Electrochemical element

Abstract

Provided is an electrochemical element with which it is possible to ensure excellent reliability.　An electrochemical element 1 comprises: a case 10 having a recessed container 11, which has a bottom part 111 and a lateral wall part 112, and a lid member 12 that covers the opening of the recessed container 11; a power generation element 20 which has a multilayer body obtained by layering an electrode layer 21, an electrode layer 22, and a solid electrolyte layer 23, and is accommodated in the internal space of the case 11 such that the bottom part 111 and the electrode layer 21 face each other; and a conductive plate 30 which is positioned between the electrode layer 22 and the lid member 12 on the opening side of the recessed container 11. The lid member 12 is recessed toward the conductive plate by reducing the pressure in the internal space of the case 10. The depth D of the recess in the lid member 12 is 0.02 mm or more. A gap G having a size of 0.05 mm or more is formed between the conductive plate and the lid member.

Description

Electrochemical elements

[0001] This disclosure relates to an electrochemical element in which a power generation element is sealed within a case.

[0002] Conventionally, various types of batteries have been disclosed in which a power generation element is housed in an internal space formed by a concave container and a lid covering the opening of the concave container.

[0003] Japanese Patent Publication No. 2012-69508 (Patent Document 1) discloses an electrochemical cell with stable electrochemical properties. The electrochemical cell has a sealed container. The sealed container consists of a base member and a lid member. A storage space for housing an electrochemical element (electrode body) is formed between the two members. An elastic member that presses the electrochemical element is disposed between the lid member and the electrochemical element. Patent Document 1 discloses embodiments using a leaf spring bent in a V-shape in cross-section, a torsion bar unit that utilizes the elastic restoring force caused by twisting, or a diaphragm-shaped spring formed in a concave curved surface that curves from the center towards the outer edge as the elastic member.

[0004] Furthermore, International Publication No. 2022 / 030424 (Patent Document 2) discloses a battery package and a battery module. The battery package comprises an insulating substrate made of ceramics with a recess formed in the center of a first surface, a frame portion surrounding the recess on the first surface, and a lid that closes the frame portion. The battery module is composed of the battery package and the battery housed inside it. A conductive metal sheet is placed between the lid of the battery package and the battery to maintain an electrical connection with the battery while pressing it. The conductive sheet is joined to a second electrode provided on the first surface via a conductive bonding material made of conductive adhesive, and the second external electrode, which is an external terminal, is electrically connected to one electrode of the battery. In addition, in Patent Document 2, to prepare for cases where external stress is applied to the lid, the gap between the flat lid and the conductive sheet is set to, for example, 0.1 mm to 0.8 mm during assembly.

[0005] Japanese Patent Publication No. 2012-69508, International Publication No. 2022 / 030424

[0006] If the battery contained within the aforementioned battery package contains materials that readily react with moisture, it is conceivable to seal the battery package in a vacuum environment. However, it has been found that when the battery module described in Patent Document 2 is sealed in a vacuum environment, the metal lid deforms inward (towards the battery) when the assembled battery module is placed in a normal pressure environment. Therefore, even if a certain gap is provided between the lid and the conductive sheet during assembly, the risk of contact between the lid and the conductive sheet increases when the battery module is subjected to a strong impact, compared to when the battery module is sealed in a normal pressure environment, making it difficult to ensure the reliability of the battery module. Vacuum is a state where the pressure is reduced below normal pressure (1 atmosphere).

[0007] Furthermore, it is possible to confirm whether the battery module is properly sealed by examining the deformation of the lid. However, even if the battery module is properly sealed in a vacuum environment, if the deformation of the lid is small when the battery module is placed in an atmospheric pressure environment, it becomes difficult to determine whether it is properly sealed. In other words, it becomes difficult to ensure the reliability of the battery module. Therefore, considering the confirmation of a good sealing state, it is desirable that the lid deforms to a certain extent when a battery module sealed in a vacuum environment is placed in an atmospheric pressure environment.

[0008] Patent Document 2 does not propose how to set the amount of deformation of the lid and the gap between the deformed lid and the conductive sheet when the battery module is sealed in a vacuum environment in order to ensure the reliability of the battery module described above.

[0009] Therefore, the present disclosure aims to ensure excellent reliability in an electrochemical element in which the internal space of a case composed of a concave container and a metal lid is sealed under reduced pressure.

[0010] To solve the above problems, this disclosure is configured as follows. Specifically, the electrochemical element according to this disclosure comprises a case having a concave container with a bottom and side walls and a metal lid covering the opening of the concave container; a power generation element sealed inside the case and having a first electrode layer located on the bottom side, a second electrode layer located on the lid side, and an isolation layer located between the first and second electrode layers; and a conductive plate located between the power generation element and the lid. The first electrode layer is electrically connected to a first conductive path that leads from the inside to the outside of the case. The second electrode layer is electrically connected to a second conductive path that leads from the inside to the outside of the case via the conductive plate. The lid is recessed toward the conductive plate because the internal space of the case is under reduced pressure compared to the external space of the case. The depth of the recess in the lid is 0.02 mm or more. A gap of 0.05 mm or more is formed between the conductive plate and the lid.

[0011] The electrochemical element according to this disclosure can prevent the reaction between the power generation element and moisture in the internal space of the case, allow for easy confirmation of sealing performance, and prevent electrical conductivity between the lid material and the second electrode layer due to contact between the lid material and the conductive plate when subjected to impact or the like. As a result, the electrochemical element according to this disclosure can ensure excellent reliability.

[0012] Figure 1 is a cross-sectional view showing an electrochemical element according to the first embodiment. Figure 2 is an external perspective view showing the concave container of the electrochemical element of Figure 1. Figure 3 is an external perspective view showing another concave container of the electrochemical element. Figure 4 is a plan view showing the electrochemical element of Figure 1 (excluding the lid and conductive plate). Figure 5 is a cross-sectional view showing a conductive plate according to a modified example. Figure 6 is a cross-sectional view showing an electrochemical element according to the second embodiment. Figure 7 is a cross-sectional view showing an electrochemical element according to the third embodiment. Figure 8 is a cross-sectional view showing the electrochemical element of Figure 1 immediately after sealing, i.e., before the lid becomes concave.

[0013] (Configuration 1) The electrochemical element according to the embodiment of the present disclosure comprises a case having a concave container with a bottom and side walls and a metal lid covering the opening of the concave container; a power generation element sealed inside the case and having a first electrode layer disposed on the bottom side, a second electrode layer disposed on the lid side, and an isolation layer disposed between the first and second electrode layers; and a conductive plate disposed between the power generation element and the lid. The first electrode layer is electrically connected to a first conductive path that leads from the inside to the outside of the case. The second electrode layer is electrically connected to a second conductive path that leads from the inside to the outside of the case via the conductive plate. The lid is recessed toward the conductive plate because the internal space of the case is under reduced pressure compared to the external space of the case. The depth of the recess in the lid is 0.02 mm or more. A gap of 0.05 mm or more is formed between the conductive plate and the lid.

[0014] In this way, the internal space of the case is depressurized, and the lid material is recessed by 0.02 mm or more toward the conductive plate. This removes moisture contained in the internal space of the case, preventing reaction with the power generation element. Furthermore, it is easy to confirm whether the electrochemical element is properly sealed under normal pressure conditions, thereby improving the reliability of the electrochemical element. In addition, because a gap of a certain size or larger is formed between the lid material and the conductive plate, it is possible to prevent the lid material from making electrical contact with the second electrode layer, thereby improving the reliability of the electrochemical element when mounted on a circuit board, etc.

[0015] (Configuration 2) In the electrochemical element of Configuration 1, the conductive plate may include a flat portion facing the power generation element and a spring portion that rises from the flat portion and presses the power generation element toward the bottom of the concave container. As a result, even if the thickness of the power generation element changes due to charging and discharging, the elasticity of the spring portion allows the conductive plate to more stably conduct electricity between the power generation element and the first and second conduction paths.

[0016] (Configuration 3) In the electrochemical element of Configuration 2, the spring portion may be cantilevered on a flat surface and have a spring piece that presses the power generation element toward the bottom of the concave container. This makes it possible to easily manufacture the conductive plate, i.e., the electrochemical element, since it is only necessary to form the spring piece on a part of the flat surface of the conductive plate.

[0017] (Configuration 4) In the electrochemical element of Configuration 3, the tip of the spring piece may be bent in the direction opposite to the power generation element. This prevents the sharp tip of the spring piece from coming into contact with and damaging the power generation element.

[0018] (Configuration 5) In any of the electrochemical elements of Configurations 1 to 4, the conductive plate is locked to the side wall of the concave container at a point outside the outer edge of the power generation element in a plan view. Because the conductive plate is locked to the side wall of the concave container at a point outside the outer edge of the power generation element, processes such as welding of the conductive plate are unnecessary, and the portion of the conductive plate facing the power generation element can be freely positioned in the height direction (thickness direction of the power generation element), allowing for conductive connection between the conductive plate and the second electrode layer in various ways.

[0019] (Configuration 6) In any of the electrochemical elements of Configurations 1 to 5, the depth of the recess in the lid material is 0.2 mm or less. This makes it possible to reduce the gap that needs to be pre-provided between the lid and the conductive plate when assembling the electrochemical element.

[0020] (Configuration 7) In any of the electrochemical elements of Configurations 1 to 6, the size of the gap formed between the conductive plate and the lid material is 0.5 mm or less. This makes it possible to suppress an increase in the internal volume of the electrochemical element.

[0021] (Configuration 8) In any of the electrochemical elements of Configurations 1 to 7, the power generation element may have a porous metal substrate integrated with the conductive plate side portion of the second electrode layer. This allows the conductive plate and the porous metal substrate to come into contact, thereby creating electrical conductivity between the conductive plate and the second electrode layer, and as a result, the electrical resistance at the point of contact between the conductive plate and the power generation element can be reduced.

[0022] (Configuration 9) In any of the electrochemical elements of Configurations 1 to 8, the amount of helium gas leaked based on the "Helium Leakage Test Method" (Bombing Method) described in Japanese Industrial Standard JIS-Z2331 is 1 × 10⁻⁶ －１０ Pa・m ３ It may be less than or equal to / s.

[0023] (First Embodiment) Hereinafter, the first embodiment of the present disclosure will be specifically described using Figures 1 to 7, with the example of the case in which the electrochemical element is an all-solid-state battery. First, as shown in Figure 1, the electrochemical element 1 consists of a case 10, a power generation element 20 and a conductive plate 30 housed in the case 10, and external terminals 13 and 14 arranged on the outer surface of the case 10.

[0024] The case 10 comprises a concave container 11 and a lid 12. The concave container 11 is made of ceramics. The concave container 11 includes a rectangular bottom 111 and a rectangular cylindrical side wall 112 that is formed continuously from the outer circumference of the bottom 111 and has a cylindrical space inside for housing the power generation element 20. In a longitudinal cross-sectional view, the side wall 112 is provided to extend substantially perpendicular to the bottom 111. A conductive portion 113 is formed inside the bottom 111. The conductive portion 113 extends between the power generation element 20 and the bottom 111 so as to be electrically connected to the power generation element 20, and forms a conductive path corresponding to the electrode layer 21. A conductive portion 114 is formed inside the side wall 112. As shown in Figure 1, a portion of the conductor portion 114 is formed on the inner circumferential surface of the side wall portion 112, exposed to the lower and side surfaces of the support portion 115, which will be described later, and forms a conductive path corresponding to the electrode layer 22. The manufacturing method of the concave container 11 will be described later. The material of the concave container 11 is not particularly limited, and various materials such as resin, glass (borosilicate glass, glass ceramics, etc.), metal, and ceramic can be used as examples. It may also be a composite material in which ceramic or glass powder is dispersed in resin. When the concave container 11 is made of a metal material, it is preferable to cover the inner surface of the bottom portion 111 and the inner circumferential surface of the side wall portion 112 of the concave container 11 with an insulating material such as resin or glass in order to ensure insulation between the concave container 11 and the power generation element 20. Furthermore, the concave container 11 is not limited to a rectangular shape in plan view, but may be circular, elliptical, or polygonal. The internal space for housing the power generation element 20 is not limited to a cylindrical shape, but may be formed in a polygonal cylindrical shape, such as a square cylindrical shape, depending on the shape of the power generation element 20. Furthermore, the conductor portion 114 may be formed on the inner surface of the side wall portion 112 rather than inside the side wall portion 112, and may also be made electrically connected to the external terminal 14 by penetrating the inside of the bottom portion 111. In this case, it is preferable to form an insulating layer between the outer surface of the power generation element 20 and the conductor portion 114, for example, on the inner surface of the conductor portion 114, so that the outer surface of the power generation element 20 and the conductor portion 114 do not come into contact.

[0025] The side wall portion 112 has a plurality of support portions 115 that support the conductive plate 30, which will be described later. In this embodiment, the support portions 115 are protruding portions formed at the upper end of the inner circumferential surface of the side wall portion 112 and extending outward along the circumferential direction of the inner circumferential surface. More specifically, as shown in Figure 2, the support portions 115 are the top walls of a plurality of recesses formed outward from the inner circumferential surface of the side wall portion 112 in a plan view. As a result, the support portions 115 are formed to protrude outward in the circumferential direction of the inner circumferential surface. The lower surface of each support portion 115, that is, the lower surface of each top wall, can engage and support the supported portion 31 of the conductive plate 30, which will be described later, outside the outer edge of the power generation element 20 in a plan view. In addition, although two support portions 115 are provided in this embodiment, the number is not limited, and for example, if the conductive plate 30 has four supported portions 31, four support portions 115 should be provided at positions corresponding to the supported portions 31.

[0026] The lid material 12 is a rectangular metal sheet that covers the opening of the concave container 11. The material of the lid material 12 is preferably one that has a certain level of strength, but can be deformed to some extent when placed in an atmospheric pressure environment after sealing. Preferably, carbon steel (cold-rolled steel sheet, hot-rolled steel sheet, etc.), iron-nickel alloy (alloy with Ni content: 36 mass%, alloy with Ni content: 42 mass%, etc.), iron-nickel-cobalt alloy (alloy with Ni content: 29 mass% and Co content: 17 wt%, alloy with Ni content: 31.5 mass% and Co content: 5 wt%, alloy with Ni content: 36 mass% and Co content: 12 wt%, etc.) is used. The thickness of the lid material 12 is preferably 0.05 mm or more, more preferably 0.07 mm or more, in order to ensure a certain level of strength, and preferably 0.2 mm or less, more preferably 0.15 mm or less, in order to ensure that the depth D of the recess in the lid material 12 is above a certain value and to make it easier to check whether the sealing is good or bad.

[0027] As shown in Figures 1 and 3, the lid material 12 is joined (seam welded) to the concave container 11 by a square frame-shaped sealing ring 15 positioned between the lower surface of its outer peripheral end and the upper end of the concave container 11. This completely seals the internal space of the case 10. The internal space of the case 10 is kept under vacuum to minimize the impact on the power generation element 20. The pressure inside the internal space of the case 10 at this time is preferably 1 Pa or less, more preferably 0.1 Pa or less, in order to reduce the amount of moisture remaining inside the internal space of the case 10. －２ It is particularly preferable to keep it below Pa.

[0028] This reduced pressure state within the internal space of case 10 can be achieved by joining the concave container 11 and the lid material 12 in a vacuum environment, thereby sealing the internal space of case 10. As a result, moisture contained in the internal space of case 10 is removed before sealing the internal space of case 10, i.e., before sealing case 10, and the internal space of case 10 is maintained in a reduced pressure state even after sealing case 10, thus preventing the reaction between moisture and the power generation element 20. Furthermore, when case 10 is placed in an atmospheric pressure environment after sealing, the lid material 12 deforms inward (towards the power generation element) due to the external pressure which is higher than the pressure inside the internal space of case 10, causing it to dent. Therefore, when joining the lid material 12 to the concave container 11, it is necessary to determine the distance between the lid material 12 and the conductive plate 30 in advance, taking into account the depth D of the dent formed in the lid material 12, so that a predetermined gap G is formed between the deformed lid material 12 and the conductive plate 30. In this disclosure, the depth D of the recess in the cover material 12 can be defined as the maximum displacement amount that the cover material 12 deforms from its position at the time of joining (see Figure 8) toward the power generation element.

[0029] The depth D of the recess in the lid material 12 needs to be 0.02 mm or more, and preferably 0.04 mm or more, from the viewpoint that it is easy to confirm whether or not the electrochemical element 1 is properly sealed under normal pressure conditions. If the depth D is less than 0.02 mm, the difference in value between well-sealed and insufficiently sealed elements becomes small, making it difficult to distinguish between them. Furthermore, from the viewpoint of reducing the gap that is pre-provided between the lid material 12 and the conductive plate 30 during the assembly of the electrochemical element 1, thereby suppressing an increase in the thickness of the electrochemical element 1, the depth D needs to be 0.2 mm or less, preferably 0.15 mm or less, and more preferably 0.1 mm or less.

[0030] The depth D of the recess in the lid material 12 can be adjusted by the material, thickness, or size of the lid material 12. Even if the material and thickness of the lid material 12 are the same, the larger the lid material 12, the greater the depth D of the recess in the lid material 12 when the case 10 is placed in an atmospheric pressure environment. Therefore, as long as the lid material 12 is above a certain size, the required depth D can be achieved with various materials and thicknesses. For this reason, the size of the lid material 12, which will be set according to the size of the electrochemical element 1 (size of the concave container 11), should, for example, be larger than a square with sides of approximately 5 mm, and larger than a square with sides of approximately 7 mm. Therefore, it is desirable to make the electrochemical element 1 the size that corresponds to the size of such a lid material 12. On the other hand, if the lid material 12 becomes too large, it becomes difficult to keep the depth D below 0.2 mm. Therefore, if the lid material 12 is rectangular, it is desirable that it be smaller than a square with sides of approximately 30 mm, and even more desirable that it be smaller than a square with sides of approximately 20 mm. Consequently, it is desirable that the electrochemical element 1 be sized to match the size of such a lid material 12.

[0031] Furthermore, as shown in Figure 1, a gap G is formed between the deformed lid material 12 and the conductive plate 30. The size of the gap G needs to be 0.05 mm or more, and preferably 0.07 mm or more, in order to prevent the lid material 12 and the conductive plate 30 from coming into contact when the electrochemical element 1 is subjected to an impact. On the other hand, as the gap G increases, the internal volume of the electrochemical element 1 increases and extra dead space is formed, so it is preferable that the size of the gap G be 0.5 mm or less, and more preferably 0.3 mm or less.

[0032] The lid material 12 may be bonded to the concave container 11 with an adhesive, and the method of joining the lid material 12 to the concave container 11 is not particularly limited as long as the internal space of the case 10 can be sealed. Also, the lid material 12 is not limited to a rectangular shape, and can be changed to various shapes such as circular, elliptical, and polygonal depending on the shape of the concave container 11 in plan view.

[0033] The external terminal 13 is located on the outer surface of the bottom 111 of the concave container 11. The external terminal 13 is electrically connected to the electrode layer 21, which will be described later, via the conductive portion 113. The electrode layer 21 functions as a positive electrode layer, as will be described later. Therefore, the conductive portion 113 serves as a conductive path that connects the external terminal 13 and the positive electrode layer, and the external terminal 13 functions as a positive electrode terminal.

[0034] The external terminal 14 is positioned on the outer surface of the bottom 111 of the concave container 11, away from the external terminal 13. The external terminal 14 is electrically connected to the supported portion 31 of the conductive plate 30, which will be described later, via the conductive portion 114. As will be described later, the conductive plate 30 is electrically connected to the electrode layer 22, which functions as a negative electrode layer. Therefore, the conductive portion 114 becomes a conductive path that connects the external terminal 14 and the negative electrode layer, and the conductive plate 30 becomes a connecting terminal that connects this conductive path and the electrode layer 22, so the external terminal 14 functions as a negative electrode terminal. Note that the arrangement of the external terminals 13 and 14 is not limited to the above, and they may be positioned on the outer surface of the side wall portion 112 of the concave container 11, or the lid material 12 may function as the conductive portion 114 and the external terminal 14 may be formed on the outer surface of the lid material 12. However, by positioning both of these terminals on the outer surface of the bottom 111 of the concave container 11 with a certain distance between them, mounting to the surface of the circuit board becomes easier.

[0035] Here, the manufacturing method for the concave container 11 will be described. First, a metal paste is printed onto a ceramic green sheet to form printed patterns that will become the conductive parts 113 and 114. Next, multiple green sheets with these printed patterns are stacked and fired. By stacking multiple green sheets of different shapes, the support portion 115 described above is formed. This makes it possible to manufacture a concave container 11 having conductive parts 113 and 114 inside, and the support portion 115 described above on the inner circumferential surface of the side wall portion 112. Note that the manufacturing method is not limited to this method as long as the support portion 115 can be formed on the inner circumferential surface of the side wall portion 112. External terminals 13 and 14 can also be formed by the printed patterns of this metal paste.

[0036] The power generation element 20 includes a laminate in which an electrode layer (positive electrode layer) 21, an electrode layer (negative electrode layer) 22, and a solid electrolyte layer 23 are laminated. The solid electrolyte layer 23 is disposed between the electrode layer 21 and the electrode layer 22 as a separation layer. That is, in the present embodiment, the separation layer is the solid electrolyte layer 23. The power generation element 20 is formed in a cylindrical shape. The power generation element 20 is laminated in the order of the electrode layer 21, the solid electrolyte layer 23, and the electrode layer 22 from the bottom 111 side (lower side in the drawing) of the concave container 11. That is, the power generation element 20 is arranged such that the electrode layer 21, which is one end thereof, is on the bottom 111 side of the concave container 11, and the electrode layer 22, which is the other end thereof, is on the lid material 12 side, and is housed in the internal space of the case 10. Note that the power generation element 20 is not limited to a cylindrical shape, and can be variously changed such as a rectangular parallelepiped shape or a polygonal prism shape. Further, the power generation element 20 may have a plurality of laminates. The plurality of laminates may be laminated so as to be connected in series.

[0037] The electrode layer 21 is a positive electrode pellet formed in a cylindrical shape from a positive electrode mixture containing lithium cobaltate, a sulfide-based solid electrolyte, and graphene as a conductive assistant in a mass ratio of 65:30:5 as a positive electrode active material. Note that the positive electrode active material of the electrode layer 21 is not particularly limited as long as it can function as the positive electrode layer of the power generation element 20. For example, it may be lithium nickelate, lithium manganate, lithium nickel cobalt manganese composite oxide, olivine-type composite oxide, etc., or a mixture of these appropriately. Other constituent materials and ratios are not particularly limited either. Further, the size and shape of the electrode layer 21 are not limited to a cylindrical shape, and can be variously changed according to the size and shape of the electrochemical element 1.

[0038] The electrode layer 22 is LTO (Li ４ Ti ５ O １２The negative electrode pellet is formed into a cylindrical shape from a negative electrode mixture containing lithium titanate, a sulfide-based solid electrolyte, and graphene in a weight ratio of 50:40:10. The negative electrode active material of the electrode layer 22 is not particularly limited as long as it can function as the negative electrode layer of the power generation element 20. For example, it may be metallic lithium, lithium alloy, carbon materials such as graphite and low-crystallinity carbon, or oxides such as SiO, or a mixture of these as appropriate. Other components and their proportions are also not particularly limited. Furthermore, the size and shape of the electrode layer 22 are not limited to a cylindrical shape and can be changed in various ways depending on the size and shape of the electrochemical element 1.

[0039] The solid electrolyte layer (isolation layer) 23 contains a sulfide-based solid electrolyte. The solid electrolyte layer 23 is molded into a cylindrical shape. The solid electrolyte contained in the electrode layer 21, electrode layer 22, and solid electrolyte layer 23 is not particularly limited, but from the viewpoint of ionic conductivity, a sulfide-based solid electrolyte, particularly an argyrodite-type sulfide-based solid electrolyte, is preferably used. When using a sulfide-based solid electrolyte, it is preferable to cover the surface of the positive electrode active material with a lithium-ion conductive material such as niobium oxide to prevent reaction with the positive electrode active material. The solid electrolyte contained in the solid electrolyte layer 23, electrode layer 21, and electrode layer 22 may also be a hydride-based solid electrolyte or an oxide-based solid electrolyte. Furthermore, the size and shape of the solid electrolyte layer 23 are not limited to a cylindrical shape and can be changed in various ways depending on the size and shape of the electrochemical element 1.

[0040] As shown in FIGS. 1 and 4, the conductive plate 30 is a metal plate having a rectangular shape in plan view and is installed at the opening of the concave container 11 of the case 10. The conductive plate 30 has a plurality of supported portions 31 corresponding to the positions of the respective support portions 115 described above outside the outer edge of the power generation element 20 in plan view. In the present embodiment, the supported portion 31 is the above-described support portion 115, that is, a hook-shaped locking piece locked to the lower surface of the top wall. More specifically, the supported portion 31 extends from the edge of the conductive plate 30 toward the above-described support portion 115 (downward in FIG. 1). The supported portion 31 has a tip portion that is folded back toward the support portion 115, that is, the lower surface of the top wall. The tip of the supported portion 31 is in contact with the conductor portion 114 exposed on the lower surface and the side surface of the above-described top wall. Thereby, the conductive plate 30 functions as a current collector and also functions as a connection terminal that electrically connects the electrode layer 22 and the conduction path leading to the external terminal 14. The conductive plate 30 is supported by the support portion 115 formed on the inner peripheral surface of the concave container 11 and covers a part of the opening of the concave container 11. The area of the conductive plate 30 in plan view is smaller than the opening area of the concave container 11. Even if the hook-shaped locking piece is not locked to the lower surface of the top wall, if the conductive plate 30 can be fixed in a state where the hook-shaped locking piece is press-fitted into the recess formed in the inner peripheral surface of the side wall portion 112, the conductive plate 30 is considered to be locked to the side wall portion 112 of the concave container 11.

[0041] As shown in Figure 1, the conductive plate 30 has a spring portion 33 that rises from the flat portion 32 of the conductive plate 30 toward the electrode layer 22 of the power generation element 20 so as to contact the upper surface of the electrode layer 22, which is the other end of the power generation element 20. The shape of the spring portion 33 is not particularly limited as long as it can press the power generation element 20 toward the bottom 111 of the concave container 11. In this embodiment, the spring portion 33 is a spring piece that is inclined toward the electrode layer 22 of the power generation element 20 from the flat portion 32 (hereinafter, the spring portion 33 may be referred to as the spring piece 33). As shown in Figure 4, the spring piece 33 is formed by cutting out a U-shaped part of the flat portion 32 and is cantilevered to the flat portion 32. That is, in this embodiment, the spring piece 33 is a leaf spring. In this way, since it is only necessary to form the spring piece 33 in a part of the flat portion 32, the conductive plate can be easily manufactured, i.e., the electrochemical element can be manufactured. Furthermore, by cutting out the flat portion 32 to form the spring piece 33, the manufacturing of the conductive plate, i.e., the manufacturing of the electrochemical element, can be made even easier. The spring piece 33 has a boundary 331 with the flat portion 32 and a tip 332 that contacts the electrode layer 22 of the power generation element 20 to establish electrical contact with the electrode layer 22. The spring piece 33 is bent at the boundary 331 and slopes toward the power generation element 20 from the boundary 331 toward the tip 332. The height from the bottom surface of the flat portion 32 to the tip 332 (height of the spring portion 33) before assembling the electrochemical element 1 is greater than the height from the bottom surface of the flat portion 32 to the power generation element 20 after assembling the electrochemical element 1. As a result, the tip 332 of the spring piece 33 can press against the power generation element 20, maintaining a good electrical connection between the conductive plate 30 and the power generation element 20. In addition, by constructing the spring portion 33 from a spring piece, the thickness of the conductive plate 30, excluding the supported portion 31, can be reduced. For example, before assembling the electrochemical element 1, the thickness of the conductive plate 30 excluding the supported portion 31 can be the sum of the thickness of the plate material constituting the flat portion 32 and the height of the spring piece 33. Specifically, by combining the thickness of the plate material (0.2 mm) and the height of the spring piece 33 (0.5 mm), the thickness of the conductive plate 30 excluding the supported portion 31 can be made 0.7 mm. Alternatively, the width of the spring piece 33 can be 1.5 mm and its length 3 mm, etc.When multiple spring pieces 33 are provided, the shape of each spring piece 33, including its width and length, may differ for reasons such as preventing resonance. The thickness of the conductive plate 30 excluding the supported portion 31 is preferably 1.2 mm or less, more preferably 1 mm or less, and particularly preferably 0.8 mm or less. On the other hand, in order to generate the necessary pressing force in the spring portion 33, the thickness of the conductive plate 30 excluding the supported portion 31 is preferably 0.3 mm or more, more preferably 0.4 mm or more, and particularly preferably 0.5 mm or more.

[0042] Furthermore, since the position of the edge of the conductive plate 30, i.e., the supported portion 31, can be freely set in the height direction (thickness direction of the conductive plate 30), even if a gap is formed between the lid material 12 and the conductive plate 30, the distance between the lid material 12 and the tip portion 332 of the spring piece 33 does not increase. As a result, the gap between the lid material 12 and the power generation element 20 can be suppressed, thereby increasing the capacitance of the electrochemical element 1. Here, the overall thickness of the conductive plate 30, including the supported portion 31, can be appropriately adjusted according to the height from the bottom portion 111 of the side wall portion 112 of the concave container 11. The supported portion 31 only needs to have the height necessary for locking to the support portion 115. For this reason, the overall thickness of the conductive plate 30, including the supported portion 31, can be, for example, 3 mm or less, preferably 2.7 mm or less, and more preferably 2.5 mm or less. The thickness direction refers to the vertical direction in Figure 1 (the height direction of the electrochemical element 1), and can also be described as the direction perpendicular to the bottom surface of the flat portion 32 in the illustration. The spring piece 33 may be formed by cutting out the flat portion 32 as described above, and similarly, as in the modified example described later, the spring piece 33 may be attached to the bottom surface of the flat portion 32 by welding or the like. Alternatively, a base for attaching the spring piece 33 may be provided separately from the flat portion 32, and the spring piece 33 may be attached to the base to form the entire spring portion. In other words, the spring piece 33 may rise directly from the flat portion 32, or it may rise from the flat portion 32 with another element such as a base interposed therebetween. Furthermore, both ends of the spring piece 33 may be supported by the flat portion 32 so that it has a convex shape toward the power generation element 20.

[0043] Examples of metals that make up the conductive plate 30 include nickel, iron, copper, chromium, cobalt, titanium, aluminum, and alloys thereof. To facilitate its function as a leaf spring, spring stainless steels such as SUS301-CSP, SUS304-CSP, SUS316-CSP, SUS420J2-CSP, SUS631-CSP, and SUS632J1-CSP are preferably used.

[0044] Furthermore, the thickness of the conductive plate 30 is preferably 0.05 mm or more, more preferably 0.07 mm or more, and particularly preferably 0.1 mm or more, in order to ensure that the pressing force against the power generation element 20 is above a certain level. On the other hand, in order to prevent the thickness of the conductive plate 30 from becoming too thick and increasing the storage volume inside the case 10, and in order to make the conductive plate 30 easily deformable so that it can be easily locked to the side wall portion 112, the thickness of the conductive plate 30 is preferably 0.5 mm or less, more preferably 0.4 mm or less, and particularly preferably 0.3 mm or less.

[0045] The conductive plate 30 is placed on the upper surface of the power generation element 20 after the power generation element 20 is housed inside the concave container 11. With the conductive plate 30 placed on the upper surface of the power generation element 20, the tip of the supported portion 31 is positioned between the upper surface of the power generation element 20 and the support portion 115, i.e., the lower surface of the top wall, in the axial direction of the power generation element 20 (up and down direction in Figure 1). Then, the supported portion 31 of the conductive plate 30 is pushed toward the bottom 111 of the concave container 11, thereby supporting the supported portion 31 with the support portion 115. More specifically, the tip of the supported portion 31 is locked to the support portion 115, i.e., the lower surface of the top wall. As the supported portion 31 is pushed downward, the spring piece 33 of the conductive plate 30 is pushed in the opposite direction to the electrode layer 22 while in contact with the power generation element 20. The spring piece 33 presses the power generation element 20 toward the bottom 111 of the concave container 11 by its elastic force. As a result, the conductive plate 30 makes more stable contact with the power generation element 20, and good electrical connection can be maintained without displacement due to vibration or the like. The spring piece 33 is not particularly limited as long as it can press the power generation element 20 toward the bottom 111 of the concave container 11 by its elastic force. In addition, the concave container 11 has two support parts 115, but the number of support parts 115 may be two or more. The supported part 31 can be formed according to the number of support parts 115. As an example of a method for fixing the edge (supported part 31) of the conductive plate 30 to the inner circumferential surface of the side wall 112 of the concave container 11, one example is to bond the edge of the conductive plate 30 to the inner circumferential surface of the side wall 112 of the concave container 11.

[0046] When the lid material 12 and the concave container 11 are welded together via the seal ring 15 as described above, the gap G between the conductive plate 30 and the lid material 12 suppresses the influence of welding heat on the power generation element 20. Furthermore, since the conductive plate 30 and the lid material 12 do not come into contact, the lid material 12 is not affected by the pressure from the conductive plate 30 when joining it to the upper end surface of the side wall portion 112 of the concave container 11, thereby further improving the sealing performance of the case 10.

[0047] (Modified Version) As shown in Figure 5, the modified conductive plate 30 has a spring piece 33 at its tip 332 that is bent in the direction opposite to the electrode layer 22. That is, the tip 332 is formed in a convex shape toward the electrode layer 22. It is preferable that the tip 332 has a convex curved surface toward the electrode layer 22. Alternatively, the tip 332 may be bent multiple times so that the tip 332 and the electrode layer 22 make surface contact. For example, by bending the tip 322 twice, a contact surface with the electrode layer 22 can be formed on the tip 332. This prevents the sharp part of the tip 332 from contacting and damaging the electrode layer 22.

[0048] The spring piece 33 in the first embodiment can be of various shapes, and multiple spring pieces may be provided on the conductive plate 30.

[0049] (Second Embodiment) Next, the electrochemical element 1 of the second embodiment will be described in detail with reference to Figure 6. In the electrochemical element 1 of this embodiment, the same configuration as the electrochemical element 1 of the first embodiment will be omitted from the explanation, and only the configuration that differs from the electrochemical element 1 of the first embodiment will be described.

[0050] In the electrochemical element 1 of this embodiment, the power generation element 20 has a porous metal substrate 24. The porous metal substrate 24 is positioned on the upper side of the electrode layer 22, that is, on the conductive plate 30 side, and makes electrical contact between the electrode layer 22 and the conductive plate 30 by contacting the tip 332 of the spring piece 33.

[0051] The porous metal substrate 24 is a porous metal substrate with a high porosity and voids penetrating from one surface to the other, similar to a foamed porous metal, and functions as a current collector. The porous metal substrate 24 is integrated with the portion of the electrode layer 22 on the conductive plate 30 side and constitutes a part of the electrode layer 22. To reduce electrical resistance, it is preferable that the porous metal substrate 24 not only contacts the electrode layer 22, but that at least a portion of it, excluding the end face on the conductive plate 30 side, is embedded in the negative electrode mixture of the electrode layer 22 and integrated with the electrode layer 22. As shown in Figure 6, the porous metal substrate 24 may also be placed on the lower side of the electrode layer 21, i.e., on the bottom 111 side, and it is preferable that at least a portion of the porous metal substrate 24, excluding the end face on the bottom 111 side, is embedded in the positive electrode mixture of the electrode layer 21 and integrated with the electrode layer 21.

[0052] The porosity of the porous metal substrate 24 is preferably 80% or more, and more preferably 90% or more, in order to easily adjust for variations in the thickness of the power generation element 20 due to compression. On the other hand, in order to ensure good conductivity, the porosity of the porous metal substrate 24 is preferably 99% or less. The thickness of the porous metal substrate 24 before assembling the electrochemical element 1 is preferably 0.1 mm or more, more preferably 0.3 mm or more, and particularly preferably 0.5 mm or more, while it is preferably 3 mm or less, more preferably 2 mm or less, and particularly preferably 1.5 mm or less.

[0053] By providing the porous metal substrate 24 in this way, the electrical resistance at the point of contact between the spring portion 33 and the power generation element 20 can be reduced.

[0054] (Third Embodiment) Next, the electrochemical element 1 of the third embodiment will be described in detail with reference to Figure 7. In the electrochemical element 1 of this embodiment, the same configuration as the electrochemical element 1 of the first embodiment will be omitted from the explanation, and only the configuration that differs from the electrochemical element 1 of the first embodiment will be described.

[0055] The electrochemical element 1 of this embodiment has a conductive sheet 40 between the electrode layer 22 and the conductive plate 30. In this embodiment, the conductive sheet 40 is a conductive carbon sheet made of expanded graphite, that is, a graphite sheet. The graphite sheet is manufactured as follows. First, particles of acid-treated graphite obtained by subjecting natural graphite to acid treatment are heated. Then, the acid-treated graphite expands as the acid between its layers vaporizes and foams. The expanded graphite (expanded graphite) is formed into a felt shape and further rolled using a roll rolling machine to form a sheet body. The conductive sheet 40 is manufactured by punching out a sheet body of this expanded graphite into a circular shape. As described above, expanded graphite is formed by the acid vaporizing and the acid-treated graphite foaming. Therefore, the graphite sheet is formed in a porous shape. Accordingly, the graphite sheet has both the conductivity of graphite itself and flexibility that conventional graphite products do not have. Note that the manufacturing method of the graphite sheet is not limited to this, and it may be composed of a material other than expanded graphite, and the graphite sheet may be manufactured by any method.

[0056] The apparent density of only the graphite sheet is preferably 0.3 g / cm ３ or more, more preferably 0.7 g / cm ３ or more, and preferably 1.5 g / cm ３ or less, more preferably 1.3 g / cm ３ or less. This is because if the apparent density of the graphite sheet is too low, the graphite sheet is likely to be damaged, and if the apparent density is too high, the flexibility decreases. Note that the apparent density is not limited to the graphite sheet, and is also applicable to the conductive sheet 40 formed of other materials such as conductive tape.

[0057] The thickness of the graphite sheet is preferably 0.05 mm or more, more preferably 0.07 mm or more, preferably 0.5 mm or less, and more preferably 0.2 mm or less. This is because if the thickness of the graphite sheet is too small, the graphite sheet is likely to be damaged, and if the thickness is too large, the internal space of the case 10 that houses the power generation element 20 is narrowed, and the volume (thickness) of the power generation element 20 that can be housed decreases.

[0058] As described above, by providing a conductive sheet 40 that is more flexible than the conductive plate 30, i.e., more easily deformable, the pressing force of the spring piece 33 of the conductive plate 30 is transmitted more uniformly to the power generation element 20, thereby suppressing damage to the power generation element 20 and stabilizing the electrical connection. The conductive sheet 40 may also be placed between the electrode layer 21 and the bottom 111 of the concave container 11, as shown in Figure 7. This further suppresses damage to the power generation element 20 and stabilizes the electrical connection.

[0059] In the first to third embodiments described above, electrode layer 21 functions as the positive electrode layer and electrode layer 22 functions as the negative electrode layer. However, electrode layer 21 may function as the negative electrode layer and electrode layer 22 may function as the negative electrode layer. In this case, external terminal 13 functions as the negative electrode terminal and external terminal 14 functions as the positive electrode terminal.

[0060] In the first to third embodiments described above, the power generation element 20 was constructed as a laminate formed by stacking an electrode layer 21, an electrode layer 22, and a solid electrolyte layer 23. However, by providing a separator (not shown) instead of the solid electrolyte layer 23 as an isolation layer, and housing the electrolyte together with the power generation element 20 in the internal space of the case 10, the electrochemical element can be a lithium-ion secondary battery, a lithium-ion capacitor, an electric double-layer capacitor, etc. In this case, the separator and electrolyte are those commonly used in lithium-ion secondary batteries, lithium-ion capacitors, or electric double-layer capacitors. Furthermore, the electrode layers 21 and 22 can be replaced with composite layers of positive and negative electrodes commonly used in various electrochemical elements 1.

[0061] Furthermore, according to the present invention, it is possible to contribute to Goal 7, "Affordable and Clean Energy," and Goal 12, "Responsible Consumption and Production," of the Sustainable Development Goals (SDGs) advocated by the United Nations.

[0062] First, the electrochemical element (all-solid-state battery) shown in Figure 8 was fabricated using the following procedure. Note that the electrochemical element in Figure 8 has the same configuration as the electrochemical element in Figure 1, except that the lid material does not have a recess.

[0063] More specifically, a conductive plate made of SUS304-CSP with a thickness of 0.2 mm was used, and the power generation element was housed in a concave ceramic container. The conductive plate was then secured to the side wall of the concave container, thereby creating electrical contact between the negative electrode layer of the power generation element and the conductor exposed on the inner surface of the side wall of the concave container via the conductive plate. Furthermore, approximately 10 －３ Under a Pa vacuum environment, a lid made of an iron-nickel-cobalt alloy (Ni content: 29% by mass, Co content: 17% by weight) measuring 10 mm x 10 mm and having a thickness of 0.1 mm was joined to the side wall of a concave container via a sealing ring to seal the inside of the case, thereby fabricating an electrochemical element A, shown in Figure 8, measuring 10.5 mm x 10.5 mm and having a height of 4 mm. In this state, the gap formed between the conductive plate and the lid was 0.3 mm.

[0064] Furthermore, electrochemical element B was fabricated in the same manner as electrochemical element A, except that the lid material was not completely joined. In addition, electrochemical element C was fabricated in the same manner as electrochemical element A, except that the gap between the conductive plate and the lid material was set to 0.1 mm.

[0065] When each electrochemical element was left exposed to the air after assembly, the cover material deformed inward (towards the power generation element), forming a depression, as shown in Figure 1. Using a laser displacement meter, the depth D of the depression was measured to be 0.06 mm for electrochemical elements A and C, and 0.02 mm for electrochemical element B. Therefore, after the deformation of the cover material, the gap G formed between the conductive plate and the cover material was 0.24 mm for electrochemical element A, 0.28 mm for electrochemical element B, and 0.04 mm for electrochemical element C.

[0066] [Evaluation of Sealing Performance] The sealing performance of each electrochemical element case was confirmed using the "Helium Leakage Test Method" (Bombing Method) described in Japanese Industrial Standard JIS-Z2331. After placing the electrochemical elements in a tank and pressurizing them with helium gas for 2 hours, the area around the electrochemical elements was evacuated in a vacuum chamber for 1 minute to determine the amount of helium gas leakage. For electrochemical elements A and C, where the depth D of the recess in the lid material was 0.06 mm, the leakage amount after 10 minutes was 1 × 10⁻⁶.－１０ Pa・m ３ The leakage rate was less than / s, confirming excellent sealing performance. On the other hand, in electrochemical element B, where the depth of the recess D was small at 0.02 mm, the leakage amount after 10 minutes was 1 × 10⁻⁶. －９ Pa・m ３ It was confirmed that batteries with a value greater than / s and small deformation of the lid material were insufficiently sealed. Therefore, by pre-measuring the depth D of the indentation in the lid material of a properly sealed electrochemical element, it is possible to easily determine the quality of the sealing of the electrochemical element from the amount of deformation of the lid material.

[0067] Furthermore, as with electrochemical element B, even if the sealing is insufficient, the depth D of the indentation in the lid material may exceed 0.02 mm immediately after being left exposed to the atmosphere. However, with insufficiently sealed electrochemical elements, the pressure difference between the internal and external spaces of the case disappears over time, and the indentation depth D actually becomes less than 0.02 mm. Therefore, such electrochemical elements are distinguished from the present invention.

[0068] [Relationship between lid dimensions and recess depth D] Table 1 shows the recess depth D of the lid when the dimensions of the lid (length of one side and thickness) are changed, and the dimensions of components such as recessed containers are changed accordingly for sealing. From the results in Table 1, it was found that the recess depth D can be adjusted to a certain range by adjusting the dimensions of the lid.

[0069]

[0070] [Vibration Test] A test was conducted in which sinusoidal vibrations were sequentially applied to the three directions (length, width, and height) of electrochemical elements A and C. The sinusoidal sweep was performed as a logarithmic sweep, moving back and forth over 15 minutes in the range of 7 Hz to 200 Hz while changing the frequency, and this sweep was repeated 12 times in each of the three directions. Between 7 Hz and 18 Hz, the sweep was performed so that the peak acceleration was maintained at 1 G. From 18 Hz onward, the sweep was performed up to the frequency (approximately 50 Hz) where the peak acceleration reached 8 G while maintaining the total amplitude at 0.8 mm, and further up to 200 Hz, the sweep was performed so that the peak acceleration was maintained at 1 G.

[0071] ​Upon checking the electrochemical elements after testing to see if contact had occurred between the conductive plate and the lid, it was found that in electrochemical element A, there was sufficient space between the conductive plate and the lid, so there was no contact between them. However, in electrochemical element C, the space between the conductive plate and the lid was insufficient, and when an impact was applied to electrochemical element C, the conductive plate and the lid came into contact, resulting in electrical conductivity between the negative electrode layer and the lid.

[0072] Although embodiments have been described above, this disclosure is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the disclosure.

[0073] 1 Electrochemical element, 10 Case, 11 Concave container, 12 Lid material, 13 External terminal, 14 External terminal, 15 Seal ring, 111 Bottom, 112 Side wall, 113 Conductor part, 114 Conductor part, 115 Support part, 20 Power generation element, 30 Conductive plate, 31 Supported part, 32 Flat part, 33 Spring piece, 331 Boundary, 332 Tip, 40 Conductive sheet, G Gap, D Depth

Claims

1. An electrochemical element comprising: a case having a concave container having a bottom and side walls and a metal lid covering the opening of the concave container; a power generation element sealed inside the case and having a first electrode layer disposed on the bottom side, a second electrode layer disposed on the lid side, and an isolation layer disposed between the first electrode layer and the second electrode layer; and a conductive plate disposed between the power generation element and the lid, wherein the first electrode layer is electrically connected to a first conductive path leading from the inside to the outside of the case, the second electrode layer is electrically connected to a second conductive path leading from the inside to the outside of the case via the conductive plate, the lid is recessed toward the conductive plate due to the internal space of the case being under reduced pressure compared to the external space of the case, the depth of the recess in the lid is 0.02 mm or more, and a gap of 0.05 mm or more is formed between the conductive plate and the lid.

2. An electrochemical element according to claim 1, wherein the conductive plate includes a flat portion facing the power generation element and a spring portion rising from the flat portion and pressing the power generation element toward the bottom of the concave container.

3. An electrochemical element according to claim 2, wherein the spring portion is cantilevered to the flat portion and has a spring piece that presses the power generation element toward the bottom of the concave container.

4. An electrochemical element according to claim 3, wherein the tip of the spring piece is bent in the direction opposite to the power generation element.

5. An electrochemical element according to claim 1, wherein the conductive plate is locked to the side wall of the concave container in a plan view, outside the outer edge of the power generation element.

6. An electrochemical element according to claim 1, wherein the depth of the recess in the lid material is 0.2 mm or less.

7. An electrochemical element according to claim 1, wherein the size of the gap formed between the conductive plate and the lid material is 0.5 mm or less.

8. An electrochemical element according to claim 1, wherein the power generation element has a porous metal substrate integrated with the conductive plate side portion of the second electrode layer.

9. An electrochemical element according to any one of claims 1 to 8, wherein the amount of helium gas leaked based on the "helium leak test method" (bombing method) described in Japanese Industrial Standard JIS-Z2331 is 1 × 10⁻⁶ －１０ Pa・m ３ An electrochemical element with a value of less than or equal to / s.

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