Power storage element

Abstract

This power storage element comprises: an electrode body in which a positive electrode plate having a positive electrode active material layer formed on a positive electrode current collector foil, is stacked with a negative electrode plate having a negative electrode active material layer formed on a negative electrode current collector foil; an electrolyte comprising a potassium ion nonaqueous electrolyte or a sodium ion nonaqueous electrolyte; a rectangular container that houses the electrode body and electrolyte; a positive electrode terminal that is disposed outside the rectangular container and is electrically connected to the positive electrode plate; and a negative electrode terminal that is disposed outside the rectangular container and is electrically connected to the negative electrode plate. The positive electrode terminal and negative electrode terminal are formed from aluminum or an aluminum alloy.

Description

Energy storage element

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

[0002] Conventionally, a known secondary battery is a lithium-ion secondary battery that includes an electrode assembly in which a positive electrode material and a negative electrode material are wound, a battery case that houses the electrode assembly, and a positive electrode external terminal and a negative electrode external terminal that are electrically connected to the electrode assembly and disposed outside the battery case (see, for example, Patent Document 1). In this lithium-ion secondary battery, the positive electrode external terminal is made of aluminum, and the negative electrode external terminal is made of copper.

[0003] JP 2024-084930 A

[0004] In recent years, there has been a demand for improving the manufacturability of energy storage elements.

[0005] Therefore, an object of the present invention is to provide an energy storage element that can be manufactured with improved productivity.

[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; an electrolyte made of a potassium ion nonaqueous electrolyte or a sodium ion nonaqueous electrolyte; a prismatic container that houses the electrode body and the electrolyte; a positive electrode terminal that is disposed outside the prismatic container and electrically connected to the positive electrode plate; and a negative electrode terminal that is disposed outside the prismatic container and electrically connected to the negative electrode plate, wherein the positive electrode terminal and the negative electrode terminal are formed from aluminum or an aluminum alloy.

[0007] The present invention can provide an energy storage element that can be manufactured with improved productivity.

[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 an energy storage element according to an embodiment when disassembled. FIG. 4 is a cross-sectional view showing a schematic configuration of an energy storage element according to an embodiment. FIG. 5 is a perspective view showing a configuration of an electrode body according to an embodiment. FIG. 6A is a perspective view showing a prismatic container according to Modification 1. FIG. 6B is a perspective view showing a prismatic container according to Modification 1.

[0009] (1) 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; an electrolyte made of a potassium ion nonaqueous electrolyte or a sodium ion nonaqueous electrolyte; a prismatic container that houses the electrode body and the electrolyte; a positive electrode terminal disposed outside the prismatic container and electrically connected to the positive electrode plate; and a negative electrode terminal disposed outside the prismatic container and electrically connected to the negative electrode plate, wherein the positive electrode terminal and the negative electrode terminal are formed from aluminum or an aluminum alloy.

[0010] According to the energy storage element described above in (1), the electrolyte is a potassium ion non-aqueous electrolyte or a sodium ion non-aqueous electrolyte that does not alloy with aluminum, so the positive electrode terminal and the negative electrode terminal can be formed of aluminum or an aluminum alloy, and therefore the positive electrode terminal and the negative electrode terminal can be made of a common member, thereby improving manufacturability.

[0011] (2) The energy storage element described in (1) above may further include an insulating positive electrode insulating part that insulates the positive electrode terminal from the prismatic container, and an insulating negative electrode insulating part that insulates the negative electrode terminal from the prismatic container.

[0012] According to the energy storage element described in (2) above, the positive electrode insulating portion insulates the positive electrode terminal from the prismatic container, and the negative electrode insulating portion insulates the negative electrode terminal from the prismatic container. Therefore, a conductive material may be used for the prismatic container. It is possible to use a highly corrosion-resistant metal such as aluminum or stainless steel, which is a relatively lightweight metal. Therefore, the reliability of the energy storage element can be further improved.

[0013] (3) In the energy storage device described in (1) or (2) above, the prismatic container may be made of aluminum or an aluminum alloy.

[0014] According to the energy storage element described in (3) 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.

[0015] (4) The energy storage element according to any one of (1) to (3) above may further include a positive electrode current collector housed in the prismatic container and electrically connected to the positive electrode plate and the positive electrode terminal, and a negative electrode current collector housed in the prismatic container and electrically connected to the negative electrode plate and the negative electrode terminal, wherein the positive electrode current collector foil, the positive electrode current collector, the negative electrode current collector foil, and the negative electrode current collector are made 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 member. Furthermore, because the positive electrode current collector foil, the positive electrode current collector, the negative electrode current collector foil, and the negative electrode current collector are formed of aluminum or an aluminum alloy, the proportion of aluminum in the energy storage element as a whole 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 housing 2. As shown in Fig. 2 , a plurality of energy storage elements 10, a plurality of spacers 20, a plurality of bus bars, and the like are housed inside the exterior housing 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 elements 10, bus bar holders that hold the bus bars, bus bar covers, circuit boards that monitor or control the charge and discharge states of the energy storage elements 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 energy storage elements 10 and the spacers 20, etc., to house and protect the energy storage elements 10, the spacers 20, etc. from impacts and the like. The exterior body 2 is a metal exterior body formed of a metal member such as aluminum, aluminum alloy, stainless steel, iron, or 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 elements 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 bottomed rectangular cylindrical housing (chassis) with an opening 31 formed in the positive direction of the Z axis, and houses a plurality of energy storage elements 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 elements 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 spacer 20 is a flat plate-like member that is arranged alongside the energy storage element 10 in the Y-axis direction and that insulates and / or heats the energy storage element 10 from other members. The spacer 20 is an insulating or heat-insulating plate that is arranged adjacent to the energy storage element 10 in the positive or negative Y-axis direction of the energy storage element 10 and that insulates and / or heats the energy storage elements 10 from each other or the energy storage element 10 from 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.

[0028] Of the spacers 20, the spacers 20 arranged between adjacent energy storage elements 10 are intermediate spacers, and the two spacers 20 arranged at the ends of the plurality of energy storage elements 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.

[0029] 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.

[0030] The busbar is connected (joined) to terminals (first terminals 300a and second terminals 300b described below) of the multiple energy storage elements 10. Specifically, the multiple busbars connect the terminals of the multiple energy storage elements 10 to each other and electrically connect the terminals of the end energy storage elements 10 to the external terminal 11. That is, one busbar may connect the terminals of the multiple energy storage elements 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 elements 10 may be connected in series or in parallel in any combination, or all of the energy storage elements 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 conductive metal members such as aluminum, aluminum alloy, copper, copper alloy, and nickel, or a combination thereof, or conductive members other than metals. 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 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.

[0031] [Energy Storage Element] Next, the configuration of the energy storage element 10 in this embodiment will be described. The energy storage element 10 is a secondary battery (single cell) that can charge and discharge electricity. More specifically, the energy storage element 10 is a non-aqueous electrolyte secondary battery such as a potassium ion secondary battery. The energy storage element 10 is a non-pouch type battery. The energy storage element 10 may also be a capacitor. A plurality of energy storage elements 10 are arranged in the Y-axis direction.

[0032] Fig. 3 is a perspective view showing each component of the energy storage element 10 according to the embodiment when disassembled. Fig. 4 is a cross-sectional view showing a schematic configuration of the energy storage element 10 according to the embodiment. As shown in Figs. 3 and 4 , the energy storage element 10 includes a prismatic container 100, a first terminal 300a, a first outer gasket 400a, a second terminal 300b, and a second outer gasket 400b. A first inner gasket 500a, a first current collector 600a, a second inner gasket 500b, a second current collector 600b, an electrode assembly 700, and an electrolyte are housed inside the prismatic container 100.

[0033] The electrolyte is a potassium ion non-aqueous electrolyte (nonaqueous electrolytic solution). Specifically, the electrolyte is composed mainly of a potassium salt dissolved in a non-aqueous solvent.

[0034] 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.

[0035] Potassium salts include potassium hexafluorophosphate (KPF ６ ) and the like. Multiple potassium salts may be used. The electrolyte may contain an additive such as biphenyl.

[0036] In addition to the above components, the interior of the rectangular container 100 may also include spacers arranged on the sides, above, or below the electrode body 700, an insulating film that wraps around the electrode body 700, etc.

[0037] The rectangular container 100 is a container having an outer shape (rectangular parallelepiped shape) based on a rectangular parallelepiped. Specifically, the rectangular container 100 has an outer shape of a rectangular parallelepiped that is elongated in the X-axis direction. The rectangular container 100 includes a container body 110 and a lid 120, and the container body 110 and the lid 120 are assembled together to form the rectangular parallelepiped shape.

[0038] The container body 110 is a rectangular box-shaped body that is open in the positive direction of the Z axis. The container body 110 includes 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 lid body 120 is a rectangular metal plate that is long in the X axis direction and closes the opening of the container body 110. A first through-hole 121a through which the first terminal 300a passes is formed at the end of the lid body 120 in the negative direction of the X axis. Meanwhile, a second through-hole 121b through which the second terminal 300b passes is formed at the end of the lid body 120 in the positive direction of the X axis.

[0039] Although not shown here, the lid 120 is formed with a liquid injection portion and a gas release valve. The liquid injection portion is a portion for injecting electrolyte into the prismatic container 100 during the manufacture of the energy storage element 10. The gas release valve is a safety valve that releases pressure inside the prismatic container 100 when the pressure rises excessively.

[0040] With this configuration, the prismatic container 100 has a structure in which the electrode assembly 700 and the like are housed inside the container body 110, and then the container body 110 and the lid 120 are joined by welding or the like, thereby sealing the interior. The prismatic container 100 (container body 110 and lid 120) is formed from a highly corrosion-resistant metal such as aluminum, which is a relatively lightweight metal, or SUS (stainless steel). In this embodiment, it is formed from SUS.

[0041] The first terminal 300a is a terminal electrically connected to the electrode body 700 via the first 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 current collector 600a by crimping, welding, or the like, and is attached to the lid body 120.

[0042] 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 that protrudes outward (in the positive direction of the Z axis) from the lid 120. The shaft 320a is inserted into a first through-hole 121a of the lid 120 and penetrates the lid 120. The shaft 320a is connected (joined) to the first current collector 600a by being crimped while passing through the lid 120, the first outer gasket 400a, the first inner gasket 500a, and the first current collector 600a.

[0043] The first current collector 600a is disposed in the negative X-axis direction of the electrode body 700, and is connected (joined) to the electrode body 700 and the first terminal 300a, and is a conductive current collecting member that electrically connects the electrode body 700 and the first terminal 300a. The first current collector 600a is made of aluminum or an aluminum alloy.

[0044] The second terminal 300b is a terminal electrically connected to the electrode body 700 via the second 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 current collector 600b by crimping, welding, or the like, and is attached to the lid body 120.

[0045] 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 that protrudes outward (in the positive direction of the Z axis) from the lid 120. The shaft 320b is inserted into a second through-hole 121b of the lid 120 and penetrates the lid 120. The shaft 320b is connected (joined) to the second current collector 600b by being crimped while passing through the lid 120, the second outer gasket 400b, the second inner gasket 500b, and the second current collector 600b.

[0046] The second current collector 600b is disposed in the positive direction of the X axis of the electrode body 700, and is connected (joined) to the electrode body 700 and the second terminal 300b, and is a conductive current collecting member that electrically connects the electrode body 700 and the second terminal 300b. The second current collector 600b is made of aluminum or an aluminum alloy.

[0047] The first outer gasket 400a is a plate-shaped, rectangular insulating sealing member that is disposed between the lid 120 of the prismatic container 100 and the first terminal 300a, and provides insulation and a seal between the lid 120 and the first terminal 300a. The second outer gasket 400b is a plate-shaped, rectangular insulating sealing member that is disposed between the lid 120 of the prismatic container 100 and the second terminal 300b, and provides insulation and a seal between the lid 120 and the second terminal 300b.

[0048] The first internal gasket 500a is a plate-shaped, rectangular insulating sealing member that is disposed between the lid 120 and the first current collector 600a and that insulates and seals between the lid 120 and the first current collector 600a. The second internal gasket 500b is a plate-shaped, rectangular insulating sealing member that is disposed between the lid 120 and the second current collector 600b and that insulates and seals between the lid 120 and the second current collector 600b.

[0049] The first outer gasket 400a and the first inner gasket 500a are an example of an insulating positive electrode insulator that insulates the first terminal 300a and the first current collector 600a from the rectangular container 100. On the other hand, the second outer gasket 400b and the second inner gasket 500b are an example of an insulating negative electrode insulator that insulates the second terminal 300b and the second current collector 600b from the rectangular container 100. In this way, the positive electrode insulator and the negative electrode insulator prevent the rectangular container 100 from having a positive or negative potential.

[0050] The first outer gasket 400a, the first inner gasket 500a, the second outer gasket 400b and the second inner gasket 500b 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 of any of these with filler added.

[0051] Next, the electrode assembly 700 will be described. Fig. 5 is a perspective view showing the configuration of the electrode assembly 700 according to the embodiment. Specifically, Fig. 5 shows the configuration in a partially developed state in which the wound state of the electrode plates in the electrode assembly 700 is shown. As shown in Fig. 5, the electrode assembly 700 has a positive electrode plate 740, a negative electrode plate 750, and separators 761 and 762.

[0052] 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) ６ Examples 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] The separators 761, 762 are microporous sheets made of resin. Any known material can be used as the material for the separators 761, 762 as long as it does not impair the performance of the energy storage element 10. The separators 761, 762 may be made of a woven fabric or nonwoven fabric that is insoluble in organic solvents, or a synthetic resin microporous film made of a polyolefin resin such as polyethylene. The separators 761, 762 may be a laminated film formed by laminating a heat-resistant porous layer and a porous film.

[0057] The electrode assembly 700 is formed by winding a positive electrode plate 740, a negative electrode plate 750, and separators 761 and 762. The electrode assembly 700 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 electrode assembly 700. 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 electrode assembly 700 and is parallel to the X-axis direction.

[0058] 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. 5 , 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.

[0059] 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 the multiple pieces (protruding pieces 743) of the electrode plates (positive electrode plate 740 and negative electrode plate 750) of the same polarity are stacked. The first current collector 600a is connected (joined) to the positive electrode tab portion 721. Therefore, the first current collector 600a is at a positive electrode potential. In other words, the first current collector 600a is an example of a positive electrode current collector. Furthermore, the first terminal 300a connected to the first current collector 600a has a positive electrode potential and is used as a positive electrode terminal.

[0060] 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 portion where multiple pieces (protruding pieces 753) provided on the electrode plate (negative electrode plate 750) of the same polarity among the multiple electrode plates (positive electrode plate 740 and negative electrode plate 750) are stacked. The second current collector 600b is connected (joined) to the negative electrode tab portion 722. Therefore, the second current collector 600b has a negative electrode potential. In other words, the second current collector 600b is an example of a negative electrode current collector. Furthermore, the second terminal 300b connected to the second current collector 600b has a negative electrode potential and is used as a negative electrode terminal.

[0061] The shape of the electrode body 700 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 in an accordion-like shape (a shape in which the separator is folded in an accordion-like shape to sandwich a rectangular electrode plate, a shape in which the electrode plate and separator are stacked and then folded in an accordion-like shape, etc.).

[0062] [Explanation of Effects] As described above, according to the embodiment, the electrolyte is a potassium ion nonaqueous electrolyte that does not alloy with aluminum, so the first terminal 300a (positive electrode terminal) and the second terminal 300b (negative electrode terminal) can be formed of aluminum or an aluminum alloy. Therefore, the first terminal 300a and the second terminal 300b can be made of a common member, thereby improving manufacturability.

[0063] Here, the prismatic container 100 is more effective in suppressing the expansion of the electrode assembly 700 than a pouch-type container or a cylindrical container. Furthermore, in the case of a cylindrical container, expansion may be suppressed by integrating it with glass wool or the like, but because the cylindrical container and the glass wool are integrated, disassembly is difficult and recyclability is poor. In contrast, with the prismatic container 100, expansion is suppressed by restraining it with a restraining member that is easy to disassemble. The restraining member and the prismatic container can also be easily separated, which improves recyclability. In other words, in this embodiment, the prismatic container 100 can improve the expansion suppression effect on the electrode assembly 700 while also improving recyclability.

[0064] The positive electrode insulating portion (first outer gasket 400a and first inner gasket 500a) insulates the first terminal 300a from the prismatic container 100, while the negative electrode insulating portion (second outer gasket 400b and second inner gasket 500b) insulates the second terminal 300b from the prismatic container 100. For this reason, a conductive material may be used for the prismatic container 100. It is possible to use aluminum, which is a lightweight metal, or a highly corrosion-resistant metal such as SUS. This further improves the reliability of the energy storage element 10.

[0065] The positive electrode current collector (first current collector 600 a) and the negative electrode current collector (second current collector 600 b) are formed of aluminum or an aluminum alloy, and therefore, these can be made into a common member. Furthermore, because the positive electrode current collector foil 741, the negative electrode current collector foil 751, the first current collector 600 a, and the second current collector 600 b are formed of aluminum or an aluminum alloy, the proportion of aluminum in the energy storage element 10 as a whole can be increased, and recyclability can be improved.

[0066] Here, it is assumed that the energy storage element 10 is a lithium-ion battery. In lithium-ion batteries, lithium and aluminum alloy at the negative electrode potential, so it has been difficult to form the negative electrode terminal (second terminal 300b), negative electrode current collector (second current collector 600b), negative electrode current collector foil 751, and the like from aluminum or an aluminum alloy. In the present embodiment, the electrolyte is a potassium ion nonaqueous electrolyte that does not alloy with aluminum, so it is possible to form the negative electrode terminal, negative electrode current collector, and negative electrode current collector foil 751 from aluminum or an aluminum alloy.

[0067] (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.

[0068] [Modification 1] Modification 1 describes another shape of the prismatic container. In the above embodiment, the case where the outer shape of the prismatic container 100 is a rectangular parallelepiped is exemplified, but the prismatic container may have any outer shape based on a rectangular parallelepiped.

[0069] 6A and 6B are perspective views showing prismatic containers 100c and 100d according to Modification 1. The prismatic container 100c shown in FIG. 6A has an outer shape based on a rectangular parallelepiped, with corners in the negative X-axis direction and the positive Z-axis direction and corners in the positive 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 the cutout 171c in the negative X-axis direction of the prismatic container 100c. A second terminal 300b and a second outer gasket 400b are disposed in the cutout 171c in the positive X-axis direction of the prismatic container 100c. A container having at least one corner cut out like this may be included in the prismatic container.

[0070] The prismatic container 100d shown in FIG. 6B has a rectangular parallelepiped-like shape with a top surface 172d and a bottom surface 173d that are convexly curved. Specifically, the top surface 172d of the 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, and a second terminal 300b is disposed on the top surface 172d via a second outer gasket 400b. The bottom surface 173d of the 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.

[0071] [Variation 2] In the above embodiment, the electrolyte of the energy storage element 10 is a potassium ion nonaqueous electrolyte. However, the electrolyte may be a sodium ion nonaqueous electrolyte. Because a sodium ion nonaqueous electrolyte does not alloy with aluminum, even in this case, the first terminal 300a and the second terminal 300b can be formed of aluminum or an aluminum alloy. Therefore, the amount of copper used in the energy storage element 10 as a whole can be reduced. Furthermore, short circuits caused by copper can be suppressed.

[0072] The sodium ion non-aqueous electrolyte (nonaqueous electrolyte solution) is composed of a non-aqueous solvent and a sodium salt dissolved therein. ６In this case, any known material can be used as the positive electrode active material for forming the positive electrode active material layer 742 as long as it is a material that can absorb and release sodium ions. ２ Layered oxides such as NaMPO ４ And Na ４ M ３ (P.O. ４ ) P ２ O ７ Polyanionic sodium metalates such as Na ｘ M(CN) ６ and sodium hexacyanometallates such as those mentioned above. Here, "M" is a metal element such as Ti, V, Cr, Fe, Co, Ni, Cu, and Zn. The positive electrode active material is preferably a positive electrode active material that can be doped and dedoped with sodium ions.

[0073] On the other hand, any known material can be used as the negative electrode active material forming the negative electrode active material layer 752 as long as it is capable of absorbing and releasing sodium ions. Specific examples of the negative electrode active material include sodium metal, an alloy capable of absorbing and releasing sodium, and carbon materials (soft carbon, hard carbon). The negative electrode active material is preferably one that can be doped and dedoped with sodium ions.

[0074] (Others) Although the energy storage element according to the embodiment of the present invention (including its modified examples, the same applies hereinafter) has 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.

[0075] In the above embodiment, the prismatic container 100 is formed from aluminum or SUS. However, the prismatic container 100 may be formed from an aluminum alloy, iron, plated steel, or the like. In particular, when the prismatic container is formed from aluminum or an aluminum alloy, the aluminum content of the entire energy storage element 10 can be increased, thereby improving recyclability. In an energy storage device including a plurality of such energy storage elements 10, it is preferable to use aluminum or aluminum alloy members for some or all of the components of the energy storage device (such as bus bars and exterior body). This increases the aluminum content of the entire energy storage device, thereby improving recyclability.

[0076] In the above embodiment, the first current collector 600a and the second current collector 600b are made of aluminum or an aluminum alloy. However, at least one of the first current collector 600a and the second current collector 600b may be made of another conductive material.

[0077] In the above embodiment, the terminal 300 is disposed on the lid 120. However, the terminal 300 may be disposed on a side surface (long side surface or short side surface) or a bottom surface of the container 100.

[0078] Any combination of the components included in the above-described embodiments and their modifications is also included within the scope of the present invention.

[0079] The present invention can be applied to an energy storage element such as a secondary battery.

[0080] REFERENCE SIGNS LIST 1 Energy storage device 10 Energy storage element 100, 100c, 100d Prismatic container 110 Container body 120 Lid 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 current collector (positive electrode current collector) 600b Second current collector (negative electrode current collector) 700 Electrode body 710 Main 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 743, 753 Protruding piece 750 Negative electrode plate 751 Negative electrode current collector foil 752 Negative electrode active material layer 761, 762 Separator L Winding shaft

Claims

1. An energy storage element comprising: an electrode assembly 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; an electrolyte consisting of a potassium ion non-aqueous electrolyte or a sodium ion non-aqueous electrolyte; a prismatic container that houses the electrode assembly and the electrolyte; a positive electrode terminal disposed outside the prismatic container and electrically connected to the positive electrode plate; and a negative electrode terminal disposed outside the prismatic container and electrically connected to the negative electrode plate, wherein the positive electrode terminal and the negative electrode terminal are formed from aluminum or an aluminum alloy.

2. The energy storage element according to claim 1, comprising: an insulating positive electrode insulating part that insulates the positive electrode terminal from the prismatic container; and an insulating negative electrode insulating part that insulates the negative electrode terminal from the prismatic container.

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

4. The energy storage element according to any one of claims 1 to 3, comprising: a positive electrode current collector housed in the prismatic container and electrically connected to the positive electrode plate and the positive electrode terminal; and a negative electrode current collector housed in the prismatic container and electrically connected to the negative electrode plate and the negative electrode terminal, wherein the positive electrode current collector foil, the positive electrode current collector, the negative electrode current collector foil, and the negative electrode current collector are formed from aluminum or an aluminum alloy.

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