Energy storage devices

Abstract

An electricity storage device 200 comprises: a case 210 in the shape of a bottomed cylinder; a wound element 100 accommodated in the case and having an end surface to which a current collector is exposed; a current collector plate 14 joined to the end surface of the wound element; and sealing rubber 220 which is accommodated in an opening portion of the case, and which is pressed by a side surface portion of the case to seal the case. At least one protruding portion 221 which projects toward the current collector plate is provided in an opposing surface of the sealing rubber 220 that opposes the current collector plate. At least one of the protruding portions 221 is in contact with the current collector plate 14.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an electrical storage device.

BACKGROUND ART

[0002] Along with the expanding demand for in-vehicle applications and the like, electrical storage devices typified by secondary batteries are required to have even higher output and higher capacity. As a current collecting structure for obtaining high output, a so-called end face current collecting structure has been studied, in which exposed portions of a negative electrode current collector or a positive electrode current collector are protruded from the end face of a wound electrode group and welded to a current collecting plate.

[0003] Patent Document 1 describes an electrical storage device that includes: an electrical storage element having a first electrode and a second electrode and having a first end portion from which the first electrode is drawn out; an electrolyte with which the electrical storage element is impregnated; a terminal plate having an element connection portion electrically connected to the first electrode at the first end portion and an external terminal portion connected to the element connection portion; a cylindrical exterior body having an opening and accommodating the electrical storage element together with an electrolytic solution; and a sealing member having an insertion hole into which the external terminal portion is inserted and sealing the opening of the exterior body together with the external terminal portion. The external terminal portion is a columnar body or a cylindrical body having a tapered portion on the outer periphery of the tip end, and in the direction extending from the bottom surface of the exterior body to the opening, the edge of the side wall at the opening of the exterior body is located between both end portions of the tapered portion.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0004]

PATENT DOCUMENT 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] The energy storage device described in Patent Document 1 is manufactured by stacking energy storage elements, terminal boards, and sealing members while inserting them into a bottomed cylindrical outer casing (battery can), and then crimping the open end of the battery can to the sealing member. In this case, the component tolerances and assembly tolerances of the energy storage elements, terminal boards, and sealing member accumulate in the axial direction of the battery can, resulting in large positional variations in the sealing member in the axial direction. As a result, the adhesion between the crimped portion of the battery can and the sealing member may decrease, and the sealing strength may decrease. [Means for solving the problem]

[0006] One aspect of the present disclosure relates to an energy storage device comprising a bottomed cylindrical case, a wound element housed in the case with a current collector exposed at its end face, a current collector plate joined to the end face of the wound element, and a sealing rubber housed in an opening in the case and sealing the case by being pressed through the side surface of the case, wherein at least one protrusion is provided on the opposing surface of the sealing rubber facing the current collector plate, and at least one of the protrusions is in contact with the current collector plate.

[0007] Novel features of the present invention are described in the appended claims, but the present invention, both in terms of structure and content, and in conjunction with other objects and features of the present invention, will be better understood by the following detailed description in conjunction with the drawings. [Effects of the Invention]

[0008] This allows for a high degree of adhesion between the case and the sealing material, thereby suppressing a decrease in sealing strength. [Brief explanation of the drawing]

[0009] [Figure 1] This is a longitudinal cross-sectional view showing the configuration of an energy storage device according to an embodiment of this disclosure. [Figure 2] These are a side view and a top view of the sealing rubber used in an energy storage device according to an embodiment of this disclosure, in an unloaded state. [Figure 3] This figure shows an example of the arrangement of the protrusions that are positioned on the surface of the sealing rubber facing the current collector plate. [Figure 4] This figure shows an example of the arrangement of the protrusions that are positioned on the surface of the sealing rubber facing the current collector plate. [Figure 5] This figure shows an example of the arrangement of the protrusions that are positioned on the surface of the sealing rubber facing the current collector plate. [Figure 6] This figure shows an example of the protruding shape of the convex part of the sealing rubber. [Figure 7] This figure shows an example of the protruding shape of the convex part of the sealing rubber. [Modes for carrying out the invention]

[0010] Embodiments of this disclosure will be described below. While the embodiments of this disclosure will be described with examples, this disclosure is not limited to the examples described below. The following description may include specific numerical values, materials, etc., but other numerical values, materials, etc. may be applied as long as the effects of this disclosure are achieved. In this specification, the phrase "numerical value A to numerical value B" includes numerical value A and numerical value B, and can be interpreted as "greater than or equal to numerical value A and less than or equal to numerical value B." In the following description, when lower and upper limits of numerical values ​​relating to specific physical properties or conditions are given as examples, either of the given lower limits and either of the given upper limits can be arbitrarily combined, as long as the lower limit is not greater than or equal to the upper limit. When multiple materials are given as examples, one may be selected and used alone, or two or more may be used in combination.

[0011] Furthermore, this disclosure encompasses any combination of matters described in two or more claims, which may be arbitrarily selected from the multiple claims set forth in the attached claims. In other words, any combination of matters described in two or more claims, which may be arbitrarily selected from the multiple claims set forth in the attached claims, is possible, provided that no technical inconsistency arises.

[0012] An energy storage device according to one embodiment of the present disclosure comprises a bottomed cylindrical case, a winding element housed in the case with a current collector exposed at its end face, a current collector plate joined to the end face of the winding element, and a sealing rubber housed in the opening of the case and sealing the case by being pressed through the side surface of the case. At least one protrusion is provided on the opposing surface of the sealing rubber facing the current collector plate, projecting toward the current collector plate. At least one of the protrusions is in contact with the current collector plate.

[0013] Energy storage devices are manufactured by housing a wound element, a current collector plate, and a sealing rubber in that order within a case, and then crimping the open end of the case to the sealing rubber to seal the opening of the case. In this case, the manufacturing process of the energy storage device can be simplified, but the tolerances of each component, such as the wound element, current collector plate, and sealing rubber, and the assembly tolerances are stacked in the axial direction of the case (the direction in which the cylindrical part of the cylindrical case extends), making it easy for the positional variation of the sealing rubber in the axial direction to become large.

[0014] The protrusions on the sealing rubber are appropriately compressed and / or deformed when in contact with the current collector plate, absorbing or offsetting material tolerances and assembly tolerances during device manufacturing. This allows the sealing rubber to adhere tightly to the case, resulting in consistently high sealing strength.

[0015] Due to tolerances in the components and assembly of the winding element and current collector plate, variations occur in the height of the current collector plate relative to the bottom of the case. Depending on these variations, the height of the sealing rubber relative to the bottom of the case may also change. If the case opening is sealed with variations in the height of the sealing rubber, for example, the length of the curled portion at the opening end of the case that is crimped to the sealing rubber may change, which can lead to variations in the tightness of the seal between the sealing rubber and the case, depending on the height of the sealing rubber.

[0016] However, in the power storage device according to the present embodiment, since the sealing rubber is provided with the convex portion, the opening end of the case can be caulked to the sealing rubber in a state where the sealing rubber is positioned at a fixed height relative to the bottom of the case, and sealing can be performed with the length of the curled portion kept constant, so that the sealing strength can be stably maintained at a high level. For example, during assembly, if the height of the current collector plate relative to the bottom of the case is high due to component tolerances and assembly tolerances, the deformation amount or compression amount of the convex portion is large, and if the height is low, the deformation amount or compression amount of the convex portion is small. That is, the convex portion is deformed and / or compressed according to the tolerances, which facilitates performing the sealing while keeping the height of the sealing rubber constant.

[0017] A plurality of convex portions may be provided on the facing surface of the sealing rubber that faces the current collector plate. The plurality of convex portions may be arranged intermittently along the circumferential direction of the current collector plate. The plurality of convex portions may be arranged intermittently along the circumferential direction at positions that are equiangular with respect to the center position of the sealing rubber, or may not necessarily be equiangular.

[0018] The cross-sectional shape of the convex portion in the plane perpendicular to its protruding direction is not particularly limited, and may be a circle, a square, or a regular polygon. The cross-sectional shape may be a shape such as a rectangle, in which the width in a specific first direction is larger than the width in a second direction intersecting the first direction (a shape with a large aspect ratio). The protruding direction is usually a direction perpendicular to the facing surface, and is parallel to the direction in which the cylindrical portion of the case extends. The cross-sectional shape may be an arc or an arcuate shape. In that case, the arc or arcuate shape preferably extends along the circumferential direction of the current collector plate.

[0019] A slit (groove) may be provided on the contact surface of the convex portion with the current collector plate. Thereby, when the convex portion comes into contact with the current collector and receives pressure, each part of the convex portion divided by the slit is easily deformed, and the effect of absorbing component tolerances and assembly tolerances is enhanced. The slit may have a cross shape.

[0020] The protruding portion may have a side surface perpendicular to its protruding direction. The protruding portion having a side surface perpendicular to the protruding direction may have a columnar shape. However, the present invention is not limited thereto, and the protruding portion may have a side surface inclined in the protruding direction. The side surface is inclined such that the cross-sectional area in the plane perpendicular to the protruding direction decreases toward the tip of the protruding portion (that is, the tip is sharpened). The protruding portion may have a plurality of side surfaces with different inclination angles with respect to the protruding direction within the protruding portion. In this case, the direction in which the protruding portion deforms can be easily controlled.

[0021] For example, the inclination angle can be varied within the protruding portion such that the inclination angle of the side surface of the protruding portion with respect to the protruding direction is larger on the side closer to the central axis of the sealing rubber than on the side farther from the central axis. In this case, when the protruding portion comes into contact with the current collector and receives pressure, the protruding portion is easily deformed so as to fall outward in the radial direction in the direction away from the central axis. This suppresses the sealing rubber from tilting relative to the current collector plate as the protruding portion deforms.

[0022] At least one of the protruding portions preferably presses the current collector plate. However, the protruding portion is configured to receive stress from the pressurization and deform at a stress lower than the stress at which the wound element buckles, so that the wound element is not subjected to deformation such as buckling due to the pressurization. The stress received by the protruding portion can be adjusted by the protrusion height of the protruding portion, the shape and area of the cross section in the plane perpendicular to the protruding direction, the number of the protruding portions, and the like. For example, in the case of an 18715-type cylindrical device with a diameter of 18.0 mm and a height of 71.5 mm, in which the sealing rubber is butyl rubber (Young's modulus at room temperature of 10 to 20 MPa), the protrusion height, cross-sectional shape and cross-sectional area of the protruding portions, the number of the protruding portions, and the like can be adjusted such that the repulsive force generated by the deformation of the protruding portions falls within the range of 50 N to 240 N.

[0023] The protrusion height of the protruding portion is, for example, in the range of 0.5 mm to 2.0 mm. When the cross-sectional shape is a circle, the size of the protruding portion is, for example, in the range of 1.0 mm to 2.0 mm in diameter. Such a protruding portion is also compatible with the 18715-type cylindrical device described above.

[0024] When multiple protrusions are provided, their protruding heights may be made different between them.

[0025] A counterbore (recess) may be provided on the opposing surface of the sealing rubber, and a protrusion may be placed within the counterbore. This allows the height of the protrusion to be increased, making it more easily deformable. As a result, the effect of absorbing material tolerances and assembly tolerances is enhanced. The depth of the counterbore relative to the opposing surface is, for example, 0.1 mm to 1.5 mm.

[0026] In this disclosure, the energy storage device includes batteries such as lithium-ion secondary batteries and lithium primary batteries, and capacitors such as lithium-ion capacitors and electric double-layer capacitors. The positive and negative electrodes of the energy storage device may be polarizable electrodes or non-polarizable electrodes, respectively. An energy storage device according to one embodiment of this disclosure can be adopted in any energy storage device structure, regardless of whether it is a primary or secondary battery, and regardless of the configuration of the positive and negative electrodes. The energy storage device is suitable for configuration as, for example, a non-aqueous electrolyte secondary battery, an alkaline storage battery, or a capacitor, and contributes to increasing the output power of non-aqueous electrolyte batteries. Non-aqueous electrolyte batteries include lithium-ion secondary batteries and all-solid-state batteries.

[0027] Below, an energy storage device according to one embodiment of this disclosure will be specifically described with reference to the drawings, using a lithium-ion secondary battery as an example.

[0028] Figure 1 is a longitudinal cross-sectional view showing the configuration of the battery 200 according to this embodiment. Figure 2 is a cross-sectional view and a top view of the sealing rubber 220 used in the battery 200 in an unloaded state. Figure 2(A) is a cross-sectional view along the line X1-X2 in Figure 2(B), and Figure 2(B) is a top view of the sealing rubber 220 as seen from the side facing the current collector plate 14.

[0029] The battery 200 comprises a winding element 100 formed in a columnar shape by winding a positive electrode 10 and a negative electrode 20 via a separator 30, a non-aqueous electrolyte (not shown), a metal bottomed case 210 housing the winding element 100 and the non-aqueous electrolyte, a sealing rubber 220 sealing the opening of the case 210, a current collector plate 14, and terminals 230.

[0030] The sealing rubber 220 has a through hole 223 in the center, through which the terminal 230 is inserted. One end of the terminal 230 is electrically connected to the current collector plate (positive electrode current collector plate) 14. The other end of the terminal 230 is exposed to the outside of the battery 200 and functions as an external terminal of the battery 200 (external positive electrode terminal in the example in Figure 1).

[0031] The sealing rubber 220 is pressed against the side portion (cylindrical portion) 210a of the case 210, and the inside of the case 210 is sealed by crimping the open end of the case 210 to the sealing rubber 220. A curled portion 210b is formed at the open end of the case 210 by the crimping.

[0032] On the opposing surface of the sealing rubber that faces the current collector plate 14, a protrusion 221 is provided that protrudes toward the current collector plate 14. The protrusion 221 can contact the current collector plate 14 or, under pressure, can contact the current collector plate 14. The protrusion 221 can also contact the current collector plate 14 while compressed or deformed by pressure.

[0033] In the example shown in Figure 2(B), four protrusions 221 are arranged at equiangled positions in the circumferential direction. However, the present invention is not limited to the number of protrusions. There may be multiple protrusions 221, or there may be just one. One or more protrusions 221 may be arranged in positions that do not interfere with the electrolyte injection port provided on the current collector plate 14.

[0034] The more protrusions 221 are provided on the opposing surfaces, the less likely the sealing rubber is to be inserted into the case at an angle relative to the bottom of the case, allowing the sealing rubber to be positioned horizontally within the case and improving assembly stability.

[0035] In the examples shown in Figures 1 and 2, the protrusion 221 is positioned within a counterbore (recess) 222 provided on the opposing surface of the sealing rubber that faces the current collector plate 14. This increases the protruding height of the protrusion 221, making it more susceptible to compression or deformation under pressure. However, the present invention is not limited to this, and as shown in the following examples, the protrusion 221 may be positioned within a flat area of ​​the opposing surface.

[0036] The non-aqueous electrolyte is lithium ion conductive and contains a lithium salt and a non-aqueous solvent that dissolves the lithium salt.

[0037] The positive electrode 10 is in the form of a long sheet and comprises a positive electrode current collector and a positive electrode active material layer supported thereon. The positive electrode active material layer is formed on both sides of the positive electrode current collector. However, a positive electrode current collector exposed portion 11x without the positive electrode active material layer may be formed at one end along the longitudinal direction of the positive electrode current collector. The positive electrode current collector exposed portion 11x is exposed on one end face of the winding element 100, and the positive electrode is electrically connected to the current collector plate 14 via the positive electrode current collector exposed portion 11x. The positive electrode current collector exposed portion 11x is connected to the current collector plate 14, for example, by welding. On the other hand, the other end along the longitudinal direction of the positive electrode current collector is covered with an insulating layer 13.

[0038] The negative electrode 20 is in the form of a long sheet and comprises a negative electrode current collector and a negative electrode active material layer supported thereon. The negative electrode active material layer is formed on both sides of the negative electrode current collector. However, one end of the negative electrode current collector along the longitudinal direction (the end opposite to the positive electrode current collector exposed portion 11x) has a negative electrode current collector exposed portion 21x which does not have the negative electrode active material layer. The negative electrode current collector exposed portion 21x is exposed on the other end face of the winding element 100, and the negative electrode is electrically connected to the current collector plate (negative electrode current collector plate) 24 via the negative electrode current collector exposed portion 21x. The negative electrode current collector exposed portion 21x is connected to the current collector plate 24 by welding, for example. On the other hand, the other end of the negative electrode current collector along the longitudinal direction is covered with an insulating layer 23. The current collector plate 24 is welded to a welding member 25 provided on the inner bottom surface of the case 210. Therefore, case 210 functions as an external negative terminal.

[0039] Figures 3 to 5 show other examples of the arrangement of the protrusions 221 positioned on the surface of the sealing rubber facing the current collector plate 14. Each of the figures 3 to 5 is a top view of the sealing rubber as seen from the side facing the current collector plate 14.

[0040] Figure 3(a) shows an example in which three protrusions 221 are arranged at equilateral angles to each other in the circumferential direction. Figure 3(b) shows an example in which two protrusions 221 are arranged at equilateral angles to each other in the circumferential direction (i.e., opposite each other with the through hole 223 located in the center of the sealing rubber). Figure 3(c) shows an example in which eight protrusions 221 are arranged on opposing surfaces. The eight protrusions 221 can be arranged symmetrically while avoiding the electrolyte injection port provided on the current collector plate 14.

[0041] Only one protrusion 221 may be provided on the opposing surface. Figure 4(a) shows an example in which one protrusion 221 is positioned at the center of the sealing rubber. In this example, two through holes 223 are positioned opposite each other, with the protrusion 221 in between.

[0042] Figure 4(b) shows an example of the configuration of the sealing rubber when the present invention is applied to an elliptical or track-shaped cylindrical device. Two protrusions 221 are located at both ends in the longitudinal direction of the sealing rubber having a track-shaped cross-section.

[0043] Figure 5 shows an example of another configuration of the sealing rubber, where Figure 5(a) is a top view of the sealing rubber viewed from the opposite surface, and Figure 5(b) is a side view of the sealing rubber. In this example, eight protrusions 221 are arranged on the opposite surface. The eight protrusions 221 consist of four protrusions 221A positioned at equilateral angles to each other in the circumferential direction, and four protrusions 221B positioned radially outward from the protrusions 221A and at equilateral angles to each other in the circumferential direction. The protrusion height of the protrusions 221B is greater than the protrusion height of the protrusions 221A.

[0044] Furthermore, Figures 6 and 7 show examples of the protruding shape of the convex portion 221. In the examples shown in Figures 6(a) to (e) and Figures 7(a) and (b), the upper diagram is a side view of the convex portion viewed from a direction perpendicular to the protruding direction, and the lower diagram is a top view viewed from the protruding surface (the surface opposite the current collector plate).

[0045] As shown in Figures 6(a) and (b), the protrusion 221 may be a cylinder or a rectangular prism. The protrusion 221 has a side surface perpendicular to its protruding direction. In these cases, the protrusion 221 has a simple shape and is easy to manufacture.

[0046] Furthermore, as shown in Figures 6(c) and (d), the side surface of the protrusion 221 perpendicular to its protruding direction may be inclined. The inclined side surface may form a pointed tip for the protrusion 221. The inclined side surface may be a curved surface, may be formed by one or more planes, or may include a combination thereof. Figure 6(c) shows an example in which the tip of the protrusion 221 is formed by a curved surface, and an example in which the tip of the protrusion 221 is formed by a spherical or ellipsoidal surface. Figure 6(d) shows an example in which the tip of the protrusion 221 is formed in the shape of a frustocone. In these cases, the protrusion 221 is easy to process and easily deformed.

[0047] Figure 6(e) shows an example in which the protrusion 221 has multiple sides with different inclination angles with respect to the direction of protrusion. In the example shown in Figure 6(e), the tip of the protrusion 221 is notched, thereby forming an inclined side. In this case, the protrusion 221 is easy to process and is more easily deformed, and is particularly susceptible to deformation that causes it to tilt toward the opposite side of the notched surface.

[0048] In Figure 7(a), a slit is provided at the tip of the protrusion 221. The slit divides the tip of the protrusion 221 into multiple parts. Since each part divided by the slit can be deformed independently, the protrusion 221 is easily deformable. In the example in Figure 7(a), the shape of the slit is cross-shaped, but it is not limited to this.

[0049] Figure 7(b) shows an example where the cross-sectional shape of the protrusion 221 on the plane perpendicular to the protrusion direction is an arc shape. The arc-shaped protrusion 221 has greater rigidity and is less prone to deformation compared to the examples shown in Figures 6(a) to (e) and Figure 7(a), but it is also possible to use the protrusion 221 shown in Figure 7(b) depending on the structure of the device.

[0050] (Sealing rubber) Using rubber material as a sealing component provides a stable sealing repulsion force, improving the airtightness of the energy storage device. Furthermore, because the protrusions are made of rubber, they deform when they come into contact with the current collector and are subjected to pressure, absorbing component tolerances and assembly tolerances. Sealing rubber with protrusions is manufactured, for example, by molding techniques such as compression molding.

[0051] On the other hand, rubber materials are prone to deformation in response to increased internal pressure, which can result in insufficient rigidity from the standpoint of preventing blistering. To improve the rigidity of the sealing rubber and achieve both high sealing resilience and blistering suppression, the sealing rubber may be made into a laminated structure having at least two layers: a rubber material layer (e.g., a butyl rubber layer) and a fluororesin layer. In that case, the protrusions are provided in the rubber material layer.

[0052] The Young's modulus of the rubber material layer may be in the range of 4 MPa to 80 MPa, depending on the ambient temperature. In contrast, the Young's modulus of the fluororesin may be 0.4 GPa or higher as a general value.

[0053] The sealing rubber may consist of a single layer of rubber material containing rubber material, or it may be a multilayer structure of rubber material layer and fluororesin layer. Butyl rubber (isobutylene-isoprene copolymer) (IIR) is preferred as the rubber material. Butyl rubber can be given stable elasticity by peroxide crosslinking or resin crosslinking, and a stable sealing repulsion force can be obtained. Because butyl rubber has lower gas permeability and higher insulation properties compared to other rubber materials, the performance of the energy storage device can be maintained at a high level even during long-term storage.

[0054] Preferred materials for the fluororesin layer include PTFE (polytetrafluoroethylene), PVDF (polyvinylidene fluoride), PFA (perfluoroalkoxyalkane), ETFE (ethylene-tetrafluoroethylene copolymer), and FEP (perfluoroethylene-propene copolymer). When forming a multilayer structure of a butyl rubber layer and a fluororesin layer, it is preferable to roughen the surface of the fluororesin layer on the butyl rubber layer side by corona treatment, plasma treatment, sodium treatment, or application of an organic solvent containing activated sodium to improve adhesion with the butyl rubber layer, and then perform compression molding.

[0055] (Current collector plate) The material used to construct the current collector plate is determined according to the materials used to construct the positive and negative electrodes. For example, when used as the negative electrode current collector plate in a lithium-ion secondary battery, the material of the current collector plate may be copper, copper alloy, nickel, stainless steel, etc. The material of the negative electrode current collector plate may be the same as the material of the negative electrode current collector. For example, when used as the positive electrode current collector plate in a lithium-ion secondary battery, the material of the current collector plate may be aluminum, aluminum alloy, titanium, stainless steel, etc. The material of the positive electrode current collector plate may be the same as the material of the positive electrode current collector.

[0056] The exposed portion of the current collector and the current collector plate can be joined, for example, by laser welding. The laser can be irradiated radially at multiple points from, for example, the opposite side of the surface facing the end face of the winding element of the current collector plate (i.e., the side facing the sealing rubber).

[0057] (positive electrode) A sheet-like metal material is used for the positive electrode current collector. This sheet-like metal material can be metal foil, porous metal, etched metal, etc. Suitable metal materials include aluminum, aluminum alloys, nickel, and titanium. The thickness of the positive electrode current collector is, for example, 10 μm to 100 μm.

[0058] The positive electrode active material layer includes, for example, a positive electrode active material, a conductive material, and a binder. The positive electrode active material layer can be obtained, for example, by applying a positive electrode mixture slurry containing the positive electrode active material, conductive material, and binder to both sides of a positive electrode current collector, drying the coating, and then rolling it. The positive electrode active material is a material that intercepts and releases lithium ions. Examples of positive electrode active materials include lithium-containing transition metal oxides, transition metal fluorides, polyanions, fluorinated polyanions, and transition metal sulfides.

[0059] When the energy storage device is a capacitor such as a lithium-ion capacitor or an electric double-layer capacitor, the positive electrode active material layer may include a positive electrode active material to which anions are reversibly doped. When anions are adsorbed onto the positive electrode active material, an electric double layer is formed, and capacitance is exhibited. The positive electrode may be a polarizable electrode, or it may be an electrode that has the properties of a polarizable electrode while also contributing to capacitance through the Faraday reaction. Examples of positive electrode active materials include carbon materials and conductive polymers.

[0060] As the conductive polymer, π-conjugated polymers are preferred. Examples of π-conjugated polymers include polypyrrole, polythiophene, polyfuran, polyaniline, polythiophene vinylene, polypyridine, or derivatives thereof. These may be used individually or in combination of two or more. The weight-average molecular weight of the conductive polymer is, for example, 1,000 to 1,000,000. A derivative of a π-conjugated polymer refers to a polymer whose basic skeleton is a π-conjugated polymer such as polypyrrole, polythiophene, polyfuran, polyaniline, polythiophene vinylene, or polypyridine. For example, polythiophene derivatives include poly(3,4-ethylenedioxythiophene) (PEDOT).

[0061] As the carbon material, porous carbon materials are preferred, such as activated carbon and the carbon materials exemplified as negative electrode active materials (e.g., non-graphitizable carbon). Examples of raw materials for activated carbon include wood, coconut shells, coal, pitch, and phenolic resin. It is preferable that the activated carbon has been activated.

[0062] (Negative electrode) A sheet-like metal material is used for the negative electrode current collector. This sheet-like metal material can be metal foil, porous metal, etched metal, etc. Suitable metal materials include copper, copper alloys, nickel, and stainless steel. The thickness of the negative electrode current collector is, for example, 10 μm to 100 μm.

[0063] The negative electrode active material layer includes, for example, a negative electrode active material, a conductive agent, and a binder. The negative electrode active material layer can be obtained, for example, by applying a negative electrode composite slurry containing the negative electrode active material, conductive agent, and binder to both sides of a negative electrode current collector, drying the coating, and then rolling it. The negative electrode active material is a material that intercepts and releases lithium ions. Examples of negative electrode active materials include carbon materials, metal compounds, alloys, and ceramic materials. Examples of carbon materials include graphite and hard carbon.

[0064] (Separator) As the separator, for example, a microporous membrane made of resin such as polyolefin, a woven fabric, or a nonwoven fabric can be used. The thickness of the separator is, for example, 10 to 300 μm, and preferably 10 to 40 μm.

[0065] (Non-aqueous electrolytes) The non-aqueous electrolyte is lithium ion conductive and contains a lithium salt and a non-aqueous solvent that dissolves the lithium salt.

[0066] Although the present invention has been described in relation to preferred embodiments at present, such disclosure should not be interpreted restrictively. Various modifications and alterations will undoubtedly become apparent to those skilled in the art in the field to which the invention pertains by reading the above disclosure. Accordingly, the appended claims should be interpreted as encompassing all modifications and alterations without departing from the true spirit and scope of the invention. [Industrial applicability]

[0067] The current collector plate according to this disclosure is suitable for automotive applications, for example, because it can be used to realize a high-output energy storage device. [Explanation of Symbols]

[0068] 100: Winding element 10: Positive electrode 11x: Positive electrode current collector exposed part 13: Insulating layer 14: Current collector plate (positive electrode current collector plate) 20: Negative electrode 21x: Negative electrode current collector exposed part 23: Insulating layer 24: Current collector plate (negative electrode current collector plate) 30: Separator 200: Battery (energy storage device) 210: Case 210a: Side part 210b: Curl section 220: Sealing rubber 221, 221A, 221B: Convex part 222: Counterbore (recess) 223: Through hole 230: Terminal

Claims

1. A cylindrical case with a bottom, A winding element housed in the aforementioned case, with a current collector exposed at its end face, A current collector plate joined to the end face of the winding element, The case comprises a sealing rubber that is housed in the opening of the case and is pressed against the side of the case to seal the case, The sealing rubber is provided with at least one protrusion that projects toward the current collector plate on the opposing surface facing the current collector plate. An energy storage device in which at least one of the protrusions is in contact with the current collector plate.

2. The energy storage device according to claim 1, having a plurality of the aforementioned protrusions on the opposing surfaces.

3. The energy storage device according to claim 1, wherein the cross-sectional shape of the protrusion on a plane perpendicular to its protruding direction is arc-shaped.

4. The energy storage device according to claim 1, wherein a slit is provided on the contact surface of the protrusion with the current collector plate.

5. The energy storage device according to claim 4, wherein the slit is cross-shaped.

6. The energy storage device according to claim 1, wherein the protrusion has a side surface inclined with respect to the direction of protrusion such that the area of ​​the cross-section on the plane perpendicular to the direction of protrusion decreases as it approaches its tip.

7. The energy storage device according to claim 6, wherein the angle of inclination of the side surface of the protrusion with respect to the protruding direction is greater on the side closer to the central axis of the sealing rubber than on the side further from the central axis.

8. The energy storage device according to any one of claims 1 to 7, wherein at least one of the protrusions pressurizes the current collector plate.

9. The energy storage device according to any one of claims 1 to 7, wherein the convex portion deforms at a stress lower than the stress at which the winding element buckles.

10. A counterbore portion is provided on the opposing surface of the sealing rubber. The energy storage device according to any one of claims 1 to 7, wherein the protrusion is disposed within the counterbore portion.

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