Battery cover with safety valve

Abstract

To provide a battery lid that has a structure resistant to external impacts on a thin wall portion and opens with a wide safe opening area when opened.SOLUTION: A battery lid 1 is formed by press working and is equipped with a safety valve 2 that opens when a predetermined pressure is reached, and is composed of a flat member and a safety valve, the safety valve 2 includes a rising portion 20 that rises from the flat member 10 and is formed circumferentially along the safety valve 2, a thin-walled portion 21 that is located on the inner side of the rising portion 20 and is formed circumferentially, and an expanded portion 22 that is located on the inner side of the thin-walled portion and is formed in a circular shape, and a top portion 20c of the rising portion on the outer periphery side and an outer end portion 23a of the expanded portion on the inner periphery side are located above an upper surface of the thin-walled portion 21.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a battery lid equipped with a safety valve which is provided in a sealed battery and which deploys with a wide opening area when the pressure (internal pressure) within the battery case rises to a predetermined value. [Background technology]

[0002] Conventionally, when non-aqueous electrolyte secondary batteries such as lithium-ion batteries are short-circuited due to charging / discharging or external impact, a large current is concentrated locally in the material, generating heat and generating gas, which causes the pressure (internal pressure) inside the battery case to rise. For this reason, batteries are equipped with a safety valve to release the increased internal pressure.

[0003] Regarding such safety valves, a safety valve that is ruptured by concentrating stress on the thinnest part of the metal plate (Patent Document 1) has been disclosed.Also, a safety valve that is ruptured and deployed by providing a thick part in a part of a thin part, thereby making the ease of rupturing against stress different depending on the difference in thickness (Patent Document 2) has been disclosed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5237341 [Patent Document 2] JP 2000-285892 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the above-mentioned safety valve limits the location of stress concentration by the difference in thickness, but there is a problem that the location of rupture varies depending on the corresponding thickness, and rupture occurs unintentionally. In addition, the smaller the opening range, the longer it takes to release the internal pressure. Furthermore, there is a possibility that the safety valve itself will be blown off and hit the surroundings. As such, conventional safety valves may rupture and deploy incompletely, and there has been a demand for a safety valve that has a wide opening area (safe opening area) that can safely discharge the electrode solution that has reached a predetermined internal pressure, and can safely and appropriately discharge it to the outside.

[0006] In addition, conventional safety valves are formed by processing stainless steel plates, and the part that splits open is often formed with a relatively thin wall thickness. If an external impact is applied to such a part, the safety valve may be damaged and split open. Conventional battery lids are designed to house lithium-ion batteries inside a housing, and are not designed to withstand external impacts. However, there is a certain probability that the battery lid may be subjected to an impact from inside or outside the housing, and in that case, the safety valve may suddenly open. Thus, many conventional safety valves have a structure that is vulnerable to external impacts, and there has been a demand for a safety valve structure that is resistant to external impacts, especially to the thin part that splits open.

[0007] Therefore, the battery lid equipped with a safety valve according to the present invention is structured to be resistant to external impacts on the thin-walled portion, and by opening with a safety opening area that provides a wide opening area, the pressurized electrolyte can be appropriately discharged to the outside. [Means for solving the problem]

[0008] In view of the above problems, the present invention provides a battery lid which is formed by press working and is equipped with a safety valve which opens when a predetermined pressure is reached, and which comprises a flat plate member and a safety valve, wherein the safety valve has a rising portion which rises from the flat plate member and is formed circumferentially along the safety valve, a thin-walled portion which is located on the inner side of the rising portion and is formed circumferentially, and an expansion portion which is located on the inner side of the thin-walled portion and is formed in a circular shape, and wherein the apex of the rising portion is located higher on the outer periphery side than an upper surface of the thin-walled portion, and the outer end of the expansion portion is located higher on the inner periphery side than an upper surface of the thin-walled portion.

[0009] In addition to the above-mentioned configuration, it is preferable that the expansion portion comprises a curved portion formed circumferentially on the outer periphery and curved convexly downward, and a central portion formed in a circular shape on the inner periphery of the curved portion, and that the lower surface of the central portion of the curved portion is lower than the lower surface of the flat plate member, and the upper surface of the central portion of the curved portion is lower than the upper surface of the flat plate member and higher than the lower surface.

[0010] In addition to the above-mentioned configuration, it is preferable that the thin-walled portion formed in a circular shape has a thin-walled main body portion and a thin-walled base end portion having a portion of the circumference thicker than the thin-walled main body portion, the width of the thin-walled portion is 5 to 6% of the diameter of the expanded portion, the base end length, which is the diametric length perpendicular to the width length of the thin-walled base end portion, is 16 to 17% of the diameter of the expanded portion, and the step value obtained by subtracting the thickness of the thin-walled main body portion from the thickness of the thin-walled base end portion is 5 to 7% of the width of the thin-walled portion. Effect of the Invention

[0011] According to the invention described in claim 1, when an impact is applied from above outside toward the thin-walled portion, the top of the rising portion rises to be in a high position on the outer periphery side of the thin-walled portion, preventing the thin-walled portion 21 from being directly impacted from diagonally above outside. Also, when an impact is applied from above inside toward the thin-walled portion, the outer end of the curved portion rises to be in a high position on the inner periphery side of the thin-walled portion, preventing the thin-walled portion from being directly impacted from diagonally above inside. In this way, by sandwiching the thin-walled portion between members that are in high positions on the outer periphery and inner periphery sides, a configuration is created in which it is difficult for an impact to be applied directly to the thin-walled portion.

[0012] According to the invention described in claim 2, when an impact is applied from above to the entire safety valve, the external impact may be received by the curved part, but if the curved part is greatly curved, the force may be concentrated at the curved bottom, causing it to rupture. However, since the curved part is gently curved and the bottom of the curve protrudes slightly downward from the lower surface of the flat plate member, it is possible to prevent the force from being concentrated at the bottom of the curved part and prevent it from rupturing due to an external impact.

[0013] According to the invention described in claim 3, the standard internal pressure for the electrolyte to cleave is set to be equal to or greater than 0.8 MPa and less than 1.0 MPa. At the standard internal pressure, the electrolyte can be cleaved with a wide range of opening area (safe opening area) where the opening angle α of the opening part is 60 degrees or more. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a perspective view showing an example of a battery lid provided with a safety valve of the present invention. [Diagram 2] FIG. [Diagram 3] FIG. 2 is a partially enlarged end view taken along line AA in FIG. 1, with a partially enlarged view of the thin-walled base end portion at the lower right and a partially enlarged view of the thin-walled main body portion at the lower left within the circle. [Figure 4] 1 shows the deployed state of the deployment section, where (a) is a perspective view, (b) is a front view, and (c) is a side view. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] An example of a battery lid 1 according to an embodiment of the present invention will be described with reference to the drawings. In this description, "unfolded" refers to a state in which the unfolded portion 22 of this embodiment is opened upward with the thin-walled base end portion 21a as a fulcrum (see FIG. 4), and "split open" refers to an initial state in which any position of the thin-walled portion 21 of the safety valve 2 begins to tear. "Open" refers to a state in which the unfolded portion 22 unfolds to communicate with the inside and outside of the battery. In addition, the "inner peripheral side" refers to the side of the central portion 24 of the safety valve 2, and the "outer peripheral side" refers to the side of the central portion 24 toward the surrounding flat plate member 10.

[0016] The battery lid 1 shown in Fig. 1 uses a rectangular metal plate made of a soft metal such as aluminum, and is pressed with an opposing punch and die to form a safety valve 2 by the meshing of the punch and die when pressed. The battery lid 1 has a rectangular plate-like flat member 10 and an outer edge 11 that stands on the outer periphery of the flat member 10. The outer edge 11 is joined so as to seal the opening of a container (not shown) that contains the components that make up the battery, such as electrodes, a separator, and an electrolyte. The safety valve 2 is located in the center of the flat member 10, but the position of the safety valve 2 in the present invention is not limited to this position.

[0017] The form of the safety valve 2 formed in the battery lid 1 of this embodiment will be described. As shown in Figs. 2 and 3, the battery lid 1 has a rising portion 20 formed so as to rise from the flat plate member 10 of the battery lid 1 at a steep gradient over the circumference, and a thin-walled portion 21 formed over the circumference in a front view on the inner periphery side of the rising portion 20. The thin-walled portion 21 is formed over the circumference in a front view, but is formed in a C-shape except for a part, and a thin-walled base end portion 21a which is a part of the thin-walled portion and is thicker than the thin-walled main body portion 21b. The inner periphery side of the thin-walled portion 21 has a development portion 22 which is circular in a front view and is composed of a curved portion 23 curved so as to be convex downward and a central flat plate-shaped central portion 24.

[0018] The form of the safety valve 2 will be described in detail. The rising portion 20, which is the outermost edge, rises at a steep gradient from the flat plate member 10 on the outer periphery side. The rising portion 20 of this embodiment rises at a substantially right angle to the flat plate member 10, and the rising angle of the rising portion 20 is such that the inner peripheral side surface that continues from the lower surface side of the flat plate member 10 rises at 90 degrees, while the outer peripheral side surface that continues from the upper surface of the flat plate member 10 rises at 80 degrees, slightly inclined toward the inner peripheral side surface. Therefore, the rising portion 20 of this embodiment rises in the vertical direction from the horizontal flat plate member 10, but has a form having an inclined surface on the outer peripheral side surface. The rising angle of the rising portion 20 is not limited to this embodiment.

[0019] The specific form of the rising portion 20 is composed of a lower portion 20b which is a rising portion, and an upper portion 20a which is continuous from the lower portion 20b, and the reference is the lower surface of the thin wall portion 21 described later (see FIG. 3). The lower portion 20b rises continuously from the flat plate member 10 on the outer periphery side, and has a portion where the rising inner peripheral side surface further protrudes toward the inner periphery side. The thickness of the lower portion 20b (thickness in the left-right direction in the drawing) is about one third of the thickness of the flat plate member 10 (thickness in the up-down direction in the drawing). The upper portion 20a extends vertically continuously from the lower portion 20b, rises further upward than the upper surface of the thin wall portion 21, the inner peripheral side surface inclines toward the outside, and then curves at the apex 20c which is the highest position, to reach the outer surface, and has a shape protruding toward the inner periphery side together with the lower portion 20b.

[0020] The thin-walled portion 21 is between the upper portion 20a and the lower portion 20b of the rising portion 20, and is formed in a thin-plate annular shape from the lower end of the inner peripheral side surface that protrudes most in the inner peripheral direction of the rising portion 20 toward the inner peripheral side. The thin-walled portion 21 is the thinnest among the members that constitute the battery lid 1, and is composed of only a partial thin-walled base end portion 21a and a thin-walled main body portion 21b excluding the thin-walled base end portion 21a. As shown in FIG. 2, the thin-walled base end portion 21a is only a portion of the thin-walled portion 21 formed around the periphery, which has a predetermined base end length S, and the base end length S is preferably about 1 / 10 to 1 / 5 of the diameter when the outer edge of the thin-walled portion 21 is made into a circle. The width W of the thin-walled base end portion 21a is continuous with the thin-walled main body portion 21b, so it is made the same width as the thin-walled main body portion 21b. Similarly, the width W is preferably about 1 / 20 of the diameter when the outer edge of the thin-walled portion is made into a circle. The thin-walled base end 21a is thicker than the thin-walled main body 21b, and the bottom surfaces of the thin-walled base end 21a and the thin-walled main body 21b are flush with each other, and the top surface of the thin-walled main body 21b is located lower than the top surface of the thin-walled base end 21a (see the enlarged view in FIG. 3). The position of the thin-walled base end 21a of the thin-walled portion 21 is not limited to the right side in FIG. 2, and may be any position, such as the upper side of the thin-walled portion 21.

[0021] An expansion portion 22 is formed on the inner peripheral side of the thin portion 21. The expansion portion 22 is a portion of the safety valve 2 where the thin main body portion 21b breaks open when the pressure of the electrolyte rises, and expands with the thin base end portion 21a as a fulcrum to open the inside of the battery. The expansion portion 22 has a curved portion 23 that is curved from the outside to the inner peripheral side so as to be convex downward of the battery lid 1, and a disk-shaped central portion 24 is formed further inward from the curved portion 23.

[0022] The curved portion 23 has an outer end 23a that rises from the upper surface of the thin-walled portion 21 on the outer peripheral side toward the inner peripheral side, and has an outer curved portion 23b that is continuous from the outer end 23a toward the inner peripheral side and has an arc-shaped outer curved portion 23b that is convex downward. The thickness of the curved portion 23 gradually increases in the outer curved portion 23b, and is maximum in a central portion 23c including the lowest position (bottom) of the outer curved portion 23b, and thereafter has the same thickness in the inner curved portion 23d on the inside and the central portion 24.

[0023] The lowest position of the central portion 23c of the curved portion 23 is located one step lower than the flat plate member 10. That is, the upper and lower surfaces of the central portion 23c of the curved portion 23 are both flat, and are located lower than the upper and lower surfaces of the flat plate member 10, respectively. On the other hand, the upper surface of the central portion 23c is located between the upper and lower surfaces of the flat plate member 10 (dotted line K1 in FIG. 3), and the lower surface of the flat plate member 10 is located between the upper and lower surfaces of the central portion 23c (dotted line K2 in FIG. 3). Because of this shape, the curve of the curved portion 23 is a relatively gentle curve. A gentle curve may be a curve in which the radius of curvature is smaller than half the length of the curved portion 23 from the inner circumference side to the outer circumference side. The lower surface of the central portion 23c of the curved portion 23 is located below the lower surface of the flat plate member 10, but the downward protrusion width D of the curved portion 23 is approximately one-third the thickness of the flat plate member 10 and the central portion 23c. Note that even if the central portion 23c is continuously curved as a whole, unlike the present embodiment, it is sufficient to have the above-mentioned shape based on the lowest position (bottom).

[0024] The central portion 24 of the development portion 22 is a circular portion located at the very center of the safety valve 2. The height of the upper surface of the central portion 24 is the same height as the apex of the outer end portion 23a of the curved portion 23, but the apex 20c, which is the upper end portion of the upper part 20a of the rising portion 20, is located higher than the height of the upper surface of this central portion 24 (the height of the apex of the outer end portion 23a) (dotted chain line K3 in FIG. 3).

[0025] The configuration of the safety valve 2 of the battery lid 1 according to this embodiment has been described above. The safety valve 2 according to this embodiment has a configuration that is resistant to external impacts received by the battery lid 1. In the safety valve 2 of the battery lid 1, the part that is vulnerable to external impacts is the thin-walled part 21 that is thinned in thickness so that it will rupture due to an increase in internal pressure, and the assumed external impact is assumed to be that some member in the housing becomes dislodged and receives the impact, and as shown in FIG. 3, possible directions are G1 direction in which the impact is applied from the outside toward the thin-walled part 21, G2 direction in which the impact is applied from the inside toward the thin-walled part 21, and G3 direction in which the impact is applied from above to the entire safety valve 2.

[0026] When an impact is applied from the outside toward the thin-walled portion 21 in the G1 direction, the rising portion 20 of this embodiment rises at a substantially right angle from the flat plate member 10, preventing the impact from being directly applied to the thin-walled portion 21. Also, when an impact is applied from the inside toward the thin-walled portion 21 in the G2 direction, the outer end 23a of the curved portion 23 rises, preventing the impact from being directly applied to the thin-walled portion 21. The height from the upper surface of the thin-walled portion 21 to the apex 20c of the rising portion 20 and the height from the upper surface of the thin-walled portion 21 to the outer end 23a of the curved portion 23 are approximately half the width W of the thin-walled portion 21. It is preferable that the height of the apex 20c and the outer end 23a are half the width W of the thin-walled portion 21 and sandwich both sides, but this is not necessarily limited to this height, and it is preferable that each is at least one-third the width W.

[0027] In addition, in the case of the G3 direction in which an impact is applied from above to the entire safety valve 2, the height of the central portion 24 is the same as the outer end portion 23a of the curved portion 23, and the top portion 21c of the rising portion 20 is located at an even higher position, so that the impact is unlikely to be applied directly to the thin-walled portion 21. Furthermore, although the external impact in the G3 direction may be partially received by the curved portion 23, if the curved portion 23 is greatly curved, there is a possibility that the force will concentrate on the curved bottom and cause the valve to break open. However, as in this embodiment, the curved portion 23 is gently curved and the bottom of the curve protrudes slightly downward from the lower surface of the flat plate member 10, so that the force is prevented from concentrating on the bottom of the curved portion and the valve to break open due to the external impact. In this way, the configuration of the safety valve 2 according to this embodiment makes it possible to prevent the safety valve 2 from unexpectedly opening by preventing a direct impact on the thin-walled portion 21 in response to an expected external impact.

[0028] Furthermore, by making the curved portion 23 gently curved and making the protruding length of the lower surface of the curved portion 23 about one third the thickness of the flat plate member 10, it can be naturally guided to the thin-walled portion 21 under a predetermined internal pressure state, enabling stable cleavage. If the curved portion 23 is made sharply curved or the protruding length of the lower surface is large, unexpected pressure will be applied to the thin-walled portion 21, preventing the deployment portion 22 from coming off and flying off without deploying.

[0029] Next, an embodiment and an experimental example in which the safety valve of this embodiment is configured to secure a wide opening area when it is ruptured and deployed, and to appropriately release the internal electrolyte that has reached a predetermined internal pressure to the outside will be described.

[0030] The wide open area required in this embodiment will now be described. In the safety valve 2 shown in Fig. 1, when the electrolyte inside reaches a certain internal pressure, the thin-walled main body portion 21b ruptures, and the expansion portion 22 expands upward with the thin-walled base end portion 21a as a fulcrum, and the valve is opened. When the valve ruptures, it is often the case that either the inner or outer periphery of the thin-walled main body portion 21b begins to tear, but in this experiment, the inner periphery (the expansion portion side) of the thin-walled portion 21 is assumed to have ruptured.

[0031] In the safety valve 2 of this embodiment, the diameter of the development portion 22 (the inner peripheral side of the thin wall portion) is 18 mm, and the area of ​​the development portion is 254.34 mm 2 When the deployment portion 22 is deployed at an angle α as shown in Figure 4(a) to (c) from the undeployed state shown in Figure 1, the open area (upper visible area R) of the safety valve 2 viewed from above is 75 mm 2 It is preferable that the upper visible area is equal to or larger than the above. In other words, the area of ​​the open portion is the area obtained by subtracting the portion Q hidden by the unfolded unfolding portion 22 when viewed from above. In order to ensure such an upper visible area, a minimum area can be ensured even if the unfolding angle α of the unfolding portion 22 is 45 degrees, but it is more preferable that the unfolding angle α is 60 degrees or larger.

[0032] In this embodiment, the reference internal pressure is set to 0.8 MPa or more and less than 1.0 MPa when the internal electrolyte is torn. In other words, the experiment was performed under the assumption that the optimum state is that the deployment angle α is 60 degrees or more when the deployment portion 22 is deployed at the reference internal pressure. The diameter of the deployment portion 22 is set to 18 mm, and the width W of the thin portion 21 is set to 1 mm. In the experiment, the base end length S of the thin base end 21a is set to 2 to 5 mm, and the thickness of the thin portion 21 (the difference in thickness between the thin base end 21a and the thin main body portion 21b is set to the step value) is changed, and the battery lid 1 equipped with the safety valve 2 is welded and liquid-sealed to the battery storage container, and water is fed from the liquid inlet to increase the water pressure, and the internal pressure, the deployment state of the deployment portion 22, and the deployment angle α when the safety valve 2 is torn are examined.

[0033] (Experiment 1) The base end length S of the thin-walled base end 21a was set to 5 mm, and the step value, which is the difference between the thickness of the thin-walled base end 21a and the thickness of the thin-walled main body portion 21b, was set to 0.1 mm.Eight battery lids 1 were created in which the thicknesses of the thin-walled base end 21a and the thin-walled main body portion 21b were varied, and experiments were conducted to determine the unfolded state as shown in Table 1.

[0034] [Table 1]

[0035] The ratings of ◯, ×, and △ in the table are based on whether the deployment portion 22 reaches a deployment state of 60 degrees or more and breaks at the standard internal pressure, with ◯ being given if both are met and △ being given if only one is met. If neither are met, or if the deployment portion does not reach a deployment state and only partially breaks, or if the deployment portion itself comes off, it is given an ×.

[0036] When the base end length S of the thin base end 21a is 5 mm and the step value is 0.1 mm, regardless of the thickness of the thin base end 21a and the thin main body 21b, even when the internal pressure is increased to 1.5 MPa, the thin part does not split open, or only a part splits open, and the deployment part 22 does not deploy stably. It was also found that the configuration of Experiment 1 does not deploy at the reference internal pressure.

[0037] (Experiment 2) Next, seven battery lids 1 were created in which the base end length S of the thin-walled base end 21a was 4 mm, and the step value, which is the difference between the thickness of the thin-walled base end 21a and the thickness of the thin-walled main body portion 21b, was 0.04 mm, and experiments were performed to see what the expanded state would be, as shown in Table 2.

[0038] [Table 2]

[0039] As shown in Table 2, it was found that the flaps burst at the standard internal pressure, compared to Table 1. On the other hand, it was difficult to say that the flaps were stable, and although they burst, they did not reach a deployment angle of 60 degrees or more.

[0040] (Experiment 3) Eighteen battery lids 1 were created in which the thicknesses of the thin-walled base end 21a and the thin-walled main body portion 21b were changed so that the diameter length S of the thin-walled base end 21a was 3 mm and the step value, which is the difference between the thickness of the thin-walled base end 21a and the thickness of the thin-walled main body portion 21b, was 0.05 to 0.09 mm, and experiments were conducted to determine the unfolded state as shown in Table 3.

[0041] [Table 3]

[0042] As shown in Table 3, when the base end length S is 3 mm and the step value is 0.07 mm, it was found that the deployment angle α is 80 degrees and the deployment is stable at the standard internal pressure. On the other hand, when the step value is 0.08 mm or 0.09 mm, it only operates at an internal pressure higher than the standard internal pressure, and the deployment part comes off when it operates. Also, when the step value is 0.06 mm, the deployment angle may be less than 60 degrees, even though it is within the standard internal pressure. When the step value is 0.05 mm, the deployment angle α remains at about 15 degrees, and stable deployment is not achieved.

[0043] (Experiment 4) Three battery lids 1 were created in which the base end length S of the thin-walled base end 21a was 2 mm, and the thicknesses of the thin-walled base end 21a and the thin-walled main body portion 21b were changed so that the step value, which is the difference between the thickness of the thin-walled base end 21a and the thickness of the thin-walled main body portion 21b, was 0.04 and 0.05 mm, and experiments were conducted to determine the unfolded state as shown in Table 4.

[0044] [Table 4]

[0045] As shown in Table 4, when the base end length S was set to 2 mm, the deployment became easier, but the edge of the thin-walled base end 21a was sometimes torn or the safety valve 2 itself was sometimes detached, so the deployment was not stable.

[0046] As shown in Tables 1 to 4 above, when the diameter of the expansion portion 22 is 18 mm and the width W of the thin-walled portion 21 is 1 mm, it is preferable that the base end length S of the thin-walled base end 21a is 3.0 mm, the reference internal pressure is 0.8 or more and less than 1.0 MPa, and the step value is 0.05 to 0.07 mm, with a step value of 0.07 mm being optimal.

[0047] In other words, since a thin wall portion having a width of 1 mm is arranged around the periphery of the disk-shaped development portion 22 having a diameter of 18 mm, the width of the thin wall portion 21 is 5 to 6% of the diameter of the development portion 22. Since the base end length S of the thin wall base end 21a is 3 mm, the base end length S is 16 to 17% of the diameter of the development portion 22. Since a step value of 0.05 mm to 0.07 mm is preferable, it is preferable to set the step value to 5 to 7% of the width W (1 mm) of the thin wall portion 21, and it has been found that a step value of 7% of the width W of the thin wall portion 21 is optimal. [Explanation of symbols]

[0048] 1 ... battery cover, 2 ... safety valve, 10 ... flat plate member, 20 ... rising portion, 20c ... top portion, 21 ... thin portion, 21a ... thin base end portion, 21b ... thin main body portion, 22 ... deployment portion, 23 ... curved portion, 23a ... outer end portion, 23b ... outer curved portion, 23c ... central portion, 23d ... inner curved portion, 24 ... central portion,

Claims

1. A battery lid formed by pressing and equipped with a safety valve that opens when a predetermined pressure is reached, the battery lid comprising a flat plate member and a safety valve, the safety valve has a rising portion rising from the flat plate member and formed circumferentially along the safety valve, a thin-walled portion located on the inner circumferential side of the rising portion and formed circumferentially, and a developed portion located on the inner circumferential side of the thin-walled portion and formed in a circular shape, A battery lid equipped with a safety valve, characterized in that the top of the raised portion on the outer periphery side and the outer end of the expanded portion on the inner periphery side are located above the upper surface of the thin-walled portion.

2. The development portion includes a curved portion formed circumferentially on the outer circumferential side and curved so as to be convex downward, and a central portion formed in a circular shape on the inner circumferential side of the curved portion, A battery lid equipped with a safety valve as described in claim 1, characterized in that the lower surface of the central portion of the curved portion is lower than the lower surface of the flat member, and the upper surface of the central portion of the curved portion is lower than the upper surface of the flat member and higher than the lower surface.

3. the thin-walled portion formed in a circumferential shape has a thin-walled main body portion and a thin-walled base end portion having a part of a circumference that is thicker than the thin-walled main body portion; A battery lid equipped with a safety valve as described in claim 1 or claim 2, characterized in that the width of the thin-walled portion is 5 to 6% of the diameter of the expansion portion, the base end length which is the diametric length perpendicular to the width length of the thin-walled base end is 16 to 17% of the diameter of the expansion portion, and a step value obtained by subtracting the thickness of the thin-walled main body portion from the thickness of the thin-walled base end is 5 to 7% of the width of the thin-walled portion.

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