Power storage element

Abstract

A power storage element comprises: an electrode body in which a positive electrode plate in which a positive electrode active material layer is formed on a positive electrode current collector foil, and a negative electrode plate in which a negative electrode active material layer is formed on a negative electrode current collector foil are laminated; a potassium ion nonaqueous electrolyte; and a rectangular container that accommodates the electrode body and the potassium ion nonaqueous electrolyte. The negative electrode current collector foil is formed from aluminum or an aluminum alloy.

Description

Energy storage element

[0001] The present invention relates to an energy storage element.

[0002] Conventionally, a prismatic secondary battery includes a wound electrode assembly in which a positive electrode plate and a negative electrode plate are wound, and a prismatic outer casing that houses the wound electrode assembly. The positive electrode plate is formed by applying a positive electrode active material to an aluminum foil, and the negative electrode plate is formed by applying a negative electrode active material to a copper foil (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2022-180650

[0004] In recent years, there has been a demand to reduce the amount of copper used in order to prevent short circuits caused by copper.

[0005] Therefore, an object of the present invention is to provide an energy storage element that can reduce the amount of copper used.

[0006] An energy storage element according to one aspect of the present invention includes an electrode body formed by stacking a positive electrode plate having a positive electrode active material layer formed on a positive electrode current collector foil and a negative electrode plate having a negative electrode active material layer formed on a negative electrode current collector foil, a potassium ion nonaqueous electrolyte, and a rectangular container that contains the electrode body and the potassium ion nonaqueous electrolyte, wherein the negative electrode current collector foil is formed from aluminum or an aluminum alloy.

[0007] The present invention can provide an energy storage element that can reduce the amount of copper used.

[0008] FIG. 1 is a perspective view showing the appearance of an energy storage device according to an embodiment. FIG. 2 is an exploded perspective view showing each component of an energy storage device according to an embodiment when disassembled. FIG. 3 is a perspective view showing each component of a first energy storage element according to an embodiment when disassembled. FIG. 4 is a perspective view showing a configuration of a first electrode body according to an embodiment. FIG. 5 is a perspective view showing each component of a second energy storage element according to an embodiment when disassembled. FIG. 6 is a cross-sectional view schematically showing internal configurations of a first energy storage element and a second energy storage element according to an embodiment. FIG. 7A is an explanatory diagram showing another connection configuration between a first energy storage element and a second energy storage element according to Modification 1. FIG. 7B is an explanatory diagram showing another connection configuration between a first energy storage element and a second energy storage element according to Modification 1. FIG. 7C is an explanatory diagram showing another connection configuration between a first energy storage element and a second energy storage element according to Modification 1. FIG. 8A is a perspective view showing a first prismatic container according to Modification 2. FIG. 8B is a perspective view showing a first prismatic container according to Modification 2. FIG. 9 is a cross-sectional view showing a schematic configuration of a first energy storage element according to Modification 3.

[0009] (1) An energy storage element according to one aspect of the present invention includes an electrode assembly including a positive electrode plate having a positive electrode active material layer formed on a positive electrode current collector foil and a negative electrode plate having a negative electrode active material layer formed on a negative electrode current collector foil, a potassium ion nonaqueous electrolyte, and a rectangular container that contains the electrode assembly and the potassium ion nonaqueous electrolyte, wherein the negative electrode current collector foil is formed from aluminum or an aluminum alloy.

[0010] The energy storage element described in (1) above includes a potassium ion nonaqueous electrolyte that does not alloy with aluminum, so the negative electrode current collector foil can be formed of aluminum or an aluminum alloy. This allows the amount of copper used in the entire energy storage element to be reduced. Furthermore, short circuits caused by copper can be suppressed.

[0011] (2) In the energy storage device described in (1) above, the prismatic container may be made of aluminum or an aluminum alloy.

[0012] According to the energy storage element described in (2) above, the rectangular container is formed from aluminum or an aluminum alloy, so that the proportion of aluminum in the entire energy storage element can be increased, and recyclability can be improved.

[0013] (3) The energy storage element described in (2) above may further include a positive electrode current collector housed in the prismatic container and electrically connected to the positive electrode plate, a positive electrode terminal disposed outside the prismatic container and electrically connected to the positive electrode current collector, an insulating positive electrode insulating part that insulates the positive electrode terminal and the positive electrode current collector from the prismatic container, and a negative electrode current collector housed in the prismatic container and electrically connected to the negative electrode plate and the prismatic container, wherein the positive electrode current collector foil, the positive electrode current collector, the positive electrode terminal, and the negative electrode current collector are formed of aluminum or an aluminum alloy.

[0014] According to the energy storage element described in (3) above, the positive electrode current collector and the negative electrode current collector are formed of aluminum or an aluminum alloy, so they can be used as a common component. Furthermore, because the positive electrode current collector foil, the positive electrode current collector, the positive electrode terminal, and the negative electrode current collector are all formed of aluminum or an aluminum alloy, the proportion of aluminum in the entire energy storage element can be increased, thereby improving recyclability.

[0015] (4) The energy storage element described in (2) above may further include a positive electrode current collector housed in the prismatic container and electrically connected to the positive electrode plate, a positive electrode terminal disposed outside the prismatic container and electrically connected to the positive electrode current collector, an insulating positive electrode insulator that insulates the positive electrode terminal and the positive electrode current collector from the prismatic container, a negative electrode current collector housed in the prismatic container and electrically connected to the negative electrode plate, a negative electrode terminal disposed outside the prismatic container and electrically connected to the negative electrode current collector, and an insulating negative electrode insulator that insulates the negative electrode terminal and the negative electrode current collector from the prismatic container, wherein the positive electrode current collector foil, the positive electrode terminal, the negative electrode current collector, and the negative electrode terminal are formed of aluminum or an aluminum alloy.

[0016] According to the energy storage element described in (4) above, the positive electrode current collector and the negative electrode current collector are formed of aluminum or an aluminum alloy, so they can be used as a common component. This also applies to the positive electrode terminal and the negative electrode terminal. Furthermore, because the positive electrode current collector foil, the positive electrode current collector, the positive electrode terminal, the negative electrode current collector, and the negative electrode terminal are formed of aluminum or an aluminum alloy, the proportion of aluminum in the entire energy storage element can be increased, thereby improving recyclability.

[0017] (Embodiments) Hereinafter, with reference to the drawings, an energy storage element according to an embodiment of the present invention (including its modified examples) will be described. Note that the embodiments described below all show comprehensive or specific examples. The numerical values, shapes, materials, components, component placement and connection configurations, manufacturing processes, and the order of manufacturing processes shown in the following embodiments are examples and are not intended to limit the present invention. In each drawing, dimensions and the like are not strictly illustrated. In each drawing, the same reference numerals are used for identical or similar components. The names of each component (each component) in this embodiment are those used in this embodiment and may differ from the names of each component (each component) in the background art.

[0018] In the following description and drawings, the longitudinal direction of the container of the energy storage element, and the direction along the winding axis of the electrode body provided in the energy storage element, are defined as the X-axis direction. The thickness direction of the container of the energy storage element is defined as the Y-axis direction. The direction in which the bottom and top surfaces of the container of the energy storage element are aligned, or the up-down direction, is defined as the Z-axis direction. The X-axis direction, Y-axis direction, and Z-axis direction intersect with each other (orthogonal in this embodiment). Depending on the mode of use, the Z-axis may not be the up-down direction, but for convenience of explanation, the following description will be made assuming that the Z-axis direction is the up-down direction. In the following description, when the term "insulation" is used, it means "electrical insulation". An insulating material has a volume resistivity of 1×10 ６ Ωm or more is preferable, and 1×10 ７ Ωm or more is more preferable, and 1×10 １０ More preferably, it is Ωm or more.

[0019] In the following description, the positive X-axis direction refers to the direction of the X-axis arrow, and the negative X-axis direction refers to the direction opposite to the positive X-axis direction. The same applies to the Y-axis and Z-axis directions. Furthermore, expressions indicating relative directions or attitudes, such as parallel and perpendicular, also include cases where the direction or attitude is not strictly that. "Two directions are perpendicular" does not only mean that the two directions are completely perpendicular, but also means that the directions are substantially perpendicular, i.e., there is a difference of about a few percent.

[0020] [Electricity Storage Device] First, a schematic configuration of an electricity storage device 1 according to the present embodiment will be described. Fig. 1 is a perspective view showing the appearance of the electricity storage device 1 according to the embodiment. Fig. 2 is an exploded perspective view showing each component of the electricity storage device 1 according to the embodiment.

[0021] The power storage device 1 is a device capable of charging with electricity from an external source and discharging electricity to an external source, and in this embodiment, has a substantially rectangular parallelepiped shape. The power storage device 1 is used as a battery for driving or starting the engine of a moving object such as an automobile, a motorcycle, a personal watercraft, a ship, a snowmobile, an agricultural machine, a construction machine, an automatic guided vehicle (AGV), or a rolling stock for an electric railway. Examples of the automobile include an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and a fossil fuel (gasoline, diesel, liquefied natural gas, etc.) vehicle. Examples of the electric railway vehicle include a train, a monorail, a linear motor car, and a hybrid train equipped with both a diesel engine and an electric motor. The power storage device 1 may also be used as a stationary battery for home or business use.

[0022] As shown in Fig. 1 , the energy storage device 1 includes an exterior body 2. As shown in Fig. 2 , a plurality of energy storage units 10, a plurality of spacers 20, a plurality of bus bars, and the like are housed inside the exterior body 2. The energy storage device 1 also includes external terminals 11 (positive electrode external terminals and negative electrode external terminals) for electrically connecting to an external device. In addition to the above-mentioned components, the energy storage device 1 may also include restraining members (end plates, side plates, etc.) that restrain the plurality of energy storage units 10, bus bar holders that hold the bus bars, bus bar covers, circuit boards that monitor or control the charge state, discharge state, etc. of the energy storage units 10, and electrical components such as relays, fuses, shunt resistors, and connectors.

[0023] The exterior body 2 is a rectangular parallelepiped (box-shaped) container (module case) that constitutes the exterior body (housing, outer shell) of the energy storage device 1. A rectangular parallelepiped is a hexahedron with all faces formed of rectangles or squares. The exterior body 2 is disposed outside the plurality of energy storage units 10 and the plurality of spacers 20, etc., to house the plurality of energy storage units 10, the plurality of spacers 20, etc., and protect them from impacts and the like. The exterior body 2 is a metal exterior body formed of metal members such as aluminum, aluminum alloy, stainless steel, iron, and plated steel sheet. The exterior body 2 may be formed of an insulating material, such as any resin material that can be used for the spacers 20 described below. If the exterior body 2 is formed of a conductive material, the inner surface of the exterior body 2 may be coated with an insulating material to ensure insulation from the energy storage units 10.

[0024] 2 , the exterior body 2 includes an exterior body main body 30 that constitutes the main body of the exterior body 2, and an exterior body lid 40 that constitutes the lid of the exterior body 2. The exterior body main body 30 is a rectangular cylindrical housing (chassis) with a bottom and an opening 31 formed in the positive direction of the Z axis, and houses a plurality of energy storage units 10, a plurality of spacers 20, and the like. Although not shown, the exterior body 2 may be formed with an exhaust port that connects the inside and outside of the exterior body 2. This exhaust port exhausts gas discharged from the energy storage units 10 to the outside of the exterior body 2.

[0025] Specifically, the exterior body main body 30 includes a bottom wall 32 and a side wall 33. The bottom wall 32 is a flat, rectangular portion located at the end of the exterior body main body 30 in the negative Z-axis direction. The side wall 33 is a rectangular, annular wall extending in the positive Z-axis direction from the outer peripheral edge of the bottom wall 32, and is provided continuously around the entire circumference of the bottom wall 32. The opening 31 is located inside the side wall 33.

[0026] The exterior body lid 40 is a flat, rectangular member that closes the rectangular opening 31 of the exterior body main body 30. The exterior body main body 30 and the exterior body lid 40 are joined by welding, fusing, screwing, or the like to form a tight seal (sealed). The exterior body main body 30 and the exterior body lid 40 may be formed of members made of the same material, or may be formed of members made of different materials. On the top surface of the exterior body lid 40, a pair of external terminals 11 are arranged side by side in the Y-axis direction at the end in the positive direction of the X-axis.

[0027] The energy storage units 10 are secondary batteries that can charge and discharge electricity. The energy storage units 10 are arranged in the Y-axis direction. Specifically, the energy storage units 10 include a first energy storage element 10A and a second energy storage element 10B, which are electrically connected. The first energy storage element 10A and the second energy storage element 10B are aligned in the X-axis direction, with the first energy storage element 10A disposed in the negative X-axis direction of the second energy storage element 10B. An end of the first energy storage element 10A facing the positive X-axis direction and an end of the second energy storage element 10B facing the negative X-axis direction are joined together. The first energy storage element 10A and the second energy storage element 10B will be described in detail below.

[0028] The spacer 20 is a flat plate-like member that is arranged alongside the energy storage unit 10 in the Y-axis direction and provides insulation and / or heat between the energy storage unit 10 and other members. The spacer 20 is an insulating plate or heat insulating plate that is arranged adjacent to the energy storage unit 10 in the positive or negative Y-axis direction of the energy storage unit 10 and provides insulation and / or heat between the energy storage units 10 and each other or between the energy storage unit 10 and the exterior body 2. The spacer 20 is formed from an insulating material such as polycarbonate (PC), 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 a composite material containing any of these materials and a filler added thereto, or a material having heat insulating properties such as mica.

[0029] Of the spacers 20, the spacers 20 arranged between adjacent energy storage units 10 are intermediate spacers, and the two spacers 20 arranged at the ends of the plurality of energy storage units 10 in the Y-axis direction are end spacers. All the spacers 20 may be formed of the same material, or some of the spacers 20 may be formed of different materials. When viewed from the Y-axis direction, the spacers 20 are formed in the shape of a rectangular parallelepiped that is elongated in the X-axis direction.

[0030] The spacers 20 may be cooling plates. In this case, the spacers 20 are made of a material with high thermal conductivity, such as metal. In this case, it is preferable that the surfaces of the spacers 20 are subjected to an insulating treatment. All of the plurality of spacers 20 may be cooling plates, or at least one of them may be a cooling plate.

[0031] The busbars are connected (joined) to terminals (first terminals 300a and second terminals 300b described below) of the multiple energy storage units 10. Specifically, the multiple busbars connect the terminals of the multiple energy storage units 10 to each other and electrically connect the terminals of the end energy storage units 10 to the external terminal 11. That is, one busbar may connect the terminals of the multiple energy storage units 10 to each other, or may connect the terminals to the external terminal 11. The connection form of the busbars is not particularly limited, and the multiple energy storage units 10 may be connected in series or in parallel in any combination, or all of the energy storage units 10 may be connected in series or in parallel. The busbars and the terminals are connected (joined) by welding or the like, but the connection form is not particularly limited. The busbars are formed of a conductive metal member such as aluminum, an aluminum alloy, copper, a copper alloy, or nickel, or a combination thereof, or a conductive material other than a metal. However, from the viewpoint of reducing the amount of copper used, it is preferable that the busbars be formed of a material other than copper or a copper alloy. In particular, from the viewpoint of weight reduction, it is preferable that the bus bar be made of aluminum or an aluminum alloy.

[0032] [First Energy Storage Element and Second Energy Storage Element] Next, the configurations of the first energy storage element 10A and the second energy storage element 10B in this embodiment will be described. The first energy storage element 10A and the second energy storage element 10B are each a secondary battery (single cell) that can charge and discharge electricity, and more specifically, a non-aqueous electrolyte secondary battery such as a potassium ion secondary battery. The first energy storage element 10A and the second energy storage element 10B are non-pouch type batteries. The first energy storage element 10A and the second energy storage element 10B may also be capacitors.

[0033] First, the first energy storage element 10A will be described. Fig. 3 is a perspective view showing the components of the first energy storage element 10A according to the embodiment when disassembled. As shown in Fig. 3, the first energy storage element 10A includes a first rectangular container 100a, a first terminal 300a, and a first outer gasket 400a. A first inner gasket 500a, a first terminal current collector 600a, a first container current collector 650a, and a first electrode body 700a are housed inside the first rectangular container 100a.

[0034] A first electrolyte (not shown) is enclosed inside the first rectangular container 100a. The first electrolyte is a potassium ion non-aqueous electrolyte (nonaqueous electrolytic solution). Specifically, the first electrolyte is composed of a potassium salt primarily dissolved in a non-aqueous solvent. When the first rectangular container 100a and the negative electrode plate 750 of the first electrode body 700a are electrically connected, lithium salt may alloy with the first rectangular container 700a, so it is preferable that the first electrolyte does not contain lithium salt above the impurity level.

[0035] The non-aqueous solvent can be appropriately selected from known non-aqueous solvents. Examples of the non-aqueous solvent include cyclic carbonates such as ethylene carbonate (EC) or propylene carbonate (PC), chain carbonates such as ethyl methyl carbonate (EMC), carboxylic acid esters, phosphate esters, sulfonic acid esters, ethers, amides, and nitriles. The non-aqueous solvent may be a compound in which some of the hydrogen atoms contained in these compounds are substituted with halogen.

[0036] Potassium salts include potassium hexafluorophosphate (KPF ６ A plurality of potassium salts may be used. The first electrolyte may contain an additive such as biphenyl.

[0037] In addition to the above components, the inside of the first rectangular container 100a may contain spacers arranged on the sides, above, or below the first electrode body 700a, an insulating film that wraps around the first electrode body 700a, etc.

[0038] The first prismatic container 100a is a container having an outer shape (rectangular parallelepiped) based on a rectangular parallelepiped. Specifically, the first prismatic container 100a has an outer shape of a rectangular parallelepiped that is elongated in the X-axis direction. The first prismatic container 100a includes a first container body 110a and a first lid 120a, and the first container body 110a and the first lid 120a are assembled together to form the rectangular parallelepiped shape.

[0039] The first container body 110a is a rectangular box-shaped body that is open in the positive direction of the Z axis. The first container body 110a has a rectangular bottom plate that is long in the X axis direction and a square cylindrical wall portion that extends in the positive direction of the Z axis from the outer periphery of the bottom plate. The first lid body 120a is a rectangular metal plate that is long in the X axis direction and closes the opening of the first container body 110a. A first through-hole 121a through which the first terminal 300a passes is formed at the end of the first lid body 120a in the negative direction of the X axis.

[0040] Although not shown, the first lid 120a is formed with a liquid injection portion and a gas release valve. The liquid injection portion is a portion for injecting the first electrolyte into the first rectangular container 100a during the manufacture of the first energy storage element 10A. The gas release valve is a safety valve that releases pressure inside the first rectangular container 100a if the pressure inside the first rectangular container 100a increases excessively.

[0041] With this configuration, the first prismatic container 100a has a structure in which, after the first electrode body 700a and the like are housed inside the first container body 110a, the first container body 110a and the first lid body 120a are joined by welding, etc., thereby sealing the interior. The first prismatic container 100a (the first container body 110a and the first lid body 120a) is made of aluminum or an aluminum alloy.

[0042] The first terminal 300a is electrically connected to the first electrode body 700a via the first terminal current collector 600a. The first terminal 300a is made of aluminum or an aluminum alloy. The first terminal 300a is connected (joined) to the first terminal current collector 600a by crimping, welding, or the like, and is attached to the first cover 120a.

[0043] In the present embodiment, the first terminal 300a has a terminal body 310a and a shaft 320a protruding from the terminal body 310a. The terminal body 310a is a portion protruding outward (in the positive direction of the Z axis) from the first lid 120a. The shaft 320a is inserted into a first through-hole 121a in the first lid 120a and penetrates the first lid 120a. The shaft 320a is connected (joined) to the first terminal current collector 600a by being crimped while passing through the first lid 120a, the first outer gasket 400a, the first inner gasket 500a, and the first terminal current collector 600a.

[0044] The first terminal current collector 600a is disposed in the negative X-axis direction of the first electrode body 700a, and is connected (joined) to the first electrode body 700a and the first terminal 300a, and is a conductive current collecting member that electrically connects the first electrode body 700a and the first terminal 300a. The first terminal current collector 600a is made of aluminum or an aluminum alloy.

[0045] The first container current collector 650a is disposed in the positive direction of the X-axis of the first electrode body 700a, and is connected (joined) to the first electrode body 700a and the first lid body 120a of the first rectangular container 100a, thereby serving as a conductive current collecting member that electrically joins the first electrode body 700a and the first rectangular container 100a. The first container current collector 650a is made of aluminum or an aluminum alloy.

[0046] The first outer gasket 400a is a plate-shaped, rectangular insulating sealing member disposed between the first lid 120a and the first terminal 300a of the first prismatic container 100a to insulate and seal between the first lid 120a and the first terminal 300a. The first inner gasket 500a is a plate-shaped, rectangular insulating sealing member disposed between the first lid 120a and the first terminal current collector 600a to insulate and seal between the first lid 120a and the first terminal current collector 600a. The first outer gasket 400a and the first inner gasket 500a are examples of an insulating positive electrode insulator that insulates the first terminal 300a and the first terminal current collector 600a from the first prismatic container 100a. The first outer gasket 400a and the first inner gasket 500a are formed from an electrically insulating resin such as PP, PE, PS, PPS, PPE (including modified PPE), PET, PBT, PEEK, PFA, PTFE, PES, ABS resin, or a composite material made by adding filler to any of these.

[0047] Next, the first electrode assembly 700a will be described. Fig. 4 is a perspective view showing the configuration of the first electrode assembly 700a according to the embodiment. Specifically, Fig. 4 shows the configuration of the first electrode assembly 700a in a partially developed state, with the electrode plates in the wound state in the first electrode assembly 700a. As shown in Fig. 4, the first electrode assembly 700a has a positive electrode plate 740, a negative electrode plate 750, and separators 761 and 762.

[0048] The positive electrode plate 740 is an electrode plate in which a positive electrode active material layer 742 made of a positive electrode active material is disposed on both sides of a positive electrode current collector foil 741, which is a long strip-shaped metal foil. The positive electrode current collector foil 741 is formed from aluminum or an aluminum alloy. Any known material can be used as the positive electrode active material as long as it is capable of absorbing and releasing potassium ions. Specifically, KMO is used as the positive electrode active material. ２ Layered oxides such as KMPO ４ , K. ４ M ３ (P.O. ４ ) P ２ O ７ Polyanionic metal oxides such as KxM(CN) ６Examples of the positive electrode active material include potassium hexacyanometallates such as those mentioned above. Here, "M" is a metal element such as Ti, V, Cr, Fe, Co, Ni, Cu, and Zn. Furthermore, the positive electrode active material is preferably a positive electrode active material that can be doped and dedoped with potassium ions.

[0049] The negative electrode plate 750 is an electrode plate in which a negative electrode active material layer 752 made of a negative electrode active material is disposed on both sides of a negative electrode current collector foil 751, which is a long strip of metal foil. The negative electrode current collector foil 751 is formed of aluminum or an aluminum alloy. Any known material can be used as the negative electrode active material as long as it is capable of absorbing and releasing potassium ions. Specific examples of the negative electrode active material include carbon materials capable of absorbing and releasing potassium ions, simple substances or intermetallic compounds of elements that alloy with potassium, and oxides containing these elements. The negative electrode active material is preferably a negative electrode active material that can be doped and dedoped with potassium ions.

[0050] Examples of carbon materials capable of absorbing and releasing potassium ions include those containing graphite; soft carbon, which is an example of low-crystalline carbon; fullerene; carbon nanomaterials in general; polyacene; carbon black (e.g., ketjen black, acetylene black, channel black, lamp black, oil furnace black, thermal black); hard carbon; and the like.

[0051] Examples of elements that alloy with potassium include Ge, Sn, Pb, In, Zn, Ca, Sr, Ba, Ru, Rh, Ir, Pd, Pt, Ag, Au, Cd, Hg, Ga, Tl, C, N, Sb, Bi, O, S, Se, Te, and Cl.

[0052] Separators 761, 762 are microporous sheets made of resin. Any known material can be used as the material for separators 761, 762 as long as it does not impair the performance of first energy storage element 10A. Separators 761, 762 may be made of a woven fabric or nonwoven fabric that is insoluble in organic solvents, a synthetic resin microporous film made of a polyolefin resin such as polyethylene, or the like. Separators 761, 762 may be a laminated film formed by laminating a heat-resistant porous layer and a porous film.

[0053] The first electrode assembly 700a is formed by winding a positive electrode plate 740, a negative electrode plate 750, and separators 761 and 762. The first electrode assembly 700a is formed by stacking the positive electrode plate 740, the separator 761, the negative electrode plate 750, and the separator 762 in this order and winding them. In this embodiment, the positive electrode plate 740, the negative electrode plate 750, and the separators 761 and 762 are wound around a winding axis L extending in the X-axis direction, thereby forming the wound first electrode assembly 700a. The winding axis L is an imaginary axis that serves as the central axis when winding the positive electrode plate 740, the negative electrode plate 750, and the separators 761 and 762. In this embodiment, the winding axis L is a straight line that passes through the center of the first electrode assembly 700a and is parallel to the X-axis direction.

[0054] A plurality of protruding pieces 743 protruding outward are arranged at intervals on the edge of the positive electrode plate 740 in the negative X-axis direction. Similarly, a plurality of protruding pieces 753 protruding outward are arranged at intervals on the edge of the negative electrode plate 750 in the positive X-axis direction. The plurality of protruding pieces 743 are portions where no positive electrode active material layer is disposed and the positive electrode current collector foil 741 is exposed (positive electrode active material layer non-formed portions). The plurality of protruding pieces 753 are portions where no negative electrode active material layer is disposed and the negative electrode current collector foil 751 is exposed (negative electrode active material layer non-formed portions). In FIG. 4 , the active material layer non-formed portions (positive electrode active material layer non-formed portions, negative electrode active material layer non-formed portions) are indicated by diagonal lines.

[0055] When the positive electrode plate 740, the negative electrode plate 750, and the separators 761, 762 are wound, the multiple protruding pieces 743 of the positive electrode plate 740 substantially overlap at the end face (one end face) of the main body 710 in the negative X-axis direction, and the multiple protruding pieces 753 of the negative electrode plate 750 substantially overlap at the end face (the other end face) in the positive X-axis direction. The portion of the positive electrode plate 740 where the multiple protruding pieces 743 overlap is the positive electrode tab portion 721. In other words, the positive electrode tab portion 721 is a portion where multiple pieces (protruding pieces 743) of the same polarity electrode plates (positive electrode plate 740) among the multiple electrode plates (positive electrode plate 740 and negative electrode plate 750) are stacked. The first terminal current collector 600a is connected (joined) to the positive electrode tab portion 721. Therefore, the first terminal current collector 600a is at a positive electrode potential. In other words, the first terminal current collector 600a is an example of a positive electrode current collector. Furthermore, the first terminal 300a connected to the first terminal current collector 600a has a positive electrode potential and is used as a positive electrode terminal.

[0056] Similarly, the portion of the negative electrode plate 750 where multiple protruding pieces 753 overlap is the negative electrode tab portion 722. In other words, the negative electrode tab portion 722 is a region where multiple pieces (protruding pieces 753) of the same polarity electrode plate (negative electrode plate 750) among multiple electrode plates (positive electrode plate 740 and negative electrode plate 750) are stacked. A first container current collector 650a is connected (joined) to the negative electrode tab portion 722. Therefore, the first container current collector 650a has a negative electrode potential. In other words, the first container current collector 650a is an example of a negative electrode current collector. Furthermore, the first prismatic container 100a connected to the first container current collector 650a has a negative electrode potential. In other words, the first prismatic container 100a can be used as a negative electrode terminal.

[0057] The shape of the first electrode body 700a is not limited to a wound type, but may be a stack type in which flat electrode plates are stacked, or a shape in which the electrode plates and / or separators are folded accordion-like (a form in which the separator is folded accordion-like to sandwich a rectangular electrode plate, a form in which the electrode plate and separator are stacked and then folded accordion-like, etc.).

[0058] Next, the second energy storage element 10B will be described. Fig. 5 is a perspective view showing the components of the second energy storage element 10B according to the embodiment when disassembled. As shown in Fig. 5, the second energy storage element 10B includes a second prismatic container 100b, a second terminal 300b, and a second outer gasket 400b. A second inner gasket 500b, a second terminal current collector 600b, a second container current collector 650b, and a second electrode body 700b are housed inside the second prismatic container 100b.

[0059] Although not shown, a second electrolyte is enclosed inside the second rectangular container 100b. The second electrolyte is a potassium ion non-aqueous electrolyte (nonaqueous electrolytic solution). Specifically, the second electrolyte is formed by dissolving a potassium salt in a non-aqueous solvent. The second electrolyte may be the same as the first electrolyte.

[0060] In addition to the above components, the inside of the second rectangular container 100b may contain spacers arranged on the sides, above, or below the second electrode body 700b, an insulating film that wraps around the second electrode body 700b, etc.

[0061] The second prismatic container 100b is a container having an outer shape based on a rectangular parallelepiped. Specifically, the second prismatic container 100b has an outer shape of a rectangular parallelepiped that is elongated in the X-axis direction. The second prismatic container 100b includes a second container body 110b and a second lid 120b, and the second container body 110b and the second lid 120b are assembled together to form the rectangular parallelepiped shape.

[0062] The second container body 110b and the second lid body 120b have the same basic structure as the first container body 110a and the first lid body 120a, so only the differences will be described here.

[0063] A second through-hole 121b through which the second terminal 300b passes is formed at the end of the second lid 120b in the positive direction of the X-axis. The second terminal 300b is electrically connected to the second electrode body 700b via the second terminal current collector 600b. The second terminal 300b is made of aluminum or an aluminum alloy. The second terminal 300b is connected (joined) to the second terminal current collector 600b by crimping, welding, or the like, and is attached to the second lid 120b.

[0064] In the present embodiment, the second terminal 300b has a terminal body 310b and a shaft 320b protruding from the terminal body 310b. The terminal body 310b is a portion protruding outward (in the positive direction of the Z axis) from the second lid 120b. The shaft 320b is inserted into the second through-hole 121b of the second lid 120b and penetrates the second lid 120b. The shaft 320b is connected (joined) to the second terminal current collector 600b by being crimped while passing through the second lid 120b, the second outer gasket 400b, the second inner gasket 500b, and the second terminal current collector 600b.

[0065] The second terminal current collector 600b is disposed in the positive direction of the X-axis of the second electrode body 700b, and is connected (joined) to the second electrode body 700b and the second terminal 300b, and is a conductive current collecting member that electrically connects the second electrode body 700b and the second terminal 300b. The second terminal current collector 600b is made of aluminum or an aluminum alloy.

[0066] The second container current collector 650b is disposed in the negative X-axis direction of the second electrode body 700b, and is connected (joined) to the second electrode body 700b and the second lid body 120b of the second rectangular container 100b. The second container current collector 650b is a conductive current collecting member that electrically joins the second electrode body 700b and the second rectangular container 100b. The second container current collector 650b is made of aluminum or an aluminum alloy.

[0067] The second outer gasket 400b is a rectangular, plate-shaped insulating seal member disposed between the second lid 120b and the second terminal 300b of the second rectangular container 100b, providing insulation and sealing between the second lid 120b and the second terminal 300b. The second inner gasket 500b is a rectangular, plate-shaped insulating seal member disposed between the second lid 120b and the second terminal current collector 600b, providing insulation and sealing between the second lid 120b and the second terminal current collector 600b. The second outer gasket 400b and the second inner gasket 500b are examples of insulating negative electrode insulators that insulate the second terminal 300b and the second terminal current collector 600b from the second rectangular container 100b. The second outer gasket 400b and the second inner gasket 500b are formed from the same material as the first outer gasket 400a and the first inner gasket 500a.

[0068] The second electrode body 700b has a structure basically similar to that of the first electrode body 700a (see FIG. 4). The second container current collector 650b is connected (joined) to the positive electrode tab portion 721 of the second electrode body 700b. Therefore, the second container current collector 650b has a positive electrode potential. In other words, the second container current collector 650b is an example of a positive electrode current collector. Furthermore, the second prismatic container 100b connected to the second container current collector 650b has a positive electrode potential, and the second prismatic container 100b can be used as a positive electrode terminal.

[0069] The second terminal current collector 600b is connected (joined) to the negative electrode tab portion 722 of the second electrode body 700b. Therefore, the second terminal current collector 600b has a negative electrode potential. In other words, the second terminal current collector 600b is an example of a negative electrode current collector. Furthermore, the second terminal 300b connected to the second terminal current collector 600b has a negative electrode potential and is used as a negative electrode terminal.

[0070] FIG. 6 is a cross-sectional view schematically illustrating the internal configuration of a first energy storage element 10A and a second energy storage element 10B according to an embodiment. As shown in FIG. 6, the first rectangular container 100a of the first energy storage element 10A and the second rectangular container 100b of the second energy storage element 10B are directly connected and integrated. Specifically, the end face (short side face) of the first rectangular container 100a facing in the positive X-axis direction and the end face (short side face) of the second rectangular container 100b facing in the negative X-axis direction are overlapped and connected. In other words, the first rectangular container 100a, which serves as the negative electrode terminal, and the second rectangular container 100b, which serves as the positive electrode terminal, are electrically connected, so that the first energy storage element 10A and the second energy storage element 10B are electrically connected in series.

[0071] The first rectangular container 100a and the second rectangular container 100b can be joined by any connection method that can electrically connect the first rectangular container 100a and the second rectangular container 100b. Connection methods include welding such as laser welding or resistance welding, fusion welding, fitting, and adhesion using a conductive adhesive. Welding is preferred.

[0072] As shown in FIG. 6 , the energy storage device 1 includes a first balancer circuit 190a and a second balancer circuit 190b for each energy storage unit 10. The first balancer circuit 190a and the second balancer circuit 190b are included on the circuit board. The first balancer circuit 190a and the second balancer circuit 190b are balancer circuits that suppress the voltage difference between the first energy storage element 10A and the second energy storage element 10B by discharging the energy storage element with a relatively higher voltage from among the first energy storage element 10A and the second energy storage element 10B. The first balancer circuit 190a is electrically connected to the first rectangular container 100a and the first terminal 300a. The second balancer circuit 190b is electrically connected to the second rectangular container 100b and the second terminal 300b. The first balancer circuit 190 a and the second balancer circuit 190 b may cooperate with each other among the power storage units 10 to reduce the difference in the remaining amount of electricity among the power storage units 10 .

[0073] [Explanation of Effects] As described above, according to the embodiment, the first electrolyte provided in the first energy storage element 10A and the second electrolyte provided in the second energy storage element 10B are potassium ion nonaqueous electrolytes that do not alloy with aluminum, so that the negative electrode current collector foil 751 can be formed of aluminum or an aluminum alloy. Therefore, the amount of copper used in the energy storage elements (first energy storage element 10A and second energy storage element 10B) as a whole can be reduced. This makes it possible to suppress short circuits caused by copper.

[0074] In the first energy storage element 10A, the negative electrode tab portion 722 of the negative electrode plate 750 is electrically connected to the first rectangular container 100a, so that the first rectangular container 100a can be set to a negative electrode potential. This allows the entire first rectangular container 100a to serve as a negative electrode terminal, eliminating the need for a dedicated negative electrode terminal or an insulating member for insulating the negative electrode terminal from the first rectangular container 100a, thereby reducing the number of parts.

[0075] Similarly, in the second energy storage element 10B, the positive electrode plate 740 is electrically connected to the second rectangular container 100b, so that the second rectangular container 100b can be at a positive electrode potential. This allows the entire second rectangular container 100b to serve as a positive electrode terminal, eliminating the need for a dedicated positive electrode terminal or an insulating member for insulating this positive electrode terminal from the second rectangular container 100b, thereby reducing the number of parts. As a result, the number of parts in the energy storage device 1 including the first energy storage element 10A and the second energy storage element 10B electrically connected in series can be reduced.

[0076] Here, it is assumed that the first energy storage element 10A and the second energy storage element 10B are lithium ion batteries. In lithium ion batteries, it has been difficult to electrically connect the first rectangular container 100a, which is electrically connected to the negative electrode plate 750 of the first electrode body 700a, and the second rectangular container 100b, which is electrically connected to the positive electrode plate 740 of the second electrode body 700b.

[0077] If aluminum or an aluminum alloy is used for the first rectangular container 100a, the first rectangular container 100a electrically connected to the negative electrode plate 750 of the first electrode body 700a will form an alloy with lithium, resulting in holes being formed in the first rectangular container 100a.

[0078] If stainless steel is used for the first rectangular container 100a, if a segregation layer of stainless steel is present in the first rectangular container 100a, there is a risk that this segregation layer will form an alloy with lithium, resulting in the formation of a hole in the first rectangular container 100a.

[0079] If iron, plated steel plate, or the like is used for the second rectangular container 100b, the second rectangular container 100b electrically connected to the positive electrode plate 740 of the second electrode body 700b will dissolve due to the positive electrode potential, forming a hole in the second rectangular container 100b.

[0080] In this embodiment, the first electrolyte and the second electrolyte are potassium ion non-aqueous electrolytes that do not alloy with aluminum, so even if the first rectangular container 100a and the second rectangular container 100b are electrically connected, damage to the first rectangular container 100a and the second rectangular container 100b as described above can be suppressed.

[0081] Furthermore, prismatic containers are more effective at suppressing the expansion of the electrode assembly than pouch-shaped containers and cylindrical containers. Furthermore, in the case of cylindrical containers, expansion may be suppressed by integrating them with glass wool or the like. However, because the cylindrical container and the glass wool are integrated, disassembly is difficult and recyclability is poor. In contrast, in the case of prismatic containers, expansion is suppressed by restraints using restraint members that are easy to disassemble. Separation of the restraint members from the prismatic containers is also easy, which improves recyclability. In other words, in this embodiment, the first prismatic container 100a and the second prismatic container 100b can enhance the expansion suppression effect on the first electrode assembly 700a and the second electrode assembly 700b while also improving recyclability.

[0082] In the series-connected first and second energy storage elements 10A and 10B, the first rectangular container 100a and the second rectangular container 100b are directly connected, eliminating the need for a conductive member to electrically connect them. This further reduces the number of components. Furthermore, because the first rectangular container 100a and the second rectangular container 100b are directly connected, the electrical resistance between the first and second energy storage elements 10A and 10B can be reduced.

[0083] Since the first balancer circuit 190a is connected to the first rectangular container 100a and the first terminal 300a (positive terminal), and the second balancer circuit 190b is connected to the second rectangular container 100b and the second terminal 300b (negative terminal), the voltage difference between the first storage element 10A and the second storage element 10B can be suppressed, and overcharging of one of the storage elements can be prevented.

[0084] Since the first rectangular container 100a and the second rectangular container 100b are formed from aluminum or an aluminum alloy, the proportion of aluminum in the first storage element 10A and the second storage element 10B as a whole can be increased, thereby improving recyclability.

[0085] In the first energy storage element 10A, the positive electrode current collector (first terminal current collector 600a) and the negative electrode current collector (first container current collector 650a) are formed of aluminum or an aluminum alloy, and therefore, these can be made of a common material. Furthermore, because the positive electrode current collector foil 741, the first terminal current collector 600a, the first terminal 300a, and the first container current collector 650a are formed of aluminum or an aluminum alloy, the proportion of aluminum in the first energy storage element 10A as a whole can be increased, thereby improving recyclability. The same applies to the second energy storage element 10B.

[0086] (Modifications) Modifications of the above-described embodiment will be described below. In the following description, the same parts as those in the above-described embodiment or other modifications will be denoted by the same reference numerals, and the description thereof may be omitted.

[0087] [Modification 1] In Modification 1, another connection configuration between first energy storage elements 10A and second energy storage elements 10B will be described. Figures 7A to 7C are explanatory diagrams showing another connection configuration between first energy storage elements 10A and second energy storage elements 10B according to Modification 1.

[0088] In the above embodiment, a case has been illustrated in which the short side surface of the first rectangular container 100a of the first energy storage element 10A and the short side surface of the second rectangular container 100b of the second energy storage element 10B are joined together, but the joining surface between the first rectangular container 100a and the second rectangular container 100b may be any surface. Fig. 7A shows a case in which the bottom surface of the first rectangular container 100a and the bottom surface of the second rectangular container 100b are overlapped and joined together. Fig. 7B shows a case in which the long side surface of the first rectangular container 100a and the long side surface of the second rectangular container 100b are overlapped and joined together.

[0089] As shown in FIG. 7C , the first rectangular container 100a of the first energy storage element 10A and the second rectangular container 100b of the second energy storage element 10B may be electrically connected via a bus bar 199. The bus bar 199 is connected to the first lid 120a of the first rectangular container 100a and the second lid 120b of the second rectangular container 100b. Since the first rectangular container 100a and the second rectangular container 100b are connected via the bus bar 199 in this manner, the first energy storage element 10A and the second energy storage element 10B can be easily connected in series. The bus bar 199 may be connected at any location as long as it can electrically connect the first rectangular container 100a and the second rectangular container 100b. The first energy storage element 10A and the second energy storage element 10B may be arranged with a gap therebetween or without a gap therebetween.

[0090] [Variation 2] In Variation 2, another shape of the prismatic container will be described. Here, the first prismatic container will be described as an example, but the same applies to the second prismatic container. In the above embodiment, the first prismatic container 100a has a rectangular parallelepiped outer shape, but the first prismatic container may have any outer shape based on a rectangular parallelepiped.

[0091] 8A and 8B are perspective views showing first rectangular containers 100c and 100d according to Modification 2. The first rectangular container 100c shown in FIG. 8A has an outer shape based on a rectangular parallelepiped, with the corners in the negative X-axis direction and the positive Z-axis direction cut out in rectangular shapes. A first terminal 300a and a first outer gasket 400a are disposed in cutout portions 171c of this first rectangular container 100c. A rectangular container having at least one corner cut out in this manner may be included in the rectangular container.

[0092] The first prismatic container 100d shown in FIG. 8B has a rectangular parallelepiped-based outer shape with a top surface 172d and a bottom surface 173d that are convexly curved. Specifically, the top surface 172d of the first prismatic container 100d is a curved surface that protrudes in the positive direction of the Z axis when viewed in the X axis direction. A first terminal 300a is disposed on the top surface 172d via a first outer gasket 400a. The bottom surface 173d of the first prismatic container 100d is a curved surface that protrudes in the negative direction of the Z axis when viewed in the X axis direction. In this way, the prismatic container may include a container in which at least one surface of the rectangular parallelepiped is a curved surface.

[0093] In the above embodiment, the first rectangular container 100a of the first energy storage element 10A is at a negative electrode potential. However, the first container of the first energy storage element may be at an intermediate potential. In Modification 3, a first energy storage element 10E in which the first container is at an intermediate potential will be described.

[0094] Fig. 9 is a cross-sectional view showing a schematic configuration of a first energy storage element 10E according to Modification 3. As shown in Fig. 9, the first energy storage element 10E includes a second terminal 300b, a second outer gasket 400b, a second inner gasket 500b, and a second terminal current collector 600b. Here, a first lid 120e of a first container 100e of the first energy storage element 10E has through holes formed therein, through which the first terminal 300a and the second terminal 300b each pass.

[0095] The second terminal 300b is connected (joined) to the second terminal collector 600b by being crimped while passing through the first cover 120e, the second outer gasket 400b, the second inner gasket 500b, and the second terminal collector 600b.

[0096] The second terminal current collector 600b is disposed in the positive direction of the X-axis of the first electrode body 700a and is connected (joined) to the negative electrode tab portion 722 and the second terminal 300b, electrically connecting the first electrode body 700a and the second terminal 300b. The first container 100e is insulated from the first terminal 300a and the first terminal current collector 600a by the first outer gasket 400a and the first inner gasket 500a. Furthermore, the first container 100e is insulated from the second terminal 300b and the second terminal current collector 600b by the second outer gasket 400b and the second inner gasket 500b. This places the first container 100e at an intermediate potential.

[0097] Thus, even in the first energy storage element 10E in which the first container 100e has an intermediate potential, the positive electrode current collector (first terminal current collector 600a) and the negative electrode current collector (second terminal current collector 600b) are formed of aluminum or an aluminum alloy, and therefore can be made of a common material. The same applies to the first terminal 300a and the second terminal 300b. Furthermore, the positive electrode current collector foil 741, the first terminal current collector 600a, the first terminal 300a, the second terminal current collector 600b, and the second terminal 300b are formed of aluminum or an aluminum alloy. This allows the proportion of aluminum in the entire first energy storage element 10E in which the first container 100e has an intermediate potential to be increased, thereby improving recyclability.

[0098] (Others) Although the energy storage element and the like according to the embodiment of the present invention (including its modified examples, the same applies hereinafter) have been described above, the present invention is not limited to the above-described embodiment. The embodiment disclosed herein is an example in all respects, and the scope of the present invention includes all modifications within the meaning and scope of the claims.

[0099] In the above embodiment, the first prismatic container 100a and the second prismatic container 100b are made of aluminum or an aluminum alloy. However, at least one of the first prismatic container 100a and the second prismatic container 100b may be made of other materials, such as stainless steel, iron, or plated steel.

[0100] In the above embodiment, the first terminal 300a, the second terminal 300b, the first terminal current collector 600a, the first container current collector 650a, the second terminal current collector 600b, and the second container current collector 650b are formed of aluminum or an aluminum alloy. However, at least one of the first terminal 300a, the second terminal 300b, the first terminal current collector 600a, the first container current collector 650a, the second terminal current collector 600b, and the second container current collector 650b may be formed of another conductive material.

[0101] Any combination of the components included in the above-described embodiments and their modifications is also included within the scope of the present invention.

[0102] The present invention can be applied to an energy storage element such as a secondary battery.

[0103] LIST OF REFERENCE SIGNS 1 Energy storage device 10A First energy storage element 10B Second energy storage element 100a, 100c, 100d First rectangular container 100b Second rectangular container 190a First balancer circuit 190b Second balancer circuit 199 Bus bar 300a First terminal (positive electrode terminal) 300b Second terminal (negative electrode terminal) 400a First outer gasket (positive electrode insulating portion) 400b Second outer gasket (negative electrode insulating portion) 500a First inner gasket (positive electrode insulating portion) 500b Second inner gasket (negative electrode insulating portion) 600a First terminal current collector (positive electrode current collector) 600b Second terminal current collector 650a First container current collector (negative electrode current collector) 650b Second container current collector 700a First electrode body 700b Second electrode body 721 Positive electrode tab portion 722 Negative electrode tab portion 740 Positive electrode plate 741 Positive electrode current collector foil 742 Positive electrode active material layer 750 Negative electrode plate 751 Negative electrode current collector foil 752 Negative electrode active material layer L Winding axis

Claims

1. An energy storage element comprising: an electrode assembly in which a positive electrode plate having a positive electrode active material layer formed on a positive electrode current collector foil and a negative electrode plate having a negative electrode active material layer formed on a negative electrode current collector foil are stacked; a potassium ion nonaqueous electrolyte; and a prismatic container that contains the electrode assembly and the potassium ion nonaqueous electrolyte, wherein the negative electrode current collector foil is made of aluminum or an aluminum alloy.

2. The energy storage element according to claim 1, wherein the prismatic container is made of aluminum or an aluminum alloy.

3. The energy storage element according to claim 2, comprising: a positive electrode current collector housed in the prismatic container and electrically connected to the positive electrode plate; a positive electrode terminal disposed outside the prismatic container and electrically connected to the positive electrode current collector; an insulating positive electrode insulating part that insulates the positive electrode terminal and the positive electrode current collector from the prismatic container; and a negative electrode current collector housed in the prismatic container and electrically connected to the negative electrode plate and the prismatic container, wherein the positive electrode current collector foil, the positive electrode current collector, the positive electrode terminal, and the negative electrode current collector are formed from aluminum or an aluminum alloy.

4. The energy storage element according to claim 2, comprising: a positive electrode current collector housed in the prismatic container and electrically connected to the positive electrode plate; a positive electrode terminal arranged outside the prismatic container and electrically connected to the positive electrode current collector; an insulating positive electrode insulator that insulates the positive electrode terminal and the positive electrode current collector from the prismatic container; a negative electrode current collector housed in the prismatic container and electrically connected to the negative electrode plate; a negative electrode terminal arranged outside the prismatic container and electrically connected to the negative electrode current collector; and an insulating negative electrode insulator that insulates the negative electrode terminal and the negative electrode current collector from the prismatic container; and the positive electrode current collector, the positive electrode terminal, the negative electrode current collector, and the negative electrode terminal are formed from aluminum or an aluminum alloy.

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