JP7738591B2 - Energy storage devices - Google Patents

Description

This disclosure relates to an electricity storage device.

For example, Patent Documents 1 and 2 listed below disclose a hexahedral rectangular case that houses an electrode assembly. Such a case has a case body and a sealing plate that seals the opening of the case body.

Japanese Patent Application Laid-Open No. 2022-114916 Japanese Patent Application Laid-Open No. 2006-040684

The above-described case can be produced, for example, by joining the case body and sealing plate along the periphery of the opening of the case body. The inventors' research has revealed that, as the capacity of electricity storage devices (e.g., batteries) has increased in recent years, the amount of gas generated inside the case has increased, making it easier for the internal pressure of the case to rise. This can cause the case to deform (expand), placing a strain on the joint between the case body and sealing plate, which is undesirable from the perspective of the reliability of the electricity storage device.

This disclosure has been made in light of these circumstances, and its main purpose is to provide an electricity storage device with suitably improved reliability.

To achieve this objective, the present disclosure provides an electricity storage device including an electrode assembly having a positive electrode and a negative electrode, and a case that houses the electrode assembly. The case includes a case body having a bottom wall, a pair of first side walls that extend from the bottom wall and face each other, a pair of second side walls that extend from the bottom wall and face each other, and an opening that faces the bottom wall; and a sealing plate that seals the opening of the case body. A joint where the sealing plate is joined to the case body is present along the periphery of the opening, and at least a portion of the joint is covered by a protective member that is disposed from the surface of the sealing plate to a position that reaches the first side wall or the second side wall while covering the joint. As will be described in detail below, an electricity storage device with such a configuration can advantageously achieve improved reliability.

FIG. 1 is a perspective view schematically illustrating a battery according to an embodiment. FIG. 2 is a schematic vertical cross-sectional view taken along line II-II in FIG. 1 . FIG. 2 is a schematic vertical cross-sectional view taken along line III-III in FIG. 1 . FIG. 4 is a schematic cross-sectional view taken along line IV-IV in FIG. 1. FIG. 2 is a perspective view schematically showing an electrode body attached to a sealing plate. FIG. 2 is a perspective view schematically showing an electrode assembly to which a positive electrode second current collecting portion and a negative electrode second current collecting portion are attached. FIG. 2 is a schematic diagram showing the configuration of a wound electrode body according to one embodiment. FIG. 2 is a schematic diagram of the battery of FIG. 1 as viewed from above. 2 is a schematic diagram of the battery of FIG. 1 as viewed from the first side wall side. FIG. FIG. 9 is a schematic longitudinal sectional view taken along line X-X in FIG. 8. 8 according to another embodiment. FIG. FIG. 12 is a schematic longitudinal sectional view taken along line XII-XII in FIG. 11. FIG. 10 is a schematic diagram of a battery pack including a plurality of batteries according to another embodiment.

Below, several embodiments of the technology disclosed herein are described with reference to the drawings. Naturally, the following description is not intended to limit the technology disclosed herein to the following embodiments. In the following drawings, components and parts that perform the same function are denoted by the same reference numerals. Furthermore, dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect actual dimensional relationships. Matters not specifically mentioned in this specification but necessary for implementing the technology disclosed herein (for example, the general structure and manufacturing process of a battery that do not characterize the present invention) can be understood as design matters of a person skilled in the art based on prior art in the relevant field. The technology disclosed herein can be implemented based on the contents disclosed in this specification and common technical knowledge in the relevant field. In this specification, the notation "A to B" indicating a range means "greater than A and less than B." It also encompasses the meanings of "greater than A" and "less than B."

In this specification, the term "energy storage device" refers to a device that can be charged and discharged. Energy storage devices include batteries such as primary batteries and secondary batteries (e.g., lithium-ion secondary batteries and nickel-metal hydride batteries), as well as capacitors (physical batteries) such as electric double-layer capacitors. The electrolyte may be a liquid electrolyte (electrolytic solution), a gel electrolyte, or a solid electrolyte. Below, the present technology will be described using a lithium-ion secondary battery, which is one embodiment of an energy storage device, as an example.

<Battery configuration>
FIG. 1 is a perspective view of the battery 100. FIG. 2 is a schematic longitudinal cross-sectional view taken along line II-II in FIG. 1. FIG. 3 is a schematic longitudinal cross-sectional view taken along line III-III in FIG. 1. FIG. 4 is a schematic transverse cross-sectional view taken along line IV-IV in FIG. 1. In the following description, the symbols L, R, F, Rr, U, and D in the drawings represent left, right, front, rear, top, and bottom, and the symbols X, Y, and Z in the drawings represent the short side direction, long side direction perpendicular to the short side direction, and up-down direction of the battery 100, respectively. However, these directions are merely used for convenience of description and do not limit the installation form of the battery 100 in any way.

As shown in FIG. 2, the battery 100 includes a case 10 (battery case) and an electrode assembly 20. In addition to the case 10 and the electrode assembly 20, the battery 100 according to this embodiment also includes a positive electrode terminal 30, a positive electrode external conductive member 32, a negative electrode terminal 40, a negative electrode external conductive member 42, an external insulating member 92, a positive electrode current collector 50, a negative electrode current collector 60, a positive electrode internal insulating member 70, and a negative electrode internal insulating member 80. Although not shown, the battery 100 according to this embodiment also includes an electrolyte. The battery 100 is a lithium-ion secondary battery.

The case 10 is a housing that houses the electrode assembly 20. Here, the case 10 has a flat, bottomed, rectangular (square) outer shape. Here, the case 10 has a square hexahedral outer shape. Note that square cases include cases in which all eight corners are perfect corners, as well as cases in which at least one of the eight corners is rounded (i.e., a rounded corner). The case 10 may be flat, as in this embodiment, or it may not be flat (for example, it may be cubic, etc.). The material of the case 10 may be the same as that conventionally used, and is not particularly limited. The case 10 is preferably made of a metal with a predetermined strength. Examples of metal materials that can be used to form the case 10 include aluminum, aluminum alloys, iron, and iron alloys.

The case 10 includes a case body 12, a sealing plate 14, and a gas exhaust valve 17. The case body 12 is a flat, rectangular container with an opening 12h on one side. Specifically, as shown in FIG. 1, the case body 12 includes a substantially rectangular bottom wall 12a, a pair of opposing second side walls 12c extending upward in the U direction from the short sides of the bottom wall 12a, and a pair of opposing first side walls 12b extending upward in the U direction from the long sides of the bottom wall 12a. The area of the second side walls 12c is smaller than the area of the first side walls 12b. The opening 12h is formed on the upper surface of the case body 12, surrounded by the pair of first side walls 12b and the pair of second side walls 12c. The sealing plate 14 is attached to the case body 12 so as to close the opening 12h of the case body 12. The sealing plate 14 is a substantially rectangular plate material in a plan view. The sealing plate 14 faces the bottom wall 12a of the case body 12. The case 10 is formed by joining (e.g., welding) the sealing plate 14 to the periphery of the opening 12h of the case body 12. The sealing plate 14 can be joined by welding, such as laser welding. Specifically, each of the pair of first side walls 12b is joined to the short sides of the sealing plate 14, and each of the pair of second side walls 12c is joined to the long sides of the sealing plate 14. The case 10 has a joint A along the periphery of the opening 12h where the sealing plate 14 is joined to the case body 12. Furthermore, at least a portion of the joint A is covered by a protective member 1, as will be described in detail below.

As shown in Figures 1 and 2, the gas exhaust valve 17 is formed on the sealing plate 14. The gas exhaust valve 17 is configured to open when the pressure inside the case 10 reaches or exceeds a predetermined value, thereby exhausting gas from inside the case 10. In this embodiment, the gas exhaust valve 17 is a flat, approximately circular recess that is recessed from the outer surface of the sealing plate 14 toward the electrode assembly 20. The bottom surface of the gas exhaust valve 17 has a thin-walled portion that is thinner than the thickness of the sealing plate 14. This thin-walled portion of the gas exhaust valve 17 ruptures when the internal case pressure reaches or exceeds a predetermined value. This allows gas inside the case 10 to be exhausted to the outside, reducing the increased internal case pressure.

In addition to the gas release valve 17, the sealing plate 14 is also provided with a liquid inlet 15 and two terminal insertion holes 18 and 19. The liquid inlet 15 is connected to the internal space of the case body 12 and is an opening provided for injecting electrolyte during the manufacturing process of the battery 100. The liquid inlet 15 is sealed with a sealing member 15a. A blind rivet, for example, is suitable as the sealing member 15a. This allows the sealing member 15a to be firmly fixed inside the case 10. The terminal insertion holes 18 and 19 are formed at both ends of the sealing plate 14 in the long side direction Y. The terminal insertion holes 18 and 19 penetrate the sealing plate 14 in the vertical direction Z. As shown in FIG. 2 , a positive terminal 30 is inserted into the terminal insertion hole 18 on one side (left side) in the long side direction Y. A negative terminal 40 is inserted into the terminal insertion hole 19 on the other side (right side) in the long side direction Y.

Figure 5 is a perspective view schematically illustrating the electrode assembly 20 attached to the sealing plate 14. Figure 6 is a perspective view schematically illustrating the electrode assembly 20a to which the positive electrode second current collector 52 and the negative electrode second current collector 62 are attached. In this embodiment, multiple (three in this example) electrode assemblies 20a, 20b, and 20c are housed inside the case 10. The number of electrode assemblies housed inside one case 10 is not particularly limited and may be one or two or more (plural). As shown in Figure 5, the positive electrode current collector 50 is disposed on one side of each electrode assembly in the long side direction Y (left side in Figure 5), and the negative electrode current collector 60 is disposed on the other side of the long side direction Y (right side in Figure 5). The electrode assemblies 20a, 20b, and 20c are connected in parallel. However, the electrode assemblies 20a, 20b, and 20c may also be connected in series. The electrode assembly 20 is housed inside the case body 12 of the case 10 while covered with an electrode holder 29 (see Figure 3), which is made of a resin sheet.

Figure 7 is a perspective view showing a schematic diagram of electrode body 20a. While electrode body 20a will be described in detail below as an example, electrode bodies 20b and 20c can also be configured in a similar manner.

As shown in FIG. 7 , the electrode body 20a has a positive electrode 22, a negative electrode 24, and a separator 26. Here, the electrode body 20a is a wound electrode body in which a strip-shaped positive electrode 22 and a strip-shaped negative electrode 24 are stacked with two strip-shaped separators 26 interposed therebetween and wound around a winding axis WL. However, the structure of the electrode body does not limit the technology disclosed herein. For example, the electrode body may be a laminated electrode body in which multiple square-shaped (typically rectangular) positive electrodes and multiple square-shaped (typically rectangular) negative electrodes are stacked in an insulated state.

The electrode body 20a has a flat shape. The electrode body 20a is disposed inside the case body 12 with the winding axis WL oriented approximately parallel to the long side direction Y. Specifically, as shown in FIG. 3, the electrode body 20a has a pair of curved portions (R portions) 20r that face the bottom wall 12a and sealing plate 14 of the case body 12, and a flat portion 20f that connects the pair of curved portions 20r and faces the second side wall 12c of the case body 12. The flat portion 20f extends along the second side wall 12c.

As shown in FIG. 7, the positive electrode 22 has a positive electrode current collector 22c, and a positive electrode active material layer 22a and a positive electrode protective layer 22p adhered to at least one surface of the positive electrode current collector 22c. However, the positive electrode protective layer 22p is not essential and may be omitted in other embodiments. The positive electrode current collector 22c is strip-shaped. The positive electrode current collector 22c is made of a conductive metal such as aluminum, an aluminum alloy, nickel, or stainless steel. In this example, the positive electrode current collector 22c is a metal foil, specifically, aluminum foil.

Multiple positive electrode tabs 22t are provided at one end of the positive electrode current collector 22c in the long side direction Y (the left end in Figure 7). The multiple positive electrode tabs 22t are provided at intervals (intermittently) along the longitudinal direction of the strip-shaped positive electrode 22. The multiple positive electrode tabs 22t protrude outward from the separator 26 toward one axial side of the winding axis WL (the left side in Figure 7). Note that the positive electrode tabs 22t may be provided on the other axial side of the winding axis WL (the right side in Figure 7), or on both axial sides of the winding axis WL. The positive electrode tabs 22t are part of the positive electrode current collector 22c and are made of metal foil (aluminum foil). However, the positive electrode tabs 22t may be separate components from the positive electrode current collector 22c. In at least a portion of the positive electrode tab 22t, the positive electrode active material layer 22a and the positive electrode protective layer 22p are not formed, and an area is formed in which the positive electrode current collector 22c is exposed.

As shown in FIG. 4, multiple positive electrode tabs 22t are stacked at one axial end of the winding axis WL (the left end in FIG. 4) to form a positive electrode tab group 23. Each of the multiple positive electrode tabs 22t is bent so that their outer edges are aligned. This improves fit into the case 10 and allows the battery 100 to be more compact. As shown in FIG. 2, the positive electrode tab group 23 is electrically connected to the positive electrode terminal 30 via the positive electrode current collector 50. Specifically, the positive electrode tab group 23 and the positive electrode second current collector 52 are connected at connection J (see FIG. 4). The positive electrode second current collector 52 is electrically connected to the positive electrode terminal 30 via the positive electrode first current collector 51. The size of the multiple positive electrode tabs 22t (the length along the long side direction Y and the width perpendicular to the long side direction Y; see FIG. 7) can be adjusted appropriately, for example, by their formation positions, taking into account the state of connection to the positive electrode current collector 50. Here, the multiple positive electrode tabs 22t are different sizes so that the outer edges are aligned when bent.

As shown in FIG. 7 , the positive electrode active material layer 22a is provided in a strip-like shape along the longitudinal direction of the strip-shaped positive electrode current collector 22c. The positive electrode active material layer 22a contains a positive electrode active material (e.g., a lithium transition metal composite oxide such as lithium nickel cobalt manganese composite oxide) capable of reversibly absorbing and releasing charge carriers. When the total solid content of the positive electrode active material layer 22a is taken as 100% by mass, the positive electrode active material may account for approximately 80% by mass or more, typically 90% by mass or more, for example, 95% by mass or more. The positive electrode active material layer 22a may contain optional components other than the positive electrode active material, such as a conductive material, a binder, various additives, etc. Examples of conductive materials that can be used include carbon materials such as acetylene black (AB). Examples of binders that can be used include polyvinylidene fluoride (PVdF).

As shown in FIG. 7 , the positive electrode protective layer 22p is provided at the boundary between the positive electrode collector 22c and the positive electrode active material layer 22a in the long side direction Y. Here, the positive electrode protective layer 22p is provided at one end (the left end in FIG. 7 ) of the positive electrode collector 22c in the axial direction of the winding axis WL. However, the positive electrode protective layer 22p may also be provided at both axial ends. The positive electrode protective layer 22p is provided in a strip shape along the positive electrode active material layer 22a. The positive electrode protective layer 22p contains an inorganic filler (e.g., alumina). When the total solid content of the positive electrode protective layer 22p is taken as 100% by mass, the inorganic filler may account for approximately 50% by mass or more, typically 70% by mass or more, for example, 80% by mass or more. The positive electrode protective layer 22p may also contain optional components other than the inorganic filler, such as a conductive material, a binder, and various additives. The conductive material and binder may be the same as those exemplified as those that may be contained in the positive electrode active material layer 22a.

As shown in FIG. 7, the negative electrode 24 has a negative electrode current collector 24c and a negative electrode active material layer 24a adhered to at least one surface of the negative electrode current collector 24c. The negative electrode current collector 24c is strip-shaped. The negative electrode current collector 24c is made of a conductive metal such as copper, a copper alloy, nickel, or stainless steel. In this example, the negative electrode current collector 24c is a metal foil, specifically, copper foil.

A plurality of negative electrode tabs 24t are provided at one axial end (the right end in FIG. 7 ) of the winding axis WL of the negative electrode current collector 24c. The multiple negative electrode tabs 24t are provided at intervals (intermittently) along the longitudinal direction of the strip-shaped negative electrode 24. Each of the multiple negative electrode tabs 24t protrudes outward from the separator 26 toward one axial end (the right end in FIG. 7 ). However, a negative electrode tab 24t may be provided at the other axial end (the left end in FIG. 7 ) or at each of both axial ends. The negative electrode tab 24t is part of the negative electrode current collector 24c and is made of metal foil (copper foil). However, the negative electrode tab 24t may be a separate member from the negative electrode current collector 24c. At least a portion of the negative electrode tab 24t has an area where the negative electrode active material layer 24a is not formed and the negative electrode current collector 24c is exposed.

As shown in FIG. 4 , the negative electrode tabs 24t are stacked at one axial end (the right end in FIG. 4 ) to form a negative electrode tab group 25. The negative electrode tab group 25 is preferably positioned symmetrically to the positive electrode tab group 23 in the axial direction. The negative electrode tabs 24t are bent so that their outer edges are aligned. This improves the fitment into the case 10 and enables the battery 100 to be miniaturized. As shown in FIG. 2 , the negative electrode tab group 25 is electrically connected to the negative electrode terminal 40 via the negative electrode current collector 60. Specifically, the negative electrode tab group 25 and the negative electrode second current collector 62 are connected at connection J (see FIG. 4 ). The negative electrode second current collector 62 is electrically connected to the negative electrode terminal 40 via the negative electrode first current collector 61. As with the positive electrode tabs 22t, the negative electrode tabs 24t are different sizes so that their outer edges are aligned when bent.

As shown in FIG. 7 , the negative electrode active material layer 24a is provided in a strip-like shape along the longitudinal direction of the strip-shaped negative electrode current collector 24c. The negative electrode active material layer 24a contains a negative electrode active material (e.g., a carbon material or a silicon-based material) capable of reversibly absorbing and releasing charge carriers. For example, when the negative electrode active material contains a silicon-based material, gas is likely to be generated inside the case 10, making it suitable for application of the technology disclosed herein. Examples of such carbon materials include graphite, hard carbon, soft carbon, amorphous carbon, and combinations thereof. Examples of such silicon-based materials include silicon, silicon oxide (silica), and combinations thereof. The silicon-based material may contain, for example, other metal elements (e.g., alkaline earth metals) or their oxides. When the total solid content of the negative electrode active material layer 24a is taken as 100% by mass, the negative electrode active material may account for approximately 80% by mass or more, typically 90% by mass or more, for example 95% by mass or more. The negative electrode active material layer 24a may contain optional components other than the negative electrode active material, such as a binder, a dispersant, and various additives. Examples of binders that can be used include rubbers such as styrene butadiene rubber (SBR). Examples of dispersants that can be used include celluloses such as carboxymethyl cellulose (CMC).

As shown in FIG. 7, the separator 26 is a member that insulates the positive electrode active material layer 22a of the positive electrode 22 from the negative electrode active material layer 24a of the negative electrode 24. A suitable separator 26 is a porous resin sheet made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP). The separator 26 may have a substrate made of a porous resin sheet and a heat resistance layer (HRL) containing an inorganic filler that is provided on at least one surface of the substrate. Examples of inorganic fillers that can be used include alumina, boehmite, aluminum hydroxide, and titania.

The electrolyte may be the same as conventional ones and is not particularly limited. The electrolyte is, for example, a non-aqueous electrolyte containing a non-aqueous solvent and a supporting salt. The non-aqueous solvent contains, for example, a carbonate such as ethylene carbonate, dimethyl carbonate, or ethyl methyl carbonate. The supporting salt is, for example, a fluorine-containing lithium salt such as _LiPF6 . However, the electrolyte may be solid (solid electrolyte) and integrated with the electrode assembly 20.

As shown in FIG. 2, the positive electrode terminal 30 is inserted into a terminal insertion hole 18 formed at one end of the sealing plate 14 in the long side direction Y (the left end in FIG. 2). The positive electrode terminal 30 is preferably made of metal, more preferably aluminum or an aluminum alloy. Meanwhile, the negative electrode terminal 40 is inserted into a terminal insertion hole 19 formed at the other end of the sealing plate 14 in the long side direction Y (the right end in FIG. 2). The negative electrode terminal 40 is preferably made of metal, more preferably copper or a copper alloy. Here, these electrode terminals (positive electrode terminal 30, negative electrode terminal 40) each protrude from the same surface of the case 10 (specifically, the sealing plate 14). However, the positive electrode terminal 30 and negative electrode terminal 40 may each protrude from different surfaces of the case 10. The electrode terminals (positive electrode terminal 30, negative electrode terminal 40) inserted into the terminal insertion holes 18, 19 are preferably fixed to the sealing plate 14 by crimping or other means.

As described above, as shown in FIG. 2, the positive electrode terminal 30 is electrically connected to the positive electrode 22 (see FIG. 7) of each electrode body 20a, 20b, 20c via the positive electrode current collector 50 (positive electrode first current collector 51, positive electrode second current collector 52) inside the case body 12. The positive electrode terminal 30 is insulated from the sealing plate 14 by a positive electrode internal insulating member 70 and a gasket 90. The positive electrode internal insulating member 70 includes a base portion 70a interposed between the positive electrode first current collector 51 and the sealing plate 14 and a protrusion portion 70b protruding from the base portion 70a toward the electrode body 20a. The positive electrode terminal 30 exposed to the outside of the case 10 through the terminal insertion hole 18 is connected to the positive electrode external conductive member 32 outside the sealing plate 14. On the other hand, as shown in FIG. 2 , the negative electrode terminal 40 is electrically connected to the negative electrode 24 (see FIG. 7 ) of each electrode body 20 a via a negative electrode current collector 60 (negative electrode first current collector 61, negative electrode second current collector 62) inside the case body 12. The negative electrode terminal 40 is insulated from the sealing plate 14 by a negative electrode internal insulating member 80 and a gasket 90. Like the positive electrode internal insulating member 70, the negative electrode internal insulating member 80 also has a base portion 80 a interposed between the negative electrode first current collector 61 and the sealing plate 14 and a protrusion 80 b protruding from the base portion 80 a toward the electrode body 20 a. The negative electrode terminal 40 exposed to the outside of the case 10 through the terminal insertion hole 19 is connected to a negative electrode external conductive member 42 outside the sealing plate 14. An external insulating member 92 is interposed between the external conductive members (positive electrode external conductive member 32, negative electrode external conductive member 42) and the outer surface of the sealing plate 14. This external insulating member 92 insulates the external conductive members 32, 42 from the sealing plate 14.

In addition, the protrusions 70b, 80b of the internal insulating members (positive electrode internal insulating member 70, negative electrode internal insulating member 80) described above are positioned between the sealing plate 14 and the electrode body 20a. These protrusions 70b, 80b of the internal insulating members restrict upward movement of the electrode body 20a, preventing contact between the sealing plate 14 and the electrode body 20a.

Next, we will explain the protective member 1 that characterizes the battery 100 according to this embodiment. Here, Fig. 8 is a schematic diagram of the battery 100 of Fig. 1 when viewed from above. Fig. 9 is a schematic diagram of the battery 100 of Fig. 1 when viewed from the first side wall 12b side. Fig. 10 is a schematic longitudinal cross-sectional view along line X-X in Fig. 8. As described above, the battery 100 comprises an electrode body (here, electrode bodies 20a, 20b, 20c) having a positive electrode 22 and a negative electrode 24, and a case 10 that houses the electrode body. The case 10 also includes a case body 12 having a bottom wall 12a, a pair of first side walls 12b extending from the bottom wall 12a and facing each other, a pair of second side walls 12c extending from the bottom wall 12a and facing each other, and an opening 12h facing the bottom wall 12a; and a sealing plate 14 sealing the opening 12h of the case body 12. As shown in FIGS. 1 and 8 , a joint A where the sealing plate 14 is joined to the case body 12 is present along the periphery of the opening 12h, and at least a portion of the joint A is covered by a protective member 1. Here, the protective member 1 is disposed from the surface of the sealing plate 14, covering the joint A, to a position spanning the corner to the adjacent first side wall 12b or second side wall 12c. Note that, as shown in FIG. 1 , in this embodiment, the protective member 1 is disposed from the surface of the sealing plate 14, covering the joint A, to a position spanning the corner to the adjacent first side wall 12b.

For example, in conventional batteries, when gas is generated inside the case, the internal pressure of the case increases, causing the case to deform (expand), which tends to place a load on the joint between the case body and the sealing plate. In contrast, in the battery 100 according to this embodiment, at least a portion of joint A is disposed from the surface of the sealing plate 14 to the first side wall 12b. In other words, the protective member 1 covers joint 1 and the side wall that is prone to deformation (here, first side wall 12b). This distributes the load applied to joint A when the internal pressure of the battery 100 increases, thereby suppressing variations in the pressure resistance of the case 10. This effectively prevents damage to the case 10, resulting in a battery 100 with improved reliability.

The protective member 1 may be made of, for example, metal or resin. Alternatively, it may be a combination of these (for example, a metal protective member with resin disposed in part). From the perspective of providing insulation and thereby improving ease of handling, it is preferable that the protective member 1 be made of resin. Examples of metal materials that may be used to make the protective member 1 include aluminum, copper, stainless steel (SUS), and combinations thereof. Examples of resin materials that may be used to make the protective member 1 include polypropylene (PP), polyethylene (PE), polystyrene (PS), and combinations thereof.

The thickness of the protective member 1 (thickness in the X direction in FIG. 10 ) is not particularly limited as long as the effects of the technology disclosed herein are achieved, but it is preferably equal to or greater than the thickness of the case 10 (thickness in the X direction in FIG. 10 ). This configuration can more effectively suppress deformation of the case 10. Here, assuming that the thickness of the protective member 1 is t3 and the thickness of the case 10 is t4, the ratio of t3 to t4 (t3/t4) is, for example, 1 or greater. From the perspective of more effectively suppressing deformation of the case 10, it is preferably 1.2 or greater, more preferably 1.5 or greater, and may be, for example, 2 or greater. The upper limit of the ratio (t3/t4) is, for example, 3 or less, or may be 2.5 or less. The thickness of the protective member 1 can be, for example, 0.1 mm to 20 mm (preferably 0.5 mm to 10 mm). The thickness of the case 10 can be, for example, 0.1 mm to 20 mm (preferably 0.5 mm to 10 mm).

As shown in FIG. 1 , in this embodiment, deformation (expansion) of the case 10 can be effectively suppressed by sandwiching the side of the joint A between a pair of first side walls 12b in the longitudinal direction. Preferably, as in this embodiment, the protective member 1 is positioned so as not to cover the upper surfaces of the gas release valve 17 and the electrode terminals (positive terminal 30 and negative terminal 40). This configuration allows the gas release valve 17 and the electrode terminals to function optimally in the battery 100. Preferably, as in this embodiment, the protective member 1 is not positioned on the corners (which may be rounded corners) or short sides of the sealing plate 14. This configuration is preferable from the perspective of cost reduction. Because the corners and short sides of the sealing plate 14 near the corners have high rigidity, these areas do not need to be covered by the protective member 1. Furthermore, because corrosion of the joint A is not suppressed, the protective member 1 does not need to completely cover the joint A. In other embodiments, the protective member 1 may also be arranged on the corners (which may be rounded corners) of the sealing plate 14 or on the short sides of the sealing plate 14.

In a preferred embodiment, the opening 12h and bottom wall 12a are rectangular, and the first side wall 12b is a wide surface that extends along the longitudinal direction of the opening 12h (the Y direction in Figure 1). The protective member 1 is disposed from the sealing plate 14 across the corner to the wide first side wall 12b. When the case 10 deforms (expands), the wide first side wall 12b is more likely to deform. Therefore, the above-described configuration effectively suppresses deformation of the case 10, thereby effectively reducing the load applied to the joint A.

In a preferred embodiment, the protective member 1 is disposed in the central region of the first side wall 12b. In other words, the protective member 1 includes a protective member 1b disposed in the central region of the first side wall 12b and a protective member 1a disposed outside the central region. In the direction from the sealing plate 14 toward the bottom wall 12a (direction D in Figure 9), the protective member 1b disposed in the central region is disposed closer to the bottom wall 12a than the protective member 1a disposed outside the central region. When the case 10 deforms (expands), the central region of the wider first side wall 12b is particularly susceptible to deformation. Therefore, the above-described configuration can more effectively suppress deformation of the case 10, thereby effectively reducing the load applied to the joint A. The central region of the first side wall 12b can be defined as the area within the center of the long side of the first side wall 12b, for example, when the long side of the first side wall 12b is divided into thirds, fifths, or sevenths. In this embodiment, this central region is defined as the region within the range l2 when the long side of the first side wall 12b is divided into three equal parts l1, l2, and l3.

Here, in the short-side direction of the first side wall 12b (Z direction in FIG. 9), the length of the protective member 1a arranged outside the central region of the first side wall 12b is defined as t1, and the length of the protective member 1b arranged in the central region of the first side wall 12b is defined as t2. The lower limit of the ratio of t2 to t1 (t2/t1) is, for example, 1.2 or greater. From the perspective of more effectively suppressing deformation of the first side wall 12b, it is preferably 1.5 or greater, and more preferably 2 or greater (or greater than 2). The upper limit of the ratio (t2/t1) is, for example, 5 or less, and may be 4 or less, or 3 or less. It is also preferable that the protective member 1b be within the range of L2, which will be described later. Because the case 10 is more susceptible to deformation within the L2 range compared to the L1 and L3 ranges, the effects disclosed herein are more easily achieved.

In a preferred embodiment, the protective member 1 has one or more bridges 1c extending from one of the first side walls 12b through the sealing plate 14 to the other first side wall 12b. This configuration improves the rigidity of the protective member 1 within its frame, thereby effectively suppressing deformation of the case 10. As shown in FIG. 8 , in this embodiment, the protective member 1 has two bridges 1c. However, in other embodiments, the number of bridges may be one, three, or more. The location of the bridges 1c is not particularly limited as long as the effects of the technology disclosed herein are achieved. However, it is preferable that the bridges 1c be located in the central region of the sealing plate 14 in the longitudinal direction (the Y direction in FIG. 8 ). This configuration can more effectively improve the rigidity of the protective member 1 within its frame. The central region of the sealing plate 14 can be defined as the area within the center of the sealing plate 14 when the long side of the sealing plate 14 is divided into thirds, fifths, or sevenths. In this embodiment, this central region is defined as the region within the range of L2 when the long side of the sealing plate 14 is divided into three equal parts L1, L2, and L3.

In a preferred embodiment, the protective member 1 is disposed on the first side wall 12b in the direction from the sealing plate 14 toward the bottom wall 12a (direction D in FIG. 10 ) up to a position closer to the bottom wall 12a than the portion where the joint A exists (in other words, the lower end Q of the joint A). This configuration makes it possible to suitably suppress the load applied to the joint A when the internal pressure of the battery 100 increases. In a more preferred embodiment, the protective member 1 is disposed on the first side wall 12b in the direction from the sealing plate 14 toward the bottom wall 12a (direction D in FIG. 10 ) up to a position closer to the bottom wall 12a than the lower end R of the sealing plate 14. This configuration makes it possible to more suitably distribute the load applied to the joint A when the internal pressure of the battery 100 increases.

In a preferred embodiment, the protective member 1 extends further inward than the inner peripheral edge P of the joint A on the top surface of the case 10. This configuration more effectively distributes the load applied to the joint A when the internal pressure of the battery 100 increases.

For example, large batteries (e.g., high-capacity batteries) in which internal pressure within the case is likely to increase due to gas generation within the case are suitable targets for applying the technology disclosed herein. Examples of external dimensions of such large batteries include a length of 80 mm to 100 mm, a width of 200 mm to 300 mm, and a depth of 30 mm to 40 mm. Note that, using battery 100 as an example, the above-mentioned length, width, and depth can refer to the length of the first side wall 12b in the short side direction (the length in the Z direction in FIG. 1), the length of the first side wall 12b in the long side direction (the length in the Y direction in FIG. 1), and the thickness of the case 10 (the thickness in the X direction in FIG. 1). By increasing the length in the longitudinal direction (the Y direction in FIG. 1) of such large batteries, the case tends to be relatively more susceptible to deformation due to an increase in internal pressure within the battery.

<Battery manufacturing method>
Next, an example of a manufacturing method for the battery 100 according to this embodiment will be described. The battery 100 according to this embodiment can be fabricated, for example, by preparing the electrode bodies 20a, 20b, and 20c, inserting them into the case 10, and sealing them. More specifically, as shown in FIG. 5 , first, the positive electrode second current collector 52 is joined to the positive electrode tab group 23 of each electrode body, and the negative electrode second current collector 62 is joined to the negative electrode tab group 25. Then, as shown in FIG. 4 , the electrode bodies are arranged so that their flat portions face each other. A sealing plate 14 is placed above each electrode body, and the positive electrode tab group 23 of each electrode body is bent so that the positive electrode second current collector 52 faces one side surface 20e of the electrode body. This connects the positive electrode first current collector 51 and the positive electrode second current collector 52. Similarly, the negative electrode tab group 25 of each electrode body 20 is bent so that the negative electrode second current collecting portion 62 faces the other side surface 20h of the electrode body. This connects the negative electrode first current collecting portion 61 and the negative electrode second current collecting portion 62. As a result, the electrode body is attached to the sealing plate 14 via the positive electrode current collecting portion 50 and the negative electrode current collecting portion 60. Next, each electrode body attached to the sealing plate 14 is covered with an electrode body holder 29 (see FIG. 3 ) and then housed inside the case body 12. As a result, the flat portion of the electrode body 20 faces the long side wall 12b of the case body 12 (i.e., the flat surface of the case 10). Furthermore, the upper curved portion 20r faces the sealing plate 14, and the lower curved portion 20r faces the bottom wall 12a of the case body 12. Then, after closing the opening 12h on the top surface of the case body 12 with the sealing plate 14, the case body 12 and the sealing plate 14 are joined (welded) to construct the case 10. After that, an electrolyte is injected into the inside of the case 10 through the liquid injection hole 15 of the sealing plate 14, and the liquid injection hole 15 is closed with a sealing member 15a.

Next, the protective member 1 is fixed (placed) on the case 10. Methods for fixing the protective member 1 to the case 10 include, for example, mechanically fitting the protective member 1 to the case 10, fixing the protective member 1 to the case 10 with an adhesive, or forming the protective member 1 directly on the joint A using a UV-curable resin. Examples of such adhesives include epoxy resins, acrylic resins, and silicone resins. Furthermore, any conventionally known UV-curable resin can be used without any particular restrictions. In this manner, a battery 100 equipped with the protective member 1 can be obtained.

<Battery uses>
Battery 100 can be used for a variety of purposes, but can be suitably used, for example, as a power source (driving power source) for a motor mounted on a vehicle such as a passenger car or truck. The type of vehicle is not particularly limited, but examples include plug-in hybrid electric vehicles (PHEVs), hybrid electric vehicles (HEVs), and battery electric vehicles (BEVs). Battery 100 has reduced variation in battery reaction, and can therefore be suitably used to construct a battery pack.

The above describes one embodiment of the present disclosure, but the above embodiment is merely one example. The present disclosure can be implemented in various other forms. The present disclosure can be implemented based on the content disclosed in this specification and the common general technical knowledge in the relevant field. The technology described in the claims includes various modifications and variations of the above-exemplified embodiment. For example, it is possible to replace part of the above-described embodiment with other modified embodiments, and it is also possible to add other modified embodiments to the above-described embodiment. Furthermore, if a technical feature is not described as essential, it may be deleted as appropriate.

For example, in the above embodiment, only a portion of joint A is covered by protective member 1, but in other embodiments, the entire joint A may be covered by protective member 1. Also, for example, in the above embodiment, protective member 1 is arranged from the surface of sealing plate 14 to a position spanning the corner and reaching the adjacent first side wall 12b while covering joint A, but this is not limited to this. In other embodiments, protective member 1 may be arranged from the surface of sealing plate 14 to a position spanning the corner and reaching the adjacent second side wall 12c while covering joint A, or may be arranged to a position spanning both first side wall 12b and second side wall 12c. Also, protective member 1 may cover the entire joint A.

Figure 11 is a view corresponding to Figure 8 and relating to another embodiment. Figure 12 is a schematic longitudinal cross-sectional view taken along line XII-XII in Figure 11. Figure 13 is a schematic diagram of a battery pack including multiple batteries according to another embodiment. As shown in Figure 11, in this embodiment, the protective member 101 is disposed from the sealing plate 14 across the corner to the first side wall 12b, and the protective member 101 disposed on the first side wall 12b has one or more ribs 101a. With this configuration, for example, when multiple batteries 200 each equipped with the protective member 101 are arranged to form a battery pack 300, the strength of the batteries 200 is suitably improved, thereby enabling the joint A to be suitably protected.

In a preferred embodiment, when the long side of the sealing plate 14 is divided into thirds, L1, L2, and L3, the number of ribs 101a provided in the region L2 is greater than the number of ribs 101a provided in the region L1 and L3. Because the case 10 deforms more in the region L2 than in the region L1 and L3, the strength of the case 10 can be suitably improved by providing a relatively large number of ribs 101a in L2. Furthermore, in a preferred embodiment, the thickness of the ribs 101a (thickness in the X direction in FIG. 12) is greater than the thickness of the protective member 101 (thickness in the X direction in FIG. 12). This configuration can suitably improve the strength of the case 10. Here, when the thickness of the rib 101a is t5 and the thickness of the protective member 101 is T6, the lower limit of the ratio of t5 to t6 (t5/t6) is, for example, 1.2 or more, and from the viewpoint of more suitably suppressing deformation on the first side wall 12b side, it is preferably 1.5 or more, and more preferably 2 or more. The upper limit of the ratio (t5/t6) is, for example, 5 or less, and may be 4 or less, or 3 or less.

In a preferred embodiment, the rib 101a arranged on one of the pair of first side walls 12b and the rib 101a arranged on the other first side wall 12b are arranged asymmetrically in the long side direction of the first side wall 12b. With this configuration, when multiple batteries 200 are arranged side by side to form a battery pack 300, the ribs 101a do not overlap, thereby reducing the distance between the batteries 200. This allows for favorable improvement in the strength of the case 10 and favorable increase in the capacity of the battery pack 300.

As described above, specific aspects of the technology disclosed herein include those described in the following items.
Item 1: An electricity storage device comprising: an electrode assembly having a positive electrode and a negative electrode; and a case that houses the electrode assembly, wherein the case has a case body that has a bottom wall, a pair of first side walls that extend from the bottom wall and face each other, a pair of second side walls that extend from the bottom wall and face each other, and an opening that faces the bottom wall; and a sealing plate that seals the opening of the case body, wherein a joint where the sealing plate is joined to the case body exists along the periphery of the opening, and at least a portion of the joint is covered by a protective member, wherein the protective member is arranged from the surface of the sealing plate to a position that reaches the first side wall or the second side wall while covering the joint.
Item 2: The energy storage device according to Item 1, wherein the opening and the bottom wall are rectangular, the first side wall is a wide surface that extends along the longitudinal direction of the opening, and the protective member is arranged from the sealing plate to a position that reaches the wide first side wall.
Item 3: The energy storage device according to Item 2, wherein the protective member is arranged on the first side wall in a direction from the sealing plate toward the bottom wall up to a portion closer to the bottom wall than the portion where the joint is present.
Item 4: The electricity storage device according to Item 2 or Item 3, wherein the protection member is disposed in a central region of the first side wall.
Item 5: The electricity storage device according to any one of Items 2 to 4, wherein the protective member has one or more bridge portions extending from one of the first side walls through the sealing plate to the other first side wall.

1 Protective member 10 Case 12 Case body 14 Sealing plate 15 Liquid inlet 15a Sealing member 17 Gas exhaust valve 18, 19 Terminal insertion hole 20 Electrode body group 20a to 20c Electrode body 22 Positive electrode 23 Positive electrode tab group 24 Negative electrode 25 Negative electrode tab group 26 Separator 27 Base material layer 28 Heat-resistant layer 30 Positive electrode terminal 32 Positive electrode external conductive member 40 Negative electrode terminal 42 Negative electrode external conductive member 50 Positive electrode current collecting portion 60 Negative electrode current collecting portion 70 Positive electrode internal insulating member 80 Negative electrode internal insulating member 90 Gasket 92 External insulating member 100 Battery A Joint

Claims (4)

a flat electrode body having a positive electrode and a negative electrode;
a flat rectangular parallelepiped case that houses the electrode assembly;
An electricity storage device comprising:
The case includes a case body having a rectangular bottom wall, a pair of rectangular first side walls extending from the bottom wall and facing each other, a pair of rectangular second side walls extending from the bottom wall and facing each other, and a rectangular opening facing the bottom wall;
a rectangular sealing plate that seals the opening of the case body;
It has
The first side wall is a wide surface that exists along the longitudinal direction of the rectangular opening,
a joint portion where the sealing plate is joined to the case body is present along the periphery of the opening,
At least a portion of the joint is covered with a protective member,
wherein the protective member is disposed from a surface of the sealing plate to a position reaching the first side wall while covering the joint portion ,
the protective member includes a second protective portion disposed in a central region obtained by dividing a long side of the rectangular first side wall into thirds, and first protective portions located on both sides of the second protective portion,
the second protection portion is disposed up to a portion closer to the bottom wall than the first protection portion in a direction from the sealing plate toward the bottom wall . 2. The energy storage device according to claim 1, wherein, when a length of the first protection portion is t1 and a length of the second protection portion is t2 in a direction from the sealing plate toward the bottom wall, a ratio of t2 to t1 (t2/t1) is 2 or more and 5 or less. 3 . The power storage device according to claim 1 , wherein the protective member is disposed on the first side wall up to a portion closer to the bottom wall than a portion where the joint portion is present in a direction from the sealing plate toward the bottom wall. The electricity storage device according to claim 1 , wherein the protective member has one or more bridge portions extending from one of the first side walls through the sealing plate to the other of the first side walls.