Battery cell and electric device

Abstract

Provided in the present application are a battery cell and an electric device. The battery cell comprises an electrode assembly, wherein the electrode assembly is formed by winding a positive electrode sheet, a separator and a negative electrode sheet which are stacked, the outermost electrode sheet being the positive electrode sheet; the positive electrode sheet comprises a double-sided coated region, a single-sided coated region and a double-sided bare foil region which are sequentially arranged from the start to the end of winding; a first adhesive tape of the battery cell is attached to the side of the single-sided coated region where no active material layer is provided, and at least part of the first adhesive tape is arranged on the positive electrode sheet in the second turn from the outside to the inside of the battery cell; in the direction of winding, the first adhesive tape extends beyond a first edge of the double-sided bare foil region away from the single-sided coated region; and in the direction of a winding axis, the first adhesive tape extends beyond a second edge and a third edge of the double-sided bare foil region. The capacity of the battery cell is less than 3 Ah. The risk of a short circuit due to contact between an edge of the double-sided bare foil region and the negative electrode sheet is reduced, thereby improving the safety of the battery cell; moreover, the first adhesive tape does not increase the thickness of the battery cell, thereby helping improve the energy density of the battery cell.

Description

Battery cells and electrical equipment Cross-reference to related applications

[0001] This application claims priority to Chinese patent application CN202411404303.X, entitled "Battery Cell and Electrical Equipment", filed on October 09, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of battery technology, and more specifically, to a battery cell and an electrical device. Background Technology

[0003] With the rapid development of new energy technologies, batteries have been widely used in electronic devices, electric vehicles, electric two-wheelers, power tools, and other fields. The requirements for battery quality, safety, and miniaturization are also becoming increasingly stringent.

[0004] In wound battery cells, adhesive tape is typically placed at the head and tail of the wound electrode assembly to improve the cell's drop test pass rate. However, this increases the cell's thickness and affects its energy density. If the adhesive tape at the head and tail of the electrode assembly is removed, short circuits can easily occur at the tail end of the electrode assembly, affecting the cell's safety. Summary of the Invention

[0005] This application provides a battery cell and an electrical device that can improve the energy density of the battery cell.

[0006] In a first aspect, this application provides a battery cell, which includes an electrode assembly formed by winding a positive electrode sheet, a separator, and a negative electrode sheet stacked together. The outermost electrode sheet of the electrode assembly is a positive electrode sheet. The positive electrode sheet includes a double-sided coated area, a single-sided coated area, and a double-sided empty foil area arranged sequentially from the starting end to the ending end of the winding. The battery cell also includes a first adhesive tape, which is attached to the side of the single-sided coated area where no active material layer is provided. The first adhesive tape is at least partially disposed on the positive electrode sheet of the second winding from the outside to the inside of the battery cell. Along the winding direction, the double-sided empty foil area has a first edge away from the single-sided coated area, and the first adhesive tape extends beyond the first edge. Along the winding axis, the double-sided empty foil area has opposing second and third edges, and the first adhesive tape extends beyond the second and third edges. The battery cell capacity is less than 3Ah.

[0007] In the above technical solution, by attaching the first adhesive tape to the side of the single-sided coated area without the active material layer, and by having the double-sided empty foil area have a first edge away from the single-sided coated area along the winding direction, with the first adhesive tape extending beyond the first edge, the first adhesive tape can isolate the first edge of the double-sided empty foil area from the negative electrode sheet along the winding direction, reducing the possibility of a short circuit between the first edge of the double-sided empty foil area and the negative electrode sheet, thus improving the safety of the battery cell. Furthermore, by having the double-sided empty foil area have opposing second and third edges along the winding axis, with the first adhesive tape extending beyond the second and third edges, the first adhesive tape can isolate the second and third edges of the double-sided empty foil area from the negative electrode sheet along the winding axis, reducing the possibility of a short circuit between the second and third edges of the double-sided empty foil area and the negative electrode sheet, thus improving the safety of the battery cell. Moreover, the adhesive tape at the head and tail of the middle electrode assembly in a small-capacity battery cell can be eliminated, and the first adhesive tape does not increase the thickness of the battery cell, which is beneficial for improving the energy density of the battery cell. At the same time, when the capacity of the battery cell is less than 3Ah, because the battery with a smaller capacity is lighter, the possibility of it malfunctioning when dropped is also lower, even if the rubber wrapping is removed.

[0008] In some embodiments of this application, the first adhesive tape includes a first part and a second part, the first part being attached to a double-sided coated area and the second part being attached to a single-sided coated area.

[0009] In the above technical solution, since errors in the manufacturing process are unavoidable, if the first adhesive paper is entirely placed on the single-sided coating area of ​​the positive electrode, there may be gaps between the first adhesive paper and the double-sided coating area, which could lead to a short circuit between the positive and negative electrodes. Therefore, by making the first adhesive paper include a first part and a second part, with the first part attached to the double-sided coating area and the second part attached to the single-sided coating area, the first adhesive paper can cover the end of the single-sided coating area near the double-sided coating area, thereby reducing the risk of a short circuit between the positive and negative electrodes and improving the safety of the battery cell.

[0010] In some embodiments of this application, along the winding axis, the length of the second part is L1, and the length of the double-sided empty foil area is L2, satisfying L1 > L2; along the winding direction, the width of the second part is W1, and the width of the double-sided empty foil area is W2, satisfying W1 > W2; viewed radially along the winding, the second part completely covers the double-sided empty foil area.

[0011] In the above technical solution, the length L1 of the second part and the length L2 of the double-sided empty foil area along the winding axis satisfy L1 > L2; the width of the second part is W1 and the width of the double-sided empty foil area is W2 along the winding direction, satisfying W1 > W2; the second part completely covers the double-sided empty foil area when viewed radially along the winding; the second part can cover the double-sided empty foil area along both the winding axis and the winding direction. Here, covering the double-sided empty foil area refers to covering the side of the double-sided empty foil area opposite to the second part, thereby reducing the possibility of short circuit between the double-sided empty foil area and the negative electrode plate and improving the safety of the battery cell.

[0012] In some embodiments of this application, 0 < L1 - L2 ≤ 10 mm.

[0013] In the above technical solution, when L1-L2 is greater than 0, the second part can cover the double-sided empty foil area along the winding axis, thereby reducing the possibility of short circuit between the double-sided empty foil area and the negative electrode plate, and improving the safety of the battery cell. When L1-L2 is less than or equal to 10mm, the length of the second part extending beyond the positive electrode plate along the winding axis is shorter, which can reduce the possibility of interference between the first adhesive tape and other components of the battery cell, making it easier for the part of the second part extending beyond the positive electrode plate to be attached to the head and / or tail of the electrode assembly, and saving the material of the first adhesive tape. Therefore, when 0 < L1-L2 ≤ 10mm, the second part can cover the double-sided empty foil area along the winding axis, thereby reducing the possibility of short circuit between the double-sided empty foil area and the negative electrode plate, improving the safety of the battery cell, and also reducing the possibility of interference between the first adhesive tape and other components of the battery cell, making it easier for the part of the second part extending beyond the positive electrode plate to be attached to the head and / or tail of the electrode assembly, and saving the material of the first adhesive tape.

[0014] In some embodiments of this application, the width of the first portion along the winding direction is W3, which satisfies 0 < W3 ≤ 10 mm.

[0015] In the above technical solution, due to unavoidable errors in the manufacturing process, if the first adhesive tape is entirely placed on the single-sided coating area of ​​the positive electrode (i.e., W3 = 0), there may be gaps between the first adhesive tape and the double-sided coating area, leading to a short circuit between the positive and negative electrodes. Therefore, by making W3 greater than 0, the first part is attached to the double-sided coating area, and the second part is attached to the single-sided coating area, so that the first adhesive tape can cover the end of the single-sided coating area closest to the double-sided coating area, thereby reducing the risk of a short circuit between the positive and negative electrodes and improving the safety of the battery cell; when W3 is less than or equal to 10mm, the overlap between the first adhesive tape and the double-sided coating area is increased. With a smaller area, the first adhesive tape has a lower probability of interfering with other components on the double-sided coating area, and its impact on the cell thickness is smaller. This is beneficial for improving the cell's energy density and saving on the amount of first adhesive tape used. Therefore, when 0 < W3 ≤ 10 mm, the first adhesive tape can cover the end of the single-sided coating area closest to the double-sided coating area, thereby reducing the risk of short circuit between the positive and negative electrodes and improving the cell's safety. At the same time, it also minimizes the possibility of interference between the first adhesive tape and other components on the double-sided coating area, and its impact on the cell thickness is smaller. This is beneficial for improving the cell's energy density and saving on the amount of first adhesive tape used.

[0016] In some embodiments of this application, a portion of the double-sided empty foil area is located on one side of the electrode assembly along its thickness direction, and another portion of the double-sided empty foil area is located on one side of the electrode assembly along a first direction; the first direction, the winding axis direction, and the thickness direction of the electrode assembly are perpendicular to each other.

[0017] In the above technical solution, by placing a portion of the double-sided empty foil area on one side of the electrode assembly along its thickness direction and the other portion of the double-sided empty foil area on one side of the electrode assembly along the first direction, after the electrode assembly is wound and formed, the double-sided empty foil area only occupies the space on one side of the electrode assembly along its thickness direction and one side along the first direction, and will not extend to other sides of the electrode assembly. This makes the double-sided empty foil area have a smaller impact on the thickness of the electrode assembly, which is beneficial to improving the energy density of the battery cell.

[0018] In some embodiments of this application, the first adhesive tape includes a base layer and a first adhesive layer, the first adhesive layer being disposed on the side of the base layer facing the single-sided coating area.

[0019] In the above technical solution, by making the first adhesive paper include a base layer and a first adhesive layer, and the first adhesive layer is disposed on the side of the base layer facing the single-sided coating area, the first adhesive layer can be bonded to the single-sided coating area, the connection strength between the first adhesive paper and the single-sided coating area is high, and the first adhesive paper is not easy to detach from the single-sided coating area, so as to maintain the insulation between the positive electrode and the negative electrode, and make the safety of the battery cell high.

[0020] In some embodiments of this application, the first adhesive tape includes a second adhesive layer disposed on the side of the substrate facing away from the single-sided coating area.

[0021] In the above technical solution, by making the first adhesive paper include a second adhesive layer, and the second adhesive layer is disposed on the side of the base layer facing away from the single-sided coating area, the second adhesive layer can be bonded to the double-sided empty foil area, thereby fixing the double-sided empty foil area and reducing the possibility of displacement of the double-sided empty foil area relative to the single-sided coating area. This reduces the possibility of short circuit between the double-sided empty foil area and the negative electrode sheet, thereby improving the safety of the battery cell.

[0022] In some embodiments of this application, the thickness of the base layer is H1, which satisfies 4μm≤H1≤20μm; the thickness of the first adhesive layer is H2, which satisfies 2μm≤H2≤10μm; and the thickness of the second adhesive layer is H3, which satisfies 1μm≤H3≤5μm.

[0023] In the above technical solution, when H1 is greater than or equal to 4μm, the supporting force of the base layer is stronger, and the first adhesive paper is less prone to deformation, thereby reducing the possibility of short circuit between the positive and negative electrode plates due to deformation of the first adhesive paper and improving the safety of the battery cell. When H1 is less than or equal to 20μm, the base layer has less impact on the thickness of the battery cell, which is beneficial to improving the energy density of the battery cell. Therefore, when 4μm≤H1≤20μm, the supporting force of the base layer is stronger, and the first adhesive paper is less prone to deformation, thereby reducing the possibility of short circuit between the positive and negative electrode plates due to deformation of the first adhesive paper and improving the safety of the battery cell, while the base layer has less impact on the thickness of the battery cell and is beneficial to improving the energy density of the battery cell.

[0024] When H2 is greater than or equal to 2μm, the adhesion of the first adhesive layer is high, the connection strength between the first adhesive tape and the single-sided coating area is high, and the first adhesive tape is less likely to detach from the single-sided coating area, thus maintaining the insulation between the positive and negative electrode plates, resulting in higher cell safety. Furthermore, the first adhesive tape effectively binds metal ions in the coating area, reducing the possibility of metal ion deposition and extending the cell's lifespan. When H2 is less than or equal to 10μm, the first adhesive layer has a smaller impact on the cell's thickness, which is beneficial for improving the cell's energy density. Therefore, when 2μm≤H2≤10μm, the adhesion of the first adhesive layer is high, the connection strength between the first adhesive tape and the single-sided coating area is high, the first adhesive tape is less likely to detach from the single-sided coating area, maintaining the insulation between the positive and negative electrode plates, resulting in higher cell safety. The first adhesive tape also effectively binds metal ions in the coating area, reducing the possibility of metal ion deposition and extending the cell's lifespan, while simultaneously minimizing the impact of the first adhesive layer on the cell's thickness, which is beneficial for improving the cell's energy density.

[0025] When H3 is greater than or equal to 1 μm, the adhesion of the second adhesive layer is higher, and the connection strength between the first adhesive tape and the double-sided empty foil area is higher, reducing the possibility of displacement of the double-sided empty foil area relative to the single-sided coated area. This reduces the possibility of short circuit between the double-sided empty foil area and the negative electrode plate, thus improving the safety of the battery cell. When H3 is less than or equal to 5 μm, the second adhesive layer has a smaller impact on the thickness of the battery cell, which is beneficial to improving the energy density of the battery cell. Therefore, when 1 μm ≤ H3 ≤ 5 μm, the adhesion of the second adhesive layer is higher, the connection strength between the first adhesive tape and the double-sided empty foil area is higher, reducing the possibility of displacement of the double-sided empty foil area relative to the single-sided coated area. This reduces the possibility of short circuit between the double-sided empty foil area and the negative electrode plate, improving the safety of the battery cell. At the same time, the second adhesive layer has a smaller impact on the thickness of the battery cell, which is beneficial to improving the energy density of the battery cell.

[0026] In some embodiments of this application, the base layer comprises polyethylene terephthalate and / or polyimide, the first adhesive layer comprises polyolefin and / or rubber, and the second adhesive layer comprises polyolefin and / or rubber.

[0027] In the above technical solution, by making the base layer include polyethylene terephthalate material and / or polyimide material, the base layer has stronger support and the first adhesive paper is less prone to deformation. This reduces the possibility of short circuit between the positive and negative electrode plates due to deformation of the first adhesive paper, thereby improving the safety of the battery cell.

[0028] By including polyolefin and / or rubber materials in the first adhesive layer, the adhesion of the first adhesive layer is high, the connection strength between the first adhesive tape and the single-sided coating area is high, and the first adhesive tape is not easily detached from the single-sided coating area, thus maintaining the insulation between the positive and negative electrode plates and improving the safety of the battery cell. Furthermore, the first adhesive layer has strong corrosion resistance, which can reduce the risk of short circuit between the positive and negative electrode plates after the first adhesive layer is corroded by the electrolyte, further improving the safety of the battery cell.

[0029] By including polyolefin and / or rubber materials in the second adhesive layer, the adhesive force of the second adhesive layer can be increased, and the connection strength between the first adhesive paper and the double-sided empty foil area can be increased. This reduces the possibility of displacement of the double-sided empty foil area relative to the single-sided coated area, thereby reducing the possibility of short circuit between the double-sided empty foil area and the negative electrode plate, and improving the safety of the battery cell. Furthermore, the second adhesive layer has strong corrosion resistance, which can reduce the risk of short circuit between the positive and negative electrode plates after the second adhesive layer is corroded by the electrolyte, further improving the safety of the battery cell.

[0030] In some embodiments of this application, the battery cell includes a second adhesive tape for fixing the winding end of the positive electrode sheet; the battery cell includes a positive electrode tab and a third adhesive tape, the positive electrode tab being connected to the positive electrode sheet, a portion of the third adhesive tape being attached to the positive electrode tab and another portion being attached to the positive electrode sheet, and the projections of the second and third adhesive tapes do not overlap along the thickness direction of the electrode assembly; the battery cell includes a negative electrode tab and a fourth adhesive tape, the negative electrode tab being connected to the negative electrode sheet, a portion of the fourth adhesive tape being attached to the negative electrode tab and another portion being attached to the negative electrode sheet, and the projections of the second and fourth adhesive tapes do not overlap along the thickness direction of the electrode assembly.

[0031] In the above technical solution, by including a second adhesive tape in the battery cell, which is used to fix the winding end of the positive electrode sheet, the possibility of displacement of the double-sided empty foil area of ​​the positive electrode sheet relative to the single-sided coated area can be further reduced, thereby reducing the possibility of short circuit between the double-sided empty foil area and the negative electrode sheet, and improving the safety of the battery cell. By attaching a portion of the third adhesive tape to the positive electrode tab and another portion to the positive electrode sheet, the projections of the second and third adhesive tapes do not overlap along the thickness direction of the electrode assembly. A portion of the fourth adhesive tape is attached to the negative electrode tab and another portion to the negative electrode sheet, and the projections of the second and fourth adhesive tapes do not overlap along the thickness direction of the electrode assembly. This ensures that the thickness of the second, third, and fourth adhesive tapes does not overlap in the thickness direction of the electrode assembly, which helps to reduce the thickness of the battery cell and increase its energy density.

[0032] In some embodiments of this application, the battery cell includes a fifth adhesive tape attached to the side of the double-sided empty foil area facing the winding center of the electrode assembly.

[0033] In the above technical solution, by including a fifth adhesive tape in the battery cell, the fifth adhesive tape is attached to the side of the double-sided empty foil area facing the winding center of the electrode assembly, so that the fifth adhesive tape can play an insulating role between the double-sided empty foil area and the negative electrode plate, reducing the possibility of short circuit between the positive electrode plate and the negative electrode plate, and improving the safety of the battery cell.

[0034] In some embodiments of this application, the first adhesive tape is at least partially disposed on the negative electrode sheet of the second ring from the outside to the inside of the battery cell.

[0035] In the above technical solution, by attaching the first adhesive tape to the negative electrode sheet of the second turn from the outside to the inside of the battery cell, and extending the first adhesive tape beyond the first edge along the winding direction, the first adhesive tape can isolate the first edge of the double-sided empty foil area from the negative electrode sheet along the winding direction, thereby reducing the possibility of short circuit between the first edge of the double-sided empty foil area and the negative electrode sheet, and improving the safety of the battery cell.

[0036] Secondly, this application provides an electrical device including a battery cell as described above, the battery cell being used to provide electrical energy. Attached Figure Description

[0037] 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 of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings.

[0038] Figure 1 is a cross-sectional schematic diagram of the electrode assembly of a battery cell provided in some embodiments of this application;

[0039] Figure 2 is a schematic diagram of the unfolded structure of the positive electrode sheet of the battery cell provided in some embodiments of this application;

[0040] Figure 3 is a schematic diagram of the electrode assembly of a battery cell provided in some embodiments of this application from one perspective;

[0041] Figure 4 is a schematic diagram of the structure of the first adhesive paper of the battery cell provided in some embodiments of this application.

[0042] Icons: 10-Battery cell; 100-Electrode assembly; 110-Positive electrode sheet; 111-Double-sided coated area; 112-Single-sided coated area; 113-Double-sided empty foil area; 120-Separator; 130-Negative electrode sheet; 210-First adhesive tape; 211-First part; 212-Second part; 210a-Base layer; 210b-First adhesive layer; 210c-Second adhesive layer; 220-Second adhesive tape; 230-Third adhesive tape; 240-Fourth adhesive tape; 250-Fifth adhesive tape; 310-Positive electrode tab; 320-Negative electrode tab; X-Wound axis direction; Y-First direction; Z-Thickness direction of electrode assembly. Specific embodiment methods.

[0043] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0044] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the specification of this application is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms "comprising" and "having" and any variations thereof in the specification, claims and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0045] The terms "first," "second," etc., in the specification, claims, or the accompanying drawings of this application are used to distinguish different objects, rather than to describe a specific order or primary / secondary relationship.

[0046] In this application, the reference to "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0047] In the embodiments of this application, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this application.

[0048] With the development of the new energy industry, batteries are gradually moving towards higher energy density and higher power density. Currently, in wound battery cells, adhesive tape is applied to both the head (the end of the cell with the positive and negative tabs) and the tail (the end along the length of the cell corresponding to the head) of the wound electrode assembly to improve the drop test pass rate. However, some application scenarios have low or no requirements for the drop test pass rate, making the adhesive tape at the head and tail of the electrode assembly redundant and increasing the cell thickness, thus affecting the energy density. However, if the adhesive tape at the head and tail of the electrode assembly is completely removed, the outermost electrode's winding end is prone to displacement, causing short circuits between two electrodes with opposite polarities, affecting the cell's safety.

[0049] To improve the energy density of a battery cell, this application provides a battery cell including an electrode assembly. The electrode assembly is formed by winding a positive electrode sheet, a separator, and a negative electrode sheet stacked together. The outermost electrode sheet of the electrode assembly is a positive electrode sheet. The positive electrode sheet includes a double-sided coated area, a single-sided coated area, and a double-sided empty foil area arranged sequentially from the starting end to the ending end of the winding. The battery cell also includes a first adhesive paper, which is attached to the side of the single-sided coated area where no active material layer is provided. Along the winding direction, the double-sided empty foil area has a first edge away from the single-sided coated area, and the first adhesive paper extends beyond the first edge. Along the winding axis, the double-sided empty foil area has opposing second and third edges, and the first adhesive paper extends beyond the second and third edges.

[0050] In this type of battery cell, by attaching a first adhesive tape to the side of the single-sided coated area where no active material layer is provided; along the winding direction, the double-sided empty foil area has a first edge away from the single-sided coated area, and the first adhesive tape extends beyond the first edge, so that along the winding direction, the first adhesive tape can isolate the first edge of the double-sided empty foil area from the negative electrode plate, reducing the possibility of a short circuit between the first edge of the double-sided empty foil area and the negative electrode plate, thus improving the safety of the battery cell; by having the double-sided empty foil area have opposing second and third edges along the winding axis direction, and the first adhesive tape extending beyond the second and third edges, so that along the winding axis direction, the first adhesive tape can isolate the second and third edges of the double-sided empty foil area from the negative electrode plate, reducing the possibility of a short circuit between the second and third edges of the double-sided empty foil area and the negative electrode plate, thus improving the safety of the battery cell; and since the adhesive tape at the head and tail of the electrode assembly is eliminated, and the first adhesive tape does not increase the thickness of the battery cell, it is beneficial to improve the energy density of the battery cell.

[0051] The battery cell provided in this application embodiment can be a secondary battery or a primary battery, such as a lithium-ion battery, a sodium-ion battery, or a magnesium-ion battery, etc., and this application embodiment is not limited in this respect. The battery cell can be cylindrical, flat, cuboid, or other shapes, etc., and this application embodiment is not limited in this respect either.

[0052] This application provides an electrical device that uses battery cells as a power source. The electrical device can be, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc.

[0053] Referring to Figures 1 to 3, Figure 1 is a cross-sectional schematic diagram of the electrode assembly of the battery cell provided in some embodiments of this application; Figure 2 is a structural schematic diagram of the positive electrode sheet of the battery cell provided in some embodiments of this application after unfolding; Figure 3 is a structural schematic diagram of the electrode assembly of the battery cell provided in some embodiments of this application from one perspective.

[0054] In some embodiments, the battery cell includes a casing, an electrode assembly 100, and an electrolyte. The casing houses the electrode assembly 100 and the electrolyte. The electrode assembly 100 consists of a positive electrode 110, a negative electrode 130, and a separator 120. The battery cell primarily operates by the movement of metal ions between the positive electrode 110 and the negative electrode 130. The positive electrode 110 includes a positive current collector and a positive active material layer. The positive active material layer is coated on the surface of the positive current collector, and the portion of the positive current collector not coated with the positive active material layer serves as a positive electrode tab 310, through which electrical energy is input or output to the positive electrode 110. The positive electrode tab and the positive current collector can also be separate components that are then connected as a single unit, for example, by welding, conductive adhesive, or other methods. Taking a lithium-ion battery as an example, the material of the positive current collector can be aluminum, and the positive active material can be lithium cobalt oxide, lithium iron phosphate, ternary materials, or lithium manganese oxide, etc. The negative electrode 130 includes a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer is coated on the surface of the negative electrode current collector, and the portion of the negative electrode current collector without the negative electrode active material layer serves as the negative electrode tab 320, through which electrical energy is input or output to the negative electrode 130. The negative electrode tab and the negative electrode current collector can also be separate components that are then connected as a single unit, for example, by welding or using conductive adhesive. The negative electrode current collector can be made of copper, and the negative electrode active material can be made of carbon or silicon, etc. The separator 120 can be made of polypropylene (PP) or polyethylene (PE), etc. The electrolyte can include organic solvents, lithium salts, etc.

[0055] This application provides a battery cell with a capacity of less than 3Ah. The battery cell includes an electrode assembly 100, which is formed by winding a positive electrode 110, a separator 120, and a negative electrode 130 stacked together. The outermost electrode of the electrode assembly 100 is the positive electrode 110. The positive electrode 110 includes a double-sided coated area 111, a single-sided coated area 112, and a double-sided empty foil area 113 arranged sequentially from the starting end to the ending end of the winding. The battery cell also includes a first adhesive tape 210, which is attached to the side of the single-sided coated area 112 that does not have an active material layer, and is at least partially disposed on the second ring of the positive electrode 110 from the outside to the inside of the battery cell. Along the winding direction, the double-sided empty foil area 113 has a first edge 1131 away from the single-sided coated area 112, and the first adhesive tape 210 extends beyond the first edge 1131. Along the winding axis X, the double-sided empty foil area 113 has opposing second edges 1132 and third edges 1133, with the first adhesive tape 210 extending beyond the second edges 1132 and third edges 1133. The second ring of positive electrode 110 from the outside in refers to the positive electrode 110 adjacent to the outermost ring of electrodes. When the cell capacity is less than 3Ah, the battery is lighter due to its smaller capacity, thus reducing the likelihood of malfunctions during drops.

[0056] In some embodiments, the positive electrode 110 includes a positive current collector 110a, a first positive active material layer 110b, and a second positive active material layer 110c, wherein the first positive active material layer 110b and the second positive active material layer 110c are respectively disposed on both sides of the positive current collector 110a along its thickness direction. The double-sided coating area 111 is the area where both sides of the positive current collector 110a along its thickness direction are coated with positive active material layers, that is, the area where both sides of the positive current collector 110a along its thickness direction are covered by the first positive active material layer 110b and the second positive active material layer 110c. The single-sided coating area 112 is the area where one side of the positive current collector 110a along its thickness direction is coated with a positive active material layer, that is, the area where one side of the positive current collector 110a along its thickness direction is covered by the first positive active material layer 110b, and the other side is not covered by the second positive active material layer 110c. The double-sided empty foil area 113 is the area on both sides of the positive electrode current collector 110a along its thickness direction where the positive electrode active material layer is not coated, that is, the area on both sides of the positive electrode current collector 110a along its thickness direction is not covered by the first positive electrode active material layer 110b and the second positive electrode active material layer 110c.

[0057] By attaching the first adhesive tape 210 to the side of the single-sided coated area 112 where no active material layer is provided; along the winding direction, the double-sided empty foil area 113 has a first edge 1131 away from the single-sided coated area 112, and the first adhesive tape 210 extends beyond the first edge 1131, so that along the winding direction, the first adhesive tape 210 can isolate the first edge 1131 of the double-sided empty foil area 113 from the negative electrode plate 130, reducing the possibility of short circuit between the first edge 1131 of the double-sided empty foil area 113 and the negative electrode plate 130, and improving the safety of the battery cell; by making the double-sided empty foil area 113 have a relative second edge along the winding axis direction X. The first adhesive tape 210 extends beyond the second edge 1132 and the third edge 1133 along the winding axis direction X, so that the first adhesive tape 210 can isolate the second edge 1132 and the third edge 1133 of the double-sided empty foil area 113 from the negative electrode plate 130, thereby reducing the possibility of short circuit between the second edge 1132 and the third edge 1133 of the double-sided empty foil area 113 and the negative electrode plate 130, and improving the safety of the battery cell; and since the adhesive tape at the head and tail of the electrode assembly 100 is eliminated, and the first adhesive tape 210 does not increase the thickness of the battery cell, it is beneficial to improve the energy density of the battery cell.

[0058] In some embodiments, the first adhesive tape 210 is at least partially disposed on the negative electrode sheet 130 of the second ring from the outside to the inside of the battery cell.

[0059] By attaching the first adhesive tape 210 to the negative electrode 130 of the second turn of the battery cell from the outside in, and extending beyond the first edge along the winding direction, the first adhesive tape 210 can isolate the first edge of the double-sided empty foil area 113 from the negative electrode 130 along the winding direction, reducing the possibility of a short circuit between the first edge of the double-sided empty foil area 113 and the negative electrode 130, thereby improving the safety of the battery cell. In some embodiments, the first adhesive tape 210 includes a first portion 211 and a second portion 212, with the first portion 211 attached to the double-sided coated area 111 and the second portion 212 attached to the single-sided coated area 112.

[0060] Since errors in the manufacturing process are unavoidable, if the first adhesive tape 210 is entirely placed on the single-sided coating area 112 of the positive electrode 110, there may be gaps between the first adhesive tape 210 and the double-sided coating area 111, which could cause a short circuit between the positive electrode 110 and the negative electrode 130. Therefore, by making the first adhesive tape 210 include a first part 211 and a second part 212, with the first part 211 attached to the double-sided coating area 111 and the second part 212 attached to the single-sided coating area 112, the first adhesive tape 210 can cover the end of the single-sided coating area 112 near the double-sided coating area 111, thereby reducing the risk of a short circuit between the positive electrode 110 and the negative electrode 130 and improving the safety of the battery cell.

[0061] In some embodiments, along the winding axis direction X, the length of the second portion 212 is L1, and the length of the double-sided empty foil area 113 is L2, satisfying L1 > L2. For example, L1 can be 1.1*L2, 1.2*L2, or 1.5*L2, etc. Along the winding direction, the width of the second portion 212 is W1, and the width of the double-sided empty foil area 113 is W2, satisfying W1 > W2. For example, W1 can be 1.1*W2, 1.2*W2, or 1.5*W2, etc. Viewed radially along the winding direction, the second portion 212 completely covers the double-sided empty foil area 113.

[0062] By ensuring that the length L1 of the second part 212 and the length L2 of the double-sided empty foil area 113 satisfy L1 > L2 along the winding axis direction X; the width of the second part 212 is W1 and the width of the double-sided empty foil area 113 is W2 along the winding direction, satisfying W1 > W2; and the second part 212 completely covers the double-sided empty foil area 113 when viewed radially along the winding axis direction X and along the winding direction, the second part 212 can cover the double-sided empty foil area 113. Here, covering the double-sided empty foil area 113 refers to covering the side of the double-sided empty foil area 113 opposite to the second part 212, thereby reducing the possibility of short circuit between the double-sided empty foil area 113 and the negative electrode plate 130, and improving the safety of the battery cell.

[0063] In some embodiments, 0 < L1-L2 ≤ 10 mm. For example, L1-L2 can be 1 mm, 5 mm, or 10 mm, etc.

[0064] When L1-L2 is greater than 0, the second part 212 can cover the double-sided empty foil area 113 along the winding axis direction X, thereby reducing the possibility of short circuit between the double-sided empty foil area 113 and the negative electrode plate 130, and improving the safety of the battery cell. When L1-L2 is less than or equal to 10mm, the length of the second part 212 extending beyond the positive electrode plate 110 along the winding axis direction X is shorter, which can reduce the possibility of interference between the first adhesive tape 210 and other components of the battery cell, and facilitate the attachment of the part of the second part 212 extending beyond the positive electrode plate 110 to the head of the electrode assembly 100. / or the tail, and can save the material of the first adhesive tape 210; therefore, when 0 < L1-L2 ≤ 10mm, the second part 212 can cover the double-sided empty foil area 113 along the winding axis direction X, thereby reducing the possibility of short circuit between the double-sided empty foil area 113 and the negative electrode plate 130, improving the safety of the battery cell, and also reducing the possibility of interference between the first adhesive tape 210 and other components of the battery cell, making it easier for the part of the second part 212 that extends beyond the positive electrode plate 110 to be attached to the head and / or tail of the electrode assembly 100, and can save the material of the first adhesive tape 210.

[0065] In some embodiments, the width of the first portion 211 along the winding direction is W3, satisfying 0 < W3 ≤ 10 mm. For example, W3 can be 1 mm, 6 mm, or 10 mm, etc.

[0066] Since errors in the manufacturing process are unavoidable, if the first adhesive tape 210 is entirely placed on the single-sided coating area 112 of the positive electrode 110 (i.e., W3 = 0), there may be gaps between the first adhesive tape 210 and the double-sided coating area 111, leading to a short circuit between the positive electrode 110 and the negative electrode 130. Therefore, by making W3 greater than 0, the first part 211 is attached to the double-sided coating area 111, and the second part 212 is attached to the single-sided coating area 112, so that the first adhesive tape 210 can cover the end of the single-sided coating area 112 near the double-sided coating area 111, thereby reducing the risk of a short circuit between the positive electrode 110 and the negative electrode 130 and improving the safety of the battery cell; when W3 is less than or equal to 10 mm, the gap between the first adhesive tape 210 and the double-sided coating area 111 is reduced. With a smaller overlap area, the possibility of interference between the first adhesive tape 210 and other components on the double-sided coating area 111 is smaller, and the first adhesive tape 210 has a smaller impact on the thickness of the battery cell, which is beneficial to improving the energy density of the battery cell and can save the material used for the first adhesive tape 210. Therefore, when 0 < W3 ≤ 10 mm, the first adhesive tape 210 can cover the end of the single-sided coating area 112 near the double-sided coating area 111, thereby reducing the risk of short circuit between the positive electrode 110 and the negative electrode 130 and improving the safety of the battery cell. At the same time, the possibility of interference between the first adhesive tape 210 and other components on the double-sided coating area 111 is smaller, and the first adhesive tape 210 has a smaller impact on the thickness of the battery cell, which is beneficial to improving the energy density of the battery cell and can save the material used for the first adhesive tape 210.

[0067] In some embodiments, a portion of the double-sided empty foil area 113 is located on one side of the electrode assembly 100 along its thickness direction Z, and another portion of the double-sided empty foil area 113 is located on one side of the electrode assembly 100 along the first direction Y.

[0068] In some embodiments, the first direction Y, the winding axis direction X, and the thickness direction Z of the electrode assembly are perpendicular to each other.

[0069] By positioning a portion of the double-sided empty foil area 113 on one side of the electrode assembly 100 along its thickness direction and the other portion on one side of the electrode assembly 100 along the first direction Y, after the electrode assembly 100 is wound and formed, the double-sided empty foil area 113 only occupies the space on one side of the electrode assembly 100 along its thickness direction and the other side along the first direction Y, and will not extend to other sides of the electrode assembly 100. This makes the double-sided empty foil area 113 have a smaller impact on the thickness of the electrode assembly 100, which is beneficial to improving the energy density of the battery cell.

[0070] Referring to Figure 4, Figure 4 is a schematic diagram of the structure of the first adhesive paper of the battery cell provided in some embodiments of this application.

[0071] In some embodiments, the first adhesive tape 210 includes a base layer 210a and a first adhesive layer 210b, wherein the first adhesive layer 210b is disposed on the side of the base layer 210a facing the single-sided coating area 112.

[0072] By making the first adhesive tape 210 include a base layer 210a and a first adhesive layer 210b, with the first adhesive layer 210b disposed on the side of the base layer 210a facing the single-sided coating area 112, the first adhesive layer 210b can be bonded to the single-sided coating area 112. The connection strength between the first adhesive tape 210 and the single-sided coating area 112 is high, and the first adhesive tape 210 is not easy to detach from the single-sided coating area 112, so as to maintain the insulation between the positive electrode 110 and the negative electrode 130, thereby making the battery cell safer.

[0073] In some embodiments, the first adhesive tape 210 includes a second adhesive layer 210c, which is disposed on the side of the base layer 210a facing away from the single-sided coating area 112.

[0074] By including a second adhesive layer 210c in the first adhesive tape 210, and disposing the second adhesive layer 210c on the side of the base layer 210a facing away from the single-sided coating area 112, the second adhesive layer 210c can bond with the double-sided empty foil area 113, thereby fixing the double-sided empty foil area 113 and reducing the possibility of displacement of the double-sided empty foil area 113 relative to the single-sided coating area 112. This reduces the possibility of short circuit between the double-sided empty foil area 113 and the negative electrode plate 130, thus improving the safety of the battery cell.

[0075] In other embodiments, the first adhesive tape 210 may consist of only one adhesive layer, with one side of the adhesive layer bonded to the single-sided coating area 112 and the other side bonded to the double-sided empty foil area 113. This allows the first adhesive tape 210 to be thinner, which is beneficial for improving the energy density of the battery cell.

[0076] In some embodiments, the thickness of the base layer 210a is H1, satisfying 4μm≤H1≤20μm. For example, H1 can be 4μm, 12μm, or 20μm, etc.

[0077] When H1 is greater than or equal to 4μm, the supporting force of the base layer 210a is stronger, and the first adhesive paper 210 is less prone to deformation. This reduces the possibility of a short circuit between the positive electrode 110 and the negative electrode 130 due to deformation of the first adhesive paper 210, thus improving the safety of the battery cell. When H1 is less than or equal to 20μm, the base layer 210a has a smaller impact on the thickness of the battery cell, which is beneficial to improving the energy density of the battery cell. Therefore, when 4μm≤H1≤20μm, the supporting force of the base layer 210a is stronger, and the first adhesive paper 210 is less prone to deformation. This reduces the possibility of a short circuit between the positive electrode 110 and the negative electrode 130 due to deformation of the first adhesive paper 210, thus improving the safety of the battery cell. At the same time, the base layer 210a has a smaller impact on the thickness of the battery cell, which is beneficial to improving the energy density of the battery cell.

[0078] In some embodiments, the thickness of the first adhesive layer 210b is H2, satisfying 2μm≤H2≤10μm. For example, H2 can be 2μm, 6μm, or 10μm, etc.

[0079] When H2 is greater than or equal to 2 μm, the adhesion of the first adhesive layer 210b is higher, the connection strength between the first adhesive tape 210 and the single-sided coating area 112 is higher, and the first adhesive tape 210 is less likely to detach from the single-sided coating area 112, thus maintaining the insulation between the positive electrode 110 and the negative electrode 130, resulting in higher cell safety. Furthermore, the first adhesive tape 210 has a better binding effect on metal ions in the coating area, reducing the possibility of metal ion deposition and extending the cell's lifespan. When H2 is less than or equal to 10 μm, the first adhesive layer 210b has less impact on the cell's thickness, which is beneficial for improving the cell's energy efficiency. Energy density; therefore, when 2μm≤H2≤10μm, the adhesion of the first adhesive layer 210b is high, the connection strength between the first adhesive tape 210 and the single-sided coating area 112 is high, the first adhesive tape 210 is not easy to detach from the single-sided coating area 112, so as to maintain the insulation between the positive electrode plate 110 and the negative electrode plate 130, which makes the safety of the battery cell high, and the binding effect of the first adhesive tape 210 on the metal ions in the coating area is good, reducing the possibility of metal ion precipitation, which is conducive to extending the service life of the battery cell. At the same time, the first adhesive layer 210b has little impact on the thickness of the battery cell, which is conducive to improving the energy density of the battery cell.

[0080] In some embodiments, the thickness of the second adhesive layer 210c is H3, satisfying 1μm≤H3≤5μm. For example, H3 can be 1μm, 3μm, or 5μm, etc.

[0081] When H3 is greater than or equal to 1 μm, the adhesion of the second adhesive layer 210c is higher, and the connection strength between the first adhesive tape 210 and the double-sided empty foil area 113 is higher. This reduces the possibility of displacement of the double-sided empty foil area 113 relative to the single-sided coated area 112, thereby reducing the possibility of short circuit between the double-sided empty foil area 113 and the negative electrode plate 130, and improving the safety of the battery cell. When H3 is less than or equal to 5 μm, the influence of the second adhesive layer 210c on the thickness of the battery cell is smaller, which is beneficial to improving the energy efficiency of the battery cell. Energy density; therefore, when 1μm≤H3≤5μm, the adhesion of the second adhesive layer 210c is high, the connection strength between the first adhesive paper 210 and the double-sided empty foil area 113 is high, the possibility of displacement of the double-sided empty foil area 113 relative to the single-sided coated area 112 is reduced, thereby reducing the possibility of short circuit between the double-sided empty foil area 113 and the negative electrode plate 130, which can improve the safety of the battery cell, and the effect of the second adhesive layer 210c on the thickness of the battery cell is small, which is beneficial to improving the energy density of the battery cell.

[0082] In some embodiments, the base layer 210a comprises polyethylene terephthalate material and / or polyimide material.

[0083] By including polyethylene terephthalate and / or polyimide materials in the base layer 210a, the base layer 210a can be made to have stronger support and the first adhesive paper 210 is less prone to deformation. This reduces the possibility of short circuit between the positive electrode 110 and the negative electrode 130 due to deformation of the first adhesive paper 210, thereby improving the safety of the battery cell.

[0084] In some embodiments, the first adhesive layer 210b comprises a polyolefin material and / or a rubber material.

[0085] By including polyolefin and / or rubber materials in the first adhesive layer 210b, the adhesive force of the first adhesive layer 210b is high, the connection strength between the first adhesive tape 210 and the single-sided coating area 112 is high, and the first adhesive tape 210 is not easy to detach from the single-sided coating area 112, so as to maintain the insulation between the positive electrode 110 and the negative electrode 130, thus making the safety of the battery cell higher; and the first adhesive layer 210b has strong corrosion resistance, which can reduce the risk of short circuit between the positive electrode 110 and the negative electrode 130 after the first adhesive layer 210b is corroded by the electrolyte, further improving the safety of the battery cell.

[0086] In some embodiments, the second adhesive layer 210c comprises a polyolefin material and / or a rubber material.

[0087] By including polyolefin and / or rubber materials in the second adhesive layer 210c, the adhesive force of the second adhesive layer 210c is higher, and the connection strength between the first adhesive paper 210 and the double-sided empty foil area 113 is higher. This reduces the possibility of displacement of the double-sided empty foil area 113 relative to the single-sided coated area 112, thereby reducing the possibility of short circuit between the double-sided empty foil area 113 and the negative electrode 130, and improving the safety of the battery cell. Furthermore, the second adhesive layer 210c has strong corrosion resistance, which reduces the risk of short circuit between the positive electrode 110 and the negative electrode 130 after the second adhesive layer 210c is corroded by the electrolyte, further improving the safety of the battery cell.

[0088] In some embodiments, the battery cell includes a second adhesive tape 220 for fixing the winding end of the positive electrode 110.

[0089] By including a second adhesive tape 220 in the battery cell, which is used to fix the winding end of the positive electrode 110, the possibility of displacement of the double-sided empty foil area 113 of the positive electrode 110 relative to the single-sided coated area 112 can be further reduced, thereby reducing the possibility of short circuit between the double-sided empty foil area 113 and the negative electrode 130, and improving the safety of the battery cell.

[0090] In some embodiments, the winding end of the positive electrode 110 can also be achieved by using a first adhesive tape 210 including two adhesive layers, which eliminates the need for a second adhesive tape 220, thereby further reducing the thickness of the electrode assembly 100 and increasing the energy density of the battery cell.

[0091] In some embodiments, the battery cell includes a positive electrode tab 310 and a third adhesive tape 230. The positive electrode tab 310 is connected to the positive electrode plate 110. A portion of the third adhesive tape 230 is attached to the positive electrode tab 310 and another portion is attached to the positive electrode plate 110. Along the thickness direction Z of the electrode assembly, the projection of the second adhesive tape 220 does not overlap with the projection of the third adhesive tape 230.

[0092] By attaching a portion of the third adhesive tape 230 to the positive electrode tab 310 and another portion to the positive electrode plate 110, the projections of the second adhesive tape 220 and the third adhesive tape 230 do not overlap along the thickness direction Z of the electrode assembly. This prevents the thickness of the second adhesive tape 220 from overlapping with the thickness of the third adhesive tape 230 in the thickness direction Z of the electrode assembly, which helps to reduce the thickness of the battery cell and increase its energy density.

[0093] In some embodiments, the battery cell includes a negative electrode tab 320 and a fourth adhesive tape 240. The negative electrode tab 320 is connected to the negative electrode plate 130. A portion of the fourth adhesive tape 240 is attached to the negative electrode tab 320 and another portion is attached to the negative electrode plate 130. Along the thickness direction Z of the electrode assembly, the projection of the second adhesive tape 220 does not overlap with the projection of the fourth adhesive tape 240.

[0094] By attaching a portion of the fourth adhesive tape 240 to the negative electrode tab 320 and another portion to the negative electrode sheet 130, the projections of the second adhesive tape 220 and the fourth adhesive tape 240 do not overlap along the thickness direction Z of the electrode assembly. This prevents the thickness of the second adhesive tape 220 from overlapping with the thickness of the fourth adhesive tape 240 in the thickness direction Z of the electrode assembly, which helps to reduce the thickness of the battery cell and increase its energy density.

[0095] In some embodiments, the positive electrode tab 310 and the positive electrode sheet 110 can be integrally formed, or they can be connected by welding, bonding, or other methods. The negative electrode tab 320 and the negative electrode sheet 130 can be integrally formed, or they can be connected by welding, bonding, or other methods.

[0096] In some embodiments, the battery cell further includes a fifth adhesive tape 250, which is attached to the side of the double-sided empty foil area 113 facing the winding center of the electrode assembly.

[0097] By including a fifth adhesive tape 250 in the battery cell, which is attached to the side of the double-sided empty foil area 113 facing the winding center of the electrode assembly, the fifth adhesive tape 250 can serve as an insulator between the double-sided empty foil area 113 and the negative electrode plate 130, reducing the possibility of short circuit between the positive electrode plate 110 and the negative electrode plate 130, and improving the safety of the battery cell.

[0098] In some embodiments, a portion of the fifth adhesive tape 250 is attached to the double-sided empty foil area 113, and another portion is attached to the side of the single-sided coating area 112 where the active material layer is provided.

[0099] Since errors in the manufacturing process are unavoidable, if the fifth adhesive tape 250 is entirely placed in the double-sided empty foil area 113, there may be gaps between the fifth adhesive tape 250 and the active material layer of the single-sided coating area 112, which could cause a short circuit between the positive electrode 110 and the negative electrode 130. Therefore, by attaching a portion of the fifth adhesive tape 250 to the double-sided empty foil area 113 and another portion to the side of the single-sided coating area 112 where the active material layer is located, the fifth adhesive tape 250 can cover the end of the double-sided empty foil area 113 near the single-sided coating area 112, thereby reducing the risk of a short circuit between the positive electrode 110 and the negative electrode 130 and improving the safety of the battery cell.

[0100] Refer to Table 1. In Table 1, comparative example X shows a scheme where adhesive tape is provided at the head and tail of the wound electrode assembly. W1 is the width of the second part of the first adhesive tape, W2 is the width of the double-sided empty foil area, L1 is the length of the second part of the first adhesive tape, L2 is the length of the double-sided empty foil area, and W3 is the width of the first part of the first adhesive tape.

[0101] Comparative Example X represents the structure mentioned in the background art where the head and tail adhesive tape have not been removed.

[0102] The test method for the energy density of a battery cell is as follows:

[0103] (1) Place the battery cell in an environment of 25℃±2℃.

[0104] (2) Charge the cell to 4.5V with a constant current of 1C, and then charge it to 0.05C with a constant voltage.

[0105] (3) Discharge the cell to 3.0V with a constant current of 0.2C.

[0106] (4) Repeat steps 2-3 three times, and take the last capacity as the cell capacity.

[0107] (5) Cell energy density = cell capacity * discharge platform / cell volume.

[0108] Table 1. Energy density, drop pass rate, and encapsulation leakage rate of the battery cells

[0109] The test method for drop pass rate is as follows:

[0110] (1) Place the battery cell in an environment of 25℃±2℃.

[0111] (2) Charge the cell to 4.5V with a constant current of 1C, and then charge it to 0.05C with a constant voltage.

[0112] (3) The battery cell was dropped from a height of 1.5m, with each of the six surfaces facing down once and each of the four corners facing down once, onto the marble floor. A total of 10 tests were conducted, with the drop order being front-back-bottom-top-left-right-top-left-top-right-bottom-right.

[0113] (4) Judgment criteria: No fire, no explosion, no smoke, no leakage, and the voltage drop of the cell compared to the initial state is less than 100mV.

[0114] The test method for encapsulation leakage rate is as follows:

[0115] (1) In an environment of 25℃±2℃, the electrode assembly is placed between two 100um aluminum-plastic films to form a sandwich structure.

[0116] (2) Place the sandwich structure as a whole in the upper and lower 200±5℃ hot press head, and press it with a force of 120±10kg for 15±0.1s to complete the sealing of the three sides.

[0117] (3) Inject 10g of electrolyte into the unsealed side of the battery cell that has been encapsulated on three sides.

[0118] (4) Place the unsealed side in a hot press head at 200±5℃ and press it with a force of 120±10kg for 15±0.1s to complete the sealing.

[0119] (5) Place the packaged battery cell in a 60°C environment for 48 hours and visually inspect the sealing area for electrolyte leakage.

[0120] Based on Table 1, the following conclusions can be drawn:

[0121] 1. Referring to Comparative Example X and Examples 1-10, the energy density of the battery cell is lower in the scheme where the head and tail adhesive tape is not removed.

[0122] 2. Referring to Comparative Examples 1-4 and Examples 1-10, W1 being greater than W2 indicates that the width direction of the adhesive tape extends beyond the edge of the double-sided empty foil area. L1-L2 being greater than 0 indicates that the length direction of the surface adhesive tape extends beyond the end edge of the double-sided empty foil area. When the length or width direction of the adhesive tape does not extend beyond the double-sided empty foil area, the drop pass rate is low.

[0123] 3. Referring to Comparative Examples 3-4, Examples 1, and 3-5, as L1-L2 increases, the drop pass rate of the battery cell improves, which is beneficial to improving the reliability of the battery cell. However, the leakage rate of the encapsulation also increases, affecting the safety of the battery cell. When L1-L2≤0, the drop pass rate of the battery cell is low, affecting the reliability of the battery cell. When L1-L2>10mm, the first adhesive tape may extend into the sealing area of ​​the battery cell's packaging bag, resulting in a higher leakage rate of the encapsulation and affecting the safety of the battery cell. When 0<L1-L2≤10mm, both a high drop pass rate and a low leakage rate of the encapsulation can be achieved.

[0124] 4. Referring to Examples 1 and 6-10, as W3 increases, the energy density of the battery cell decreases, affecting its range. When W3 = 0, although the energy density of the battery cell is high, there is a risk of short circuit, and the drop survival rate of the battery cell is low. When W3 > 10 mm, the energy density of the battery cell is low, affecting its range. When 0 < W3 ≤ 10 mm, both the energy density and drop survival rate of the battery cell are high.

[0125] This application provides an electrical device including a battery cell from any of the above-described solutions, the battery cell being used to provide electrical energy to the electrical device.

[0126] The electrical equipment can be any of the aforementioned devices or systems that use battery cells.

[0127] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0128] 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. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A battery cell, characterized in that, The electrode assembly includes an electrode assembly formed by winding a positive electrode sheet, a separator, and a negative electrode sheet that are stacked together, wherein the outermost electrode sheet of the electrode assembly is the positive electrode sheet; The positive electrode sheet includes a double-sided coated area, a single-sided coated area, and a double-sided empty foil area arranged sequentially from the starting end to the ending end of the winding. The battery cell also includes a first adhesive tape, which is attached to the side of the single-sided coating area where the active material layer is not provided, and is at least partially provided on the positive electrode sheet of the second ring from the outside to the inside of the battery cell; Along the winding direction, the double-sided empty foil area has a first edge away from the single-sided coated area, and the first adhesive paper extends beyond the first edge; Along the winding axis, the double-sided empty foil area has opposing second and third edges, the first adhesive paper extends beyond the second and third edges, and the cell capacity is less than 3Ah.

2. The battery cell according to claim 1, characterized in that, The first adhesive tape includes a first part and a second part, the first part being attached to the double-sided coating area and the second part being attached to the single-sided coating area.

3. The battery cell according to claim 2, characterized in that, Along the winding axis, the length of the second part is L1, and the length of the double-sided empty foil area is L2, satisfying L1 > L2; Along the winding direction, the width of the second part is W1, and the width of the double-sided empty foil area is W2, satisfying W1 > W2; Viewed radially along the winding, the second portion completely covers the double-sided empty foil area.

4. The battery cell according to claim 3, characterized in that, 0 < L1 - L2 ≤ 10 mm.

5. The battery cell according to claim 2, characterized in that, Along the winding direction, the width of the first portion is W3, which satisfies 0 < W3 ≤ 10 mm.

6. The battery cell according to claim 1, characterized in that, A portion of the double-sided empty foil area is located on one side of the electrode assembly along its thickness direction, and another portion of the double-sided empty foil area is located on one side of the electrode assembly along the first direction; The first direction, the winding axis direction, and the thickness direction of the electrode assembly are perpendicular to each other.

7. The battery cell according to claim 1, characterized in that, The first adhesive tape includes a base layer and a first adhesive layer, wherein the first adhesive layer is disposed on the side of the base layer facing the single-sided coating area.

8. The battery cell according to claim 7, characterized in that, The first adhesive tape includes a second adhesive layer, which is disposed on the side of the base layer opposite to the single-sided coating area.

9. The battery cell according to claim 8, characterized in that, The thickness of the base layer is H1, which satisfies 4μm≤H1≤20μm; the thickness of the first adhesive layer is H2, which satisfies 2μm≤H2≤10μm; and the thickness of the second adhesive layer is H3, which satisfies 1μm≤H3≤5μm.

10. The battery cell according to claim 8, characterized in that, The base layer comprises polyethylene terephthalate and / or polyimide, the first adhesive layer comprises polyolefin and / or rubber, and the second adhesive layer comprises polyolefin and / or rubber.

11. The battery cell according to claim 1, characterized in that, The battery cell includes a second adhesive tape, which is used to fix the winding end of the positive electrode sheet; The battery cell includes a positive electrode tab and a third adhesive tape. The positive electrode tab is connected to the positive electrode plate. A portion of the third adhesive tape is attached to the positive electrode tab, and another portion is attached to the positive electrode plate. Along the thickness direction of the electrode assembly, the projection of the second adhesive tape and the projection of the third adhesive tape do not overlap. The battery cell includes a negative electrode tab and a fourth adhesive tape. The negative electrode tab is connected to the negative electrode sheet. A portion of the fourth adhesive tape is attached to the negative electrode tab, and another portion is attached to the negative electrode sheet. Along the thickness direction of the electrode assembly, the projection of the second adhesive tape and the projection of the fourth adhesive tape do not overlap.

12. The battery cell according to claim 1, characterized in that, The battery cell includes a fifth adhesive tape, which is attached to the side of the double-sided empty foil area facing the winding center of the electrode assembly.

13. The battery cell according to any one of claims 1-12, characterized in that, The first adhesive tape is at least partially disposed on the negative electrode sheet of the second ring from the outside to the inside of the battery cell.

14. An electrical appliance, characterized in that, Includes a battery cell as described in any one of claims 1-13, the battery cell being used to provide electrical energy.

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