Battery cell and electric equipment

Abstract

The invention provides a battery cell and electric equipment, the battery cell comprises an electrode assembly, and the electrode assembly is formed by winding a positive pole piece, a diaphragm and a negative pole piece which are stacked. A negative active material of the negative pole piece comprises a silicon-based material, and two surfaces of the negative current collector are completely coated with the negative active material. And the first straight section, the first corner section and the second straight section of the innermost ring of the positive pole piece and two surfaces of the positive current collector are coated with positive active materials. And the innermost ring of the negative pole piece comprises a third straight section, a second corner section and a fourth straight section. In the thickness direction of the electrode assembly, the first straight section is located between the third straight section and the fourth straight section, and the third straight section is located between the first straight section and the second straight section. The possibility of breakage caused by non-uniform stress of the negative electrode current collector can be reduced, and the service life of the battery cell can be prolonged; and the utilization rate of active materials is higher.

Description

Technical Field

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

[0002] With the rapid development of electronic information technology, various electronic devices are also moving towards intelligence and multi-functions, and the requirements for battery energy density are becoming higher and higher.

[0003] Batteries with silicon-based negative electrodes are favored because of their higher energy density, but their high expansion rate can cause breakage between the double-sided coated area and the single-sided coated area of ​​the negative electrode plate, and between the single-sided coated area and the double-sided empty foil area due to different expansion forces, which in turn leads to the problem of metal ion precipitation, affecting the battery's service life. Summary of the invention

[0004] The present application provides a battery cell and an electrical device, which can increase the service life of the battery cell.

[0005] In the first aspect, the present application provides a battery cell, which includes an electrode assembly, and the electrode assembly is wound by stacking a positive electrode sheet, a separator, and a negative electrode sheet. The negative electrode sheet includes a negative electrode collector and a negative electrode active material, the negative electrode active material includes a silicon-based material, and the negative electrode active material is completely coated on both surfaces of the negative electrode collector. The innermost circle of the positive electrode sheet includes a first straight section, a first corner section, and a second straight section, the first corner section connects the first straight section and the second straight section, and the end of the first straight section away from the first corner section is the winding starting end of the positive electrode sheet. The positive electrode sheet includes a positive electrode collector and a positive electrode active material, and the positive electrode active material is coated on both surfaces of the positive electrode collector in the first straight section, the first corner section, and the second straight section. The innermost circle of the negative electrode sheet includes a third straight section, a second corner section, and a fourth straight section, the second corner section connects the third straight section and the fourth straight section, and the end of the third straight section away from the second corner section is the winding starting end of the negative electrode sheet. Along the thickness direction of the electrode assembly, the first straight segment is located between the third straight segment and the fourth straight segment, and the third straight segment is located between the first straight segment and the second straight segment.

[0006] In the above technical solution, the negative electrode plate includes a negative electrode current collector and a negative electrode active material, and the negative electrode active material includes a silicon-based material, so that the negative electrode material can accommodate more metal ions, so that the energy density of the battery cell is higher. By completely coating the negative electrode active material on both surfaces of the negative electrode current collector, when the negative electrode active material expands, the difference in the expansion force at various locations of the negative electrode current collector is small, which can reduce the possibility of the negative electrode current collector being broken due to uneven force, thereby reducing the possibility of metal ion precipitation due to the breakage of the negative electrode current collector, which is beneficial to improving the service life of the battery cell; and there is no need to change the type during the coating process of the negative electrode active material, which can improve the efficiency of the coating process. The negative electrode active material is completely coated on both surfaces of the negative electrode current collector; the positive electrode active material is coated on both surfaces of the positive electrode current collector in the first straight section, the first corner section and the second straight section; along the thickness direction of the electrode assembly, the first straight section is located between the third straight section and the fourth straight section, and the third straight section is located between the first straight section and the second straight section, so that the positive electrode active material in the first straight section and the second straight section and the negative electrode active material in the third straight section and the fourth straight section can be used for the embedding and de-embedding of metal ions, thereby making the volume proportion of the positive electrode active material and the negative electrode active material larger and the utilization rate higher, which is beneficial to improving the energy density of the battery cell.

[0007] In some embodiments of the present application, in the negative electrode active material, the mass percentage of the silicon-based material is 4%-100%.

[0008] In the above technical solution, by making the mass percentage of the silicon-based material in the negative electrode active material be 4%-100%, the negative electrode material can accommodate more metal ions, so that the energy density of the battery cell is higher.

[0009] In some embodiments of the present application, the positive electrode plate includes a double-sided coating area and a single-sided coating area, one end of the double-sided coating area is the starting end of the winding of the positive electrode plate, and the other end is connected to the single-sided coating area; the single-sided coating area is located on the outer side of the outermost circle of the negative electrode plate, and the single-sided coating area is coated with positive active material on the side facing the negative electrode plate.

[0010] In the above technical scheme, by making the positive electrode plate include a double-sided coating area and a single-sided coating area, one end of the double-sided coating area is the starting end of the winding of the positive electrode plate, and the other end is connected to the single-sided coating area, so that the positive electrode active material in the double-sided coating area can cooperate with the corresponding negative electrode active material to realize the embedding and de-embedding of metal ions, and the double-sided coating area is beneficial to increase the volume proportion of the positive electrode active material, thereby facilitating the improvement of the energy density of the battery cell; since the single-sided coating area is located on the outer side of the outermost circle of the negative electrode plate, the positive electrode active material is arranged on the side of the single-sided coating area facing the negative electrode plate, that is, there is no negative electrode active material on the outer side of the single-sided coating area, so by setting the single-sided coating area, the positive electrode active material on the inner side of the single-sided coating area can cooperate with the negative electrode active material located on the outer side of the outermost circle of the negative electrode plate to realize the embedding and de-embedding of metal ions, and the positive electrode active material is not arranged on the outer side of the single-sided coating area, which can improve the utilization rate of the positive electrode active material, and can reduce the total thickness of the battery cell, which is beneficial to improve the energy density of the battery cell.

[0011] In some embodiments of the present application, the positive electrode plate further includes a double-sided empty foil area, one end of the double-sided empty foil area is connected to the single-sided coated area, and the other end is the winding end of the positive electrode plate.

[0012] In the above technical solution, the positive electrode plate also includes a double-sided empty foil area, one end of the double-sided empty foil area is connected to the single-sided coated area, and the other end is the winding end of the positive electrode plate, which can be easily finished and fixed through the double-sided empty foil area.

[0013] In some embodiments of the present application, the battery cell includes a first adhesive tape, and the first adhesive tape is attached to the inner surface of the first corner section.

[0014] In the above technical solution, since the first corner section corresponds to the starting end of the winding of the negative electrode sheet, the metal ions deintercalated from the positive electrode active materials on the inner side of the first corner section do not have enough corresponding negative electrode active materials for embedding. Therefore, the battery cell includes a first adhesive tape, and the first adhesive tape is attached to the inner surface of the first corner section, so that the first adhesive tape can cover the positive electrode active material on the inner side of the first corner section, reducing the possibility of metal ion precipitation in the first corner section, which is beneficial to extending the service life of the battery cell. In addition, the first adhesive tape covers the inner side of the first corner section, which can reduce the risk of powder falling caused by bending of the first corner section. The first adhesive tape can also play an insulating role between the starting end of the winding of the negative electrode sheet and the first corner section, reducing the possibility of short circuit between the negative electrode sheet and the positive electrode sheet, which is beneficial to improving the safety of the battery cell.

[0015] In some embodiments of the present application, along the thickness direction of the electrode assembly, the projection of the first adhesive tape and the projection of the third straight section have an overlapping area. Along the first direction, the length of the overlapping area is L1, satisfying 2mm≤L1≤5mm. The first direction, the thickness direction of the electrode assembly, and the winding axis direction of the electrode assembly are perpendicular to each other.

[0016] In the above technical solution, by making the projection of the first adhesive tape and the projection of the third straight segment have an overlapping area along the thickness direction of the electrode assembly, the area of ​​the positive electrode active material covered by the first adhesive tape corresponding to the starting end of the winding of the negative electrode sheet is larger, further reducing the possibility of metal ion precipitation in the first corner segment, which is beneficial to extending the service life of the battery cell.

[0017] When L1 is greater than or equal to 2mm, the area of ​​the positive electrode active material covered by the first adhesive tape can be larger, further reducing the possibility of metal ion precipitation in the first corner segment, which is beneficial to extending the service life of the battery cell; when L1 is less than or equal to 5mm, the space occupied by the first adhesive tape can be smaller, which is beneficial to reducing the overall volume of the electrode assembly and improving the energy density of the battery cell; therefore, when 2mm≤L1≤5mm, it can reduce the possibility of metal ion precipitation in the first corner segment, which is beneficial to extending the service life of the battery cell and improving the energy density of the battery cell.

[0018] In some embodiments of the present application, a first groove is provided on the inner surface of the first corner section, and at least a portion of the first adhesive tape is accommodated in the first groove.

[0019] In the above technical solution, by providing the inner surface of the first corner section with a first groove, at least part of the first adhesive tape is accommodated in the first groove, so that the first adhesive tape does not protrude from the positive electrode active material or the thickness of the part protruding from the positive electrode active material is smaller, thereby reducing the overall thickness of the first adhesive tape and the positive electrode plate, reducing the overall volume of the electrode assembly, and improving the energy density of the battery cell.

[0020] In some embodiments of the present application, the battery cell includes a second adhesive tape, which is attached to the outer surface of the first corner segment; along the winding direction of the battery cell, the length of the second adhesive tape is greater than the length of the first adhesive tape.

[0021] In the above technical solution, since the first adhesive tape is attached to the inner surface of the first corner section, the ductility of the inner surface of the first corner section will be reduced. When the positive electrode active material expands, the inner surface and the outer surface of the first corner section are unevenly stressed, which may cause the positive electrode collector of the first corner section to break. After the positive electrode collector breaks, the positive electrode active material on the inner surface of the first corner section will move to the outer surface of the first corner section through the crack, increasing the risk of metal ion precipitation. By making the battery cell include the second adhesive tape, the second adhesive tape is attached to the outer surface of the first corner section, so that when the positive electrode active material expands, the inner surface and the outer surface of the first corner section can be more evenly stressed, reducing the possibility of the positive electrode collector of the first corner section breaking. When the positive electrode collector of the first corner section breaks, the positive electrode active material on the inner surface of the first corner section moves to the outer surface of the first corner section through the crack. The second adhesive tape can reduce the risk of metal ion precipitation in the positive electrode active material on the outer surface of the first corner section, thereby improving the safety of the battery cell.

[0022] After the positive electrode sheet is wound, the outer surface of the first corner section extends longer than the inner surface along the winding direction of the battery cell. By making the length of the second tape greater than the length of the first tape along the winding direction of the battery cell, the overlapping area of ​​the projection of the second tape and the projection of the first tape along the thickness direction of the positive electrode sheet can be made larger, and further when the positive active material expands, the inner and outer surfaces of the first corner section are subjected to more uniform force, thereby reducing the possibility of breakage of the positive electrode collector in the first corner section.

[0023] In some embodiments of the present application, the electrode assembly includes two layers of diaphragms, which are respectively arranged on both sides of the negative electrode sheet along its thickness direction; the diaphragm and the negative electrode sheet are connected by thermal composite, and the end face of the diaphragm is aligned with the end face of the winding starting end of the negative electrode sheet.

[0024] In the above technical solution, the electrode assembly includes two layers of diaphragms, which are respectively arranged on both sides of the negative electrode sheet along its thickness direction, so that the diaphragm can play a role of isolating the positive electrode sheet and the negative electrode sheet, thereby reducing the risk of short circuit between the positive electrode sheet and the negative electrode sheet and improving the safety of the battery cell.

[0025] Since the diaphragm may shrink due to heat during subsequent processes such as the formation of the battery cell, the diaphragm and the negative electrode sheet are connected through thermal composite connection, and the end face of the diaphragm is aligned with the end face of the starting end of the winding of the negative electrode sheet. This makes it difficult for the end face of the diaphragm to separate from the end face of the starting end of the winding of the negative electrode sheet after the diaphragm is heated, thereby making the diaphragm have a better isolation effect between the positive electrode sheet and the negative electrode sheet, and the volume of the diaphragm is smaller. The end of the diaphragm will not be stacked in the winding center of the electrode assembly, which is beneficial to reducing the volume of the electrode assembly and improving the energy density of the battery cell.

[0026] In some embodiments of the present application, the electrode assembly includes two layers of separators, which are respectively arranged on both sides of the negative electrode sheet along its thickness direction; along the reverse direction of the winding of the battery cell, the two layers of separators extend beyond the winding start end of the negative electrode sheet and are connected. The length of the portion of the separator extending beyond the winding start end of the negative electrode sheet is L2, satisfying 0mm<L2≤20mm.

[0027] In the above technical solution, since the diaphragm may shrink due to heat during the subsequent formation process of the battery cell, by making the two layers of diaphragm extend beyond the starting end of the winding of the negative electrode sheet and connected in the opposite direction of the winding of the battery cell, the starting end of the winding of the negative electrode sheet can always be covered by the two layers of diaphragm without being exposed, thereby reducing the possibility of short circuit between the negative electrode sheet and the positive electrode sheet and improving the safety of the battery cell.

[0028] When L2 is greater than 0, the diaphragm can better isolate the negative electrode sheet from the positive electrode sheet, reduce the possibility of short circuit between the negative electrode sheet and the positive electrode sheet, and improve the safety of the battery cell; when L2 is less than or equal to 20mm, the volume of the diaphragm that exceeds the starting end of the winding of the negative electrode sheet can be smaller, thereby making the volume of the electrode assembly smaller, which is beneficial to improving the energy density of the battery cell; therefore, when 0mm<L2≤20mm, the diaphragm can better isolate the negative electrode sheet from the positive electrode sheet, reduce the possibility of short circuit between the negative electrode sheet and the positive electrode sheet, and improve the safety of the battery cell, and the volume of the diaphragm that exceeds the starting end of the winding of the negative electrode sheet can be smaller, thereby making the volume of the electrode assembly smaller, which is beneficial to improving the energy density of the battery cell.

[0029] In some embodiments of the present application, the battery cell includes a negative electrode tab, and the negative electrode tab is riveted to the negative electrode sheet.

[0030] In the above technical solution, since the welding method requires forming an empty foil area on the negative electrode sheet, by riveting the negative electrode tab to the negative electrode sheet, the process of forming the empty foil area on the negative electrode sheet can be omitted, further improving the preparation efficiency of the battery cell.

[0031] In some embodiments of the present application, the negative electrode plate has a first surface and a second surface arranged opposite to each other along the thickness direction thereof, and the negative electrode plate is provided with a through hole penetrating along the thickness direction thereof. The negative electrode tab includes a main body and a riveted portion, the main body is arranged on the first surface, the riveted portion is protruding from the main body and penetrating through the through hole, and an end of the riveted portion away from the main body is pressed against the second surface.

[0032] In the above technical solution, the negative electrode tab includes a main body and a rivet portion, the main body is arranged on the first surface, the rivet portion is protruded from the main body and passes through the through hole, and the end of the rivet portion away from the main body is pressed against the second surface. The riveting method between the negative electrode tab and the negative electrode sheet is simple and easy to prepare, and the connection between the negative electrode tab and the negative electrode sheet can be made stable, the negative electrode tab is not easy to separate from the negative electrode sheet, the reliability of the battery cell is high, and the tab connection can be achieved without removing the active material.

[0033] In a second aspect, the present application provides an electrical device, including a battery cell as described above, and the battery cell is used to provide electrical energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can also be obtained based on these drawings.

[0035] Figure 1 A schematic cross-sectional view of an electrode assembly of a battery cell provided in some embodiments of the present application;

[0036] Figure 2 A schematic diagram of the structure of the negative electrode sheet of the battery cell after unfolding provided in some embodiments of the present application;

[0037] Figure 3 A schematic diagram of the structure of a positive electrode sheet of a battery cell after unfolding provided in some embodiments of the present application;

[0038] Figure 4 A schematic diagram of the structure of a positive electrode sheet of a battery cell after unfolding provided in some other embodiments of the present application;

[0039] Figure 5 A schematic diagram of a partial structure of a battery cell provided in some other embodiments of the present application;

[0040] Figure 6 A schematic cross-sectional view of a battery cell provided in some other embodiments of the present application;

[0041] Figure 7 A schematic diagram of the structure of a battery cell after the diaphragm is unfolded provided in other embodiments of the present application;

[0042] Figure 8 A schematic cross-sectional view of a battery cell provided in some other embodiments of the present application;

[0043] Fig. 9 A schematic cross-sectional view of a partial structure of a battery cell provided in some embodiments of the present application;

[0044] Fig.10 Schematic diagram of the structure of the unfolded negative electrode sheet provided in other embodiments of the present application.

[0045] Icon: 10-electrode assembly; 100-positive electrode plate; 101-first straight section; 102-first corner section; 1021-first groove; 1022-second groove; 103-second straight section; 100a-double-sided coating area; 100b-single-sided coating area; 100c-double-sided empty foil area; 110-positive electrode collector; 120-positive electrode active material; 200-diaphragm; 210-base layer; 220-adhesive layer; 300-negative electrode plate; 301-third straight section; 302-second corner section; 303-fourth straight section; 300a-first surface ; 300b-second surface; 310-negative electrode current collector; 320-negative electrode active material; 330-through hole; 410-first adhesive tape; 420-second adhesive tape; 510-negative electrode tab; 511-main body; 512-rivet portion; 520-positive electrode tab; X-thickness direction of the electrode assembly; Y-first direction; Z-winding axis direction of the electrode assembly; A-length direction of the positive electrode sheet (negative electrode sheet / diaphragm) after unfolding; B-thickness direction of the positive electrode sheet (negative electrode sheet / diaphragm) after unfolding; C-width direction of the positive electrode sheet (negative electrode sheet / diaphragm) after unfolding. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be clearly described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of this application.

[0047] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by technicians in the technical field to which this application belongs; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0048] The terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order or a primary and secondary relationship.

[0049] Reference to "embodiment" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiment may be included in at least one embodiment of the present application. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments.

[0050] In the embodiments of the present application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width and other dimensions of various components in the embodiments of the present application shown in the drawings, as well as the overall thickness, length, width and other dimensions of the integrated device are only exemplary descriptions and should not constitute any limitation to the present application.

[0051] With the development of the new energy industry, batteries are gradually developing in the direction of high energy density and high power density. The negative electrode active materials of the battery generally include materials such as graphite and silicon, and among them, the silicon-based negative electrode is favored because of its high energy density, but the expansion rate of the silicon-based negative electrode is high, which will affect the performance of the battery. For example, the negative electrode plate in the current wound battery generally includes a double-sided coating area, a single-sided coating area and a double-sided empty foil area. Due to the high expansion force of the silicon-based negative electrode, the expansion force difference between the double-sided coating area, the single-sided coating area and the double-sided empty foil area is large, resulting in fractures between the double-sided coating area and the single-sided coating area, and between the single-sided coating area and the double-sided empty foil area due to uneven force, resulting in the precipitation of metal ions, which affects the service life of the battery.

[0052] In order to improve the service life of a battery cell, the present application provides a battery cell, which includes an electrode assembly, and the electrode assembly is wound by stacking a positive electrode sheet, a separator, and a negative electrode sheet. The negative electrode sheet includes a negative electrode collector and a negative electrode active material, the negative electrode active material includes a silicon-based material, and the negative electrode active material is completely coated on both surfaces of the negative electrode collector. The innermost circle of the positive electrode sheet includes a first straight section, a first corner section, and a second straight section, the first corner section connects the first straight section and the second straight section, and the end of the first straight section away from the first corner section is the winding starting end of the positive electrode sheet. The positive electrode sheet includes a positive electrode collector and a positive electrode active material, and the positive electrode active material is coated on both surfaces of the first straight section, the first corner section, and the second straight section. The innermost circle of the negative electrode sheet includes a third straight section, a second corner section, and a fourth straight section, the second corner section connects the third straight section and the fourth straight section, and the end of the third straight section away from the second corner section is the winding starting end of the negative electrode sheet. Along the thickness direction of the electrode assembly, the first straight segment is located between the third straight segment and the fourth straight segment, and the third straight segment is located between the first straight segment and the second straight segment.

[0053] In the battery cell of this structure, the negative electrode plate includes a negative electrode current collector and a negative electrode active material, and the negative electrode active material includes a silicon-based material, so that the negative electrode material can accommodate more metal ions, and the energy density of the battery cell is higher. By completely coating the negative electrode active material on both surfaces of the negative electrode current collector, when the negative electrode active material expands, the difference in the expansion force at various locations of the negative electrode current collector is small, which can reduce the possibility of the negative electrode current collector being broken due to uneven force, thereby reducing the possibility of metal ion precipitation due to the breakage of the negative electrode current collector, which is beneficial to improving the service life of the battery cell; and there is no need to change the type during the coating process of the negative electrode active material, which can improve the efficiency of the coating process. The negative electrode active material is completely coated on both surfaces of the negative electrode current collector; the positive electrode active material is coated on both surfaces of the positive electrode current collector in the first straight section, the first corner section and the second straight section; along the thickness direction of the electrode assembly, the first straight section is located between the third straight section and the fourth straight section, and the third straight section is located between the first straight section and the second straight section, so that the positive electrode active material in the first straight section and the second straight section and the negative electrode active material in the third straight section and the fourth straight section can be used for the embedding and de-embedding of metal ions, thereby making the volume proportion of the positive electrode active material and the negative electrode active material larger and the utilization rate higher, which is beneficial to improving the energy density of the battery cell.

[0054] The battery cell provided in the embodiment of the present application can be a secondary battery or a primary battery, for example, a lithium ion battery, a sodium ion battery or a magnesium ion battery, etc., which is not limited in the embodiment of the present application. The battery cell can be cylindrical, flat, rectangular or other shapes, etc., which is not limited in the embodiment of the present application.

[0055] The embodiments of the present application provide an electrical device that uses a battery cell as a power source. The electrical device may be, but is not limited to, a mobile phone, a tablet, a laptop computer, an electric toy, an electric tool, an electric vehicle, an electric car, a ship, a spacecraft, and the like.

[0056] See also Figure 1 and Figure 2 , Figure 1 A schematic cross-sectional view of an electrode assembly of a battery cell provided in some embodiments of the present application; Figure 2 This is a schematic diagram of the structure of the negative electrode sheet of the battery cell after it is unfolded provided in some embodiments of the present application.

[0057] The embodiment of the present application provides a battery cell, which includes an electrode assembly 10, which is formed by winding a stacked positive electrode sheet 100, a separator 200, and a negative electrode sheet 300. The negative electrode sheet 300 includes a negative electrode current collector 310 and a negative electrode active material 320, and the negative electrode active material 320 includes a silicon-based material. The negative electrode active material 320 is completely coated on both surfaces of the negative electrode current collector 310.

[0058] By making the negative electrode sheet 300 include a negative electrode current collector 310 and a negative electrode active material 320, and the negative electrode active material 320 includes a silicon-based material, the negative electrode material can accommodate more metal ions, so that the energy density of the battery cell is higher. By making the negative electrode active material 320 completely coated on both surfaces of the negative electrode current collector 310, when the negative electrode active material 320 expands, the difference in the expansion force received by each part of the negative electrode current collector 310 is small, which can reduce the possibility of the negative electrode current collector 310 being broken due to uneven force, thereby reducing the possibility of the negative electrode current collector 310 breaking and causing metal ion precipitation, which is beneficial to improving the service life of the battery cell; and there is no need to change the type during the coating process of the negative electrode active material 320 (changing the type means that the equipment types corresponding to double-sided coating and single-sided coating are different, and different types of equipment need to be replaced for different coating methods), which can improve the efficiency of the coating process.

[0059] In some embodiments, after the negative electrode sheet 300 is prepared, part of the negative electrode active material 320 is cleaned by laser or other methods to form an empty foil area for welding with the negative electrode tab 510. However, it does not affect the coating process of the negative electrode active material 320, so this solution also falls within the scope of completely coating the negative electrode active material 320 on both surfaces of the negative electrode current collector 310 in this application.

[0060] In some embodiments, the silicon-based material may include elemental silicon, a compound containing silicon, or the like.

[0061] In some embodiments, the innermost circle of the positive electrode sheet 100 includes a first straight section 101, a first corner section 102, and a second straight section 103. The first corner section 102 connects the first straight section 101 and the second straight section 103. The end of the first straight section 101 away from the first corner section 102 is the winding start end of the positive electrode sheet 100. The positive electrode sheet 100 includes a positive current collector 110 and a positive active material 120. The positive active material 120 is coated on both surfaces of the first straight section 101, the first corner section 102, and the second straight section 103. The innermost circle of the negative electrode sheet 300 includes a third straight section 301, a second corner section 302 and a fourth straight section 303. The second corner section 302 connects the third straight section 301 and the fourth straight section 303. The end of the third straight section 301 away from the second corner section 302 is the winding start end of the negative electrode sheet 300. Along the thickness direction X of the electrode assembly, the first straight section 101 is located between the third straight section 301 and the fourth straight section 303, and the third straight section 301 is located between the first straight section 101 and the second straight section 103.

[0062] The negative electrode active material 320 is completely coated on both surfaces of the negative electrode current collector 310; the positive electrode active material 120 is coated on both surfaces of the first straight section 101, the first corner section 102 and the second straight section 103; along the thickness direction X of the electrode assembly, the first straight section 101 is located between the third straight section 301 and the fourth straight section 303, and the third straight section 301 is located between the first straight section 101 and the second straight section 103, so that the positive electrode active material 120 of the first straight section 101 and the second straight section 103 and the negative electrode active material 320 of the third straight section 301 and the fourth straight section 303 can be used for the embedding and de-embedding of metal ions, so that the volume proportion of the positive electrode active material 120 and the negative electrode active material 320 is larger and the utilization rate is higher, which is beneficial to improve the energy density of the battery cell.

[0063] In some embodiments, along the first direction Y, the winding starting end of the positive electrode sheet 100 and the winding starting end of the negative electrode sheet 300 are in opposite directions, so that the winding starting end of the positive electrode sheet 100 and the winding starting end of the negative electrode sheet 300 form a plug-in structure, so that the positive electrode active material 120 at the winding starting end of the positive electrode sheet 100 and the negative electrode active material 320 at the winding starting end of the negative electrode sheet 300 can both be utilized, which is beneficial to improving the energy density of the battery cell, and the plug-in structure makes the battery cell more wrapped, which can further suppress the expansion of the negative electrode sheet 300.

[0064] The battery cell mainly relies on the movement of metal ions between the positive electrode sheet 100 and the negative electrode sheet 300 to work. Taking lithium-ion batteries as an example, the material of the positive electrode current collector 110 can be aluminum, and the positive electrode active material 120 can be lithium cobalt oxide, lithium iron phosphate, ternary materials or lithium manganese oxide. The material of the negative electrode current collector 310 can be copper. The material of the separator 200 can be polypropylene (PP) or polyethylene (PE).

[0065] In some embodiments, in the negative electrode active material 320, the mass percentage of the silicon-based material is 4%-100%. For example, the mass percentage of the silicon-based material may be 4%, 50% or 100%.

[0066] By making the mass percentage of the silicon-based material in the negative electrode active material 320 be 4%-100%, the negative electrode material can accommodate more metal ions, so that the energy density of the battery cell is higher.

[0067] When the mass percentage of the silicon-based material in the negative electrode active material 320 is less than 100%, the negative electrode active material 320 may further include a carbon material, such as graphite, to reduce the expansion rate of the negative electrode active material 320 .

[0068] See also Figure 3 , Figure 3This is a schematic diagram of the structure of the positive electrode sheet of the battery cell after it is unfolded provided in some embodiments of the present application.

[0069] In some embodiments, the positive electrode plate 100 includes a double-sided coating area 100a and a single-sided coating area 100b, one end of the double-sided coating area 100a is the starting end of the winding of the positive electrode plate 100, and the other end is connected to the single-sided coating area 100b; the single-sided coating area 100b is located on the outer side of the outermost circle of the negative electrode plate 300, and the single-sided coating area 100b is coated with the positive active material 120 facing the side of the negative electrode plate 300.

[0070] By making the positive electrode sheet 100 include a double-sided coating area 100a and a single-sided coating area 100b, one end of the double-sided coating area 100a is the winding start end of the positive electrode sheet 100, and the other end is connected to the single-sided coating area 100b, so that the positive electrode active material 120 of the double-sided coating area 100a can cooperate with the corresponding negative electrode active material 320 to achieve the embedding and de-embedding of metal ions, and the double-sided coating area 100a is conducive to increasing the volume proportion of the positive electrode active material 120, thereby facilitating the improvement of the energy density of the battery cell; since the single-sided coating area 100b is located outside the outermost circle of the negative electrode sheet 300, the positive electrode active material 120 is The material 120 is arranged on the side of the single-sided coating area 100b facing the negative electrode plate 300, that is, there is no negative electrode active material 320 on the outside of the single-sided coating area 100b. Therefore, by setting the single-sided coating area 100b, the positive electrode active material 120 on the inner side of the single-sided coating area 100b can cooperate with the negative electrode active material 320 located on the outer side of the outermost circle of the negative electrode plate 300 to realize the embedding and de-embedding of metal ions. The positive electrode active material 120 is not arranged on the outer side of the single-sided coating area 100b, which can improve the utilization rate of the positive electrode active material 120 and reduce the total thickness of the battery cell, which is beneficial to improve the energy density of the battery cell.

[0071] In some embodiments, the positive electrode sheet 100 further includes a double-sided empty foil area 100 c , one end of which is connected to the single-sided coated area 100 b , and the other end is the winding end of the positive electrode sheet 100 .

[0072] By making the positive electrode plate 100 also include a double-sided empty foil area 100c, one end of the double-sided empty foil area 100c is connected to the single-sided coated area 100b, and the other end is the winding end of the positive electrode plate 100, which can be easily finished and fixed by the double-sided empty foil area 100c.

[0073] See also Figure 4 , Figure 4 A schematic diagram of the structure of the positive electrode sheet of a battery cell after unfolding provided in other embodiments of the present application.

[0074] In some embodiments, the positive electrode plate 100 includes a double-sided coating area 100a and a single-sided coating area 100b, one end of the double-sided coating area 100a is the starting end of the winding of the positive electrode plate 100, and the other end is connected to the single-sided coating area 100b; one end of the single-sided coating area 100b is connected to the double-sided coating area 100a, and the other end is the winding end of the positive electrode plate 100; the single-sided coating area 100b is located on the outside of the outermost circle of the negative electrode plate 300.

[0075] See also Figure 1 In some embodiments, the battery cell includes a first adhesive tape 410 , and the first adhesive tape 410 is attached to the inner surface of the first corner section 102 .

[0076] Since the first corner section 102 corresponds to the winding starting end of the negative electrode sheet 300, the metal ions extracted from the positive electrode active material 120 on the inner side of the first corner section 102 do not have enough corresponding negative electrode active materials 320 for embedding. Therefore, the battery cell includes a first adhesive tape 410, and the first adhesive tape 410 is attached to the inner surface of the first corner section 102, so that the first adhesive tape 410 can cover the positive electrode active material 120 on the inner side of the first corner section 102, thereby reducing the possibility of metal ion precipitation in the first corner section 102, which is beneficial to extending the service life of the battery cell. In addition, the first adhesive tape 410 covers the inner side of the first corner section 102, which can reduce the risk of powder falling of the first corner section 102 due to bending. The first adhesive tape 410 can also play an insulating role between the winding starting end of the negative electrode sheet 300 and the first corner section 102, thereby reducing the possibility of short circuit between the negative electrode sheet 300 and the positive electrode sheet 100, which is beneficial to improving the safety of the battery cell.

[0077] In some embodiments, the first adhesive tape 410 may include at least one of epoxy resin, polypropylene, polyolefin, rubber and the like.

[0078] In some embodiments, along the thickness direction X of the electrode assembly, the projection of the first adhesive tape 410 and the projection of the third straight segment 301 have an overlapping area.

[0079] By making the projection of the first adhesive tape 410 and the projection of the third straight section 301 have an overlapping area along the thickness direction X of the electrode assembly, the area of ​​the positive electrode active material 120 covered by the first adhesive tape 410 corresponding to the starting end of the winding of the negative electrode plate 300 is larger, further reducing the possibility of metal ion precipitation in the first corner section 102, which is beneficial to extending the service life of the battery cell.

[0080] In some embodiments, along the first direction Y, the length of the overlapping area is L1, which satisfies 2mm≤L1≤5mm. For example, L1 may be 2mm, 3mm, or 5mm.

[0081] The first direction Y, the thickness direction X of the electrode assembly and the winding axis direction Z of the electrode assembly are perpendicular to each other.

[0082] When L1 is greater than or equal to 2 mm, the area of ​​the positive electrode active material 120 covered by the first adhesive tape 410 can be larger, further reducing the possibility of metal ion precipitation in the first corner segment 102, which is beneficial to extending the service life of the battery cell; when L1 is less than or equal to 5 mm, the space occupied by the first adhesive tape 410 can be smaller, which is beneficial to reducing the overall volume of the electrode assembly 10 and improving the energy density of the battery cell; therefore, when 2 mm ≤ L1 ≤ 5 mm, the possibility of metal ion precipitation in the first corner segment 102 can be reduced, which is beneficial to extending the service life of the battery cell and improving the energy density of the battery cell.

[0083] See also Figure 5 , Figure 5 A schematic diagram of an enlarged local structure of a battery cell provided in some other embodiments of the present application.

[0084] In some embodiments, a first groove 1021 is disposed on the inner surface of the first corner section 102 , and at least a portion of the first adhesive tape 410 is accommodated in the first groove 1021 .

[0085] By providing the first groove 1021 on the inner surface of the first corner section 102, at least part of the first adhesive tape 410 is accommodated in the first groove 1021, so that the first adhesive tape 410 does not protrude from the positive electrode active material 120 or the thickness of the part protruding from the positive electrode active material 120 is smaller, thereby reducing the overall thickness of the first adhesive tape 410 and the positive electrode plate 100, reducing the overall volume of the electrode assembly 10, and improving the energy density of the battery cell.

[0086] See also Figure 1 and Figure 5 In some embodiments, the battery cell includes a second adhesive tape 420 , and the second adhesive tape 420 is attached to the outer surface of the first corner section 102 .

[0087] Since the ductility of the inner surface of the first corner segment 102 will be reduced after the first adhesive tape 410 is attached to the inner surface of the first corner segment 102, when the positive electrode active material 120 expands, the inner and outer surfaces of the first corner segment 102 are subjected to uneven force, which may cause the positive electrode collector 110 of the first corner segment 102 to break. After the positive electrode current collector 110 breaks, the positive electrode active material 120 on the inner surface of the first corner segment 102 will move to the outer surface of the first corner segment 102 through the cracks, increasing the risk of metal ion precipitation. By making the battery cell include the second adhesive tape 420, and the second adhesive tape 420 is attached to the outer surface of the first corner segment 102, when the positive electrode active material 120 expands, the inner and outer surfaces of the first corner segment 102 can be subjected to more uniform force, thereby reducing the possibility of the positive electrode collector 110 of the first corner segment 102 breaking. When the positive electrode collector 110 of the first corner segment 102 breaks, the positive electrode active material 120 on the inner surface of the first corner segment 102 moves to the outer surface of the first corner segment 102 through the crack. The second adhesive tape 420 can reduce the risk of metal ion precipitation in the positive electrode active material 120 on the outer surface of the first corner segment 102, thereby improving the safety of the battery cell.

[0088] In some embodiments, along the winding direction of the battery cell, the length of the second adhesive tape 420 is greater than the length of the first adhesive tape 410. For example, the length of the second adhesive tape 420 may be 1.1 times, 1.3 times, or 1.5 times the length of the first adhesive tape 410.

[0089] After the positive electrode sheet 100 is wound, the outer surface of the first corner section 102 extends longer than the inner surface along the winding direction of the battery cell. By making the length of the second tape 420 greater than the length of the first tape 410 along the winding direction of the battery cell, the overlapping area between the projection of the second tape 420 and the projection of the first tape 410 along the thickness direction of the positive electrode sheet can be made larger, and further when the positive active material 120 expands, the inner and outer surfaces of the first corner section 102 are subjected to more uniform force, thereby reducing the possibility of breakage of the positive electrode collector 110 of the first corner section 102.

[0090] In some embodiments, the second adhesive tape 420 may include at least one of epoxy resin, polypropylene, polyolefin, rubber and the like.

[0091] In some embodiments, the projections of the first adhesive tape 410 and the second adhesive tape 420 overlap in the thickness direction of the positive electrode current collector 110. This can further make the inner and outer surfaces of the first corner section 102 more evenly stressed, reducing the possibility of the positive electrode current collector 110 of the first corner section 102 being broken.

[0092] In some embodiments, a second groove 1022 is disposed on the outer surface of the first corner section 102 , and at least a portion of the second adhesive tape 420 is accommodated in the second groove 1022 .

[0093] By providing the second groove 1022 on the outer surface of the first corner section 102, at least a portion of the second adhesive tape 420 is accommodated in the second groove 1022, so that the second adhesive tape 420 does not protrude from the positive electrode active material 120 or the thickness of the portion protruding from the positive electrode active material 120 is smaller, thereby reducing the overall thickness of the second adhesive tape 420 and the positive electrode plate 100, reducing the overall volume of the electrode assembly 10, and improving the energy density of the battery cell.

[0094] See also Figure 6 , Figure 6 Schematic diagram of the cross-sectional structure of the battery cell provided in some other embodiments of the present application.

[0095] In other embodiments, the first corner section 102 may also be provided with only the first adhesive tape 410 , which can reduce the thickness of the positive electrode plate 100 and is beneficial to improving the energy density of the battery cell.

[0096] See also Figure 1 In some embodiments, the electrode assembly 10 includes two layers of separators 200 , and the two layers of separators 200 are respectively disposed on both sides of the negative electrode plate 300 along the thickness direction thereof.

[0097] By making the electrode assembly 10 include two layers of separators 200, the two layers of separators 200 are respectively arranged on both sides of the negative electrode plate 300 along its thickness direction, so that the separator 200 can play a role of isolating the positive electrode plate 100 and the negative electrode plate 300, reducing the risk of short circuit between the positive electrode plate 100 and the negative electrode plate 300, and improving the safety of the battery cell.

[0098] See also Figure 7 , Figure 7 A schematic diagram of the structure of a battery cell after the diaphragm is unfolded provided in other embodiments of the present application.

[0099] In some embodiments, the diaphragm 200 includes a base layer 210 and two adhesive layers 220 , and the two adhesive layers 220 are respectively disposed on both sides of the base layer 210 along the thickness direction thereof.

[0100] By making the diaphragm 200 include a base layer 210 and two adhesive layers 220, the two adhesive layers 220 are respectively arranged on both sides of the base layer 210 along its thickness direction, so that the two adhesive layers 220 can be used to bond with the positive electrode plate 100 and the negative electrode plate 300 respectively, and the positive electrode plate 100 relative to the diaphragm 200 and the negative electrode plate 300 relative to the diaphragm 200 are not easily displaced, thereby making the overall structure of the electrode assembly 100 more stable.

[0101] In some embodiments, the base layer 210 may include a polyethylene material, and the adhesive layer 220 may include a polyvinylidene fluoride material.

[0102] By making the base layer 210 include polyethylene material, the base layer 210 can have stronger support force and better stability. By making the adhesive layer 220 include polyvinylidene fluoride material, the adhesive force of the adhesive layer 220 can be made stronger.

[0103] In some embodiments, the thickness of the base layer 210 is 4 μm-6 μm. For example, the thickness of the base layer 210 may be 4 μm, 5 μm, or 6 μm.

[0104] When the thickness of the base layer 210 is greater than or equal to 4 μm, the base layer 210 can have stronger supporting force and better stability, the diaphragm 200 is less likely to be deformed, and the overall structure of the electrode assembly 100 is more stable; when the thickness of the base layer 210 is or equal to 6 μm, the base layer 210 can occupy a smaller space, thereby reducing the volume of the electrode assembly 100, which is beneficial to improving the energy density of the battery cell; therefore, when the thickness of the base layer 210 is 4 μm-6 μm, the base layer 210 can have stronger supporting force and better stability, the diaphragm 200 is less likely to be deformed, and the overall structure of the electrode assembly 100 is more stable, and the base layer 210 can occupy a smaller space, thereby reducing the volume of the electrode assembly 100, which is beneficial to improving the energy density of the battery cell.

[0105] In some embodiments, the thickness of the adhesive layer 220 is 0.5 μm-1.5 μm. For example, the thickness of the adhesive layer 220 may be 0.5 μm, 1 μm, or 1.5 μm.

[0106] When the thickness of the adhesive layer 220 is greater than or equal to 0.5 μm, the adhesive force of the adhesive layer 220 can be made stronger, the possibility of displacement of the positive electrode sheet 100 and the negative electrode sheet 300 relative to the diaphragm 200 is lower, and the overall structure of the electrode assembly 100 can be made more stable; when the thickness of the adhesive layer 220 is less than or equal to 1.5 μm, the space occupied by the adhesive layer 220 is smaller, thereby reducing the volume of the electrode assembly 100, which is beneficial to improving the energy density of the battery cell; therefore, when the thickness of the adhesive layer 220 is 0.5 μm-1.5 μm, the adhesive force of the adhesive layer 220 can be made stronger, the possibility of displacement of the positive electrode sheet 100 and the negative electrode sheet 300 relative to the diaphragm 200 is lower, and the overall structure of the electrode assembly 100 is more stable, and the space occupied by the adhesive layer 220 is smaller, thereby reducing the volume of the electrode assembly 100, which is beneficial to improving the energy density of the battery cell.

[0107] In some other embodiments, the electrode assembly 10 includes two layers of separators 200 , and the two layers of separators 200 are respectively disposed on both sides of the positive electrode plate 100 along the thickness direction thereof.

[0108] See also Figure 1 In some embodiments, the separator 200 is connected to the negative electrode plate 300 by thermal bonding, and the end surface of the separator 200 is aligned with the end surface of the winding start end of the negative electrode plate 300 .

[0109] Among them, along the first direction Y, the distance between the end surface of the separator 200 and the end surface of the winding starting end of the negative electrode plate 300 is less than or equal to 0.5 mm, which is within the range of alignment between the end surface of the separator 200 and the end surface of the winding starting end of the negative electrode plate 300.

[0110] Since the diaphragm 200 may shrink due to heat during subsequent processes such as the formation of the battery cell, the diaphragm 200 is connected to the negative electrode sheet 300 through thermal composite connection, and the end face of the diaphragm 200 is aligned with the end face of the winding starting end of the negative electrode sheet 300, so that the end face of the diaphragm 200 is not easily separated from the end face of the winding starting end of the negative electrode sheet 300 after the diaphragm 200 is heated, thereby making the diaphragm 200 have a better isolation effect between the positive electrode sheet 100 and the negative electrode sheet 300, and the volume of the diaphragm 200 is smaller, and the end of the diaphragm 200 will not be stacked at the winding center of the electrode assembly 10, which is beneficial to reducing the volume of the electrode assembly 10 and improving the energy density of the battery cell.

[0111] See also Figure 8 , Figure 8 Schematic diagram of the cross-sectional structure of the battery cell provided in some other embodiments of the present application.

[0112] In some embodiments, along the reverse direction of the battery cell winding, the two layers of separator 200 extend beyond the winding start end of the negative electrode plate 300 and are connected. In this embodiment, the separator 200 and the negative electrode plate 300 can be connected by thermal composite or stacked.

[0113] Since the separator 200 may shrink due to heat during the subsequent formation process of the battery cell, by making the two layers of separator 200 extend beyond the starting end of the negative electrode sheet 300 and connect in the opposite direction of the battery cell winding, the starting end of the negative electrode sheet 300 can always be covered by the two layers of separator 200 and not exposed, thereby reducing the possibility of short circuit between the negative electrode sheet 300 and the positive electrode sheet 100 and improving the safety of the battery cell.

[0114] In some embodiments, the length of the portion of the separator 200 that extends beyond the winding start end of the negative electrode sheet 300 is L2, which satisfies 0 mm < L2 ≤ 20 mm. For example, L2 may be 1 mm, 10 mm, or 20 mm.

[0115] When L2 is greater than 0, the diaphragm 200 can have a better isolation effect on the negative electrode sheet 300 and the positive electrode sheet 100, reduce the possibility of short circuit between the negative electrode sheet 300 and the positive electrode sheet 100, and improve the safety of the battery cell; when L2 is less than or equal to 20mm, the volume of the diaphragm 200 that exceeds the starting end of the winding of the negative electrode sheet 300 can be smaller, thereby making the volume of the electrode assembly 10 smaller, which is beneficial to improving the energy density of the battery cell; therefore, when 0mm<L2≤20mm, the diaphragm 200 can have a better isolation effect on the negative electrode sheet 300 and the positive electrode sheet 100, reduce the possibility of short circuit between the negative electrode sheet 300 and the positive electrode sheet 100, and improve the safety of the battery cell, and can also make the volume of the diaphragm 200 that exceeds the starting end of the winding of the negative electrode sheet 300 smaller, thereby making the volume of the electrode assembly 10 smaller, which is beneficial to improving the energy density of the battery cell.

[0116] See also Figure 1 , Figure 2 and Fig. 9 , Fig. 9 A schematic cross-sectional view of a partial structure of a battery cell provided in some embodiments of the present application.

[0117] In some embodiments, the battery cell 10 includes a negative electrode tab 510 , and the negative electrode tab 510 is riveted to the negative electrode sheet 300 .

[0118] Since the welding method requires forming an empty foil area on the negative electrode sheet 300, by riveting the negative electrode tab 510 to the negative electrode sheet 300, the process of forming the empty foil area on the negative electrode sheet 300 can be omitted, further improving the preparation efficiency of the battery cell.

[0119] In some embodiments, the negative electrode plate 300 has a first surface 300a and a second surface 300b arranged opposite to each other along the thickness direction thereof, and the negative electrode plate 300 is provided with a through hole 330 penetrating along the thickness direction thereof. The negative electrode tab 510 includes a main body 511 and a rivet portion 512, the main body 511 is arranged on the first surface 300a, the rivet portion 512 is protruding from the main body 511 and penetrating the through hole 330, and one end of the rivet portion 512 away from the main body 511 is pressed against the second surface 300b.

[0120] By making the negative electrode tab 510 include a main body 511 and a rivet portion 512, the main body 511 is arranged on the first surface 300a, the rivet portion 512 is protruded from the main body 511 and passes through the through hole 330, and the end of the rivet portion 512 away from the main body 511 is pressed against the second surface 300b. The riveting method of the negative electrode tab 510 and the negative electrode sheet 300 is simple and easy to prepare, and can make the connection between the negative electrode tab 510 and the negative electrode sheet 300 stable, the negative electrode tab 510 is not easy to separate from the negative electrode sheet 300, the reliability of the battery cell is high, and the use of riveting can avoid removing active materials, which is more cost-effective.

[0121] See also Fig.10 , Fig.10 Schematic diagram of the structure of the unfolded negative electrode sheet provided in other embodiments of the present application.

[0122] In other embodiments, the negative electrode tab 510 is welded to the negative electrode sheet 300. The negative electrode sheet 300 may be cleaned by laser to form a groove, so that the negative electrode current collector 310 is exposed at the groove, and then the negative electrode tab 510 is welded to the negative electrode sheet 300 by ultrasonic welding.

[0123] See also Figure 1 and Figure 3 In some embodiments, the battery cell includes a positive electrode tab 520, and the positive electrode tab 520 is welded to the positive electrode sheet 100. The double-sided coating area 100a of the positive electrode sheet 100 can be cleaned by laser to form a groove, so that the positive current collector 110 is exposed at the groove, and then the positive electrode tab 520 is welded to the positive electrode sheet 100 by ultrasonic welding.

[0124] In other embodiments, the positive electrode tab 520 and the positive electrode plate 100 may be riveted.

[0125] In some embodiments, the battery cell further includes a shell or a packaging bag (not shown in the figure), and the electrode assembly 10 is accommodated in the shell or the packaging bag.

[0126] In some embodiments, the packaging bag can be an aluminum-plastic film, a steel-plastic film, etc.

[0127] In some embodiments, the shell can be made of a material with higher strength, such as metal materials such as steel, aluminum alloy, etc., so that the shell has a higher force-bearing capacity, and thus the shell is not easily deformed or damaged due to force or environmental changes, thereby making the battery cell more reliable.

[0128] In other embodiments, the shell may also be made of non-metallic materials with relatively high strength, such as carbon fiber, hard plastic, etc.

[0129] In some embodiments, the battery cell further includes an electrolyte, and the shell or packaging bag is used to contain the electrode assembly 10 and the electrolyte.

[0130] In some embodiments, the electrolyte may include an organic solvent, an electrolyte lithium salt, and the like.

[0131] In some embodiments, the method for preparing a battery cell includes:

[0132] S1. Provide a negative electrode current collector, and completely coat the negative electrode active material on both surfaces of the negative electrode current collector by continuous coating to form a negative electrode sheet; cold press the negative electrode sheet into strips to form a small rolled negative electrode sheet.

[0133] S2. The negative electrode tab is connected to the negative electrode sheet by riveting.

[0134] Since ultrasonic welding can only be achieved in the empty foil area of ​​the electrode sheet, and the area coated with active materials cannot be ultrasonically welded, a first empty foil area is currently formed on the negative electrode sheet by intermittent coating or laser etching to connect the negative electrode tab to the first empty foil area. In the present application, the negative electrode tab is connected to the negative electrode sheet by riveting, and there is no need to form an empty foil area on the negative electrode sheet, which can make the preparation process of the electrode assembly simpler and help reduce the preparation cost.

[0135] S3. Provide a positive electrode current collector, and coat positive electrode active materials on the two surfaces of the positive electrode current collector respectively to form a positive electrode sheet including a double-sided coating area, a single-sided coating area, and a double-sided empty foil area; cold-press the positive electrode sheet into strips to form a small rolled positive electrode sheet.

[0136] S4. Form a second empty foil area on the double-sided coating area of ​​the positive electrode plate by laser etching, and connect the positive electrode tab and the negative electrode tab by ultrasonic welding.

[0137] S5. Provide two separators, and respectively arrange the two separators on both sides of the negative electrode sheet along its thickness direction, and align the end surface of the separator with the end surface of the winding starting end of the negative electrode sheet; activate the two adhesive layers on both sides of the base layer of the separator by thermal composite, so that the adhesive layer is bonded to the negative electrode sheet.

[0138] S6. The positive electrode sheet and the negative electrode sheet are wound in opposite directions, and the winding starting end of the positive electrode sheet is a double-sided coating area; a first adhesive tape is set on the inner surface of the positive electrode sheet corresponding to the first corner section, and a second adhesive tape is set on the outer surface of the positive electrode sheet corresponding to the first corner section.

[0139] S7. Make the double-sided empty foil area of ​​the positive electrode plate the winding end of the electrode assembly, and set adhesive tape at the winding end of the electrode assembly.

[0140] S8. Provide a packaging bag so that the wound electrode assembly can be accommodated in the packaging bag, and the finished battery cell is manufactured through processes such as liquid injection and formation.

[0141] An embodiment of the present application provides an electrical device, including a battery cell as described above, and the battery cell is used to provide electrical energy.

[0142] The electrical device may be any of the aforementioned devices or systems that use the battery cells.

[0143] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0144] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A battery cell, characterized in that: The electrode assembly comprises an electrode assembly, wherein the electrode assembly is formed by winding a positive electrode sheet, a separator, and a negative electrode sheet stacked in layers; The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material, wherein the negative electrode active material comprises a silicon-based material, and the negative electrode active material is completely coated on both surfaces of the negative electrode current collector; The innermost circle of the positive electrode sheet includes a first straight section, a first corner section and a second straight section, the first corner section connects the first straight section and the second straight section, and an end of the first straight section away from the first corner section is the winding starting end of the positive electrode sheet; The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material, and the positive electrode active material is coated on both surfaces of the positive electrode current collector in the first straight section, the first corner section and the second straight section; The innermost circle of the negative electrode sheet includes a third straight section, a second corner section and a fourth straight section, the second corner section connects the third straight section and the fourth straight section, and an end of the third straight section away from the second corner section is a winding starting end of the negative electrode sheet; Along the thickness direction of the electrode assembly, the first straight segment is located between the third straight segment and the fourth straight segment, and the third straight segment is located between the first straight segment and the second straight segment.

2. The battery cell according to claim 1, characterized in that: In the negative electrode active material, the mass percentage of the silicon-based material is 4%-100%.

3. The battery cell according to claim 1, characterized in that: The positive electrode plate includes a double-sided coating area and a single-sided coating area, one end of the double-sided coating area is the winding starting end of the positive electrode plate, and the other end is connected to the single-sided coating area; the single-sided coating area is located outside the outermost circle of the negative electrode plate, and the single-sided coating area is coated with the positive electrode active material on the side facing the negative electrode plate.

4. The battery cell according to claim 3, characterized in that: The positive electrode plate also includes a double-sided empty foil area, one end of the double-sided empty foil area is connected to the single-sided coated area, and the other end is the winding end of the positive electrode plate.

5. The battery cell according to claim 1, characterized in that: The battery core includes a first adhesive tape, and the first adhesive tape is attached to the inner surface of the first corner section.

6. The battery cell according to claim 5, characterized in that: Along the thickness direction of the electrode assembly, the projection of the first adhesive tape and the projection of the third straight section have an overlapping area; Along the first direction, the length of the overlapping area is L1, satisfying 2mm≤L1≤5mm; The first direction, the thickness direction of the electrode assembly and the winding axis direction of the electrode assembly are perpendicular to each other.

7. The battery cell according to claim 5, characterized in that: The inner surface of the first corner section is provided with a first groove, and at least a portion of the first adhesive tape is accommodated in the first groove.

8. The battery cell according to claim 5, characterized in that: The battery core includes a second adhesive tape, and the second adhesive tape is attached to the outer surface of the first corner section; Along the winding direction of the battery core, the length of the second adhesive tape is greater than the length of the first adhesive tape.

9. The battery cell according to claim 1, characterized in that: The electrode assembly includes two layers of the diaphragm, which are respectively arranged on both sides of the negative electrode sheet along its thickness direction; the diaphragm is connected to the negative electrode sheet by thermal recombination, and the end face of the diaphragm is aligned with the end face of the winding starting end of the negative electrode sheet.

10. The battery cell according to claim 1, characterized in that: The electrode assembly comprises two layers of the separator, and the two layers of the separator are respectively arranged on both sides of the negative electrode sheet along the thickness direction thereof; Along the reverse direction of the winding of the battery core, the two layers of the separator extend beyond the winding start end of the negative electrode sheet and are connected; The length of the portion of the separator that exceeds the winding start end of the negative electrode sheet is L2, which satisfies 0mm<L2≤20mm.

11. The battery cell according to claim 1, characterized in that: The battery cell comprises a negative electrode tab, and the negative electrode tab is riveted to the negative electrode sheet.

12. The battery cell according to claim 11, characterized in that: The negative electrode plate has a first surface and a second surface arranged opposite to each other along the thickness direction thereof, and the negative electrode plate is provided with a through hole penetrating along the thickness direction thereof; The negative electrode tab includes a main body and a rivet portion, wherein the main body is disposed on the first surface, the rivet portion is protruded from the main body and passes through the through hole, and an end of the rivet portion away from the main body is pressed against the second surface.

13. An electrical equipment, characterized in that: The invention comprises a battery cell as described in any one of claims 1 to 12, wherein the battery cell is used to provide electrical energy.

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