Cylindrical battery positive end cap and its cylindrical battery

Abstract

The present invention provides a positive end cap for a cylindrical battery and the cylindrical battery. The positive end cap for the cylindrical battery includes a positive top cover plate, a positive electrode post, a positive seal, a temperature sensing resistor, a first insulating member, a flipping piece, and a connecting piece connecting to the positive electrode of the cylindrical battery cell. The positive top cover plate is provided with a positive electrode through hole, and the positive electrode post passes through and is fixed in the positive electrode through hole. The positive seal is disposed around the positive electrode post. The flipping piece includes a fixing portion connecting to the positive top cover plate and a flipping portion connecting to the fixing portion. The flipping portion connects to the connecting piece, and when the internal air pressure of the battery exceeds a preset value, the flipping portion is driven by the air pressure to flip towards the positive top cover plate direction to disconnect the connection with the connecting piece. The connecting piece is fixedly connected to the first insulating member and is isolated from the fixing portion by the first insulating member. The temperature sensing resistor is disposed between the flipping piece and the positive electrode post and is electrically connected to the flipping piece and the positive electrode post. The positive electrode post is provided with a through hole penetrating itself in the up and down direction, and the through hole communicates the flipping piece with the outside. It has high safety and high flipping sensitivity.

Description

Technical Field

[0001] The present invention relates to the field of energy storage devices, and particularly to a positive end cap of a cylindrical battery. Background Art

[0002] Compared with square batteries, cylindrical batteries have a high filling rate and thus have the characteristic of high energy ratio. Currently, some battery manufacturers have adopted cylindrical batteries to replace square batteries and apply them in vehicle batteries. In order to satisfy the electrical connection between the positive end cap and the positive electrode of the battery cell, traditional cylindrical batteries usually use a current collector sheet or a current collector plate to connect the two. However, when used as a power battery, the cylindrical battery is vulnerable to violent impacts, resulting in the disconnection or loosening of the connection between the current collector or the current collector plate and the positive end cap, thus affecting its use. At the same time, in the event of an accidental situation such as overcharging of the battery, in order to cut off the circuit, there is currently a flip piece provided between the positive electrode post of the positive end cap and the current collector sheet. When the internal air pressure of the battery exceeds a preset value, the flip piece flips to disconnect the connection with the current collector. However, the current flip piece is not sensitive enough and usually requires a pressure much larger than the preset value to flip, so it cannot provide perfect safety protection. Summary of the Invention

[0003] The purpose of the present invention is to provide a new type of positive end cap of a cylindrical battery and its cylindrical battery. The flip structure of this positive end cap of the cylindrical battery is highly sensitive, and the use of a double safety protection device can greatly improve the safety of the cylindrical battery.

[0004] To achieve the above purpose, in the first aspect of the present invention, there is provided a positive end cap of a cylindrical battery for sealing one end of a housing accommodating a cylindrical battery cell, including a positive top cover sheet, a positive electrode post, a positive seal, a temperature-sensitive resistor, a first insulating member, a flip piece, and a connecting piece connecting the positive electrode of the cylindrical battery cell. The positive top cover sheet is provided with a positive electrode through hole, the positive electrode post passes through and is fixed in the positive electrode through hole, the positive seal surrounds the positive electrode post. The flip piece includes a fixing portion connecting the positive top cover sheet and a flipping portion connecting the fixing portion. The flipping portion is connected to the connecting piece, and when the internal air pressure of the battery exceeds a preset value, the flipping portion is driven by the air pressure to flip towards the positive top cover sheet to disconnect the connection with the connecting piece. The connecting piece is fixedly connected to the first insulating member and is isolated from the fixing portion through the first insulating member. The temperature-sensitive resistor is arranged between the flip piece and the positive electrode post and is electrically connected to the flip piece and the positive electrode post. The positive electrode post is provided with a through hole penetrating itself in the up and down direction, and the through hole communicates the flip piece with the outside.

[0005] Compared with the prior art, a temperature-sensitive resistor is provided between the flipping piece and the positive electrode post in the positive end cap of the cylindrical battery of the present invention. As the temperature inside the battery increases, the resistance value of the temperature-sensitive resistor will increase accordingly, thereby reducing the current passing through the positive electrode post to achieve safety protection for the positive electrode post. If the temperature inside the battery drops, the resistance value of the temperature-sensitive resistor will slowly decrease and return to its original state, so that the positive electrode post can restore the normal current and the battery can maintain normal operation. At the same time, when the temperature inside the battery rises, chemical reactions will occur in the electrolyte and the positive electrode material to generate gas. When the air pressure rises to a certain value, the flipping piece will flip and disconnect the electrical connection between the positive electrode post and the connecting piece, thereby cutting off the current at the positive end to achieve the purpose of safety. Moreover, a through hole penetrating the positive electrode post itself and communicating the flipping piece and the outside is provided in the positive electrode post in the up and down direction. The setting of the through hole can balance the air pressure between the flipping piece and the outside, thereby improving the flipping sensitivity of the flipping piece.

[0006] Preferably, the through hole includes a first straight through hole, a tapered hole, and a second straight through hole connected in sequence. The first straight through hole is connected to the outside, and the size of the tapered hole gradually decreases from the direction of the first straight through hole to the second straight through hole. The change in the size of the through hole forms a vortex effect, so that when the flipping piece is flipped under great pressure and then ruptured, the air pressure rushing out of the housing becomes smaller.

[0007] Preferably, the positive electrode post includes a columnar part provided with the through hole and a first platform part and a second platform part provided at both ends of the columnar part. The first platform part is away from the connecting piece.

[0008] Preferably, a second insulating member is snap-fitted on the first platform part.

[0009] Preferably, the positive electrode seal is sleeved on the columnar part and abuts against the positive electrode top cover piece and the second platform part.

[0010] Preferably, a third insulating member is provided around the second platform part. The third insulating member includes a main body part provided between the positive electrode top cover piece and the second platform part and an extension part provided between the fixing part and the second platform part.

[0011] Preferably, the temperature-sensitive resistor abuts against the top surface or the side surface of the extension part. When the temperature-sensitive resistor abuts against the top surface of the extension part, the temperature-sensitive resistor can also play an auxiliary sealing role.

[0012] Preferably, the positive electrode seal includes a main body and a convex part extending vertically from one end of the main body. The main body is sleeved on the columnar part and abuts against the positive electrode top cover piece and the second platform part. The convex part is between the fixing part and the second platform part and abuts against the temperature-sensitive resistor.

[0013] Preferably, the connecting piece is snap-fitted or adhesively fixed to the first insulating member. Snap-fitting is preferably adopted. The two are snap-fitted to each other, which can increase the connection reliability, and can prevent the connecting piece from being misaligned, moving and disconnecting from the top cover when the battery is violently impacted. At the same time, the snap-fitting fixation of the first insulating member can also play a role in welding positioning and prevent welding defects such as false soldering. Snap-fitting can first injection-mold the first insulating member to have a snap-fitting structure, and then snap-fit the connecting piece to the first insulating member, or the connecting piece and the first insulating member can be injection-molded together to make the connecting piece snap-fit into the first insulating member. Injection molding is preferably used as its connectivity is better. Adhesive fixation is to fix the connecting piece to the insulating member by using an adhesive layer.

[0014] Preferably, the connecting piece includes a first connecting portion snap-fitted to the first insulating member, a second connecting portion connected to the positive electrode of the battery cell, and a transition portion connecting the first connecting portion and the second connecting portion. The transition portion is bent to fold the second connecting portion below the first connecting portion.

[0015] Preferably, a boss facing the flipping piece is provided in the middle of the first connecting portion, and the bottom of the flipping piece is welded or contacted with the boss. To increase the reliability, it is preferred that the boss and the flipping piece are fixed by spot welding.

[0016] Preferably, a plurality of air holes penetrating up and down are provided around the boss on the first connecting portion. The air holes communicate the battery cell and the flipping piece. The air holes can drain the gas inside the battery to the flipping piece. Therefore, when the internal air pressure of the battery exceeds the preset value, the flipping piece will flip and disconnect the connection with the connecting piece.

[0017] Preferably, a convex bulge is provided in the middle of the flipping portion in the direction facing the connecting piece. The setting of the convex bulge can improve the strength to prevent the flipping piece and the connecting piece from being penetrated during spot welding.

[0018] In a second aspect of the present invention, a cylindrical battery is provided, which includes a cylindrical battery cell, a housing for accommodating the cylindrical battery cell, a positive end cap sealed at one end of the housing, and a negative end cap sealed at the other end of the housing. The positive end cap is the positive end cap of the aforementioned cylindrical battery.

[0019] Preferably, the negative end cap includes a negative top cover piece, a negative pole, a negative seal, a fourth insulating member, and an explosion-proof valve provided on the negative top cover piece. A negative through hole and a liquid injection hole are provided on the negative top cover piece. The negative pole passes through and is fixed in the negative through hole. The negative seal is disposed around the negative pole. The fourth insulating member is interposed between the negative pole and the negative top cover piece. Description of the Drawings

[0020] Figure 1Stereogram of an embodiment of the cylindrical battery of the present invention.

[0021] Figure 2 Stereogram of an embodiment of the positive end cap of the cylindrical battery of the present invention.

[0022] Figure 3 It is Figure 2 Top view of the positive end cap of the cylindrical battery before the connecting piece is bent.

[0023] Figure 4 It is Figure 2 Exploded view of the positive end cap of the cylindrical battery in one direction.

[0024] Figure 5 It is Figure 2 Exploded view of the positive end cap of the cylindrical battery in another direction.

[0025] Figure 6 It is Figure 4 The first variation diagram of

[0026] Figure 7 It is Figure 5 The first variation diagram of

[0027] Figure 8 It is Figure 4 The second variation diagram of

[0028] Figure 9 It is Figure 5 The second variation diagram of

[0029] Figure 10 It is Figure 3 Cross-sectional view in the A-A direction.

[0030] Figure 11 It is Figure 10 The first variation diagram of

[0031] Figure 12 It is Figure 10 The second variation diagram of

[0032] Figure 13 Stereogram of an embodiment of the negative end cap of the cylindrical battery of the present invention.

[0033] Figure 14 It is Figure 13 Bottom view of the negative end cap of the cylindrical battery.

[0034] Figure 15 It is Figure 13 Exploded view of the negative end cap of the cylindrical battery in one direction.

[0035] Figure 16 It is Figure 13Explosion diagram of the negative end cap of the cylindrical battery in another direction.

[0036] Figure 17 is Figure 14 Cross-sectional view in the B-B direction.

[0037] Component description

[0038] 100 - Cylindrical battery; 10 - Housing; 30 - Positive end cap; 31 - Positive top cover sheet; 311 - Positive through hole; 32 - Positive terminal; 321 - Cylindrical part; 323 - Second platform part; 325 - First platform part; 327 - Through hole; 3271 - First straight through hole; 3273 - Tapered hole; 3275 - Second straight through hole; 33 - Positive seal; 331 - Body; 333 - Protrusion; 34 - Temperature-sensitive resistor; 35 - First insulating part; 36 - Flipping piece; 361 - Fixed part; 363 - Flipping part; 3631 - Convex hull; 37 - Connecting piece; 371 - First connecting part; 3711 - Boss; 3713 - Vent hole; 373 - Transition part; 375 - Second connecting part; 38 - Third insulating part; 381 - Body part; 383 - Extension part; 39 - Second insulating part; 50 - Negative end cap; 51 - Negative top cover sheet; 511 - Negative through hole; 513 - Explosion-proof valve hole; 515 - Liquid injection hole; 52 - Negative terminal; 521 - Negative terminal cylindrical part; 523 - Negative boss; 53 - Negative riveting block; 54 - Plastic part; 55 - Negative seal; 56 - Fourth insulating part; 57 - Explosion-proof valve Detailed implementation mode

[0039] For ease of understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. The preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the understanding of the disclosure of the present invention more thorough and comprehensive. It should be noted that unless otherwise clearly defined or limited, terms such as "connected", "connected to", "fixed" and the like should be understood in a broad sense. For example, the connection can be a fixed connection, a detachable connection, a direct connection, an indirect connection through an intermediate medium, or a communication between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] The following will illustrate the positive end cap of the cylindrical battery and the cylindrical battery of the present invention with reference to the drawings.

[0041] As Figure 1As shown, the cylindrical battery 100 includes a cylindrical battery cell (not shown in the figure), a housing 10 for accommodating the cylindrical battery cell, a positive end cap 30 sealed to one end of the housing 10, and a negative end cap 50 sealed to the other end of the housing 10. Both the positive end cap 30 and the negative end cap 50 can be fixed to the housing 10 by welding.

[0042] As Figures 2 to 12 shown, the positive end cap 30 includes a positive top cover sheet 31, a positive electrode post 32, a positive seal 33, a temperature sensing resistor 34, a first insulating member 35, a flipping piece 36, and a connecting piece 37 connecting to the positive electrode of the cylindrical battery cell. The positive top cover sheet 31 is provided with a positive electrode through hole 311. The positive electrode post 32 passes through and is fixed to the positive electrode through hole 311, and the positive seal 33 is disposed around the positive electrode post 32. The flipping piece 36 includes a fixing portion 361 connecting to the positive top cover sheet 31 and a flipping portion 363 connecting to the fixing portion 361. The flipping portion 363 is connected to the connecting piece 37, and when the internal air pressure of the battery exceeds a preset value, the flipping portion 363 is driven by the air pressure to flip towards the positive top cover sheet 31 to disconnect the connection with the connecting piece 37. When the internal temperature of the battery rises, chemical reactions occur to generate gas between the electrolyte and the positive electrode material, etc. When the air pressure rises to a certain value, the flipping portion 363 flips to disconnect the electrical connection between the positive electrode post 32 and the connecting piece 37, thereby cutting off the current at the positive end to achieve the purpose of safety. The connecting piece 37 is fixedly connected to the first insulating member 35 and is isolated from the fixing portion 361 by the first insulating member 35. The temperature sensing resistor 34 is disposed between the flipping piece 36 and the positive electrode post 32 and is electrically connected to the flipping piece 36 and the positive electrode post 32. As the internal temperature of the battery rises, the resistance value of the temperature sensing resistor 34 will increase accordingly, thereby reducing the current passing through the positive electrode post 32 to achieve the safety protection of the positive electrode post 32. If the internal temperature of the battery drops, the resistance value of the temperature sensing resistor 34 slowly decreases and returns to its original state to enable the positive electrode post 32 to resume normal current and the battery to maintain normal operation. The positive electrode post 32 is provided with a through hole 327 penetrating itself in the up and down direction, and the through hole 327 communicates the flipping piece 36 with the outside. The setting of the through hole 327 can balance the air pressure between the flipping piece 36 and the outside, thereby improving the flipping sensitivity of the flipping piece 36.

[0043] As Figures 4 to 12 shown, the positive electrode post 32 includes a column body portion 321 provided with the through hole 327, and a first platform portion 325 and a second platform portion 323 disposed at both ends of the column body portion 321. The first platform portion 325 is away from the connecting piece 37, and a second insulating member 39 is snap-fitted to the first platform portion 325. The second insulating member 39 can be formed by injection molding.

[0044] The positive electrode post 32 can be of various types, such as Figures 4 to 5 and Figure 10As shown, the positive electrode seal 33 is sleeved on the columnar portion 321 and abuts against the positive electrode top cover sheet 31 and the second platform portion 323. The second platform portion 323 is surrounded by a third insulating member 38. The third insulating member 38 includes a main body portion 381 disposed between the positive electrode top cover sheet 31 and the second platform portion 323 and an extension portion 383 disposed between the fixing portion 361 and the second platform portion 323. The temperature sensing resistor 34 abuts against the side surface of the extension portion 383.

[0045] The positive electrode column 32 can also be as Figures 6 to 7 and Figure 11 As shown, the positive electrode seal 33 includes a main body 331 and a convex portion 333 extending vertically from one end of the main body 331. The main body 331 is sleeved on the columnar portion 321 and abuts against the positive electrode top cover sheet 31 and the second platform portion 323. The convex portion 333 is between the fixing portion 361 and the second platform portion 323 and abuts against the temperature sensing resistor 34.

[0046] The positive electrode column 32 can also be as Figures 8 to 9 and Figure 12 As shown, the positive electrode seal 33 is sleeved on the columnar portion 321 and abuts against the positive electrode top cover sheet 31 and the second platform portion 323. The second platform portion 323 is surrounded by a third insulating member 38. The third insulating member 38 includes a main body portion 381 disposed between the positive electrode top cover sheet 31 and the second platform portion 323 and an extension portion 383 disposed between the fixing portion 361 and the second platform portion 323. The temperature sensing resistor 34 abuts against the top surface of the extension portion 383. When the temperature sensing resistor 34 abuts against the top surface of the extension portion 383, the temperature sensing resistor 34 can also play a role in auxiliary sealing.

[0047] Continuing as Figures 4 to 9 As shown, the connecting piece 37 is snap-fitted or adhesively fixed to the first insulating member 35. Preferably, it is snap-fitted. The two are snap-fitted to increase the connection reliability, and can prevent the connecting piece from being misaligned, moving and disconnecting from the top cover when the battery is violently impacted. At the same time, the snap-fitting of the first insulating member 35 can also play a role in welding positioning and prevent welding defects such as false soldering. The snap-fitting can first form a snap-fitting structure by injection molding the first insulating member 35, and then snap-fix the connecting piece 37 to the first insulating member 35. It can also injection mold the connecting piece 37 and the first insulating member 35 together so that the connecting piece 37 is snap-fitted into the first insulating member 35. Preferably, injection molding has better connectivity. The adhesive fixing is to fix the connecting piece to the insulating member by using an adhesive layer.

[0048] The connecting piece 37 includes a first connecting portion 371 fixedly clamped to the first insulating member 35, a second connecting portion 375 connected to the positive electrode of the battery cell, and a transition portion 373 connecting the first connecting portion 371 and the second connecting portion 375. The transition portion 373 is bent to fold the second connecting portion 375 below the first connecting portion 371. A boss 3711 facing the flipping piece 36 is provided in the middle of the first connecting portion 371. The bottom of the flipping piece 36 is fixedly welded or in contact with the boss 3711. To increase the reliability, it is preferably that the boss 3711 and the flipping piece 36 are fixed by spot welding. The first connecting portion 371 is provided with a plurality of air vent holes 3713 penetrating up and down around the boss 3711. The air vent holes 3713 communicate the battery cell and the flipping piece 36, and the air vent holes 3713 can drain the gas inside the battery to the flipping piece 36. Therefore, when the internal air pressure of the battery exceeds the preset value, the flipping piece 36 will flip and disconnect the connection with the connecting piece 37. A convex bump 3631 is provided in the middle of the flipping portion 363 in the direction facing the connecting piece 37. The setting of the convex bump 3631 can improve the strength to prevent the flipping piece 36 and the connecting piece 37 from being penetrated during spot welding.

[0049] Continue as Figures 10 to 12 shown, the through hole 327 includes a first straight through hole 3271, a tapered hole 3273 and a second straight through hole 3275 connected in sequence. The first straight through hole 3271 is connected to the outside. The size of the tapered hole 3273 gradually becomes smaller from the direction of the first straight through hole 3271 to the second straight through hole 3275. The change in the size of the through hole forms an eddy current to control the air pressure rushing out of the housing to become smaller when the flipping piece 36 is flipped and broken under great pressure.

[0050] Furthermore, as Figures 13 to 17 shown, the negative end cap 50 includes a negative top cover piece 51, a negative pole 52, a negative seal 55, a fourth insulating member 56 and an explosion-proof valve 57 provided on the negative top cover piece 51. The negative top cover piece 51 is provided with a negative through hole 511 and a liquid injection hole 515. The negative pole 52 passes through and is fixed in the negative through hole 511. The negative seal 55 is disposed around the negative pole 52. The fourth insulating member 56 is interposed between the negative pole 52 and the negative top cover piece 51. The negative pole 52 includes a negative pole body portion 521 passing through the negative through hole 511 and a negative boss 523 connected to the negative pole body portion 521 and located below the negative top cover piece 51. The fourth insulating member 56 is interposed between the negative boss 523 and the negative top cover piece 51. One end of the negative pole body portion 521 away from the negative boss 523 is connected to a negative riveting block 53, and a plastic part 54 is disposed around the negative riveting block 53.

[0051] It should be noted that the above specific embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. After reading the present invention, various equivalent modifications made by those skilled in the art to the present invention all fall within the scope defined by the appended claims of this application.

Claims

1. A positive end cap (30) for a cylindrical battery, used to seal one end of a housing (10) that accommodates a cylindrical battery cell, characterized in that, it includes a positive top cover plate (31), a positive terminal (32), a positive seal (33), a temperature sensing resistor (34), a first insulating member (35), a flipping piece (36), and a connecting piece (37) that connects to the positive electrode of the cylindrical battery cell. The positive top cover plate (31) is provided with a positive through hole (311). The positive terminal (32) passes through and is fixed in the positive through hole (311). The positive seal (33) surrounds the positive terminal (32). The flipping piece (36) includes a fixing portion (361) that connects to the positive top cover plate (31) and a flipping portion (363) that connects to the fixing portion (361). The flipping portion (363) connects to the connecting piece (37), and when the internal air pressure of the battery exceeds a preset value, the flipping portion (363) is driven by the air pressure to flip towards the positive top cover plate (31) and disconnect the connection with the connecting piece (37). The connecting piece (37) is fixedly connected to the first insulating member (35) and is isolated from the fixing portion (361) by the first insulating member (35). The temperature sensing resistor (34) is disposed between the flipping piece (36) and the positive terminal (32) and is electrically connected to the flipping piece (36) and the positive terminal (32). The positive terminal (32) is provided with a through hole (327) that penetrates itself in the up and down direction, and the through hole (327) communicates with the flipping piece (36) and the outside. The positive terminal (32) includes a column body portion (321) where the through hole (327) is provided, and a first platform portion (325) and a second platform portion (323) disposed at both ends of the column body portion (321). The first platform portion (325) is away from the connecting piece (37). The second platform portion (323) is surrounded by a third insulating member (38). The third insulating member (38) includes a body portion (381) disposed between the positive top cover plate (31) and the second platform portion (323) and an extension portion (383) disposed between the fixing portion (361) and the second platform portion (323). The temperature sensing resistor (34) abuts against the top surface of the extension portion (383); The through hole (327) includes a first straight through hole (3271), a tapered hole (3273), and a second straight through hole (3275) that are connected in sequence. The first straight through hole (3271) connects to the outside. The size of the tapered hole (3273) gradually becomes smaller from the first straight through hole (3271) towards the second straight through hole (3275); The connecting piece (37) is fixedly connected to the first insulating member (35) by clamping; The connecting piece (37) includes a first connecting portion (371) snap-fitted and fixed to the first insulating member (35), a second connecting portion (375) connected to the positive electrode of the battery cell, and a transition portion (373) connecting the first connecting portion (371) and the second connecting portion (375). The transition portion (373) is bent to fold the second connecting portion (375) below the first connecting portion (371). A boss (3711) facing the flipping piece (36) is provided in the middle of the first connecting portion (371), and the bottom of the flipping piece (36) is spot-welded to the boss (3711). The first connecting portion (371) is provided with a plurality of through ventilation holes (3713) penetrating up and down around the boss (3711). The ventilation holes (3713) communicate the battery cell and the flipping piece (36), and the ventilation holes (3713) can drain the gas inside the battery to the flipping piece (36). Therefore, when the internal pressure of the battery exceeds a preset value, the flipping piece (36) will flip and disconnect the connection with the connecting piece (37). A convex bump (3631) is provided in the middle of the flipping portion (363) in the direction facing the connecting piece (37). The setting of the convex bump (3631) can improve the strength to prevent the flipping piece (36) and the connecting piece (37) from being penetrated during spot welding. Wherein, when the flipping piece (36) is flipped under great pressure and then ruptured, the gas inside the battery sequentially passes through the ventilation holes (3713), the flipping piece (36), the second straight through hole (3275), the tapered hole (3273), the first straight through hole (3271), and flows to the outside.

2. A cylindrical battery (100), characterized in that it includes a cylindrical battery cell, a housing (10) for accommodating the cylindrical battery cell, a positive end cap (30) sealed at one end of the housing (10), and a negative end cap (50) sealed at the other end of the housing (10). It is characterized in that the positive end cap is the cylindrical battery positive end cap (30) described in claim 1.

3. The cylindrical battery (100) according to claim 2, characterized in that the negative end cap (50) includes a negative top cover sheet (51), a negative electrode post (52), a negative electrode seal (55), a fourth insulating member (56), and an explosion-proof valve (57) provided on the negative top cover sheet (51). A negative electrode through hole (511) and a liquid injection hole (515) are provided on the negative top cover sheet (51). The negative electrode post (52) passes through and is fixed in the negative electrode through hole (511). The negative electrode seal (55) is disposed around the negative electrode post (52). The fourth insulating member (56) is interposed between the negative electrode post (52) and the negative top cover sheet (51).

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