End caps, battery cells, batteries, and electrical devices

Abstract

This application discloses an end cap, a battery cell, a battery, and an electrical device. The end cap of an embodiment of this application includes: a first recess, recessed from the side of the end cap facing the electrode assembly along a direction away from the electrode assembly; a second recess, recessed from the side of the end cap away from the electrode assembly of the battery cell along a direction facing the electrode assembly, the bottom wall of the second recess including a first portion and a second portion surrounding the outside of the first portion, the first portion and the bottom wall of the first recess being disposed opposite each other along the thickness direction of the end cap; and a pressure relief portion formed between the first portion and the bottom wall of the first recess, the pressure relief portion being actuated to release internal pressure when the internal pressure of the battery cell reaches a threshold, the side of the second portion away from the electrode assembly forming a clearance space to avoid the pressure relief portion when it is actuated. This application can improve the safety of the battery cell.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese patent application 202122434797.4, filed on October 9, 2021, entitled “End Cap, Battery Cell, Battery and Electrical Device”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of batteries, and in particular to an end cap, a battery cell, a battery, and an electrical device. Background Technology

[0004] Battery cells are widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and power tools. Battery cells can include nickel-cadmium battery cells, nickel-metal hydride battery cells, lithium-ion battery cells, and rechargeable alkaline zinc-manganese battery cells, among others.

[0005] In the development of battery technology, besides improving the performance of individual battery cells, safety is also a crucial issue. If the safety of a battery cell cannot be guaranteed, then that cell cannot be used. Therefore, how to enhance the safety of individual battery cells is a pressing technical problem that needs to be solved in battery technology. Summary of the Invention

[0006] This application provides an end cap, a battery cell, a battery, and an electrical device that can improve the safety of the battery cell.

[0007] In a first aspect, embodiments of this application provide an end cap for a battery cell, comprising:

[0008] The first recess is recessed from the side of the end cap facing the electrode assembly in a direction away from the electrode assembly;

[0009] The second recess is recessed from the side of the end cap away from the electrode assembly of the battery cell, in the direction facing the electrode assembly. The bottom wall of the second recess includes a first portion and a second portion surrounding the outside of the first portion. The first portion and the bottom wall of the first recess are disposed opposite to each other along the thickness direction of the end cap.

[0010] A pressure relief section is formed between the bottom wall of the first portion and the first recess. The pressure relief section is used to be actuated to release the internal pressure when the internal pressure of the battery cell reaches a threshold. A clearance space is formed on the side of the second portion away from the electrode assembly to avoid the pressure relief section when it is actuated.

[0011] In the above solution, when a battery cell experiences a short circuit or overcharge, the pressure relief section partially ruptures and folds outward to form a channel for releasing internal pressure, reducing the risk of battery cell explosion and fire, thereby improving safety. This solution creates a clearance space on the side of the second part away from the electrode assembly to reduce the risk of the pressure relief section being blocked by other parts of the end cap, thus ensuring efficient internal pressure release and improving the safety of the battery cell.

[0012] In some embodiments, the bottom wall and / or the first portion of the first recess are provided with a third recess, and the pressure relief portion is configured to rupture at the third recess to release the internal pressure when the internal pressure of the battery cell reaches a threshold.

[0013] In the above scheme, by setting a third recess, when the internal pressure of the battery cell reaches a threshold, the pressure relief part can be ruptured and folded along a predetermined position.

[0014] In some embodiments, when the pressure relief portion is actuated, at least a portion of the pressure relief portion folds into the second recess.

[0015] In some embodiments, the projection of the third recess along the thickness direction is a straight line, a cross, a U, or a ring.

[0016] In some embodiments, the third recess is annular and includes a first sub-recess and a second sub-recess continuously arranged along its circumference. The depth of the first sub-recess is greater than the depth of the second sub-recess, so that when the internal pressure of the battery cell reaches a threshold, the pressure relief portion ruptures at the first sub-recess and folds over along the bottom of the second sub-recess.

[0017] In the above scheme, by setting a first sub-recess and a second sub-recess with different depths, the pressure relief part ruptures at a predetermined position, and the folding direction of the pressure relief part is limited. This scheme, by setting a second sub-recess at the folding position, can reduce the difficulty of folding the pressure relief part and improve the efficiency of internal pressure relief.

[0018] In some embodiments, the end cap includes: a body portion including an inner surface and an outer surface disposed opposite to each other in the thickness direction, the inner surface facing the electrode assembly; a first protrusion protruding from the inner surface, the first recess being recessed from the top surface of the first protrusion in a direction away from the electrode assembly; and a second protrusion protruding from the outer surface, the second recess being recessed from the top surface of the second protrusion in a direction facing the electrode assembly.

[0019] In the above scheme, by setting the first protrusion and the second protrusion, the strength of the end cover around the pressure relief part is increased, the deformation of the pressure relief part during the reciprocating flipping process of the end cover is reduced, the force transmitted to the pressure relief part is reduced, the fatigue aging of the pressure relief part is slowed down, and the risk of premature rupture and pressure relief of the end cover under normal use of the battery cell is reduced, which is conducive to improving the safety and stability of the battery cell.

[0020] In some embodiments, the depth of the second recess in the thickness direction is greater than the dimension of the second protrusion in the thickness direction, so that the bottom wall of the second recess is closer to the electrode assembly than the outer surface.

[0021] The above solution can ensure the depth of the second recess, thereby increasing the distance between the bottom wall of the second recess and the top surface of the second convex part along the thickness direction, reducing the risk of the pressure relief part being damaged by external components, and improving safety.

[0022] In some embodiments, the depth of the first recess in the thickness direction is less than the dimension of the first protrusion in the thickness direction, so that the bottom wall of the first recess is closer to the electrode assembly than the inner surface.

[0023] When the battery cell is used upside down, the end cap is located on the underside of the electrode assembly. In the above solution, the bottom wall of the first recess is closer to the electrode assembly than the inner surface. Therefore, in the later stages of battery cell cycling, electrolyte is more likely to accumulate on the inner surface than on the bottom wall of the first recess. In other words, this solution can reduce the amount of electrolyte stored in the first recess and reduce the risk of corrosion and aging of the pressure relief section.

[0024] In some embodiments, the size of the first protrusion is larger than the size of the second protrusion in the thickness direction.

[0025] The above solution ensures the strength of the portion of the end cap near the pressure relief section while allowing the second protrusion to have a relatively small size. This reduces the maximum size of the battery cell and increases the energy density.

[0026] In some embodiments, the end cap further includes: a connecting portion surrounding the outside of the body portion and extending in a direction facing the electrode assembly to form a fourth recess on the side of the body portion facing the electrode assembly; a plate portion surrounding the outside of the connecting portion, the fourth recess being recessed relative to the surface of the plate portion facing the electrode assembly; wherein the first protrusion is received within the fourth recess.

[0027] In the above solution, by providing a fourth recess, the internal space of the battery cell can be increased, thereby improving the capacity of the battery cell. At the same time, the fourth recess also provides space for the first protrusion, allowing the first protrusion to protrude by a sufficient size and preventing the first protrusion from pressing against the electrode assembly.

[0028] In some embodiments, the end cap is an integrally formed structure.

[0029] The above solution integrates the pressure relief section with pressure relief function into the end cover to simplify the structure of the battery cell.

[0030] Secondly, embodiments of this application provide a battery cell comprising: a housing having an opening; an electrode assembly housed within the housing; and an end cap as described in any embodiment of the first aspect, for covering the opening of the housing.

[0031] Thirdly, embodiments of this application provide a battery, which includes a housing and a battery cell, wherein the battery cell is housed within the housing.

[0032] Fourthly, embodiments of this application provide an electrical device, characterized in that it includes a battery as described in the third aspect, the battery being used to provide electrical energy. Attached Figure Description

[0033] The features, advantages, and technical effects of exemplary embodiments of this application will now be described with reference to the accompanying drawings.

[0034] Figure 1 This application provides structural schematic diagrams of vehicles for some embodiments;

[0035] Figure 2 Explosion diagrams of batteries provided for some embodiments of this application;

[0036] Figure 3 for Figure 2 An exploded view of the battery module shown.

[0037] Figure 4 This is an exploded schematic diagram of a battery cell provided in some embodiments of this application;

[0038] Figure 5 A schematic diagram of the end cap structure of a battery cell provided in some embodiments of this application;

[0039] Figure 6 for Figure 5 A top view of the end cap shown;

[0040] Figure 7 for Figure 6 The diagram shows a cross-sectional view of the end cap along line AA.

[0041] Figure 8 for Figure 7 The enlarged schematic diagram of the end cap at point B in the circle is shown.

[0042] Figure 9 Top view of the end cap provided for other embodiments of this application;

[0043] Figure 10 A top view of an end cap provided for some embodiments of this application;

[0044] Figure 11 This is a top view of an end cap provided for some embodiments of this application.

[0045] The accompanying drawings are not necessarily drawn to scale. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0047] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the description of this application is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms "comprising" and "having," and any variations thereof, in the description, claims, and accompanying drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the description, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or hierarchy.

[0048] In this application, the reference to "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0049] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "attachment" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0050] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0051] In the embodiments of this application, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this application.

[0052] In this application, "multiple" means two or more (including two).

[0053] In this application, the battery cell may include a lithium-ion secondary battery cell, a lithium-ion primary battery cell, a lithium-sulfur battery cell, a sodium-lithium-ion battery cell, a sodium-ion battery cell, or a magnesium-ion battery cell, etc., and the embodiments of this application are not limited thereto. The battery cell may be cylindrical, flat, cuboid, or other shapes, etc., and the embodiments of this application are not limited thereto.

[0054] The battery mentioned in the embodiments of this application refers to a single physical module comprising one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in this application may include a battery module or a battery pack. A battery generally includes a housing for encapsulating one or more battery cells. The housing prevents liquids or other foreign matter from affecting the charging or discharging of the battery cells.

[0055] A single battery cell includes electrode components and an electrolyte. The electrode components include a positive electrode, a negative electrode, and a separator. The battery cell primarily functions by the movement of metal ions between the positive and negative electrodes. The positive electrode includes a positive current collector and a positive active material layer, which is coated on the surface of the positive current collector. The positive current collector includes a positive electrode coating area and a positive electrode tab connected to the coating area. The coating area is coated with the positive active material layer, while the tab is not. Taking a lithium-ion battery as an example, the positive current collector can be made of aluminum, and the positive active material layer includes the positive active material, which can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc. The negative electrode sheet includes a negative current collector and a negative active material layer, the negative active material layer being coated on the surface of the negative current collector. The negative current collector includes a negative electrode coating area and a negative electrode tab connected to the negative electrode coating area. The negative electrode coating area is coated with the negative active material layer, while the negative electrode tab is not coated with the negative active material layer. The material of the negative current collector can be copper, and the negative active material layer includes negative active material, which can be carbon or silicon, etc. The material of the separator can be PP (polypropylene) or PE (polyethylene), etc.

[0056] The battery cell also includes a housing and end caps. The housing has an opening for accommodating electrode assemblies, which can be assembled into the housing through the opening. The end caps are used to close the opening of the housing.

[0057] The development of battery technology must take into account multiple design factors, such as energy density, cycle life, discharge capacity, charge / discharge rate and other performance parameters. In addition, battery safety also needs to be considered.

[0058] The pressure relief mechanism on a battery cell has a significant impact on its safety. For example, in the event of a short circuit or overcharging, thermal runaway may occur inside the battery cell, causing a sudden increase in pressure. In such cases, the pressure relief mechanism can be activated to release the internal pressure, preventing the battery cell from exploding or catching fire.

[0059] A pressure relief mechanism is a component or part that is activated to release internal pressure when the internal pressure of a battery cell reaches a predetermined threshold. This threshold design varies depending on design requirements. It may depend on the materials of one or more of the components in the battery cell: the positive electrode, the negative electrode, the electrolyte, and the separator.

[0060] The pressure relief mechanism can take the form of an explosion-proof valve, a gas valve, a pressure relief valve, or a safety valve, and can specifically adopt a pressure-sensitive element or structure. That is, when the internal pressure of a battery cell reaches a predetermined threshold, the pressure relief mechanism performs an action or a weak structure in the pressure relief mechanism breaks, thereby forming an opening or channel for internal pressure to be released.

[0061] The term "actuation" as used in this application refers to the activation or actuation of the pressure relief mechanism to a certain state, thereby releasing the internal pressure of the battery cell. The actions of the pressure relief mechanism may include, but are not limited to, at least a portion of the mechanism rupturing, breaking, tearing, or opening. When the pressure relief mechanism is actuated, the high-temperature, high-pressure substances inside the battery cell are discharged as waste from the actuated portion. This method allows for pressure relief of the battery cell under controlled pressure, thereby preventing potentially more serious accidents.

[0062] The emissions from battery cells mentioned in this application include, but are not limited to: electrolyte, dissolved or split positive and negative electrode plates, fragments of separators, high-temperature and high-pressure gases generated by the reaction, flames, etc.

[0063] To simplify the structure of individual battery cells, the inventors attempted to integrate a pressure relief mechanism into the end cap. For example, they created a recess in the end cap to form a pressure relief section, which is activated to release internal pressure when the internal pressure of the battery cell reaches a threshold. In the event of a short circuit or overcharging, thermal runaway may occur inside the battery cell, causing a sudden pressure surge. In such cases, the pressure relief section partially ruptures and folds outward to create a channel for releasing internal pressure, reducing the risk of battery cell explosion and fire, thereby improving safety.

[0064] However, after discovering the problem of a low rate of internal pressure release in a single battery cell during thermal runaway, the inventors analyzed and studied the structure of the battery cell. They found that the location of the pressure relief section corresponds to the location of the recess. When the pressure relief section folds outward under internal pressure, it is easily blocked by the sidewall of the recess, limiting the degree of outward folding and thus resulting in a low rate of pressure release.

[0065] In view of this, this application provides a technical solution in which the end cap of the battery cell includes: a first recess, recessed from the side of the end cap facing the electrode assembly along a direction away from the electrode assembly; a second recess, recessed from the side of the end cap away from the electrode assembly of the battery cell along a direction facing the electrode assembly, the bottom wall of the second recess including a first portion and a second portion surrounding the outside of the first portion, the first portion and the bottom wall of the first recess being disposed opposite to each other along the thickness direction of the end cap; and a pressure relief portion formed between the first portion and the bottom wall of the first recess, the pressure relief portion being actuated to release the internal pressure when the internal pressure of the battery cell reaches a threshold, the side of the second portion away from the electrode assembly forming a clearance space to avoid the pressure relief portion when it is actuated. An end cap with this structure can reduce the risk of the pressure relief portion being blocked, thereby ensuring the efficiency of internal pressure release and improving the safety of the battery cell.

[0066] The technical solutions described in the embodiments of this application are applicable to batteries and electrical devices that use batteries.

[0067] Electrical devices can include vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and power tools, etc. Vehicles can be gasoline-powered cars, natural gas-powered cars, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose any special limitations on the above-mentioned electrical devices.

[0068] For ease of explanation, the following embodiments will use a vehicle as an example of an electrical device.

[0069] Figure 1 The diagram shows the structural features of a vehicle as provided in some embodiments of this application. Figure 1 As shown, a battery 2 is installed inside the vehicle 1. The battery 2 can be located at the bottom, front, or rear of the vehicle 1. The battery 2 can be used to power the vehicle 1; for example, the battery 2 can serve as the operating power source for the vehicle 1.

[0070] Vehicle 1 may also include controller 3 and motor 4. Controller 3 is used to control battery 2 to supply power to motor 4, for example, for the power needs of vehicle 1 during start-up, navigation and driving.

[0071] In some embodiments of this application, the battery 2 can not only serve as the operating power source for the vehicle 1, but also as the driving power source for the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

[0072] Figure 2 This is a schematic diagram of a battery explosion provided for some embodiments of this application. For example... Figure 2 As shown, battery 2 includes a housing 5 and battery cells ( Figure 2 (Not shown), the battery cells are housed inside the casing 5.

[0073] The housing 5 is used to house individual battery cells, and the housing 5 can have various structures. In some embodiments, the housing 5 may include a first housing portion 5a and a second housing portion 5b, which overlap each other, and together define a housing space 5c for housing the individual battery cells. The second housing portion 5b may be a hollow structure with one end open, and the first housing portion 5a may be a plate-like structure, with the first housing portion 5a covering the open side of the second housing portion 5b to form a housing 5 with the housing space 5c; alternatively, both the first housing portion 5a and the second housing portion 5b may be hollow structures with one side open, with the open side of the first housing portion 5a covering the open side of the second housing portion 5b to form a housing 5 with the housing space 5c. Of course, the first housing portion 5a and the second housing portion 5b can have various shapes, such as cylinders, cuboids, etc.

[0074] To improve the sealing performance after the first housing part 5a and the second housing part 5b are connected, a sealing element, such as sealant or sealing ring, can also be provided between the first housing part 5a and the second housing part 5b.

[0075] Assuming that the first box section 5a covers the top of the second box section 5b, the first box section 5a can also be called the upper box cover, and the second box section 5b can also be called the lower box.

[0076] In battery 2, there can be one or more individual battery cells. If there are multiple individual battery cells, they can be connected in series, parallel, or in a mixed configuration. A mixed configuration means that multiple individual battery cells are connected in both series and parallel configurations. Multiple individual battery cells can be directly connected in series, parallel, or in a mixed configuration and then housed within housing 5. Alternatively, multiple individual battery cells can first be connected in series, parallel, or in a mixed configuration to form battery module 6, and then multiple battery modules 6 can be connected in series, parallel, or in a mixed configuration to form a whole and housed within housing 5.

[0077] Figure 3 for Figure 2 The diagram shows an exploded view of the battery module.

[0078] In some embodiments, such as Figure 3 As shown, there are multiple battery cells 7, which are first connected in series, parallel, or a combination of both to form a battery module 6. These battery modules 6 are then connected in series, parallel, or a combination of both to form a whole, which is housed within the casing.

[0079] Multiple battery cells 7 in battery module 6 can be electrically connected through a busbar component to achieve parallel, series, or mixed connection of multiple battery cells 7 in battery module 6.

[0080] Figure 4 This is an exploded schematic diagram of a battery cell provided in some embodiments of this application.

[0081] like Figure 4 As shown, the battery cell 7 in this embodiment includes: a housing 20 having an opening 21; an electrode assembly 10 housed within the housing 20; and an end cap 30 for covering the opening 21 of the housing 20.

[0082] The electrode assembly 10 includes a first electrode, a second electrode, and a separator, the separator being used to separate the first electrode and the second electrode. The first electrode and the second electrode have opposite polarities; in other words, one of the first electrode and the second electrode is the positive electrode, and the other of the first electrode and the second electrode is the negative electrode.

[0083] Optionally, the first electrode, the second electrode, and the separator are all strip-shaped structures, and are wound together to form a wound structure. The wound structure can be a cylindrical structure, a flat structure, or other shapes. Alternatively, the first electrode and the second electrode are plate-shaped structures, with multiple first electrodes and multiple second electrodes, which are alternately stacked.

[0084] In the battery cell 7, the electrode assembly 10 can be set as one or more according to actual usage requirements; in some examples, the battery cell 7 is provided with four independent electrode assemblies 10.

[0085] The housing 20 can be a hollow structure with an opening on one side or a hollow structure with openings on both sides. The end cap 30 closes to the opening 21 of the housing 20 and forms a sealed connection to form a receiving cavity for accommodating the electrode assembly 10 and the electrolyte.

[0086] The housing 20 can be of various shapes, such as a cylinder or a cuboid. The shape of the housing 20 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 is a cylindrical structure, a cylindrical housing can be selected; if the electrode assembly 10 is a cuboid structure, a cuboid housing can be selected.

[0087] In some embodiments, the battery cell 7 further includes two electrode terminals 40, which may be disposed on the end cover 30. The two electrode terminals 40 are a positive electrode terminal and a negative electrode terminal, respectively. Each electrode terminal 40 is provided with a corresponding connecting member 50, or a current collector, which is located between the end cover 30 and the electrode assembly 10, for electrically connecting the electrode assembly 10 and the electrode terminal 40.

[0088] Figure 5 A schematic diagram of the end cap structure of a battery cell provided in some embodiments of this application; Figure 6 for Figure 5 A top view of the end cap shown; Figure 7 for Figure 6 The diagram shows a cross-sectional view of the end cap along line AA. Figure 8 for Figure 7 The diagram shows an enlarged view of the end cap at point B in the circular frame.

[0089] like Figures 5 to 8 As shown, the end cap 30 of the battery cell in this embodiment includes: a first recess 31, recessed from the side of the end cap 30 facing the electrode assembly in a direction away from the electrode assembly; a second recess 32, recessed from the side of the end cap 30 away from the electrode assembly of the battery cell in a direction facing the electrode assembly, the bottom wall 321 of the second recess includes a first portion 321a and a second portion 321b surrounding the outside of the first portion 321a, the first portion 321a and the bottom wall 311 of the first recess are disposed opposite to each other along the thickness direction Z of the end cap 30; and a pressure relief portion 33, formed between the first portion 321a and the bottom wall 311 of the first recess, the pressure relief portion 33 is used to be actuated to release the internal pressure when the internal pressure of the battery cell reaches a threshold, and the side of the second portion 321b away from the electrode assembly forms a clearance space to avoid the pressure relief portion 33 when it is actuated.

[0090] The first recess 31 is located on the side of the pressure relief portion 33 facing the electrode assembly, while the second recess 32 is located on the side of the pressure relief portion 33 away from the electrode assembly.

[0091] The projection of the first part 321a along the thickness direction Z completely overlaps with the projection of the bottom wall 311 of the first recess along the thickness direction Z, while the projection of the second part 321b along the thickness direction Z does not overlap with the projection of the bottom wall 311 of the first recess along the thickness direction Z.

[0092] The second part 321b is an annular surface surrounding the outside of the first part 321a. Correspondingly, the second part 321b surrounds the outside of the pressure relief part 33.

[0093] Optionally, the bottom wall 311 of the first recess and the bottom wall 321 of the second recess are both planar and parallel to each other.

[0094] Optionally, the second recess 32 further includes a sidewall 322, which is connected to the bottom wall 321 of the second recess.

[0095] When the pressure relief part 33 is actuated, at least a portion of the pressure relief part 33 ruptures, and the pressure relief part 33 folds outward along the rupture location under the action of internal pressure to form a channel for releasing internal pressure.

[0096] The inventors reduced the thickness of the pressure relief section by creating a recess, thereby reducing its strength. This allows the pressure relief section to be actuated to release internal pressure when the internal pressure of the battery cell reaches a threshold. With a fixed thickness, if the recess is only provided on one side of the pressure relief section, the depth of the recess is relatively large, making its molding more difficult.

[0097] In this embodiment, the pressure relief portion 33 is formed by providing a first recess 31 and a second recess 32. This reduces the depth requirements of the first recess 31 and the second recess 32, thus lowering the molding difficulty. In addition, by reducing the depth of the second recess 32, this embodiment reduces the risk of the sidewall 322 of the second recess 32 obstructing the pressure relief portion 33 when it is folded outward.

[0098] The second recess 32 is located on the side of the pressure relief portion 33 away from the electrode assembly, that is, the second recess 32 is located on the outside of the pressure relief portion 33. In this embodiment, by providing the second recess 32, the distance between the pressure relief portion 33 and other components outside the battery cell can be increased, reducing the risk of the pressure relief portion 33 being damaged by other components.

[0099] In this embodiment, when a battery cell experiences a short circuit or overcharge, the pressure relief section 33 partially ruptures and folds outward to form a channel for releasing internal pressure, reducing the risk of battery cell explosion and fire, thereby improving safety. This embodiment also reduces the risk of the pressure relief section 33 being blocked by other parts of the end cap 30 by creating a clearance space on the side of the second part 321b away from the electrode assembly, thus ensuring efficient internal pressure release and improving the safety of the battery cell.

[0100] In some embodiments, the bottom wall 311 of the first recess and / or the first portion 321a are provided with a third recess 331, and the pressure relief portion 33 is configured to rupture at the third recess 331 to release the internal pressure when the internal pressure of the battery cell reaches a threshold.

[0101] In this embodiment, the third recess 331 may be provided only in the bottom wall 311 of the first recess, or only in the first part 321a, or both the bottom wall 311 and the first part 321a of the first recess may be provided simultaneously.

[0102] When the third recess 331 is disposed on the bottom wall 311 of the first recess, the third recess 331 is recessed from the bottom wall 311 of the first recess in a direction away from the electrode assembly; when the third recess 331 is disposed on the first portion 321a, the third recess 331 is recessed from the first portion 321a in a direction facing the electrode assembly.

[0103] In this embodiment, a weak structure is formed on the pressure relief part 33 by providing a third recess 331. The strength of the weak structure is less than the strength of other parts of the pressure relief part 33.

[0104] For example, the third recess 331 can be formed by machining material removed from the pressure relief portion 33, which helps to reduce processing costs and processing difficulty. Along the thickness direction Z of the end cap 30, the weak structure and the third recess 331 are correspondingly provided. Alternatively, the third recess 331 can also be formed by extruding the pressure relief portion 33.

[0105] In this embodiment, by providing a third recess 331, the pressure relief portion 33 can be ruptured and folded along a predetermined position when the internal pressure of the battery cell reaches a threshold.

[0106] In some embodiments, when the pressure relief portion 33 is actuated, at least a portion of the pressure relief portion 33 folds into the second recess 32. When the pressure relief portion 33 is actuated, the pressure relief portion 33 folds outward under the pressure of the internal pressure.

[0107] In some embodiments, when the pressure relief portion 33 is actuated, at least a portion of the pressure relief portion 33 folds over to make way for the space. In other words, when the pressure relief portion 33 is actuated, the pressure relief portion 33 and the second portion 321b at least partially overlap in the thickness direction Z.

[0108] In this embodiment, the clearance space can be used to accommodate at least a portion of the pressure relief section 33, thereby increasing the folding range of the pressure relief section 33, reducing the obstruction of the pressure relief section 33 to the internal pressure, and improving the efficiency of internal pressure relief.

[0109] In some embodiments, the third recess 331 is annular and includes a first sub-recess 331a and a second sub-recess 331b continuously arranged along its circumference. The depth of the first sub-recess 331a is greater than the depth of the second sub-recess 331b, so that when the internal pressure of the battery cell reaches a threshold, the pressure relief portion 33 breaks at the first sub-recess 331a and folds over along the bottom of the second sub-recess 331b.

[0110] The strength of the first sub-recess 331a is less than the strength of the second sub-recess 331b.

[0111] This embodiment uses a first sub-recess 331a and a second sub-recess 331b of different depths to cause the pressure relief part 33 to rupture at a predetermined position and to limit the folding direction of the pressure relief part 33. By providing the second sub-recess 331b at the folding position, this embodiment reduces the difficulty of folding the pressure relief part 33 and improves the efficiency of internal pressure relief.

[0112] In some embodiments, the projection of the second sub-recess 331b along the thickness direction Z is linear. In other words, the portion of the pressure relief portion 33 opposite to the second sub-recess 331b is linear.

[0113] In some embodiments, the projection of the third recess 331 along the thickness direction Z is a straight line, a cross, a U, or an annular shape.

[0114] In some embodiments, the end cap 30 includes: a body portion 34 including an inner surface 341 and an outer surface 342 disposed opposite to each other in the thickness direction Z, the inner surface 341 facing the electrode assembly; a first protrusion 35 protruding from the inner surface 341, a first recess 31 recessed from the top surface 351 of the first protrusion in a direction away from the electrode assembly; and a second protrusion 36 protruding from the outer surface 342, a second recess 32 recessed from the top surface 361 of the second protrusion in a direction facing the electrode assembly.

[0115] During transportation, temperature changes, or charging and discharging, the internal pressure of a battery cell fluctuates, causing the end cap to repeatedly flip. Prolonged flipping of the end cap can lead to fatigue and aging of the pressure relief section, potentially causing it to activate before the internal pressure of the battery cell reaches a threshold.

[0116] This embodiment increases the strength of the end cap 30 around the pressure relief part 33 by providing the first protrusion 35 and the second protrusion 36, reduces the deformation of the pressure relief part 33 during the reciprocating flipping process of the end cap 30, reduces the force transmitted to the pressure relief part 33, slows down the fatigue aging of the pressure relief part 33, and reduces the risk of premature rupture and pressure relief of the end cap 30 under normal use of the battery cell, which is beneficial to improving the safety and stability of the battery cell.

[0117] In some embodiments, the depth of the second recess 32 in the thickness direction Z is greater than the dimension of the second protrusion 36 in the thickness direction Z, so that the bottom wall 321 of the second recess is closer to the electrode assembly than the outer surface 342.

[0118] This embodiment can ensure the depth of the second recess 32, thereby increasing the distance between the bottom wall 321 of the second recess and the top surface 361 of the second convex part along the thickness direction Z, reducing the risk of the pressure relief part 33 being damaged by external components, and improving safety.

[0119] In some embodiments, the depth of the first recess 31 in the thickness direction Z is less than the dimension of the first protrusion 35 in the thickness direction Z, so that the bottom wall 311 of the first recess is closer to the electrode assembly than the inner surface 341.

[0120] When the battery cell is used upside down, the end cap 30 is located on the lower side of the electrode assembly. In this embodiment, the bottom wall 311 of the first recess is closer to the electrode assembly than the inner surface 341. Therefore, in the later stages of battery cell cycling, electrolyte is more likely to accumulate on the inner surface 341 than on the bottom wall 311 of the first recess. In other words, this embodiment can reduce the amount of electrolyte stored in the first recess 31 and reduce the risk of corrosion and aging of the pressure relief part 33.

[0121] In some embodiments, the size of the first protrusion 35 is larger than the size of the second protrusion 36 in the thickness direction Z.

[0122] In this embodiment, while ensuring the strength of the portion of the end cap 30 near the pressure relief portion 33, the second protrusion 36 has a relatively small size, which can reduce the maximum size of the battery cell and improve the energy density.

[0123] In some embodiments, the end cap 30 further includes: a connecting portion 37, which surrounds the outside of the body portion 34 and extends in a direction facing the electrode assembly to form a fourth recess 38 on the side of the body portion 34 facing the electrode assembly; a plate portion 39, which surrounds the outside of the connecting portion 37, wherein the fourth recess 38 is recessed relative to the surface of the plate portion 39 facing the electrode assembly; wherein the first protrusion 35 is received within the fourth recess 38.

[0124] The plate portion 39 is used to connect to the housing.

[0125] This embodiment, by providing a fourth recess 38, can increase the internal space of the battery cell and improve its capacity. Simultaneously, the fourth recess 38 also provides space for the first protrusion 35, allowing it to protrude sufficiently and preventing it from pressing against the electrode assembly.

[0126] In some embodiments, the end cap 30 is an integrally formed structure. In this embodiment, a pressure relief section 33 with a pressure relief function is integrated into the end cap 30 to simplify the structure of the battery cell.

[0127] Figure 9 This is a top view of an end cap provided for other embodiments of this application.

[0128] like Figure 9 As shown, in some embodiments, the projection of the third recess 331 along the thickness direction is a straight line. The molding process of the straight third recess 331 is simple.

[0129] Figure 10 This is a top view of an end cap provided for some embodiments of this application.

[0130] like Figure 10 As shown, the projection of the third recess 331 along the thickness direction is cross-shaped. When the internal pressure of the battery cell reaches the threshold, the pressure relief part 33 cracks at the intersection of the cross and splits into four pieces that fold outward in four directions.

[0131] Figure 11 This is a top view of an end cap provided for some embodiments of this application. For example... Figure 11 As shown, the projection of the third recess 331 along the thickness direction is U-shaped. When the internal pressure of the battery cell reaches the threshold, the pressure relief part 33 cracks along the U-shaped third recess 331, and the area enclosed by the U-shaped third recess 331 will fold outward.

[0132] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0133] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features. However, these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. An end cap for a single battery cell, comprising: The first recess is recessed from the side of the end cap facing the electrode assembly in a direction away from the electrode assembly; The second recess is recessed from the side of the end cap away from the electrode assembly of the battery cell in the direction facing the electrode assembly. The bottom wall of the second recess includes a first part and a second part surrounding the outside of the first part. The first part and the bottom wall of the first recess are disposed opposite to each other in the thickness direction of the end cap. as well as A pressure relief section is formed between the bottom wall of the first portion and the first recess. The pressure relief section is actuated to release the internal pressure when the internal pressure of the battery cell reaches a threshold. A clearance space is formed on the side of the second portion opposite to the electrode assembly to avoid the pressure relief section when it is actuated. The end cap includes a body portion and a second protrusion. The body portion includes an outer surface that is disposed away from the electrode assembly. The second protrusion protrudes from the outer surface. The second recess is recessed from the top surface of the second protrusion in a direction facing the electrode assembly. The depth of the second recess in the thickness direction is greater than the dimension of the second protrusion in the thickness direction, so that the bottom wall of the second recess is closer to the electrode assembly than the outer surface.

2. The end cap of claim 1, wherein, The bottom wall of the first recess and / or the first portion is provided with a third recess, and the pressure relief portion is configured to rupture at the third recess to release the internal pressure when the internal pressure of the battery cell reaches a threshold.

3. The end cap according to claim 2, wherein, When the pressure relief section is actuated, at least a portion of the pressure relief section folds into the second recess.

4. The end cap according to claim 2, wherein, The projection of the third recess along the thickness direction is a straight line, a cross, a U, or a ring.

5. The end cap according to claim 2, wherein, The third recess is annular and includes a first sub-recess and a second sub-recess continuously arranged along its circumference. The depth of the first sub-recess is greater than the depth of the second sub-recess, so that when the internal pressure of the battery cell reaches a threshold, the pressure relief portion ruptures at the first sub-recess and folds over along the bottom of the second sub-recess.

6. The end cap according to any one of claims 1-5, wherein the body portion further includes an inner surface disposed opposite to the outer surface along the thickness direction, the inner surface facing the electrode assembly; The end cap also includes a first protrusion protruding from the inner surface, and a first recess recessing from the top surface of the first protrusion in a direction away from the electrode assembly.

7. The end cap according to claim 6, wherein, The depth of the first recess in the thickness direction is less than the dimension of the first protrusion in the thickness direction, so that the bottom wall of the first recess is closer to the electrode assembly than the inner surface.

8. The end cap according to claim 6, wherein, In the thickness direction, the size of the first protrusion is larger than the size of the second protrusion.

9. The end cap according to claim 6, further comprising: A connecting portion surrounds the outside of the body portion and extends in the direction facing the electrode assembly to form a fourth recess on the side of the body portion facing the electrode assembly; The plate portion surrounds the outside of the connecting portion, and the fourth recess is recessed relative to the surface of the plate portion facing the electrode assembly. The first protrusion is accommodated within the fourth recess.

10. The end cap according to claim 1, wherein, The end cap is a one-piece structure.

11. A single battery cell, comprising: A housing having an opening; an electrode assembly housed within the housing; And an end cap as described in any one of claims 1-10, for covering the opening of the housing.

12. A battery comprising a housing and a battery cell as claimed in claim 11, wherein the battery cell is housed within the housing.

13. An electrical device comprising the battery according to claim 12, the battery being used to provide electrical energy.

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