Power storage device

Abstract

To provide a power storage device having a safety valve part that is a temperature-opening safety valve part that is softened or melted by heat to open the valve and that suppresses an occurrence of deformation due to creep and permeation of gas or water vapor.SOLUTION: A power storage device 1 includes a metal case 4 having a safety valve part 6s1. Each of safety valve parts 6s1, 116s1, 126s1, 136s1 includes a hole peripheral edge part 6hp that forms a valve hole 6h penetrating the case, and valve members 12, 112, 122, and 132 that hermetically seal a valve hole. The valve member includes metal sealing plates 13, 113, and 133, and annular resin valve members 14, 114, 124, and 134 which are made of a thermoplastic resin material and hermetically seal between plate peripheral edge portions 13p, 113p, and 133p of the metal sealing plates and the hole peripheral edge part of the case, and is a first safety valve part of a temperature opening type which is opened by softening or melting of each resin valve member by heat.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an electricity storage device including a metal case having a safety valve portion. [Background technology]

[0002] Secondary batteries (hereinafter simply referred to as batteries) such as lithium-ion secondary batteries that house an electrode assembly in a metal case are typically provided with a safety valve for the case. This is to allow gas to be released to the outside of the case to reduce the internal pressure of the case in the event that the battery collapses due to an accident or other reason, causing an internal short circuit in the housed electrode assembly, resulting in abnormal heat generation and gas being generated inside the case.

[0003] An example of a battery equipped with such a pressure-release type safety valve is disclosed in Patent Document 1. The battery in Patent Document 1 comprises an electrode assembly housed in a rectangular box-shaped metal case. The case comprises a case body in the shape of a rectangular cylinder with a bottom and a lid body in the shape of a long, narrow rectangular plate that seals the rectangular opening of the case body. The safety valve is provided in the lid body.

[0004] Furthermore, Patent Document 2 discloses a battery that is provided with a pressure-release type safety valve and also has one or more temperature-release type safety valves in which the entire valve member is made of thermoplastic resin and the valve member is softened or melted by heat generated during a short circuit to open the valve.

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-117750 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-4917 Summary of the Invention [Problem to be solved by the invention]

[0006] During use, gas may be generated in a battery, causing the internal pressure of the case to remain higher than the external pressure (atmospheric pressure). However, in the case of the temperature-release safety valve described above, which uses a thermoplastic resin valve member, if the internal pressure of the case remains high for a long period of time, the resin valve member may deform or rupture due to creep. Furthermore, unlike metal plates, when a resin valve member is used, gas and water vapor can pass through the resin material.

[0007] The present invention has been made in consideration of these problems and findings, and provides an electricity storage device having a temperature-release type safety valve portion that opens by softening or melting with heat, while suppressing deformation due to creep and the permeation of gas and water vapor. [Means for solving the problem]

[0008] (1) One aspect of the present invention for solving the above problem is an electricity storage device including a metal case having a safety valve portion, the safety valve portion having a hole periphery forming a valve hole penetrating the case and a valve member that airtightly seals the valve hole, the valve member including a metal sealing plate and an annular resin valve member made of a thermoplastic resin material that airtightly seals the gap between the plate periphery of the metal sealing plate and the hole periphery of the case, the electricity storage device being a temperature-release type first safety valve portion that opens when the resin valve member is softened or melted by heat.

[0009] This electricity storage device has a temperature-release first safety valve portion in the case, so that in the event that the internal pressure of the case increases and the temperature of the electricity storage device becomes abnormally high due to an internal short circuit, a nail penetration test, or the like, a portion of the annular resin valve member softens or melts, opening the first safety valve portion and releasing the high-temperature gas inside to the outside, thereby reducing the internal pressure and suppressing the temperature rise of the electricity storage device.

[0010] Furthermore, this first safety valve portion is not sealed by joining a resin valve member to the periphery of the valve hole, but rather uses a metal sealing plate and an annular resin valve member surrounding the periphery as the valve member that seals the valve hole, and the annular resin valve member airtightly seals the gap between the plate periphery of the metal sealing plate and the hole periphery of the case. This allows some of the pressure in the valve member that seals the valve hole to be borne by the metal sealing plate, thereby suppressing creep that may occur in the resin valve member. Furthermore, because the amount of resin valve member used as the valve member can be reduced, the amount of gas and water vapor that permeates the resin valve member can be suppressed.

[0011] Examples of the power storage device include secondary batteries such as lithium-ion secondary batteries and sodium-ion secondary batteries, and power storage devices such as lithium-ion capacitors. In addition to rectangular power storage devices using rectangular parallelepiped cases, examples of the power storage device include cylindrical power storage devices using cylindrical cases.

[0012] To ensure airtight bonding with the resin valve member, the peripheral surface of the metal sealing plate and the peripheral surface of the valve hole in the case should be roughened along the entire circumference. Methods for roughening include surface roughening with sandpaper, anodizing, sandblasting, and laser roughening.

[0013] The thermoplastic resin for the resin valve member may be selected in consideration of softening point, melting point, strength, gas permeability, water vapor permeability, etc., and may have a melting point in the range of 100 to 200°C. Specific examples include PPS, PP, PE, PET, PVDC (polyvinylidene chloride), and PVDF (polyvinylidene fluoride).

[0014] The metal sealing plate may be flat, or may have a convex shape facing outward or inward from the case. It is also possible to use a metal sealing plate with an overall spherical shell (dome-shaped) shape, or one with a ring-shaped peripheral edge and a dome-shaped or top hat-shaped inner edge that is convex outward or inward in the thickness direction. The size of the metal sealing plate in a plan view may be smaller, equal to, or larger than the size of the valve hole in the case. When the size of the metal sealing plate is smaller than the valve hole, the peripheral edge of the metal sealing plate may be positioned within the valve hole, or may be positioned outside or inside the hole peripheral edge of the case in the thickness direction. When the size of the metal sealing plate is equal to or larger than the valve hole, the peripheral edge of the metal sealing plate may be positioned outside the hole peripheral edge of the case in the thickness direction.

[0015] (2) In the energy storage device described in (1), the metal sealing plate may be larger than the valve hole, be positioned outside the hole peripheral portion in the plate thickness direction, and cover the entire hole peripheral portion with the plate peripheral portion via the resin valve member.

[0016] The first safety valve portion of this energy storage device uses a metal sealing plate that is larger than the valve hole. This metal sealing plate is disposed outside the hole periphery in the thickness direction, and the plate periphery of the metal sealing plate covers the entire hole periphery via the resin valve member. As described above, in an energy storage device, gas may be generated during use, causing the internal pressure to remain higher than the external pressure (atmospheric pressure). However, even in this case, in the first safety valve portion of this energy storage device, stresses such as shear stress are less likely to be applied to the annular intermediate portion of the resin valve member located between the plate periphery of the metal sealing plate and the hole periphery. This is because the hole periphery is located inside this annular portion in the thickness direction. Furthermore, the aforementioned intermediate portion of the resin valve member is less likely to experience strength reduction due to creep, cracking, etc., thereby reliably maintaining airtightness between the plate periphery of the metal sealing plate and the hole periphery.

[0017] (3) In the energy storage device described in (1) or (2), the hole periphery has a ring-shaped roughened hole periphery extending in the circumferential direction of the valve hole, and has a forest of first nanopillars with a height of 50 nm or more formed around the entire circumference, which are formed by first particles originating from the hole periphery of the case being linked together in a string of beads, and the resin valve member has a thermoplastic resin material that forms the resin valve member filled between the forest of first nanopillars, and has a hole periphery that is airtightly adhered to the roughened hole periphery around the entire circumference.

[0018] In this electricity storage device, the resin valve member can be firmly and airtightly fixed to the periphery of the hole in the case.

[0019] (4) In the energy storage device described in any one of (1) to (3), the metal sealing plate has a roughened peripheral edge portion in the shape of a ring extending in the circumferential direction of the metal sealing plate, and the roughened peripheral edge portion is composed of second nanopillars, each having a height of 50 nm or more, formed by second particles originating from the metal sealing plate's peripheral edge portion and linked together in a string of beads, all around the circumference; and the resin valve member has a thermoplastic resin material filling the spaces between the second nanopillars, forming a resin valve member, and the resin valve member has a tightly sealed peripheral edge portion that is airtightly attached to the roughened peripheral edge all around the circumference.

[0020] In this electricity storage device, the resin valve member can be firmly and airtightly fixed to the peripheral edge of the metal sealing plate.

[0021] (5) The electric storage device according to any one of (1) to (4), wherein the case has, in addition to the first safety valve portion, a pressure-release type second safety valve portion that opens at a second operating pressure that is lower than a first operating pressure at which the first safety valve portion opens under the internal pressure of the case.

[0022] This electricity storage device has a second safety valve unit that is a pressure-release type and opens at a second operating pressure lower than the first operating pressure, in addition to a first safety valve unit that is a temperature-release type and operates at a first operating pressure. Therefore, if the internal pressure of the case increases due to an internal short circuit, a nail penetration test, or the like, the second safety valve unit can be opened in addition to the first safety valve unit that is a temperature-release type. [Brief explanation of the drawings]

[0023] [Figure 1] 3 is a longitudinal cross-sectional view of the battery according to the embodiment taken along line AA in FIG. 2. FIG. [Figure 2] FIG. 2 is a top view of the battery according to the embodiment. [Figure 3] 3 is a partially enlarged cross-sectional view showing the cross-sectional structure of a first safety valve portion of the battery according to the embodiment. FIG. [Figure 4] 3 is an explanatory diagram showing the appearance of a roughened hole periphery portion and a roughened plate periphery portion in a battery according to an embodiment. FIG. [Figure 5] 10 is a partially enlarged cross-sectional view showing the cross-sectional structure of a first safety valve portion in a battery according to a first modified embodiment. FIG. [Figure 6] 10 is a partially enlarged cross-sectional view showing the cross-sectional structure of a first safety valve portion in a battery according to a second modified embodiment. FIG. [Figure 7] 10 is a partially enlarged cross-sectional view showing the cross-sectional structure of a first safety valve portion in a battery according to a third modified embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0024] (Embodiment) Hereinafter, a lithium-ion secondary battery 1 (an example of an electricity storage device) according to this embodiment will be described with reference to Figures 1 to 4. This battery 1 is a rectangular, sealed lithium-ion secondary battery, and is installed in various devices such as vehicles such as hybrid cars, plug-in hybrid cars, and electric vehicles (BEVs), as well as drones. The width direction AH, thickness direction BH, and height direction CH of battery 1 will be described as directions indicated by arrows in Figures 1 and 2.

[0025] The battery 1 of this embodiment is composed of a rectangular case 4 that is thin in the thickness direction BH, an electrode assembly 2 that is housed and sealed inside the case 4, and an electrolyte 3 that is housed in the case 4 and impregnates the electrode assembly 2. The case 4 is made of metal (aluminum in this embodiment) and has a rectangular box shape. It has a case body 5 that is a rectangular cylinder with a bottom and a lid 6 that is welded to a rectangular opening 5o of the case body 5 and seals the rectangular opening 5o. The electrode assembly 2 is covered in an insulating film 10 that is a rectangular bag with a bottom inside the case 4. The aforementioned electrolyte 3 is also housed inside the case 4, with a portion of the electrolyte 3 impregnating the electrode assembly 2 and another portion pooling at the bottom of the case 4.

[0026] The electrode assembly 2 housed in the case 4 is a known so-called flat wound electrode assembly, which is formed by winding a strip-shaped positive electrode plate 2P and a strip-shaped negative electrode plate 2N with a pair of strip-shaped separators 2S interposed between them and flattening them by pressing them in the thickness direction BH perpendicular to the paper surface in Fig. 1. This electrode assembly 2 is housed in the case 4 lying on its side with the winding axis 2X extending in the width direction AH.

[0027] Of the electrode body 2, the strip-shaped positive electrode plate 2P is formed by laminating positive electrode active material layers on both surfaces of a positive electrode current collector foil made of aluminum foil. The positive electrode active material layer is made of positive electrode active material particles, conductive particles, and a binder. In this embodiment, the positive electrode active material particles are, for example, lithium transition metal composite oxide particles such as lithium nickel cobalt manganese composite oxide particles. Note that, at one end of the strip-shaped positive electrode plate 2P in the width direction (the left side in FIG. 1), the exposed positive electrode current collector foil is spirally overlapped to form a positive electrode current collector part 2pc.

[0028] On the other hand, the strip-shaped negative electrode plate 2N of the electrode body 2 is formed by laminating negative electrode active material layers on both surfaces of a negative electrode current collector foil made of copper foil. The negative electrode active material layer is made of negative electrode active material particles and a binder. In this embodiment, graphite particles are used as the negative electrode active material particles. At the end of the other widthwise side (the right side in FIG. 1) of the strip-shaped negative electrode plate 2N, the exposed negative electrode current collector foil is spirally overlapped to form a negative electrode current collector portion 2nc.

[0029] The electrolyte solution 3 is a non-aqueous electrolyte solution containing an organic solvent and a fluorine-containing lithium salt as a supporting salt. In this embodiment, the organic solvent used is a mixture of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate. The fluorine-containing lithium salt used is LiPF6. The salt concentration of the lithium salt in the electrolyte solution 3 at the time of injection is 1.1M.

[0030] The lid 6 of the case 4 has a rectangular plate shape that is elongated in the longitudinal direction LH (the left-right direction that coincides with the width direction AH in FIGS. 1 and 2). A rectangular positive electrode insertion hole 6p is formed on one side LH1 in the longitudinal direction LH (the left side in FIGS. 1 and 2) and a rectangular negative electrode insertion hole 6n is formed on the other side LH2 in the longitudinal direction LH (the right side in FIGS. 1 and 2). The lid 6 also has a liquid filling port 6i. Specifically, in the first embodiment, the liquid filling port 6i is provided between the negative electrode insertion hole 6n and a first safety valve portion 6s1, which will be described below. After the electrolyte 3 is poured, the liquid filling port 6i is airtightly closed by a metal liquid filling plug 11. The lid 6 also has a first safety valve portion 6s1 on the other side LH2 of a center 6C in the longitudinal direction LH. Meanwhile, a second safety valve portion 6s2 is provided on the one side LH1 of the center 6C.

[0031] A positive electrode terminal member 7 made by bending an aluminum plate is inserted into the positive electrode insertion hole 6p of the lid body 6, and this positive electrode terminal member 7 is fixed to the lid body 6 while being insulated from the lid body 6 via a terminal insulating member 9p. The positive electrode terminal member 7 comprises a rectangular flat plate-shaped positive electrode external terminal portion 7G that is surrounded by the terminal insulating member 9p and exposed to the outside, a positive electrode internal connection portion 7C that is connected to a positive electrode current collecting portion 2pc located at one end (the left end in FIG. 1 ) of the electrode body 2, and a positive electrode intermediate portion 7I that connects these together.

[0032] Similarly, a negative electrode terminal member 8 made by bending a copper plate is inserted into the negative electrode insertion hole 6n of the lid body 6, and this negative electrode terminal member 8 is fixed to the lid body 6 while being insulated from the lid body 6 via a terminal insulating member 9n. The negative electrode terminal member 8 consists of a rectangular, flat negative electrode external terminal portion 8G that is surrounded by the terminal insulating member 9n and exposed to the outside, a negative electrode internal connection portion 8C that is connected to the negative electrode current collector 2nc located at the other end (the right end in FIG. 1 ) of the electrode body 2, and a negative electrode intermediate portion 8I that connects these. As a result, the electrode body 2 is fixed and held to the lid body 6 via the positive electrode terminal member 7 and the negative electrode terminal member 8.

[0033] This battery 1 is constructed by covering an electrode assembly 2, which is fixed to a lid 6 via a positive electrode terminal member 7 and a negative electrode terminal member 8, with a rectangular bag-shaped insulating film 10. The electrode assembly 2 is then inserted into a case body 5, and the rectangular opening 5o of the case body 5 and the peripheral edge 6F of the lid 6 are hermetically welded and sealed to form a case 4. Furthermore, electrolyte 3 is poured into the case 4 through a liquid filling port 6i, and a portion of the electrolyte 3 is impregnated into the electrode assembly 2, and the liquid filling port 6i is then sealed with a liquid filling plug 11. The battery 1 is then completed by performing initial charging, high-temperature aging, inspection, etc.

[0034] Among the cases 4, the first safety valve portion 6s1 provided in the lid body 6, as shown in FIG. 3, forms an oval valve hole 6h that penetrates the lid body 6 and is long in the longitudinal direction LH, and includes a hole peripheral edge portion 6hp surrounding the valve hole 6h and a valve member 12 that hermetically seals the valve hole 6h. Among these, the valve member 12 is made of aluminum, and is an oval flat metal sealing plate 13 that is similar to the valve hole 6h but smaller than the valve hole 6h, and an annular resin valve member 14 that hermetically seals between the plate peripheral edge portion 13p of the metal sealing plate 13 and the hole peripheral edge portion 6hp of the lid body 6. This resin valve member 14 is made of a thermoplastic resin material, specifically, PPS with a heat-resistant temperature of 220°C. This first safety valve portion 6s1 is a temperature-release type safety valve portion that opens due to the softening or melting of the resin valve member 14 when the internal pressure PI of the case 4 rises and the temperature of the battery 1 becomes abnormally high. However, even when the resin valve member 14 does not soften or melt, the first safety valve portion 6s1 also functions as a non-return type and pressure-release type safety valve portion that opens when the resin valve member 14 breaks due to a large increase in the internal pressure PI of the case 4 exceeding the first operating pressure P1.

[0035] On the other hand, the second safety valve portion 6s2 is a non-return type and a pressure-release type safety valve portion that opens at a second operating pressure P2 (P2 < P, P2 = 0.7P1) lower than the first operating pressure P1 of the first safety valve portion 6s1.

[0036] Thus, in the battery 1 of this embodiment, in addition to having the temperature-release type first safety valve portion 6s1, it also has a second safety valve portion 6s2 with a second operating pressure P2 lower than the first operating pressure P1 of the first safety valve portion 6s1. Therefore, when the internal pressure of the case 4 rises due to an internal short circuit or a nail penetration test of the battery 1, the second safety valve portion 6s2 can be opened separately from the temperature-release type first safety valve portion 6s1.

[0037] Moreover, the first safety valve portion 6s1 of this embodiment is not configured such that a valve member made entirely of resin is joined to the periphery of the valve hole, as in the temperature-release type safety valve described in Patent Document 2, for example. In the first safety valve portion 6s1 of this embodiment, a metal sealing plate 13 and an annular resin valve member 14 surrounding the metal sealing plate 13 are used as the valve member 12 that seals the valve hole 6h, and the annular resin valve member 14 airtightly seals the gap between the plate periphery 13p of the metal sealing plate 13 and the hole periphery 6hp of the cover 6, thereby airtightly sealing the valve hole 6h. Therefore, when the internal pressure PI of the case 4 increases, part of the pressure acting on the valve member 12 that seals the valve hole 6h can be borne by the metal sealing plate 13, thereby suppressing creep that may occur in the resin valve member 14. Furthermore, since the amount of resin valve member 14 used as valve member 12 can be reduced, the amount of gas or water vapor that permeates resin valve member 14 and enters case 4 or is emitted from case 4 can be suppressed.

[0038] Furthermore, in the first safety valve portion 6s1 of this embodiment, an upper surface 6hpu and a lower surface 6hpd of the hole peripheral portion 6hp forming the oval valve hole 6h are provided with a roughened hole peripheral portion 6hpr, which has a roughened surface, extending in the hole circumferential direction HH of the valve hole 6h, around the entire circumference, as shown by a thick line in Fig. 3. Furthermore, in the valve member 12 of the first safety valve portion 6s1, an upper surface 13pu and a lower surface 13pd of the plate peripheral portion 13p of the oval metal sealing plate 13 are also provided with a roughened plate peripheral portion 13pr, which has a roughened surface, extending in the plate circumferential direction PH of the metal sealing plate 13, around the entire circumference, as shown by a thick line in Fig. 3.

[0039] Furthermore, in the first safety valve portion 6s1 of this embodiment, the roughened hole periphery portion 6hpr of the hole periphery portion 6hp is subjected to a roughening treatment using pulsed laser light, as described below, to form a nano-roughened portion at the nano-level. Specifically, the roughened hole periphery portion 6hpr has numerous bowl-shaped recesses (not shown) with diameters of 30 to 300 μm (approximately 80 μm in this embodiment) arranged in a grid pattern with some overlapping. On the surface of each bowl-shaped recess constituting the roughened hole periphery portion 6hpr, numerous first nanopillars NP1 are formed around the entire circumference. These first particles PC1 originating from the hole periphery portion 6hp of the lid body 6 are linked together in a string-like pattern, forming columns with a height ha of 50 nm or more (approximately 200 nm in this embodiment), as shown in FIG. 4 . As described above, since the lid body 6 is made of aluminum, the first nanopillars NP1 are composed of first particles PC1 made of aluminum and aluminum oxide.

[0040] The roughened peripheral portion 13pr of the metal sealing plate 13 is also a nano-roughened portion that has been roughened using pulsed laser light. Specifically, the roughened peripheral portion 13pr also has numerous bowl-shaped recesses (not shown) with diameters of 30 to 300 μm (approximately 80 μm in this embodiment) that are arranged in a grid pattern with some overlapping portions. The surface of each bowl-shaped recess that makes up the roughened peripheral portion 13pr is also lined with numerous second nanopillars NP2 around the entire periphery. These second nanopillars NP2 are formed by linking together second particles PC2 derived from the peripheral portion 13p of the metal sealing plate 13 in a string-like fashion, as shown in FIG. 4 , to form columns. Each second nanopillar has a height hb of 50 nm or more (approximately 200 nm in this embodiment). As mentioned above, the metal sealing plate 13 is also made of aluminum, and therefore the second nanopillars NP2 are also composed of second particles PC2 made of aluminum and aluminum oxide.

[0041] The hole periphery contacting portion 14ha of the resin valve member 14 is airtightly adhered to the annular roughened hole periphery portion 6hpr that extends in the hole circumferential direction HH of the hole periphery portion 6hp of the lid 6. That is, as shown in Fig. 4, the resin valve member 14 has the thermoplastic resin material that forms the resin valve member 14 filled between the standing first nanopillars NP1 in the hole periphery roughened portion 6hpr, and has the hole periphery contacting portion 14ha that is airtightly adhered to the roughened hole periphery portion 6hpr all around.

[0042] Furthermore, the peripheral contact portion 14pa of the resin valve member 14 is in airtight contact with the annular roughened peripheral portion 13pr extending in the circumferential direction PH of the peripheral portion 13p of the metal sealing plate 13. That is, as shown in Fig. 4, the resin valve member 14 has the thermoplastic resin material that forms the resin valve member 14 filled between the standing second nanopillars NP2 in the roughened peripheral portion 13pr, and has the peripheral contact portion 14pa that is in airtight contact with the roughened peripheral portion 13pr all around.

[0043] In this way, the resin valve member 14 can be firmly and airtightly fixed to the hole peripheral portion 6hp of the lid 6. The resin valve member 14 can also be firmly and airtightly fixed to the plate peripheral portion 13p of the metal sealing plate 13. Thus, the annular resin valve member 14 can airtightly seal the gap between the plate peripheral portion 13p of the metal sealing plate 13 and the hole peripheral portion 6hp of the lid 6 of the case 4. On the other hand, if the internal pressure of the case 4 increases and the temperature of the battery 1 rises abnormally, causing the resin valve member 14 to soften or melt, the resin valve member 14 will break and open the first safety valve portion 6s1.

[0044] As described above, the same aluminum as that of the lid 6 is used as the material for the metal sealing plate 13, but a different material, such as stainless steel, may also be used. In this embodiment, a flat plate-shaped member is used as the metal sealing plate 13 (see FIG. 3 ). However, for example, a metal sealing plate having a ring-shaped peripheral edge 13p and a dome-shaped or top-hat-shaped inner surface that is convex outward or inward in the thickness direction may also be used. In addition, a plate material thinner than the lid 6 is used as the metal sealing plate 13, but the thickness can be selected taking into consideration the strength of the metal sealing plate 13, and a plate material having a thickness approximately the same as that of the lid 6 may also be used.

[0045] Furthermore, in the first safety valve portion 6s1 of this embodiment, the metal sealing plate 13 is disposed within the valve hole 6h, i.e., on the inner side RHI of the valve hole 6h in the hole diameter direction RH, and between the upper surface 6hpu and the lower surface 6hpd of the hole peripheral portion 6hp that forms the valve hole 6h in the plate thickness direction TH of the cover body 6. However, as shown by the dashed line in Fig. 3, the metal sealing plate 13 may be disposed on the inner side RHI of the valve hole 6h in the hole diameter direction RH, and on the outer side THO (upper side in Fig. 3) of the upper surface 6hpu of the hole peripheral portion 6hp in the plate thickness direction TH. Alternatively, as shown by the dashed line in Fig. 3, the metal sealing plate 13 may be disposed on the inner side RHI of the valve hole 6h in the hole diameter direction RH, and on the inner side THI of the lower surface 6hpd of the hole peripheral portion 6hp (lower side in Fig. 3).

[0046] To form the first safety valve portion 6s1 of the lid 6, first, the lid 6 is formed in advance by press molding, with the valve hole 6h drilled therein. Then, a roughened hole peripheral portion 6hpr is formed on the upper surface 6hpu and lower surface 6hpd of the hole peripheral portion 6hp by a roughening treatment using pulsed laser light. Specifically, the upper surface 6hpu or lower surface 6hpd of the hole peripheral portion 6hp is irradiated with pulsed laser light. This forms a bowl-shaped depression (not shown) at the irradiated position, and the aluminum constituting the hole peripheral portion 6hp vaporizes and then condenses into first particles PC1 composed of aluminum and aluminum oxide, which then deposit on the bowl-shaped depression. Therefore, when pulsed laser light is irradiated intermittently in a lattice pattern while shifting the irradiation position, multiple cup-shaped recesses are formed in a lattice pattern with some overlapping, and the first particles PC1 are deposited and bonded in a string-like pattern on the surface of each cup-shaped recess, forming roughened hole edge regions 6hpr with a forest of numerous first nanopillars NP1, as shown in Figure 4. The pulsed laser irradiation conditions are, for example, a wavelength of 1064 nm, a peak output of 5 kW, a pulse width of 150 ns, a spot diameter of 80 μm, and a feed pitch of the irradiation position of 75 μm, which is slightly smaller than the spot diameter (80 μm).

[0047] In parallel with the manufacture of the lid 6, the metal sealing plate 13 is obtained in advance by press punching. Furthermore, similar to the hole peripheral portion 6hp of the lid 6, a roughened peripheral portion 13pr is formed on the upper surface 13pu and the lower surface 13pd of the peripheral portion 13p of the metal sealing plate 13 by a roughening treatment using pulsed laser light. Specifically, the upper surface 13pu or the lower surface 13pd of the peripheral portion 13p is irradiated with pulsed laser light. As a result, a bowl-shaped depression (not shown) is formed at the irradiated position, and the aluminum constituting the peripheral portion 13p becomes vapor and then condenses into second particles PC2 composed of aluminum and aluminum oxide, which deposit on the bowl-shaped depression. Therefore, when the pulsed laser beam is irradiated intermittently in a lattice pattern while shifting the irradiation position, a plurality of partially overlapping bowl-shaped recesses are formed in a lattice pattern, and the second particles PC2 are deposited and bonded in a string-like pattern on the surface of each bowl-shaped recess, forming a roughened peripheral plate portion 13pr with a forest of numerous second nanopillars NP2, as shown in Figure 4. The pulsed laser irradiation conditions are the same as those for roughening the peripheral hole portion 6hp of the lid 6 described above.

[0048] Next, a resin valve member 14 made of thermoplastic resin is injected by insert molding between the hole peripheral portion 6hp of the lid 6 and the plate peripheral portion 13p of the metal sealing plate 13. As a result, the thermoplastic resin material that forms the resin valve member 14 is filled between the first nanopillars NP1 of the hole peripheral roughened portion 6hpr of the lid 6, forming hole peripheral adhesive portions 14ha. The thermoplastic resin material that forms the resin valve member 14 is also filled between the second nanopillars NP2 of the plate peripheral roughened portion 13pr of the metal sealing plate 13, forming plate peripheral adhesive portions 14pa.

[0049] On the other hand, the second safety valve portion 6s2 is press-formed at the same time as forming the cover body 6 by press-forming a plate material. However, an attachment hole (not shown) for the second safety valve portion may be drilled in the cover body 6, and a separately formed metal safety valve member may be airtightly fixed to this attachment hole by welding or adhesive.

[0050] (Variation 1) The battery 1 according to the first modified embodiment (see FIGS. 1, 2, and 5) is a rectangular, sealed lithium ion secondary battery similar to the battery 1 according to the embodiment, but has a different shape for the first safety valve portion 116s1. Therefore, the description of the similar parts will be omitted or simplified, and the first safety valve portion 116s1 of the battery 1 according to the first modified embodiment, which differs from the embodiment, will be described with reference to FIG.

[0051] The first safety valve portion 6s1 (see FIG. 3) of the first embodiment described above uses a metal sealing plate 13 that is similar in shape to the valve hole 6h but is relatively small, and this metal sealing plate 13 is disposed within the valve hole 6h. That is, the metal sealing plate 13 is disposed on the inside RHI of the valve hole 6h in the hole diameter direction RH, and between the upper surface 6hpu and the lower surface 6hpd of the hole peripheral portion 6hp that forms the valve hole 6h, in the plate thickness direction TH of the cover body 6. In addition, an annular resin valve member 14 airtightly seals the gap between the plate peripheral portion 13p of the metal sealing plate 13 and the hole peripheral portion 6hp of the cover body 6, thereby forming the first safety valve portion 6s1.

[0052] Incidentally, there are cases where gas is generated inside the case 4 of the battery 1 due to decomposition of the organic solvent that constitutes the electrolyte 3, and the internal pressure PI of the case 4 remains higher than the external atmospheric pressure for a long period of time. In this case, in the first safety valve portion 6s1 (see FIG. 3), shear stress continues to be applied to the annular intermediate portion 14B of the resin valve member 14 between the hole periphery contact portion 14ha and the plate periphery contact portion 14pa, which may cause creep or cracks in this intermediate portion 14B, raising concerns about a decrease in strength.

[0053] In contrast, in the first safety valve portion 116s1 (see FIG. 5) of the present modified embodiment 1, the cover 6 is provided with an oval valve hole 6h similar to that of the embodiment. However, in addition to this, a relatively large oval metal sealing plate 113 is used, which is similar in shape to the valve hole 6h but is the opposite of the metal sealing plate 13 of the embodiment. This metal sealing plate 113 is positioned to block the valve hole 6h on the outer side THO (upper side in FIG. 5) in the thickness direction TH of the cover 6, higher than the upper surface 6hpu of the hole peripheral portion 6hp that forms the valve hole 6h. In other words, the metal sealing plate 13 is positioned so that the plate peripheral portion 113p of the metal sealing plate 13 covers the entire circumference of the hole peripheral portion 6hp of the cover 6. Additionally, an annular resin valve member 114 airtightly seals the gap between the plate peripheral edge 113p of the metal sealing plate 113 and the hole peripheral edge 6hp of the lid 6, thereby forming a first safety valve portion 116s1.

[0054] As described above, gas may be generated during battery use, causing the internal pressure PI of the case 4 to remain higher than atmospheric pressure. However, even in this case, in the first safety valve portion 116s1, stresses such as shear stress are less likely to be applied to the annular intermediate portion 114B of the resin valve member 114, which is located between the plate peripheral portion 113p of the metal sealing plate 113 and the hole peripheral portion 6hp. This is because the hole peripheral portion 6hp of the lid 6 is located on the inner side THI of this intermediate portion 114B in the plate thickness direction TH. Furthermore, the intermediate portion 114B of the resin valve member 114 is less likely to experience a decrease in strength due to creep or cracking, thereby reliably maintaining airtightness between the plate peripheral portion 113p of the metal sealing plate 113 and the hole peripheral portion 6hp of the lid 6.

[0055] In the first safety valve portion 116s1 of the present modified embodiment 1, too, an annular roughened hole periphery portion 6hpr (see FIG. 4) that has been roughened by pulsed laser light is provided over the entire circumference on the upper surface 6hpu and lower surface 6hpd of the hole periphery 6hp, as shown by the bold line in Fig. 5. Furthermore, an annular roughened plate periphery portion 113pr (see FIG. 4) that has been roughened by pulsed laser light is provided over the entire circumference on the upper surface 113pu and lower surface 113pd of the plate periphery 113p of the metal sealing plate 113 of the valve member 112 of the first safety valve portion 116s1, as shown by the bold line in Fig. 5.

[0056] Therefore, even in the first safety valve portion 116s1 of the first modified embodiment, the hole peripheral contact portion 114ha of the resin valve member 114 can be firmly and airtightly fixed to the hole peripheral portion 6hp of the lid 6. Furthermore, the plate peripheral contact portion 114pa of the resin valve member 114 can be firmly and airtightly fixed to the plate peripheral portion 113p of the metal sealing plate 113. Thus, the annular resin valve member 114 can airtightly seal the gap between the plate peripheral portion 113p of the metal sealing plate 113 and the hole peripheral portion 6hp of the lid 6. On the other hand, if the internal pressure of the case 4 increases and the temperature of the battery 1 rises abnormally, causing the resin valve member 114 to soften or melt, the resin valve member 114 will break, opening the first safety valve portion 116s1.

[0057] (Variation 2) The battery 1 according to the second modified embodiment (see FIGS. 1, 2, and 6) is similar to the battery 1 according to the first modified embodiment, but differs in the shape of the first safety valve portion 126s1. The first safety valve portion 126s1 will now be described with reference to FIG.

[0058] The first safety valve portion 126s1 (see FIG. 6) of the present modified embodiment 2 also has a valve hole 6h in the cover 6 similar to the embodiment and modified embodiment 1, and uses an oval metal sealing plate 113 larger than the valve hole 6h, similar to modified embodiment 1. Furthermore, in the first safety valve portion 126s1 of modified embodiment 2, the metal sealing plate 113 is positioned so that it closes the valve hole 6h on the outer side THO of the cover 6 (upper side in FIG. 6) rather than on the upper surface 6hpu of the hole peripheral portion 6hp. That is, the plate peripheral portion 113p is positioned so that it covers the entire circumference of the hole peripheral portion 6hp of the cover 6. Additionally, an annular resin valve member 124 airtightly seals the gap between the plate peripheral portion 113p of the metal sealing plate 113 and the hole peripheral portion 6hp of the cover 6, thereby constituting the first safety valve portion 126s1. However, unlike the resin valve member 114 of the first modified embodiment (see FIG. 5), the resin valve member 124 is not provided on the plate peripheral edge portion 113p of the metal sealing plate 113 on the outer side THO of the upper surface 113pu.

[0059] In the first safety valve portion 126s1 of this modified embodiment 2, as in the modified embodiment 1, even if the internal pressure P1 of the case 4 remains high, stresses such as shear stress are unlikely to be applied to the annular intermediate portion 124B of the resin valve member 124, which is located between the hole peripheral portion 6hp of the cover 6 and the plate peripheral portion 113p of the metal sealing plate 113. This is because the hole peripheral portion 6hp of the cover 6 is located on the inside T1 in the plate thickness direction TH of this intermediate portion 124B. Furthermore, since the intermediate portion 124B of the resin valve member 124 is unlikely to experience a decrease in strength due to creep, cracks, or the like, it is possible to reliably maintain airtightness between the plate peripheral portion 113p of the metal sealing plate 113 and the hole peripheral portion 6hp of the cover 6.

[0060] As shown by the thick line in Fig. 6, also in the first safety valve portion 126s1 of modified embodiment 2, an annular roughened hole periphery portion 6hpr (see Fig. 4) that has been roughened by pulsed laser light is provided over the entire circumference on the upper surface 6hpu and lower surface 6hpd of the hole periphery portion 6hp. On the other hand, an annular roughened plate periphery portion 113pr (see Fig. 4) that has been roughened by pulsed laser light is provided over the entire circumference only on the lower surface 113pd of the plate periphery 113p of the metal sealing plate 113.

[0061] In the first safety valve portion 126s1 of the second modified embodiment, the hole peripheral contact portion 124ha of the resin valve member 124 can be firmly and airtightly fixed to the hole peripheral portion 6hp of the lid 6, and the plate peripheral contact portion 124pa of the resin valve member 124 can be firmly and airtightly fixed to the plate peripheral portion 113p of the metal sealing plate 113. Thus, the annular resin valve member 124 can airtightly seal the gap between the plate peripheral portion 113p of the metal sealing plate 113 and the hole peripheral portion 6hp of the lid 6. On the other hand, if the internal pressure of the case 4 increases and the temperature of the battery 1 rises abnormally, causing the resin valve member 124 to soften or melt, the resin valve member 124 can break and open the first safety valve portion 126s1.

[0062] (Variation 3) The battery 1 according to the third modified embodiment (see FIGS. 1, 2, and 7) is similar to the batteries 1 according to the first and second modified embodiments, but differs in the configuration of the first safety valve portion 136s1. The first safety valve portion 136s1 will now be described with reference to FIG.

[0063] The first safety valve portion 136s1 (see FIG. 7) of the present modified embodiment 3 also has a valve hole 6h in the cover 6 similar to the embodiment and modified embodiments 1 and 2, and uses an oval metal sealing plate 133 that is larger than the valve hole 6h and larger than the metal sealing plate 113 of modified embodiments 1 and 2. Furthermore, in the first safety valve portion 136s1 of modified embodiment 3, the metal sealing plate 133 is positioned so that it closes the valve hole 6h on the outside THO of the cover 6 (upper side in FIG. 7) above the upper surface 6hpu of the hole peripheral portion 6hp, i.e., so that the plate peripheral portion 133p covers the entire circumference of the hole peripheral portion 6hp. Additionally, an annular resin valve member 134 airtightly seals the gap between the plate peripheral portion 133p of the metal sealing plate 133 and the hole peripheral portion 6hp of the cover 6, thereby constituting the first safety valve portion 126s1. However, unlike the first and second modified embodiments, in the third modified embodiment, the resin valve member 134 is provided only between the upper surface 6hpu of the hole peripheral portion 6hp of the lid 6 and the lower surface 133pd of the plate peripheral portion 133p of the metal sealing plate 133.

[0064] In the first safety valve portion 136s1 of this third modified embodiment, as in the first and second modified embodiments, even if the internal pressure P1 of the case 4 remains high, stresses such as shear stress are unlikely to be applied to the resin valve member 134, i.e., the annular intermediate portion 134B located between the hole peripheral portion 6hp of the lid 6 and the plate peripheral portion 133p of the metal sealing plate 133. This is because the hole peripheral portion 6hp of the lid 6 is located on the inside T1 in the plate thickness direction TH of this intermediate portion 134B. Furthermore, the intermediate portion 134B of the resin valve member 134 is unlikely to experience a decrease in strength due to creep, cracks, or the like, so that airtightness between the plate peripheral portion 133p of the metal sealing plate 133 and the hole peripheral portion 6hp of the lid 6 can be reliably maintained.

[0065] 6, in the first safety valve portion 136s1 of the present modified embodiment 3, a roughened hole periphery portion 6hpr (see FIG. 4) formed by roughening treatment using pulsed laser light is provided only on the upper surface 6hpu of the hole periphery portion 6hp, over the entire circumference in an annular shape extending in the hole circumferential direction HH. Also, a roughened plate periphery portion 133pr (see FIG. 4) formed by roughening treatment using pulsed laser light is provided only on the lower surface 133pd of the plate periphery portion 133p of the metal sealing plate 133, over the entire circumference in an annular shape extending in the plate circumferential direction PH.

[0066] In the first safety valve portion 136s1 of the third modified embodiment, the hole peripheral contact portion 134ha of the resin valve member 134 can be firmly and airtightly fixed to the hole peripheral portion 6hp of the lid 6, and the plate peripheral contact portion 134pa of the resin valve member 134 can be firmly and airtightly fixed to the plate peripheral portion 133p of the metal sealing plate 133. Thus, the annular resin valve member 134 can airtightly seal the gap between the plate peripheral portion 133p of the metal sealing plate 133 and the hole peripheral portion 6hp of the lid 6. On the other hand, if the internal pressure of the case 4 increases and the temperature of the battery 1 rises abnormally, causing the resin valve member 134 to soften or melt, the resin valve member 134 can break and open the first safety valve portion 136s1.

[0067] The present invention has been described above in accordance with the embodiments and variants 1 to 3, but it goes without saying that the present invention is not limited to the embodiments, etc., and can be modified and applied as appropriate within the scope of the gist of the present invention. For example, in the embodiments, an example has been shown in which the first safety valve portion 6s1, etc., having an oval valve hole 6h is formed in the cover 6, but the valve hole may be a circular or rectangular hole. Furthermore, a metal sealing plate 13, etc., oval in shape similar to the valve hole 6h is used as a part of the valve member 12, etc. Similarly, it is preferable to use a disk-shaped or rectangular plate similar to the shape of the valve hole. Meanwhile, in the embodiments, the metal sealing plate has a shape similar to the shape of the valve hole, but it does not have to have a shape similar to the valve hole.

[0068] 3 and 5 to 7, the hole peripheral roughened portion 6hpr is provided on the upper surface 6hpu and the lower surface 6hpd of the hole peripheral portion 6hp, or on the upper surface 6hpu, but in addition, it may also be provided on the inner peripheral surface 6hpi of the hole peripheral portion 6hp. Furthermore, the plate peripheral roughened portions 13pr, 113pr, 133pr are provided on the upper surfaces 13pu, 113pu and the lower surfaces 13pd, 113pd of the plate peripheral portions 13p, 113p, or on the lower surfaces 113pd, 133pd, but they may also be provided on the outer peripheral surfaces 13po, 113po of the plate peripheral portions 13p, 113p.

[0069] In the embodiments and the like, a battery 1 has been exemplified in which a flat wound electrode assembly 2 is housed in a case 4. However, the present invention may also be applied to a battery in which a stacked electrode assembly in which multiple discrete positive and negative electrode plates are alternately stacked with discrete separators interposed therebetween is housed in a case. Furthermore, the present invention may also be applied to a battery in which multiple electrode assemblies, for example, three flat wound electrode assemblies, are housed in a case.

[0070] Furthermore, in the embodiments and the like, an example has been shown in which both the first safety valve portion 6s1, etc. and the second safety valve portion 6s2 are provided on the same surface of the rectangular parallelepiped case 4, i.e., on the same cover 6. However, the temperature-release type first safety valve and the pressure-release type second safety valve may be provided on different surfaces outside each other. Also, it is sufficient that a temperature-release type first safety valve portion is provided, and it is not necessary to provide a pressure-release type second safety valve portion. [Explanation of symbols]

[0071] 1. Battery (energy storage device) 2 Electrode body 2pc positive electrode current collector 2nc negative electrode current collector 4 cases PI (case) internal pressure 6 Lid TH Thickness direction THO (thickness direction) outside 6s1, 116s1, 126s1, 136s1 First safety valve section 6h valve hole HH Hole circumferential direction 6hp hole periphery 6hpu (Top of hole) 6hpd (bottom of hole) 6hpr Roughened hole periphery 12,112,122,132 Valve member 13,113,133 Metal sealing plate PH Plate circumferential direction 13p, 113p, 133p Plate edge 13pr, 113pr, 133pr Roughened edge of plate 14,114,124,134 Resin valve members 14ha, 114ha, 124ha, 134ha Hole periphery contact area 14pa, 114pa, 124pa, 134pa, Plate edge contact area 14B,114B,124B,134B Intermediate part PC1 1st particle PC2 2nd particle NP1 First nanopillar NP2 Second nanopillar ha,hb (nanopillar) height 6s2 Second safety valve section P1 First operating pressure P2 Second operating pressure

Claims

1. Equipped with a metal case with a safety valve An electricity storage device, The safety valve portion is a hole periphery that forms a valve hole penetrating the case; a valve member that airtightly seals the valve hole, The valve member is a metal sealing plate, and a ring-shaped resin valve member made of a thermoplastic resin material that airtightly seals the gap between a peripheral edge of the metal sealing plate and a peripheral edge of the hole in the case; The valve opens when the resin valve member softens or melts due to heat. Temperature release type first safety valve Energy storage device.

2. The electricity storage device according to claim 1 , The metal sealing plate is larger than the valve hole, The resin valve member is disposed on the outer side of the hole peripheral portion in the plate thickness direction, and the plate peripheral portion covers the entire periphery of the hole peripheral portion via the resin valve member. Energy storage device.

3. The electricity storage device according to claim 1 or 2, The hole periphery is a roughened hole periphery portion having a ring shape extending in the circumferential direction of the valve hole, the roughened hole periphery portion being composed of first nanopillars each having a height of 50 nm or more, the first nanopillars being formed by first particles originating from the hole periphery portion of the case being linked together in a string-like pattern around the entire periphery; The resin valve member is A thermoplastic resin material constituting the resin valve member is filled between the forest of first nanopillars, and a hole periphery contact portion is provided that is in airtight contact with the hole periphery roughened portion over the entire circumference. Energy storage device.

4. The electricity storage device according to claim 1 or 2, The plate peripheral portion of the metal sealing plate is a roughened peripheral portion having a ring shape extending in the peripheral direction of the metal sealing plate, the second nanopillars being formed in a columnar shape with a height of 50 nm or more around the entire periphery, the second nanopillars being formed by linking second particles originating from the peripheral portion of the metal sealing plate in a string-like manner, The resin valve member is A thermoplastic resin material constituting the resin valve member is filled between the forest of second nano-pillars, and a plate peripheral contact portion is provided that is in airtight contact with the plate peripheral roughened portion over the entire periphery. Energy storage device.

5. The electricity storage device according to claim 1 or 2, The case is In addition to the first safety valve portion, the valve also has a pressure-release type second safety valve portion that opens at a second operating pressure lower than a first operating pressure at which the first safety valve portion opens at the internal pressure of the case. Energy storage device.

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