Battery cell, battery and electrical equipment

Abstract

The present application provides a battery cell, a battery and an electrical device, relating to the technical field of batteries. The battery cell includes an electrode assembly; a plurality of welding portions are provided on one side in the width direction of the first pole piece of the electrode assembly, and the plurality of welding portions are arranged at intervals along the length direction of the first pole piece; the first pole piece includes a winding starting end and a winding ending end, the one of the plurality of welding portions closest to the winding starting end is the first welding portion, and the one of the plurality of welding portions closest to the winding ending end is the second welding portion. The first pole piece includes a main body section from the first welding portion to the second welding portion, the main body section is equally divided into a plurality of sub-sections with a length of L, and the total length of the welding portions of each sub-section is not less than 5%*L, where 200 mm ≤ L ≤ 1200 mm, so that the distribution of the welding portions formed by welding the first pole piece and the current collector member is more reasonable, the internal resistance of the battery cell is reduced, the actual over-current requirement can be met, and thus the power performance of the battery cell is improved.

Description

Technical Field

[0001] This application relates to the technical field of batteries, and in particular, to a battery cell, a battery, and an electrical device. Background Art

[0002] Batteries are widely used in electronic devices, such as mobile phones, laptop computers, battery cars, electric vehicles, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and electric tools.

[0003] In the development of battery technology, in addition to the safety performance of the battery, the power performance of the battery is also an issue that cannot be ignored. Due to the large internal resistance of existing batteries, the power performance of the batteries is relatively low. Therefore, how to improve the power performance of the battery has become an urgent problem to be solved in the field of battery technology. Summary of the Invention

[0004] Embodiments of this application provide a battery cell, a battery, and an electrical device to improve the power performance of the battery.

[0005] In a first aspect, an embodiment of this application provides a battery cell, including an electrode assembly; the electrode assembly includes a first electrode tab, and a plurality of welding parts are provided on one side in the width direction of the first electrode tab, and the plurality of welding parts are arranged at intervals along the length direction of the first electrode tab;

[0006] The electrode assembly is a wound structure. The first electrode tab includes a winding start end and a winding end. The one of the plurality of welding parts closest to the winding start end is the first welding part, and the one of the plurality of welding parts closest to the winding end is the second welding part. The first electrode tab includes a main body section, and the main body section extends from the edge of the first welding part close to the winding start end to the edge of the second welding part close to the winding end. The main body section is equally divided into a plurality of sub-sections with a length of L, and the total length of the welding parts of each sub-section is not less than 5%*L, where 200 mm ≤ L ≤ 1200 mm.

[0007] In the above technical solution, in the existing welding of the current collector member and the electrode assembly, laser continuous linear welding or pulsed spot welding is used, and the shapes of the welding marks include X-shaped, annular, etc. After the pole piece is unfolded, it will be found that along the length direction of the pole piece, the welding parts in some sections are denser, and the welding parts in some sections are sparser, and the distribution of the welding parts on the pole piece is uneven. For the sections with sparser welding parts, the effective welding length of the pole piece (i.e., the total length of the welding parts in this section) is not sufficient to match the length of the pole piece, resulting in poor current-carrying capacity between the pole piece and the current collector member, large internal resistance of the battery cell, and reduced power performance of the battery cell. After welding on one side in the width direction of the current collector member and the first pole piece, a plurality of welding parts arranged at intervals are formed in the length direction of the first pole piece. Along the length direction of the first pole piece, the main body part of the first pole piece defined by the first welding part near the winding starting end and the second welding part near the winding ending end is divided into a plurality of equal-length sub-segments. The total length of the welding parts of each sub-segment is not less than 5% of the length of the sub-segment, so that the distribution of the welding parts formed by welding the first pole piece and the current collector member is more reasonable, the internal resistance of the battery cell is reduced, the actual current-carrying requirements can be met, and thus the power performance of the battery cell is improved. The length of the sub-segment is between 200 mm and 1200 mm, so that the winding length of the first pole piece meets the actual product requirements and the battery cell has a high energy density.

[0008] In some embodiments of the first aspect of the present application, the absolute value of the difference between the total lengths of the welding parts of any two of the sub-segments is less than or equal to 10 mm.

[0009] In the above technical solution, the absolute value of the difference between the total lengths of the welding parts of any two sub-segments is controlled within 10 mm, and the difference in the total lengths of the welding parts of each sub-segment is minimized as much as possible, so that the distribution of the welding parts is more reasonable, which is beneficial to reducing the internal resistance of the battery cell, and the difference in the current-carrying capacity of each sub-segment is small, meeting the actual current-carrying requirements, and thus improving the power performance of the battery cell. Controlling the absolute value of the difference between the total lengths of the welding parts of any two sub-segments within 10 mm is equivalent to the welding width error of each sub-segment being within 10 mm, allowing an error in the total welding length between each sub-segment, and the welding difficulty can be reduced.

[0010] In some embodiments of the first aspect of the present application, the total lengths of the welding parts of any two of the sub-segments are the same.

[0011] In the above technical solution, if the total lengths of the welding parts of any two sub-segments are the same, there is no difference in the total lengths of the welding parts of each sub-segment, so that the distribution of the welding parts is more reasonable, the internal resistance of the battery cell is minimized as much as possible, and the current-carrying capacity of each sub-segment is the same, meeting the actual current-carrying requirements, and thus the power performance of the battery cell is improved.

[0012] In some embodiments of the first aspect of the present application, the absolute value of the difference in the number of the welding portions of any two of the sub-segments is less than or equal to 10.

[0013] In the above technical solution, the absolute value of the difference in the number of the welding portions of any two sub-segments is controlled within 10, and the difference in the total length of the welding portions of each sub-segment is minimized as much as possible, so that the distribution of the welding portions is more reasonable, which is beneficial to reducing the internal resistance of the battery cell, making the over-current capabilities of each sub-segment less different, meeting the actual over-current requirements, and thus improving the power performance of the battery cell. Controlling the absolute value of the difference in the number of the welding portions of any two sub-segments within 10 is equivalent to allowing the number of the welding portions of each sub-segment to be different, allowing an error in the total welding length between each sub-segment, and being able to reduce the welding difficulty.

[0014] In some embodiments of the first aspect of the present application, the number of the welding portions of any two of the sub-segments is the same.

[0015] In the above technical solution, if the number of the welding portions of any two sub-segments is the same, the difference in the total length of the welding portions of each sub-segment is minimized as much as possible, so that the distribution of the welding portions is more reasonable, which is beneficial to reducing the internal resistance of the battery cell, making the over-current capabilities of each sub-segment the same, meeting the actual over-current requirements, and thus improving the power performance of the battery cell.

[0016] In some embodiments of the first aspect of the present application, the first pole piece further includes a winding start segment continuously provided with the main body segment, and the winding start segment extends from the winding start end to the edge of the first welding portion close to the winding start end.

[0017] In the above technical solution, the winding start segment extends from the winding start end to the edge of the first welding portion close to the winding start end, that is, the winding start end and the edge of the first welding portion close to the winding start end define the winding start segment. No welding portion is formed on the winding start segment, and there is no welding relationship between the winding start segment and the current collecting member, which is convenient for welding the current collecting member and the electrode terminal to output the electric energy of the battery cell.

[0018] In some embodiments of the first aspect of the present application, the length of the winding start segment is A, and A≤L is satisfied.

[0019] In the above technical solution, along the length direction of the first pole piece, the distance between the winding start end and the first welding portion is less than the length of the characteristic segment, that is, the length of the winding start segment without the welding portion is less than the sub-segment provided with the welding portion, so that the length of the section of the first pole piece without the welding portion will not be too long, ensuring the stable output of the electric energy of the battery cell.

[0020] In some embodiments of the first aspect of the present application, the first pole piece further includes a winding end section continuously provided with the main body section, and the winding end section extends from the winding end to the edge of the second welding part close to the winding end.

[0021] In the above technical solution, the winding end section extends from the winding end to the edge of the second welding part close to the winding end, that is, the winding end and the edge of the second welding part close to the winding end define the winding end section. No welding part is provided on the winding end section, and there is no welding relationship between the winding end section and the corresponding current collector member, which facilitates the welding of the current collector member and the electrode terminal to output the electric energy of the battery cell.

[0022] In some embodiments of the first aspect of the present application, the length of the winding end section is B, and B ≤ L is satisfied.

[0023] In the above technical solution, along the length direction of the first pole piece, the length of the winding end section is less than the length of the sub-section, that is, the length of the winding start section without a welding part is less than the length of the sub-section with a welding part, so that the length of the section of the first pole piece without a welding part will not be too long, ensuring the stable output of the electric energy of the battery cell.

[0024] In some embodiments of the first aspect of the present application, in two adjacent turns of the first pole pieces, the number of welding parts in the turn close to the winding center of the electrode assembly is less than the number of welding parts in the turn far from the winding center.

[0025] In the above technical solution, for a wound electrode assembly, in two adjacent turns of the first pole pieces, the length of the turn close to the winding center is less than the length of the turn far from the winding center. During welding, the number of welding parts formed in the turn close to the winding center of the wound electrode assembly is less than the number of welding parts in the turn far from the winding center, so that the length of each turn of the first pole piece and the number and total length of the welding parts corresponding to each turn of the first pole piece are matched, which can make the distribution of the welding parts more reasonable, reduce the internal resistance of the battery cell, meet the actual over-current demand, and thus improve the power performance of the battery cell.

[0026] In some embodiments of the first aspect of the present application, the battery cell further includes a housing, an end cover assembly and a current collector member; the housing is used to accommodate the electrode assembly, and the housing has an opening; the end cover assembly includes an end cover and an electrode terminal, the end cover is used to cover the opening, and the electrode terminal is installed on the end cover; the current collector member is located between the end cover and the electrode assembly and is used to connect the pole ear part of the electrode assembly and the electrode terminal. The pole ear part is formed by winding through the uncoated area of the first pole piece, and at least a part of the current collector member is welded to the pole ear part to form the plurality of welding parts.

[0027] In the above technical solution, at least a part of the current collector member is welded to the tab portion to form a plurality of welding portions. Along the length direction of the first electrode sheet, the main body portion of the first electrode sheet defined by the first welding portion near the winding start end and the second welding portion near the winding end is divided into a plurality of equal-length sub-segments. The total length of the welding portions of each sub-segment is not less than 5% of the length of the sub-segment, so that the distribution of the welding portions formed by welding the first electrode sheet and the current collector member is more reasonable, the internal resistance of the battery cell is reduced, the actual over-current requirement can be met, and thus the power performance of the battery cell is improved.

[0028] In some embodiments of the first aspect of the present application, the first electrode sheet further includes a winding start segment from the winding start end to the edge of the first welding portion near the winding start end. The uncoated area of the main body segment is wound to form a first part, and the uncoated area of the winding start segment is wound to form a second part. The second part is located radially inside the first part. The current collector member includes a first current collector portion and a second current collector portion arranged continuously in the radial direction. The first current collector portion is disposed opposite to the first part along the width direction of the first electrode sheet and is welded to the first part to form the plurality of welding portions. The second current collector portion is disposed opposite to the second part along the width direction of the first electrode sheet and is welded to the electrode terminal.

[0029] In the above technical solution, the uncoated area of the main body segment is wound to form a first part and is welded to the first current collector portion of the current collector member to realize the electrical connection between the electrode assembly and the current collector member. The winding start segment extends from the winding start end to the edge of the first welding portion near the winding start end, that is, the winding start end and the edge of the first welding portion near the winding start end define the winding start segment. No welding portion is formed on the winding start segment, that is, there is no welding relationship between the second part formed by winding the uncoated area of the winding start segment and the current collector member, and no welding mark is formed on the second current collector portion opposite to the second part, which facilitates the welding of the current collector member to the electrode terminal through the second current collector portion to output the electrical energy of the battery cell.

[0030] In some embodiments of the first aspect of the present application, the first electrode sheet further includes a winding end segment from the winding end to the edge of the second welding portion near the winding end. The uncoated area of the main body segment is wound to form a first part, and the uncoated area of the winding end segment is wound to form a third part. The third part is located radially outside the first part. The current collector member includes a first current collector portion and a third current collector portion arranged continuously in the radial direction. The first current collector portion is disposed opposite to the first part along the width direction of the first electrode sheet and is welded to the first part to form the plurality of welding portions. The third current collector portion is disposed opposite to the third part along the width direction of the first electrode sheet and is welded to the electrode terminal.

[0031] In the above technical solution, the uncoated area of the main body section is wound to form a first part and welded to the first current collector part of the current collector member, realizing the electrical connection between the electrode assembly and the current collector member. The winding end section is defined from the winding end to the edge of the second welding part close to the winding end, that is, the winding end and the edge of the second welding part close to the winding end define the winding end section. No welding part is formed on the winding end section, that is, there is no welding relationship between the third part formed by winding the uncoated area of the winding end section and the current collector member. Then, no welding mark is formed on the third current collector part opposite to the third part, which facilitates the welding of the current collector member to the electrode terminal through the third current collector part to output the electric energy of the battery cell.

[0032] In a second aspect, an embodiment of the present application provides a battery, including the battery provided by the embodiment of the first aspect.

[0033] In the above technical solution, for a battery including the battery cell provided by the embodiment of the first aspect, the main body part of the first pole piece of the battery cell defined by the first welding part near the winding start end and the second welding part near the winding end is divided into a plurality of equal-length sub-segments. The total length of the welding parts of each sub-segment is not less than 5% of the length of the sub-segment, so that the distribution of the welding parts formed by welding the first pole piece and the current collector member is more reasonable, reducing the internal resistance of the battery cell, meeting the actual overcurrent requirement, and thus improving the power performance of the battery.

[0034] In a third aspect, an embodiment of the present application provides an electrical device, including the battery provided by the embodiment of the second aspect.

[0035] In the above technical solution, for the electrical device using the battery provided by the embodiment of the second aspect, the main body part of the first pole piece of the battery cell defined by the first welding part near the winding start end and the second welding part near the winding end is divided into a plurality of equal-length sub-segments. The total length of the welding parts of each sub-segment is not less than 5% of the length of the sub-segment, so that the distribution of the welding parts formed by welding the first pole piece and the current collector member is more reasonable, reducing the internal resistance of the battery, meeting the actual overcurrent requirement, and thus improving the power performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present application, so they should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0037] Figure 1 It is a schematic structural diagram of a vehicle provided by some embodiments of the present application;

[0038] Figure 2Schematic diagram of the structure of the battery provided by some embodiments of the present application;

[0039] Figure 3 Explosion diagram of the battery cell provided by some embodiments of the present application;

[0040] Figure 4 Schematic diagram of the structure of the electrode assembly provided by some embodiments of the present application;

[0041] Figure 5 Expanded view of the first electrode tab provided by some embodiments of the present application;

[0042] Figure 6 Schematic diagram of the dimensions of the first electrode tab in the expanded state provided by some embodiments of the present application;

[0043] Figure 7 Schematic diagram of the structure of the electrode assembly provided by other embodiments of the present application;

[0044] Figure 8 Expanded view of the first electrode tab provided by other embodiments of the present application;

[0045] Figure 9 Schematic diagram of the dimensions of the first electrode tab in the expanded state provided by other embodiments of the present application;

[0046] Figure 10 Expanded view of the first electrode tab provided by still other embodiments of the present application;

[0047] Figure 11 Schematic diagram of the dimensions of the first electrode tab in the expanded state provided by still other embodiments of the present application;

[0048] Figure 12 Schematic diagram of the electrode assembly provided by still other embodiments of the present application;

[0049] Figure 13 Schematic diagram of the structure of the electrode assembly provided by yet other embodiments of the present application;

[0050] Figure 14 Schematic diagram of the current collector member after welding provided by some embodiments of the present application;

[0051] Figure 15 Schematic diagram of the current collector member after welding provided by other embodiments of the present application;

[0052] Figure 16 Schematic diagram of the current collector member after welding provided by still other embodiments of the present application.

[0053] Icons: 1000 - vehicle; 100 - battery; 10 - housing; 11 - accommodation space; 12 - first part; 13 - second part; 20 - battery cell; 21 - housing; 211 - opening; 22 - electrode assembly; 221 - first electrode tab; 2211 - coated area; 2212 - uncoated area; 222 - welding part; 222a - first welding part; 222b - second welding part; 223 - winding start end; 224 - winding end; 225 - main body section; 2251 - sub - section; 226 - winding center hole; 226a - first area; 226b - second area; 226c - third area; 226d - fourth area; 226e - fifth area; 226f - sixth area; 227a - first ring; 227b - second ring; 227c - third ring; 227d - fourth ring; 227e - fifth ring; 228 - winding start section; 229 - winding end section; 23 - end - cap assembly; 231 - end - cap; 232 - electrode terminal; 24 - current - collecting member; 241 - first current - collecting part; 242 - second current - collecting part; 243 - third current - collecting part; 200 - controller; 300 - motor; X - width direction of the first electrode tab; Y - length direction of the first electrode tab. Detailed implementation manners

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Apparently, the described embodiments are some, but not all, of the embodiments of the present application. The components of the embodiments of the present application usually described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0055] Therefore, the 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 that is claimed, but merely represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts fall within the scope of protection of the present application.

[0056] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0057] It should be noted that like reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0058] 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 drawings, or the orientation or positional relationship in which the product of this application is usually placed during use, or the orientation or positional relationship commonly understood by those skilled in the art. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application. In addition, the terms "first", "second", "third", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0059] At present, from the perspective of the development of the market situation, the application of power batteries is becoming more and more extensive. Power batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power, and solar power stations, but also widely used in electric transportation such as electric bicycles, electric motorcycles, and electric vehicles, as well as in multiple fields such as military equipment and aerospace. With the continuous expansion of the application fields of power batteries, the market demand for them is also constantly increasing.

[0060] The inventor noticed that the battery cell includes a housing, an end cap assembly, and an electrode assembly. The end cap assembly covers the housing to provide a sealed space for the electrode assembly and the electrolyte. The electrical energy of the electrode assembly can be led out of the housing through the electrode terminals of the end cap assembly. Among them, the electrode assembly is welded to the current collector member through tabs, and the electrode terminals are electrically connected to the current collector member to lead out the electrical energy of the battery. The electrode assembly includes electrode plates, and the electrode plates include a coated area coated with an active material layer and an uncoated area not coated with an active material layer. The uncoated area of the electrode plate is wound to form tab ears, and the current collector member is welded to the tab ears to form a plurality of welding parts.

[0061] For a wound full-tab electrode assembly, the tabs need to be flattened before being welded to the current collector member. Currently, the welding of the current collector member and the electrode assembly adopts the methods of laser continuous linear welding or pulsed spot welding, and the shapes of the weld marks are X-shaped, annular, etc. After the electrode plate is unfolded, it will be found that along the length direction of the electrode plate, the welding parts in some sections are denser, and the welding parts in some sections are sparser. The distribution of the welding parts on the electrode plate is uneven. For the sections with sparser welding parts, the effective welding length of the electrode plate (i.e., the total length of the welding parts in this section) is not sufficient to match the length of the electrode plate, resulting in poor current-carrying capacity between the electrode plate and the current collector member, large internal resistance of the battery cell, and reduced power performance of the battery cell.

[0062] In view of this, in order to solve the problem that the unreasonable distribution of the welding positions between the electrode tabs and the current collector components results in a large internal resistance and a weak overcurrent capacity of the battery cell, the inventor has conducted in-depth research and designed a battery cell. By dividing the main body portion of the first electrode tab, which is defined by the first welding portion near the winding start end and the second welding portion near the winding end, into multiple equal-length sub-segments, and making the total length of the welding portions of each sub-segment not less than 5% of the length of the sub-segment, the distribution of the welding portions formed by welding the first electrode tab and the current collector component is made more reasonable, so as to reduce the internal resistance of the battery cell and meet the actual overcurrent requirements, thereby improving the power performance of the battery cell.

[0063] The technical solutions described in the embodiments of the present application are applicable to batteries and electrical equipment using the batteries.

[0064] The electrical equipment can be vehicles, mobile phones, portable devices, laptop computers, ships, spacecraft, electric toys, and electric tools, etc. The vehicle can be a fuel vehicle, a gas vehicle, or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid electric vehicle, or an extended-range electric vehicle, etc.; the spacecraft includes airplanes, rockets, space shuttles, and spaceships, etc.; the electric toys include fixed or mobile electric toys, for example, game consoles, electric vehicle toys, electric ship toys, and electric airplane toys, etc.; the electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools, and railway electric tools, for example, electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact electric drills, concrete vibrators, and electric planers, etc. The embodiments of the present application do not impose special restrictions on the above-mentioned electrical equipment.

[0065] For the convenience of description in the following embodiments, the electrical equipment is taken as an example of a vehicle for illustration.

[0066] Please refer to Figure 1 , Figure 1 which is a schematic structural diagram of a vehicle 1000 provided by some embodiments of the present application. A battery 100 is disposed inside the vehicle 1000. The battery 100 can be disposed at the bottom, the head, or the tail of the vehicle 1000. The battery 100 can be used for power supply of the vehicle 1000. For example, the battery 100 can be used as the operating power source of the vehicle 1000.

[0067] The vehicle 1000 may further include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to supply power to the motor 300. For example, it is used for the working power requirements during the start, navigation, and driving of the vehicle 1000.

[0068] In some embodiments of the present application, the battery 100 can not only be used as the operating power source of the vehicle 1000, but also be used as the driving power source of the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0069] Please refer to Figure 2 , Figure 2 , which is a schematic structural view of the battery 100 provided for some embodiments of the present application. The battery 100 includes a box body 10 and battery cells 20, and the battery cells 20 are housed in the box body 10.

[0070] The box body 10 is used to provide an accommodation space 11 for the battery cells 20. In some embodiments, the box body 10 may include a first part 12 and a second part 13, and the first part 12 and the second part 13 cover each other to define an accommodation space 11 for housing the battery cells 20. Of course, the connection between the first part 12 and the second part 13 can be sealed by a sealing member (not shown in the figure), and the sealing member can be a sealing ring, a sealant, etc.

[0071] The first part 12 and the second part 13 can be of various shapes, for example, a cuboid, a cylinder, etc. The first part 12 is a hollow structure with one end open and formed with an accommodation part for housing the battery cells 20. The second part 13 can also be a hollow structure with one side open and formed with an accommodation part for housing the battery cells 20. When the open side of the second part 13 covers the open side of the first part 12, a box body 10 with a sealed space is formed. Of course, it can also be that the first part 12 is a hollow structure with one end open and formed with an accommodation part for housing the battery cells 20, and the second part 13 is a plate-like structure. When the second part 13 covers the open side of the first part 12, a box body 10 with a sealed space is formed.

[0072] In the battery 100, the battery cells 20 can be one or multiple. If there are multiple battery cells 20, the multiple battery cells 20 can be connected in series, in parallel, or in a series-parallel combination. A series-parallel combination means that there are both series and parallel connections among the multiple battery cells 20. The multiple battery cells 20 can be directly connected in series, in parallel, or in a series-parallel combination together, and then the whole formed by the multiple battery cells 20 is housed in the box body 10. Of course, it can also be that multiple battery cells 20 are first connected in series, in parallel, or in a series-parallel combination to form battery modules, and then multiple battery modules are connected in series, in parallel, or in a series-parallel combination to form a whole and are housed in the box body 10. The battery cells 20 can be in the shape of a cylinder, a flat body, a cuboid, or other shapes, etc. Figure 2 An example shows the case where the battery cells 20 are in the shape of a cylinder.

[0073] In some embodiments, the battery 100 may further include a busbar component (not shown in the figure), and the multiple battery cells 20 can be electrically connected through the busbar component to achieve series, parallel, or series-parallel connection of the multiple battery cells 20.

[0074] Please refer to Figure 3 , Figure 3Explosion diagram of battery cell 20 provided by some embodiments of the present application. The battery cell 20 may include a housing 21, an electrode assembly 22, and an end cap assembly 23. The housing 21 has an opening 211, the electrode assembly 22 is accommodated in the housing 21, and the end cap assembly 23 is used to seal the opening 211.

[0075] The housing 21 can be in various shapes, such as a cylinder, a cuboid, etc. The shape of the housing 21 can be determined according to the specific shape of the electrode assembly 22. For example, if the electrode assembly 22 is a cylindrical structure, the housing 21 can be selected as a cylindrical structure; if the electrode assembly 22 is a cuboid structure, the housing 21 can be selected as a cuboid structure. Figure 3 An exemplary case where the housing 21 and the electrode assembly 22 are cylindrical is shown.

[0076] The material of the housing 21 can also be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc., and the embodiments of the present application do not make special restrictions on this.

[0077] The electrode assembly 22 may include 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).

[0078] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer. The positive electrode active material layer is coated on the surface of the positive electrode current collector. The positive electrode current collector without the coated positive electrode active material layer protrudes from the positive electrode current collector with the coated positive electrode active material layer. The positive electrode current collector without the coated positive electrode active material layer serves as the positive electrode tab. Taking a lithium-ion battery as an example, the material of the positive electrode current collector can be aluminum, and the positive electrode active material can be lithium cobaltate, lithium iron phosphate, ternary lithium, or lithium manganate, etc. The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer is coated on the surface of the negative electrode current collector. The negative electrode current collector without the coated negative electrode active material layer protrudes from the negative electrode current collector with the coated negative electrode active material layer. The negative electrode current collector without the coated negative electrode active material layer serves as the negative electrode tab. The material of the negative electrode current collector can be copper, and the negative electrode active material can be carbon or silicon, etc.

[0079] The electrode assembly 22 can be a wound structure formed by winding the positive electrode sheet, the separator, and the negative electrode sheet. The electrode assembly 22 also includes a positive electrode tab (not shown in the figure) and a negative electrode tab (not shown in the figure). The positive electrode current collector without the coated positive electrode active material layer in the positive electrode sheet can serve as the positive electrode tab, and the negative electrode current collector without the coated negative electrode active material layer in the negative electrode sheet can serve as the negative electrode tab.

[0080] The end cap assembly 23 is used to cover the opening 211 of the housing 21 to form a sealed accommodation cavity (not shown in the figure), and the accommodation cavity is used to accommodate the electrode assembly 22. The accommodation cavity is also used to accommodate an electrolyte, such as an electrolytic solution. The end cap assembly 23 is a component for outputting the electrical energy of the electrode assembly 22, and the electrode terminal 232 in the end cap assembly 23 is used for electrically connecting with the electrode assembly 22, that is, the electrode terminal 232 is electrically connected with the tab of the electrode assembly 22.

[0081] It should be noted that the opening 211 of the housing 21 can be one or two. If the opening 211 of the housing 21 is one, the end cap assembly 23 can also be one, and two electrode terminals 232 can be provided in the end cap assembly 23. The two electrode terminals 232 are respectively used for electrically connecting with the positive tab and the negative tab of the electrode assembly 22, and the two electrode terminals 232 in the end cap assembly 23 are the positive electrode terminal 232 and the negative electrode terminal 232 respectively. As Figure 3 shown, if the opening 211 of the housing 21 is two, for example, the two openings 211 are arranged on opposite sides of the housing 21, the end cap assembly 23 can also be two, and the two end cap assemblies 23 respectively cover the two openings 211 of the housing 21. In this case, the electrode terminal 232 in one end cap assembly 23 can be the positive electrode terminal for electrically connecting with the positive tab of the electrode assembly 22; the electrode terminal 232 in the other end cap assembly 23 can be the negative electrode terminal for electrically connecting with the negative plate of the electrode assembly 22.

[0082] Please refer to Figure 4 、 Figure 5 、 Figure 6 , Figure 4 which is a schematic structural diagram of the electrode assembly 22 provided by some embodiments of the present application, Figure 5 which is a developed view of the first electrode plate 221 provided by some embodiments of the present application, Figure 6Schematic diagram of the dimensions of the first pole piece in the unfolded state provided by some embodiments of the present application. The battery cell 20 includes an electrode assembly 22. The electrode assembly 22 includes a first pole piece 221. On one side in the width direction X of the first pole piece, a plurality of welding parts 222 are provided, and the plurality of welding parts 222 are arranged at intervals along the length direction Y of the first pole piece; the electrode assembly 22 is a wound structure. The first pole piece 221 includes a winding start end 223 and a winding end end 224. The one of the plurality of welding parts 222 closest to the winding start end 223 is the first welding part 222a, and the one of the plurality of welding parts 222 closest to the winding end end 224 is the second welding part 222b. The first pole piece 221 includes a main body section 225. The main body section 225 extends from the edge of the first welding part 222a close to the winding start end 223 to the edge of the second welding part 222b close to the winding end end 224. The main body section 225 is equally divided into a plurality of sub-sections 2251 with a length of L. The total length of the welding parts 222 of each sub-section 2251 is not less than 5%*L, where 200 mm ≤ L ≤ 1200 mm.

[0083] Along the width direction X of the first pole piece, the first pole piece 221 includes a coated area 2211 coated with an active material layer and an uncoated area 2212 not coated with an active material layer. The first pole piece 221 can be a positive electrode piece or a negative electrode piece. The electrode assembly 22 further includes a second pole piece. If the first pole piece 221 is a positive electrode piece and the coated area 2211 is coated with a positive electrode active material, then the second pole piece is a negative electrode piece; if the first pole piece 221 is a negative electrode piece and the coated area 2211 is coated with a negative electrode active material, then the second pole piece is a positive electrode piece. In an embodiment where the tabs of the electrode assembly 22 are full tabs of a wound electrode assembly, the tabs of the first pole piece 221 and the tabs of the second pole piece are respectively located at both ends of the axis of the electrode assembly 22.

[0084] The winding start end 223 means that when the first pole piece 221 is wound to form the electrode assembly 22, the winding start end 223 serves as the winding starting point of the first pole piece 221. After winding is completed, the winding start end 223 is located on the innermost side of the electrode assembly 22 relative to other parts of the first pole piece 221.

[0085] The winding end end 224 means that when the first pole piece 221 is wound to form the electrode assembly 22, the winding end end 224 serves as the winding ending point of the first pole piece 221. After winding is completed, the winding end end 224 is located on the outermost side of the electrode assembly 22 relative to other parts of the first pole piece 221.

[0086] When the first pole piece 221 is in the unfolded state, the length of the welding part 222 refers to the distance between the edge of the welding part 222 close to the winding start end 223 and the edge close to the winding end 224, that is, the dimension of the welding part 222 in the length direction Y of the first pole piece. The total length of the welding part 222 of the sub-segment 2251 refers to the sum of the lengths of all the welding parts 222 located in the sub-segment 2251.

[0087] Each sub-segment 2251 may include one or more welding parts 222. In an embodiment where each sub-segment 2251 includes a plurality of welding parts 222, the plurality of welding parts 222 may be arranged at uniform intervals or non-uniform intervals.

[0088] The length of the main body segment 225 should be not less than the sum of the lengths of two sub-segments 2251, that is to say, the main body segment 225 is at least equally divided into two sub-segments 2251.

[0089] In actual welding, the flattened tab of the first pole piece 221 of the electrode assembly 22 is radially divided into a plurality of regions surrounding the winding center of the electrode assembly 22. Each region includes at least one turn of the first pole piece 221. Each region may include one or more sub-segments 2251, and each sub-segment 2251 may include at least one turn.

[0090] Exemplarily, as Figure 4 shown, around the winding center hole 226 of the electrode assembly 22, the tab part of the first pole piece 221 is divided into six concentrically arranged regions, which are defined as the first region 226a, the second region 226b, the third region 226c, the fourth region 226d, the fifth region 226e and the sixth region 226f from the inside to the outside. Figure 4 In, the six regions are divided by the first ring 227a, the second ring 227b, the third ring 227c, the fourth ring 227d and the fifth ring 227e shown by dotted lines respectively. Each region contains one sub-segment 2251.

[0091] In the present application, the "from the inside to the outside" described herein is relative to the winding center of the electrode assembly 22. Among the two, the one closer to the winding center is located inside the one farther from the winding center.

[0092] In the battery cell verification, the discharge internal resistance of the battery within 0.1 s is used as the ohmic resistance. The magnitude of the ohmic resistance affects the charge and discharge internal resistance and the charge and discharge overcurrent capacity of the battery cell 20. In order to test the influence of the ratio of the total length of the welding part 222 of the sub-segment 2251 to the length of the sub-segment 2251 on the charge and discharge internal resistance and the charge and discharge overcurrent capacity of the battery cell 20, the following tests were carried out:

[0093] Test conditions: The length of the sub-segment is 800 mm. The test ambient temperature is 25 °C. SOC (state of charge) refers to the ratio of the remaining capacity of a storage battery after being used for a period of time or left unused for a long time to its fully charged state capacity, usually expressed as a percentage. Its value range is 0 to 1. When SOC = 0, it means the battery is completely discharged. When SOC = 1, it means the battery is fully charged. In this application, the ohmic internal resistance and the full-cell internal resistance of the battery cell 20 are tested with SOC = 0.5 as an example. In order to obtain the full-cell internal resistance of the battery cell 20, DCIR (Direct Current Internal Resistance) test is adopted. The full-cell internal resistance of the battery cell 20 includes two parts: ohmic internal resistance and polarization internal resistance. The DCIR (Direct Current Internal Resistance) test is a method that takes into account and measures the resistance of both parts, also known as dynamic internal resistance.

[0094] Table 1 Test results of ohmic internal resistance and full-cell internal resistance corresponding to different ratios of the total length of the welded part to the length of the sub-segment

[0095]

[0096] From the above test results, it can be seen that when the ratio of the total length of the welded part 222 of the sub-segment 2251 to the length of the sub-segment 2251 is between 3% and 5%, both the ohmic internal resistance and the full-cell internal resistance of the battery cell 20 gradually decrease as the ratio of the total length of the welded part 222 of the sub-segment 2251 to the length of the sub-segment 2251 increases; when the ratio of the total length of the welded part 222 of the sub-segment 2251 to the length of the sub-segment 2251 is greater than or equal to 5%, both the ohmic internal resistance and the full-cell internal resistance of the battery cell 20 tend to be stable. Therefore, in this application, the total length of the welded part 222 of the sub-segment 2251 is not less than 5% of the length of the sub-segment 2251, so that the battery cell 20 has a smaller charge-discharge internal resistance and a stronger charge-discharge overcurrent capacity.

[0097] In the prior art, the current collector member 24 ( Figure 3As shown (in [reference], the welding of the electrode assembly 22 is carried out by continuous laser linear welding or pulsed spot welding. The shapes of the welding imprints include X-shaped, annular, etc. After the electrode tab is unfolded, it can be found that along the length direction of the electrode tab, the welding parts in some sections are denser, while those in some sections are sparser, and the distribution of the welding parts on the electrode tab is uneven. For the sections with sparser welding parts, the effective welding length of the electrode tab (i.e., the total length of the welding parts in this section) is not sufficient to match the length of the electrode tab, resulting in poor current-carrying capacity between the electrode tab and the current collector member 24, a large internal resistance of the battery cell, and a reduction in the power performance of the battery cell 20. After welding on one side of the current collector member 24 and the first electrode tab in the width direction X, a plurality of welding parts 222 arranged at intervals are formed in the length direction Y of the first electrode tab. Along the length direction Y of the first electrode tab, the main body part of the first electrode tab 221 defined by the first welding part 222a near the winding starting end 223 and the second welding part 222b near the winding ending end 224 is divided into a plurality of equal-length sub-segments 2251. The total length of the welding parts 222 in each sub-segment 2251 is not less than 5% of the length of the sub-segment 2251, so that the distribution of the welding parts 222 formed by welding the first electrode tab 221 and the current collector member 24 is more reasonable, to reduce the internal resistance of the battery cell 20, meet the actual current-carrying requirements, and thus improve the power performance of the battery cell 20. The length range of each sub-segment 2251 is between 200 mm and 1200 mm, so that the winding length of the first electrode tab 221 meets the actual product requirements and the battery cell 20 has a high energy density.

[0098] Please refer to Figure 5 、 Figure 6 , in some embodiments, the absolute value of the difference between the total lengths of the welding parts 222 of any two sub-segments 2251 is less than or equal to 10 mm.

[0099] In Figure 5 、 Figure 6 , it is defined that the lengths of the welding parts 222 in one sub-segment of any two sub-segments 2251 are L1, ……, Ln respectively, and the lengths of the welding parts 222 in the other sub-segment of any two sub-segments 2251 are H1, ……, Hm respectively, where n and m are both natural numbers greater than or equal to 1. It satisfies -10 mm ≤ (L1 + …… + Ln) - (H1 + …… + Hm) ≤ 10 mm.

[0100] The absolute value of the difference in the total length of the welded portions 222 of any two sub-segments 2251 is controlled within 10 mm. As much as possible, the difference in the total length of the welded portions 222 of each sub-segment 2251 is reduced, making the distribution of the welded portions 222 more reasonable, which is beneficial to reducing the internal resistance of the battery cell 20, and making the difference in the over-current capacity of each sub-segment 2251 smaller, meeting the actual over-current requirements, thereby improving the power performance of the battery cell 20. Controlling the absolute value of the difference in the total length of the welded portions 222 of any two sub-segments 2251 within 10 mm is equivalent to the welding width error of each sub-segment 2251 being within 10 mm. Allowing an error in the total welding length between each sub-segment 2251 can reduce the welding difficulty.

[0101] In some embodiments, the total lengths of the welded portions 222 of any two sub-segments 2251 are the same.

[0102] The total lengths of the welded portions 222 of any two sub-segments 2251 being the same can be understood as the difference in the total lengths of the welded portions 222 of any two sub-segments 2251 being zero.

[0103] If the total lengths of the welded portions 222 of any two sub-segments 2251 are the same, then there is no difference in the total lengths of the welded portions 222 of each sub-segment 2251, making the distribution of the welded portions 222 more reasonable, reducing the internal resistance of the battery cell 20 as much as possible, and making the over-current capacities of each sub-segment 2251 the same, meeting the actual over-current requirements, thereby improving the power performance of the battery cell 20.

[0104] In some embodiments, the absolute value of the difference in the number of the welded portions 222 of any two sub-segments 2251 is less than or equal to 10.

[0105] In Figure 5 , -10 ≤ n - m ≤ 10, that is, the absolute value of the difference in the number of the welded portions 222 of any two sub-segments 2251 is less than 10.

[0106] Controlling the absolute value of the difference in the number of the welded portions 222 of any two sub-segments 2251 within 10 can reduce the internal resistance of the battery cell 20 as much as possible by reducing the welded portions of each sub-segment 2251, making the difference in the over-current capacity of each sub-segment 2251 smaller, meeting the actual over-current requirements, thereby improving the power performance of the battery cell 20. Controlling the absolute value of the difference in the number of the welded portions 222 of any two sub-segments 2251 within 10 is equivalent to the number of the welded portions 222 of each sub-segment 2251 can have differences. Allowing an error in the total welding length between each sub-segment 2251 can reduce the welding difficulty.

[0107] In some embodiments, the number of the welded portions 222 of any two sub-segments 2251 is the same.

[0108] The number of the welding portions 222 of any two sub - segments 2251 is the same. It can be understood that the difference in the number of the welding portions 222 of any two sub - segments 2251 is zero. In Figure 6 it is n - m = 0. As Figure 4 shown, the second region 226b, the third region 226c, the fourth region 226d, the fifth region 226e, and the sixth region 226f each have one sub - segment 2251, and the number of the welding portions 222 of the second region 226b, the third region 226c, the fourth region 226d, the fifth region 226e, and the sixth region 226f is the same.

[0109] If the number of the welding portions 222 of any two sub - segments 2251 is the same, then the difference in the total length of the welding portions 222 of each sub - segment 2251 can be minimized as much as possible, making the distribution of the welding portions 222 more reasonable, which is beneficial to reducing the internal resistance of the battery cell 20, making the current - carrying capacity of each sub - segment 2251 the same, meeting the actual current - carrying requirements, and thus improving the power performance of the battery cell 20.

[0110] Please continue to refer to Figure 4 and Figure 5 and Figure 6 , in some embodiments, the first pole piece 221 further includes a winding start segment 228 continuously provided with the main body segment 225. The winding start segment 228 extends from the winding start end 223 to the edge of the first welding portion 222a close to the winding start end 223.

[0111] The continuous setting of the main body segment 225 and the winding start segment 228 means that the winding start segment 228 is directly connected to the main body segment 225. After winding, the layer formed by winding the winding start segment 228 is located inside the layer formed by winding the main body segment 225. As Figure 4 and Figure 5 and Figure 6 shown, the winding start segment 228 is located in the first region 226a and no welding portion 222 is provided.

[0112] In some embodiments, the first pole piece 221 may only include the winding start segment 228 and the main body segment 225. In other embodiments, the first pole piece 221 may only include the main body segment 225.

[0113] The winding start segment 228 extends from the winding start end 223 to the edge of the first welding portion 222a close to the winding start end 223, that is, the winding start end 223 and the edge of the first welding portion 222a close to the winding start end 223 define the winding start segment 228. In other words, the winding start end 223 extends beyond the first welding portion 222a, no welding portion 222 is formed on the winding start segment 228, and the winding start segment 228 is connected to the current - collecting member 24 ( Figure 3There is no welding relationship between them (as shown in the figure), and the part of the current collector member 24 corresponding to the tab of the winding start section 228 Figure 3 shown in the figure) is not welded and can be used to weld with the electrode terminal 232 to output the electric energy of the battery cell 20.

[0114] For different battery cells 20, the length of the winding start section 228 can be different. In some embodiments, the length of the winding start section 228 is A, satisfying A ≤ L.

[0115] The length of the winding start section 228 refers to the distance between the winding start end 223 and the edge of the first welding part 222a close to the winding start end 223 when the first electrode sheet 221 is in the unfolded state.

[0116] Along the length direction Y of the first electrode sheet, the distance between the winding start end 223 and the first welding part 222a is less than the length of the sub-section, that is, the length of the winding start section 228 without the welding part 222 is less than the length of the sub-section 2251 provided with the welding part 222, so that the length of the section of the first electrode sheet 221 without the welding part 222 will not be too long, ensuring stable output of the electric energy of the battery cell 20.

[0117] Please refer to Figure 7 、 Figure 8 、 Figure 9 , Figure 7 which is a schematic structural diagram of the electrode assembly 22 provided in some other embodiments of the present application, Figure 8 which is an unfolded view of the first electrode sheet 221 provided in some other embodiments of the present application, Figure 9 which is a schematic dimension diagram of the unfolded state of the first electrode sheet 221 provided in some other embodiments of the present application. In some embodiments, the first electrode sheet 221 further includes a winding end section 229 continuously provided with the main body section 225, and the winding end section 229 extends from the winding end 224 to the edge of the second welding part 222b close to the winding end 224.

[0118] The continuous setting of the main body section 225 and the winding end section 229 means that the winding end section 229 is directly connected to the main body section 225. After winding, the layer formed by winding the winding end section 229 is located outside the layer formed by winding the main body section 225. As Figure 6 、 Figure 7 shown, the winding end section 229 is located in the sixth region 226f and no welding part 222 is provided.

[0119] In some embodiments, the first electrode sheet 221 may only include the winding end section 229 and the main body section 225. In some other embodiments, as Figure 10 、 Figure 11As shown, the first electrode tab 221 may include a winding start segment 228, a main body segment 225, and a winding end segment 229 that are connected in sequence.

[0120] The winding end segment 229 extends from the winding end 224 to the edge of the second welding portion 222b close to the winding end 224, that is, the winding end 224 and the edge of the second welding portion 222b close to the winding end 224 define the winding end segment 229. In other words, the winding end 224 extends beyond the second welding portion 222b, and no welding portion 222 is formed on the winding end segment 229. There is no welding relationship between the winding end segment 229 and the current collector member 24 ( Figure 3 shown in). The portion of the current collector member 24 ( Figure 3 shown in) corresponding to the tab portion of the winding end segment 229 is not welded and can be used for welding with the electrode terminal 232 to output the electrical energy of the battery cell 20.

[0121] For different battery cells 20, the length of the winding end segment 229 may be different, and the length of the winding end segment 229 should satisfy the actual requirements of the electrode assembly 22. In some embodiments, the length of the winding end segment 229 is B, satisfying B ≤ L.

[0122] When the first electrode tab 221 is in the unfolded state, the length of the winding end segment 229 refers to the distance between the winding end 224 and the edge of the second welding portion 222b close to the winding end 224.

[0123] Along the length direction Y of the first electrode tab, the length of the winding end segment 229 is less than the length of the sub-segment 2251, that is, the length of the winding start segment 228 without the welding portion 222 is less than the sub-segment 2251 provided with the welding portion 222, so that the length of the section of the first electrode tab 221 without the welding portion 222 is not too long, ensuring stable output of the electrical energy of the battery cell 20.

[0124] Please refer to Figure 12 、 Figure 13 , Figure 12 which is a schematic diagram of the electrode assembly 22 provided by some other embodiments of the present application, Figure 13 and which is a structural schematic diagram of the electrode assembly 22 provided by some further embodiments of the present application. In some embodiments, among two adjacent turns of the first electrode tab 221, the number of welding portions 222 in the turn closer to the winding center of the electrode assembly 22 is less than the number of welding portions 222 in the turn farther from the winding center.

[0125] The "among two adjacent turns of the first electrode tab 221" described here may be any two adjacent turns of the first electrode tab 221, or may be some two adjacent turns of the first electrode tab 221.

[0126] Exemplarily, as Figure 12As shown, each region has a circle of first pole pieces 221. In the first region 226a, each circle of first pole pieces 221 is provided with two welding parts 222; in the second region 226b, each circle of first pole pieces 221 is provided with four welding parts 222; in the third region 226c, each circle of first pole pieces 221 is provided with six welding parts 222; in the fourth region 226d, each circle of first pole pieces 221 is provided with six welding parts 222; in the fifth region 226e, each circle of first pole pieces 221 is provided with six welding parts 222. The welding parts 222 are radially distributed.

[0127] As Figure 13 shown, each region has a circle of first pole pieces 221. In the second region 226b, some circles of first pole pieces 221 are provided with four welding parts 222, some circles of first pole pieces 221 are provided with five welding parts 222, and some other circles of first pole pieces 221 are provided with six welding parts 222; in the third region 226c, each circle of first pole pieces 221 is provided with six welding parts 222; in the fourth region 226d, each circle of first pole pieces 221 is provided with six welding parts 222; in the fifth region 226e, each circle of first pole pieces 221 is provided with six welding parts 222; in the sixth region 226f, some circles of first pole pieces 221 are provided with six welding parts 222, and some other circles of first pole pieces 221 are provided with five welding parts 222. Some of the welding parts 222 are radially distributed, and some of the welding parts 222 are connected to form an arc segment around the winding center of the electrode assembly 22. The arc segment is located in the sixth region 226f, and the arc segment connects two adjacent radiations formed by the welding parts 222.

[0128] In other embodiments, the number of welding parts 222 of any two adjacent circles of first pole pieces 221 can also be the same.

[0129] For the wound electrode assembly 22, among two adjacent circles of first pole pieces 221, the length of the circle closer to the winding center is less than the length of the circle farther from the winding center. During welding, the number of welding parts 222 formed on the circle closer to the winding center of the wound electrode assembly 22 is less than the number of welding parts 222 of the circle farther from the winding center, so that the length of each circle of first pole pieces 221 and the number and total length of the welding parts 222 corresponding to each circle of first pole pieces 221 are matched, which can make the distribution of the welding parts 222 more reasonable, reduce the internal resistance of the battery cell 20, and meet the actual over-current demand, thereby improving the power performance of the battery cell 20.

[0130] Please refer to Figure 3 , Figure 4 , Figure 5 , Figure 6, in some embodiments, the battery cell 20 further includes a housing 21, an end cap assembly 23, and a current collector member 24; the housing 21 is used to accommodate the electrode assembly 22, and the housing 21 has an opening 211; the end cap assembly 23 includes an end cap 231 and an electrode terminal 232, the end cap 231 is used to cover the opening 211, and the electrode terminal 232 is mounted on the end cap 231; the current collector member 24 is located between the end cap 231 and the electrode assembly 22 and is used to connect the tab of the electrode assembly 22 and the electrode terminal 232. The tab is formed by winding the uncoated area of the first electrode tab 221, and at least a part of the current collector member 24 is welded to the tab to form a plurality of welding portions 222.

[0131] At least a part of the current collector member 24 is welded to the tab to form a plurality of welding portions 222. Along the length direction Y of the first electrode tab, the main body portion of the first electrode tab 221 defined by the first welding portion 222a near the winding start end 223 and the second welding portion 222b near the winding end 224 is divided into a plurality of equal-length sub-segments 2251. The total length of the welding portions 222 of each sub-segment 2251 is not less than 5% of the length of the sub-segment 2251, so that the distribution of the welding portions 222 formed by welding the first electrode tab 221 and the current collector member 24 is more reasonable, thereby reducing the internal resistance of the battery cell 20, meeting the actual over-current demand, and improving the power performance of the battery cell 20.

[0132] Please refer to Figure 14 , Figure 14 , which is a schematic diagram of the current collector member 24 after welding provided by some embodiments of the present application. In some embodiments, the first electrode tab 221 further includes a winding start segment 228 from the winding start end 223 to the edge near the winding start end 223 of the first welding portion 222a. The uncoated area of the main body segment 225 is wound to form a first part 12 (not shown in the figure), and the uncoated area of the winding start segment 228 is wound to form a second part 13 (not shown in the figure). The second part 13 is located radially inside the first part 12; the current collector member 24 includes a first current collector portion 241 and a second current collector portion 242 arranged continuously in the radial direction. The first current collector portion 241 is disposed opposite to the first part 12 in the width direction X of the first electrode tab and is welded to the first part 12 to form a plurality of welding portions 222. The second current collector portion 242 is disposed opposite to the second part 13 in the width direction X of the first electrode tab and is welded to the electrode terminal 232.

[0133] When the first electrode tab 221 is in a wound state, the width direction X of the first electrode tab is consistent with the winding axis direction of the electrode assembly 22. Since the uncoated area of the first electrode tab 221 is used to form the tab of the first electrode tab 221, both the first part 12 and the second part 13 belong to the tab of the first electrode tab 221. The second part 13 is located radially inside the first part 12. It can be that part of the second part 13 is located inside the first part 12, and the other part of the second part 13 and part of the first part 12 are located on the same circumference; or it can be that the entire second part 13 is located inside the first part 12, and the first part 12 surrounds the outer periphery of the second part 13.

[0134] The first current collector part 241 is disposed opposite to the first part 12 along the width direction X of the first electrode tab. It can be understood that along the width direction X of the first electrode tab, the projection of the first part 12 on the current collector member 24 at least partially coincides with the first current collector part 241, and the coincident parts are welded to each other to form a plurality of welding parts 222, realizing the electrical connection between the electrode assembly 22 and the current collector member 24. The second current collector part 242 and the second current collector part 242 are arranged continuously in the radial direction. The winding start segment 228 is from the winding start end 223 to the edge of the first welding part 222a close to the winding start end 223, that is, the winding start end 223 and the edge of the first welding part 222a close to the winding start end 223 define the winding start segment 228. No welding part 222 is formed on the winding start segment 228, that is, there is no welding relationship between the second part 13 formed by winding the uncoated area of the winding start segment 228 and the current collector member 24, and no welding mark is formed on the second current collector part 242 opposite to the second part 13, which is convenient for the current collector member 24 to be welded to the electrode terminal 232 through the second current collector part 242 to output the electric energy of the battery cell 20.

[0135] Please refer to Figure 15 , Figure 15 For some other embodiments of the present application, a schematic diagram of the current collector member 24 after welding is provided. In some embodiments, the first electrode tab 221 further includes a winding end segment 229 from the winding end 224 to the edge of the second welding part 222b close to the winding end segment 229. The uncoated area of the main body segment 225 is wound to form the first part 12, and the uncoated area of the winding end segment 229 is wound to form a third part (not shown in the figure). The third part is located radially outside the first part 12; the current collector member 24 includes a first current collector part 241 and a third current collector part 243 arranged continuously in the radial direction. The first current collector part 241 is disposed opposite to the first part 12 along the width direction X of the first electrode tab and is welded to the first part 12 to form a plurality of welding parts 222. The third current collector part 243 is disposed opposite to the third part along the width direction X of the first electrode tab and is welded to the electrode terminal 232.

[0136] Since the uncoated area of the first electrode tab 221 is used to form the tab of the first electrode tab 221, both the first part 12 and the third part belong to the tab of the first electrode tab 221. The third part is located radially outside the first part 12. It may be that part of the third part is located outside the first part 12 and the other part of the third part is located on the same circumference as part of the first part 12; or it may be that the entire third part is located inside the first part 12 and the third part surrounds the outer periphery of the first part 12.

[0137] Please refer to Figure 16 , Figure 16 FIG. shows a schematic diagram of the current collector member 24 after welding for some other embodiments of the present application. In an embodiment where the first electrode tab 221 includes a winding start segment 228, a main body segment 225, and a winding end segment 229, the current collector member 24 may include a second current collecting portion 242, a first current collecting portion 241, and a third current collecting portion 243 arranged radially from the inside to the outside. The first current collecting portion 241 is welded to the first part 12, the second current collecting portion 242 is disposed opposite to the second part 13 in the width direction X of the first electrode tab, the third current collecting portion is disposed opposite to the third part in the width direction X of the first electrode tab, and the second current collecting portion 242 and the third current collecting portion 243 are welded to the electrode terminal 232 to output the electrical energy of the battery cell 20.

[0138] By welding the first current collecting portion 241 and the first part 12, the electrical connection between the electrode assembly 22 and the current collector member 24 is achieved. The third current collecting portion 243 and the first current collecting portion 241 are arranged continuously in the radial direction. The winding end segment 229 is from the winding end 224 to the edge near the winding end 224 of the second welding portion 222b, that is, the winding end 224 and the edge near the winding end 224 of the second welding portion 222b define the winding end segment 229. No welding portion 222 is formed on the winding end segment 229, that is, there is no welding relationship between the third part formed by winding the uncoated area of the winding end segment 229 and the current collector member 24, and no welding mark is formed on the third current collecting portion 243 opposite to the third part, which facilitates the welding of the current collector member 24 and the electrode terminal 232 through the third current collecting portion 243 to output the electrical energy of the battery cell 20.

[0139] An embodiment of the present application provides a cylindrical battery, which includes a cylindrical housing 21, a cylindrical electrode assembly 22, a current collector member 24, and an end cap assembly 23. The electrode assembly 22 is accommodated in the housing. The end cap 231 of the end cap assembly 23 seals the opening 211 of the housing 21. The electrode assembly 22 includes a first electrode tab 221, and the first electrode tab 221 includes a winding start end 223 and a winding end 224. Among the plurality of welding portions 222, the one closest to the winding start end 223 is the first welding portion 222a, and the one closest to the winding end 224 is the second welding portion 222b. The first electrode tab 221 includes a main body section 225 from the edge of the first welding portion 222a close to the winding start end 223 to the edge of the second welding portion 222b close to the winding end 224. The main body section 225 is equally divided into a plurality of sub-sections 2251 with a length of L, and the total length of the welding portions 222 of each sub-section 2251 is not less than 5%*L, where 200 mm ≤ L ≤ 1200 mm. The absolute value of the difference in the total length of the welding portions 222 between any two sub-sections 2251 is less than or equal to 10 mm, and the absolute value of the difference in the number of the welding portions 222 between any two sub-sections 2251 is less than or equal to 10. The first electrode tab 221 further includes a winding start section 228 and a winding end section 229 continuously arranged with the main body section 225. The winding start section 228 extends from the winding start end 223 to the edge of the first welding portion 222a close to the winding start end 223. The winding end section 229 extends from the winding end 224 to the edge of the second welding portion 222b close to the winding end 224. The length of the winding start section 228 is A and the length of the winding end section 229 is B, satisfying A ≤ L and B ≤ L. The current collector member 24 includes a second current collector portion 242, a first current collector portion 241, and a third current collector portion 243 continuously arranged from the inside to the outside in the radial direction. The uncoated area of the main body section 225 is wound to form a first part 12, the uncoated area of the winding start section 228 is wound to form a second part 13, and the uncoated area of the winding end section 229 is wound to form a third part. Along the width direction X of the first electrode tab, the first current collector portion 241 is disposed opposite to the first part 12 and welded to the first part 12 to form a plurality of welding portions 222. The second current collector portion 242 is disposed opposite to the second part 13 and welded to the electrode terminal 232. The third current collector portion 243 is disposed opposite to the third part and welded to the electrode terminal 232 to output the electric energy of the cylindrical battery.

[0140] An embodiment of the present application further provides a battery 100, which includes the battery cell 20 provided in any of the above embodiments.

[0141] An embodiment of the present application further provides an electrical device, which includes the battery 100 provided in the above embodiment.

[0142] The above are only the preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A battery cell, characterized in that, Comprising: An electrode assembly, including a first pole piece, on one side in the width direction of the first pole piece, there are a plurality of welding parts, and the plurality of welding parts are arranged at intervals along the length direction of the first pole piece; A housing for accommodating the electrode assembly, the housing has an opening, and the housing is a cylindrical structure; An end cap assembly, including an end cap and an electrode terminal, the end cap is used to cover the opening, and the electrode terminal is installed on the end cap; The electrode assembly is a wound structure, the first pole piece includes a winding start end and a winding end end, the one of the plurality of welding parts closest to the winding start end is the first welding part, and the one of the plurality of welding parts closest to the winding end end is the second welding part. The first pole piece includes a main body section, and the main body section extends from the edge of the first welding part close to the winding start end to the edge of the second welding part close to the winding end end. The main body section is equally divided into a plurality of sub-sections with a length of L, and the total length of the welding parts of each sub-section is not less than 5%*L, where 200mm ≤ L ≤ 1200mm.

2. The battery cell according to claim 1, wherein, The absolute value of the difference in the total length of the welding parts between any two of the sub-sections is less than or equal to 10mm.

3. The battery cell according to claim 1, wherein, The total length of the welding parts of any two of the sub-sections is the same.

4. The battery cell according to claim 1, characterized in that The absolute value of the difference in the number of the welding parts between any two of the sub-sections is less than or equal to 10.

5. The battery cell according to claim 1, characterized in that The number of the welding parts of any two of the sub-sections is the same.

6. The battery cell according to claim 1, characterized in that The first pole piece further includes a winding start section continuously arranged with the main body section, and the winding start section extends from the winding start end to the edge of the first welding part close to the winding start end.

7. The battery cell according to claim 6, wherein, The length of the winding start section is A, and A ≤ L is satisfied.

8. The battery cell according to any one of claims 1-7, characterized in that, The first pole piece further includes a winding end section continuously arranged with the main body section, and the winding end section extends from the winding end end to the edge of the second welding part close to the winding end end.

9. The battery cell according to claim 8, wherein The length of the winding end section is B, and B ≤ L is satisfied.

10. The battery cell according to any one of claims 1-7, characterized in that, In two adjacent turns of the first pole piece, the number of the welding parts in the turn closer to the winding center of the electrode assembly is less than the number of the welding parts in the turn farther from the winding center.

11. The battery cell according to claim 1, characterized in that, The battery cell further includes: A current collecting member, located between the end cap and the electrode assembly, and used to connect the pole ear part of the electrode assembly and the electrode terminal. The pole ear part is formed by winding the uncoated area of the first pole piece, and at least a part of the current collecting member is welded to the pole ear part to form the plurality of welding parts.

12. The battery cell according to claim 11, wherein, The first pole piece further includes a winding start section extending from the winding start end to the edge of the first welding part close to the winding start end. The uncoated area of the main body section is wound to form a first part, and the uncoated area of the winding start section is wound to form a second part. The second part is located radially inside the first part; The current collecting member includes a first current collecting portion and a second current collecting portion that are arranged continuously in the radial direction. The first current collecting portion is disposed opposite to the first portion in the width direction of the first pole piece, and is welded to the first portion to form the plurality of welding portions. The second current collecting portion is disposed opposite to the second portion in the width direction of the first pole piece, and is welded to the electrode terminal.

13. The battery cell according to claim 11 or 12, characterized in that, The first pole piece further includes a winding end section from the winding end to the edge of the second welding portion close to the winding end. The uncoated area of the main section is wound to form the first portion, and the uncoated area of the winding end section is wound to form the third portion. The third portion is located radially outside the first portion. The current collecting member includes a first current collecting portion and a third current collecting portion that are arranged continuously in the radial direction. The first current collecting portion is disposed opposite to the first portion in the width direction of the first pole piece, and is welded to the first portion to form the plurality of welding portions. The third current collecting portion is disposed opposite to the third portion in the width direction of the first pole piece, and is welded to the electrode terminal.

14. A battery, characterized in that, Comprising a battery cell according to any one of claims 1-13.

15. An electrical device, characterized in that, Comprising a battery according to claim 14.

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