Power storage element

Abstract

This power storage element comprises an electrode body, and a current collector connected to the electrode body. The electrode body comprises a first current collecting foil and a second current collecting foil that are stacked in a first direction. The first current collecting foil comprises a first conductive layer and a first insulating layer that are arranged in the first direction. The second current collecting foil comprises a second conductive layer and a second insulating layer that are arranged in the first direction. The second current collecting foil comprises a first protruding part that protrudes further in a second direction intersecting the first direction than the first current collecting foil, the first protruding part being a protruding portion of the second conductive layer and the second insulating layer. The first conductive layer and the second conductive layer of the first protruding part are electrically connected to the current collector in a state of being in contact with the current collector.

Description

Energy storage element

[0001] This invention relates to an energy storage element.

[0002] Patent Document 1 discloses a non-aqueous secondary battery comprising a positive electrode including a positive electrode current collector having a multilayer structure in which a resin layer is sandwiched between metal foils, and a positive electrode active material layer formed on the positive electrode current collector, and a tab electrode electrically connected to the positive electrode, wherein the positive electrode current collector has a connection region in which no resin layer is interposed, and the tab electrode is welded and fixed to the connection region of the positive electrode current collector such that it overlaps with a part of the resin layer.

[0003] Japanese Patent Publication No. 2012-155974

[0004] In the non-aqueous secondary battery disclosed in Patent Document 1, the configuration of the positive electrode current collector is complex.

[0005] The present invention aims to provide an energy storage element that allows a current collector foil having an insulating layer to be connected to a current collector with a simple configuration.

[0006] An energy storage element according to one aspect of the present invention comprises an electrode body and a current collector connected to the electrode body, wherein the electrode body comprises a first current collector foil and a second current collector foil laminated in a first direction, the first current collector foil comprises a first conductive layer and a first insulating layer aligned in the first direction, the second current collector foil comprises a second conductive layer and a second insulating layer aligned in the first direction, the second current collector foil comprises a first protrusion which is a protruding portion of the second conductive layer and the second insulating layer that protrudes in a second direction intersecting the first direction from the first current collector foil, and the first conductive layer and the second conductive layer of the first protrusion are electrically connected to the current collector while in contact with the current collector.

[0007] A power storage element according to another aspect of the present invention comprises an electrode body, a current collector connected to the electrode body, and an auxiliary member sandwiching the electrode body between the current collector and the electrode body, wherein the electrode body comprises a third current collector foil and a fourth current collector foil laminated in a first direction, the third current collector foil comprises a third conductive layer and a third insulating layer aligned in the first direction, the fourth current collector foil comprises a fourth conductive layer and a fourth insulating layer aligned in the first direction, the fourth current collector foil comprises a second protrusion which is a protruding portion of the fourth conductive layer and the fourth insulating layer that protrudes in a second direction intersecting the first direction from the third current collector foil, the third conductive layer and the fourth conductive layer of the second protrusion are electrically connected to the auxiliary member in contact with the auxiliary member, and the auxiliary member is electrically connected to the current collector.

[0008] According to the energy storage element of the present invention, a current collector foil having an insulating layer can be connected to a current collector with a simple configuration.

[0009] Figure 1 is a perspective view showing the external appearance of an energy storage element according to an embodiment. Figure 2 is an exploded perspective view showing each component of the energy storage element according to an embodiment in a disassembled state. Figure 3 is a perspective view and a cross-sectional view showing the configuration of the electrode body according to an embodiment. Figure 4 is a cross-sectional view showing the configuration for joining the current collector, electrode body and auxiliary member according to an embodiment. Figure 5A is a simplified cross-sectional view showing the configuration for joining the current collector, electrode body and auxiliary member according to an embodiment. Figure 5B is a simplified cross-sectional view showing the configuration for joining the current collector, electrode body and auxiliary member according to an embodiment. Figure 6 is a plan view showing an example of an energy storage device according to an embodiment. Figure 7A is a simplified cross-sectional view showing the configuration for joining the current collector, electrode body and auxiliary member according to Modification 1 of the embodiment. Figure 7B is a simplified cross-sectional view showing the configuration for joining the current collector, electrode body and auxiliary member according to Modification 1 of the embodiment. Figure 8 is a simplified cross-sectional view showing the configuration for joining the current collector, electrode body and auxiliary member according to Modification 2 of the embodiment.

[0010] The inventors of the present invention have found that the following problems arise with respect to the non-aqueous secondary battery described in Patent Document 1. In the non-aqueous secondary battery described in Patent Document 1, a connection region without a resin layer is formed in a multilayer positive electrode current collector in which a resin layer is sandwiched between metal foils, and this connection region is welded and fixed to the tab electrode. Thus, in the conventional configuration, in order to connect the positive electrode current collector having a resin layer to the tab electrode, it is necessary to form a connection region without a resin layer in the positive electrode current collector, resulting in a complex structure for the positive electrode current collector.

[0011] (1) An energy storage element according to one aspect of the present invention comprises an electrode body and a current collector connected to the electrode body, wherein the electrode body comprises a first current collector foil and a second current collector foil laminated in a first direction, the first current collector foil comprises a first conductive layer and a first insulating layer arranged in the first direction, the second current collector foil comprises a second conductive layer and a second insulating layer arranged in the first direction, the second current collector foil comprises a first protrusion which is a protruding portion of the second conductive layer and the second insulating layer that protrudes in a second direction intersecting the first direction from the first current collector foil, and the first conductive layer and the second conductive layer of the first protrusion are electrically connected to the current collector while in contact with the current collector.

[0012] According to one aspect of the present invention, the first current collector foil comprises a first conductive layer and a first insulating layer, and the second current collector foil comprises a second conductive layer and a second insulating layer. In this way, since the first and second current collector foils are partially made of insulating layers, it is possible to reduce weight, reduce the amount of conductive material (metal material, etc.) used, and improve the strength of the current collector foils. In this configuration, the second current collector foil comprises a first protrusion, which is the protruding portion of the second conductive layer and the second insulating layer that protrudes from the first current collector foil, and the first conductive layer and the second conductive layer of the first protrusion are electrically connected to the current collector while in contact with the current collector. In this way, by making the second current collector foil protrude from the first current collector foil and bringing the first conductive layer of the first current collector foil and the second conductive layer of the first protrusion of the second current collector foil into contact with the current collector, the first and second current collector foils can be electrically connected to the current collector. This eliminates the need for a complex configuration in which the first and second current collector foils are electrically connected to the current collector after forming a region in the current collector foil where no insulating layer is interposed. Therefore, with a simple configuration, current collector foils (first and second current collector foils) equipped with an insulating layer can be electrically connected to the current collector.

[0013] (2) In the energy storage element described in (1) above, the first current collector foil may be arranged between the current collector and the second current collector foil in the first direction.

[0014] According to the energy storage element described in (2) above, the first current collector foil is placed between the current collector and the second current collector foil, and the second conductive layer of the first protrusion of the second current collector foil can be brought into contact with the current collector by bending the first protrusion toward the current collector, etc.

[0015] (3) In the energy storage element described in (1) or (2) above, the second current collector foil may have a pair of first protrusions which are protruding portions of the second conductive layer and the second insulating layer that protrude on both sides in the second direction from the first current collector foil, and the second conductive layer of the pair of first protrusions may be electrically connected to the current collector while in contact with the current collector.

[0016] According to the energy storage element described in (3) above, the second current collector foil has a pair of first protrusions that protrude from both sides of the first current collector foil, and the second conductive layer of the pair of first protrusions is electrically connected to the current collector while in contact with the current collector. In this way, by making both sides of the second current collector foil protrude more than the first current collector foil and bringing the second conductive layer of the pair of first protrusions of the second current collector foil into contact with the current collector, both sides of the second current collector foil can be electrically connected to the current collector. This makes it possible to more reliably connect the second current collector foil to the current collector.

[0017] (4) The energy storage element described in any one of (1) to (3) above further comprises an auxiliary member that sandwiches the first current collector foil and the second current collector foil with the current collector, wherein the auxiliary member is bent toward the current collector at the position of the first protrusion and sandwiches the first protrusion with the current collector.

[0018] According to the energy storage element described in (4) above, the auxiliary member that sandwiches the first current collector foil and the second current collector foil with the current collector bends toward the current collector at the position of the first protrusion of the second current collector foil, and sandwiches the first protrusion with the current collector. This makes it possible to easily bring the second conductive layer of the first protrusion into contact with the current collector.

[0019] (5) The energy storage element described in any one of (1) to (4) above further comprises an auxiliary member that sandwiches the electrode body between itself and the current collector, the electrode body further comprises a third current collector foil and a fourth current collector foil laminated in the first direction together with the first current collector foil and the second current collector foil, the third current collector foil comprises a third conductive layer and a third insulating layer arranged in the first direction, the fourth current collector foil comprises a fourth conductive layer and a fourth insulating layer arranged in the first direction, the fourth current collector foil comprises a second protrusion which is a protruding portion of the fourth conductive layer and the fourth insulating layer that protrudes in the second direction from the third current collector foil, the third conductive layer and the fourth conductive layer of the second protrusion are electrically connected to the auxiliary member in contact with the auxiliary member, and the auxiliary member is electrically connected to the current collector.

[0020] According to the energy storage element described in (5) above, the third current collector foil comprises a third conductive layer and a third insulating layer, and the fourth current collector foil comprises a fourth conductive layer and a fourth insulating layer. In this way, since the third and fourth current collector foils are partially made of insulating layers, it is possible to reduce weight, reduce the amount of conductive material (metal material, etc.) used, and improve the strength of the current collector foils. In this configuration, the fourth current collector foil has a second protrusion which is the protruding portion of the fourth conductive layer and the fourth insulating layer that protrudes from the third current collector foil, and the third conductive layer and the fourth conductive layer of the second protrusion are electrically connected to the auxiliary member while in contact with the auxiliary member. In this way, by making the fourth current collector foil protrude from the third current collector foil and bringing the third conductive layer of the third current collector foil and the fourth conductive layer of the second protrusion of the fourth current collector foil into contact with the auxiliary member, the third and fourth current collector foils can be electrically connected to the auxiliary member. Furthermore, by electrically connecting the auxiliary member to the current collector, the third and fourth current collector foils can be electrically connected to the current collector via the auxiliary member. As a result, even in the third and fourth current collector foils, there is no need to create a complex configuration in which an area without an insulating layer is formed in the current collector foil before electrically connecting it to the current collector, thus enabling electrical connection to the current collector with a simple configuration.

[0021] (6) A power storage element according to another aspect of the present invention comprises an electrode body, a current collector connected to the electrode body, and an auxiliary member sandwiching the electrode body between the current collector, wherein the electrode body comprises a third current collector foil and a fourth current collector foil laminated in a first direction, the third current collector foil comprises a third conductive layer and a third insulating layer aligned in the first direction, the fourth current collector foil comprises a fourth conductive layer and a fourth insulating layer aligned in the first direction, the fourth current collector foil comprises a second protruding portion which is a protruding portion of the fourth conductive layer and the fourth insulating layer that protrudes in a second direction intersecting the first direction from the third current collector foil, the third conductive layer and the fourth conductive layer of the second protruding portion are electrically connected to the auxiliary member in contact with the auxiliary member, and the auxiliary member is electrically connected to the current collector.

[0022] In another embodiment of the present invention, the third current collector foil comprises a third conductive layer and a third insulating layer, and the fourth current collector foil comprises a fourth conductive layer and a fourth insulating layer. In this way, since the third and fourth current collector foils are partially made of insulating layers, it is possible to reduce weight, reduce the amount of conductive material (metal material, etc.) used, and improve the strength of the current collector foils. In this configuration, the fourth current collector foil comprises a second protrusion, which is a protruding portion of the fourth conductive layer and fourth insulating layer that protrudes from the third current collector foil, and the third conductive layer and the fourth conductive layer of the second protrusion are electrically connected to the auxiliary member while in contact with the auxiliary member. In this way, by making the fourth current collector foil protrude from the third current collector foil and bringing the third conductive layer of the third current collector foil and the fourth conductive layer of the second protrusion of the fourth current collector foil into contact with the auxiliary member, the third and fourth current collector foils can be electrically connected to the auxiliary member. Furthermore, by electrically connecting the auxiliary member to the current collector, the third and fourth current collector foils can be electrically connected to the current collector via the auxiliary member. This eliminates the need for a complex configuration in which the third and fourth current collector foils are electrically connected to the current collector after forming a region on the current collector foil where no insulating layer is interposed. Therefore, current collector foils (third and fourth current collector foils) equipped with insulating layers can be electrically connected to the current collector with a simple configuration.

[0023] The following description of an energy storage element according to an embodiment (including its modifications) of the present invention will be given with reference to the drawings. 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 and are not intended to limit the present invention. Dimensions and other specifications are not strictly illustrated in each figure. In each figure, the same or similar components are denoted by the same reference numerals.

[0024] In the following description and drawings, the direction in which a pair of terminals (positive and negative, hereinafter the same) of a power storage element are aligned, the direction in which a pair of current collectors are aligned, the direction in which a pair of auxiliary members are aligned, the direction in which a pair of tab bundles of an electrode body are aligned, or the direction in which a pair of short sides of a container are opposed to each other is defined as the X-axis direction. The thickness direction of the container or electrode body (the direction in which the width is smallest), or the direction in which a pair of long sides of a container are opposed to each other is defined as the Y-axis direction. The direction in which the container body and lid of the container are aligned, the direction in which the terminals and electrode body are aligned, the direction in which the current collectors and auxiliary members are aligned, the direction in which the tab bundles of the electrode body are sandwiched between the current collectors and auxiliary members, the lamination direction of the current collector foil at the connection portion of the tab bundle with the current collector, or the vertical direction 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 the vertical direction, but for the sake of explanation below, the Z-axis direction will be described as the vertical direction.

[0025] In the following explanation, 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. When simply referred to as the X-axis direction, it refers to either the X-axis positive direction or the X-axis negative direction, or either direction. The same applies to the Y-axis and Z-axis directions. In the following, the Z-axis direction will also be referred to as the first direction, the X-axis direction as the second direction, and the Y-axis direction as the third direction. Expressions indicating relative directions or orientations, such as parallel and orthogonal, include cases where they are not strictly those directions or orientations. When two directions are said to be parallel (or orthogonal), it means not only that the two directions are perfectly parallel (or orthogonal), but also that they are substantially parallel (or orthogonal), that is, that they include a difference of, for example, a few percent. In the following explanation, when "insulation" is used, it means "electrical insulation". The volume resistivity of an insulating material is 1 × 10⁻⁶ ６ Preferably Ωm or more, 1 × 10 ７ Ωm or greater is more preferable, 1 × 10 １０ A value of Ωm or greater is even more preferable.

[0026] (Embodiment) [1. General Description of the Energy Storage Element 10] 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 this embodiment. Figure 2 is an exploded perspective view showing each component of the energy storage element 10 in a disassembled state according to this embodiment.

[0027] The energy storage element 10 is a secondary battery (single cell) capable of charging and discharging electricity, and more specifically, a non-aqueous electrolyte secondary battery such as a lithium-ion secondary battery. The energy storage element 10 is used as a battery for driving or starting the engine of mobile vehicles such as automobiles, motorcycles, watercraft, ships, snowmobiles, agricultural machinery, construction machinery, automated guided vehicles (AGVs), aircraft, or railway vehicles for electric railways. Examples of automobiles 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 include electric trains, monorails, maglev trains, and hybrid trains equipped with both diesel engines and electric motors. The energy storage element 10 can also be used as a stationary battery for household or commercial use.

[0028] The energy storage element 10 is not limited to a non-aqueous electrolyte secondary battery, but may be a secondary battery other than a non-aqueous electrolyte secondary battery, or a capacitor. The energy storage element 10 may be a primary battery instead of a secondary battery. The energy storage element 10 may be a battery using a solid electrolyte. The energy storage element 10 may be a pouch-type energy storage element. In this embodiment, the energy storage element 10 is shown as a rectangular parallelepiped (square) shape that is flattened in the Y-axis direction, but the shape of the energy storage element 10 is not limited to a rectangular parallelepiped shape, but may be a polygonal prism shape, an oblong cylinder shape, an elliptical cylinder shape, or a cylinder shape, etc.

[0029] As shown in Figure 1, the energy storage element 10 comprises a container 100, a pair of terminals 200 (positive and negative), and a pair of upper gaskets 300 (positive and negative). The energy storage element 10 further comprises a pair of lower gaskets 400 (positive and negative), a pair of current collectors 500 (positive and negative), a pair of auxiliary members 510 (positive and negative), and an electrode body 600, all of which are housed inside the container 100. An electrolyte (non-aqueous electrolyte) is sealed inside the container 100, but this is not shown in the illustration. 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. In addition to the above components, spacers placed to the side, above, or below the electrode body 600, an insulating film enclosing the electrode body 600, etc., may also be placed.

[0030] The container 100 is a rectangular parallelepiped (square or box-shaped) case comprising a container body 110 having an opening facing the positive Z-axis direction, 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. The container body 110 has a pair of flat, rectangular long side walls (long sides) on both sides in the Y-axis direction, a pair of flat, rectangular short side walls (short sides) on both sides in the X-axis direction, and a flat, rectangular bottom wall (bottom surface) on the side in the negative Z-axis direction. The lid 120 is a flat, rectangular member extending in the X-axis direction that constitutes the lid of the container 100 and is positioned in the positive Z-axis direction of the container body 110. The lid 120 is provided with a gas discharge valve 121 that releases pressure when the pressure inside the container 100 rises excessively, and an injection section 122 for injecting electrolyte into the container 100, etc.

[0031] The container 100 is sealed by joining the container body 110 and the lid 120 by welding or other means after the electrode body 600 and the lid 110 are placed inside the container body 110. The material of the container 100 (container body 110 and lid 120) is not particularly limited, and weldable (joinable) metals such as stainless steel, aluminum, aluminum alloy, iron, and plated steel sheet can be used, but resin can also be used. The container body 110 and the lid 120 may be formed from the same material or from different materials.

[0032] Terminals 200 are electrode terminals (positive and negative terminals) electrically connected to the electrode body 600 via the current collector 500. 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. Terminals 200 are made of a conductive material such as aluminum, aluminum alloy, copper, or copper alloy. Terminals 200 are positioned so as to protrude in the positive Z-axis direction from the outer surface (Z-axis positive direction surface) of the cover body 120. In this embodiment, terminals 200 are welded terminals that are joined to an external conductive material such as a busbar by welding. Terminals 200 may also be bolted terminals that have a bolt portion with a male screw portion that protrudes in the positive Z-axis direction and are joined to the conductive material by bolt connection.

[0033] The terminal 200 is connected (joined) to the current collector 500 by crimping or the like, and is attached to the cover 120. Specifically, the terminal 200 has a shaft portion 201 (rivet portion) that extends in the negative Z-axis direction. The shaft portion 201 is inserted into the through hole 301 of the upper gasket 300, the through hole 123 of the cover 120, the through hole 401 of the lower gasket 400, and the through hole 501 of the current collector 500, and crimped. In this way, the terminal 200 is fixed to the cover 120 together with the upper gasket 300, the lower gasket 400, and the current collector 500. The method of connecting (joining) the terminal 200 and the current collector 500 is not limited to crimping, and welding such as ultrasonic welding, laser welding or resistance welding, or mechanical joining other than crimping such as screw joining may be used.

[0034] The upper gasket 300 is a plate-shaped and rectangular gasket that is disposed between the lid 120 of the container 100 and the terminal 200 and bears insulation and sealing between the lid 120 and the terminal 200. The lower gasket 400 is a plate-shaped and rectangular gasket that is disposed between the lid 120 and the current collector 500 and insulates between the lid 120 and the current collector 500. The upper gasket 300 and the lower gasket 400 are formed of insulating members such as polypropylene (PP), polyethylene (PE), polystyrene (PS), polyphenylene sulfide resin (PPS), polyphenylene ether (PPE (including modified PPE)), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyether ether ketone (PEEK), tetrafluoroethylene / perfluoroalkyl vinyl ether (PFA), polytetrafluoroethylene (PTFE), polyethersulfone (PES), polyamide (PA), ABS resin, or composite materials thereof.

[0035] The current collector 500 is a current collecting member (positive current collector and negative current collector) that is connected (joined) to the terminal 200 and the electrode body 600 and electrically connects the terminal 200 and the electrode body 600. The positive current collector 500 of the positive electrode is connected (joined) to the tab bundle 620 of the positive electrode of the electrode body 600 by ultrasonic bonding or the like, and as described above, is connected (joined) to the positive electrode terminal 200 by caulking or the like. The negative current collector 500 of the negative electrode is connected (joined) to the tab bundle 630 of the negative electrode of the electrode body 600 by ultrasonic bonding or the like, and as described above, is connected (joined) to the negative electrode terminal 200 by caulking or the like. In the present embodiment, the current collector 500 is a flat and rectangular member. The material of the current collector 500 is not particularly limited, but the positive current collector 500 of the positive electrode is formed of a conductive member such as metal such as aluminum or an aluminum alloy, similar to the positive conductive layer 643 of the positive current collecting foil 641 of the electrode body 600 to be described later. The negative current collector 500 of the negative electrode is formed of a conductive member such as metal such as copper or a copper alloy, similar to the negative conductive layer 653 of the negative current collecting foil 651 of the electrode body 600 to be described later.

[0036] The auxiliary member 510 is positioned to sandwich the tab bundle 620 or 630 of the electrode body 600 between the current collector 500 and the auxiliary member 510, and is a member (backing plate) that is joined to the tab bundle 620 or 630 together with the current collector 500 while the tab bundle 620 or 630 is sandwiched between the current collector 500 and the auxiliary member 510. In this embodiment, the auxiliary member 510 is a flat and rectangular member, positioned in the negative Z-axis direction of the tab bundle 620 or 630, and sandwiches the tab bundle 620 or 630 between the current collector 500 and the auxiliary member 510 in the Z-axis direction (see Figure 4). The material of the auxiliary member 510 is not particularly limited, but the auxiliary member 510 of the positive electrode is made of a metal such as aluminum or an aluminum alloy, similar to the positive electrode conductive layer 643 of the positive electrode current collector foil 641 of the electrode body 600. The auxiliary member 510 of the negative electrode is made of a metal such as copper or a copper alloy, similar to the negative electrode conductive layer 653 of the negative electrode current collector foil 651 of the electrode body 600.

[0037] The electrode body 600 is an energy storage element (power generation element) that comprises a positive electrode plate, a negative electrode plate, and a separator, and is capable of storing electricity. The electrode body 600 is formed by winding layers of material arranged so that a separator is sandwiched between the positive electrode plate and the negative electrode plate. As a result, the non-active material layer portion (uncoated active material portion) of the positive electrode plate is stacked to form the positive electrode tab bundle 620. The non-active material layer portion (uncoated active material portion) of the negative electrode plate is stacked to form the negative electrode tab bundle 630. In other words, the electrode body 600 comprises an electrode body main body portion 610 and tab bundles 620 and 630 that extend in the positive Y-axis direction while protruding in the positive Z-axis direction from a part of the electrode body main body portion 610.

[0038] The electrode body main body portion 610 is a portion that constitutes the main body of the electrode body 600. Specifically, it is a portion other than the tab bundles 620 and 630 of the electrode body 600. The electrode body main body portion 610 is a portion having an oval columnar shape or an oval cylindrical shape formed by winding a positive electrode plate, a negative electrode plate, and a separator. Thereby, the electrode body main body portion 610 includes a pair of curved electrode body curved portions 611 on both sides in the X-axis direction, and a pair of flat electrode body flat portions 612 that connect the pair of electrode body curved portions 611 on both sides in the Y-axis direction. In the present embodiment, the electrode body 600 is a wound electrode body having an oval shape when viewed from the Z-axis direction, but it may have an elliptical shape, a circular shape, or any other shape when viewed from the Z-axis direction. A detailed description of the configuration of the electrode body 600 will be described later.

[0039] With such a configuration, in a state where the tab bundle 620 or 630 of the electrode body 600 is sandwiched between the current collector 500 and the auxiliary member 510, the current collector 500, the tab bundle 620 or 630 of the electrode body 600, and the auxiliary member 510 are joined. In the present embodiment, by performing ultrasonic bonding over the entire region where the tab bundle 620 of the electrode body 600 is sandwiched between the current collector 500 and the auxiliary member 510, the tab bundle 620 of the electrode body 600 is joined in a state of being sandwiched between the current collector 500 and the auxiliary member 510. The same applies to the tab bundle 630 of the electrode body 600. The method of connecting (joining) the current collector 500, the electrode body 600, and the auxiliary member 510 is not limited to ultrasonic bonding, and mechanical bonding such as caulking or screw connection may be used. A detailed description of the configuration for joining the current collector 500, the electrode body 600, and the auxiliary member 510 will be described later.

[0040] [2 Explanation of the Configuration of the Electrode Body 600] Next, the configuration of the electrode body 600 will be described in detail. FIG. 3 is a perspective view and a cross-sectional view showing the configuration of the electrode body 600 according to the present embodiment. Specifically, FIG. 3(a) shows the configuration in a state where a part of the wound state of the electrode body 600 shown in FIG. 2 is developed, and FIG. 3(b) is a cross-sectional view showing an enlarged cross-section of a part of the electrode body 600 and the laminated state of the electrode plates.

[0041] As shown in Figure 3, the electrode body 600 is formed by alternately stacking and winding a positive electrode plate 640, a negative electrode plate 650, and separators 661 and 662. In other words, the electrode body 600 is formed by stacking and winding the positive electrode plate 640, separator 661, negative electrode plate 650, and separator 662 in this order.

[0042] The positive electrode plate 640 is a positive electrode plate (electrode plate) comprising a positive electrode current collector foil 641, which is a long strip-shaped current collector foil, and a positive electrode active material layer 642, which is an active material layer formed on the surface of the positive electrode current collector foil 641. The positive electrode current collector foil 641 comprises a positive electrode conductive layer 643, which is a conductive layer on which the positive electrode active material layer 642 is arranged, and a positive electrode insulating layer 644, which is an insulating layer that sandwiches the positive electrode conductive layer 643 between the positive electrode active material layer 642 and the positive electrode insulating layer 644. In this embodiment, a pair of positive electrode active material layers 642 are arranged on both sides of the positive electrode current collector foil 641, and a pair of positive electrode conductive layers 643 are arranged between the pair of positive electrode active material layers 642 and the positive electrode insulating layer 644. Thus, the positive electrode current collector foil 641 has both sides of the positive electrode insulating layer 644 covered with the positive electrode conductive layer 643.

[0043] The thickness of the positive electrode conductive layer 643 is smaller than the thickness of the positive electrode insulating layer 644. In other words, the thickness of one positive electrode conductive layer 643, which is arranged on one side of the positive electrode insulating layer 644, is smaller than the thickness of the positive electrode insulating layer 644. In this embodiment, the sum of the thicknesses of the two positive electrode conductive layers 643, which are arranged on both sides of the positive electrode insulating layer 644, is smaller than the thickness of the positive electrode insulating layer 644. This prevents the thickness of the positive electrode current collector foil 641 from becoming too small, even if the thickness of the positive electrode conductive layer 643 is small, and makes it easier to handle the positive electrode current collector foil 641.

[0044] Specifically, the thickness of the positive electrode conductive layer 643 is preferably 1 / 2 or less of the thickness of the positive electrode insulating layer 644, more preferably 1 / 4 or less of the thickness of the positive electrode insulating layer 644, and even more preferably 1 / 6 or less of the thickness of the positive electrode insulating layer 644. The thickness of a single layer of positive electrode conductive layer 643 is preferably 0.1 μm or more and 5 μm or less, more preferably 0.5 μm or more and 3 μm or less, and even more preferably about 1 μm. The thickness of the positive electrode insulating layer 644 is preferably 2 μm or more and 10 μm or less, more preferably 4 μm or more and 8 μm or less, and even more preferably about 6 μm. If the thickness of the positive electrode conductive layer 643 or the positive electrode insulating layer 644 is not constant, it is preferable that the maximum thickness of the positive electrode conductive layer 643 is smaller than the maximum thickness of the positive electrode insulating layer 644, more preferably smaller than the average thickness of the positive electrode insulating layer 644, and even more preferably smaller than the minimum thickness of the positive electrode insulating layer 644.

[0045] The negative electrode plate 650 is a negative electrode electrode plate (electrode plate) comprising a long, strip-shaped current collector foil, the negative electrode current collector foil 651, and a negative electrode active material layer 652, which is an active material layer formed on the surface of the negative electrode current collector foil 651. The negative electrode current collector foil 651 comprises a negative electrode conductive layer 653, which is a conductive layer on which the negative electrode active material layer 652 is arranged, and a negative electrode insulating layer 654, which is an insulating layer that sandwiches the negative electrode conductive layer 653 between the negative electrode active material layer 652 and the negative electrode insulating layer 654. In this embodiment, a pair of negative electrode active material layers 652 are arranged on both sides of the negative electrode current collector foil 651, and a pair of negative electrode conductive layers 653 are arranged between the pair of negative electrode active material layers 652 and the negative electrode insulating layer 654. Thus, the negative electrode current collector foil 651 has both surfaces of the negative electrode insulating layer 654 covered with the negative electrode conductive layer 653.

[0046] The thickness of the negative electrode conductive layer 653 is smaller than the thickness of the negative electrode insulating layer 654. In other words, the thickness of the single negative electrode conductive layer 653 placed on one side of the negative electrode insulating layer 654 is smaller than the thickness of the negative electrode insulating layer 654. In this embodiment, the sum of the thicknesses of the two negative electrode conductive layers 653 placed on both sides of the negative electrode insulating layer 654 is smaller than the thickness of the negative electrode insulating layer 654. This prevents the thickness of the negative electrode current collector foil 651 from becoming too small, even if the thickness of the negative electrode conductive layer 653 is small, and makes it easier to handle the negative electrode current collector foil 651.

[0047] Specifically, the thickness of the negative electrode conductive layer 653 is preferably 1 / 2 or less of the thickness of the negative electrode insulating layer 654, more preferably 1 / 4 or less of the thickness of the negative electrode insulating layer 654, and even more preferably 1 / 6 or less of the thickness of the negative electrode insulating layer 654. The thickness of a single negative electrode conductive layer 653 is preferably 0.1 μm or more and 5 μm or less, more preferably 0.5 μm or more and 3 μm or less, and even more preferably about 1 μm. The thickness of the negative electrode insulating layer 654 is preferably 2 μm or more and 10 μm or less, more preferably 3 μm or more and 7 μm or less, and even more preferably about 4.5 μm (that is, the thickness of the negative electrode insulating layer 654 is preferably smaller than the thickness of the positive electrode insulating layer 644). If the thickness of the negative electrode conductive layer 653 or the negative electrode insulating layer 654 is not constant, it is preferable that the maximum thickness of the negative electrode conductive layer 653 is smaller than the maximum thickness of the negative electrode insulating layer 654, more preferably smaller than the average thickness of the negative electrode insulating layer 654, and even more preferably smaller than the minimum thickness of the negative electrode insulating layer 654.

[0048] In this embodiment, the positive electrode conductive layer 643 is a conductive coating layer formed by coating the surface of the positive electrode insulating layer 644 with a conductive material such as aluminum or an aluminum alloy by vapor deposition or coating. The negative electrode conductive layer 653 is a conductive coating layer formed by coating the surface of the negative electrode insulating layer 654 with a conductive material such as copper or a copper alloy by vapor deposition or coating. At least one of the positive electrode conductive layer 643 and the negative electrode conductive layer 653 may contain carbon. That is, at least one of the positive electrode conductive layer 643 and the negative electrode conductive layer 653 may be formed by incorporating carbon into a metal, or it may be formed of carbon alone. As the material for the positive electrode conductive layer 643 and the negative electrode conductive layer 653, any known material that is stable against oxidation-reduction reactions during charging and discharging can be used, such as nickel, iron, stainless steel, titanium, calcined carbon, conductive polymer, conductive glass, or Al-Cd alloy.

[0049] The positive electrode insulating layer 644 and the negative electrode insulating layer 654 are formed of an insulating member such as any resin material that can be used for the above-described upper gasket 300 (lower gasket 400), such as polypropylene (PP) or polyethylene terephthalate (PET).

[0050] As the positive electrode active material used in the positive electrode active material layer 642 and the negative electrode active material used in the negative electrode active material layer 652, any known material can be appropriately used as long as it is a positive electrode active material and a negative electrode active material capable of occluding and releasing charge-transporting ions.

[0051] As the positive electrode active material, LiMPO ４ , LiMSiO ４ , LiMBO ３ (M is one or more transition metal elements selected from Fe, Ni, Mn, Co, etc.) and other polyanion compounds, lithium titanate, LiMn ２ O ４ or LiMn １．５ Ni ０．５ O ４ and other spinel-type lithium manganese oxides, LiMO ２ (M is one or more transition metal elements selected from Fe, Ni, Mn, Co, etc.) and other lithium transition metal oxides can be used. As the negative electrode active material, in addition to lithium metal and lithium alloys (lithium metal-containing alloys such as lithium-silicon, lithium-aluminum, lithium-lead, lithium-tin, lithium-aluminum-tin, lithium-gallium, and wood alloy), alloys capable of occluding and releasing lithium ions, carbon materials (graphite, non-graphitizable carbon, graphitizable carbon, low-temperature fired carbon, amorphous carbon, etc.), silicon oxides, metal oxides, lithium metal oxides (Li ４ Ti ５ O １２ etc.), polyphosphoric acid compounds, or compounds of transition metals and Group 14 to Group 16 elements, such as Co ３ O ４ or Fe ２ P, etc., which are generally called conversion negative electrodes, can be mentioned.

[0052] The separator 660 (661 and 662) is a microporous insulating sheet made of resin or the like. Any known material can be used for the separator 660, as long as it does not impair the performance of the energy storage element 10. Examples of separator 660 include woven fabric, nonwoven fabric, and porous resin film. Among these examples, porous resin film is preferred from the viewpoint of strength, and nonwoven fabric is preferred from the viewpoint of electrolyte retention. Polyolefins such as polyethylene and polypropylene are preferred as the material for the separator 660 from the viewpoint of shutdown function, and polyimide and aramid are preferred from the viewpoint of oxidative degradation resistance. A composite material of these resins may also be used for the separator 660. Separators 661 and 662 may be formed from the same material or from different materials.

[0053] The positive electrode current collector foil 641 has a plurality of rectangular tabs 621 that protrude in the positive Z-axis direction at its end in the positive Z-axis direction, and the plurality of tabs 621 are arranged in a stacked state in the Y-axis direction. The tabs 621 are the portion of the positive electrode plate 640 where the positive electrode active material layer 642 is not formed and the positive electrode current collector foil 641 is exposed. Similarly, the negative electrode current collector foil 651 has a plurality of rectangular tabs 631 that protrude in the positive Z-axis direction at its end in the positive Z-axis direction, and the plurality of tabs 631 are arranged in a stacked state in the Y-axis direction. The tabs 631 are the portion of the negative electrode plate 650 where the negative electrode active material layer 652 is not formed and the negative electrode current collector foil 651 is exposed.

[0054] As shown in Figure 3(a), multiple stacked tabs 621 are bundled together to form a tab bundle 620 that extends in a state protruding in the positive Z-axis direction. Similarly, multiple stacked tabs 631 are bundled together to form a tab bundle 630 that extends in a state protruding in the positive Z-axis direction. These tab bundles 620 and 630 are joined together with the current collector 500 and the auxiliary member 510 in the Y-axis direction, sandwiched between them, and then bent in the positive Y-axis direction together with the current collector 500 and the auxiliary member 510. Alternatively, the tab bundles 620 and 630 are bent in the positive Y-axis direction and joined together with the current collector 500 and the auxiliary member 510 in the Z-axis direction, sandwiched between them. As a result, the tab bundle 620 has tabs 621 stacked in the Z-axis direction and is sandwiched between the current collector 500 and the auxiliary member 510 in the Z-axis direction. Similarly, the tab bundle 630 has tabs 631 stacked in the Z-axis direction and is sandwiched between the current collector 500 and the auxiliary member 510 in the Z-axis direction.

[0055] [3. Explanation of the Joining Configuration of the Current Collector 500, Electrode Body 600, and Auxiliary Member 510] Next, the configuration for joining the current collector 500, electrode body 600, and auxiliary member 510 will be explained in detail. Here, the configuration for joining the current collector 500, the tab bundle 620 of the electrode body 600, and the auxiliary member 510 is the same as the configuration for joining the current collector 500, the tab bundle 630 of the electrode body 600, and the auxiliary member 510. For this reason, the configuration for joining the current collector 500, the tab bundle 620 of the electrode body 600, and the auxiliary member 510 will be explained below, and the configuration for joining the current collector 500, the tab bundle 630 of the electrode body 600, and the auxiliary member 510 will not be explained. Furthermore, for the sake of clarity, in the following explanation, the tab bundle 620 of the electrode body 600 will be described as being sandwiched between the current collector 500 and the auxiliary member 510 in the Z-axis direction, and joined together with the current collector 500 and the auxiliary member 510.

[0056] Figure 4 is a cross-sectional view showing the configuration for joining the current collector 500, electrode body 600, and auxiliary member 510 according to this embodiment. Figure 4 shows a cross-section taken from a plane parallel to the XZ plane when the tab bundle 620 of the electrode body 600 is sandwiched between the current collector 500 and the auxiliary member 510 in the Z-axis direction, before joining the current collector 500, the tab bundle 620 of the electrode body 600, and the auxiliary member 510. Figures 5A and 5B are simplified cross-sectional views showing the configuration for joining the current collector 500, electrode body 600, and auxiliary member 510 according to this embodiment. Figure 5A shows a simplified view of the state before joining the current collector 500, electrode body 600, and auxiliary member 510 as shown in Figure 4. Figure 5B shows the state after joining the current collector 500, electrode body 600, and auxiliary member 510 as shown in Figure 5A.

[0057] As shown in Figure 4, in the state before joining the current collector 500, electrode body 600 and auxiliary member 510, the tab bundle 620 of the electrode body 600 is arranged such that multiple tabs 621 are stacked in the Z-axis direction and sandwiched between the current collector 500 and the auxiliary member 510 in the Z-axis direction. Specifically, the current collector 500 is positioned in the Z-positive direction of the tab bundle 620, and the auxiliary member 510 is positioned in the Z-negative direction of the tab bundle 620.

[0058] In this configuration, the multiple tabs 621 of the tab bundle 620 have a width in the X-axis direction that increases as they move toward the negative Z-axis direction. In other words, the multiple tabs 621 have a width in the X-axis direction that increases as they move from the current collector 500 toward the auxiliary member 510. To put it another way, in two tabs 621 aligned in the Z-axis direction, the tab 621 in the negative Z-axis direction protrudes more in the X-axis direction (both sides in the X-axis direction in this embodiment) than the tab 621 in the positive Z-axis direction.

[0059] For the sake of clarity, the multiple tabs 621 shown in Figure 4 will be simplified to three tabs 621 in the following explanation. Furthermore, since the tabs 621 are part of the positive electrode current collector foil 641, the three tabs 621 will be referred to as current collector foils 641a, 641b, and 641c, which constitute the three positive electrode current collector foils 641. The relationship between the three positive electrode current collector foils 641 (current collector foils 641a, 641b, and 641c) described below can be similarly applied to the relationship between four or more positive electrode current collector foils 641. Furthermore, the relationship between these multiple positive electrode current collector foils 641 can be similarly applied to the relationship between multiple negative electrode current collector foils 651.

[0060] As shown in Figure 5A, in the state before joining the current collector 500, electrode body 600, and auxiliary member 510, the current collector foils 641a, 641b, and 641c of the electrode body 600 are positioned sandwiched between the current collector 500 and the auxiliary member 510 in the Z-axis direction. Specifically, the current collector 500 is positioned at the Z-axis positive end, and the current collector foils 641a, 641b, 641c, and auxiliary member 510 are positioned sequentially from the current collector 500 toward the Z-axis negative direction. In other words, the electrode body 600 comprises current collector foils 641a, 641b, and 641c stacked in the Z-axis direction. The current collector foil 641a is positioned between the current collector 500 and the current collector foil 641b in the Z-axis direction. The current collector foil 641b is positioned between the current collector foil 641a and the current collector foil 641c in the Z-axis direction. The current collector foil 641c is positioned between the current collector foil 641b and the auxiliary member 510 in the Z-axis direction. The auxiliary member 510 sandwiches the current collector foils 641a, 641b, and 641c between itself and the current collector 500.

[0061] The current collector foil 641a comprises a conductive layer 643a as a positive electrode conductive layer 643 and an insulating layer 644a as a positive electrode insulating layer 644, arranged in the Z-axis direction. The current collector foil 641b comprises a conductive layer 643b as a positive electrode conductive layer 643 and an insulating layer 644b as a positive electrode insulating layer 644, arranged in the Z-axis direction. The current collector foil 641c comprises a conductive layer 643c as a positive electrode conductive layer 643 and an insulating layer 644c as a positive electrode insulating layer 644, arranged in the Z-axis direction. The current collector foil 641b comprises a protruding portion 645a, which is a protruding portion of the conductive layer 643b and insulating layer 644b, that protrudes in the X-axis direction from the current collector foil 641a. In this embodiment, the current collector foil 641b comprises a pair of protruding portions 645a that protrude on both sides in the X-axis direction from the current collector foil 641a. The current collector foil 641c has protruding portions 645b, which are protruding parts of the conductive layer 643c and the insulating layer 644c, that protrude in the X-axis direction from the current collector foil 641b. In this embodiment, the current collector foil 641c has a pair of protruding portions 645b that protrude on both sides in the X-axis direction from the current collector foil 641b.

[0062] The protruding portion 645a is a portion formed by both the conductive layer 643b and the insulating layer 644b protruding to the tip in the X-axis direction. The amount of protrusion of the protruding portion 645a is preferably greater than the thickness of the current collector foil 641a in the Z-axis direction, more preferably greater than twice that thickness, and even more preferably greater than three times that thickness. The amount of protrusion of the protruding portion 645a is the length of the protruding portion 645a (the length of the portion of the current collector foil 641b that protrudes from the current collector foil 641a) in the direction in which the protruding portion 645a protrudes (the X-axis direction in Figure 5A). The protruding portion 645b is a portion formed by both the conductive layer 643c and the insulating layer 644c protruding to the tip in the X-axis direction. The amount of protrusion of the protruding portion 645b is preferably greater than the thickness of the current collector foil 641b in the Z-axis direction, more preferably greater than twice that thickness, and even more preferably greater than three times that thickness. The amount of protrusion of the protrusion 645b is the length of the protrusion 645b in the direction in which the protrusion 645b protrudes (the X-axis direction in Figure 5A) (the length of the portion of the current collector foil 641c that protrudes from the current collector foil 641b).

[0063] Hereafter, the current collector foil 641a will also be referred to as the first current collector foil 641a, the conductive layer 643a as the first conductive layer 643a, and the insulating layer 644a as the first insulating layer 644a. The current collector foil 641b will also be referred to as the second current collector foil 641b, the conductive layer 643b as the second conductive layer 643b, and the insulating layer 644b as the second insulating layer 644b. The protruding portion 645a will also be referred to as the first protruding portion 645a.

[0064] In this configuration, the electrode body 600 comprises a first current collector foil 641a and a second current collector foil 641b stacked in the Z-axis direction (first direction). The first current collector foil 641a comprises a first conductive layer 643a and a first insulating layer 644a arranged in the Z-axis direction (first direction). The second current collector foil 641b comprises a second conductive layer 643b and a second insulating layer 644b arranged in the Z-axis direction (first direction). The first current collector foil 641a is positioned between the current collector 500 and the second current collector foil 641b in the Z-axis direction (first direction). The auxiliary member 510 sandwiches the first current collector foil 641a and the second current collector foil 641b between itself and the current collector 500. The second current collector foil 641b has first protrusions 645a, which are protruding portions of the second conductive layer 643b and the second insulating layer 644b, that protrude in the X-axis direction (second direction intersecting the first direction) more than the first current collector foil 641a. Specifically, the second current collector foil 641b has a pair of first protrusions 645a, which are protruding portions of the second conductive layer 643b and the second insulating layer 644b, that protrude on both sides in the X-axis direction (second direction) more than the first current collector foil 641a.

[0065] When joining the current collector 500, electrode body 600, and auxiliary member 510, the current collector 500 and auxiliary member 510 are sandwiched from both sides in the Z-axis direction, causing the auxiliary member 510 to be pressed toward the current collector 500. As a result, as shown in Figure 5B, the X-axis end of the auxiliary member 510 is bent toward the current collector 500 at the positions of the protrusions 645a of the current collector foil 641b and the protrusions 645b of the current collector foil 641c. In this embodiment, both ends of the auxiliary member 510 in the X-axis direction are bent toward the current collector 500 at the positions of the pair of protrusions 645a and the pair of protrusions 645b. As a result, the protrusions 645a and 645b are sandwiched between the auxiliary member 510 and the current collector 500.

[0066] In this state, the current collector 500, the electrode body 600, and the auxiliary member 510 are joined together. In this embodiment, ultrasonic bonding is performed over the entire region where the current collector foils 641a, 641b, and 641c are sandwiched between the current collector 500 and the auxiliary member 510, thereby joining the current collector 500, the current collector foils 641a, 641b, and 641c, and the auxiliary member 510. As a result, the conductive layer 643a and the conductive layer 643b of the pair of protrusions 645a are electrically connected to the current collector 500 while in contact with the current collector 500. The conductive layer 643c of the pair of protrusions 645b are electrically connected to the current collector 500 while in contact with the current collector 500. Therefore, the conductive layer 643a of the current collector foil 641a, the conductive layer 643b of the current collector foil 641b, and the conductive layer 643c of the current collector foil 641c are all electrically connected to the current collector 500.

[0067] Specifically, the conductive layer 643a of the current collector foil 641a in the Z-positive direction is electrically connected to the current collector 500 while in contact with the current collector 500. The conductive layer 643a of the current collector foil 641a in the Z-negative direction is in contact with the conductive layer 643b of the current collector foil 641b in the Z-positive direction, and is therefore electrically connected to the current collector 500 via the conductive layer 643b. The conductive layer 643b of the current collector foil 641b in the Z-positive direction is electrically connected to the current collector 500 while in contact with the current collector 500. The conductive layer 643b of the current collector foil 641b in the Z-negative direction is in contact with the conductive layer 643c of the current collector foil 641c, and is therefore electrically connected to the current collector 500 via the conductive layer 643c. The conductive layer 643c of the current collector foil 641c in the Z-axis positive direction is electrically connected to the current collector 500 while in contact with the current collector 500.

[0068] In this embodiment, the X-axis end (both ends in Figure 5B) of the auxiliary member 510 is in contact with the current collector 500. As a result, the conductive layer 643c in the Z-axis negative direction of the current collector foil 641c is electrically connected to the current collector 500 via the auxiliary member 510. Alternatively, the conductive layer 643c in the Z-axis negative direction of the current collector foil 641c may be brought into contact with the current collector 500. In this case, the conductive layer 643c can be electrically connected to the current collector 500 without the auxiliary member 510 being in contact with the current collector 500. Similarly, the conductive layer 643b in the Z-axis negative direction of the current collector foil 641b may be brought into contact with the current collector 500, or the conductive layer 643a in the Z-axis negative direction of the current collector foil 641a may be brought into contact with the current collector 500.

[0069] In this way, the auxiliary member 510 bends toward the current collector 500 at the position of the first protrusion 645a, sandwiching the first protrusion 645a between itself and the current collector 500. The first conductive layer 643a and the second conductive layer 643b of the first protrusion 645a are electrically connected to the current collector 500 while in contact with it. Specifically, the second conductive layers 643b of the pair of first protrusions 645a are electrically connected to the current collector 500 while in contact with it.

[0070] [4. Explanation of Effects] As described above, according to the energy storage element 10 of the embodiment of the present invention, the first current collector foil 641a comprises a first conductive layer 643a and a first insulating layer 644a, and the second current collector foil 641b comprises a second conductive layer 643b and a second insulating layer 644b. In this way, since the first current collector foil 641a and the second current collector foil 641b are partially insulating layers, it is possible to reduce weight, reduce the amount of conductive material (metal material, etc.) used, and improve the strength of the current collector foil. In this configuration, the second current collector foil 641b comprises a first protruding portion 645a which is a protruding portion of the second conductive layer 643b and the second insulating layer 644b that protrudes from the first current collector foil 641a, and the first conductive layer 643a and the second conductive layer 643b of the first protruding portion 645a are electrically connected to the current collector 500 while in contact with the current collector 500. In this way, by making the second current collector foil 641b protrude more than the first current collector foil 641a, and bringing the first conductive layer 643a of the first current collector foil 641a and the second conductive layer 643b of the first protrusion 645a of the second current collector foil 641b into contact with the current collector 500, the first current collector foil 641a and the second current collector foil 641b can be electrically connected to the current collector 500. This eliminates the need for a complex configuration in which the first current collector foil 641a and the second current collector foil 641b are electrically connected to the current collector 500 after forming a region on the current collector foil where no insulating layer is interposed. Therefore, current collector foils (first current collector foil 641a and second current collector foil 641b) equipped with an insulating layer can be electrically connected to the current collector 500 with a simple configuration.

[0071] The second current collector foil 641b (tab 621) is preferable to protrude in the X-axis direction rather than the Y-axis direction because it is easier to adjust its length. Therefore, by configuring the second current collector foil 641b to protrude more in the X-axis direction than the first current collector foil 641a, the tab 621 can be easily formed.

[0072] By positioning the first current collector foil 641a between the current collector body 500 and the second current collector foil 641b, the second conductive layer 643b of the first protrusion 645a of the second current collector foil 641b can be brought into contact with the current collector body 500 by bending the first protrusion 645a toward the current collector body 500.

[0073] The second current collector foil 641b is provided with a pair of first protrusions 645a that protrude from both sides of the first current collector foil 641a, and the second conductive layer 643b of the pair of first protrusions 645a is electrically connected to the current collector 500 while in contact with the current collector 500. In this way, by making both sides of the second current collector foil 641b protrude more than the first current collector foil 641a, and bringing the second conductive layer 643b of the pair of first protrusions 645a of the second current collector foil 641b into contact with the current collector 500, both sides of the second current collector foil 641b can be electrically connected to the current collector 500. This makes it possible to more reliably connect the second current collector foil 641b to the current collector 500.

[0074] The auxiliary member 510, which sandwiches the first current collector foil 641a and the second current collector foil 641b between itself and the current collector 500, bends toward the current collector 500 at the position of the first protrusion 645a of the second current collector foil 641b, and sandwiches the first protrusion 645a between itself and the current collector 500. This allows the second conductive layer 643b of the first protrusion 645a to easily come into contact with the current collector 500.

[0075] In the above explanation, the effects were illustrated using the first current collector foil 641a and the second current collector foil 641b as examples of positive electrode current collector foil 641, but similar effects are obtained with other positive electrode current collector foils 641. The same effects are obtained with the negative electrode current collector foil 651.

[0076] The energy storage element 10 may be used in an energy storage device. In this case, the technology of the present invention only needs to be applied to at least one energy storage element 10 provided in the energy storage device. Figure 6 is a plan view showing an example of an energy storage device 30 according to this embodiment. As shown in Figure 6, a plurality of energy storage units 20 are arranged inside the energy storage device 30. The energy storage unit 20 is composed of a plurality of electrically connected energy storage elements 10. The energy storage device 30 may include busbars (not shown) that electrically connect the plurality of energy storage elements 10, busbars (not shown) that electrically connect the plurality of energy storage units 20, etc. The energy storage unit 20 or the energy storage device 30 may include a state monitoring device (not shown) that monitors the state of one or more energy storage elements 10. The energy storage device 30 may have only one energy storage unit 20 (that is, the energy storage unit 20 may be referred to as the energy storage device).

[0077] [5. Description of Modifications] The energy storage element 10 according to this embodiment has been described above, but the present invention is not limited to the above embodiment. The embodiments disclosed herein are illustrative and not restrictive in all respects, and the scope of the present invention includes all modifications in the sense and scope equivalent to the claims.

[0078] (Modification 1) In the above embodiment, the positive electrode conductive layer 643 (first conductive layer 643a and second conductive layer 643b, etc.) of the positive electrode current collector foil 641 (first current collector foil 641a and second current collector foil 641b, etc.) is electrically connected to the current collector 500 while in contact with the current collector 500, but is not limited to this. The positive electrode conductive layer 643 of the positive electrode current collector foil 641 may be electrically connected to the current collector 500 via the auxiliary member 510 while in contact with the auxiliary member 510. Figures 7A and 7B are simplified cross-sectional views showing the configuration for joining the current collector 500, electrode body 601 and auxiliary member 510 according to Modification 1 of this embodiment. Figure 7A corresponds to Figure 5A (view before joining), and Figure 7B corresponds to Figure 5B (view after joining).

[0079] As shown in Figure 7A, in this modified example, the electrode body 601 includes current collector foils 641d, 641e, and 641f instead of the three positive electrode current collector foils 641a, 641b, and 641c of the electrode body 600 in the above embodiment. Similar to the above embodiment, the relationship between the three positive electrode current collector foils 641 (current collector foils 641d, 641e, and 641f) described below can be similarly applied to the relationship between four or more positive electrode current collector foils 641. Furthermore, the relationship between these multiple positive electrode current collector foils 641 can be similarly applied to the relationship between multiple negative electrode current collector foils 651.

[0080] Before joining the current collector 500, electrode body 601, and auxiliary member 510, the current collector foils 641d, 641e, and 641f of the electrode body 601 are positioned between the current collector 500 and the auxiliary member 510 in the Z-axis direction. Specifically, the auxiliary member 510 is positioned at the Z-axis negative end, and the current collector foils 641d, 641e, 641f, and current collector 500 are positioned sequentially from the auxiliary member 510 toward the Z-axis positive direction. In other words, the electrode body 601 comprises current collector foils 641d, 641e, and 641f stacked in the Z-axis direction. The current collector foil 641d is positioned between the auxiliary member 510 and the current collector foil 641e in the Z-axis direction. The current collector foil 641e is positioned between the current collector foil 641d and the current collector foil 641f in the Z-axis direction. The current collector foil 641f is positioned between the current collector foil 641e and the current collector body 500 in the Z-axis direction. The current collector body 500 sandwiches the current collector foils 641d, 641e, and 641f between itself and the auxiliary member 510.

[0081] The current collector foil 641d comprises a conductive layer 643d as a positive electrode conductive layer 643 and an insulating layer 644d as a positive electrode insulating layer 644, arranged in the Z-axis direction. The current collector foil 641e comprises a conductive layer 643e as a positive electrode conductive layer 643 and an insulating layer 644e as a positive electrode insulating layer 644, arranged in the Z-axis direction. The current collector foil 641f comprises a conductive layer 643f as a positive electrode conductive layer 643 and an insulating layer 644f as a positive electrode insulating layer 644, arranged in the Z-axis direction. The current collector foil 641e comprises protruding portions 645c, which are protruding parts of the conductive layer 643e and insulating layer 644e, that protrude in the X-axis direction from the current collector foil 641d. In this modified example, the current collector foil 641e comprises a pair of protruding portions 645c that protrude on both sides in the X-axis direction from the current collector foil 641d. The current collector foil 641f has protruding portions 645d, which are protruding parts of the conductive layer 643f and the insulating layer 644f, that protrude in the X-axis direction from the current collector foil 641e. In this modified example, the current collector foil 641f has a pair of protruding portions 645d that protrude on both sides in the X-axis direction from the current collector foil 641e. Since the protruding portions 645c and 645d have the same configuration as the protruding portions 645a and 645b, a detailed explanation is omitted.

[0082] Hereafter, the current collector foil 641d will also be referred to as the third current collector foil 641d, the conductive layer 643d as the third conductive layer 643d, and the insulating layer 644d as the third insulating layer 644d. The current collector foil 641e will also be referred to as the fourth current collector foil 641e, the conductive layer 643e as the fourth conductive layer 643e, and the insulating layer 644e as the fourth insulating layer 644e. The protrusion 645c will also be referred to as the second protrusion 645c.

[0083] In this configuration, the electrode body 601 includes a third current collector foil 641d and a fourth current collector foil 641e stacked in the Z-axis direction (first direction). The third current collector foil 641d includes a third conductive layer 643d and a third insulating layer 644d aligned in the Z-axis direction (first direction). The fourth current collector foil 641e includes a fourth conductive layer 643e and a fourth insulating layer 644e aligned in the Z-axis direction (first direction). The third current collector foil 641d is positioned between the auxiliary member 510 and the fourth current collector foil 641e in the Z-axis direction (first direction). The current collector 500 sandwiches the third current collector foil 641d and the fourth current collector foil 641e between itself and the auxiliary member 510. The fourth current collector foil 641e has second protrusions 645c which are protruding portions of the fourth conductive layer 643e and the fourth insulating layer 644e that protrude in the X-axis direction (second direction intersecting the first direction) more than the third current collector foil 641d. Specifically, the fourth current collector foil 641e has a pair of second protrusions 645c which are protruding portions of the fourth conductive layer 643e and the fourth insulating layer 644e that protrude on both sides in the X-axis direction (second direction) more than the third current collector foil 641d.

[0084] When joining the current collector 500, electrode body 601, and auxiliary member 510, the current collector 500 and auxiliary member 510 are sandwiched from both sides in the Z-axis direction, causing the auxiliary member 510 to be pressed toward the current collector 500. As a result, as shown in Figure 7B, the X-axis end of the auxiliary member 510 is bent toward the current collector 500 at the positions of the protrusions 645c of the current collector foil 641e and 645d of the current collector foil 641f. In this modified example, both ends of the auxiliary member 510 in the X-axis direction are bent toward the current collector 500 at the positions of the pair of protrusions 645c and 645d. As a result, the protrusions 645c and 645d are sandwiched between the auxiliary member 510 and the current collector 500.

[0085] In this state, the current collector 500, the electrode body 601, and the auxiliary member 510 are joined together. In this modified example, ultrasonic bonding is performed over the entire region where the current collector foils 641d, 641e, and 641f are sandwiched between the current collector 500 and the auxiliary member 510, thereby joining the current collector 500, the current collector foils 641d, 641e, and 641f, and the auxiliary member 510. As a result, the conductive layer 643d and the conductive layer 643e of the pair of protrusions 645c are electrically connected to the auxiliary member 510 while in contact with it. The conductive layer 643f of the pair of protrusions 645d are electrically connected to the auxiliary member 510 while in contact with it. Therefore, when the auxiliary member 510 is electrically connected to the current collector 500, the conductive layer 643d of the current collector foil 641d, the conductive layer 643e of the current collector foil 641e, and the conductive layer 643f of the current collector foil 641f are electrically connected to the current collector 500 via the auxiliary member 510.

[0086] Specifically, the conductive layer 643d of the current collector foil 641d in the Z-axis negative direction is electrically connected to the auxiliary member 510 while in contact with the auxiliary member 510. The conductive layer 643d of the current collector foil 641d in the Z-axis positive direction is in contact with the conductive layer 643e of the current collector foil 641e in the Z-axis negative direction, and is therefore electrically connected to the auxiliary member 510 via the conductive layer 643e. The conductive layer 643e of the current collector foil 641e in the Z-axis negative direction is electrically connected to the auxiliary member 510 while in contact with the auxiliary member 510. The conductive layer 643e of the current collector foil 641e in the Z-axis positive direction is in contact with the conductive layer 643f of the current collector foil 641f, and is therefore electrically connected to the auxiliary member 510 via the conductive layer 643f. The conductive layer 643f of the current collector foil 641f in the negative Z-axis direction is in contact with the auxiliary member 510 and is electrically connected to the auxiliary member 510. The conductive layer 643f of the current collector foil 641f in the positive Z-axis direction is in contact with the current collector 500 and is electrically connected to the current collector 500. The auxiliary member 510 is electrically connected to the current collector 500.

[0087] In this way, the auxiliary member 510 bends toward the current collector 500 at the position of the second protrusion 645c, sandwiching the second protrusion 645c between the current collector 500 and the auxiliary member 510. The third conductive layer 643d and the fourth conductive layer 643e of the second protrusion 645c are electrically connected to the auxiliary member 510 while in contact with it. Specifically, the third conductive layer 643d and the fourth conductive layer 643e of the pair of second protrusions 645c are electrically connected to the current collector 500 via the auxiliary member 510.

[0088] The other configurations of this modified example are the same as those of the above embodiment, so a detailed explanation will be omitted. This modified example can also achieve the same effects as the above embodiment. In particular, in this modified example, the third current collector foil 641d comprises a third conductive layer 643d and a third insulating layer 644d, and the fourth current collector foil 641e comprises a fourth conductive layer 643e and a fourth insulating layer 644e. In this way, since the third current collector foil 641d and the fourth current collector foil 641e are partially insulating layers, it is possible to reduce weight, reduce the amount of conductive material (metal material, etc.) used, and improve the strength of the current collector foil. In this configuration, the fourth current collector foil 641e comprises a second protrusion 645c which is a protruding portion of the fourth conductive layer 643e and the fourth insulating layer 644e that protrudes from the third current collector foil 641d, and the third conductive layer 643d and the fourth conductive layer 643e of the second protrusion 645c are electrically connected to the auxiliary member 510 while in contact with the auxiliary member 510. In this way, by making the fourth current collector foil 641e protrude more than the third current collector foil 641d, and bringing the third conductive layer 643d of the third current collector foil 641d and the fourth conductive layer 643e of the second protrusion 645c of the fourth current collector foil 641e into contact with the auxiliary member 510, the third current collector foil 641d and the fourth current collector foil 641e can be electrically connected to the auxiliary member 510. Furthermore, since the auxiliary member 510 is electrically connected to the current collector 500, the third current collector foil 641d and the fourth current collector foil 641e can be electrically connected to the current collector 500 via the auxiliary member 510. This eliminates the need for a complex configuration in which the third current collector foil 641d and the fourth current collector foil 641e are electrically connected to the current collector 500 after forming a region on the current collector foil where no insulating layer is interposed. Therefore, with a simple configuration, the current collector foils (third current collector foil 641d and fourth current collector foil 641e) equipped with an insulating layer can be electrically connected to the current collector 500.

[0089] In the above explanation, the effects were illustrated using the third current collector foil 641d and the fourth current collector foil 641e as examples of positive electrode current collector foil 641, but similar effects are obtained with other positive electrode current collector foils 641. The same effects are obtained with the negative electrode current collector foil 651.

[0090] (Modification 2) In the above embodiment, the first conductive layer 643a of the first current collector foil 641a and the second conductive layer 643b of the second current collector foil 641b are electrically connected to the current collector 500 while in contact with the current collector 500. In Modification 1, the third conductive layer 643d of the third current collector foil 641d and the fourth conductive layer 643e of the fourth current collector foil 641e are electrically connected to the auxiliary member 510 while in contact with the auxiliary member 510. However, both of these configurations may be included. Figure 8 is a simplified cross-sectional view showing the configuration for joining the current collector 500, electrode body 602 and auxiliary member 510 according to Modification 2 of this embodiment. Figure 8 is the diagram corresponding to Figure 5A (diagram before joining).

[0091] As shown in Figure 8, the electrode body 602 in this modified example includes current collector foils 641d and 641e in Modification 1, in addition to the current collector foils 641a, 641b and 641c of the electrode body 600 in the above embodiment. Similar to the above embodiment and Modification 1, the relationship between the five positive electrode current collector foils 641 (current collector foils 641a, 641b, 641c, 641d and 641e) described below can be similarly applied to the relationship between six or more positive electrode current collector foils 641. Furthermore, the relationship between these multiple positive electrode current collector foils 641 can be similarly applied to the relationship between multiple negative electrode current collector foils 651.

[0092] Specifically, in addition to the configuration in the above embodiment, the electrode body 602 further comprises a third current collector foil 641d and a fourth current collector foil 641e laminated in the Z-axis direction (first direction) together with the first current collector foil 641a and the second current collector foil 641b. Similar to the above modified example 1, the third current collector foil 641d comprises a third conductive layer 643d and a third insulating layer 644d arranged in the Z-axis direction (first direction). The fourth current collector foil 641e comprises a fourth conductive layer 643e and a fourth insulating layer 644e arranged in the Z-axis direction (first direction). The fourth current collector foil 641e comprises a second protrusion 645c, which is a protruding portion of the fourth conductive layer 643e and the fourth insulating layer 644e, that protrudes in the X-axis direction (second direction) more than the third current collector foil 641d. The protrusion 645b of the current collector foil 641c protrudes in the X-axis direction more than the second current collector foil 641b and the fourth current collector foil 641e. The auxiliary member 510 sandwiches the electrode body 602 between itself and the current collector 500.

[0093] When joining the current collector 500, electrode body 602, and auxiliary member 510, the current collector 500 and auxiliary member 510 are sandwiched from both sides in the Z-axis direction, causing the auxiliary member 510 to be pressed toward the current collector 500. As a result, the auxiliary member 510 bends toward the current collector 500 at the positions of the first protrusion 645a and the second protrusion 645c, etc., and sandwiches the first protrusion 645a and the second protrusion 645c, etc. between the current collector 500 and the auxiliary member 510. Consequently, similar to the above embodiment, the first conductive layer 643a of the first current collector foil 641a and the second conductive layer 643b of the first protrusion 645a of the second current collector foil 641b are electrically connected to the current collector 500 while in contact with the current collector 500. Similar to the modified example 1 described above, the third conductive layer 643d of the third current collector foil 641d and the fourth conductive layer 643e of the second protrusion 645c of the fourth current collector foil 641e are electrically connected to the auxiliary member 510 while in contact with it. The auxiliary member 510 is electrically connected to the current collector 500. Therefore, the third conductive layer 643d of the third current collector foil 641d and the fourth conductive layer 643e of the fourth current collector foil 641e are electrically connected to the current collector 500 via the auxiliary member 510.

[0094] This modified version can achieve the same effects as the above embodiment. In particular, this modified version can achieve the same effects as the above embodiment, as well as the following effects as the first modified version. The third current collector foil 641d comprises a third conductive layer 643d and a third insulating layer 644d, and the fourth current collector foil 641e comprises a fourth conductive layer 643e and a fourth insulating layer 644e. In this way, since the third current collector foil 641d and the fourth current collector foil 641e are partially insulating layers, it is possible to reduce weight, reduce the amount of conductive material (metal material, etc.) used, and improve the strength of the current collector foil. In this configuration, the fourth current collector foil 641e comprises a second protrusion 645c which is a protruding portion of the fourth conductive layer 643e and the fourth insulating layer 644e that protrudes from the third current collector foil 641d, and the third conductive layer 643d and the fourth conductive layer 643e of the second protrusion 645c are electrically connected to the auxiliary member 510 while in contact with the auxiliary member 510. In this way, by making the fourth current collector foil 641e protrude more than the third current collector foil 641d, and bringing the third conductive layer 643d of the third current collector foil 641d and the fourth conductive layer 643e of the second protrusion 645c of the fourth current collector foil 641e into contact with the auxiliary member 510, the third current collector foil 641d and the fourth current collector foil 641e can be electrically connected to the auxiliary member 510. Furthermore, since the auxiliary member 510 is electrically connected to the current collector 500, the third current collector foil 641d and the fourth current collector foil 641e can be electrically connected to the current collector 500 via the auxiliary member 510. As a result, even in the third current collector foil 641d and the fourth current collector foil 641e, there is no need to create a complex configuration in which an area without an insulating layer is interposed in the current collector foil before electrically connecting it to the current collector 500, so that they can be electrically connected to the current collector 500 with a simple configuration.

[0095] According to this modified example, the length of the electrode body 602 sandwiched between the current collector 500 and the auxiliary member 510 in the X-axis direction can be shortened, thereby shortening the length of the current collector 500 and the auxiliary member 510 in the X-axis direction as well. In this modified example, the current collector foil 641c protrudes the most in the X-axis direction, but the second current collector foil 641b or the fourth current collector foil 641e may protrude the most in the X-axis direction.

[0096] (Other Modifications) In the above embodiment, the electrode body 600 is a wound-type electrode body in which the winding axis is perpendicular to the cover body 120. However, it may also be a stack-type electrode body in which flat plates are stacked, or a bellows-type electrode body in which the plates and / or separators are folded in a bellows-like manner. The electrode body 600 may also be a wound-type electrode body in which the winding axis is parallel to the cover body 120.

[0097] In the above embodiment, the electrode body 600 includes tab bundles 620 and 630, and the tab bundles 620 and 630 are joined to the current collector 500, but it is not limited to this. The electrode body 600 may not include tab bundles 620 and 630, and the ends of the electrode body 600 that protrude from the entire electrode body main body portion 610 may be joined to the current collector 500.

[0098] In the above embodiment, the auxiliary member 510 is a separate component from the current collector 500, but the auxiliary member 510 may be integrated (formed as a single unit) with the current collector 500.

[0099] In the above embodiment, the energy storage element 10 is provided with an auxiliary member 510, but it is not necessary to provide the auxiliary member 510. In other words, the current collector 500 and the electrode body 600 may be joined together with the electrode body 600 in contact with the current collector 500, without the electrode body 600 being sandwiched between the current collector 500 and the auxiliary member 510.

[0100] In the above embodiment, the tab bundles 620 and 630 of the electrode body 600 are bent in the Y-axis direction while sandwiched between the current collector 500 and the auxiliary member 510, but they do not have to be bent in the Y-axis direction. In other words, the tab bundles 620 and 630 are not limited to being positioned sandwiched between the current collector 500 and the auxiliary member 510 in the Z-axis direction, but may be positioned sandwiched between the current collector 500 and the auxiliary member 510 in the Y-axis direction or in other directions. In this case, the Y-axis direction or other direction is an example of the first direction.

[0101] In the above embodiment, the second current collector foil 641b is provided with a pair of first protrusions 645a that protrude on both sides in the X-axis direction from the first current collector foil 641a, but it is not limited to this. The second current collector foil 641b may only have a first protrusion 645a that protrudes on one side in the X-axis direction from the first current collector foil 641a. In other words, the second current collector foil 641b may only protrude on one side in the X-axis direction from the first current collector foil 641a. The same applies to the other current collector foils (current collector foil 641c). Similarly in the above modified example 1 (or modified example 2), the fourth current collector foil 641e may only have a second protrusion 645c that protrudes on one side in the X-axis direction from the third current collector foil 641d. In other words, the fourth current collector foil 641e may only protrude on one side in the X-axis direction from the third current collector foil 641d. The same applies to the other current collector foils (current collector foil 641f).

[0102] In the above embodiment, the second current collector foil 641b is configured to protrude in the X-axis direction more than the first current collector foil 641a, but it is not limited to this. The second current collector foil 641b may also protrude in the Y-axis direction more than the first current collector foil 641a. In other words, the first protrusion 645a may be the portion of the second current collector foil 641b that protrudes in the Y-axis direction more than the first current collector foil 641a (the portion where the tip of the tab 621 is extended). Alternatively, the second current collector foil 641b may protrude in both the X-axis and Y-axis directions more than the first current collector foil 641a. The same applies to the other current collector foils (excluding the third current collector foil 641d).

[0103] In the above embodiment, the auxiliary member 510 is bent toward the current collector 500 at the position of the first protrusion 645a, etc., and sandwiches the first protrusion 645a, etc. between the current collector 500 and the auxiliary member 510, but it is not limited to this. The current collector 500 may be bent toward the auxiliary member 510 at the position of the first protrusion 645a, etc., and sandwiches the first protrusion 645a, etc. Both the current collector 500 and the auxiliary member 510 may be bent toward each other and sandwich the first protrusion 645a, etc.

[0104] In the above embodiment, both the positive electrode side (tab bundle 620 side) and the negative electrode side (tab bundle 630 side) are assumed to have the above configuration, but it is not necessary for either the positive electrode side or the negative electrode side to have the above configuration.

[0105] In the above embodiment, the positive electrode plate 640 is configured such that a positive electrode active material layer 642 is formed on both sides of the positive electrode current collector foil 641. However, the positive electrode active material layer 642 may be formed on only one side of the positive electrode current collector foil 641. In this case, the positive electrode conductive layer 643 may be arranged only on one side of the positive electrode insulating layer 644 (between the positive electrode insulating layer 644 and the positive electrode active material layer 642). In other words, the positive electrode current collector foil 641 is not limited to a three-layer structure in which one positive electrode insulating layer 644 is sandwiched between two positive electrode conductive layers 643, but may also be a two-layer structure in which one positive electrode insulating layer 644 is placed on one positive electrode conductive layer 643. If the positive electrode conductive layer 643 is arranged on the side of the positive electrode insulating layer 644 facing the current collector 500, the positive electrode conductive layer 643 can be brought into contact with the current collector 500. The positive electrode current collector foil 641 may have a structure of four or more layers, including, in addition to its three-layer structure, other types of conductive layers, other types of insulating layers, or other layers. The same applies to the negative electrode plate 650.

[0106] In the above embodiment, the thickness of the positive electrode conductive layer 643 in the positive electrode current collector foil 641 is smaller than the thickness of the positive electrode insulating layer 644, but it may be greater than or equal to the thickness of the positive electrode insulating layer 644. The same applies to the negative electrode current collector foil 651.

[0107] In the above embodiment, all positive electrode current collector foils 641 on the positive electrode plate 640 are assumed to have the above configuration, but it is not necessary for any of the positive electrode current collector foils 641 to have the above configuration. The same applies to the negative electrode plate 650.

[0108] The present invention also includes forms constructed by arbitrarily combining the components included in the above embodiments and their modified examples.

[0109] This invention can be applied to energy storage elements such as lithium-ion secondary batteries.

[0110] 10 Energy storage element 100 Container 200 Terminal 500 Current collector 510 Auxiliary members 600, 601, 602 Electrode body 620, 630 Tab bundle 621, 631 Tab 640 Positive electrode plate 641 Positive electrode current collector foil 641a First current collector foil (current collector foil) 641b Second current collector foil (current collector foil) 641d Third current collector foil (current collector foil) 641e Fourth current collector foil (current collector foil) 642 Positive electrode active material layer 643 Positive electrode conductive layer 643a First conductive layer (conductive layer) 643b Second conductive layer (conductive layer) 643d Third conductive layer (conductive layer) 643e Fourth conductive layer (conductive layer) 644 Positive electrode insulating layer 644a First insulating layer (insulating layer) 644b Second insulating layer (insulating layer) 644d Third insulating layer (insulating layer) 644e Fourth insulating layer (insulating layer) 645a First protrusion (protrusion) 645c Second protrusion (protrusion) 650 Negative electrode plate 651 Negative electrode current collector foil 652 Negative electrode active material layer 653 Negative electrode conductive layer 654 Negative electrode insulating layer 660, 661, 662 Separator

Claims

1. An energy storage element comprising an electrode body and a current collector connected to the electrode body, wherein the electrode body comprises a first current collector foil and a second current collector foil laminated in a first direction, the first current collector foil comprises a first conductive layer and a first insulating layer aligned in the first direction, the second current collector foil comprises a second conductive layer and a second insulating layer aligned in the first direction, the second current collector foil comprises a first protruding portion which is a protruding part of the second conductive layer and the second insulating layer that protrudes in a second direction intersecting the first direction from the first current collector foil, and the first conductive layer and the second conductive layer of the first protruding portion are in contact with the current collector and electrically connected to the current collector.

2. The energy storage element according to claim 1, wherein the first current collector foil is disposed between the current collector and the second current collector foil in the first direction.

3. The energy storage element according to claim 1 or 2, wherein the second current collector foil comprises a pair of first protrusions which are protruding portions of the second conductive layer and the second insulating layer, and the second conductive layer of the pair of first protrusions is electrically connected to the current collector while in contact with the current collector.

4. The energy storage element according to claim 1 or 2, further comprising an auxiliary member that sandwiches the first current collector foil and the second current collector foil with the current collector, wherein the auxiliary member is bent toward the current collector at the position of the first protrusion and sandwiches the first protrusion with the current collector.

5. The energy storage element according to claim 1 or 2, further comprising an auxiliary member that sandwiches the electrode body between the current collector and the electrode body, further comprising a third current collector foil and a fourth current collector foil laminated in the first direction together with the first current collector foil and the second current collector foil, the third current collector foil comprising a third conductive layer and a third insulating layer aligned in the first direction, the fourth current collector foil comprising a fourth conductive layer and a fourth insulating layer aligned in the first direction, the fourth current collector foil comprising a second protrusion which is a protruding portion of the fourth conductive layer and the fourth insulating layer that protrudes in the second direction from the third current collector foil, the third conductive layer and the fourth conductive layer of the second protrusion being electrically connected to the auxiliary member in contact with the auxiliary member, and the auxiliary member being electrically connected to the current collector.

6. An energy storage element comprising an electrode body, a current collector connected to the electrode body, and an auxiliary member sandwiching the electrode body between the current collector and the electrode body, wherein the electrode body comprises a third current collector foil and a fourth current collector foil laminated in a first direction, the third current collector foil comprises a third conductive layer and a third insulating layer aligned in the first direction, the fourth current collector foil comprises a fourth conductive layer and a fourth insulating layer aligned in the first direction, the fourth current collector foil comprises a second protruding portion which is a protruding portion of the fourth conductive layer and the fourth insulating layer that protrudes in a second direction intersecting the first direction from the third current collector foil, the third conductive layer and the fourth conductive layer of the second protruding portion are electrically connected to the auxiliary member while in contact with the auxiliary member, and the auxiliary member is electrically connected to the current collector.

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