Power storage cell and method for manufacturing power storage cell

Abstract

In the present invention, a power storage cell comprises an electrode body, a case in which the electrode body is accommodated, and a safety valve provided in the case. The case includes: a pair of terminal wall parts in which electrode terminals are positioned, said terminal wall parts facing each other in a first direction; and a first wall part that is connected to the pair of terminal wall parts, welding marks that extend in the first direction being positioned in first wall part. The safety valve is disposed in the first wall part.

Description

Energy storage cell and method for manufacturing the same

[0001] The present disclosure relates to an energy storage cell and a method for manufacturing the energy storage cell.

[0002] For example, Japanese Patent Application Laid-Open No. 2010-176867 discloses a storage cell (sealed battery) having a safety valve with a cleavage groove formed in a sealed battery case that houses a power generating element inside. In this storage cell, a safety valve is disposed on the sealing plate of the battery case where the electrode terminals are disposed, and the valve opens when the pressure inside the battery rises beyond an allowable range, thereby discharging gas and the like inside the battery case to the outside.

[0003] A known case for a storage cell has electrode terminals arranged on wall portions of a housing that face each other in a first direction. For example, this case is formed by connecting a cylindrical housing to a pair of terminal wall portions that face each other in the first direction. Therefore, weld marks are formed on the side walls of the housing, where the ends of the flat plates used as the material are welded together.

[0004] However, if a safety valve is provided on the terminal wall (sealing plate) as in the technology described in JP 2010-176867 A, when gas is generated inside the storage cell, the internal pressure tends to cause deformation of the case near the relatively weak welding marks, which may result in gas not being released in the intended direction.

[0005] The present disclosure provides a storage cell and a method for manufacturing the storage cell that can suppress variation in the direction of gas discharge when gas inside the storage cell is discharged and facilitate management of the gas discharged from inside the storage cell.

[0006] The energy storage cell described in a first aspect of the present disclosure is an energy storage cell comprising an electrode body, a case in which the electrode body is housed, and a safety valve provided in the case, wherein the case includes a pair of terminal wall portions on which electrode terminals are arranged and which face each other in a first direction, and a first wall portion which is a wall portion connected to the pair of terminal wall portions and on which weld marks extending in the first direction are arranged, and the safety valve is arranged in the first wall portion.

[0007] In the energy storage cell according to the first aspect, a case containing the electrode assembly is provided with a safety valve that opens when the internal pressure exceeds an allowable range, thereby discharging gas and the like from within the case to the outside.

[0008] Here, the case includes a pair of terminal walls facing each other in a first direction and a first wall connected to the pair of terminal walls. A safety valve is disposed on the first wall along with a weld mark extending in the first direction. Therefore, when internal pressure increases, deformation of the case due to the opening of the safety valve and deformation near the weld mark can be concentrated on the first wall. As a result, variation in the direction of gas discharge when gas inside the energy storage cell is discharged is suppressed. Furthermore, even if the case is split near the weld mark, the direction of gas discharge from the split portion and the direction of gas discharge from the safety valve can be made to be substantially the same, which also suppresses variation in the direction of gas discharge when gas inside the energy storage cell is discharged.

[0009] In the energy storage cell according to a second aspect of the present disclosure, in the configuration according to the first aspect, the safety valve extends along the weld mark, and the first direction is a longitudinal direction.

[0010] In the energy storage cell according to the second aspect, the safety valve extends along the weld mark and has a longitudinal direction in the first direction, whereby deformation of the case along the weld mark can efficiently prompt the safety valve to open.

[0011] In the energy storage cell according to a third aspect of the present disclosure, in the configuration according to the first or second aspect, the safety valve is formed on an outer surface of the first wall portion.

[0012] In the energy storage cell according to the third aspect, the welding marks and the safety valve are visible from the outer surface, which facilitates quality inspection during the manufacturing process.

[0013] The storage cell described in a fourth aspect of the present disclosure is configured as any one of the first to third aspects, wherein the weld mark extends from one end to the other end of the first wall portion in the first direction.

[0014] In the storage cell described in the fourth aspect, the weld mark extends from one end to the other end in the first direction in the first wall portion, which more effectively promotes deformation of the case along the weld mark, making it easier to control the discharge direction of the gas discharged from the safety valve.

[0015] The storage cell described in a fifth aspect of the present disclosure is configured as any one of the first to fourth aspects, wherein the first wall portion extends with the first direction as its longitudinal direction and a second direction intersecting the first direction as its short direction, and the weld marks are arranged on the first wall portion at a distance from the end of the first wall portion in the second direction.

[0016] In the energy storage cell according to the fifth aspect, the weld mark extends in the first direction (longitudinal direction) in the first wall portion and is spaced apart from the end in the second direction (transverse direction). Here, when the pressure inside the case increases, stress concentrates at the end in the transverse direction of the first wall portion, but the weld mark is spaced apart from the end in the transverse direction. This suppresses stress concentration near the weld mark and prevents the weld mark on the case from cracking.

[0017] In a sixth aspect of the present disclosure, in the configuration of any one of the first to fifth aspects, the weld mark is located at the center of the first wall portion in the second direction. Therefore, the weld mark is located at a position sufficiently separated from the short-side end of the first wall portion where stress concentrates when pressure inside the case increases. This effectively prevents the case from cracking.

[0018] In the energy storage cell according to the sixth aspect, the weld mark extends in the first direction (longitudinal direction) in the first wall portion and is located at the center in the second direction (transverse direction), thereby suppressing stress concentration near the weld mark and preventing the weld mark on the case from cracking.

[0019] In the energy storage cell according to a seventh aspect of the present disclosure, in the configuration according to any one of the first to sixth aspects, the safety valve overlaps the weld mark in a thickness direction of the first wall portion.

[0020] In the energy storage cell according to the seventh aspect, the safety valve is arranged so that at least a portion thereof overlaps the weld mark in the thickness direction of the first wall portion. This allows a force caused by deformation of the case along the weld mark when pressure inside the case increases to be efficiently applied to the safety valve, assisting in opening the safety valve. This makes it easier to control the direction of gas discharge when pressure inside the case increases.

[0021] An eighth aspect of the present disclosure provides a storage cell according to the seventh aspect, wherein the safety valve includes at least one groove portion, and at least a portion of the groove portion overlaps with the weld mark in the thickness direction.

[0022] In the energy storage cell according to the eighth aspect, the safety valve has at least one groove that opens when the groove is ruptured. The groove is configured so that at least a portion of the groove overlaps with the weld mark in the thickness direction of the first wall portion. This makes it easier to control the direction of gas discharge when pressure inside the case increases.

[0023] A ninth aspect of the present disclosure provides a storage cell according to the eighth aspect, wherein the groove portion has a straight portion extending in the first direction, and the straight portion overlaps with the weld mark in the thickness direction.

[0024] In the energy storage cell according to the ninth aspect, in the groove constituting the safety valve, the straight portion extending in the first direction is configured to overlap the weld mark in the thickness direction of the first wall portion, whereby the direction of deformation of the case when pressure inside the case increases and the direction of rupture of the straight portion are substantially the same, making it possible to easily open the safety valve.

[0025] The storage cell described in a tenth aspect of the present disclosure is the configuration described in the ninth aspect, wherein the groove portion has an extension portion that intersects with the straight portion, and the portion of the extension portion that intersects with the straight portion overlaps with the weld mark in the thickness direction.

[0026] In the energy storage cell according to the tenth aspect, the groove constituting the safety valve further includes an extension portion intersecting with the straight portion. The extension portion is arranged so that the portion intersecting with the straight portion overlaps with the weld mark in the thickness direction of the first wall portion. Therefore, when pressure inside the case increases, the force caused by deformation of the case is transmitted in multiple directions around the portion where the straight portion and the extension portion intersect, making it even easier to open the safety valve.

[0027] The storage cell described in an eleventh aspect of the present disclosure is configured as described in the fourth aspect, wherein the first wall portion extends with the first direction as the longitudinal direction and a second direction intersecting the first direction as the short direction, and the weld mark is arranged at one end of the first wall portion in the second direction.

[0028] In the energy storage cell according to the eleventh aspect, the weld mark extends in the first direction (longitudinal direction) in the first wall portion and is located at one end in the second direction (transverse direction). Here, when pressure inside the case increases, stress concentrates at the end in the transverse direction of the first wall portion, but the weld mark is located at the end in the transverse direction. This allows the case to deform early in the vicinity of the weld mark when pressure inside the case increases, thereby assisting in opening of the safety valve. This allows the safety valve to open quickly when gas is generated inside the energy storage cell.

[0029] A storage cell described in a twelfth aspect of the present disclosure is a storage cell comprising an electrode body, a case in which the electrode body is housed, and a safety valve provided in the case, wherein the case includes a pair of terminal wall portions on which electrode terminals are arranged and which face each other in a first direction, and a wall portion connected to the pair of terminal wall portions, and the wall portion connected to the pair of terminal wall portions includes a first wall portion on which the safety valve is arranged, and a second wall portion provided adjacent to the first wall portion and on which a weld mark extending along the first direction is arranged at an end adjacent to the first wall portion.

[0030] In the energy storage cell according to the twelfth aspect, the case housing the electrode assembly includes a pair of terminal walls facing each other in a first direction and a wall connected to the pair of terminal walls. The wall connected to the pair of terminal walls includes a first wall in which a safety valve is disposed and a second wall adjacent to the first wall. The second wall has a weld mark extending along the first direction at an end adjacent to the first wall. Therefore, when the internal pressure of the case increases, deformation of the case occurs along the weld mark near the safety valve. This deformation of the case assists in opening the safety valve, thereby reducing variation in the direction of gas discharge when gas inside the energy storage cell is discharged. Even if the case were to split near the weld mark, the direction of gas discharge from the split portion and the direction of gas discharge from the safety valve can be made substantially the same, thereby reducing variation in the direction of gas discharge when gas inside the energy storage cell is discharged.

[0031] In a storage cell according to a thirteenth aspect of the present disclosure, in the configuration according to the twelfth aspect, the weld mark extends from one end to the other end in the first direction on the second wall portion.

[0032] In the storage cell described in the thirteenth aspect, the weld mark extends from one end to the other end in the first direction in the second wall portion, which more effectively promotes deformation of the case along the weld mark, making it easier to control the discharge direction of the gas discharged from the safety valve.

[0033] A manufacturing method for a storage cell according to a fourteenth aspect of the present disclosure is a manufacturing method for a storage cell including an electrode body, a case in which the electrode body is housed, and a safety valve provided in the case, and includes a pressing process for pressing and bending a flat plate, a welding process for welding ends of the flat plate bent in the pressing process in a first direction to form a cylindrical housing, and a burr removal process for removing welding burrs formed in the welding process, wherein the burr removal process irradiates a laser onto a weld mark formed in the welding process to remove the welding burrs, and forms a groove portion extending in the first direction as the safety valve in at least a portion of the weld mark.

[0034] In a method for manufacturing a storage cell according to a fourteenth aspect, a flat plate is pressed and bent, and the ends of the bent plate are welded together in a first direction to form a cylindrical housing. Then, when a laser is irradiated onto the weld mark to remove the welding burr, a groove extending in the first direction is formed in at least a portion of the weld mark as a safety valve. This results in a safety valve that overlaps with the weld mark in the thickness direction of the first wall portion, resulting in a storage cell in which variation in the gas discharge direction when gas inside the storage cell is discharged is suppressed. Furthermore, during manufacturing, the process of removing the welding burr and the process of forming the safety valve can be performed in a single process, thereby reducing the number of manufacturing steps.

[0035] The method for manufacturing a storage cell described in a fifteenth aspect of the present disclosure is the configuration described in the fourteenth aspect, wherein in the welding process, the intensity of the laser for forming the groove portion is greater than the intensity of the laser required to remove the welding burr.

[0036] In the method for manufacturing a storage cell according to the fifteenth aspect, by adjusting the intensity of the laser irradiated onto the weld mark, the safety valve can be easily formed in the same manner as in the process of removing welding burrs.

[0037] A sixteenth aspect of the present disclosure provides a method for manufacturing a storage cell including an electrode body, a case in which the electrode body is housed, and a safety valve provided in the case, and includes a first pressing step of pressing and bending a flat plate, a welding step of welding ends of the flat plate bent in the first pressing step in a first direction to form a cylindrical casing, and a second pressing step of pressing at least a portion of the weld marks formed in the welding step to form a groove extending in the first direction as the safety valve.

[0038] In the method for manufacturing an energy storage cell according to the sixteenth aspect, a flat plate is pressed and bent, and the ends of the bent plate are welded together in a first direction to form a cylindrical housing. Then, at least a portion of the weld marks is pressed to form a groove extending in the first direction as a safety valve. This forms a safety valve that overlaps with the weld marks in the thickness direction of the first wall portion, thereby obtaining an energy storage cell in which variation in the gas discharge direction when gas inside the energy storage cell is discharged is suppressed.

[0039] A manufacturing method for a storage cell according to a seventeenth aspect of the present disclosure is a manufacturing method for a storage cell including an electrode body, a case in which the electrode body is housed, and a safety valve provided in the case, and includes a first pressing step in which at least a portion of an end of a flat plate is pressed to form a groove portion extending in a first direction as the safety valve, a second pressing step in which the flat plate is pressed and bent, and a welding step in which the ends of the flat plate bent in the second pressing step are welded together in the first direction to form a cylindrical housing, and the safety valve is positioned along a weld mark extending in the first direction.

[0040] In the method for manufacturing an energy storage cell according to the seventeenth aspect, at least a portion of an end of a flat plate is pressed to form a groove extending in a first direction as a safety valve. Therefore, in a subsequent step, the flat plate is pressed and bent, and the ends of the bent plate are welded together in the first direction to form a cylindrical housing, thereby forming a safety valve that overlaps with the weld mark in the thickness direction of the first wall portion. This allows for the production of an energy storage cell in which variation in the gas discharge direction when gas inside the energy storage cell is discharged is suppressed.

[0041] As described above, the energy storage cell and the method for manufacturing the energy storage cell according to the present disclosure can suppress variation in the direction in which gas is discharged from inside the energy storage cell.

[0042] 3A and 3B are perspective views of an energy storage cell according to an embodiment; a bottom view of an energy storage cell according to an embodiment, as viewed from below; a partial cross-sectional view of a case illustrating an example of a groove constituting a safety valve according to an embodiment, taken along line 3-3 in FIG. 2; a partial cross-sectional view of a case illustrating an example of a groove constituting a safety valve according to an embodiment, taken along line 3-3 in FIG. 2; a partial cross-sectional view of a case illustrating an example of a groove constituting a safety valve according to an embodiment, taken along line 3-3 in FIG. 2; a partial cross-sectional view of a case, for explaining deformation of the case when pressure inside the case increases and opening of the safety valve; a diagram illustrating an example of a manufacturing method of an energy storage cell according to an embodiment, showing a cutting step; a diagram illustrating an example of a manufacturing method of an energy storage cell according to an embodiment, showing a welding step; a diagram illustrating an example of a manufacturing method of an energy storage cell according to an embodiment, showing a burr removal step; a diagram illustrating an example of a manufacturing method of an energy storage cell according to an embodiment, showing a sealing step; a diagram illustrating an example of a manufacturing method of an energy storage cell according to an embodiment, showing a burr removal step; a diagram illustrating an example of a manufacturing method of an energy storage cell according to an embodiment, showing a state before pressing in a pressing step to form a safety valve; a diagram illustrating an example of a manufacturing method of an energy storage cell according to an embodiment, showing a state after pressing in a pressing step to form a safety valve. 1 shows an example of a manufacturing method of an energy storage cell according to an embodiment, showing a sealing step; FIG. 2 shows an example of a manufacturing method of an energy storage cell according to an embodiment, showing a pressing step for forming a safety valve; FIG. 3 shows an example of a manufacturing method of an energy storage cell according to an embodiment, showing a welding step; FIG. 4 shows an example of a manufacturing method of an energy storage cell according to an embodiment, showing a burr removal step; FIG. 5 shows an example of a manufacturing method of an energy storage cell according to an embodiment, showing a sealing step; FIG. 6 is a partial bottom view of a storage cell according to a first modified example of the embodiment, showing an example of a configuration in which a groove portion of a safety valve has a straight portion and an extended portion; FIG. 7 is a partial bottom view of a storage cell according to a first modified example of the embodiment, showing an example of a configuration in which a groove portion of a safety valve has a straight portion and an extended portion; FIG. 8 is a partial bottom view of a storage cell according to a second modified example of the embodiment, showing an example of a configuration in which a welded portion is formed at an end portion in the short direction of a first wall portion; FIG. 9 is a perspective view of a storage cell according to a third modified example of the embodiment, corresponding to FIG. 1; FIG. 10 is a bottom view of a storage cell according to a third modified example of the embodiment, corresponding to FIG. 2.12 is a partial cross-sectional view of the case taken along line 12-12 of FIG. 11 , showing a third modified example of the embodiment; FIG. 13 is a partial bottom view of the storage cell showing a fourth modified example of the embodiment, showing another example of the safety valve; FIG. 14 is a partial bottom view of the storage cell showing a fifth modified example of the embodiment, showing another example of the safety valve; and FIG. 15 is a partial cross-sectional view of the case showing a sixth modified example of the embodiment, showing another example of the safety valve.

[0043] The energy storage cell 10 according to the embodiment will be described below with reference to FIGS. 1 to 7D. Note that the arrow W1 shown in each drawing indicates a first direction, the arrow W2 indicates a second direction, and the arrow W3 indicates a third direction. The first direction, the second direction, and the third direction are perpendicular to one another. In the embodiment, the first direction W1 coincides with the width direction of the energy storage cell. The second direction W2 coincides with the thickness direction of the energy storage cell. The third direction W3 coincides with the height direction of the energy storage cell.

[0044] Unless otherwise specified in the specification, each element is not limited to one and may be present in multiple numbers. Furthermore, in the drawings, substantially identical elements are given the same reference numerals, and duplicated explanations in the specification are omitted. Furthermore, in the drawings, substantially identical elements are given the same reference numerals, and duplicated explanations in the specification are omitted.

[0045] Furthermore, in this specification, the term "process" includes not only a process that is independent of other processes, but also a process that cannot be clearly distinguished from other processes as long as the purpose of that process is achieved. Furthermore, unless otherwise specified in this specification, the term "extending in a direction..." includes both cases where the direction is extending in the same direction as the specified direction indicated by that direction, and cases where the direction is extending in a direction inclined relative to the specified direction indicated by that direction.

[0046] 1 is a perspective view of a storage cell 10. As shown in this figure, the storage cell 10 is, for example, a lithium ion secondary battery, and includes an electrode body 12, a case 14 that houses the electrode body 12, and a safety valve 30A provided in the case 14.

[0047] (Electrode body) The electrode body 12 is formed in a flat rectangular parallelepiped shape with the second direction W2 as its thickness direction, and constitutes the positive and negative electrodes of a lithium-ion secondary battery. This electrode body 12 is configured, for example, like a known electrode body, to include one or more laminates in which a positive electrode current collector, a positive electrode active material layer, an electrolyte layer, a negative electrode active material layer, a negative electrode current collector, a negative electrode active material layer, an electrolyte layer, and a positive electrode active material layer are laminated in this order in the second direction W2. Note that the electrolyte layer may include a liquid electrolyte or a solid electrolyte.

[0048] (Case) The case 14 is composed of a case body 16 that forms a cylindrical housing, and a pair of terminal wall portions 18 that seal two openings of the case body 16. The case body 16 and the pair of terminal wall portions 18 are formed from a metal plate such as aluminum or iron.

[0049] The case body 16 has a pair of first walls 20 facing each other in the third direction W3 and a pair of second walls 22 facing each other in the second direction W2. The pair of first walls 20 form the top and bottom surfaces of the case 14 and extend with the first direction W1 as the longitudinal direction and the second direction W2 as the lateral direction. The pair of second walls 22 form both side surfaces (front and back) of the case 14 and extend with the first direction W1 as the longitudinal direction and the third direction W3 as the lateral direction.

[0050] The case body 16 is formed, for example, by bending a flat plate using a press and welding the ends of the plate together to form a cylindrical housing.

[0051] The pair of first walls 20 and the pair of second walls 22 that constitute the case body 16 are connected at their opposite ends in the first direction W1 to a pair of terminal walls 18 that will be described later.

[0052] The pair of terminal walls 18 are sealing bodies that seal the opening 17 of the case body 16, which has openings on two sides, and are formed in the shape of a rectangular plate with its thickness direction aligned in the first direction W1. The pair of terminal walls 18 extend with their longitudinal direction aligned in the third direction W3 and their lateral direction aligned in the second direction W2.

[0053] A positive electrode terminal 24A and a negative electrode terminal 24B are respectively disposed on the pair of terminal wall portions 18 and protrude in the first direction W1 as electrode terminals. The positive electrode terminal 24A is electrically connected to a positive electrode current collector (not shown) of the electrode body 12. The negative electrode terminal 24B is electrically connected to a negative electrode current collector (not shown) of the electrode body 12.

[0054] Fig. 2 is a bottom view of the energy storage cell 10 as viewed from below. As shown in Fig. 2, a weld mark 26 is formed on the first wall portion 20 that constitutes the bottom surface of the case body 16, joining the ends of the flat plates. This weld mark 26 extends from one end to the other end of the first wall portion 20 in the first direction W1 (longitudinal direction). Furthermore, the weld mark 26 is disposed at a distance from the end of the first wall portion 20 in the second direction W2 (transverse direction). In this embodiment, in particular, the weld mark 26 is disposed in the center of the first wall portion 20 in the second direction W2.

[0055] (Safety Valve) A safety valve 30A is provided in the first wall portion 20 that forms the bottom surface of the case body 16. The safety valve 30A is a thin-walled portion that is thinner than other portions of the first wall portion 20, and will rupture if the pressure of gas generated inside the case 14 of the energy storage cell 10 rises excessively. This allows the gas generated inside the case 14 to be discharged to the outside.

[0056] Furthermore, in this embodiment, when the pressure inside the case 14 increases, the force caused by the deformation of the case 14 along the weld mark 26 assists in opening (cracking) the safety valve 30A. For this reason, the safety valve 30A is disposed on the same side of the first wall portion 20 as the weld mark 26.

[0057] To further explain the safety valve 30A, in order to use the deformation of the case 14 along the weld mark 26 as an auxiliary force when the safety valve 30A opens (ruptures), it is preferable that the safety valve 30A extend along the weld mark 26 and have a shape whose longitudinal direction is the first direction W1 in a plan view. In this embodiment, the safety valve 30A is configured with a groove portion 32 formed on the outer surface 20A of the first wall portion 20, and is visible from the outside.

[0058] 2, the groove 32 has a straight portion 321 extending in the first direction W1, and the straight portion 321 extends from one end of the first wall 20 in the first direction W1 to the other end. The straight portion 321 is formed in the center of the first wall 20 in the second direction W2, and is arranged so as to overlap the weld mark 26 in the thickness direction of the first wall 20.

[0059] The cross-sectional shape of the groove portion 32 is not particularly limited, and various cross-sections can be employed. Figures 3A to 3C are partial cross-sectional views of the case body 16 corresponding to a cross section taken along line 3-3 in Figure 2, illustrating examples of the cross-sectional shape of the groove portion 32. The cross-sectional shape of the groove portion 32 may be a substantially trapezoidal cross-section, as in groove portion 32A shown in Figure 3A. It may also be a substantially arc-shaped (U-shaped) cross-section, as in groove portion 32B shown in Figure 3B. It may also be a substantially triangular (V-shaped) cross-section, as in groove portion 32C shown in Figure 3C.

[0060] In the above, it is not essential that the safety valve 30A (groove 32) extend from one end to the other end in the first direction W1 of the first wall portion 20, and it may be formed only in a portion of the first direction. For example, the groove serving as the safety valve may be formed only in the center and disposed at a distance from the end of the first wall portion 20 in the first direction W1 (longitudinal direction). Furthermore, the safety valve 30A may be composed of multiple grooves disposed along the first direction W1. Furthermore, it is not essential that the safety valve 30A (groove 32) be disposed so as to overlap the weld mark 26 in the thickness direction of the first wall portion 20, and it may be disposed at a position spaced apart from the weld mark 26.

[0061] [Regarding the Opening of the Safety Valve] Figure 4 is a partial cross-sectional view showing the lower part of the case 14, illustrating the deformation of the case 14 and the opening of the safety valve 30A when the pressure inside the case 14 increases. As shown in Figure 4, a weld mark 26 of the case body 16 extends in the first direction W1 on the first wall portion 20 that forms the bottom surface of the case 14. The portion where the weld mark 26 is located is relatively weaker than other portions of the case body 16. Therefore, when the pressure F inside the case 14 increases excessively, the first wall portion 20 of the case 14 bends along the weld mark 26 and deforms into a convex shape facing outward.

[0062] At this time, the safety valve 30A provided in the case 14 deforms along the weld mark 26, similar to the first wall portion 20. As a result, the pressure F inside the case 14 acts in a direction that ruptures the groove portion 32. If the pressure F inside the case 14 subsequently rises beyond the allowable range, the groove portion 32 ruptures, the safety valve 30A opens, and gas and the like are discharged downward from the case 14.

[0063] [Method for Manufacturing Energy Storage Cell] Hereinafter, a method for manufacturing the energy storage cell 10 will be described. Three examples will be described below with reference to Figs. 5A to 7D.

[0064] (First Method) In the first method, as shown in FIG. 5A, a cutting step is first carried out in which a flat plate 3 of a predetermined size is cut out from a roll 2 of a metal plate material (FIG. 5A).

[0065] Next, a pressing process is carried out in which the flat plate 3 produced in the cutting process is pressed and bent, and a welding process is carried out in which the ends of the flat plate 3 bent in the pressing process are welded together in the first direction W1 to form a cylindrical housing 4 (Figure 5B).

[0066] Next, a deburring process is carried out to remove welding burrs 27 formed in the welding process (FIG. 5C). Note that welding burrs 27 are protrusions that occur on the joining surfaces during welding.

[0067] In this burr removal process, a laser is irradiated onto the weld mark 26 formed by the welding process to remove the weld burr 27, and a groove portion 32 extending in the first direction W1 is formed over the weld mark 26 as a safety valve 30A.

[0068] The laser intensity for forming the groove 32 is greater than the laser intensity required for removing the welding burr 27. In this embodiment, the groove 32 constituting the safety valve 30A extends from one end to the other end in the first direction W1 of the first wall 20, so the laser intensity is set to an intensity for forming the groove 32 and irradiated along the weld mark 26. This allows the groove 32 to be formed simultaneously with the removal of the welding burr 27, thereby reducing the number of manufacturing steps.

[0069] Alternatively, after the welding burrs 27 are removed by irradiating the welding mark 26 with a laser, the intensity of the laser may be increased and the laser may be irradiated again onto the welding mark to form the groove 32 .

[0070] Furthermore, when the groove portion 32 is set so as to overlap a portion of the weld mark 26, the removal of the weld burr 27 and the formation of the groove portion 32 can be completed in one step by changing the laser intensity while moving the laser irradiation position along the weld mark 26.

[0071] Then, the electrode body 12 is inserted into the housing 4, and the outer periphery of a pair of terminal wall portions 18 is welded to openings provided on two sides of the housing 4 (case main body 16), thereby manufacturing the storage cell 10 (Figure 5D).

[0072] (Second Method) In the second method, similarly to the first method, a cutting step is first performed in which a flat plate 3 of a predetermined size is cut out from a roll 2 of metal plate material ( FIG. 5A ). Next, a pressing step (first pressing step) is performed in which one flat plate 3 produced in the cutting step is pressed and folded, and a welding step is performed in which ends of the flat plate 3 folded in the pressing step are welded together in a first direction W1 to form a cylindrical housing 4 ( FIG. 5B ).

[0073] Next, a deburring process is carried out in which a laser is irradiated onto the weld mark 26 formed in the welding process to remove the welding burr 27 (FIG. 6A).

[0074] Next, a pressing step (second pressing step) is carried out in which at least a part of the weld mark 26 formed in the welding step is pressed to form a groove portion 32 extending in the first direction W1 as the safety valve 30A.

[0075] In this process, for example, the cylindrical housing 4 is turned upside down, the first wall 20 with the weld marks 26 formed thereon is placed on the upper surface, a rectangular block-shaped jig 5 is inserted into the housing 4, and the weld marks 26 on the first wall 20 are pressed from above with a press 6 to form grooves 32 ( FIG. 6B ). Note that the press 6 has a protrusion 6A formed thereon that corresponds to the groove 32, and the upper surface of the jig 5 has a recess 5A formed thereon that corresponds to the protrusion 6A (groove 32) ( FIG. 6C ).

[0076] As shown in Figure 6C, when a substantially trapezoidal groove portion 32 is formed by press processing, the thickness T2 of the inclined surface connecting the opening of the groove portion 32 to the bottom surface may be smaller than the thickness T1 of the bottom surface, making it a thinner portion compared to other parts of the first wall portion 20.

[0077] Then, the electrode body 12 is inserted into the housing 4, and the outer periphery of a pair of terminal wall portions 18 is welded to openings provided on two sides of the housing 4 (case main body 16), thereby manufacturing the storage cell 10 (Figure 6D).

[0078] In the second method, if the welding burrs 27 are formed only inside the grooves 32, as in the illustrated example, the burr removal step may be omitted.

[0079] (Third Method) In the third method, first, a cutting step is carried out in which a flat plate 3 of a predetermined size is cut out from a roll 2 of a metal plate material (FIG. 7A).

[0080] Next, a pressing step (first pressing step) is carried out in which at least a part of the end of one flat plate is pressed to form a groove 32 extending in the first direction W1 as the safety valve 30A (FIG. 7A).

[0081] Next, a pressing process (second pressing process) is performed in which one flat plate 3 is pressed and bent, and a welding process is performed in which ends of the flat plate 3 bent in the pressing process are welded together in the first direction W1 to form the cylindrical housing 4 ( FIG. 7B ). This process includes, simultaneously with the process of welding the ends of the flat plate together in the first direction W1, a process of arranging the safety valve 30A along the weld mark 26 extending in the first direction W1. In the illustrated example, a groove 32 serving as the safety valve 30A is formed at a position overlapping the weld mark 26 in the thickness direction of the first wall portion 20.

[0082] Next, a deburring process is carried out in which a laser is irradiated onto the weld mark 26 formed in the welding process to remove the welding burr 27 (FIG. 7C).

[0083] Then, the electrode body 12 is inserted into the housing 4, and the outer periphery of a pair of terminal wall portions 18 is welded to openings provided on two sides of the housing 4 (case main body 16), thereby manufacturing the storage cell 10 (Figure 7D).

[0084] (Functions and Effects) As described above, in the energy storage cell 10 according to the embodiment, the case 14 that houses the electrode assembly 12 is provided with a safety valve 30A. This safety valve 30A is configured to open when the internal pressure rises beyond an allowable range, thereby discharging gas and the like inside the case 14 to the outside.

[0085] Here, the case 14 includes a pair of terminal walls 18 facing each other in the first direction W1 and a first wall 20 connected to the pair of terminal walls 18. The safety valve 30A is disposed on the first wall 20 along with a weld mark 26 extending in the first direction W1. Therefore, when the internal pressure increases, the opening of the safety valve 30A and deformation of the case due to deformation near the weld mark 26 can be concentrated on the first wall 20. As a result, as shown in FIG. 4 , the deformation of the case 14 assists the opening of the safety valve 30A, thereby suppressing variation in the direction of gas discharge when gas inside the energy storage cell is discharged. Furthermore, even if the case 14 should split near the weld mark 26, the direction of gas discharge from the split portion and the direction of gas discharge from the safety valve 30A can be made substantially the same. This also suppresses variation in the direction of gas discharge when gas inside the energy storage cell is discharged.

[0086] In this embodiment, the safety valve 30A extends along the weld mark 26, and the longitudinal direction is the first direction W1. This allows the case 14 to deform along the weld mark 26 in the event of an abnormality, thereby efficiently urging the safety valve 30A to open.

[0087] In addition, in this embodiment, the weld marks 26 and the safety valve 30A are visible from the outer surface 20A, which facilitates quality inspection during the manufacturing process.

[0088] In addition, in this embodiment, the weld mark 26 extends from one end to the other end in the first direction W1 in the first wall portion 20, which more effectively promotes deformation of the case 14 along the weld mark 26, making it easier to control the discharge direction of the gas discharged from the safety valve 30A.

[0089] In this embodiment, the weld mark 26 extends in the first direction W1 (longitudinal direction) on the first wall portion 20 and is spaced apart from the end in the second direction W2 (transverse direction). When the pressure inside the case 14 increases, stress concentrates on the end in the transverse direction of the first wall portion 20, but the weld mark 26 is spaced apart from the end in the transverse direction. This suppresses stress concentration near the weld mark 26 and prevents the weld mark 26 on the case 14 from cracking.

[0090] In particular, in this embodiment, the weld mark 26 is disposed in the center of the first wall portion 20 in the second direction W2 (short direction), which suppresses stress concentration near the weld mark 26 and prevents the weld mark 26 of the case 14 from cracking.

[0091] Furthermore, in this embodiment, the safety valve 30A is disposed so as to overlap the weld mark 26 in the thickness direction of the first wall portion 20. As a result, when the pressure inside the case 14 increases, the force caused by the deformation of the case 14 along the weld mark 26 is efficiently applied to the safety valve 30A, assisting in the opening of the safety valve 30A. This makes it easier to manage the direction in which gas is discharged when the pressure inside the case 14 increases.

[0092] In this embodiment, the safety valve 30A has at least one groove 32, and the safety valve 30A can be opened by rupturing the groove 32.

[0093] Furthermore, the groove 32 is configured so that at least a portion thereof overlaps the weld mark 26 in the thickness direction of the first wall 20. Specifically, the groove has a straight portion 321 extending in the first direction W1, and the straight portion 321 overlaps the weld mark 26 in the thickness direction of the first wall 20. This makes it even easier to control the direction in which gas is discharged when the pressure inside the case 14 increases.

[0094] 5A to 5D , the energy storage cell 10 according to this embodiment can be manufactured by the first method shown in FIGS. 5A to 5D , whereby a groove 32 extending in the first direction W1 can be formed as a safety valve 30A in at least a portion of the weld mark 26 when the weld burr 27 is removed by irradiating the weld mark 26 with a laser. This allows the safety valve 30A to be formed so as to overlap with the weld mark 26 in the thickness direction of the first wall portion 20, thereby making it possible to obtain an energy storage cell 10 in which variation in the gas discharge direction when gas inside the energy storage cell 10 is discharged is suppressed. Furthermore, during manufacturing, the process of removing the weld burr 27 and the process of forming the safety valve 30A can be performed in a single process, thereby reducing the number of manufacturing steps.

[0095] Furthermore, since the intensity of the laser used to form the groove portion 32 is greater than the intensity of the laser required to remove the welding burr 27, by adjusting the intensity of the laser irradiated onto the welding mark 26, the safety valve 30A can be easily formed in the same manner as the process of removing the welding burr 27.

[0096] 6A to 6D , the energy storage cell 10 according to this embodiment can be manufactured by pressing at least a portion of the weld mark 26 to form a groove 32 extending in the first direction W1 as the safety valve 30A. This forms the safety valve 30A that overlaps with the weld mark 26 in the thickness direction of the first wall portion 20, thereby obtaining an energy storage cell 10 in which variation in the gas discharge direction when gas inside the energy storage cell 10 is discharged is suppressed.

[0097] In the second method, it is not essential to form the safety valve 30A so as to overlap the weld mark 26 in the thickness direction of the first wall portion 20. For example, the vicinity of the weld mark may be pressed to form the safety valve at a position spaced apart from the weld mark.

[0098] 7A to 7D , the energy storage cell 10 according to this embodiment is manufactured by the third method shown in FIGS. 7A to 7D , whereby at least a portion of the end of one flat plate 3 is pressed to form a groove 32 extending in the first direction W1 as the safety valve 30A. Therefore, in a subsequent process, the one flat plate 3 is pressed and bent, and the ends of the bent flat plate 3 are welded together in the first direction W1 to form the cylindrical housing 4, thereby forming the safety valve 30A that overlaps with the weld mark 26 in the thickness direction of the first wall 20. This makes it possible to obtain an energy storage cell 10 in which variation in the gas discharge direction when gas inside the energy storage cell 10 is discharged is suppressed.

[0099] In the third method, it is not essential to form the safety valve 30A overlapping with the weld mark 26 in the thickness direction of the first wall portion 20. For example, in the pressing process of the flat plate, the vicinity of the intended position where the weld mark is to be formed may be pressed, and the safety valve may be formed at a position separated from the weld mark.

[0100] Although one embodiment of the present disclosure has been described above, the present disclosure is not limited to the configuration of the above embodiment. Below, several modifications that can be applied to the above embodiment will be listed and described.

[0101] (First Modification) In the above embodiment, the safety valve may have groove 32 including extension portions 322A and 322B that intersect with straight portion 321, like safety valves 30B and 30C shown in FIGS. 8A and 8B.

[0102] The extension portion 322A in FIG. 8A extends linearly along the second direction W2 on the first wall portion 20 and intersects the linear portion 321 of the groove portion 32 so as to be perpendicular to the first wall portion 20A.

[0103] 8B has a V-shaped branched shape from both ends in the first direction W1 of the straight portion 321. Each extension portion 322B extends in one direction and the other in the second direction W2 along a direction inclined at an acute angle with respect to the second direction W2.

[0104] 8A and 8B extend in the second direction W2 (short direction) through the first wall portion 20, and are arranged such that the portions where they intersect with the straight portion 321 overlap the weld marks 26 in the thickness direction of the first wall portion 20. Therefore, when the pressure inside the case 14 increases, the auxiliary force caused by the deformation of the case 14 is transmitted in multiple directions around the portion where the straight portion 321 and the extended portion 322A (or the extended portion 322B) intersect, making it even easier to open the safety valve.

[0105] 9, the weld mark 26 may extend in the first direction W1 (longitudinal direction) and be located at one end in the second direction W2 (transverse direction) of the first wall portion 20. In this configuration, when the internal pressure of the case 14 increases, the case 14 can be deformed early in the vicinity of the weld mark 26, thereby assisting in opening the safety valve 30A.

[0106] That is, when the internal pressure of the case 14 increases, stress is concentrated at the end of the first wall portion 20 in the second direction W2 (short direction). Therefore, by arranging the weld marks 26 at the end of the first wall portion 20 in the second direction W2, the case 14 can be deformed early in the vicinity of the weld marks 26 when the internal pressure of the case 14 increases. As a result, when the internal pressure increases due to the discharge of gas from inside the energy storage cell, the safety valve 30A can be opened quickly.

[0107] Furthermore, the weld marks 26 according to the second modification are arranged at the corners of the case body 16, which forms the cylindrical housing. Therefore, in the manufacturing process, the number of times the flat plate is bent during the pressing process in which a single flat plate is bent by pressing can be reduced, which is advantageous for reducing manufacturing costs.

[0108] 10 to 12, the weld mark 26 may be disposed on the second wall portion 22. In this third modification, the weld mark 26 is provided on the second wall portion 22 adjacent to the first wall portion 20 on which the safety valve 30A is disposed. The weld mark 26 is configured to extend along the first direction W1 at the end of the second wall portion 22 in the third direction W3, the end adjacent to the first wall portion 20.

[0109] As in the above embodiment, the first wall portion 20 has a groove portion 32 formed in the center of the first wall portion 20 in the second direction W2 (short-side direction), which constitutes a safety valve 30A.

[0110] The weld mark 26 extends from one end to the other end of the second wall portion 22 in the first direction W1.

[0111] In this configuration, the safety valve 30A extending in the first direction W1 is disposed on the first wall portion 20 near the weld mark 26 extending in the first direction W1 at the end of the second wall portion 22. Therefore, in the configuration of the third modified example, as in the above embodiment, when the internal pressure of the case 14 increases, the case 14 deforms along the weld mark 26 near the safety valve 30A. This deformation of the case 14 acts as an auxiliary force when opening the safety valve 30A, thereby reducing variation in the direction of gas discharge when gas inside the energy storage cell is discharged. Furthermore, even if the case 14 should split open near the weld mark 26, the direction of gas discharged from the split portion and the direction of gas discharged from the safety valve 30A can be made substantially the same. This also reduces variation in the direction of gas discharge when gas inside the energy storage cell is discharged. This facilitates management of the safety valve 30A.

[0112] Furthermore, since the weld mark 26 extends from one end to the other end in the first direction W1 in the second wall portion 22, deformation of the case 14 along the weld mark 26 is effectively promoted, making it even easier to control the discharge direction of the gas discharged from the safety valve.

[0113] In the third modified example, the safety valve 30A may be provided at the end of the first wall portion 20 on the second wall portion 22 side, and the weld mark 26 and the safety valve 30A may be brought close to each other.

[0114] (Fourth Modification) In the above embodiment, the safety valve may be configured with a recess 34 of a predetermined shape, as in the safety valve 30D shown in FIG. 13 . As an example, the recess 34 may be elliptical in shape with the first direction W1 as the longitudinal direction in a plan view (as viewed in the third direction W3). The recess 34 may be disposed in the center of the first wall portion 20 in the first direction W1 and in the second direction W2, and may be configured to overlap the weld mark 26 in the thickness direction of the first wall portion 20. The recess 34 may be rectangular in plan view. The recess 34 may be formed by irradiating the first wall portion 20 with a laser or by press working.

[0115] (Fifth Modification) In the above-described embodiment, the safety valve may be configured with only a groove portion 36 extending in the second direction W2, as in a safety valve 30E shown in Fig. 14. As an example, the groove portion 36 shown in Fig. 14 is arranged so as to overlap with the weld mark 26 at the center in the first direction W1.

[0116] (Sixth Modification) In the above embodiment, the safety valve may be formed on the inner surface 20B of the first wall portion 20, as in the safety valve 30F shown in Fig. 15. The safety valve 30F is configured as a groove portion 38 extending in the first direction W1 on the inner surface 20B of the first wall portion 20, and as one example, is arranged so as to overlap the weld mark 26 in the thickness direction of the first wall portion 20. Other than that, as a detailed configuration of the groove portion 38, the configuration applicable to the groove portion 32 of the above embodiment can be similarly applied.

[0117] (Seventh Modification) Although not shown in the drawings, in the above embodiment, the weld mark 26 and the safety valve 30A are arranged on the first wall 20 that constitutes the bottom surface of the case 14, but the present disclosure is not limited to this. For example, the weld mark 26 and the safety valve 30A may be arranged on the first wall 20 that constitutes the top surface of the case 14, or on one of the pair of second wall portions 22 that face in the second direction W2, or on one of the pair of wall portions that face in the first direction W1.

[0118] Although one embodiment and several modified examples of the present disclosure have been described above, the present disclosure allows substitutions and modifications of each configuration within the scope of the gist thereof. Furthermore, it is also possible to apply a combination of the configurations of the embodiment and the modified examples.

[0119] The disclosure of Japanese Patent Application No. 2024-134646, filed on August 9, 2024, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards mentioned herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A storage cell comprising: an electrode body; a case in which the electrode body is housed; and a safety valve provided in the case, wherein the case includes a pair of terminal wall portions on which electrode terminals are arranged and which face each other in a first direction; and a first wall portion which is a wall portion connected to the pair of terminal wall portions and on which weld marks extending in the first direction are arranged; and the safety valve is arranged in the first wall portion.

2. The energy storage cell according to claim 1, wherein the safety valve extends along the weld mark and has a longitudinal direction in the first direction.

3. The energy storage cell according to claim 1, wherein the safety valve is formed on the outer surface of the first wall portion.

4. The energy storage cell according to claim 1, wherein the weld mark extends from one end to the other end in the first direction on the first wall portion.

5. The energy storage cell according to claim 4, wherein the first wall portion extends with the first direction as its longitudinal direction and a second direction intersecting the first direction as its lateral direction, and the weld marks are arranged on the first wall portion at a distance from an end portion in the second direction.

6. The energy storage cell according to claim 5, wherein the weld mark is located at a center portion of the first wall portion in the second direction.

7. The energy storage cell according to claim 1, wherein at least a portion of the safety valve overlaps with the weld mark in the thickness direction of the first wall portion.

8. The energy storage cell according to claim 7, wherein the safety valve includes at least one groove, and at least a portion of the groove overlaps with the weld mark in the thickness direction.

9. The energy storage cell according to claim 8, wherein the groove portion has a straight portion extending in the first direction, and the straight portion overlaps the weld mark in the thickness direction.

10. The energy storage cell according to claim 9, wherein the groove portion has an extension portion that intersects with the straight portion, and the portion of the extension portion that intersects with the straight portion overlaps with the weld mark in the thickness direction.

11. The energy storage cell according to claim 4, wherein the first wall portion extends with the first direction as its longitudinal direction and a second direction intersecting the first direction as its lateral direction, and the weld mark is located at one end of the first wall portion in the second direction.

12. A storage cell comprising: an electrode body; a case in which the electrode body is housed; and a safety valve provided in the case, wherein the case includes a pair of terminal wall portions on which electrode terminals are arranged and which face each other in a first direction, and a wall portion connected to the pair of terminal wall portions, and the wall portion connected to the pair of terminal wall portions includes a first wall portion on which the safety valve is arranged, and a second wall portion provided adjacent to the first wall portion and on which a weld mark extending along the first direction is arranged at an end adjacent to the first wall portion.

13. The energy storage cell according to claim 12, wherein the weld mark extends from one end to the other end in the first direction on the second wall portion.

14. A method for manufacturing an energy storage cell including an electrode body, a case that houses the electrode body, and a safety valve provided in the case, the method comprising: a pressing process that presses and bends a flat plate; a welding process that welds ends of the flat plate bent in the pressing process in a first direction to form a cylindrical casing; and a burr removal process that removes welding burrs formed in the welding process, wherein the burr removal process irradiates a weld mark formed in the welding process with a laser to remove the welding burrs and forms a groove portion extending in the first direction in at least a part of the weld mark as the safety valve.

15. The method for manufacturing a storage cell according to claim 14, wherein in the welding step, the intensity of the laser used to form the groove is greater than the intensity of the laser required to remove the welding burrs.

16. A method for manufacturing a storage cell comprising an electrode body, a case in which the electrode body is housed, and a safety valve provided in the case, the method comprising: a first pressing step of pressing and bending a flat plate; a welding step of welding ends of the flat plate bent in the first pressing step in a first direction to form a cylindrical casing; and a second pressing step of pressing at least a portion of the weld marks formed in the welding step to form a groove portion extending in the first direction as the safety valve.

17. A method for manufacturing a storage cell comprising an electrode body, a case in which the electrode body is housed, and a safety valve provided in the case, the method comprising: a first pressing step of pressing at least a portion of an end of a flat plate to form a groove extending in a first direction as the safety valve; a second pressing step of pressing and bending the flat plate; and a welding step of welding the ends of the flat plate bent in the second pressing step together in the first direction to form a cylindrical casing, and arranging the safety valve along the weld marks extending in the first direction.

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