solid-state accumulator

Abstract

Solid-state accumulator comprising: a laminated body in which a positive electrode layer with a positive electrode current collector layer and a positive electrode active material layer and a negative electrode layer with a negative electrode current collector layer and a negative electrode active material layer are laminated over a solid electrolyte layer; a first external terminal;and a second outer connection, wherein the laminated body has a first side face parallel to a lamination direction and a second side face parallel to the lamination direction and perpendicular to the first side face, the first outer connection and the second outer connection are connected to the first side face, and the laminated body has a curvature that is curved in the lamination direction and satisfies equations (1) and (2): 0.5° ≤ ((A1 + A2) / 2) ≤ 5° A1 ≤ 8.0° where A1 is an angle of curvature of the laminated body when viewed from a side of the first side face, and A2 is an angle of curvature of the laminated body when viewed from a side of the second side face.

Description

TECHNICAL AREA

[0001] The present invention relates to a solid-state accumulator. Priority is claimed in Japanese patent application No. 2019-048907, filed on March 15, 2019, the contents of which are incorporated herein by reference. BACKGROUND

[0002] In recent years, the development of electronic technology has been remarkable, and portable electronic devices have become smaller, lighter, thinner, and more multifunctional. At the same time, there is a pressing need to reduce the size, weight, thickness, and reliability of the battery that powers an electronic device. Currently, widely used lithium-ion batteries typically employ an electrolyte (electrolytic solution), such as an organic solvent or similar, as the medium for ion movement. However, in batteries with the configuration mentioned above, the electrolyte solution can leak.

[0003] Since the organic solvent or similar substance used in the electrolyte solution is flammable, it is necessary to further improve battery safety. One proposed measure to enhance battery safety is the use of a solid electrolyte instead of the electrolyte solution. In addition to using a solid electrolyte, a solid-state battery is currently being developed, which consists of other components that are also solids.

[0004] Patent literature 1 discloses, for example, a solid-state lithium battery in which all components are formed from solids using a non-flammable solid electrolyte. A laminated body for the solid-state lithium battery includes an active material layer and a solid electrolyte layer, which is sintered and bonded to the active material layer. The active material layer contains a first crystalline material capable of releasing and encapsulating lithium ions, and the solid electrolyte layer contains a second crystalline material exhibiting lithium-ion conductivity. Patent literature 1 discloses that the fill level of the solid electrolyte layer is preferably greater than 70%.

[0005] In patent literature 2, however, a lithium-ion conductive solid electrolyte is disclosed in which a shaped body containing an inorganic powder is fired, and in which a porosity is equal to or less than 10 vol%.

[0006] As disclosed in patent literature 1 and patent literature 2, it is generally preferred that the solid electrolyte forming a solid-state battery be dense. List of citations from patent literature [Patent Literature 1] Unexamined Japanese patent application, first publication no. 2007-5279 [Patent Literature 2] Unexamined Japanese patent application, first publication no. 2007-294429 [Patent Literature 3] PCT International Publication No. 2013 / 175993 SUMMARY OF THE INVENTION Technical Problem

[0007] However, as disclosed in patent literature 1 and patent literature 2, in solid-state batteries where the solid electrolyte layer is dense, internal stress can concentrate in the solid electrolyte layer, and cracks can occur due to expansion and contraction of a volume of the electrode layer during charging and discharging of the solid-state battery. This has been found to lead to an increase in internal resistance and a deterioration of the cycle characteristics.

[0008] To solve such problems, patent literature 3 discloses a solid electrolyte layer in which a low-porosity portion is formed in a region near the electrode layer of the solid electrolyte layer, and a high-porosity portion is formed in a region separated from the electrode layer. However, according to the inventor's investigation, as disclosed in patent literature 3, the internal resistance of the solid electrolyte layer was further increased when the high- and low-porosity sections were formed in the solid electrolyte layer, and sufficient cycling properties could not be achieved.

[0009] The present invention aims to provide a solid-state accumulator with good cycle characteristics by providing a curvature with a predetermined angle. Solution to the problem

[0010] To achieve the aforementioned objectives, the present invention provides the following means. (1) A solid-state accumulator according to a first aspect of the present invention comprises a laminated body in which a positive electrode layer with a positive electrode current collector layer and a positive electrode active material layer, and a negative electrode layer with a negative electrode current collector layer and a negative electrode active material layer are laminated within a solid electrolyte layer, a first external terminal, and a second external terminal, wherein the laminated body has a first side surface parallel to a lamination direction and a second side surface parallel to the lamination direction and perpendicular to the first side surface, the first external terminal and the second external terminal are connected to the first side surface, and the laminated body has a curvature which is curved in the lamination direction and satisfies equations (1) and (2); 0.5°≤((A1+A2) / 2)≤5° A1 8.0° where A1 is an angle of curvature of the laminated body when viewed from one side of the first face, and A2 is an angle of curvature of the laminated body when viewed from one side of the second face. (2) In the solid-state accumulator according to (1) mentioned above, equation (3) can be satisfied: 0.5°≤((A1+A2) / 2)≤4° Advantageous effects of the invention

[0011] According to the present invention, it is possible to provide a solid-state accumulator with good cycle characteristics by providing a curvature with a predetermined angle. List of characters Fig. Figure 1 is a schematic cross-sectional view of a solid-state accumulator according to one embodiment. Fig. Figure 2 is a top view of a laminated body according to the embodiment. Fig.Figure 3 is a schematic view to describe the definition of an angle A1 of a bulge, which schematically shows the laminated body from one side of a first lateral surface. Fig. Figure 4 is a schematic view describing the definition of an angle A2 of the curvature, which schematically shows the laminated body from one side of a second lateral surface. DESCRIPTION OF THE EXECUTION FORMS

[0012] An embodiment of the present invention is described in detail below with reference to the accompanying drawings. In the drawings used in the following description, features of the embodiment may be enlarged for clarity, and the dimensions of the components may differ from the actual dimensions. The materials, dimensions, and the like listed in the following description are examples, and the embodiment is not limited to them and may be suitably modified and implemented within the scope of the present invention's effectiveness.

[0013] Solid-state batteries include, for example, solid-state lithium-ion batteries, solid-state sodium-ion batteries, solid-state magnesium-ion batteries, or similar devices. While a solid-state lithium-ion battery is described below as an example, the present invention can be applied generally to solid-state batteries.

[0014] Fig. Figure 1 is a schematic cross-sectional view of an enlarged main part of a solid-state lithium-ion battery according to one embodiment.

[0015] The in Fig.The solid-state lithium-ion battery shown contains a laminated body with a first electrode layer, a second electrode layer, and a solid electrolyte layer. Either the first or the second electrode layer acts as the positive electrode and the other as the negative electrode. The positive and negative positions of the electrode layers change depending on which polarity is connected to an external terminal. For ease of understanding, the first electrode layer is referred to as the positive electrode layer and the second electrode layer as the negative electrode layer.

[0016] The solid-state lithium-ion battery 100 has positive electrode layers 1, comprising positive electrode current collector layers 1A and positive electrode active material layers 1B, negative electrode layers 2, comprising negative electrode current collector layers 2A and negative electrode active material layers 2B, and the solid electrolyte layer 3, which comprises a solid electrolyte, and is provided with a laminated body 20 in which the positive electrode layers 1 and the negative electrode layers 2 are laminated alternately over the solid electrolyte layer 3.

[0017] The positive electrode layers 1 are connected to a first external terminal 6, and the negative electrode layers 2 are connected to a second external terminal 7. The first external terminal 6 and the second external terminal 7 are external electrical contacts. (Laminated body)

[0018] The laminated body 20 has the positive electrode layers 1, the negative electrode layers 2 and the solid electrolyte layer 3.

[0019] The positive electrode layers 1 and the negative electrode layers 2 are laminated alternately over the solid electrolyte layer 3 (more precisely, a solid electrolyte intermediate layer 3A) in the laminated body 20. The charging and discharging of the solid-state lithium-ion battery 100 takes place through the exchange of lithium ions between the positive electrode layers 1 and the negative electrode layers 2 via the solid electrolyte layer 3.

[0020] While the number of positive electrode layers 1 and negative electrode layers 2 stacked is not limited, the total number of positive electrode layers 1 and negative electrode layers 2 is generally in a range of 10 layers or more and 200 layers or less, preferably in a range of 20 layers or more and 100 layers or less.

[0021] The laminated body 20 is essentially hexahedral and has four face surfaces (a first face surface 21, a second face surface 22, a first face surface 23 and a second face surface 24) which are considered surfaces parallel to a lamination direction (a z-direction in Fig. 2) are formed, as well as an upper surface formed on an upper side and a lower surface formed on a lower side, the surfaces being substantially perpendicular to the lamination direction.

[0022] The first side surface is a surface on which the electrode layers are exposed, and in which the Fig. and Fig.In the illustrated example, the positive electrode layers 1 are exposed on the first side surface 21 and the negative electrode layers 2 are exposed on the first side surface 23. The second side surface is a surface on which the electrode layers are not exposed. The second side surface 22 is a right-hand side surface when viewed from the side of the first side surface 21, with one upper surface facing upwards, and a surface that is parallel in the lamination direction and substantially perpendicular to the first side surface 21 and the first side surface 23. Furthermore, the second side surface 24 is a left-hand side surface when viewed from the side of the first side surface 21, with one upper surface facing upwards, and a surface that is parallel in the lamination direction and substantially perpendicular to the first side surface 21 and the first side surface 23.

[0023] Here, in a curve of the laminated body described below, one of the first side surfaces 21 and the first side surface 23 can be selected as the first side surface, and furthermore, one of the second side surfaces 22 and the second side surface 24 can be selected as the second side surface. (Curvature of the laminated body)

[0024] The laminated body 20 has the first side surface 21 (or the first side surface 23) parallel to the lamination direction and the second side surface 22 (or the second side surface 24) parallel to the lamination direction (a z-direction) and perpendicular to the first side surface 21 and has a curvature that is curved in the lamination direction and satisfies equations (1) and (2); 0.5°≤((A1+A2) / 2)≤5° A1≤8.0°

[0025] Here, A1 is an angle of curvature of the laminated body 20 when viewed from the side of the first face 21 (or the first face 23), and A2 is an angle of curvature of the laminated body 20 when viewed from the side of the second face 22 (or the second face 24).

[0026] Fig. Figure 3 is a schematic view to describe the definition of the angle A1 of the curvature, which schematically shows the laminated body 20 as seen from the side of the first lateral surface 21.

[0027] The angle A1 of the curvature of the laminated body 20, when viewed from the side of the first face 21, is determined by Fig. 3 described. The laminated body 20 is arranged such that a side convex in the z-direction is directed towards a flat base S.

[0028] P1 is a point in contact with a surface Sa of the planar base S on the first side face 21 or a point that is closest to the surface Sa of the planar base S in the first side face 21, and P2 is a point on a side L1 shared by the first side face 21 and the second side face 22, that is closest to the surface Sa of the planar base S.

[0029] An angle enclosed by the surface Sa of the flat base S and a line segment connecting P1 and P2 is the angle A1 of the curvature of the laminated body 20.

[0030] If, instead of P2, a point P3 on a side L2 shared by the first face 21 and the second face 24 is used, and which is closest to the surface Sa of the planar base S, then an angle formed by the surface Sa of the planar base S and a line segment connecting P1 and P3 is the angle A1 of the curvature of the laminated body 20. If an angle formed by the line segment connecting P1 and P2 and an angle formed by the line segment connecting P1 and P3 are different from each other, then the angle formed by the line segment with the larger angle is the angle A1 of the curvature of the laminated body 20.

[0031] Fig. Figure 4 is a schematic view describing the definition of the angle A2 of the curvature, which schematically shows the laminated body 20 as seen from the side of the second side surface 22.

[0032] The angle A2 of the curvature of the laminated body 20, as seen from the second side surface 22, is determined by Fig. 4 described. The laminated body 20 is arranged such that a side convex in the z-direction is directed towards the flat base S.

[0033] Q1 is a point in contact with the surface Sa of the planar base S in the second side face 22 or a point in the second side face 22 that is closest to the surface Sa of the planar base S, and Q2 is a point in a side L3 that is shared by the second side face 22 and the first side face 23 that is closest to the surface Sa of the planar base S.

[0034] An angle enclosed by the surface Sa of the flat base and a line segment connecting Q1 and Q2 is the angle A2 of the curvature of the laminated body 20.

[0035] If, instead of Q2, a point Q3 is used on side L1, which is shared by the second face 22 and the first face 21, and which is closest to the surface Sa of the planar base S, then an angle enclosed by the surface Sa of the planar base S and a line segment connecting Q1 and Q3 can be the angle A2 of the curvature of the laminated body 20. If an angle formed by the line segment enclosing Q1 and Q2 and an angle formed by the line segment connecting Q1 and Q3 are different, then the angle formed by the line segment with the larger angle is the angle A2 of the curvature of the laminated body 20.

[0036] The present inventor has discovered that a solid-state battery with good cycle characteristics can be produced if the curvature of the laminated body satisfies the aforementioned equations (1) and (2). While the mechanism by which a configuration in which the curvature of the laminated body lies within a predetermined range leads to good cycle characteristics is not clear at this time, it is conceivable that if the laminated body already has the curvature within the predetermined range, the stress of volume expansion and contraction is reduced, resulting in good cycle characteristics, since the expansion and contraction of a volume of the electrode layer generated during charging and discharging of the solid-state battery follow the direction of the curvature.

[0037] The curvature of the laminated body 20 preferentially satisfies equation (3); 0.5°≤((A1+A2) / 2)≤4°

[0038] Better cycle properties are achieved when the curvature of the laminated body 20 satisfies equation (3).

[0039] The curvature of the laminated body 20 more preferentially satisfies equation (4); A1≤4.5°

[0040] Better cycle properties are achieved when the curvature of the laminated body 20 satisfies equation (4). (Positive electrode layers and negative electrode layers)

[0041] The positive electrode layers 1 have the positive electrode current collector layers 1A and the positive electrode active material layers 1B, which contain a positive electrode active material. The negative electrode layers 2 have the negative electrode current collector layers 2A and the negative electrode active material layers 2B, which contain a negative electrode active material.

[0042] The positive electrode current collector layers 1A and the negative electrode current collector layers 2A each contain a positive electrode current collector or a negative electrode current collector with high conductivity. For example, a metal or alloy containing at least one metallic element from the group consisting of silver (Ag), palladium (Pd), gold (Au), platinum (Pt), aluminum (Al), copper (Cu), and nickel (Ni), or a nonmetal such as carbon (C), is used as the high-conductivity positive electrode current collector and negative electrode current collector. For these metallic elements, copper or nickel are preferred due to their high conductivity and cost-effectiveness. Furthermore, copper does not readily react with the positive electrode active material, the negative electrode active material, or the solid electrolyte.For this reason, the internal resistance of the lithium-ion battery 100 can be reduced by using copper in the positive electrode current collector layers 1A and the negative electrode current collector layers 2A. The materials used to form the positive electrode current collector layers 1A and the negative electrode current collector layers 2A can be the same or different. While there is no limit to the thickness of the positive electrode current collector layers 1A and the negative electrode current collector layers 2A, as a guideline, the thicknesses are in the range of 0.5 µm or more and 30 µm or less.

[0043] The positive electrode active material layers 1B are formed on one or both surfaces of the positive electrode current collector layers 1A. For example, the negative electrode layers 2, which face a top side in the lamination direction, are not provided on the positive electrode layers 1, which are arranged on the top layer of the lithium-ion battery 100 in the lamination direction. Therefore, the positive electrode active material layer 1B in the positive electrode layer 1, which is arranged on the top layer of the lithium-ion battery 100, can only be provided on the single surface on the bottom side in the lamination direction, and there is no particular problem even if it is provided on both surfaces.

[0044] Like the positive electrode active material layers 1B, the negative electrode active material layers 2B are also formed on one or both surfaces of the current collector layers of the negative electrode 2A. The thicknesses of the positive electrode active material layers 1B and the negative electrode active material layers 2B are preferably in the range of 0.5 µm or more and 5.0 µm or less. If the thicknesses of the positive electrode active material layers 1B and the negative electrode active material layers 2B are 0.5 µm or more, the electrical capacity of the lithium-ion battery can be increased, whereas if the thicknesses are 5.0 µm or less, the internal resistance of the lithium-ion battery can be further reduced because the diffusion length of the lithium ions is decreased.

[0045] The positive electrode active material layers 1B and the negative electrode active material layers 2B each contain a positive electrode active material or a negative electrode active material that transfers lithium ions and electrons. In addition, a conductive additive or similar material may be included. Preferably, the positive electrode active material and the negative electrode active material are capable of efficiently incorporating and removing lithium ions.

[0046] There is no clear distinction between the active materials forming the positive electrode active material layers 1B and the negative electrode active material layers 2B. By comparing the potentials of two types of compounds, the compound with the more noble potential can be used as the positive electrode active material, and the compound with the lower potential can be used as the negative electrode active material. For this reason, the active materials are described together below.

[0047] The active materials can contain a transition metal oxide, a transition metal composite oxide, or similar compounds. For example, a lithium-manganese composite oxide (Li₂Mn₂) can be used as a transition metal oxide or transition metal composite oxide. a Ma 1-aO3 (0.8 ≤ a ≤ 1, Ma = Co, Ni), lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNi2), lithium manganese spinel (LiMn2O4), a composite metal oxide with the general formula: LiNi x Co y Mn z O2 (x + y + z = 1, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1), a lithium-vanadium compound (UV2O5), olivine of the LiM type b PO4 (where Mb is one or more elements selected from the group consisting of Co, Ni, Mn, Fe, Mg, Nb, Ti, Al, and Zr), vanadium-lithium phosphate (Li3V2(PO4)3 or LiVOPO4), a Li-excess positive mixed crystal electrode, expressed by Li2MnO3-LiM c O2 (M c = Mn, Co, Ni), lithium titanate (Li4Ti5O 12 ), a composite metal oxide, expressed by Li8Ni t Co u Al v O2 (0.9 < s < 1.3, 0.9 < t + u + v < 1.1), or similar examples.

[0048] The positive electrode current collector layers 1A and the negative electrode current collector layers 2A can contain a positive electrode active material and a negative electrode active material, respectively. The ratio of the active material contained in each of the current collector layers is not particularly limited, as long as it functions as a current collector. For example, it is preferred that the positive electrode current collector / positive electrode active material or the negative electrode current collector / negative electrode active material have a volume ratio in the range of 90 / 10 to 70 / 30.

[0049] Since the positive electrode current collector layers 1A and the negative electrode current collector layers 2A enclose the positive electrode active material and the negative electrode active material respectively, the adhesion between the positive electrode current collector layers 1A and the positive electrode active material layers 1B, as well as between the negative electrode current collector layers 2A and the negative electrode active material layers 2B, is improved. (Solid electrolyte layer)

[0050] As in Fig. As shown in Figure 1, the solid electrolyte layer 3 has the solid electrolyte intermediate layer 3A, which is arranged between the positive electrode active material layer 1B and the negative electrode active material layer 2B.

[0051] The solid electrolyte layer 3 can further comprise an outermost solid electrolyte layer 3B, which is located on an outer surface of the positive electrode layer 1 (the positive electrode current collector layer 1A) or the negative electrode layer 2 (the negative electrode current collector layer 2A) or both (both in Fig. 1) is arranged. The “outer side” here refers to an outer side of the positive electrode layer 1 or the negative electrode layer 2 that is closest to the surfaces 5A and 5B of the layer body 20.

[0052] Furthermore, the solid electrolyte layer 3 cannot have the outermost solid electrolyte layer 3B, and in this case the surfaces 5A and 5B of the laminated body 20 are the positive electrode layer 1 and the negative electrode layer 2.

[0053] Preferably, a material with low electronic conductivity and high lithium-ion conductivity is used in the solid electrolyte layer 3. The solid electrolyte layer 3 is preferably at least one material from the group consisting of perovskite-type compounds such as La 0.5 Li 0.5 TiO3 or similar lisicone-type compound such as Lii4Zn(GeO4)4 or similar, garnet-type compound such as Li7La3Zr2O 12 or similar, Nasicon-type compound such as LiZr2(PO4)3, Li 1.3 Al 0.3 Ti 1.7 (PO4)3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, or similar, thio-lisicium-type compound, such as Li 3.25 Ge 0.25 P 0.75 S4, Li3PS4 or similar, glass compounds such as Li2S-P2S5, Li2O-V2O5-SiO2 or similar, and phosphate compounds such as Li3PO4, Li 3.5 Si 0.5 P 0.5 O4, Li 2.9 PO 3.3 N 0.46 or similar is selected.

[0054] The solid electrolyte layer 3 is preferably selected depending on the active material used in the positive electrode layer 1 and the negative electrode layer 2. For example, the solid electrolyte layer 3 more preferably contains the same element as the element that forms the active material. Since the solid electrolyte layer 3 contains the same element as the element that forms the active material, the bond at the interface between the positive electrode active material layer 1B and the negative electrode active material layer 2B and the solid electrolyte layer 3 is strengthened. In addition, the contact area at the interface between the positive electrode active material layer 1B and the negative electrode active material layer 2B and the solid electrolyte layer 3 can be increased.

[0055] The thickness of the solid electrolyte interlayer 3A is preferably in the range of 0.5 µm or more and 20.0 µm or less. Since a short circuit between the positive electrode layer 1 and the negative electrode layer 2 can be reliably prevented if the thickness of the solid electrolyte interlayer 3A is 0.5 µm or more, and the movement distance of the lithium ions is reduced if the thickness is 20.0 µm or less, the internal resistance of the lithium-ion battery can be further reduced.

[0056] While the thickness of the outermost solid electrolyte layer 3B is not particularly limited, it can, for example, be 1% to 40% of the thickness of the laminated body 20. Since the outermost solid electrolyte layer 3B is provided, the solid electrolyte layer 3 and the electrode layers can be physically and chemically protected as with an edge layer described below, and durability or moisture resistance can be improved. (edge ​​layer)

[0057] As in Fig. As shown in Figure 1, the laminated body 20 contains the solid electrolyte and may include an outer layer 4 arranged in line with each of the positive electrode layer 1 and the negative electrode layer 2. The solid electrolyte contained in the outer layer 4 may be identical to or different from the solid electrolyte contained in the solid electrolyte layer 3.

[0058] Preferably, the boundary layer 4 is provided to eliminate a step difference between the solid electrolyte intermediate layer 3A and the positive electrode layer 1, and a step difference between the solid electrolyte intermediate layer 3A and the negative electrode layer 2. Accordingly, the boundary layer 4 is formed in a different region than the positive electrode layer 1 and the negative electrode layer 2 on a major surface of the solid electrolyte layer 3, essentially at the same level as the positive electrode layer 1 or the negative electrode layer 2 (i.e., in line with each of the positive electrode layer 1 and the negative electrode layer 2).Since the step differences between the solid electrolyte layer 3 and the positive electrode layer 1 and between the solid electrolyte layer 3 and the negative electrode layer 2 are resolved due to the presence of the boundary layer 4, the compactness between the solid electrolyte layer 3 and the electrode layers is increased, and separation between the layers (delamination) or bulging due to the firing of the solid-state battery is less likely.

[0059] The material forming the outer layer 4 is preferably at least one of the following groups, for example, a perovskite-type compound such as Lao.eLio.eTiOs or similar, or a lisicone-type compound such as Li 14 Zn(GeO4)4 or similar, garnet-type compound such as Li7La3Zr2O 12 or similar, Nasicon-type compound such as LiZr2(PO4)3, Li 1.3 Al 0.3 Ti 1.7 (PO4)3, Li 1.5 Al 0.5 Ge 1.5(PO4)3 or similar, thio-lisicium-type compound such as Li 3.25 Ge 0.25 P 0.75 S4, Li3PS4 or similar, glass compounds such as P2S5, Li2O-V2O5-SiO2 or similar, and phosphate compounds such as Li3PO4, Li 3.5 Si 0.5 P 0.5 O4, Li 2.9 PO 3.3 N 0.46 or similar, has been selected. (Connection)

[0060] The first outer terminal 6 and the second outer terminal 7 of the lithium-ion battery 100 preferably use a material with high conductivity. For example, silver (Ag), gold (Au), platinum (Pt), aluminum (Al), copper (Cu), tin (Sn), nickel (Ni), chromium (Cr), or similar materials may be used. The terminal may be formed from a single layer or from multiple layers. (protective layer)

[0061] The solid-state lithium-ion battery 100 can have a protective layer (not shown) configured to electrically, physically, or chemically protect the laminated body 20 or the terminal on an outer circumference of the laminated body 20. The material from which the protective layer is formed preferably has excellent insulation, durability, and moisture resistance and is environmentally safe. For example, glass, ceramic, a thermosetting resin, a light-curing resin, or the like are preferably used. Only one type of material can be used for the protective layer, or several materials can be used in combination. Furthermore, the protective layer can be a single layer, but it preferably has a plurality of layers. Among these, an organic-inorganic hybrid in which a thermosetting resin and a ceramic powder are mixed is particularly preferred. (Method for manufacturing a solid-state lithium-ion battery)

[0062] A process for manufacturing the solid-state lithium-ion battery 100 can employ a simultaneous firing process. This process involves producing laminated bodies by batch firing different materials of the active material layer, the current collector layer, and the solid electrolyte layer, which together form the laminated body 20. When the simultaneous firing process is used, the manufacturing process for the solid-state lithium-ion battery 100 can be reduced. Furthermore, the resulting laminated body 20 is denser when the simultaneous firing process is used. An example using the simultaneous firing process is described below.

[0063] The simultaneous firing process comprises a method for producing a paste from materials forming the laminated body 20, a method for producing a solid electrolyte film by applying and drying the paste for a solid electrolyte, a method for producing a positive electrode unit and a negative electrode unit by forming a positive electrode layer and a negative electrode layer on the solid electrolyte film, a method for producing the laminated body by alternately laminating the positive electrode unit and the negative electrode unit, and a method for simultaneously firing the produced laminated bodies. The methods are described in more detail below.

[0064] First, the materials of the positive electrode current collector layer 1A, the positive electrode active material layer 1B, the solid electrolyte layer 3, the negative electrode active material layer 2B, the negative electrode current collector layer 2A and the outer layer 4, which form the laminated body 20, are pasted together.

[0065] The pasting process is not particularly limited. For example, the powdered materials are mixed in a vehicle to obtain the paste. Here, "vehicle" is a general term for a medium in a liquid phase. The vehicle contains a solvent and a binder. Using this process, a paste for a positive electrode current collector layer 1A, a paste for a positive electrode active material layer 1B, a paste for a solid electrolyte layer 3, a paste for a negative electrode active material layer 2B, a paste for a negative electrode current collector layer 2A, and a paste for a surface layer 4 are produced.

[0066] When the laminated body 20 is manufactured, a positive electrode unit and a negative electrode unit, which will be described later, can be manufactured, and the laminated body can be produced.

[0067] First, the paste for a solid electrolyte layer 3 is formed on a PET film in a film mold using a doctor blade process and dried to form the solid electrolyte layer film. The paste for a positive electrode active material layer 1B is then screen-printed onto the resulting solid electrolyte layer film and dried to form the positive electrode active material layer 1B.

[0068] Next, the paste for a positive electrode current collector layer 1A is screen-printed onto the fabricated positive electrode active material layer 1B and dried to form the positive electrode current collector layer 1A. Then, the paste for a positive electrode active material layer 1B is again screen-printed on top of this and dried. Finally, the boundary layer, which is essentially the same height as the positive electrode layer, is formed by screen-printing the paste for a boundary layer onto the area of ​​the solid electrolyte film outside the positive electrode layer and drying the paste.Then, by separating the PET film, a positive electrode unit is obtained in which the positive electrode layer 1, the positive electrode active material layer 1B, the positive electrode current collector layer 1A and the positive electrode active material layer 1B are laminated successively, and the boundary layer 4 is formed on a main surface of the solid electrolyte layer 3.

[0069] A negative electrode unit is obtained by the same procedure, in which the negative electrode layer 2, the negative electrode active material layer 2B, the negative electrode current collector layer 2A and the negative electrode active material layer 2B are laminated successively, and the boundary layer 4 is formed on a main surface of the solid electrolyte layer 3.

[0070] The positive and negative electrode units are then laminated alternately such that their respective ends are offset and do not coincide, thus producing the laminated body of the solid-state battery. Furthermore, the solid electrolyte layer can be formed at both ends of the laminated body in the lamination direction. For the positive or negative electrode unit to be positioned, the solid electrolyte layer 3 utilizes the outermost solid electrolyte layer 3B, and for an intermediate positive or negative electrode unit, the solid electrolyte layer 3 utilizes the intermediate solid electrolyte layer 3A.

[0071] While the manufacturing process is intended to produce a solid-state battery of the parallel type, a process for producing a solid-state battery of the series type can be carried out to laminate the positive electrode layer 1 and the negative electrode layer 2 such that the respective one ends of both coincide with each other while no offset is carried out.

[0072] Furthermore, adhesion can be improved by pressing the manufactured laminated bodies together using compression molding, hot isostatic pressing (WIP), cold isostatic pressing (CIP), isostatic pressing, or similar methods. Pressing is preferably carried out under heat, for example at 40 °C to 95 °C.

[0073] The manufactured laminated bodies are cut into chips using a cutting device, and then the laminated body of the solid-state battery is produced by debinding and firing.

[0074] In the debinding process, the binder components contained in the laminated body 20 are preheated and decomposed before firing, thus suppressing excessive and rapid decomposition of the binder components during the firing process. During debinding, the manufactured laminated body 20 is placed on a ceramic base, and the debinding process is carried out, for example, in a temperature range of 300 °C to 800 °C for 0.1 to 10 hours under a nitrogen atmosphere. If a reducing atmosphere is required, the debinding process can be carried out, for example, under an argon atmosphere or a nitrogen / hydrogen mixture instead of nitrogen. If the current collector layer of the metal does not oxidize, a reducing atmosphere with a low oxygen content can also be used.

[0075] During firing, the sintered body can be obtained, for example, through heat treatment in a temperature range of 600 °C to 1000 °C under a nitrogen atmosphere. The firing time is, for example, 0.1 to 3 hours. If a reducing atmosphere is required, firing can be carried out, for example, under an argon atmosphere or a nitrogen-hydrogen mixture instead of a nitrogen atmosphere.

[0076] Various methods can be used to produce the layered body 20 with a desired curvature. For example, a method in which a ceramic attachment for a lid is arranged to control an amount of curvature at a height h1, which is the sum of a height increase Δh corresponding to a desired curvature angle after firing and the height of a side face of the laminated body before firing (a height h0 of the side face of the laminated body from the ceramic attachment for a base), and to prevent the laminated body from curving further by utilizing the knowledge that curvature is likely to occur if a rapid firing is carried out in the firing process. In this method, a gap is provided between the ceramic attachment for a lid and the laminated body to form a desired curvature angle.Furthermore, the height position h1, in which the ceramic cap for a lid is positioned, is a height position that accounts for a shrinkage percentage of the laminated body after firing. The height position of the ceramic cap for a lid can be easily adjusted by positioning the laminated body at four corners of the ceramic cap for a base to adjust the height. For example, if the gap between the pre-firing laminated body and the ceramic cap for a lid is to be 10 µm, the laminated body can be provided with a height that is 10 µm thicker than that of the pre-firing laminated body. Additionally, rapid firing is defined as firing with a temperature rise rate of, for example, 1000 °C / hour or more. Furthermore, the ceramic cap used for a base and lid is preferably a flat ceramic cap to further control the curvature.For example, a ceramic top is used where one main surface is polished. Furthermore, the ceramic top can be a dense substrate or a porous substrate with holes. A material with a higher sintering temperature than the firing temperature of the laminated body is preferred, e.g., zirconium dioxide, aluminum oxide, or similar materials.

[0077] Furthermore, by changing the thickness of the outermost solid electrolyte layer 3B of the laminated body 20 on the sides of side surface 5A and side surface 5B, a difference in the burning shrinkage rate can be achieved between the outermost solid electrolyte layers of side surface 5A and side surface 5B, and the laminated body 20 with a desired curvature can be produced.

[0078] The sintered body can be placed in a cylindrical container along with a polishing agent such as aluminum oxide or similar, and then tumbling can be performed. The edges of the laminated body can be chamfered accordingly. Alternatively, the laminated body can be polished by sandblasting. (Shaping of the connections)

[0079] The first outer terminal 6 and the second outer terminal 7 are attached to the sintered laminated body 20 (the sintered body). The first outer terminal 6 and the second outer terminal 7 are configured to make electrical contact with the positive electrode layer 1 and the negative electrode layer 2, respectively. The first outer terminal 6 and the second outer terminal 7 can, for example, be formed on the positive electrode layer 1 and the negative electrode layer 2, facing away from the side surface of the sintered body, by known processes such as sputtering, dip coating, screen printing, spray coating, or similar methods.

[0080] If the connections are only formed in a predetermined area, they are formed, for example, after masking with tape.

[0081] While the embodiment of the present invention has been described in detail above with reference to the accompanying drawings, the components and combinations thereof in the embodiment are exemplary, and additions, omissions, substitutions and other modifications may be made without departing from the spirit of the present invention.

[0082] For example, in the Fig. 2 laminated bodies 20 shown, while the electrode layer of the second side surface is not exposed, at least one of the positive electrode layer 1 and the negative electrode layer 2 of the second side surface is exposed. EXAMPLES[Example 1](Production of the paste for the solid electrolyte layer)

[0083] Based on 100 parts of the Li 1.3 Al 0.3 Ti 1.7(PO4)3 powder was mixed with 100 parts ethanol and 200 parts toluene as solvents using a ball mill. Then, 16 parts of a binder and 4.8 parts benzyl butyl phthalate as a plasticizer were added and mixed to produce a paste for the outermost solid electrolyte layer.

[0084] The paste for a solid electrolyte layer was formed into a film using a PET film as the base material and a doctor blade process, resulting in the outermost solid electrolyte layer film and the solid electrolyte intermediate layer film. The thicknesses of the outermost solid electrolyte layer and the solid electrolyte intermediate layer were each set at 20 µm. (Production of the paste for the positive electrode active material layer and the paste for the negative electrode active material layer)

[0085] In the paste for a positive electrode active material layer and the paste for a negative electrode active material layer, after mixing Li3V2(PO4)3 in a predetermined weight ratio, 15 parts of a binder and 65 parts of dihydroterpionol as a solvent were added to 100 parts of the powder, and they were mixed and distributed to produce the paste for a positive electrode active material layer and the paste for a negative electrode active material layer. (Production of the paste for the positive electrode current collector layer and the paste for the negative electrode current collector layer)

[0086] In the paste for a positive electrode current collector layer and the paste for a negative electrode current collector layer, 100 parts Cu as current collector, 10 parts of a binder and 50 parts dihydroterpioneol as solvent were mixed and distributed to produce the paste for a positive electrode current collector layer and the paste for a negative electrode current collector layer. (Manufacturing the electrode unit)

[0087] The positive electrode unit and the negative electrode unit were manufactured as follows.

[0088] An active material paste was screen-printed to a thickness of 5 µm onto the solid electrolyte interlayer. The printed active material paste was then dried, and a current collector paste, also 5 µm thick, was screen-printed onto it. This current collector paste was then dried again, and another 5 µm thick active material paste was screen-printed onto it. The printed active material paste was dried, and then a PET film was separated. In this way, an electrode assembly film was obtained, in which the active material paste, the current collector paste, and the active material paste were successively printed and dried onto the solid electrolyte interlayer film. (Production of the laminated body)

[0089] The outermost solid electrolyte film was stacked, and 30 electrode units (15 positive and 15 negative) were alternately stacked on top of it over a solid electrolyte intermediate layer 3A. The units were shifted and stacked such that the current collector paste layers of the odd number of electrode units extended only to one end face, and the current collector paste layers of the even number of electrode units extended only to the other end face. The solid electrolyte film for an outermost solid electrolyte layer 3B was stacked onto the stacked unit. This was then formed by thermocompression bonding and subsequently cut to produce the laminated chip. The chip size was first side face (W) × second side face (L) × height (H) = 4.1 mm × 6.0 mm × 2.0 mm. Accordingly, W:L, the aspect ratio of the chip, was approximately 1:1.5.

[0090] Next, the laminated chips were placed on a ceramic base attachment, and a ceramic lid attachment was installed at a height where the average angle of a bulge A1, as seen from the side of a first face, and a bulge A2, as seen from the side of a second face, was 0.5°. The laminated chips were then fired simultaneously to obtain the laminated body 20. Furthermore, the laminated bodies were positioned at four corners of the ceramic base attachment to set a height 14 µm greater than the thickness of the laminated chip after firing, and the ceramic lid attachment was installed on top. During simultaneous firing, the firing temperature was increased to 840 °C under a nitrogen atmosphere at a rate of 1000 °C / hour, held at this temperature for two hours, and then naturally cooled after firing. (Evaluation of the degree of curvature)

[0091] The resulting laminated body (sintered body) was, as in Fig. Figure 3 shows the object being placed on a flat base, photographed in the x-direction, and a curvature angle A1 was determined by image processing. Similarly, as in Fig. Figure 4 shows that the photograph was taken in the y-direction, and a curvature angle A2 was captured by image processing. (Manufacturing and evaluation of the solid-state accumulator)

[0092] The first external connection and the second external connection were attached to the sintered laminated body (sintered body) by a known method to form the solid-state accumulator.

[0093] The first and second outer terminals were clamped between spring contacts so that they faced each other, and the initial discharge capacity of the solid-state battery and the capacity retention rate (cycle characteristic) after 1000 cycles were measured by performing a charge / discharge test. Under the measurement conditions, the charging and discharging currents were 0.2 C, and the final voltages during charging and discharging were 1.6 V and 0 V, respectively. The results are shown in Table 1. Furthermore, a capacity at the time of the first discharge was defined as the initial discharge capacity. Additionally, a capacity retention rate was obtained by dividing the discharge capacity at the 1000th cycle by the initial discharge capacity.

[0094] The results are shown in Table 1. [Table 1] Curvature angle (°) Cycle characteristics (%) Curvature as seen from the side of the first face (A1) Curvature as seen from the side of the second face (A2) Average Comparative example 1 0.0 0.0 0.0 81 Comparative example 2 0.2 0.2 0.2 82 Example 1 0.6 0.4 0.5 87 Example 2 1.2 0.8 1.0 92 Example 3 2.0 1.5 1.8 93 Example 4 2.2 1.9 2.1 92 Example 5 3.0 2.0 2.5 92 Example 6 3.5 3.0 3.3 91 Example 7 4.0 3.0 3.5 91 Example 8 4.5 3.5 4.0 90 Example 9 7.0 2.0 4.5 88 Example 10 8.0 2.0 5.0 86 Comparative example 3 7.0 6.0 6.5 73 Comparative example 4 9.0 1.0 5.0 72 Example 11 1.5 1.5 1.5 92 Example 12 2.0 2.0 2.0 93 Example 13 3.0 3.0 3.0 92 Comparative example 5 6.0 6.0 6.0 78 Example 14 1.2 0.8 1.0 93 Example 15 2.0 1.5 1.8 93 Example 16 2.5 2.0 2.3 92 Example 17 3.0 2.0 2.5 93 Example 18 3.3 2.7 3.0 92 [Example 2 to Example 8]

[0095] In Examples 2 through 8, solid-state accumulators were fabricated similarly to those in Example 1, except that laminated chips were placed on ceramic bases, and laminated bodies for height adjustment and ceramic lid attachments were installed at height positions where the average angles of curvature A1, when viewed from the side of the first face, and curvature A2, when viewed from the side of the second face, were 1.0°, 1.8°, 2.1°, 2.5°, 3.3°, 3.5°, and 4.0°, respectively. The curvature A1, when viewed from the side of the first face, and the curvature A2, when viewed from the side of the second face, are shown in Table 1. [Example 9 to Example 10]

[0096] In Examples 9 and 10, solid-state accumulators were fabricated similarly to those in Example 1, except that chips with aspect ratios W:L of 1:3.5 and 1:4.0 were used, laminated chips were placed on ceramic bases, and laminated bodies were installed for height adjustment, along with ceramic caps for lids, at height positions where the average angles of curvature A1, as viewed from the side of the first face, and curvature A2, as viewed from the side of the second face, were 4.5° and 5.0°, respectively. The curvature A1, as viewed from the side of the first face, and the curvature A2, as viewed from the side of the second face, are as shown in Table 1. [Example 11 to Example 13]

[0097] In Examples 11 to 13, solid-state accumulators were also fabricated similarly to those in Example 1, except that chips with a W:L aspect ratio of 1:1 were used, laminated chips were placed on ceramic bases, and laminated bodies were installed for height adjustment, along with ceramic caps for lids at height positions where the average angles of curvature A1, as viewed from the side of the first face, and curvature A2, as viewed from the side of the second face, were 1.5°, 2.0°, and 3.0°, respectively. The curvature A1, as viewed from the side of the first face, and the curvature A2, as viewed from the side of the second face, are as shown in Table 1. [Example 14 to Example 18]

[0098] In Examples 14 to 18, solid-state accumulators were also manufactured similarly to those in Example 1, except that chips with a chip size of first side surface (W) × second side surface (L) × height (H) = 3.0 mm × 4.4 mm × 1.1 mm (corresponding to chips with an aspect ratio W:L of 1:1.5) were used, laminated chips were placed on ceramic bases, and laminated bodies for adjusting heights and ceramic caps for lids were installed in height positions where average angles of a bulge A1, when viewed from the side of the first side surface, and of a bulge A2, when viewed from the side of the second side surface, were 1.0°, 1.8°, 2.3°, 2.5°, and 3.0°. The curvature A1, when viewed from the side of the first face, and the curvature A2, when viewed from the side of the second face, are as shown in Table 1. [Comparison example 1 to Comparison example 2]

[0099] In each of Comparison Example 1 through Comparison Example 2, solid-state accumulators were fabricated similarly to those in Example 1, except that laminated chips were placed on ceramic bases, and laminated bodies for height adjustment and ceramic lid attachments were installed at height positions where the average angles of a bulge A1, as seen from the side of the first face, and a bulge A2, as seen from the side of the second face, were 0° and 0.2°, respectively. The bulge A1, as seen from the side of the first face, and the bulge A2, as seen from the side of the second face, are shown in Table 1. [Comparison example 3 to Comparison example 4]

[0100] In Comparative Examples 3 and 4, solid-state accumulators were manufactured similarly to those in Example 1, except that chips with aspect ratios W:L of 1:1.2 and 1:9.0 were used, laminated chips were placed on ceramic bases, and laminated bodies were installed for height adjustment, along with ceramic caps for lids, at height positions where the average angles of curvature A1, as viewed from the side of the first face, and curvature A2, as viewed from the side of the second face, were 6.5° and 5.0°, respectively. The curvature A1, as viewed from the side of the first face, and the curvature A2, as viewed from the side of the second face, are listed in Table 1. [Comparative example 5]

[0101] In Comparative Example 5, a solid-state accumulator was fabricated similarly to that in Example 11, except that the same chips as in Examples 11 to 13 were used, laminated chips were placed on ceramic bases, and laminated bodies were installed for height adjustment and ceramic caps for lids were fitted at height positions where the average angle of a bulge A1, when viewed from the side of the first face, and a bulge A2, when viewed from the side of the second face, was 6.0°. The bulge A1, when viewed from the side of the first face, and the bulge A2, when viewed from the side of the second face, are as shown in Table 1.

[0102] Based on the results shown in Table 1, cycle characteristics of 86% or more were obtained in examples 1 to 18, where the average angles of the bulge A1, when viewed from the side of the first side face, and of the bulge A2, when viewed from the side of the second side face, were 0.5° or more and 5.0° or less, and the angle of the bulge A1, when viewed from the side of the first side face, was 8.0° or less.

[0103] On the other hand, if the average angles of the curvature A1, when viewed from the side of the first face, and of the curvature A2, when viewed from the side of the second face, were less than 0.5° (Comparison Examples 1 and 2), or if the average angles of the curvature A1, when viewed from the side of the first face, and of the curvature A2, when viewed from the side of the second face, were greater than 5.0° (Comparison Examples 3 and 5), the cycle characteristics were 82% or less.

[0104] Furthermore, even if the average angle is 5.0°, in comparison example 4, where an angle of the curvature A1, when viewed from the side of the first lateral surface, exceeds 8.0°, the cycle characteristics were 72%.

[0105] In Examples 1 to 8 and 11 to 18, where the average angles of curvature A1, when viewed from the side of the first face, and curvature A2, when viewed from the side of the second face, were 0.5° or more and 4.0° or less, respectively, cycle characteristics of 90% or more were obtained. Furthermore, in these examples, the angle A1 of curvature, when viewed from the side of the first face, was 4.5° or less.

[0106] It was found that while examples 1 to 6, 11 to 13 and 14 to 18 have different chip sizes and / or aspect ratios, the examples with essentially the same average curvature angle have essentially the same cycle characteristics. INDUSTRIAL APPLICABILITY

[0107] According to the present invention, it is possible to provide a solid-state accumulator with good cycle characteristics, wherein a curvature with a predetermined angle is provided. Reference symbol list 1 Positive electrode layer 1A Positive electrode current collector layer 1B Positive electrode active material layer 2 Negative electrode layer 2A Negative electrode current collector layer 2B Negative electrode active material layer 3 Solid electrolyte layer 6 First external connection 7 Second external connection 20 Laminated Body 100 solid-state accumulator QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2019048907

[0001] JP 20075279

[0006] JP 2007294429

[0006] JP 2013 / 175993

[0006]

Claims

[1] Solid-state accumulator comprising: a laminated body in which a positive electrode layer with a positive electrode current collector layer and a positive electrode active material layer and a negative electrode layer with a negative electrode current collector layer and a negative electrode active material layer are laminated over a solid electrolyte layer; a first external connection; and a second external connection wherein the laminated body has a first side surface parallel to a lamination direction and a second side surface parallel to the lamination direction and perpendicular to the first side surface, the first outer connection and the second outer connection are connected to the first side face, and the laminated body has a curvature that is curved in the lamination direction and satisfies equations (1) and (2): 0.5°≤((A1+A2) / 2)≤5° A1≤8.0° where A1 is an angle of curvature of the laminated body when viewed from one side of the first face, and A2 is an angle of curvature of the laminated body when viewed from one side of the second face. [2] Solid-state accumulator according to claim 1, wherein the following equation (3) is satisfied: 0.5°≤((A1+A2) / 2)≤4°