Battery cells and electrical equipment

Abstract

The present application provides a battery cell and an electrical device, which relate to the field of battery technology. The battery cell includes an electrode assembly, a shell and a cover; the shell is used to accommodate the electrode assembly, and the shell has an opening; the cover is used to close the opening; the cover is connected to the shell through a connecting portion, and the connecting portion includes a first part and a second part arranged along the circumference of the opening, and the connection strength of the first part is less than the connection strength of the second part. The battery cell is configured to rupture from the first part when the internal pressure reaches a preset value to form a pressure relief channel, thereby reducing the risk of explosion, fire and other safety problems of the battery cell due to the failure to release the internal pressure in time, and improving the safety performance of the battery cell. In the above scheme, the pressure can be released from the first part with weaker connection strength, so that there is no need to laser groove on the cover and / or shell to form a weak area for pressure relief, so that the cover and / or shell have good structural strength, and the integrity of the shell and cover structure can be ensured.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and more specifically, to a battery cell and an electrical device. Background Art

[0002] With the development of new energy technology, battery cells are used more and more widely, for example, they can be used in mobile phones, laptops, electric vehicles, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes and electric tools, etc.

[0003] The battery cell generates electrical energy through an electrochemical reaction between the electrode assembly and the electrolyte. For battery cells, safety is one of the main concerns of users. Therefore, how to improve the safety of battery cells is a technical problem that needs to be solved urgently. Summary of the invention

[0004] The embodiments of the present application provide a battery cell and an electrical device to improve the safety performance of the battery cell.

[0005] In a first aspect, an embodiment of the present application provides a battery cell, comprising an electrode assembly, a shell and a cover; the shell is used to accommodate the electrode assembly, and the shell has an opening; the cover is used to close the opening; wherein the cover is connected to the shell by a connecting portion, the connecting portion comprises a first part and a second part arranged along the circumference of the opening, the connection strength of the first part is less than the connection strength of the second part, and the battery cell is configured to rupture from the first part when the internal pressure reaches a preset value to form a pressure relief channel.

[0006] In the above technical solution, the connection strength of the first part of the connection part is less than the connection strength of the second part of the connection part. When the pressure inside the battery cell reaches a preset value, the connection between the first part and the cover body and the shell fails, and the area where the cover body and the shell are connected by the first part forms a pressure relief channel. The pressure inside the battery cell is promptly released from the pressure relief channel formed by the failure of the first part connection, reducing the risk of safety problems such as explosion and fire in the battery cell due to the failure of internal pressure to be released in time, thereby improving the safety performance of the battery cell. In the above solution, by releasing pressure from the first part with weaker connection strength, it is not necessary to laser groove the cover body and / or the shell to form a weak area for pressure relief, so that the cover body and / or the shell have better structural strength, and the integrity of the shell and cover structure can be ensured.

[0007] In some embodiments of the first aspect of the present application, the connecting portion is a weld.

[0008] In the above technical solution, the connecting portion is a weld, and the cover body and the shell body are connected by welding, which is convenient and has good connection stability.

[0009] In some embodiments of the first aspect of the present application, on the joint surface of the cover and the housing, the width of the first portion is smaller than the width of the second portion. The width of the first portion is H1, the width of the second portion is H2, and H1 and H2 satisfy 20μm≤H2-H1≤300μm.

[0010] In some embodiments of the first aspect of the present application, on the joint surface of the cover and the housing, the width of the first portion is smaller than the width of the second portion. The width of the first portion is H1, the width of the second portion is H2, and H1 and H2 satisfy 80μm≤H2-H1≤150μm.

[0011] In the above technical solution, the width of the first part on the joint surface is smaller than the width of the second part on the joint surface. The implementation method is simple. The connection strength of the first part is smaller than the connection strength of the second part in a simple way, which is beneficial to simplify the manufacturing process of the battery cell and improve production efficiency.

[0012] In some embodiments of the first aspect of the present application, the weld includes a first weld, which is circumferentially arranged around the opening, and a second weld, which is adjacent to the first weld, and when observed in the direction perpendicular to the cover body, the first weld is a closed structure, and the second weld is a non-closed structure; the first weld includes a first section and a second section, and the disconnection positions of the first section and the second weld correspond to each other, and the two ends of the second section are respectively connected to the two ends of the first section, the first section forms a first part, and the second section and the second weld together form a second part.

[0013] In the above technical solution, the first weld is a closed structure, and the second weld is a non-closed structure. The first section of the second weld corresponds to the disconnection point of the first weld, so that the first section forms the first part, and the second section and the second weld together form the second part, that is, the first part can be formed by welding at one place, and the second part can be formed by welding at two places, so that the connection strength of the first part is less than the connection strength of the second part, and the implementation method is simple and reliable.

[0014] In some embodiments of the first aspect of the present application, the shell includes a bottom wall and a side wall, the side wall is arranged around the outer periphery of the bottom wall, one end of the side wall is connected to the bottom wall, and the other end forms an opening; the side wall has a stress concentration area, and at least part of the first part corresponds to the position of the stress concentration area.

[0015] In the above technical solution, at least part of the first part corresponds to the position of the stress concentration area. The characteristic that the stress concentration area will increase sharply when subjected to the internal pressure of the battery cell is utilized, combined with the property that the connection strength of the first part is relatively weak. When the internal pressure of the battery cell reaches a preset value, the first part can quickly connect and fail. The area where the cover and the shell are connected by the first part forms a pressure relief channel and relieves pressure, which can improve the pressure relief efficiency.

[0016] In some embodiments of the first aspect of the present application, the side wall includes a first wall portion, a step portion, and a second wall portion arranged in sequence along the circumference of the opening, the first wall portion protrudes from the second wall portion to the outside of the shell, the step portion connects the first wall portion and the second wall portion, and the stress concentration area is the step portion.

[0017] In the above technical solution, the first wall portion protrudes from the second wall portion to the outside of the shell, and the side wall of the shell changes shape sharply from the first wall portion to the second wall portion to form a step portion, thereby forming a stress concentration area at the step portion. Combined with the property that the connection strength of the first part is relatively weak, when the internal pressure of the battery cell reaches a preset value, the first part can quickly fail to connect, and the area where the cover and the shell are connected by the first part forms a pressure relief channel and relieves pressure, which can improve the pressure relief efficiency. By forming a stress concentration area by a sharp change in the shape of the side wall of the shell, the integrity of the structure of the shell can be maintained without destroying it and the structural strength of the shell can be maintained without reducing it.

[0018] In some embodiments of the first aspect of the present application, the side wall includes a third wall portion, a first corner portion and a fourth wall portion arranged in sequence along the circumference of the opening, the first corner portion connects the third wall portion and the fourth wall portion, and the stress concentration area is the first corner portion.

[0019] In the above technical solution, the first corner portion of the shell side wall structure itself is used to form a stress concentration area, and the defective area originally existing in the shell structure is used to help the battery cell to release pressure. There is no need to set up an additional stress concentration area, which simplifies the shell structure and the shell manufacturing process.

[0020] In some embodiments of the first aspect of the present application, the second part includes a first end and a second end, the first end and the second end are respectively connected to the two ends of the first part, and the second part and the first part together form a closed structure extending along the circumference of the opening; the distance from the first end to the stress concentration area is D1, and the distance from the second end to the stress concentration area is D2, 0≤D1≤3mm, 0≤D2≤3mm.

[0021] In some embodiments of the first aspect of the present application, 0≤D1≤1.5mm, 0≤D2≤1.5mm.

[0022] In the above technical solution, the provision of D1 and D2 can prevent the components inside the battery cell from flying out of the casing, and on the other hand, it also ensures a sufficient valve opening size to ensure the pressure relief rate.

[0023] In a second aspect, an embodiment of the present application provides an electrical device, comprising a battery cell provided by any embodiment of the first aspect.

[0024] In the above technical solution, the battery cell provided by the first aspect embodiment has higher safety performance, thereby improving the power safety of electrical equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 A schematic diagram of the structure of a battery cell provided in some embodiments of the present application;

[0027] Figure 2 A schematic diagram of a housing and a cover provided in some embodiments of the present application being connected;

[0028] Figure 3 This is a view observed along the thickness direction of the cover body after the housing and the cover body are connected in some embodiments of the present application;

[0029] Figure 4 for Figure 3 A1-A1 sectional view;

[0030] Figure 5 for Figure 4 The enlarged view of B1 in the middle;

[0031] Figure 6 for Figure 3 A2-A2 sectional view;

[0032] Figure 7 for Figure 6 The enlarged view of B2 in the middle;

[0033] Figure 8 A schematic diagram of the relative relationship between a first weld and a second weld provided in some embodiments of the present application;

[0034] Fig. 9 A schematic diagram of the relative relationship between a first weld and a second weld provided in some other embodiments of the present application;

[0035] Fig.10 A schematic diagram of the structure of a housing provided in some embodiments of the present application;

[0036] Fig.11 A view of the shell and the cover body observed along the thickness direction of the cover body after the shell and the cover body are connected according to some embodiments of the present application;

[0037] Fig.12 for Fig.11 The enlarged view of point A in the middle;

[0038] Fig.13 A view of the shell and the cover body observed along the thickness direction of the cover body after they are connected in some other embodiments of the present application;

[0039] Fig.14 for Fig.13 The enlarged view of B4 in the middle;

[0040] Fig.15 A view of the shell and the cover body observed along the thickness direction of the cover body after they are connected according to some other embodiments of the present application;

[0041] Fig.16 A view of the shell and the cover body observed along the thickness direction of the cover body after they are connected, provided in some other embodiments of the present application;

[0042] Fig.17 A view of the shell and the cover body observed along the thickness direction of the cover body after they are connected in some embodiments of the present application;

[0043] Fig.18 Some other embodiments of the present application provide views of the shell and the cover body after being connected, observed along the thickness direction of the cover body.

[0044] Icon: 100-battery core; 20-housing; 21-opening; 22-bottom wall; 23-side wall; 231-first surface; 232-first wall; 233-step; 2331-first arc wall; 2332-second arc wall; 234-second wall; 235-fifth wall; 256-third wall; 257-first corner; 258-fourth wall; 259-sixth wall; 2601-seventh wall; 2602-eighth wall; 2603-ninth wall; 2604-second corner; 2605-first side wall; 2606-second side wall; 2607-third side wall; 2608-fourth arc wall; 2609-fifth arc wall; 2701-sixth arc wall; 2702-main arc wall; 2703-chord wall; 24-stress concentration area; 30-cover body; 31-second surface; 32-first edge; 33-step edge; 34-second edge; 40-connecting part; 41-first part; 42-second part; 421-first end; 422-second end; 43-weld; 431-first weld; 4311-first section; 4312-second section; 432-second weld; 4321-disconnection; 50-pole; 60-liquid injection hole; 70-sealing pin; 80-joining surface; X-circumferential direction of the opening; X1-thickness direction of the cover body; X2-thickness direction of the bottom wall; Y1-thickness direction of the first wall; Z1-first direction; Z2-second direction. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0046] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0047] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0048] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0049] In the description of the embodiments of the present application, it should be noted that the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the application is usually placed when in use, or the orientation or positional relationship commonly understood by those skilled in the art, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0050] At present, judging from the development of the market situation, the application of battery cells is becoming more and more extensive. Battery cells have been widely used in electric vehicles such as electric bicycles, electric motorcycles, electric vehicles, as well as electric tools, drones, energy storage equipment and other fields. With the continuous expansion of the application field of secondary batteries, the market demand is also constantly expanding.

[0051] The battery cell includes a shell, a cover and an electrode assembly. The cover seals the opening of the shell so that the shell and the cover together form a space for accommodating the electrode assembly. Gas and high temperature are generated during the charging and discharging process of the battery cell. If the pressure is not released in time, thermal runaway may easily cause explosions, fires and other safety accidents in severe cases.

[0052] The inventors have found that in the related art, a notch is formed on the cover and / or the shell, such as by laser notching, to form a weak portion at the position corresponding to the notch. When the pressure inside the battery cell reaches a preset value, the position corresponding to the notch ruptures to form a pressure relief port to release the pressure inside the battery cell. If the notch is small, the pressure relief port formed by the rupture of the position corresponding to the notch is small, the pressure relief rate is low, the risk of explosion and fire in the battery cell is still very high, and the safety performance of the battery cell is low; if the notch is large, the structural strength of the cover and the shell will be reduced, and the safety performance of the battery cell is also low. In addition, the processing accuracy requirements and costs of the notch are high.

[0053] Based on the above considerations, in order to alleviate the problem of low safety performance of pressure relief of the battery cell through the notched groove, the inventor, after in-depth research, provides a battery cell, wherein the battery cell, the cover body and the shell are connected by a connecting part, the connecting part includes a first part and a second part arranged circumferentially along the opening of the shell, the connection strength of the first part is less than the connection strength of the second part, and the battery cell is configured to rupture from the first part when the internal pressure reaches a preset value to form a pressure relief channel.

[0054] By setting the connection strength of the first part of the connection part to be smaller than the connection strength of the second part of the connection part, when the pressure inside the battery cell reaches a preset value, the connection of the first part to the cover body and the shell fails, and a pressure relief channel is formed in the area where the cover body and the shell are connected by the first part. The pressure inside the battery cell is promptly released from the pressure relief channel formed by the failure of the connection of the first part, thereby reducing the risk of safety problems such as explosion and fire in the battery cell due to the internal pressure not being released in time, thereby improving the safety performance of the battery cell.

[0055] In the above scheme, the pressure can be released from the first part with weaker connection strength, so there is no need to laser groove the cover and / or shell to form a weak area for pressure release, so that the cover and / or shell have better structural strength and the integrity of the shell and cover structure can be ensured.

[0056] The battery cells disclosed in the embodiments of the present application can be used in, but are not limited to, electric two-wheeled vehicles, electric tools, drones, energy storage devices and other electrical equipment. The battery cells with the working conditions of the present application can be used as the power supply system of the electrical equipment, which is conducive to improving the safety performance of the battery cells and the power safety of the electrical equipment.

[0057] The embodiment of the present application provides an electric device using a battery as a power source, and the electric device may be, but is not limited to, electronic equipment, electric tools, electric vehicles, drones, and energy storage devices. Among them, electronic equipment may include mobile phones, tablets, laptops, etc., electric tools may include electric drills, electric saws, etc., and electric vehicles may include electric cars, electric motorcycles, electric bicycles, etc.

[0058] like Figure 1As shown, an embodiment of the present application provides a battery cell 100, which includes an electrode assembly (not shown in the figure), a shell 20 and a cover 30; the shell 20 is used to accommodate the electrode assembly, and the shell 20 has an opening 21; the cover 30 is used to close the opening 21; wherein the cover 30 is connected to the shell 20 through a connecting portion 40, and the connecting portion 40 includes a first portion 41 and a second portion 42 arranged along the circumferential direction X of the opening, the connection strength of the first portion 41 is less than the connection strength of the second portion 42, and the battery cell 100 is configured to rupture from the first portion 41 when the internal pressure reaches a preset value to form a pressure relief channel.

[0059] The electrode assembly is composed of a positive electrode sheet (not shown in the figure), a negative electrode sheet (not shown in the figure) and a separator (not shown in the figure). The battery mainly relies on the movement of metal ions back and forth between the positive electrode sheet and the negative electrode sheet to work. The positive electrode sheet includes a positive electrode collector and a positive electrode active material layer, and the positive electrode active material layer is coated on the surface of the positive electrode collector. In some embodiments, the positive electrode collector also has a portion that is not coated with the positive electrode active material layer, and the positive electrode collector that is not coated with the positive electrode active material layer protrudes from the positive electrode collector that has been coated with the positive electrode active material layer, and the positive electrode collector that is not coated with the positive electrode active material layer serves as a positive electrode ear. In other embodiments, the positive electrode ear can also be a structure that is separately arranged with the positive electrode collector and then electrically connected. Taking lithium-ion batteries as an example, the material of the positive electrode collector can be aluminum, and the positive electrode active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium or lithium manganese oxide, etc. The negative electrode sheet includes a negative electrode collector and a negative electrode active material layer, and the negative electrode active material layer is coated on the surface of the negative electrode collector. In some embodiments, the negative electrode current collector also has a portion that is not coated with a negative electrode active material layer, and the negative electrode current collector that is not coated with a negative electrode active material layer protrudes from the negative electrode current collector that is coated with a negative electrode active material layer, and the negative electrode current collector that is not coated with a negative electrode active material layer serves as a negative electrode ear. In other embodiments, the negative electrode ear can also be a structure that is separately provided with the negative electrode current collector and then electrically connected. The material of the negative electrode current collector can be copper, and the negative electrode active material can be carbon or silicon, etc. In order to ensure that a large current passes without melting, the number of positive electrode ears is multiple and stacked together, and the number of negative electrode ears is multiple and stacked together.

[0060] The material of the isolation film may be PP (polypropylene) or PE (polyethylene), etc. In addition, the electrode assembly may be a winding structure or a stacked structure, but the embodiments of the present application are not limited thereto.

[0061] In some embodiments, the battery cell 100 includes a pole 50, which can be insulated and arranged on the housing 20, and the pole 50 is used to be electrically connected to one of the positive ear and the negative ear, and one of the positive ear and the negative ear is electrically connected to the housing 20 or the cover 30. Of course, the pole 50 can also be insulated and arranged on the cover 30. In some embodiments, the battery cell 100 may include two poles 50, and the two poles 50 are electrically connected to the positive ear and the negative ear respectively. The two poles 50 can be both insulated and arranged on the housing 20, or both can be insulated and arranged on the end cover, or one pole 50 is insulated and arranged on the cover 30, and the other pole 50 is insulated and arranged on the housing 20.

[0062] A liquid injection hole 60 may be further provided on the cover 30 or the housing 20 , and electrolyte may be injected into the battery cell 100 through the liquid injection hole 60 , and the liquid injection hole 60 may be sealed by a sealing nail 70 .

[0063] The battery cell 100 may include one electrode assembly or may include a plurality of electrode assemblies, where a plurality refers to two or more.

[0064] The housing 20 and the cover 30 may be in various shapes, such as a cuboid, a cylinder, etc. Housings 20 and covers 30 of different shapes form battery cells 100 of different shapes.

[0065] The shell 20 is formed with a housing cavity for accommodating the electrode assembly. The shell 20 includes a bottom wall 22 and a side wall 23, the side wall 23 is arranged around the outer periphery of the bottom wall 22, one end of the side wall 23 is connected to the bottom wall 22, and the other end of the side wall 23 facing away from the bottom wall 22 forms an opening 21. The opening 21 and the bottom wall 22 are arranged relative to each other. The bottom wall 22 and the side wall 23 jointly define a housing cavity for accommodating the electrode assembly. The electrode assembly can enter the housing cavity from the opening 21 of the shell 20. The side wall 23 and the bottom wall 22 can be separately arranged and connected as a whole by welding connection, adhesive connection, bolt screw connection, etc. to form the shell 20. The side wall 23 and the bottom wall 22 can also be integrally formed.

[0066] The cover 30 may be a plate-like structure. Of course, the cover 30 may also be a hollow structure with an opening 21 on one side to form a cavity for accommodating the electrode assembly. In this embodiment, the opening side of the cover 30 and the opening side of the shell 20 overlap each other to form a space for accommodating the electrode assembly. The embodiment of the present application takes the cover 30 as a plate-like structure as an example to describe the relevant structure of the battery cell 100.

[0067] The shell 20 and the cover 30 may be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not impose any special restrictions on this.

[0068] The connection part 40 is a structure for connecting the cover body 30 and the shell 20 so that the cover body 30 can maintain a state of closing the opening 21 of the shell 20. The connection part 40 can be a component independent of the cover body 30 and the shell 20, for example, the connection part 40 can be a bolt, a screw, a buckle, etc. The connection part 40 can be a structure derived from connecting the shell 20 and the cover body 30 using a specific connection process. For example, the connection part 40 can be a weld 43 formed during the welding process of the cover body 30 and the shell 20 by using a welding process. For example, the cover body 30 and the shell 20 are connected by a fusion process, and the connection part 40 can be a fusion part formed during the fusion process of the cover body 30 and the shell 20. Therefore, according to the different connection processes between the shell 20 and the cover body 30, the structure of the connection part 40 can be expressed in different forms.

[0069] The connection strength of the connection part 40 can be understood as the structural strength of the connection part 40, the ability of the connection part 40 to resist fracture. The smaller the connection strength of the connection part 40, the smaller the force that the connection part 40 can withstand to separate the shell 20 and the cover 30. The greater the connection strength of the connection part 40, the greater the force that the connection part 40 can withstand to separate the shell 20 and the cover 30, and the connection between the shell 20 and the cover 30 is more stable.

[0070] The connection strength of the first part 41 is smaller than that of the second part 42. When the first part 41 and the second part 42 are subjected to forces increasing at the same speed, the first part 41 breaks before the second part 42. The preset value may be a structural strength limit value of the first part 41, which is smaller than the connection strength limit value of the second part 42.

[0071] The connection strength of the first part 41 of the connection part 40 is less than the connection strength of the second part 42 of the connection part 40. When the pressure inside the battery cell 100 reaches a preset value, the connection between the first part 41 and the cover 30 and the shell 20 fails, and the area where the cover 30 and the shell 20 are connected by the first part 41 forms a pressure relief channel. The pressure inside the battery cell 100 is promptly released from the pressure relief channel formed by the failure of the connection of the first part 41, reducing the risk of safety problems such as explosion and fire in the battery cell 100 due to the failure of the internal pressure to be released in time, thereby improving the safety performance of the battery cell 100. In the above scheme, the pressure can be released from the first part 41 with weaker connection strength, so that there is no need to laser groove on the cover 30 and / or the shell 20 to form a weak area for pressure relief, so that the cover 30 and / or the shell 20 have good structural strength, and the structural integrity of the shell 20 and the cover 30 can also be ensured.

[0072] Please continue to refer to Figure 1 In some embodiments, the connection portion 40 is a weld 43 .

[0073] It can be understood that the shell 20 and the cover 30 are connected by a welding process. The high temperature of the welding heat source is used to melt the welding rod and the metal at the joint of the shell 20 and the cover 30 to form a seam. After the metal of the weld 43 cools, the two shells 20 and the cover 30 are connected as a whole.

[0074] The shell 20 and the cover 30 can be welded together by using welding techniques such as gas welding, resistance welding, arc welding, and laser welding.

[0075] The connecting portion 40 is a weld 43 , and the cover 30 and the shell 20 are connected by welding, which is convenient and has good connection stability.

[0076] In order to achieve that the connection strength of the first portion 41 of the connection portion 40 is less than the connection strength of the second portion 42 of the connection portion 40, in an embodiment where the connection portion 40 is a weld 43, as shown in FIG. Figure 3-Figure 7 As shown, on the joint surface 80 of the cover body 30 and the shell body 20 , the width of the first portion 41 is smaller than the width of the second portion 42 .

[0077] The opening 21 of the housing 20 is formed on the first surface 231 of the housing 20. The cover 30 has a second surface 31 facing the first surface 231 of the housing 20. The first surface 231 and the second surface 31 are attached to form a joint surface 80 between the cover 30 and the housing 20.

[0078] The width of the first portion 41 on the joint surface 80 refers to the width of the portion where the first portion 41 intersects the joint surface 80, which can also be understood as the width of the portion where the first portion 41 intersects the first surface 231 or the width of the portion where the first portion 41 intersects the second surface 31. It is the dimension of the first portion 41 on the joint surface 80 along the thickness direction of the side wall 23, that is, Figure 5 The greater the width of the first portion 41 on the bonding surface 80 , the higher the connection strength of the first portion 41 .

[0079] The width of the second portion 42 on the joint surface 80 refers to the width of the portion where the second portion 42 intersects the joint surface 80, which can also be understood as the width of the portion where the second portion 42 intersects the first surface 231 or the width of the portion where the second portion 42 intersects the second surface 31, and is the dimension of the second portion 42 along the thickness direction of the side wall 23 on the joint surface 80, i.e., H2 in FIG. 7 . The larger the width of the second portion 42 on the joint surface 80, the higher the connection strength of the second portion 42.

[0080] The width of the first portion 41 on the bonding surface 80 is smaller than the width of the second portion 42 on the bonding surface 80 , ie, H1 < H2 , so that the connection strength of the first portion 41 is smaller than the connection strength of the second portion 42 .

[0081] The width of the first part 41 on the joint surface 80 is smaller than the width of the second part 42 on the joint surface 80. The implementation method is simple. The connection strength of the first part 41 is smaller than the connection strength of the second part 42 in a simple way, which is beneficial to simplifying the manufacturing process of the battery cell 100 and improving production efficiency.

[0082] There are many ways to make the width of the first part 41 on the joint surface 80 smaller than the width of the second part 42 on the joint surface 80. For example, during welding, a low-power welding gun is used for the first part 41 and a high-power welding gun is used for the second part 42, so that the width of the first part 41 on the joint surface 80 is smaller than the width of the second part 42 on the joint surface 80.

[0083] Specifically, on the joint surface of the cover body and the shell body, the width of the first part is H1, the width of the second part is H2, and H1 and H2 satisfy 20μm≤H2-H1≤300μm.

[0084] More preferably, H1 and H2 satisfy 80 μm ≤ H2 - H1 ≤ 150 μm. The connection strength between the first part and the second part is accurately controlled by limiting the width, so that the formation of pressure relief can be more intuitively controlled.

[0085] For example, Figure 1 , Figure 8 , Fig. 9 As shown, in some embodiments, the weld 43 includes a first weld 431 and a second weld 432. When viewed in a direction perpendicular to the cover body 30, the first weld 431 is a closed structure, and the second weld 432 is a non-closed structure; the first weld 431 includes a first section 4311 and a second section 4312, and the positions of the disconnection point 4321 of the first section 4311 and the second weld 432 correspond to each other, and the two ends of the second section 4312 are respectively connected to the two ends of the first section 4311, and the first section 4311 forms the first part 41, and the second section 4312 and the second weld 432 together form the second part 42.

[0086] The first weld 431 is continuous and closed along the circumferential direction X of the opening to form a closed structure. The first weld 431 may be a closed structure that matches the contour of the opening 21. For example, if the opening 21 of the shell 20 is circular, the first weld 431 may be an annular closed structure; if the opening 21 of the shell 20 is rectangular, the first weld 431 may be a rectangular closed structure.

[0087] Along the circumferential direction X of the opening, the second weld 432 is continuous but the head and tail ends are not closed, and the unclosed head and tail ends of the second weld 432 are the disconnection points 4321 of the second weld 432. The second weld 432 can also extend along the extension direction of the contour line of the opening 21 to form a non-enclosed structure that matches the shape of a partial area of ​​the contour of the opening 21.

[0088] The second weld 432 may be arranged around the outer periphery of the second weld 432. Of course, the first weld 431 may also be arranged around the outer periphery of the second weld 432. On the joint surface 80, there may be a gap between the first weld 431 and the second weld 432, or the first weld 431 and the second weld 432 may be connected and integrated with each other. On the surface of the cover 30 facing away from the shell 20, there may be a gap between the first weld 431 and the second weld 432, or the first weld 431 and the second weld 432 may be connected and integrated with each other.

[0089] In the embodiment where the first weld 431 and the second weld 432 are connected and integrated with each other on the joint surface 80, the width of the second portion 42 on the joint surface 80 is the dimension of the overall structure formed by connecting the first weld 431 and the second weld 432 along the thickness direction of the side wall 23 on the joint surface 80, that is, Figure 8 H1 in.

[0090] In the embodiment where there is a gap between the first weld 431 and the second weld 432, the width of the second portion 42 on the joint surface 80 is the sum of the dimension of the first weld 431 on the joint surface 80 along the thickness direction of the side wall 23 and the dimension of the second weld 432 on the joint surface 80 along the thickness direction of the side wall 23. Fig. 9 As shown, the width of the first weld 431 on the joint surface 80 is H 21 The width of the second weld 432 on the joint surface 80 is H 22 , then the width H2 of the second portion 42 on the joint surface 80 is H 21 +H 22 , 9 is not marked in Figure H2.

[0091] The first weld 431 is a closed structure, and the second weld 432 is a non-closed structure. The first section 4311 of the second weld 432 and the disconnection point 4321 of the first weld 431 correspond to each other, so that the first section 4311 forms the first part 41, and the second section 4312 and the second weld 432 together form the second part 42, that is, the first part 41 can be formed by welding at one place, and the second part 42 can be formed by welding at two places, so that the connection strength of the first part 41 is less than the connection strength of the second part 42, and the implementation method is simple and reliable.

[0092] like Figure 1 , Figure 2 As shown, in some embodiments, the shell 20 includes a bottom wall 22 and a side wall 23, the side wall 23 is arranged around the outer periphery of the bottom wall 22, one end of the side wall 23 is connected to the bottom wall 22, and the other end forms an opening 21; the side wall 23 has a stress concentration area 24, and at least a portion of the first portion 41 corresponds to the position of the stress concentration area 24.

[0093] The stress concentration region 24 of the side wall 23 is a region where stress is significantly increased in the side wall 23. Fatigue cracks are easily generated in the stress concentration region 24 of the side wall 23. If the material of the side wall 23 is a brittle material, the stress concentration region 24 of the side wall 23 can also cause static load fracture.

[0094] At least part of the first portion 41 corresponds to the stress concentration area 24. It can be understood that, when viewed along the thickness direction X2 of the bottom wall, at least part of the first portion 41 overlaps with the stress concentration area 24. In the embodiment where the end cover is a plate-like structure, the thickness direction X2 of the bottom wall is parallel to the thickness direction X1 of the cover body.

[0095] At least a portion of the first portion 41 corresponds to the position of the stress concentration area 24. By utilizing the characteristic that the stress of the stress concentration area 24 will increase sharply when subjected to the internal pressure of the battery cell 100, combined with the property of the first portion 41 having a relatively weak connection strength, when the internal pressure of the battery cell 100 reaches a preset value, the first portion 41 can quickly connect and fail, and the area where the cover body 30 and the shell body 20 are connected by the first portion 41 forms a pressure relief channel and relieves pressure, thereby improving the pressure relief efficiency.

[0096] There are many ways to form the stress concentration area 24 on the side wall 23, such as Figure 3 , Fig.10 As shown, in some embodiments, the side wall 23 includes a first wall portion 232, a step portion 233, and a second wall portion 234 arranged in sequence along the circumferential direction X of the opening, the first wall portion 232 protrudes from the second wall portion 234 to the outside of the shell 20, the step portion 233 connects the first wall portion 232 and the second wall portion 234, and the stress concentration area 24 is the step portion 233.

[0097] The first wall and the second wall are arranged in parallel, and when viewed along the thickness direction of the first wall, the first wall and the second wall do not overlap at all. The thickness direction of the first wall is parallel to the thickness direction of the second wall, and the thickness direction of the first wall is perpendicular to the thickness direction X2 of the bottom wall. Along the thickness direction Y1 of the first wall portion, the side wall 23 also has a fifth wall portion 235 opposite to the first wall. Along the thickness direction Y1 of the first wall portion, the distance between the first wall portion 232 and the fifth wall portion 235 is greater than the distance between the second wall portion 234 and the fifth wall portion 235, that is, L1>L2 in the figure.

[0098] The step portion 233 is located between the first wall and the second wall. The step portion 233 is a connecting structure that transitions from the first wall to the second wall. The step portion 233 is a part of the side wall 23. One end of the step portion 233 is connected to the first wall, and the other end of the step portion 233 is connected to the second wall. Fig.10As shown, the step portion 233 includes a first arc wall 2331 and a second arc wall 2332 connected to each other. The end of the first arc wall 2331 away from the second arc wall 2332 is connected to one end of the first wall, and the end of the second arc wall 2332 away from the first arc wall 2331 is connected to one end of the second wall.

[0099] In other embodiments, the step portion 233 may also include a straight wall (not shown in the figure), which connects the end of the first arc wall 2331 away from the first wall and the end of the second arc wall 2332 away from the second wall. It can be understood that the first wall and the straight wall are indirectly connected through the first arc wall 2331, and the second wall and the straight wall are indirectly connected through the second arc wall 2332.

[0100] In other embodiments, the step portion 233 may also include only a straight portion, one end of the straight portion is directly connected to the first wall, and the other end of the straight portion is directly connected to the second wall.

[0101] The straight wall and the first wall can be arranged vertically, or at an acute angle or an obtuse angle. The straight wall and the second wall can be arranged vertically, or at an acute angle or an obtuse angle.

[0102] The first wall portion 232 protrudes from the second wall portion 234 to the outside of the shell 20, and the side wall 23 of the shell 20 changes shape sharply from the first wall portion 232 to the second wall portion 234 to form a step portion 233, thereby forming a stress concentration area 24 at the step portion 233. Combined with the property of the first portion 41 having a weak connection strength, when the internal pressure of the battery cell 100 reaches a preset value, the first portion 41 can quickly fail to connect, and the area where the cover 30 and the shell 20 are connected by the first portion 41 forms a pressure relief channel and relieves pressure, which can improve the pressure relief efficiency. By forming the stress concentration area 24 by the sharp change in shape of the side wall 23 of the shell 20, the integrity of the structure of the shell 20 can be maintained and the structural strength of the shell 20 can be maintained.

[0103] In some embodiments, the side wall 23 is further provided with a pole 50 and a liquid injection hole 60, and one of the positive electrode ear and the negative electrode ear is electrically connected to the pole 50. Fig.10 The pole 50 shown can be arranged on the first wall portion 232, the injection hole 60 can be arranged on the second wall portion 234, and the injection hole 60 is sealed by the sealing nail 70. Of course, the pole 50 can also be arranged on the second wall portion 234, so that the space difference between the first wall portion 232 and the second wall portion 234 in the thickness direction Y1 of the first wall portion can be fully utilized to reduce the overall size of the battery cell 100.

[0104] like Fig.11 , Fig.12As shown, in the embodiment where the side wall 23 includes the first wall portion 232, the step portion 233 and the second wall portion 234, the cover 30 has a first side portion 32, a step side portion 33 and a second side portion 34, the first side portion 32 corresponds to the first wall portion 232, the step side portion 33 corresponds to the step portion 233, and the second side portion 34 corresponds to the second wall portion 234, so that the cover 30 can better match the contour shape of the opening 21 of the shell 20 to better close the opening 21. Among them, the outer surfaces of the first side portion 32 and the first wall portion 232 are coplanar, and the outer surface of the first wall portion 232 is the surface away from the inside of the battery cell 100 along the thickness direction of the first wall. The outer surfaces of the step side portion 33 and the step portion 233 are coplanar, and the outer surface of the step portion 233 refers to the surface of the step portion 233 away from the inside of the battery cell 100. The second side portion 34 and the outer surface of the second wall portion 234 are coplanar, and the outer surface of the second wall portion 234 is a surface away from the interior of the battery cell 100 along the thickness direction of the second wall (the thickness direction Y1 of the first wall portion).

[0105] In some embodiments, the second portion 42 includes a first end 421 and a second end 422 that are disconnected from each other, the first end 421 and the second end 422 are respectively connected to the two ends of the first portion 41, and the second portion 42 and the first portion 41 together form a closed structure extending along the circumferential direction X of the opening; the distance from the first end 421 to the stress concentration area 24 is D1, and the distance from the second end 422 to the stress concentration area is D2, 0≤D1≤3mm, 0≤D2≤3mm.

[0106] Observing along the thickness direction X1 of the cover body, the projection of the second portion 42 completely covers the projection of the stress concentration area 24. In the embodiment where the weld 43 includes a first weld 431 and a second weld 432, and the first weld 431 is a closed structure and the second weld 432 is a non-closed structure, the first end 421 and the second end 422 are at positions corresponding to the tail end of the second weld 432.

[0107] In the embodiment where the side wall 23 includes the first wall portion 232, the step portion 233, and the second wall portion 234, the first end 421 is disposed close to the first wall portion 232, and the second end 422 is disposed close to the second wall portion 234. The distance D1 from the first end 421 to the stress concentration region 24 is the distance between the first end 421 and the end of the first arc wall 2331 away from the second arc wall 2332. The distance D2 from the second end 422 to the stress concentration region 24 is the distance between the second end 422 and the end of the second arc wall 2332 away from the second arc wall 2332.

[0108] D1 can be 0mm, 0.3mm, 0.5mm, 0.8mm, 1mm, 1.3mm, 1.5mm, 1.8mm, 2mm, 2.3mm, 2.5mm, 2.8mm, 3mm, etc. D2 can be 0mm, 0.3mm, 0.5mm, 0.8mm, 1mm, 1.3mm, 1.5mm, 1.8mm, 2mm, 2.3mm, 2.5mm, 2.8mm, 3mm, etc. D1 and D2 can be the same or different.

[0109] Such arrangement of D1 and D2 can prevent the components inside the battery cell from flying out of the casing.

[0110] Preferably, 0≤D1≤1.5mm, 0≤D2≤1.5mm.

[0111] Exemplarily, D1 may be 0 mm, 0.2 mm, 0.4 mm, 0.6 mm, 1.1 mm, 1.4 mm, 1.5 mm, etc. D1 may be 0 mm, 0.2 mm, 0.4 mm, 0.6 mm, 1.1 mm, 1.4 mm, 1.5 mm, etc.

[0112] Set 0≤D1≤1.5mm, 0≤D2≤1.5mm to ensure that the battery cell has sufficient valve opening size to ensure the pressure relief rate.

[0113] In some embodiments, Fig.13 As shown, the side wall 23 includes a third wall portion 256 , a first corner portion 257 and a fourth wall portion 258 arranged in sequence along the circumferential direction X of the opening, the first corner portion 257 connects the third wall portion 256 and the fourth wall portion 258 , and the stress concentration area 24 is the first corner portion 257 .

[0114] The battery cell 100 is a rectangular structure. The side wall 23 is a rectangular frame structure. The third side wall 2607 and the fourth side wall 23 are two adjacent and perpendicular wall portions of the side wall 23, and the third wall portion 256 and the fourth wall portion 258 are connected by the first corner portion 257. The first corner portion 257 is a third arc wall. For the structure of the shell 20 itself, there is a stress concentration phenomenon in the first corner portion 257, therefore, the stress concentration area 24 is the first corner portion 257, i.e., the structural characteristics of the shell 20 itself are utilized.

[0115] The stress concentration area 24 is formed by utilizing the first corner portion 257 of the side wall 23 of the shell 20 , and the defective area originally existing in the structure of the shell 20 is used to help the battery cell 100 release pressure. There is no need to set up an additional stress concentration area 24 , thereby simplifying the structure of the shell 20 and the manufacturing process of the shell 20 .

[0116] In this embodiment, if Fig.14As shown, the first end 421 is disposed close to the third wall portion 256, and the second end 422 is disposed close to the fourth wall portion 258. The distance D1 from the first end 421 to the stress concentration region 24 is the distance between the first end 421 and the end of the first corner portion 257 away from the fourth side wall 23. The distance D2 from the second end 422 to the stress concentration region 24 is the distance between the second end 422 and the end of the first corner portion 257 away from the third wall portion 256.

[0117] The housing 20 may also be in other structural forms, such as Fig.15 As shown, the housing 20 is in an L-shaped structure. The side wall 23 includes a sixth wall portion 259 and a seventh wall portion 2601 arranged relatively spaced apart along a first direction Z1, and an eighth wall portion 2602 and a ninth wall portion 2603 arranged relatively spaced apart along a second direction Z2, wherein the first direction Z1 is perpendicular to the second direction Z2. The sixth wall portion 259 and the eighth wall portion 2602 are connected and arranged vertically, and the connecting position of the sixth wall portion 259 and the eighth wall portion 2602 forms the outer corner area of ​​the L-shaped housing 20. The seventh wall portion 2601 and the ninth wall portion 2603 are arranged vertically and connected through the second corner portion 2604, and the second corner portion 2604 is a third arc wall, and the second corner portion 2604 forms the inner corner area of ​​the L-shaped housing 20. The stress concentration area 24 of the housing 20 is the second corner portion 2604.

[0118] For example, Fig.16 As shown, the side wall 23 includes a first side wall 2605 and a second side wall 2606 arranged relatively spaced apart along a first direction Z1, and a third side wall 2607 and a fourth arc wall 2608 arranged relatively along a second direction Z2, and the first direction Z1 is perpendicular to the second direction Z2. The first side wall 2605, the second side wall 2606 and the third side wall 2607 are plate-like structures. One end of the first side wall 2605 and one end of the second side wall 2606 are connected through the fourth arc wall 2608. The other end of the first side wall 2605 away from the fourth arc wall 2608 is connected to the third side wall 2607 through the fifth arc wall 2609, and the other end of the second side wall 2606 away from the fourth arc wall 2608 is connected to the third side wall 2607 through the sixth arc wall 2701. The fifth arc wall 2609 and the sixth arc wall 2701 can both be stress concentration areas 24.

[0119] like Fig.17 As shown, the side wall 23 includes a major arc wall 2702 and a chord wall 2703 , two ends of the major arc wall 2702 are respectively connected to two ends of the chord wall 2703 , and the stress concentration area 24 may be the chord wall 2703 .

[0120] Of course, the side wall 23 of the housing 20 may not form the stress concentration area 24. Fig.18As shown, the shell 20 is a cylindrical structure, and the side wall 23 of the shell 20 is also a cylindrical structure. The side wall 23 has the same structure at any point along the circumference X of the opening, and no stress concentration area 24 is formed. When the internal pressure of the battery cell 100 reaches a preset value.

[0121] The above are only preferred embodiments 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 variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A battery cell, characterized in that: include: Electrode assembly; A shell, used to accommodate the electrode assembly, the shell having an opening; A cover body, used for closing the opening; Wherein, the cover body is connected to the shell through a connecting part, and the connecting part includes a first part and a second part arranged along the circumference of the opening, the connection strength of the first part is less than the connection strength of the second part, and the battery cell is configured to rupture from the first part when the internal pressure reaches a preset value to form a pressure relief channel.

2. The battery cell according to claim 1, characterized in that: The connecting portion is a weld.

3. The battery cell according to claim 2, characterized in that: On the joint surface of the cover body and the shell, the width of the first part is H1, the width of the second part is H2, and H1 and H2 satisfy 20μm≤H2-H1≤300μm.

4. The battery cell according to claim 3, characterized in that: On the joint surface of the cover body and the shell, the width of the first part is H1, the width of the second part is H2, and H1 and H2 satisfy 80μm≤H2-H1≤150μm.

5. The battery cell according to claim 2, characterized in that: The weld includes a first weld, which is circumferentially arranged around the opening, and a second weld, which is adjacent to the first weld. When viewed in a direction perpendicular to the cover body, the first weld is a closed structure, and the second weld is a non-closed structure. The first weld includes a first section and a second section, the first section and the second weld are disconnected at corresponding positions, two ends of the second section are respectively connected to two ends of the first section, the first section forms the first part, and the second section and the second weld together form the second part.

6. The battery cell according to claim 1, characterized in that: The housing comprises: bottom wall; A side wall is arranged around the outer periphery of the bottom wall, one end of the side wall is connected to the bottom wall, and the other end of the side wall surrounds the opening; The side wall has a stress concentration area, and at least a portion of the first portion corresponds to a position of the stress concentration area.

7. The battery cell according to claim 6, characterized in that: The side wall includes a first wall portion, a step portion, and a second wall portion which are sequentially arranged along the circumference of the opening, the first wall portion protrudes from the second wall portion to the outside of the shell, the step portion connects the first wall portion and the second wall portion, and the stress concentration area is the step portion.

8. The battery cell according to claim 6, characterized in that: The side wall includes a third wall portion, a first corner portion, and a fourth wall portion which are sequentially arranged along the circumference of the opening, the first corner portion connects the third wall portion and the fourth wall portion, and the stress concentration area is the first corner portion.

9. The battery cell according to claim 6, characterized in that: The second part includes a first end and a second end, the first end and the second end are respectively connected to two ends of the first part, and the second part and the first part together form a closed structure extending along the circumference of the opening; The distance from the first end to the stress concentration area is D1, and the distance from the second end to the stress concentration area is D2, 0≤D1≤3mm, 0≤D2≤3mm.

10. The battery cell according to claim 9, characterized in that: 0≤D1≤1.5mm, 0≤D2≤1.5mm.

11. An electrical device, characterized in that: Comprising the battery cell according to any one of claims 1-10.

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