Battery cell and electric device

Abstract

This application provides a battery cell and an electrical device, relating to the field of batteries. The battery cell includes an electrode assembly and a packaging bag. The electrode assembly includes at least two electrode sheets stacked together. Each electrode sheet includes a main body region and a first thinned region, with the thickness of the main body region being greater than the thickness of the first thinned region. The packaging bag has a receiving cavity for accommodating the electrode assembly. The receiving cavity includes a first space for accommodating the main body region and a second space for accommodating the first thinned region. Along the thickness direction of the battery cell, the size of the second space is smaller than the size of the first space. The main body region is accommodated in the first space, and the first thinned region is accommodated in the second space. The size of the second space along the thickness direction of the battery cell is smaller than the size of the first space along the thickness direction of the battery cell. The first thinned regions of multiple electrode sheets will move closer together under the action of the inner wall of the second space, reducing the distance between two adjacent first thinned regions, decreasing the lithium-ion transport path, reducing the risk of lithium plating, and improving the safety of the battery cell.

Description

Technical Field

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

[0002] With the development of new energy technologies, battery cells, with their high energy density and high degree of customization, are widely used in portable electronic devices, electric vehicles, power tools, drones, energy storage devices, and other fields. Battery cell design needs to consider many factors, such as energy density, discharge capacity, and charge / discharge rate. Additionally, battery cell safety must be considered. However, current battery cells have relatively poor safety. Summary of the Invention

[0003] The purpose of this application is to provide a battery cell, a secondary battery, and an electrical device, which aims to improve the problem of poor safety of battery cells in related technologies.

[0004] In a first aspect, embodiments of this application provide a battery cell, which includes an electrode assembly and a packaging bag. The electrode assembly includes at least two electrode sheets stacked together, each electrode sheet including a main body region and a first thinned region, the thickness of the main body region being greater than the thickness of the first thinned region. The packaging bag has a receiving cavity for accommodating the electrode assembly, the receiving cavity including a first space for accommodating the main body region and a second space for accommodating the first thinned region. Specifically, along the thickness direction of the battery cell, the size of the second space is smaller than the size of the first space.

[0005] In the above technical solution, the main body area is housed in the first space, and the first thinning area is housed in the second space. Since the dimension of the second space along the thickness direction of the cell is smaller than the dimension of the first space along the thickness direction of the cell, the first thinning areas of at least two electrodes will move closer to each other under the action of the inner wall of the second space, thereby reducing the distance between the first thinning areas of two adjacent electrodes, reducing the lithium ion transport path, reducing the risk of lithium plating, improving the safety of the cell, and improving the cycle performance of the cell.

[0006] In some embodiments of the first aspect of this application, the encapsulation bag includes a first encapsulation film and a second encapsulation film, and an electrode assembly is disposed between the first encapsulation film and the second encapsulation film. The first encapsulation film includes a first portion and a second portion, and the second encapsulation film includes a third portion and a fourth portion. A first space is formed between the first portion and the third portion, and a second space is formed between the second portion and the fourth portion. Specifically, along the thickness direction of the battery cell, the distance between the inner surface of the second portion and the inner surface of the fourth portion is less than the distance between the inner surface of the first portion and the inner surface of the third portion.

[0007] In the above technical solution, the main body area is located between the first part and the third part, and the first thinning area is located between the second part and the fourth part. Since the distance between the inner surface of the second part and the inner surface of the fourth part is less than the distance between the inner surface of the first part and the inner surface of the third part, the first thinning areas of at least two electrodes will move closer to each other under the action of the second part and the fourth part, thereby reducing the distance between the first thinning areas of two adjacent electrodes, reducing the lithium ion transport path, reducing the risk of lithium plating, and improving the safety of the battery cell.

[0008] In some embodiments of the first aspect of this application, the thickness of the second portion is greater than the thickness of the first portion, and / or the thickness of the fourth portion is greater than the thickness of the third portion.

[0009] In the above technical solution, the second part can be considered as a local thickening of the first encapsulation film. By making the thickness of the second part greater than the thickness of the first part, the distance between the inner surfaces of the second and fourth parts is less than the distance between the inner surfaces of the first and third parts. This causes the first thinned areas of at least two electrodes to move closer together under the action of the second and fourth parts, reducing the lithium-ion transport path, lowering the risk of lithium plating, and improving the safety of the battery cell. Similarly, the fourth part can be considered as a local thickening of the second encapsulation film. By making the thickness of the fourth part greater than the thickness of the third part, the distance between the inner surfaces of the second and fourth parts is less than the distance between the inner surfaces of the first and third parts. This causes the first thinned areas of at least two electrodes to move closer together under the action of the second and fourth parts, reducing the lithium-ion transport path, lowering the risk of lithium plating, and improving the safety of the battery cell.

[0010] In some embodiments of the first aspect of this application, the outer surface of the second portion is coplanar with the outer surface of the first portion. And / or, the outer surface of the fourth portion is coplanar with the outer surface of the third portion.

[0011] In the above technical solution, when the outer surface of the second part is coplanar with the outer surface of the first part, the distance between the inner surface of the second part and the outer surface of the second part is greater than the distance between the inner surface of the first part and the outer surface of the first part. This allows the second part to be closer to the second encapsulation film, which helps to reduce the distance between the first thinning areas of two adjacent electrodes, reducing the risk of lithium plating and improving the safety of the battery cell. Furthermore, when the outer surface of the second part is coplanar with the outer surface of the first part, the outer surface of the first encapsulation film is smoother and less prone to wrinkling, which helps to improve the reliability of the encapsulation. Similarly, when the outer surface of the fourth part is coplanar with the outer surface of the third part, the distance between the inner surface of the fourth part and the outer surface of the fourth part is greater than the distance between the inner surface of the third part and the outer surface of the third part. This allows the fourth part to be closer to the first encapsulation film, which helps to reduce the distance between the first thinning areas of two adjacent electrodes, reducing the risk of lithium plating and improving the safety of the battery cell. Furthermore, when the outer surface of the fourth part is coplanar with the outer surface of the third part, the outer surface of the second encapsulation film is smoother and less prone to wrinkling, which helps to improve the reliability of the encapsulation.

[0012] In some embodiments of the first aspect of this application, the second portion has a first end close to the first portion and a second end away from the first portion, and the thickness of the second portion gradually increases from the first end to the second end. And / or, the fourth portion has a third end close to the third portion and a fourth end away from the third portion, and the thickness of the fourth portion gradually increases from the third end to the fourth end.

[0013] In the above technical solution, since the thickness of the first thinning region gradually decreases from the end closer to the main body region to the end farther away from the main body region, and the thickness of the second part gradually increases from the first end to the second end, the second part has a larger thickness at the end where the thickness of the first thinning region is thinner, and a smaller thickness at the end where the thickness of the first thinning region is thicker. This allows the second part to complement the first thinning region, which is beneficial for uniform stress on the electrode sheet, reduces stress concentration, and improves the lifespan of the battery cell. Similarly, by gradually increasing the thickness of the fourth part from the third end to the fourth end, the fourth part has a larger thickness at the end where the thickness of the first thinning region is thinner, and a smaller thickness at the end where the thickness of the first thinning region is thicker. This allows the fourth part to complement the first thinning region, which is beneficial for uniform stress on the electrode sheet, reduces stress concentration, and improves the lifespan of the battery cell.

[0014] In some embodiments of the first aspect of this application, the maximum thickness of the second part is T1, and the thickness of the first part is T2, satisfying: 1.02≤T1 / T2≤3.

[0015] In the above technical solution, the maximum thickness of the second part is 1.02 to 3 times the thickness of the first part. This reduces the distance between the first thinned areas of two adjacent electrodes, shortens the lithium-ion transport path, and lowers the risk of lithium plating. It also prevents the first thinned area from tilting excessively relative to the main body area, thus avoiding stress concentration on the electrode. When T1 / T2 < 1.02, the distance between the first thinned areas of two adjacent electrodes cannot be effectively reduced, and the effect of reducing lithium plating is not significant. When T1 / T2 > 3, the first thinned area may tilt excessively relative to the main body area, causing stress concentration at the connection point between the first thinned area and the main body area, which can easily lead to electrode damage.

[0016] In some embodiments of the first aspect of this application, the sum of the minimum thicknesses of the first thinned regions of at least two electrodes is T3, and the sum of the thicknesses of the main regions of at least two electrodes is T4, satisfying: 1.02≤(T1+T3) / (T2+T4)≤1.1.

[0017] In the above technical solution, by making (T1+T3) / (T2+T4) between 1.02 and 1.1, the first thinning areas of at least two electrodes are brought closer to each other under the action of the second and fourth parts, so that the distance between the main body areas of two adjacent electrodes is the same as or similar to the distance between the first thinning areas of two adjacent electrodes, thereby reducing the lithium ion transport path, reducing the risk of lithium plating, and improving the safety of the battery cell.

[0018] In some embodiments of the first aspect of this application, the length of the second part along the length direction of the battery cell is W1, which satisfies: 0 < W1 ≤ 30 mm.

[0019] In the above technical solution, the length of the second part along the length direction of the battery cell is between 0 and 30 mm (excluding 0), so as to adapt to the length of the first thinning zone.

[0020] In some embodiments of the first aspect of this application, the second portion extends obliquely from the first portion, and the angle between the second portion and the first portion is an obtuse angle; and / or, the fourth portion extends obliquely from the third portion, and the angle between the fourth portion and the third portion is an obtuse angle.

[0021] In the above technical solution, the second part slopes towards the second encapsulation film starting from the first part. The end of the second part closer to the first part is further away from the second encapsulation film than the end of the second part farther from the first part. This results in the maximum distance between the inner surface of the second part and the inner surface of the fourth part being less than the minimum distance between the inner surface of the first part and the inner surface of the third part. Similarly, the fourth part slopes towards the first encapsulation film starting from the third part. The end of the fourth part closer to the third part is further away from the first encapsulation film than the end of the fourth part farther from the third part. This again results in the maximum distance between the inner surface of the second part and the inner surface of the fourth part being less than the minimum distance between the inner surface of the first part and the inner surface of the third part.

[0022] In some embodiments of the first aspect of this application, a first groove and a second groove are formed on the side of the first encapsulation film facing the second encapsulation film. The position of the first groove corresponds to the position of the main body region, and the position of the second groove corresponds to the position of the first thinning region. Along the thickness direction of the battery cell, the depth of the second groove is less than the depth of the first groove. And / or, a third groove and a fourth groove are formed on the side of the second encapsulation film facing the first encapsulation film. The position of the third groove corresponds to the position of the main body region, and the position of the fourth groove corresponds to the position of the first thinning region. Along the thickness direction of the battery cell, the depth of the fourth groove is less than the depth of the third groove.

[0023] In the above technical solution, the bottom wall of the first groove forms a first portion of the first encapsulation film, and the bottom wall of the second groove forms a second portion of the first encapsulation film. Along the thickness direction of the battery cell, the depth of the second groove is less than the depth of the first groove. Therefore, the bottom wall of the first groove is farther away from the second encapsulation film than the bottom wall of the second groove. In other words, along the thickness direction of the battery cell, the first portion is farther away from the second encapsulation film than the second portion, making the distance between the inner surface of the second portion and the inner surface of the fourth portion smaller than the distance between the inner surface of the first portion and the inner surface of the third portion. The bottom wall of the third groove forms a third portion of the second encapsulation film, and the bottom wall of the fourth groove forms a fourth portion of the second encapsulation film. Along the thickness direction of the battery cell, the depth of the fourth groove is less than the depth of the third groove. Therefore, the bottom wall of the third groove is farther away from the first encapsulation film than the bottom wall of the fourth groove. In other words, along the thickness direction of the battery cell, the third portion is farther away from the first encapsulation film than the fourth portion, making the distance between the inner surface of the second portion and the inner surface of the fourth portion smaller than the distance between the inner surface of the first portion and the inner surface of the third portion.

[0024] In some embodiments of the first aspect of this application, the encapsulation bag includes a first encapsulation film and a second encapsulation film, with an electrode assembly disposed between the first and second encapsulation films. A first insulating layer is disposed on the inner surface of the first encapsulation film, and when viewed along the thickness direction of the battery cell, the first insulating layer at least partially overlaps with a first thinning region. And / or, a second insulating layer is disposed on the inner surface of the second encapsulation film, and when viewed along the thickness direction of the battery cell, the second insulating layer at least partially overlaps with the first thinning region.

[0025] In the above technical solution, by providing a first insulating layer on the inner surface of the first encapsulation film, the position of the first insulating layer corresponding to the position of the first thinning area, and along the thickness direction of the battery cell, the size of the second space is the distance between the first insulating layer and the second encapsulation film or the second insulating layer, and the size of the first space is the distance between the first encapsulation film and the second encapsulation film, such that along the thickness direction of the battery cell, the size of the second space is smaller than the size of the first space. Similarly, by providing a second insulating layer on the inner surface of the second encapsulation film, the position of the second insulating layer corresponding to the position of the first thinning area, and along the thickness direction of the battery cell, the size of the second space is the distance between the second insulating layer and the first encapsulation film or the first insulating layer, and the size of the first space is the distance between the first encapsulation film and the second encapsulation film, such that along the thickness direction of the battery cell, the size of the second space is smaller than the size of the first space.

[0026] In some embodiments of the first aspect of this application, the thickness of the first insulating layer gradually increases in the direction away from the main body region. And / or, the thickness of the second insulating layer gradually increases in the direction away from the main body region.

[0027] In the above technical solution, since the thickness of the first thinning region gradually decreases from the end closer to the main body region to the end farther away from the main body region, and the thickness of the first insulating layer gradually increases in the direction away from the main body region, the first insulating layer has a larger thickness at the thinner end of the first thinning region and a smaller thickness at the thicker end of the first thinning region. This allows the first insulating layer to complement the first thinning region, which is beneficial for uniform stress on the electrode sheet, reduces stress concentration, and improves the lifespan of the battery cell. Similarly, by gradually increasing the thickness of the second insulating layer in the direction away from the main body region, the second insulating layer has a larger thickness at the thinner end of the first thinning region and a smaller thickness at the thicker end of the first thinning region. This allows the second insulating layer to complement the first thinning region, which is beneficial for uniform stress on the electrode sheet, reduces stress concentration, and improves the lifespan of the battery cell.

[0028] In some embodiments of the first aspect of this application, the sum of the maximum thickness of the first insulating layer and the thickness of the first encapsulation film is T5, and the thickness of the first encapsulation film is T6, satisfying: 1.02≤T5 / T6≤3.

[0029] In the above technical solution, the maximum thickness of the first insulating layer is 1.02 to 3 times the thickness of the first encapsulation film. This reduces the distance between the first thinned areas of two adjacent electrodes, decreases the lithium-ion transport path, and lowers the risk of lithium plating. It also prevents the first thinned area from tilting excessively relative to the main body area, thus avoiding stress concentration on the electrode. When T5 / T6 < 1.02, the distance between the first thinned areas of two adjacent electrodes cannot be effectively reduced, and the effect of reducing lithium plating is not significant. When T5 / T6 > 3, the first thinned area may tilt excessively relative to the main body area, causing stress concentration at the connection point between the first thinned area and the main body area, which can easily lead to electrode damage.

[0030] In some embodiments of the first aspect of this application, the sum of the minimum thicknesses of the first thinned regions of at least two electrodes is T3, and the sum of the thicknesses of the main regions of at least two electrodes is T4, satisfying: 1.02≤(T5+T3) / (T6+T4)≤1.1.

[0031] In the above technical solution, by making (T5+T3) / (T6+T4) between 1.02 and 1.1, the first thinning areas of at least two electrodes are brought closer to each other under the action of the first insulating layer, so that the distance between the main body areas of two adjacent electrodes is the same as or similar to the distance between the first thinning areas of two adjacent electrodes, thereby reducing the lithium ion transport path, reducing the risk of lithium plating, and improving the safety of the battery cell.

[0032] In some embodiments of the first aspect of this application, the length of the first insulating layer along the length direction of the battery cell is W2, which satisfies: 0 < W2 ≤ 30 mm.

[0033] In the above technical solution, the length of the first insulating layer along the length direction of the battery cell is between 0 and 30 mm (excluding 0), so as to adapt to the length of the first thinning zone.

[0034] In some embodiments of the first aspect of this application, the sum of the minimum thicknesses of the first thinned regions of at least two electrodes is T3, and the sum of the thicknesses of the main regions of at least two electrodes is T4, satisfying: 0.92≤T3 / T4<1.

[0035] In the above technical solution, limiting the ratio of the sum of the minimum thicknesses of the first thinned regions of at least two electrodes to the sum of the thicknesses of the main regions of at least two electrodes to between 0.92 and 1 (excluding 1) is beneficial for minimizing the distance between the first thinned regions of two adjacent electrodes, resulting in a shorter lithium-ion transport path, which helps reduce the risk of lithium plating and improves the safety of the battery cell. When T3 / T4 < 0.92, the difference between the minimum thickness of the first thinned region and the thickness of the main region is too large, and the distance between the first thinned regions of two adjacent electrodes is too large, making lithium plating relatively easier.

[0036] In some embodiments of the first aspect of this application, the electrode further includes a second thinning region, the thickness of the main body region being greater than the thickness of the second thinning region, and the first and second thinning regions being located at opposite ends of the main body region. The receiving cavity further includes a third space for accommodating the second thinning region, the size of the third space being smaller than the size of the first space along the thickness direction of the cell.

[0037] In the above technical solution, the main body area is housed in the first space, and the second thinning area is housed in the third space. Since the dimension of the third space along the thickness direction of the cell is smaller than the dimension of the first space along the thickness direction of the cell, the second thinning areas of at least two electrodes will move closer to each other under the action of the inner wall of the third space, thereby reducing the distance between the second thinning areas of two adjacent electrodes, reducing the lithium ion transport path, reducing the risk of lithium plating, and improving the safety of the cell.

[0038] Secondly, embodiments of this application also provide a secondary battery, including the battery cell provided in the first aspect embodiment.

[0039] In the above technical solutions, the cell provided in the first aspect embodiment has a lower risk of lithium plating and higher safety. Therefore, the secondary battery including this cell also has high safety.

[0040] Thirdly, embodiments of this application provide an electrical device, including the secondary battery provided in the second aspect embodiment.

[0041] In the above technical solutions, the secondary battery provided in the second aspect embodiment has better safety performance and can improve the electrical safety of electrical equipment. Attached Figure Description

[0042] 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 from these drawings without creative effort.

[0043] Figure 1 A cross-sectional view of a battery cell (with thickened first encapsulation film) provided for some embodiments of this application;

[0044] Figure 2 A cross-sectional view of a battery cell (with thickened second encapsulation film) provided for some embodiments of this application;

[0045] Figure 3 A cross-sectional view of a battery cell (both the first and second encapsulation films are thickened) provided in some embodiments of this application;

[0046] Figure 4Cross-sectional views of the battery cell provided for other embodiments of this application;

[0047] Figure 5 A cross-sectional view of a battery cell provided for some embodiments of this application;

[0048] Figure 6 A cross-sectional view of a battery cell (with the first encapsulation film tilted) provided for some embodiments of this application;

[0049] Figure 7 A cross-sectional view of a battery cell (with the second encapsulation film tilted) provided for some embodiments of this application;

[0050] Figure 8 A cross-sectional view of a battery cell (both the first and second encapsulation films are inclined) provided in some embodiments of this application;

[0051] Figure 9 A cross-sectional view of a battery cell (with a groove in the first encapsulation film) provided in some embodiments of this application;

[0052] Figure 10 This is a schematic diagram of the unfolded structure of the encapsulation bag of the battery cell (with a groove in the first encapsulation film) provided in some embodiments of this application;

[0053] Figure 11 for Figure 10 A cross-sectional view at position AA in the middle;

[0054] Figure 12 A cross-sectional view of a battery cell (with a groove in the second encapsulation film) provided in some embodiments of this application;

[0055] Figure 13 This is a schematic diagram of the unfolded structure of the encapsulation bag of the battery cell (with a groove in the second encapsulation film) provided in some embodiments of this application;

[0056] Figure 14 for Figure 13 A cross-sectional view at position BB in the middle;

[0057] Figure 15 A cross-sectional view of a battery cell (both the first and second encapsulation films have slots) provided in some embodiments of this application;

[0058] Figure 16 A schematic diagram of the unfolded structure of the packaging bag of a battery cell (both the first and second packaging films have grooves) provided in some embodiments of this application;

[0059] Figure 17 for Figure 16 A cross-sectional view at position CC;

[0060] Figure 18 A cross-sectional view of a battery cell (with a first insulating layer disposed on the inner surface of a first encapsulation film) provided in some embodiments of this application;

[0061] Figure 19 A cross-sectional view of a battery cell (with a second insulating layer disposed on the inner surface of the second encapsulation film) provided in some embodiments of this application;

[0062] Figure 20 A cross-sectional view of a battery cell (with a first insulating layer disposed on the inner surface of a first encapsulation film and a second insulating layer disposed on the inner surface of a second encapsulation film) provided in some embodiments of this application;

[0063] Figure 21 A cross-sectional view of a battery cell provided for some embodiments of this application;

[0064] Figure 22 Cross-sectional views of the battery cell provided in some other embodiments of this application;

[0065] Figure 23 A cross-sectional view of a battery cell provided in some further embodiments of this application;

[0066] Figure 24 A schematic diagram of the unfolded structure of the battery cell packaging bag provided in some embodiments of this application;

[0067] Figure 25 for Figure 24 A cross-sectional view of the DD position in the middle;

[0068] Figure 26 A cross-sectional view of a battery cell provided for further embodiments of this application;

[0069] Figure 27 A cross-sectional view of a battery cell provided for some other embodiments of this application.

[0070] Icons: 100-Cell; 10-Electrode assembly; 11-Electrode sheet; 111-Main area; 112-First thinning area; 113-Second thinning area; 12-Taper; 20-Encapsulation bag; 21-First encapsulation film; 211-First part; 212-Second part; 2121-First end; 2122-Second end; 213-First groove; 214-Second groove; 215-Fifth part; 216-Fifth groove; 22-Second... Encapsulation film; 221-Third part; 222-Fourth part; 2222-Fourth end; 223-Third groove; 224-Fourth groove; 225-Sixth part; 226-Sixth groove; 23-Folded part; 231-First space; 232-Second space; 233-Third space; 24-First insulating layer; 25-Second insulating layer; 26-Third insulating layer; 27-Fourth insulating layer; 30-Taper lead; 40-Connector. Detailed Implementation

[0071] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0072] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0073] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0074] The terms “first,” “second,” “third,” etc., are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0075] Currently, the application of rechargeable batteries is becoming increasingly widespread in the market. They are widely used in electric bicycles, electric motorcycles, electric cars, and other electric vehicles, as well as in power tools, drones, energy storage devices, and many other fields. As the application areas of rechargeable batteries continue to expand, the market demand is also constantly increasing.

[0076] The inventors discovered that the battery cell manufacturing process involves a coating step, where a slurry containing active materials is coated onto a current collector (such as a copper foil substrate) by a specific weight. However, due to the natural fluidity of the slurry, the coated edges of the electrode are thinner than the main body (i.e., the thinned area), resulting in a thinner cell thickness at the corresponding location in the thinned area. Thus, after the electrodes are wound or stacked to form an electrode assembly, the distance between the thinned areas of adjacent electrodes is relatively large, resulting in a longer lithium-ion transport path. As the electrolyte is consumed during cycling, lithium plating is more likely to occur. Lithium plating not only leads to accelerated cycle degradation but also poses safety hazards, resulting in poor battery cell safety.

[0077] Based on the above considerations, in order to improve the poor safety of battery cells in related technologies, this application provides a battery cell comprising an electrode assembly and a packaging bag. The electrode assembly includes at least two electrode sheets stacked together, each electrode sheet including a main body region and a first thinned region, the thickness of the main body region being greater than the thickness of the first thinned region. The packaging bag has a receiving cavity for accommodating the electrode assembly, the receiving cavity including a first space for accommodating the main body region and a second space for accommodating the first thinned region. Specifically, along the thickness direction of the battery cell, the size of the second space is smaller than the size of the first space.

[0078] The main body area is housed in the first space, and the first thinning area is housed in the second space. Since the dimension of the second space along the thickness direction of the cell is smaller than that of the first space along the thickness direction of the cell, the first thinning areas of at least two electrodes will move closer to each other under the action of the inner wall of the second space, thereby reducing the distance between the first thinning areas of two adjacent electrodes, reducing the lithium-ion transport path, reducing the risk of lithium plating, and improving the safety of the cell.

[0079] The battery cells disclosed in this application can be used, but are not limited to, in electrical devices such as electric two-wheelers, power tools, drones, and energy storage devices. Using the battery cells provided in this application as the power supply system for electrical devices can improve their safety.

[0080] This application provides an embodiment of an electrical device that uses a battery as a power source. The electrical device can be, but is not limited to, electronic devices, power tools, electric vehicles, drones, and energy storage devices. Electronic devices can include mobile phones, tablets, laptops, etc.; power tools can include electric drills, chainsaws, etc.; and electric vehicles can include electric cars, electric motorcycles, electric bicycles, etc.

[0081] Please refer to Figure 1 This application provides a battery cell 100, which includes an electrode assembly 10 and a packaging bag 20. The electrode assembly 10 includes at least two electrode sheets 11 stacked together. Each electrode sheet 11 includes a main body region 111 and a first thinned region 112. The thickness of the main body region 111 is greater than the thickness of the first thinned region 112. The packaging bag 20 has a receiving cavity for accommodating the electrode assembly 10. The receiving cavity includes a first space 231 for accommodating the main body region 111 and a second space 232 for accommodating the first thinned region 112. Along the thickness direction of the battery cell 100, the size of the second space 232 is smaller than the size of the first space 231.

[0082] The electrode assembly 10 includes a separator and at least two electrodes 11, which are wound or stacked together to form the electrode assembly 10. The at least two electrodes 11 include a positive electrode and a negative electrode. Please refer to... Figure 1 Regardless of whether it is a wound electrode assembly or a stacked electrode assembly, its cross-sectional view shows that the electrode assembly includes at least two stacked electrode sheets 11. Therefore, this application does not limit the electrode assembly 10 to be a wound electrode assembly or a stacked electrode assembly.

[0083] The battery cell 100 primarily operates by the movement of metal ions between the positive and negative electrode plates. The positive electrode plate includes a positive current collector and a positive active material layer, the positive active material layer being coated on the surface of the positive current collector. In some embodiments, the positive current collector also has a portion uncoated with the positive active material layer, protruding beyond the coated positive current collector, and serving as a positive tab. In other embodiments, the positive tab may be separate from the positive current collector and then electrically connected. 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 (such as NCM), or lithium manganese oxide, etc. The negative electrode plate includes a negative current collector and a negative active material layer, the negative active material layer being coated on the surface of the negative current collector. The portions of the positive and negative electrode plates containing the active material constitute the main body of the electrode assembly 10. In some embodiments, the negative current collector further includes a portion uncoated with a negative active material layer, protruding beyond the negative current collector coated with a negative active material layer. This uncoated negative current collector serves as a negative electrode tab. In other embodiments, the negative electrode tab may be separately disposed from the negative current collector and then electrically connected. The material of the negative current collector can be copper, and the negative active material can be carbon or silicon, etc. To ensure that a large current can pass through without melting, multiple positive electrode tabs are stacked together, and multiple negative electrode tabs are stacked together.

[0084] The separator can be made of PP (polypropylene) or PE (polyethylene), etc. Furthermore, the electrode assembly 10 can be a wound structure or a stacked structure. This embodiment uses a wound structure, and its cell 100 production process is a conventional process, including the manufacturing of positive and negative electrode sheets and separators; the positive and negative electrode sheets and separators are formed into the electrode assembly 10 by winding or stacking; and conventional processes such as encapsulation, electrolyte injection, formation, and voltage monitoring.

[0085] The main body region 111 is the region on the electrode 11 that mainly receives and releases lithium ions, and it is the main part of the electrode 11 that performs its function. The first thinning region 112 can be a region on the electrode 11 that is thinner due to the natural fluidity of the slurry when the active material slurry is coated onto the current collector in a certain weight. In other words, the thickness of the main body region 111 is greater than the thickness of the first thinning region 112.

[0086] The encapsulation bag 20 has an internal cavity. The encapsulation process creates a sealed space within this cavity, enclosing the electrode assembly 10. The encapsulation bag 20 can be a flexible shell, such as an aluminum-plastic film, thus forming a pouch cell. The encapsulation process for the encapsulation bag 20 includes, but is not limited to, melting, welding, and the application of seals.

[0087] The receiving cavity includes a first space 231 and a second space 232, wherein the first space 231 is used to receive the main body region 111, and the second space 232 is used to receive the first thinned region 112. The first space 231 and the second space 232 are connected.

[0088] Please refer to Figure 1 The thickness direction of the battery cell 100 can be the X direction as shown in the figure.

[0089] "The size of the second space 232 is smaller than the size of the first space 231 along the thickness direction of the cell 100" means that the maximum size of the second space 232 is smaller than the minimum size of the first space 231 along the thickness direction of the cell 100. Please refer to... Figure 1 The minimum size of the first space 231 is L1, and the maximum size of the second space 232 is L2, satisfying L1 > L2. Of course, if the maximum size of the second space 232 is equal at all positions along the thickness direction of the cell 100, then any position can be chosen as its maximum size. Similarly, if the minimum size of the first space 231 is equal at all positions along the thickness direction of the cell 100, then any position can be chosen as its minimum size.

[0090] Table 1 presents test data for some embodiments and comparative examples of the battery cell 100 of this application. In this table, the battery cell 100 was tested for lithium plating after cycling at 25°C, 5C charging, and 10C discharging until it reached 90% of its initial capacity. Lithium plating in the battery cell 100 can be determined by visually inspecting the cell 100 for bulging after every 100 charge-discharge cycles. If bulging is present, the battery cell 100 is disassembled to confirm whether lithium plating has occurred on the electrode 11. In Table 1, for the battery cells 100 of each embodiment and comparative example, other parts of the battery cell 100 not listed in Table 1 (such as the positive electrode, negative electrode, separator, electrolyte, etc.) are the same.

[0091] The positive electrode preparation process is as follows: The positive electrode active material ternary material (NCM811), conductive carbon black (SuperP), and polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 97.0:1.4:1.6. N-methylpyrrolidone (NMP) is added as a solvent to prepare a slurry with a solid content of 0.70%, and the mixture is stirred evenly. The slurry is then uniformly coated onto the positive electrode current collector. The weight of the effective positive electrode material on electrode 11 is 130 g / m². 2 Drying at 90℃ completes the single-sided coating of the positive electrode sheet; the other side is then coated using the same method. After coating, the effective material layer of the positive electrode 11 is cold-pressed to 3.4 g / cm³. 3 The compaction density indicates that the entire preparation process of the positive electrode sheet has been completed.

[0092] The negative electrode preparation process is as follows: Graphite (a negative electrode active material), Super P (conductive carbon black), and SBR (styrene-butadiene rubber) are mixed in a weight ratio of 96:1.5:2.5. Deionized water (H2O) is added as a solvent to prepare a slurry with a solid content of 0.7%, and the mixture is stirred evenly. The slurry is then uniformly coated onto the negative electrode current collector. The weight of the effective negative electrode material on electrode 11 is 80 g / m². 2 Drying at 110℃ completes the single-sided coating of the negative electrode sheet; the other side is then coated using the same method. After coating, the effective negative electrode material layer of electrode 11 is cold-pressed to 1.6 g / cm³. 3 The compaction density is achieved, thus completing the entire preparation process of the negative electrode.

[0093] The electrolyte preparation process is as follows: In a dry argon atmosphere, the organic solvents ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are first mixed in a mass ratio of EC:EMC:DEC = 30:50:20. Then, lithium salt lithium hexafluorophosphate (LiPF6) is added to the organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15M.

[0094] The preparation process of the battery cell 100 is as follows: a 7μm thick polyethylene (PE) is selected as the separator, the prepared positive and negative electrode sheets and separator are wound into an electrode assembly 10 by winding, and then the assembly is packaged in a packaging bag 20 to form the battery cell 100.

[0095] Cyclic test procedure: Temperature 25℃, charge cell 100 to 4.28V with 5C constant current, charge cell 100 to 0.5C with 4.28V constant voltage, and discharge cell 100 to 3.0V with 10C constant current.

[0096] Table 1

[0097]

[0098] As shown in Table 1, when the size of the second space 232 is smaller than the size of the first space 231 along the thickness direction of the cell 100, and the size of the second space 232 is equal to or greater than the size of the first space 231, the risk of lithium plating in the cell 100 is significantly reduced. Therefore, it can be concluded that when the size of the second space 232 is smaller than the size of the first space 231 along the thickness direction of the cell 100, the risk of lithium plating in the cell 100 can be significantly reduced, thus improving the safety of the cell 100.

[0099] The main body region 111 is housed in the first space 231, and the first thinned region 112 is housed in the second space 232. Since the dimension of the second space 232 along the thickness direction of the cell 100 is smaller than the dimension of the first space 231 along the thickness direction of the cell 100, the first thinned regions 112 of at least two electrodes 11 will move closer to each other under the action of the inner wall of the second space 232, thereby reducing the distance between the first thinned regions 112 of two adjacent electrodes 11, reducing the lithium-ion transport path, reducing the risk of lithium plating, and improving the safety of the cell 100.

[0100] In some embodiments, the packaging bag 20 includes a first packaging film 21 and a second packaging film 22, and the electrode assembly 10 is disposed between the first packaging film 21 and the second packaging film 22. The first packaging film 21 includes a first portion 211 and a second portion 212, and the second packaging film 22 includes a third portion 221 and a fourth portion 222. A first space 231 is formed between the first portion 211 and the third portion 221, and a second space 232 is formed between the second portion 212 and the fourth portion 222. The distance between the inner surface of the second portion 212 and the inner surface of the fourth portion 222 is less than the distance between the inner surface of the first portion 211 and the inner surface of the third portion 221.

[0101] The first encapsulation film 21 may include an adhesive layer, a metal layer, and a protective layer. The metal layer is located between the adhesive layer and the protective layer, and the protective layer is located outside the metal layer. In some embodiments, the adhesive layer is a polypropylene layer, which serves to seal and bond the package when the package bag 20 is sealed. The metal layer is an aluminum layer, which prevents external moisture and other contaminants from entering and the internal electrolyte from leaking out after the package bag 20 is sealed. The protective layer is a nylon layer, which has a high melting point and strong mechanical properties, and protects the electrode assembly 10 inside the package bag 20. The structure of the second encapsulation film 22 may be the same as that of the first encapsulation film 21.

[0102] The first encapsulation film 21 and the second encapsulation film 22 together form the encapsulation bag 20. Before forming the encapsulation bag 20, the first encapsulation film 21 and the second encapsulation film 22 can be two separate parts. The electrode assembly 10 is placed on the first encapsulation film 21, and then the first encapsulation film 21 and the second encapsulation film 22 are arranged opposite to each other along the thickness direction of the cell 100 so that the second encapsulation film 22 covers the first encapsulation film 21, and then the first encapsulation film 21 and the second encapsulation film 22 are encapsulated into one piece.

[0103] Before forming the encapsulation bag 20, the first encapsulation film 21 and the second encapsulation film 22 can also be connected as a single unit. The first encapsulation film 21 and the second encapsulation film 22 are connected by a folding portion 23. The second encapsulation film 22 can be folded around the folding portion 23 so that the second encapsulation film 22 and the first encapsulation film 21 are arranged opposite each other along the thickness direction of the cell 100. The folding portion 23 can be along the length direction of the cell 100 (e.g., the length direction of the cell 100 is as follows). Figure 1 The electrode assembly 10 is placed on the first encapsulation film 21, and then the second encapsulation film 22 is folded around the fold portion 23 so that the second encapsulation film 22 and the first encapsulation film 21 are arranged opposite each other along the thickness direction of the cell 100. Then the unconnected areas of the first encapsulation film 21 and the second encapsulation film 22 are connected and encapsulated into one piece.

[0104] In some embodiments, the battery cell 100 further includes a tab lead 30, which is connected to the tab 12 of the electrode assembly 10 and extends through the encapsulation bag 20 between the first encapsulation film 21 and the second encapsulation film 22. The tab 12 and the tab lead 30 are connected to form a connection portion 40. The portions of the first encapsulation film 21 and the second encapsulation film 22 extending beyond the connection portion 40 along the length direction of the battery cell constitute a partial encapsulation area of ​​the battery cell 100.

[0105] The first encapsulation film 21 includes a first portion 211 and a second portion 212. Correspondingly, the second encapsulation film 22 includes a third portion 221 and a fourth portion 222. A first space 231 is formed between the first portion 211 and the third portion 221, and the main body region 111 is located between the first portion 211 and the third portion 221. A second space 232 is formed between the second portion 212 and the fourth portion 222, and a first thinning region 112 is located between the second portion 212 and the fourth portion 222.

[0106] "The distance between the inner surface of the second part 212 and the inner surface of the fourth part 222" refers to the maximum distance between the surface of the second part 212 facing the fourth part 222 and the surface of the fourth part 222 facing the second part 212 along the thickness direction of the cell 100.

[0107] "The distance between the inner surface of the first part 211 and the inner surface of the third part 221" refers to the minimum distance between the surface of the first part 211 facing the third part 221 and the surface of the third part 221 facing the first part 211 along the thickness direction of the cell 100.

[0108] "The distance between the inner surface of the second part 212 and the inner surface of the fourth part 222 is less than the distance between the inner surface of the first part 211 and the inner surface of the third part 221" means that, along the thickness direction of the cell 100, the maximum distance between the surface of the second part 212 facing the fourth part 222 and the surface of the fourth part 222 facing the second part 212 is less than the minimum distance between the surface of the first part 211 facing the third part 221 and the surface of the third part 221 facing the first part 211.

[0109] Please refer to Figure 1 Along the thickness direction of the cell 100, the minimum distance between the surface of the first part 211 facing the third part 221 and the surface of the third part 221 facing the first part 211 can be L1 as shown in the figure, and the maximum distance between the surface of the second part 212 facing the fourth part 222 and the surface of the fourth part 222 facing the second part 212 can be L2 as shown in the figure, satisfying: L1 > L2.

[0110] The main body region 111 is located between the first part 211 and the third part 221, and the first thinning region 112 is located between the second part 212 and the fourth part 222. Since the distance between the inner surface of the second part 212 and the inner surface of the fourth part 222 is less than the distance between the inner surface of the first part 211 and the inner surface of the third part 221, the first thinning regions 112 of at least two electrodes 11 will move closer to each other under the action of the second part 212 and the fourth part 222, thereby reducing the distance between the first thinning regions 112 of two adjacent electrodes 11, reducing the lithium-ion transport path, reducing the risk of lithium plating, and improving the safety of the cell 100.

[0111] In some embodiments, the thickness of the second portion 212 is greater than the thickness of the first portion 211, and / or the thickness of the fourth portion 222 is greater than the thickness of the third portion 221.

[0112] "The thickness of the second part 212 is greater than the thickness of the first part 211" means that, along the thickness direction of the cell 100, the minimum thickness of the second part 212 is greater than the maximum thickness of the first part 211. When the thickness of the second part 212 is the same at all positions, the thickness at any position can be taken as the minimum thickness of the second part 212. Similarly, when the thickness of the first part 211 is the same at all positions, the thickness at any position can be taken as the maximum thickness of the first part 211.

[0113] Please refer to Figure 1 ,exist Figure 1In the embodiment shown, the thickness of the second part 212 is greater than the thickness of the first part 211, and the thickness of the fourth part 222 is equal to the thickness of the third part 221. Therefore, the surface of the second part 212 facing the fourth part 222 is closer to the second encapsulation film 22 than the surface of the first part 211 facing the third part 221, thereby making the size of the second space 232 smaller than the size of the first space 231 along the thickness direction of the cell 100.

[0114] Please refer to Figure 2 ,exist Figure 2 In the embodiment shown, the thickness of the second part 212 is equal to the thickness of the first part 211, and the thickness of the fourth part 222 is greater than the thickness of the third part 221. Therefore, the surface of the fourth part 222 facing the second part 212 is closer to the first encapsulation film 21 than the surface of the third part 221 facing the first part 211, thereby making the size of the second space 232 smaller than the size of the first space 231 along the thickness direction of the cell 100.

[0115] Please refer to Figure 3 ,exist Figure 3 In the embodiment shown, the thickness of the second part 212 is greater than the thickness of the first part 211, and the thickness of the fourth part 222 is greater than the thickness of the third part 221. Therefore, the distance between the second part 212 and the fourth part 222 is less than the distance between the first part 211 and the third part 221, so that the size of the second space 232 is smaller than the size of the first space 231 along the thickness direction of the cell 100.

[0116] The second part 212 can be regarded as a local thickening of the first encapsulation film 21. By making the thickness of the second part 212 greater than the thickness of the first part 211, the distance between the inner surface of the second part 212 and the inner surface of the fourth part 222 is less than the distance between the inner surface of the first part 211 and the inner surface of the third part 221. This allows the first thinning areas 112 of at least two electrodes 11 to move closer to each other under the action of the second part 212 and the fourth part 222, reducing the lithium ion transport path, lowering the risk of lithium plating, and improving the safety of the cell 100. The fourth part 222 can be regarded as a local thickening of the second encapsulation film 22. By making the thickness of the fourth part 222 greater than the thickness of the third part 221, the distance between the inner surface of the second part 212 and the inner surface of the fourth part 222 is less than the distance between the inner surface of the first part 211 and the inner surface of the third part 221. This allows the first thinning areas 112 of at least two electrodes 11 to move closer to each other under the action of the second part 212 and the fourth part 222, reducing the lithium ion transport path, lowering the risk of lithium plating, and improving the safety of the cell 100.

[0117] Please refer to Figure 1, Figure 2 and Figure 3 In some embodiments, the outer surface of the second portion 212 is coplanar with the outer surface of the first portion 211. And / or, the outer surface of the fourth portion 222 is coplanar with the outer surface of the third portion 221.

[0118] The outer surface of the second part 212 refers to the surface of the second part 212 that faces away from the second encapsulation film 22 along the thickness direction of the cell 100. The outer surface of the first part 211 refers to the surface of the first part 211 that faces away from the second encapsulation film 22 along the thickness direction of the cell 100. The outer surfaces of the second part 212 and the first part 211 are located in the same plane.

[0119] The outer surface of the fourth part 222 refers to the surface of the fourth part 222 that faces away from the first encapsulation film 21 along the thickness direction of the cell 100. The outer surface of the third part 221 refers to the surface of the third part 221 that faces away from the first encapsulation film 21 along the thickness direction of the cell 100. The outer surfaces of the fourth part 222 and the third part 221 are located in the same plane.

[0120] When the outer surface of the second portion 212 is coplanar with the outer surface of the first portion 211, the distance between the inner surface of the second portion 212 and the outer surface of the second portion 212 is greater than the distance between the inner surface of the first portion 211 and the outer surface of the first portion 211. This allows the second portion 212 to be closer to the second encapsulation film 22, which helps to reduce the distance between the first thinning areas 112 of two adjacent electrode sheets 11, reducing the risk of lithium plating and improving the safety of the cell 100. In addition, when the outer surface of the second portion 212 is coplanar with the outer surface of the first portion 211, the outer surface of the first encapsulation film 21 is smoother and less prone to wrinkling, which helps to improve the reliability of the encapsulation. When the outer surface of the fourth portion 222 is coplanar with the outer surface of the third portion 221, the distance between the inner surface of the fourth portion 222 and the outer surface of the fourth portion 222 is greater than the distance between the inner surface of the third portion 221 and the outer surface of the third portion 221. This allows the fourth portion 222 to be closer to the first encapsulation film 21, which helps to reduce the distance between the first thinning areas 112 of two adjacent electrode sheets 11, reducing the risk of lithium plating and improving the safety of the cell 100. Furthermore, when the outer surface of the fourth portion 222 is coplanar with the outer surface of the third portion 221, the outer surface of the second encapsulation film 22 is smoother and less prone to wrinkling, which helps to improve the reliability of the encapsulation.

[0121] Please refer to Figure 4In other embodiments, the outer surface of the second portion 212 is not coplanar with the outer surface of the first portion 211, and the outer surface of the fourth portion 222 is not coplanar with the outer surface of the third portion 221. Optionally, along the thickness direction of the cell 100, the outer surface of the second portion 212 is closer to the fourth portion 222 than the outer surface of the first portion 211. The outer surface of the fourth portion 222 is closer to the second portion 212 than the outer surface of the third portion 221.

[0122] Please refer to Figures 1-4 In some embodiments, the second portion 212 has a first end 2121 near the first portion 211 and a second end 2122 away from the first portion 211, and the thickness of the second portion 212 gradually increases from the first end 2121 to the second end 2122. And / or, the fourth portion 222 has a third end near the third portion 221 and a fourth end 2222 away from the third portion 221, and the thickness of the fourth portion 222 gradually increases from the third end to the fourth end 2222.

[0123] Along the length of the battery cell 100, the second portion 212 has a first end 2121 and a second end 2122 disposed opposite to each other. Please refer to... Figures 1-4 The length direction of the battery cell 100 is the Y direction as shown in the figure. The first end 2121 is connected to the first portion 211, and the second end 2122 is located away from the first portion 211. Along the length direction of the battery cell 100, the thickness of the second portion 212 gradually increases from the first end 2121 towards the second end 2122. The fourth portion 222 has a third end and a fourth end 2222 disposed opposite to each other. The third end is connected to the third portion 221, and the fourth end 2222 is located away from the third portion 221. Along the length direction of the battery cell 100, the thickness of the fourth portion 222 gradually increases from the third end towards the fourth end 2222.

[0124] Please refer to Figure 1 ,exist Figure 1 In the illustrated embodiment, the thickness of the second portion 212 gradually increases from the first end 2121 to the second end 2122. The thickness of the fourth portion 222 is equal to the thickness of the third portion 221.

[0125] Please refer to Figure 2 ,exist Figure 2 In the illustrated embodiment, the thickness of the fourth portion 222 gradually increases from the third end to the fourth end 2222. The thickness of the second portion 212 is equal to the thickness of the first portion 211.

[0126] Please refer to Figure 3 ,exist Figure 3In the illustrated embodiment, the thickness of the second portion 212 gradually increases from the first end 2121 to the second end 2122. Similarly, the thickness of the fourth portion 222 gradually increases from the third end to the fourth end 2222.

[0127] Since the thickness of the first thinning region 112 gradually decreases from the end closer to the main body region 111 to the end farther away from the main body region 111, and the thickness of the second part 212 gradually increases from the first end 2121 to the second end 2122, the second part 212 has a larger thickness at the thinner end of the first thinning region 112 and a smaller thickness at the thicker end of the first thinning region 112. This allows the second part 212 to complement the first thinning region 112, which helps to make the electrode 11 bear force evenly, prevents stress concentration, and helps to improve the life of the cell 100. Similarly, by gradually increasing the thickness of the fourth part 222 from the third end to the fourth end 2222, the fourth part 222 has a larger thickness at the end where the first thinning region 112 is thinner, and a smaller thickness at the end where the first thinning region 112 is thicker. This allows the fourth part 222 to complement the first thinning region 112, which helps to make the electrode 11 bear force evenly, reduces stress concentration, and helps to improve the lifespan of the cell 100.

[0128] In some embodiments, the maximum thickness of the second part 212 is T1, and the thickness of the first part 211 is T2, satisfying: 1.02≤T1 / T2≤3.

[0129] The thickness of the first part 211 is the distance between the outer surface and the inner surface of the first part 211 along the thickness direction of the cell 100. The thickness of the first part 211 can be obtained by measuring any length.

[0130] For the maximum thickness of the second part 212, the thickness can be measured along the length of the cell 100. The minimum sampling interval is 2mm. Generally, continuous laser testing or height gauge interval testing is used. The average of the three points with the maximum thickness is T1. The difference between three adjacent points that is ≥2um is regarded as the starting position of the second part 212.

[0131] The ratio of the maximum thickness of the second part 212 to the thickness of the first part 211 can be: T1 / T2 = 1.02, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.8, 3, etc.

[0132] The maximum thickness of the second part 212 is 1.02 to 3 times the thickness of the first part 211. This reduces the distance between the first thinned areas 112 of two adjacent electrodes 11, shortening the lithium-ion transport path and reducing the risk of lithium plating. It also prevents the first thinned area 112 from tilting excessively relative to the main body region 111, thus avoiding stress concentration on the electrode 11. When T1 / T2 < 1.02, the distance between the first thinned areas 112 of two adjacent electrodes 11 cannot be effectively reduced, and the effect of reducing lithium plating is not significant. When T1 / T2 > 3, the first thinned area 112 may tilt excessively relative to the main body region 111, causing stress concentration at the connection point between the first thinned area 112 and the main body region 111, which can easily damage the electrode 11.

[0133] In some embodiments, the sum of the minimum thicknesses of the first thinning regions 112 of at least two electrodes 11 is T3, and the sum of the thicknesses of the main regions 111 of at least two electrodes 11 is T4, satisfying: 1.02≤(T1+T3) / (T2+T4)≤1.1.

[0134] The sum of the minimum thicknesses of the first thinning regions 112 of at least two electrodes 11 can be obtained by first measuring the minimum thickness of the first thinning region 112 of each electrode 11 individually and then adding the minimum thicknesses of the first thinning regions 112 of all electrodes 11 together. Alternatively, the average thickness of the first thinning regions 112 of several electrodes 11 can be measured first and then multiplied by the number of electrodes 11.

[0135] The sum of the thicknesses of the main body regions 111 of at least two electrodes 11 can be obtained by first measuring the thickness of the main body region 111 of each electrode 11 individually and then adding the thicknesses of the main body regions 111 of all electrodes 11 together, or by first measuring the average thickness of the main body regions 111 of several electrodes 11 and then multiplying it by the number of electrodes 11.

[0136] The possible values ​​for (T1+T3) / (T2+T4) are: (T1+T3) / (T2+T4) = 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.1, etc.

[0137] By setting (T1+T3) / (T2+T4) between 1.02 and 1.1, the first thinning regions 112 of at least two electrodes 11 are brought closer to each other under the action of the second part 212 and the fourth part 222, so that the distance between the main body regions 111 of two adjacent electrodes 11 is the same as or similar to the distance between the first thinning regions 112 of two adjacent electrodes 11, thereby reducing the lithium ion transport path, reducing the risk of lithium plating, and improving the safety of the cell 100.

[0138] In some embodiments, along the length direction of the cell 100, the length of the second part 212 is W1, which satisfies: 0 < W1 ≤ 30 mm.

[0139] The length of the second part 212 along the length direction of the cell 100 can also be obtained by measuring the distance between the first end 2121 and the second end 2122 along the length direction of the cell 100.

[0140] Along the length direction of the battery cell 100, the length of the second part 212 can be: W1 = 1mm, 3mm, 5mm, 7mm, 9mm, 10mm, 12mm, 15mm, 18mm, 20mm, 22mm, 25mm, 28mm, 30mm, etc.

[0141] The length of the second part 212 along the length direction of the cell 100 is between 0 and 30 mm (excluding 0), so as to be adapted to the length of the first thinning zone 112.

[0142] In some embodiments, the length of the fourth portion 222 along the length direction of the cell 100 is also between 0 and 30 mm (excluding 0) to adapt to the length of the first thinning region 112.

[0143] Please refer to Figure 5 In some embodiments, the position where the thickness of the second portion 212 is greatest corresponds to the position where the thickness of the first thinned region 112 is least, and vice versa. And / or, the position where the thickness of the fourth portion 222 is greatest corresponds to the position where the thickness of the first thinned region 112 is least, and vice versa. In this way, the second portion 212 and / or the fourth portion 222 can complement the first thinned region 112, which helps to ensure uniform stress on the electrode 11, reduces stress concentration, and improves the lifespan of the cell 100.

[0144] Additionally, it should be noted that the dimensional constraints of the fourth part 222 can be the same as those of the second part 212, but the values ​​can be different. For example, the ratio of the maximum thickness of the fourth part 222 to the thickness of the second part 212 is also limited to between 1.02 and 3, but when T1 / T2 = 1.5, the ratio of the maximum thickness of the fourth part 222 to the thickness of the second part 212 can be 1.5, or it can be 1.2, 1.8, 2, 2.5, etc.

[0145] Please refer to Figure 6 , Figure 7 and Figure 8In some embodiments, the second portion 212 extends obliquely from the first portion 211, and the angle between the second portion 212 and the first portion 211 is an obtuse angle. And / or, the fourth portion 222 extends obliquely from the third portion 221, and the angle between the fourth portion 222 and the third portion 221 is an obtuse angle.

[0146] The area of ​​the first encapsulation film 21 corresponding to the main body area 111 forms a first portion 211. The area of ​​the first encapsulation film 21 corresponding to the first thinning area 112 is inclined toward the second encapsulation film 22 to form a second portion 212. One end of the second portion 212 is connected to the first portion 211. The phrase "the angle between the second portion 212 and the first portion 211 is an obtuse angle" can be understood as the angle between the inner surface of the second portion 212 and the inner surface of the first portion 211 being an obtuse angle. It can also be understood as the angle between the outer surface of the second portion 212 and the outer surface of the first portion 211 being an obtuse angle. Alternatively, it can be understood as the first portion 211 extending along a first trajectory, the second portion 212 extending along a second trajectory, and the angle between the first and second trajectories being an obtuse angle.

[0147] The area of ​​the second encapsulation film 22 corresponding to the main body area 111 forms the third part 221. The area of ​​the second encapsulation film 22 corresponding to the first thinning area 112 is inclined towards the first encapsulation film 21 to form the fourth part 222. One end of the fourth part 222 is connected to the third part 221. The phrase "the angle between the fourth part 222 and the third part 221 is an obtuse angle" can be understood as the angle between the inner surface of the fourth part 222 and the inner surface of the third part 221 being an obtuse angle. It can also be understood as the angle between the outer surface of the fourth part 222 and the outer surface of the third part 221 being an obtuse angle. Alternatively, it can be understood as the third part 221 extending along a third trajectory, and the fourth part 222 extending along a fourth trajectory, with the angle between the third and fourth trajectories being an obtuse angle.

[0148] Please refer to Figure 6 ,exist Figure 6 In the illustrated embodiment, the region corresponding to the first encapsulation film 21 and the first thinning region 112 is inclined toward the second encapsulation film 22 to form the second portion 212. The second encapsulation film 22 is not partially inclined, and the inner surface of the third portion 221 and the inner surface of the fourth portion 222 are located in the same plane, as are the outer surface of the third portion 221 and the outer surface of the fourth portion 222. Thus, the maximum distance between the inner surfaces of the second portion 212 and the fourth portion 222 is less than the minimum distance between the inner surfaces of the first portion 211 and the third portion 221.

[0149] Please refer to Figure 7 ,exist Figure 7In the illustrated embodiment, the region of the second encapsulation film 22 corresponding to the first thinning region 112 is inclined toward the first encapsulation film 21 to form the fourth portion 222. The first encapsulation film 21 is not partially inclined, and the inner surface of the first portion 211 and the inner surface of the second portion 212 are located in the same plane, as are the outer surfaces of the first portion 211 and the second portion 212. Thus, the maximum distance between the inner surface of the second portion 212 and the inner surface of the fourth portion 222 is less than the minimum distance between the inner surface of the first portion 211 and the inner surface of the third portion 221.

[0150] Please refer to Figure 8 ,exist Figure 8 In the illustrated embodiment, the region of the first encapsulation film 21 corresponding to the first thinned area 112 is inclined toward the second encapsulation film 22 to form a second portion 212. The region of the second encapsulation film 22 corresponding to the first thinned area 112 is inclined toward the first encapsulation film 21 to form a fourth portion 222. Thus, the maximum distance between the inner surface of the second portion 212 and the inner surface of the fourth portion 222 is less than the minimum distance between the inner surface of the first portion 211 and the inner surface of the third portion 221.

[0151] The second portion 212 slopes towards the second encapsulation film 22 starting from the first portion 211. The end of the second portion 212 closer to the first portion 211 is further away from the second encapsulation film 22 than the end of the second portion 212 further away from the first portion 211. This results in the maximum distance between the inner surface of the second portion 212 and the inner surface of the fourth portion 222 being less than the minimum distance between the inner surface of the first portion 211 and the inner surface of the third portion 221. The fourth portion 222 slopes towards the first encapsulation film 21 starting from the third portion 221. The end of the fourth portion 222 closer to the third portion 221 is further away from the first encapsulation film 21 than the end of the fourth portion 222 further away from the third portion 221. This results in the maximum distance between the inner surface of the second portion 212 and the inner surface of the fourth portion 222 being less than the minimum distance between the inner surface of the first portion 211 and the inner surface of the third portion 221.

[0152] Please refer to Figures 9-17In some embodiments, a first groove 213 and a second groove 214 are formed on the side of the first encapsulation film 21 facing the second encapsulation film 22. The position of the first groove 213 corresponds to the position of the main body region 111, and the position of the second groove 214 corresponds to the position of the first thinning region 112. Along the thickness direction of the cell 100, the depth of the second groove 214 is less than the depth of the first groove 213. And / or, a third groove 223 and a fourth groove 224 are formed on the side of the second encapsulation film 22 facing the first encapsulation film 21. The position of the third groove 223 corresponds to the position of the main body region 111, and the position of the fourth groove 224 corresponds to the position of the first thinning region 112. Along the thickness direction of the cell 100, the depth of the fourth groove 224 is less than the depth of the third groove 223.

[0153] Along the thickness direction of the cell 100, a first groove 213 is recessed from the surface of the first encapsulation film 21 facing the second encapsulation film 22 toward the surface of the first encapsulation film 21 away from the second encapsulation film 22, forming a groove structure. The projection of the main body region 111 is located within the bottom wall area of ​​the first groove 213. A second groove 214 is recessed from the surface of the first encapsulation film 21 facing the second encapsulation film 22 toward the surface of the first encapsulation film 21 away from the second encapsulation film 22, forming a groove structure. The projection of the first thinning region 112 is located within the bottom wall area of ​​the second groove 214.

[0154] The statement "the depth of the second groove 214 is less than the depth of the first groove 213 along the thickness direction of the cell 100" can also be understood as: the distance from the surface of the first encapsulation film 21 facing the second encapsulation film 22 to the bottom surface of the first groove 213 along the thickness direction of the cell 100 is greater than the distance from the surface of the first encapsulation film 21 facing the second encapsulation film 22 to the bottom surface of the second groove 214.

[0155] Along the thickness direction of the cell 100, the third groove 223 is recessed from the surface of the second encapsulation film 22 facing the first encapsulation film 21 towards the surface of the second encapsulation film 22 away from the first encapsulation film 21, forming a groove structure. The projection of the main body region 111 is located within the bottom wall area of ​​the third groove 223. The fourth groove 224 is recessed from the surface of the second encapsulation film 22 facing the first encapsulation film 21 towards the surface of the second encapsulation film 22 away from the first encapsulation film 21, forming a groove structure. The projection of the first thinning region 112 is located within the bottom wall area of ​​the fourth groove 224.

[0156] The statement "the depth of the fourth groove 224 is less than the depth of the third groove 223 along the thickness direction of the cell 100" can also be understood as: the distance from the surface of the second encapsulation film 22 facing the first encapsulation film 21 to the bottom surface of the third groove 223 along the thickness direction of the cell 100 is greater than the distance from the surface of the second encapsulation film 22 facing the first encapsulation film 21 to the bottom surface of the fourth groove 224.

[0157] Please refer to Figure 9 , Figure 10 and Figure 11 ,exist Figures 9-11 In the embodiment shown, the first encapsulation film 21 is provided with a first groove 213 and a second groove 214, and the second encapsulation film 22 is not provided with a groove, such that the distance between the inner surface of the second part 212 and the inner surface of the fourth part 222 is less than the distance between the inner surface of the first part 211 and the inner surface of the third part 221.

[0158] Please refer to Figure 12 , Figure 13 and Figure 14 ,exist Figures 12-14 In the embodiment shown, the second encapsulation film 22 is provided with a third groove 223 and a fourth groove 224, and the first encapsulation film 21 is not provided with grooves, so that the distance between the inner surface of the second part 212 and the inner surface of the fourth part 222 is less than the distance between the inner surface of the first part 211 and the inner surface of the third part 221.

[0159] Please refer to Figure 15 , Figure 16 and Figure 17 ,exist Figures 15-17 In the embodiment shown, the first encapsulation film 21 is provided with a first groove 213 and a second groove 214, and the second encapsulation film 22 is provided with a third groove 223 and a fourth groove 224, such that the distance between the inner surface of the second part 212 and the inner surface of the fourth part 222 is less than the distance between the inner surface of the first part 211 and the inner surface of the third part 221.

[0160] The bottom wall of the first groove 213 forms the first portion 211 of the first encapsulation film 21, and the bottom wall of the second groove 214 forms the second portion 212 of the first encapsulation film 21. Along the thickness direction of the cell 100, the depth of the second groove 214 is less than the depth of the first groove 213. Therefore, the bottom wall of the first groove 213 is further away from the second encapsulation film 22 than the bottom wall of the second groove 214. That is, along the thickness direction of the cell 100, the first portion 211 is further away from the second encapsulation film 22 than the second portion 212. This results in the distance between the inner surface of the second portion 212 and the inner surface of the fourth portion 222 being less than the distance between the inner surface of the first portion 211 and the inner surface of the third portion 221. The bottom wall of the third groove 223 forms the third portion 221 of the second encapsulation film 22, and the bottom wall of the fourth groove 224 forms the fourth portion 222 of the second encapsulation film 22. Along the thickness direction of the cell 100, the depth of the fourth groove 224 is less than the depth of the third groove 223. Therefore, the bottom wall of the third groove 223 is further away from the first encapsulation film 21 than the bottom wall of the fourth groove 224. In other words, along the thickness direction of the cell 100, the third part 221 is further away from the first encapsulation film 21 than the fourth part 222. This makes the distance between the inner surface of the second part 212 and the inner surface of the fourth part 222 less than the distance between the inner surface of the first part 211 and the inner surface of the third part 221.

[0161] Please refer to Figure 18 , Figure 19 and Figure 20 In some embodiments, the packaging bag 20 includes a first packaging film 21 and a second packaging film 22, with the electrode assembly 10 disposed between the first packaging film 21 and the second packaging film 22. A first insulating layer 24 is disposed on the inner surface of the first packaging film 21, and when viewed along the thickness direction of the cell 100, the first insulating layer 24 at least partially overlaps with the first thinning region 112. And / or, a second insulating layer 25 is disposed on the inner surface of the second packaging film 22, and when viewed along the thickness direction of the cell 100, the second insulating layer 25 at least partially overlaps with the first thinning region 112.

[0162] The first insulating layer 24 is formed of an insulating material and has an insulating effect. The first insulating layer 24 is disposed on the surface of the first encapsulation film 21 facing the second encapsulation film 22. Along the thickness direction of the cell 100, the projection of the first insulating layer 24 at least partially overlaps with the projection of the first thinning region 112. The first insulating layer 24 can be formed by adding an insulating material such as glue or adhesive tape to the inner surface of the first encapsulation film 21.

[0163] Similarly, the second insulating layer 25 is formed of an insulating material and has an insulating effect. The second insulating layer 25 is disposed on the surface of the second encapsulation film 22 facing the first encapsulation film 21. Along the thickness direction of the cell 100, the projection of the second insulating layer 25 at least partially overlaps with the projection of the first thinning region 112. The second insulating layer 25 can be formed by adding an insulating material such as adhesive or adhesive tape to the inner surface of the second encapsulation film 22.

[0164] Please refer to Figure 18 ,exist Figure 18 In the embodiment shown, a first insulating layer 24 is provided on the inner surface of the first encapsulation film 21, and a second insulating layer 25 is not provided on the inner surface of the second encapsulation film 22, so that the size of the second space 232 is smaller than the size of the first space 231 along the thickness direction of the cell 100.

[0165] Please refer to Figure 19 ,exist Figure 19 In the embodiment shown, a second insulating layer 25 is provided on the inner surface of the second encapsulation film 22, and a first insulating layer 24 is not provided on the inner surface of the first encapsulation film 21, so that the size of the second space 232 is smaller than the size of the first space 231 along the thickness direction of the cell 100.

[0166] Please refer to Figure 20 ,exist Figure 20 In the embodiment shown, a first insulating layer 24 is provided on the inner surface of the first encapsulation film 21, and a second insulating layer 25 is provided on the inner surface of the second encapsulation film 22, such that the size of the second space 232 is smaller than the size of the first space 231 along the thickness direction of the cell 100.

[0167] By providing a first insulating layer 24 on the inner surface of the first encapsulation film 21, with the position of the first insulating layer 24 corresponding to the position of the first thinning region 112, along the thickness direction of the cell 100, the size of the second space 232 is the distance between the first insulating layer 24 and the second encapsulation film 22 or the second insulating layer 25, and the size of the first space 231 is the distance between the first encapsulation film 21 and the second encapsulation film 22, such that along the thickness direction of the cell 100, the size of the second space 232 is smaller than the size of the first space 231. Similarly, by providing a second insulating layer 25 on the inner surface of the second encapsulation film 22, with the position of the second insulating layer 25 corresponding to the position of the first thinning region 112, along the thickness direction of the cell 100, the size of the second space 232 is the distance between the second insulating layer 25 and the first encapsulation film 21 or the first insulating layer 24, and the size of the first space 231 is the distance between the first encapsulation film 21 and the second encapsulation film 22, such that along the thickness direction of the cell 100, the size of the second space 232 is smaller than the size of the first space 231.

[0168] Please refer to Figure 18 , Figure 19 and Figure 20In some embodiments, the thickness of the first insulating layer 24 gradually increases in the direction away from the main body region 111. And / or, the thickness of the second insulating layer 25 gradually increases in the direction away from the main body region 111.

[0169] The phrase “the thickness of the first insulating layer 24 gradually increases in the direction away from the main body region 111” can be understood as: along the length of the cell 100, the thickness of the first insulating layer 24 gradually increases from the main body region 111 toward the first thinning region 112.

[0170] The phrase “the thickness of the second insulating layer 25 gradually increases in the direction away from the main body region 111” can be understood as: along the length of the cell 100, the thickness of the second insulating layer 25 gradually increases from the main body region 111 toward the first thinning region 112.

[0171] Since the thickness of the first thinned region 112 gradually decreases from the end near the main body region 111 to the end away from the main body region 111, and the thickness of the first insulating layer 24 gradually increases in the direction away from the main body region 111, the first insulating layer 24 has a larger thickness at the thinner end of the first thinned region 112 and a smaller thickness at the thicker end of the first thinned region 112. This allows the first insulating layer 24 to complement the first thinned region 112, which is beneficial for the electrode 11 to be subjected to uniform force, less prone to stress concentration, and beneficial for improving the life of the cell 100. Similarly, by gradually increasing the thickness of the second insulating layer 25 away from the main body region 111, the second insulating layer 25 has a larger thickness at the thinner end of the first thinning region 112 and a smaller thickness at the thicker end of the first thinning region 112. This allows the second insulating layer 25 to complement the first thinning region 112, which helps to ensure that the electrode 11 is subjected to uniform force, is less prone to stress concentration, and helps to improve the lifespan of the cell 100.

[0172] Please refer to Figure 20 In some embodiments, the sum of the maximum thickness of the first insulating layer 24 and the thickness of the first encapsulation film 21 is T5, and the thickness of the first encapsulation film 21 is T6, satisfying: 1.02≤T5 / T6≤3.

[0173] The thickness of the first encapsulation film 21 is the distance between the outer surface and the inner surface of the first encapsulation film 21 along the thickness direction of the battery cell 100. The thickness of the first encapsulation film 21 can be obtained by any length measurement method.

[0174] For the sum of the maximum thickness of the first insulating layer 24 and the thickness of the first encapsulation film 21, the thickness can be measured along the length of the cell 100. The minimum sampling interval is 2mm. Generally, continuous laser testing or height gauge interval testing is used. The average of the three points with the maximum thickness is T5. The difference between three adjacent points that is ≥2um is regarded as the starting position of the first insulating layer 24.

[0175] The ratio of the sum of the maximum thickness of the first insulating layer 24 and the thickness of the first encapsulation film 21 to the thickness of the first encapsulation film 21 can be: T5 / T6 = 1.02, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.8, 3, etc.

[0176] The maximum thickness of the first insulating layer 24 is 1.02 to 3 times the thickness of the first encapsulation film 21. This reduces the distance between the first thinned areas 112 of two adjacent electrodes 11, decreasing the lithium-ion transport path and lowering the risk of lithium plating. It also prevents excessive tilting of the first thinned area 112 relative to the main body region 111, thus avoiding stress concentration on the electrode 11. When T5 / T6 < 1.02, the distance between the first thinned areas 112 of two adjacent electrodes 11 cannot be effectively reduced, and the effect of reducing lithium plating is not significant. When T5 / T6 > 3, the first thinned area 112 may tilt excessively relative to the main body region 111, causing stress concentration at the connection point between the first thinned area 112 and the main body region 111, which can easily damage the electrode 11.

[0177] In some embodiments, the sum of the minimum thicknesses of the first thinning regions 112 of at least two electrodes 11 is T3, and the sum of the thicknesses of the main regions 111 of at least two electrodes 11 is T4, satisfying: 1.02≤(T5+T3) / (T6+T4)≤1.1.

[0178] The possible values ​​for (T5+T3) / (T6+T4) are: (T5+T3) / (T6+T4) = 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.1, etc.

[0179] By setting (T5+T3) / (T6+T4) between 1.02 and 1.1, the first thinned regions 112 of at least two electrodes 11 are brought closer to each other under the action of the first insulating layer 24, so that the distance between the main body regions 111 of two adjacent electrodes 11 is the same as or similar to the distance between the first thinned regions 112 of two adjacent electrodes 11, thereby reducing the lithium ion transport path, reducing the risk of lithium plating, and improving the safety of the cell 100.

[0180] In some embodiments, the length of the first insulating layer 24 along the length direction of the cell 100 is W2, which satisfies: 0 < W2 ≤ 30 mm.

[0181] Along the length direction of the battery cell 100, the length of the first insulating layer 24 can be: W2 = 1mm, 3mm, 5mm, 7mm, 9mm, 10mm, 12mm, 15mm, 18mm, 20mm, 22mm, 25mm, 28mm, 30mm, etc.

[0182] The length of the first insulating layer 24 along the length direction of the cell 100 is between 0 and 30 mm (excluding 0), so as to adapt to the length of the first thinning region 112.

[0183] In some embodiments, the position where the thickness of the first insulating layer 24 is greatest corresponds to the position where the thickness of the first thinned region 112 is least, and vice versa. And / or, the position where the thickness of the second insulating layer 25 is greatest corresponds to the position where the thickness of the first thinned region 112 is least, and vice versa. In this way, the first insulating layer 24 and / or the second insulating layer 25 can complement the first thinned region 112, which helps to ensure uniform stress on the electrode 11, reduces stress concentration, and improves the lifespan of the cell 100.

[0184] Additionally, it should be noted that the size limitation of the second insulating layer 25 can be the same as that of the first insulating layer 24, but the values ​​can be different. For example, the ratio of the sum of the maximum thickness of the second insulating layer 25 and the thickness of the second encapsulation film 22 to the thickness of the second encapsulation film 22 is also limited to between 1.02 and 3. However, when T5 / T6 = 1.5, the ratio of the sum of the maximum thickness of the second insulating layer 25 and the thickness of the second encapsulation film 22 to the thickness of the second encapsulation film 22 can be 1.5, or it can be 1.2, 1.8, 2, 2.5, etc.

[0185] In some embodiments, the sum of the minimum thicknesses of the first thinning regions 112 of at least two electrodes 11 is T3, and the sum of the thicknesses of the main regions 111 of at least two electrodes 11 is T4, satisfying: 0.92≤T3 / T4<1.

[0186] The ratio of the minimum thickness of the first thinned region 112 of at least two electrodes 11 to the thickness of the main region 111 of at least two electrodes 11 can be: T3 / T4 = 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, etc.

[0187] Limiting the ratio of the sum of the minimum thicknesses of the first thinned regions 112 of at least two electrodes 11 to the sum of the thicknesses of the main regions 111 of at least two electrodes 11 to between 0.92 and 1 (excluding 1) helps to minimize the distance between the first thinned regions 112 of adjacent electrodes 11, resulting in a shorter lithium-ion transport path, reducing the risk of lithium plating, and improving the safety of the cell 100. When T3 / T4 < 0.92, the difference between the minimum thickness of the first thinned region 112 and the thickness of the main region 111 is too large, and the distance between the first thinned regions 112 of adjacent electrodes 11 is too large, making lithium plating relatively easier.

[0188] Please refer to Figures 21-26 In some embodiments, the electrode 11 further includes a second thinning region 113, the thickness of the main body region 111 is greater than the thickness of the second thinning region 113, and the first thinning region 112 and the second thinning region 113 are located at opposite ends of the main body region 111. The receiving cavity also includes a third space 233 for receiving the second thinning region 113, and the size of the third space 233 is smaller than the size of the first space 231 along the thickness direction of the cell 100.

[0189] The second thinning region 113 is a thinner region on the electrode 11 formed when the active material slurry is coated onto the current collector at a certain weight, due to the natural fluidity of the slurry. In other words, the thickness of the main body region 111 is greater than the thickness of the second thinning region 113. Along the length of the cell 100, the first thinning region 112 and the second thinning region 113 are located at opposite ends of the main body region 111.

[0190] The third space 233 is part of the receiving cavity. The third space 233 is used to receive the second thinning area 113. The third space 233 is connected to the first space 231.

[0191] "The size of the third space 233 is smaller than the size of the first space 231 along the thickness direction of the cell 100" means that the maximum size of the third space 233 is smaller than the minimum size of the first space 231 along the thickness direction of the cell 100. Of course, if the maximum size of the third space 233 is equal at all positions along the thickness direction of the cell 100, then any position can be chosen as its maximum size. Similarly, if the minimum size of the first space 231 is equal at all positions along the thickness direction of the cell 100, then any position can be chosen as its minimum size.

[0192] The main body region 111 is housed in the first space 231, and the second thinned region 113 is housed in the third space 233. Since the dimension of the third space 233 along the thickness direction of the cell 100 is smaller than the dimension of the first space 231 along the thickness direction of the cell 100, the second thinned regions 113 of at least two electrodes 11 will move closer to each other under the action of the inner wall of the third space 233, thereby reducing the distance between the second thinned regions 113 of two adjacent electrodes 11, reducing the lithium-ion transport path, lowering the risk of lithium plating, and improving the safety of the cell 100.

[0193] Please refer to Figures 21-25 In some embodiments, the first encapsulation film 21 further includes a fifth portion 215, and the second encapsulation film 22 further includes a sixth portion 225, with a third space 233 formed between the fifth portion 215 and the sixth portion 225. The distance between the inner surface of the fifth portion 215 and the inner surface of the sixth portion 225 is less than the distance between the inner surface of the first portion 211 and the inner surface of the third portion 221.

[0194] The fifth part 215 can be formed in the same way as the second part 212. For example, the fifth part 215 can also be formed by locally thickening, locally tilting, or locally slotting the first encapsulation film 21. The sixth part 225 can be formed in the same way as the fourth part 222. For example, the sixth part 225 can also be formed by locally thickening, locally tilting, or locally slotting the second encapsulation film 22.

[0195] Please refer to Figure 21 ,exist Figure 21 In the illustrated embodiment, the fifth portion 215 is formed by locally thickening the first encapsulation film 21, and the thickness of the fifth portion 215 is greater than the thickness of the first portion 211. Simultaneously, the sixth portion 225 is formed by locally thickening the second encapsulation film 22, and the thickness of the sixth portion 225 is greater than the thickness of the third portion 221, so that the size of the third space 233 is smaller than the size of the first space 231 along the thickness direction of the cell 100. Of course, if either the first encapsulation film 21 or the second encapsulation film 22 is locally thickened to form the fifth portion 215 or the sixth portion 225, the size of the third space 233 will be smaller than the size of the first space 231 along the thickness direction of the cell 100; this will not be elaborated further here.

[0196] Please refer to Figure 22 ,exist Figure 22In the illustrated embodiment, the fifth portion 215 is formed by partially tilting the first encapsulation film 21, and the sixth portion 225 is formed by partially tilting the second encapsulation film 22, so that the size of the third space 233 is smaller than the size of the first space 231 along the thickness direction of the cell 100. Of course, either the first encapsulation film 21 or the second encapsulation film 22 can be partially tilted to form the fifth portion 215 or the sixth portion 225, thus ensuring that the size of the third space 233 is smaller than the size of the first space 231 along the thickness direction of the cell 100; this will not be elaborated further here.

[0197] Please refer to Figure 23 , Figure 24 and Figure 25 ,exist Figure 23 , Figure 24 and Figure 25 In the illustrated embodiment, the fifth portion 215 is formed by partially creating a fifth groove 216 in the first encapsulation film 21. The depth of the fifth groove 216 is less than the depth of the first groove 213, and the depth of the fifth groove 216 can be greater than, less than, or equal to the depth of the second groove 214. Simultaneously, the sixth portion 225 is formed by partially creating a sixth groove 226 in the second encapsulation film 22. The depth of the sixth groove 226 is less than the depth of the third groove 223, and the depth of the sixth groove 226 can be greater than, less than, or equal to the depth of the fourth groove 224. This ensures that the size of the third space 233 is smaller than the size of the first space 231 along the thickness direction of the cell 100. Of course, as long as either the first encapsulation film 21 or the second encapsulation film 22 partially grooves to form the fifth portion 215 or the sixth portion 225, the size of the third space 233 will be smaller than the size of the first space 231 along the thickness direction of the cell 100; this will not be elaborated further here.

[0198] In some embodiments, a third insulating layer 26 is provided on the inner surface of the first encapsulation film 21, and when viewed along the thickness direction of the cell 100, the third insulating layer 26 at least partially overlaps with the second thinning region 113. And / or, a fourth insulating layer 27 is provided on the inner surface of the second encapsulation film 22, and when viewed along the thickness direction of the cell 100, the fourth insulating layer 27 at least partially overlaps with the second thinning region 113.

[0199] Please refer to Figure 26 ,exist Figure 26In the illustrated embodiment, a third insulating layer 26 is provided on the inner surface of the first encapsulation film 21. When viewed along the thickness direction of the cell 100, the third insulating layer 26 at least partially overlaps with the second thinning region 113. Furthermore, a fourth insulating layer 27 is provided on the inner surface of the second encapsulation film 22. When viewed along the thickness direction of the cell 100, the fourth insulating layer 27 at least partially overlaps with the second thinning region 113. Of course, by providing the third insulating layer 26 only on the inner surface of the first encapsulation film 21 or the fourth insulating layer 27 only on the inner surface of the second encapsulation film 22, the size of the third space 233 along the thickness direction of the cell 100 can be smaller than the size of the first space 231; this will not be elaborated further here.

[0200] The above embodiments can be combined to obtain new embodiments without contradicting each other. For example, please refer to... Figure 27 In some embodiments, the first encapsulation film 21 includes a first portion 211 and a second portion 212, and the second encapsulation film 22 includes a third portion 221 and a fourth portion 222. A first space 231 is formed between the first portion 211 and the third portion 221, and a second space 232 is formed between the second portion 212 and the fourth portion 222. The distance between the inner surface of the second portion 212 and the inner surface of the fourth portion 222 is less than the distance between the inner surface of the first portion 211 and the inner surface of the third portion 221, such that the size of the second space 232 is smaller than the size of the first space 231 along the thickness direction of the cell 100. A third insulating layer 26 is provided on the inner surface of the first portion 211, and when viewed along the thickness direction of the cell 100, the first insulating layer 26 at least partially overlaps with the second thinning region 113. The inner surface of the third part 221 is provided with a fourth insulating layer 27. When viewed along the thickness direction of the cell 100, the fourth insulating layer 27 at least partially overlaps with the second thinning area 113, such that the size of the third space 233 is smaller than the size of the first space 231 along the thickness direction of the cell 100.

[0201] This application also provides a secondary battery, which includes the cell 100 provided in any of the above embodiments.

[0202] A secondary battery may include multiple cells 100, which may be connected in series, in parallel, or in a mixed manner. A mixed manner means that the multiple cells 100 are connected in both series and parallel.

[0203] The battery cell 100 provided in the above embodiment has a low risk of lithium plating and high safety. Therefore, the secondary battery including this battery cell 100 also has high safety.

[0204] This application also provides an electrical device, which includes the secondary battery provided in the above embodiments.

[0205] Secondary batteries provide electrical energy for electrical equipment to perform its functions. Electrical equipment may include one or more secondary batteries.

[0206] Electrical equipment can include, but is not limited to, mobile phones, tablets, laptops, electric drills, chainsaws, electric cars, electric motorcycles, and electric bicycles.

[0207] The secondary batteries provided in the above embodiments have good safety performance and can improve the electrical safety of electrical equipment.

[0208] The above description is merely a preferred embodiment of this application and is 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 battery cell is a pouch cell, and the battery cell includes: An electrode assembly includes at least two electrode sheets stacked together. Each electrode sheet includes a main body region, a first thinning region, and a second thinning region. The thickness of the main body region is greater than the thickness of the first thinning region and the thickness of the second thinning region are greater than the thickness of the second thinning region. The first thinning region and the second thinning region are located at opposite ends of the main body region. A packaging bag has a receiving cavity for accommodating the electrode assembly. The receiving cavity includes a first space for accommodating the main body region, a second space for accommodating the first thinned region, and a third space for accommodating the second thinned region. The packaging bag includes a first packaging film and a second packaging film. The electrode assembly is disposed between the first packaging film and the second packaging film. The first packaging film includes an integrally formed first part, a second part, and a fifth part. The second packaging film includes an integrally formed third part, a fourth part, and a sixth part. The first space is formed between the first part and the third part, the second space is formed between the second part and the fourth part, and the third space is formed between the fifth part and the sixth part. Wherein, along the thickness direction of the battery cell, the distance between the inner surface of the second part and the inner surface of the fourth part is less than the distance between the inner surface of the first part and the inner surface of the third part, and at least one of the second part and the fourth part always abuts against the electrode assembly, so that the first thinned areas of the at least two electrodes are brought closer to each other under the action of the second part and the fourth part; the distance between the inner surface of the fifth part and the inner surface of the sixth part is less than the distance between the inner surface of the first part and the inner surface of the third part, and at least one of the fifth part and the sixth part always abuts against the electrode assembly, so that the second thinned areas of the at least two electrodes are brought closer to each other under the action of the fifth part and the sixth part.

2. The battery cell according to claim 1, characterized in that, The thickness of the second part is greater than the thickness of the first part, and / or the thickness of the fourth part is greater than the thickness of the third part.

3. The battery cell according to claim 2, characterized in that, The outer surface of the second part is coplanar with the outer surface of the first part, and / or the outer surface of the fourth part is coplanar with the outer surface of the third part.

4. The battery cell according to claim 1, characterized in that, The second portion has a first end close to the first portion and a second end away from the first portion, and the thickness of the second portion gradually increases from the first end to the second end; and / or, The fourth portion has a third end close to the third portion and a fourth end away from the third portion, and the thickness of the fourth portion gradually increases from the third end to the fourth end.

5. The battery cell according to claim 4, characterized in that, The maximum thickness of the second part is T1, and the thickness of the first part is T2, satisfying: 1.02≤T1 / T2≤3.

6. The battery cell according to claim 5, characterized in that, The sum of the minimum thicknesses of the first thinned regions of the at least two electrodes is T3, and the sum of the thicknesses of the main regions of the at least two electrodes is T4, satisfying: 1.02≤(T1+T3) / (T2+T4)≤1.

1.

7. The battery cell according to claim 1, characterized in that, Along the length of the battery cell, the length of the second part is W1, which satisfies: 0 < W1 ≤ 30 mm.

8. The battery cell according to claim 1, characterized in that, The second portion extends obliquely from the first portion, and the angle between the second portion and the first portion is an obtuse angle; and / or, The fourth part extends obliquely from the third part, and the angle between the fourth part and the third part is an obtuse angle.

9. The battery cell according to claim 1, characterized in that, The first encapsulation film has a first groove and a second groove formed on the side facing the second encapsulation film. The position of the first groove corresponds to the position of the main body area, and the position of the second groove corresponds to the position of the first thinning area. Along the thickness direction of the battery cell, the depth of the second groove is less than the depth of the first groove; and / or, The second encapsulation film has a third groove and a fourth groove formed on the side facing the first encapsulation film. The position of the third groove corresponds to the position of the main body area, and the position of the fourth groove corresponds to the position of the first thinning area. Along the thickness direction of the battery cell, the depth of the fourth groove is less than the depth of the third groove.

10. The battery cell according to claim 1, characterized in that, The inner surface of the first encapsulation film is provided with a first insulating layer, which, when viewed along the thickness direction of the battery cell, at least partially overlaps with the first thinned area; and / or, the inner surface of the second encapsulation film is provided with a second insulating layer, which, when viewed along the thickness direction of the battery cell, at least partially overlaps with the first thinned area.

11. The battery cell according to claim 10, characterized in that, The thickness of the first insulating layer gradually increases in the direction away from the main body region, and / or the thickness of the second insulating layer gradually increases in the direction away from the main body region.

12. The battery cell according to claim 11, characterized in that, The sum of the maximum thickness of the first insulating layer and the thickness of the first encapsulation film is T5, and the thickness of the first encapsulation film is T6, satisfying: 1.02≤T5 / T6≤3.

13. The battery cell according to claim 12, characterized in that, The sum of the minimum thicknesses of the first thinned regions of the at least two electrodes is T3, and the sum of the thicknesses of the main regions of the at least two electrodes is T4, satisfying: 1.02≤(T5+T3) / (T6+T4)≤1.

1.

14. The battery cell according to claim 1, characterized in that, The sum of the minimum thicknesses of the first thinned regions of the at least two electrodes is T3, and the sum of the thicknesses of the main regions of the at least two electrodes is T4, satisfying: 0.92≤T3 / T4<1.

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

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