Energy storage devices and energy storage modules

Abstract

To provide a technology that suppresses deformation of the side wall of a power storage device case, where a gas release valve is located, when the internal pressure of the case rises. [Solution] The energy storage device 1 comprises a first metal case 10. The case 10 comprises first side walls 11a, 11b and a second side wall 12 adjacent to the first side walls 11a, 11b. The area of ​​the second side wall 12 is smaller than that of the first side walls 11a, 11b. The second side wall 12 has a gas discharge valve 17 and metal members 50a, 50b around the gas discharge valve 17. The metal members 50a, 50b include a second metal which has higher rigidity than the first metal.

Description

[Technical Field]

[0001] This disclosure relates to energy storage devices and energy storage modules. [Background technology]

[0002] An example of an energy storage device is a secondary battery, such as a lithium-ion secondary battery. In recent years, this type of energy storage device has been suitably used as a power source for vehicles such as electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs).

[0003] International Publication No. 2018 / 123578 discloses a sealing body for closing the opening of an energy storage device having an outer casing with an opening. This sealing body comprises a metal plate for closing the opening, a gas discharge valve, and a ceramic layer. The gas discharge valve is integrally formed with the metal plate and opens when the internal pressure of the energy storage device rises to a predetermined pressure. The ceramic layer is provided on the inner surface of the metal plate of the energy storage device, around the gas discharge valve. The publication states that this configuration can suppress the melting of the portion of the sealing body around the gas discharge valve in the event of an internal short circuit or the like. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2018 / 123578 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] For example, if a power storage device experiences a short circuit, gas may be generated inside the case, causing the internal pressure to rise and potentially deforming the case. In such cases, if the side wall where the gas exhaust valve is located deforms, the gas exhaust valve may not function properly when needed, which is undesirable for the safe use of the power storage device. The inventors of this invention wanted to suppress the deformation of the side wall of the case where the gas exhaust valve is located when the internal pressure of the power storage device case rises. [Means for solving the problem]

[0006] The technology disclosed herein provides an energy storage device. The energy storage device comprises a first metal case. The case comprises a first side wall and a second side wall adjacent to the first side wall. The area of ​​the second side wall is smaller than that of the first side wall. The second side wall has a gas vent valve and a metal member around the gas vent valve. The metal member includes a second metal which is more rigid than the first metal. This configuration makes it possible to suppress deformation of the side wall of the case where the gas vent valve is located when the internal pressure of the case of the energy storage device increases.

[0007] From another perspective, the technology disclosed herein provides an energy storage module. The energy storage module comprises a plurality of energy storage devices and a busbar spanning two adjacent energy storage devices among the plurality of energy storage devices. The plurality of energy storage devices include at least one energy storage device having the above configuration. With such a configuration, the energy storage module includes energy storage devices in which deformation of the side wall of the case, where a gas release valve is provided, is suppressed when the internal pressure of the case increases. This enhances the safety of using the energy storage module. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a perspective view of the energy storage device 1. [Figure 2] Figure 2 is a perspective view of the energy storage device 1. [Figure 3]Figure 3 is a cross-sectional view taken along line III-III in Figure 1. [Figure 4] Figure 4 is a schematic diagram of the electrode body 20. [Figure 5] Figure 5 is a schematic cross-sectional view of the energy storage device 1 and the cooling member 200. [Figure 6] Figure 6 is a schematic perspective view of the metal member 150. [Figure 7] Figure 7 is a plan view of the second side wall 12 in Example 2. [Figure 8] Figure 8 is a plan view of the second side wall 12 in Embodiment 3. [Modes for carrying out the invention]

[0009] An embodiment of the energy storage device disclosed herein is described below. The embodiment described herein is not limited to the technology disclosed herein. Unless otherwise specified, the technology disclosed herein is not limited to the embodiment described herein. The drawings are schematic and do not necessarily reflect the actual objects. Components and parts that perform the same function are appropriately denoted by the same reference numerals, and redundant explanations may be omitted. The reference numerals "X", "Y", and "Z" in the drawings indicate the "first direction", "second direction", and "third direction" in this specification, respectively. The reference numerals "X1", "X2", "Y1", "Y2", "Z1", and "Z2" in the drawings indicate the orientation in the drawings. However, these directions are defined for the convenience of explanation and do not limit the installation method of the energy storage device in any way. The notation "A~B" indicating a numerical range means "A or more and B or less" unless otherwise specified, and also includes the meaning of "greater than A and less than B".

[0010] As used herein, the "electric energy storage device" refers to a device in which charge carriers move between a pair of electrodes (a positive electrode and a negative electrode) through an electrolyte to cause charge charging and discharging. Electric energy storage devices include secondary batteries such as lithium-ion secondary batteries, nickel-metal hydride batteries, and nickel-cadmium batteries; capacitors such as lithium-ion capacitors and electric double layer capacitors. The electric energy storage device may be, for example, a lithium-ion secondary battery.

[0011] Figures 1 and 2 are perspective views of the electric energy storage device 1. In Figure 1, the electric energy storage device 1 is shown with the Z1 side as the upper side in the drawing. In Figure 1, the third side wall 13 of the electric energy storage device 1 is arranged on the upper side in the drawing. In Figure 2, the electric energy storage device 1 is shown with the Z2 side as the upper side in the drawing. In Figure 2, the second side wall 12 of the electric energy storage device 1 is arranged on the upper side in the drawing. Figure 3 is a cross-sectional view taken along line III-III of Figure 1. Figure 3 shows the cross-sectional structure of the electric energy storage device 1 when one of the first side walls 11a is arranged in the front.

[0012] As shown in Figures 1 to 3, the electric energy storage device 1 includes a case 10, an electrode body 20, a positive electrode terminal 30, a negative electrode terminal 40, various insulating members, and an electrolytic solution (not shown). Here, the electric energy storage device 1 is a lithium-ion secondary battery.

[0013] As shown in FIGS. 1 and 2, the case 10 has a rectangular parallelepiped shape. In this embodiment, the case 10 has first side walls 11a, 11b, a second side wall 12, a third side wall 13, and fourth side walls 14a, 14b. The first side walls 11a, 11b, the second side wall 12, the third side wall 13, and the fourth side walls 14a, 14b are all rectangular. The first side walls 11a, 11b face each other and have the largest area in the case 10. The first side walls 11a, 11b extend from the long sides 12a1, 12a2 of the second side wall 12. Here, the second side wall 12 constitutes the bottom surface of the case 10. The third side wall 13 faces the second side wall 12 here and constitutes the upper surface of the case 10. The fourth side walls 14a, 14b face each other and extend from the short sides 12b1, 12b2 of the second side wall 12. In this embodiment, the fourth side walls 14a, 14b are surrounded by the first side walls 11a, 11b, the second side wall 12, and the third side wall 13.

[0014] As shown in FIGS. 1 and 2, the case 10 includes a case body 10A, a first sealing plate 10B, and a second sealing plate 10C. The case body 10A is, for example, in the shape of a square tube and has first side walls 11a, 11b and a second side wall 12 and a third side wall 13. In this embodiment, in the case body 10A, the portion surrounded by the first side walls 11a, 11b, the second side wall 12, and the third side wall 13 is an opening. As shown in FIG. 3, the power storage device 1 has two openings 15.

[0015] The case body 10A can be manufactured, for example, by bending a single metal plate to form a cylindrical shape and joining the joint (for example, by welding). Therefore, as shown in Figure 1, the case body 10A has a joint portion 16 extending along the first direction X in the third side wall 13. The case body 10A is made of a first metal. The first metal may be, for example, aluminum, an aluminum alloy, a plywood made of aluminum and at least one of copper and aluminum alloys, iron, an iron alloy (stainless steel, etc.), an iron alloy (stainless steel, etc.), an iron alloy (stainless steel, etc.), aluminum, copper, and an aluminum alloy.

[0016] As shown in Figure 2, the case body 10A has a gas discharge valve 17 and metal members 50a and 50b on the second side wall 12. The gas discharge valve 17 is a thin-walled portion designed to rupture and release internal pressure when the internal pressure of the case 10 reaches a predetermined value. In Figure 2, the gas discharge valve 17 is cross-shaped. The shape of the gas discharge valve 17 is not particularly limited and can be set as appropriate.

[0017] In this embodiment, the metal members 50a and 50b are arranged on the outside of the case body 10A. Here, the metal members 50a and 50b are plate-shaped. Here, the metal members 50a and 50b include a second metal. The metal members 50a and 50b may be the second metal, or they may be a clad material including the second metal. Such a clad material may be, for example, a clad material of the second metal and another metal different from the second metal. The second metal is a metal with higher rigidity than the first metal. The rigidity of the metal may be defined here by the Young's modulus measured in accordance with JIS K 7161. The larger the Young's modulus, the higher the rigidity of the metal. The second metal may be, for example, copper, copper alloy, iron, iron alloy (stainless steel, etc.). The other metal is not limited as long as the effects of the technology disclosed herein are realized, but may be, for example, the first metal.

[0018] In this embodiment, the metal members 50a and 50b are joined to the second side wall 12. The metal members 50a and 50b and the second side wall 12 can be joined using, for example, ultrasonic welding, laser welding, resistance welding, etc. Alternatively, the metal members 50a and 50b and the second side wall 12 may be joined using a conductive paste containing metal powder and a binder resin (epoxy resin, acrylic resin, urethane resin, silicone resin, etc.). In this case, the metal powder may include, for example, a first metal, a second metal, silver, nickel, gold-plated metal, palladium, etc.

[0019] The total area of ​​the metal members 50a and 50b relative to the second side wall 12 is, for example, 50% or more, preferably 60% or more, more preferably 70% or more, even more preferably 80%, particularly preferably 90% or more, or 98%, but may be 95% or less, assuming the area of ​​the second side wall 12 is 100%. The total area of ​​the metal members 50a and 50b relative to the second side wall 12 referred to here is the sum of the areas of the contact portions of the metal members 50a and 50b with the second side wall 12.

[0020] The first sealing plate 10B is, for example, a member that seals one of the openings 15. The first sealing plate 10B is, for example, a substantially rectangular plate-shaped member. In this embodiment, the first sealing plate 10B is fitted into one of the openings 15 and joined by welding (for example, laser welding). As shown in Figures 1 and 3, a positive terminal 30 is attached to the first sealing plate 10B.

[0021] In this embodiment, the first sealing plate 10B has an electrolyte injection section 19. The electrolyte injection section 19 has an electrolyte injection hole 19A and a sealing plug 19B. The electrolyte injection hole 19A is, in this case, the part where electrolyte is injected into the case 10 during the manufacturing process of the energy storage device 1. In this embodiment, the electrolyte injection hole 19A is provided on the first sealing plate 10B close to the third side wall 13. The sealing plug 19B is, in this case, a member that closes the electrolyte injection hole 19A. In this embodiment, the first sealing plate 10B constitutes the fourth side wall 14a.

[0022] The second sealing plate 10C is, for example, a member that seals the other opening 15. The second sealing plate 10C is, for example, a substantially rectangular plate-shaped member. In this embodiment, the second sealing plate 10C is fitted into the other opening 15 and joined by welding (for example, laser welding). As shown in Figures 2 and 3, a negative electrode terminal 40 is attached to the second sealing plate 10C. In this embodiment, the second sealing plate 10C constitutes the fourth side wall 14b.

[0023] The first sealing plate 10B and the second sealing plate 10C are, for example, both made of the same metal material as the metal material that constitutes the case body 10A. Preferably, the first sealing plate 10B and the second sealing plate 10C are made of the first metal.

[0024] The electrode body 20 is a power generation element in the energy storage device 1. As shown in Figure 3, the electrode body 20 is housed in the case 10. Figure 4 is a schematic diagram of the electrode body 20. As shown in Figure 4, the electrode body 20 includes a positive electrode 22, a negative electrode 24, and a separator 26. The electrode body 20 is a wound electrode body formed by stacking a long sheet-like positive electrode 22 and a long sheet-like negative electrode 24 with a long sheet-like separator 26 interposed between them, and winding them in the longitudinal direction. As shown in Figure 3, the electrode body 20 comprises a main body portion 20a, a group of positive electrode tabs 23, and a group of negative electrode tabs 25. The main body portion 20a is the portion in which the positive electrode 22, the negative electrode 24, and the separator 26 are stacked, and is, for example, flattened in shape.

[0025] In this embodiment, the electrode body 20 is positioned inside the case 10 with the winding axis WL parallel to the first direction X (see Figures 1, 3, and 4). In this embodiment, the electrode body 20 is positioned inside the case 10 with the winding axis WL parallel to the second side wall 12 and perpendicular to the first side walls 11a and 11b. The end face of the electrode body 20 in the direction along the winding axis WL faces either the first sealing plate 10B or the second sealing plate 10C. For convenience of explanation, in this specification, the end face of the electrode body 20 (main body portion 20a) facing the first sealing plate 10B is referred to as the "first end face 201". The end face of the electrode body 20 (main body portion 20a) facing the second sealing plate 10C is referred to as the "second end face 202".

[0026] The positive electrode 22 comprises a long, strip-shaped positive electrode current collector foil 22c (e.g., aluminum foil) and a positive electrode active material layer 22a fixed to at least one surface of the positive electrode current collector foil 22c. Although not particularly limited, a protective layer 22p may be provided on one side edge in the short direction of the positive electrode 22, if necessary.

[0027] The positive electrode active material layer 22a is a layer containing a positive electrode active material. Examples of positive electrode active materials include lithium transition metal composite oxides, such as lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel manganese composite oxide, and lithium nickel cobalt composite oxide. From the viewpoint of increasing the capacity of the energy storage device 1, it is preferable that the positive electrode active material is a composite oxide containing Ni and Li, wherein the Ni content in the composite oxide is in the range of 70 mol% to 100 mol% relative to the total number of moles of constituent elements excluding Li and oxygen in the composite oxide.

[0028] A composite oxide containing Ni and Li is, for example, LiNi x Co y Al z It is best to represent it using the general formula for O2, with x = 70% to 98%, y = 1% to 15%, and z = 1% to 15%, such that x + y + z = 100. A composite oxide containing Ni and Li, or LiNi x Coy Mn z It can be represented by the general formula for O2, and may be configured such that x + y + z = 100 in the range of x = 70% to 98%, y = 1% to 15%, and z = 1% to 15%. The positive electrode active material may include those in which some of Ni, Co, and Mn are substituted with Al, Ti, P, B, Si, Nb, C, etc., or those in which the surface of the positive electrode active material particles is covered with a compound containing Al, Ti, P, B, Si, Nb, C, etc. The total amount of substitution and addition should be approximately 0.1% to 7%.

[0029] The positive electrode active material layer 22a may contain, in addition to the positive electrode active material, a binder, a conductive material, etc. Examples of binders include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF); polyacrylonitrile (PAN); polyimide; acrylic resin; polyolefin; etc. These may be used individually or in combination of two or more types. Examples of conductive materials include carbon materials such as carbon black, acetylene black, Ketjen black, and graphite. These may be used individually or in combination of two or more types. The content of the binder or conductive material in the positive electrode active material layer 22a is, for example, 0.1% to 5% by mass, and preferably 0.5% to 1.5% by mass. The density of the positive electrode active material layer 22a is, for example, 3 g / cm³. 3 The above is preferable, and preferably 3.5 g / cm³. 3 That's all.

[0030] Multiple positive electrode tabs 22t are provided at one end of the positive electrode current collector foil 22c in the short direction. Each of the multiple positive electrode tabs 22t protrudes toward one side in the short direction. The multiple positive electrode tabs 22t are provided at intervals (intermittently) along the longitudinal direction of the positive electrode 22. The positive electrode tabs 22t are part of the positive electrode current collector foil 22c and are exposed portions of the current collector foil where neither the positive electrode active material layer 22a nor the protective layer 22p of the positive electrode current collector foil 22c is formed. In this embodiment, the multiple positive electrode tabs 22t protrude outward from the separator 26. The multiple positive electrode tabs 22t are stacked to form a group of positive electrode tabs 23 (see Figure 3).

[0031] The negative electrode 24 has a long strip-shaped negative electrode current collector foil 24c (for example, a copper foil) and a negative electrode active material layer 24a fixed on at least one surface of the negative electrode current collector foil 24c.

[0032] The negative electrode active material layer 24a is a layer containing a negative electrode active material. Examples of the negative electrode active material include carbon materials such as artificial graphite, natural graphite, amorphous coated graphite, amorphous carbon (low-crystalline carbon, amorphous carbon, for example, furnace black, ketjen black, channel black, thermal black, acetylene black, carbon nanotubes, graphene); non-carbon materials such as Si, SiO, SiC, Sn; mixtures of carbon materials and non-carbon materials; and the like. Although not particularly limited, when a mixture of a carbon material and SiO is used as the negative electrode active material, the amount of SiO is preferably, for example, 4% to 70% by mass with respect to the total amount (100% by mass) of the mixture. SiO may contain Li in advance. In this case, the ratio of Si in the Li-Si-O compound is preferably 10% to 80% by mass. It is preferable that the surface of the SiO particles is covered with amorphous carbon (low-crystalline carbon, amorphous carbon, etc.).

[0033] The negative electrode active material layer 24a may contain a binder or the like in addition to the negative electrode active material. The binder may be the same binder as that contained in the positive electrode active material layer 22a, and carboxymethyl cellulose (CMC) or its salt, styrene-butadiene rubber (SBR), polyacrylic acid (PAA) or its salt, polyvinyl alcohol (PVA), etc. may be used. These may be used alone or in combination of two or more. The content of the binder in the negative electrode active material layer 24a is, for example, 0.1% to 5% by mass, and preferably 0.5% to 1.5% by mass. The density of the negative electrode active material layer 24a is, for example, 3 g / cm 3 or more, and preferably 3.5 g / cm 3 or more.

[0034] Multiple negative electrode tabs 24t are provided at one end of the negative electrode current collector foil 24c in the short direction. The multiple negative electrode tabs 24t protrude toward one side in the short direction. The multiple negative electrode tabs 24t are provided at intervals (intermittently) along the longitudinal direction of the negative electrode 24. The negative electrode tabs 24t are, in this embodiment, part of the negative electrode current collector foil 24c and are the exposed portion of the current collector foil where the negative electrode active material layer 24a of the negative electrode current collector foil 24c is not formed. In this embodiment, the negative electrode tabs 24t protrude outward from the separator 26. The multiple negative electrode tabs 24t are stacked to form a group of negative electrode tabs 25 (see Figure 3).

[0035] The separator 26 includes, for example, a porous sheet as a base material and a heat-resistant layer provided on the surface of the base material. The base material preferably has, for example, ion permeability and insulating properties. Examples of base materials include microporous thin films, woven fabrics, nonwoven fabrics, etc. The materials constituting the base material may be, for example, polyolefins such as polyethylene (PE) and polypropylene (PP); cellulose; etc. The base material may be, for example, a laminate having a PE layer only, or a laminate structure of PP layer / PE layer / PP layer. The thickness of the base material is preferably, for example, 5 μm to 30 μm. If the base material is the laminate described above, the PP layer may have a thickness of 1 μm to 10 μm, and the PE layer may have a thickness of 2 μm to 10 μm.

[0036] The heat-resistant layer may be provided on one or both sides of the substrate. The heat-resistant layer contains a filler and a binder. Examples of fillers include boehmite, alumina, titania (rutile type or anatase type; in the case of anatase type, the heat-resistant layer should be positioned so as not to contact the negative electrode), zirconia, magnesia, aluminum hydroxide, magnesium hydroxide, zinc hydroxide, etc. Examples of binders include PVDF, acrylic resin, aramid, SBR, PTFE, etc. The binder content is, for example, 2% to 40% by mass relative to the total amount of the heat-resistant layer (100% by mass). The thickness of the heat-resistant layer is, for example, 2 μm to 12 μm. Although not particularly limited, if necessary, an adhesive may be applied to the surface of the heat-resistant layer in dots, lines, etc., from the viewpoint of improving the adhesion between the electrode and the separator 26. Note that the inclusion of the heat-resistant layer in the separator 26 is not mandatory and may be omitted if necessary.

[0037] The electrolyte comprises a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. The non-aqueous solvent may be, for example, esters; ethers; nitriles such as acetonitrile; amides such as dimethylformamide; etc., or a mixture of two or more of these. The non-aqueous solvent may also contain halogen-substituted solvents in which at least some of the hydrogen atoms of the solvent are replaced by halogen atoms such as fluorine. Examples of esters include cyclic carbonate esters such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate; linear carbonate esters such as ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), methyl propyl carbonate, ethyl propyl carbonate, and methyl isopropyl carbonate; cyclic carboxylic acid esters such as γ-butyrolactone (GBL) and γ-valerolactone (GVL); and linear carboxylic acid esters such as methyl acetate, ethyl acetate, propyl acetate, methyl propionate (MP), ethyl propionate, and γ-butyrolactone. Ethers include cyclic ethers such as 1,3-dioxolane, 4-methyl-1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, propylene oxide, 1,2-butylene oxide, 1,3-dioxane, 1,4-dioxane, 1,3,5-trioxane, furan, 2-methylfuran, 1,8-cineole, and crown ethers; 1,2-dimethoxyethane, diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, dihexyl ether, ethyl vinyl ether, butyl vinyl ether, and methylphenyl ether. Examples include chain-like ethers such as ethylphenyl ether, butylphenyl ether, pentylphenyl ether, methoxytoluene, benzyl ethyl ether, diphenyl ether, dibenzyl ether, o-dimethoxybenzene, 1,2-diethoxyethane, 1,2-dibutoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, 1,1-dimethoxymethane, 1,1-diethoxyethane, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.Examples of halogen-substituted compounds include fluorinated cyclic carbonate esters such as fluoroethylene carbonate (FEC); fluorinated linear carbonate esters, fluorinated linear carboxylic acid esters such as methyl fluoropropionate (FMP); and the like.

[0038] The electrolyte salt may be, for example, a lithium salt. Examples of lithium salts include LiBF4, LiClO4, LiPF6, LiAsF6, LiSbF6, LiAlCl4, LiSCN, LiCF3SO3, LiCF3CO2, Li(P(C2O4)F4), and LiPF 6-x (C n F 2n+1 ) x (1 <x<6,nは1または2)、LiB 10 Cl 10 , LiCl, LiBr, LiI, lithium chloroborane, lithium lower aliphatic carboxylate, borates such as Li2B4O7, Li(B(C2O4)F2), LiN(SO2CF3)2, LiN(C m F 2m+1 SO2)(C n F 2n+1 Examples include imide salts such as SO2){m,n are integers greater than or equal to 0}. From the viewpoint of ionic conductivity and electrochemical stability, LiPF6, lithium bis(fluorosulfonyl)imide (LiFSI), etc., can be preferably used. The concentration of the lithium salt is preferably 0.6 mol to 1.8 mol per liter, when ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) are mixed as non-aqueous solvents in a range of 1% to 99% each, so that the total ratio is 100%.

[0039] The positive electrode terminal 30 is electrically connected to the positive electrode 22 (see Figure 4) of the electrode body 20. As shown in Figures 1 and 3, the positive electrode terminal 30 is mounted on the first sealing plate 10B. As shown in Figure 3, the positive electrode terminal 30 has a first portion 31 located on the outside of the case 10 and a second portion 32 located on the inside of the case 10. The second portion 32 is electrically connected to the group of positive electrode tabs 23. The positive electrode terminal 30 is made of metal, preferably aluminum or an aluminum alloy.

[0040] The negative electrode terminal 40 is electrically connected to the negative electrode 24 (see Figure 4) of the electrode body 20. As shown in Figures 2 and 3, the negative electrode terminal 40 is attached to the second sealing plate 10C. As shown in Figure 3, the negative electrode terminal 40 has a first portion 41 located on the outside of the case 10 and a second portion 42 located on the inside of the case 10. The second portion 42 is electrically connected to the negative electrode tab group 25. The negative electrode terminal 40 is made of metal, preferably copper or a copper alloy.

[0041] Various insulating members include, for example, spacers 60a, 60b, and a resin film (not shown). As shown in Figure 3, spacers 60a and 60b are positioned between the case 10 and the electrode body 20. In the configuration shown in Figure 3, spacer 60a is positioned between the case 10 and the first end face 201 of the electrode body 20. Spacer 60b is positioned between the case 10 and the second end face 202 of the electrode body 20. Spacers 60a and 60b may be made of, for example, an insulating resin (e.g., polyamide resin) that has been conventionally used in this type of energy storage device. The resin film insulates between the case 10 and the electrode body 20. Here, the resin film is cylindrical and houses the electrode body 20 inside. The resin material constituting the resin film is not particularly limited and may be, for example, a polyolefin such as polyethylene or polypropylene. Various insulating members other than those exemplified here may include insulating members that have been conventionally used in this type of energy storage device.

[0042] The energy storage device 1 can be used for various purposes, but it is particularly suitable for use as a power source (driving power supply) for motors mounted on vehicles such as passenger cars and trucks. The type of vehicle is not particularly limited, but preferred examples include plug-in hybrid vehicles (PHEVs), hybrid electric vehicles (HEVs), and battery electric vehicles (BEVs).

[0043] As described above, the energy storage device 1 comprises a first metal case 10. The case 10 comprises first side walls 11a, 11b and a second side wall 12 adjacent to the first side walls 11a, 11b. The area of ​​the second side wall 12 is smaller than that of the first side walls 11a, 11b. The second side wall 12 has a gas discharge valve 17 and metal members 50a, 50b around the gas discharge valve 17. The metal members 50a, 50b include a second metal which has higher rigidity than the first metal.

[0044] In other words, in the energy storage device 1, metal members 50a and 50b, which include a second metal that is more rigid than the first metal constituting the second side wall 12, are arranged around the gas discharge valve 17 in the second side wall 12. Therefore, even if the energy storage device 1 experiences an internal short circuit or the like, causing gas to be generated inside the case 10 and the internal pressure to rise, deformation of the second side wall 12 can be suppressed. This prevents the gas discharge valve 17 from malfunctioning.

[0045] The case 10 may be rectangular in shape. The case 10 may comprise a pair of opposing first side walls 11a, 11b, a second side wall 12, a third side wall 13 opposite the second side wall 12, and a pair of opposing fourth side walls 14a, 14b. The fourth side walls 14a, 14b may be side walls surrounded by the pair of opposing first side walls 11a, 11b, the second side wall 12, and the third side wall 13. The above-described effects can preferably be realized in an energy storage device 1 equipped with a case 10 of such shape.

[0046] The energy storage device 1 may further include a positive terminal 30 and a negative terminal 40. The positive terminal 30 may be provided on one of the fourth side walls 14a. The negative terminal 40 may be provided on the other fourth side wall 14b. The above-described effects can preferably be realized in an energy storage device 1 equipped with a case 10 of such shape.

[0047] The metal members 50a and 50b may be joined to the second side wall 12. This integrates the metal members 50a and 50b with the second side wall 12, thereby further reducing the risk of deformation of the second side wall 12.

[0048] The metal members 50a and 50b may be laser-welded to the second side wall 12. This increases the joint strength between the metal members 50a and 50b and the second side wall 12. As a result, the risk of deformation of the second side wall 12 can be further reduced. In this case, the metal members 50a and 50b and / or the second side wall 12 will have weld marks.

[0049] The metal members 50a and 50b may be resistance welded to the second side wall 12. This increases the joint strength between the metal members 50a and 50b and the second side wall 12. As a result, the risk of deformation of the second side wall 12 can be further reduced. In this case, there are no weld marks on the metal members 50a and 50b and / or the second side wall 12. As a result, variations in the dimensions of the energy storage device 1 can be suppressed.

[0050] The metal members 50a and 50b may be joined to the second sidewall 12 by a conductive paste containing metal powder. This suppresses the formation of intermetallic compounds during the joining of the metal members 50a and 50b to the second sidewall 12. As a result, the formation of weak areas in the case 10 can be suppressed. In addition, since the conductive paste is conformable to both, it can buffer any deformation that occurs in the first sidewalls 11a and 11b.

[0051] The first metal may be aluminum or an aluminum alloy. The second metal may be copper or a copper alloy. This allows the effects of the technology disclosed herein to be more preferably realized. Furthermore, copper or copper alloys have higher thermal conductivity than aluminum or aluminum alloys. Therefore, when the temperature of the energy storage device 1 rises, heat is dissipated from the metal members 50a and 50b. This prevents the temperature of the energy storage device 1 from rising too high.

[0052] The energy storage device 1 may be included in, for example, an energy storage module. In this case, the energy storage module may include, for example, a plurality of energy storage devices 1 and a busbar. The plurality of energy storage devices 1 are preferably arranged so that the positive terminal 30 of one energy storage device 1 and the negative terminal of another energy storage device 1 are adjacent to each other (see Figures 1 to 3). Here, in two adjacent energy storage devices 1, the first side wall 11a of one energy storage device 1 faces the first side wall 11a of the other energy storage device 1 (see Figures 1 and 2). In two adjacent energy storage devices 1, the first side wall 11b of one energy storage device 1 faces the first side wall 11b of the other energy storage device 1 (see Figures 1 and 2). The busbar here spans two adjacent energy storage devices 1 among the plurality of energy storage devices 1. The busbar spans between the positive terminal 30 of one energy storage device 1 and the negative terminal of the other energy storage device 1 in two adjacent energy storage devices 1.

[0053] The energy storage module includes an energy storage device 1. This enhances the safety of using the energy storage module. Furthermore, the effect of enhancing the safety of using the energy storage module can be achieved if the energy storage module includes at least one energy storage device 1.

[0054] Figure 5 is a schematic cross-sectional view of the energy storage device 1 and the cooling member 200. While not particularly limited, the energy storage module may further include the cooling member 200 (see Figure 5). In this case, the cooling member 200 is plate-shaped. As shown in Figure 5, the cooling member 200 has a plate portion 210, a convex portion 220, and a plurality of recesses 230. The plate portion 210 is plate-shaped and constitutes the main body of the cooling member 200. The convex portion 220 is provided on the surface of the plate portion 210. The plan view of the convex portion 220, as seen from above the plate portion 210, may be, for example, grid-like, island-like, etc. The recesses 230 are recessed portions from the upper end surface of the convex portion 220. The cooling member 200 may be made of, for example, metal. Any metal used for cooling members in this type of application can be used as the metal constituting the cooling member 200 without particular limitation.

[0055] In this embodiment, the energy storage device 1 is placed on the cooling member 200. As shown in Figure 5, the energy storage device 1 is placed on the protrusion 220 of the cooling member 200. This allows the energy storage device 1 to be cooled, thereby increasing safety when using the energy storage module. Although not shown, the energy storage device 1 may also be placed on the cooling member 200 such that, for example, the side wall constituting the bottom of the energy storage device 1 faces the cooling member 200. In this embodiment, the second side wall 12 is placed on the cooling member 200. This allows the metal members 50a and 50b to better perform their heat dissipation function, enabling the energy storage device 1 to operate efficiently.

[0056] In the configuration shown in Figure 5, a heat transfer member 300 is positioned between the energy storage device 1 and the cooling member 200. Any heat transfer member used in this type of application can be used as the heat transfer member 300 without particular limitations. The heat transfer member 300 may be, for example, a paste containing a binder such as silicone resin, acrylic resin, or epoxy resin, and an inorganic filler such as aluminum, alumina, or silica; a heat-conductive sheet member; or a heat-conductive (heat-dissipating) adhesive. Commercially available heat-conductive sheet members and heat-conductive (heat-dissipating) adhesives may be used. By positioning the heat transfer member 300, heat dissipation from the energy storage device 1 and cooling of the energy storage device 1 can be performed more efficiently.

[0057] While embodiments of the technology disclosed herein have been described above, these embodiments are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the embodiments illustrated above.

[0058] For example, the metal members 50a and 50b may be attached to the second side wall 12 inside the case 10. Alternatively, the second side wall 12 may have through holes or recesses around the gas exhaust valve 17. The recesses are preferably recessed from the outer surface of the second side wall 12. The metal members 50a and 50b may be fitted into such through holes or recesses. The metal members 50a and 50b and the second side wall 12 may be joined at the periphery of the through holes or recesses. This configuration makes it possible to maintain a constant thickness of the second side wall 17. This makes it possible to make the arrangement of the energy storage device 1 more stable, for example.

[0059] Alternatively, the metal member may have recesses or protrusions as appropriate. Figure 6 is a schematic perspective view of the metal member 150. As shown in Figure 6, the metal member 150 has a first surface 151 and a second surface 152. The first surface 151 is located, for example, on the second side wall 12 side of the case 10. In the embodiment shown in Figure 6, the first surface 151 is a flat surface with no irregularities. The second surface 152 is the surface opposite to the first surface 151. In this embodiment, the metal member 150 has a plurality of recesses 150r that are recessed from the second surface 152. The number, shape, etc. of the recesses 150r are not particularly limited and can be appropriately set, for example, according to the size, material, etc. of the metal member 150r. Although not particularly limited, for example, conductive paste (or its cured product) may be placed inside the recesses 150r from the viewpoint of improving heat dissipation from the case 10.

[0060] The following describes test examples related to the technology disclosed herein. However, there is no intention to limit the technology disclosed herein to the following test examples. Please refer to the drawings as appropriate for reference numerals used in the description of the following test examples.

[0061] <Preparing the test cells> -Example 1- A test cell for this example was prepared. The test cell consisted of an electrode body 20 which was a wound electrode body, a non-aqueous electrolyte, and a rectangular case 10 that housed the electrode body 20 and the non-aqueous electrolyte (see Figures 1 to 4). A gas discharge valve 17 was provided in the center of the second side wall 12 of the case 10. The case 10 was made of aluminum. The thickness of the second side wall 12 was 0.7 mm.

[0062] In preparing the test cell, metal members 50a and 50b were attached to case 10. Rectangular flat metal members 50a and 50b were prepared. Metal members 50a and 50b were made of copper. The total area of ​​metal members 50a and 50b was 60% of the area of ​​the second side wall 12. Metal members 50a and 50b were positioned on the second side wall 12 of case 10 so as to symmetrically sandwich the gas exhaust valve 17. Then, metal members 50a and 50b were resistance welded to the second side wall 12. The thickness of metal members 50a and 50b was 0.7 mm each.

[0063] -Example 2- Figure 7 is a plan view of the second side wall 12 in Example 2. As shown in Figure 7, in this example, a gas exhaust valve 217 was provided on the second side wall 12. The position of the gas exhaust valve 217 was closer to one of the shorter sides of the second side wall 12 than to the center of the longer side. Metal members 250a and 250b were attached to the second side wall 12. Here, elliptical flat metal members 250a and 250b of different sizes were prepared. The total area of ​​metal members 250a and 250b was 70% of the area of ​​the second side wall 12. In the second side wall 12 of case 10, the metal members 250a and 250b were positioned so as to sandwich the gas exhaust valve 217. Then, the metal members 250a and 250b were resistance welded to the second side wall 12. The thickness of the metal members 250a and 250b was 0.7 mm each. Otherwise, the test cells for this example were prepared in the same manner as in Example 1.

[0064] -Example 3- Figure 8 is a plan view of the second side wall 12 in Example 3. As shown in Figure 8, a metal member 350 was attached to the second side wall 12. In this example, a rectangular flat metal member 350 was prepared. The metal member 350 had a through hole 350h in the portion that overlapped with the gas exhaust valve 17 when superimposed on the second side wall 12, and was large enough to allow the gas exhaust valve 17 to be exposed to the outside. The area of ​​the metal member 350 (excluding the through hole 350h) was 95% of the area of ​​the second side wall 12. In the second side wall 12 of case 10, the metal member 350 was positioned so that the gas exhaust valve 17 was placed within the through hole 350h. The metal member 350 was then resistance welded to the second side wall 12. The thickness of the metal member 350 was 1 mm. Otherwise, the test cell for this example was prepared in the same manner as in Example 1.

[0065] -Example 4- In this example, a gas discharge valve 17 was provided on the third side wall 13 in addition to the second side wall 12. Metal members 50a and 50b were attached to the second side wall 12 and the third side wall 13, respectively. Otherwise, the test cell for this example was prepared in the same manner as in Example 1.

[0066] -Example 5- In this example, metal members 50a and 50b were ultrasonically bonded to the second side wall 12. Otherwise, the test cell for this example was prepared in the same manner as in Example 1.

[0067] -Example 6- In this example, metal members 50a and 50b made of copper alloy (Cu80Zn20 (wt%)) were prepared. Metal members 50a and 50b were laser-welded to the second side wall 12. Otherwise, the test cell for this example was prepared in the same manner as in Example 1.

[0068] -Example 7- In this example, instead of metal members 50a and 50b, a metal member 150, as shown in Figure 6, was prepared. Metal member 150 was made of a copper alloy (Cu92Al8 (wt%)). Otherwise, the test cell for this example was prepared in the same manner as in Example 6.

[0069] -Example 8- In this example, iron metal members 50a and 50b were prepared. Otherwise, the test cell for this example was prepared in the same manner as in Example 6.

[0070] -Example 9- In this example, metal components 50a and 50b made of iron alloy (stainless steel) were prepared. Otherwise, the test cell for this example was prepared in the same manner as in Example 6.

[0071] -Example 10- In this example, metal members 50a and 50b were bonded to the second side wall 12 using a conductive paste. Otherwise, the test cell for this example was prepared in the same manner as in Example 1. ThreeBond's adhesive "3303B" was used as the conductive paste.

[0072] -Example 11- In this example, metal members 50a and 50b, which are clad materials of copper and aluminum, were prepared. The thickness of the metal members 50a and 50b was the same as the thickness of the second side wall 12. The metal members 50a and 50b were laser-welded to the second side wall 12. At this time, the aluminum portion of the metal members 50a and 50b was positioned so that it faced the second side wall 12. Otherwise, the test cell for this example was prepared in the same manner as in Example 1.

[0073] -Comparative Example- In this example, metal members 50a and 50b were not attached to the second side wall 12. Otherwise, the test cell for this example was prepared in the same manner as in Example 1.

[0074] <Safety Evaluation> Each test cell was discharged (SOC 0%) and then confined to a constant pressure range of 0.1 MPa to 1 MPa using a 5 cm thick aluminum metal block with thermal insulation material in between, from the pair of first side walls 11a and 11b. After that, each test cell was charged to SOC 100%, and a nail-piercing test was performed. In the nail-piercing test, a nail was driven through a hole in the center of the metal block to forcibly short-circuit the test cell and raise its temperature. The test temperature was room temperature (approximately 25°C). The nail used was a round nail SIZE: N65 (Φ3 mm / shape not specified). The nail-piercing speed was 1 mm / s, and the test was stopped when the test cell overheated.

[0075] The morphological changes of each test cell after overheating were evaluated using five ranks, from rank 1 to rank 5. The morphological changes of the battery in each rank are shown below. The results are shown in the corresponding column of Table 1. Note that a lower rank indicates a better result (a result indicating higher safety of the test cell). The residual weight percentage (%) is the ratio of the weight of the test cell after the nail-piercing test to the weight of the test cell before the nail-piercing test. The smaller the residual weight percentage, the more of the contents such as gas that have overheated have been released to the outside of the cell, so the pressure inside the cell does not rise as much, and the deformation (bulging) of the second side wall of the case is small. As a result, more heat can be dissipated from the second side wall (because the contact area with the outside is large). Thus, because the residual weight percentage is small and the heat dissipation is good, the amount of residual heat in the cell is small. Therefore, the amount of heat transferred to adjacent cells due to heat chain is also small, fire spread is suppressed, and it can be seen that this is a good result with high safety.

[0076] • Rank 1 Except for the opening of the gas discharge valve, there is almost no deformation of the case, and the remaining weight ratio is 35% or less. Here, "almost no deformation of the case" means that the degree of bulging (expansion) on the second side wall of the case is less than 1 mm. Rank 2 The gas discharge valve opens, the second side wall of the case bulges by 1mm to 2mm, and the remaining weight percentage is 35% to 40%. • Rank 3 The gas discharge valve is open, the second side wall of the case bulges by more than 2 mm but less than or equal to 3 mm, and the remaining weight ratio is 40% to 45%. • Rank 4 The gas discharge valve is open, the second side wall of the case bulges by more than 3 mm but less than or equal to 5 mm, and the remaining weight percentage is 45% to 50%. • Rank 5 The gas discharge valve is open, the second side wall of the case is bulging by more than 5 mm, and the remaining weight percentage is 50% or more.

[0077] Regarding the residual weight ratio, the inventors consider the following: For example, when assembling an energy storage module using rectangular cells, several to several dozen rectangular cells are arranged in a row with their long sides facing each other, with insulating material or the like in between each cell. If one of these cells (the trigger cell) generates heat due to an internal short circuit caused by foreign matter, and falls into an overheating state, a heat chain reaction occurs to the adjacent cell, and the adjacent cell is heated. When the temperature of the adjacent cell exceeds a certain level, it begins to generate its own heat and eventually overheats. At this time, the heat generation behavior of the adjacent cell changes depending on how much heat is transferred from the trigger cell to the adjacent cell. For example, if the trigger cell overheats and a large amount of its contents, such as gas, is released to the outside of the cell, the pressure inside the cell does not rise so much, and the deformation (bulging) of the second side wall of the case is small. As a result, because the contact area with the outside is large, a lot of heat can be dissipated from the second side wall. Furthermore, because the trigger cell has less contents (low residual weight percentage), the amount of heat remaining in the cell (residual heat) is small. As a result, less heat is transferred to adjacent cells via heat chain, causing the temperature rise of adjacent cells to be slower, and it takes longer for adjacent cells to overheat. In other words, from a module perspective, overheating due to heat chain is less likely to occur, potentially increasing safety. On the other hand, if the trigger cell overheats and little contents are discharged from the gas exhaust valve (high residual weight percentage), much of the contents, such as the overheated gas, remains in the cell, increasing the pressure inside the cell and causing greater deformation (bulging) of the second side wall of the case. As a result, the contact area with the outside becomes smaller, reducing heat dissipation from the second side wall. Moreover, because the trigger cell also has a large amount of contents (high residual weight percentage), the amount of heat remaining in the cell (residual heat) is large. As a result, the amount of heat transferred to adjacent cells via heat chain is also large. Consequently, the time it takes for adjacent cells to overheat may also be shortened. In other words, as a module, the overheating of cells due to heat chain reactions becomes more likely, potentially reducing safety. Therefore, the smaller the remaining weight percentage (lower heat) of a cell that overheats, the higher the safety.

[0078] [Table 1]

[0079] As shown in Table 1, by comparing Examples 1 to 11 with the comparative example, it was found that deformation of the second side wall of the case can be suppressed by providing a metal member containing a second metal with higher rigidity than the first metal constituting the case, around the gas exhaust valve.

[0080] The technologies disclosed herein may include the embodiments described in the following sections. Section 1: A first energy storage device comprising a metal case, The aforementioned case is, The first side wall and, A second side wall adjacent to the first side wall, having a smaller area than the first side wall. It is equipped with, The second side wall is, Gas exhaust valve, A metal member including a second metal which has higher rigidity than the first metal is placed around the gas discharge valve. It has, Energy storage device. Section 2: The aforementioned case is, It has a rectangular prism shape, A pair of opposing first side walls, The second side wall and, A third side wall opposite the second side wall, A pair of opposing first side walls, a pair of opposing fourth side walls surrounded by the second side wall and the third side wall, It is equipped with The energy storage device described in item 1. Section 3: It further includes a positive terminal and a negative terminal, The positive terminal is provided on one of the fourth side walls, The negative terminal is provided on the other fourth side wall. A power storage device as described in item 1 or 2. Section 4: The metal member is joined to the second side wall. A power storage device as described in any one of items 1 to 3. Section 5: The metal member is laser-welded to the second side wall. A power storage device as described in any one of items 1 to 4. Item 6: The metal member is resistance-welded to the second side wall. A power storage device as described in any one of items 1 to 4. Section 7: The metal member is bonded to the second side wall by a conductive paste containing metal powder. A power storage device as described in any one of items 1 to 4. Section 8: The second side wall has through holes or recesses around the gas discharge valve, The metal member is fitted into the through hole or the recess. A power storage device as described in any one of items 1 to 7. Section 9: The first metal is aluminum or an aluminum alloy. The second metal is copper or a copper alloy. A power storage device as described in any one of items 1 to 8. Section 10: Multiple energy storage devices, A busbar spanning two adjacent energy storage devices among the aforementioned plurality of energy storage devices, Equipped with, The plurality of energy storage devices include at least one of the energy storage devices described in any one of items 1 to 9. Energy storage module. Section 11: Further equipped with cooling components, The plurality of energy storage devices are mounted on the cooling member. The energy storage module described in item 10. [Explanation of Symbols]

[0081] 1. Energy storage device 10 cases 11a,11b 1st side wall 12. Second side wall 13 Third side wall 14a,14b 4th side wall 17 Gas discharge valve 20 Electrode body 30 Positive terminal 40 Negative terminal 50a, 50b Metal components

Claims

1. A first energy storage device comprising a metal case, The aforementioned case is, The first side wall and, A second side wall adjacent to the first side wall, having a smaller area than the first side wall. It is equipped with, The second side wall is Gas exhaust valve, A metal member including a second metal which has higher rigidity than the first metal is placed around the gas discharge valve. It has, Energy storage device.

2. The aforementioned case is, It has a rectangular prism shape, A pair of opposing first side walls, The second side wall and, A third side wall opposite the second side wall, A pair of opposing first side walls, a pair of opposing fourth side walls surrounded by the second side wall and the third side wall, It is equipped with The energy storage device according to claim 1.

3. It further includes a positive terminal and a negative terminal, The positive terminal is provided on one of the fourth side walls, The negative terminal is provided on the other fourth side wall. The energy storage device according to claim 2.

4. The metal member is joined to the second side wall. The energy storage device according to claim 1.

5. The metal member is laser-welded to the second side wall. The energy storage device according to claim 4.

6. The metal member is resistance-welded to the second side wall. The energy storage device according to claim 4.

7. The energy storage device according to claim 4, wherein the metal member is bonded to the second side wall by a conductive paste containing metal powder.

8. The second side wall has through holes or recesses around the gas discharge valve, The metal member is fitted into the through hole or the recess. The energy storage device according to claim 1.

9. The first metal is aluminum or an aluminum alloy. The second metal is copper or a copper alloy. The energy storage device according to claim 1.

10. Multiple energy storage devices, A busbar spanning two adjacent energy storage devices among the aforementioned plurality of energy storage devices, Equipped with, The plurality of energy storage devices include at least one of the energy storage devices described in any one of claims 1 to 9. Energy storage module.

11. Further equipped with cooling components, The plurality of energy storage devices are mounted on the cooling member. The energy storage module according to claim 10.

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