Solid electrolyte battery and transportation equipment

Abstract

Provided is a solid electrolyte battery that is suited for warm isotropic pressing and that can suppress the occurrence of internal shorting.　A solid electrolyte battery 10 includes: a charge / discharge body 14 including a positive electrode layer 15, a negative electrode layer 16, and a solid electrolyte layer 17 disposed between the positive electrode layer 15 and the negative electrode layer 16; an outer packing 11 that accommodates the charge / discharge body 14; and a collector having one end that is exposed to the outer packing 11 and another end that is electrically connected to the positive electrode layer 15 and the negative electrode layer 16. The outer packing 11 is formed from: a heat welding layer 20 that covers the charge / discharge body 14 from the outside and that includes an insulating first resin; a heat-resistant layer 21 that is layered so as to cover the heat welding layer 20 from the outside and that includes an insulating second resin having a higher melting point than the first resin; and a metal layer 22 that is layered so as to cover the heat-resistant layer 21 from the outside and that includes metal.

Description

[Technical field]

[0001] The present invention relates to a secondary battery used in various industrial equipment, and more particularly to a solid electrolyte battery, a manufacturing method for a solid electrolyte battery, and transportation equipment. [Background technology]

[0002] Electrolyte batteries, which include positive and negative electrodes capable of absorbing and releasing lithium ions, are widely used as high-energy density batteries in various fields such as electric vehicles, power storage devices, and information devices.

[0003] On the other hand, the larger the discharge capacity per unit weight or unit volume, the more of an issue safety becomes, and batteries with even better safety are required, and recently solid electrolyte batteries have been developed. Solid electrolyte batteries are batteries that use solid electrolytes instead of the organic electrolyte used up until now. Since solid electrolyte batteries do not use organic electrolytes, they are less likely to catch fire even if the discharge capacity per unit weight or unit volume becomes large, making them highly safe batteries.

[0004] In such solid electrolyte batteries, it is known that pressure is applied by plate pressing or roll pressing to improve the adhesion between the electrode active material layer (hereinafter referred to as the positive electrode layer and the negative electrode layer) and the solid electrolyte layer. However, the surfaces of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer have fine protrusions and depressions (so-called cavities), and it is difficult to apply uniform pressure to the surfaces by plate pressing or roll pressing. For this reason, there is a problem that the adhesion between the positive electrode layer and the negative electrode layer and the solid electrolyte layer cannot be sufficiently improved.

[0005] In order to address such issues, for example, International Publication No. 2012 / 164723 (Patent Document 1) discloses isostatic pressing in which an outer casing encapsulating a charge / discharge unit having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer formed between the positive electrode layer and the negative electrode layer is pressed from an equal direction (a direction surrounding the entire charge / discharge unit) using liquid pressure or gas pressure.

[0006] Here, the isostatic pressing in Patent Document 1 is a warm isostatic press (WIP) in which isostatic pressing is performed in a warm state, and the maximum temperature condition is 120° C. when gas is used. In this way, by pressing the exterior body containing the charge / discharge body by warm isostatic pressing, it is possible to obtain a solid electrolyte battery that improves the adhesion between the positive electrode layer and the negative electrode layer and the solid electrolyte layer and reduces the resistance between each layer. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2012 / 164723 Summary of the Invention [Problem to be solved by the invention]

[0008] Incidentally, a laminate sheet may be used for the exterior body enclosing the above-mentioned charge / discharge unit, and this laminate sheet is composed of, for example, a heat-sealed layer that covers the charge / discharge unit from the outside, a metal layer that covers the heat-sealed layer from the outside, and, if necessary, a protective layer that covers the metal layer from the outside. The heat-sealed layer is made of polypropylene, polyethylene, etc., and the metal layer is made of aluminum, etc. Also, the protective layer is made of a required synthetic resin selected from various synthetic resins.

[0009] When a charge / discharge body covered with such an outer casing is pressed using a warm isostatic press, the charge / discharge body is compressed from an equal direction by hydraulic pressure, which sufficiently increases the adhesion between the positive and negative electrode layers and the solid electrolyte layer and reduces the resistance between each layer.

[0010] However, when the heat-sealed layer is pressed at a high temperature by warm isostatic pressing, the heat-sealed layer is excessively softened or melted, and the laminate sheet is pressed in this state, causing defects in the heat-sealed layer. This tendency is particularly strong in the shape-changing portions of the charge / discharge body.

[0011] For this reason, in the missing area of ​​the thermally welded layer, there is a risk of electrical contact between the metal layer that constitutes the laminate sheet and the metal collector foil, collector tab, etc. that are electrically connected to the positive electrode layer or the negative electrode layer, resulting in an internal short circuit.

[0012] Therefore, there is a demand for a solid electrolyte battery having a structure suitable for warm isostatic pressing. There is also a demand for a method for manufacturing a solid electrolyte battery that can sufficiently increase the adhesion between the positive electrode layer and the negative electrode layer and the solid electrolyte layer while suppressing the occurrence of internal short circuits, and can reduce the resistance between each layer.

[0013] A first object of the present invention is to provide a solid electrolyte battery suitable for warm isostatic pressing, which can suppress the occurrence of internal short circuits.

[0014] A second object of the present invention is to provide a method for manufacturing a solid electrolyte battery capable of sufficiently increasing the adhesion between the positive electrode layer and the negative electrode layer and the solid electrolyte layer, thereby reducing the resistance between each layer. [Means for solving the problem]

[0015] The first feature of the present invention is A solid electrolyte battery including a charge / discharge body having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, an exterior body that houses the charge / discharge body, and a current collector having one end exposed to the outside of the exterior body and the other end electrically connected to the positive electrode layer or the negative electrode layer, wherein the exterior body is The charging / discharging body is formed from a heat-sealed layer which covers the charging / discharging body from the outside and contains a first resin with insulating properties, a heat-resistant layer which is laminated on the outside of the heat-sealed layer and contains a second resin which has a higher melting point than the first resin and has insulating properties, and a metal layer which is laminated on the outside of the heat-resistant layer and contains a metal, and the charging / discharging body is sealed by the outer casing when the heat-sealed layer is welded around the charging / discharging body.

[0016] The second feature of the present invention is A method for manufacturing a solid electrolyte battery having a charge / discharge body including a positive electrode layer, a negative electrode layer, a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, a positive electrode current collector foil electrically connected to the positive electrode layer, and a negative electrode current collector foil electrically connected to the negative electrode layer, comprising: The step of bonding the positive electrode layer and the negative electrode layer to the solid electrolyte layer is a pressurizing step by warm isostatic pressing in which the charge / discharge body is immersed in a liquid in a pressure-resistant container and the liquid is pressurized to bond the positive electrode layer, the negative electrode layer, and the solid electrolyte layer to each other, and the pressurizing step is performed under conditions in which the temperature of the liquid is 140°C or higher and 250°C or lower. Effect of the Invention

[0017] According to the present invention, it is possible to obtain a solid electrolyte battery suitable for warm isostatic pressing, which can suppress the occurrence of internal short circuits.

[0018] Furthermore, according to the present invention, it is possible to obtain a method for manufacturing a solid electrolyte battery in which the adhesion between the positive electrode layer and the negative electrode layer and the solid electrolyte layer is sufficiently increased to reduce the resistance between the layers. [Brief description of the drawings]

[0019] [Figure 1] 1 is an external view of a solid electrolyte battery according to an embodiment of the present invention; [Diagram 2] FIG. [Diagram 3] 2 is a cross-sectional view taken along the line AA of the solid electrolyte battery shown in FIG. 1. [Figure 4] FIG. 2 is a cross-sectional view of the solid electrolyte battery shown in FIG. 1 . [Diagram 5] FIG. 2 is an exploded cross-sectional view of a solid electrolyte battery according to an embodiment of the present invention. [Figure 6] FIG. 4 is a cross-sectional view corresponding to FIG. 3 and showing a modified example of the embodiment of the present invention. [Figure 7] 6 is a cross-sectional view of the solid electrolyte battery shown in FIG. 5 after being pressed by warm isostatic pressing. [Figure 8] 8 is a cross-sectional view of a modified example of the solid electrolyte battery shown in FIG. 7. [Figure 9] 3A to 3C are process diagrams illustrating a method for manufacturing a solid electrolyte battery according to an embodiment of the present invention. [Figure 10] FIG. 10 is an explanatory diagram of the relationship between temperature and internal resistance of a solid electrolyte battery produced by the manufacturing method shown in FIG. [Figure 11] FIG. 10 is a graph showing the relationship between pressure and internal resistance of a solid electrolyte battery produced by the manufacturing method shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiment, and various modifications and application examples within the technical concept of the present invention are also included within its scope.

[0021] 1 is an external view of a solid electrolyte battery 10 according to an embodiment of the present invention, in which a charge / discharge unit described below is sealed and housed between two exterior bodies 11 made of, for example, laminate sheets. The exterior shape of the exterior body 11 is formed into a rectangular shape, and a positive electrode current collector tab 12 and a negative electrode current collector tab 13 are exposed from opposing sides or the same side. This solid electrolyte battery 10 is a unit cell, and a plurality of solid electrolyte batteries 10 are combined to form a secondary battery.

[0022] This secondary battery can be used in transportation equipment such as electric vehicles and hybrid vehicles, and the secondary battery drives an electric motor to rotate the wheels of the electric vehicle or hybrid vehicle to run. Hereinafter, the solid electrolyte battery 10 will be described as a charge / discharge unit.

[0023] Next, the configuration of the charge / discharge body will be described with reference to Fig. 2. The charge / discharge body 14 mainly comprises a positive electrode layer 15, a negative electrode layer 16, and a solid electrolyte layer 17 sandwiched between the positive electrode layer 15 and the negative electrode layer 16. A positive electrode current collector foil 18 is provided on the surface of the positive electrode layer 15 opposite the solid electrolyte layer 17, and a negative electrode current collector foil 19 is similarly provided on the surface of the negative electrode layer 16 opposite the solid electrolyte layer 17.

[0024] The positive electrode layer 15 is a layer containing a positive electrode active material, and may contain at least one of a solid electrolyte material, a conductive material, and a binder, as necessary. The positive electrode active material is not particularly limited, but an oxide active material or a sulfide active material can be used. As the oxide active material, for example, a rock salt layer type active material, a spinel type active material, an olivine type active material, etc. can be used. As the sulfide active material, for example, lithium sulfide, copper chevrel, iron sulfide, cobalt sulfide, nickel sulfide, etc. can be used.

[0025] The negative electrode layer 16 is a layer containing a negative electrode active material, and may further contain at least one of a solid electrolyte material, a conductive material, and a binder, as necessary. The negative electrode active material is not particularly limited, but may be, for example, a carbon active material, a metal active material, or an oxide active material.

[0026] The solid electrolyte layer 17 is a layer containing a solid electrolyte material. For example, a sulfide solid electrolyte material and an oxide solid electrolyte material can be used as the solid electrolyte material. The sulfide solid electrolyte material is preferred in that it has higher ion conductivity than the oxide solid electrolyte material, and the oxide solid electrolyte material is preferred in that it has higher chemical stability than the sulfide solid electrolyte material.

[0027] The thickness of the solid electrolyte layer 17 is about 15 μm to 100 μm, and in consideration of the energy density of the battery, the thickness is preferably 15 μm to 30 μm In this embodiment, the thickness of the solid electrolyte layer 17 is set to 30 μm.

[0028] The central region of the solid electrolyte layer 17 is the active area of ​​the battery, and therefore the lithium ion conductivity at 25° C. is, for example, 1×10 -7 S / cm or more, preferably 1×10 -3 S / cm or more.

[0029] Next, the configuration of the charge / discharge unit 10 (having the same configuration as the solid electrolyte battery shown in FIG. 1) will be described with reference to FIG. 3 and FIG. 4. Note that FIG. 3 shows a cross section taken along line AA in FIG. 1, and FIG. 4 shows a cross section taken along line BB in FIG. 1.

[0030] 3 and 4, the charge / discharge unit 10 is formed by electrically connecting a positive electrode current collector tab 12 and a negative electrode current collector tab 13 to a charge / discharge body 14, and covering them with an upper exterior body 11A and a lower exterior body 11B. The positive electrode current collector tab 12 exposed from the exterior body 11 is electrically connected to a positive electrode current collector foil 18. In addition, the negative electrode current collector tab 13 exposed from the exterior body 11 is electrically connected to a negative electrode current collector foil 19. The positive electrode current collector foil 18 and the positive electrode current collector tab 12 form a "positive electrode current collector," and the negative electrode current collector foil 19 and the negative electrode current collector tab 13 form a "negative electrode current collector."

[0031] The charging / discharging body 14, a part of the positive electrode current collecting tab 12 facing the charging / discharging body 14, and a part of the negative electrode current collecting tab 13 facing the charging / discharging body 14 are covered from the outside by exterior bodies 11A and 11B. In other words, the charging / discharging body 14 is sealed in the bag-shaped exterior bodies 11A and 11B. Note that Figures 3 and 4 show a state before pressure treatment by warm isostatic pressing is performed.

[0032] As described above, the outer casing 11 is composed of an upper outer casing 11A and a lower outer casing 11B, and the charge / discharge body 14, a portion of the positive electrode current collecting tab 12 facing the charge / discharge body 14, and a portion of the negative electrode current collecting tab 13 facing the charge / discharge body 14 are sandwiched between the upper outer casing 11A and the lower outer casing 11B and bonded around the outer periphery.

[0033] The charge / discharge unit in this state is then subjected to a pressure treatment using a warm isostatic press, but as described in the "Problems to be Solved by the Invention" section, when pressure is applied at high temperatures using a warm isostatic press, the heat-sealed layer is excessively softened or melted, and the exterior body is pressurized in this state, causing defects in the heat-sealed layer. As a result, there is a risk that the metal layer constituting the exterior body and the metal current collector foil or current collector tab electrically connected to the positive electrode layer or negative electrode layer may come into electrical contact in the defective area of ​​the heat-sealed layer, causing an internal short circuit.

[0034] In order to address such issues, the present embodiment proposes the following. Fig. 5 shows a cross section of the charge / discharge unit according to this embodiment, in which the upper exterior body 11A and the lower exterior body 11B have at least a three-layer structure. The configuration of the charge / discharge unit 14 is the same as that shown in Fig. 3.

[0035] 5, the upper exterior body 11A and the lower exterior body 11B are formed from a three-layer laminate sheet consisting of a thermally welded layer 20 made of an electrically insulating synthetic resin (a first resin in the claims), a heat-resistant layer 21 made of an electrically insulating synthetic resin (a second resin in the claims), and a metal layer 22 made of a thin metal film, from the outward direction as viewed from the charge / discharge body 14. The thermally welded layer 20 is made of a resin such as polyethylene or polypropylene, and the metal layer 22 is made of aluminum.

[0036] The upper exterior body 11A is adhered to the positive electrode current collector tab 12 by adhesive resin 23, and the lower exterior body 11B is adhered to the negative electrode current collector tab 13 by adhesive resin 23, and each is positioned accordingly. In this state, the upper exterior body 11A and the lower exterior body 11B are not welded to the charge / discharge body 14, and by carrying out warm isostatic pressing, which will be described later, the heat-welded layers 20 on the insides of the upper exterior body 11A and the lower exterior body 11B are adhered to each other, sandwiching the charge / discharge body 14 therebetween.

[0037] Here, the thermal welding layer 20 is provided for the purpose of heat welding the exterior bodies 11A and 11B to the charge / discharge body 14. The metal layer 22 is provided for the purpose of ensuring a barrier performance for preventing the intrusion of moisture from the outside. The present embodiment is characterized in that a heat-resistant layer 21 is provided between the thermal welding layer 20 and the metal layer 22.

[0038] As described above, when the charge / discharge unit 10 is warm isostatically pressed, if the heat-resistant layer 21 is not present, the thermally welded layer 20 of the exterior body 11 may melt and expose the metal layer 22 of the exterior body 11. The exposed metal layer 22 may come into contact with, for example, the positive electrode current collector or the negative electrode current collector, which may cause a short circuit in the charge / discharge unit 10.

[0039] For this reason, in this embodiment, in order to prevent the occurrence of an internal short circuit due to exposure of the metal layer 22 of the exterior body 11, a heat-resistant layer 21 is provided between the metal layer 22 and the thermal welding layer 20. This heat-resistant layer 21 has superior heat resistance to the thermal welding layer 20, and is made of a material that does not melt and maintains its form as a "layer" even when the temperature reaches the temperature at which the thermal welding layer 20 melts.

[0040] Generally, the exterior body 11 has a protective layer on the outermost layer (the layer outside the metal layer), but since this is not a fundamentally essential component, the present embodiment has a three-layer structure. Of course, it goes without saying that a protective layer may also be provided.

[0041] Here, it is important to select an insulating material for the heat-resistant layer 21 that has higher heat resistance (higher melting point) than the thermal welding layer 20. For example, it is preferable to select from heat-resistant resins such as "engineering plastics" and "super engineering plastics."

[0042] For example, nylon, polyamide, polyethylene terephthalate, etc. can be used as "engineering plastics", and polyimide, polyetherimide, etc. can be used as "super engineering plastics".

[0043] Using such an exterior body 11, the charge / discharge unit 10 is assembled by sandwiching the charge / discharge body 14 from above and below, as shown in Fig. 5. In this state, the thermally welded layer 20 of the exterior body 11 is not welded because no heat has been applied. Naturally, when viewed in the stacking direction of the positive electrode current collector foil 18, the positive electrode layer 15, the solid electrolyte layer 17, the negative electrode layer 16, and the negative electrode current collector foil 19, the upper exterior body 11A and the lower exterior body 11B are arranged so as to cover a first main surface (SF) of the positive electrode current collector foil 18 and a second main surface (SS) of the negative electrode current collector foil 19, which are planes perpendicular to the stacking direction of the positive electrode current collector foil 18, the positive electrode layer 15, the solid electrolyte layer 17, the negative electrode layer 16, and the negative electrode current collector foil 19.

[0044] The charge / discharge unit 10, which is composed of the charge / discharge body 14 and the exterior body 11 that covers it, is subjected to pressure application by warm isostatic pressing. Here, the charge / discharge body 14 shown in Fig. 5 is a combination of a positive electrode layer 15, a negative electrode layer 16, and a solid electrolyte layer 17, but in order to increase the generated power, it is also possible to have a plurality of combinations of the positive electrode layer 15, the negative electrode layer 16, and the solid electrolyte layer 17.

[0045] For example, as shown in Fig. 6, a pair of positive electrode layers 15 are placed in the center, and a pair of solid electrolyte layers 17 and a pair of negative electrode layers 16 are arranged in this order toward the outside. A positive electrode current collector foil 18 is sandwiched between each of the positive electrode layers 15, and a negative electrode current collector foil 19 is provided on the outside of each of the negative electrode layers. Each current collector foil 19 is electrically connected by a negative electrode current collector tab 13. In this case, more uniform pressure is required, so pressure application by warm isostatic pressing is an effective method. It goes without saying that the positive electrode layers 15 and the negative electrode layers 16 may be interchanged.

[0046] Fig. 7 shows a cross section of the charge / discharge unit 10 that has been pressurized by warm isostatic pressing. As shown in Fig. 7, by warm isostatic pressing, the thermally welded layers 20 of the upper exterior body 11A and the lower exterior body 11B are welded to the charge / discharge body 14, and further, the thermally welded layers 20 of the parts other than the charge / discharge body 14 are welded to each other. In this way, the exterior body 11 seals the charge / discharge body 14, the positive electrode current collector foils 18, 12, and the negative electrode current collector foils 19, 13 with the thermally welded layers 20.

[0047] In this manner, in this embodiment, the exterior body 11 is configured to be disposed in close contact with the peripheral surface of the charge / discharge unit 10 from the entire periphery of the charge / discharge unit 10. Therefore, the charge / discharge unit 10 has the following configuration.

[0048] The charge / discharge unit 10 includes a charge / discharge body 14 having a positive electrode layer 15, a negative electrode layer 16, and a solid electrolyte layer 17 arranged between the positive electrode layer 15 and the negative electrode layer 16, an exterior body 11 that houses the charge / discharge body 14, and current collecting foils 18, 19 having one end exposed to the outside of the exterior body and the other end electrically connected to the positive electrode layer 15 or the negative electrode layer 16, wherein the exterior body 11 is formed from a thermally welded layer 20 that covers the charge / discharge body 14 from the outside and contains a first resin having insulating properties, a heat-resistant layer 21 that is laminated so as to cover the thermally welded layer 20 from the outside and contains a second resin having a higher melting point than the first resin and having insulating properties, and a metal layer 22 that is laminated so as to cover the heat-resistant layer 21 from the outside and contains a metal, and the charge / discharge body is sealed by the exterior body by the thermally welded layer being welded around the charge / discharge body.

[0049] In this embodiment, since the heat-resistant layer 21 is provided on the outside of the heat-sealed layer 20, even if the heat-sealed layer 20 melts and a defect occurs due to warm isostatic pressing, the heat-resistant layer 21 is formed as a "layer." Therefore, the metal layer 22 does not reach the defect area of ​​the heat-sealed layer 20 due to the heat-resistant layer 21, and the metal layer 22 constituting the exterior body does not electrically contact the metallic current collecting foils 18, 19 and current collecting tabs 12, 13 electrically connected to the positive electrode layer 15 or the negative electrode layer 16, and the like, so that the risk of an internal short circuit occurring is suppressed.

[0050] In addition, because pressure is applied from all directions, the exterior body 11 adheres closely to the shape of the charging / discharging body 14 on both the main surfaces (SF, SS) and the side surfaces (SL) perpendicular thereto. This allows the entire outer surface of the charging / discharging body 14 to be sealed with the heat-sealed layer 20, thereby improving the impact resistance of the discharge unit 10 during use and providing significant effects such as preventing the current collecting tabs 12, 13 and the solid electrolyte layer 17 from falling off. Note that, since general welding and sealing involves heat-sealing only the four outer periphery sides of the exterior body 11 (welding between exterior bodies, and welding between the exterior body and the current collector), such effects and advantages cannot be expected from this embodiment.

[0051] Next, a modified example of this embodiment will be described. In the above-mentioned embodiment, the exterior body 11 is in close contact with the side surface (SL) of the charge / discharge body 14, and when the exterior body 11 changes direction from the main surface (SF, SS) to the side surface (SL), it changes at an angle close to a right angle. For this reason, it is expected that the displacement of the charge / discharge body 14 due to vibration will cause stress concentration at the portions where the ends of the positive electrode layer 15 and the negative electrode layer 16 bend at right angles, resulting in a decrease in electrode performance, and that damage to the exterior body 11 will allow moisture and dust to enter from the outside, resulting in deterioration of the charge / discharge body 14.

[0052] For this reason, in the modification shown in FIG. 7, when exterior body 11 changes direction from main surfaces (SF, SS) to side surfaces (SL), it changes direction toward side surfaces (SL) at an angle greater than a right angle.

[0053] 8, the bending angle of upper exterior body 11A, which changes direction from the main surface (SF) to the side surface (SL) of positive electrode current collector foil 18 constituting charge / discharge body 14, is formed as an obtuse angle portion (OA) larger than a right angle. Similarly, the bending angle of lower exterior body 11B, which changes direction from the main surface (SF) to the side surface (SL) of negative electrode current collector foil 19 constituting charge / discharge body 14, is formed as an obtuse angle portion (OA) larger than a right angle. As a result, a space (SP) is formed between inclined regions RS of exterior bodies 11A and 11B and the side surface (SL) of charge / discharge body 14.

[0054] Therefore, when the exterior body 11 changes direction from the main surfaces (SF, SS) to the side surfaces (SL), the corners that bend at right angles at the ends of the positive electrode current collector foil 18 and the positive electrode layer 15, and the negative electrode current collector foil 19 and the negative electrode layer 16 are prevented from coming into contact with the exterior body 11 located at the obtuse angle portion (OA). This reduces stress concentration at the corners, making it possible to avoid problems such as a decrease in electrode performance due to stress generation and deterioration of the charge / discharge body 14 due to moisture and dust entering from the outside due to damage to the exterior body 11.

[0055] However, if a space is formed between the side surface (SL) of the charging / discharging unit 14 and the exterior body 11 corresponding to the side surface (SL), the above-mentioned problem can be solved. For this reason, the angle of the upper exterior body 11A, which changes direction from the main surface (SF) of the positive electrode current collector foil 18 constituting the charging / discharging unit 14 to the side surface (SL), does not need to be formed as an obtuse angle portion (OA), but may be changed direction at a substantially right angle so as to form a space at a distance from the side surface (SL). The same applies to the lower exterior body 11B. Note that there are various methods for forming the space (S), but as a simple method, the space can be formed by applying pressure while preventing the air inside from escaping.

[0056] In the above description, the space is formed by air, but the space can be formed by using insulating liquid or resin other than air.

[0057] Next, a method for manufacturing the charge / discharge unit 10 by warm isostatic pressing according to an embodiment of the present invention will be described with reference to FIG.

[0058] 9A shows the assembly process of the charge / discharge unit 10. In this assembly process, the positive electrode layer 15, the negative electrode layer 16, and the solid electrolyte layer 17 are laminated, and the positive electrode current collector foil 18 and the negative electrode current collector foil 19 are provided. Then, the positive electrode current collector tab 12 and the negative electrode current collector tab 13 are provided to assemble the charge / discharge body 14, and the exterior body 11 is placed on the charge / discharge body 14 to assemble the charge / discharge unit 10. The positive electrode current collector foil 18 and the negative electrode current collector foil 19 can be exposed to the outside of the exterior body 11, and the positive electrode current collector tab 12 and the negative electrode current collector tab 13 can be attached to the exposed portions later. When this assembly process is completed, the next pressurizing process is carried out.

[0059] (B) of Fig. 9 shows a pressurizing process using warm isostatic pressing. As the isostatic pressing, for example, pressurization using a liquid or pressurization using a gas can be performed. When a liquid is used as the pressure medium, water, ethylene glycol, silicon oil, etc. can be used. When a gas is used as the pressure medium, argon gas, etc. can be used.

[0060] Isostatic pressing has the advantage that even if the applied pressure is set higher due to the characteristics of the pressing mechanism, cracks are less likely to occur in the electrode layers 15 and 16 and the solid electrolyte layer 17. In this embodiment, a pressing machine using a liquid as a pressure medium is used.

[0061] In the warm isostatic press, a pressure-resistant container PC is filled with liquid LQ, the charge / discharge unit 10 is immersed therein, and then the plunger PL is pressed down by a pressure source, so that the liquid LQ pressurizes the charge / discharge unit 10 from all directions. This causes the exterior body 11 to deform and adhere to the shape of the charge / discharge unit 10. Note that since the temperature of the liquid LQ is high, the exterior body 11 and the charge / discharge unit 10 are welded together by the thermal welding layer 20 of the exterior body 11.

[0062] In this embodiment, the temperature of the liquid LQ is controlled to improve the adhesion between the positive electrode layer 15, the negative electrode layer 16, and the solid electrolyte layer 17. In order to improve the adhesion, it is generally sufficient to increase the applied pressure, but since the positive electrode layer 15, the negative electrode layer 16, and the solid electrolyte layer 17 are fragile, the applied pressure cannot be increased unnecessarily.

[0063] Therefore, in this embodiment, based on the new finding that increasing the temperature of the liquid LQ can increase the adhesion between the positive electrode layer 15, the negative electrode layer 16, and the solid electrolyte layer 17, this embodiment is characterized in that the temperature of the liquid LQ is set to 140° C. or higher.

[0064] When the temperature of the liquid LQ is set to 140°C or higher, it is most preferable to use silicone oil in terms of boiling point. More specifically, the temperature of the silicone oil is preferably 140°C to 250°C. The higher the temperature, the stronger the adhesion between the electrode layers 15, 16 and the solid electrolyte layer 17, and a solid electrolyte battery with low resistance can be obtained. For this reason, in consideration of productivity, the range of 140°C to 200°C is preferable.

[0065] High temperatures may have the following effects in some cases: For example, if the temperature exceeds 250°C, the active material, solid electrolyte, binder, and other constituent materials may be denatured, resulting in a significant decrease in properties, and if the temperature exceeds 200°C, the solid electrolyte, binder, and other constituent materials may be denatured, resulting in a decrease in properties.

[0066] Therefore, preferably, if the temperature is controlled at 200° C. or less, the denaturation of the active material, solid electrolyte, binder and other constituent materials can be minimized, and the characteristics of the solid electrolyte battery can be improved.

[0067] It is not desirable to increase the pressure applied by the warm isostatic press excessively, and it is preferable that the pressure be within the range of 100 MPa to 1000 MPa. The higher the pressure, the higher the adhesion between the electrode layers 15, 16 and the solid electrolyte layer 17, and a battery with low resistance can be obtained. However, if the pressure is too high, problems such as damage to the electrode layers 15, 16 and the solid electrolyte layer 17 and internal short circuits occur.

[0068] In this embodiment, a pressure in the range of 100 MPa to 1000 MPa is proposed, but for example, 100 MPa or more is preferable, and 300 MPa or more is more preferable. If the pressure is too low, there is a risk that the adhesion between the electrode layers 15 and 16 and the solid electrolyte layer 17 cannot be sufficiently improved.

[0069] On the other hand, the pressurizing pressure is preferably, for example, 1000 MPa or less. If the pressure is higher than 1000 MPa, in some cases, problems such as damage to the electrode layers 15 and 16 and the solid electrolyte layer 17 and internal short circuits may occur. In addition, there is a risk of high equipment costs such as changing the pressurizing source and the pressure-resistant container.

[0070] The time for which the set pressure is maintained varies depending on the type of isostatic press (liquid, gas), but in this embodiment, for example, it is preferably within a range of 10 seconds to 10 minutes, and more preferably within a range of 1 minute to 5 minutes. If pressure is applied to the charge / discharge unit 10 for a long period of time at a high temperature of 140°C, the exterior body 11 may be damaged.

[0071] Generally, plate pressing and roll pressing are known as methods for pressurizing and bonding the charge / discharge body 14, which is a laminate of the positive electrode layer 15, the solid electrolyte layer 17, and the negative electrode layer 16. Since plate pressing and roll pressing are not isostatic pressing, pressing the charge / discharge body 14 with high pressure may damage, for example, the solid electrolyte layer 17, increasing the possibility of a short circuit.

[0072] In contrast, in the present embodiment, the charge / discharge unit 10 including the exterior body 11 is pressurized by warm isostatic pressing, so that the possibility of a short circuit occurring can be suppressed even if the charge / discharge body 14 is pressurized at high pressure. This makes it possible to manufacture low-resistance solid electrolyte batteries with good yield, providing a new effect of excellent productivity.

[0073] Furthermore, a charge / discharge unit in which current collectors 12, 13, 18, and 19 of charge / discharge body 14 are arranged is formed by warm isostatic pressing, and this is pressed in a sealed state inside outer casing 11, so that it can be made into a product as is, which has the effect of providing excellent productivity.

[0074] Before performing the warm isostatic pressing, the positive electrode layer 15, the negative electrode layer 16, and the solid electrolyte layer 17 may be preliminarily pressed in advance by a roll press, a plate press, or the like, so that the warm isostatic pressing can be performed in a state in which the packing ratio of these layers is increased. In this case, it is important that the preliminarily pressing pressure is lower than the pressing pressure in the warm isostatic pressing.

[0075] In addition, when performing warm isostatic pressing using gas, the charge / discharge body is housed in a pressure-resistant container, and pressurized gas is supplied to the pressure-resistant container to bond the positive electrode layer, the negative electrode layer, and the solid electrolyte layer together. The temperature range of the gas is as described above.

[0076] 9(c), when the warm isostatic pressing process is completed, the charge / discharge unit 10 is removed from the pressure-resistant container PC and subjected to a drying and inspection process. At this time, the shape of the exterior body 11 is changed so as to fit closely to the shape of the charge / discharge unit 10.

[0077] Incidentally, in this embodiment, the pressure medium for the warm isostatic press is liquid LQ, which is set at a temperature of 140° C. or higher. If the temperature is set at this level, it is expected that the thermally welded layer 20 may melt.

[0078] However, as explained in Figures 7 and 8, a heat-resistant layer 21 having a higher melting point than the heat-sealed layer 20 is interposed between the heat-sealed layer 20 and the metal layer 22. Therefore, even if the heat-sealed layer 20 is damaged, the heat-resistant layer 21 can prevent the metal layer 22 from coming into contact with the positive electrode current collector foil 18 or the negative electrode current collector foil 19, which could cause a short circuit in the charge / discharge unit 10.

[0079] In other words, by using the charge / discharge unit 10 shown in FIG. 5, it becomes possible to set the temperature of the liquid LQ, which is the pressure medium for the warm isostatic press, to a temperature of 140° C. or higher.

[0080] 10 shows data obtained by measuring the internal resistance of the charge / discharge unit 10, which has been subjected to a warm isostatic press pressing process, sandwiched between metal plates. This data was obtained by CCCV (constant current constant voltage) charging up to 4.35 V at a current value of 0.1 C, followed by CCCV discharging up to 3.0 V three times, charging up to 3.7 V to adjust the voltage, and then performing impedance analysis with an impedance analyzer to determine the internal resistance.

[0081] As can be seen from this data, the pressurization pressure was fixed at 980 MPa, and the pressurized liquid temperature was varied. As a result, it was confirmed that the higher the temperature, the lower the internal resistance of the solid electrolyte battery. In particular, when heated to 140°C or higher, the adhesion between the positive electrode layer 15, the negative electrode layer 16, and the solid electrolyte layer 17 can be improved, and the internal resistance of the solid electrolyte battery can be sufficiently reduced. A low internal resistance of a solid electrolyte battery means that secondary batteries used in electric vehicles and the like can be charged in a short time.

[0082] 11 shows data obtained by measuring the internal resistance of the charge / discharge unit 10 that has been subjected to a pressing process using a warm isostatic press and sandwiched between metal plates. As described above, this data was obtained by CCCV (constant current constant voltage) charging up to 4.35 V at a current value of 0.1 C, and then repeating CCCV charging and discharging up to 3.0 V three times, charging to 3.7 V to adjust the voltage, and performing impedance analysis with an impedance analyzer to determine the internal resistance.

[0083] As can be seen from this data, the temperature was fixed at 150°C and 190°C, and the applied pressure was varied, and it was confirmed that the higher the applied pressure, the lower the internal resistance of the solid electrolyte battery. In particular, if the applied pressure is 1500 MPa or more and 1000 MPa or less, the adhesion between the positive electrode layer 15, the negative electrode layer 16, and the solid electrolyte layer 17 can be improved, and the internal resistance of the solid electrolyte battery can be sufficiently reduced. As described above, a low internal resistance of a solid electrolyte battery means that a secondary battery used in an electric vehicle or the like can be charged in a short time.

[0084] The characteristic configurations of the above-described embodiment will be listed below, which will clarify the features of the present invention.

[0085] (1) The solid electrolyte battery of the present invention is a solid electrolyte battery having a charge / discharge body having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer arranged between the positive electrode layer and the negative electrode layer, an exterior body that houses the charge / discharge body, and a current collector having one end exposed to the outside of the exterior body and the other end electrically connected to the positive electrode layer or the negative electrode layer, characterized in that the exterior body is formed from a heat-sealed layer that covers the charge / discharge body from the outside and contains a first resin with insulating properties, a heat-resistant layer that is laminated on the outside of the heat-sealed layer and contains a second resin with a higher melting point than the first resin and with insulating properties, and a metal layer that is laminated on the outside of the heat-resistant layer and contains a metal, and the charge / discharge body is sealed by the exterior body by welding the heat-sealed layer around the charge / discharge body.

[0086] (2) The solid electrolyte battery of the present invention is characterized in that a space is formed between the side of the positive electrode layer and the exterior body, where the side of the positive electrode layer does not come into contact with the exterior body, and between the side of the positive electrode layer and the exterior body, where the side of the positive electrode layer changes direction from the main surface of the negative electrode current collector foil provided on the side opposite the solid electrolyte layer of the positive electrode layer to the side of the positive electrode layer, and a space is formed between the side of the negative electrode layer and the exterior body, where the side of the negative electrode layer does not come into contact with the exterior body, and

[0087] (3) The solid electrolyte battery of the present invention is characterized in that an exterior body that changes direction from a main surface of a positive electrode current collector foil provided on the side opposite the solid electrolyte layer of the positive electrode layer toward a side surface of the positive electrode layer is welded along the side surface of the positive electrode layer, and an exterior body that changes direction from a main surface of a negative electrode current collector foil provided on the side opposite the solid electrolyte layer of the negative electrode layer toward the side surface of the negative electrode layer is welded along the side surface of the negative electrode layer.

[0088] (4) The solid electrolyte battery of the present invention is characterized in that the second resin of the heat-resistant layer is a heat-resistant resin made of an engineering plastic or a super-engineering plastic.

[0089] (5) The solid electrolyte battery of the present invention is characterized in that the engineering plastic is any one of nylon, polyamide, and polyethylene terephthalate.

[0090] (6) The solid electrolyte battery of the present invention is characterized in that the super engineering plastic is polyimide or polyetherimide.

[0091] (7) The solid electrolyte battery of the present invention is characterized in that the charge / discharge body is made up of a plurality of combinations of a positive electrode layer, a negative electrode layer, and a solid electrolyte layer.

[0092] (8) The solid electrolyte battery of the present invention is characterized in that it is a solid electrolyte battery used in transportation equipment that is driven by an electric motor that is rotated by the electric power of the solid electrolyte battery.

[0093] (9) The solid electrolyte battery of the present invention is characterized in that a heat-resistant layer having a higher heat resistance than the heat-sealed layer is provided between the metal layer and the heat-sealed layer, and even when the temperature reaches the temperature at which the heat-sealed layer melts, the heat-resistant layer does not melt and maintains its shape as a "layer."

[0094] (10) The solid electrolyte battery of the present invention is characterized in that a protective layer is provided on the outside of the metal layer.

[0095] (11) The solid electrolyte battery of the present invention is characterized in that the bending angle of the upper exterior body, which changes direction from the main surface of the positive electrode current collector foil that constitutes the charging / discharging body toward the side surface, is formed as an obtuse angle larger than a right angle, and similarly, the bending angle of the lower exterior body, which changes direction from the main surface of the negative electrode current collector foil that constitutes the charging / discharging body toward the side surface, is formed as an obtuse angle larger than a right angle.

[0096] (12) The solid electrolyte battery of the present invention is characterized in that an upper exterior body, which changes direction from the main surface of the positive electrode current collector foil that constitutes the charging / discharging body to the side surface, changes direction at approximately a right angle so as to form a space at a distance from the side surface, and similarly, a lower exterior body, which changes direction from the main surface of the negative electrode current collector foil that constitutes the charging / discharging body to the side surface, changes direction at approximately a right angle so as to form a space at a distance from the side surface.

[0097] (13) A method for producing a solid electrolyte battery in the present invention is a method for producing a solid electrolyte battery having a charge / discharge body including a positive electrode layer and a negative electrode layer, a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, a positive electrode current collector foil electrically connected to the positive electrode layer, and a negative electrode current collector foil electrically connected to the negative electrode layer, wherein the step of bonding the positive electrode layer, the negative electrode layer, and the solid electrolyte layer is a pressurizing step by warm isostatic pressing in which the charge / discharge body is immersed in a liquid in a pressure-resistant container and the liquid is pressurized to bond the positive electrode layer, the negative electrode layer, and the solid electrolyte layer, and the pressurizing step is performed under conditions in which the temperature of the liquid in the pressurizing step is 140° C. or more and 250° C. or less.

[0098] (14) In the method for producing a solid electrolyte battery according to the present invention, the liquid pressure in the pressurizing step using warm isostatic pressing is set to 100 MPa or more and 1000 MPa or less.

[0099] (15) In the method for producing a solid electrolyte battery according to the present invention, the execution time of the pressing step by warm isostatic pressing is set in the range of 10 seconds to 10 minutes.

[0100] (16) The method for producing a solid electrolyte battery according to the present invention is characterized in that the charge / discharge body is sealed by an exterior body, and the charge / discharge body including the exterior body is pressed by warm isostatic pressing.

[0101] (17) The method for manufacturing a solid electrolyte battery in the present invention is characterized in that the outer casing is formed from a heat-sealed layer covering the charging / discharging body from the outside and containing a first resin with insulating properties, a heat-resistant layer laminated so as to cover the heat-sealed layer from the outside and containing a second resin with insulating properties having a melting point higher than that of the first resin, and a metal layer laminated so as to cover the heat-resistant layer from the outside and containing a metal, and the charging / discharging body is sealed by the outer casing in a pressurizing process by welding the heat-sealed layer around the charging / discharging body.

[0102] (18) The method for manufacturing a solid electrolyte battery according to the present invention is characterized in that, prior to the warm isostatic press, the upper and lower exterior bodies are not welded to the charge / discharge body, and by performing the warm isostatic press, the heat-welded layers on the insides of the upper and lower exterior bodies are bonded to each other, sandwiching the charge / discharge body.

[0103] (19) The method for producing a solid electrolyte battery according to the present invention is characterized in that the charge / discharge body is preliminarily pressed by a plate press or a roll press before pressing by warm isostatic pressing.

[0104] (20) The method for producing a solid electrolyte battery according to the present invention is characterized in that the pressurizing pressure in the preliminary pressurizing is smaller than the pressurizing pressure in the warm isostatic press.

[0105] (21) A method for manufacturing a solid electrolyte battery according to the present invention is characterized in that an exterior body covers the positive electrode layer and positive electrode current collecting foil, the negative electrode layer and negative electrode current collecting foil, and the solid electrolyte layer, and portions of the positive electrode current collecting foil and the negative electrode current collecting foil are exposed to the outside of the exterior body, and a positive electrode current collecting tab and a negative electrode current collecting tab are later attached to these exposed portions.

[0106] (22) A method for producing a solid electrolyte battery according to the present invention is a method for producing a solid electrolyte battery having a charge / discharge body including a positive electrode layer and a negative electrode layer, a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, a positive electrode current collector foil electrically connected to the positive electrode layer, and a negative electrode current collector foil electrically connected to the negative electrode layer, wherein the step of bonding the positive electrode layer and the negative electrode layer to the solid electrolyte layer is a pressurizing step by warm isostatic pressing in which the charge / discharge body is housed in a pressure vessel and pressurized gas is supplied to the pressure vessel to bond the positive electrode layer, the negative electrode layer, and the solid electrolyte layer to each other.

[0107] The present invention is not limited to the above-mentioned embodiment, but includes various modified examples. For example, the above-mentioned embodiment has been described in detail to easily explain the present invention, and is not necessarily limited to those including all of the configurations described. Also, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Also, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration. [Explanation of symbols]

[0108] 10...solid electrolyte battery (charge / discharge unit), 11...exterior body, 12...positive electrode current collecting tab, 13...negative electrode current collecting tab, 14...charge / discharge body, 15...positive electrode layer, 16...negative electrode layer, 17...solid electrolyte layer, 18...positive electrode current collecting foil, 19...negative electrode current collecting foil, 20...thermal welding layer, 21...heat-resistant layer, 22...metal layer, PC...pressure-resistant container, PL...plunger, LQ...liquid.

Claims

1. a charging / discharging body having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer; an exterior body that houses the charging / discharging body; and a current collector having one end exposed to the outside of the exterior body and the other end electrically connected to the positive electrode layer or the negative electrode layer, the exterior body being formed from a thermally sealed layer that covers the charging / discharging body from the outside and contains a first resin having insulating properties, a heat-resistant layer that is laminated on the outside of the thermally sealed layer and contains a second resin having a higher melting point than the first resin and having insulating properties, and a metal layer that is laminated on the outside of the heat-resistant layer and contains a metal, the thermally sealed layer being welded around the charging / discharging body to seal the charging / discharging body, In a state where the periphery of the charge / discharge body and the thermal welding layer are welded together, Between the exterior body and the side surface of the positive electrode layer, which turns toward the side surface of the positive electrode layer, a space is provided to prevent the side surface of the positive electrode layer from contacting the exterior body; Between the exterior body and the side surface of the negative electrode layer, which turns toward the side surface of the negative electrode layer, a space is provided to prevent the side surface of the negative electrode layer from contacting the exterior body. A solid electrolyte battery comprising:

2. The solid electrolyte battery according to claim 1, The bending angle of the exterior body, which turns and bends toward the side surface of the positive electrode layer, is an obtuse angle, The bending angle of the exterior body, which turns and bends toward the side surface of the negative electrode layer, is an obtuse angle. A solid electrolyte battery comprising:

3. The solid electrolyte battery according to claim 1, The second resin of the heat-resistant layer is a heat-resistant resin made of engineering plastic or super engineering plastic. A solid electrolyte battery comprising:

4. The solid electrolyte battery according to claim 3, The engineering plastic is any one of nylon, polyamide, and polyethylene terephthalate. A solid electrolyte battery comprising:

5. 4. The solid electrolyte battery according to claim 3, The super engineering plastic is polyimide or polyetherimide. A solid electrolyte battery comprising:

6. The solid electrolyte battery according to claim 1, The charge / discharge body is formed by combining a plurality of sets each including the positive electrode layer, the negative electrode layer, and the solid electrolyte layer. A solid electrolyte battery comprising:

7. A transportation device that runs on an electric motor rotated by power from a solid electrolyte battery, the solid electrolyte battery being the solid electrolyte battery described in any one of claims 1 to 5. A transportation device characterized by:

Images