Energy storage devices

Abstract

To improve the strength of the case. [Solution] The energy storage device 1 disclosed herein comprises a case 10 and an electrode body 40 housed in the case 10. The case 10 includes a case body 20 having an opening surrounded by side walls including a pair of first walls 22, and a sealing body 30 that seals the opening. The electrode body 40 has a laminated portion in which the positive electrode and the negative electrode are laminated toward the sealing body 30 in an insulated state. The sealing body 30 has a base portion 31 and a pair of first bent portions 33 that extend from the base portion 31 along the pair of first walls 22 of the case body 20 and face each other. The first bent portions 33 are joined to the first walls 22 of the case body 20 via a first welded joint 80.

Description

Technical Field

[0001] The present disclosure relates to a power storage device.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2013-171729 discloses a container for a power storage device including a main body member having an opening and a lid member having an insertion portion inserted into the main body member through the opening. The laminated electrode body accommodated in the container for the power storage device is pressed from both the insertion portion and the main body member. Thereby, it is said that the separation distance between the electrode sheets constituting the electrode body can be preferably made uniform.

Prior Art Documents

[0006] The above energy storage device offers improved case strength. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is an exploded view schematically showing the configuration of an energy storage device according to one embodiment. [Figure 2] Figure 2 is a schematic diagram showing the internal structure of an energy storage device according to one embodiment. [Figure 3] Figure 3 is a schematic diagram showing the internal structure of an energy storage device according to one embodiment, viewed from a different direction than Figure 2. [Figure 4] Figure 4 is a perspective view of the sealing body shown in Figure 1, but turned inside out. [Figure 5] Figure 5 is a schematic diagram showing the structure of an electrode body according to one embodiment. [Figure 6] Figure 6 is a schematic diagram of a modified energy storage device corresponding to Figure 3. [Figure 7] Figure 7 is a schematic diagram of a modified energy storage device corresponding to Figure 2. [Modes for carrying out the invention]

[0008] Hereinafter, several embodiments of the technology disclosed herein will be described in detail with reference to the drawings. Matters other than those specifically mentioned herein but necessary for implementation (e.g., general configuration and manufacturing processes of energy storage devices not characterizing this disclosure) can be understood as design matters for those skilled in the art based on the prior art. This disclosure can be implemented based on the contents disclosed herein and common technical knowledge in the art. In the following drawings, the same reference numerals are used to denote components and parts that perform the same function. Also, the dimensional relationships (length, width, thickness, etc.) in each drawing do not necessarily reflect the actual dimensional relationships.

[0009] In this specification, "energy storage device" is a concept that encompasses devices in which a charge-discharge reaction occurs through the movement of a charge carrier between a pair of electrodes (positive electrode and negative electrode). In other words, energy storage devices include batteries such as secondary batteries (e.g., lithium-ion secondary batteries, nickel-metal hydride batteries, nickel-cadmium batteries) and capacitors (physical batteries) such as lithium-ion capacitors and electric double-layer capacitors.

[0010] In this specification, "approximately rectangular" includes shapes other than a perfect rectangle. For example, it includes shapes where the corners connecting the long and short sides of a rectangle are rounded, or shapes with notches at the corners.

[0011] Generally, energy storage devices are known that comprise a case comprising a case body and a sealing body, and an electrode body housed inside the case. A welded joint is often provided at the boundary between the sealing body and the case body. The electrode body may expand during charging and discharging, etc. In particular, the electrode body expands during charging. When the electrode body expands, a force may be applied that pushes the sealing body outward. At this time, greater stress is generated at the ends of the sealing body than at the center of the sealing body. If a welded joint for joining the sealing body to the case body is formed at the ends of the sealing body, stress will concentrate at the welded joint. Since the welded joint has relatively low strength, the case is prone to damage and deformation. Therefore, this disclosure provides a technology for improving the strength of the case. As one aspect of this technology, an energy storage device is provided that has case strength that makes the case less susceptible to damage and deformation even when the electrode body expands.

[0012] <Energy storage devices> The following describes the energy storage device 1 as one embodiment. Figure 1 is a schematic exploded view showing the configuration of the energy storage device according to one embodiment. Figure 2 is a schematic diagram showing the internal structure of the energy storage device according to one embodiment. Figure 3 is a schematic diagram showing the internal structure of the energy storage device according to one embodiment from a different direction than Figure 2. Figure 4 is a perspective view of the sealing body shown in Figure 1 turned inside out. Figure 5 is a schematic diagram showing the structure of the electrode body 40 according to one embodiment. The symbols L, R, F, Rr, U, and D in the drawings represent left, right, front, back, up, and down. The symbols X, Y, and Z in the drawings represent the short side direction, the long side direction perpendicular to the short side direction, and the up and down direction of the energy storage device 1, respectively. However, these are merely directions for the convenience of explanation and do not limit the installation configuration of the energy storage device 1. Note that each drawing is schematic, and the dimensional relationships (length, width, thickness, etc.) do not necessarily reflect the actual dimensional relationships. Furthermore, in the drawings described below, the same reference numerals are used for members and parts that perform the same function, and redundant explanations may be omitted or simplified.

[0013] As shown in Figures 1 to 3, the energy storage device 1 comprises a case 10 and an electrode body 40. The electrode body 40 is housed in the case 10. The energy storage device 1 is a lithium-ion secondary battery in this case. The energy storage device 1 comprises a positive electrode 50, a negative electrode 60, and a non-aqueous electrolyte (not shown). The respective components will be described below.

[0014] (1) Case As shown in Figures 1-3, the case 10 comprises a case body 20 and a sealing body 30. The case body 20 includes an opening 28 surrounded by side walls. The side walls of the case body 20 include a pair of first walls 22 and a pair of second walls 24. The case body 20 has a bottom wall 26 on the opposite side of the opening 28.

[0015] As shown in Figure 1, the opening 28 is formed by being surrounded by a pair of long sides and a pair of short sides. In a top view, the opening 28 is substantially rectangular. Here, a pair of first walls 22 constitute the pair of long sides, and a pair of second walls 24 constitute the pair of short sides. The opening 28 is sized to allow the electrode body 40 to be inserted into the case body 20. In some embodiments, the opening 28 may be substantially square or substantially polygonal in a top view.

[0016] As shown in Figures 1 and 3, the pair of first walls 22 face each other in the short-side direction X. Here, the first wall 22 has a larger area than the second wall 24. The first wall 22 is substantially rectangular in shape. The first wall 22 has a pair of long sides in the long-side direction Y and a pair of short sides in the height direction Z. In some embodiments, the first wall 22 may be substantially square in shape, or substantially polygonal in shape. Alternatively, the first wall 22 may be substantially rectangular in shape with a long side in the height direction Z and a short side in the long-side direction Y.

[0017] As shown in FIGS. 1 and 2, a pair of second walls 24 face each other in the long side direction Y. The pair of second walls 24 are adjacent to the pair of first walls 22. Here, the second wall 24 has a smaller area than the first wall 22. The second wall 24 is substantially rectangular. The second wall 24 has a pair of long sides in the short side direction X and a pair of short sides in the height direction Z. In some embodiments, the second wall 24 may be substantially square or substantially polygonal. Also, the second wall 24 may be substantially rectangular with a long side in the height direction Z and a short side in the long side direction Y.

[0018] As shown in FIGS. 1 to 3, the bottom wall 26 is disposed on the side opposite to the opening 28 in the height direction Z. The bottom wall 26 is substantially rectangular here. The first wall 22 extends from the long side of the bottom wall 26. The second wall 24 extends from the short side of the bottom wall 26. In some embodiments, the second wall 24 may be substantially square or substantially polygonal.

[0019] In some embodiments, a second opening may be formed instead of the bottom wall 26. That is, the case body 20 may be formed in a cylindrical shape including two openings. In this case, the second opening may be sealed by a second sealing body. The second sealing body may have the same configuration as the sealing body 30.

[0020] The material of the case body 20 can be, for example, a metal material such as aluminum, aluminum alloy, iron, or iron alloy. From the viewpoint of ease of processing, the case body 20 is preferably made of aluminum or an aluminum alloy. The case body 20 is manufactured, for example, by pressing a metal plate. Note that the case body 20 may be composed of a plurality of members.

[0021] As shown in FIGS. 2 and 3, the sealing body 30 is attached to the opening 28 of the case body 20 and seals the opening 28. As shown in FIGS. 1 to 4, the sealing body 30 has a base portion 31, a first corner portion 32, and a first bending portion 33. Here, the sealing body 30 further has a second corner portion 34 and a second bending portion 35.

[0022] The base portion 31 is the main surface that covers the opening of the case body 20. As shown in Figures 1 to 4, the base portion 31 is a plate-like portion. The base portion 31 faces the bottom wall 26 of the case body 20. In plan view, the base portion 31 has a shape corresponding to the opening 28. Here, the base portion 31 is roughly rectangular and has a pair of long sides and a pair of short sides.

[0023] As shown in Figures 1, 3, and 4, the first corner portion 32 is located at the end of the base portion 31. The first corner portion 32 is located between the base portion 31 and the first bent portion 33. Here, the first corner portion 32 is a pair of long side portions of the base portion 31. Here, the first corner portion 32 is located inside the opening 28 of the case body 20. The first corner portion 32 may be curved (R-shaped) and may have corners. From the viewpoint of improving the strength of the first corner portion 32, it is preferable that the first corner portion 32 does not contain welding marks (welded parts).

[0024] As shown in Figure 3, the pair of first bent portions 33 are located at both ends of the base portion 31 in the short-side direction X. Each of the pair of first bent portions 33 extends from the base portion 31 along the pair of first walls 22 of the case body 20. The pair of first bent portions 33 face each other. Here, the first bent portions 33 extend from the first corner portion 32 located at the end of the base portion 31 along the first wall 22. The first bent portions 33 are joined to the first wall 22 of the case body 20 via the first welded joint 80. Here, the first bent portions 33 are in contact with the inner surface of the first wall 22 of the case body 20 (the inner surface of the case 10). That is, the first bent portions 33 are joined to the inner surface of the first wall 22 of the case body 20 via the first welded joint 80.

[0025] As shown in Figure 3, the first welded joint 80 is formed by welding the first bent portion 33 and the first wall 22. Here, the first welded joint 80 is formed by joining the first bent portion 33 and the first wall 22 in such a way that no gap is created between the first bent portion 33 and the first wall 22 that allows the inside and outside of the case 10 to communicate. The first welded joint 80 is formed, for example, by irradiating the overlapping portion of the first bent portion 33 and the first wall 22 with a laser from the outer surface of the first wall 22.

[0026] The length of the first bent portion 33 in the height direction Z of the energy storage device 1 is preferably half or less of the length of the first wall 22 in the height direction Z, and preferably one-third or less. This makes it less likely for the arrangement of other components to be restricted in the internal space of the case 10. Furthermore, the length of the first bent portion 33 is preferably one-twentieth or more of the length of the first wall 22 in the height direction Z, and preferably one-tenth or more. This makes it possible to increase the area of ​​the first welded joint 80 and increase the bonding strength between the sealing body 30 and the case body 20.

[0027] As shown in Figures 1-3, the second corner portion 34 is located at the end of the base portion 31. The second corner portion 34 is located between the base portion 31 and the second bent portion 35. Here, the second corner portion 34 is a pair of short side portions of the base portion 31. Here, the second corner portion 34 is located inside the opening 28 of the case body 20. The second corner portion 34 may be curved (R-shaped) and may have corners. From the viewpoint of improving the strength of the second corner portion 34, it is preferable that the second corner portion 34 does not contain welding marks (welded parts).

[0028] As shown in Figure 2, the pair of second bent portions 35 are located at both ends of the long side direction Y of the base portion 31. Each of the pair of second bent portions 35 extends from the base portion 31 along the pair of second walls 24 of the case body 20. The pair of second bent portions 35 face each other. Here, the second bent portions 35 extend from the second corner portion 34 located at the end of the base portion 31 along the second wall 24. The second bent portions 35 are joined to the second wall 24 of the case body 20 via a second welded joint 82. Here, the second bent portions 35 are in contact with the inner surface of the second wall 24 of the case body 20 (the inner surface of the case 10). That is, the second bent portions 35 are joined to the inner surface of the second wall 24 of the case body 20 via a second welded joint 82. Here, the second bent portions 35 are formed continuously with the first bent portion 33. In some embodiments, a slit may be present between the second bent portion 35 and the first bent portion 33.

[0029] As shown in Figure 2, the second welded joint 82 is formed by welding the second bent portion 35 and the second wall 24. Here, the second welded joint 82 is formed by joining the second bent portion 35 and the second wall 24 in such a way that there is no gap between the second bent portion 35 and the second wall 24 that allows the inside and outside of the case 10 to communicate. The second welded joint 82 is formed, for example, by irradiating the overlapping portion of the second bent portion 35 and the second wall 24 with a laser from the outer surface of the second wall 24. Here, the sealing body 30 is fixed to the case body 20 by the first welded joint 80 and the second welded joint 82, and the opening 28 of the case body 20 is sealed.

[0030] The length of the second bent portion 35 in the height direction Z of the energy storage device 1 is preferably half or less of the length of the second wall 24 in the height direction Z, and preferably one-third or less. This makes it less likely for the arrangement of other components to be restricted in the internal space of the case 10. Furthermore, the length of the second bent portion 35 is preferably one-twentieth or more of the length of the second wall 24 in the height direction Z, and preferably one-tenth or more. This makes it possible to increase the area of ​​the second welded joint 82 and increase the bonding strength between the sealing body 30 and the case body 20.

[0031] As shown in Figure 4, the sealing body 30 has a recess 36 surrounded by a base portion 31, a first bent portion 33, and a second bent portion 35. The presence of the recess 36 in the sealing body 30 increases the space that the electrode body 40 can occupy inside the case 10. This makes it possible to increase the capacity of the energy storage device 1.

[0032] The material of the sealing body 30 may be a metallic material such as aluminum, aluminum alloy, iron, or iron alloy. From the viewpoint of ease of processing, the case body 20 is preferably made of aluminum or an aluminum alloy. The sealing body 30 is manufactured, for example, by press-forming a metal sheet. Alternatively, the sealing body 30 can also be manufactured by bending a metal sheet. Therefore, in this specification, the "bent portion" is not limited to a portion formed by bending, but may also be a portion formed by other processing such as press-forming.

[0033] Incidentally, in the energy storage device 1, when the electrode body 40 expands, the electrode body 40 can generate a force that pushes the sealing body 30 outward from the case 10. As a result, a relatively large stress is generated in the sealing body 30, specifically at the first corner portion 32, which is the end of the base portion 31. Therefore, in the energy storage device 1, the sealing body 30 is joined to the first wall 22 of the case body 20 via a first welded joint 80. This prevents stress from concentrating at the first welded joint 80. As a result, the strength of the case 10 can be improved.

[0034] Furthermore, in the energy storage device 1, when the electrode body 40 expands, stress may also be generated in the second corner portion 34 located on the short side of the base portion 31. For this reason, it is preferable that the sealing body 30 is joined to the second wall 24 of the case body 20 via the second welded joint 82 on the short side of the base portion 31 as well. This prevents stress from concentrating in the second welded joint 82. As a result, the strength of the case 10 can be improved.

[0035] Furthermore, when the electrode body 40 expands and generates a force that pushes the sealing body 30 outward, a relatively larger stress is generated on the longer side of the sealing body 30 than on the shorter side. For this reason, it is preferable that the first bent portion 33 be provided along the first wall 22 that constitutes the longer side of the opening 28 of the case body 20.

[0036] As shown in Figure 3, the first corner portion 32 of the sealing body 30 may be positioned above the opening 28 of the case body 20 (away from the bottom wall 26 of the case body 20). Also, as shown in Figure 2, the second corner portion 34 of the sealing body 30 may be positioned above the opening 28 of the case body 20 (away from the bottom wall 26 of the case body 20). This increases the internal space of the case 10, which can enable a higher capacity energy storage device 1.

[0037] As shown in Figure 1, the case 10 has a safety valve 12. Here, the safety valve 12 is provided in the first wall 22. The safety valve 12 is a thin-walled section designed to rupture and release internal pressure when the inside of the case 10 reaches a predetermined pressure. In some embodiments, the safety valve 12 may be provided in the second wall 24, the bottom wall 26, or the sealing body 30. Also, two or more safety valves 12 may be provided. Furthermore, the safety valve 12 may not be provided at all.

[0038] As shown in Figure 1, the case 10 has an injection hole 14. The injection hole 14 is a through-hole through which a non-aqueous electrolyte can be injected into the interior of the case 10. The injection hole 14 connects the inside and outside of the case 10. Here, the injection hole 14 is provided in the first wall 22. In the manufacture of the energy storage device 1, the electrolyte is injected into the interior of the case 10 through the injection hole 14. After the electrolyte is injected, the injection hole 14 is sealed with a sealing plug or the like. This seals the case 10 and prevents leakage of the electrolyte. In some embodiments, the injection hole 14 may be provided in the second wall 24, the bottom wall 26, or the sealing body 30. Also, the injection hole 14 may not be provided at all.

[0039] As shown in Figures 1 and 2, the case 10 has a positive terminal insertion hole 16 and a negative terminal insertion hole 18. The positive terminal insertion hole 16 and the negative terminal insertion hole 18 communicate the inside and outside of the case 10. A positive terminal 57 is attached to the positive terminal insertion hole 16. A negative terminal 67 is attached to the negative terminal insertion hole 18. Here, the positive terminal insertion hole 16 is provided in one second wall 24. The negative terminal insertion hole 18 is provided in another second wall 24 facing the first second wall 24. In some embodiments, the positive terminal insertion hole 16 and the negative terminal insertion hole 18 may be provided in the first wall 22, the bottom wall 26, or the sealing body 30. The positive terminal insertion hole 16 and the negative terminal insertion hole 18 may be provided on the same surface (wall).

[0040] (2) Positive electrode The positive electrode 50 includes a positive electrode plate 51, a positive electrode current collector 56, and a positive electrode terminal 57. The positive electrode plate 51 is electrically connected to the positive electrode current collector 56. The positive electrode current collector 56 is electrically connected to the positive electrode terminal 57.

[0041] As shown in Figure 5, the positive electrode plate 51 comprises a positive electrode current collector 52 and a positive electrode active material layer 53 fixed to at least one surface of the positive electrode current collector 52. The positive electrode plate 51 may be in the form of a sheet. The material of the positive electrode current collector 52 is a conductive metallic material. The positive electrode current collector 52 is, for example, a metal foil. As the material of the positive electrode current collector 52, for example, aluminum, an aluminum alloy, etc., can be used.

[0042] The positive electrode active material layer 53 contains a positive electrode active material. The positive electrode active material is a material capable of reversibly intercalating and releasing charge carriers. The positive electrode active material is preferably an oxide containing at least one of Ni, Co, and Mn. Examples include lithium transition metal composite oxides such as lithium cobaltate, lithium manganeseate, lithium nickelate, lithium nickel manganese composite oxide, and lithium nickel cobalt manganese composite oxide. The positive electrode active material is more preferably a lithium composite oxide containing Ni (in other words, a Ni-containing lithium composite oxide). In the Ni-containing lithium composite oxide, the Ni content may be, for example, 60 mol% to 100 mol% relative to the total number of moles of metals other than Li. In the lithium transition metal composite oxide, some of the Ni, Co, and Mn may be substituted with Al, Ti, Zr, P, B, Si, Nb, C, etc. Furthermore, the particle surface of the lithium transition metal composite oxide of the positive electrode active material may be coated with a compound containing Al, Ti, Zr, W, P, B, Si, Nb, C, etc. The total amount of substitution and addition may be approximately 0.1 to 7% by mass. Alternatively, lithium transition metal phosphate compounds such as lithium iron phosphate can be used as the positive electrode active material. The positive electrode active material layer 53 may contain conductive materials, binders, etc. Carbon materials such as carbon black and carbon nanotubes are preferred as conductive materials. Resin binders such as polyvinylidene fluoride are preferred as binders.

[0043] As shown in Figure 2, an extended positive electrode tab 54 is provided at the end of the positive electrode current collector 52. The positive electrode tab 54 has a positive electrode current collector exposed portion in which at least a part of the surface of the positive electrode current collector 52 is exposed. A positive electrode connection portion 55 is formed by stacking multiple positive electrode tabs 54. The positive electrode connection portion 55 is formed, for example, by joining the positive electrode current collector exposed portions of multiple positive electrode tabs 54 together by ultrasonic bonding, laser welding, or the like. In this case, the positive electrode connection portion 55 is positioned opposite the second wall 24 in which the positive electrode terminal insertion hole 16 is provided. Note that the positive electrode tab 54 does not have to extend from the end of the positive electrode current collector 52. For example, the positive electrode tab 54 may have a positive electrode current collector exposed portion provided in a strip shape at the end of the positive electrode current collector 52.

[0044] As shown in Figure 2, the positive electrode current collector 56 is electrically connected to the positive electrode connection 55. The positive electrode current collector 56 may be made of a metallic material. The positive electrode current collector 56 may be made of, for example, a conductive metal member. The positive electrode current collector 56 may be made of, for example, one or more plate-shaped metal members. It is preferable that the positive electrode current collector 56 is made of the same material as the positive electrode current collector body 52. ​​The positive electrode current collector 56 may be made of, for example, aluminum, an aluminum alloy, etc. The positive electrode current collector 56 and the positive electrode connection 55 are joined by, for example, ultrasonic bonding, laser welding, resistance welding, etc.

[0045] As shown in Figure 2, the positive electrode terminal 57 is mounted in the positive electrode terminal insertion hole 16 and attached to the case 10. A portion of the positive electrode terminal 57 is exposed to the outside of the case 10. The positive electrode terminal 57 is preferably made of metal, and more preferably of aluminum or an aluminum alloy. Inside the case 10, the positive electrode terminal 57 is electrically connected to the positive electrode current collector 56. This connects the positive electrode terminal 57 to the positive electrode plate 51. The positive electrode terminal 57 and the positive electrode current collector 56 are joined by, for example, crimping, ultrasonic bonding, laser welding, resistance welding, etc. In some embodiments, the positive electrode current collector 56 and the positive electrode terminal 57 can be configured as a single component.

[0046] As shown in Figure 2, an insulating member 90 is placed between the positive terminal 57 and the case 10 (specifically the second wall 24). This prevents electrical conductivity between the positive terminal 57 and the case 10. The insulating member 90 may be, for example, a polyolefin resin such as polypropylene (PP) or polyethylene (PE), a fluorinated resin such as tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), or polyphenylene sulfide (PPS).

[0047] (3) Negative electrode The negative electrode 60 includes a negative electrode plate 61, a negative electrode current collector 66, and a negative electrode terminal 67. The negative electrode plate 61 is electrically connected to the negative electrode current collector 66. The negative electrode current collector 66 is electrically connected to the negative electrode terminal 67.

[0048] As shown in Figure 5, the negative electrode plate 61 comprises a negative electrode current collector 62 and a negative electrode active material layer 63 fixed to at least one surface of the negative electrode current collector 62. The negative electrode plate 61 may be in sheet form. The material of the negative electrode current collector 62 is a conductive metallic material. The negative electrode current collector 62 is, for example, a metal foil. As the material of the negative electrode current collector 62, for example, copper, copper alloy, etc. can be used.

[0049] The negative electrode active material layer 63 contains a negative electrode active material. The negative electrode active material is a material that can reversibly absorb and release charge carriers. Examples of negative electrode active materials include carbon-based negative electrode active materials such as graphite, hard carbon, and soft carbon; Si-containing negative electrode active materials such as Si and silicon oxide; silicon-carbon composite negative electrode active materials; and Sn-based negative electrode active materials such as Sn. The negative electrode active material layer 63 may also contain conductive materials, thickeners, binders, etc. It is preferable that the binder contains styrene-butadiene rubber or carboxymethylcellulose.

[0050] In some embodiments, a Si-containing anode active material is used as the anode active material. The Si-containing anode active material has a higher theoretical capacity density than the carbon-based anode active material. On the other hand, the Si-containing anode active material undergoes a larger volume change due to charging and discharging than the carbon-based anode active material. This increases the expansion rate of the electrode body 40, increasing the force pushing the case 10 from the inside out, which may cause deformation or breakage of the case. In the technology of this disclosure, the case strength is high, so even when using a material with a large volume change, such as a Si-containing anode active material, the risk of deformation or breakage of the case can be reduced.

[0051] As shown in Figure 2, an extended negative electrode tab 64 is provided at the end of the negative electrode current collector 62. The negative electrode tab 64 has a negative electrode current collector exposed portion in which at least a part of the surface of the negative electrode current collector 62 is exposed. A negative electrode connection portion 65 is formed by stacking multiple negative electrode tabs 64. The negative electrode connection portion 65 is formed, for example, by joining the negative electrode current collector exposed portions of multiple negative electrode tabs 64 together by, for example, ultrasonic bonding, laser welding, etc. In this case, the negative electrode connection portion 65 is positioned opposite the second wall 24 in which the negative electrode terminal insertion hole 18 is provided. Note that the negative electrode tab 64 does not have to extend from the end of the negative electrode current collector 62. For example, the negative electrode tab 64 may have a negative electrode current collector exposed portion provided in a strip shape at the end of the negative electrode current collector 62.

[0052] As shown in Figure 2, the negative electrode current collector 66 is electrically connected to the negative electrode connection 65. The negative electrode current collector 66 may be made of a metallic material. The negative electrode current collector 66 may be made of, for example, a conductive metal member. The negative electrode current collector 66 may be made of, for example, one or more plate-shaped metal members. It is preferable that the negative electrode current collector 66 is made of the same material as the negative electrode current collector 62. The negative electrode current collector 66 may be made of, for example, copper, a copper alloy, etc. The negative electrode current collector 66 and the negative electrode connection 65 are joined by, for example, ultrasonic bonding, laser welding, resistance welding, etc.

[0053] As shown in Figure 2, the negative electrode terminal 67 is mounted in the negative electrode terminal insertion hole 18 and attached to the case 10. A portion of the negative electrode terminal 67 is exposed to the outside of the case 10. The negative electrode terminal 67 is preferably made of metal, and more preferably of copper or a copper alloy. Inside the case 10, the negative electrode terminal 67 is electrically connected to the negative electrode current collector 66. This connects the negative electrode terminal 67 to the negative electrode plate 61. The negative electrode terminal 67 and the negative electrode current collector 66 are joined by, for example, crimping, ultrasonic bonding, laser welding, resistance welding, etc. In some embodiments, the negative electrode current collector 66 and the negative electrode terminal 67 can be configured as a single component.

[0054] As shown in Figure 2, an insulating member 90 is placed between the negative terminal 67 and the case 10 (specifically the second wall 24). This prevents electrical conductivity between the negative terminal 67 and the case 10.

[0055] (4) Electrode body The electrode body 40 is a power generation element in the energy storage device 1. The electrode body 40 is constructed by stacking a positive electrode 50 and a negative electrode 60 in an insulated state. Here, as shown in Figure 5, the electrode body 40 comprises a positive electrode plate 51, a negative electrode plate 61, and a separator 70. The positive electrode plate 51 and the negative electrode plate 61 are stacked alternately via the separator 70 to form a stacked portion 42. Inside the case 10, the electrode body 40 is arranged such that the stacking direction of the stacked portion 42 faces the sealing body 30. The positive electrode plate 51 and the negative electrode plate 61 are formed in a substantially rectangular shape in plan view.

[0056] The stacking direction of the laminated section 42 is particularly susceptible to volume changes when the electrode body 40 is charged and discharged. Therefore, in the energy storage device 1, where the electrode body 40 is arranged so that the stacking direction of the laminated section 42 faces the sealing body 30, the force pushing the sealing body 30 outward becomes stronger when the electrode body 40 expands. In this technology, since the strength of the case 10 is improved, the risk of damage or deformation of the case 10 can be reduced even with the above configuration.

[0057] As shown in Figure 5, in this embodiment, the separator 70 is folded in a zigzag pattern (also called a bellows pattern) with alternating folds at predetermined intervals. The electrode plates (positive electrode plate 51 and negative electrode plate 61) have their surfaces in the thickness direction (stacking direction) sandwiched between the folded separator 70. The separator 70 is wrapped around the outermost part of the zigzag structure and forms the outer surface of the electrode body 40. A winding stopper tape 44 is attached to the end of the separator 70 to prevent winding slack.

[0058] The separator 70 may be the same as in the conventional design and is not particularly limited. The separator 70 may be a single-layer structure, or it may be a structure of two or more layers with different properties and characteristics (such as thickness and porosity), for example, a three-layer structure. The separator 70 is made of resin, for example, and is preferably made of polyolefin resin. As the polyolefin resin, polyethylene, polypropylene, or a mixture thereof is preferred.

[0059] An insulating electrode holder (not shown) may be placed between the electrode body 40 and the case 10 to prevent electrical conductivity between the electrode body 40 and the case 10. The material of the electrode holder may be, for example, polyamide resin, polyolefin resin (e.g., polypropylene, polyethylene), etc.

[0060] In the stacking direction of the stacked portion 42 of the electrode body 40, it is preferable that the base portion 31 of the sealing body 30 is in direct or indirect contact with the electrode body 40. It is more preferable that the electrode body 40 is in direct or indirect contact with the base portion 31 of the sealing body 30 when the electrode body 40 is in a discharge state (for example, when the SOC is 20% or less). With this configuration, the sealing body 30 can apply restraining pressure to the electrode body 40 from the stacking direction. This makes it possible to reduce or eliminate the restraining pressure by external members when the energy storage device 1 is used as a battery constituting a battery module. For this reason, an example of a method for manufacturing the energy storage device 1 includes welding the sealing body 30 to the case body 20 while holding down the electrode body 40 housed in the case body 20 with the base portion 31 of the sealing body 30 from the stacking direction. Furthermore, "the base portion 31 of the sealing body 30 indirectly contacts the electrode body 40" means that the base portion 31 of the sealing body 30 and the electrode body 40 are in contact via other components, and that the base portion 31 can press down on the electrode body 40 via other components.

[0061] The thickness of the laminated portion 42 of the electrode body 40 in the stacking direction may be greater than the height Z of the case body 20. The base portion 31 of the sealing body 30 can more easily press down on the electrode body 40 from the stacking direction. As a result, when the energy storage device 1 is used as a battery constituting the battery module, the restraining pressure by external members can be reduced or eliminated.

[0062] (5) Electrolyte The electrolyte can be the same as in the conventional method and is not particularly limited. The electrolyte is, for example, a non-aqueous electrolyte containing a non-aqueous solvent (organic solvent) and a supporting salt (electrolyte salt, such as a lithium salt or sodium salt). Examples of non-aqueous solvents include carbonates such as ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. Examples of supporting salts include fluorine-containing lithium salts such as lithium hexafluoride phosphate (LiPF6).

[0063] The energy storage device 1 can be used for various applications. Suitable applications include automotive applications, specifically as a power source for vehicles such as battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs). The energy storage device 1 can also be used as a battery for small-scale power storage devices. The energy storage device 1 can typically be used in the form of a battery module, which consists of multiple devices connected in series and / or parallel.

[0064] Although several embodiments have been described above, these embodiments are merely examples. This technology can be implemented in various other forms. The technologies described in the claims include various modifications and changes to the embodiments exemplified above. For example, it is possible to replace parts of the above embodiments with other variations, and it is also possible to add other variations to the above embodiments. Furthermore, if a technical feature is not described as essential, it may be deleted as appropriate.

[0065] In the above-described embodiment, the first bent portion 33 of the sealing body 30 was joined to the inner surface of the first wall 22 of the case body 20. However, the invention is not limited to this. Figure 6 is a schematic diagram of a modified energy storage device 100 corresponding to Figure 3. Figure 7 is a schematic diagram of a modified energy storage device 100 corresponding to Figure 2. As shown in Figure 6, in the energy storage device 100, the first bent portion 33 of the sealing body 30 is located on the outside of the case body 20. The first bent portion 33 is joined to the outer surface of the first wall 22 of the case body 20 via a first welded joint 80. With this configuration, the concentration of stress on the first welded joint 80 can be suppressed, thereby improving the strength of the case 10. Also, as shown in Figure 7, in the energy storage device 100, the second bent portion 35 of the sealing body 30 is located on the outside of the case body 20. The second bent portion 35 is joined to the outer surface of the second wall 24 of the case body 20 via a second welded joint 82. With this configuration, the concentration of stress in the second welded joint 82 can be suppressed, thereby improving the strength of case 10.

[0066] Furthermore, in the above-described embodiment, the electrode body 40 was a laminated electrode body having a zigzag structure using strip-shaped separators 70, but it is not limited to this. For example, the electrode body may be a laminated electrode body prepared by preparing a plurality of substantially rectangular separator sheets and stacking one or more separator sheets between a positive electrode plate 51 and a negative electrode plate 61. Alternatively, it may be a flat-shaped wound electrode body in which a strip-shaped positive electrode sheet and a strip-shaped negative electrode sheet are stacked via strip-shaped separator sheets and wound up. In the case of a flat-shaped wound electrode body, the laminated portion 42 is formed, for example, in the thickness direction where the flat surfaces of the wound electrode body face each other.

[0067] Furthermore, in the above-described embodiment, one electrode body 40 was housed in the case 10, but in some embodiments, there may be multiple electrode bodies 40.

[0068] As described above, specific embodiments of the technology disclosed herein include those described in the following sections.

[0069] Item 1: Cases and, The electrode body housed in the above case and Equipped with, The above case is, A case body having an opening surrounded by side walls including a pair of first walls, A sealing body that seals the above opening and Includes, The electrode body has a laminated portion that is stacked toward the sealing body in a state in which the positive electrode and the negative electrode are insulated, The above sealing body is The base part, A pair of first bent portions extend from the base portion along the pair of first walls of the case body and face each other. It has, The first bent portion is joined to the first wall of the case body via a welded joint. Energy storage device. Item 2: The above opening is surrounded by a pair of long sides and a pair of short sides, The energy storage device according to item 1, wherein the pair of first walls described above constitute the pair of long sides described above. Item 3: The above side wall further comprises a pair of second walls, The second wall mentioned above constitutes the pair of short sides mentioned above. The energy storage device according to item 2, wherein the sealing body extends from the base portion along the pair of second walls of the case body and has a pair of opposing second bends. Item 4: The energy storage device according to Item 3, wherein the second bent portion is joined to the second wall of the case body via the second welded joint. Item 5: The energy storage device according to any one of items 1 to 4, wherein the first bent portion is joined to the inner surface of the first wall of the case body via the welded joint. Item 6: The energy storage device according to any one of items 1 to 5, wherein the first bent portion is joined to the outer surface of the first wall of the case body via the welded joint. Item 7: The energy storage device according to any one of items 1 to 6, wherein the base portion of the sealing body is in direct or indirect contact with the electrode body in the stacking direction of the stacked portion of the electrode body. [Explanation of Symbols]

[0070] 1. Energy storage device 10 cases 12 Safety valve 14 Liquid injection hole 16 Positive terminal insertion hole 18 Negative terminal insertion hole 20 Case body 22 1st wall 24 Second wall 26 Bottom wall 28 Aperture 30 Sealing body 31 Base section 32 First Corner 33 First folding section 34. Second corner section 35 Second folding section 36 recesses 40 Electrode body 42 Laminated section 44. Retaining tape 50 positive electrode 51 Positive plate 52 Positive electrode current collector 53 Cathode active material layer 54 Positive Tab 55 Positive electrode connection 56 Positive electrode current collector 57 Positive terminal 60 negative electrode 61 Negative plate 62 Negative electrode current collector 63 Negative electrode active material layer 64 Negative Electrode Tabs 65 Negative electrode connection 66 Negative electrode current collector 67 Negative terminal 70 Separators 80 First welded joint 82 Second welded joint 90 Insulating material

Claims

1. The case and, The electrode body housed in the aforementioned case and Equipped with, The aforementioned case is, A case body having an opening surrounded by side walls including a pair of first walls, A sealing body that seals the aforementioned opening and Includes, The electrode body has a laminated portion that is stacked toward the sealing body in a state in which the positive electrode and the negative electrode are insulated, The aforementioned sealing body is The base part, A pair of first bent portions extend from the base portion along the pair of first walls of the case body and face each other. It has, The first bent portion is joined to the first wall of the case body via the first welded joint. Energy storage device.

2. The opening is surrounded by a pair of long sides and a pair of short sides. The energy storage device according to claim 1, wherein the pair of first walls constitute the pair of long sides.

3. The aforementioned side wall further comprises a pair of second walls, The second wall constitutes the pair of short sides, The energy storage device according to claim 2, wherein the sealing body extends from the base portion along the pair of second walls of the case body and has a pair of opposing second bent portions.

4. The energy storage device according to claim 3, wherein the second bent portion is joined to the second wall of the case body via a second welded joint.

5. The energy storage device according to claim 1, wherein the first bent portion is joined to the inner surface of the first wall of the case body via the first welded joint.

6. The energy storage device according to claim 1, wherein the first bent portion is joined to the outer surface of the first wall of the case body via the first welded joint.

7. The energy storage device according to any one of claims 1 to 6, wherein the base portion of the sealing body is in direct or indirect contact with the electrode body in the stacking direction of the stacked portion of the electrode body.

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