Square-type power storage device

Abstract

To provide a square-type power storage device capable of preventing gas emission from being made difficult by blockage of a safety valve due to debris of an electrode body, etc., in a case where a nailing test is performed.SOLUTION: A square-type power storage device 1, 101 includes a case main body 5, a case 4 in a parallelepiped box shape having a lid body 6, 106 in a rectangular plate shape, an electrode body 2 which is stored in the case, a positive electrode terminal member 7, 107 which penetrates a positive electrode insertion hole 6p, 106p disposed in the lid body and extends to the outside, and a negative electrode terminal member 8, 108 which penetrates a negative electrode insertion hole 6n, 106n and extends to the outside. The lid body includes: a first safety valve 6s1, 106s1 which is disposed in a central region 6C, 106C of the lid body and opened with a first working pressure P1; a second safety valve 6s2, 106s2 which is disposed on one side LH1 from the central region and opened with a second working pressure P2 which is higher than the first working pressure; and a third safety valve 6s3, 106s3 which is disposed on another side LH2 from the central region and opened with a third working pressure P3 which is higher than the first working pressure P1.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a rectangular electricity storage device in which an electrode assembly is housed and sealed in a rectangular box-shaped case made of metal. [Background technology]

[0002] For secondary batteries (hereinafter simply referred to as batteries) such as lithium-ion secondary batteries containing an electrode assembly in a rectangular box-shaped metal case, a nail penetration test is sometimes performed to observe the battery's behavior, such as by piercing the center of the main side (the largest side) of the case so as to penetrate the stacked positive and negative electrode plates of the housed electrode assembly. The nail penetration test is performed to confirm whether the safety valve provided in the case operates and suppress the increase in internal pressure in a scenario where, for example, a vehicle accident involving a battery in which the main side of the case collides with another component, causing the case and electrode assembly to collapse, resulting in a short circuit within the electrode assembly, resulting in abnormal heat generation and gas generation, and an increase in internal pressure. In the nail penetration test, the metal rod is inserted near the center of the main side of the case because, although the main side has a large area and therefore low strength, the strength near the center is particularly low, making it more susceptible to significant deformation due to collapse and causing a short circuit within the electrode assembly.

[0003] An example of a battery equipped with such a 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 having a long, narrow rectangular plate shape in the longitudinal direction and sealing the rectangular opening of the case body. The safety valve is provided in the approximate longitudinal center of the long, narrow rectangular plate-shaped lid body, between a positive electrode terminal provided on one longitudinal side and a negative electrode terminal provided on the other longitudinal side.

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-117750 Summary of the Invention [Problem to be solved by the invention]

[0005] However, it has been found that when gas is generated and the safety valve opens, such as when the above-mentioned nail penetration test is performed, cracks in the electrode body can cause fragments of the positive and negative electrode plates that make up the electrode body to fly toward the safety valve along with the gas flowing toward the safety valve, causing the safety valve to become clogged with the fragments, preventing sufficient gas from being released from the safety valve.

[0006] The present invention has been made in consideration of these problems and findings, and provides a rectangular electricity storage device that can prevent difficulty in releasing gas due to blockage of the safety valve caused by broken pieces of the electrode body, etc., when it becomes necessary to open the safety valve when a short circuit occurs in the electrode body, causing abnormal heat generation and gas generation. [Means for solving the problem]

[0007] (1) One aspect of the present invention for solving the above problem includes a rectangular parallelepiped box-shaped case body made of metal and having a bottomed rectangular cylindrical shape, and a metal lid body made of metal and having a rectangular plate shape that closes a rectangular opening of the case body; an electrode body housed and sealed within the case and having a positive electrode current collector and a negative electrode current collector; a positive electrode terminal member having one end connected to the positive electrode current collector and penetrating a positive electrode insertion hole provided on one side of the lid in a longitudinal direction to extend to the outside of the case; and a negative electrode terminal member having one end connected to the negative electrode current collector and provided on the other side of the lid in the longitudinal direction. a negative electrode terminal member passing through an insertion hole and extending to the outside of the case, wherein the lid body has, between the positive electrode insertion hole and the negative electrode insertion hole, a first safety valve provided in a central region in the longitudinal direction and opening at a first operating pressure, a second safety valve provided on one side in the longitudinal direction from the central region and opening at a second operating pressure higher than the first operating pressure, and a third safety valve provided on the other side in the longitudinal direction from the central region and opening at a third operating pressure higher than the first operating pressure.

[0008] In this rectangular electricity storage device, a first safety valve with a relatively low operating pressure is provided in the longitudinal central region of the lid, between the positive electrode insertion hole and the negative electrode insertion hole. Therefore, when a short circuit in the electrode assembly causes abnormal heat generation and gas to be generated, causing the internal pressure of the case to rise, the first safety valve with a low operating pressure opens first due to the internal pressure rise, releasing the internal gas to the outside. In this way, the increase in internal pressure of the battery can be suppressed. Moreover, because the first safety valve is provided in the central region near the center of the main side surface where short circuits are likely to occur, it is easy to quickly release the generated gas to the outside.

[0009] Furthermore, in this rectangular electricity storage device, second and third safety valves that open at a higher operating pressure than the first safety valve are also provided on one and the other longitudinal sides of the central region. Therefore, even if gas flows toward the open first safety valve and fragments of the electrode body are scattered toward the first safety valve, and the first safety valve becomes clogged with debris, preventing gas from being released and causing the internal pressure to rise again, at least one of the second and third safety valves can open, thereby suppressing the rise in internal pressure again. Moreover, since two safety valves, the second and third safety valves, are provided, the possibility of suppressing the rise in internal pressure again by opening at least one of them is increased.

[0010] Furthermore, the second safety valve is located on one side of the longitudinal central region where the first safety valve is located. The third safety valve is located on the other side of the central region. Therefore, the second and third safety valves are farther away than the first safety valve when viewed from the center of the main side of the case where the metal rod is inserted during the nail penetration test. Therefore, scattered electrode fragments are less likely to reach the second and third safety valves than the first safety valve. Furthermore, since the second and third safety valves open later than the first safety valve, it is believed that most of the electrode body fragments have already been scattered toward the first safety valve. From this perspective, the electrode body fragments are unlikely to reach the second and third safety valves. As a result, the second and third safety valves are unlikely to become clogged with electrode body fragments.

[0011] Examples of rectangular electricity storage devices include secondary batteries such as lithium ion secondary batteries and sodium ion secondary batteries, and electricity storage devices such as lithium ion capacitors. In this specification, the longitudinal central region of the lid refers to a range of 30% of the entire length of the lid centered at the longitudinal center. The electrode body housed in the case may be a flat wound electrode body or a laminated electrode body. In the electrode body, the positive electrode current collector to which the positive terminal member is connected and the negative electrode current collector to which the negative terminal member is connected are examples of the positive electrode current collector foil and the negative electrode current collector foil, respectively, which are spirally overlapped portions of the exposed positive electrode current collector foil and the exposed negative electrode current collector foil. In addition, in the flat wound or laminated electrode body, the tab-shaped protruding portions of the exposed positive electrode current collector foil and the exposed negative electrode current collector foil may also serve as the positive electrode current collector and the negative electrode current collector.

[0012] (2) In the rectangular electricity storage device according to (1), the second safety valve may be provided on the one side in the longitudinal direction relative to the positive electrode insertion hole.

[0013] (3) In the rectangular electricity storage device according to (1) or (2), the third safety valve may be provided on the other side in the longitudinal direction relative to the negative electrode insertion hole.

[0014] In this prismatic energy storage device, the second safety valve is located on one longitudinal side of the positive electrode insertion hole, i.e., on the longitudinal outside of the positive electrode insertion hole. The third safety valve is located on the other longitudinal side of the negative electrode insertion hole, i.e., on the longitudinal outside of the negative electrode insertion hole. In this prismatic energy storage device, if the first safety valve is blocked by electrode body fragments or the like, and the second or third safety valve opens, causing gas to flow toward the opened second or third safety valve, the electrode body fragments may be scattered toward the second or third safety valve along with the gas. However, in this prismatic energy storage device, a positive or negative electrode terminal member is located in the path of the gas flowing to the second or third safety valve. The positive or negative electrode terminal member also functions as a blocking member that catches scattered fragments and prevents them from reaching the second or third safety valve. Thus, in this rectangular electricity storage device, the risk of even the second and third safety valves being blocked by debris can be further reduced. [Brief explanation of the drawings]

[0015] [Figure 1] 3 is a longitudinal cross-sectional view of the battery according to the first embodiment taken along the line AA in FIG. 2. FIG. [Figure 2] FIG. 1 is a top view of a battery according to a first embodiment. [Figure 3] 5 is a longitudinal cross-sectional view of the battery according to the second embodiment taken along the line AA in FIG. 4. FIG. [Figure 4] FIG. 10 is a top view of a battery according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] (Embodiment 1) Hereinafter, a lithium-ion secondary battery 1 (an example of a secondary battery) according to embodiment 1 will be described with reference to Figures 1 and 2. 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. Note that 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.

[0017] 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 1) 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 a rectangular bag-shaped insulating film 10 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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. In the first embodiment, specifically, the liquid filling port 6i is provided between the negative electrode insertion hole 106n and a first safety valve 6s1, which will be described below. After the electrolyte 3 is poured into the lid 6, the liquid filling port 6i is airtightly closed by a liquid filling plug 11.

[0023] Furthermore, when a central area 6CA is defined as an area of ​​30% of the overall length of the cover 6 centered around the center 6C in the longitudinal direction LH of the cover 6, the first safety valve 6s1 is provided within this central area 6CA. More specifically, the first safety valve 6s1 is a non-returnable pressure-release type that opens at operating pressure P1, provided in a portion of the central area 6CA closer to one side LH1 (to the left in FIGS. 1 and 2) than the center 6C. Note that it is sufficient for the center of the first safety valve 6s1 to be provided within the central area 6CA. For example, as shown in the first embodiment, this includes cases where the entire first safety valve 6s1 is included in the central area 6CA, as well as cases where the center of the first safety valve 6s1 in the longitudinal direction LH is included in the central area 6CA but where a portion of it extends outside the central area 6CA.

[0024] Furthermore, in the battery 1 of the first embodiment, outside the central region 6CA of the lid 6 and in a region outside the positive electrode insertion hole 6p, that is, in the first hole outer region 6o1 on one side LH1 from the positive electrode insertion hole 6p, a second safety valve 6s2 is provided. This second safety valve 6s2 is also a non-return type and is a pressure release type safety valve that opens at an operating pressure P2 (P2 > P1, P2 = 1.1P1) higher (for example, 10% higher) than the operating pressure P1 of the first safety valve 6s1.

[0025] Also, outside the central region 6CA of the lid 6 and in a region outside the negative electrode insertion hole 6n, that is, in the second hole outer region 6o2 on the other side LH2 from the negative electrode insertion hole 6n, a third safety valve 6s3 is provided. This third safety valve 6s3 is also a non-return type and is a pressure release type safety valve that opens at an operating pressure P3 (P3 > P1, P3 = 1.1P1) higher (for example, 10% higher) than the operating pressure P1 of the first safety valve 6s1. In the first embodiment, the operating pressure P2 of the second safety valve 6s2 and the operating pressure P3 of the third safety valve 6s3 are set to be equal (P1 < P2 = P3).

[0026] However, the operating pressure P2 and the operating pressure P3 depend on the magnitude of the operating pressure P1 and the strength of the case 4, but it is preferable to select them within the range of 1.05 to 2.0 times the operating pressure P1. Considering the variation in the operating pressure of each safety valve, in order to ensure that the first safety valve 6s1 opens first, it is preferably 1.05 times or more. On the other hand, when the first safety valve 6s1 is blocked by flying objects, it is preferably 2.0 times or less in order to quickly open the second safety valve 6s2 or the third safety valve 6s3 before the internal pressure of the case 4 becomes too high. Also, in the first embodiment, the operating pressure P2 and the operating pressure P3 are set to be equal, but the operating pressure P2 and the operating pressure P3 may be made different, that is, the operating pressure P2 may be lower than the operating pressure P3 (P2 < P3), or the operating pressure P3 may be lower than the operating pressure P2 (P3 < P2).

[0027] The three safety valves 6s1, 6s2, and 6s3 of the cover 6 of the present embodiment 1 are press-formed at the same time that the cover 6 is formed by press-forming a plate material. However, it is also possible to drill mounting holes (not shown) for the safety valves in the cover 6, and then secure separately formed safety valve members in the mounting holes by welding or adhesive in an airtight manner.

[0028] 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.

[0029] 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.

[0030] This battery 1 is constructed by covering the electrode assembly 2, which is fixed to the lid 6 via the positive electrode terminal member 7 and the negative electrode terminal member 8, with a rectangular bag-shaped insulating film 10, inserting the electrode assembly 2 into the case body 5, and hermetically sealing the rectangular opening 5o of the case body 5 and the peripheral edge 6F of the lid 6 by welding them together to form the case 4. Furthermore, the electrolyte 3 is poured into the case 4 through the liquid pouring port 6i, and a portion of the electrolyte 3 is impregnated into the electrode assembly 2, and the liquid pouring port 6i is then sealed with a liquid pouring plug 11. The battery 1 is then completed after initial charging, high-temperature aging, inspection, etc.

[0031] Incidentally, nail penetration tests may be performed on completed batteries 1 before shipment, as well as on batteries 1 after shipment and use. This test is conducted to verify that the safety valve in the case 4 can operate to suppress the increase in internal pressure in a scenario where the battery 1 collides with another component in an accident involving a vehicle carrying the battery 1, crushing the case 4 and electrode assembly 2 and causing a short circuit within the electrode assembly 2, resulting in abnormal heat generation and gas generation, leading to an increase in internal pressure. In the nail penetration test, the metal rod NL is inserted into the rectangular parallelepiped case 4 at the center (center 4MC) of the main side surface 4M, which has the largest area and faces the thickness direction BH. The main side surface 4M of the case 4 has a large area and therefore has low strength. This is because the strength near the center 4MC is particularly low, leading to significant deformation due to crushing and a high likelihood of causing a short circuit within the electrode assembly 2.

[0032] For example, in a nail penetration test, a 3 mm thick stainless steel metal rod NL with a hemispherical tip is pierced into the center 4MC of the main side surface 4M of a battery 1 with an SOC of 100% and a battery temperature of 60°C, penetrating a portion of the electrode body 2. This short-circuits the positive electrode plate 2P and the negative electrode plate 2N at the nailed portion of the electrode body 2, causing a large current to flow and abnormal heat generation. This evaporates the organic solvent constituting the electrolyte 3, as well as the materials constituting the positive electrode plate 2P, the negative electrode plate 2N, and the separator 2S, generating gas and increasing the internal pressure of the case 4. However, if the internal pressure of the case 4 exceeds the operating pressure P1 of the first safety valve 6s1, the first safety valve 6s1 opens, releasing gas to the outside through the first safety valve 6s1, thereby suppressing the increase in internal pressure.

[0033] However, as shown by the dashed line in Figure 1, for example, a crack 2K may occur in the electrode body 2, starting near the pierced metal rod NL. If this occurs, fragments of the positive electrode plate 2P, negative electrode plate 2N, and separator 2S that make up the electrode body 2 may be carried by the gas flow GF1 toward the opened first safety valve 6s1 and fly toward the first safety valve 6s1, causing the first safety valve 6s1 to become clogged with the fragments, preventing the first safety valve 6s1 from releasing gas and causing the internal pressure to rise again.

[0034] In contrast, the battery 1 of the first embodiment is also provided with a second safety valve 6s2 and a third safety valve 6s3 that open at operating pressures P2 and P3 higher than the operating pressure P1 of the first safety valve 6s1. Opening at least one of the second safety valve 6s2 and the third safety valve 6s3 can prevent the internal pressure from rising again. Moreover, providing both the second safety valve 6s2 and the third safety valve 6s3 increases the possibility of this happening.

[0035] Furthermore, the second safety valve 6s2 is provided outside the central region 106CA where the first safety valve 6s1 is provided, i.e., on one side LH1 of the central region 6CA in the longitudinal direction LH. The third safety valve 6s3 is provided on the other side LH2 of the central region 6CA. Therefore, the distances to the second safety valve 6s2 and the third safety valve 6s3 are greater than the distance to the first safety valve 6s1 when viewed from the inserted metal rod NL. Therefore, scattered fragments of the electrode assembly 2 are less likely to reach the second safety valve 6s2 and the third safety valve 6s3 than the first safety valve 6s1, making clogging by the fragments of the electrode assembly 2 less likely to occur.

[0036] Furthermore, since the second safety valve 6s2 or the third safety valve 6s3 opens with a delay from the opening of the first safety valve 6s1, it is believed that most of the fragments of the electrode body 2 have already been scattered toward the first safety valve 6s1. From this perspective, too, the fragments of the electrode body 2 are unlikely to reach the second safety valve 6s2 or the third safety valve 6s3, making blockage by the fragments unlikely to occur.

[0037] As mentioned above, in this battery 1, if the first safety valve 6s1 is blocked by fragments of the electrode body 2 or the like and then the second safety valve 6s2 or the third safety valve 6s3 opens, causing gas to flow toward the open second safety valve 6s2 or third safety valve 6s3, there remains a possibility that the fragments of the electrode body 2 will be carried by the gas flow GF1 and scattered toward the second safety valve 6s2 or the third safety valve 6s3 along with the gas.

[0038] However, in the battery 1 of the first embodiment, the second safety valve 6s2 is located on one side LH1 of the positive electrode insertion hole 6p in the longitudinal direction LH, i.e., further outward in the longitudinal direction LH than the positive electrode insertion hole 6p. Similarly, the third safety valve 6s3 is located on the other side LH2 of the negative electrode insertion hole 6n in the longitudinal direction LH, i.e., further outward in the longitudinal direction LH than the negative electrode insertion hole 6n. Therefore, as can be easily understood from FIG. 1 , the positive electrode terminal member 7, specifically its positive electrode intermediate portion 7I, connected to the positive electrode current collector 2pc of the electrode assembly 2 is located in the middle of the gas flow GF2 toward the one side LH1 in the longitudinal direction LH toward the second safety valve 6s2. Furthermore, the negative electrode intermediate portion 8I of the negative electrode terminal member 8 connected to the negative electrode current collector 2nc of the electrode assembly 2 is located in the middle of the gas flow GF3 toward the other side LH2 in the longitudinal direction LH toward the third safety valve 6s3.

[0039] Therefore, even if fragments of the electrode assembly 2 fly toward the second safety valve 6s2 or the third safety valve 6s3, the fragments are likely to get caught in the positive electrode intermediate portion 7I or the negative electrode intermediate portion 8I. That is, the positive electrode intermediate portion 7I of the positive electrode terminal member 7 and the negative electrode intermediate portion 8I of the negative electrode terminal member 8 also function as blocking members that prevent the fragments from reaching the second safety valve or the third safety valve. Thus, in the battery 1 of this embodiment 1, the risk of the second safety valve 6s2 or the third safety valve 6s3 being blocked by fragments of the electrode assembly 2 can be further reduced.

[0040] (Embodiment 2) Hereinafter, a battery 101 (an example of a secondary battery) which is a lithium ion secondary battery according to embodiment 2 will be described with reference to FIGS. 3 and 4. This battery 101 is a rectangular, sealed lithium ion secondary battery similar to battery 1 according to embodiment 1, but differs in the arrangement of the second safety valve 106s2 and the third safety valve 106s3, etc. Therefore, the description of the similar parts will be omitted or simplified, and the description will focus on the different parts. Note that the width direction AH, thickness direction BH, and height direction CH of battery 101 will be described as the directions indicated by arrows in FIGS. 3 and 4.

[0041] The battery 101 of the second embodiment is also composed of a rectangular case 4 that is thin in the thickness direction BH, an electrode assembly 2 housed inside the case 4, and an electrolyte 3 housed in the case 4 and partially impregnating the electrode assembly 2. The rectangular box-shaped case 4 has a case body 5 and a lid 106 that seals a rectangular opening 5o of the case body 5 and is different from the lid 6 of the first embodiment.

[0042] Of the case 4, the lid body 106 of this embodiment 2 is also in the shape of a rectangular plate that is elongated in the longitudinal direction LH, similar to the lid body 6, and has a rectangular positive electrode insertion hole 106p on one side LH1 in the longitudinal direction LH (leftward in Figures 3 and 4) and a rectangular negative electrode insertion hole 106n on the other side LH2 in the longitudinal direction LH (rightward in Figures 3 and 4).

[0043] 4 and 2, the positive electrode insertion hole 106p of the lid body 106 of the second embodiment is disposed on one side LH1 (outside) in the longitudinal direction LH compared to the positive electrode insertion hole 6p of the lid body 6 of the first embodiment. Moreover, the negative electrode insertion hole 106n of the lid body 106 of the second embodiment is disposed on the other side LH2 (outside) in the longitudinal direction LH compared to the negative electrode insertion hole 6n of the lid body 6 of the first embodiment.

[0044] On the other hand, the first safety valve 106s1 of the cover 106 is provided in the same position as the first safety valve 6s1 of the cover 6, i.e., in the central region 106CA. More specifically, the first safety valve 106s1, which is a non-returnable pressure-release type that opens at operating pressure P1, is provided in a portion of the central region 106CA closer to one side LH1 (to the left in FIGS. 3 and 4) than the center 106C. The liquid filling port 106i of the cover 106 is also provided in the same position as the liquid filling port 6i of the cover 6, and is airtightly closed by the liquid filling tap 11 after the electrolyte 3 is poured.

[0045] Furthermore, in the battery 101 of the second embodiment, a second safety valve 106s2 is provided outside the central region 106CA of the lid body 106, that is, on one side LH1 with respect to the central region 106CA. More specifically, the second safety valve 106s2 is provided at a position on one side LH1 with respect to the central region 106CA, but inside (the other side LH2) the positive electrode insertion hole 106p. This second safety valve 106s2 is a non-return type, pressure-release type safety valve that opens at an operating pressure P2 (P2 > P1, P2 = 1.1P1) higher (for example, 10% higher) than the operating pressure P1 of the first safety valve 106s1, similar to the second safety valve 6s2 of the first embodiment.

[0046] Also, a third safety valve 106s3 is provided outside the central region 106CA of the lid body 106, that is, on the other side LH2 with respect to the central region 106CA. More specifically, the third safety valve 106s3 is provided at a position on the other side LH2 with respect to the central region 106CA, but inside (one side LH1) the negative electrode insertion hole 106n. This third safety valve 106s3 is also a non-return type, pressure-release type safety valve that opens at an operating pressure P3 (P3 > P1, P3 = 1.1P1) higher (for example, 10% higher) than the operating pressure P1 of the first safety valve 106s1, similar to the third safety valve 6s3 of the first embodiment. In the second embodiment, the operating pressure P2 of the second safety valve 106s2 and the operating pressure P3 of the third safety valve 106s3 are set to be equal (P1 < P2 = P3). The three safety valves 106s1, 106s2, 106s3 of the lid body 106 in the second embodiment are also formed by press-forming the lid body 106 from a plate material and press-forming.

[0047] In the positive electrode insertion hole 106p of the lid body 106, a positive electrode terminal member 107 formed by bending an aluminum plate is inserted and fixed to the lid body 106 while being insulated through a terminal insulating member 109p. The positive electrode terminal member 107 includes a rectangular flat plate-shaped positive electrode external terminal portion 107G surrounded by the terminal insulating member 109p and exposed to the outside, a positive electrode internal connection portion 107C connected to the positive electrode current collector portion 2pc of the electrode body 2, and a positive electrode intermediate portion 107I connecting these and extending in the height direction CH.

[0048] Similarly, a negative electrode terminal member 108 formed by bending a copper plate is inserted into a negative electrode insertion hole 106n of the lid body 106 and is fixed to the lid body 106 while being insulated via a terminal insulating member 9n. The negative electrode terminal member 108 comprises a rectangular flat plate-shaped negative electrode external terminal portion 108G surrounded by a terminal insulating member 109n and exposed to the outside, a negative electrode internal connection portion 108C connected to the negative electrode current collecting portion 2nc of the electrode body 2, and a negative electrode intermediate portion 108I connecting these portions and extending in the height direction CH.

[0049] In the battery 101 of the second embodiment, as in the battery 1 of the first embodiment, when a nail penetration test is performed in which a metal rod NL is pierced into the center 4MC of the main side surface 4M, the positive electrode plate 2P and the negative electrode plate 2N are short-circuited at the nailed portion of the electrode body 2, causing a large current to flow and abnormal heat generation, generating gas and increasing the internal pressure of the case 4. However, when the internal pressure of the case 4 exceeds the operating pressure P1 of the first safety valve 106s1, the first safety valve 106s1 opens to release the gas to the outside, thereby suppressing the increase in internal pressure.

[0050] However, as shown by the dashed line in Fig. 3, for example, a crack 2K may occur in the electrode body 2, starting from near the pierced metal rod NL. If this occurs, fragments of the electrode body 2 may be scattered on the gas flow GF1 toward the first safety valve 106s1, causing the first safety valve 106s1 to become blocked by the fragments, preventing gas from being released from the first safety valve 6s1 and causing the internal pressure to rise again.

[0051] In contrast, the battery 101 of the second embodiment is also provided with a second safety valve 106s2 and a third safety valve 106s3 that open at operating pressures P2 and P3 higher than the operating pressure P1 of the first safety valve 106s1. Opening at least one of the second safety valve 106s2 and the third safety valve 106s3 can prevent the internal pressure from rising again. Moreover, providing both the second safety valve 106s2 and the third safety valve 106s3 increases the possibility of this happening.

[0052] Furthermore, in the first embodiment, the second safety valve 106s2 and the third safety valve 106s3 are provided outside the central region 106CA, i.e., on one side LH1 and the other side LH2 in the longitudinal direction LH of the central region 106CA. Therefore, the distance from the inserted metal rod NL to the second safety valve 106s2 and the third safety valve 106s3 is greater than the distance from the metal rod NL to the first safety valve 106s1. Therefore, scattered fragments of the electrode assembly 2 are less likely to reach the second safety valve 106s2 and the third safety valve 106s3 than the first safety valve 106s1, and clogging by the fragments of the electrode assembly 2 is less likely to occur.

[0053] Furthermore, since the second safety valve 106s2 or the third safety valve 106s3 opens with a delay from the opening of the first safety valve 106s1, it is believed that most of the fragments of the electrode body 2 have already been scattered toward the first safety valve 106s1. From this perspective, too, the fragments of the electrode body 2 are unlikely to reach the second safety valve 106s2 or the third safety valve 106s3, making blockage by the fragments unlikely to occur.

[0054] The present invention has been described above in accordance with embodiments 1 and 2, 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 first embodiment, as shown in Fig. 2, the second safety valve 6s2 and the third safety valve 6s3 are smaller than the first safety valve 6s1, but if installation space can be secured, they may be the same size as the first safety valve 6s1. Furthermore, although the second safety valve 6s2 and the third safety valve 6s3 have the same shape and size, they may also have different shapes and sizes.

[0055] In addition, in the first and second embodiments, an example of a battery 1 was shown in which the electrode assembly 2 was a single flat wound electrode assembly in which a strip-shaped positive electrode plate 2P and a strip-shaped negative electrode plate 2N were wound and flattened with a pair of strip-shaped separators 2S between them, and the battery 1 was housed in a case 4. However, a stacked electrode assembly in which multiple sheet-shaped positive and negative electrode plates are alternately stacked with sheet-shaped separators between them may also be used, and the battery may be housed in a case. Furthermore, the battery may be housed in a case in which multiple electrode assemblies, for example, three flat wound electrode assemblies, are housed in a case. [Explanation of symbols]

[0056] 1,101 Batteries (secondary batteries) 2 Electrode body 2pc positive electrode current collector 2nc negative electrode current collector 4 cases 6,106 Lids LH (Lid) Longitudinal direction LH1 (longitudinal) one side LH2 (longitudinal) other side 6CA,106CA central area 6p,106p Positive electrode insertion hole 6n, 106n Negative electrode insertion hole 6s1,106s1 First safety valve 6s2,106s2 Second safety valve 6s3,106s3 Third safety valve P1 First operating pressure P2 Second operating pressure P3 Third operating pressure 7,107 Positive electrode terminal material 7C,107C Positive internal connection 7I,107I Positive electrode middle part 7G,107G Positive external terminal section 8,108 Negative electrode terminal member 8C,108C Negative electrode internal connection 8I,108I Negative electrode middle part 8G,108G Negative external terminal section 9p, 9n, 109p, 109n terminal insulating material

Claims

1. a metal case body in the shape of a rectangular cylinder with a bottom; The case is made of metal and has a rectangular plate-shaped lid that closes the rectangular opening of the case body. A rectangular box-shaped case, an electrode assembly housed and sealed in the case and having a positive electrode current collecting portion and a negative electrode current collecting portion; a positive electrode terminal member having one end connected to the positive electrode current collecting portion, passing through a positive electrode insertion hole provided on one side of the lid in the longitudinal direction, and extending to the outside of the case; a negative electrode terminal member having one end connected to the negative electrode current collecting portion, passing through a negative electrode insertion hole provided on the other side of the lid in the longitudinal direction, and extending to the outside of the case; A rectangular electricity storage device, The lid body is a first safety valve that is provided in a central region in the longitudinal direction between the positive electrode insertion hole and the negative electrode insertion hole and that opens at a first operating pressure; a second safety valve that is provided on the one side of the central region in the longitudinal direction and that opens at a second operating pressure higher than the first operating pressure; a third safety valve that is provided on the other side of the central region in the longitudinal direction and that opens at a third operating pressure that is higher than the first operating pressure; A rectangular energy storage device.

2. The rectangular electricity storage device according to claim 1, The second safety valve is provided on the one side in the longitudinal direction of the positive electrode insertion hole A rectangular energy storage device.

3. The rectangular electricity storage device according to claim 1 or 2, The third safety valve is provided on the other side in the longitudinal direction of the negative electrode insertion hole A rectangular energy storage device.

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