Solid-state battery and method for manufacturing a solid-state battery

Abstract

To provide a solid-state battery that absorbs the expansion of the electrode layer due to charging and discharging, and a method for manufacturing a solid-state battery. [Solution] A solid battery and a method for manufacturing a solid battery, comprising a structure in which a first current collector, a first electrode layer, a solid electrolyte layer, a second electrode layer, and a second current collector are arranged in this order in the first axial direction, wherein there is a void inside the first electrode layer and around the first electrode layer, and the shape of the void in a cross-sectional view along the first axial direction is elongated in the in-plane direction of the first electrode layer.

Description

[Technical Field]

[0001] This disclosure relates to a solid-state battery and a method for manufacturing a solid-state battery. [Background technology]

[0002] In recent years, the importance of rechargeable batteries has increased, and in addition to rechargeable batteries with electrolytes, the development of solid-state batteries using solid electrolytes is progressing. All-solid-state batteries, an example of solid-state batteries, are batteries that have a solid electrolyte layer instead of an electrolyte, and because they do not use flammable organic solvents, safety devices can be simplified, and they are superior in terms of manufacturing cost and productivity.

[0003] In an all-solid-state battery in which an all-solid-state battery stack is covered with a resin layer, a gap exists between the side surface of the negative electrode active material layer and the resin layer, thereby suppressing cracking of the resin layer due to volume changes in the all-solid-state battery stack. This all-solid-state battery is known (Patent Document 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2019-121532 [Overview of the project] [Problems that the invention aims to solve]

[0005] In some cases, the electrode active material contained in the electrode layer of a solid-state battery expands during charging and discharging, causing cracks to form in the electrode layer itself and degrading battery performance.

[0006] One embodiment of this disclosure aims to solve the problem of providing a solid-state battery that absorbs the expansion of the electrode layer due to charging and discharging. Another embodiment of this disclosure aims to solve the problem of providing a method for manufacturing a solid-state battery that absorbs the expansion of the electrode layer due to charging and discharging. [Means for solving the problem]

[0007] The means for solving the problem include the following: <1> A solid-state battery comprising a structure in which a first current collector, a first electrode layer, a solid electrolyte layer, a second electrode layer, and a second current collector are arranged in this order in the first axial direction, wherein there is a void inside the first electrode layer and at least around the first electrode layer, and the shape of the void in a cross-sectional view along the first axial direction is elongated in the in-plane direction of the first electrode layer. <2> The void has a minor axis length of 1 μm or less in a cross-sectional view along the first axis. <1> Solid-state batteries as described above. <3> The void has an aspect ratio of 10 to 40 in a cross-sectional view along the first axis. <1> or <2> Solid-state batteries as described above. <4> The void is formed in at least one of the following locations: inside the first electrode layer and between the first electrode layer and the solid electrolyte layer. <1> ~ <3> A solid battery as described in any one of the following. <5> One or more voids are formed in a cross-sectional view along the first axial direction, and they occupy 1% to 10% of the total area of ​​the first electrode layer. <1> ~ <4> Solid batteries listed in any one of the following <6> The first electrode layer comprises multiple layers, and has voids between the layers of the multiple layers and around the first electrode layer. <1> ~ <5> A solid battery as described in any one of the following. <7> A method for manufacturing a solid-state battery, comprising a structure in which a first current collector, a first electrode layer, a solid electrolyte layer, a second electrode layer, and a second current collector are arranged in this order in the first axial direction, the method comprising the steps of: transferring a solid electrolyte layer transfer material comprising a solid electrolyte layer onto the surface of the second electrode layer of a first laminate comprising a second current collector and a second electrode layer, and applying a linear pressure P1 in the first axial direction to obtain a second laminate comprising a second electrode layer and a solid electrolyte layer; transferring a first electrode layer transfer material comprising a first electrode layer onto the surface of the solid electrolyte layer of the second laminate, and applying a linear pressure P2 in the first axial direction to obtain a third laminate further comprising a first electrode layer; and arranging a first current collector on the surface of the first electrode layer of the third laminate, wherein the linear pressure P1 is greater than 0.25 t / cm, the linear pressure P2 is less than 4.0 t / cm, and the linear pressure P1 is less than the linear pressure P2. <8> A method for manufacturing a solid-state battery, comprising a structure in which a first current collector, a first electrode layer split B, a first electrode layer split A, a solid electrolyte layer, a second electrode layer, and a second current collector are arranged in this order in the first axial direction, comprising the steps of: transferring a solid electrolyte layer transfer material comprising a solid electrolyte layer onto the surface of the second electrode layer of a first laminate comprising a second current collector and a second electrode layer to obtain a second laminate comprising a second electrode layer and a solid electrolyte layer; and transferring a first electrode layer split A transfer material comprising a first electrode layer split A onto the surface of the solid electrolyte layer of the second laminate and applying a linear pressure P3 in the first axial direction. A method for manufacturing a solid-state battery, comprising the steps of: obtaining a third laminate A including a first electrode layer A; obtaining a third laminate B including a first electrode layer B by transferring a first electrode layer B transfer material, which comprises a first electrode layer B, onto the surface of the solid electrolyte layer of the third laminate A and applying a linear pressure P4 in the first axial direction; and arranging a first current collector on the surface of the first electrode layer B of the third laminate B, wherein the linear pressure P3 is greater than 0.25 t / cm, the linear pressure P4 is less than 3.0 t / cm, and the linear pressure P3 is less than the linear pressure P4. [Effects of the Invention]

[0008] According to one embodiment of this disclosure, a solid-state battery is provided that absorbs the expansion of the electrode layer due to charging and discharging. Furthermore, according to one embodiment of this disclosure, a method for manufacturing a solid-state battery that absorbs the expansion of the electrode layer due to charging and discharging is provided. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic SEM image showing a cross-section of a solid-state battery cut along the first axial direction, which is the stacking direction of the electrode stacking structure. [Figure 2] Figure 2 is a schematic plan view showing an example of the position where the surface of a solid-state battery, viewed from above, is cut by a plane parallel to the first axis direction. [Figure 3] Figure 3 is a schematic image showing a portion of a cross-sectional SEM photograph of a solid-state battery cut along the first axial direction, which is the stacking direction of the electrode stacking structure. [Figure 4]FIG. 4 is a schematic partial SEM photograph of a cross-section obtained by cutting a solid-state battery in the first axial direction, which is the stacking direction of the electrode stack structure, and is an explanatory diagram for explaining the short axis a and the long axis b. [Figure 5] FIG. 5 is an image diagram schematically showing a partial SEM photograph of a cross-section obtained by cutting a solid-state battery having two first electrode layers in the first axial direction, which is the stacking direction of the electrode stack structure. [Figure 6] FIG. 6 is an explanatory diagram for explaining a method of manufacturing a solid-state battery. [Figure 7] FIG. 7 is an explanatory diagram for explaining a method of manufacturing a solid-state battery having two first electrode layers.

Embodiments for Carrying Out the Invention

[0010] In the present disclosure, a numerical range indicated using "~" means a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively. In the numerical ranges described stepwise in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in other stepwise descriptions. In the numerical ranges described in the present disclosure, the upper limit value or the 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 "step" includes not only an independent step but also a step included in this term if the intended purpose of the step is achieved even when it cannot be clearly distinguished from other steps. In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In the present disclosure, the amount of each component means the total amount of a plurality of substances corresponding to each component unless otherwise specified when there are a plurality of substances corresponding to each component. When embodiments in 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. Also, the sizes of the members in each figure are conceptual, and the relative relationships of the sizes between the members are not limited thereto.

[0011] <Solid-state battery> Hereinafter, an embodiment of a solid-state battery of this disclosure will be described using Figures 1 to 5. A solid-state battery (hereinafter also referred to as a solid battery) according to one embodiment of the present disclosure includes a structure (hereinafter also referred to as an electrode stacked structure) in which a first current collector, a first electrode layer, a solid electrolyte layer, a second electrode layer, and a second current collector are arranged in this order in the first axial direction. The solid battery has a void formed inside the first electrode layer and at least around the first electrode layer. The shape of the void in a cross-sectional view along the first axial direction is elongated in the in-plane direction of the first electrode layer.

[0012] The area surrounding the electrode layer refers to the entire surface of the electrode layer, including both the exposed surface and the surface that is not exposed because it is in contact with an adjacent layer. A void refers to a closed space. A void formed inside the first electrode layer is a space closed by the first electrode layer, and a void formed around the first electrode layer is a space closed by the first electrode layer and one or more components of the solid-state battery adjacent to the first electrode layer.

[0013] In solid-state batteries, it is known that expansion and contraction can occur in the negative electrode active material contained in the negative electrode layer during charging and discharging. This expansion and contraction of the negative electrode active material can cause the negative electrode layer to expand and contract, leading to cracks in the negative electrode layer itself and a decrease in battery performance. For example, while Si-based active materials are high-capacity active materials, they tend to expand significantly. Thus, especially when using negative electrode active materials with large expansion rates, such as Si-based active materials, it is preferable to be able to absorb the expansion of the negative electrode layer due to charging and discharging and suppress cracks in the negative electrode layer, as this can greatly contribute to suppressing the degradation of battery performance.

[0014] The inventors investigated ways to absorb the expansion of the electrode layer in order to suppress crack formation caused by the expansion and contraction of the electrode layer during charging and discharging in solid-state batteries. They found that by forming a specific shaped void inside or around the electrode layer, the expansion of the electrode layer is absorbed by this void without impairing battery performance.

[0015] Although the mechanism by which the expansion of the electrode layer is absorbed is not clear, it is presumed that by forming a void of a specific shape at a specific location, the effect of appropriately absorbing the expansion of the electrode layer without causing a decrease in battery performance due to the formed void is effectively achieved.

[0016] In a solid-state battery, the first current collector may be either a negative electrode current collector or a positive electrode current collector. Furthermore, in a solid-state battery, the first electrode layer may be either a negative electrode layer or a positive electrode layer. From the viewpoint of absorbing the expansion of the electrode layer, it is preferable that the first current collector is a negative electrode current collector and the first electrode layer is a negative electrode layer.

[0017] In a solid-state battery, when the first current collector is a negative electrode current collector, the second current collector is a positive electrode current collector, and when the first current collector is a positive electrode current collector, the second current collector is a negative electrode current collector. In a solid-state battery, when the first electrode layer is a negative electrode layer, the second electrode layer is a positive electrode layer, and when the first electrode layer is a positive electrode layer, the second electrode layer is a negative electrode layer. From the viewpoint of absorbing the expansion of the electrode layers, it is preferable that the first current collector is a negative electrode current collector, the first electrode layer is a negative electrode layer, the second current collector is a positive electrode current collector, and the second electrode layer is a positive electrode layer.

[0018] As shown in Figure 1, for example, the solid battery 10 has a battery stack structure in which a first current collector 11, a first electrode layer 12, a solid electrolyte layer 13, a second electrode layer 14, and a second current collector 15 are arranged in this order in the first axial direction X.

[0019] A solid-state battery may have multiple independent layers constituting the battery stack structure. For example, the first electrode layer 12 may have multiple sublayers. Alternatively, the second electrode layer 14 may be provided on each of the two surfaces of the second current collector 15, and the battery stack structure may be arranged in this order in the first axial direction X: first current collector 11, first electrode layer 12, solid electrolyte layer 13, second electrode layer 14, second current collector 15, second electrode layer 14, solid electrolyte layer 13, first electrode layer 12, and first current collector 11.

[0020] In solid-state batteries, the first and second current collectors may be referred to simply as "current collectors" without distinction, and the first and second electrode layers may be referred to simply as "electrode layers" without distinction. Furthermore, the first electrode layer segment A and the first electrode layer segment B may be referred to simply as "first electrode layer" without distinction.

[0021] (void) In a solid-state battery, a void is formed inside the first electrode layer and around the first electrode layer, at least in one of these locations. The shape of the void, when viewed in cross-section along the first axial direction, is elongated in the in-plane direction of the first electrode layer. The in-plane direction includes the direction parallel to the plane of the first electrode layer. The void is formed in at least one location within the first electrode layer and around the first electrode layer, and the shape of the void is elongated in the in-plane direction of the first electrode layer when viewed in cross-section along the first axial direction. This prevents impairment of battery performance and, even if the electrode layer expands and contracts, the void absorbs the expansion of the electrode layer, suppressing the occurrence of cracks in the electrode layer. Cracks that occur in the electrode layer can hinder ion movement within the battery, potentially leading to an increase in internal resistance.

[0022] The void may be formed only inside the first electrode layer, only around the first electrode layer, or both inside and around the first electrode layer. Furthermore, it is sufficient for one or more voids to be formed, and multiple voids may be formed.

[0023] When a void is formed around the first electrode layer, it is preferable that the void is formed on the main surface of the first electrode layer. Specifically, the void around the first electrode layer 12 includes the space between the first electrode layer 11 and the first current collector 11, and at least one of the space between the first electrode layer 12 and the solid electrolyte layer 13. As shown in Figure 1, the solid battery 10 has a void 16 formed inside the first electrode layer 12 and at least one of the spaces around the first electrode layer 12.

[0024] The void, when viewed in cross-section along the first axis, has a shape that is elongated in the in-plane direction of the first electrode layer. The first axial direction X (see Figure 1) is the stacking direction of the battery stack structure. Therefore, a cross-sectional view along the first axial direction X means a view of a cross-section obtained by cutting the solid battery along the stacking direction of the battery stack structure. Specifically, a cross-sectional view along the first axial direction X can be an SEM (Scanning Electron Microscope) image of a cross-section obtained by cutting the solid battery in the stacking direction of the battery stack structure. The method of cutting the solid battery does not need to be limited to the cutting position, as long as the cross-section of the first electrode layer is included. For example, the cross-section in the cross-sectional view along the first axial direction preferably includes the area near the center of the solid battery. Specifically, if the solid battery is a prismatic battery, it is preferable to have a cross-sectional view obtained by cutting along a line that divides the prismatic shape approximately in half lengthwise or widthwise.

[0025] When the solid battery 10 is a prismatic battery, the cross-sectional view along the first axis X can be a cross-sectional view of a cross section cut by line AA, which approximately bisects the shorter side of the rectangle viewed from above in a plan view, as shown in Figure 2. In Figure 2, the stacking direction of the battery stacking structure of the solid battery 10 is the first axis X (the direction perpendicular to the rectangular surface in the plan view from above in Figure 2).

[0026] The shape of the void in a cross-sectional view along the first axial direction is elongated in the in-plane direction of the first electrode layer. The void is elongated in shape and extends along the in-plane direction of the first electrode layer. The void has a major axis in the in-plane direction of the first electrode layer and a minor axis perpendicular to the in-plane direction of the first electrode layer, i.e., in the first axial direction. The in-plane direction of the first electrode layer refers to the direction of the surface of the first electrode layer and the direction parallel thereto. The direction of the surface of the first electrode layer may be the direction of a virtual surface if the surface of the first electrode layer has irregularities. For example, the arithmetic mean position in the depth direction of the irregularities on the first electrode surface may be considered the surface of the first electrode layer.

[0027] Furthermore, since the voids are formed as gaps when stacking the various layers such as the current collector and electrode layer to form a battery stack structure, the voids formed will not necessarily be of the same shape. The direction of the long axis of the void does not need to be strictly parallel to the in-plane direction of the first electrode layer, and may have an angle (in the range of -5° to 5°) that can be considered parallel to the in-plane direction at first glance. The same applies to the direction of the short axis; it does not need to be strictly parallel to the first axis direction, and may have an angle (in the range of -5° to 5°) that can be considered parallel to the first axis direction at first glance.

[0028] As shown in Figure 3, in the solid-state battery 10, a void 16a is formed inside the first electrode layer 12, and a void 16b is formed around the first electrode layer 12. The void 16, including voids 16a and 16b, has a cross-sectional shape along the first axial direction X that is elongated along the in-plane direction Y of the first electrode layer 12.

[0029] If a void is formed around the first electrode layer 12, a void 16 may be formed in the adjacent first current collector 11 or solid electrolyte layer 13 at a position where the void 16 fits into it. In other words, a void around the first electrode layer 12 may be formed by irregularities present at the interface with the adjacent first current collector 11 or the interface with the solid electrolyte layer 13.

[0030] From the viewpoint of not impairing battery performance and absorbing the expansion of the electrode layer, the length of the short axis of the shape of the void in a cross-sectional view along the first axial direction is preferably 1 μm or less, and more preferably 0.2 μm to 0.5 μm.

[0031] From the viewpoint of not impairing battery performance and absorbing the expansion of the electrode layer, the aspect ratio of the shape of the void in a cross-sectional view along the first axial direction is preferably 10 to 40. The aspect ratio refers to the length of the major axis when the minor axis is set to 1. Therefore, when the length of the minor axis is set to 1, the length of the major axis of the void is preferably 10 to 40, and more preferably 15 to 30. The shape of the void in a cross-sectional view along the first axial direction is preferably slit-like or elongated string-like.

[0032] As shown in Figure 4, in the solid-state battery 10, the air gap 16a has a short axis a and a long axis b. The length of the long axis b is longer than the length of the short axis a.

[0033] The void formed around the first electrode layer is preferably formed between the first electrode layer and the solid electrolyte layer, from the viewpoint of not impairing battery performance and absorbing the expansion of the electrode layer. The void 16b (see Figure 3 or Figure 4) is formed between the first electrode layer and the solid electrolyte layer.

[0034] From the viewpoint of not impairing battery performance and absorbing the expansion of the electrode layer, one or more voids may be formed in a cross-sectional view along the first axial direction. From the viewpoint of not impairing battery performance and absorbing the expansion of the electrode layer, it is preferable that the voids occupy 1% to 10% of the total area of ​​the first electrode layer in a cross-sectional view along the first axial direction, and more preferably occupy 2% to 5% of the total area.

[0035] From the viewpoint of not impairing battery performance and absorbing the expansion of the electrode layer, the voids are preferably formed at a rate of 10% to 60% and more preferably at a rate of 20% to 40% of a 400 μm band area on a straight line substantially parallel to the in-plane direction Y of the first electrode layer 12, when viewed in cross-section along the first axial direction. If multiple voids are formed, they may be unevenly distributed relative to the first electrode layer or they may be uniformly distributed.

[0036] The first electrode layer may include multiple layers. The number of layers may be two or three or more. The multiple layers may be the same type of layer or different types of layers, as long as they function as the first electrode layer. The type of layer includes composition, shape, dimensions, etc. When the first electrode layer includes multiple layers, it is preferable that voids are formed between the layers of the multiple layers and around the first electrode layer, at least. Since voids are formed as gaps when forming a battery stack structure using battery components such as current collectors and electrode layers, voids are formed between the layers of the multiple layers when forming a battery stack structure with each of the multiple layers. The voids formed inside the first electrode layer may be voids formed between the layers of the multiple layers.

[0037] As shown in Figure 5, the first electrode layer 12 includes a split layer 12a and a split layer 12b. The void 16a is formed at the interface between the split layer 12a and the split layer 12b.

[0038] <Each element of a solid-state battery> (Current collector) This section describes the various elements that make up the electrode stack structure of a solid-state battery. The type of current collector included in the solid-state battery can be selected and used from known current collectors. Specifically, the material of the current collector may be a metal selected from Ag, Cu, Au, Al, Ni, Fe, and Ti, or an alloy containing these metals. Examples of positive electrode current collectors include stainless steel, Al, Ni, Fe, Ti, and carbon, with aluminum alloy foil or aluminum foil being preferred. The negative electrode current collector may be made of metal, resin, or any other material. Examples of metal negative electrode current collectors include aluminum foil, nickel foil, titanium foil, and copper foil. For resin negative electrode current collectors, known resin current collectors can be used, and conductive resin current collectors, which are composite materials containing resins such as polyethylene and phenolic resin and conductive fillers such as graphite, can be used. Aluminum alloy foil and aluminum foil may be manufactured using powder. The shape of the positive electrode current collector and the negative electrode current collector may be, for example, foil-like or mesh-like.

[0039] The thickness of the current collector is not particularly limited and can be selected considering the type and size of the battery obtained using the current collector. The current collector may include multiple layers. The total thickness of the current collector may be, for example, 5 μm or more, 10 μm or more, or 20 μm or more. The total thickness of the current collector may be, for example, 120 μm or less, 80 μm or less, or 60 μm or less.

[0040] (electrode layer) The type of electrode layer included in the solid-state battery is not particularly limited and can be selected and used from known electrode layers. The electrode layer contains at least an electrode active material and may optionally contain a binder, conductive material, solid electrolyte, etc. If the solid electrolyte layer contains a solid electrolyte, at least one of the first electrode layer and the second electrode layer, which are positioned on both sides of the solid electrolyte layer, may also contain a solid electrolyte. In this disclosure, the electrode active material contained in the first electrode layer is also referred to as the first electrode active material, and the electrode active material contained in the second electrode layer is also referred to as the second electrode active material. When the first electrode layer is the negative electrode layer, the first electrode active material is the negative electrode active material, and when the first electrode layer is the positive electrode layer, the first electrode active material is the positive electrode active material. When the second electrode layer is the negative electrode layer, the second electrode active material is the negative electrode active material, and when the second electrode layer is the positive electrode layer, the second electrode active material is the positive electrode active material.

[0041] Examples of negative electrode active materials include carbon materials, active materials containing Si elements, metallic lithium, lithium-containing alloys, metals or alloys that can be alloyed with lithium, oxides, and transition metal nitrides. Examples of carbon materials include graphite materials, amorphous carbon materials, carbon black, and activated carbon. Examples of graphite materials include natural graphite and artificial graphite. Examples of amorphous carbon materials include hard carbon, soft carbon, coke, mesocarbon microbeads (MCMB), and mesophase pitch carbon fiber (MCF). Graphite materials may be coated with metal or amorphous carbon. Active materials containing the Si element include elemental silicon, silicon alloys (for example, alloys of Si with one or more metals selected from the group consisting of Sn, Ti, Fe, Ni, Cu, Co, and Al), porous silicon, silicon clathrate compounds, silicon oxides, and the like.

[0042] Specifically, examples of positive electrode active materials include composite oxides containing lithium and transition metals (hereinafter also referred to as composite oxides). Examples of composite oxides include composite oxides having a layered crystal structure, composite oxides having a spinel-type crystal structure, and composite oxides having an olivine-type crystal structure. Specific examples of composite oxides having a layered crystal structure include compounds represented as LiMO2 (where M is at least one transition metal selected from the group consisting of Ni, Co, and Mn), and compounds to which heterogeneous elements are added. Representative examples of composite oxides having a layered crystal structure include LCO (lithium cobaltate), NCM (lithium nickel-cobalt-manganate), and NCA (lithium nickelate or lithium nickel-cobalt-aluminate). LiMn2O4 is a specific example of a composite oxide having a spinel-type crystal structure. A specific example of a composite oxide having an olivine-type crystal structure is LiMPO4 (where M is Fe, Co, Ni, or Mn).

[0043] The electrode active material contained in the electrode layer may be a single type or a combination of two or more types. The electrode active material may take the form of, for example, fibers, spheres, flakes, etc. The volume-average particle size of the electrode active material may be selected from, for example, a range of 5 μm to 50 μm. The volume-average particle size of the electrode active material is defined as the value (D50) at which the cumulative amount from the smaller diameter side in the volume-based particle size distribution obtained using the laser diffraction-scattering method becomes 50%.

[0044] Examples of binders include polyvinylidene fluoride (PVdF), polyethylene, polypropylene, polyethylene terephthalate, cellulose, nitrocellulose, carboxymethylcellulose, polyethylene oxide, polyepichlorohydrin, polyacrylonitrile, styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), polyacrylate, polymethacrylate, and polytetrafluoroethylene (PTFE).

[0045] Examples of conductive materials include carbon materials, metals, conductive oxides, and conductive nitrides. Specifically, carbon materials include graphite, carbon black (acetylene black, thermal black, furnace black, etc.), carbon nanotubes (CNTs), carbon nanofibers (CNFs), and vapor-grown carbon fibers (VGCFs). TM Examples include: The conductive material may be of one type only, or two or more types may be used in combination.

[0046] Examples of solid electrolytes include sulfide solid electrolytes, oxide solid electrolytes, and polymer solid electrolytes. From the viewpoint of battery performance, sulfide solid electrolytes and polymer solid electrolytes are preferred as solid electrolytes, and from the viewpoint of thermal stability, sulfide solid electrolytes are more preferred. Solid electrolytes may be used individually or in combination of two or more types.

[0047] Examples of sulfide solid electrolytes include compounds containing a metal element that acts as a conductive ion and sulfur (S). Examples of metallic elements include Li, Na, K, Mg, and Ca. Among these, Li is preferred as a metallic element. The sulfide solid electrolyte may contain Li and S, and at least one selected from the group consisting of P, Si, Ge, Al, and B. Among these, a sulfide solid electrolyte containing Li, S, and P (hereinafter also referred to as an LPS-type sulfide solid electrolyte) is preferred. From the viewpoint of ionic conductivity, sulfide solid electrolytes may contain halogen elements such as Cl, Br, and I. From the viewpoint of chemical stability, sulfide solid electrolytes may contain oxygen (O).

[0048] Specifically, LPS-type sulfide solid electrolytes include Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, and LiI-Li Examples include 2S-P2O5, LiI-Li3PO4-P2S5, LiBr-LiI-Li2S-P2S5, Li2S-P2S5-ZmSn (where m and n are positive numbers and Z is Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, and Li2S-SiS2-LixMOy (where x and y are positive numbers and M is P, Si, Ge, B, Al, Ga, or In).

[0049] In the above, the term "Li2S-P2S5" refers to a sulfide solid electrolyte obtained using Li2S and P2S5 as raw materials, and the same applies to other terms.

[0050] Among LPS-type sulfide solid electrolytes, sulfide solid electrolytes obtained using Li2S and P2S5 are preferred, and sulfide solid electrolytes satisfying the following formula are more preferred. Li 3+x+5y P 1-y S4(0 <x≦0.6、0<y≦0.2)

[0051] As an oxide solid electrolyte, NASICON(Na3Zr2PSi2O 12Compounds having a NASICON-type crystal structure are exemplified. Compounds having a NASICON-type crystal structure have high ionic conductivity and excellent stability in the atmosphere. Examples of compounds having a NASICON-type crystal structure include phosphates containing lithium. Examples of phosphates include composite lithium phosphate salts with Ti (e.g., Li 1+x Al x Ti 2-x (PO4)3), compounds in which all or part of Ti in the above composite lithium phosphate salt is substituted with a tetravalent transition metal such as Ge, Sn, Hf, Zr, or a trivalent transition metal such as Al, Ga, In, Y, La, etc. Specific examples of compounds having a NASICON-type crystal structure include Li-Al-Ge-P-O-based materials (Li 1+x Al x Ge 2-x (PO4)3), Li-Al-Zr-P-O-based materials (Li 1+x Al x Zr 2-x (PO4)3), Li-Al-Ti-P-O-based materials (Li 1+x Al x Ti 2-x (PO4)3), etc.

[0052] Examples of the polymer solid electrolyte include mixtures (complexes) of a polymer compound and an electrolyte salt. Specific examples of the polymer compound include polyether-based polymer compounds such as polyethylene oxide (PEO) and polypropylene oxide (PPO), polyamine-based polymer compounds such as polyethyleneimine (PEI), polysulfide-based polymer compounds such as polyalkylene sulfide (PAS), etc. Among these, polyether-based polymer compounds are preferred.

[0053] (Solid electrolyte layer) Examples of the solid electrolyte layer used in the battery of the present disclosure include electrolyte layers used in semi-solid batteries and all-solid batteries. The thickness of the solid electrolyte layer is not particularly limited and can be selected, for example, from the range of 1 μm to 30 μm.

[0054] The type of solid electrolyte contained in the solid electrolyte layer is not particularly limited. For example, it may be selected and used from the solid electrolytes that may be contained in the electrode layer described above. In the solid electrolyte layer, the first electrode layer and the second electrode layer may each contain a solid electrolyte. In this case, the types of solid electrolytes contained in each layer may be the same or different.

[0055] The electrode stacked structure including a solid electrolyte layer comprises a first current collector 11, a first electrode layer 12, an electrolyte layer which is a solid electrolyte layer 13, a second electrode layer 14, and a second current collector 15 (see Figure 1). The first electrode layer 12 may contain a first electrode active material, a conductive material, a binder, and a solid electrolyte. The second electrode layer 14 may contain a second electrode active material, a conductive material, a binder, and a solid electrolyte. The solid electrolyte layer may be a single layer or a multilayer structure of two or more layers.

[0056] If a solid battery, which is one embodiment of the present disclosure, includes a solid electrolyte, it may also include an electrolyte solution in an amount of less than 10% by mass relative to the total amount of electrolyte. If a solid battery, which is one embodiment of the present disclosure, includes a solid electrolyte, the solid electrolyte may be a composite solid electrolyte comprising an inorganic solid electrolyte and a polymer electrolyte.

[0057] When a solid-state battery, which is one embodiment of the present disclosure, includes an electrolyte as the electrolyte, the type of electrolyte is not particularly limited, and known electrolytes can be used. Specific examples of electrolytes include liquids obtained by dissolving lithium salts such as LiPF6 and LiFSi in an organic solvent. Examples of organic solvents include cyclic or linear carbonates such as ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). The solvent may be a mixture of two or more solvents, or a mixture containing both cyclic and linear carbonates. The solvent may contain additives such as vinylene carbonate (VC).

[0058] (Exterior) A solid-state battery, which is one embodiment of the present disclosure, may further include an outer casing. The outer casing at least houses the electrode laminate described above. Examples of outer casings include laminate-type outer casings and case-type outer casings. A laminate-type outer casing may be formed from a laminate (laminate film) having a metal layer containing a metal such as aluminum and a heat-seal layer containing a resin that melts upon heating.

[0059] (Restraining member) A solid-state battery, which is one embodiment of the present disclosure, may further include a restraining member. The restraining member applies restraining pressure to the electrode stack described above in the thickness direction. The restraining pressure applied in the thickness direction of the electrode stack may be, for example, 0.1 MPa or more, 1 MPa or more, or 5 MPa or more. The restraining pressure applied in the thickness direction of the electrode stack may be, for example, 100 MPa or less, 50 MPa or less, or 20 MPa or less.

[0060] <Method of manufacturing solid-state batteries> Hereinafter, an embodiment of the manufacturing method for a solid-state battery according to this disclosure will be described with reference to Figures 6 and 7. A method for manufacturing a solid-state battery, which is one embodiment of the present disclosure, is a method for manufacturing a solid-state battery that includes a structure in which a first current collector, a first electrode layer, a solid electrolyte layer, a second electrode layer, and a second current collector are arranged in this order in the first axial direction, and includes a second laminate preparation step, a third laminate preparation step, and a first current collector arrangement step. The second laminate preparation step involves transferring a solid electrolyte layer transfer material, which includes a solid electrolyte layer, onto the surface of the second electrode layer of a first laminate comprising a second current collector and a second electrode layer, and applying a linear pressure P1 in the first axial direction to obtain a second laminate containing a second electrode layer and a solid electrolyte layer. The third laminate preparation step involves transferring a first electrode layer transfer material, which includes a first electrode layer, to the surface of the solid electrolyte layer of the second laminate, and then applying a linear pressure P2 in the first axial direction to obtain a third laminate further containing a first electrode layer. The first current collector placement step is the step of placing the first current collector on the surface of the first electrode layer of the third laminate. In the second laminate preparation process, the linear pressure P1 is greater than 0.25 t / cm, and in the third laminate preparation process, the linear pressure P2 is less than 4.0 t / cm, and the linear pressure P1 is less than the linear pressure P2.

[0061] In this disclosure, the linear pressure may be the value measured by the following formula (1) as the linear pressure applied by the roll press. Roll thrust ÷ (workpiece width × compression allowance in the flow direction) Equation (1)

[0062] The solid-state battery described above, in which a void is formed in at least one of the interior and periphery of the first electrode layer, and whose cross-sectional shape along the first axial direction is elongated in the in-plane direction of the first electrode layer, can be well manufactured by a solid-state battery manufacturing method according to one embodiment of the present disclosure, which involves transferring each layer of the solid-state battery stack structure with a specific linear pressure. The linear pressure is applied by a press process, and more specifically, by a roll press, from the viewpoint of well forming the void. Each layer can also be densified by the press process.

[0063] (Second laminate preparation process) In the second laminate preparation step, a solid electrolyte layer is transferred to the surface side of the second electrode layer of the first laminate, which comprises a second current collector and a second electrode layer, using a solid electrolyte layer transfer material. A linear pressure P1 is applied in the first axial direction when transferring the solid electrolyte layer. This yields a second laminate comprising a second current collector, a second electrode layer, and a solid electrolyte layer in that order. The linear pressure P1 is preferably applied by a roll press.

[0064] From the viewpoint of forming a good void around the first electrode layer, preferably between the first electrode layer and the solid electrolyte layer, the linear pressure P1 is preferably greater than 0.25 t / cm and 0.4 t / cm or greater. Also, the linear pressure P1 is less than the linear pressure P2, which will be described later. The linear pressure P1 is preferably less than 4.0 t / cm and 1.5 t / cm or less.

[0065] When applying linear pressure P1 by roll pressing, the temperature should be adjusted according to the linear pressure P1, although this depends on the material of each layer being pressed. This is preferable from the viewpoint of maintaining each layer in good condition. Specifically, when the linear pressure P1 is 0.4t / cm to 1.5t / cm, the temperature should preferably be 40°C to 180°C.

[0066] (Third laminate preparation process) In the third laminate preparation step, a first electrode layer transfer material, which includes the first electrode layer, is transferred to the surface side of the solid electrolyte layer of the second laminate. When transferring the first electrode layer, a linear pressure P2 is applied in the first axial direction. This yields a third laminate comprising a second current collector, a second electrode layer, a solid electrolyte layer, and a first electrode layer in that order. The linear pressure P2 is preferably applied by a roll press.

[0067] From the viewpoint of forming a good gap inside or around the first electrode layer, the linear pressure P2 is preferably less than 4.0 t / cm and 3.0 t / cm or less. Also, the linear pressure P2 is greater than the linear pressure P1. The linear pressure P2 is preferably greater than 0.25 t / cm and 0.4 t / cm or more.

[0068] When applying linear pressure P2 by roll pressing, the temperature should be adjusted according to the linear pressure P2, although this depends on the material of each layer being pressed. This is preferable from the viewpoint of maintaining each layer in good condition. Specifically, when the linear pressure P2 is 0.4t / cm to 3.0t / cm, the temperature should preferably be 40°C to 180°C.

[0069] (First current collector placement process) In the first current collector placement step, the first current collector is placed on the surface of the first electrode layer of the third stack. This results in a battery stack structure comprising the second current collector, the second electrode layer, the solid electrolyte layer, the first electrode layer, and the first current collector in that order.

[0070] As shown in Figure 6, for example, a method for manufacturing a solid battery involves preparing a first laminate 10a comprising a second current collector 15 and a second electrode layer 14 (step S100), and then performing the second laminate preparation step (step S110), the third laminate preparation step (step S120), and the first current collector placement step (step S130) in this order. In the second laminate preparation step (S110), a solid electrolyte layer transfer material comprising a solid electrolyte layer 13 is transferred to the surface of the second electrode layer 14 of the first laminate 10a, and a linear pressure P1 is applied in the first axial direction to obtain a second laminate 10b containing the second electrode layer 14 and the solid electrolyte layer 13. In the third laminate preparation step (S120), a first electrode layer transfer material containing a first electrode layer 12 is transferred to the surface of the solid electrolyte layer 13 of the second laminate 10b, and a linear pressure P2 is applied in the first axial direction to obtain a third laminate 10c further containing a first electrode layer 12. In the first current collector placement step (S130), the first current collector 11 is placed on the surface of the first electrode layer 12 of the third laminate 10c to obtain a solid battery 10 including a battery stack structure.

[0071] Each layer constituting the battery stack structure may be a single layer or multiple layers of two or more. In the case of layers that are stacked by transfer, a transfer material having multiple pre-defined layers may be used, or a transfer material having one layer may be transferred sequentially multiple times.

[0072] A method for manufacturing a solid-state battery, which is one embodiment of the present disclosure, is a method for manufacturing a solid-state battery that includes a structure in which a first current collector, a first electrode layer split B, a first electrode layer split A, a solid electrolyte layer, a second electrode layer, and a second current collector are arranged in this order in the first axial direction, and includes a second laminate preparation step, a third laminate A preparation step, a third laminate B preparation step, and a first current collector arrangement step. The second laminate preparation step involves transferring a solid electrolyte layer transfer material, which includes a solid electrolyte layer, onto the surface of the second electrode layer of a first laminate comprising a second current collector and a second electrode layer, thereby obtaining a second laminate containing the second electrode layer and the solid electrolyte layer. In the step of obtaining the second laminate, a linear pressure P1 may be applied when transferring the solid electrolyte layer. The third laminate A preparation step involves transferring a first electrode layer A transfer material containing the first electrode layer A onto the surface of the solid electrolyte layer of the second laminate, and then applying a linear pressure P3 in the first axial direction to obtain a third laminate A further containing the first electrode layer A. The third laminate B preparation step involves transferring a first electrode layer B transfer material containing the first electrode layer B to the surface of the first electrode layer A of the third laminate A, and then applying a linear pressure P4 in the first axial direction to obtain a third laminate B that further contains the first electrode layer B. The first current collector placement step is the step of placing the first current collector on the surface of the first electrode layer separation B of the third laminate B. In the preparation process for the third laminate A, the linear pressure P3 is greater than 0.25 t / cm, and in the preparation process for the third laminate B, the linear pressure P4 is less than 3.0 t / cm, and the linear pressure P3 is less than the linear pressure P4.

[0073] The solid-state battery described above, in which a void is formed in at least one of the interior and periphery of the first electrode layer, and whose cross-sectional shape along the first axial direction is elongated in the in-plane direction of the first electrode layer, can be well manufactured by a solid-state battery manufacturing method which is one embodiment of the present disclosure, in which each layer of the solid-state battery stack structure is formed by transferring it with a specific linear pressure. From the viewpoint of well forming the void, the linear pressure is preferably applied by a roll press. Each layer can also be densified by the roll press.

[0074] (Second laminate preparation process) In the second laminate preparation step, a solid electrolyte layer is transferred to the surface side of the second electrode layer of the first laminate, which comprises a second current collector and a second electrode layer, using a solid electrolyte layer transfer material. A linear pressure P1 is applied in the first axial direction when transferring the solid electrolyte layer. This results in a second laminate comprising a second current collector, a second electrode layer, and a solid electrolyte layer in that order.

[0075] (Preparation process for the third laminate A) In the third laminate A preparation step, a first electrode layer splitting A transfer material, which contains the first electrode layer splitting A, is transferred to the surface side of the solid electrolyte layer of the second laminate. When transferring the first electrode layer splitting A, a linear pressure P3 is applied in the first axial direction. This yields a third laminate A having the second current collector, the second electrode layer, the solid electrolyte layer, and the first electrode layer splitting A in that order. The linear pressure P3 is preferably applied by a roll press.

[0076] From the viewpoint of forming a good gap around the first electrode layer, preferably between the first electrode layer and the solid electrolyte layer, the linear pressure P3 is preferably greater than 0.25 t / cm and 0.4 t / cm or more. Also, the linear pressure P3 is less than the pressure P4, which will be described later. The linear pressure P3 is preferably less than 3.0 t / cm and 2.0 t / cm or less.

[0077] When applying linear pressure P3 by roll pressing, the temperature should be adjusted according to the linear pressure P3, although this depends on the material of each layer being pressed. This is preferable from the viewpoint of maintaining each layer in good condition. Specifically, when the linear pressure P3 is 0.4t / cm to 2.0t / cm, the temperature should preferably be 40°C to 180°C.

[0078] (Third laminate B preparation process) In the preparation step for the third laminate B, a transfer material containing the first electrode layer B is transferred to the surface side of the first electrode layer A of the third laminate A. A linear pressure P4 is applied in the first axial direction when transferring the first electrode layer B. This yields the third laminate B, which comprises the second current collector, the second electrode layer, the solid electrolyte layer, the first electrode layer A, and the first electrode layer B in that order. The linear pressure P is preferably applied by a roll press.

[0079] From the viewpoint of forming a good gap inside or around the first electrode layer, the linear pressure P4 is preferably less than 3.0 t / cm and 2.5 t / cm or less. Also, the linear pressure P4 is greater than the linear pressure P3. The linear pressure P4 is preferably greater than 0.25 t / cm and 0.8 t / cm or more.

[0080] When applying linear pressure P4 using a roll press, the temperature should be adjusted according to the linear pressure P4, although this depends on the material of each layer being pressed. This is preferable from the viewpoint of maintaining each layer in good condition. Specifically, when the linear pressure P4 is 0.8 t / cm to 2.5 t / cm, the temperature should preferably be 40°C to 180°C.

[0081] (First current collector placement process) In the first current collector placement step, the first current collector is placed on the surface of the first electrode layer division B of the third laminate B. This results in a battery laminate structure having the second current collector, second electrode layer, solid electrolyte layer, first electrode layer division A, first electrode layer division B, and first current collector in this order.

[0082] As shown in Figure 7, for example, a method for manufacturing a solid battery involves preparing a first laminate 10a comprising a second current collector 15 and a second electrode layer 14 (step S200), and then performing the second laminate preparation step (step S210), the third laminate A preparation step (step S220), the third laminate B preparation step (step S230), and the first current collector placement step (step S240) in this order. In the second laminate preparation step (S110), a solid electrolyte layer transfer material comprising a solid electrolyte layer 13 is transferred to the surface of the second electrode layer 14 of the first laminate 10a, and a linear pressure P1 is applied in the first axial direction to obtain a second laminate 10b containing the second electrode layer 14 and the solid electrolyte layer 13. In the third laminate A preparation step (S220), a first electrode layer A transfer material containing the first electrode layer A12b is transferred to the surface of the solid electrolyte layer 13 of the second laminate 10b, and a linear pressure P3 is applied in the first axial direction to obtain a third laminate A10d further containing the first electrode layer A12b. In the third laminate B preparation step (S225), a first electrode layer B transfer material containing the first electrode layer B12a is transferred to the surface of the first electrode layer A12b of the third laminate A10d, and a linear pressure P4 is applied in the first axial direction to obtain a third laminate B10e further containing the first electrode layer B12a. In the first current collector placement step (S230), the first current collector 11 is placed on the surface of the first electrode layer separation B12a of the third laminate B10e to obtain a solid battery 10 including a battery stack structure.

[0083] The method for manufacturing a solid-state battery may further include other steps. These other steps may include, for example, a step of applying restraining pressure to the battery stack structure using a restraining member, or a step of sealing the battery stack structure with the restraining member into an outer casing.

[0084] <Types and uses of batteries> The type of solid-state battery is not particularly limited, but is typically a lithium-ion battery. Furthermore, the solid-state battery in one embodiment of this disclosure may be a primary battery or a secondary battery, but is preferably a secondary battery. This is because it can be repeatedly charged and discharged, making it useful, for example, as an in-vehicle battery. The solid-state battery may be a semi-solid-state battery or a fully solid-state battery. A fully solid-state battery is preferred.

[0085] The applications of the solid-state battery according to one embodiment of this disclosure are not particularly limited. Typical applications include power sources for vehicles, electronic devices, and electrical storage systems. It may also be used as a power source for mobile devices other than vehicles (e.g., railways, ships, aircraft), or as a power source for electrical products such as information processing devices. Among these, the application of the solid-state battery according to one embodiment of this disclosure is preferably as a power source for vehicles, and more preferably as a power source for hybrid vehicles, plug-in hybrid vehicles, or electric vehicles. Examples of vehicles include electric four-wheeled vehicles, electric two-wheeled vehicles, gasoline-powered vehicles, and diesel-powered vehicles. Examples of electric four-wheeled vehicles include battery electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), and hybrid electric vehicles (HEVs). Examples of electric two-wheeled vehicles include electric motorcycles and electric-assist bicycles. [Examples]

[0086] Embodiments of this disclosure will be described below with reference to examples. However, this disclosure is not limited to these embodiments. Details of the materials indicated by abbreviations are as follows. Sulfide solid electrolyte represented by the chemical formula SE:Li2S-P2S5 NCA:LiNi0.8 Co 0.15 Al 0.05 Positive electrode active material represented by the composition formula of O2 NBR: Acrylonitrile Butadiene Rubber PVdF: Polyvinylidene fluoride VGCF: Vapor-phase grown carbon fiber SUS: Stainless steel

[0087] <Example 1> (Preparation of the second layer) A cathode slurry was prepared by mixing NCA (78.3 parts by mass), SE (18.8 parts by mass), VGCF (2.9 parts by mass), and PVdF (2.8 parts by mass) as cathode active materials with a solvent (butyl butyrate). This cathode slurry was coated onto aluminum foil and dried to prepare the cathode layer, which is the first laminate. SE slurry was prepared by mixing SE (99.4 parts by mass) and NBR (0.6 parts by mass) with solvents (heptane and butyl butyrate). This SE slurry was coated onto SUS foil and dried to form an electrolyte layer (SE layer). A SUS foil with an SE layer formed on it was placed on top of a positive electrode layer formed on an aluminum foil, and pressed using a roll press at a linear pressure of 0.50 t / cm (P1) and 170°C. Afterward, the SUS foil was peeled off the SE layer, and the SE layer was transferred onto the positive electrode layer to prepare a second laminate. The linear pressure P1 and temperature during the pressing process are shown in Table 1.

[0088] (Preparation of the third layer) A negative electrode slurry was prepared by mixing silicon (49 parts by mass), SE (41.2 parts by mass), VGCF (7.5 parts by mass), and PVdF (6.6 parts by mass) as negative electrode active materials with a solvent (butyl butyrate). This negative electrode slurry was coated onto a SUS foil and dried to form a negative electrode layer. A SUS foil with a negative electrode layer formed on it was placed on the surface of the SE layer of a second laminate, on which an SE layer had been transferred onto the positive electrode layer. Pressing was performed by roll pressing under the conditions of 1.0 t / cm (linear pressure P2) and 170°C. Subsequently, the SUS foil was peeled off from the negative electrode layer, and the negative electrode layer was transferred onto the SE layer to prepare a third laminate. The linear pressure P1 and temperature during the pressing process are shown in Table 1.

[0089] (Formation of a battery stack structure) As the material for the negative electrode current collector, aluminum foil with a nickel-plated layer formed on one side was prepared. The thickness of the aluminum foil was 15 μm. A negative electrode current collector was placed on the surface of the negative electrode layer of the third stacked structure to form a battery stacked structure.

[0090] <Comparative Example 1> A battery stack structure was formed in the same manner as in Example 1, except that the conditions for transferring the SE layer onto the positive electrode layer to prepare the second stack were 0.25 t / cm (linear pressure P1) and 25°C, and the conditions for transferring the negative electrode layer onto the SE layer to prepare the third stack were 2.0 t / cm (linear pressure P2) and 170°C. The linear pressure P1 or P2 and the respective temperatures during the pressing process are shown in Table 1.

[0091] <Example 2> A battery stack structure was formed in the same manner as in Example 1, except that the conditions for transferring the SE layer onto the positive electrode layer to prepare the second stack were 0.50 t / cm (linear pressure P1) and 170°C, and the conditions for transferring the negative electrode layer onto the SE layer to prepare the third stack were 2.5 t / cm (linear pressure P2) and 170°C. The linear pressure P1 or P2 and the respective temperatures during the pressing process are shown in Table 1.

[0092] <Example 3> (Preparation of the second layer) The second laminate was prepared in the same manner as in Example 1.

[0093] (Preparation of the third layer B) A negative electrode slurry was prepared by mixing silicon (49 parts by mass), SE (41.2 parts by mass), VGCF (7.5 parts by mass), and PVdF (6.6 parts by mass) as negative electrode active materials with a solvent (butyl butyrate). This negative electrode slurry was coated onto a SUS foil and dried to form negative electrode layers. Two transfer materials for these negative electrode layers were prepared: a negative electrode layer A transfer material for negative electrode layer A, and a negative electrode layer B transfer material for negative electrode layer B. A SUS foil with a negative electrode layer A formed on it was placed on the surface of the SE layer of a second laminate, on which an SE layer had been transferred onto the positive electrode layer, and pressed using a roll press at a linear pressure of 1.0 t / cm (linear pressure P3) and 170°C. Subsequently, the SUS foil was peeled off from the negative electrode layer A, and the negative electrode layer A was transferred onto the SE layer to prepare the third laminate A. The linear pressure P3 and temperature during the pressing process are shown in Table 1.

[0094] A SUS foil with negative electrode layer B formed on it was placed on the surface of negative electrode layer A of a third laminate A, which had negative electrode layer A transferred onto the SE layer, and pressed using a roll press at a linear pressure of 2.0 t / cm (linear pressure P4) and 170°C. Subsequently, the SUS foil was peeled off from negative electrode layer B, and negative electrode layer B was transferred onto negative electrode layer A to prepare the third laminate B. The linear pressure P4 and temperature during the pressing process are shown in Table 1.

[0095] (Formation of a battery stack structure) As the material for the negative electrode current collector, aluminum foil with a nickel-plated layer formed on one side was prepared. The thickness of the aluminum foil was 15 μm. A negative electrode current collector was placed on the surface of the negative electrode layer B of the third laminate B to form a battery laminate structure.

[0096] <Example 4> A battery stack structure was formed in the same manner as in Example 2, except that the SUS foil with the negative electrode layer split A formed on it was placed on the surface of the SE layer of the second stack, on which the SE layer had been transferred onto the positive electrode layer, and the conditions for preparing the third stack A were 0.50 t / cm (linear pressure P3) and 170°C, and the conditions for transferring the negative electrode layer split B onto the negative electrode layer split A and preparing the third stack were 1.0 t / cm (linear pressure P4) and 170°C. The linear pressure P3 or linear pressure P4 and the respective temperatures during the pressing process are shown in Table 1.

[0097] <Comparative Example 2> The SUS foil on which the negative electrode layer split A is formed is placed on the surface of the SE layer of the second laminate, on which the SE layer has been transferred onto the positive electrode layer. The conditions for preparing the third laminate A are 0.25 t / cm (linear pressure P3) and 25°C, and the negative electrode layer split B is transferred onto the negative electrode layer split A. A battery stack structure was formed in the same manner as in Example 2, except that the conditions for preparation were 2.0 t / cm (linear pressure P4) and 170°C. The linear pressure P3 or linear pressure P4 and the respective temperatures during the pressing process are shown in Table 1.

[0098] <Comparative Example 3> A battery stack structure was formed in the same manner as in Example 2, except that the SUS foil with the negative electrode layer split A formed on it was placed on the surface of the SE layer of the second stack, on which the SE layer had been transferred onto the positive electrode layer, and the conditions for preparing the third stack A were 0.50 t / cm (linear pressure P3) and 170°C, and the conditions for transferring the negative electrode layer split B onto the negative electrode layer split A and preparing the third stack were 3.0 t / cm (linear pressure P4) and 170°C. The linear pressure P3 or P4 and the respective temperatures during the pressing process are shown in Table 1.

[0099] <Rating> The battery stack structures obtained in the examples and comparative examples were cut along the first axis, which is the thickness direction of the battery stack structure, and observed using SEM imaging. The SEM imaging conditions were 300x and 1500x magnification, and an acceleration voltage of 2.0kV. The voids inside the negative electrode layer or between the negative electrode layer and the solid electrolyte layer were observed, and it was evaluated whether there were voids that met the conditions of shape, short axis, and aspect ratio. Hereinafter, "void" refers to the voids inside the negative electrode layer or between the negative electrode layer and the solid electrolyte layer.

[0100] The evaluation criteria are as follows. The evaluation results are shown in Table 1. (Transferability) A: Each layer has been successfully transferred. B: There were layers that could not be transferred.

[0101] (short axis) For Examples 1 to 4 and Comparative Example 3, where each layer was joined, the length (short axis) of the void in the first axial direction (battery stacking direction) was measured. The measured values ​​are shown in Table 1. If multiple voids were observed, the average length is shown in Table 1. In Comparative Example 3, no void was formed, so 0 was entered in the corresponding column in Table 1.

[0102] (Aspect ratio) For Examples 1 to 4 and Comparative Example 3, in which each layer was joined, the length of the void in the first axial direction (battery stacking direction) (short axis) and the length of the long axis were measured, and the aspect ratio was calculated from the measured values. The calculated values ​​are shown in Table 1. When multiple voids were observed, the average length value was used.

[0103] (Percentage of total void area (%)) For each battery stack structure obtained in the examples and comparative examples, the proportion of the total area of ​​the void was measured when a long void was formed in the in-plane direction of the negative electrode layer, either inside the negative electrode layer or between the negative electrode layer and the solid electrolyte layer. In a cross-sectional view along the first axis of the battery stack structure, the proportion of the total area occupied by the void to the total area of ​​the first electrode layer was measured. The measurement results are shown in Table 1.

[0104] (Rate of resistance increase) The battery stacked structure and lithium foil used as the positive electrode current collector obtained in the examples and comparative examples were molded to form a circle with a diameter of 11.28 mm. SE (100 mg) was pressed at 100 MPa using a jig with a 10 mm diameter hole to produce SE pellets with a diameter of 10 mm. A half-cell was fabricated by arranging a negative electrode current collector, SE pellets, and a positive electrode current collector in that order in a cylindrical container with a diameter of 11.28 mm, and then restraining them with a restraining jig so that a pressure of 2 MPa was applied. This half-cell was used as the evaluation battery.

[0105] A cycle test was performed on evaluation batteries, which were half-cells using the battery stacks prepared in the examples and comparative examples, by performing 5 charge-discharge cycles under conditions of 1C and 1.5-4.1V. After the cycle test, DC-IR measurement (Direct Current Internal Resistance measurement) was performed on the evaluation batteries to measure the resistance increase rate after 10 seconds of discharge. The measured resistance increase rates are shown in Table 1. A resistance increase rate of 35% or less was considered acceptable.

[0106] [Table 1]

[0107] As shown in Table 1, in the solid-state battery according to the embodiment of the present disclosure, it was confirmed that at least one of the following is formed: inside the first electrode layer and around the first electrode layer, the shape of which in a cross-sectional view along the first axial direction is elongated in the in-plane direction of the first electrode layer. Furthermore, it was confirmed that in the solid-state battery according to the embodiment of the present disclosure, the resistance increase rate after cycle testing is suppressed by the formation of an elongated void in the in-plane direction of the first electrode layer in a cross-sectional view along the first axial direction. [Explanation of symbols]

[0108] 10 solid state battery 10a First Laminate 10b Second layer 10c Third layer 10d Third layer A 10e Third layer B 11 First collector 12 First electrode layer 12a First electrode layer layer B 12b First electrode layer layer A 13 Solid electrolyte layer 14 Second electrode layer 15. Second collector Gap 16, 16a, 16b a short axis of the gap b long axis of the gap P1~P4 line pressure S100~S230 ステップ X-axis (first axis direction, battery stacking direction) Y-axis direction (in-plane direction) Z-axis direction

Claims

1. The structure includes a first current collector, a first electrode layer, a solid electrolyte layer, a second electrode layer, and a second current collector arranged in this order in the first axial direction. The first electrode layer has a void inside and around the first electrode layer, The aforementioned void is a solid-state battery in which the shape of the void in a cross-sectional view along the first axial direction is elongated in the in-plane direction of the first electrode layer.

2. The solid battery according to claim 1, wherein the length of the minor axis of the shape of the gap in a cross-sectional view along the first axial direction is 1 μm or less.

3. The solid battery according to claim 1, wherein the void has an aspect ratio of 10 to 40 in a cross-sectional view along the first axial direction.

4. The solid battery according to claim 1, wherein the void is formed inside the first electrode layer and between the first electrode layer and the solid electrolyte layer, at least in one of these cases.

5. The solid battery according to claim 1, wherein one or more voids are formed in a cross-sectional view along the first axial direction, and occupy an area of ​​1% to 10% of the total area of ​​the first electrode layer.

6. The first electrode layer includes multiple layers, The solid battery according to claim 1, having voids between the layers of the plurality of layers and around the first electrode layer.

7. A method for manufacturing a solid-state battery, comprising a structure in which a first current collector, a first electrode layer, a solid electrolyte layer, a second electrode layer, and a second current collector are arranged in this order in the first axial direction, A step of obtaining a second laminate including the second electrode layer and the solid electrolyte layer by transferring a solid electrolyte layer transfer material, which includes the solid electrolyte layer, onto the surface of the second electrode layer of a first laminate comprising the second current collector and the second electrode layer, and applying a linear pressure P1 in the first axial direction, A step of obtaining a third laminate further including the first electrode layer by transferring a first electrode layer transfer material, which includes the first electrode layer, onto the surface of the solid electrolyte layer of the second laminate, and applying a linear pressure P2 in the first axial direction, The process includes the step of placing the first current collector on the surface of the first electrode layer of the third laminate, The linear pressure P1 is greater than 0.25 t / cm. The linear pressure P2 is less than 4.0 t / cm, and A method for manufacturing a solid-state battery in which the linear pressure P1 is less than the linear pressure P2.

8. A method for manufacturing a solid-state battery, comprising a structure in which a first current collector, a first electrode layer split B, a first electrode layer split A, a solid electrolyte layer, a second electrode layer, and a second current collector are arranged in this order in the first axial direction, A step of transferring a solid electrolyte layer transfer material comprising the solid electrolyte layer onto the surface of the second electrode layer of a first laminate comprising the second current collector and the second electrode layer, thereby obtaining a second laminate comprising the second electrode layer and the solid electrolyte layer, A step of obtaining a third laminate A further containing the first electrode layer A by transferring a first electrode layer A transfer material, which includes the first electrode layer A, onto the surface of the solid electrolyte layer of the second laminate, and applying a linear pressure P3 in the first axial direction, A step of obtaining a third laminate B further containing the first electrode layer B by transferring a first electrode layer B transfer material, which includes the first electrode layer B, onto the surface of the solid electrolyte layer of the third laminate A, and applying a linear pressure P4 in the first axial direction, The process includes placing the first current collector on the surface of the first electrode layer separation B of the third laminate B, The linear pressure P3 is greater than 0.25 t / cm. The linear pressure P4 is less than 3.0 t / cm, and A method for manufacturing a solid-state battery where the linear pressure P3 is lower than the linear pressure P4.

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