Energy storage element

Abstract

To provide a power storage element with improved reliability.SOLUTION: A power storage element 10 includes a container 100, and an electrode body 600 which is housed in the container 100 and has a first electrode plate 630 and a second electrode plate 640 having mutually different polarities. The electrode body 600 includes a laminated body 601 which is formed of the second electrode plate 640 whose thickness direction is oriented in a Y-axis direction, and the pair of first electrode plates 630 sandwiching the second electrode plate 640 from both sides in the Y-axis direction via a separator 650, and is folded into a bellows shape.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a power storage element including a container and an electrode body housed in the container.

Background Art

[0002] Patent Document 1 discloses a lithium-ion secondary battery including a flat wound type electrode body formed by interposing a separator between a positive electrode plate and a negative electrode plate and winding them in a flat shape, and a battery case.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The wound type electrode body included in the conventional lithium-ion secondary battery described above is formed into a flat shape by winding a positive electrode plate (anode plate) and a negative electrode plate (cathode plate) with a separator interposed therebetween and further compressing them in a direction orthogonal to the winding axis direction. In such a wound type electrode body, curved portions exist at both longitudinal ends in a cross section orthogonal to the winding axis direction. Therefore, when the wound type electrode body is housed in a container, a gap is likely to occur between the curved portion and the inner surface of the container, which is disadvantageous from the viewpoint of, for example, improving the energy density.

[0005] The present invention has been made by the inventors of the present application newly paying attention to the above problems, and an object thereof is to provide a power storage element with improved energy density.

Means for Solving the Problems

[0006] An energy storage element according to one aspect of the present invention comprises a container and an electrode body housed in the container, having a first electrode plate and a second electrode plate having opposite polarities, wherein the electrode body is a laminate formed of a second electrode plate with its thickness direction oriented in a first direction and a pair of first electrode plates, each sandwiching the second electrode plate from both sides in the first direction via a separator, and has a laminate folded in a bellows-like manner. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an energy storage element with improved energy density. [Brief explanation of the drawing]

[0008] [Figure 1] This is a perspective view showing the external appearance of the energy storage element according to the embodiment. [Figure 2] This is an exploded perspective view of the energy storage element according to the embodiment. [Figure 3] This is a first plan view showing the configuration of the laminated body of the electrode body according to the embodiment. [Figure 4] This is a second plan view showing the configuration of the laminated body of the electrode body according to the embodiment. [Figure 5] This is a plan view showing the laminated structure in the flat portion of the laminate according to the embodiment. [Figure 6] This is a plan view showing the laminated structure in the bent portion of the laminate according to the embodiment. [Figure 7] This is a plan view showing the configuration of the laminated body of the electrode body according to a modified example 1 of the embodiment. [Figure 8] This is a perspective view showing the general configuration of the electrode body according to a modified example 2 of the embodiment. [Figure 9] This is a schematic diagram showing the junction between the first focusing portion and the first current collector of the electrode body according to a modified example 2 of the embodiment. [Figure 10] This is a plan view showing the structure of a laminate having a second convergence section containing multiple second sub-bundles. [Modes for carrying out the invention]

[0009] (1) An energy storage element according to one aspect of the present invention is an energy storage element comprising a container and an electrode body housed in the container, having a first electrode plate and a second electrode plate having opposite polarities, wherein the electrode body is a laminate formed of a second electrode plate with its thickness direction oriented in a first direction and a pair of first electrode plates, each sandwiching the second electrode plate from both sides in the first direction via a separator, and has a laminate folded in an accordion shape.

[0010] According to this configuration, the electrode body according to this embodiment does not have a curved portion like that found in a wound electrode body. Therefore, it is easy to improve the volume occupancy rate of the electrode body within the container. Consequently, the energy storage element according to this embodiment can improve energy density.

[0011] (2) The energy storage element described in (1) above further comprises a first current collector housed in the container, which electrically connects the first electrode plate of the electrode body and the first electrode terminal arranged in the container, wherein each of the pair of first electrode plates has a first base material layer and a first composite layer formed on the surface of the first base material layer facing the second electrode plate, and the laminate has a first focusing portion provided at one end in a second direction perpendicular to the first direction, which is formed by arranging first connection portions, which are portions of the first base material layer on which the first composite layer is not formed, along the first direction, and the first current collector is joined to the first focusing portion.

[0012] With this configuration, the first connection section, which is folded in an accordion-like manner and arranged along the first direction, can be joined to the first current collector as the first focusing section. For example, the current flowing from the first electrode plate can be efficiently collected by the first current collector.

[0013] (3) In the energy storage element described in (2) above, the first focusing portion may be a plurality of first partial bundles each including one or more of the first connection portions, and may be divided into a plurality of first partial bundles formed at different positions from each other in the first direction, and each of the plurality of first partial bundles may be joined to different positions in the first current collector.

[0014] According to this configuration, since the pair (two sheets) of first electrode plates are folded in a bellows shape, the first focusing portion including a relatively large number of first connection portions is divided into a plurality of first partial bundles and joined to the first current collector. As a result, compared with the case where the first connection portions included in the first focusing portion are joined to the first current collector in a lump, the joining of the first focusing portion to the first current collector is facilitated.

[0015] (4) In the energy storage element described in (3) above, the first focusing portion may include at least one of the first connection portions belonging to two or more of the plurality of first partial bundles.

[0016] According to this configuration, one or more of the first connection portions included in the first focusing portion are allowed to belong to a plurality of first partial bundles. That is, it is not necessary to completely divide the plurality of first connection portions. For example, one or more first connection portions may be commonly included in two adjacent first partial bundles. As a result, the joining leakage of the first connection portion to the first current collector (the occurrence of a first connection portion not joined to the first current collector) is suppressed.

[0017] (5) In the energy storage element described in (3) above, the first focusing portion may include two of the first partial bundles arranged at different positions from each other in a third direction orthogonal to the first direction and the second direction.

[0018] According to this configuration, since the two first partial bundles are arranged at different positions from each other in the first direction and the third direction, the joining operation of each of the two first partial bundles to the first current collector becomes easier.

[0019] (6) In the energy storage element described in any one of (2) to (5) above, the first composite layer may be formed on each of the pair of first electrode plates only on the surface of the first base material layer facing the second electrode plate out of the two surfaces in the first direction.

[0020] In the electrode body according to this embodiment, the laminate has a structure in which a second electrode plate is sandwiched between a pair of first electrode plates. Therefore, when the laminate is folded in an accordion shape, in the parts of the laminate that face each other, the two opposing surfaces are the surfaces of one of the first electrode plates that do not face the second electrode plate. Therefore, the parts of the laminate that face each other do not contribute to power generation. Consequently, by not forming a first composite material layer on the two opposing surfaces in the parts of the laminate that face each other, it is possible to reduce the thickness of the electrode body in the lamination direction while maintaining the power generation amount (storage capacity) of the electrode body.

[0021] (7) In the energy storage element described in any one of (2) to (6) above, the second electrode plate has a second base material layer and a second composite material layer formed on both sides of the second base material layer in the first direction, and the thickness of the first base material layer of the first electrode plate is thinner than the thickness of the second base material layer of the second electrode plate.

[0022] In this configuration, the first substrate layer of the first electrode plate, which is included in the laminate, is thinner than the second substrate layer of the second electrode plate. Therefore, the increase in the thickness of the electrode body due to the accumulation of the thickness of the first substrate layer is suppressed. This is advantageous for improving the energy density of the energy storage element.

[0023] The following description of an energy storage element according to an embodiment of the present invention will be made with reference to the drawings. Note that the embodiments described below are all general or specific examples. The numerical values, shapes, materials, components, arrangement and connection configurations of components, manufacturing processes, and the order of manufacturing processes shown in the following embodiments are examples only and are not intended to limit the present invention. Furthermore, dimensions and other specifications in each figure are not strictly illustrated. Additionally, the same or similar components are denoted by the same reference numerals in each figure.

[0024] In the following description and drawings, the direction in which the pair of electrode terminals (positive and negative, hereinafter the same) of the energy storage element are aligned, the direction in which the pair of current collectors are aligned, or the direction in which the short sides of the container face each other is defined as the X-axis direction. The direction in which the long sides of the container face each other, the direction in which the short sides of the container face each other is defined as the Y-axis direction. The direction in which the container body and lid of the energy storage element are aligned, or the direction in which the short sides of the container face each other is defined as the Z-axis direction. These X-axis, Y-axis, and Z-axis directions intersect each other (orthogonal in this embodiment). Depending on the usage, the Z-axis direction may not be vertical, but for the sake of explanation below, the Z-axis direction will be described as vertical.

[0025] In the following explanation, for example, the "X-axis positive direction" refers to the direction of the X-axis arrow, and the "X-axis negative direction" refers to the opposite direction. The same applies to the Y-axis and Z-axis directions. When simply referred to as "X-axis direction," it means either the bidirectional or unidirectional direction parallel to the X-axis. The same applies to the terminology related to the Y-axis and Z-axis.

[0026] Furthermore, expressions indicating relative directions or orientations, such as parallel and orthogonal, include cases where the directions or orientations are not strictly accurate. For example, two directions being orthogonal does not only mean that the two directions are perfectly orthogonal, but also that they are substantially orthogonal, i.e., include a difference of a few percent. In the following explanation, when the term "insulation" is used, it means "electrical insulation."

[0027] (Embodiment) [1. General explanation of energy storage elements] First, a general description of the energy storage element 10 in this embodiment will be given using Figures 1 and 2. Figure 1 is a perspective view showing the external appearance of the energy storage element 10 according to the embodiment. Figure 2 is an exploded perspective view of the energy storage element 10 according to the embodiment. In Figure 2, the electrode body 600 is shown with the insulating film 690 shifted downward relative to the laminate 601.

[0028] The energy storage element 10 is a secondary battery capable of charging and discharging electricity, and specifically, it is a non-aqueous electrolyte secondary battery such as a lithium-ion secondary battery. The energy storage element 10 can be used, for example, as a battery for driving or starting the engine of a mobile vehicle such as an automobile, motorcycle, watercraft, ship, snowmobile, agricultural machinery, construction machinery, or railway vehicle for electric railways. Examples of the automobile mentioned above include electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and fossil fuel (gasoline, diesel, liquefied natural gas, etc.) vehicles. Examples of railway vehicles for electric railways mentioned above include electric trains, monorails, maglev trains, and hybrid trains equipped with both a diesel engine and an electric motor. The energy storage element 10 can also be used as a stationary battery for household or commercial use.

[0029] The energy storage element 10 is not limited to a non-aqueous electrolyte secondary battery; it may be a secondary battery other than a non-aqueous electrolyte secondary battery, or it may be a capacitor. Furthermore, the energy storage element 10 may not be a secondary battery, but a primary battery that allows the user to use the stored electricity without charging.

[0030] As shown in Figure 1, the energy storage element 10 comprises a container 100, a pair of electrode terminals 200 (positive and negative, hereinafter the same), and a pair of upper insulating members 300. Hereinafter, when distinguishing between the positive and negative electrode terminals 200, the positive electrode terminal 200 will be referred to as the first electrode terminal 200A, and the negative electrode terminal 200 will be referred to as the second electrode terminal 200B. As shown in Figure 2, the container 100 houses an electrode body 600, a pair of current collectors 500, and a pair of lower insulating members 400. Hereinafter, when distinguishing between the positive and negative electrode current collectors 500, the positive electrode current collector 500 will be referred to as the first current collector 500A, and the negative electrode current collector 500 will be referred to as the second current collector 500B. An electrolyte (non-aqueous electrolyte) is sealed inside the container 100, but its illustration is omitted. There are no particular restrictions on the type of electrolyte, as long as it does not impair the performance of the energy storage element 10, and various types can be selected. Furthermore, spacers or the like (not shown) may be placed inside the container 100.

[0031] The container 100 is a rectangular parallelepiped (box-shaped) case having a container body 110 with an opening and a lid 120 that closes the opening of the container body 110. The container 100 is structured so that after the electrode body 600 and the like are placed inside the container body 110, the container body 110 and the lid 120 are welded together to seal the inside. The material of the container body 110 and the lid 120 is not particularly limited, but it is preferable that they be weldable metals such as stainless steel, aluminum, aluminum alloy, iron, or plated steel sheet.

[0032] The container body 110 is a rectangular cylindrical member with a bottom that constitutes the main body of the container 100, and has an opening at its top. The lid 120 is a long, rectangular plate-like member in the X-axis direction and is positioned to close the opening of the container body 110. The lid 120 is equipped with a gas discharge valve 122 that discharges gas from inside the container 100 when the internal pressure of the container 100 rises excessively. The lid 120 may also be provided with an injection port or the like for injecting electrolyte into the container 100.

[0033] The electrode body 600 is an energy storage element (power generation element) that includes a positive electrode plate, a negative electrode plate, and a separator, and is capable of storing electricity. As shown in Figure 2, the electrode body 600 has an electrode body main body 610 that performs energy storage and power generation, and a first focusing portion 635 and a second focusing portion 645 located at the Z-axis positive end of the electrode body main body 610, which is one side in the Z-axis direction. The first focusing portion 635, which is the focusing portion of the positive electrode, includes a plurality of first connection portions 632 arranged along the Y-axis direction and is joined to the first current collector 500A. The second focusing portion 645, which is the focusing portion of the negative electrode, includes a plurality of second connection portions 642 arranged along the Y-axis direction and is joined to the second current collector 500B. A detailed explanation of the configuration of the electrode body 600 will be given later with reference to Figures 3 to 6.

[0034] The electrode terminals 200 are terminals (positive terminals and negative terminals) that are electrically connected to the positive and negative plates of the electrode body 600 via the current collector 500. In other words, the electrode terminals 200 are metal members that lead the electricity stored in the electrode body 600 to the external space of the energy storage element 10 and introduce electricity into the internal space of the energy storage element 10 in order to store electricity in the electrode body 600. The electrode terminals 200 are attached to a cover 120 positioned above the electrode body 600. Specifically, the electrode terminals 200 have a shaft portion 201 that penetrates the cover 120. The shaft portion 201 of the electrode terminals 200 is inserted into and crimped into the through hole 301 of the upper insulating member 300, the through hole 121 of the cover 120, the through hole 401 of the lower insulating member 400, and the through hole 501 of the current collector 500. As a result, the electrode terminal 200 is fixed to the cover 120 together with the upper insulating member 300, the lower insulating member 400, and the current collector 500. The first electrode terminal 200A, which is the positive electrode terminal 200, is made of aluminum or an aluminum alloy, and the second electrode terminal 200B, which is the negative electrode terminal 200, is made of copper or a copper alloy.

[0035] The current collector 500 is a component that is joined to the first focusing portion 635 or the second focusing portion 645 of the electrode body 600. Methods for joining include ultrasonic welding, laser welding, resistance welding, or crimping. The material of the current collector 500 is not limited, but for example, the first current collector 500A, which is the positive electrode current collector 500, is made of a metal such as aluminum or an aluminum alloy. The second current collector 500B, which is the negative electrode current collector 500, is made of a metal such as copper or a copper alloy.

[0036] The upper insulating member 300 is a member that insulates the lid 120 from the electrode terminal 200. In this embodiment, the upper insulating member 300 also functions as a gasket that seals the space between the lid 120 and the shaft portion 201 of the electrode terminal 200. The lower insulating member 400 is a member that insulates the lid 120 from the current collector 500. Both the upper insulating member 300 and the lower insulating member 400 are formed from a resin material that has electrical insulating properties. Examples of this resin material include 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), polyamide (PA), or ABS resin.

[0037] [2. Electrode Configuration] Next, the configuration of the electrode body 600 according to the embodiment will be described with reference to Figures 3 to 6, in addition to Figure 2 described above. Figure 3 is a first plan view (viewed from the Z-axis positive direction) showing the configuration of the laminate 601 of the electrode body 600 according to the embodiment. In Figure 3, the first connection portion 632 of the laminate 601 is represented by a thick solid line, and the second connection portion 642 of the laminate 601 is represented by a thick dashed line. Figure 4 is a second plan view showing the configuration of the laminate 601 of the electrode body 600 according to the embodiment. In Figure 4, the first connection portion 632, which is part of the first electrode plate 630, is represented by a rectangle with diagonal lines, and the second connection portion 642, which is part of the second electrode plate 640, is represented by a rectangle with dots.

[0038] Figure 5 is a plan view showing the laminated structure in the flat portion 603 of the laminated body 601 according to the embodiment. In Figure 5, the rectangular region V in Figure 3 is shown in an enlarged view. Figure 6 is a plan view showing the laminated structure in the folded portion 602 of the laminated body 601 according to the embodiment. In Figure 6, the rectangular region VI in Figure 3 is shown in an enlarged view. Figures 3 to 6 are all schematic diagrams to clearly explain the configuration of the laminated body 601, and the insulating film 690 of the electrode body 600 is not shown.

[0039] As shown in Figures 3 and 4, the electrode body 600 according to this embodiment has a laminated body 601 that is folded in an accordion shape. The electrode body 600 includes a flat portion 603 which is the portion of the laminated body 601 that extends along the X-axis direction, and a plurality of bent portions 602 connected to both ends of the flat portion 603 in the X-axis direction. In the flat portion 603, when the strip-shaped laminated body 601 is folded in an accordion shape, multiple flat plate-like portions, each being a part of the laminated body 601, are arranged in the Y-axis direction. In other words, the number of flat plate-like portions arranged in the Y-axis direction in the flat portion 603 by folding one laminated body 601 in an accordion shape (in other words, the number of stacks of flat plate-like portions in the Y-axis direction) is sometimes simply called the "number of laminated bodies 601". For example, in the electrode body 600 shown in Figure 3, it is said that nine laminated bodies 601 are arranged in the Y-axis direction in the flat portion 603. In this embodiment, the Y-axis direction is an example of a first direction, the Z-axis direction is an example of a second direction, and the X-axis direction is an example of a third direction.

[0040] The number of folds (number of folded sections 602) of the laminate 601 shown in Figures 3 and 4 are examples. When the laminate 601 is folded in an accordion shape, it has at least two folded sections 602. In other words, the number of folds (number of folded sections 602) of the laminate 601 only needs to be 2 or more.

[0041] As shown in Figures 3 and 4, the laminate 601 according to this embodiment has a first electrode plate 630 and a second electrode plate 640 having opposite polarities. In this embodiment, the first electrode plate 630 is a positive electrode plate, and the second electrode plate 640 is a negative electrode plate. Specifically, as shown in Figures 4 and 5, the laminate 601 is formed of a second electrode plate 640 with its thickness direction oriented in the Y-axis direction, and a pair of first electrode plates 630 that sandwich the second electrode plate 640 from both sides in the Y-axis direction. More specifically, each of the pair of first electrode plates 630 is arranged to sandwich the second electrode plate 640 via a separator 650.

[0042] In this embodiment, the pair of first electrode plates 630 are separate electrode plates, and to distinguish them, they are referred to as first electrode plate 630a and first electrode plate 630b, as shown in Figures 4 to 6. In this embodiment, the separator 650 placed between the first electrode plate 630a and the second electrode plate 640, and the separator 650 placed between the first electrode plate 630b and the second electrode plate 640 are also separate. That is, the laminate 601 according to this embodiment consists of one second electrode plate 640, two first electrode plates 630, and two separators 650, all of which are strip-shaped members, arranged in the Y-axis direction in the order shown in Figures 4 to 6, and folded in an accordion-like manner. At least one of the two separators 650 may extend further from the longitudinal end of the laminate 601. In this case, the extended portion of the separator 650 may be wrapped around the bellows-folded laminate 601 at least once, thereby functioning as a member for fixing the laminate 601 and / or as a member for insulating the laminate 601 from other members. In this case, the electrode body 600 does not need to have an insulating film 690 (see Figure 2).

[0043] As shown in Figures 5 and 6, the first electrode plate 630 has a first base material layer 631 and a first composite material layer 633 formed on the surface of the first base material layer 631 facing the second electrode plate 640. In this embodiment, the first base material layer 631 is the base material layer for the positive electrode and is a long, strip-shaped metal foil made of aluminum or an aluminum alloy. The first composite material layer 633 is formed of a composite material containing the positive electrode active material. As shown in Figures 5 and 6, the second electrode plate 640 has a second base material layer 641 and a second composite material layer 643 formed on both sides of the second base material layer 641 in the thickness direction (Z-axis direction). In this embodiment, the second base material layer 641 is the base material layer for the negative electrode and is a long, strip-shaped metal foil made of copper or a copper alloy. The second composite material layer 643 is formed of a composite material containing the negative electrode active material. The separator 650 can be, for example, a microporous sheet or nonwoven fabric made of resin.

[0044] In the first electrode plate 630 according to this embodiment, the first composite material layer 633 is formed continuously from one end to the other in the longitudinal direction of the first base material layer 631. Similarly, in the second electrode plate 640, the second composite material layer 643 is formed continuously from one end to the other in the longitudinal direction of the second base material layer 641. The longitudinal directions of the first base material layer 631 and the second base material layer 641 are the longitudinal directions of the first base material layer 631 and the second base material layer 641 when the laminate 601 is not folded in an accordion shape. Therefore, even in the bent portion 602 (see Figure 6), each of the first electrode plates 630a and 630b has the first composite material layer 633, and the second electrode plate 640 has the second composite material layer 643 at a position opposite each of the first electrode plates 630a and 630b. Therefore, the bent portion 602 is a part of the electrode body 610 and functions as a part that stores and generates electricity.

[0045] As the material for forming the metal foil which is the first base layer 631 or the second base layer 641, in addition to the materials mentioned above, any known material such as nickel, iron, stainless steel, titanium, calcined carbon, conductive polymer, conductive glass, or Al-Cd alloy can be used as appropriate. As the positive electrode active material and negative electrode active material used in the first composite layer 633 and the second composite layer 643, any known material can be used as long as it is an active material capable of intercalating and deintercalating lithium ions. The portion of the first base layer 631 on which the first composite layer 633 is formed and the portion of the second base layer 641 on which the second composite layer 643 is formed are stacked in multiple layers in the Y-axis direction as shown in Figures 2 to 5. This forms the electrode body 610, which is the part of the electrode body 600 that stores and generates electricity.

[0046] Each of the first electrode plate 630 and the second electrode plate 640 has a portion at its end in the Z-axis positive direction where the asphalt mixture layer is not formed in the base material layer (hereinafter referred to as the "asphalt mixture non-formed portion"). Specifically, the first electrode plate 630 has a first connecting portion 632 which is the asphalt mixture non-formed portion, and the second electrode plate 640 has a second connecting portion 642 which is the asphalt mixture non-formed portion. The first connecting portion 632 has a shape that protrudes from one end of the strip-shaped first electrode plate 630 in the short direction (in this embodiment, the Z-axis positive direction) (see Figure 2), and is a portion called, for example, a "tab" or "tab portion". The second connecting portion 642 has a shape that protrudes from one end of the strip-shaped second electrode plate 640 in the short direction (in this embodiment, the Z-axis positive direction), and is a portion called, for example, a "tab" or "tab portion". In this embodiment, as shown in Figures 2 to 4, a first focusing section 635 is formed by a plurality of first connecting sections 632 arranged along the Y-axis, and a second focusing section 645 is formed by a plurality of second connecting sections 642 arranged along the Y-axis. That is, each of the first focusing section 635 and the second focusing section 645 is an assembly of metal foils, which are brought together in the direction of the alignment of the first connecting sections 632 or the second connecting sections 642 (Y-axis direction) and joined to the current collector 500.

[0047] As described above, the energy storage element 10 according to this embodiment comprises a container 100 and an electrode body 600 housed in the container 100, having a first electrode plate 630 and a second electrode plate 640 having opposite polarities. The electrode body 600 is a laminate 601 formed of a second electrode plate 640 whose thickness direction is oriented in the Y-axis direction and a pair of first electrode plates 630, each sandwiching the second electrode plate 640 from both sides in the Y-axis direction via a separator 650, and has a laminate 601 that is folded in an accordion shape.

[0048] According to this configuration, the electrode body 600 in this embodiment does not have a curved portion containing, for example, several dozen layers of positive and negative electrode plates, as found in a wound electrode body. Specifically, the portion corresponding to the curved portion of a wound electrode body is formed in the electrode body 600 of this embodiment by a plurality of bent portions 602 arranged in the Y-axis direction, as shown in Figures 2, 3, and 6. Therefore, it is easy to improve the volume occupancy rate of the electrode body 600 within the container 100. Consequently, the energy storage element 10 of this embodiment can improve energy density.

[0049] In this embodiment, the bent portion 602 includes only a single-layer second electrode plate 640 and two layers of first electrode plates 630 sandwiching the second electrode plate 640 as electrode plates. Therefore, even if the electrode body 600 expands, the stress generated in the bent portion 602 due to that expansion will not be large enough to cause defects in the first electrode plate 630 and the second electrode plate 640. In this way, the accordion-like folding of the laminated body 601 makes it easier to improve the volume occupancy rate of the electrode body 600 within the container 100, and suppresses the occurrence of electrode plate defects caused by the expansion of the electrode body 600.

[0050] In the electrode body 600 according to this embodiment, both outer surfaces of the laminate 601 in the stacking direction (Y-axis direction) are first electrode plates 630. Therefore, when the laminate 601 is folded in an accordion-like manner, the two opposing surfaces have the same polarity (first electrode plate 630). Consequently, a separator 650 is not required between these two opposing surfaces. This is advantageous, for example, in improving energy density.

[0051] In laminated electrode bodies, the process of stacking the electrode plates and separators one by one is required, which presents a problem in improving manufacturing efficiency. In contrast, the electrode body 600 according to this embodiment is formed by folding a laminate 601 that includes a second electrode plate 640 and a pair of first electrode plates 630, each sandwiching the second electrode plate 640 via a separator 650, thus enabling efficient manufacturing.

[0052] In this embodiment, the pair of first electrode plates 630 are composed of two separate first electrode plates, 630a and 630b, as shown in Figures 3 and 4. Therefore, the electrode body 600 can be manufactured by stacking and folding three electrode plates of approximately the same length (the second electrode plate 640 and the pair of first electrode plates 630 (630a and 630b)). Thus, compared to, for example, manufacturing a first electrode plate 630 that is about twice the length of the second electrode plate 640 and folding the first electrode plate 630 in the longitudinal center to sandwich the second electrode plate 640, the electrode body 600 can be manufactured more efficiently.

[0053] In this embodiment, the energy storage element 10 is a first current collector 500A housed in a container 100, as shown in Figure 2, and comprises a first current collector 500A that electrically connects the first electrode plate 630 of the electrode body 600 to the first electrode terminal 200A arranged in the container 100. Each of the pair of first electrode plates 630 has a first base material layer 631 and a first composite material layer 633 formed on the surface of the first base material layer 631 facing the second electrode plate 640, as shown in Figures 4 to 6. The laminate 601 has a first focusing portion 635 provided at one end in the Z-axis direction perpendicular to the Y-axis direction (in this embodiment, the Z-axis positive direction). The first focusing portion 635 is formed by arranging first connection portions 632, which are portions of the first base material layer 631 where the first composite material layer 633 is not formed, along the Y-axis direction. The first current collector 500A is joined to the first focusing portion 635.

[0054] With this configuration, the first connecting portion 632, which is folded in an accordion-like manner and arranged along the Y-axis, can be joined to the first current collector 500A as the first focusing portion 635. Therefore, the current flowing from the first electrode plate 630 can be efficiently collected by the first current collector 500A.

[0055] In this embodiment, as shown in Figures 2 to 4, the first focusing section 635 is divided into a plurality of first sub-bundles 636, each containing one or more first connecting sections 632. The plurality of first sub-bundles 636 are formed at different positions in the Y-axis direction. Each of the plurality of first sub-bundles 636 is joined to a different position on the first current collector 500A.

[0056] In this embodiment, as described above, the laminate 601 includes a pair (2) of first electrode plates 630, and therefore the two first electrode plates 630 are folded in an accordion-like manner. As a result, the first focusing section 635 includes a relatively large number of first connection sections 632. Specifically, as shown in Figures 3 and 4, the number of first connection sections 632 included in the first focusing section 635 is twice the number of second connection sections 642 included in the second focusing section 645. As shown in Figure 2, the first focusing section 635, which includes such a relatively large number of first connection sections 632, is divided into a plurality of first sub-bundles 636 and joined to the first current collector 500A. This makes it easier to join the first focusing section 635 to the first current collector 500A compared to the case where all the first connection sections 632 included in the first focusing section 635 are joined to the first current collector 500A at once.

[0057] In this embodiment, as shown in Figures 2 to 4, the first focusing unit 635 has two first sub-bundles 636. When these two first sub-bundles 636 are distinguished as first sub-bundle 636a and first sub-bundle 636b, as shown in Figure 2, first sub-bundle 636a is joined to the joint 502a of the first current collector 500A, and first sub-bundle 636b is joined to the joint 502b of the first current collector 500A. Each of the joints 502a and 502b is a part of the back surface (the surface facing the electrode body 600) of the first current collector 500A, and in Figure 2, the approximate range of each is represented by the dotted area.

[0058] More specifically, in this embodiment, as shown in Figures 2 to 4, the first focusing unit 635 includes two first sub-bundles 636 arranged at different positions in the X-axis direction, which is perpendicular to the Y-axis and Z-axis directions.

[0059] Thus, in this embodiment, the two first sub-bundles 636 are positioned at different locations in the Y-axis and X-axis directions, respectively. Specifically, as shown in Figures 2 to 4, the first sub-bundle 636a is positioned at a different location from the first sub-bundle 636b in the Y-axis and X-axis directions, respectively. This makes it easier to connect the first sub-bundles 636a and 636b to the first current collector 500A.

[0060] The position of the first sub-bundle 636 is based on the end of the first sub-bundle 636 in the negative Z-axis direction (i.e., the end closest to the electrode body 610). For example, the position of the first sub-bundle 636a is within a roughly rectangular area that includes the four first connection parts 632 in the positive Y-axis direction, which are schematically shown in Figures 3 and 4. In this embodiment, the first sub-bundle 636a and the first sub-bundle 636b are positioned so as not to overlap in both the Y-axis and X-axis directions. However, the two first sub-bundles 636 of the first focusing unit 635 may be positioned so as to overlap in either the Y-axis or X-axis direction. A first focusing unit 635 having two first sub-bundles 636 positioned so as to overlap in the X-axis direction will be described later as Modification 1.

[0061] The number of first connecting portions 632 included in the first subbundles 636a and 636b, respectively, as shown in Figures 3 and 4, is illustrative. The first subbundle 636 only needs to contain one or more first connecting portions 632.

[0062] In this embodiment, the first connecting portion 632 is a convex portion of the first electrode plate 630 that protrudes from the portion where the first composite material layer 633 is formed, and is, as described above, a portion called, for example, a "tab". However, a portion of the first electrode plate 630 that is continuous over almost the entire longitudinal direction may be treated as the first connecting portion. In this case, the number of layers of the portions of the first electrode plate 601 that are continuous along the Y-axis direction when the laminate 601 is folded in an accordion shape is treated as the number of first connecting portions. An electrode body having a portion of the first electrode plate 630 that is continuous over almost the entire longitudinal direction will be described later as Modification 2.

[0063] In this embodiment, as shown in Figures 5 and 6, the first composite layer 633 is formed on each of the pair of first electrode plates 630 only on the surface of the first base material layer 631 facing the second electrode plate 640 in the Y-axis direction. In other words, on the first electrode plate 630, the first composite layer 633 is formed on only one side of the first base material layer 631.

[0064] In the electrode body 600 according to this embodiment, as shown in Figures 3 to 6, the laminate 601 has a structure in which a second electrode plate 640 is sandwiched between a pair of first electrode plates 630. Therefore, when the laminate 601 is folded in an accordion shape, in the parts of the laminate 601 that face each other, the two opposing surfaces are the surfaces of one of the pair of first electrode plates 630 that do not face the second electrode plate 640. Therefore, the parts of the laminate 601 that face each other do not contribute to power generation. Consequently, by not forming the first composite material layer 633 on these two opposing surfaces, it is possible to reduce the thickness of the electrode body 600 in the lamination direction while maintaining the power generation amount (storage capacity) of the electrode body 600.

[0065] In this embodiment, as shown in Figures 5 and 6, the second electrode plate 640 has a second base material layer 641 and a second composite material layer 643 formed on both sides of the second base material layer 641 in the Y-axis direction. The thickness of the first base material layer 631 of the first electrode plate 630 is thinner than the thickness of the second base material layer 641 of the second electrode plate 640.

[0066] In this configuration, the first base material layer 631 of the two first electrode plates 630 included in the laminate 601 is thinner than the second base material layer 641 of the second electrode plate 640. Therefore, the increase in the thickness of the electrode body 600 due to the accumulation of the thickness of the first base material layer 631 is suppressed. This is advantageous for improving the energy density of the energy storage element 10.

[0067] The above description focuses on the electrode body 600 of the energy storage element 10 according to the embodiment. However, the electrode body to which the energy storage element 10 is provided may have a configuration different from that of the electrode body 600 shown in Figures 2 to 6. Therefore, the following describes variations in the configuration of the electrode body 600, focusing on the differences from the above embodiment.

[0068] [3-1. Variation 1] Figure 7 is a plan view showing the configuration of the laminate 601 of the electrode body 600a according to the first modified embodiment. In Figure 7, the insulating film 690 (see Figure 2) of the electrode body 600a is not shown.

[0069] The electrode body 600a shown in Figure 7 is a laminate 601 formed of a second electrode plate 640 oriented in the thickness direction in the Y-axis direction and a pair of first electrode plates 630, each sandwiching the second electrode plate 640 from both sides in the Y-axis direction via a separator 650, and has a bellows-like folded laminate 601. The laminate 601 has a first focusing portion 635 provided at one end in the Z-axis direction (in this modified example, the Z-axis positive direction). The first focusing portion 635 is divided into a plurality of first sub-bundles 636, each containing one or more first connecting portions 632. The plurality of first sub-bundles 636 are formed at different positions in the Y-axis direction. These configurations are common to the electrode body 600 according to the embodiment shown in Figures 2 to 6.

[0070] The electrode body 600a according to this modified example differs from the electrode body 600 according to the embodiment in that a plurality of first sub-bundles 636 are formed at different positions in the Y-axis direction and are arranged at overlapping positions in the X-axis direction. Specifically, in this modified example, the first focusing unit 635 has two first sub-bundles 636, namely first sub-bundles 636a and 636b. The first sub-bundles 636a and 636b are arranged on a straight line parallel to the Y-axis direction. That is, in the Y-axis direction, the positions of the first sub-bundles 636a and 636b do not overlap, while in the X-axis direction, the positions of the first sub-bundles 636a and 636b overlap. More specifically, in this modified example, in the X-axis direction, the positions of the first sub-bundles 636a and 636b coincide.

[0071] In other words, in this modified example, the multiple first connection parts 632 included in the first focusing section 635 are arranged in a single row along the Y-axis direction. Even in this case, the first focusing section 635 can be divided into a first sub-bundle 636a in the positive Y-axis direction and a first sub-bundle 636b in the negative Y-axis direction, each containing one or more first connection parts 632. This makes it easier to connect the first focusing section 635 to the first current collector 500A compared to the case where all the first connection parts 632 included in the first focusing section 635 are connected to the first current collector 500A at once.

[0072] [3-2. Variation 2] Figure 8 is a perspective view showing the general configuration of the electrode body 600b according to the modified example 2 of the embodiment. Figure 9 is a schematic diagram showing the junction between the first focusing portion 635 and the first current collector 500Aa of the electrode body 600b according to the modified example 2 of the embodiment.

[0073] The electrode body 600b according to this modified example shown in Figure 8 comprises a laminated body 601 folded in a bellows-like manner. Although not clearly shown in Figures 8 and 9, the laminated body 601 according to this modified example, like the electrode body 600 according to the embodiment, has a second electrode plate 640 with its thickness direction oriented in the Y-axis direction, and a pair of first electrode plates 630, each sandwiching the second electrode plate 640 from both sides in the Y-axis direction via a separator 650.

[0074] In this modified example, a first focusing portion 635 is provided at one end in the X-axis direction (the positive X-axis direction in this modified example), and a second focusing portion 645 is provided at the other end in the X-axis direction (the negative X-axis direction in this modified example), which differs from the electrode body 600 according to the embodiment. Furthermore, the first electrode plate 630 according to this modified example has a continuous non-composite layer portion along almost the entire length. That is, the first connecting portion 632 according to this modified example is arranged continuously along the length of the first electrode plate 630 at the X-axis end of the first electrode plate 630 and is folded in an accordion-like manner. This forms a first focusing portion 635 including the first connecting portion 632 arranged along the Y-axis direction. The same applies to the second electrode plate 640. That is, the second connecting portion 642 is arranged continuously along the length of the second electrode plate 640 at the X-axis end of the second electrode plate 640 and is folded in an accordion-like manner. This forms a second focusing portion 645, which includes a second connecting portion 642 arranged along the Y-axis.

[0075] In the energy storage element 10a equipped with the electrode body 600b configured in this way, the electrode body 600b and the electrode terminal 200 are electrically connected by a current collector 500 having legs 510 extending along the Z-axis direction. For example, as shown in Figure 9, a first focusing portion 635 provided at the X-axis end of the electrode body 600b is joined to a first current collector 500Aa having a pair of elongated legs 510a and 510b in the Z-axis direction. Specifically, the first focusing portion 635 is inserted between the pair of legs 510a and 510b, and each of the pair of legs 510a and 510b is joined to the first focusing portion 635 by ultrasonic bonding or the like. At this time, the first focusing portion 635 is divided into two first sub-bundles 637, each joined to the pair of legs 510a and 510b. More specifically, as shown in Figure 9, the first focusing section 635 has a first sub-bundle 637a joined to the leg portion 510a and a first sub-bundle 637b joined to the leg portion 510b. In this way, when the first sub-bundle 637a and the first sub-bundle 637b are separated, one or more first connecting portions 632 may be included in both the first sub-bundle 637a and the first sub-bundle 637b. Specifically, this will be explained as follows.

[0076] First, in order to distinguish the multiple first connection sections 632 included in the first focusing section 635 from one another, each of the multiple first connection sections 632 is assigned an alphabet letter (A, B, ..., N) as shown in Figure 8. In this case, the multiple first connection sections 632 can be represented as first connection section 632A, first connection section 632B, ... first connection section 632N. Note that in Figure 8, the designation "632" is omitted for first connection sections 632 other than first connection sections 632A and 632N. These multiple first connection sections 632 are divided into first sub-bundles 637a and first sub-bundles 637b, as shown in Figure 9.

[0077] Specifically, the eight first connection parts 632, from the first connection part 632A to the first connection part 632H, belong to the first sub-bundle 637a, and the seven first connection parts 632, from the first connection part 632H to the first connection part 632N, belong to the first sub-bundle 637b. In other words, the first connection part 632H is included in both the first sub-bundle 637a and the first sub-bundle 637b.

[0078] Thus, in the electrode body 600b according to this modified example, the first focusing portion 635 includes at least one first connecting portion 632 belonging to two or more of the first sub-bundles 637 among the plurality of first sub-bundles 637.

[0079] In other words, one or more first connection parts 632 included in the first focusing section 635 are permitted to belong to a plurality of first sub-bundles 637. That is, it is not necessary to completely separate the plurality of first connection parts 632; for example, one or more first connection parts 632 may be included in common in two adjacent first sub-bundles 637. Therefore, when a plurality of first connection parts 632 aligned in the Y-axis direction are divided in the Y-axis direction so that they belong to two first sub-bundles 637 (see Figure 9), they may be divided so that each of the two first sub-bundles 637 contains more than half the number of first connection parts 632. As a result, it is easy to create a state in which all of the plurality of first connection parts 632 are included in at least one of the two first sub-bundles 637. This suppresses leakage of connection between the first connection parts 632 and the first current collector 500Aa (the occurrence of first connection parts 632 that are not connected to the first current collector 500Aa).

[0080] The connection configuration between the electrode body 600b and the current collector 500 is not limited to the configuration shown in Figure 9. For example, a portion of the current collector 500 inserted between the first connection portion 632H and the first connection portion 632I may be joined to the first sub-bundle 637a. Another portion of the current collector 500 inserted between the first connection portion 632G and the first connection portion 632H may be joined to the second sub-bundle 637b.

[0081] [4. Other variations] Although an embodiment of the present invention has been described above, the present invention is not limited to this embodiment. In other words, the embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is intended to include all modifications in the sense and scope equivalent to the claims.

[0082] In the above embodiment, the first electrode plate 630 is a positive electrode plate and the second electrode plate 640 is a negative electrode plate. However, the first electrode plate 630 may be a negative electrode plate and the second electrode plate 640 may be a positive electrode plate. In this case, the first current collector 500A is a negative electrode current collector 500, and the first electrode terminal 200A is a negative electrode terminal 200. That is, the first electrode terminal 200A, which is the negative electrode terminal 200, may be electrically connected via the first current collector 500A to the first focusing section 635 of the negative electrode, which has a plurality of first sub-bundles 636.

[0083] The second focusing portion 645 of the electrode body 600 may have multiple sub-bundles, similar to the first focusing portion 635. Figure 10 is a plan view showing the configuration of a laminate 601 having a second focusing portion 645 that includes multiple second sub-bundles 646. As shown in Figure 10, the second focusing portion 645 may have multiple second sub-bundles 646, each containing one or more second connecting portions 642, and arranged at different positions in the Y-axis direction. Each of the multiple second sub-bundles 646 may be joined to a different position on the second current collector 500B. This configuration is particularly useful when the second focusing portion 645 contains a relatively large number of second connecting portions 642. Specifically, compared to the case where all the second connecting portions 642 included in the second focusing portion 645 are joined to the second current collector 500B at once, joining the second focusing portion 645 to the second current collector 500B is easier.

[0084] The two second sub-bundles 646a and 646b, which are the two second sub-bundles 646, may have different positions in the X-axis direction, similar to the first sub-bundles 636a and 636b shown in Figure 10. This makes it easier, for example, to connect each of the two second sub-bundles 646 to the second current collector 500B.

[0085] The first focusing portion 635 and the second focusing portion 645 of the electrode body 600 do not need to protrude in the same direction from the electrode body 610 (see Figure 2). The first focusing portion 635 and the second focusing portion 645 of the electrode body 600 may protrude from the electrode body 610 in opposite directions. For example, in the electrode body 600 shown in Figure 2, the first focusing portion 635 may be positioned to protrude in the positive Z-axis direction from the Z-axis positive end of the electrode body 610, and the second focusing portion 645 may be positioned to protrude in the negative Z-axis direction from the Z-axis negative end of the electrode body 610. In this case, the second current collector 500B may have a portion that extends in the Z-axis direction to connect the second focusing portion 645 located at the Z-axis negative end of the electrode body 600 to the second electrode terminal 200B.

[0086] The electrode body 600 may have two or more first focusing portions 635. For example, two first focusing portions 635 aligned in the X-axis direction may be arranged at the Z-positive end of the electrode body 610. In this case, two second focusing portions 645 aligned in the X-axis direction may be arranged at the Z-negative end of the electrode body 610.

[0087] The features of the above modified example 2 may also be applied to a focusing portion that is provided in a convex shape from a part of the electrode body 610, such as the first focusing portion 635 (see Figures 2 to 4) according to the embodiment. For example, if the width of the first connecting portion 632 in the X-axis direction according to the embodiment is relatively large, the multiple first connecting portions 632 included in the first focusing portion 635 may be divided so that one or more first connecting portions 632 are commonly included in both the first partial bundles 636a and 636b.

[0088] Furthermore, forms constructed by arbitrarily combining the components included in the above embodiments and their modified examples are also included within the scope of the present invention. [Industrial applicability]

[0089] This invention can be applied to energy storage elements such as lithium-ion secondary batteries. [Explanation of symbols]

[0090] 10 Energy storage elements 100 containers 110 Container body 120 Lid 121, 301, 401, 501 through holes 122 Gas discharge valve 200 electrode terminal 200A first electrode terminal 200B Second electrode terminal 201 Shaft 300 Upper insulating material 400 Lower insulating member 500 Current collector 500A, 500Aa first current collector 500B Second current collector 502a, 502b joint 510a, 510b Legs 600, 600a, 600b electrode body 601 Laminate 602 Folding section 603 Flat area 610 Electrode Body 630, 630a, 630b first plate 631 First base layer 632, 632A~632N First connection section 633 First composite layer 635 First focusing section 636, 636a, 636b, 637, 637a, 637b First partial bundle 640 Second plate 641 Second base layer 642 Second connection section 643 Second composite material layer 645 Second focusing section 646, 646a, 646b second partial bundle 650 Separator 690 Insulating film

Claims

1. A storage element comprising a container and an electrode body housed in the container, having a first electrode plate and a second electrode plate having opposite polarities, The electrode body is A laminate formed of a second electrode plate oriented in the thickness direction in a first direction, and a pair of first electrode plates each sandwiching the second electrode plate from both sides in the first direction via a separator, the laminate having a bellows-like folded structure. Energy storage element.

2. Furthermore, the container comprises a first current collector housed within the container, which electrically connects the first electrode plate of the electrode body with the first electrode terminals arranged in the container. Each of the pair of first electrode plates has a first base material layer and a first composite material layer formed on the surface of the first base material layer facing the second electrode plate. The laminate has a first convergence portion provided at one end in a second direction perpendicular to the first direction, which is formed by arranging first connection portions, which are portions of the first base material layer in which the first composite material layer is not formed, along the first direction. The first current collector is connected to the first focusing section. The energy storage element according to claim 1.

3. The first focusing section is divided into a plurality of first subbundles, each containing one or more first connecting sections, and formed at mutually different positions in the first direction. Each of the aforementioned plurality of first subbundles is joined to a different position in the first current collector. The energy storage element according to claim 2.

4. The first focusing unit includes at least one first connecting unit belonging to two or more first subbundles among the plurality of first subbundles, The energy storage element according to claim 3.

5. The first focusing unit includes two of the first sub-bundles, which are positioned at different locations in a third direction perpendicular to the first and second directions. The energy storage element according to claim 3.

6. The first composite layer is formed on each of the pair of first electrode plates, only on the surface of the first base material layer facing the second electrode plate, out of the two surfaces in the first direction. The energy storage element according to any one of claims 2 to 5.

7. The second electrode plate comprises a second base material layer and a second composite material layer formed on both sides of the second base material layer in the first direction. The thickness of the first substrate layer of the first electrode plate is thinner than the thickness of the second substrate layer of the second electrode plate. The energy storage element according to any one of claims 2 to 5.

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