Patent Publication Number: US-2023155262-A1

Title: Housing, battery cell, battery and electric apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of International Patent Application No. PCT/CN2021/115772, filed on Aug. 31, 2021, which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present application relates to the technical field of batteries, and specifically, to a case, a battery cell, a battery, and an electrical apparatus. 
     BACKGROUND 
     Energy saving and emission reduction being the key to the sustainable development of automobile industry, electric vehicles have become an important part of the sustainable development of automotive industry due to their advantages of energy saving and environmental protection. For electric vehicles, battery technology is an important factor related to their development. 
     In the development of the battery technologies, in addition to improving the performance of the battery, the safety issue is also a problem that needs to be considered. Therefore, how to improve the safety of the battery cells is an urgent problem to be solved in the battery technologies. 
     SUMMARY 
     Embodiments of the present application provides a case, a battery cell, a battery, and an electrical apparatus, which can effectively improve the safety of the battery cell. 
     In a first aspect, the embodiments of the present application provide a case, comprising: a case body for accommodating an electrode assembly; and a pressure relief structure comprising a plurality of first pressure relief grooves disposed at intervals on the case body along the circumferential direction of the case body; wherein the case body is configured to rupture along the first pressure relief grooves when the pressure or temperature inside the case body reaches a threshold so as to release the pressure inside the case body. 
     In the technical solution above, the case body being provided with a plurality of first pressure relief grooves arranged at intervals in the circumferential direction, and the case body can be ruptured along the first pressure relief grooves when the internal pressure or temperature thereof reaches a threshold, so as to achieve the purpose of releasing the pressure inside the case body. During a pressure relief process, even if one of the first pressure relief grooves is shielded, the case body can still be ruptured along other first pressure relief grooves, so as to ensure normal pressure relief of the case body, reduce the risk of fire and explosion of the battery cell, and improve the safety of the battery cell. 
     In some embodiments, the pressure relief structure further includes a second pressure relief groove disposed on the case body, the first pressure relief groove intersects with the second pressure relief grooved to form an opening position, and the case body is configured to rupture along the first pressure relief groove from the opening position when the pressure or temperature inside the case body reaches a threshold. 
     In the technical solution above, the case body being provided with a second pressure relief groove, the second pressure relief groove intersects with the first pressure relief groove to form an opening position, so that the case body is more likely to be ruptured at the opening position, so that the case body is rapidly ruptured along the first pressure relief groove from the opening position when the pressure or temperature inside the case body reaches a threshold, thereby realizing rapid pressure relief. The case body may also be partially ruptured along the second pressure relief groove after rupturing at the opening position, thereby increasing the pressure relief area of the case body. 
     In some embodiments, the second pressure relief groove extends along the circumferential direction of the case body, and each first pressure relief groove intersects with the second pressure relief groove to form an opening position. 
     In the technical solution above, each first pressure relief groove intersects with the second pressure relief groove to form an opening position, that is, a plurality of the first pressure relief grooves intersect with the second pressure relief groove to form opening positions, which is simple in structure and can effectively reduce the production cost. 
     In some embodiments, the second pressure relief groove is a closed structure extending along the circumferential direction of the case body and connected end-to-end. 
     In the technical solution above, the second pressure relief groove is a closed structure extending along the circumferential direction of the case body and connected end-to-end, which has a simple structure and is easy to process and form. 
     In some embodiments, the second pressure relief groove includes a plurality of groove segments disposed at intervals along the circumferential direction of the case body, each groove segment intersects with the first pressure relief groove to form an opening position. 
     In the technical solution above, the plurality of groove segments being disposed at intervals along the circumferential direction of the case body, and each groove segment intersects with a first pressure relief groove to form an opening position, so that each first pressure relief groove does not interfere with each other during the pressure relief process, and is independent from each other. In addition, since the plurality of groove segments are disposed at intervals along the circumferential direction of the case body, the second pressure relief groove is not continuous, and the strength of the case body is higher, which is beneficial to improve the service life of the case. 
     In some embodiments, the pressure relief structure further includes third pressure relief grooves and fourth pressure relief grooves, each first pressure relief groove is correspondingly provided with a third pressure relief groove and a fourth pressure relief groove. The third pressure relief groove and the fourth pressure relief groove are disposed at intervals along the extending direction of the first pressure relief groove, and both the third pressure relief groove and the fourth pressure relief groove intersect with the first pressure relief groove, and the first pressure relief groove, the third pressure relief groove and the fourth pressure relief groove together define an opening portion; the opening portion is configured to be opened with the first pressure relief groove, the third pressure relief groove, and the fourth pressure relief groove as boundaries when the pressure or temperature inside the case body reaches a threshold, so as to release the pressure inside the case body. 
     In the technical solution above, the first pressure relief groove, the third pressure relief groove and the fourth pressure relief groove together define the opening portion, and when the case body is depressurized, the pressure relief structure can be opened with the first pressure relief groove, the third pressure relief groove and the fourth pressure relief groove as boundaries, and has a large pressure relief area, thereby improving the pressure relief rate, and reducing the risk of fire and explosion of the battery cell. 
     In some embodiments, the first pressure relief groove, the third pressure relief groove and the fourth pressure relief groove together define two opening portions, and the two opening portions are respectively located on both sides of the first pressure relief groove. 
     In the technical solution above, the first pressure relief groove, the second pressure relief groove and the third pressure relief groove together define two opening portions respectively located on both sides of the first pressure relief groove, and during a pressure relief process, the two opening portions can be opened quickly in a side-by-side manner, thereby improving the pressure relief rate of the case body. 
     In some embodiments, the first pressure relief groove has an opening position, the third pressure relief groove intersects with the first pressure relief groove to form a first weak position, and the fourth pressure relief groove intersects with the first pressure relief groove to form a second weak position, in the extending direction of the first pressure relief groove, the opening position is located between the first weak position and the second weak position; the case body is configured to rupture at the first pressure relief groove from the opening position to the first weak position and the second weak position and form a crack when the pressure or temperature inside the case body reaches a threshold, so that the open portion is opened along the third pressure relief groove and the fourth pressure relief groove after the crack being formed on the case body. 
     In the technical solution above, the opening position of the first pressure relief groove is the pressure relief starting position, the case body at the opening position is weaker than that at the first weak position and the second weak position, so the case body is more likely to be ruptured at the opening position. When the internal pressure or temperature of the case body reaches a threshold, the case body first being ruptured along the first pressure relief groove from the opening position towards the first weak position and the second weak position, and then being ruptured along the third pressure relief groove and the fourth pressure relief groove, so that the opening portion is opened along the third pressure relief groove and the fourth pressure relief groove, thereby realizing quick opening of the opening portion. 
     In some embodiments, the wall thickness of the case body at the first weak position and the wall thickness of the case body at the second weak position are both greater than the wall thickness of the case body at the opening position. 
     In the technical solution above, the wall thickness of the case body at the first weak position and the wall thickness of the case body at the second weak position being greater than the wall thickness of the case body at the opening position, that is, the wall thickness of the case body at the opening position is thinner, so that the case body at the opening position is weaker than that at the first weak position and the second weak position, so the case body is more likely to be ruptured at the opening position, thereby ensuring that, during a pressure relief process, the opening position splits along the first pressure relief groove from the opening position towards the first weak position and the second weak position. 
     In some embodiments, the case body is of a cylindrical structure, and the first pressure relief groove extends along the axial direction of the case body. 
     In the above technical solution, the first pressure relief groove extending along the axial direction of the cylindrical case body, which is beneficial to ensure the length of the first pressure relief groove. 
     In some embodiments, the pressure relief structure is disposed on the outer surface of the case body. 
     In the above technical solution, the pressure relief structure being disposed on the outer surface of the case body, which facilitates the processing of each pressure relief groove in the pressure relief structure. 
     In some embodiments, the case body includes a bottom wall and a peripheral wall, the peripheral wall is arranged around the edge of the bottom wall, and the pressure relief structure is disposed on the peripheral wall. 
     In the above technical solution, the pressure relief structure being disposed on the peripheral wall of the case body, which can realize pressure relief in multiple directions. 
     In a second aspect, the embodiments of the present application provide a battery cell, comprising: 
     an electrode assembly; and a case provided by any one of the embodiments of the first aspect, the case is used for accommodating the electrode assembly. 
     In a third aspect, the embodiments of the present application provide a battery, comprising: the battery cell provided by any one of the embodiments of the second aspect; and a box body for accommodating the battery cell. 
     In a fourth aspect, the embodiments of the present application provide an electrical apparatus, including a battery provided by any one of the embodiments of the third aspect. 
     In a fifth aspect, the embodiments of the present application provide a method for manufacturing a case, the method comprising: providing a case body for accommodating an electrode assembly; processing to obtain a pressure relief structure on the case body to form a plurality of first pressure relief grooves disposed at intervals on the case body along the circumferential direction of the case body; wherein the case body is configured to rupture along the first pressure relief grooves when the pressure or temperature inside the case body reaches a threshold to release the pressure inside the case body. 
     In a sixth aspect, the embodiments of the present application provide a manufacturing apparatus for a case, the manufacturing apparatus comprising: a providing device for providing a case body, the case body being used for accommodating an electrode assembly; a processing device for processing to obtain a pressure relief structure on the case body, so as to form a plurality of first pressure relief grooves disposed at intervals on the case body along the circumferential direction of the case body; wherein the case body is configured to rupture along the first pressure relief grooves when the pressure or temperature inside the case body reaches a threshold to release the pressure inside the case body. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       To more clearly describe the technical solutions of the embodiments of the present application, the drawings to be used in the embodiments will be briefly introduced below, and it should be understood that the following drawings only show some embodiments of the present application, and therefore should not be considered as limiting the scope of the present application. For those of ordinary skills in the art, other relevant drawings may also be obtained based on these drawings without creative efforts. 
         FIG.  1    is a schematic structural view of a vehicle provided by some embodiments of the present application. 
         FIG.  2    is a schematic structural view of a battery provided by some embodiments of the present application. 
         FIG.  3    is an exploded view of a battery cell provided by some embodiments of the present application. 
         FIG.  4    is a schematic structural view of a case provided by some embodiments of the present application. 
         FIG.  5    is a schematic structural view of a case provided by other embodiments of the present application. 
         FIG.  6    is a front view of the case shown in  FIG.  4   . 
         FIG.  7    is a partial enlarged view at position A of the case shown in  FIG.  6   . 
         FIG.  8    is a flowchart of a manufacturing method of a case provided by some embodiments of the present application. 
         FIG.  9    is a schematic block diagram of a manufacturing apparatus for a case provided by some embodiments of the present application. 
     
    
    
     DESCRIPTION OF REFERENCE NUMERALS 
       10 -box body; 
       11 -first portion; 
       12 -second portion; 
       20 -battery cell; 
       21 -case; 
       211 -case body; 
       212 -pressure relief structure; 
       2121 -first pressure relief groove; 
       2122 -second pressure relief groove; 
       2122   a -groove segment; 
       2123 -opening position; 
       2124 -third pressure relief groove; 
       2125 -fourth pressure relief groove; 
       2126 -opening portion; 
       2127 -first weak position; 
       2128 -second weak position; 
       22 -electrode assembly; 
       23 -end cap; 
       231 -electrode terminal; 
       24 -current collecting member; 
       100 -battery; 
       200 -controller; 
       300 -motor; 
       1000 -vehicle; 
       2000 -manufacturing apparatus; 
       2100 -providing device; 
       2200 -processing device; 
     Z-height direction. 
     DETAILED DESCRIPTION 
     In order to make the objects, technical solutions and advantages of embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly described below with reference to the drawings for the embodiments of the present application. Apparently, the described embodiments are some of, rather than all of, the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort fall within the protection scope of the present application. 
     Unless otherwise defined, all technical and scientific terms used in the present application have the same meanings as those commonly understood by those skilled in the art to which the present application belongs. The terms used in the specification of the present application are merely for the purpose of describing specific embodiments, but are not intended to limit the present application. The terms “comprising” and “having” and any variations thereof in the specification and the claims of the present application as well as the foregoing description of the drawings are intended to cover non-exclusive inclusions. The terms “first”, “second” and the like in the specification and the claims of the present application as well as the above drawings are used to distinguish different objects, rather than to describe a specific order or primary-secondary relationship. 
     Reference in the present application to “embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present 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. 
     In the description of the present application, it should be noted that the terms “mounting”, “connecting”, “connection” and “attachment” should be understood in a broad sense, unless otherwise explicitly specified or defined. For example, it may be a fixed connection, a detachable connection, or an integrated connection; and it may be a direct connection or an indirect connection through an intermediate medium, or may be a communication between the interior of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations. 
     In the present application, the term “and/or” is only an association relationship for describing associated objects, indicating that three relationships may exist. For example, A and/or B may represent three situations: A exists alone, both A and B exist, and B exists alone. In addition, the character “/” in the present application generally means that the associated objects before and after it are in an “or” relationship. 
     In the embodiments of the present 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 the present application shown in the drawings, as well as the overall thickness, length and width, etc. of the integrated device are only exemplary descriptions, and should not constitute any limitation to the present application. 
     The “plurality” in the present application refers to two or more (including two). 
     In the present application, battery cells may include a lithium-ion secondary battery, a lithium-ion primary battery, a lithium-sulfur battery, a sodium-lithium-ion battery, a sodium-ion battery, or a magnesium-ion battery, etc., which is not limited in the embodiments of the present application. The battery cell may be cylindrical, flat, rectangular, or in other shapes, which is also not limited in the embodiments of the present application. The battery cells are generally divided into three types according to packaging manners: cylindrical battery cells, square battery cells, and pouch cells, which are not limited in the embodiments of the present application. 
     The battery mentioned in the embodiments of the present application refers to a single physical module including one or more battery cells to provide a higher voltage and capacity. For example, the battery mentioned in the present application may include a battery module, a battery pack, or the like. The battery typically includes a box body for encapsulating one or more battery cells. The box body can prevent liquids or other foreign matters from affecting charging or discharging of the battery cells. 
     The battery cells include electrode assemblies and electrolyte solutions, and each electrode assembly is composed of a positive electrode sheet, a negative electrode sheet and a separator. The battery cells work mainly relying on the movement of metal ions between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet includes a positive current collector and a positive electrode active material layer, a surface of the positive current collector is coated with the positive electrode active material layer, the positive current collector not coated with the positive electrode active material layer protrudes from the positive electrode collector already coated with the positive electrode active material layer, and the positive current collector not coated with the positive electrode active material layer is used as a positive electrode tab. Taking a lithium-ion battery as an example, the material of the positive current collector may be aluminum, and the positive active material may be lithium cobalt oxide, lithium iron phosphate, ternary lithium, lithium manganate, or the like. The negative electrode sheet includes a negative current collector and a negative electrode active material layer, a surface of the negative current collector is coated with the negative electrode active material layer, the negative current collector not coated with the negative electrode active material layer protrudes from the negative electrode collector already coated with the negative electrode active material layer, and the negative current collector not coated with the negative electrode active material layer is used as a negative electrode tab. The material of the negative electrode current collector may be copper, and the negative electrode active material may be carbon, silicon, or the like. In order to ensure that no fusing occurs when a large current passes, there are a plurality of positive electrode tabs which are stacked together, and there are a plurality of negative electrode tabs which are stacked together. A diaphragm may be made from polypropylene (PP), polyethylene (PE), or the like. In addition, the electrode assembly may be of a wound structure or a laminated structure, which is not limited in the embodiments of the present application. 
     Many design factors, such as energy density, cycle life, discharge capacity, charge-discharge rate and other performance parameters, should be considered in the development of the battery technology. In addition, the safety of the battery also needs to be taken into account. 
     In a battery cell, in order to ensure the safety of the battery cell, it is generally necessary to provide a pressure relief structure on the case, and the pressure inside the battery cell is released by means of the pressure relief structure to ensure the safety of the battery cell. 
     The inventors found that even if a pressure relief structure is provided on the case, the battery cells may still have the risk of fire and explosion. After further research by the inventor, at present, a pressure relief groove is generally deposed on the case, and the pressure relief is realized by rupture of the case at the position of pressure relief groove. The pressure relief position of the case is likely to be shielded by other battery cells, and the position of the case in the pressure relief groove cannot be opened, which results in that the internal emissions cannot be discharged smoothly when the battery cells being in thermal runaway, which is likely to cause the risk of explosion and fire, and the safety is poor. 
     In view of this, the embodiments of the present application provide a case, a plurality of first pressure relief grooves are disposed at intervals on the case body along the circumferential direction of the case body, and the case body is configured to rupture along the first pressure relief groove when the pressure or temperature inside the case body reaches a threshold to release the pressure inside the case body. 
     In such a case, the case body being provided with a plurality of first pressure relief grooves disposed at intervals in the circumferential direction, and during a pressure relief process, even if one of the first pressure relief grooves is shielded, the case body may still be ruptured along other first pressure relief grooves, so as to ensure the normal pressure relief of the case body, reduce the risk of fire and explosion of the battery cell, and improve the safety of battery cells. 
     The case described in the embodiments of the present application are suitable for battery cells, batteries, and electrical apparatus using batteries. 
     The electrical apparatus may be, but not limited to, a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, an electric tool, and the like. The vehicle may be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle may be an all-electric vehicle, a hybrid electric vehicle, an extended-range vehicle, or the like. The spacecraft includes airplanes, rockets, space shuttles, spaceships, and the like. The electric toy includes fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys and electric aircraft toys. The electric tool includes metal cutting electric tools, grinding electric tools, assembly electric tools and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators and electric planers. The embodiments of the present application do not impose special limitations on the above powered apparatus. 
     For convenience of explanation, the following embodiments are described by taking an electric apparatus is a vehicle as an example. 
     Please refer to  FIG.  1   , which is a schematic structural view of a vehicle  1000  provided by some embodiments of the present application, the interior of the vehicle  1000  is provided with a battery  100 , and the battery  100  may be provided at the bottom or head or rear of the vehicle  1000 . The battery  100  can be used to power the vehicle  1000 , for example, the battery  100  can serve as an operating power source for the vehicle  1000 . 
     The vehicle  1000  may further include a controller  200  and a motor  300 , wherein the controller  200  is used to control the battery  100  to power the motor  300 , for example, for the operating power demand when the vehicle  1000  is starting, navigating and driving. 
     In some embodiments of the present application, the battery  100  not only may serve as an operating power source of the vehicle  1000 , but also may serve as a driving power source of the vehicle  1000 , thus replacing or partially replacing fuel or natural gas to provide driving power for the vehicle  1000 . 
     Please refer to  FIG.  2   , which is a schematic structural diagram of a battery  100  according to some embodiments of the present application, where the battery  100  includes a box body  10  and a battery cell  20 , and the box body  10  is used for accommodating the battery cell  20 . 
     The box body  10  is a component for accommodating the battery cell  20 , the box body  10  provides an accommodating space for the battery cell  20 , and the box body  10  can be of various structures. In some embodiments, the box body  10  may include a first portion  11  and a second portion  12 , the first portion  11  and the second portion  12  being covered to each other to define an accommodating space for accommodating the battery cell  20 . The first portion  11  and the second portion  12  may be of a variety of shapes, such as a rectangular parallelepiped, a cylinder, or the like. The first portion  11  may be a hollow structure with one side open, the second portion  12  may also be a hollow structure with one side open, and the opening side of the second portion  12  covers the opening side of the first portion  11 , so as to form a box body  10  with an accommodating space. Alternatively, the first portion  11  may be a hollow structure with one side open, the second portion  12  may be a plate-like structure, and the second portion  12  covers the opening side of the first portion  11  to form a box body  10  with an accommodating space. The first portion  11  and the second portion  12  may be sealed by a sealing member, which may be a sealing ring, a sealant, or the like. 
     There may be one or more battery cell  20  in a battery  100 . If there are a plurality of battery cells  20 , the plurality of battery cells  20  can be connected in series or parallel or in a mixed connection, wherein the mixed connection means that the plurality of battery cells  20  are connected in both series and parallel. The plurality of battery cells  20  may be connected in series or in parallel or in mixed connection to form a battery module first, then a plurality of battery modules are connected in series or in parallel or in mixed connection to form a whole, and accommodated in the box body  10 . It may also be that all the battery cells  20  are directly connected in series or in parallel or in mixed connection, and then the whole composed of all the battery cells  20  is accommodated in the box body  10 . 
     In some embodiments, the battery  100  may also include a confluence component, and a plurality of battery cells  20  may be electrically connected through the confluence component, so as to realize series, parallel or mixed connection of the plurality of battery cells  20 . The confluence component may be metal conductors such as copper, iron, aluminum, stainless steel, aluminum alloys, and the like. 
     Please refer to  FIG.  3   , which is an exploded view of a battery cell  20  provided by some embodiments of the present application. The battery cell  20  includes a case  21 , an electrode assembly  22  and an end cap  23 , the electrode assembly  22  is accommodated in the case  21 , the end cap  23  is used for covering the opening of the case  21 . 
     The case  21  is a component for accommodating the electrode assembly  22 , and the case  21  may be a hollow structure with an opening formed at one end, and the case  21  may also be a hollow structure with openings formed at opposite ends. If the case  21  being a hollow structure with an opening formed at one end, then, one end cap  23  may be provided; if the case  21  being a hollow structure with openings formed at two opposite ends, then, two end caps  23  may be provided, and the two end caps  23  cover the openings at both ends of the case  21  respectively. The case  21  may be made of various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, or the like. The case  21  may be of a variety of shapes, such as a cylinder, a rectangular parallelepiped, or the like. Exemplarily, in  FIG.  3   , the case  21  is a cylindrical structure, and the case  21  is a hollow structure with an opening formed at one end. 
     The electrode assembly  22  is a component in which an electrochemical reaction occurs in the battery cell  20 . The electrode assembly  22  may be a cylinder, a rectangular parallelepiped, or the like, and if the electrode assembly  22  is a cylindrical structure, the case  21  may also be a cylindrical structure, and if the electrode assembly  22  is a rectangular parallelepiped structure, the case  21  may also be a rectangular parallelepiped structure. The electrode assembly  22  may comprise a positive electrode sheet, a negative electrode sheet and a separator. The electrode assembly  22  may be a wound-type structure formed by winding a positive electrode sheet, a separator and a negative electrode sheet, or may be a stacked-type structure formed by stacking a positive electrode sheet, a separator, and a negative electrode sheet. 
     The positive electrode sheet may include a positive electrode current collector and a positive electrode active material layer coated on opposite sides of the positive electrode current collector. The negative electrode sheet may include a negative electrode current collector and a negative electrode active material layer coated on opposite sides of the negative electrode current collector. The electrode assembly  22  has a positive electrode tab and a negative electrode tab, the positive electrode tab may be a portion of the positive electrode sheet on which the positive electrode active material layer is not coated, and the negative electrode tab may be a portion of the negative electrode sheet on which the negative electrode active material layer is not coated. 
     The end cap  23  is a component that covers the opening of the case  21  to isolate the internal environment of the battery cell  20  from the external environment. The shape of the end cap  23  may be adapted to the shape of the case  21 , for example, the case  21  is of a rectangular parallelepiped structure, and the end cap  23  is of a rectangular plate-like structure adapted to the case  21 ; for another example, as shown in  FIG.  3   , the case  21  is of a cylindrical structure, and the end cap  23  is of a circular plate-like structure adapted to the case  21 . The material of the end cap  23  can also be various, for example, copper, iron, aluminum, steel, aluminum alloy, or the like, and the material of the end cap  23  and the material of the case  21  may be the same or different. 
     Electrode terminals  231  may be disposed on the end cap  23 , and the electrode terminals  231  are used for electrical connection with the positive electrode tab or the negative electrode tab of the electrode assembly  22 . 
     In some embodiments, the battery cell  20  may further include a current collecting member  24 , and the electrode terminals  231  are electrically connected with the positive electrode tab or the negative electrode tab of the electrode assembly  22  through the current collecting member  24 . 
     The number of the current collecting member  24  of the battery cell  20  may be one or two. For example, the case  21  is a hollow structure with an opening formed at one end, the end cap  23  covers the opening of the case  21 , one of the positive electrode tab and the negative electrode tab is electrically connected to an electrode terminal  231  through a current collecting member  24 , and the other is electrically connected to the case  21 ; for another example, the case  21  is a hollow structure in which openings are formed at opposite ends, two end caps  23  cover the openings of the case  21 , one of the positive electrode tab and the negative electrode tab is electrically connected to an electrode terminal  231  on one end cap  23  through a current collecting member  24 , and the other is electrically connected to an electrode terminal  231  on the other end cap  23  through another current collecting member  24 . 
     Please refer to  FIG.  4   , which is a schematic structural view of a case  21  provided by some embodiments of the present application. The case  21  includes a case body  211  and a pressure relief structure  212 , the case body  211  is used for accommodating the electrode assembly  22 , and the pressure relief structure  212  includes a plurality of first pressure relief grooves  2121  disposed at intervals on the case body  211  along the circumferential direction of the case body  211 . The case body  211  is configured to rupture along the first pressure relief groove  2121  when the pressure or temperature inside the case body  211  reaches a threshold, so as to release the pressure inside the case body  211 . 
     The case body  211  is a component for accommodating the electrode assembly  22 , and the case body  211  may be of a variety of shapes, such as a rectangular parallelepiped, a cylinder, and the like. The circumferential direction of the case body  211  refers to the direction around the center line of the case body  211 , and the center line extends along the height direction Z of the case body  211 . Taking the case body  211  is a cylinder as an example, the circumferential direction of the case body  211  refers to the direction around the axis of the case body  211 , which is perpendicular to the axis of the case body  211 , and also perpendicular to the radial direction of the case body  211 . Taking the case body  211  is a rectangular parallelepiped as an example, the case body  211  has four side walls parallel to its length direction and are connected end-to-end, and if a plurality of first pressure relief grooves  2121  are distributed at intervals along the four side walls, it is also belongs to the case where a plurality of pressure relief grooves are disposed at intervals along the circumferential direction of the case body  211 , for example, at least two of the four side walls of the case body  211  are provided with the first pressure relief grooves  2121 . 
     The pressure relief structure  212  may be disposed on the outer surface of the case body  211 , or may be disposed on the inner surface of the case body  211 . If the pressure relief structure  212  is disposed on the outer surface of the case body  211 , the first pressure relief grooves  2121  are disposed on the outer surface of the case body  211 , and if the pressure relief structure  212  is disposed on the inner surface of the case body  211 , the first pressure relief grooves  2121  are disposed on the inner surface of the case body  211 . 
     The wall thickness of the case body  211  in the position where the first pressure relief groove  2121  is provided is smaller, and is more likely to be ruptured, so that when the pressure or temperature inside the case body  211  reaches a threshold, it ruptures along the first pressure relief grooves  2121 , so that emissions (gas, electrolyte, etc.) inside the case body  21  can be discharged, so as to release the pressure inside the case body  211 . For the battery cell  20 , the pressure inside the case body  211  is the pressure inside the battery cell  20 . 
     The first pressure relief groove  2121  can be formed in various ways, such as stamping, milling, rolling, and the like. The extending direction of the first pressure relief groove  2121  may be consistent with the height direction Z of the case body  211 , or may form a certain angle with the height direction Z of the case body  211 , for example, the extending direction of the first pressure relief groove  2121  is perpendicular to the height direction Z of the case body  211 . Taking the case body  211  is a cylinder as an example, the first pressure relief groove  2121  may extend along the axial direction (the height direction Z) of the case body  211 , and may extend along the circumferential direction of the case body  211 . 
     In the case  21 , the case body  211  is provided with a plurality of first pressure relief grooves  2121  disposed at intervals in the circumferential direction, and the case body  211  can be ruptured along the first pressure relief grooves  2121  when the internal pressure or temperature thereof reaches a threshold, thereby achieving the purpose of releasing the pressure inside the case body  211 . During a pressure relief process, even if one of the first pressure relief grooves  2121  is shielded (for example, in the case where the battery  100  includes a plurality of battery cells  20 , the plurality of battery cells  20  are arranged side by side, a first pressure relief groove  2121  of a case  21  of a battery cell  20  may be shielded by a case  21  of another battery cell  20 ), the case body  211  may still be ruptured along other first pressure relief grooves  2121 , so as to ensure normal pressure relief of the case body  211 , reduce the risk of fire and explosion of the battery cells  20 , and improve the safety of the battery cells  20 . 
     In some embodiments, the pressure relief structure  212  further includes a second pressure relief groove  2122  disposed on the case body  211 , the first pressure relief groove  2121  intersects with the second pressure relief groove  2122  to form opening position  2123 , and the case body  211  is configured to rupture from the opening position  2123  along the first pressure relief groove  2121  when the pressure or temperature inside the case body  211  reaches a threshold. 
     The first pressure relief groove  2121  intersects with the second pressure relief groove  2122  to form an opening position  2123 , and the position where the first pressure relief groove  2121  intersects with the second pressure relief groove  2122  is the opening position  2123 . The opening position  2123  is a weaker position of the case body  211  in the region of the first pressure relief groove  2121 . The case body  211  first ruptures from the opening position  2123  during pressure relief, and then ruptures along the first pressure relief groove  2121 . In the extending direction of the first pressure relief groove  2121 , the opening position  2123  may be located at the midpoint position of the first pressure relief groove  2121 , or may be offset from the midpoint position of the first pressure relief groove  2121 . 
     The second pressure relief groove  2122  may be formed in a variety of ways, such as stamping, milling, rolling, and the like. After the first pressure relief groove  2121  and the second pressure relief groove  2122  being processed on the case body  211 , the opening position  2123  is formed at the intersection position of the first pressure relief groove  2121  and the second pressure relief groove  2122 . 
     In this embodiment, the case body  211  is provided with a second pressure relief groove  2122 , and the second pressure relief groove  2122  intersects with the first pressure relief groove  2121  to form an opening position  2123 , so that the case body  211  is more likely to be ruptured at the opening position  2123 , so that when the pressure or temperature inside the case body  211  reaches a threshold, the case body  211  ruptures rapidly from the opening position  2123  along the first pressure relief groove  2121 , thereby realizing rapid pressure relief. The case body  211  can also rupture along the second pressure relief groove  2122  after being ruptured at the opening position  2123 , thereby increasing the pressure relief area of the case body  211 . 
     In some embodiments, the second pressure relief groove  2122  extends along the circumferential direction of the case body  211 , each first pressure relief groove  2121  intersects with the second pressure relief groove  2122  to form an opening position  2123 . 
     The second pressure relief groove  2122  extends along the circumferential direction of the case body  211 , that is to say, the extending direction of the second pressure relief groove  2122  is consistent with the arrangement direction of the plurality of first pressure relief grooves  2121 . Since the second pressure relief groove  2122  intersects with the first pressure relief groove  2121 , the second pressure relief groove  2122  does not overlap with the first pressure relief groove  2121 , the second pressure relief groove  2122  and the first pressure relief groove  2121  are arranged at an angle, and the first pressure relief groove  2121  may extend along the height direction Z of the case body  211 . 
     Each of the first pressure relief grooves  2121  intersects with the second pressure relief groove  2122  to form an opening position  2123 , that is to say, all of the plurality of first pressure relief grooves  2121  intersect with the second pressure relief groove  2122  to form opening positions  2123 , which is simple in structure and can effectively reduce the production cost. 
     In some embodiments, the second pressure relief groove  2122  is a closed structure extending along the circumference of the case body  211  and being connected end-to-end. 
     The second pressure relief groove  2122  extending along the circumferential direction of the case body  211  and being connected end-to-end, i.e., the second pressure relief groove  2122  is arranged as a whole ring along the circumferential direction of the case body  211 , so as to ensure intersecting with a plurality of the first pressure relief grooves  2121 . In an embodiment in which the case body  211  being a cylinder, the second pressure relief groove  2122  is an annular structure extending along the circumferential direction of the case body  211  and being connected end-to-end; in an embodiment in which the case body  211  being a rectangular parallelepiped, the second pressure relief groove  2122  is a rectangular structure extending along the circumferential direction of the case body  211  and being connected end-to-end. 
     In this embodiment, the second pressure relief groove  2122  is a closed structure extending along the circumferential direction of the case body  211  and being connected end-to-end, which has a simple structure and is easy to process and form. 
     In some embodiments, please refer to  FIG.  5   , which is a schematic structural view of the case  21  provided by other embodiments of the present application, the second pressure relief groove  2122  includes a plurality of groove segments  2122   a  disposed at intervals along the circumferential direction of the case body  211 , each groove segment  2122   a  intersects with a first pressure relief groove  2121  to form an opening position  2123 . 
     The second pressure relief groove  2122  includes a plurality of groove segments  2122   a  disposed at intervals along the circumferential direction of the case body  211 , that is, the second pressure relief groove  2122  is divided into a plurality of groove segments  2122   a  disposed along the circumferential direction of the case body  211 . In the circumferential direction of the case body  211 , two adjacent groove segments  2122   a  are disposed at intervals, that is, two adjacent groove segments  2122   a  are not continuous. Among a plurality of groove segments  2122   a , each groove segment  2122   a  is used to intersect with a first pressure relief groove  2121  to form an opening position  2123  at the intersection position of the two. It should be understood that each first pressure relief groove  2121  is correspondingly forms an opening position  2123 . Of course, the opening position  2123  may be located at the midpoint position of the first pressure relief groove  2121 , and may also be located at the midpoint position of the groove segment  2122   a , so that the first pressure relief groove  2121  and the groove segment  2122   a  form an approximately “+” shaped structure. 
     In this embodiment, since the plurality of groove segments  2122   a  are disposed at intervals along the circumferential direction of the case body  211 , and each groove segment  2122   a  intersects with a first pressure relief groove  2121  to form an opening position  2123 , so that each first pressure relief groove  2121  does not interfere with each other during pressure relief, and is independent from each other. In addition, since the plurality of groove segments  2122   a  are disposed at intervals along the circumferential direction of the case body  211 , so that the second pressure relief groove  2122  is not continuous, and the strength of the case body  211  is higher, which is beneficial to increase the service life of the case  21 . 
     In some embodiments, please refer to  FIG.  6   , which is a front view of the case  21  shown in  FIG.  4   , the pressure relief structure  212  may further includes third pressure relief grooves  2124  and fourth pressure relief grooves  2125 , each first pressure relief groove  2121  is correspondingly provided with a third pressure relief groove  2124  and a fourth pressure relief groove  2125 , the third pressure relief groove  2124  and the fourth pressure relief groove  2125  are disposed at intervals along the extending direction of the first pressure relief groove  2121 , both of the third pressure relief groove  2124  and the fourth pressure relief groove  2125  intersect with the first pressure relief groove  2121 , the first pressure relief groove  2121 , the third pressure relief groove  2124  and the fourth pressure relief groove  2125  together define an opening portion  2126 . The opening portion  2126  is configured to be opened with the first pressure relief groove  2121 , the third pressure relief groove  2124 , and the fourth pressure relief groove  2125  as boundaries when the pressure or temperature inside the case body  211  reaches a threshold, so as to release the pressure inside the case body  211 . 
     The opening portion  2126  is a region of the case body  211  that is defined by the first pressure relief groove  2121 , the third pressure relief groove  2124  and the fourth pressure relief groove  2125  together. Three side portions of the opening portion  2126  that are sequentially connected are respectively located at positions corresponding to the third pressure relief groove  2124 , the first pressure relief groove  2121  and the fourth pressure relief groove  2125 . 
     The opening portion  2126  is configured to be opened with the first pressure relief groove  2121 , the third pressure relief groove  2124  and the fourth pressure relief groove  2125  as boundaries when the pressure or temperature inside the case body  211  reaches a threshold, that is, when the internal pressure or temperature inside the case body  211  reaches a threshold, the case body  211  will eventually rupture at the positions of the first pressure relief groove  2121 , the third pressure relief groove  2124  and the fourth pressure relief groove  2125  to open the opening portion  2126 . During the opening of the opening portion  2126 , after the case body  211  being ruptured at the position of the first pressure relief groove  2121  and forming a crack, the case body  211  ruptures along the third pressure relief groove  2124  and the fourth pressure relief groove  2125 , so that the opening portion  2126  is turned outward and opened. After the opening portion  2126  is opened, an open part is formed at the position of the case body  211  corresponding to the opening portion  2126 , and emissions inside the case body  211  can be discharged through the open part, so as to release the pressure inside the case body  211 . 
     When the pressure or temperature inside the case body  211  reaches a threshold, the opening portion  2126  is opened with the first pressure relief groove  2121 , the third pressure relief groove  2124  and the fourth pressure relief groove  2125  as the boundaries. After the opening portion  2126  being opened, the case body  211  may be completely split or only partially split at the position of the third pressure relief groove  2124 , and the case body  211  may be completely split or only partially split at the position of the fourth pressure relief groove  2125 . Of course, if the case body  211  is completely split at both of the position of the third pressure relief groove  2124  and the position of the fourth pressure relief groove  2125 , then the opening portion  2126  is completely opened, and the pressure relief area is larger. 
     The third pressure relief groove  2124  and the fourth pressure relief groove  2125  may also be formed in various ways, such as stamping, milling, rolling, and the like. 
     The number of the opening portion  2126  defined by the first pressure relief groove  2121 , the third pressure relief groove  2124  and the fourth pressure relief groove  2125  together may be one or two. In the embodiment in which one opening portion  2126  is defined by the first pressure relief groove  2121 , the third pressure relief groove  2124  and the fourth pressure relief groove  2125  together, the first pressure relief groove  2121  may be disposed at one end of the third pressure relief groove  2124  and the fourth pressure relief groove  2125 , so that the first pressure relief groove  2121 , the third pressure relief groove  2124 , and the fourth pressure relief groove  2125  form an approximate “right open box” shaped structure. In the embodiment in which two opening portions  2126  are defined by the first pressure relief groove  2121 , the third pressure relief groove  2124  and the fourth pressure relief groove  2125  together, the first pressure relief groove  2121  may be disposed at the midpoint position of the third pressure relief groove  2124  and the fourth pressure relief groove  2125 , so that the first pressure relief groove  2121 , the third pressure relief groove  2124  and the fourth pressure relief groove  2125  form an approximate “H” shaped structure. 
     In this embodiment, the first pressure relief groove  2121 , the third pressure relief groove  2124 , and the fourth pressure relief groove  2125  together define the opening portion  2126 , and when the case body  211  is depressurized, the pressure relief structure  212  can be opened with the first pressure relief groove  2121 , the third pressure relief groove  2124 , and the fourth pressure relief groove  2125  as boundaries, which has a large pressure relief area, thereby improving the pressure relief rate, and reducing the risk of fire and explosion of the battery cells  20 . 
     In some embodiments, please continue to refer to  FIG.  6   , the first pressure relief groove  2121 , the third pressure relief groove  2124  and the fourth pressure relief groove  2125  together define two opening portions  2126 , and the two opening portions  2126  are located at both sides of the first pressure relief groove  2121  respectively. 
     The first pressure relief groove  2121 , the third pressure relief groove  2124  and the fourth pressure relief groove  2125  together define two opening portions  2126 . The first pressure relief groove  2121 , the third pressure relief groove  2124  and the fourth pressure relief groove  2125  may form an approximately “H” shaped structure. The two opening portions  2126  are located on both sides of the first pressure relief groove  2121  respectively, so that the two opening portions  2126  are bounded by the first pressure relief groove  2121 , and after the case body  211  ruptures at the position of the first pressure relief groove  2121 , the two opening portions  2126  will be opened in a side-by-side manner to release the pressure inside the case body  211 . The two opening portions  2126  may be symmetrically distributed on both sides of the first pressure relief groove  2121 . 
     Since the first pressure relief groove  2121 , the second pressure relief groove  2122  and the third pressure relief groove  2124  together define two opening portions  2126  respectively located at both sides of the first pressure relief groove  2121 , during a pressure relief process, the two opening portions  2126  can be opened quickly in a side-by-side manner, thereby improving the pressure relief rate of the case body  211 . 
     In some embodiments, please refer to  FIG.  7   , which is a partial enlarged view at position A of the case  21  shown in  FIG.  6   , the first pressure relief groove  2121  has an opening position  2123 , the third pressure relief groove  2124  intersects with the first pressure relief groove  2121  to form a first weak position  2127 , the fourth pressure relief groove  2125  intersects with the first pressure relief groove  2121  to form a second weak position  2128 , and in the extending direction of the first pressure relief groove  2121 , the opening position  2123  is located between the first weak position  2127  and the second weak position  2128 . The case body  211  is configured to rupture at the first pressure relief groove  2121  from the opening position  2123  towards the first weak position  2127  and the second weak position  2128  and form a crack when the pressure or temperature inside the case body  211  reaches a threshold, so that the open portion  2126  is opened along the third pressure relief groove  2124  and the fourth pressure relief groove  2125  after the case body  211  forms the crack. 
     The case body  211  is configured to rupture at the first pressure relief groove  2121  from the opening position  2123  towards the first weak position  2127  and the second weak position  2128  and form a crack when the pressure or temperature inside the case body  211  reaches a threshold, it should be understood that the opening position  2123  is weaker than the first weak position  2127  and the second weak position  2128 , and the case body  211  is more likely to be ruptured at the opening position  2123  than the first weak position  2127  and the second weak position  2128 . During the rupture of the case body  211  at the position of the first pressure relief groove  2121 , the case body  211  first ruptures at the opening position  2123 , and then ruptures along the first pressure relief groove  2121  towards the first weak position  2127  and the second weak position  2128  to form a crack at the position of the first pressure relief groove  2121 . The opening position  2123  is the position where the case body  211  first ruptures at the first pressure relief groove  2121 , the first weak position  2127  is the position where the case body  211  first ruptures at the third pressure relief groove  2124 , and the second weak position  2128  is the position where the case body  211  first ruptures at the fourth pressure relief groove  2125 . 
     The third pressure relief groove  2124  intersects with the first pressure relief groove  2121  to form the first weak position  2127 , that is, the position where the third pressure relief groove  2124  intersects with the first pressure relief groove  2121  forms the first weak position  2127 . The fourth pressure relief groove  2125  intersects with the first pressure relief groove  2121  to form the second weak position  2128 , that is, the position where the fourth pressure relief groove  2125  intersects with the first pressure relief groove  2121  forms the second weak position  2128 . 
     The distance between the opening position  2123  and the first weak position  2127  may be equal to the distance between the opening position  2123  and the second weak position  2128 , so that after the case body  211  being ruptured at the opening position  2123 , the case body  211  can be ruptured almost simultaneously at the first weak position  2127  and the second weak position  2128 , so that during the opening of the opening portion  2126 , the case body  211  ruptures synchronously at the positions of the third pressure relief groove  2124  and the fourth pressure relief groove  2125 . 
     The opening position  2123  can be formed in various ways. For example, the first pressure relief groove  2121  is a gradually-changed groove with a gradually changed depth, the depth of the first pressure relief groove  2121  gradually decreases from the opening position  2123  to both ends, and the opening position  2123  is formed at the deepest position of the first pressure relief groove  2121 . For another example, as shown in  FIG.  7   , in an embodiment where the pressure relief structure  212  further includes a second pressure relief groove  2122  disposed on the case body  211 , the first pressure relief groove  2121  intersects with the second pressure relief groove  2122  to form an opening position  2123 . 
     The opening position  2123  of the first pressure relief groove  2121  is the pressure relief starting position of the case body  211 , and the case body  211  is weaker at the opening position  2123  than at the first weak position  2127  and the second weak position  2128 , and the case body  211  is more likely to be ruptured at the opening position  2123 . When the internal pressure or temperature of the case body  211  reaches a threshold, the case body  211  first ruptures along the first pressure relief groove  2121  from the opening position  2123  towards the first weak position  2127  and the second weak position  2128 , and then ruptures along the third pressure relief groove  2124  and the fourth pressure relief groove  2125 , so that the opening portion  2126  is opened along the third pressure relief groove  2124  and the fourth pressure relief groove  2125 , thereby realizing quick opening of the opening portion  2126 . 
     In some embodiments, the wall thickness of the case body  211  at the first weak position  2127  and the wall thickness of the case body  211  at the second weak position  2128  are both greater than the wall thickness of the case body  211  at the opening position  2123 . 
     Taking the intersection of the third pressure relief groove  2124  and the first pressure relief groove  2121  forms the first weak position  2127 , the intersection of the fourth pressure relief groove  2125  and the first pressure relief groove  2121  forms the second weak position  2128 , and the intersection of the second pressure relief groove  2122  and the first pressure relief groove  2121  forms the opening position  2123  as an example, the wall thickness of the case body  211  at the first weak position  2127  refers to the thickness of the remaining part at the first weak position  2127  after the third pressure relief groove  2124  and the first pressure relief groove  2121  are disposed on the case body  211 , the wall thickness of the case body  211  at the second weak position  2128  refers to the thickness of the remaining part at the second weak position  2128  after the fourth pressure relief groove  2125  and the first pressure relief groove  2121  are disposed on the case body  211 , and the wall thickness of the case body  211  at the opening position  2123  refers to the thickness of the remaining part at the opening position  2123  after the second pressure relief groove  2122  and the first pressure relief groove  2121  are disposed on the case body  211 . 
     By making the depth of the second pressure relief groove  2122  greater than the depth of the first pressure relief groove  2121 , the depth of the third pressure relief groove  2124  and the depth of the fourth pressure relief groove  2125 , the wall thickness of the case body  211  at the first weak position  2127  and the wall thickness of the case body  211  at the second weak position  2128  are both greater than the wall thickness of the case body  211  at the opening position  2123  can be realized. By making the depth of the second pressure relief groove  2122  equal to the depth of the first pressure relief groove  2121 , and the depth of the second pressure relief groove  2122  greater than the depth of the third pressure relief groove  2124  and the fourth pressure relief groove  2125 , the wall thickness of the case body  211  at the first weak position  2127  and the wall thickness of the case body  211  at the second weak position  2128  are both greater than the wall thickness of the case body  211  at the opening position  2123  may also be realized Exemplarily, all of the first pressure relief groove  2121 , the second pressure relief groove  2122 , the third pressure relief groove  2124  and the fourth pressure relief groove  2125  may be of V-shaped grooves with a V-shaped cross section. 
     Since the wall thickness of the case body  211  at the first weak position  2127  and the wall thickness of the case body  211  at the second weak position  2128  are greater than the wall thickness of the case body  211  at the opening position  2123 , i.e. the wall thickness of the case body  211  at the opening position  2123  is thinner, so that the case body  211  is weaker at the opening position  2123  than at the first weak position  2127  and the second weak position  2128 , and the case body  211  is more likely to be ruptured at the opening position  2123 , thus ensuring that, during a pressure relief process, the opening position  2123  splits from the opening position  2123  towards the first weak position  2127  and the second weak position  2128  along the first pressure relief groove  2121 . 
     In some embodiments, the case body  211  is of a cylindrical structure, and the first pressure relief groove  2121  extends along the axial direction of the case body  211 . 
     The case body  211  is of a cylindrical structure, in the case where a plurality of battery cells  20  are arranged side by side, it is not likely to appear that two adjacent first pressure relief grooves  2121  on the case body  211  of one battery cell  20  are shielded by another battery cell at the same time, which has a good pressure relief effect. The first pressure relief groove  2121  extends along the axial direction of the case body  211 , that is, the first pressure relief groove  2121  extends along the height direction Z of the case body  211 , which is beneficial to ensure the length of the first pressure relief groove  2121 . 
     In some embodiments, the pressure relief structure  212  is disposed on the outer surface of the case body  211 . 
     It should be noted that, in the embodiment in which the pressure relief structure  212  includes a plurality of first pressure relief grooves  2121  disposed at intervals along the circumferential direction of the case body  211 , the first pressure relief grooves  2121  are disposed on the outer surface of the case body  211 . In the embodiment in which the pressure relief structure  212  further includes a second pressure relief groove  2122  disposed on the case body  211 , the second pressure relief groove  2122  is also disposed on the outer surface of the case body  211 . In the embodiment in which the pressure relief structure  212  further includes third pressure relief grooves  2124  and fourth pressure relief grooves  2125 , the third pressure relief grooves  2124  and the fourth pressure relief grooves  2125  are also disposed on the outer surface of the case body  211 . 
     The pressure relief structure  212  being disposed on the outer surface of the case body  211  facilitates processing of each pressure relief groove in the pressure relief structure  212 . 
     In some embodiments, the case body  211  includes a bottom wall and a peripheral wall, the peripheral wall is arranged around the edge of the bottom wall, and the pressure relief structure  212  is disposed on the peripheral wall, so as to achieve pressure relief in multiple directions. 
     The peripheral wall is arranged around the edge of the bottom wall, so that the case body  211  forms an opening at the end opposite to the bottom wall, and a end cover  23  is used to cover the opening. 
     In the embodiment in which the case body  211  is of a cylindrical structure, the peripheral wall of the case body  211  is a circular peripheral wall, and the peripheral wall of the case body  211  is a cylinder. In the embodiment in which the case body  211  is of a rectangular parallelepiped structure, the peripheral wall of the case body  211  includes four side walls parallel to the length direction thereof and connected end-to-end. 
     An embodiment of the present application provides a battery cell  20 , comprising an electrode assembly  22  and a case  21  provided in any one of the above embodiments, the case  21  is used for accommodating the electrode assembly  22 . 
     An embodiment of the present application provides a battery  100 , comprising a box body  10  and a battery cell  20  provided in any one of the above embodiments, and the box body  10  is used for accommodating the battery cell  20 . 
     An embodiment of the present application provides an electrical apparatus, comprising the battery  100  provided in any one of the above embodiments. 
     The electrical apparatus can be any of the aforementioned apparatus that use the battery  100 . 
     Referring to  FIGS.  6  and  7   , an embodiment of the present application further provides a cylindrical case, including a case body  211  and a pressure relief structure  212 . The case body  211  is used for accommodating the electrode assembly  22 , and the pressure relief structure  212  includes: a plurality of first pressure relief grooves  2121  disposed at intervals on the case body  211  along the circumferential direction of the case body  211 ; a second pressure relief groove  2122 , the second pressure relief groove  2122  intersects with the first pressure relief groove  2121  to form an opening position  2123 , so that the case body  211  can be ruptured from the opening position  2123  along the first pressure relief groove  2121  when the pressure or temperature inside the case body  211  reaches a threshold; and third pressure relief grooves  2124  and fourth pressure relief grooves  2125 , wherein each first pressure relief groove  2121  is correspondingly provided with a third pressure relief groove  2124  and a fourth pressure relief groove  2125 , the third pressure relief groove  2124  and the fourth pressure relief groove  2125  are arranged at intervals along the extending direction of the first pressure relief groove  2121 , the third pressure relief groove  2124  and the fourth pressure relief groove  2125  both intersect with the first pressure relief groove  2121 , and the first pressure relief groove  2121 , the third pressure relief groove  2124  and the fourth pressure relief groove  2125  together define an opening portion  2126 . The opening portion  2126  is configured to be opened with the first pressure relief groove  2121 , the third pressure relief groove  2124 , and the fourth pressure relief groove  2125  as boundaries when the pressure or temperature inside the case body  211  reaches a threshold, so as to release the pressure inside the case body  211 . The case of this structure has a large pressure relief area, which improves the pressure relief rate. During a pressure relief process, even if one of the first pressure relief grooves  2121  is shielded, the case body  211  can still rupture along other first pressure relief grooves  2121 , so as to ensure normal pressure relief of the case body  211 , reduce the risk of fire and explosion of the battery cell  20 , and improve the safety of the battery cell  20 . 
     An embodiment of the present application provides a method for manufacturing a case  21 . Please refer to  FIG.  8   . which is a flowchart of a method for manufacturing a case  21  provided by some embodiments of the present application. The method comprising: 
     S 100 : providing a case body  211 , where the case body  211  is used for accommodating the electrode assembly  22 ; 
     S 200 : processing to obtain a pressure relief structure  212  on the case body  211  to form a plurality of first pressure relief grooves  2121  disposed at intervals on the case body  211  along the circumferential direction of the case body  211 ; 
     wherein the case body  211  is configured to rupture along the first pressure relief groove  2121  when the pressure or temperature inside the case body  211  reaches a threshold to release the pressure inside the case body. 
     It should be noted that, for the related structures of the case  21  manufactured by the manufacturing methods provided by each of the above-mentioned embodiments, reference may be made to the case  21  provided by each of the foregoing embodiments, and details will not be described herein again. 
     In addition, an embodiment of the present application further provides a manufacturing apparatus  2000  for a case  21 . Please refer to  FIG.  9   , which is a schematic block diagram of a manufacturing apparatus  2000  for a case  21  provided by some embodiments of the present application, the manufacturing apparatus  2000  includes a providing apparatus  2100  and a processing apparatus  2200 , the providing apparatus  2100  is used for providing a case body  211 , the case body  211  is used for accommodating an electrode assembly  22 , and the processing apparatus  2200  is used for processing to obtain a pressure relief structure  212  on the case body  211  to form a plurality of first pressure relief grooves  2121  disposed at intervals on the case body  211  along the circumferential direction of the case body  211 . 
     Wherein the case body  211  is configured to rupture along the first pressure relief groove  2121  when the pressure or temperature inside the case body  211  reaches a threshold, so as to release the pressure inside the case body. 
     It should be noted that, for the related structures of the case  21  manufactured by the manufacturing apparatus  2000  provided in the embodiments above, reference may be made to the case  21  provided by each of the foregoing embodiments, and details will not be described herein again. 
     It should be noted that in case of no conflicts, the features of the embodiments in the present application may be combined with each other. 
     The above embodiments are merely used to illustrate the technical solutions of the present application, and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall fall within the scope of protection of the present application.