Energy storage device

Abstract

To provide a power storage element capable of improving reliability.SOLUTION: An energy storage device 10 includes an electrode assembly 200 in which an electrode plate is wound and which has recessed parts 221 at both ends in a winding axis direction, a container 100 which houses the electrode assembly 200, and an insulating cushioning material 700 which is arranged in the recessed part 221 and is smaller than the recessed part 221 when viewed from the winding axis direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an energy storage element including an electrode assembly and a container that houses the electrode assembly. [Background technology]

[0002] Conventionally, there has been known an energy storage element including an electrode assembly and a container that houses the electrode assembly. For example, in Patent Document 1, a wound electrode assembly is housed in a metal container. A pair of current collectors is housed in the container, and each current collector is joined to a positive electrode terminal and a negative electrode terminal fixed to the wall of the container. The pair of current collectors support the electrode assembly within the container while being connected to the positive and negative electrodes of the electrode assembly. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-179664 Summary of the Invention [Problem to be solved by the invention]

[0004] If an impact is applied to the container, the electrode assembly may move within the container even if it is supported by the current collectors. This movement may cause the electrode assembly to interfere with the container wall or other components within the container, resulting in a short circuit or damage to the electrode assembly and potentially compromising the reliability of the energy storage element itself.

[0005] An object of the present invention is to provide an energy storage element that can improve reliability. [Means for solving the problem]

[0006] An energy storage element according to one embodiment of the present invention comprises an electrode body in which electrode plates are wound and which has recesses at both ends in the direction of the winding axis, a container for accommodating the electrode body, and an insulating buffer material disposed within the recesses and smaller in size than the recesses when viewed in the direction of the winding axis.

[0007] According to this, since the buffer material is disposed in the recess of the electrode body, when the electrode body moves in the direction of the winding axis inside the container, the buffer material abuts against the container or other components inside the container. This restricts further movement of the electrode body, thereby suppressing damage to the end of the electrode body in the direction of the winding axis and short-circuiting caused by such movement. In particular, because the buffer material has insulating properties, even if the buffer material abuts against the inner surface of the container, the end of the electrode body will not be short-circuited via the buffer material. Therefore, it is possible to provide a highly reliable energy storage element.

[0008] The energy storage element may be housed in a container and have a spacer disposed outward in the direction of the winding axis of the electrode assembly, with the spacer and the buffer material being separate bodies.

[0009] This allows the buffer material to restrict movement of the electrode body even in an energy storage element in which the spacer is arranged outside the winding axis direction of the electrode body, thereby preventing damage and short circuits to the ends of the electrode body.

[0010] Here, if the spacer and the buffer material are integral, they move in unison. For example, if the end of the electrode body abuts the spacer first, the buffer material moves along with the spacer, and the buffer material moves away from its predetermined position in the recess of the electrode body, even if only temporarily. In other words, the restraining force of the buffer material is temporarily weakened, which could cause the electrode body to move in the direction of the winding axis and result in a large stress being applied. In this embodiment, the spacer and the buffer material are separate, making it difficult for them to move in unison. This allows the buffer material to be stably maintained in its predetermined position in the recess of the electrode body, and more reliably suppresses movement of the electrode body in the direction of the winding axis.

[0011] The buffer material may be a cylinder extending in a direction intersecting the winding axis direction.

[0012] With this, since the buffer material is cylindrical, even if the buffer material is placed in the recess of the electrode body, the electrolyte can be filled up to the inside of the buffer material, which means that it is possible to suppress a decrease in the amount of electrolyte caused by providing the buffer material.

[0013] Furthermore, because the buffer material is a cylinder extending in a direction intersecting the winding axis direction, the buffer material can be arranged along the extension direction of the recesses of the electrode body. This allows the buffer material to be arranged over a wide area along the extension direction of the recesses, reducing the stress that the recesses (the ends of the electrode body in the winding axis direction) receive from the buffer material when the buffer material abuts against the container or other components within the container. This further reduces damage to the ends of the electrode body in the winding axis direction.

[0014] The buffer material may have a curved portion that is convex toward the bottom surface of the recess.

[0015] According to this, the curved portion of the buffer material is convex toward the bottom surface of the recess and has a shape that matches the cross-sectional shape of the bottom surface of the recess. This makes it difficult for the shape of the recess to be damaged even if the buffer material is pressed toward the electrode assembly from the container. Therefore, damage to the edge of the electrode assembly can be more reliably suppressed.

[0016] The buffer material may have through holes.

[0017] In this case, since the buffer material has through holes, the electrolyte can be guided to the end of the electrode assembly through the through holes, thereby suppressing a decrease in the permeability of the electrolyte into the electrode assembly due to the provision of the buffer material. [Effects of the Invention]

[0018] According to the energy storage device of the present invention, reliability can be improved. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a perspective view showing the appearance of an energy storage element according to an embodiment; [Figure 2] FIG. 2 is a perspective view showing components arranged inside a container of an energy storage device according to an embodiment. [Figure 3] FIG. 2 is an exploded perspective view showing the components of the energy storage device according to the embodiment. [Figure 4] 10 is a plan view showing a recess in the positive direction of the X-axis of the electrode body according to the embodiment, and a buffer material disposed in the recess. FIG. [Figure 5] 10 is a cross-sectional view showing a recess in the positive direction of the X-axis of the electrode body according to the embodiment, and a buffer material disposed in the recess. FIG. [Figure 6] 10 is a cross-sectional view showing a recess in the positive direction of the X-axis of the electrode body according to the embodiment, and a buffer material disposed in the recess. FIG. [Figure 7] FIG. 10 is a perspective view showing an electrode body and a buffer material according to Modification 1. [Figure 8] FIG. 10 is a perspective view showing a cushioning material according to Modification 2. [Figure 9] 10A to 10C are explanatory diagrams showing various forms of the cushioning material according to Modification 3. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, with reference to the drawings, a description will be given of energy storage elements according to embodiments and modifications of the present invention. The embodiments and modifications described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component placement and connection configurations, manufacturing processes, and the order of manufacturing processes shown in the following embodiments are merely examples and are not intended to limit the present invention. Among the components in the following embodiments, components that are not described in the independent claims that represent the highest concept are described as optional components. In each drawing, dimensions, etc. are not strictly illustrated.

[0021] In the following description and drawings, the X-axis direction is defined as the direction in which a pair of electrode terminals (positive and negative electrodes, hereinafter the same) of an energy storage element, the direction in which a pair of current collectors, the direction in which a pair of buffer materials, the direction in which a pair of upper gaskets, the direction in which a pair of lower gaskets, the direction in which a pair of spacers, the direction in which both ends of an electrode assembly are aligned, the winding axis direction of the electrode assembly, or the opposing direction of the short side surfaces of a container. The Y-axis direction is defined as the direction in which the long side surfaces of a container are aligned, the lateral direction of the short side surfaces of a container, or the thickness direction of a container. The Z-axis direction is defined as the direction in which the container body and lid of an energy storage element are aligned, the longitudinal direction of the short side surfaces of a container, or the extending direction of the legs (electrode assembly connection portions) of the current collectors. The X-axis direction, Y-axis direction, and Z-axis direction intersect each other (orthogonal in this embodiment). Note that depending on the usage mode, the Z-axis direction may not be the vertical direction; however, for convenience of explanation, the Z-axis direction will be described below as the vertical direction.

[0022] In the following description, for example, the positive X-axis direction refers to the direction of the X-axis arrow, and the negative X-axis direction refers to the opposite direction to the positive X-axis direction. The same applies to the Y-axis and Z-axis. Expressions indicating relative directions or attitudes, such as parallel and perpendicular, also include cases where the direction or attitude is not strictly that. For example, saying that two directions are perpendicular does not only mean that the two directions are completely perpendicular, but also means that the directions are substantially perpendicular, that is, there is a difference of, for example, a few percent.

[0023] (Embodiment) [General explanation of energy storage elements] First, an overall description of an energy storage element 10 according to the present embodiment will be given using FIGS. 1 to 3. FIG. 1 is a perspective view showing the exterior of the energy storage element 10 according to the embodiment. FIG. 2 is a perspective view showing components arranged inside a container 100 of the energy storage element 10 according to the embodiment. Specifically, FIG. 2 is a perspective view showing a configuration in which a container body 110, a spacer 800, and an insulating sheet 600 are separated from the energy storage element 10, and shows a state after a current collector 300 has been joined to an electrode assembly 200 and a buffer material 700 has also been attached. FIG. 3 is an exploded perspective view showing each component of the energy storage element 10 according to the embodiment. Specifically, FIG. 3 is a perspective view showing components other than the container body 110, the spacer 800, and the insulating sheet 600 shown in FIG. 2 in an exploded state, showing a state before the current collector 300 has been joined to the electrode assembly 200 and before the buffer material 700 has been attached.

[0024] The energy storage element 10 is a secondary battery capable of charging and discharging electricity, specifically a nonaqueous electrolyte secondary battery such as a lithium-ion secondary battery. The energy storage element 10 is used as a power source for automobiles such as electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs), a power source for electronic devices, or a power storage power source. The energy storage element 10 may also be installed in vehicles such as gasoline-powered vehicles and diesel-powered vehicles as a starting battery for the engine. The energy storage element 10 is not limited to a nonaqueous electrolyte secondary battery and may be a secondary battery other than a nonaqueous electrolyte secondary battery or a capacitor. The energy storage element 10 may not be a secondary battery, but may be a primary battery that allows stored electricity to be used without the user having to charge it. The energy storage element 10 may also be a battery using a solid electrolyte. In this embodiment, the energy storage element 10 is illustrated as having a rectangular parallelepiped (prismatic) shape, but the shape of the energy storage element 10 is not limited to a rectangular parallelepiped shape and may be a cylindrical shape, an elongated cylindrical shape, a polygonal prism shape other than a rectangular parallelepiped, or the like. Energy storage element 10 may be a laminate type energy storage element.

[0025] As shown in Fig. 1, the energy storage element 10 includes a container 100, positive and negative electrode terminals 130, and positive and negative upper gaskets 140. As shown in Figs. 2 and 3, the container 100 contains positive and negative lower gaskets 150, an electrode assembly 200, positive and negative current collectors 300, positive and negative spacers 800, and an insulating sheet 600. An electrolyte (non-aqueous electrolyte) is sealed inside the container 100, but is not shown. There are no particular limitations on the type of electrolyte, and various electrolytes can be selected as long as they do not impair the performance of the energy storage element 10.

[0026] The container 100 is a rectangular parallelepiped (square) container having a container body 110 with an opening formed therein and a lid 120 that closes the opening of the container body 110. The container body 110 is a rectangular cylindrical member with a bottom that constitutes the main body of the container 100, and has two first wall portions 111 on both side surfaces in the X-axis direction, two second wall portions 112 on both side surfaces in the Y-axis direction, and a third wall portion 113 on the negative Z-axis side. Specifically, the first wall portion 111 is a rectangular, plate-shaped short side surface portion that forms the short side of the container 100. In other words, the first wall portion 111 is a wall portion that is adjacent to the second wall portion 112 and the third wall portion 113 and has a smaller surface area (area of ​​the outer surface) than the second wall portion 112. The second wall portion 112 is a rectangular, plate-shaped long side surface portion that forms the long side of the container 100. In other words, the second wall portion 112 is a wall portion that is adjacent to the first wall portion 111 and the third wall portion 113 and has a larger surface area (area of ​​the outer surface) than the first wall portion 111. The third wall portion 113 is a rectangular, plate-shaped bottom wall portion that forms the bottom surface of the container 100.

[0027] Lid 120 is a rectangular plate-like member that constitutes the lid of container 100, and is disposed on the positive side of container body 110 in the Z-axis direction. That is, lid 120 is a wall that faces third wall 113 and is adjacent to first wall 111 and second wall 112. In this embodiment, positive and negative electrode terminals 130 are disposed on lid 120, and further, a gas exhaust valve 121 that releases pressure inside container 100 when the pressure inside container 100 increases, a liquid injection part 122 for injecting electrolyte into container 100, and the like are also provided.

[0028] With this configuration, the container 100 has a structure in which the electrode assembly 200, to which the buffer material 700 and spacer 800 are attached, is housed inside the container body 110, and then the container body 110 and the lid 120 are joined by welding or the like, thereby sealing the interior. The materials for the container body 110 and the lid 120 are not particularly limited, and can be weldable metals such as stainless steel, aluminum, and aluminum alloys. Resin can also be used as the material for the container body 110 and the lid 120.

[0029] The electrode assembly 200 is an electricity storage element (power generating element) that includes a positive electrode plate, a negative electrode plate, and a separator and can store electricity. The positive electrode plate is an electrode plate in which a positive electrode active material layer is formed on a positive electrode substrate layer, which is a long, strip-shaped current collecting foil made of aluminum, aluminum alloy, or the like. The negative electrode plate is an electrode plate in which a negative electrode active material layer is formed on a negative electrode substrate layer, which is a long, strip-shaped current collecting foil made of copper, copper alloy, or the like. The current collecting foil can be made of any known material, such as nickel, iron, stainless steel, titanium, baked carbon, conductive polymer, conductive glass, or Al-Cd alloy. The positive electrode active material and negative electrode active material used in the positive electrode active material layer and negative electrode active material layer can be any known material, as long as they are active materials capable of absorbing and releasing lithium ions. The separator can be a microporous resin sheet or nonwoven fabric. In this embodiment, the cross-sectional shape of the electrode assembly 200 is illustrated as an oval shape, but it may also be circular, elliptical, or the like.

[0030] The electrode assembly 200 is formed by winding a positive electrode plate and a negative electrode plate with a separator disposed between them. Specifically, the electrode assembly 200 is wound with the positive electrode plate and the negative electrode plate interposed between the separator and shifted relative to each other in the direction of the winding axis W (in this embodiment, a virtual axis parallel to the X-axis direction). The positive electrode plate and the negative electrode plate have, at their respective ends in the shifted direction, portions where no active material is applied (no active material layer is formed) and the base material layer is exposed (active material layer non-formed portions).

[0031] That is, the electrode body 200 has an electrode body main body portion 210, which is a main body portion on which an active material layer is formed, and electrode body end portions 220 that protrude from the electrode body main body portion 210 in the positive or negative X-axis direction. One of these two electrode body end portions 220 is provided with a positive electrode gathering portion in which active material layer-free portions of positive electrode plates are stacked and bundled. The other electrode body end portion 220 is provided with a negative electrode gathering portion in which active material layer-free portions of negative electrode plates are stacked and bundled. The two electrode body end portions 220 have recesses 221 extending in the Z-axis direction. Specifically, the electrode body end portion 220 in the positive X-axis direction has a recess 221 that is open in the positive X-axis direction and has a bottom in the negative X-axis direction. The electrode body end portion 220 in the negative X-axis direction has a recess (not shown) that is open in the negative X-axis direction and has a bottom in the positive X-axis direction.

[0032] 3, the electrode assembly 200 is formed in a flat shape with a narrow width in the Y-axis direction, and the electrode plates (positive electrode plates and negative electrode plates) are mainly stacked in the Y-axis direction. Therefore, in this embodiment, when we say the stacking direction of the electrode plates in the electrode assembly 200, we mean the Y-axis direction.

[0033] The electrode terminals 130 are terminals (positive and negative terminals) electrically connected to the positive and negative electrode plates of the electrode assembly 200 via the current collector 300. In other words, the electrode terminals 130 are metal members for guiding electricity stored in the electrode assembly 200 to the external space of the energy storage element 10 and for introducing electricity into the internal space of the energy storage element 10 to store electricity in the electrode assembly 200. The electrode terminals 130 are attached to the lid 120 disposed above the electrode assembly 200. Specifically, as shown in FIG. 3 , the shaft 131 of the electrode terminal 130 is inserted into the through-hole 140a of the upper gasket 140, the through-hole 120a of the lid 120, the through-hole 150a of the lower gasket 150, and the through-hole 310a of the current collector 300, and is then crimped, thereby fixing the electrode terminal 130 together with the current collector 300 to the lid 120. The positive electrode terminal 130 is made of aluminum or an aluminum alloy, and the negative electrode terminal 130 is made of copper or a copper alloy.

[0034] The current collectors 300 are members (positive and negative current collectors) arranged on both sides of the electrode assembly 200 in the X-axis direction and connected to the electrode assembly end portions 220. Specifically, the current collectors 300 have a fixed end portion 310, which is an end portion fixed to the container 100 together with a lower gasket 150, which is an example of an insulating member, and a pair of legs 320 extending from the fixed end portion 310. The pair of legs 320 of the positive electrode side current collector 300 are joined to the positive electrode side electrode assembly end portion 220, and the pair of legs 320 of the negative electrode side current collector 300 are joined to the negative electrode side electrode assembly end portion 220. Ultrasonic welding, crimping, or the like is used as the joining method. With this configuration, the electrode assembly 200 is held (supported) in a suspended state from the lid 120 by the two current collectors 300, thereby suppressing shaking due to vibration, impact, or the like. The material of the current collectors 300 is not limited. For example, the positive electrode current collector 300 is formed of a metal member such as aluminum or an aluminum alloy, similar to the positive electrode substrate layer of the electrode body 200. The negative electrode current collector 300 is formed of a metal member such as copper or a copper alloy, similar to the negative electrode substrate layer of the electrode body 200.

[0035] The buffer material 700 is an insulating cylinder extending in a direction (Z-axis direction) perpendicular to the winding axis direction (Y-axis direction). Specifically, the buffer material 700 is a cylinder with a uniform wall thickness around its entire circumference. The buffer material 700 is formed of an insulating material such as polypropylene (PP), polyethylene (PE), polyphenylene sulfide resin (PPS), polyethylene terephthalate (PET), polyether ether ketone (PEEK), tetrafluoroethylene perfluoroalkyl vinyl ether (PFA), polytetrafluoroethylene (PTFE), polybutylene terephthalate (PBT), polyether sulfone (PES), or a composite material thereof. In other words, the buffer material 700 as a whole is insulating.

[0036] Two buffer materials 700 are provided, each disposed in a recess 221 of the electrode assembly 200. The positional relationship between the buffer materials 700 and the recesses 221 of the electrode assembly 200 will be described later.

[0037] 2, the spacer 800 is a spacer disposed between the electrode assembly 200 and the container 100. In this embodiment, the spacer 800 is a side spacer disposed to the side (positive or negative X-axis direction) of the electrode assembly 200 and the current collector 300, and formed to extend in the Z-axis direction.

[0038] More specifically, the spacer 800 is a U-shaped spacer in a top view (as viewed from the Z-axis direction) that is disposed between the electrode body 200 and the current collector 300 and the ends of the first wall portion 111 and the second wall portion 112 of the container body 110, and that is disposed so as to extend along the ends of the first wall portion 111 and the second wall portion 112. In other words, the spacer 800 is disposed so as to sandwich the electrode body end portion 220 and the current collector 300 from both ends in the Y-axis direction.

[0039] Here, the spacer 800 is formed of an insulating material such as PP, PE, PPS, PET, PEEK, PFA, PTFE, PBT, PES, ceramic, or a composite material thereof. In other words, the spacer 800 insulates the electrode assembly 200 and the current collector 300 from the container 100. The spacer 800 fills the space between the electrode assembly 200 and the current collector 300 and the container 100, thereby supporting the electrode assembly 200 and the current collector 300 so that they do not vibrate relative to the container 100.

[0040] The upper gasket 140 is a member (positive electrode upper gasket and negative electrode upper gasket) that is disposed between the lid 120 and the electrode terminal 130 of the container 100 and that insulates and seals between the lid 120 and the electrode terminal 130. Specifically, the upper gasket 140 has a shape in which a through-hole 140a into which the shaft portion 131 of the electrode terminal 130 is inserted is formed in the center of a rectangular, approximately plate-like member. The shaft portion 131 is inserted into the through-hole 140a and crimped, thereby fixing the upper gasket 140 to the lid 120. The upper gasket 140 is formed from a resin or the like, such as PP, PE, PPS, PET, PEEK, PFA, PTFE, PBT, or PES.

[0041] The lower gasket 150 is a member (positive electrode lower gasket and negative electrode lower gasket) that is disposed between the lid 120 of the container 100 and the current collector 300, and provides insulation between the lid 120 and the current collector 300. Specifically, the lower gasket 150 has a shape in which a through-hole 150a into which the shaft portion 131 of the electrode terminal 130 is inserted is formed in the approximate center of a rectangular, approximately plate-like member. The shaft portion 131 is inserted into the through-hole 150a and crimped, thereby fixing the lower gasket 150 to the lid 120. The lower gasket 150 is formed from a resin or the like, such as PP, PE, PPS, PET, PEEK, PFA, PTFE, PBT, or PES.

[0042] [Positional relationship between the recess of the electrode body and the buffer material] Next, a description will be given of the positional relationship between the recess 221 of the electrode body 200 and the buffer material 700. Here, the recess 221 in the positive X-axis direction of the electrode body 200 will be described as an example, but the same is basically true for the recess in the negative X-axis direction of the electrode body 200, so a description thereof will be omitted.

[0043] FIG. 4 shows a recess 221 in the positive X-axis direction of the electrode body 200 according to the embodiment, and the recess 221. 4. FIG. 5 is a plan view showing recess 221 in the positive direction of the X-axis of electrode body 200 according to the embodiment, and buffer material 700 arranged in recess 221. FIG. 5 is a cross-sectional view showing recess 221 in the positive direction of the X-axis of electrode body 200 according to the embodiment, and buffer material 700 arranged in recess 221. Specifically, FIG. 5 is a cross-sectional view showing a cut surface including cutting line VV in FIG. 4. FIG. 6 is a cross-sectional view showing recess 221 in the positive direction of the X-axis of electrode body 200 according to the embodiment, and buffer material 700 arranged in recess 221. Specifically, FIG. 6 is a cross-sectional view showing a cut surface including cutting line VI-VI in FIG.

[0044] 4 to 6, the recess 221 is formed in the electrode body end 220 of the electrode body 200 in the positive X-axis direction. The recess 221 is open in the positive X-axis direction and has a bottom surface 222 in the negative X-axis direction. Specifically, the recess 221 is formed in an oval shape when viewed in the X-axis direction (see FIG. 4), and the bottom surface 222 of the recess 221 is recessed so as to taper in both the Y-axis direction and the Z-axis direction toward the negative X-axis direction (see FIGS. 5 and 6).

[0045] As shown in FIG. 4, the buffer material 700 is formed to be smaller than the recess 221 when viewed in the X-axis direction (when viewed in the winding axis direction). Therefore, when viewed in the X-axis direction, the buffer material 700 is arranged in the recess 221 so that the entire buffer material 700 fits within the recess 221. The length of the buffer material 700 in the Z-axis direction is longer than half the length of the recess 221 in the Z-axis direction. Furthermore, the length of the buffer material 700 in the Y-axis direction is longer than half the length of the recess 221 in the Y-axis direction. In other words, the buffer material 700 occupies more than one-quarter of the area of ​​the recess 221 when viewed in the X-axis direction. In particular, if the buffer material 700 is fitted into the recess 221, the buffer material 700 can be positioned within the recess 221 without using any other members, which is preferable.

[0046] As shown in FIG. 5, the cushioning material 700 is disposed such that its end in the positive X-axis direction protrudes from the recess 221 when viewed in the Z-axis direction. Because the cushioning material 700 is formed in a cylindrical shape, the end of the cushioning material 700 in the negative X-axis direction, i.e., the end closest to the bottom surface 222 of the recess 221, forms a curved portion 701 that is convex toward the bottom surface 222. As described above, the bottom surface 222 of the recess 221 tapers in the Y-axis direction toward the negative X-axis direction, and therefore the curved portion 701 of the cushioning material 700 also has a shape that follows the cross-sectional shape of the bottom surface 222. Furthermore, as shown in FIG. 6, a spacer 800 is interposed between the cushioning material 700 and the first wall portion 111 of the container body 110.

[0047] [Buffering effect] Next, the function of the buffer material 700 will be described. Here, assume that an external impact is applied to the energy storage device 10, causing the electrode assembly 200 to move in the X-axis direction (winding axis direction) within the container 100. The electrode assembly 200 is limited in its movement within the container 100 by being joined to the pair of current collectors 300 and by friction with the second wall portion 112 of the container body 110. However, if an impact exceeding these limits is applied, the electrode assembly 200 will move. Even if the electrode assembly 200 moves in the X-axis direction, the buffer material 700 arranged in the recess 221 of the electrode assembly 200 will first abut against the spacer 800. This restricts further movement of the electrode assembly 200, thereby suppressing damage or short-circuiting of the electrode assembly end portion 220 of the electrode assembly 200.

[0048] Although the present embodiment illustrates a case in which the curved portion 701 of the buffer material 700 is in contact with the bottom surface 222 of the recess 221 before the energy storage element 10 receives an impact, the curved portion 701 of the buffer material 700 may be spaced apart from the bottom surface 222. In this case, the electrode body 200 moves when the energy storage element 10 receives an impact, causing the bottom surface 222 to come into contact with the curved portion 701 of the buffer material 700.

[0049] Furthermore, curved portion 701 of buffer material 700 is convex toward bottom surface 222 of recess 221, and has a shape that follows the cross-sectional shape of bottom surface 222 of recess 221. As a result, even if buffer material 700 is pressed from container 100 toward electrode body 200, the shape of recess 221 is unlikely to be damaged.

[0050] [Effect description] As described above, the energy storage element 10 of this embodiment comprises an electrode body 200 in which electrode plates are wound and which has recesses 221 at both ends in the direction of the winding axis, a container 100 that houses the electrode body 200, and an insulating buffer material 700 that is arranged within the recesses 221 and is smaller in size than the recesses 221 when viewed in the direction of the winding axis.

[0051] According to this, since the buffer material 700 is disposed in the recess 221 of the electrode assembly 200, when the electrode assembly 200 moves in the direction of the winding axis within the container 100, the buffer material 700 abuts against the spacer 800. This restricts further movement of the electrode assembly 200, thereby suppressing damage to the electrode assembly end portion 220 of the electrode assembly 200 and short-circuiting caused by such movement. In particular, since the buffer material 700 is insulating as a whole, even if the buffer material 700 abuts against the inner surface of the container 100, the electrode assembly end portion 220 of the electrode assembly 200 will not be short-circuited via the buffer material 700. Therefore, it is possible to provide a highly reliable energy storage element 10.

[0052] The energy storage device 10 is housed in a container 100 and has a spacer 800 arranged outward in the winding axis direction of the electrode body 200, and the spacer 800 and the buffer material 700 are separate bodies.

[0053] According to this, even in a storage element 10 in which the spacer 800 is arranged outside the winding axis direction of the electrode body 200, the movement of the electrode body 200 can be restricted by the buffer material 700, thereby preventing damage and short circuits to the electrode body end portion 220.

[0054] Here, if the spacer 800 and the buffer material 700 are integral, they move in unison. For example, if the electrode assembly end portion 220 abuts the spacer 800 first, the buffer material 700 moves along with the spacer 800, and the buffer material 700 moves away from its predetermined position in the recess 221 of the electrode assembly 200, even if only temporarily. In other words, the restraining force of the buffer material 700 is temporarily weakened, which may cause the electrode assembly 200 to move in the direction of the winding axis and result in a large stress being applied. In this embodiment, the spacer 800 and the buffer material 700 are separate, making it difficult for them to move in unison. This allows the buffer material 700 to be stably maintained in its predetermined position in the recess 221 of the electrode assembly 200, and more reliably suppresses movement of the electrode assembly 200 in the direction of the winding axis.

[0055] The buffer material 700 is a cylindrical body that extends in a direction intersecting the winding axis direction.

[0056] According to this, because the buffer material 700 is a cylindrical body, even if the buffer material 700 is placed in the recess 221 of the electrode body 200, the electrolyte can be filled up to the inside of the buffer material 700. In other words, it is possible to suppress a decrease in the amount of electrolyte caused by providing the buffer material 700.

[0057] Furthermore, because the buffer material 700 is a cylinder extending in a direction intersecting the winding axis direction, the buffer material 700 can be arranged along the extension direction of the recesses 221 of the electrode assembly 200. This allows the buffer material 700 to be arranged over a wide area along the extension direction of the recesses 221, and when the buffer material 700 abuts against the spacer 800, it is possible to reduce the stress that the recesses 221 (electrode assembly end portion 220) receive from the buffer material 700. Therefore, damage to the electrode assembly end portion 220 of the electrode assembly 200 can be further suppressed.

[0058] Furthermore, because the buffer material 700 is cylindrical, the buffer material 700 itself can exhibit a certain degree of elasticity. As a result, the buffer material 700 absorbs the impact when the electrode body 200 moves, so damage to the electrode body end portion 220 can be more reliably suppressed.

[0059] The cushioning material 700 has a curved portion 701 that is convex toward the bottom surface 222 of the recess 221 .

[0060] According to this, the curved portion 701 of the buffer material 700 is convex toward the bottom surface 222 of the recess 221, and has a shape that follows the cross-sectional shape of the bottom surface 222 of the recess 221. As a result, even if the buffer material 700 is pressed from the container 100 toward the electrode assembly 200, the shape of the recess 221 is unlikely to be damaged. Therefore, damage to the electrode assembly end portion 220 can be more reliably suppressed.

[0061] (Variation) Modifications of the above embodiment will be described below. In the following description, the same parts as those in the above embodiment will be denoted by the same reference numerals, and the description thereof may be omitted.

[0062] [Variation 1] A first modification of the embodiment will be described with reference to FIG. 7 . FIG. 7 is a perspective view showing an electrode assembly 200a and a buffer material 700 according to the first modification. In the above embodiment, the electrode assembly 200 is exemplified in which the winding axis direction is the X-axis direction. However, in this modification, an electrode assembly 200a is exemplified in which the winding axis direction is the Z-axis direction. That is, in the electrode assembly 200a, a recess 221a is provided at a position facing the third wall portion 113 of the container 100. A buffer material 700 is disposed within this recess 221a. In this case, too, the buffer material 700 extends in a direction (X-axis direction) perpendicular to the winding axis direction of the electrode assembly 200a. The buffer material 700 is disposed facing the third wall portion 113 of the container 100 via an insulating sheet 600. In this case, the insulating sheet 600 is an example of a spacer disposed outward in the winding axis direction of the electrode assembly 200a.

[0063] Even if an external impact is applied to the energy storage device 10 and the electrode body 200a moves in the Z-axis direction, the buffer material 700 arranged in the recess 221a of the electrode body 200a first comes into contact with the container 100 via the insulating sheet 600. This restricts further movement of the electrode body 200a, thereby suppressing damage or short-circuiting of the end of the electrode body 200a in the winding axis direction (electrode body end 220a). Therefore, even in this modified example, it is possible to provide a highly reliable energy storage device 10.

[0064] [Variation 2] A second modification of the embodiment will be described with reference to Fig. 8. Fig. 8 is a perspective view showing a cushioning material 700b according to the second modification. In the above embodiment, the cushioning material 700 is a cylindrical body having a uniform thickness all around, but the cushioning material 700b according to this modification is a cylindrical body in which a plurality of through holes 703 are formed discretely in the circumferential and axial directions.

[0065] In this way, since the buffer material 700b has the through-holes 703, the electrolyte can be guided to the electrode body end portion 220 of the electrode body 200 through the through-holes 703. Therefore, it is possible to suppress a decrease in the permeability of the electrolyte into the electrode body 200 caused by the provision of the buffer material 700b.

[0066] [Variation 3] A third modification of the embodiment will be described with reference to Fig. 9. Specifically, other modifications of the cushioning material will be listed in the third modification. Fig. 9 is an explanatory diagram showing various forms of the cushioning material according to the third modification.

[0067] In the above embodiment, a cushioning material 700 made of a cylindrical body has been exemplified. However, the cushioning material may be an elongated cylinder, an elliptical cylinder, or a polygonal cylinder. FIG. 9(a) shows a cushioning material 700c made of a hexagonal cylinder as an example of a polygonal cylinder. In this cushioning material 700c, each corner is formed in an R-shape, and the corners that are convex toward the bottom surface 222 of the recess 221 become curved portions 701c.

[0068] As shown in (b) of Fig. 9, the buffer material 700d may be made of a porous material. Although (b) of Fig. 9 shows a cylindrical buffer material 700d as an example, the buffer material 700d may have any shape, and other shapes include an elongated cylinder, an elliptical cylinder, and a polygonal cylinder.

[0069] The buffer material may also be formed from a solid member. Figure 9(c) shows an example of a buffer material 700e that is solid as a whole. The buffer material 700e has a curved portion 701e and a flat portion 702e. The curved portion 701e is convex toward the bottom surface 222 of the recess 221. The flat portion 702e protrudes from the recess 221 and is disposed parallel to the end surface of the electrode body end portion 220.

[0070] 9(d) shows a U-shaped cushioning material 700f. The curved bottom of the cushioning material 700f is a curved portion 701f that is convex toward the bottom surface 222 of the recess 221.

[0071] (others) Although the energy storage device according to the embodiment and its modification of the present invention has been described above, the present invention is not limited to this embodiment and its modification. In other words, the embodiment and its modification disclosed herein are illustrative in all respects and are not restrictive. The scope of the present invention is defined by the claims, and includes all modifications within the meaning and scope of the claims.

[0072] In the above embodiment and the like, a case has been illustrated in which a portion of the buffer material 700 protrudes from the recess 221 of the electrode body 200. However, the entire buffer material 700 may be contained within the recess 221.

[0073] In the above embodiment, the buffer material 700 is elastic, but the buffer material may be rigid. Also, a plurality of buffer materials may be disposed in one recess 221.

[0074] In the above embodiment, the buffer material 700 and the spacer 800 are separate bodies, but they may be an integrated body.

[0075] In the above embodiment and the like, a case has been exemplified in which the spacer 800 is interposed between the buffer material 700 and the container body 110, but the spacer 800 may not be present. Even in this case, when the electrode assembly 200 moves in the direction of the winding axis within the container 100, the buffer material 700 comes into contact with the container body 110, and further movement of the electrode assembly 200 can be restricted.

[0076] In the above embodiment, both the positive electrode side and the negative electrode side have the above configuration, but only one of the positive electrode side and the negative electrode side may have the above configuration.

[0077] Any combination of the components included in the embodiments and their modifications is also included within the scope of the present invention. [Industrial Applicability]

[0078] The present invention can be applied to an electric storage element such as a lithium ion secondary battery. [Explanation of symbols]

[0079] 10. Energy storage element 100 containers 110 Container body 111 First wall 112 Second wall 113 Third wall 120 Lid 120a, 140a, 150a, 310a, 703 through hole 121 Gas exhaust valve 122 Injection section 130 Electrode terminal 131 Shaft 140 Upper gasket 150 Lower Gasket 200, 200a Electrode body 210 Electrode body part 220, 220a Electrode body end 221, 221a recess 222 bottom 300 current collector 310 Fixed end 320 Legs 600 Insulation Sheet 700, 700b, 700c, 700d, 700e buffer material 701, 701c, 701d, 701e, 701f curved section 702e flat part 800 spacer W winding shaft

Claims

1. an electrode body in which electrode plates are wound and which has recesses at both ends in the direction of the winding axis; a container for accommodating the electrode assembly; an insulating buffer material that is disposed in the recess and is smaller than the recess when viewed in the winding axis direction; Energy storage element.

2. a spacer housed in the container and arranged outwardly of the electrode body in the direction of the winding axis, The spacer and the buffer material are separate bodies. The energy storage element according to claim 1 .

3. The buffer material is a cylindrical body extending in a direction intersecting the winding axis direction. The energy storage element according to claim 1 or 2.

4. The buffer material has a curved portion that is convex toward the bottom surface of the recess. The energy storage element according to any one of claims 1 to 3.

5. The buffer material has a through hole. The energy storage element according to any one of claims 1 to 4.

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