in-plane direction of the cell stack is likely to vary.

[0026] In the present disclosure, the method for comparing the variation in thickness of the structure of the all-solid-state battery with the variation in thickness of the cell laminate is not particularly limited, and can be performed by a known method. For example, one method is to measure the thickness of the structure and the cell stack at multiple locations (preferably five or more locations) and use the difference between the maximum and minimum measured values ​​as an index of thickness variation, or to calculate the standard deviation σ and use 6σ as an index of thickness variation. 6σ means the range that is included with a probability of 99.7% when the variation follows a normal distribution. If there is a trend or regularity in the thickness variation of the object to be measured, such as a slope, it is preferable to use the difference between the maximum and minimum values ​​as an index. If the thickness variation is irregular and there is no trend such as a slope, it is preferable to use 6σ as an index. Alternatively, an image of a cross section of the all-solid-state battery may be obtained, and the thickness variations may be compared based on the length A of the contour line of the portion corresponding to the structure observed in the image and the length B of the contour line of the portion corresponding to the cell stack.

[0027] In the present disclosure, "the resin layer is adhered to the cell stack" means that the resin layer is fixed in a state of being in close contact with the cell stack. When the resin layer is adhered to the cell stack, the resin layer continues to absorb variations in the thickness of the cell stack, thereby maintaining uniformity in the degree of compression in the in-plane direction of the cell stack.

[0028] From the viewpoint of sealing the inside of the all-solid-state battery, it is preferable that the resin layer is bonded to both the cell laminate and the exterior material. From the viewpoint of flatness of the main surfaces of the all-solid-state battery, it is preferable that the surface of the resin layer that comes into contact with the exterior material is flat.

[0029] The cell laminate, exterior material, and resin layer that constitute the all-solid-state battery will be described below.

[0030] (cell stack) The cell stack includes one or more unit cells. The components of the unit cells are not particularly limited and may be components known as components of an all-solid-state battery. The unit cell included in the cell stack may include a negative electrode layer, a solid electrolyte layer, and a positive electrode layer.

[0031] The negative electrode layer contains at least a negative electrode active material, the positive electrode layer contains at least a positive electrode active material, and the solid electrolyte layer contains at least a solid electrolyte. The negative electrode layer and the positive electrode layer may further include a solid electrolyte.

[0032] The negative electrode active material can be selected from materials that can absorb and release metal ions such as lithium ions. Examples of the negative electrode active material include metallic lithium, lithium alloys, carbon materials such as graphite and hard carbon, metal alloys, silicon materials such as silicon alloys, and Li4Ti5O 12 (LTO) is one example.

[0033] Examples of the solid electrolyte include sulfide-based amorphous solid electrolytes, oxide-based amorphous solid electrolytes, sulfide-based crystalline solid electrolytes, oxide-based crystalline solid electrolytes, iodide-based crystalline solid electrolytes, and nitride-based solid electrolytes. Examples of sulfide-based amorphous solid electrolytes include Li2S-P2S5, Li2O-Li2S-P2S5, Li2S, P2S5, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2S-P2O5, LiI-LiBr-Li2S-P2S5, and LiI-Li3PO4-P2S5. Examples of oxide-based amorphous solid electrolytes include Li2O-B2O3-P2O5 and Li2O-SiO2. The oxide-based crystalline solid electrolyte is Li5La3Ta2O 12 , Li7Zr2O 12 , Li6BaLa2Ta2O 12 , Li3PO( 4-3 / 2w )N w (w<1), etc. As a sulfide-based crystalline solid electrolyte, Li7P3S 11 , Li 3.25 P 0.75 Glass ceramics such as S4 or Li 3.24 P 0.24 Ge 0.76 Examples include Thio-Lisicon crystals such as S4, and those having an argyrodite-type crystal structure such as Li6PS5X (X = Cl, Br) (hereinafter sometimes referred to as "argyrodite-type sulfide solid electrolytes"). An example of an iodide-based crystalline solid electrolyte is LiI. An example of a nitride-based crystalline solid electrolyte is Li3N. From the viewpoint of lithium ion conductivity and electrochemical stability, an argyrodite-type sulfide solid electrolyte is preferred.

[0034] Examples of the positive electrode active material include metal oxides containing lithium and transition metals such as manganese, cobalt, nickel, and titanium. Specific examples include lithium cobalt oxide, lithium nickel oxide, lithium manganate, lithium nickel cobalt manganate, Li-Mn spinel substituted with different elements, lithium titanate, and lithium metal phosphate.

[0035] The negative electrode layer may be composed of a negative electrode active material layer and a negative electrode current collector. The positive electrode layer may be composed of a positive electrode active material layer and a positive electrode current collector. Examples of materials for the negative electrode current collector or the positive electrode current collector include metals such as Ag, Cu, Au, Al, Ni, Fe, and Ti, and alloys containing these metals. As the negative electrode current collector, Cu and Ni are preferred from the viewpoint of chemical stability. When a sulfide-based solid electrolyte is used, Ni is preferred from the viewpoint of preventing sulfidation of the negative electrode current collector. As the positive electrode current collector, Al is preferred from the viewpoint of chemical stability.

[0036] The negative electrode layer, which is composed of the negative electrode active material layer and the negative electrode current collector, is formed, for example, by applying a negative electrode mixture containing a negative electrode active material and a binder to the surface of the negative electrode current collector and drying it. The negative electrode active material layer may be formed on one surface or both surfaces of the negative electrode current collector. The negative electrode mixture may contain a solvent for the binder, a conductive material, and the like.

[0037] Examples of methods for forming the solid electrolyte layer include a method of compressing and molding a powder or pellet-like material containing a solid electrolyte, and a method of applying a paste-like material containing a solid electrolyte to the surface of a base plate and drying it.

[0038] The positive electrode layer, which is composed of a positive electrode active material layer and a positive electrode current collector, is formed, for example, by applying a positive electrode mixture containing a positive electrode active material and a binder to the surface of the positive electrode current collector and drying it. The positive electrode active material layer may be formed on one surface or both surfaces of the positive electrode current collector. The positive electrode mixture may contain a solvent for the binder, a conductive material, and the like.

[0039] The thickness of the cell laminate is not particularly limited and can be set depending on the application and performance of the all-solid-state battery. For example, the thickness of the cell stack can be selected from the range of 0.1 mm to 20 mm, 0.5 mm to 10 mm, or 1 mm to 5 mm.

[0040] (resin layer) The resin layer is preferably capable of adhering to the cell stack. An example of a resin layer that can be bonded to the cell stack is a layer containing a resin that melts or softens when heated. Specific examples of resins that melt or soften when heated include thermoplastic resins such as polyolefins such as polyethylene and polypropylene, polyesters such as polyamide and polyethylene terephthalate, polyurethanes, and ethylene vinyl acetate copolymers.

[0041] From the viewpoint of fully absorbing variations in the thickness of the cell stack, the thickness of the resin layer is preferably 10 μm or more, more preferably 30 μm or more, and even more preferably 50 μm or more, and may be 500 μm or less.

[0042] The resin layer may be integrated with the exterior material, or may not be integrated with the exterior material. From the viewpoint of workability when producing an all-solid-state battery, it is preferable that the resin layer be integrated with the exterior material.

[0043] (exterior materials) The material of the exterior material is not particularly limited and can be set depending on the application and performance of the all-solid-state battery. For example, the jacket may include a substrate layer and a barrier layer. The material of the base layer is not particularly limited and may be a resin, a metal, etc. Examples of the resin include the thermoplastic resins described above. Among these, a thermoplastic resin that does not melt or soften at the temperature at which the resin contained in the resin layer melts or softens is preferred. Examples of metals include aluminum, aluminum alloys, copper, copper alloys, stainless steel, and nickel. Examples of the barrier layer include a metal foil and a vapor deposition layer.

[0044] The shape of the all-solid-state battery of the present disclosure is not particularly limited. From the viewpoint of exerting the effect of the present invention, that is, increasing the degree of compression and thickness uniformity in the in-plane direction of the cell stack by providing a resin layer between the cell stack and the exterior material, the all-solid-state battery of the present disclosure is preferably a laminate type.

[0045] The thickness of the all-solid-state battery is not particularly limited and can be set depending on the application and performance of the all-solid-state battery. For example, the thickness of the all-solid-state battery can be selected from the range of 0.2 mm to 21 mm, 0.5 mm to 10 mm, or 1 mm to 5 mm. [Example]

[0046] The present disclosure will be described in more detail below with reference to examples, but the invention of the present disclosure is not limited to these examples.

[0047] <Embodiment 1> (Preparation of positive electrode layer) LiNi as the positive electrode material 0.5 Co 0.2 Mn 0.3 A slurry was prepared by dispersing O2, an argyrodite-type sulfide solid electrolyte, a conductive additive, and a binder in a solvent. This slurry was applied to both sides of an Al current collector foil and dried to produce a cathode layer (cathode active material layer / cathode current collector foil / cathode active material layer) with a thickness of approximately 100 μm formed on both sides of the current collector foil.

[0048] (Production of negative electrode layer) A slurry containing graphite, an argyrodite-type sulfide solid electrolyte, and a binder dispersed in a solvent was prepared as the negative electrode composite. This slurry was applied to both sides of a Cu current collector foil and dried to form a negative electrode active material layer approximately 200 μm thick on both sides of the current collector foil. Separately, a slurry was prepared by dispersing an argyrodite-type solid electrolyte and a binder in a solvent. This slurry was then coated on one side of a metal foil and dried to produce a solid electrolyte sheet in which a solid electrolyte layer with a thickness of approximately 30 μm was formed on one side of the metal foil. Next, the solid electrolyte sheet was placed on the negative electrode active material layers on both sides of the current collector foil so that the solid electrolyte layer of the solid electrolyte sheet faced the negative electrode active material layer, and roll pressing was performed to peel off the metal foil of the solid electrolyte sheet, thereby producing a negative electrode layer (solid electrolyte layer / negative electrode active material layer / negative electrode current collector foil / negative electrode active material layer / solid electrolyte layer) with the solid electrolyte layers transferred to both sides.

[0049] (Fabrication of all-solid-state batteries) Negative electrode layers and positive electrode layers cut to a predetermined size were alternately stacked to prepare a cell stack having a thickness of 2 mm. The cell stack was sandwiched between two resin-layered exterior materials (a polypropylene resin layer, an aluminum barrier layer, and a polyethylene terephthalate substrate layer), and the outer periphery of the cell stack was vacuum-sealed. In this state, a warm isostatic pressing (WIP) process was carried out at 190°C.

[0050] After the WIP process, the exterior material was removed from the cell stack, and a tablet was bonded to the tab (the uncoated part of the current collector foil) of the cell stack. The cell stack was then sandwiched between exterior materials with the same resin layers integrated as above, and the outer periphery of the cell stack was vacuum-sealed to produce a structure. Next, flat plates heated to 180°C were placed on both sides of the structure and pressed against it to produce a 2.5 mm-thick all-solid-state battery.

[0051] When the cross section of the fabricated all-solid-state battery was cut and observed, a polypropylene resin layer was found to be adhered to the cell stack. Furthermore, the resin layer had deformed along the undulations on the surface of the cell stack, and the thickness variation of the cell stack was absorbed by the resin layer. As a result, the thickness variation in the in-plane direction of the entire all-solid-state battery was smaller than the thickness variation in the in-plane direction of the cell stack. [Explanation of symbols]

[0052] 10: First exterior material, 20: First resin layer, 30: Cell laminate, 40: Second resin layer, 50: Second exterior material, 60: Structure, 100: All-solid-state battery

Claims

1. preparing a structure including a first exterior material, a first resin layer, a cell stack, a second resin layer, and a second exterior material in this order; applying pressure to the structure in a thickness direction at a temperature at which the first resin layer and the second resin layer melt or soften, thereby bonding at least one of the first resin layer and the second resin layer to the cell stack; the pressure is applied using a member having a flat surface facing the structure.

2. The method for producing an all-solid-state battery according to claim 1 , further comprising the step of applying an isostatic pressure to the structure.

3. a structure including a first exterior material, a first resin layer, a cell stack, a second resin layer, and a second exterior material in this order; At least one of the first resin layer and the second resin layer is bonded to the cell stack; The thickness variation in the in-plane direction of the entire structure is smaller than the thickness variation in the in-plane direction of the cell stack, an all-solid-state battery, wherein surfaces of the first resin layer and the second resin layer facing the cell stack are in a state of being deformed along the undulations of the surface of the cell stack.

4. The all-solid-state battery according to claim 3 , wherein each of the first resin layer and the second resin layer is adhered to the cell laminate.

5. The all-solid-state battery according to claim 3 or 4, wherein the first resin layer and the second resin layer each contain a thermoplastic resin.

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