Energy storage element

Abstract

To provide a power storage element capable of enhancing reliability.SOLUTION: A power storage element 10 comprises: an electrode body 600 that includes a lamination part 630 in which a pole plate (a positive electrode plate 640) is laminated; and a conductive member bonded to the lamination part 630 (a positive electrode collector 500a and a positive electrode patch 700a). The pole plate includes a base material (a positive electrode base material 641), and a mixture layer (a positive electrode activation material layer 642) formed by the base material. The lamination part 630 is formed by laminating a non-formation part (a tab 643) in which the mixture layer is not formed in the base material. The non-formation part includes an annealed part (a tab 643) in at least one part. The power storage element 10 comprises a laser welding part (a melting part 800) in which the annealed part and the conductive member are welded with a laser.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a power storage element including an electrode body and a current collector.

Background Art

[0002] Conventionally, a power storage element including an electrode body in which electrode plates are laminated and a current collector, and in which the electrode body and the current collector are welded, is widely known. For example, Patent Document 1 discloses a secondary battery (power storage element) in which an electrode body in which positive and negative electrodes are laminated and a current collecting terminal (current collector) are welded.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above conventional power storage element, when welding the electrode body and the current collector, due to the thermal contraction of the melted part, breakage may occur at the boundary between the melted part and the non-melted part, resulting in cracks. As a result, there is a risk that the reliability of the power storage element decreases, such as a decrease in the bonding strength between the laminated part and the current collector or an increase in resistance.

[0005] An object of the present invention is to provide a power storage element capable of enhancing reliability.

Means for Solving the Problems

[0006] An energy storage element according to one aspect of the present invention comprises an electrode body having a laminated portion in which electrode plates are stacked, and a conductive member joined to the laminated portion, wherein the electrode plates have a base material and a composite layer formed on the base material, the laminated portion is formed by stacking non-formed portions of the base material in which the composite layer is not formed, the non-formed portions have at least a portion of an annealed portion, and the energy storage element comprises a laser-welded portion in which the annealed portion and the conductive member are laser-welded. [Effects of the Invention]

[0007] The energy storage element of the present invention makes it possible to improve reliability. [Brief explanation of the drawing]

[0008] [Figure 1] This is a perspective view showing the external appearance of the energy storage element according to the embodiment. [Figure 2] These are perspective and side views showing the individual components of a disassembled energy storage element according to an embodiment. [Figure 3] This is a perspective view showing the configuration of the electrode body according to the embodiment. [Figure 4] These are cross-sectional and plan views showing the configuration of the positive electrode current collector, the laminated portion of the electrode body, and the positive electrode backing plate in a welded state according to the embodiment. [Figure 5] This is a cross-sectional view showing the process of welding the positive electrode current collector, laminated portion, and positive electrode backing plate according to the embodiment. [Modes for carrying out the invention]

[0009] An energy storage element according to one aspect of the present invention comprises an electrode body having a laminated portion in which electrode plates are stacked, and a conductive member joined to the laminated portion, wherein the electrode plates have a base material and a composite layer formed on the base material, the laminated portion is formed by stacking non-formed portions of the base material in which the composite layer is not formed, the non-formed portions have at least a portion of an annealed portion, and the energy storage element comprises a laser-welded portion in which the annealed portion and the conductive member are laser-welded.

[0010] When a non-formed portion and a conductive member are joined by laser welding, a laser-welded portion is formed where the non-formed portion and the conductive member are molten. The laser-welded portion shrinks due to heat as it cools and solidifies. Generally, because the electrode plate is thinner than the conductive member, when the laser-welded portion shrinks due to heat, fracture of the electrode plate occurs at the boundary between the molten and unmolten portions in the non-formed portion, making it prone to cracking. In this embodiment, at least a portion of the non-formed portion is formed from an annealed portion, increasing its elongation rate. This allows the annealed portion to more easily follow the thermal shrinkage of the laser-welded portion, thereby suppressing the occurrence of cracks.

[0011] The electrode body is a wound-type electrode body in which the electrode plate is wound, and only the unformed portion is formed from the annealed portion, and the annealed portion may have a higher elongation rate than the portion of the substrate other than the unformed portion.

[0012] In wound electrode bodies, a high elongation rate in the wound portion may hinder stable winding. In this embodiment, since the portion of the electrode body other than the non-formed portion, that is, the portion that is mainly wound, is not an annealed portion, the electrode plate can be easily and stably wound.

[0013] The annealing portion may be provided next to the laser welding portion.

[0014] According to this, since the annealed portion is located next to the laser-welded portion, it will be held down by the conductive material. Here, the annealed portion has the characteristic of deforming significantly under low load compared to the non-annealed portion. In other words, because the annealed portion deforms significantly when held down by the conductive material, the gap between layers can be reduced, and the occurrence of cracks can be suppressed.

[0015] The substrate may be made of Al.

[0016] Crack generation in the non-formation part is prominent in a base material made of aluminum. In this aspect, even in a base material made of aluminum where cracks are likely to occur, at least a part of the non-formation part is formed from a heat-treated part, so it is possible to suppress crack generation.

[0017] The base material has a tab protruding from an end of the base material, and the non-formation part may be the tab.

[0018] According to this, since the non-formation part is a tab protruding from the end of the base material, it is easy to perform heat treatment on the tab during manufacturing. For this reason, stable heat treatment can be performed on the tab which is the non-formation part.

[0019] The energy storage element according to one aspect of the present invention includes an electrode body having a stacked part where electrode plates are stacked, and a conductive member joined to the stacked part. The electrode plate has a base material and a composite layer formed on the base material. The stacked part is formed by stacking non-formation parts where the composite layer is not formed on the base material, and the non-formation part has a higher elongation rate than other parts of the base material other than the non-formation part.

[0020] As described above, when the non-formation part and the conductive member are joined by laser welding, since the melted part melted by laser welding thermally shrinks when cooled and solidified, there is a risk that the electrode plate breaks and cracks occur at the boundary of the melted part. In this aspect, since at least a part of the non-formation part has a higher elongation rate than other parts of the base material other than the non-formation part, the melted non-formation part is likely to follow the thermal shrinkage during welding, and it is possible to suppress crack generation. Therefore, the reliability of the energy storage element can be enhanced.

[0021] (Embodiment) The following description of an energy storage element according to an embodiment (including its modifications) of the present invention will be given with reference to the drawings. The embodiments described below are all general or specific examples. The numerical values, shapes, materials, components, arrangement and connection configurations of components, manufacturing processes, and the order of manufacturing processes shown in the following embodiments are examples only and are not intended to limit the present invention. Dimensions in each figure are not precisely illustrated. In each figure, the same or similar components are denoted by the same reference numerals.

[0022] In the following description and drawings, the direction in which the pair of electrode terminals (positive and negative, hereinafter the same) of the energy storage element are aligned, the direction in which the pair of current collectors are aligned, the direction in which the pair of backing plates are aligned, or the direction in which the short sides of the container face each other is defined as the X-axis direction. The direction in which the long sides of the container face each other, or the thickness direction of the container or electrode body is defined as the Y-axis direction. The direction in which the current collector and electrode body are aligned, the direction in which the current collector and backing plate are aligned, the direction in which the electrode terminals and electrode body are aligned, the direction in which the container body and lid of the energy storage element are aligned, or the vertical direction is defined as the Z-axis direction. These X-axis, Y-axis, and Z-axis directions intersect each other (orthogonal in this embodiment). Note that depending on the usage, the Z-axis direction may not be the vertical direction, but for the sake of explanation below, the Z-axis direction will be described as the vertical direction.

[0023] In the following explanation, the X-axis positive direction refers to the direction of the X-axis arrow, and the X-axis negative direction refers to the opposite direction. When simply referred to as the X-axis direction, it refers to either the X-axis positive direction or the X-axis negative direction, or either direction. The same applies to the Y-axis and Z-axis directions. Expressions indicating relative directions or orientations, such as parallel and orthogonal, include cases where they are not strictly those directions or orientations. For example, two directions being parallel means not only that the two directions are perfectly parallel, but also that they are substantially parallel, i.e., they may have a difference of a few percent. Furthermore, in the following explanation, when the term "insulation" is used, it means "electrical insulation."

[0024] [1. General explanation of energy storage elements] First, a general description of the energy storage element 10 in this embodiment will be given. Figure 1 is a perspective view showing the external appearance of the energy storage element 10 according to this embodiment. Figure 2 is a perspective view and a side view showing each component of the energy storage element 10 according to this embodiment when it is disassembled. Specifically, Figure 2(a) is a disassembled perspective view of the energy storage element 10. Figure 2(b) is a side view showing the configuration when the laminated portion 620 of the electrode body 600 is sandwiched between the current collector 500 and the backing plate 700 and welded, as viewed from the X-axis positive direction.

[0025] The energy storage element 10 is a secondary battery (single cell) capable of charging and discharging electricity, and specifically, is a non-aqueous electrolyte secondary battery such as a lithium-ion secondary battery. The energy storage element 10 is used for power storage or power supply purposes. Specifically, the energy storage element 10 is used as a battery for driving or starting the engine of mobile vehicles such as automobiles, motorcycles, watercraft, ships, snowmobiles, agricultural machinery, construction machinery, or railway vehicles for electric railways. Examples of automobiles include electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and fossil fuel (gasoline, diesel, liquefied natural gas, etc.) vehicles. Examples of railway vehicles for electric railways include electric trains, monorails, maglev trains, and hybrid trains equipped with both diesel engines and electric motors. The energy storage element 10 can also be used as a stationary battery for household or commercial use.

[0026] The energy storage element 10 is not limited to a non-aqueous electrolyte secondary battery, but may be a secondary battery other than a non-aqueous electrolyte secondary battery, or a capacitor. The energy storage element 10 may not be a secondary battery, but a primary battery that allows the user to use the stored electricity without charging. The energy storage element 10 may be a battery using a solid electrolyte. The energy storage element 10 may be a pouch-type energy storage element. In this embodiment, the energy storage element 10 is shown in a flat rectangular parallelepiped shape (square), but the shape of the energy storage element 10 is not limited to a rectangular parallelepiped shape, but may be cylindrical, oval cylindrical, or a polygonal prism shape other than a rectangular parallelepiped.

[0027] As shown in Figure 1, the energy storage element 10 comprises a container 100, a pair of electrode terminals 200 (positive and negative), and a pair of upper gaskets 300 (positive and negative). As shown in Figure 2, the container 100 houses a pair of lower gaskets 400 (positive and negative), a pair of current collectors 500 (positive and negative), an electrode body 600, and a pair of backing plates 700 (positive and negative). An electrolyte (non-aqueous electrolyte) is sealed inside the container 100, but this is not shown in the illustration. There are no particular restrictions on the type of electrolyte, as long as it does not impair the performance of the energy storage element 10, and various types can be selected. In addition to the above components, spacers placed to the side or below the electrode body 600, an insulating film enclosing the electrode body 600, etc., may also be arranged.

[0028] The container 100 is a rectangular parallelepiped (square or box-shaped) case having a container body 110 with an opening formed therein and a lid 120 that closes the opening of the container body 110. The container body 110 is a rectangular cylindrical member with a bottom that constitutes the main body of the container 100. The container body 110 has a pair of short sides on both sides in the X-axis direction, a pair of long sides on both sides in the Y-axis direction, and a bottom surface on the Z-axis negative side. The lid 120 is a rectangular plate-shaped member that constitutes the lid of the container 100 and is arranged extending in the X-axis direction in the Z-axis positive direction of the container body 110. The lid 120 is provided with a gas discharge valve 121 that releases pressure when the pressure inside the container 100 rises excessively, and an injection part 122 for injecting electrolyte into the container 100, etc.

[0029] With this configuration, the container 100 is sealed inside by welding or other means to the container body 110 and the lid 120 after the electrode body 600 and the lid 120 have been placed inside the container body 110. The material of the container 100 (container body 110 and lid 120) is not particularly limited and can be made of weldable metals such as stainless steel, aluminum, aluminum alloy, iron, or plated steel sheet, but resin can also be used.

[0030] The electrode body 600 is an energy storage element (power generation element) that comprises a positive electrode plate, a negative electrode plate, and a separator, and is capable of storing electricity. The electrode body 600 is formed by winding layers of material arranged so that a separator is sandwiched between the positive electrode plate and the negative electrode plate. As a result, the non-formed portion (uncoated portion of the active material) of the positive electrode plate, where the active material layer is not formed, is stacked to form the stacked portion 620 of the positive electrode. Similarly, the non-formed portion (uncoated portion of the active material) of the negative electrode plate, where the active material layer is not formed, is stacked to form the stacked portion 630 of the negative electrode. In other words, the electrode body 600 has an electrode body main body portion 610 and stacked portions 620 and 630 that protrude from a part of the electrode body main body portion 610 in the Z-axis positive direction and extend in the Y-axis positive direction. In this embodiment, the electrode body 600 is an oval-shaped wound electrode body when viewed from the Z-axis direction, but it may be elliptical, circular, or any other shape when viewed from the Z-axis direction. A detailed explanation of the configuration of the electrode body 600 will be given later.

[0031] The electrode terminals 200 are terminal members (positive and negative terminals) that are electrically connected to the electrode body 600 via the current collector 500. The electrode terminals 200 are metallic members that lead the electricity stored in the electrode body 600 to the external space of the energy storage element 10 and introduce electricity into the internal space of the energy storage element 10 in order to store electricity in the electrode body 600. The electrode terminals 200 are made of a conductive material such as aluminum, aluminum alloy, copper, or copper alloy. The electrode terminals 200 are connected (joined) to the current collector 500 by crimping or the like and are attached to the cover 120.

[0032] Specifically, the electrode terminal 200 has a shaft portion 201 (rivet portion) that extends downward (in the negative Z-axis direction). The shaft portion 201 is then inserted into the through hole 301 of the upper gasket 300, the through hole 123 of the cover 120, the through hole 401 of the lower gasket 400, and the through hole 501 of the current collector 500, and crimped. In this way, the electrode terminal 200 is fixed to the cover 120 together with the upper gasket 300, the lower gasket 400, and the current collector 500. The method of connecting (joining) the electrode terminal 200 and the current collector 500 is not limited to crimping, and welding methods such as ultrasonic welding, laser welding or resistance welding, or mechanical joining other than crimping, such as screw fastening, may also be used.

[0033] The current collector 500 is a flat, rectangular current collector (positive electrode current collector 500a and negative electrode current collector 500b) that electrically connects the electrode body 600 and the electrode terminals 200. The current collector 500 is an example of a conductive member according to the present invention. The positive electrode current collector 500a is connected (joined) to the laminated portion 620 of the positive electrode of the electrode body 600 by welding, and as described above, it is joined to the electrode terminals 200 of the positive electrode by crimping or the like. The negative electrode current collector 500b is connected (joined) to the laminated portion 630 of the negative electrode of the electrode body 600 by welding, and as described above, it is joined to the electrode terminals 200 of the negative electrode by crimping or the like. The positive electrode current collector 500a is made of a conductive member such as aluminum or an aluminum alloy, similar to the positive electrode base material of the electrode body 600 described later. The negative electrode current collector 500b is formed of a metal such as copper or a copper alloy, similar to the negative electrode substrate of the electrode body 600 described later.

[0034] The backing plate 700 is positioned to sandwich the laminated portion 620 or 630 of the electrode body 600 between the current collector 500 and the backing plate 700, and is an example of a member (positive electrode backing plate 700a, negative electrode backing plate 700b) that is joined (welded) to the laminated portion 620 or 630 together with the current collector 500 while the laminated portion 620 or 630 is sandwiched between the current collector 500 and the backing plate 700. The current collector 500 is an example of a conductive member according to the present invention. In this embodiment, the backing plate 700 is a flat and rectangular member, positioned in the negative Z-axis direction of the laminated portion 620 or 630, and sandwiches the laminated portion 620 or 630 between the current collector 500 and the backing plate 700 in the Z-axis direction (see Figure 2(b)). The positive electrode backing plate 700a is made of a conductive member such as aluminum or an aluminum alloy, similar to the positive electrode current collector 500a. The negative electrode backing plate 700b is made of a metal such as copper or a copper alloy, similar to the negative electrode substrate of the electrode body 600.

[0035] In this configuration, the laminated portion 620 or 630 of the electrode body 600 is sandwiched between the current collector 500 and the backing plate 700, and the current collector 500, the laminated portion 620 or 630, and the backing plate 700 are welded together to form a molten portion 800 (see Figure 2(b)). In this embodiment, one molten portion 800 is formed for one current collector 500, but the number of molten portions 800 is not particularly limited. A detailed explanation of the configuration in which the current collector 500, the laminated portion 620 or 630 of the electrode body 600, and the backing plate 700 are welded together will be given later.

[0036] The upper gasket 300 is a flat plate-shaped insulating sealing member (gasket) that is placed between the lid 120 of the container 100 and the electrode terminal 200, and insulates and seals the space between the lid 120 and the electrode terminal 200. The lower gasket 400 is a flat plate-shaped insulating sealing member (gasket) that is placed between the lid 120 and the current collector 500, and insulates and seals the space between the lid 120 and the current collector 500. The upper gasket 300 and lower gasket 400 are formed from insulating resins such as polypropylene (PP), polyethylene (PE), polystyrene (PS), polyphenylene sulfide resin (PPS), polyphenylene ether (PPE (including modified PPE)), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyether ether ketone (PEEK), tetrafluoroethylene perfluoroalkyl vinyl ether (PFA), polytetrafluoroethylene (PTFE), polyethersulfone (PES), ABS resin, or composite materials thereof.

[0037] [2. Explanation of the electrode structure] Next, the configuration of the electrode body 600 will be described in detail. Figure 3 is a perspective view showing the configuration of the electrode body 600 according to the embodiment. Specifically, Figure 3(a) shows the configuration of the electrode body 600 shown in Figure 2 with a portion of the winding state unfolded, and Figure 3(b) shows the configuration of the electrode body 600 after winding.

[0038] As shown in Figure 3(a), the electrode body 600 is formed by alternately stacking and winding a positive electrode plate 640, a negative electrode plate 650, and separators 661 and 662. In other words, the electrode body 600 is formed by stacking and winding the positive electrode plate 640, separator 661, negative electrode plate 650, and separator 662 in this order.

[0039] The positive electrode plate 640 is an electrode plate in which a positive electrode active material layer 642 is formed on the surface of a positive electrode substrate 641. The positive electrode substrate 641 is an example of a substrate according to the present invention, and the positive electrode active material layer 642 is an example of a composite layer according to the present invention. The positive electrode substrate 641 is a long, strip-shaped metal foil made of aluminum or an aluminum alloy, etc. In other words, the positive electrode substrate 641 is mainly made of aluminum (Al).

[0040] The negative electrode plate 650 is an electrode plate in which a negative electrode active material layer 652 is formed on the surface of a negative electrode substrate 651, which is a long, strip-shaped metal foil made of copper or a copper alloy. As the negative electrode substrate, any known material that is stable against oxidation-reduction reactions during charging and discharging can be used, such as nickel, iron, stainless steel, titanium, calcined carbon, conductive polymer, conductive glass, or Al-Cd alloy. As the positive electrode active material used in the positive electrode active material layer 642 and the negative electrode active material used in the negative electrode active material layer 652, any known material that is capable of intercalating and deintercalating lithium ions can be used.

[0041] For example, as positive electrode active materials, polyanionic compounds such as LiMPO4, LiMSiO4, LiMBO3 (where M is one or more transition metal elements selected from Fe, Ni, Mn, Co, etc.), lithium titanate, LiMn2O4, and LiMn 1.5 Ni 0.5 Spinel-type lithium manganese oxides such as O4, lithium transition metal oxides such as LiMO2 (where M is one or more transition metal elements selected from Fe, Ni, Mn, Co, etc.) can be used. As negative electrode active materials, lithium metals, lithium alloys (lithium-silicon, lithium-aluminum, lithium-lead, lithium-tin, lithium-aluminum-tin, lithium-gallium, and lithium metal-containing alloys such as Wood's alloys), alloys capable of intercalating and deintercalating lithium, carbon materials (e.g., graphite, non-graphitizable carbon, easily graphitizable carbon, low-temperature calcined carbon, amorphous carbon, etc.), silicon oxides, metal oxides, lithium metal oxides (Li4Ti5O 12Examples include polyphosphate compounds, or compounds of transition metals and group 14 to 16 elements, such as Co3O4 and Fe2P, which are generally called conversion negative electrodes.

[0042] Separators 661 and 662 are microporous sheets made of resin. Any known material can be used for separators 661 and 662, as long as it does not impair the performance of the energy storage element 10. For example, separators 661 and 662 can be woven fabrics, nonwoven fabrics, or synthetic resin microporous membranes made of polyolefin resins such as polyethylene, which are insoluble in organic solvents.

[0043] The positive electrode plate 640 has a plurality of rectangular tabs 643 protruding in the positive Z-axis direction at its end in the positive Z-axis direction, and the plurality of tabs 643 are arranged in a stacked state in the Y-axis direction. Similarly, the negative electrode plate 650 has a plurality of rectangular tabs 653 protruding in the positive Z-axis direction at its end in the positive Z-axis direction, and the plurality of tabs 653 are arranged in a stacked state in the Y-axis direction. Tabs 643 and 653 are portions where the active material layer (composite layer) is not formed and the base material is exposed. In other words, the tabs 643 of the positive electrode plate 640 are an example of a non-formed portion according to the present invention. The shape of tabs 643 and 653 is not particularly limited.

[0044] Here, the tab 643 of the positive electrode plate 640 is an annealed portion that has undergone annealing treatment. In contrast, the portion of the positive electrode substrate 641 other than the tab 643 has not undergone annealing treatment. Therefore, the tab 643 has a higher elongation rate than the portion of the positive electrode substrate 641 other than the tab 643. The elongation rate is measured by a tensile test. Specifically, a test specimen is made by cutting out a certain area from the tab 643, and a test specimen is also made by cutting out a certain area from the portion of the positive electrode substrate 641 other than the tab 643. The shape and size of each test specimen are the same. By performing a tensile test on each test specimen, the elongation rates of the tab 643 and the portion other than the tab 643 can be measured.

[0045] Then, as shown in Figure 3(b), the stacked tabs 643 are bundled together to form a stacked portion 620 that extends in a state protruding in the positive Z-axis direction. Similarly, the stacked tabs 653 are bundled together to form a stacked portion 630 that extends in a state protruding in the positive Z-axis direction. These stacked portions 620 and 630 are welded together with the current collector 500 and the backing plate 700, for example, while sandwiched between the current collector 500 and the backing plate 700 in the Y-axis direction, and then bent together with the current collector 500 and the backing plate 700 in the positive Y-axis direction. As a result, as shown in Figure 2(b), the stacked portions 620 and 630 are sandwiched between the current collector 500 and the backing plate 700 in the Z-axis direction. Alternatively, the stacked portions 620 and 630 may not be bent in the positive Y-axis direction and may be positioned sandwiched between the current collector 500 and the backing plate 700 in the Y-axis direction.

[0046] The electrode body portion 610 is the part that constitutes the main body of the electrode body 600, and specifically, it is the part of the electrode body 600 other than the laminated portions 620 and 630. The electrode body portion 610 is an elongated cylindrical or oval-shaped portion formed by winding the portions on which the active material layer of the positive electrode plate 640 and the negative electrode plate 650 is formed with the separators 661 and 662. If the electrode body 600 has a non-formed portion (uncoated active material portion) at the end of the electrode plate (positive electrode plate 640 or negative electrode plate 650) where the active material layer is not formed, and tabs (tabs 643 or 653) extend from the non-formed portion, then the electrode body portion 610 does not include the non-formed portion. In other words, in this configuration, the laminated portion 620 (or 630) is the portion in which multiple tabs 643 (or multiple tabs 653) and the non-formed portion are laminated. As a result, the electrode body portion 610 has a pair of curved electrode body curved portions 611 on both sides in the X-axis direction, and a pair of flat electrode body flat portions 612 connecting the pair of curved electrode body portions 611 on both sides in the Y-axis direction.

[0047] In the case of a wound electrode body without tabs, portions where unformed parts are wound and laminated are provided at both ends in the winding axis direction. In this case, these portions correspond to the laminated portions. In other words, regardless of whether or not there are tabs, a wound electrode body can include portions where unformed parts are laminated as part of the laminated portion.

[0048] [3. Description of the welding configuration of the positive electrode current collector, laminated section, and positive electrode backing plate] Next, the configuration in which the positive electrode current collector 500a, the laminated section 620, and the positive electrode backing plate 700a are welded together will be described in detail. Note that the configuration in which the negative electrode current collector 500b, the laminated section 630, and the negative electrode backing plate 700b are welded together is basically the same, so that configuration will be omitted.

[0049] Figure 4 is a cross-sectional and plan view showing the configuration of the positive electrode current collector 500a, the laminated portion 620 of the electrode body 600, and the positive electrode backing plate 700a in a welded state according to the embodiment. Specifically, Figure 4(a) is a cross-sectional view showing the configuration when the positive electrode current collector 500a, the laminated portion 620, and the positive electrode backing plate 700a are welded together and cut by a plane that includes the central axis of the molten portion 800 and is parallel to the YZ plane. In Figure 4(a), for the sake of explanation, the top and bottom of Figure 2 are reversed, and the negative Z-axis direction is shown facing upwards. Figure 4(b) is a plan view (top view, bottom view in Figure 2) showing the configuration of Figure 4(a) when viewed from the negative Z-axis direction (upwards, downwards in Figure 2).

[0050] Figure 5 is a cross-sectional view showing the process of welding the positive electrode current collector 500a, the laminated portion 620, and the positive electrode backing plate 700a according to the embodiment. Specifically, Figure 5(a) shows the state before welding the positive electrode current collector 500a, the laminated portion 620, and the positive electrode backing plate 700a, and Figure 5(b) shows the state after welding the positive electrode current collector 500a, the laminated portion 620, and the positive electrode backing plate 700a. Figures 5(a) and 5(b) correspond to Figure 4(a).

[0051] As shown in Figure 4, the positive electrode current collector 500a and the backing plate 700 are positioned to sandwich the laminated portion 620, which is formed by stacking tabs 643 of the positive electrode plate 640 of the electrode body 600, and are welded together with the laminated portion 620. As a result, a molten portion 800 is formed on the positive electrode current collector 500a, the laminated portion 620, and the positive electrode backing plate 700a, where the positive electrode current collector 500a, the laminated portion 620, and the positive electrode backing plate 700a are fused together.

[0052] The molten section 800 is the area where the positive electrode current collector 500a, the laminated section 620, and the positive electrode backing plate 700a have been melted and solidified by laser welding. In other words, the molten section 800 is a laser-welded section where the tab 643, which is the annealed section, and the conductive members, the positive electrode current collector 500a and the positive electrode backing plate 700a, have been laser-welded together.

[0053] Specifically, as shown in Figure 5(a), the flat portion of the positive electrode current collector 500a and the flat portion of the positive electrode backing plate 700a are positioned with the flat portion of the laminated section 620 in between. Then, laser light L is irradiated onto these portions from the negative Z-axis direction. As a result, as shown in Figure 5(b), the flat portion of the positive electrode current collector 500a, the flat portion of the laminated section 620, and the flat portion of the positive electrode backing plate 700a melt, forming a molten section 800.

[0054] The molten portion 800 undergoes thermal shrinkage when it cools and solidifies after laser welding. In the laminated portion 620, there are multiple layers of unmelted tabs 643 adjacent to the molten portion 800. These tabs 643 are formed in the annealed portion and have a high elongation rate, so they can easily follow the thermal shrinkage of the molten portion 800 and crack formation is suppressed.

[0055] Furthermore, the multiple layers of tabs 643 that did not melt are held between the positive electrode current collector 500a and the positive electrode backing plate 700a. In other words, these tabs 643 are pressed down by the positive electrode current collector 500a and the positive electrode backing plate 700a. Here, the annealed portion has the characteristic of deforming more significantly under a lower load than the non-annealed portion. In other words, the tabs 643, which are the annealed portion, deform significantly when pressed down by the positive electrode current collector 500a and the positive electrode backing plate 700a, thereby reducing the gap between layers and suppressing the occurrence of cracks.

[0056] [4. Explanation of Effects] As described above, according to the embodiment of the present invention, when the non-formed portion (tab 643) and the conductive member (positive electrode current collector 500a and positive electrode backing plate 700a) are joined by laser welding, a laser-welded portion (molten portion 800) is formed where the non-formed portion and the conductive member are molten. As the laser-welded portion cools and solidifies, it undergoes thermal shrinkage, which may cause the electrode plate (positive electrode plate 640) to fracture and crack at the boundary of the laser-welded portion. However, in this embodiment, at least a part of the non-formed portion is formed from an annealed portion, and its elongation rate is higher than that of the portion of the positive electrode base material 641 other than the non-formed portion. Therefore, the annealed portion can more easily follow the thermal shrinkage of the laser-welded portion, and the occurrence of cracks can be suppressed. Thus, the reliability of the energy storage element 10 can be improved.

[0057] In a wound electrode body 600, if the elongation rate of the wound portion (electrode body main portion 610) is high, stable winding may be hindered. In this embodiment, since the portion of the electrode body 600 other than the non-formed portion (tab 643), that is, the portion mainly wound (electrode body main portion 610), is not an annealed portion, the electrode plates (positive electrode plate 640 and negative electrode plate 650) can be easily and stably wound. Therefore, the reliability of the energy storage element 10 can be further improved.

[0058] Since the annealed portion (tab 643) is located next to the laser-welded portion (molten portion 800), it is held down by the conductive members (positive electrode current collector 500a and positive electrode backing plate 700a). Here, the O material (annealed material) has the characteristic of deforming more significantly under lower load than the H material (work-hardened material). In other words, the annealed portion deforms significantly when held down by the conductive members, so the gap between layers can be reduced and the occurrence of cracks can be suppressed. Therefore, the reliability of the energy storage element 10 can be further improved.

[0059] Crack formation in the uncoated area is particularly pronounced in the positive electrode plate 640, which is made of aluminum. In this embodiment, even if the positive electrode substrate 641 is made of aluminum, which is prone to cracking, the entire tab 643 is formed from an annealed portion, making it possible to suppress the occurrence of cracks.

[0060] Since the unformed portion is a tab 643 protruding from the end of the positive electrode base material 641, it is easy to anneal the tab 643 during manufacturing. Therefore, stable annealing can be applied to the tab 643, which is the unformed portion.

[0061] [5 Explanation of variations] Although the energy storage element 10 according to this embodiment has been described above, the present invention is not limited to the above embodiment. The embodiments disclosed herein are illustrative and not restrictive in all respects, and the scope of the present invention includes all modifications in the sense and scope equivalent to the claims.

[0062] In the above embodiment, the electrode body 600 is a wound-type electrode body with a winding axis perpendicular to the cover body 120, but it may also be a stack-type electrode body with flat plates stacked on top of each other, or a bellows-type electrode body with plates and / or separators folded in a bellows-like manner. The electrode body 600 may also be a wound-type electrode body with a winding axis parallel to the cover body 120. The stacked portions 620 and 630 may not be tabs, but rather ends of the electrode body 600 that protrude from the entire electrode body portion 610 of the electrode body 600.

[0063] In the above embodiment, the molten portion 800 is assumed to be circular when viewed from the Z-axis direction, but it may be an elliptical, oblong, polygonal, or other shape, or it may be an annular shape.

[0064] In the above embodiment, the molten portion 800 is formed by penetrating the backing plate 700 in the thickness direction (Z-axis direction), but it may also be formed by penetrating the current collector 500 in the thickness direction (Z-axis direction). In this case, the molten portion 800 does not have to penetrate the backing plate 700 in the thickness direction (Z-axis direction). In other words, the molten portion 800 of the current collector 500, the laminated portion 620, and the backing plate 700 may be formed by irradiating with laser light from the current collector 500 side (Z-axis positive direction).

[0065] In the above embodiment, the case in which the current collector 500 and the backing plate 700 are welded to the laminated sections 620 and 630 respectively was illustrated, but the laminated sections may have only the current collector welded to them, or they may not have a backing plate.

[0066] The present invention also includes forms constructed by arbitrarily combining the components included in the above embodiments and their modified examples. [Industrial applicability]

[0067] This invention can be applied to energy storage elements such as lithium-ion secondary batteries. [Explanation of Symbols]

[0068] 10 Energy storage elements 100 containers 110 Container body 120 Lid 121 Gas discharge valve 122 Injection section 123 Through hole 200 electrode terminal 201 Shaft 300 Upper gasket 301, 401, 501 through holes 400 Lower gasket 500 Current collector 500A positive electrode current collector (conductive material) 500b negative electrode current collector 600 Electrode body 610 Electrode body part 611 Electrode body curved section 612 Flat part of electrode body 620, 630 Laminated section 640 Positive electrode plate (electrode plate) 641 Positive electrode substrate (substrate) 642 Positive electrode active material layer (mixture material layer) 643 Tabs (unformed area, annealed area) 650 Negative plate 651 Negative electrode substrate 652 Negative electrode active material layer 653 tabs 661, 662 Separators 700 backing plate 700a Positive electrode backing plate (conductive material) 700b Negative electrode backing plate 800 Molten section

Claims

1. A power storage element comprising an electrode body having a laminated portion in which electrode plates are stacked, and a conductive member joined to the laminated portion, The electrode plate has a base material and a composite layer formed on the base material, The laminated portion is formed by laminating the non-formed portion of the substrate where the composite material layer is not formed. The non-formed portion has at least a portion of it that is annealed, The energy storage element includes a laser-welded portion formed by laser welding the annealed portion and the conductive member, The substrate has tabs protruding from its ends. The non-formed portion is the tab, The conductive member includes a current collector and a backing plate that clamp the tab, The aforementioned backing plate is flat overall. Energy storage element.

2. The electrode body is a wound type electrode body in which the electrode plate is wound, Only the unformed portion is formed from the annealed portion. The annealed portion has a higher elongation rate than the non-formed portion of the substrate. The energy storage element according to claim 1.

3. The annealing section is provided next to the laser welding section. The energy storage element according to claim 1 or 2.

4. The aforementioned substrate is formed from Al. The energy storage element according to any one of claims 1 to 3.

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