Battery cell and electric device

Abstract

This application provides a battery cell and an electrical device. The battery cell includes an electrode assembly, which has a wound structure. The electrode assembly includes an electrode sheet, which includes a main body region and an electrode tab. Along the axial direction of the electrode assembly, the electrode tab protrudes from one end of the main body region. Along the winding direction of the electrode assembly, the main body region has a winding start end and a winding end end. When the electrode sheet is in an unfolded state, the end of the electrode tab away from the main body region is the first end. The electrode sheet is provided with multiple notches recessed from the first end toward the main body region. Along the thickness direction of the electrode sheet, the notches penetrate two opposite surfaces of the electrode sheet. The electrode sheet has a mid-section, which is perpendicular to the length direction of the electrode sheet. The multiple notches include a first notch located between the mid-section and the winding start end and a second notch located between the mid-section and the winding end end. The sum of the maximum lengths of all the first notches is greater than the sum of the maximum lengths of all the second notches.

Description

Technical Field

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

[0002] Currently, with the rapid development of new energy technologies, battery cells have been widely used in electronic devices, electric vehicles, electric two-wheelers, power tools, and other fields. As the application of battery cells becomes more widespread, higher requirements are being placed on their safety performance. Summary of the Invention

[0003] This application provides a battery cell and an electrical device to improve the safety performance of the battery cell.

[0004] In a first aspect, embodiments of this application provide a battery cell, which includes an electrode assembly. The electrode assembly has a wound structure and includes an electrode sheet. The electrode sheet includes a main body region and an electrode tab. Along the axial direction of the electrode assembly, the electrode tab protrudes from one end of the main body region. Along the winding direction of the electrode assembly, the main body region has a winding start end and a winding end end. When the electrode sheet is in an unfolded state, the end of the electrode tab away from the main body region is the first end. The electrode sheet is provided with a plurality of notches recessed from the first end toward the main body region. Along the thickness direction of the electrode sheet, the notches penetrate two opposite surfaces of the electrode sheet. The electrode sheet has a mid-section. The mid-section is perpendicular to the length direction of the electrode sheet. The plurality of notches include a first notch located between the mid-section and the winding start end and a second notch located between the mid-section and the winding end end. The sum of the maximum lengths of all the first notches is greater than the sum of the maximum lengths of all the second notches.

[0005] In one or more of the above optional embodiments, when the electrode sheet is in the unfolded state, the end of the electrode tab away from the main body area is the first end. Multiple notches are provided on the electrode sheet, recessed from the first end towards the main body area. These notches provide channels for the electrolyte to enter the electrode assembly, which is beneficial for improving the wetting performance and efficiency of the electrode assembly. Along the thickness direction of the electrode sheet, the notches penetrate two opposite surfaces of the electrode sheet. The electrode sheet has a mid-section perpendicular to its length direction. The multiple notches include a first notch located between the mid-section and the winding start end, and a second notch located between the mid-section and the winding end end. The sum of the maximum lengths of all the first notches is greater than the sum of the maximum lengths of all the second notches. This results in a larger sum of the notch lengths corresponding to the inner rings near the winding axis after the electrode sheet is wound. This facilitates the entry of electrolyte into the inner rings, promoting the wetting of the inner rings of the electrode assembly, reducing the wetting difference between the inner and outer rings of the electrode assembly, improving the wetting consistency of the inner and outer rings of the electrode assembly, reducing the risk of lithium plating in the cell, improving the safety performance of the cell, and improving the cycle performance of the cell.

[0006] In some embodiments of the first aspect of this application, when the electrode is in an unfolded state, the depth of at least one notch along the width direction of the electrode is less than the width of the tab.

[0007] In one or more of the above optional embodiments, by ensuring that the depth of at least one notch along the width direction of the electrode sheet is less than the width of the tab when the electrode sheet is in the unfolded state, the main body area of ​​the electrode sheet is cut less or avoided during the notch formation process, thereby reducing energy density loss and enabling the cell to have better energy density.

[0008] In some embodiments of the first aspect of this application, when the electrode is in an unfolded state, the depth of at least one notch along the width direction of the electrode is equal to the width of the tab.

[0009] In one or more of the above optional embodiments, when the electrode is in the unfolded state, at least one notch has a depth equal to the width of the tab along the width direction of the electrode, which facilitates the manufacturing and shaping of the notch.

[0010] In some embodiments of the first aspect of this application, when the electrode is in an unfolded state, the depth of the notch is greater than the width of the tab along the width direction of the electrode.

[0011] In one or more of the above optional embodiments, when the electrode is in the unfolded state, the depth of the notch along the width direction of the electrode is greater than the width of the tab, and the size of the notch is larger. This allows the notch to form a larger channel for the electrolyte to enter the electrode assembly, which is beneficial for the electrode assembly to be fully wetted by the electrolyte, improving the cycle performance of the cell and reducing the risk of lithium plating, thus improving the safety performance of the cell. The larger notch size can also improve the efficiency of electrolyte entering the electrode assembly, thereby improving the wetting efficiency of the electrode assembly.

[0012] In some embodiments of the first aspect of this application, when the electrode is in the unfolded state, the maximum length of the electrode along the length direction of the electrode is L, the sum of the maximum lengths of all notches is L', and L'≤0.8L.

[0013] In one or more of the above optional embodiments, by making L' less than or equal to 0.8L, the sum of the maximum lengths of all the notches is not too large, thereby making the size of the tab in the length direction of the electrode larger, so that the tab has better current carrying capacity, which is conducive to realizing high current charging and discharging, making the cell have better rate performance and reducing the distance of electron transmission, reducing the internal resistance of the cell, thereby reducing the heat generation of the cell and extending the life of the cell.

[0014] In some embodiments of the first aspect of this application, 2mm≤L'≤0.5L.

[0015] In one or more of the above optional embodiments, by making L' greater than or equal to 2mm, the sum of the maximum lengths of all the notches is larger, allowing the notches to form larger channels for the electrolyte to enter the electrode assembly. This facilitates the full wetting of the electrode assembly by the electrolyte, improves the cycle performance of the cell, reduces the risk of lithium plating, and enhances the cell's safety performance. Larger notches also improve the efficiency of electrolyte entry into the electrode assembly, thus increasing the wetting efficiency of the electrode assembly. By making L' less than or equal to 0.5L, the sum of the maximum lengths of all the notches is not too large, resulting in a larger tab in the length direction of the electrode sheet. This gives the tab better current carrying capacity, which is beneficial for achieving high-current charging and discharging. This gives the cell better rate performance, reduces the electron transmission distance, lowers the cell's internal resistance, reduces cell heat generation, and extends the cell's lifespan. Therefore, 2mm≤L'≤0.5L results in a cell with good cycle performance, safety performance, rate performance, and lifespan.

[0016] In some embodiments of the first aspect of this application, 0.1L ≤ L' ≤ 0.4L.

[0017] In one or more of the above optional embodiments, by ensuring L' is greater than or equal to 0.1L, the sum of the maximum lengths of all the notches is larger, allowing the notches to form larger channels for the electrolyte to enter the electrode assembly. This facilitates the full wetting of the electrode assembly by the electrolyte, improves the cycle performance of the cell, reduces the risk of lithium plating, and enhances the cell's safety performance. Larger notches also improve the efficiency of electrolyte entry into the electrode assembly, further enhancing the wetting efficiency. By ensuring L' is less than or equal to 0.4L, the sum of the maximum lengths of all the notches is not excessively large, resulting in a larger tab size along the length of the electrode sheet. This provides the tab with better current carrying capacity, facilitating high-current charging and discharging, giving the cell better rate performance, reducing electron transport distance, further reducing internal resistance, and thus further reducing heat generation and extending cell lifespan. Therefore, 0.1L ≤ L' ≤ 0.4L results in better cycle performance, safety performance, rate performance, and lifespan for the cell.

[0018] In some embodiments of the first aspect of this application, when the electrode is in the unfolded state, the maximum length of the electrode along the length direction of the electrode is L, and the sum of the maximum lengths of all the first notches is L1, where 1mm≤L1≤0.5L.

[0019] In one or more of the above optional embodiments, by making L1 greater than or equal to 1 mm, the sum of the maximum lengths of all the first gaps is relatively large. This facilitates the formation of larger channels for the electrolyte to enter the electrode assembly within the inner ring of the electrode assembly, which is beneficial for the electrode assembly to be fully wetted by the electrolyte, improving the cycle performance of the cell and reducing the risk of lithium plating, thus improving the cell's safety performance. A larger sum of the maximum lengths of all the first gaps also improves the efficiency of the electrolyte entering the electrode assembly, thereby improving the wetting efficiency of the electrode assembly. By making L1 less than or equal to 0.5 L, the sum of the maximum lengths of all the first gaps is not too large, which makes the tab larger in the length direction of the electrode sheet. This gives the tab better current carrying capacity, which is beneficial for achieving high current charging and discharging, giving the cell better rate performance, reducing the electron transmission distance, reducing the cell's internal resistance, thereby reducing cell heat generation and extending the cell's lifespan. Therefore, 1 mm ≤ L1 ≤ 0.5 L gives the cell better cycle performance, safety performance, and the tab better current carrying capacity.

[0020] In some embodiments of the first aspect of this application, 10mm ≤ L1 ≤ 0.4L.

[0021] In one or more of the above optional embodiments, by making L1 greater than or equal to 10 mm, the sum of the maximum lengths of all the first gaps is larger, which is beneficial for forming a larger channel for the electrolyte to enter the electrode assembly within the inner ring of the electrode assembly. This facilitates the full wetting of the electrode assembly by the electrolyte, further improving the cycle performance of the cell and reducing the risk of lithium plating, thereby further improving the cell's safety performance. A larger sum of the maximum lengths of all the first gaps can also further improve the efficiency of electrolyte entering the electrode assembly, thereby further improving the wetting efficiency of the electrode assembly; by making L1 less than... The value is 10mm≤L1≤0.4L, which ensures that the sum of the maximum lengths of all the first gaps is not too large, thus making the tab larger in the length direction of the electrode. This gives the tab better current carrying capacity, which is beneficial for achieving high current charging and discharging. It also gives the cell better rate performance and reduces the distance of electron transmission, further reducing the cell internal resistance, thereby further reducing cell heat generation and further extending the cell life. Therefore, 10mm≤L1≤0.4L gives the cell better cycle performance, safety performance, rate performance and service life.

[0022] In some embodiments of the first aspect of this application, 0.1L≤L1≤0.4L.

[0023] In one or more of the above optional embodiments, by making L1 greater than or equal to 0.1L, the sum of the maximum lengths of all the first gaps is larger, which is beneficial for forming larger channels for the electrolyte to enter the electrode assembly within the inner ring of the electrode assembly. This facilitates the full wetting of the electrode assembly by the electrolyte, further improving the cycle performance of the cell and reducing the risk of lithium plating, thereby further improving the cell's safety performance. A larger sum of the maximum lengths of all the first gaps can also further improve the efficiency of electrolyte entering the electrode assembly, thereby further improving the wetting efficiency of the electrode assembly; by making L1 A value less than or equal to 0.4L ensures that the sum of the maximum lengths of all the first gaps is not too large, thus allowing the tabs to have a larger dimension in the length direction of the electrode sheet. This results in better current carrying capacity of the tabs, which is beneficial for achieving high-current charging and discharging. It also gives the cell better rate performance and can further reduce the distance of electron transmission, reduce the internal resistance of the cell, thereby reducing the heat generation of the cell and extending the life of the cell. Therefore, 0.1L≤L1≤0.4L gives the cell better cycle performance, safety performance, rate performance and service life.

[0024] In some embodiments of the first aspect of this application, when the electrode is in the unfolded state, the maximum width of the electrode is H, the maximum depth of the first notch is H1, and 1mm≤H1≤0.1H.

[0025] In one or more of the above optional embodiments, by having H1 greater than or equal to 1 mm, the size of the first notch is relatively large, providing a larger channel for the electrolyte to enter the internal layers of the electrode assembly. This facilitates the full wetting of the electrode assembly by the electrolyte, improves the cycle performance of the cell, reduces the risk of lithium plating, and enhances the cell's safety performance. The larger notch also improves the efficiency of electrolyte entry into the electrode assembly, thereby increasing the wetting efficiency of the electrode assembly. By having H1 less than or equal to 0.1 H, the depth of the first notch is not too large, reducing or avoiding energy density loss in the cell, resulting in a higher energy density and better current carrying capacity for the tabs. This facilitates high-current charging and discharging, giving the cell better rate performance and reducing electron transmission distance, thus reducing internal resistance, heat generation, and extending cell lifespan. Therefore, 1 mm ≤ H1 ≤ 0.1 H results in a cell with good cycle performance, safety performance, rate performance, and lifespan.

[0026] In some embodiments of the first aspect of this application, 0.01H ≤ H1 ≤ 0.08H.

[0027] In one or more of the above optional embodiments, by having H1 greater than or equal to 0.01H, the size of the first notch is relatively large, providing a larger channel for the electrolyte to enter the internal layers of the electrode assembly. This facilitates the full wetting of the electrode assembly by the electrolyte, improves the cycle performance of the cell, reduces the risk of lithium plating, and enhances the cell's safety performance. The larger notch also improves the efficiency of electrolyte entry into the electrode assembly, thereby further improving the wetting efficiency of the electrode assembly. By having H1 less than or equal to 0.08H, the depth of the first notch is not too large, further reducing or avoiding energy density loss in the cell, resulting in a higher energy density and better current carrying capacity of the tabs. This facilitates high-current charging and discharging, giving the cell better rate performance and reducing the electron transmission distance, further reducing the cell's internal resistance, thereby further reducing cell heat generation and extending the cell's lifespan. Therefore, 0.01H ≤ H1 ≤ 0.08H results in better cycle performance, safety performance, rate performance, and lifespan for the cell.

[0028] In some embodiments of the first aspect of this application, when the electrode is in the unfolded state, the maximum length of the electrode along the length direction of the electrode is L, and the sum of the maximum lengths of all the second notches is L2, where L2≤0.4L.

[0029] In one or more of the above optional embodiments, by ensuring that L2 is less than or equal to 0.4L, the sum of the maximum lengths of all the second gaps is not too large, thereby making the tab larger in the length direction of the electrode sheet. This gives the tab better current carrying capacity, which is beneficial for achieving high current charging and discharging. It also gives the cell better rate performance and reduces the distance of electron transmission, thereby reducing the internal resistance of the cell, reducing the heat generated by the cell, and extending the life of the cell.

[0030] In some embodiments of the first aspect of this application, L2 ≤ 0.08L.

[0031] In one or more of the above optional embodiments, by making L2 less than or equal to 0.05L, the sum of the maximum lengths of all the second gaps is not too large, thereby making the size of the tab in the length direction of the electrode larger, so that the tab has better current carrying capacity, which is conducive to realizing high current charging and discharging, making the cell have better rate performance and reducing the distance of electron transmission, reducing the internal resistance of the cell, thereby reducing the heat generation of the cell and extending the life of the cell.

[0032] In some embodiments of the first aspect of this application, when the electrode is in the unfolded state, the maximum width of the electrode is H, the maximum depth of the second notch is H2, and H2≤0.1H.

[0033] In one or more of the above optional embodiments, by ensuring that H2 is less than or equal to 0.1H, the depth of the second notch is not too large, which can reduce or avoid the energy density loss of the battery cell, enabling the battery cell to have a larger energy density and the tab to have better overcurrent capability, which is conducive to realizing high current charging and discharging, enabling the battery cell to have better rate performance, and reducing the distance of electron transmission, reducing the internal resistance of the battery cell, thereby reducing the heat generation of the battery cell and extending the life of the battery cell; therefore, H2≤0.1H enables the battery cell to have better cycle performance, safety performance, rate performance and service life.

[0034] In some embodiments of the first aspect of this application, 0.01H ≤ H2 ≤ 0.05H.

[0035] In one or more of the above optional embodiments, by ensuring that H2 is greater than or equal to 0.01H, the size of the second notch is relatively large, providing a larger channel for the electrolyte to enter the outer ring of the electrode assembly. This facilitates the full wetting of the electrode assembly by the electrolyte, improves the cycle performance of the cell, reduces the risk of lithium plating, and enhances the cell's safety performance. The larger notch also improves the efficiency of electrolyte entering the electrode assembly, thereby further improving the wetting efficiency of the electrode assembly. By ensuring that H2 is less than or equal to 0.05H, the depth of the second notch is not too large, further reducing or avoiding energy density loss in the cell, resulting in a higher energy density and better current carrying capacity for the tabs. This facilitates high-current charging and discharging, giving the cell better rate performance and reducing the electron transmission distance, thus reducing internal resistance, reducing heat generation, and extending the cell's lifespan. Therefore, 0.01H≤H2≤0.05H results in the cell having good cycle performance, safety performance, rate performance, and lifespan.

[0036] In some embodiments of the first aspect of this application, when the electrode is in the unfolded state, the maximum depth of the first notch is H1, the maximum depth of the second notch is H2, and H1 > H2.

[0037] In one or more of the above optional embodiments, by ensuring that H1 is greater than H2, all the first gaps can form larger channels for the electrolyte to enter the internal rings of the electrode assembly. This facilitates the full wetting of the internal rings of the electrode assembly by the electrolyte, improves the cycle performance of the cell, reduces the risk of lithium plating, and enhances the cell's safety performance. Furthermore, H1 being greater than H2 can reduce the wetting difference between the inner and outer rings of the electrode assembly, improve the wetting consistency between the inner and outer rings, reduce the risk of lithium plating, and enhance the cell's safety performance.

[0038] In some embodiments of the first aspect of this application, when the electrode is in the unfolded state, the sum of the maximum depths of all the first notches is greater than the sum of the maximum depths of all the second notches.

[0039] In one or more of the above optional embodiments, by ensuring that the sum of the maximum depths of all first notches is greater than the sum of the maximum depths of all second notches, all first notches can form larger channels for electrolyte to enter the internal layers of the electrode assembly. This facilitates the full wetting of the internal layers of the electrode assembly by the electrolyte, improves the cycle performance of the cell, reduces the risk of lithium plating, and enhances the cell's safety performance. Furthermore, the fact that the sum of the maximum depths of all first notches is greater than the sum of the maximum depths of all second notches can also reduce the wetting difference between the inner and outer layers of the electrode assembly, improve the wetting consistency between the inner and outer layers of the electrode assembly, reduce the risk of lithium plating, and enhance the cell's safety performance.

[0040] In some embodiments of the first aspect of this application, when the electrode is in the unfolded state and along the length direction of the electrode, the second notch closest to the winding end is the end notch, one end of the end notch extends to the winding end, the minimum distance between the notch closest to the end notch and the end notch along the length direction of the electrode is L3, and the maximum length of the electrode is L, 0.2L≤L3≤0.6L.

[0041] In one or more of the above optional embodiments, if L3 is greater than or equal to 0.2L, the length of the portion of the tab located between the end notch and the notch closest to the end notch is relatively large, thereby making the overall size of the first tab of the electrode larger. This is beneficial to improving the current carrying capacity of the tab, enabling high-current charging and discharging, giving the cell better rate performance, reducing the electron transmission distance, reducing the cell internal resistance, thereby reducing cell heat generation and extending cell life. If L3 is less than or equal to 0.6L, the length of the portion of the tab located between the end notch and the notch closest to the end notch is not too large, thereby making the sum of the lengths of all notches relatively large. This allows the notches to form larger channels for the electrolyte to enter the electrode assembly, which is beneficial to the electrode assembly being fully wetted by the electrolyte, improving the cell cycle performance, reducing the risk of lithium plating, and improving the cell safety performance. A larger notch can also improve the efficiency of electrolyte entering the electrode assembly, thereby improving the wetting efficiency of the electrode assembly; therefore, 0.2L≤L3≤0.6L gives the cell better rate performance, service life, as well as better safety and cycle performance.

[0042] In some embodiments of the first aspect of this application, when the electrode is in the unfolded state, along the length direction of the electrode, there is a distance between the one of the multiple notches closest to the winding end and the winding end, and the minimum distance between the one of the multiple notches closest to the winding end and the winding end is L4, 0.2L≤L4≤0.4L.

[0043] In one or more of the above optional embodiments, along the length direction of the electrode sheet, there is a distance between the one closest to the winding end among the multiple notches and the winding end. At least a portion of the electrode tab is located between the one closest to the winding end among the multiple notches and the winding end. By ensuring that L4 is greater than or equal to 0.2L, the portion of the electrode tab located between the one closest to the winding end among the multiple notches and the winding end has a larger dimension along the length direction of the electrode sheet. This results in the electrode tab having better current carrying capacity, which is beneficial for achieving high-current charging and discharging, and giving the battery cell a better rate capability. Performance improvements include reducing electron transport distance, lowering internal resistance, reducing heat generation, and extending cell lifespan. With L4 less than or equal to 0.4L, the portion of the electrode tab closest to the winding end among multiple notches along the electrode's length is not excessively large. This results in a larger sum of the lengths of all notches, creating a larger channel for electrolyte to enter the electrode assembly. This facilitates thorough electrolyte wetting of the electrode assembly, improves cell cycle performance, reduces the risk of lithium plating, and enhances cell safety. Larger notches also increase the efficiency of electrolyte entry into the electrode assembly, thus improving wetting efficiency. Therefore, 0.2L ≤ L4 ≤ 0.4L results in a cell with good rate performance, long lifespan, and good safety and cycle performance.

[0044] In some embodiments of the first aspect of this application, there are multiple first notches, and when the electrode is in the unfolded state, the multiple first notches are spaced apart.

[0045] In one or more of the above optional embodiments, there are multiple first notches, which are spaced apart. This allows the multiple first notches to form larger channels for the electrolyte to enter the electrode assembly, which is beneficial for the internal layers of the electrode assembly to be fully wetted by the electrolyte, improving the cycle performance of the cell, reducing the risk of lithium plating, improving the cell safety performance, and also improving the efficiency of electrolyte entering the electrode assembly, thereby improving the wetting efficiency of the electrode assembly. In addition, having multiple first notches means that the electrode tabs include multiple tab portions spaced apart along the length of the electrode, which helps to reduce the internal resistance of the electrode and increase the current flow between the electrode and the tabs.

[0046] In some embodiments of the first aspect of this application, there are multiple second notches, which are spaced apart when the electrode is in the unfolded state.

[0047] In one or more of the above optional embodiments, there are multiple second notches, which are spaced apart. This allows the multiple second notches to form larger channels for the electrolyte to enter the electrode assembly, which is beneficial for the internal layers of the electrode assembly to be fully wetted by the electrolyte, improving the cycle performance of the cell, reducing the risk of lithium plating, improving the cell safety performance, and also improving the efficiency of electrolyte entering the electrode assembly, thereby improving the wetting efficiency of the electrode assembly. In addition, having multiple second notches means that the electrode tabs include multiple tab portions spaced apart along the length of the electrode, which helps to reduce the internal resistance of the electrode and increase the current flow between the electrode and the tabs.

[0048] In some embodiments of the first aspect of this application, the tab includes an empty foil portion and a flattened portion. Along the winding axis, one end of the empty foil portion is connected to the main body region, and the other end of the empty foil portion is connected to the flattened portion.

[0049] In one or more of the above optional embodiments, the tab includes an empty foil portion and a flattened portion, which facilitates the connection of the tab of the electrode sheet to other structures, thereby improving the electrical connection stability between the tab and other structures.

[0050] In some embodiments of the first aspect of this application, the electrode assembly includes a positive electrode and a negative electrode, wherein at least one of the positive electrode and the negative electrode is the electrode.

[0051] In one or more of the above optional embodiments, if at least one of the positive electrode and the negative electrode is an electrode, it is beneficial for the electrolyte to enter the inner rings, which facilitates the wetting of the inner rings of the electrode assembly, thereby reducing the wetting difference between the inner and outer rings of the electrode assembly, improving the wetting consistency of the inner and outer rings of the electrode assembly, reducing the risk of lithium plating in the cell, improving the safety performance of the cell, and improving the cycle performance of the cell.

[0052] In some embodiments of the first aspect of this application, the battery cell is a cylindrical battery cell.

[0053] In one or more of the above optional embodiments, the cylindrical cell including the aforementioned electrode sheet facilitates the entry of electrolyte into the inner rings, which in turn facilitates the wetting of the inner rings of the electrode assembly, thereby reducing the wetting difference between the inner and outer rings of the electrode assembly, improving the wetting consistency of the inner and outer rings of the electrode assembly, reducing the risk of lithium plating in the cylindrical cell, improving the safety performance of the cylindrical cell, and improving the cycle performance of the cylindrical cell.

[0054] Secondly, embodiments of this application provide an electrical device, which includes the battery cell provided in any embodiment of the first aspect.

[0055] In one or more of the above optional embodiments, the battery cell provided in any embodiment of the first aspect has good safety performance, which is beneficial to improving the power safety and reliability of electrical equipment powered by the battery cell. Attached Figure Description

[0056] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope.

[0057] Figure 1 Cross-sectional views of the battery cell provided in some embodiments of this application; Figure 2 This is a schematic diagram of the unfolded electrode sheet provided in some embodiments of this application; Figure 3 This is a schematic diagram of the unfolded electrode sheet provided in some other embodiments of this application; Figure 4 This is a schematic diagram of the unfolded electrode sheet provided in some embodiments of this application; Figure 5 This is a schematic diagram of the unfolded electrode sheet provided in some embodiments of this application; Figure 6 This is a schematic diagram of the unfolded electrode sheet provided in some other embodiments of this application; Figure 7 This is a schematic diagram of the unfolded electrode sheet provided in some other embodiments of this application; Figure 8 This is a schematic diagram of the unfolded electrode sheet provided in some further embodiments of this application; Figure 9 A schematic diagram of the unfolded electrode sheet provided for further embodiments of this application; Figure 10 This is a schematic diagram of the unfolded electrode sheet provided for some other embodiments of this application.

[0058] Icons: 100-cell; 10-casing; 11-shell; 12-end cap; 20-electrode assembly; 21-electrode sheet; 211-main body area; 2111-winding start end; 2112-winding end; 212-tab; 212'-tab section; 2121-empty foil section; 2122-flattened section; 2123-first end; 2124-notch; 21241-first notch; 21242-second notch; 21243-end notch; 21a-positive electrode sheet; 211a - Positive electrode main body region; 212a - Positive electrode tab; 2121a - Positive electrode empty foil section; 2122a - Positive electrode flattening section; 21b - Negative electrode sheet; 211b - Negative electrode main body region; 212b - Negative electrode tab; 2121b - Negative electrode empty foil section; 2122b - Negative electrode flattening section; 22 - Separator membrane; 30 - Current collector; 40 - Electrode post; Q - Mid-section; X - Width direction of electrode sheet; X' - Winding axis direction; Y - Thickness direction of electrode sheet; Z - Length direction of electrode sheet. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0060] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of this application can be combined with each other.

[0061] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0062] In the description of the embodiments of this 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 commonly used when the product of this application is in use, or the orientation or positional relationship commonly understood by those skilled in the art. It is only for the convenience of describing this application and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation on this application. Furthermore, the terms "first," "second," "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0063] Currently, judging from market trends, the application of battery cells is becoming increasingly widespread. Battery cells are widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in power tools, drones, energy storage devices, and many other fields. As the application areas of battery cells continue to expand, the market demand is also constantly increasing.

[0064] All-tab cells are widely used due to their advantages such as high rate performance and high safety performance. However, because the tabs of all-tab cells are processed using a flattening process, they form flattened sections. The flattened sections have a high degree of compactness, making it difficult to wet the electrode components. Furthermore, for wound cells, the inner coils of electrode sheets are wound more tightly than the outer coils, resulting in poorer wettability of the inner coils. The significant difference in wettability between the inner and outer coils leads to poorer cycle performance and safety performance of the cell.

[0065] Based on the above considerations, in order to improve the cycle performance and safety performance of the battery cell, this application provides a battery cell including an electrode assembly. The electrode assembly has a wound structure and includes an electrode sheet. The electrode sheet includes a main body region and an electrode tab. Along the winding axis of the electrode assembly, the electrode tab protrudes from one end of the main body region. Along the winding direction of the electrode assembly, the main body region has a winding start end and a winding end end. When the electrode sheet is in the unfolded state, the end of the electrode tab away from the main body region is the first end. The electrode sheet is provided with multiple notches recessed from the first end toward the main body region. Along the thickness direction of the electrode sheet, the notches penetrate two opposite surfaces of the electrode sheet. The electrode sheet has a mid-section. The mid-section is perpendicular to the length direction of the electrode sheet. The multiple notches include a first notch located between the mid-section and the winding start end and a second notch located between the mid-section and the winding end end. The sum of the maximum lengths of all the first notches is greater than the sum of the maximum lengths of all the second notches.

[0066] When the electrode is in the unfolded state, the end of the electrode tab away from the main body area is the first end. The electrode has multiple recesses that are set from the first end toward the main body area. These recesses provide channels for the electrolyte to enter the electrode assembly, which helps to improve the wetting performance and efficiency of the electrode assembly.

[0067] Along the thickness direction of the electrode sheet, a notch penetrates two opposite surfaces of the electrode sheet. The electrode sheet has a mid-section perpendicular to the length direction of the electrode sheet. Multiple notches include a first notch located between the mid-section and the winding start end and a second notch located between the mid-section and the winding end end. The sum of the maximum lengths of all first notches is greater than the sum of the maximum lengths of all second notches. This makes the sum of the lengths of the notches corresponding to the inner rings near the winding axis larger after the electrode sheet is wound. This facilitates the entry of electrolyte into the inner rings, making it easier for the inner rings of the electrode assembly to be wetted. This reduces the wettability difference between the inner and outer rings of the electrode assembly, improves the wettability consistency between the inner and outer rings of the electrode assembly, reduces the risk of lithium plating in the cell, improves the safety performance of the cell, and helps improve the cycle performance of the cell.

[0068] The battery cells disclosed in the embodiments of this application can be used, but are not limited to, in electrical equipment such as electric two-wheelers, power tools, drones, and energy storage devices. Battery cells conforming to the operating conditions of this application can also be used as the power supply system for electrical equipment.

[0069] This application provides an electrical device that uses battery cells as a power source. The electrical device can be, but is not limited to, electronic devices, power tools, electric vehicles, drones, and energy storage devices. Electronic devices can include mobile phones, tablets, laptops, etc.; power tools can include electric drills, chainsaws, etc.; and electric vehicles can include electric cars, electric motorcycles, electric bicycles, etc.

[0070] like Figure 1 As shown, this application provides a battery cell 100, which includes a housing 10 and an electrode assembly 20, with the electrode assembly 20 housed within the housing 10.

[0071] The outer casing 10 can be a rigid casing, such as a stainless steel casing or an aluminum casing, to form a steel-cased battery or an aluminum-cased battery, respectively.

[0072] like Figure 1 As shown, the outer casing 10 includes a housing 11 and an end cap 12. The housing 11 is a component for housing the electrode assembly 20, with at least a portion of the electrode assembly 20 housed within the housing 11. The housing 11 can have various shapes, such as cylindrical, cuboid, etc. The housing 11 can be made of various materials, such as copper, iron, aluminum, steel, aluminum alloy, etc. The electrode assembly 20 can be partially or completely located within the housing 11. Figure 1 As shown, the housing 11 has a cylindrical structure, and the battery cell 100 is a cylindrical battery cell 100. An electrode post 40 can be provided on the end cover 12. The electrode post 40 is electrically connected to the electrode assembly 20 to form an electrode terminal of the battery cell 100.

[0073] The electrode assembly 20 includes a negative electrode 21b, a positive electrode 21a, and a separator 22. The separator 22 provides insulation between the positive electrode 21a and the negative electrode 21b to reduce the risk of short circuit in the cell 100. The material of the separator 22 may include PP (polypropylene) or PE (polyethylene), etc.

[0074] The electrode assembly 20 has a wound structure. The negative electrode 21b, the separator 22, the positive electrode 21a, and another separator 22 are stacked in a specific order and then wound to form the wound electrode assembly 20; alternatively, the separator 22, the positive electrode 21a, the other separator 22, and the negative electrode 21b are stacked in a specific order and then wound to form the wound electrode assembly 20. The wound electrode assembly 20 can be a cylindrical structure, a flat structure, etc.

[0075] The positive electrode 21a includes a positive electrode body region 211a and a positive electrode tab 212a. The positive electrode body region 211a includes a positive electrode current collector and a positive electrode active material layer. The positive electrode current collector has the positive electrode active material layer disposed on at least one side in its thickness direction. The positive electrode tab 212a is connected to one end of the positive electrode current collector in its width direction, and the positive electrode tab 212a and the positive electrode current collector can be integrally formed. For lithium-ion batteries, the positive electrode current collector can be made of aluminum. The positive electrode active material layer can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc.

[0076] The negative electrode 21b includes a negative electrode body region 211b and a negative electrode tab 212b. The negative electrode body region 211b includes a negative electrode current collector and a negative electrode active material layer. The negative electrode current collector has the negative electrode active material layer disposed on at least one side in its thickness direction. The negative electrode tab 212b is connected to one end of the negative electrode current collector in its width direction, and the negative electrode tab 212b and the negative electrode current collector can be integrally formed. For lithium-ion batteries, the material of the negative electrode current collector can be copper, and the negative electrode active material can be carbon or silicon, etc.

[0077] The positive electrode tab 212a and the negative electrode tab 212b can be a full-tab structure. The positive electrode tab 212a and the negative electrode tab 212b can be located at opposite ends of the electrode assembly 20 along the winding axis.

[0078] The positive electrode tab 212a has a positive electrode empty foil portion 2121a and a positive electrode flattening portion 2122a. The positive electrode flattening portion 2122a is formed after the positive electrode tab 212a is wound and then flattened. Specifically, the positive electrode tab 212a is operated by a rotary kneading method to knead and compress the multi-layer positive electrode tab 212a, which was originally relatively high and sparsely distributed along the winding axis Y, thereby reducing its height in the extension direction Y of the winding axis. This results in a part of the positive electrode tab 212a forming a compact positive electrode flattening portion 2122a, which is then bonded and connected to the current collector 30.

[0079] The positive electrode empty foil portion 2121a is a part of the positive electrode tab 212a connecting the positive electrode main body region 211a and the positive electrode flattening portion 2122a. The positive electrode empty foil portion 2121a has a first connecting end connecting the positive electrode main body region 211a and a second connecting end connecting the positive electrode flattening portion 2122a. The extension direction of the positive electrode empty foil portion 2121a from the first connecting end to the second connecting end can be parallel to the direction Y of the winding axis, or inclined relative to the direction Y of the winding axis. Alternatively, a part of the positive electrode empty foil portion 2121a may extend from the first connecting end to the second connecting end in a direction parallel to the direction Y of the winding axis, while another part of the positive electrode empty foil portion 2121a may extend from the first connecting end to the second connecting end in a direction inclined relative to the direction Y of the winding axis.

[0080] The negative electrode tab 212b has a negative electrode empty foil portion 2121b and a negative electrode flattening portion 2122b. The negative electrode flattening portion 2122b is formed after the negative electrode tab 212b is wound and then flattened. Specifically, the negative electrode tab 212b is flattened by a rotational bending method, which compresses the multi-layer negative electrode tab 212b that was originally relatively high and sparsely distributed along the winding axis Y direction, thereby reducing its height in the extension direction Y of the winding axis. This results in a part of the negative electrode tab 212b forming a compact negative electrode flattening portion 2122b, which is then bonded and connected to the compacted negative electrode flattening portion 2122b by another current collector 30.

[0081] The negative electrode empty foil portion 2121b is a part of the negative electrode tab 212b connecting the negative electrode main body region 211b and the negative electrode flattening portion 2122b. The negative electrode empty foil portion 2121b has a third connecting end connecting the negative electrode main body region 211b and a fourth connecting end connecting the negative electrode flattening portion 2122b. The extension direction of the negative electrode empty foil portion 2121b from the third connecting end to the fourth connecting end can be parallel to the direction Y of the winding axis, or inclined relative to the direction Y of the winding axis. Alternatively, a part of the negative electrode empty foil portion 2121b may extend from the third connecting end to the fourth connecting end in a direction parallel to the direction Y of the winding axis, while another part of the negative electrode empty foil portion 2121b may extend from the third connecting end to the fourth connecting end in a direction inclined relative to the direction Y of the winding axis.

[0082] The current collector 30 connected to the positive electrode flattening part 2122a and the current collector 30 connected to the negative electrode flattening part 2122b can be welded to the electrode post 40 and the housing 11 respectively, so that the electrode post 40 and the housing 11 respectively form two electrode terminals with opposite polarities of the cell 100.

[0083] like Figure 2 As shown, this application embodiment provides an electrode 21, which includes a main body region 211 and an electrode tab 212. Along the axial direction of the electrode assembly 20, the electrode tab 212 protrudes from one end of the main body region 211. Along the winding direction of the electrode assembly 20, the main body region 211 has a winding start end 2111 and a winding end end 2112. When the electrode 21 is in the unfolded state, the end of the electrode tab 212 away from the main body region 211 is the first end 2123. The electrode 21 is provided with a plurality of notches 2124 recessed from the first end 2123 toward the main body region 211. Along the thickness direction Y of the electrode, the notches 2124 penetrate two opposite surfaces of the electrode.

[0084] When the electrode 21 is in the unfolded state, the end of the tab 212 that is away from the main body region 211 is the first end 2123. The electrode 21 is provided with multiple notches 2124 that are recessed from the first end 2123 toward the main body region 211. The notches 2124 can provide a channel for the electrolyte to enter the electrode assembly 20, which is beneficial to improve the wetting performance and increase the wetting efficiency of the electrode assembly 20.

[0085] The electrode 21 has a mid-section Q, which is perpendicular to the length direction Z of the electrode. Multiple notches 2124 include a first notch 21241 located between the mid-section Q and the winding start end 2111 and a second notch 21242 located between the mid-section Q and the winding end end 2112. The sum of the maximum lengths of all the first notches 21241 is greater than the sum of the maximum lengths of all the second notches 21242.

[0086] At least one of the positive electrode 21a and the negative electrode 21b of the electrode assembly 20 is an electrode 21. Specifically, one of the positive electrode 21a and the negative electrode 21b can be an electrode 21, and both electrode 21a and the negative electrode 21b can be electrode 21. It should be noted that "at least one of the negative electrode 21b and the positive electrode 21a is an electrode 21" means that the structure of at least one of the negative electrode 21b and the positive electrode 21a is the same as the structure of electrode 21.

[0087] If the positive electrode 21a of the electrode assembly 20 is electrode 21, then the positive electrode main body region 211a of the positive electrode 21a is the main body region 211 of electrode 21, and the positive electrode tab 212a is the tab 212 of electrode 21. If the negative electrode 21b of the electrode assembly 20 is electrode 21, then the negative electrode main body region 211b of the negative electrode 21b is the main body region 211 of electrode 21, and the negative electrode tab 212b is the tab 212 of electrode 21.

[0088] In some embodiments, the tab 212 includes an empty foil portion 2121 and a flattened portion 2122. Along the winding axis direction X', one end of the empty foil portion 2121 is connected to the main body region 211, and the other end of the empty foil portion 2121 is connected to the flattened portion 2122.

[0089] If the positive electrode 21a of the electrode assembly 20 is electrode 21, then the positive electrode empty foil portion 2121a of the positive electrode tab 212a is the empty foil portion 2121 of the tab 212 of electrode 21, and the positive electrode flattened portion 2122a of the positive electrode tab 212a is the flattened portion 2122 of the tab 212 of electrode 21. If the negative electrode 21b of the electrode assembly 20 is electrode 21, then the negative electrode empty foil portion 2121b of the negative electrode tab 212b is the empty foil portion 2121 of the tab 212 of electrode 21, and the negative electrode flattened portion 2122b of the negative electrode tab 212b is the flattened portion 2122 of the tab 212 of electrode 21.

[0090] The mid-section Q is a plane located at the exact midpoint of the main body region 211 of the electrode 21 along its length direction Z and perpendicular to the length direction Z of the electrode 21 when the electrode 21 is in the unfolded state. The mid-section Q divides the main body region 211 of the electrode 21 into two parts of equal length along its length direction Z. It should be noted that the length direction of the electrode 21 when it is in the unfolded state corresponds to the winding direction of the electrode 21 when it is in the wound state, and the width direction of the electrode 21 when it is in the unfolded state corresponds to the winding axis direction X' of the electrode 21 when it is in the wound state. When the electrode 21 is in the unfolded state, the length direction Z, the width direction X, and the thickness direction Y of the electrode are all perpendicular to each other.

[0091] The winding start end 2111 refers to the end where the electrode 21 begins to be wound, and the winding end 2112 refers to the end where the electrode 21 ends to be wound.

[0092] like Figure 2 As shown, in some embodiments, along the length direction Z of the electrode sheet, the mid-section Q is located between two adjacent notches 2124. Then, a portion of the notches 2124 of the electrode sheet 21 can be located between the mid-section Q and the winding start end 2111, which is the first notch 21241. Another portion of the notches 2124 of the electrode sheet 21 is located between the mid-section Q and the winding end end 2112.

[0093] like Figure 2 As shown, a first notch 21241 can extend to the winding start end 2111, which facilitates the electrolyte wetting of the central region of the electrode assembly 20 and improves the cycle life of the cell 100. Of course, there can be a distance between the first notch 21241 closest to the winding start end 2111 and the winding start end 2111, which facilitates the connection between the tab 212 and other structures and improves the connection stability between the tab 212 and other structures.

[0094] like Figure 3 As shown, in some embodiments, along the length direction Z of the electrode sheet, a portion of a notch 2124 is located on the side of the mid-section Q near the winding start end 2111, and another portion of the notch 2124 is located on the side of the mid-section Q near the winding end end 2112. The portion of the notch 2124 located on the side of the mid-section Q near the winding start end 2111 is the first notch 21241, and the portion of the notch 2124 located on the side of the mid-section Q near the winding end end 2112 is the second notch 21242.

[0095] The shape of the notch 2124 can be various. For example, when the electrode 21 is in the unfolded state, when viewed along the thickness direction Y of the electrode, the shape of the notch 2124 can be U-shaped, V-shaped, semi-circular, trapezoidal, etc.

[0096] For example, such as Figure 2 , Figure 3 As shown, when the electrode 21 is in the unfolded state, when viewed along the thickness direction Y of the electrode, the shape of the notch 2124 is trapezoidal. The position where the notch 2124 is the longest along the length direction Z of the electrode is located at the first end 2123. Along the direction from the tab 212 to the main body area 211, the length of the notch 2124 gradually decreases along the length direction Z of the electrode.

[0097] When the electrode 21 is in the unfolded state, the notch 2124 has a side wall surface located in the length direction Z of the electrode and a bottom wall surface located in the width direction X of the electrode. The side wall surface and the bottom wall surface can be arranged at an obtuse angle to reduce the risk of stress concentration and reduce the risk of the electrode 21 tearing at the junction of the side wall surface and the bottom wall surface.

[0098] In some embodiments, the angle between the sidewall and the bottomwall is α, where 15° ≤ α < 180°.

[0099] For example, 'a' can be 15°, 20°, 30°, 40°, 50°, 60°, 70°, 80°, 90°, 100°, 110°, 120°, 130°, 140°, 150°, 160°, 170°, etc.

[0100] In some embodiments, 100°≤a≤160°.

[0101] For example, 'a' can be 100°, 105°, 115°, 125°, 135°, 145°, 155°, 160°, etc.

[0102] Along the length direction Z of the electrode, the maximum length of the notch 2124 is the distance between the two farthest positions.

[0103] After winding, the portion of electrode 21 located at the mid-section Q and the winding start end 2111 is wound to form the inner layer of electrode assembly 20, and the portion of electrode 21 located at the mid-section Q and the winding end end 2112 is wound to form the outer layer of electrode assembly 20.

[0104] If the sum of the maximum lengths of all first gaps 21241 is greater than the sum of the maximum lengths of all second gaps 21242, then the sum of the maximum lengths of all gaps 2124 in the inner ring of the electrode 21 is greater than the sum of the maximum lengths of all gaps 2124 in the outer ring of the electrode 21.

[0105] Therefore, since the sum of the maximum lengths of all the first notches 21241 is greater than the sum of the maximum lengths of all the second notches 21242, after the electrode sheet 21 is wound, the sum of the lengths of the notches 2124 corresponding to the inner rings near the winding axis is larger. This is beneficial for the electrolyte to enter the inner rings, which facilitates the wetting of the inner rings of the electrode assembly 20, thereby reducing the wetting difference between the inner and outer rings of the electrode assembly 20, improving the wetting consistency of the inner and outer rings of the electrode assembly 20, reducing the risk of lithium plating in the cell 100, improving the safety performance of the cell 100, and improving the cycle performance of the cell 100.

[0106] The first gap, 21241, can be a single gap. For example... Figure 3As shown, there can be multiple first notches 21241. In embodiments where there are multiple first notches 21241, when the electrode 21 is in the unfolded state, the multiple first notches 21241 are spaced apart, allowing them to form larger channels for the electrolyte to enter the electrode assembly 20. This facilitates the full wetting of the internal layers of the electrode assembly 20 by the electrolyte, improving the cycle performance of the cell 100, reducing the risk of lithium plating, improving the safety performance of the cell 100, and increasing the efficiency of electrolyte entry into the electrode assembly 20, thereby improving the wetting efficiency of the electrode assembly 20. Furthermore, having multiple first notches 21241 means that the tabs 212 of the electrode 21 include multiple tab portions 212' arranged at Z intervals along the length direction of the electrode, which helps to reduce the internal resistance of the electrode 21 and increases the current flow between the electrode and the tabs 212.

[0107] like Figure 2 As shown, the second gap 21242 can be a single gap. (As...) Figure 3 As shown, there can be multiple second notches 21242. In embodiments where there are multiple second notches 21242, when the electrode 21 is in the unfolded state, the multiple second notches 21242 are spaced apart, allowing them to form larger channels for the electrolyte to enter the electrode assembly 20. This facilitates the full wetting of the internal layers of the electrode assembly 20 by the electrolyte, improving the cycle performance of the cell 100, reducing the risk of lithium plating, improving the safety performance of the cell 100, and increasing the efficiency of electrolyte entry into the electrode assembly 20, thereby improving the wetting efficiency of the electrode assembly 20. Furthermore, having multiple second notches 21242 allows the tabs 212 of the electrode 21 to include multiple tab portions 212' spaced apart along the length direction Z of the electrode, which helps to reduce the internal resistance of the electrode 21 and increases the current flow between the electrode and the tabs 212.

[0108] like Figure 4 , Figure 5 As shown, in some embodiments, when the electrode 21 is in the unfolded state, along the width direction X of the electrode, the depth of at least one notch 2124 is less than the width of the tab 212.

[0109] The depth of the notch 2124 refers to the dimension by which the notch 2124 is recessed from the first end 2123 along the width direction X of the electrode sheet when the electrode sheet 21 is in the unfolded state. The width of the tab 212 refers to the distance from the first end 2123 to the connection position with the main body region 211 along the width direction X of the electrode sheet when the electrode sheet 21 is in the unfolded state.

[0110] Of all the notches 2124 in the electrode 21, some of the notches 2124 have a depth less than the width of the tab 212, while the depth of other notches 2124 is greater than or equal to the width of the tab 212. Figure 4 The diagram shows a case where the depth of one portion of the notch 2124 is less than the width of the tab 212, while the depth of another portion of the notch 2124 is equal to the width of the tab 212. Alternatively, as... Figure 5 As shown, the depth of all the notches 2124 of the first tab 212 is less than the width of the tab 212.

[0111] By ensuring that the depth of at least one notch 2124 is less than the width of the tab 212 when the electrode 21 is in the unfolded state, the main body area 211 of the electrode 21 is cut less or avoided during the formation of the notch 2124, thereby reducing energy density loss and enabling the cell 100 to have better energy density.

[0112] like Figures 2-4 As shown, in some embodiments, when the electrode 21 is in the unfolded state, along the width direction X of the electrode, the depth of at least one notch 2124 is equal to the width of the tab 212.

[0113] Of all the notches 2124 in the electrode 21, a portion of the notches 2124 have a depth equal to the width of the tab 212, while the depth of another portion of the notches 2124 is either less than or greater than the width of the tab 212. Alternatively, as... Figure 2 and Figure 3 As shown, the depth of all the notches 2124 of the first tab 212 is equal to the width of the tab 212.

[0114] When the electrode 21 is in the unfolded state, at least one notch 2124 has a depth equal to the width of the tab 212 along the width direction X of the electrode, which facilitates the manufacturing and shaping of the notch 2124.

[0115] like Figure 6 As shown, in some embodiments, when the electrode 21 is in the unfolded state, the depth of the notch 2124 along the width direction X of the electrode is greater than the width of the tab 212.

[0116] Of all the notches 2124 in the electrode 21, some of the notches 2124 have a depth greater than the width of the tab 212, while the depth of other notches 2124 is less than or equal to the width of the tab 212. Figure 6 The diagram shows that a portion of the notch 2124 has a depth greater than the width of the tab 212, while another portion of the notch 2124 has a depth equal to the width of the tab 212. Alternatively, as... Figure 7 As shown, the depth of all the notches 2124 of the first tab 212 is greater than the width of the tab 212.

[0117] When the electrode 21 is in the unfolded state, the depth of the notch 2124 along the width direction X of the electrode is greater than the width of the tab 212. The larger size of the notch 2124 allows for a larger channel for the electrolyte to enter the electrode assembly 20, facilitating thorough wetting of the electrode assembly 20 by the electrolyte. This improves the cycle performance of the cell 100, reduces the risk of lithium plating, and enhances the safety performance of the cell 100. The larger notch 2124 also increases the efficiency of electrolyte entry into the electrode assembly 20, thereby improving the wetting efficiency of the electrode assembly 20.

[0118] like Figures 2-7 As shown, in some embodiments, when the electrode 21 is in the unfolded state, the maximum length of the electrode 21 along the length direction Z is L, and the sum of the maximum lengths of all notches 2124 is L'≤0.8L.

[0119] L is the distance between the two ends of electrode 21 that are furthest apart along the length Z of electrode 21 when electrode 21 is in the unfolded state.

[0120] For example, L' can be 0.1L, 0.2L, 0.3L, 0.4L, 0.5L, 0.6L, 0.7L, 0.8L, etc., and any value within the range defined by any two of these values.

[0121] By ensuring that L' is less than or equal to 0.8L, the sum of the maximum lengths of all notches 2124 is not too large, thus making the tab 212 have a larger dimension in the length direction Z of the electrode. This gives the tab 212 better current carrying capacity, which is beneficial for achieving high current charging and discharging. This also gives the cell 100 better rate performance and reduces the distance of electron transmission, lowers the internal resistance of the cell 100, thereby reducing the heat generated by the cell 100 and extending the life of the cell 100.

[0122] In some embodiments, 2mm≤L'≤0.5L.

[0123] For example, L can be 2mm, 2.5mm, 3mm, 3.5mm, 5mm, 0.05L, 0.15L, 0.25L, 0.35L, 0.45L, 0.5L, etc., and any value within the range defined by any two of these values.

[0124] By ensuring that L' is greater than or equal to 2 mm, the sum of the maximum lengths of all notches 2124 is larger, allowing the notches 2124 to form larger channels for electrolyte to enter the electrode assembly 20. This facilitates the full wetting of the electrode assembly 20 by the electrolyte, improves the cycle performance of the cell 100, reduces the risk of lithium plating, and enhances the safety performance of the cell 100. Larger notches 2124 also improve the efficiency of electrolyte entry into the electrode assembly 20, thus increasing the wetting efficiency of the electrode assembly 20. By ensuring that L' is less than or equal to 0.5 L, the sum of the maximum lengths of all notches 2124 is larger, allowing the notches 2124 to form larger channels for electrolyte to enter the electrode assembly 20. The sum of the maximum lengths of the notches 2124 is not too large, thus making the tab 212 larger in the Z-direction of the electrode sheet. This gives the tab 212 better current carrying capacity, which is conducive to realizing high current charging and discharging. This allows the cell 100 to have better rate performance and can reduce the distance of electron transmission, reduce the internal resistance of the cell 100, thereby reducing the heat generation of the cell 100 and extending the life of the cell 100. Therefore, 2mm≤L'≤0.5L gives the cell 100 better cycle performance, safety performance, rate performance and service life.

[0125] In some embodiments, 0.1L ≤ L' ≤ 0.4L.

[0126] For example, L' can be 0.1L, 0.11L, 0.12L, 0.13L, 0.14L, 0.16L, 0.17L, 0.18L, 0.19L, 0.21L, 0.22L, 0.24L, 0.26L, 0.28L, 0.31L, 0.32L, 0.34L, 0.36L, 0.38L, 0.4L, etc., and any value within the range defined by any two of these values.

[0127] By ensuring that L' is greater than or equal to 0.1L, the sum of the maximum lengths of all the gaps 2124 is made larger, allowing the gaps 2124 to form larger channels for the electrolyte to enter the electrode assembly 20. This facilitates the full wetting of the electrode assembly 20 by the electrolyte, improves the cycle performance of the cell 100, reduces the risk of lithium plating, and enhances the safety performance of the cell 100. The larger notch 2124 can also improve the efficiency of electrolyte entering the electrode assembly 20, thereby further improving the wetting efficiency of the electrode assembly 20; by ensuring that L' is less than or equal to 0.4L, the sum of the maximum lengths of all notches 2124 is not too large, thus making the tab 212 larger in the length direction Z of the electrode sheet, which gives the tab 212 better current carrying capacity, which is conducive to realizing high current charging and discharging, giving the cell 100 better rate performance and reducing the distance of electron transmission, further reducing the internal resistance of the cell 100, thereby further reducing the heat generation of the cell 100 and extending the life of the cell 100. Therefore, 0.1L≤L'≤0.4L gives the cell 100 better cycle performance, safety performance, rate performance and service life.

[0128] like Figures 2-7 As shown, in some embodiments, when the electrode 21 is in the unfolded state, the maximum length of the electrode 21 along the length direction Z is L, and the sum of the maximum lengths of all the first notches 21241 is L1, where 1mm≤L1≤0.5L.

[0129] For example, L1 can be 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 0.1L, 0.2L, 0.3L, 0.4L, 0.5L, etc., and any value within the range defined by any two of these values.

[0130] By ensuring that L1 is greater than or equal to 1 mm, the sum of the maximum lengths of all first notches 21241 is larger. This facilitates the formation of larger channels for electrolyte to enter the electrode assembly 20 within its internal layers, ensuring sufficient wetting of the electrode assembly 20 by the electrolyte. This improves the cycle performance of the cell 100, reduces the risk of lithium plating, and enhances the safety performance of the cell 100. A larger sum of the maximum lengths of all first notches 21241 also increases the efficiency of electrolyte entry into the electrode assembly 20, thereby improving the wetting efficiency of the electrode assembly 20. By ensuring that L1 is less than or equal to 0.5 L, the sum of the maximum lengths of all first notches 21241 is larger. The sum of the maximum lengths of 41 is not too large, thus ensuring that the sum of the maximum lengths of all notches 2124 is not too large. This results in a larger dimension of tab 212 in the length direction Z of the electrode sheet, giving tab 212 better current carrying capacity, which is beneficial for achieving high current charging and discharging. This also gives cell 100 better rate performance and reduces the distance of electron transmission, lowers the internal resistance of cell 100, thereby reducing heat generation of cell 100 and extending the life of cell 100. Therefore, 1mm≤L1≤0.5L gives cell 100 better cycle performance, safety performance, and tab 212 better current carrying capacity.

[0131] In some embodiments, 10mm≤L1≤0.4L.

[0132] For example, L1 can be 10mm, 11.5mm, 12mm, 12.5mm, 13mm, 13.5mm, 14mm, 14.5mm, 15mm, 0.12L, 0.15L, 0.18L, 0.22L, 0.25L, 0.28L, 0.32L, 0.35L, 0.38L, 0.4L, etc., and any value within the range defined by any two of these values.

[0133] By ensuring L1 is greater than or equal to 10 mm, the sum of the maximum lengths of all first notches 21241 is increased, which facilitates the formation of larger channels for electrolyte to enter the electrode assembly 20 within its internal rings. This promotes full electrolyte wetting of the electrode assembly 20, further improving the cycle performance of the cell 100 and reducing the risk of lithium plating, thereby enhancing the safety performance of the cell 100. A larger sum of the maximum lengths of all first notches 21241 also further improves the efficiency of electrolyte entry into the electrode assembly 20, thus increasing the wetting efficiency of the electrode assembly 20. By ensuring L1 is less than or equal to 0.4 L, the sum of the maximum lengths of all first notches 21241 is increased. The sum of the maximum lengths of the first notch 21241 is not too large, thus ensuring that the sum of the maximum lengths of all notches 2124 is not too large. This results in a larger dimension of the tab 212 in the length direction Z of the electrode, giving the tab 212 better current carrying capacity, which is beneficial for achieving high-current charging and discharging. This also gives the cell 100 better rate performance and reduces the distance of electron transmission, further reducing the internal resistance of the cell 100, thereby further reducing the heat generation of the cell 100 and further extending the life of the cell 100. Therefore, 10mm≤L1≤0.4L gives the cell 100 better cycle performance, safety performance, rate performance and service life.

[0134] In some embodiments, 0.1L ≤ L1 ≤ 0.4L.

[0135] For example, L can be 0.1L, 0.12L, 0.14L, 0.16L, 0.18L, 0.22L, 0.24L, 0.26L, 0.28L, 0.32L, 0.34L, 0.36L, 0.38L, 0.4L, etc., as well as any value within the range defined by any two of these values.

[0136] By ensuring L1 is greater than or equal to 0.1L, the sum of the maximum lengths of all first notches 21241 is increased, which facilitates the formation of larger channels for electrolyte to enter the electrode assembly 20 within its internal layers. This promotes full electrolyte wetting of the electrode assembly 20, further improving the cycle performance of the cell 100 and reducing the risk of lithium plating, thereby enhancing the safety performance of the cell 100. A larger sum of the maximum lengths of all first notches 21241 also improves the efficiency of electrolyte entry into the electrode assembly 20, thus further improving the wetting efficiency of the electrode assembly 20. By ensuring L1 is less than or equal to 0.4L, the sum of the maximum lengths of all first notches 21241 is increased, which in turn improves the efficiency of electrolyte wetting of the electrode assembly 20. The sum of the maximum lengths of all the first gaps 21241 is not too large, thus ensuring that the sum of the maximum lengths of all the gaps 2124 is not too large. This results in a larger dimension of the tab 212 in the length direction Z of the electrode, giving the tab 212 better current carrying capacity, which is beneficial for achieving high current charging and discharging. This also gives the cell 100 better rate performance and can further reduce the distance of electron transmission, reduce the internal resistance of the cell 100, thereby reducing the heat generation of the cell 100 and extending the life of the cell 100. Therefore, 0.1L≤L1≤0.4L gives the cell 100 better cycle performance, safety performance, rate performance and service life.

[0137] like Figures 2-7 As shown, in some embodiments, when the electrode 21 is in the unfolded state, the maximum width of the electrode 21 is H, the maximum depth of the first notch 21241 is H1, and 1mm≤H1≤0.1H.

[0138] H1 is merely a symbol representing the maximum depth of the first gap 21241, and does not mean that all the first gaps 21241 have the same maximum depth. The maximum depth of each first gap 21241 can be the same, or at least two first gaps 21241 can have different maximum depths.

[0139] For example, H1 can be 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 0.01H, 0.02H, 0.03H, 0.04H, 0.05H, 0.06H, 0.07H, 0.08H, 0.09H, 0.1H, etc., and any value within the range defined by any two of these values.

[0140] By ensuring that H1 is greater than or equal to 1 mm, the size of the first notch 21241 is relatively large, providing a larger channel for the electrolyte to enter the internal layers of the electrode assembly 20. This facilitates the full wetting of the electrode assembly 20 by the electrolyte, improves the cycle performance of the cell 100, reduces the risk of lithium plating, and enhances the safety performance of the cell 100. The larger notch 2124 also improves the efficiency of electrolyte entry into the electrode assembly 20, thereby increasing the wetting efficiency of the electrode assembly 20. By ensuring that H1 is less than or equal to 0.1 H, the depth of the first notch 21241 is relatively large. The temperature is not too high, which can reduce or avoid the energy density loss of the battery cell 100, so that the battery cell 100 has a large energy density, and the tab 212 has a good overcurrent capability, which is conducive to realizing high current charging and discharging. This gives the battery cell 100 a good rate performance and can reduce the distance of electron transmission, reduce the internal resistance of the battery cell 100, thereby reducing the heat generation of the battery cell 100 and extending the life of the battery cell 100. Therefore, 1mm≤H1≤0.1H gives the battery cell 100 good cycle performance, safety performance, rate performance and service life.

[0141] In some embodiments, 0.01H ≤ H1 ≤ 0.08H.

[0142] For example, H1 can be 0.01H, 0.015H, 0.025H, 0.035H, 0.045H, 0.055H, 0.065H, 0.075H, 0.08H, etc., and any value within the range defined by any two of these values.

[0143] By ensuring that H1 is greater than or equal to 0.01H, the size of the first notch 21241 is relatively large, providing a larger channel for the electrolyte to enter the internal layers of the electrode assembly 20. This facilitates the full wetting of the electrode assembly 20 by the electrolyte, improves the cycle performance of the cell 100, reduces the risk of lithium plating, and enhances the safety performance of the cell 100. The larger notch 2124 also improves the efficiency of electrolyte entry into the electrode assembly 20, thereby further improving the wetting efficiency of the electrode assembly 20. By ensuring that H1 is less than or equal to 0.08H, the depth of the first notch 21241 is not less than... The larger value of H1 further reduces or avoids energy density loss in cell 100, resulting in higher energy density and better current handling capability of tab 212. This facilitates high-current charging and discharging, improves rate performance, reduces electron transmission distance, lowers internal resistance, reduces heat generation, and extends cell lifespan. Therefore, 0.01H ≤ H1 ≤ 0.08H results in better cycle performance, safety performance, rate performance, and lifespan for cell 100.

[0144] like Figures 2-7As shown, in some embodiments, when the electrode 21 is in the unfolded state, the maximum length of the electrode 21 along the length direction Z is L, and the sum of the maximum lengths of all the second notches 21242 is L2, where L2≤0.4L.

[0145] For example, L2 can be 0.05L, 0.1L, 0.15L, 0.2L, 0.25L, 0.35L, 0.4L, etc., and any value within the range defined by any two of these values.

[0146] By ensuring that L2 is less than or equal to 0.4L, the sum of the maximum lengths of all second notches 21242 is not too large, thus ensuring that the sum of the maximum lengths of all notches 2124 is not too large. This results in a larger dimension of tab 212 in the length direction Z of the electrode, giving tab 212 better current carrying capacity, which is beneficial for achieving high current charging and discharging. This also gives cell 100 better rate performance and reduces the distance of electron transmission, lowers the internal resistance of cell 100, thereby reducing heat generation of cell 100 and extending the life of cell 100.

[0147] In some embodiments, L2 ≤ 0.08L.

[0148] For example, L2 can be 0.01L, 0.015L, 0.02L, 0.025L, 0.03L, 0.035L, 0.04L, 0.045L, 0.05L, 0.055L, 0.06L, 0.065L, 0.07L, 0.075L, 0.08L, etc., and any value within the range defined by any two of these values.

[0149] By ensuring that L2 is less than or equal to 0.05L, the sum of the maximum lengths of all second notches 21242 is not too large, thus preventing the sum of the maximum lengths of all notches 2124 from becoming excessive. This results in a larger dimension of the tab 212 in the length direction Z of the electrode, enabling the tab 212 to have better current carrying capacity, which is beneficial for achieving high-current charging and discharging. This also allows the cell 100 to have better rate performance and reduce the distance of electron transmission, thereby reducing the internal resistance of the cell 100, reducing the heat generated by the cell 100, and extending the life of the cell 100.

[0150] like Figures 2-7 As shown, in some embodiments, when the electrode 21 is in the unfolded state, the maximum width of the electrode 21 is H, and the maximum depth of the second notch 21242 is H2, where H2≤0.1H.

[0151] H2 is merely a symbol representing the maximum depth of the second gap 21242, and does not mean that all second gaps 21242 have the same maximum depth. The maximum depth of each second gap 21242 can be the same, or at least two second gaps 21242 can have different maximum depths.

[0152] For example, H2 can be 0.01H, 0.02H, 0.03H, 0.04H, 0.05H, 0.06H, 0.07H, 0.08H, 0.09H, 0.1H, etc., and any value within the range defined by any two of these values.

[0153] By ensuring that H2 is less than or equal to 0.1H, the depth of the second notch 21242 is not too large, which reduces or avoids energy density loss in the cell 100, resulting in a higher energy density in the cell 100. This also allows the tab 212 to have better overcurrent capability, facilitating high-current charging and discharging. Furthermore, this results in better rate performance, reduced electron transport distance, lower internal resistance, reduced heat generation, and extended lifespan. Therefore, H2 ≤ 0.1H ensures that the cell 100 exhibits good cycle performance, safety performance, rate performance, and lifespan.

[0154] In some embodiments, 0.01H ≤ H2 ≤ 0.05H.

[0155] For example, H2 can be 0.01H, 0.012H, 0.015H, 0.018H, 0.022H, 0.024H, 0.026H, 0.028H, 0.032H, 0.034H, 0.036H, 0.038H, 0.042H, 0.044H, 0.046H, 0.048H, 0.05H, etc., and any value within the range defined by any two of these values.

[0156] By ensuring that H2 is greater than or equal to 0.01H, the second notch 21242 is larger, providing a larger channel for the electrolyte to enter the outer layer of the electrode assembly 20. This facilitates the full wetting of the electrode assembly 20 by the electrolyte, improves the cycle performance of the cell 100, reduces the risk of lithium plating, and enhances the safety performance of the cell 100. The larger notch 21242 also improves the efficiency of electrolyte entering the electrode assembly 20, thereby further improving the wetting efficiency of the electrode assembly 20. By ensuring that H2 is less than or equal to 0.05H, the depth of the second notch 21242 is... The degree of heat generation is not too large, which can further reduce or avoid the energy density loss of the battery cell 100, so that the battery cell 100 has a higher energy density and the tab 212 has a better overcurrent capability, which is conducive to realizing high current charging and discharging. This gives the battery cell 100 a better rate performance and can reduce the distance of electron transmission, reduce the internal resistance of the battery cell 100, thereby reducing the heat generation of the battery cell 100 and extending the life of the battery cell 100. Therefore, 0.01H≤H2≤0.05H gives the battery cell 100 good cycle performance, safety performance, rate performance and service life.

[0157] like Figure 8 , Figure 9 As shown, in some embodiments, H1 > H2. Figure 8 The diagram shows the case where, with the electrode 21 in the unfolded state, the depth of the second notch 21242 is equal to the width of the tab 212, and the depth of the first notch 21241 is less than the width of the tab 212. Figure 9 The diagram shows the case where, with the electrode 21 in the unfolded state, the depth of the second notch 21242 is less than the width of the tab 212, and the depth of the first notch 21241 is equal to the width of the tab 212.

[0158] By ensuring that H1 is greater than H2, all first gaps 21241 can form larger channels for electrolyte to enter the internal layers of the electrode assembly 20. This facilitates the full wetting of the internal layers of the electrode assembly 20 by the electrolyte, improving the cycle performance of the cell 100 and reducing the risk of lithium plating, thus enhancing the safety performance of the cell 100. Furthermore, H1 being greater than H2 can reduce the wetting difference between the inner and outer layers of the electrode assembly 20, improving the wetting consistency between the inner and outer layers, further reducing the risk of lithium plating in the cell 100, and enhancing the safety performance of the cell 100.

[0159] In some embodiments, when the electrode 21 is in the unfolded state, the sum of the maximum depths of all the first notches 21241 is greater than the sum of the maximum depths of all the second notches 21242.

[0160] By ensuring that the sum of the maximum depths of all first notches 21241 is greater than the sum of the maximum depths of all second notches 21242, all first notches 21241 can form larger channels for electrolyte to enter the internal layers of the electrode assembly 20. This facilitates the full wetting of the internal layers of the electrode assembly 20 by the electrolyte, improves the cycle performance of the cell 100, reduces the risk of lithium plating, and enhances the safety performance of the cell 100. Furthermore, the greater sum of the maximum depths of all first notches 21241 than the sum of the maximum depths of all second notches 21242 also reduces the wetting difference between the inner and outer layers of the electrode assembly 20, improves the wetting consistency between the inner and outer layers of the electrode assembly 20, reduces the risk of lithium plating in the cell 100, and enhances the safety performance of the cell 100.

[0161] like Figures 2-9 As shown, in some embodiments, when the electrode 21 is in the unfolded state and along the length direction Z of the electrode, the second notch 21242 closest to the winding end 2112 is the end notch 21243, one end of the end notch 21243 extends to the winding end 2112, and along the length direction Z of the electrode, the minimum distance between the notch 2124 closest to the end notch 21243 and the end notch 21243 is L3, and the maximum length of the electrode 21 is L, 0.2L≤L3≤0.6L.

[0162] Along the length Z of the electrode, the notch 2124 closest to the end notch 21243 can be a first notch 21241 (e.g. Figure 2 ), or it could be a second gap 21242 (e.g. Figure 3 (As shown). The portion between the end notch 21243 and the notch 2124 closest to the end notch 21243 is a part of the tab 212. L3 is the length of the portion of the tab 212 located between the end notch 21243 and the notch 2124 closest to the end notch 21243 along the length direction Z of the electrode.

[0163] For example, L3 can be 0.2L, 0.25L, 0.3L, 0.35L, 0.4L, 0.45L, 0.5L, 0.55L, 0.6L, etc., and any value within the range defined by any two of these values.

[0164] When L3 is greater than or equal to 0.2L, the length of the portion of the tab 212 located between the end notch 21243 and the notch 2124 closest to the end notch 21243 is larger. This results in a larger overall size of the first tab 212 of the electrode 21, which is beneficial for improving the current carrying capacity of the tab 212 of the electrode 21, facilitating high-current charging and discharging, giving the cell 100 better rate performance, reducing the electron transmission distance, lowering the internal resistance of the cell 100, thereby reducing heat generation in the cell 100, and extending the cell's lifespan. The lifespan of the cell 100 is 100. A value of L3 less than or equal to 0.6L ensures that the length of the portion of the tab 212 located between the end notch 21243 and the notch 2124 closest to the end notch 21243 is not excessive. This results in a larger sum of lengths for all notches 2124, allowing them to form larger channels for electrolyte to enter the electrode assembly 20. This facilitates full electrolyte wetting of the electrode assembly 20, improves the cycle performance of the cell 100, reduces the risk of lithium plating, and enhances the safety performance of the cell 100. A larger notch 2124 also improves the efficiency of electrolyte entry into the electrode assembly 20, thus increasing the wetting efficiency of the electrode assembly 20. Therefore, 0.2L ≤ L3 ≤ 0.6L results in the cell 100 having good rate performance, lifespan, and good safety and cycle performance.

[0165] like Figure 10 As shown, in some embodiments, when the electrode 21 is in the unfolded state, along the length direction Z of the electrode, there is a distance between the one of the multiple notches 2124 closest to the winding end 2112 and the winding end 2112. The minimum distance between the one of the multiple notches 2124 closest to the winding end 2112 and the winding end 2112 is L4, where 0.2L≤L4≤0.4L.

[0166] The one closest to the winding end 2112 among the multiple notches 2124 is a second notch 21242. The portion between the winding end 2112 and the one closest to the winding end 2112 among the multiple notches 2124 is a tab 212, where L4 is the length of the portion of the tab 212 located between the winding end 2112 and the one closest to the winding end 2112 among the multiple notches 2124 along the length direction Z of the electrode sheet.

[0167] For example, L4 can be 0.2L, 0.22L, 0.25L, 0.28L, 0.3L, 0.32L, 0.35L, 0.38L, 0.4L, etc., and any value within the range defined by any two of these values.

[0168] Along the length Z of the electrode sheet, there is a distance between the one closest to the winding end 2112 among the multiple notches 2124 and the winding end 2112. Therefore, at least a portion of the tab 212 of the electrode sheet 21 is located between the one closest to the winding end 2112 among the multiple notches 2124 and the winding end 2112. By ensuring that L4 is greater than or equal to 0.2L, the portion of the tab 212 of the electrode sheet 21 located between the one closest to the winding end 2112 among the multiple notches 2124 and the winding end 2112 has a larger dimension in the length Z of the electrode sheet. This results in the tab 212 of the electrode sheet 21 having better current carrying capacity, which is beneficial for achieving high-current charging and discharging, and gives the cell 100 better rate performance. This reduces the distance of electron transmission, lowers the internal resistance of the cell 100, thereby reducing heat generation and extending the lifespan of the cell 100. By ensuring that L4 is less than or equal to 0.4L, the portion of the tab 212 of the electrode 21 located between the closest notch 2124 to the winding end 2112 and the winding end 2112 is not too large in the length direction Z of the electrode. This results in a larger sum of the lengths of all notches 2124 in the length direction Z of the electrode, allowing the notches 2124 to form larger channels for the electrolyte to enter the electrode assembly 20. This facilitates the full wetting of the electrode assembly 20 by the electrolyte, improves the cycle performance of the cell 100, reduces the risk of lithium plating, and enhances the safety performance of the cell 100. The larger notch 2124 can also improve the efficiency of electrolyte entering the electrode assembly 20, thereby improving the wetting efficiency of the electrode assembly 20; therefore, 0.2L≤L4≤0.4L, which makes the cell 100 have better rate performance, service life, and good safety and cycle performance.

[0169] This application also provides an electrical device, which includes the battery cell 100 provided in any of the above embodiments. The battery cell 100 provides electrical energy to the electrical device.

[0170] The battery cell 100 provided in any of the above embodiments has good safety performance, which is beneficial to improving the power safety and reliability of electrical equipment powered by the battery cell 100.

[0171] The battery cell 100 was subjected to cycle life testing, and the data in Table 1 was obtained. The testing method is as follows: Cyclic life test method: Cell 100 was subjected to charge and discharge tests at different charging rates according to a specified voltage (e.g., 4.2V for full charge) at a temperature of 25℃: Cell 100 was placed in a 25℃ environment and left to stand for 30 minutes, then charged at a constant current of 2C to 4.2V, followed by a constant voltage charge of 4.2V to 0.05C; left to stand for 10 minutes; then discharged at a constant current of 8C to 2.5V, and left to stand for 30 minutes. This constituted one cycle. This cycle was repeated N times. After N cycles, the fully charged cell 100 was disassembled. If a gray, silver, or grayish-black interface appeared on the surface of the negative electrode 21b, it was considered lithium plating. During lithium plating, the more cycles the cell 100 underwent, the better its cycle life.

[0172] Example 1: Preparation method of cell 100: (a) Preparation of negative electrode 21b Artificial graphite (anode active material), silicon carbide (anode active material), sodium carboxymethyl cellulose (CMC-Na), and styrene-butadiene rubber (SBR) were mixed in a mass ratio of 82.45:14.55:1.7:1.3. Deionized water was then added as a solvent, and the mixture was stirred until homogeneous, yielding a negative electrode slurry with a solid content of 45 wt%. This negative electrode slurry was uniformly coated onto one surface of a 4 μm thick copper foil current collector. After drying at 105 °C, a negative electrode sheet 21b with a first negative electrode material layer coated on one side was obtained. The above steps were then repeated on the other surface of the same copper foil to obtain a negative electrode sheet 21b coated with both the first and second negative electrode material layers. After cold pressing, cutting, and slitting, a negative electrode sheet 21b with dimensions of 67.45 mm × 1730 mm was obtained for later use. The coating weight of the first and second negative electrode material layers was 0.06 g / 1540.25 mm. 2 The compacted density is 1.60 g / mm². 3 The first negative electrode material layer has dimensions of 62mm × 1730mm, and the second negative electrode material layer has the same dimensions as the first negative electrode material layer. The width of the empty foil area of ​​the negative electrode sheet 21b is 5.45mm. The empty foil area of ​​the negative electrode sheet 21b is the negative electrode tab 212b of the negative electrode sheet 21b. The negative electrode tab 212b does not have a notch 2124.

[0173] (II) Preparation of positive electrode 21a The positive electrode active material is lithium nickel cobalt manganese oxide (LiNi). 0.9 Co 0.5 Mn 0.5O2), polyvinylidene fluoride (PVDF) binder, and conductive carbon black were dispersed in N-methylpyrrolidone (NMP) solvent at a mass ratio of 97.1:1.6:1.3 and thoroughly mixed to obtain a positive electrode slurry with a solid content of 72 wt%. The positive electrode slurry was uniformly coated on one surface of a 11 μm thick aluminum foil for the positive electrode current collector and dried at 105 °C to obtain a positive electrode sheet 21a with a first positive electrode material layer coated on one side. Then, the above steps were repeated on the other surface of the aluminum foil for the positive electrode current collector to obtain a positive electrode sheet 21a with a first positive electrode material layer and a second positive electrode material layer coated.

[0174] The coating weight of the first and second positive electrode material layers is 0.15g / 1540.25mm. 2 The compacted density is 3.5 g / mm². 3 The positive electrode 21a has dimensions of 65.75mm × 1688mm, the first positive electrode material layer has dimensions of 60mm × 1688mm, and the second positive electrode material layer has the same dimensions as the first positive electrode material layer. The empty foil area of ​​the positive electrode 21a is the positive electrode tab 212a. Along the length of the positive electrode 21a, the positive electrode tab 212a has four first notches 21241 and one second notch 21242. The maximum sum of the maximum lengths of the four first notches 21241 is L1 = 400mm, the maximum sum of the maximum lengths of the second notches 21242 is L2 = 200mm, the maximum depth of the first notches 21241 is H1, and the maximum depth of the second notches 21242 is H2.

[0175] (iii) Thickness of the separator 22 A polyethylene (PE) film with a thickness of 9 μm was used as the separator 22.

[0176] (iv) Preparation of electrolyte In a dry argon-atmospheric glove box, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a mass ratio of 1:1:1 to obtain a base solvent (lithium salt solvent). Then, lithium hexafluorophosphate (LiPF6), along with vinylene carbonate (VC) and fluoroethylene carbonate (FEC) as additives, were added to the base solvent, with VC and FEC each added at 1%. After thorough mixing, an electrolyte was obtained. Based on the mass of the electrolyte, the mass percentage of LiPF6 was 12.5%, with the remainder being the base solvent.

[0177] (V) Preparation of Cell 100 The separator 22, negative electrode 21b, separator 22, and positive electrode 21a prepared above are stacked sequentially and wound to form an electrode assembly 20. Subsequently, the electrode assembly 20 is flattened, coated with adhesive, current collector welded, installed in a casing, bottom or end cap welded, injected with electrolyte, sealed, and formed to obtain a lithium-ion battery (cell 100). The upper limit of the formation voltage is 4.3V, and the formation temperature is 70℃.

[0178] Table 1

[0179] As shown in Table 1: (1) According to Comparative Examples 1-2 and Examples 1-3, by making the sum of the lengths of all the first gaps 21241 greater than the sum of the lengths of all the second gaps 21242, the number of cycles is significantly increased. Therefore, this solution can significantly improve the cycle life of the battery cell 100.

[0180] (2) As can be seen from Examples 1 and 2, the number of cycles of a cell 100 with a first notch 21241 extending to the winding start end 2111 is greater. Therefore, the extension of a first notch 21241 of the cell 100 to the winding start end 2111 is beneficial to improving the cycle life of the cell 100.

[0181] (3) As can be seen from Examples 2 and 3, as the sum of the lengths of all the first gaps 21241 increases, the number of cycles of the cell 100 increases. Therefore, increasing the sum of the lengths of all the first gaps 21241 is beneficial to improving the cycle life of the cell 100.

[0182] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art.

Claims

1. A battery cell, characterized in that, The battery cell includes an electrode assembly, which has a wound structure. The electrode assembly includes: An electrode sheet includes a main body region and a tab. Along the axial direction of the electrode assembly, the tab protrudes from one end of the main body region. Along the winding direction of the electrode assembly, the main body region has a winding start end and a winding end end. When the electrode sheet is in the unfolded state, the end of the electrode tab away from the main body area is the first end. The electrode sheet is provided with a plurality of notches recessed from the first end toward the main body area. Along the thickness direction of the electrode sheet, the notches penetrate two opposite surfaces of the electrode sheet. The electrode sheet has a mid-section, which is perpendicular to the length direction of the electrode sheet. The plurality of notches include a first notch located between the mid-section and the winding start end and a second notch located between the mid-section and the winding end end. The sum of the maximum lengths of all the first notches is greater than the sum of the maximum lengths of all the second notches.

2. The battery cell according to claim 1, characterized in that, When the electrode is in the unfolded state, along the width direction of the electrode, the depth of at least one of the notches is less than the width of the electrode tab; and / or, When the electrode is in the unfolded state, along the width direction of the electrode, the depth of at least one of the notches is equal to the width of the electrode tab; And / or, When the electrode is in the unfolded state, the depth of the notch is greater than the width of the tab along the width direction of the electrode.

3. The battery cell according to claim 1 or 2, characterized in that, When the electrode is in the unfolded state, along the length direction of the electrode, the maximum length of the electrode is L, and the sum of the maximum lengths of all the notches is L', where L'≤0.8L; optionally, 2mm≤L'≤0.5L; optionally, 0.1L≤L'≤0.4L.

4. The battery cell according to any one of claims 1-3, characterized in that, When the electrode is in the unfolded state, the maximum length of the electrode along the length direction of the electrode is L, and the sum of the maximum lengths of all the first notches is L1, where 1mm≤L1≤0.5L; optionally, 10mm≤L1≤0.4L; optionally, 0.1L≤L1≤0.4L.

5. The battery cell according to any one of claims 1-4, characterized in that, When the electrode is in the unfolded state, the maximum width of the electrode is H along the width direction of the electrode, and the maximum depth of the first notch is H1, where 1mm≤H1≤0.1H; optionally, 0.01H≤H1≤0.08H.

6. The battery cell according to any one of claims 1-5, characterized in that, When the electrode is in the unfolded state, the maximum length of the electrode along its length direction is L, and the sum of the maximum lengths of all the second notches is L2, where L2 ≤ 0.4L; optionally, L2 ≤ 0.08L.

7. The battery cell according to any one of claims 1-6, characterized in that, When the electrode is in the unfolded state, the maximum width of the electrode is H along the width direction of the electrode, and the maximum depth of the second notch is H2, where H2≤0.1H, and optionally, 0.01H≤H2≤0.05H.

8. The battery cell according to any one of claims 1-7, characterized in that, When the electrode is in the unfolded state, along the width direction of the electrode, the maximum depth of the first notch is H1, the maximum depth of the second notch is H2, and H1 > H2.

9. The battery cell according to any one of claims 1-8, characterized in that, When the electrode is in the unfolded state, along the width direction of the electrode, the sum of the maximum depths of all the first notches is greater than the sum of the maximum depths of all the second notches.

10. The battery cell according to any one of claims 1-9, characterized in that, When the electrode is in the unfolded state and along the length of the electrode, the second notch closest to the winding end is the end notch, and one end of the end notch extends to the winding end. Along the length of the electrode, the minimum distance between the notch closest to the end notch and the end notch is L3, and the maximum length of the electrode is L, where 0.2L≤L3≤0.6L.

11. The battery cell according to any one of claims 1-9, characterized in that, When the electrode is in the unfolded state, along the length direction of the electrode, there is a distance between the one of the plurality of notches closest to the winding end and the winding end. The minimum distance between the one of the plurality of notches closest to the winding end and the winding end is L4, where 0.2L≤L4≤0.4L.

12. The battery cell according to any one of claims 1-11, characterized in that, There are multiple first notches, and when the electrode is in the unfolded state, the multiple first notches are spaced apart; and / or, there are multiple second notches, and when the electrode is in the unfolded state, the multiple second notches are spaced apart.

13. The battery cell according to any one of claims 1-12, characterized in that, The battery cell is a cylindrical battery cell.

14. An electrical appliance, characterized in that, Includes the battery cell according to any one of claims 1-13.

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