Battery, battery system, and method for manufacturing a battery

Abstract

A battery (1000) comprises a power generation element (100) having: a positive electrode active material layer (120) that includes a positive electrode active material and a first inorganic solid electrolyte; a negative electrode active material layer (110) that includes a negative electrode active material and a second inorganic solid electrolyte; and a solid electrolyte layer (130) that is positioned between the positive electrode active material layer (120) and the negative electrode active material layer (110) and that includes a third inorganic solid electrolyte. A plurality of cavities (250) are present inside the power generation element (100), and the internal pressure of each of the plurality of cavities (250) is less than 1 atm.

Description

Technical Field

[0001] The present disclosure relates to a battery, a battery system, and a method for manufacturing a battery.

Background Art

[0002] Patent Document 1 discloses a method for manufacturing a bipolar secondary battery, including a step of preparing a bipolar electrode, a step of preparing an electrolyte, a step of laminating the bipolar electrode and an electrolyte layer or a precursor thereof to obtain a laminate including a single cell layer, and a step of forming a seal portion on the outer peripheral portion of the single cell layer. In the manufacturing method of Patent Document 1, the electrolyte contains a solvent or a dehydrating agent having a boiling point lower than that of water, and includes a step of depressurizing the electrolyte at a pressure of less than 20 Torr before or simultaneously with the step of forming the seal portion.

[0003] Patent Document 2 discloses a lithium-ion battery in which the average porosity of a solid electrolyte layer is 9% or less.

[0004] Patent Document 3 discloses depressurization to fill voids in a negative electrode and voids in a microporous separator with a lithium-ion conductive polymer solid electrolyte.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the prior art, further improvement of battery characteristics and reliability is desired.

[0007] Furthermore, batteries containing solid electrolytes are also required to exhibit high capacity and excellent charge-discharge cycle characteristics, among other high battery properties.

[0008] For example, inorganic solid electrolytes have excellent ionic conductivity, making it possible to realize high-capacity batteries containing solid electrolytes. However, inorganic solid electrolytes are generally less flexible than, for example, polymer solid electrolytes. Therefore, in order to achieve the desired characteristics of batteries using inorganic solid electrolytes, it is important to enhance the ionic conductivity of the active material layer, the solid electrolyte layer, and the interface between the active material layer and the solid electrolyte layer, and to maintain this conductivity even during repeated charging and discharging by applying an external restraining force from the direction normal to the main surface of the battery.

[0009] On the other hand, applying restraints or other mechanisms to apply external restraining forces is inconvenient for obtaining capacity density per unit volume and capacity density per unit weight of the battery, and suppressing capacity degradation due to repeated charging and discharging is an important issue for ensuring the long-term reliability of the battery.

[0010] Therefore, this disclosure provides a battery that achieves both high battery performance and high reliability. [Means for solving the problem]

[0011] A battery in one aspect of the present disclosure comprises a power generation element having a positive electrode layer containing a positive electrode active material and a first inorganic solid electrolyte, a negative electrode layer containing a negative electrode active material and a second inorganic solid electrolyte, and a solid electrolyte layer located between the positive electrode layer and the negative electrode layer and containing a third inorganic solid electrolyte, wherein a plurality of voids exist inside the power generation element, and the internal pressure of the plurality of voids is less than 1 atm.

[0012] Furthermore, a battery system in one aspect of this disclosure comprises a container having an internal space that becomes a reduced-pressure environment, and the battery disposed in the internal space.

[0013] Furthermore, a method for manufacturing a battery in one aspect of the present disclosure comprises a positive electrode layer containing a positive electrode active material and a first inorganic solid electrolyte, a negative electrode layer containing a negative electrode active material and a second inorganic solid electrolyte, and a solid electrolyte layer located between the positive electrode layer and the negative electrode layer and containing a third inorganic solid electrolyte, the method for manufacturing a battery comprising a compression step of pressing a compressible body including at least one of the positive electrode layer, the negative electrode layer and the solid electrolyte layer in a reduced pressure atmosphere.

[0014] Furthermore, a method for manufacturing a battery in one aspect of the present disclosure is a method for manufacturing a battery comprising a positive electrode layer, a negative electrode layer, and a solid electrolyte layer located between the positive electrode layer and the negative electrode layer, and includes a compression step of pressing a compressed body in a reduced-pressure atmosphere, wherein the positive electrode layer and the negative electrode layer are stacked so as to face each other via the solid electrolyte layer. [Effects of the Invention]

[0015] According to this disclosure, it is possible to achieve both high battery characteristics and high reliability in batteries and the like. [Brief explanation of the drawing]

[0016] [Figure 1] Figure 1 is a cross-sectional view showing the schematic configuration of a battery according to Embodiment 1. [Figure 2] Figure 2 is a cross-sectional view showing the schematic configuration of a battery according to Comparative Example 1. [Figure 3] Figure 3 is a cross-sectional view showing the schematic configuration of a battery according to Comparative Example 2. [Figure 4] Figure 4 is a cross-sectional view showing the schematic configuration of the battery according to Comparative Example 3. [Figure 5] Figure 5 is a diagram illustrating the damage that occurs in the battery according to Comparative Example 3. [Figure 6A] Figure 6A is a cross-sectional view showing the schematic configuration of a laminate formed by the battery manufacturing method according to Embodiment 1. [Figure 6B] Figure 6B is a cross-sectional view showing the schematic configuration of another laminate formed by the battery manufacturing method according to Embodiment 1. [Figure 7A]FIG. 7A is a cross-sectional view showing a schematic configuration of yet another laminate formed by the method for manufacturing a battery according to Embodiment 1. [Figure 7B] FIG. 7B is a cross-sectional view showing a schematic configuration of yet another laminate formed by the method for manufacturing a battery according to Embodiment 1. [Figure 8] FIG. 8 is a cross-sectional view showing a schematic configuration of yet another laminate formed by the method for manufacturing a battery according to Embodiment 1. [Figure 9] FIG. 9 is a schematic diagram for explaining a first example of a pressing method of a compressible body in the first compression step according to Embodiment 1. [Figure 10] FIG. 10 is a schematic diagram for explaining a first example of a pressing method of a compressible body in the second compression step according to Embodiment 1. [Figure 11] FIG. 11 is a schematic diagram for explaining a second example of a pressing method of a compressible body in the first compression step according to Embodiment 1. [Figure 12] FIG. 12 is a schematic diagram for explaining a second example of a pressing method of a compressible body in the second compression step according to Embodiment 1. [Figure 13] FIG. 13 is a schematic diagram for explaining a third example of a pressing method of a compressible body in the first compression step according to Embodiment 1. [Figure 14] FIG. 14 is a schematic diagram for explaining a third example of a pressing method of a compressible body in the second compression step according to Embodiment 1. [Figure 15] FIG. 15 is a schematic diagram for explaining a fourth example of a pressing method of a compressible body in the first compression step according to Embodiment 1. [Figure 16] FIG. 16 is a schematic diagram for explaining a fourth example of a pressing method of a compressible body in the second compression step according to Embodiment 1. [Figure 17] FIG. 17 is a schematic diagram showing a schematic configuration of a battery system according to Embodiment 2. [Figure 18] FIG. 18 is a schematic diagram showing a schematic configuration of another battery system according to Embodiment 2. [Modes for carrying out the invention]

[0017] (Summary of this disclosure) A battery in one aspect of the present disclosure comprises a power generation element having a positive electrode layer containing a positive electrode active material and a first inorganic solid electrolyte, a negative electrode layer containing a negative electrode active material and a second inorganic solid electrolyte, and a solid electrolyte layer located between the positive electrode layer and the negative electrode layer and containing a third inorganic solid electrolyte, wherein a plurality of voids exist inside the power generation element, and the internal pressure of the plurality of voids is less than 1 atm.

[0018] As a result, the battery in this embodiment can achieve both high battery performance and high reliability. When the internal pressure of the void is higher than the external environment, the internal pressure of the void acts in a direction that releases contact between adjacent positive electrode active material, negative electrode active material, or inorganic solid electrolyte in multiple voids, causing the void to expand and reducing the ionic and electronic conductivity inside the power generation element. For example, the expansion and contraction of the active material layer due to the insertion and deinsertion of ions during charging and discharging can trigger the expansion of the positive pressure void, damaging the power generation element. In the case of batteries containing inorganic solid electrolytes, unlike liquid-based batteries filled with electrolyte, damage to the power generation element due to void expansion is particularly likely to cause a significant decrease in ionic conductivity. In the battery according to this embodiment, since the void is under negative pressure of less than 1 atm, the expansion of the void can be suppressed.

[0019] Furthermore, the multiple negative pressure voids not only prevent the degradation of the battery from starting due to damage to the power generation element, but also attract the materials around the voids to each other, resulting in a stronger battery than one without voids. In this embodiment, since an inorganic solid electrolyte is used as the battery material, the flexibility of the battery is low, and the force attracting the materials around the multiple voids is transmitted without dissipation. As a result, an external restraining force is applied to the power generation element without the need for restraints, and the ion and electron conductivity of the power generation element can be improved without reducing the battery capacity. Therefore, the battery in this embodiment can achieve both high battery performance and high reliability.

[0020] Furthermore, for example, the plurality of voids may be located along at least one grain boundary among the first inorganic solid electrolyte, the second inorganic solid electrolyte, and the third inorganic solid electrolyte.

[0021] This improves the stability of grain boundaries in inorganic solid electrolytes.

[0022] Furthermore, for example, at least one of the plurality of voids may be located inside at least one of the positive electrode layer and the negative electrode layer.

[0023] This makes it possible to suppress damage to the power generation element caused by volume changes of the active material during charging and discharging.

[0024] Furthermore, for example, at least one of the plurality of voids may be located on the surface of at least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer.

[0025] This makes it possible to suppress delamination at the interfaces of each layer of the power generation element caused by multiple voids.

[0026] Furthermore, for example, the internal pressure of the plurality of voids may be 0.1 atm or less.

[0027] This further suppresses damage to power generation elements caused by multiple air gaps.

[0028] Furthermore, for example, the average of the maximum widths of each of the aforementioned multiple voids may be 10 μm or less.

[0029] This makes it possible to suppress the effect of multiple voids on inhibiting the conduction of ions or electrons in the power generation element.

[0030] Furthermore, for example, the density of at least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer may be 90% or more of the theoretical material density.

[0031] This can improve the battery's performance characteristics.

[0032] Furthermore, a battery system in one aspect of this disclosure comprises a container having an internal space that becomes a reduced-pressure environment, and the battery disposed in the internal space.

[0033] As a result, since the battery system is equipped with the aforementioned batteries, even if the internal space of the container becomes a reduced-pressure environment, the multiple voids are less likely to expand, and damage to the power generation element can be suppressed.

[0034] Furthermore, for example, the pressure in the reduced-pressure environment may be 0.95 atm or less.

[0035] This makes it less likely for multiple air gaps to expand even when the battery is placed in a reduced pressure environment of 0.95 atm or less, thus suppressing damage to the power generation element.

[0036] Furthermore, for example, the internal pressure of the plurality of voids may be less than or equal to the pressure of the reduced-pressure environment.

[0037] This helps to suppress damage to the power generation element originating from multiple voids. Furthermore, the multiple voids can exert a force that pulls the material of the power generation element inward.

[0038] Furthermore, a method for manufacturing a battery in one aspect of the present disclosure comprises a positive electrode layer containing a positive electrode active material and a first inorganic solid electrolyte, a negative electrode layer containing a negative electrode active material and a second inorganic solid electrolyte, and a solid electrolyte layer located between the positive electrode layer and the negative electrode layer and containing a third inorganic solid electrolyte, wherein the press of a compressible body including at least one of the positive electrode layer, the negative electrode layer and the solid electrolyte layer is performed in a reduced pressure atmosphere.

[0039] This allows the compressed material to be denser by pressing, and also allows the internal pressure of isolated voids formed inside the compressed material due to the pressing to be reduced to a negative pressure of less than 1 atm. Before pressing, some of the voids inside the compressed material are connected to the atmosphere outside the compressed material by minute conductive paths. As the densification progresses due to the compression of the compressed material, most of the conductive paths become blocked, and the residual gas in the voids loses its outlet. From this point onward, as the densification progresses, the internal pressure of the voids increases. Therefore, for example, if the atmosphere outside the compressed material is at normal pressure, when the compression process is completed, many voids with high pressure exceeding 1 atm are formed inside the compressed material, and these can become the starting point for damage to the compressed material during charging and discharging, potentially destroying the conduction paths of ions and electrons. In contrast, in the battery manufacturing method of this embodiment, the atmosphere outside the compressed material is a reduced-pressure atmosphere, so the gas in the voids of the compressed material before pressing can be exhausted through the conductive paths. Therefore, even after the majority of the conductive paths are blocked by the increasing density due to compression of the compressed material and the voids are isolated from the atmosphere outside the compressed material, the increase in internal pressure of the voids due to the increasing density can be kept small. As a result, the internal pressure of the remaining voids at the completion of the compression process can be kept at a negative pressure or a relatively small positive pressure, thereby suppressing the destruction of conductive paths due to damage to the compressed material caused by the voids and reducing the degradation of the manufactured batteries.

[0040] Furthermore, one embodiment of the present disclosure is a method for manufacturing a battery comprising a positive electrode layer, a negative electrode layer, and a solid electrolyte layer located between the positive electrode layer and the negative electrode layer, wherein the press of a workpiece in which the positive electrode layer and the negative electrode layer are stacked facing each other via the solid electrolyte layer is performed in a reduced-pressure atmosphere.

[0041] This allows each layer of the compressible body to be compressed and bonded by pressing, and also allows the internal pressure of the voids formed at the interfaces between each layer of the compressible body to be reduced to a negative pressure of 1 atm or less. At the start of the compression process, voids exist at the boundaries between each layer of the compressible body due to the surface roughness of each layer. These voids are connected to the atmosphere outside the compressible body by minute conductive paths. As the compression bonding progresses, most of the conductive paths are blocked, and the residual gas in the voids loses its outlet. Thereafter, as the compression bonding progresses, the internal pressure of the voids increases. Therefore, for example, if the atmosphere outside the compressible body is at normal pressure, when the compression process is completed, many high-pressure voids are formed along the interfaces of each layer of the compressible body, and these can become the starting points for damage to the compressible body during charging and discharging, potentially destroying the conductive paths between each layer of the compressible body. In contrast, in the battery manufacturing method according to this embodiment, the atmosphere outside the compressible body is a reduced-pressure atmosphere, so the gas in the voids at the boundaries of each layer of the compressible body before compression bonding can be exhausted through the conductive paths. Therefore, even after most of the conductive paths are blocked by the progress of compression bonding of the compressed material and the void is isolated from the atmosphere outside the compressed material, the increase in internal pressure of the void due to the progress of compression bonding can be kept small. As a result, the internal pressure of the remaining void at the completion of the compression process can be kept at a negative pressure or a relatively small positive pressure, thereby suppressing the destruction of the conductive paths due to damage to the compressed material caused by the void and reducing the progression of degradation of the manufactured battery.

[0042] Furthermore, for example, the pressure of the reduced-pressure atmosphere may be 0.1 atm or less.

[0043] This allows for a lower internal pressure in the void formed by the compression process.

[0044] Furthermore, for example, the pressure of the press may be 10 MPa or more.

[0045] This makes it possible to further improve the battery characteristics of the manufactured batteries.

[0046] Furthermore, for example, in the compression step, the object to be compressed is placed in an airtight container, the inside of the airtight container is reduced to a reduced pressure atmosphere, and the object to be compressed is pressed from outside the airtight container. The airtight container is provided with a deformable part made of an elastic material that deforms when pressed, and the pressure of the press from outside the airtight container is applied to the object to be compressed as the deformable part deforms when pressed.

[0047] This allows the object to be compressed to be pressed from outside the airtight container, eliminating the need to install the pressing device itself in a reduced-pressure atmosphere, thus enabling a miniaturization of the pressing device.

[0048] Embodiments of the present disclosure will be described below with reference to the drawings.

[0049] The embodiments described below are all general or specific examples. The numerical values, shapes, materials, components, arrangement and connection configurations of components, processes, and order of processes shown in the following embodiments are examples only and are not intended to limit this disclosure. Furthermore, any components in the following embodiments that are not described in an independent claim will be described as optional components.

[0050] Furthermore, each figure is a schematic diagram and not necessarily a strictly accurate representation. Therefore, for example, the scale may not necessarily match in each figure. Also, in each figure, substantially identical components are given the same reference numerals, and redundant explanations are omitted or simplified.

[0051] Furthermore, in this specification, terms indicating relationships between elements such as parallelism, terms indicating the shape of elements such as rectangles, and numerical ranges do not represent only strict meanings, but also include substantially equivalent ranges, such as differences of a few percent.

[0052] Furthermore, in this specification, "plan view" means the view from the direction normal to the main surface of the power generation element.

[0053] (Embodiment 1) [composition] First, the configuration of the battery according to this embodiment will be described.

[0054] Figure 1 is a cross-sectional view showing the schematic configuration of the battery 1000 according to Embodiment 1.

[0055] As shown in Figure 1, the battery 1000 according to Embodiment 1 comprises a negative electrode current collector 210, a positive electrode current collector 220, and a power generation element 100. The battery 1000 is, for example, an all-solid-state battery.

[0056] The power generation element 100 is located between the negative electrode current collector 210 and the positive electrode current collector 220. The power generation element 100 has a positive electrode active material layer 120 containing a positive electrode active material and a first inorganic solid electrolyte, a negative electrode active material layer 110 containing a negative electrode active material and a second inorganic solid electrolyte, and a solid electrolyte layer 130 located between the positive electrode active material layer 120 and the negative electrode active material layer 110 and containing a third inorganic solid electrolyte. The negative electrode active material layer 110 and the positive electrode current collector 220 face each other via the solid electrolyte layer 130. The positive electrode active material layer 120 is an example of a positive electrode layer, and the negative electrode active material layer 110 is an example of a negative electrode layer. In this specification, the first inorganic solid electrolyte, the second inorganic solid electrolyte, and the third inorganic solid electrolyte may be collectively referred to simply as "inorganic solid electrolyte". The first inorganic solid electrolyte, the second inorganic solid electrolyte, and the third inorganic solid electrolyte may, for example, be the same material, but they may also be different materials.

[0057] Furthermore, in this specification, the negative electrode current collector 210 and the positive electrode current collector 220 may be collectively referred to simply as "current collectors," and the negative electrode active material layer 110 and the positive electrode active material layer 120 may be collectively referred to simply as "active material layers."

[0058] Multiple voids 250 exist inside the power generation element 100. Details of these multiple voids 250 will be described later.

[0059] The negative electrode active material layer 110 contains a negative electrode active material as an electrode material. Examples of negative electrode active materials that can be used in the negative electrode active material layer 110 include graphite and metallic lithium. Various materials that can release and insert ions such as lithium (Li) or magnesium (Mg) can be used as the material for the negative electrode active material. The negative electrode active material is, for example, a particulate material.

[0060] Furthermore, the negative electrode active material layer 110 further contains, for example, an inorganic solid electrolyte. As the inorganic solid electrolyte, for example, a sulfide solid electrolyte or an oxide solid electrolyte may be used. As the sulfide solid electrolyte, for example, a mixture of lithium sulfide (Li2S) and phosphorus pentasulfide (P2S5) may be used. The inorganic solid electrolyte is, for example, a particulate material. In addition, as the material contained in the negative electrode active material layer 110, at least one of a conductive material such as acetylene black and a binding binder such as polyvinylidene fluoride may be used further.

[0061] The negative electrode active material layer 110 can be manufactured by coating and drying a paste-like coating, which is made by kneading the materials containing the negative electrode active material layer 110 together with a solvent, onto the surface of the negative electrode current collector 210. The thickness of the negative electrode active material layer 110 is, for example, 5 μm to 300 μm, but is not limited to this.

[0062] The positive electrode active material layer 120 contains a positive electrode active material as an electrode material. The positive electrode active material is the material that constitutes the counter electrode to the negative electrode active material. Examples of positive electrode active materials that can be used in the positive electrode active material layer 120 include lithium cobalt oxide composite oxide (LCO), lithium nickel oxide composite oxide (LNO), lithium manganese oxide composite oxide (LMO), lithium-manganese-nickel oxide composite oxide (LMNO), lithium-manganese-cobalt oxide composite oxide (LMCO), lithium-nickel-cobalt oxide composite oxide (LNCO), and lithium-nickel-manganese-cobalt oxide composite oxide (LNMCO). Various materials that can release and insert ions such as Li or Mg can be used as the material for the positive electrode active material. The positive electrode active material is, for example, a particulate material.

[0063] Furthermore, the positive electrode active material layer 120 further includes, for example, an inorganic solid electrolyte. As the inorganic solid electrolyte, the materials exemplified above as inorganic solid electrolytes used in the negative electrode active material may be used. The surface of the positive electrode active material may also be coated with the solid electrolyte. In addition, as the material contained in the positive electrode active material layer 120, at least one of a conductive material such as acetylene black and a binding binder such as polyvinylidene fluoride may be used.

[0064] The positive electrode active material layer 120 can be manufactured by coating and drying a paste-like coating, which is made by kneading the materials containing the positive electrode active material layer 120 together with a solvent, onto the surface of the positive electrode current collector 220. The thickness of the positive electrode active material layer 120 is, for example, 5 μm to 300 μm, but is not limited to this.

[0065] The solid electrolyte layer 130 is positioned between the negative electrode active material layer 110 and the positive electrode active material layer 120. The solid electrolyte layer 130 is in contact with each of the negative electrode active material layer 110 and the positive electrode active material layer 120. The size and plan view shape of the solid electrolyte layer 130 may be the same as the size and plan view shape of the negative electrode active material layer 110 and the positive electrode active material layer 120, respectively. That is, the side surfaces of the solid electrolyte layer 130 may be flush with the side surfaces of the negative electrode active material layer 110 and the positive electrode active material layer 120, respectively.

[0066] The solid electrolyte layer 130 is a layer containing an electrolyte material. Generally known electrolytes for batteries can be used as the electrolyte material. The thickness of the solid electrolyte layer 130 may be 5 μm to 300 μm, or 5 μm to 100 μm. In the example shown in Figure 1, the solid electrolyte layer 130 is a single layer, but the power generation element 100 may have a structure in which multiple solid electrolyte layers 130 are stacked.

[0067] The solid electrolyte layer 130 contains an inorganic solid electrolyte as the electrolyte material. The inorganic solid electrolyte may be one of the materials exemplified above as inorganic solid electrolytes used in the negative electrode active material. In addition to the electrolyte material, the solid electrolyte layer 130 may also contain a binding binder, such as polyvinylidene fluoride.

[0068] In battery 1000, the negative electrode active material layer 110, the positive electrode active material layer 120, and the solid electrolyte layer 130 are maintained in a parallel plate shape. This suppresses the occurrence of cracking or collapse due to bending. Alternatively, the negative electrode active material layer 110, the positive electrode active material layer 120, and the solid electrolyte layer 130 may be smoothly curved together.

[0069] The negative electrode current collector 210 and the positive electrode current collector 220 are positioned opposite the power generation element 100, with the power generation element 100 in between them. In a plan view, the outer circumferences of the negative electrode current collector 210, the positive electrode current collector 220, and the power generation element 100 coincide, for example. The negative electrode current collector 210 and the positive electrode current collector 220 are both conductive materials. The negative electrode current collector 210 and the positive electrode current collector 220 may each be, for example, a conductive thin film. As materials for constituting the negative electrode current collector 210 and the positive electrode current collector 220, metals such as stainless steel (SUS), aluminum (Al), copper (Cu), and nickel (Ni) can be used.

[0070] The negative electrode current collector 210 is positioned on the negative electrode active material layer 110 side of the power generation element 100. The negative electrode current collector 210 is positioned, for example, in contact with the negative electrode active material layer 110. As the negative electrode current collector 210, metal foils such as SUS foil, Al foil, Cu foil, and Ni foil can be used. The thickness of the negative electrode current collector 210 is, for example, 5 μm to 100 μm, but is not limited to this. The negative electrode current collector 210 may also have a current collector layer, for example, a layer containing a conductive material, in the portion in contact with the negative electrode active material layer 110.

[0071] The positive electrode current collector 220 is positioned on the positive electrode active material layer 120 side of the power generation element 100. The positive electrode current collector 220 is positioned, for example, in contact with the positive electrode active material layer 120. As the positive electrode current collector 220, metal foils such as SUS foil, Al foil, Cu foil, and Ni foil can be used. The thickness of the positive electrode current collector 220 is, for example, 5 μm to 100 μm, but is not limited to this. The positive electrode current collector 220 may also have a current collector layer in the portion in contact with the positive electrode active material layer 120, for example, a layer containing a conductive material.

[0072] At least one of the negative electrode active material layer 110, the solid electrolyte layer 130, and the positive electrode active material layer 120 is formed by a first compression step, for example, in which pressing is performed under a reduced pressure atmosphere to increase the density of each layer. This ensures ionic conductivity and electronic conductivity within each layer of the power generation element 100, thereby improving battery characteristics. In this embodiment, for example, the negative electrode active material layer 110, the solid electrolyte layer 130, and the positive electrode active material layer 120 are all formed by a first compression step. In this specification, "pressing" means applying mechanical stress to the object to be compressed.

[0073] Furthermore, the power generation element 100 is formed, for example, through a second compression step in which pressing is performed under a reduced pressure atmosphere to compress and bond each layer of the power generation element 100. This ensures ionic and electronic conductivity at the interfaces of each layer of the power generation element 100, thereby improving battery characteristics.

[0074] Details of the first and second compression steps will be described later.

[0075] In the battery 1000, there are multiple voids 250 inside the power generation element 100. These multiple voids 250 are not connected to the outside of the power generation element 100 and exist as isolated voids inside the power generation element 100. In other words, the multiple voids 250 are independent bubbles (hollow parts) located inside the power generation element 100.

[0076] The multiple voids 250 include, for example, voids 250 formed when the gaps between material particles, such as inorganic solid electrolytes, contained in each layer of the power generation element 100 are blocked by the first compression step, thereby closing the conductive paths to the outside. Therefore, unlike electrolytes such as gels, grain boundaries are formed in inorganic solid electrolytes, and the multiple voids 250 include voids 250 located along the grain boundaries of the inorganic solid electrolyte contained in each layer. Furthermore, the multiple voids 250 include voids 250 located inside at least one of the negative electrode active material layer 110, positive electrode active material layer 120, and solid electrolyte layer 130. In the example shown in Figure 1, the multiple voids 250 include voids 250 located inside any of the layers of the negative electrode active material layer 110, positive electrode active material layer 120, and solid electrolyte layer 130.

[0077] Furthermore, the multiple voids 250 include, for example, voids 250 formed when the voids between each layer of the power generation element 100 are blocked by the second compression step, thereby closing the conductive paths to the outside. Therefore, the multiple voids 250 include voids 250 located on the surface of at least one of the negative electrode active material layer 110, the positive electrode active material layer 120, and the solid electrolyte layer 130. In other words, the multiple voids 250 include voids 250 formed to be in contact with the surface of at least one of the negative electrode active material layer 110, the positive electrode active material layer 120, and the solid electrolyte layer 130. In the example shown in Figure 1, the multiple voids 250 include voids 250 located on the surface of any of the layers of the negative electrode active material layer 110, the positive electrode active material layer 120, and the solid electrolyte layer 130.

[0078] In the example shown in Figure 1, of all the multiple voids 250, at least one is located inside at least one of the negative electrode active material layer 110, positive electrode active material layer 120, and solid electrolyte layer 130, and at least one other is located on the surface of at least one of the negative electrode active material layer 110, positive electrode active material layer 120, and solid electrolyte layer 130. Note that both the voids 250 located inside at least one of the negative electrode active material layer 110, positive electrode active material layer 120, and solid electrolyte layer 130 and the voids 250 located on the surface of at least one of the negative electrode active material layer 110, positive electrode active material layer 120, and solid electrolyte layer 130 may exist, or only one of them may exist.

[0079] Here, we will describe the battery related to the comparative example.

[0080] First, we will describe a battery 1001X formed without undergoing a pressing process such as the first and second compression processes. Figure 2 is a cross-sectional view showing the schematic configuration of a battery 1001X according to Comparative Example 1. As schematically shown in Figure 2, the power generation element 100 of the battery 1001X has a plurality of voids 251 and a conductive path 251a connecting the plurality of voids 251 to the outside of the battery 1001X. The plurality of voids 251 are in communication with the outside of the battery 1001X by the conductive path 251a. Therefore, the internal pressure of the plurality of voids 251 is equal to the external pressure, i.e., atmospheric pressure = 1 atm. Since the battery 1001X is not formed through a pressing process, it is not densely packed and the contact area between particles is not increased, resulting in high resistance and low capacity.

[0081] Next, we will describe the battery 1002X formed through a process of pressing at low pressure. The battery 1002X is formed through a process of pressing each layer of the power generation element 100 at a low pressure of, for example, 1 MPa or less. Figure 3 is a cross-sectional view showing the schematic configuration of the battery 1002X according to Comparative Example 2. As schematically shown in Figure 3, the power generation element 100 of the battery 1002X has a plurality of voids 252 and conductive paths 252a connected to the plurality of voids 252. Some of the voids 252 are connected to the outside of the battery 1002X by conductive paths 252a, but some of the other voids 252 are isolated voids 252 because the conductive paths 252a connected to the voids 252 are not connected to the outside of the battery 1002X. The inside of the void 252 that communicates with the outside of the battery 1002X is at the same pressure as the outside. However, isolated voids 252 are compressed by the pressing process even after they are isolated from the outside of the battery 1002X, and the volume of multiple voids 252 decreases, resulting in a higher pressure than the outside. Since the battery 1002X is not formed through a pressing process with sufficient pressure, the density and the increase in the contact area between particles are insufficient, resulting in high resistance and low capacity.

[0082] Next, we will describe battery 1003X, which is formed by a pressing process at a higher pressure than that of battery 1002X. Battery 1003X is formed by a pressing process in which each layer of the power generation element 100 is pressed at a high pressure of 10 MPa or more. Figure 4 is a cross-sectional view showing the schematic configuration of battery 1003X according to Comparative Example 3. As schematically shown in Figure 4, the power generation element 100 of battery 1003X has a plurality of isolated voids 253 that are not in communication with the outside of battery 1003X. The plurality of voids 253 are compressed by the pressing process even after they are isolated from the outside of battery 1003X, and the volume of the plurality of voids 253 decreases, resulting in a higher pressure than the outside. Therefore, a large number of high-pressure sources are scattered inside the power generation element 100.

[0083] Because the battery 1003X is formed through a process of pressing at high pressure, high density and increased contact area between particles are achieved, resulting in low resistance and high capacity in the initial period after manufacturing. However, when the internal stress of the power generation element 100 changes due to factors such as the release from the compressive force during the pressing process, as well as during charging and discharging (i.e., volume changes of the active material due to ion insertion and deinsertion), temperature and pressure changes in the environment in which the battery 1003X is used, and external forces applied to the battery 1003X, damage to the power generation element 100 can occur starting from multiple voids 253. Figure 5 is a diagram illustrating the damage that occurs in the battery 1003X. As schematically shown in Figure 5, multiple high-pressure voids 253 expand within the positive electrode active material layer 120, the negative electrode active material layer 110, and the solid electrolyte layer 130, as well as between each layer of the power generation element 100, becoming multiple voids 254, which promotes minute damage such as grain boundary delamination and interlayer delamination. As a result, the battery characteristics of the battery 1003X deteriorate. Therefore, simply forming the battery by a process that involves pressing at high pressure makes it difficult to maintain battery characteristics in the long term, and the reliability of the battery 1003X is low.

[0084] In contrast, in the battery 1000, in order to suppress the deterioration of battery characteristics caused by the multiple voids 250 present inside the power generation element 100, the multiple voids 250 are under a negative pressure lower than atmospheric pressure. That is, the internal pressure of the multiple voids 250 is less than 1 atm. The presence of multiple voids 250 with an internal pressure of less than 1 atm means that when the battery is released from the compressive force in the first and second compression processes, when the volume of the active material changes, when the operating environment of the battery 1000 changes, and when an external force is applied to the battery 1000, the negative pressure inside the multiple voids acts in a direction that suppresses grain boundary delamination and interlayer delamination, thereby suppressing the deterioration of the battery characteristics of the battery 1000. In particular, the presence of multiple voids 250 under negative pressure in the negative electrode active material layer 110 and the positive electrode active material layer 120 suppresses damage to the power generation element 100 caused by volume changes of the active material during charging and discharging.

[0085] Furthermore, the presence of multiple voids 250 with negative pressure inside acts as a force that attracts the materials of each layer of the power generation element 100, not only when the internal pressure of the multiple voids 250 is higher than atmospheric pressure, but also when there are no multiple voids 250, thus suppressing the degradation of the battery characteristics of the battery 1000. In addition, the presence of multiple voids 250 with negative pressure inside acts as a force that attracts the materials of each layer of the power generation element 100, thereby reducing resistance at the grain boundaries of the materials in each layer and between each layer, improving the battery characteristics. Moreover, an external restraining force is applied to the power generation element 100 without the need for restraints, thus avoiding the reduction in battery capacity per unit volume and per unit weight that would occur if restraints were provided.

[0086] Multiple voids 250 exist within at least one of the positive electrode active material layer 120 and the negative electrode active material layer 110. This suppresses damage to the power generation element 100 caused by volume changes of the active material during charging and discharging. In addition, the multiple voids 250 can attract material from the surrounding active material layer, thereby reducing the resistance within the active material layer.

[0087] From the viewpoint of improving the reliability of the battery 1000, the internal pressure of the multiple air gaps 250 may be 0.8 atm or less, 0.5 atm or less, or 0.1 atm or less. Also, the internal pressure of the multiple air gaps 250 may be greater than, for example, 0 atm. In this specification, the pressures such as the internal pressure of the multiple air gaps 250 are pressures at room temperature. Room temperature is, for example, 23°C. Also, in this specification, the numerical values ​​of the pressures such as the internal pressure of the multiple air gaps 250 are numerical values ​​in absolute pressure.

[0088] Such multiple voids 250 with an internal pressure of less than 1 atm are formed, for example, in a first and / or second compression step in which pressing is performed in a reduced-pressure atmosphere. The density of at least one of the positive electrode active material layer 120, negative electrode active material layer 110, and solid electrolyte layer 130 formed through the first and / or second compression steps (specifically, the apparent density obtained by dividing weight by apparent volume) is, for example, 90% or more of the theoretical material density, and may be 95% or more. This can improve the battery characteristics of the battery 1000. The densities of all of the positive electrode active material layer 120, negative electrode active material layer 110, and solid electrolyte layer 130 may all be 90% or more of the theoretical material density of each layer.

[0089] The average of the maximum widths of each of the multiple voids 250 is, for example, 10 μm or less, and may be 1 μm or less. This suppresses the effect of the multiple voids 250 on inhibiting the conduction of ions or electrons in the power generation element 100. The maximum width of each of the multiple voids 250 is measured from the multiple voids 250 observed by observing the cross-section of the battery 1000 with an electron microscope or the like.

[0090] As described above, Battery 1000 can achieve both high battery performance and high reliability.

[0091] [Manufacturing method] Next, a method for manufacturing the battery 1000 according to this embodiment will be described. The method for manufacturing the battery 1000 includes, for example, a first compression step and a second compression step.

[0092] In the first compression step, the compressed object, which includes at least one of the positive electrode active material layer 120, the negative electrode active material layer 110, and the solid electrolyte layer 130, is pressed in a reduced pressure atmosphere of less than 1 atm. This allows for the densification of at least one of the positive electrode active material layer 120, the negative electrode active material layer 110, and the solid electrolyte layer 130. Pressing in a reduced pressure atmosphere means performing the press in a space where the pressure is reduced to less than 1 atm, for example, by exhausting the gas in the space.

[0093] Furthermore, inside the compressed material before pressing in the first compression step, there are voids connected to the atmosphere outside the compressed material by minute conductive paths, such as the void 251 connected to the conductive path 251a shown in Figure 2. These voids are caused by gaps between the material particles of the compressed material. As the compression of the compressed material progresses, most of the conductive paths are blocked, and the residual gas in the voids loses its outlet. Thereafter, as the density increases due to compression, the internal pressure of the voids rises. For example, when the volume of the voids is reduced to less than half after the conductive paths are blocked, the internal pressure of the voids becomes 2 atm or more. Therefore, for example, if the atmosphere outside the compressed material is at normal pressure, many high-pressure voids are formed inside the compressed material when the compression step is completed. These can become the starting points for damage to the compressed material during charging and discharging, and the conduction paths of ions and electrons may be destroyed. In contrast, in the first compression step, the atmosphere outside the object to be compressed is a reduced-pressure atmosphere, so the gas in the voids of the object to be compressed before pressing can be exhausted through the conductive path. Therefore, even after most of the conductive path is blocked as the compression of the object to be compressed progresses and the voids are isolated from the atmosphere outside the object to be compressed, the increase in internal pressure of the voids due to the progress of compression can be kept small. As a result, for example, the internal pressure of the remaining multiple voids 250 at the completion of the first compression step can be reduced to a negative pressure of less than 1 atm.

[0094] In the second compression step, the compressed object, in which the positive electrode active material layer 120 and the negative electrode active material layer 110 are stacked facing each other via the solid electrolyte layer 130, is pressed in a reduced pressure atmosphere of less than 1 atm. This allows the positive electrode active material layer 120 and the negative electrode active material layer 110 to be compressed and bonded together via the solid electrolyte layer 130.

[0095] Furthermore, at the boundaries of each layer of the material to be compressed before pressing in the second compression process, there are voids connected to the atmosphere outside the material to be compressed by fine conductive paths, such as the void 251 connected to the conductive path 251a shown in Figure 2. These voids are due to the surface roughness of each layer of the material to be compressed. As compression bonding progresses, most of the conductive paths are blocked, and the residual gas in the voids loses its outlet. Thereafter, as compression bonding progresses, the internal pressure of the voids increases. Therefore, for example, if the atmosphere outside the material to be compressed is at normal pressure, when the compression process is completed, many high-pressure voids are formed along the interfaces of each layer of the material to be compressed. These can become the starting points for damage to the material to be compressed during charging and discharging, and the conductive paths between the layers of the material to be compressed may be destroyed. In contrast, in the second compression process, the atmosphere outside the material to be compressed is a reduced-pressure atmosphere, so the gas in the voids at the boundaries of each layer of the material to be compressed before compression bonding can be exhausted through the conductive paths. Therefore, even after most of the conductive paths are blocked as the compression bonding of the compressed object progresses and the voids are isolated from the atmosphere outside the compressed object, the increase in internal pressure of the voids due to the progress of compression bonding can be kept small. As a result, the internal pressure of the multiple voids 250 remaining at the completion of the compression process can be made negative.

[0096] Furthermore, the manufacturing method for the battery 1000 may include only one of the first compression step and the second compression step. Also, the battery 1000 may be manufactured using a manufacturing method that includes steps other than the first and second compression steps.

[0097] In the manufacturing method of battery 1000, for example, a laminate is formed as the compressed body that is pressed in the first compression step and the second compression step. Figures 6A, 6B, 7A, 7B, and 8 are cross-sectional views showing the schematic structure of the laminate formed by the manufacturing method of battery 1000. Note that Figures 6A, 6B, 7A, 7B, and 8 omit the illustration of the voids present in each layer.

[0098] In the manufacturing method of the battery 1000, for example, at least one of the laminates 310, 320, 330, 340, and 350 shown in Figures 6A, 6B, 7A, 7B, and 8 is formed.

[0099] The laminate 310 shown in Figure 6A is formed, for example, by laminating a negative electrode active material layer 110 on a negative electrode current collector 210. The laminate 320 shown in Figure 6B is formed, for example, by laminating a positive electrode active material layer 120 on a positive electrode current collector 220. The laminate 330 shown in Figure 7A is formed, for example, by further laminating a solid electrolyte layer 130 on the negative electrode active material layer 110 of the laminate 310 shown in Figure 6A. The laminate 340 shown in Figure 7B is formed, for example, by further laminating a solid electrolyte layer 130 on the positive electrode active material layer 120 of the laminate 320 shown in Figure 6B. As shown in Figure 8, the laminate 350 is formed by laminating the negative electrode active material layer 110, the solid electrolyte layer 130, the positive electrode active material layer 120, and the positive electrode current collector 220 on the negative electrode current collector 210 in this order. Note that the lamination configuration and formation method of the laminates are not limited to the examples described above. For example, the laminate may have a laminated structure in which at least one of the positive electrode current collector 220 and the negative electrode current collector 210 is removed from the laminate 350.

[0100] Each of the above laminates is formed, for example, by applying a paste-like coating, which is made by kneading the materials of the negative electrode active material layer 110, the positive electrode active material layer 120, and the solid electrolyte layer 130 together with a solvent, onto the surface of the current collector or each layer and drying it.

[0101] In the first compression step, for example, at least one of the laminates 310 and 320 shown in Figures 6A and 6B is used as the object to be compressed, and is pressed in a reduced-pressure atmosphere. This increases the density of the materials constituting the positive electrode active material layer 120 and the negative electrode active material layer 110, and increases the contact area between particles, thereby reducing the resistance of ions and electrons within each layer. Furthermore, since the surfaces of the positive electrode active material layer 120 and the negative electrode active material layer 110 can be made smooth, it becomes possible to form a thin and uniform solid electrolyte layer 130 on top of the positive electrode active material layer 120 and the negative electrode active material layer 110, thereby reducing the risk of short circuits. Also, by using laminate 310 as the object to be compressed, multiple voids 250 are formed inside the negative electrode active material layer 110. Similarly, by using laminate 320 as the object to be compressed, multiple voids 250 are formed inside the positive electrode active material layer 120.

[0102] Furthermore, in the first compression step, for example, at least one of the laminates 330 and 340 shown in Figures 7A and 7B is used as the object to be compressed, and is pressed in a reduced-pressure atmosphere. This increases the density of the materials constituting the positive electrode active material layer 120, the negative electrode active material layer 110, and the solid electrolyte layer 130, and increases the contact area between particles, thereby reducing the resistance of ions and electrons within each layer. It also improves the adhesion between the positive electrode active material layer 120 or the negative electrode active material layer 110 and the solid electrolyte layer 130. Additionally, by using laminate 330 as the object to be compressed, multiple voids 250 are formed inside the negative electrode active material layer 110 and the solid electrolyte layer 130, respectively. Similarly, by using laminate 340 as the object to be compressed, multiple voids 250 are formed inside the positive electrode active material layer 120 and the solid electrolyte layer 130, respectively.

[0103] Furthermore, in the first compression step, for example, the laminate 350 shown in Figure 8 is used as the object to be compressed, and pressing is performed in a reduced-pressure atmosphere. This increases the density of the materials constituting the positive electrode active material layer 120, the negative electrode active material layer 110, and the solid electrolyte layer 130, and increases the contact area between particles, thereby reducing the resistance of ions and electrons within each layer. In addition, the positive electrode active material layer 120 and the negative electrode active material layer 110 can be firmly bonded together via the solid electrolyte layer 130. Moreover, by using the laminate 350 as the object to be compressed, multiple voids 250 are formed inside each of the negative electrode active material layer 110, the positive electrode active material layer 120, and the solid electrolyte layer 130. Furthermore, since the laminate 350 has a structure in which the positive electrode active material layer 120 and the negative electrode active material layer 110 are laminated facing each other via the solid electrolyte layer 130, pressing the laminate 350 as the object to be compressed allows the first and second compression steps to be performed simultaneously.

[0104] Furthermore, as described above, by performing the pressing in a reduced-pressure atmosphere during the first compression step, the internal pressure of the multiple voids 250 formed inside the power generation element 100 as a result of the first compression step can be reduced to less than 1 atm.

[0105] Furthermore, in the second compression step, the compressed material, which consists of laminates 310 and 340 as shown in Figures 6A and 7B, is pressed in a reduced-pressure atmosphere so that, for example, the positive electrode active material layer 120 and the negative electrode active material layer 110 are stacked facing each other via a solid electrolyte layer 130. Specifically, the laminates 310 and 340 are stacked so that the negative electrode active material layer 110 of laminate 310 and the solid electrolyte layer 130 of laminate 340 face each other. This compressively bonds the negative electrode active material layer 110 of laminate 310 and the solid electrolyte layer 130 of laminate 340, thereby increasing the adhesion between the negative electrode active material layer 110 and the solid electrolyte layer 130. In addition, this creates a plurality of voids 250 along the interface between the compressively bonded negative electrode active material layer 110 and the solid electrolyte layer 130.

[0106] Furthermore, in the second compression step, the compressed material, which consists of laminates 320 and 330 as shown in Figures 6B and 7A, is pressed in a reduced-pressure atmosphere so that, for example, the positive electrode active material layer 120 and the negative electrode active material layer 110 are stacked facing each other via a solid electrolyte layer 130. Specifically, the laminates 320 and 330 are stacked so that the positive electrode active material layer 120 of laminate 320 and the solid electrolyte layer 130 of laminate 330 face each other. This compressively bonds the positive electrode active material layer 120 of laminate 320 and the solid electrolyte layer 130 of laminate 330, thereby increasing the adhesion between the positive electrode active material layer 120 and the solid electrolyte layer 130. In addition, this creates a plurality of voids 250 along the interface between the compressively bonded positive electrode active material layer 120 and the solid electrolyte layer 130.

[0107] Furthermore, in the second compression step, the compressed material, which consists of laminates 330 and 340 as shown in Figures 7A and 7B, is pressed in a reduced-pressure atmosphere so that, for example, the positive electrode active material layer 120 and the negative electrode active material layer 110 are stacked facing each other via the solid electrolyte layer 130. Specifically, the laminates 330 and 340 are stacked so that the solid electrolyte layer 130 of laminate 330 and the solid electrolyte layer 130 of laminate 340 face each other. This compressively bonds the solid electrolyte layer 130 of laminate 330 and the solid electrolyte layer 130 of laminate 340, thereby increasing the adhesion between the solid electrolyte layers 130. In addition, this creates multiple voids 250 along the interface between the two solid electrolyte layers 130 that are compressed and bonded.

[0108] As described above, in the second compression step, pressing is performed in a reduced pressure atmosphere, which makes it possible to reduce the internal pressure of the multiple voids 250 formed on the surface of each layer of the power generation element 100 as a result of the second compression step to less than 1 atm.

[0109] The laminate used in the second compression step is, for example, the laminate that has undergone the first compression step. In this way, the battery 1000 is formed by going through the first and second compression steps. The laminate used in the second compression step may also be a laminate that has not undergone the first compression step. If a laminate that has not undergone the first compression step is used in the second compression step, the first and second compression steps are performed simultaneously.

[0110] As described above, due to the various effects of the first and second compression steps, a battery 1000 with low resistance and high capacity can be obtained. In addition, since multiple air gaps 250 with an internal pressure of less than 1 atm are formed, the reliability of the battery 1000 is also improved.

[0111] In battery 1000 using an inorganic solid electrolyte, numerous grain boundaries between hard particles exist inside, so the pressing pressure (i.e., the stress during compression) in the first and second compression steps is, for example, 10 MPa or more. This further enhances the battery characteristics of battery 1000. Furthermore, when pressing is performed at a high pressure of 10 MPa or more, in a method where pressing is performed under normal pressure, the conductive paths connecting the voids and the outside of the compressed object tend to be blocked, and the internal pressure of the formed voids tends to become particularly high. However, by performing the pressing under a reduced pressure atmosphere, the internal pressure of the multiple voids 250 can be lowered.

[0112] Furthermore, when the laminate that has undergone the first compression step is used in the second compression step, for example, the pressing pressure in the second compression step is higher than the pressing pressure in the first compression step. This further enhances the effectiveness of the second compression step.

[0113] Furthermore, in the first and second compression steps, the pressure of the reduced-pressure atmosphere may be 0.5 atm or less, or 0.1 atm or less. This allows for an even lower internal pressure in the multiple voids 250 that are formed. Also, the pressure of the reduced-pressure atmosphere may be greater than, for example, 0 atm.

[0114] Thus, as the pressing progresses in the first and / or second compression steps for forming the battery 1000 using an inorganic solid electrolyte, the density of the positive electrode active material layer 120, the negative electrode active material layer 110, and the solid electrolyte layer 130 increases.

[0115] Next, the method of pressing the object to be compressed in the first and second compression steps will be described. In the first and second compression steps, a reduced-pressure atmosphere is created in a space surrounded by a container or the like, and the object to be compressed is pressed in the created reduced-pressure atmosphere.

[0116] First, a first example of a method for pressing the object to be compressed will be described. Figure 9 is a schematic diagram illustrating a first example of a method for pressing the object to be compressed in the first compression step. Figure 10 is a schematic diagram illustrating a first example of a method for pressing the object to be compressed in the second compression step. As shown in Figures 9 and 10, the first and second compression steps can be performed using a flat plate press device 800 installed in the internal space 905 of a vacuum chamber 900 connected to a vacuum pump 910. The vacuum chamber 900 is provided with, for example, a door (not shown) for inserting and removing the object to be compressed. Specifically, in the first and second compression steps, first, the object to be compressed is placed between the upper and lower press plates of the flat plate press device 800. Next, the gas in the internal space 905 is exhausted by the vacuum pump 910, creating a reduced-pressure atmosphere (for example, a vacuum atmosphere) in the internal space 905. After creating a reduced-pressure atmosphere in the internal space 905, the object to be compressed is pressed using the flat plate press device 800. The direction of pressure application by the flat plate press 800 is indicated by the white arrows shown in Figures 9 and 10. Specifically, the direction of pressure application by the flat plate press 800 is the direction normal to the main surface of the current collector and each layer of the laminate, that is, the direction in which the current collector and each layer of the laminate are stacked side by side. The direction of pressure application in other pressing methods is the same.

[0117] Next, a second example of a method for pressing the object to be compressed will be described. Figure 11 is a schematic diagram illustrating the second example of a method for pressing the object to be compressed in the first compression step. Figure 12 is a schematic diagram illustrating the second example of a method for pressing the object to be compressed in the second compression step. As shown in Figures 11 and 12, in the first and second compression steps, the object to be compressed is placed in the internal space 925 of an airtight container 920 connected to a vacuum pump 910, and the object to be compressed is pressed from outside the airtight container 920 using a flat plate press device 800. Specifically, in the first and second compression steps, first, the object to be compressed is placed in the internal space 925 of the airtight container 920. Next, the gas in the internal space 925 is exhausted by the vacuum pump 910, thereby creating a reduced-pressure atmosphere in the internal space 925. After creating a reduced-pressure atmosphere in the internal space 925, the object to be compressed is pressed from outside the airtight container 920 using a flat plate press device 800.

[0118] The airtight container 920 comprises, for example, a deformation section 921, a pressing section 922, and a housing section 923. The deformation section 921, the pressing section 922, and the housing section 923 form an internal space 925 in which all parts except the connection section 911 to the vacuum pump 910 are sealed.

[0119] The deformable portion 921 is located between the press portion 922 and the housing portion 923. The deformable portion 921 is separable from at least one of the press portion 922 and the housing portion 923. The deformable portion 921 is, for example, a frame-shaped structure in plan view and is a sealing member that seals the space between the press portion 922 and the housing portion 923. This maintains the reduced pressure state of the airtight container 920. The material of the deformable portion 921 is, for example, a material that is softer than the material of each layer of the power generation element 100 and deforms when pressed by the flat plate press device 800. The deformation of the deformable portion 921 by the press of the flat plate press device 800 applies external press pressure to the compressed body of the airtight container 920. The deformable portion 921 is made of an elastic material such as rubber that deforms when pressed by the flat plate press device 800. The material of the deformable portion 921 does not have to be elastic and may be a material that undergoes plastic deformation.

[0120] The press section 922 is a plate-shaped member that constitutes the upper lid of the airtight container 920. To enable the pressing of the object to be compressed, a part of the press section 922, for example, the lower surface 922a of a protrusion provided on the press section 922, is designed to be in contact with the object to be compressed. In addition, in a plan view, the press section 922 has a protrusion in the center, and the ends without the protrusion are in contact with the deformation section 921.

[0121] The housing section 923 is a box-shaped member with an open top, and the object to be compressed is housed on the box-shaped bottom surface 923a of the housing section 923. A portion of the housing section 923 is connected to the vacuum pump 910 via a connection part 911 such as a pipe or tube. The upper end of the side wall of the housing section 923 is connected to the end of the housing section 923 via a deformable part 921.

[0122] Pressing force is applied to the press section 922 from the upper press plate of the flat plate press device 800, and pressing force is applied to the housing section 923 from the lower press plate of the flat plate press device 800. Pressing force from the flat plate press device 800 is directly applied to the press section 922 and the housing section 923, for example. The object to be compressed is positioned so as to be sandwiched between, for example, the box-shaped bottom surface 923a of the housing section 923 and the lower surface 922a of the convex portion of the press section 922. The press section 922 and the housing section 923 are each made of a rigid material that is harder than the material of each layer of the power generation element 100. This allows for stable pressing of the object to be compressed while maintaining the overall shape of the airtight container 920 and the reduced pressure state of the internal space 925 during pressing by the flat plate press device 800. Note that the same material as the deformation section 921 may be used for the press section 922 and the housing section 923.

[0123] With this configuration, the deformation section 921 deforms in the direction of the press by the press of the plate press device 800, and the force of the plate press device 800 is transmitted to the object to be compressed via the press section 922 and the storage section 923, thereby pressing the object to be compressed. Furthermore, the deformation section 921 returns to its original shape, for example, when released from the press of the plate press device 800, so the airtight container 920 can be reused by replacing the object to be compressed.

[0124] In this way, by performing the press operation from the outside of the airtight container 920, the equipment for creating a reduced-pressure atmosphere can be miniaturized.

[0125] Next, a third example of a method for pressing the object to be compressed will be described. Figure 13 is a schematic diagram illustrating the third example of a method for pressing the object to be compressed in the first compression step. Figure 14 is a schematic diagram illustrating the third example of a method for pressing the object to be compressed in the second compression step. As shown in Figures 13 and 14, the first and second compression steps can be performed using a roll press device 850 installed in the internal space 905 of a vacuum chamber 900 connected to a vacuum pump 910, and unwinding rolls 860 and winding rolls 870 arranged to sandwich the roll press device 850. The roll press device 850, unwinding rolls 860 and winding rolls 870 are all installed in the internal space 905 of the vacuum chamber 900.

[0126] As shown in Figure 13, in the first compression step, the object to be compressed 400 is transported along the transport roller 880 from the unwinding roll 860 to the winding roll 870, while the roll press device 850 continuously presses each layer of the power generation element 100. The object to be compressed 400 has a laminated structure similar to the laminate described above as the laminate used in the first compression step.

[0127] Furthermore, as shown in Figure 14, in the second compression step, the compressible bodies 410 and 420 are transported from two unwinding rolls 860 along a transport roller 880, and the roll press device 850 compresses and joins the positive electrode active material layer 120 and the negative electrode active material layer 110 so that they face each other via the solid electrolyte layer 130. Until the start of compression joining, the compressible bodies 410 and 420 are transported using a winding roll 870, and after the start of compression joining, the battery components 500 can be transported and recovered by a transport and cutting device (not shown). The compressible bodies 410 and 420 have a laminated structure similar to the laminate described above as the laminate used in the second compression step.

[0128] Next, a fourth example of a method for pressing the object to be compressed will be described. Figure 15 is a schematic diagram illustrating the fourth example of a method for pressing the object to be compressed in the first compression step. Figure 16 is a schematic diagram illustrating the fourth example of a method for pressing the object to be compressed in the second compression step. As shown in Figures 15 and 16, the first and second compression steps can be performed using a roll press device 850 installed in the internal space 935 of a vacuum chamber 930 connected to a vacuum pump 910, and unwinding rolls 860 and winding rolls 870 arranged on the outside of the vacuum chamber 930, flanking the roll press device 850. In addition, the vacuum chamber 930 is provided with seal rollers 890 to maintain the airtightness of the vacuum chamber 930 at the points where the object to be compressed 400, or the objects to be compressed 410 and 420, enter and exit. This makes it possible to miniaturize the equipment for creating a reduced-pressure atmosphere. The transport and pressing of the object to be compressed 400, or the objects to be compressed 410 and 420, in the fourth example are the same as in the third example.

[0129] The method of performing the first and second compression steps in a reduced-pressure atmosphere is not limited to these examples. For example, in the first and second compression steps, heating may be applied while pressing in order to efficiently promote densification and compression bonding. Also, in the first and second compression steps, before creating a reduced-pressure atmosphere in the internal spaces 905, 925, or 935, the internal spaces 905, 925, or 935 may be replaced with an inert gas such as argon or nitrogen.

[0130] Furthermore, although the above description described a single-cell battery 1000 having one power generation element 100, the configuration and manufacturing method of the battery 1000 according to this embodiment are also effective for stacked batteries having a configuration in which multiple power generation elements 100 are stacked in a series or parallel structure via a current collector.

[0131] (Embodiment 2) Next, Embodiment 2 will be described. Embodiment 2 describes a battery system using the battery according to Embodiment 1. In the battery 1000 according to Embodiment 1 described above, there are multiple negative pressure voids 250 inside the power generation element 100, so it has excellent environmental resistance and provides various advantages in practical operation.

[0132] Figure 17 is a schematic diagram showing the general configuration of the battery system 3000 according to Embodiment 2. As shown in Figure 17, the battery system 3000 comprises a battery 2000 and a container 600.

[0133] The battery 2000 is a stacked battery having a stacked structure in which multiple batteries 1000 according to Embodiment 1 are stacked. In Figure 17, the description of the stacked structure of the batteries 1000 is omitted, and the battery 2000 is shown as a single rectangle. The fact that the battery 2000 is a stacked battery enables high voltage or high capacity. The battery 2000 is placed in the internal space 605 of the container 600. The battery provided in the battery system 3000 may be a single-cell battery 1000.

[0134] The container 600 is a sealed container for housing the battery 2000. The container 600 has an internal space 605 that is a reduced-pressure environment. A reduced-pressure environment is an environment where the pressure of the environment in which the battery 2000 is placed is 1 atm or less. In other words, the pressure in the internal space 605 is less than 1 atm. The container 600 may become a reduced-pressure environment by housing the battery 2000 in the container 600 under reduced-pressure conditions, or the internal space 605 may become a reduced-pressure environment by a vacuum pump, or by a vent door or vent connecting the outside of the container 600 to a reduced-pressure environment, etc., although not shown. The container 600 is, for example, a battery case for protecting the power generation element 100, etc., but it is not limited to a battery-specific container such as a battery case, but may be an airplane, aerospace vehicle, or vacuum chamber, etc. The container 600 may be flown by, for example, a flight device, etc., not shown.

[0135] Figure 18 is a schematic diagram showing the general configuration of another battery system 3100 according to Embodiment 2. As shown in Figure 18, the battery system 3100 comprises a battery 2000 and a container 610.

[0136] The container 610 has an internal space 615 that becomes a reduced-pressure environment. The container 610 is also provided with a hole 612 that connects the internal space 615 to the outside of the container 610. When the container 610 is placed in or moved in a reduced-pressure environment, for example, the internal space 615 becomes a reduced-pressure environment through the hole 612. The container 610 is a battery case for protecting a power generation element 100, etc., which is mounted on a mobile body that moves in a high-altitude environment or in outer space, such as an airplane or aerospace vehicle. The container 610 is not limited to a battery case, but may also be an enclosure for equipment used in a high-altitude environment or in outer space, or an enclosure for equipment installed on an airplane or aerospace vehicle, etc.

[0137] Thus, in the battery system 3000 and the battery system 3100, for example, the battery 2000 is placed in a reduced-pressure environment and charged or discharged.

[0138] In this embodiment, the pressure of the reduced-pressure environment may be 0.95 atm or less, or 0.8 atm or less. Also, the pressure of the reduced-pressure environment may be greater than, for example, 0 atm. For example, under flight conditions at high altitude, the environment outside the container 610 is generally reduced, and the battery system 3100 may be placed in an environment of, for example, 0.95 atm or less, or even 0.8 atm or less. Even in such a reduced-pressure environment, the battery 2000 has multiple negative pressure gaps 250, which helps to suppress damage to the power generation element 100 originating from the multiple gaps 250.

[0139] Furthermore, the internal pressure of the multiple voids 250 in the battery 2000 is, for example, below the pressure of a reduced-pressure environment. This suppresses damage to the power generation element 100 originating from the multiple voids 250, and allows the multiple voids 250 to exert a force that pulls each layer of the power generation element 100 inward.

[0140] As described above, the battery system according to this embodiment includes the battery 1000 according to Embodiment 1, and therefore, even in a battery system where the battery is placed in a reduced-pressure environment, high reliability of the battery can be ensured.

[0141] (Other embodiments) The batteries and battery systems relating to this disclosure have been described above based on embodiments, but this disclosure is not limited to these embodiments. Within the scope of this disclosure, various modifications to the embodiments that a person skilled in the art could conceive, as long as they do not depart from the spirit of this disclosure, and other forms constructed by combining some of the components of the embodiments, are also included.

[0142] For example, in the above embodiment, the multiple voids 250 were located inside the negative electrode active material layer 110, the positive electrode active material layer 120, and the solid electrolyte layer 130, but this is not limited to this. The multiple voids 250 only need to be located inside at least one of the negative electrode active material layer 110, the positive electrode active material layer 120, and the solid electrolyte layer 130.

[0143] Furthermore, in the above embodiment, for example, the negative electrode active material layer 110, the positive electrode active material layer 120, and the solid electrolyte layer 130 each contain an inorganic solid electrolyte, but are not limited to this. The negative electrode active material layer 110, the positive electrode active material layer 120, and the solid electrolyte layer 130 may each contain a solid electrolyte other than an inorganic solid electrolyte in addition to, or instead of, an inorganic solid electrolyte.

[0144] Furthermore, the above embodiments may be modified, replaced, added, or omitted in various ways within the scope of the claims or their equivalents. [Industrial applicability]

[0145] The batteries and other related products described herein can be used as batteries for electronic devices, electrical appliances, electric vehicles, and the like. [Explanation of Symbols]

[0146] 100 power generation elements 110 Negative electrode active material layer 120 Cathode active material layer 130 Solid electrolyte layer 210 Negative electrode current collector 220 Positive electrode current collector 250 void 310, 320, 330, 340, 350 laminated 400, 410, 420 Compressed material 600, 610 container 605, 615, 905, 925, 935 Interior space 612 holes 800 Flat plate press machine 850 Roll press machine 860 unwinding roll 870 Reel Roll 880 Conveyor Rollers 890 Seal Roller 900, 930 vacuum chamber 910 Vacuum pump 911 Connection part 920 Airtight container 921 Deformed part 922 Press Department 922a Bottom side 923 Storage Unit 923a Bottom 1000, 2000 batteries 3000, 3100 battery system

Claims

1. A positive electrode layer comprising a positive electrode active material and a first inorganic solid electrolyte, A negative electrode layer containing a negative electrode active material and a second inorganic solid electrolyte, A solid electrolyte layer located between the positive electrode layer and the negative electrode layer, comprising a third inorganic solid electrolyte, Equipped with a power generation element having, Multiple voids exist inside the aforementioned power generation element. The internal pressure of the aforementioned multiple voids is 0.5 atm or less. battery.

2. The plurality of voids are located along the grain boundary of at least one of the first inorganic solid electrolyte, the second inorganic solid electrolyte, and the third inorganic solid electrolyte. The battery according to claim 1.

3. At least one of the plurality of voids is located inside at least one of the positive electrode layer and the negative electrode layer. The battery according to claim 1 or 2.

4. At least one of the plurality of voids is located on the surface of at least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer. The battery according to any one of claims 1 to 3.

5. The internal pressure of the aforementioned multiple voids is 0.1 atm or less. The battery according to any one of claims 1 to 4.

6. The average of the maximum widths of each of the aforementioned multiple voids is 10 μm or less. The battery according to any one of claims 1 to 5.

7. The density of at least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer is 90% or more of the theoretical material density. The battery according to any one of claims 1 to 6.

8. A container having an internal space that becomes a reduced-pressure environment, A battery according to any one of claims 1 to 7, disposed in the internal space, Equipped with, The internal pressure of the aforementioned multiple voids is lower than the pressure of the reduced-pressure environment. Battery system.

9. The pressure in the aforementioned reduced-pressure environment is 0.95 atm or less. The battery system according to claim 8.

10. A method for manufacturing a battery comprising a power generation element having a positive electrode layer containing a positive electrode active material and a first inorganic solid electrolyte, a negative electrode layer containing a negative electrode active material and a second inorganic solid electrolyte, and a solid electrolyte layer located between the positive electrode layer and the negative electrode layer and containing a third inorganic solid electrolyte, wherein a plurality of voids exist inside the power generation element and the internal pressure of the plurality of voids is 0.5 atm or less, The process includes a compression step in which the object to be compressed, which includes at least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer, is pressed in a reduced pressure atmosphere. Battery manufacturing method.

11. A method for manufacturing a battery comprising a power generation element having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer located between the positive electrode layer and the negative electrode layer, wherein a plurality of voids exist inside the power generation element, and the internal pressure of the plurality of voids is 0.5 atm or less, The process includes a compression step in which the compressed object, in which the positive electrode layer and the negative electrode layer are laminated so as to face each other via the solid electrolyte layer, is pressed in a reduced-pressure atmosphere. Battery manufacturing method.

12. The pressure of the aforementioned reduced-pressure atmosphere is 0.1 atm or less. A method for manufacturing a battery according to claim 10 or 11.

13. The pressure of the aforementioned press is 10 MPa or more. A method for manufacturing a battery according to any one of claims 10 to 12.

14. A method for manufacturing a battery comprising: a positive electrode layer containing a positive electrode active material and a first inorganic solid electrolyte; a negative electrode layer containing a negative electrode active material and a second inorganic solid electrolyte; and a solid electrolyte layer located between the positive electrode layer and the negative electrode layer and containing a third inorganic solid electrolyte, The process includes a compression step in which the object to be compressed, which includes at least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer, is pressed in a reduced pressure atmosphere. In the compression step, the object to be compressed is placed inside an airtight container, the inside of the airtight container is reduced to a pressure atmosphere, and then the object to be compressed is pressed from outside the airtight container. The airtight container is provided with a deformable part that deforms when pressed, As the deformed portion deforms due to the press, the pressure from the press from outside the airtight container is applied to the object being compressed. Battery manufacturing method.

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