Top cover assembly, single battery and battery pack

Abstract

The utility model discloses a top cover assembly, a single battery and a battery pack. The top cover assembly comprises a top cover, a device main body and a piston assembly, a fusion hole is formed in the top cover; the device main body is provided with a containing cavity, a main hole and a first auxiliary hole which are communicated with the containing cavity are formed in the two opposite ends of the device main body, a second auxiliary hole communicated with the containing cavity is formed in the side wall of the device main body, and the device main body is assembled in the fusion hole; the piston assembly is assembled in the containing cavity, the piston assembly is movably connected with the device body in the axis direction of the fusion hole, the piston assembly can movably block communication of the main hole and the second auxiliary hole, and the piston assembly can be opened under preset pressure; when the piston assembly is located at the first position, the piston assembly blocks the communication of the main hole and the first auxiliary hole and blocks the communication of the main hole and the second auxiliary hole, and when the piston assembly is located at the second position, the piston assembly blocks the communication of the main hole and the first auxiliary hole and does not block the communication of the main hole and the second auxiliary hole, so that electrolyte is injected into the second auxiliary hole through the main hole.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, and in particular to a top cover assembly, a single cell and a battery pack. Background Art

[0002] The pressure relief valve is mainly used in batteries in new energy vehicles to relieve pressure and prevent explosion in the event of thermal runaway; the injection port is the channel for injecting electrolyte into the battery. However, in the prior art, the injection port on the top cover of the battery is designed independently from the pressure relief valve. After the injection is completed, the injection port needs to be sealed by driving a formation nail. After the formation is completed, the formation nail is removed, and then the sealing is ensured by plastic sealing and metal welding. The sealing process is cumbersome, and there is also material waste, resulting in low production efficiency and unable to meet the growing battery cell market. Utility Model Content

[0003] One purpose of the utility model is to provide a top cover assembly, a single cell and a battery pack, which are intended to solve the technical problem of complex top cover assembly process.

[0004] In order to achieve the above-mentioned purpose, a solution provided by the utility model is: the top cover assembly includes a top cover, a device body and a piston assembly; the top cover is provided with a fusion hole; the device body is provided with a accommodating chamber, and the opposite ends of the device body are provided with a main hole and a first auxiliary hole connected to the accommodating chamber, and the side wall of the device body is provided with a second auxiliary hole connected to the accommodating chamber, and the device body is assembled in the fusion hole; the piston assembly is assembled in the accommodating chamber, and the piston assembly is movably connected to the device body along the axial direction of the fusion hole, the piston assembly can movably block the connection between the main hole and the second auxiliary hole, and the piston assembly can be opened under a preset pressure so that the second auxiliary hole can spray electrolyte from the main hole through the piston assembly.

[0005] Optionally, the piston assembly includes a piston and an elastic member, the piston and the elastic member are connected, the elastic member is connected to the device body, the elastic member is elastic, and the elastic member is used to elastically press the piston so that the piston can movably block the main hole from connecting with the second auxiliary hole.

[0006] Optionally, the piston assembly also includes a pressure relief film, a protective film and a dust-proof film. The piston is provided with a pressure relief hole, which is connected to the main hole. The pressure relief film is fixedly connected to the side of the piston facing the first secondary hole and covers the pressure relief hole. The protective film is movably connected to the side of the piston facing the main hole and covers the pressure relief hole. The dust-proof film is connected to the side of the device body away from the piston and covers the main hole. The dust-proof film is provided with a transition hole. The pressure relief film is used to pass air but not liquid.

[0007] Optionally, the piston assembly further comprises a sealing ring, which is sleeved on the outer circumferential surface of the piston and is used to be pressed at the connection between the piston and the device body to block the communication between the main hole and the second auxiliary hole.

[0008] Optionally, a limiting groove is provided on the outer circumferential surface of the piston, and the sealing ring is assembled in the limiting groove and further exposed outside the limiting groove.

[0009] Optionally, the contact point between the device body and the piston has a first slope, and the contact point between the piston and the device body has a second slope. In the direction from the main hole to the first auxiliary hole, the inclination angle of the first slope is α, and the inclination angle of the second slope is β, 30≤β≤α≤75.

[0010] Optionally, the piston assembly also includes a base, which is connected to the device body, and the elastic member is connected to the device body through the base. The elastic member is elastically pressed between the piston and the base, and the base is provided with a base hole connected to the first secondary hole.

[0011] Optionally, the piston assembly also includes a limit seat, which is connected to the piston, and the piston is connected to an elastic member via the limit seat, the elastic member is elastically pressed between the limit seat and the base, and the limit seat is provided with a through hole connected to the base hole.

[0012] Optionally, the base is provided with a first accommodating groove, the limiting seat is provided with a second accommodating groove, the groove wall of the first accommodating groove and the groove wall of the second accommodating groove are slidably matched with each other, and the elastic member is assembled in the first accommodating groove and the second accommodating groove; or the base is provided with a first accommodating groove, and the elastic member is assembled in the first accommodating groove; or the limiting seat is provided with a second accommodating groove, and the elastic member is assembled in the second accommodating groove.

[0013] To achieve the above object, the utility model provides a solution: a single cell, the single cell comprising: a core pack, a shell and any of the top cover components mentioned above, the core pack is arranged in the shell, and the top cover component and the shell are connected to seal the shell.

[0014] In order to achieve the above-mentioned purpose, the utility model provides a solution: a battery pack, the battery pack comprises: a box body and a plurality of single cells as described above, the plurality of single cells are assembled in the box body.

[0015] The beneficial effects of the utility model are:

[0016] The fusion hole in the top cover is equipped with a device body and a piston assembly movably connected to the device body. The piston assembly can movably block the connection between the main hole and the second auxiliary hole. The piston assembly can have a first position and a second position during the movement. In the first position, the piston assembly blocks the main hole from being connected to the first auxiliary hole and the second auxiliary hole respectively. Due to the blocking effect of the piston assembly, the external electrolyte cannot be injected into the shell through the main hole and the first auxiliary hole, and the electrolyte inside the shell cannot be discharged to the outside through the second auxiliary hole and the main hole. At this time, the single cell is in a normal working state. When the single cell works abnormally and the gas in the shell exceeds a certain value, the piston assembly will be stretched open by pressure, thereby discharging the gas and liquid in the shell together to reduce the pressure in the shell. At this time, the fusion hole plays the role of an explosion-proof hole.

[0017] In the second position, the external force forces the piston assembly to move relative to the device body, the piston assembly blocks the connection between the main hole and the first auxiliary hole, and the piston assembly does not block the connection between the main hole and the second auxiliary hole, so as to inject electrolyte into the second auxiliary hole through the main hole. At this time, the single cell is in the formation stage of the production process, thereby eliminating the need to drive the formation nail to seal the injection hole after the injection is completed. After the formation is completed, the formation nail is removed, and the injection hole is sealed by plastic sealing and metal welding. The sealing process is cumbersome, and there is also material waste, resulting in low production efficiency, which cannot meet the growing battery cell market. In this way, the fusion hole has both the functions of the injection hole and the explosion-proof hole, that is, the two holes designed independently on the traditional battery are integrated into one hole, thereby reducing the production process of the battery and reducing the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0019] Figure 1 It is a schematic diagram of the assembly structure of the top cover assembly provided by the embodiment of the utility model;

[0020] Figure 2 It is a schematic diagram of the cross-sectional structure of a top cover assembly provided by an embodiment of the utility model in a first position;

[0021] Figure 3 It is a schematic diagram of the cross-sectional structure of the top cover assembly provided by one embodiment of the utility model in the second position;

[0022] Figure 4is a schematic diagram of the cross-sectional structure of a top cover assembly provided by another embodiment of the utility model in a first position;

[0023] Figure 5 is a schematic diagram of the cross-sectional structure of a top cover assembly provided by another embodiment of the utility model in a first position;

[0024] Figure 6 It is an exploded schematic diagram of the device body and the piston assembly provided in the embodiment of the utility model.

[0025] Description of the accompanying drawings: top cover assembly 100, top cover 10, fusion hole 101, device body 20, accommodating cavity 201, main hole 202, first auxiliary hole 203, second auxiliary hole 204, first inclined surface 205, piston assembly 30, piston 31, pressure relief hole 311, limiting groove 313, second inclined surface 315

[0026] Elastic member 32, pressure relief film 33, protective film 34, dustproof film 35, transition hole 351

[0027] Sealing ring 36 , base 37 , first accommodating groove 371 , limiting seat 38 , second accommodating groove 381 . DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0029] See also Figures 1 to 3 As shown, Figure 1 1 is a schematic diagram of the assembly structure of the top cover assembly 100 provided in an embodiment of the utility model. Figure 2 is a schematic diagram of the cross-sectional structure of the top cover assembly 100 provided in an embodiment of the utility model in the first position, Figure 3 It is a schematic diagram of the cross-sectional structure of the top cover assembly 100 provided in one embodiment of the utility model in the second position.

[0030] The utility model provides a single cell battery, which includes a core pack, a shell and a top cover assembly 100. The core pack is arranged in the shell, and the core pack can be formed by stacking or winding a positive electrode sheet, a negative electrode sheet and a diaphragm, and the top cover assembly 100 is connected to the shell and seals the shell. The electrolyte is injected into the shell through the top cover assembly 100, and the electrolyte undergoes a chemical reaction in the core pack to store or generate electricity. When the single cell is used abnormally and generates gas violently, it can be discharged through the top cover assembly 100.

[0031] Specifically, the top cover assembly 100 includes a top cover 10 , a device body 20 , and a piston assembly 30 .

[0032] The top cover 10 is provided with a fusion hole 101, which is used for liquid injection and exhaust. When electrolyte needs to be injected into the shell, the electrolyte can be injected into the shell through the fusion hole 101. When the gas in the shell exceeds the normal value, the gas and electrolyte in the shell can be discharged to the outside through the fusion hole 101.

[0033] The device body 20 is provided with a accommodating cavity 201, and a main hole 202 and a first auxiliary hole 203 connected to the accommodating cavity 201 are provided at opposite ends of the device body 20, and a second auxiliary hole 204 connected to the accommodating cavity 201 is provided on the side wall of the device body 20. The main hole 202, the first auxiliary hole 203, and the second auxiliary hole 204 are connected to each other through the accommodating cavity 201, and the device body 20 is assembled in the fusion hole 101.

[0034] The piston assembly 30 is assembled in the accommodating chamber 201. The piston assembly 30 is movably connected to the device body 20 along the axial direction of the fusion hole 101. The piston assembly 30 can movably block the communication between the main hole 202 and the second auxiliary hole 204. The piston assembly 30 can move along the axial direction of the fusion hole 101 under the action of external force. The piston assembly 30 can be opened under a preset pressure to spray electrolyte from the main hole 202 through the piston assembly 30, thereby quickly exhausting and reducing the pressure in the shell. Among them, the piston assembly 30 has a first position and a second position during the activity. In the first position, the piston assembly 30 blocks the communication between the main hole 202 and the first auxiliary hole 203 and blocks the communication between the main hole 202 and the second auxiliary hole 204. Due to the blocking effect of the piston assembly 30, the external electrolyte cannot be injected into the shell through the main hole 202 and the first auxiliary hole 203, and the electrolyte inside the shell cannot be discharged to the outside through the second auxiliary hole 204 and the main hole 202. At this time, the single battery is in a normal working state. In the second position, external force forces the piston assembly 30 to move relative to the device body 20, and the piston assembly 30 blocks the connection between the main hole 202 and the first auxiliary hole 203. The piston assembly 30 does not block the connection between the main hole 202 and the second auxiliary hole 204, so as to inject electrolyte into the second auxiliary hole 204 through the main hole 202. At this time, the single cell is in the formation stage of the production process.

[0035] In this embodiment, the fusion hole 101 in the top cover 10 is equipped with a device body 20 and a piston assembly 30 movably connected to the device body 20. The piston assembly 30 can movably block the main hole 202 and the second auxiliary hole 204 from being connected. The piston assembly 30 can have a first position and a second position during the activity. In the first position, the piston assembly 30 blocks the main hole 202 from being connected to the first auxiliary hole 203 and the second auxiliary hole 204 respectively. Due to the blocking effect of the piston assembly 30, the external electrolyte cannot be injected into the shell through the main hole 202 and the first auxiliary hole 203, and the electrolyte inside the shell cannot be discharged to the outside through the second auxiliary hole 204 and the main hole 202. At this time, the single cell is in a normal working state. When the single cell works abnormally and the gas in the shell exceeds a certain value, the piston assembly 30 will be stretched open by pressure, thereby discharging the liquid in the shell to reduce the pressure in the shell. At this time, the fusion hole 101 plays the role of an explosion-proof hole. In the second position, the external force forces the piston assembly 30 to move relative to the device body 20, and the piston assembly 30 blocks the connection between the main hole 202 and the first auxiliary hole 203. The piston assembly 30 does not block the connection between the main hole 202 and the second auxiliary hole 204, so as to inject electrolyte into the second auxiliary hole 204 through the main hole 202. At this time, the single cell is in the formation stage of the production process, thereby eliminating the need to drive the formation nail to seal the injection hole after the injection is completed. After the formation is completed, the formation nail is removed, and the injection hole is sealed by plastic sealing and metal welding. The sealing process is cumbersome, and there is also material waste, resulting in low production efficiency, which cannot meet the growing battery cell market. In this way, the fusion hole 101 has both the functions of the injection hole and the explosion-proof hole, that is, the two holes independently designed on the traditional battery are integrated together to form one hole, thereby reducing the production process of the battery and reducing the production cost.

[0036] The piston assembly 30 includes a piston 31 and an elastic member 32. The piston 31 is connected to the elastic member 32. The elastic member 32 is connected to the device body 20. The elastic member 32 is elastic. The elastic member 32 can be a spring or an elastic steel sheet. The elastic member 32 is used to elastically press the piston 31 so that the piston 31 can movably block the connection between the main hole 202 and the second auxiliary hole 204. The piston 31 has a first position and a second position. It can be understood that when the piston 31 is in the second position, the elastic member 32 is in a deformed state. After the external force is eliminated, the elastic member 32 provides elastic force to make the piston 31 move toward the device body 20 until it is in the first position. When the single battery is in an abnormal state, when the pressure is greater than the preset pressure value, the air pressure inside the shell can break the piston 31 so that the first auxiliary hole 203 and the main hole 202 are connected.

[0037] In another embodiment, the piston assembly 30 further includes a sealing ring 36, which can be silicone or foam. The sealing ring 36 is sleeved on the outer peripheral surface of the piston 31, and the sealing ring 36 can move with the piston 31. When the piston 31 is in the first position, the sealing ring 36 is pressed at the connection between the piston 31 and the device body 20 to block the communication between the main hole 202 and the second auxiliary hole 204. The sealing ring 36 has excellent deformation ability, so that the gap at the connection between the piston 31 and the device body 20 can be filled, ensuring that when the piston 31 is in the first position, the main hole 202 and the second auxiliary hole 204 are completely isolated.

[0038] The outer circumferential surface of the piston 31 is provided with a limiting groove 313, and the sealing ring 36 is assembled in the limiting groove 313 and further exposed from the limiting groove 313. The limiting groove 313 can limit the sealing ring 36 in the radial direction, prevent the sealing ring 36 from radial displacement during the movement of the piston 31, and ensure that the sealing ring 36 can always be at the connection between the piston 31 and the device body 20. Furthermore, the limiting groove 313 for limiting the displacement of the sealing ring 36 is also provided on the surface of the device body 20 facing the piston 31, thereby further improving the sealing performance of the sealing ring 36.

[0039] The contact point between the device body 20 and the piston 31 has a first inclined surface 205, and the contact point between the piston 31 and the device body 20 has a second inclined surface 315. In the direction from the main hole 202 to the first auxiliary hole 203, the inclination angle of the first inclined surface 205 is α, and the inclination angle of the second inclined surface 315 is β, 30≤β≤α≤75. The first inclined surface 205 is inclined relative to the axial direction of the main hole 202, and the first inclined surface 205 faces the core package in the shell. The second inclined surface 315 is inclined relative to the axial direction of the main hole 202, and the second inclined surface 315 faces the main hole 202. The advantage of the first inclined surface 205 and the second inclined surface 315 being inclined respectively is that when the piston 31 transitions from the second position to the first position, the inclined second inclined surface 315 is similar to a guide surface for the first inclined surface 205 to abut after sliding. In addition, the second inclined surface 315 can prevent the piston 31 from continuing to move, so that the piston 31 can remain in the first position. Furthermore, the inclination angle of the first bevel 205 can be equal to the inclination angle of the second bevel 315, so that the first bevel 205 and the second bevel 315 can be completely fitted together; the inclination angle of the first bevel 205 can also be greater than the inclination angle of the second bevel 315, so that the contact point between the first bevel 205 and the second bevel 315 is closer to the main hole 202 and away from the second auxiliary hole 204, so that the second auxiliary hole 204 can be made larger due to sufficient space.

[0040] See also Figure 4 , Figure 4 It is a schematic diagram of the cross-sectional structure of a top cover assembly 100 provided in a first position according to another embodiment of the present invention.

[0041] The piston assembly 30 also includes a base 37, which is connected to the device body 20. The elastic member 32 is connected to the device body 20 through the base 37. The elastic member 32 is elastically pressed between the piston 31 and the base 37. The base 37 is provided with a base 37 hole connected to the first auxiliary hole 203. The base 37 hole allows gas and liquid to pass through, so that the piston 31 can be opened normally after the pressure in the shell exceeds the threshold. The base 37 is located on the side of the device body 20 away from the main hole 202. The base 37 and the device body 20 form a space for accommodating the elastic member 32. In this way, when assembling the elastic member 32, the elastic member 32 is directly pressed between the base 37 and the device body 20, which can save the fixing process of the elastic member 32 and the device body 20. In addition, the base 37 can provide a good support force for the elastic member 32 to ensure that the elastic member 32 will not fall off from the device body 20. The base 37 and the device body 20 can be welded or bonded.

[0042] See also Figure 5 and Figure 6 , Figure 5 is a schematic cross-sectional structural diagram of a top cover assembly 100 provided in another embodiment of the utility model in a first position. Figure 6 It is an exploded schematic diagram of the device body and the piston assembly provided in the embodiment of the utility model.

[0043] The piston assembly 30 also includes a limit seat 38, which is connected to the piston 31. The piston 31 is connected to the elastic member 32 through the limit seat 38. The elastic member 32 is elastically pressed between the limit seat 38 and the base 37. The limit seat 38 is provided with a through hole connected to the hole of the base 37. The through hole allows gas and liquid to pass through, so that the piston 31 can be opened normally after the pressure in the shell exceeds the threshold.

[0044] In this embodiment, the elastic member 32 is installed between the limit seat 38 and the base 37. Compared with being installed between the piston 31 and the base 37, the elastic member 32 can be made smaller, so that the space occupied by the elastic member 32 is reduced, which facilitates the discharge of gas and liquid in the shell when the battery is abnormal.

[0045] Further, the base 37 is provided with a first receiving groove 371, and the limiting seat 38 is provided with a second receiving groove 381. The groove wall of the first receiving groove 371 and the groove wall of the second receiving groove 381 are slidably matched with each other, and the elastic member 32 is assembled in the first receiving groove 371 and the second receiving groove 381. The first receiving groove 371 and the second receiving groove 381 jointly limit the elastic member 32, and the groove wall of the first receiving groove 371 and the groove wall of the second receiving groove 381 play a guiding role, so that they are slidably matched with each other.

[0046] Furthermore, the base 37 is provided with a first accommodating groove 371 , and the elastic member 32 is assembled in the first accommodating groove 371 , so as to limit the elastic member 32 and prevent the elastic member 32 from deforming and displacing in the radial direction.

[0047] Furthermore, the limiting seat 38 is provided with a second accommodating groove 381 , and the elastic member 32 is assembled in the second accommodating groove 381 , so as to limit the elastic member 32 and prevent the elastic member 32 from deforming and displacing in the radial direction.

[0048] In one embodiment, the piston assembly 30 further includes a pressure relief film 33, a protective film 34 and a dustproof film 35. The piston 31 is provided with a pressure relief hole 311, which is connected to the main hole 202. The pressure relief film 33 is fixedly connected to the side of the piston 31 facing the first secondary hole 203 and covers the pressure relief hole 311. The protective film 34 is movably connected to the side of the piston 31 facing the main hole 202 and covers the pressure relief hole 311. The pressure relief film 33 and the protective film 34 are located on opposite sides of the pressure relief hole 311. The dustproof film 35 is connected to the side of the device body 20 away from the piston 31 and covers the main hole 202. The dustproof film 35 is provided with a transition hole 351, which can be ventilated but can reduce the entry of dust into the accommodating chamber 201.

[0049] The pressure relief film 33 is used to pass air but not liquid, and the pressure relief film can be made of a polymer waterproof film. The protective film 34 is made of a polymer material that is resistant to acid, alkali and electrolyte. During the injection process, the protective film 34 can effectively protect the electrolyte from passing because of the support of the piston 31. During the exhaust process in the shell, there is no support above the protective film 34, so the protective film 34 can be pushed open to allow gas to pass.

[0050] In this embodiment, the pressure relief membrane 33, the protective film 34 and the dustproof membrane 35 are arranged from bottom to top along the axial direction of the fusion hole 101. The dustproof membrane 35 is provided with a transition hole 351, which can be ventilated, but can reduce the entry of dust into the accommodating chamber 201. During the injection process of the protective film 34, because of the support of the piston 31, the protective film 34 can effectively protect the electrolyte from passing through the pressure relief membrane 33. When there is excess gas in the shell of the pressure relief membrane 33, the gas can be allowed to pass through in time to achieve the effect of early pressure relief. That is, the dynamic pressure relief of the pressure relief membrane 33 ensures the stability of the internal pressure of the shell and improves safety; after the abnormal explosive exhaust of the battery, the device can be recycled and can be reused by re-attaching the pressure relief sheet, which improves the utilization efficiency of resources.

[0051] The present application also protects a battery pack, which includes: a box and a plurality of single cells according to any one of the above embodiments, wherein the plurality of single cells are assembled in the box, and the plurality of single cells can be connected in series or in series and in parallel.

[0052] The battery pack may also be provided with an exhaust gas collection device, which can continuously collect the exhaust gas discharged through the pressure relief membrane 33, thereby ensuring the stability of the working environment of the battery pack.

[0053] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0054] It should also be noted that when an element is referred to as being "fixed on" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element at the same time. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or may be indirectly connected to the other element through an intermediate element.

[0055] In addition, the descriptions of "first", "second", etc. in the present utility model are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present utility model.

[0056] The above description is only a preferred embodiment of the utility model, and does not limit the patent scope of the utility model. All equivalent structural changes made by using the contents of the utility model specification and drawings under the utility model concept, or directly / indirectly used in other related technical fields are included in the patent protection scope of the utility model.

Claims

1. A top cover assembly, characterized in that: include: The top cover is provided with a fusion hole; The device body is provided with a containing cavity, the two opposite ends of the device body are provided with a main hole and a first auxiliary hole communicating with the containing cavity, the side wall of the device body is provided with a second auxiliary hole communicating with the containing cavity, and the device body is assembled in the fusion hole; as well as A piston assembly is assembled in the accommodating chamber. The piston assembly is movably connected to the device body along the axial direction of the fusion hole. The piston assembly can movably block the connection between the main hole and the second auxiliary hole. The piston assembly can be opened under a preset pressure to allow the second auxiliary hole to spray electrolyte from the main hole through the piston assembly.

2. The top cover assembly according to claim 1, characterized in that: The piston assembly includes a piston and an elastic member, wherein the piston is connected to the elastic member, and the elastic member is connected to the device body. The elastic member is elastic and is used to elastically press the piston so that the piston can movably block the connection between the main hole and the second auxiliary hole.

3. The top cover assembly according to claim 2, characterized in that: The piston assembly further comprises a pressure relief film, a protective film and a dustproof film, the piston is provided with a pressure relief hole, the pressure relief hole is communicated with the main hole, the pressure relief film is fixedly connected to a side of the piston facing the first secondary hole and covers the pressure relief hole, the protective film is movably connected to a side of the piston facing the main hole and covers the pressure relief hole, the dustproof film is connected to a side of the device body away from the piston and covers the main hole, and the dustproof film is provided with a transition hole; The pressure relief membrane is used to pass air but not liquid.

4. The top cover assembly according to claim 2, characterized in that: The piston assembly also includes a sealing ring, which is sleeved on the outer circumferential surface of the piston and is used to be pressed at the connection between the piston and the device body to block the communication between the main hole and the second auxiliary hole.

5. The top cover assembly according to claim 4, characterized in that: The outer peripheral surface of the piston is provided with a limiting groove, and the sealing ring is assembled in the limiting groove and further exposed outside the limiting groove.

6. The top cover assembly according to claim 2, characterized in that: The contact point between the device body and the piston has a first inclined surface, and the contact point between the piston and the device body has a second inclined surface. In the direction from the main hole to the first secondary hole, the inclination angle of the first inclined surface is α, and the inclination angle of the second inclined surface is β, 30≤β≤α≤75.

7. The top cover assembly according to claim 2, characterized in that: The piston assembly also includes a base, which is connected to the device body, and the elastic member is connected to the device body through the base. The elastic member is elastically pressed between the piston and the base, and the base is provided with a base hole connected to the first auxiliary hole.

8. The top cover assembly according to claim 7, characterized in that: The piston assembly also includes a limit seat, the limit seat is connected to the piston, the piston is connected to the elastic member through the limit seat, the elastic member is elastically pressed between the limit seat and the base, and the limit seat is provided with a through hole connected to the base hole.

9. The top cover assembly according to claim 8, characterized in that: The base is provided with a first receiving groove, the limit seat is provided with a second receiving groove, the groove wall of the first receiving groove and the groove wall of the second receiving groove are slidably matched with each other, and the elastic member is assembled in the first receiving groove and the second receiving groove; or The base is provided with a first accommodating groove, and the elastic member is assembled in the first accommodating groove; or The limiting seat is provided with a second accommodating groove, and the elastic member is assembled in the second accommodating groove.

10. A single cell battery, characterized in that: The single battery comprises: a core pack, a shell, and a top cover assembly according to any one of claims 1 to 9, the core pack is arranged in the shell, and the top cover assembly and the shell are connected to seal the shell.

11. A battery pack, characterized in that: The battery pack comprises: a case and a plurality of unit batteries as claimed in claim 10 , wherein the plurality of unit batteries are assembled in the case.

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