Energy storage element

Abstract

To provide a power storage element which can prevent degradation in welding quality between an electrode body and a collector.SOLUTION: A power storage element 10 comprises: an electrode body 600 having a laminated part 620 in which electrode plates are laminated; and a collector 500 and a patch 700 which are disposed at positions across the laminated part 620 and are welded together with the laminated part 620. Around a molten part 800 where the collector 500, the laminated part 620, and the patch 700 are melted, a first space 910 is formed between the laminated part 620 and the patch 700. The patch 700 has a patch recessed part 710 where a surface facing the laminated part 620 is recessed. The first space 910 is at least partially disposed in the patch recessed part 710.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an energy storage element including an electrode assembly and a current collector. [Background technology]

[0002] Conventionally, a storage element has been widely known, which includes an electrode assembly in which electrode plates are stacked, and a current collector, and the electrode assembly and the current collector are welded together. For example, Patent Document 1 discloses a secondary battery (storage element) in which an electrode assembly in which positive and negative electrodes are stacked, and a current collector terminal (current collector) are welded together. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-207749 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-described conventional energy storage element, when the electrode assembly and the current collector are welded together, blowholes may occur around the molten part caused by the welding. In particular, when the part of the electrode assembly where the electrode plates are stacked (hereinafter also referred to as the stacked part) is welded to the current collector, gas is generated in the stacked part during welding, which makes it easy for blowholes to occur at the boundary between the stacked part and the molten part. In particular, when a relatively large blowhole occurs at the boundary between the stacked part and the molten part, there is a risk that the quality of the weld between the electrode assembly and the current collector will be reduced, for example, the bonding strength between the electrode assembly and the current collector will be reduced, or the resistance will be increased.

[0005] The present invention was made by the inventors of the present application by focusing on the above-mentioned problem, and aims to provide an energy storage element that can suppress deterioration in the welding quality between the electrode body and the current collector. [Means for solving the problem]

[0006] A storage element according to one embodiment of the present invention comprises an electrode body having a laminated portion in which electrode plates are stacked, and a current collector and a backing plate arranged on either side of the laminated portion and welded together with the laminated portion, wherein a first space is formed between the laminated portion and the backing plate around a molten portion where the current collector, the laminated portion, and the backing plate are melted, and a recess is formed in the backing plate such that the surface facing the laminated portion is recessed, and at least a portion of the first space is located within the recess.

[0007] The present invention can be realized not only as such an electricity storage element, but also as a combination of an electrode body, a current collector, and a backing plate. [Effects of the Invention]

[0008] According to the energy storage element of the present invention, deterioration in the welding quality between the electrode body and the current collector can be suppressed. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view showing the appearance of an energy storage element according to an embodiment; [Figure 2] 1A and 1B are a perspective view and a side view showing the components of an energy storage device according to an embodiment of the present invention when disassembled; [Figure 3] FIG. 2 is a perspective view showing the configuration of an electrode body according to the embodiment. [Figure 4] 3A and 3B are a cross-sectional view and a plan view showing a configuration in which a current collector, a laminated portion of an electrode body, and a backing plate according to an embodiment are welded together. [Figure 5] 10 is a cross-sectional image showing a configuration in which a current collector, a laminated portion of an electrode body, and a backing plate according to an embodiment are welded together. [Figure 6] 5A to 5C are cross-sectional views showing a process of welding together a current collector, a laminated portion of an electrode body, and a backing plate according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] A storage element according to one embodiment of the present invention comprises an electrode body having a laminated portion in which electrode plates are stacked, and a current collector and a backing plate arranged on either side of the laminated portion and welded together with the laminated portion, wherein a first space is formed between the laminated portion and the backing plate around a molten portion where the current collector, the laminated portion, and the backing plate are melted, and a recess is formed in the backing plate such that the surface facing the laminated portion is recessed, and at least a portion of the first space is located within the recess.

[0011] According to this, in the energy storage element, a first space is formed between the stacked portion and the backing plate around the fusion zone formed by melting the current collector, the stacked portion of the electrode plates in the electrode assembly, and the backing plate, and at least a portion of the first space is located within the recess of the backing plate. By thus locating the first space between the stacked portion and the backing plate around the fusion zone, gas generated in the stacked portion during welding escapes into the first space on the backing plate side, thereby preventing the formation of relatively large blowholes at the boundary between the stacked portion and the fusion zone. Furthermore, by locating at least a portion of the first space within the recess of the backing plate, it becomes difficult for recesses to form in the stacked portion, or the recesses formed in the stacked portion become smaller. This further prevents the formation of relatively large blowholes at the boundary between the stacked portion and the fusion zone. This prevents a decrease in the welding quality between the electrode assembly and the current collector.

[0012] The fusion zone may be formed so as to penetrate the backing plate in a thickness direction.

[0013] When welding is performed from the backing plate side by laser welding or the like, a molten part is formed so as to penetrate the backing plate. In this case, compared to when welding is performed from the current collector side by laser welding or the like, the heat from welding can be prevented from affecting the current collector, and therefore, the current collector can be prevented from being deformed by heat and creating a gap between the laminated part. This makes it possible to prevent a decrease in the welding quality between the electrode body and the current collector.

[0014] A second space connected to the first space may be formed between the fusion zone and a portion of the laminated portion adjacent to the fusion zone.

[0015] According to this, since a second space connected to the first space is formed between the fusion zone and the laminated portion, gas generated in the laminated portion during welding can escape to the first space through the second space, which makes it possible to prevent the generation of relatively large blowholes at the boundary between the laminated portion and the fusion zone, and therefore to prevent a decrease in the welding quality between the electrode body and the current collector.

[0016] The second space may be disposed so as to extend from the first space along the fusion zone to a position not in contact with the current collector.

[0017] In this way, since the second space does not extend to the current collector, the formation of a space on the current collector side is suppressed, and gas generated in the laminated portion during welding can be released to the first space through the second space, which prevents the formation of a space between the laminated portion and the fusion zone, thereby suppressing a decrease in the welding quality between the electrode body and the current collector.

[0018] The first space may be larger than the second space.

[0019] According to this, since the first space is larger than the second space, a larger amount of gas generated in the laminated portion during welding can be released into the first space, which prevents the generation of relatively large blowholes at the boundary between the laminated portion and the fusion zone, thereby preventing a decrease in the welding quality between the electrode body and the current collector.

[0020] The fusion zone may be a portion formed by fusing the current collector, the laminated portion, and the backing plate by laser welding.

[0021] The inventors of the present application have found that the first space is easily formed when the current collector, the laminated portion, and the backing plate are welded by laser welding. Therefore, by laser welding the current collector, the laminated portion, and the backing plate, the first space is formed, and deterioration of the welding quality between the electrode body and the current collector can be suppressed.

[0022] 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 only 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 or similar components are designated by the same reference numerals.

[0023] In the following description and drawings, the X-axis direction is defined as the direction in which a pair of electrode terminals (positive and negative, hereinafter the same) of an energy storage element, the direction in which a pair of current collectors, the direction in which a pair of backing plates are arranged, or the direction in which the short side surfaces of a container face each other. The Y-axis direction is defined as the direction in which the long side surfaces of the container face each other, or the thickness direction of the container or electrode body. The Z-axis direction is defined as the direction in which the current collectors and electrode body are arranged, the direction in which the current collectors and backing plates are arranged, the direction in which the electrode terminals and electrode body are arranged, the direction in which the container body and lid of the energy storage element are arranged, or the up-down direction. The X-axis direction, Y-axis direction, and Z-axis direction intersect each other (orthogonal in this embodiment). Note that depending on the mode of use, the Z-axis may not be the up-down direction; however, for convenience of explanation, the Z-axis direction will be described below as the up-down direction.

[0024] 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. When simply referring to the X-axis direction, it refers to both or either of the positive X-axis direction and the negative X-axis direction. The same applies to the Y-axis and Z-axis directions. Expressions indicating relative directions or attitudes, such as parallel and orthogonal, also include cases where the directions or attitudes are not strictly those of the same kind. For example, when two directions are parallel, it does not only mean that the two directions are completely parallel, but also means that the directions are substantially parallel, that is, there is a difference of, for example, a few percent. Furthermore, in the following description, when the term "insulation" is used, it means "electrical insulation."

[0025] (Embodiment) [1 General Description of Energy Storage Element 10] First, a general description of an energy storage element 10 according to the present embodiment will be given. Fig. 1 is a perspective view showing the appearance of the energy storage element 10 according to the present embodiment. Fig. 2 is a perspective view and a side view showing the components of the energy storage element 10 according to the present embodiment when disassembled. Specifically, Fig. 2(a) is an exploded perspective view of the energy storage element 10. Fig. 2(b) is a side view showing the configuration of the laminated portion 620 of the electrode body 600 sandwiched between a current collector 500 and a backing plate 700 and welded together, as viewed from the positive direction of the X-axis.

[0026] The energy storage element 10 is a secondary battery (single cell) that can charge and discharge electricity, specifically a nonaqueous electrolyte secondary battery such as a lithium-ion secondary battery. The energy storage element 10 is used for power storage or power supply applications. Specifically, the energy storage element 10 is used as a battery for driving or starting the engine of a moving object such as an automobile, motorcycle, personal watercraft, ship, snowmobile, agricultural machinery, construction machinery, or electric railway vehicle. 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 energy storage element 10 can also be used as a stationary battery for home or business use.

[0027] The energy storage element 10 is not limited to a non-aqueous electrolyte secondary battery, and may be a secondary battery other than a non-aqueous electrolyte secondary battery, or may be a capacitor. The energy storage element 10 may not be a secondary battery, but may be a primary battery that allows stored electricity to be used without the user having to charge it. The energy storage element 10 may be a battery that uses a solid electrolyte. The energy storage element 10 may also be a pouch-type energy storage element. In this embodiment, the energy storage element 10 is illustrated as having a flat rectangular parallelepiped (square) shape, but the shape of the energy storage element 10 is not limited to a rectangular parallelepiped shape, and may be a cylindrical shape, an elongated cylindrical shape, a polygonal prism shape other than a rectangular parallelepiped, or the like.

[0028] As shown in FIG. 1, the energy storage device 10 includes 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 FIG. 2, the container 100 contains a pair of lower gaskets 400 (positive and negative), a pair of current collectors 500 (positive and negative), an electrode assembly 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. The electrolyte may be of any type, provided it does not impair the performance of the energy storage device 10, and various electrolytes may be selected. In addition to the above components, spacers may be disposed on the sides or below the electrode assembly 600, and insulating films may be disposed to encase the electrode assembly 600.

[0029] 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 side surfaces on both sides in the X-axis direction, a pair of long side surfaces on both sides in the Y-axis direction, and a bottom surface on the negative Z-axis side. The lid 120 is a rectangular plate-like member that constitutes the lid of the container 100 and is disposed so as to extend in the X-axis direction in the positive Z-axis direction of the container body 110. The lid 120 is provided with a gas exhaust valve 121 that releases pressure inside the container 100 when the pressure inside the container 100 increases excessively, a liquid injection part 122 for injecting electrolyte into the container 100, and the like.

[0030] With this configuration, the container 100 is structured so that the inside is sealed by accommodating the electrode assembly 600 and the like inside the container body 110 and then joining the container body 110 and the lid body 120 by welding or the like. The material of the container 100 (container body 110 and lid body 120) is not particularly limited, and can be a weldable metal such as stainless steel, aluminum, aluminum alloy, iron, or plated steel sheet, but resin can also be used.

[0031] The electrode assembly 600 is an electricity storage element (power generation element) that includes positive and negative electrode plates and a separator and can store electricity. The electrode assembly 600 is formed by winding layers of positive and negative electrode plates with a separator sandwiched between them. As a result, multiple tabs of the positive electrode plates are stacked to form a positive electrode laminate portion 620, and multiple tabs of the negative electrode plates are stacked to form a negative electrode laminate portion 630. That is, the electrode assembly 600 includes an electrode assembly main body 610 and laminate portions 620 and 630 that protrude from a portion of the electrode assembly main body 610 in the positive Z-axis direction and extend in the positive Y-axis direction. In this embodiment, the electrode assembly 600 is a wound electrode assembly that is oval 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 description of the configuration of the electrode assembly 600 will be provided later.

[0032] The electrode terminals 200 are terminal members (positive electrode terminal and negative electrode terminal) electrically connected to the electrode body 600 via the current collector 500. The electrode terminals 200 are metal members that lead out 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 to store electricity in the electrode body 600. The electrode terminals 200 are formed of a conductive member such as a metal, such as aluminum, an aluminum alloy, copper, or a copper alloy. The electrode terminals 200 are connected (joined) to the current collector 500 by crimping or the like, and are attached to the lid body 120.

[0033] Specifically, the electrode terminal 200 has a shaft portion 201 (rivet portion) extending downward (in the negative Z-axis direction). The shaft portion 201 is inserted into the through-hole 301 of the upper gasket 300, the through-hole 123 of the lid 120, the through-hole 401 of the lower gasket 400, and the through-hole 501 of the current collector 500, and is crimped. As a result, the electrode terminal 200, together with the upper gasket 300, the lower gasket 400, and the current collector 500, is fixed to the lid 120. The method for connecting (joining) the electrode terminal 200 and the current collector 500 is not limited to crimping, and welding such as ultrasonic welding, laser welding, or resistance welding, or mechanical joining other than crimping, such as screw fastening, may also be used.

[0034] The current collectors 500 are current collecting members (positive electrode current collector and negative electrode current collector) that electrically connect the electrode assembly 600 and the electrode terminal 200. The positive electrode side current collector 500 is connected (joined) to the positive electrode side laminated portion 620 of the electrode assembly 600 by welding, and is also joined to the positive electrode side electrode terminal 200 by crimping or the like, as described above. The negative electrode side current collector 500 is connected (joined) to the negative electrode side laminated portion 630 of the electrode assembly 600 by welding, and is also joined to the negative electrode side electrode terminal 200 by crimping or the like, as described above. In this embodiment, the current collectors 500 are flat, rectangular members. The material of the current collectors 500 is not particularly limited, but the positive electrode side current collector 500 is formed of a conductive material such as a metal, such as aluminum or an aluminum alloy, similar to the positive electrode substrate of the electrode assembly 600, which will be described later. The negative electrode current collector 500 is formed of a conductive material such as a metal, such as copper or a copper alloy, similar to the negative electrode substrate of the electrode body 600, which will be described later.

[0035] The backing plate 700 is a member that is disposed at a position where it sandwiches the laminated portion 620 or 630 of the electrode assembly 600 with the current collector 500 and the laminated portion 620 or 630. The backing plate 700 is joined (welded) to the laminated portion 620 or 630 together with the current collector 500 while sandwiching the laminated portion 620 or 630 between the current collector 500 and the backing plate 700. In this embodiment, the backing plate 700 is a flat, rectangular member that is disposed 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 laminated portion 620 or 630 in the Z-axis direction (see FIG. 2(b)). The material of the backing plate 700 is not particularly limited, but the backing plate 700 on the positive electrode side is formed of a metal such as aluminum or an aluminum alloy, similar to the positive electrode substrate of the electrode assembly 600. The backing plate 700 on the negative electrode side is formed of a metal such as copper or a copper alloy, similar to the negative electrode substrate of the electrode assembly 600.

[0036] With this configuration, the current collector 500, the laminated portion 620 or 630, and the backing plate 700 are welded together with the laminated portion 620 or 630 of the electrode assembly 600 sandwiched between the current collector 500 and the backing plate 700, forming a fusion zone 800 (see FIG. 2(b)). In this embodiment, one fusion zone 800 is formed for one current collector 500, but the number of fusion zones 800 is not particularly limited. A detailed description of the configuration for welding the current collector 500, the laminated portion 620 or 630 of the electrode assembly 600, and the backing plate 700 together will be given later.

[0037] The upper gasket 300 is a flat insulating sealing member (gasket) that is disposed between the lid 120 of the container 100 and the electrode terminal 200, and provides insulation and sealing between the lid 120 and the electrode terminal 200. The lower gasket 400 is a flat insulating sealing member (gasket) that is disposed between the lid 120 and the current collector 500, and provides insulation and sealing between the lid 120 and the current collector 500. The upper gasket 300 and the 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.

[0038] [2. Description of the configuration of the electrode body 600] Next, the configuration of the electrode assembly 600 will be described in detail. Fig. 3 is a perspective view showing the configuration of the electrode assembly 600 according to this embodiment. Specifically, Fig. 3(a) shows the configuration of the electrode assembly 600 in a partially unfolded state from the wound state shown in Fig. 2, and Fig. 3(b) shows the configuration of the electrode assembly 600 after winding.

[0039] 3(a), the electrode assembly 600 is formed by alternately stacking and winding a positive electrode plate 640, a negative electrode plate 650, and separators 661 and 662. That is, the electrode assembly 600 is formed by stacking and winding a positive electrode plate 640, a separator 661, a negative electrode plate 650, and a separator 662 in this order.

[0040] The positive electrode plate 640 is an electrode plate in which a positive electrode active material layer is formed on the surface of a positive electrode substrate, which is a long strip of metal foil made of aluminum or an aluminum alloy. The negative electrode plate 650 is an electrode plate in which a negative electrode active material layer is formed on the surface of a negative electrode substrate, which is a long strip of metal foil made of copper or a copper alloy. The positive electrode substrate and the negative electrode substrate may be made of any known material that is stable against oxidation-reduction reactions during charging and discharging, such as nickel, iron, stainless steel, titanium, baked carbon, conductive polymers, conductive glass, or an Al-Cd alloy. The positive electrode active material used in the positive electrode active material layer and the negative electrode active material used in the negative electrode active material layer may be any known material that is capable of absorbing and releasing lithium ions.

[0041] For example, the positive electrode active material may be a polyanion compound such as LiMPO4, LiMSiO4, or LiMBO3 (M is one or more transition metal elements selected from Fe, Ni, Mn, Co, etc.), lithium titanate, LiMn2O4, or LiMn 1.5 Ni 0.5 Examples of the anode active material include spinel-type lithium manganese oxides such as LiTiO4, and lithium transition metal oxides such as LiMO2 (wherein M is one or more transition metal elements selected from Fe, Ni, Mn, Co, etc.). Examples of the anode active material include lithium metal, lithium alloys (lithium-metal-containing alloys such as lithium-silicon, lithium-aluminum, lithium-lead, lithium-tin, lithium-aluminum-tin, lithium-gallium, and Wood's alloy), alloys capable of absorbing and releasing lithium, carbon materials (e.g., graphite, non-graphitizable carbon, easily graphitizable carbon, low-temperature fired carbon, amorphous carbon, etc.), silicon oxides, metal oxides, and lithium metal oxides (Li4Ti5O 12and the like), polyphosphate compounds, or compounds of transition metals and elements of Groups 14 to 16, 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 as the material for separators 661 and 662 as long as it does not impair the performance of energy storage element 10. For example, separators 661 and 662 can be made of 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.

[0043] The positive electrode plate 640 has, at its end in the positive Z-axis direction, a plurality of rectangular tabs 641 protruding in the positive Z-axis direction, and the plurality of tabs 641 are arranged in a stacked state in the Y-axis direction. Similarly, the negative electrode plate 650 has, at its end in the positive Z-axis direction, a plurality of rectangular tabs 651 protruding in the positive Z-axis direction, and the plurality of tabs 651 are arranged in a stacked state in the Y-axis direction. The tabs 641 and 651 are portions where no active material layer is formed and the base material is exposed. The shapes of the tabs 641 and 651 are not particularly limited.

[0044] Then, as shown in FIG. 3B, the stacked tabs 641 are bundled together to form a laminated portion 620 that extends and protrudes in the positive direction of the Z axis. Similarly, the stacked tabs 651 are bundled together to form a laminated portion 630 that extends and protrudes in the positive direction of the Z axis. These laminated portions 620 and 630 are, for example, welded together with the current collector 500 and the backing plate 700 in a state where they are 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 direction of the Y axis. As a result, as shown in FIG. 2B, the laminated portions 620 and 630 are sandwiched between the current collector 500 and the backing plate 700 in the Z axis direction. The laminated portions 620 and 630 may be disposed in a state where they are sandwiched between the current collector 500 and the backing plate 700 in the Y axis direction without being bent in the positive direction of the Y axis.

[0045] The electrode body main body 610 is a portion that constitutes the main body of the electrode body 600, specifically, a portion of the electrode body 600 other than the laminated portions 620 and 630. The electrode body main body 610 is an elongated columnar or cylindrical portion formed by winding the portions of the positive electrode plate 640 and the negative electrode plate 650 on which the active material layers are formed and the separators 661 and 662. When the electrode body 600 has an active material layer-free portion (active material uncoated portion) on which no active material layer is formed at the end of the electrode plate (positive electrode plate 640 or negative electrode plate 650), and a tab (tab 641 or 651) extends from the active material layer-free portion, the electrode body main body 610 also includes the active material layer-free portion. In other words, in this configuration, the laminated portion 620 (or 630) is a portion where multiple tabs 641 (or multiple tabs 651) are stacked, and does not include the active material layer-free portion. As a result, the electrode body main 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 on both sides in the Y-axis direction that connect the pair of electrode body curved portions 611.

[0046] [3. Explanation of Welding Configuration of Current Collector 500, Laminated Section 620, and Backing Plate 700] Next, a detailed description will be given 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. The configuration in which the current collector 500, the laminated portion 620, and the backing plate 700 are welded together is the same as the configuration in which the current collector 500, the laminated portion 630, and the backing plate 700 are welded together. Therefore, the following description will focus on the configuration in which the current collector 500, the laminated portion 620, and the backing plate 700 are welded together, and the configuration in which the current collector 500, the laminated portion 630, and the backing plate 700 are welded together will be omitted.

[0047] FIG. 4 is a cross-sectional view and a plan view showing the configuration of the current collector 500, the laminated portion 620 of the electrode assembly 600, and the backing plate 700 according to the present embodiment in a welded state. Specifically, FIG. 4(a) is a cross-sectional view showing the configuration of the current collector 500, the laminated portion 620 of the electrode assembly 600, and the backing plate 700 in a welded state, cut along a plane that includes the central axis of the fusion zone 800 and is parallel to the YZ plane. For ease of explanation, FIG. 4(a) is shown upside down in FIG. 2, with the negative Z-axis direction facing upward. FIG. 4(b) is a plan view (top view, bottom view in FIG. 2) showing the configuration when FIG. 4(a) is viewed from the negative Z-axis direction (above, below in FIG. 2). FIG. 5 is a cross-sectional image showing the configuration of the current collector 500, the laminated portion 620 of the electrode assembly 600, and the backing plate 700 according to the present embodiment in a welded state. FIG. 5 is a cross-sectional photograph corresponding to a portion in the negative Y-axis direction of the configuration shown in FIG. 4(a).

[0048] Fig. 6 is a cross-sectional view showing a process of welding together the current collector 500, the laminated portion 620 of the electrode body 600, and the backing plate 700 according to this embodiment. Specifically, Fig. 6(a) shows the state before welding the current collector 500, the laminated portion 620, and the backing plate 700, and Fig. 6(b) shows the state after welding the current collector 500, the laminated portion 620, and the backing plate 700. Figs. 6(a) and 6(b) correspond to Fig. 4(a).

[0049] 4 and 5, the current collector 500 and the backing plate 700 are arranged at positions sandwiching a laminated portion 620 in which tabs 641 of positive electrode plates 640 of the electrode body 600 are laminated, and are welded together with the laminated portion 620. As a result, a fused portion 800 is formed in the current collector 500, the laminated portion 620, and the backing plate 700, where the current collector 500, the laminated portion 620, and the backing plate 700 are fused.

[0050] The fusion zone 800 is a region formed by fusing the current collector 500, the laminated portion 620, and the backing plate 700 by laser welding. Specifically, as shown in (a) of FIG. 6, a flat portion (flat portion) of the current collector 500 and a flat portion (flat portion) of the backing plate 700 are arranged with the flat portion (flat portion) of the laminated portion 620 sandwiched between them. Then, laser light L is irradiated onto these regions from the backing plate 700 side (negative direction of the Z axis). As a result, as shown in (b) of FIG. 6, the flat portion of the current collector 500, the flat portion of the laminated portion 620, and the flat portion of the backing plate 700 are melted to form the fusion zone 800.

[0051] The fusion zone 800 is formed in a state in which it penetrates the backing plate 700 and the laminated portion 620 in their thickness direction (Z-axis direction). That is, the fusion zone 800 is formed from the surface of the backing plate 700 in the negative Z-axis direction, penetrates the backing plate 700 and the laminated portion 620, and extends to a portion of the current collector 500 in the negative Z-axis direction. In the present embodiment, the fusion zone 800 has a circular cross section in the XY plane and has a substantially semi-elliptical spherical shape whose diameter gradually decreases toward the positive Z-axis direction.

[0052] The backing plate 700 has a backing plate recess 710 formed in a surface facing the laminated portion 620. The backing plate recess 710 is a recess formed in the negative Z-axis direction in a portion of the surface of the backing plate 700 facing the laminated portion 620 (the surface in the positive Z-axis direction) around the fusion zone 800. In this embodiment, the backing plate recess 710 has a substantially arc-shaped cross section in a plane (such as a YZ plane) including the central axis of the fusion zone 800, and this substantially arc-shaped recess has a shape in which the recesses are continuously connected in an annular shape around the entire periphery of the fusion zone 800 when viewed from the Z-axis direction. The central axis of the fusion zone 800 is a virtual axis that passes through the center of the fusion zone 800 when viewed from the Z-axis direction and extends parallel to the Z-axis direction.

[0053] The laminated portion 620 has a laminated portion recess 621 formed by recessing the surface facing the backing plate 700. The laminated portion recess 621 is a recess formed by recessing in the positive Z-axis direction in a portion of the surface of the laminated portion 620 facing the backing plate 700 (the surface in the negative Z-axis direction) around the fusion zone 800. In this embodiment, the laminated portion recess 621 has a shape that is continuously connected in an annular shape when viewed from the Z-axis direction around the entire periphery of the fusion zone 800.

[0054] The backing plate recess 710 and the stacking portion recess 621 are arranged to face each other and be connected to each other, so that a first space 910 is formed between the backing plate recess 710 and the stacking portion recess 621. In other words, the first space 910 is arranged in the backing plate recess 710 and the stacking portion recess 621. It can be said that at least a portion of the first space 910 is arranged in the backing plate recess 710, and it can also be said that at least a portion of the first space 910 is arranged in the stacking portion recess 621. In this way, the first space 910 is a space formed around the fusion zone 800 between the stacking portion 620 and the backing plate 700.

[0055] In the present embodiment, a melting portion recess 810, which is a recess, is also formed in the melting portion 800 at a position adjacent to the backing plate recess 710 and the laminated portion recess 621, and the space surrounded by this melting portion recess 810, the backing plate recess 710, and the laminated portion recess 621 becomes a first space 910. In other words, the first space 910 is a space surrounded by the laminated portion 620, the backing plate 700, and the melting portion 800. The melting portion recess 810 may not be formed, and the first space 910 may be a space surrounded by the laminated portion 620 (laminate portion recess 621) and the backing plate 700 (backing plate recess 710). Similarly, a configuration in which the laminated portion recess 621 is not formed may also be used.

[0056] As a result, the first space 910 is continuously formed in an annular (donut-shaped) shape so as to surround the entire periphery of the fusion zone 800. Therefore, as shown in (a) of Fig. 4, in a cross section in a plane (such as a YZ plane) including the central axis of the fusion zone 800, a pair of first spaces 910 are arranged on both sides (such as on both sides in the Y-axis direction) of the fusion zone 800. In other words, in a cross section including the central axis of the fusion zone 800, the fusion zone 800 is continuously arranged between the pair of first spaces 910, spanning from one first space 910 to the other first space 910.

[0057] A second space 920 connected to the first space 910 is formed between the fusion zone 800 and a portion of the laminated unit 620 adjacent to the fusion zone 800. The second space 920 is a groove-shaped space arranged adjacent to the fusion zone 800 around the fusion zone 800. The second space 920 extends along the fusion zone 800 from the end of the first space 910 in the positive direction of the Z axis in the positive direction of the Z axis, and is continuously formed in an annular shape so as to surround the entire periphery of the fusion zone 800. In this embodiment, the second space 920 has a tapered shape in which the width of its cross section in a plane (such as a YZ plane) including the central axis of the fusion zone 800 becomes smaller toward the positive direction of the Z axis.

[0058] The second space 920 is disposed so as to extend from the first space 910 along the fusion zone 800 to a position where it does not contact the current collector 500. In other words, the second space 920 extends from the first space 910 in the positive direction of the Z axis along the fusion zone 800, but does not reach the current collector 500. In the present embodiment, the second space 920 extends from the first space 910 to a central position in the Z axis direction of the laminated unit 620. In other words, the second space 920 is not formed between the fusion zone 800 and a portion of the laminated unit 620 that is further in the positive direction of the Z axis than the central position in the Z axis direction.

[0059] The first space 910 is a space larger than the second space 920. Spaces of various sizes other than the first space 910 and the second space 920 may be formed around the fusion zone 800, but it is preferable that the first space 910 is larger than these spaces. In other words, one or more spaces are formed around the fusion zone 800, and it is preferable that the first space 910 is the largest space of the one or more spaces arranged between the stacked section 620 and the backing plate 700. Specifically, it is preferable that the first space 910 is the space with the largest volume (capacity) of the one or more spaces. Whether the volume (capacity) of a space is the largest is determined by imaging the space with an X-ray CT and calculating the volume of the space from the imaging data.

[0060] The first space 910 and the second space 920 can be formed as follows. As shown in FIG. 6(a), when welding the current collector 500, the laminated portion 620, and the backing plate 700, the backing plate 700 is placed above, and laser light L is irradiated from above to perform welding. As a result, gas generated in the laminated portion 620 during welding moves upward and collects on the backing plate 700 side. Then, as shown in FIG. 6(b), when the gas generated in the laminated portion 620 moves upward, a second space 920 is formed above the laminated portion 620 around the fusion zone 800, and a first space 910 is formed between the laminated portion 620 and the backing plate 700 around the fusion zone 800. In particular, the first space 910 is easily formed by gradually heating and melting the target portion using heat conduction welding.

[0061] [4. Explanation of effects] As described above, in the energy storage device 10 according to the embodiment of the present invention, a first space 910 is formed between the laminated portion 620 and the backing plate 700 around the fusion zone 800 formed by melting the current collector 500, the electrode plate (the tab 641 of the positive electrode plate 640) of the electrode assembly 600, and the backing plate 700. At least a portion of the first space 910 is disposed within the backing plate recess 710 of the backing plate 700. By disposing the first space 910 between the laminated portion 620 and the backing plate 700 around the fusion zone 800 in this manner, gas generated in the laminated portion 620 during welding escapes into the first space 910 on the backing plate 700 side, thereby preventing the formation of relatively large blowholes at the boundary between the laminated portion 620 and the fusion zone 800. Furthermore, by disposing at least a portion of the first space 910 within the backing plate recess 710 of the backing plate 700, recesses are less likely to be formed in the laminated portion 620, or the recesses formed in the laminated portion 620 are smaller. This further reduces the occurrence of relatively large blowholes at the boundary between the laminated portion 620 and the fusion zone 800. Therefore, deterioration in the welding quality between the electrode body 600 and the current collector 500 can be reduced.

[0062] When welding is performed by laser welding from the backing plate 700 side, a fusion zone 800 is formed so as to penetrate the backing plate 700. In this case, compared to when welding is performed by laser welding or the like from the current collector 500 side, the heat from welding can be prevented from affecting the current collector 500, and therefore it is possible to prevent the current collector 500 from being deformed by heat and creating a gap between the laminated portion 620. This makes it possible to prevent a decrease in the welding quality between the electrode body 600 and the current collector 500.

[0063] The second space 920, which is connected to the first space 910, is formed between the fusion zone 800 and the laminated portion 620, so that gas generated in the laminated portion 620 during welding can escape to the first space 910 through the second space 920. This makes it possible to prevent relatively large blowholes from occurring at the boundary between the laminated portion 620 and the fusion zone 800, thereby preventing a decrease in the welding quality between the electrode body 600 and the current collector 500.

[0064] Since the second space 920 does not extend to the current collector 500, the formation of a space on the current collector 500 side is suppressed, and gas generated in the laminated portion 620 during welding can be allowed to escape to the first space 910 through the second space 920. This makes it possible to suppress the formation of a space between the laminated portion 620 and the fusion zone 800, thereby suppressing a decrease in the welding quality between the electrode body 600 and the current collector 500.

[0065] Since the first space 910 is larger than the second space 920, more of the gas generated in the laminated portion 620 during welding can escape into the first space 910. This makes it possible to prevent relatively large blowholes from occurring at the boundary between the laminated portion 620 and the fusion zone 800, thereby preventing a decrease in the welding quality between the electrode body 600 and the current collector 500.

[0066] The inventors of the present application found that the first space 910 is likely to be formed when the current collector 500, the laminated portion 620, and the backing plate 700 are welded by laser welding. Therefore, by welding the current collector 500, the laminated portion 620, and the backing plate 700 by laser welding, the first space 910 is formed, and a decrease in the welding quality between the electrode body 600 and the current collector 500 can be suppressed.

[0067] The fusion zone 800 can be formed with a simple structure by simply overlapping and fusing the flat portion of the current collector 500, the flat portion of the laminated portion 620, and the flat portion of the backing plate 700. This makes it possible to suppress deterioration in the welding quality between the electrode body 600 and the current collector 500 with a simple structure.

[0068] The above describes the effects of a configuration in which current collector 500, laminated portion 620, and backing plate 700 are welded together, but the same effects are also achieved with a configuration in which current collector 500, laminated portion 630, and backing plate 700 are welded together.

[0069] [5. Explanation of Variations] Although the energy storage device 10 according to the present embodiment has been described above, the present invention is not limited to the above embodiment. The embodiment disclosed herein is illustrative in all respects and is not restrictive, and the scope of the present invention includes all modifications within the meaning and scope of the claims.

[0070] In the above embodiment, the electrode assembly 600 is a wound electrode assembly whose winding axis is perpendicular to the lid 120, but it may also be a stack type in which flat electrode plates are stacked, or a bellows type in which the electrode plates and / or separators are folded in a bellows shape. The electrode assembly 600 may also be a wound electrode assembly whose winding axis is parallel to the lid 120. The stacked portions 620 and 630 may not be tabs, but may be end portions of the electrode assembly 600 that protrude from the entire electrode body main body portion 610 of the electrode assembly 600.

[0071] In the above embodiment, the first space 910 is formed continuously in an annular shape around the entire periphery of the fusion zone 800, but it may be formed only in a part of the periphery of the fusion zone 800, or may be formed intermittently around the entire periphery of the fusion zone 800. Therefore, the laminated portion recess 621 and the backing plate recess 710 may also be formed only in a part of the periphery of the fusion zone 800, or may be formed intermittently around the entire periphery of the fusion zone 800. The same applies to the second space 920.

[0072] In the above embodiment, the fusion zone 800 has a circular shape when viewed from the Z-axis direction, but it may have a shape other than a circle, such as an ellipse, an oval, or a polygon, or may have an annular shape such as a circular ring. Although the cross section of the backing plate recess 710 in a plane including the central axis of the fusion zone 800 has a substantially arc-shaped cross section, it may have any shape other than a substantially arc-shaped cross section.

[0073] In the above embodiment, the second space 920 is a groove-shaped space, but is not limited to a groove shape and may be a wide space, etc. The second space 920 is extended from the first space 910 to a position not in contact with the current collector 500, but may be extended to a position in contact with the current collector 500. The second space 920 is smaller than the first space 910, but may be larger than the first space 910. The second space 920 does not have to be provided.

[0074] In the above embodiment, the fusion zone 800 is formed so as to penetrate the backing plate 700 in the thickness direction (Z-axis direction). However, it may be formed so as to penetrate the current collector 500 in the thickness direction (Z-axis direction). In this case, the fusion zone 800 does not have to penetrate the backing plate 700 in the thickness direction (Z-axis direction). That is, the fusion zone 800 of the current collector 500, the laminated portion 620, and the backing plate 700 may be formed by irradiating the current collector 500 with laser light from the side of the current collector 500 (positive direction of the Z-axis). In this case, the current collector 500 is disposed below (i.e., the backing plate 700 is above) and irradiated with laser light from below. Gas generated in the laminated portion 620 during welding moves upward and gathers on the backing plate 700 side. As a result, similar to the above embodiment, a second space 920 is formed above the laminated portion 620 around the fusion zone 800, and a first space 910 is formed between the laminated portion 620 and the backing plate 700 around the fusion zone 800.

[0075] In the above embodiment, the flat portion of the current collector 500, the flat portion of the laminated portion 620, and the flat portion of the backing plate 700 are welded together to form the first space 910 and the second space 920. However, the portions to be welded do not have to be the flat portion or the flat portion. The first space 910 may be formed by forming a backing plate recess 710 in the backing plate 700 before welding.

[0076] In the above embodiment, both the positive electrode side (the laminated portion 620 side) and the negative electrode side (the laminated portion 630 side) have the above-described configuration. However, either the positive electrode side or the negative electrode side does not necessarily have to have the above-described configuration. Generally, blowholes are more likely to occur when the electrode plate substrate is made of metal. This is because an oxide film may form on the surface of the metal, and the formed oxide film may adsorb water. The adsorbed water may gasify during melting, making blowholes more likely to occur. Since the laminated portions 620 and 630 are made of multiple laminated substrates, blowholes are more likely to occur when the substrates are made of metal, because the oxide film formed on the surface of each substrate may adsorb water. Among metals, aluminum is particularly susceptible to forming an oxide film on its surface, making it particularly susceptible to blowholes. Therefore, blowholes are more likely to occur when the laminated portion 620 on the positive electrode side is made of laminated positive electrode substrates made of aluminum, aluminum alloy, or the like. Therefore, the above-described configuration is particularly effective when the positive electrode substrate is made of aluminum, aluminum alloy, or the like.

[0077] Any combination of the components included in the above-described embodiments and their modifications is also included within the scope of the present invention.

[0078] The present invention can be realized not only as such an energy storage element 10 but also as a combination of an electrode body 600, a current collector 500, and a backing plate 700. [Industrial Applicability]

[0079] The present invention can be applied to an electric storage element such as a lithium ion secondary battery. [Explanation of symbols]

[0080] 10. Energy storage element 100 containers 110 Container body 120 Lid 200 electrode terminal 300 Upper Gasket 400 Lower Gasket 500 current collector 600 Electrode body 610 Electrode body part 620, 630 laminated section 621 Laminated part recess 640 Positive electrode plate Tabs 641 and 651 650 negative electrode plate 661, 662 Separator 700 Backing Plate 710 Backing plate recess 800 fusion zone 810 Concave part of fusion zone 910 First space 920 Second space

Claims

1. an electrode body having a laminated portion in which electrode plates are laminated; a current collector and a backing plate disposed at positions sandwiching the laminated portion and welded together with the laminated portion; a first space is formed between the laminated portion and the backing plate around a fusion portion where the current collector, the laminated portion, and the backing plate are fused; The backing plate has a recess formed in a surface facing the stacked portion, At least a portion of the first space is disposed within the recess, No insulating member is disposed between the laminated portion and the backing plate. Energy storage element.

2. An electrode body having a laminated portion in which electrode plates are stacked; a current collector and a backing plate disposed at positions sandwiching the laminated portion and welded together with the laminated portion; a first space is formed between the laminated portion and the backing plate around a fusion portion where the current collector, the laminated portion, and the backing plate are fused; The backing plate has a recess formed in a surface facing the stacked portion, At least a portion of the first space is disposed within the recess, The fusion zone is formed in a state where it penetrates the backing plate in the thickness direction. Energy storage element.

3. An electrode body having a laminated portion in which electrode plates are stacked; a current collector and a backing plate disposed at positions sandwiching the laminated portion and welded together with the laminated portion; a first space is formed between the laminated portion and the backing plate around a fusion portion where the current collector, the laminated portion, and the backing plate are fused; The backing plate has a recess formed in a surface facing the stacked portion, At least a portion of the first space is disposed within the recess, A second space connected to the first space is formed between the melted portion and a portion of the laminated portion adjacent to the melted portion. Energy storage element.

4. The second space is disposed so as to extend from the first space along the fusion zone to a position where the second space does not contact the current collector. The energy storage element according to claim 3 .

5. The first space is larger than the second space. The energy storage element according to claim 3 or 4.

6. An electrode body having a laminated portion in which electrode plates are stacked; a current collector and a backing plate disposed at positions sandwiching the laminated portion and welded together with the laminated portion; a first space is formed between the laminated portion and the backing plate around a fusion portion where the current collector, the laminated portion, and the backing plate are fused; The backing plate has a recess formed in a surface facing the stacked portion, At least a portion of the first space is disposed within the recess, The fusion zone is a portion formed by fusing the current collector, the laminated portion, and the backing plate by laser welding. Energy storage element.

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