End cap assembly, energy storage device, and electric appliance

Abstract

The application discloses an end cover assembly, an energy storage device and an electric equipment. The end cover assembly comprises an end cover body and an explosion-proof valve. The end cover body comprises an outer surface and an inner surface arranged in a direction away from the thickness direction of the end cover body. The end cover body further comprises a mounting groove and a liquid injection through hole. The mounting groove is recessed from the inner surface to the outer surface. The liquid injection through hole is arranged on the groove bottom wall of the mounting groove and penetrates through the groove bottom wall and the outer surface. The explosion-proof valve comprises a fixed part and a curved part connected with the fixed part. The fixed part and the curved part are provided with a gas-permeable waterproof structure. In the thickness direction of the end cover assembly, the explosion-proof valve is arranged in the mounting groove and the liquid injection through hole. The outer side surface of the fixed part is fixedly connected with the mounting groove. The curved part abuts against the groove bottom wall and the groove side wall of the mounting groove. The curved part can be elastically deformed under the pressure of external force and is bent towards the inner surface to expose part of the liquid injection through hole. The deformation resilience of the curved part can make the curved part re-expose the liquid injection through hole.

Description

Technical Field

[0001] This application relates to the field of energy storage technology, and in particular to an end cap assembly, an energy storage device, and an electrical appliance. Background Technology

[0002] Due to the scarcity of lithium resources and the increasing demand for secondary energy storage devices, sodium, a relatively abundant resource, can be used as a substitute for lithium. Among these, aqueous sodium-ion batteries are considered one of the most promising large-scale energy storage batteries. However, in practical applications, as the battery cycles through charging and discharging, metallic sodium easily deposits at the negative electrode. This metallic sodium readily reacts with the electrolyte to generate flammable and explosive gases such as hydrogen (H2). These gases tend to accumulate within the battery, severely impacting its safety. Summary of the Invention

[0003] This application provides an end cap assembly, an energy storage device, and an electrical device that can promptly discharge flammable and explosive gases such as hydrogen (H2), thereby increasing the battery's venting performance and improving the safety of battery use.

[0004] This application provides an end cap assembly applied to an energy storage device. The end cap assembly includes an end cap body and an explosion-proof valve. The end cap body includes an outer surface and an inner surface, which are arranged opposite to each other along the thickness direction of the end cap body. The end cap body also includes a mounting groove and a liquid injection through hole. The mounting groove is recessed from the inner surface to the outer surface, and the liquid injection through hole is formed in the bottom wall of the mounting groove and penetrates the bottom wall and the outer surface. The explosion-proof valve includes a fixing part and a bent part connected to the fixing part. The fixing part and the bent part have... All components have a breathable and waterproof structure; along the thickness direction of the end cap assembly, the explosion-proof valve is installed in the mounting groove and covers the injection through hole; the outer side of the fixing part is fixedly connected to the mounting groove; the bending part abuts against the bottom wall of the mounting groove; the fixing part and the bending part share the injection through hole; the bending part can elastically deform under external pressure and bend away from the mounting groove so that the injection through hole is at least partially open; the deformation rebound force of the bending part can make the bending part cover the injection through hole again so that the injection through hole is breathable and waterproof.

[0005] In this embodiment, the end cap assembly is provided with a mounting groove for assembling an explosion-proof valve. The mounting groove communicates with the injection port. The fixed part of the explosion-proof valve is fixed to a portion of the mounting groove, and the curved part of the explosion-proof valve movably abuts against another portion of the mounting groove. When the curved part is pressed, it can bend relative to the fixed part, creating a gap between the curved part and the mounting groove, exposing the injection port, thus enabling liquid injection into the energy storage device. After liquid injection is completed, the curved part can re-abut against the mounting groove under its own deformation rebound force, covering the injection port and thus covering the energy storage device. Simultaneously, the fixed part and the curved part of the explosion-proof valve are provided with a breathable and waterproof structure. This breathable and waterproof structure is used to discharge gas generated inside the energy storage device, integrating the liquid injection and venting functions into one, improving the venting performance of the energy storage device, preventing the accumulation of gas inside the energy storage device that could lead to performance degradation, and avoiding safety accidents caused by gas accumulation inside the energy storage device, ensuring the safety of the energy storage device. In other words, the liquid filling and explosion-proof functions are achieved without the need for additional injection holes and structures, simplifying the cap structure.

[0006] In one embodiment, the explosion-proof valve includes a first valve body, a breathable protective membrane, and a second valve body. Along the thickness direction of the end cap assembly, the first valve body, the breathable protective membrane, and the second valve body are stacked sequentially, with the second valve body abutting against the bottom wall of the mounting groove. The first valve body has multiple first vent holes, and the second valve body has multiple second vent holes. The breathable protective membrane includes a breathable microporous structure, which, along with the first and second vent holes, communicates to form the breathable and waterproof structure. The outer surface of the fixing portion is formed by a portion of the peripheral surface of the first valve body, a portion of the peripheral surface of the breathable protective membrane, and a portion of the outer peripheral surface of the second valve body. The outer surface of the curved portion is formed by another portion of the outer peripheral surface of the second valve body.

[0007] It is understood that the second valve body tightly clamps the breathable and waterproof membrane and the first valve body between itself and the mounting groove. The breathable and waterproof structure, which is composed of the first exhaust port of the first valve body, the breathable microporous structure of the breathable protective membrane, and the second exhaust port of the second valve body, not only allows the gas inside the energy storage device to be discharged through the explosion-proof valve when the explosion-proof valve closes the liquid injection hole, but also provides waterproof and dustproof protection for the energy storage device, preventing impurities such as moisture, electrolyte, and dust from entering the energy storage device and causing malfunctions.

[0008] In one embodiment, the second valve body includes a third surface and a fourth surface disposed opposite to each other along the thickness direction of the second valve body. The second valve body also includes a first arc surface and a second arc surface disposed opposite to each other along the radial direction of the second valve body. The first arc surface and the second arc surface are both connected between the third surface and the fourth surface. The first arc surface forms part of the outer peripheral surface of the second valve body. The second arc surface is provided with a flange protruding from the third surface. The breathable protective membrane and the first valve body are stacked sequentially on the third surface. Part of the peripheral surface of the breathable protective membrane and the first valve body abuts against the flange. The height of the flange protruding from the third surface is equal to the sum of the thicknesses of the breathable protective membrane and the first valve body. The surface of the flange facing away from the second arc surface is the outer surface of the curved portion. The flange abuts against part of the bottom wall and part of the side wall of the mounting groove.

[0009] It is understandable that the height of the flange protruding from the second valve body is equal to the sum of the thicknesses of the breathable protective membrane and the first valve body. This allows the flange to tightly clamp the first valve body and the breathable protective membrane, which are stacked on the second valve body, between itself and the bottom and side walls of the mounting groove. At the same time, the flange can tightly abut against the bottom and side walls of the mounting groove, ensuring the flatness of the connection between the explosion-proof valve and the end cap body, and also ensuring the waterproofness of the explosion-proof valve to the liquid injection hole.

[0010] In one embodiment, the thickness of the second valve body is greater than the thickness of the first valve body.

[0011] It is understandable that toughness is related to the thickness of the material. When the thickness of the second valve body is greater than that of the first valve body, the toughness of the second valve body is better than that of the first valve body, thus the elastic deformation capacity of the second valve body is greater than that of the first valve body. When the portion of the first valve body and the portion of the second valve body corresponding to the bend are subjected to external force and bend, the second valve body has a greater deformation rebound force than the first valve body. This ensures that after the external force at the bend is removed, the second valve body can drive the first valve body to spring back to its original position and re-abut against the mounting groove, ensuring the waterproofness of the energy storage device.

[0012] In one embodiment, the thickness of the flange is less than or equal to the groove depth of the mounting groove.

[0013] It is understandable that the flange thickness needs to meet the requirements of the explosion-proof valve for the mounting groove. When the flange thickness is less than the groove depth, the explosion-proof valve can tightly abut against the bottom and side walls of the groove, achieving proper fluid injection through-hole. When the flange thickness equals the groove depth, the contact area between the explosion-proof valve and the groove increases, improving the valve's performance for the fluid injection through-hole.

[0014] In one embodiment, the sidewall of the mounting groove includes a first groove wall and a second groove wall, the second groove wall being connected to the first groove wall and surrounding the bottom wall of the mounting groove. The bottom wall includes a first bottom wall and a second bottom wall. Along the radial direction of the injection through hole, the width of the first bottom wall is smaller than the width of the second bottom wall. The first bottom wall and the first groove wall are connected, and a stop surface is formed at the connection between the first groove wall and the second groove wall. The flange abuts against the second bottom wall and the second groove wall, and the opposite end faces of the flange in the longitudinal direction abut against the stop surface.

[0015] It is understandable that the width of the first bottom wall is smaller than the width of the second bottom wall. The flange and part of the first valve body (bent portion) abut against the second bottom wall, increasing the contact area between the explosion-proof valve and the mounting groove, extending the path from the inside to the outside of the energy storage device, and improving the safety of the explosion-proof valve for the injection port. At the same time, the stop surface abuts against the end face of the flange, which can limit the degree of bending of the bent portion relative to the mounting groove or block the rebound of the bent portion when the bent portion bends or springs back, thus realizing the movable locking of the explosion-proof valve and the mounting groove.

[0016] In one embodiment, the first valve body and the second valve body are aluminum sheets, or the first valve body is a steel sheet and the second valve body is an aluminum sheet.

[0017] It is understandable that both aluminum and steel sheets are materials with good toughness, and steel sheets have stronger resilience. The explosion-proof valve is made of aluminum or steel sheets, allowing the bent part of the valve to elastically deform relative to the fixed part when subjected to external force, and possessing deformation resilience. Therefore, after the external force is removed, the bent part can spring back to abut against the mounting groove and re-cover the injection port. The second valve body, being made of aluminum, can be easily welded to the end cap.

[0018] In one embodiment, the breathable protective membrane is a Micros waterproof and breathable membrane.

[0019] It is understandable that the Weils waterproof and breathable membrane allows gas to pass through, enabling the gas inside the energy storage device to escape. This balances the internal and external air pressure of the energy storage device, preventing gas buildup and potential safety hazards. At the same time, the Weils waterproof and breathable membrane does not allow water, dust particles, or other impurities to pass through, preventing these impurities from entering the energy storage device and causing malfunctions.

[0020] This application provides an energy storage device, which includes a housing, a battery cell, and an end cap assembly. The housing includes an opening and a receiving cavity. The battery cell is installed in the receiving cavity, the end cap assembly is located in the opening, and the second valve body of the explosion-proof valve faces the receiving cavity.

[0021] In one embodiment, the energy storage device is an aqueous sodium-ion battery.

[0022] This application embodiment also provides an electrical device, the electrical device including the energy storage device, the energy storage device being used to supply power to the electrical device. Attached Figure Description

[0023] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is an application scenario diagram of the energy storage device provided in the embodiments of this application;

[0025] Figure 2 for Figure 1 The diagram shows the structure of the energy storage device.

[0026] Figure 3 for Figure 2 A partial structural schematic diagram of the end cap assembly of the energy storage device shown in the first embodiment;

[0027] Figure 4 for Figure 3 The diagram shows the structure of the end cap assembly from another angle;

[0028] Figure 5 for Figure 4 An exploded view of a portion of the end cap assembly shown;

[0029] Figure 6 for Figure 5 A schematic diagram of the cross-sectional structure of the end cap body is shown;

[0030] Figure 7 for Figure 2 The exploded structure diagram of the explosion-proof valve of the end cap assembly is shown.

[0031] Figure 8 for Figure 7 The diagram shows a cross-sectional structure of the explosion-proof valve.

[0032] Figure 9 for Figure 3 A cross-sectional structural diagram of a portion of the end cap assembly shown;

[0033] Figure 10 for Figure 9 The diagram shows a cross-sectional view of the explosion-proof valve of the end cap assembly when the injection port is exposed.

[0034] Figure 11 for Figure 2A partial structural schematic diagram of the second embodiment of the end cap assembly shown.

[0035] The terms corresponding to the reference numerals in the figures are as follows: Energy storage device 1000, end cap assembly 100, first pole post 101, second pole post 102, end cap body 10, outer surface 11, inner surface 12, first pole post through hole 13, second pole post through hole 14, liquid injection through hole 15, mounting groove 16, groove bottom wall 16a, groove side wall 16b, first groove wall 161, second groove wall 162, first bottom wall 163, second bottom wall 164, stop surface 165, first part 166, second part 167, explosion-proof valve 20, first valve body 21, first gauge Surface 211, second surface 212, first exhaust port 213, breathable protective membrane 22, second valve body 23, third surface 231, fourth surface 232, second exhaust port 24, outer peripheral surface 25, first arc surface 251, second arc surface 252, flange 26, outer side surface 261, inner side surface 262, top surface 263, bottom surface 264, end face 265, bending part 27, fixing part 28, housing 200, second electrical equipment 3000, wind energy conversion device 4000, electrical energy conversion device 4500, energy storage system 5000. Detailed Implementation

[0036] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0037] In this application, unless otherwise expressly specified and limited, the terms “installation,” “connection,” “linking,” “fixing,” etc., shall be interpreted broadly. For example, they may refer to a fixed connection, a detachable connection, or an integral part; they may refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they may refer to a direct connection or an indirect connection through an intermediate medium; they may refer to the internal connection of two components or the interaction between two components, unless otherwise expressly and specifically limited.

[0038] Taking electrochemical energy storage as an example, this solution provides an energy storage device. The energy storage device is equipped with a set of chemical batteries. It mainly uses the chemical elements in the chemical batteries as the energy storage medium. The charging and discharging process is accompanied by the chemical reaction or change of the energy storage medium. Simply put, the electrical energy generated by wind and solar energy is stored in the chemical batteries. When the use of external electrical energy reaches its peak, the stored electricity is released for use, or transferred to places with a shortage of electricity for use.

[0039] Current energy storage applications are quite widespread, including energy storage on the (wind and solar) power generation side, grid-side energy storage, base station-side energy storage, and user-side energy storage. The corresponding types of energy storage devices include:

[0040] (1) Large energy storage containers used in grid-side energy storage scenarios can serve as high-quality active and reactive power regulation power sources in the grid, enabling load matching of electrical energy in time and space, enhancing the absorption capacity of renewable energy, and playing a significant role in grid system backup, alleviating peak load power supply pressure, and peak regulation and frequency regulation.

[0041] (2) Small and medium-sized energy storage cabinets used in industrial and commercial energy storage scenarios (banks, shopping malls, etc.) on the user side mainly operate under the "peak shaving and valley filling" mode. Since there are large price differences in electricity prices at peak and valley times depending on electricity demand, users with energy storage equipment usually charge the energy storage cabinet / box during the low electricity price period in order to reduce costs; and release the electricity in the energy storage equipment for use during the peak electricity price period to achieve the purpose of saving electricity costs.

[0042] It should be noted that the aforementioned energy storage containers, small and medium-sized energy storage cabinets, and small household energy storage boxes, which contain energy storage devices, can be understood as electrical equipment.

[0043] Please see Figure 1 , Figure 1 This is an application scenario diagram of the energy storage device provided in the embodiments of this application.

[0044] The energy storage device 1000 provided in this application embodiment is applied to an energy storage system 5000. The energy storage system 5000 includes a power conversion device 4500 (photovoltaic panel), a wind power conversion device 4000 (windmill), a first electrical device (grid), a second electrical device 3000 (base station), and the energy storage device 1000. The energy storage system also includes an energy storage cabinet, in which the energy storage device 1000 is installed. The energy storage cabinet can be installed outdoors. Specifically, the first power conversion device can convert solar energy into electrical energy during periods of low electricity prices. The energy storage device 1000 stores this electrical energy and supplies it to the first or second electrical device during peak electricity demand, or provides power when the first or second electrical device experiences a power outage. The second power conversion device can convert wind energy into electrical energy. The energy storage device 1000 stores this electrical energy and supplies it to the first or second electrical device during peak electricity demand, or provides power when the first or second electrical device experiences a power outage. Among them, electrical energy can be transmitted using high-voltage cables.

[0045] It should be noted that the aforementioned first electrical equipment, second electrical equipment, and other equipment containing the energy storage device 1000 can be understood as electrical equipment.

[0046] Please refer to the following: Figure 2 , Figure 2 for Figure 1 The diagram shows the structure of the energy storage device.

[0047] For ease of description, in this application, the length direction of the energy storage device 1000 is defined as the X-axis, the width direction as the Y-axis, and the height direction as the Z-axis. The X-axis, Y-axis, and Z-axis are mutually perpendicular. The directional terms such as "inner," "outer," "upper," "top," "lower," "bottom," "left," and "right" mentioned in the description of the embodiments in this application are based on the appendix to the specification. Figure 2 The description of the orientation shown does not constitute a limitation on the actual application scenario of the energy storage device 1000. The terms "same," "equal," or "parallel" used below are subject to certain tolerances.

[0048] The energy storage device 1000 may include, but is not limited to, single-cell batteries, battery modules, battery packs, and battery systems. It is understood that the actual application form of the energy storage device 1000 provided in this application may be, but is not limited to, the products listed, or other application forms. When the energy storage device 1000 is a single-cell battery, it may be a cylindrical battery, a prismatic battery, or a battery of other shapes. In this embodiment, the energy storage device 1000 is a prismatic battery. The prismatic battery is a rechargeable battery.

[0049] The energy storage device 1000 can be a sodium-ion battery, such as an aqueous sodium-ion battery. However, with cycling, sodium deposition occurs on the negative electrode of aqueous sodium-ion batteries. Since metallic sodium is more reactive than lithium, it reacts with the aqueous electrolyte to generate flammable and explosive gases such as H2, posing a significant safety hazard in practical applications. Furthermore, the gases generated by the battery cell lead to the continuous growth of sodium dendrites and low coulombic efficiency, significantly impacting the cell's performance.

[0050] This application provides an energy storage device 1000 that can solve the technical problems existing in the prior art of aqueous sodium-ion batteries. For details, please refer to the following specific embodiments.

[0051] The energy storage device 1000 includes an end cap assembly 100, a housing 200, and a battery cell (not shown). The housing 200 has an opening (not shown) and a receiving cavity (not shown). The battery cell includes a positive electrode (not shown) and a negative electrode (not shown). The end cap assembly 100 includes a first terminal 101 and a second terminal 102. The battery cell is assembled within the receiving cavity of the housing 200. The end cap assembly 100 is located at the opening of the housing 200. The first terminal 101 is welded to and conductively connected to the positive electrode of the battery cell, and the second terminal 102 is welded to and conductively connected to the negative electrode of the battery cell. Electrolyte is injected into the energy storage device 1000 after the end cap assembly 100 is connected to it. This application does not limit the specific structure of the energy storage device 1000 except for the end cap assembly 100.

[0052] Please see Figure 3 and Figure 4 , Figure 3 for Figure 2 A partial structural schematic diagram of the end cap assembly of the energy storage device shown is presented in the first embodiment. Figure 4 for Figure 3 The diagram shows the structure of the end cap assembly from another angle.

[0053] The end cap assembly 100 includes an end cap body 10 and an explosion-proof valve 20. The edge of the end cap body 10 is connected to the opening of the housing 200. A first pole 101 and a second pole 102 are assembled to the end cap body 10. The explosion-proof valve 20 is disposed on the end cap body 10. Along the Y-axis direction, the explosion-proof valve 20 is spaced apart from the first pole 101 and the second pole 102. When flammable and explosive gases (such as hydrogen H2) are generated inside the energy storage device 1000 (inside the housing 200), these gases can be discharged through the explosion-proof valve 20. This not only avoids the explosion of the energy storage device 1000 due to gas accumulation, but also reduces the impact of these gases on the performance of the battery cells inside the energy storage device 1000.

[0054] The end cap body 10 is generally a rectangular plate. The end cap body 10 includes an outer surface 11 and an inner surface 12. The outer surface 11 and the inner surface 12 are arranged opposite to each other along the thickness direction (Z-axis direction) of the end cap body 10. When the end cap body 10 is mounted on the housing 200, the outer surface 11 faces away from the housing 200, and the inner surface 12 faces the housing 200.

[0055] Please refer to the following: Figure 4 and Figure 5 , Figure 5 for Figure 4 The diagram shown is an exploded view of a portion of the end cap assembly. It should be noted that... Figure 5 The diagram only shows the disassembled structure between the end cap body 10 and the explosion-proof valve 20, and does not show the first pole 101 and the second pole 102 of the end cap assembly 100.

[0056] The end cap body 10 also includes a first electrode through hole 13, a second electrode through hole 14, and a liquid injection through hole 15. Along the thickness direction (Z-axis direction) of the end cap body 10, the first electrode through hole 13, the second electrode through hole 14, and the liquid injection through hole 15 all penetrate the outer surface 11 and the inner surface 12 of the end cap body 10. Along the length direction (Y-axis direction) of the end cap body 10, the first electrode through hole 13, the liquid injection through hole 15, and the second electrode through hole 14 are arranged sequentially at intervals. The first electrode through hole 13 and the second electrode through hole 14 are respectively located at opposite ends along the length direction of the end cap body 10. The first electrode through hole 13 is used for the first electrode 101 to pass through. The second electrode through hole 14 is used for the second electrode 102 to pass through. In other embodiments, the first electrode through hole 13 can also be used for the second electrode 102 to pass through, and the second electrode through hole 14 can also be used for the first electrode 101 to pass through. The embodiments of this application do not limit the structure of the first pole hole 13 and the second pole hole 14.

[0057] The injection port 15 is used for injecting electrolyte into the energy storage device 1000 and for allowing gas to pass through the energy storage device 1000. It is understood that the explosion-proof valve 20 can be exposed or covered by the injection port 15. When the explosion-proof valve 20 is exposed, electrolyte can be injected into the energy storage device 1000. When the explosion-proof valve 20 is covered by the injection port 15, external moisture and impurities can be prevented from entering the energy storage device 1000, avoiding malfunctions, and the gas inside the energy storage device 1000 can be released through the injection port 15 via the explosion-proof valve 20. For example, the injection port 15 can be a circular through-hole.

[0058] The end cap body 10 also includes a mounting groove 16. The mounting groove 16 is used to accommodate the explosion-proof valve 20. The mounting groove 16 is recessed in the inner surface 12 of the end cap body 10, and the mounting groove 16 is formed by the recess from the inner surface 12 of the end cap body 10 toward the outer surface 11. The opening of the mounting groove 16 faces the receiving cavity of the housing 200.

[0059] The mounting groove 16 includes a bottom wall 16a and a side wall 16b. The side wall 16b surrounds the periphery of the surface of the bottom wall 16a. A liquid injection through-hole 15 is formed in the bottom wall 16a and penetrates both the bottom wall 16a and the outer surface 11 of the end cap body 10. Alternatively, the liquid injection through-hole 15 penetrates both the outer surface 11 and the inner surface 12 of the end cap body 10. In this embodiment, the mounting groove 16 is approximately a circular recess. The side wall 16b is annular.

[0060] Please refer to the following: Figure 5 and Figure 6 , Figure 6 for Figure 5 The diagram shows a cross-sectional structure of the end cap body.

[0061] The sidewall 16b of the mounting groove 16 includes a first groove wall 161 and a second groove wall 162 connected to the first groove wall 161. In this embodiment, the sidewall 16b is approximately annular. Both the first groove wall 161 and the second groove wall 162 are semi-circular arc walls, and their arcs are concentric. The first groove wall 161 and the second groove wall 162 are each half of the sidewall 16b, and the radius of the first groove wall 161 is smaller than the radius of the second groove wall 162. It can be understood that the two connection points of the first groove wall 161 and the second groove wall 162 are at the two ends of one diameter of the circular groove (mounting groove 16), and both the first groove wall 161 and the second groove wall 162 are semi-circular arc surfaces. The two connection points of the first groove wall 161 and the second groove wall 162 form a stop surface 165. Both stop surfaces 165 face the second groove wall 162, and the radial direction of the second groove wall 162 is parallel to the stop surface 165. The stop surface 165 is used to move and abut against the explosion-proof valve 20.

[0062] In this embodiment, the injection through-hole 15 and the mounting groove 16 are connected. The center of the injection through-hole 15 coincides with the center of the mounting groove 16. The width of the bottom wall 16a of the groove around the injection through-hole 15 is different, and it may include a first bottom wall 163 and a second bottom wall 164. Both the first bottom wall 163 and the second bottom wall 164 are semi-circular. The first bottom wall 163 is connected to the first groove wall 161, and the second bottom wall 164 is connected to the second groove wall 162. Along the radial direction of the injection through-hole 15, the width of the first bottom wall 163 is smaller than the width of the second bottom wall 164.

[0063] It can be understood that the first bottom wall 163 and the first groove wall 161 constitute the first part 166 of the mounting groove 16, and the second bottom wall 164 and the second groove wall 162 constitute the second part 167 of the mounting groove 16. The first part 166 of the mounting groove 16 is connected to the second part 167 of the mounting groove 16. The maximum radial length of the first part 166 of the mounting groove 16 is less than the maximum radial length of the second part 167. The groove depth of the first part 166 of the mounting groove 16 is equal to the groove depth of the second part 167.

[0064] Please refer to the following: Figure 7 and Figure 8 , Figure 7 for Figure 2 The diagram shown is an exploded view of the explosion-proof valve in the end cap assembly. Figure 8 for Figure 7 The diagram shows a cross-sectional view of the explosion-proof valve. It should be noted that... Figure 7 The dashed lines are only for illustrating the connection between the two end faces 265. Figure 8 The dashed line in the diagram is only to indicate the boundary between the curved part 27 and the fixed part 28 of the explosion-proof valve 20.

[0065] The explosion-proof valve 20 includes a first valve body 21, a breathable protective membrane 22, and a second valve body 23. Along the Z-axis, the first valve body 21, the breathable protective membrane 22, and the second valve body 23 are stacked and connected sequentially. The shape of the explosion-proof valve 20 is adapted to the shape of the mounting groove 16. For example, the explosion-proof valve 20 is approximately circular. The first valve body 21, the breathable protective membrane 22, and the second valve body 23 are also approximately circular. The diameter of the first valve body 21 is equal to the diameter of the breathable protective membrane 22, and the diameters of both the first valve body 21 and the breathable protective membrane 22 are equal to the minimum radial length of the second valve body 23. That is, the projections of the first valve body 21 and the breathable protective membrane 22 in the Z-axis direction coincide and fall within the projection of the second valve body 23 in the Z-axis direction.

[0066] The first valve body 21 includes a first surface 211 and a second surface 212. The first surface 211 and the second surface 212 are arranged opposite to each other along the thickness direction of the first valve body 21. The first valve body 21 also includes a plurality of first vent holes 213. The plurality of first vent holes 213 are evenly distributed on the first valve body 21. The plurality of first vent holes 213 all penetrate the first surface 211 and the second surface 212 of the first valve body 21. The first vent holes 213 are used to allow gas to pass through. The material of the first valve body 21 can be aluminum, steel, or other materials with good toughness. For example, the first valve body 21 is a circular plate made of aluminum. The first valve body 21 has better elasticity when made of steel.

[0067] In this embodiment, the breathable protective membrane 22 can be a Micros waterproof and breathable membrane. The Micros waterproof and breathable membrane includes a breathable microporous structure (not shown). The Micros waterproof and breathable membrane is mainly made of expanded polytetrafluoroethylene (ePTFE), which allows gas to pass through but not water, dust particles, etc. The breathable protective membrane 22 allows gas inside the energy storage device 1000 to escape, balancing the internal and external air pressure of the energy storage device 1000 and preventing gas accumulation inside the energy storage device 1000 that could cause safety hazards. Simultaneously, the breathable protective membrane 22 can also prevent large molecular impurities such as water and dust particles from entering the interior of the energy storage device 1000, avoiding adverse reactions; it also prevents the electrolyte inside the energy storage device from evaporating to the outside, leading to electrolyte loss and reducing the cycle life of the energy storage device.

[0068] The second valve body 23 includes a third surface 231 and a fourth surface 232. The third surface 231 and the fourth surface 232 are arranged opposite to each other along the thickness direction (Z-axis direction) of the second valve body 23. The second valve body 23 also includes a plurality of second vent holes 24. The plurality of second vent holes 24 are evenly distributed on the second valve body 23. The plurality of second vent holes 24 all penetrate the third surface 231 and the fourth surface 232 of the second valve body 23. The second vent holes 24 are used to allow gas to pass through. The material of the second valve body 23 can be aluminum, which has toughness and better weldability to aluminum end caps. For example, the second valve body 23 is a circular plate made of aluminum.

[0069] The second valve body 23 also includes an outer peripheral surface 25, which comprises a first arc surface 251 and a second arc surface 252. The first arc surface 251 and the second arc surface 252 are connected along the circumference of the second valve body 23. It can be understood that the outer peripheral surface 25 of the second valve body 23 in this embodiment is formed by the first arc surface 251 and the second arc surface 252. It is not excluded that a third arc surface may also be included. Both the first arc surface 251 and the second arc surface 252 are semi-circular arc surfaces. The arc length of the first arc surface 251 is the same as the arc length of the second arc surface 252. The first arc surface 251 and the second arc surface 252 are concentric and identical.

[0070] A flange 26 is provided on the outer peripheral surface 25 of the second valve body 23. Along the radial direction of the second valve body 23, the flange 26 is connected to and protrudes from the second arc surface 252. Along the thickness direction (Z-axis direction) of the second valve body 23, the flange 26 protrudes from the third surface 231 of the second valve body 23. The second valve body 23 and the flange 26 form an L-shaped structure.

[0071] The flange 26 includes an outer surface 261, an inner surface 262, a top surface 263, a bottom surface 264, and two end faces 265. The outer surface 261 and inner surface 262 are arranged opposite to each other along the width direction of the flange 26 (the radial direction of the second valve body 23). The top surface 263 and bottom surface 264 are arranged opposite to each other along the thickness direction (Z-axis direction) of the flange 26. The top surface 263 connects the outer surface 261 and the inner surface 262. The two end faces 265 connect the inner surface 262, the outer surface 261, the top surface 263, and the bottom surface 264. The two end faces 265 are located at opposite ends along the length direction of the flange 26. The two end faces 265 are respectively used to abut against the stop surface 165. The line connecting the two end faces 265 is the straight line containing the diameter of the second valve body 23. It should be noted that the outer surface 261 of the flange 26, the two end faces 265, and the first arc surface 251 of the second valve body 23 together constitute the outer peripheral surface of the second valve body 23.

[0072] The shape of flange 26 is adapted to the shape of the second arc surface 252. In this embodiment, flange 26 is a semi-circular annular structure. The inner side 262, outer side 261, top surface 263, and bottom surface 264 of flange 26 are all semi-circular arc surfaces. The inner side 262 of flange 26 is connected to the second arc surface 252. The angle between the inner side 262 and the third surface 231 is 90 degrees. The outer side 261 of flange 26 faces away from the second valve body 23. The two end faces 265 of flange 26 face the second valve body 23. The two end faces 265 are set at an angle to the first arc surface 251. The top surface 263 of flange 26 faces the same direction as the third surface 231 of the second valve body 23. The bottom surface 264 of flange 26 faces the same direction as the fourth surface 232 of the second valve body 23, and is coplanar with the fourth surface 232.

[0073] This can be understood as follows: along the Z-axis direction, the top surface 263 of the flange 26 protrudes from the third surface 231 of the second valve body 23. The bottom surface 264 of the flange 26 is connected to and flush with the fourth surface 232 of the second valve body 23. The thickness of the flange 26 is greater than the thickness of the second valve body 23. The flange 26 can be used to mate with the second part 167 of the mounting groove 16 and to clamp the breathable protective membrane and the first valve body 21 between the mounting groove 16 and the first valve body 21. The width of the outer side surface 261 of the flange 26 is less than or equal to the width of the groove sidewall 16b of the mounting groove 16. That is, the thickness of the flange 26 is equal to the groove depth of the mounting groove 16, increasing the contact area between the explosion-proof valve 20 and the mounting groove 16, improving the sealing performance of the explosion-proof valve 20 to the injection through hole 15, and effectively preventing the entry of moisture and impurities. In other embodiments, the thickness of the flange 26 can also be less than the groove depth of the mounting groove 16.

[0074] In this embodiment, the breathable protective membrane 22 and the first valve body 21 are sequentially assembled onto the second valve body 23. The breathable protective membrane 22 is located between the second surface 212 of the first valve body 21 and the third surface 231 of the second valve body 23, and covers the first exhaust hole 213 and the second exhaust hole 24. The first valve body 21 can be welded to the second valve body 23 firstly, and the breathable protective membrane 22 can be clamped and fixed between the second valve body 23 and the first valve body 21. One side of the peripheral side of the first valve body 21 can be connected to the inner side 262 of the flange 26 of the second valve body 23 or to the second valve body 23 by laser welding.

[0075] The explosion-proof valve 20 also features a breathable and waterproof structure (not shown). Along the Z-axis, the breathable microporous structure of the breathable protective membrane 22, the first exhaust port 213 of the first valve body 21, and the second exhaust port 24 of the second valve body 23 are connected, with each first exhaust port 213 corresponding to one second exhaust port 24. The breathable microporous structure of the breathable protective membrane 22, the first exhaust port 213 of the first valve body 21, and the second exhaust port 24 of the second valve body 23 constitute the breathable and waterproof structure of the explosion-proof valve 20. This breathable and waterproof structure allows gas inside the energy storage device 1000 to be discharged through the explosion-proof valve 20. This structure also provides waterproofing and dustproofing, preventing moisture, electrolyte, dust, and other impurities from entering the energy storage device 1000 and causing malfunctions.

[0076] In this embodiment, the diameters of the first valve body 21, the breathable protective membrane 22, and the second valve body 23 are all equal. The diameter of the second valve body 23 does not include the thickness of the flange 26. That is, the projections of the first valve body 21 and the breathable protective membrane 22 in the Z-axis direction coincide, and both coincide with the projection of the third surface 231 of the second valve body 23 in the Z-axis direction. The sum of the thicknesses of the breathable protective membrane 22 and the first valve body 21 is equal to the height of the flange 26 protruding from the third surface 231 of the second valve body 23. This allows the breathable protective membrane 22 and the first valve body 21 to be clamped between the second valve body 23 and the mounting groove 16 of the end cap body 10, ensuring the flatness of the connection between the explosion-proof valve 20 and the end cap body 10.

[0077] It should be noted that the thickness of the second valve body 23 is slightly greater than that of the first valve body 21, resulting in better toughness of the second valve body 23 compared to the first valve body 21. The elastic deformation capacity of the second valve body 23 is also greater than that of the first valve body 21. When the portion of the first valve body 21 corresponding to the bending portion 27 and the portion of the second valve body 23 are subjected to external force and bend, the second valve body 23 has a greater deformation rebound force than the first valve body 21. This ensures that after the external force is removed, the second valve body 23 can drive the first valve body 21 to rebound to its original position and re-abut against the second part 167 of the mounting groove 16, thus ensuring the waterproof, dustproof, and breathable properties of the energy storage device 1000.

[0078] like Figure 8As shown, the explosion-proof valve 20 also includes a bent portion 27 and a fixed portion 28. The bent portion 27 is connected to one side of the fixed portion 28 and can be bent relative to the fixed portion 28. The fixed portion 28 is used to weld and fix to the first part 166 of the mounting groove 16 by laser welding. The bent portion 27 is used to movably connect to the second part 167 of the mounting groove 16, thereby exposing or closing the liquid injection through hole 15, thereby realizing the liquid injection or covering of the energy storage device 1000. Both the bent portion 27 and the fixed portion 28 are provided with a breathable and waterproof structure. When the bent portion 27 is used to store the energy storage device 1000, the gas generated inside the energy storage device 1000 can be discharged through the breathable and waterproof structure. Exemplarily, both the bent portion 27 and the fixed portion 28 are semi-circular plates. The diameter of the bent portion 27 is larger than the diameter of the fixed portion 28. The sum of the arc lengths of the bent portion 27 and the fixed portion 28 is equal to the sum of the arc lengths of the explosion-proof valve 20.

[0079] Specifically, the portion of the second valve body 23 having the first arc surface 251, the breathable protective membrane 22 corresponding to the portion of the second valve body 23 having the first arc surface 251, and the first valve body 21 together constitute the fixing part 28 of the explosion-proof valve 20. That is, the outer surface of the fixing part 28 is formed by a portion of the peripheral surface of the first valve body 21, a portion of the peripheral surface of the breathable protective membrane 22, and a portion of the outer peripheral surface of the second valve body 23 (i.e., the first arc surface 251).

[0080] The portion of the second valve body 23 with the second arc surface 252, the breathable protective membrane 22 corresponding to the portion of the second valve body 23 with the second arc surface 252, and the first valve body 21 together constitute the curved portion 27 of the explosion-proof valve 20. That is, the outer surface of the curved portion 27 is formed by the outer peripheral surface of another part of the second valve body 23 (i.e., the outer surface 261 of the flange 26). The line connecting the two end faces 265 of the second valve body 23 can also be the dividing line between the curved portion 27 and the fixed portion 28 of the explosion-proof valve 20. It can be understood that the curved portion 27 and the fixed portion 28 are the two parts divided into by the explosion-proof valve 20.

[0081] Please refer to the following: Figure 6 , Figure 8 and Figure 9 , Figure 9 for Figure 3 The diagram shows a partial cross-sectional view of the end cap assembly. It should be noted that... Figure 9 Only the cross-sectional structure of the explosion-proof valve 20 and the end cap body 10 assembled is shown, i.e. Figure 9 The diagram shows the cross-sectional structure of the explosion-proof valve 20 when it covers the injection port 15. Figure 9 The first pole 101, the second pole 102 of the end cap assembly 100 and other structures of the energy storage device 1000 are not shown.

[0082] The explosion-proof valve 20 is housed within the mounting groove 16 of the end cap body 10, and the fixing part 28 of the explosion-proof valve 20 is connected to the first part 166 of the mounting groove 16. The fixing part 28 of the explosion-proof valve 20 and the first part 166 of the mounting groove 16 can be welded together using a laser welding process. The bent part 27 of the explosion-proof valve 20 is movably connected to the second part 167 of the mounting groove 16.

[0083] Specifically, the first surface 211 of the first valve body 21 faces the outer surface 11 of the end cap body 10, that is, towards the outside of the energy storage device 1000. Half of the first surface 211 of the first valve body 21 can be connected to the first bottom wall 163 of the mounting groove 16, and the other half of the first surface 211 abuts against a portion of the second bottom wall 164. The side of the peripheral surface of the first valve body 21 facing away from the flange 26 of the second valve body 23 is connected to the first groove wall 161.

[0084] The fourth surface 232 of the second valve body 23 faces the inner surface 12 of the end cap body 10, that is, towards the interior of the energy storage device 1000. The fixing portion 28 of the second valve body 23 is mounted on the first portion 166 of the mounting groove 16, and the bending portion 27 of the second valve body 23 is mounted on the second portion 167 of the mounting groove 16. Along the radial direction of the mounting groove 16, the flange 26 is clamped between the mounting groove 16 and the first valve body 21. Specifically, the first arc surface 251 is connected to the first groove wall 161 of the mounting groove 16. The top surface 263 of the flange 26 and part of the second valve body abut against the second bottom wall 164 of the second portion 167 of the mounting groove 16. The outer surface 261 of the flange 26 abuts against the second groove wall 162 of the mounting groove 16. The end face 265 of the flange 26 abuts against the stop face 165 of the mounting groove 16. When the bent portion 27 is bent, the stop face 165 can prevent the bent portion 27 from bending too far relative to the mounting groove 16, ensuring the springback and reset effect of the bent portion.

[0085] In this embodiment, the maximum radial length of the explosion-proof valve 20 is equal to the maximum radial length of the mounting groove 16. The minimum radial length of the explosion-proof valve 20 is equal to the minimum radial length of the mounting groove 16. The diameter of the first valve body 21 is greater than the diameter of the injection through-hole 15. The diameter of the first valve body 21 is equal to the maximum radial length of the first portion 166 of the mounting groove 16 and less than the maximum radial length of the second portion 167 of the mounting groove 16. The minimum radial length of the second valve body 23 is greater than the radius of the injection through-hole 15 and equal to the maximum radial length of the first portion 166 of the mounting groove 16. The maximum radial length of the second valve body 23 is equal to the maximum radial length of the second portion 167 of the mounting groove 16. The maximum radial length of the second valve body 23 includes the dimension of the flange 26. The minimum radial length of the second valve body 23 is the diameter of the second valve body 23, that is, the minimum radial length of the second valve body 23 does not include the thickness of the flange 26. Correspondingly, the width of the second bottom wall 164 of the mounting groove 16 is greater than the width of the first bottom wall 163. The curved portion 27 of the explosion-proof valve 20 abuts against the second bottom wall 164 of the mounting groove 16, making the contact area between the explosion-proof valve 20 and the mounting groove 16 larger. This extends the path from the outside of the energy storage device 1000 through the liquid injection hole 15 to the inside of the energy storage device 1000, thereby improving the waterproof and impurity-proof performance of the explosion-proof valve 20 against the liquid injection hole 15.

[0086] In other embodiments, the first valve body 21 may not be welded to the second valve body 23. The first valve body 21 and the second valve body 23 may be welded to the mounting groove 16 of the end cap body 10, respectively. Specifically, the first valve body 21 is first installed in the mounting groove 16, with a portion of its peripheral side surface welded to the first groove wall 161 or the first bottom wall 163 of the mounting groove 16, and another portion of its peripheral side surface abutting against the second groove wall 162 and the second bottom wall 164 of the mounting groove 16. Then, a breathable protective membrane 22 is installed on the second surface 212 of the first valve body 21. Next, the second valve body 23 is installed on the side of the breathable protective membrane 22 facing away from the first valve body 21. The first arc surface 251 of the second valve body 23 is welded to the first groove wall 161 of the mounting groove 16. The flange 26 is movably connected to the second portion 167 of the mounting groove 16.

[0087] Please see Figure 9 and Figure 10 , Figure 10 for Figure 9 The diagram shows a cross-sectional view of the explosion-proof valve of the end cap assembly when the injection port is exposed.

[0088] When it is necessary to inject liquid into the energy storage device 1000, pressure can be applied to the bent portion 27 of the explosion-proof valve 20 from the outside of the energy storage device 1000, such as directly using an injection needle or with the aid of other auxiliary tools. The bent portion 27 is not welded to the end cap body 10. Due to the good toughness of the first valve body 21 and the second valve body 23 of the explosion-proof valve 20, the bent portion 27 of the explosion-proof valve 20 can elastically deform under external pressure and bend towards the inside of the energy storage device 1000 relative to the fixed portion 28. A gap is formed between the bent portion 27 and the side wall 16b and bottom wall 16a of the mounting groove 16, exposing the injection through hole 15. The injection needle can be inserted into the gap between the bent portion 27 and the mounting groove 16 to inject liquid into the energy storage device 1000. At the same time, the fixed part 28 is subjected to the elastic deformation stress of the bent part 27, which will generate a deformation rebound force opposite to it, and generate a reverse pulling force on the bent part 27, so that the bent part 27 has a tendency to return to its original shape.

[0089] After the injection is completed and the injection needle is removed, the deformed bent portion 27, under its own deformation rebound force and the pulling force of the fixing portion 28, returns to its original shape and springs back to its original position. The bent portion 27 then abuts against the second part 167 of the mounting groove 16, thereby allowing the explosion-proof valve 20 to cover the injection through hole 15 again. The gas inside the energy storage device 1000 can be discharged from the energy storage device 1000 sequentially through the second exhaust port 24 of the second valve body 23 of the explosion-proof valve 20, the permeable microporous structure of the permeable protective membrane 22, and the first exhaust port 213 of the first valve body 21. This achieves a balance of internal and external gas pressure in the energy storage device 1000, preventing safety accidents caused by the accumulation of gas inside the energy storage device 1000 and ensuring the safety of the energy storage device 1000 in use. It can be understood that part of the explosion-proof valve is fixed to the end cap and part is movably connected to the end cap, enabling it to achieve waterproof and impurity-proof performance. It utilizes the elastic rebound force to reset the explosion-proof valve after deformation, resulting in a simple structure that is easy to manufacture and reduces costs.

[0090] Please see Figure 11 , Figure 11 for Figure 2 The diagram shows a partial structural schematic of the second embodiment of the end cap assembly. It should be noted that... Figure 11 The first pole 101 and the second pole 102 of the end cap assembly 100 are not shown.

[0091] In this embodiment, the contents that are the same as in the first embodiment will not be repeated. The difference is that, in this embodiment, the liquid injection through-hole 15 of the end cap body 10 is rectangular. Correspondingly, the mounting groove 16 is approximately an annular rectangular structure. The first part 166 and the second part 167 of the mounting groove 16 together surround the periphery of the liquid injection through-hole 15. Both the first part 166 and the second part 167 of the mounting groove 16 can be semi-annular rectangular structures. The explosion-proof valve 20 has a rectangular structure.

[0092] Firstly, in related technologies, for batteries like aqueous sodium batteries, as the battery cycles through charging and discharging, metallic sodium easily deposits at the negative electrode. This metallic sodium readily reacts with the electrolyte to generate flammable and explosive gases such as hydrogen (H2). These flammable and explosive gases tend to accumulate inside the battery, severely impacting both battery safety and performance. In this embodiment, the explosion-proof valve 20 is provided with a first valve body 21, a second valve body 23, and a breathable protective membrane 22 located between the first valve body 21 and the second valve body 23. Multiple corresponding vent holes are provided on the first valve body 21 and the second valve body 23. The breathable protective membrane 22 has a microporous structure for gas permeation, allowing the explosion-proof valve 20 to promptly discharge gases from inside the energy storage device 1000. This not only prevents gas accumulation that could degrade the battery cell's performance but also avoids safety accidents caused by the accumulation of flammable and explosive gases. Meanwhile, the breathable protective membrane 22 adopts the Weils waterproof and breathable protective membrane 22, which can prevent moisture, electrolyte and dust and other impurities from entering the energy storage device 1000. This avoids the energy storage device 1000 from malfunctions caused by impurities entering the energy storage device 1000, improves the exhaust performance of the energy storage device 1000, and ensures the safety of the energy storage device 1000.

[0093] Secondly, in related technologies, the liquid injection device and explosion-proof device of the energy storage device are separately installed on the end cap assembly, and the energy storage device requires components such as glue pins and nails to fill the liquid injection hole on the end cap, increasing manufacturing steps and costs. In this embodiment, the explosion-proof valve 20 and the liquid injection hole 15 are combined. The fixing part 28 of the explosion-proof valve 20 is fixed to the end cap body 10, while the bending part 27 is movably connected to the end cap body 10. Utilizing the deformation and rebound force of the first valve body 21 and the second valve body 23, the explosion-proof valve 20 can be exposed or the liquid injection hole 15 can be filled. When the explosion-proof valve 20 is exposed at the liquid injection hole 15, liquid can be injected into the energy storage device 1000; when the explosion-proof valve 20 is in the liquid injection hole 15, the energy storage device 1000 can be opened. This integrates the liquid injection function and explosion-proof venting function of the energy storage device 1000 into one unit, eliminating the need for glue pins and nails, reducing manufacturing costs and steps.

[0094] The above are merely some embodiments and implementation methods of this application. The scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An end cap assembly, applied to an energy storage device containing aqueous sodium ions, characterized in that, include: End cap body and explosion-proof valve; The end cap body includes an outer surface and an inner surface, the outer surface and the inner surface are arranged opposite to each other along the thickness direction of the end cap body, the end cap body also includes a mounting groove and a liquid injection through hole, the mounting groove is recessed from the inner surface to the outer surface, and the liquid injection through hole is opened in the bottom wall of the mounting groove; The explosion-proof valve includes a fixed part and a curved part connected to the fixed part, and both the fixed part and the curved part have a breathable and waterproof structure; Along the thickness direction of the end cap assembly, the explosion-proof valve is installed in the mounting groove and covers the injection through hole. The outer side of the fixing part is fixedly connected to the mounting groove, and the bending part abuts against the bottom wall of the mounting groove. The fixing part and the bending part together cover the injection through hole. The bending part can elastically deform under external pressure and bend away from the mounting groove so that the injection through hole is at least partially open. The deformation rebound force of the bending part can make the bending part cover the injection through hole again so that the injection through hole is breathable and waterproof.

2. The end cap assembly according to claim 1, characterized in that, The explosion-proof valve includes a first valve body, a breathable protective membrane, and a second valve body. Along the thickness direction of the end cap assembly, the first valve body, the breathable protective membrane, and the second valve body are stacked sequentially from the outer surface toward the inner surface. The first valve body is provided with multiple first exhaust holes, the second valve body is provided with multiple second exhaust holes, and the breathable protective membrane includes a breathable microporous structure. The breathable microporous structure, the first exhaust holes and the second exhaust holes are connected and constitute the breathable and waterproof structure. The outer side of the fixed part is formed by a portion of the peripheral side of the first valve body, a portion of the peripheral side of the breathable protective membrane, and a portion of the outer peripheral surface of the second valve body, while the outer side of the curved part is formed by another portion of the outer peripheral surface of the second valve body.

3. The end cap assembly according to claim 2, characterized in that, The second valve body includes a third surface and a fourth surface disposed opposite to each other along the thickness direction of the second valve body. The second valve body also includes a first arc surface and a second arc surface disposed opposite to each other along the radial direction of the second valve body. The first arc surface and the second arc surface are both connected between the third surface and the fourth surface. The first arc surface constitutes the outer side surface of the fixing part. The second arc surface is provided with a flange, which protrudes from the third surface. The breathable protective membrane and the first valve body are stacked on the third surface in sequence. Part of the peripheral side surface of the breathable protective membrane and the first valve body located in the bend abuts against the flange. The height of the flange protruding from the third surface is equal to the sum of the thicknesses of the breathable protective membrane and the first valve body. The surface of the flange facing away from the second arc surface is the outer side surface of the bend. The flange abuts against part of the bottom wall and part of the side wall of the mounting groove.

4. The end cap assembly according to claim 3, characterized in that, The thickness of the second valve body is greater than the thickness of the first valve body.

5. The end cap assembly according to claim 3, characterized in that, The thickness of the flange is less than or equal to the depth of the mounting groove.

6. The end cap assembly according to any one of claims 3-5, characterized in that, The sidewall of the mounting groove includes a first groove wall and a second groove wall, wherein the second groove wall is connected to the first groove wall and surrounds the bottom wall of the mounting groove; The bottom wall of the tank includes a first bottom wall and a second bottom wall. Along the radial direction of the injection through hole, the width of the first bottom wall is smaller than the width of the second bottom wall. The first bottom wall and the first tank wall are connected. A stop surface is formed at the connection between the first tank wall and the second tank wall. The flange abuts against the second bottom wall and the second tank wall. The opposite end faces of the flange in the length direction abut against the stop surface.

7. The end cap assembly according to claim 6, characterized in that, The first valve body and the second valve body are made of aluminum sheets, or the first valve body is made of steel sheets and the second valve body is made of aluminum sheets.

8. The end cap assembly according to claim 6, characterized in that, The breathable protective membrane is a Micros waterproof and breathable membrane.

9. An energy storage device, characterized in that, The device includes a housing, a battery cell, and an end cap assembly as described in any one of claims 1-8, wherein the housing includes an opening and a receiving cavity, the battery cell is housed in the receiving cavity, and the end cap assembly is disposed in the opening.

10. The energy storage device according to claim 9, characterized in that, The energy storage device is an aqueous sodium-ion battery.

11. An electrical appliance, characterized in that, Includes the energy storage device as described in claim 9 or 10, wherein the energy storage device is used to supply power to the electrical equipment.

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