Battery cell, battery and electric device

Abstract

A battery cell (100), a battery (1000) and an electric device (2000). The battery cell (100) comprises: a casing (10); an electrode assembly (20), which is arranged in the casing (10), wherein the electrode assembly (20) comprises an electrode sheet (21) and a separator (22), the electrode sheet (21) and the separator (22) being stacked and then wound to form the electrode assembly (20), and in the direction of winding of the electrode assembly (20), the electrode assembly (20) is provided with a winding tail end (20a); and a buffer member (30), which is arranged in the casing (10), wherein in the direction of stacking of the electrode sheet (21) and the separator (22), the buffer member (30) covers at least part of the winding tail end (20a).

Description

Battery cells, batteries and electrical devices Technical Field

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

[0002] Energy conservation and emission reduction are key to the sustainable development of the automotive industry. Electric vehicles, due to their energy-saving and environmentally friendly advantages, have become an important component of the sustainable development of the automotive industry. For electric vehicles, battery technology is a key factor in their development.

[0003] During the charge and discharge process of the battery, the electrode assembly will expand. The expansion force acting on adjacent electrode assemblies or the outer shell may easily cause uneven stress, affecting the reliability and service life of the battery.

[0004] Summary of the Invention

[0005] In view of the above problems, the present application provides a battery cell, a battery and an electrical device, which can alleviate the problem of uneven stress during battery use affecting the battery life.

[0006] In the first aspect, the present application provides a battery cell, comprising: a shell; an electrode assembly, disposed in the shell, the electrode assembly comprising a pole piece and a separator, the pole piece and the separator being stacked and wound to form the electrode assembly, and the electrode assembly having a winding end along the winding direction of the electrode assembly; a buffer, disposed in the shell, covering at least a portion of the winding end along the stacking direction of the pole piece and the separator.

[0007] In the technical solution of the embodiment of the present application, a buffer is provided at the winding end, which can cover at least a portion of the winding end. The buffer can separate the winding end of the electrode assembly from its adjacent structure. When the electrode assembly expands, the buffer deforms, which to a certain extent alleviates the stress concentration problem caused by the protrusion of the winding end from other parts, so that the two parts with height difference are evenly stressed, thereby improving the reliability and service life of the battery cell.

[0008] In some embodiments, a tail glue is provided at the end of the electrode assembly along the winding direction, with the end of the tail glue along the winding direction forming the winding end. In the above technical solution, the buffer member covers at least a portion of the tail glue, to some extent alleviating the stress concentration caused by the tail glue having a certain thickness protruding from the separator or electrode sheet, ensuring uniform force between the two parts with different heights, thereby improving the service life and reliability of the battery cell.

[0009] In some embodiments, the finishing adhesive includes a first adhesive segment and a second adhesive segment. The first adhesive segment covers the end of the separator or the end of the electrode. The second adhesive segment is located to one side of the first adhesive segment. The buffer member covers at least a portion of the second adhesive segment. In the above technical solution, the buffer member covers the second adhesive segment or a portion of the second adhesive segment. The buffer member absorbs expansion stress by deforming, to some extent alleviating the stress concentration caused by the second adhesive segment protruding from the separator or the electrode. This ensures that the two parts with different heights are evenly stressed, thereby improving the service life and reliability of the battery cell.

[0010] In some embodiments, the end cap includes a first and second adhesive segment. The first adhesive segment covers the end of the isolation diaphragm or the end of the electrode. The second adhesive segment is located to one side of the first adhesive segment. The buffer covers at least a portion of the first adhesive segment. In the above technical solution, the buffer covers the first adhesive segment or a portion of the first adhesive segment. The buffer absorbs expansion stress by deforming, to some extent alleviating the stress concentration caused by the first adhesive segment having a certain thickness and protruding from the isolation diaphragm or the electrode, thereby ensuring uniform force on the two parts with a height difference.

[0011] In some embodiments, the pole piece and the separator are wound around a winding axis. In the direction of extension of the winding axis, the end cap has a first end and a second end that are arranged opposite each other, and the buffer covers the first end and / or the second end. In the above technical solution, the buffer can cover the first end and / or the second end of the end cap in the direction of extension of the winding axis, to some extent alleviating the stress concentration caused by the first end or the second end protruding from the separator or the pole piece, ensuring that the two parts with a height difference are evenly stressed, thereby improving the service life and reliability of the battery cell.

[0012] In some embodiments, the length of the buffer member in the direction of the winding axis is not less than the length of the end cap. In the above technical solution, the buffer member can cover the end of the end cap in the direction of the winding axis, to some extent alleviating the stress concentration caused by the end of the end cap protruding from the separator or electrode, ensuring that the two parts with different heights are evenly stressed, thereby improving the service life and reliability of the battery cell.

[0013] In some embodiments, the ratio of the compression ratios of the buffer and the finishing adhesive at 1 MPa is L1 / L2, where 5 ≤ L1 / L2 ≤ 30, and preferably 10 ≤ L1 / L2 ≤ 20. In the above technical solution, the buffer not only separates the finishing adhesive from adjacent structures but also effectively deforms when the electrode assembly expands, thereby providing a buffering effect. This ensures that the two parts with a height difference are evenly stressed, reducing the probability of stress concentration when the electrode assembly expands. Furthermore, the buffer provides effective support, reducing the probability of wrinkling and deformation, and improving the service life and reliability of the battery cells.

[0014] In some embodiments, the thickness ratio of the buffer member to the finishing glue is H1 / H2, 10≤H1 / H2≤100, preferably 10≤H1 / H2≤20. This technical solution can prevent a transient decrease in the volumetric energy density of the battery cell, reduce the probability of stress concentration during electrode assembly expansion, and improve the service life and reliability of the battery cell.

[0015] In some embodiments, the ratio of the area of ​​the portion of the buffer covering the finishing adhesive to the area of ​​the finishing adhesive is S1 / S2, where 0.1≤S1 / S2≤1, and preferably 0.8≤S1 / S2≤1. In the above technical solution, by defining S1 / S2, the buffer can effectively cover the finishing adhesive, to a certain extent avoiding the stress concentration caused by the finishing adhesive protruding from the separator or electrode sheet. This ensures that the two parts with a height difference are evenly stressed, thereby improving the service life and reliability of the battery cell.

[0016] In some embodiments, along the stacking direction of the electrode sheet and the separator, the buffer member covers at least a portion of the separator and / or at least a portion of the electrode sheet. In the above technical solution, the two parts with a height difference can be evenly stressed, thereby improving the service life and reliability of the battery cell.

[0017] In some embodiments, the end of the separator forms the winding end along the winding direction of the electrode assembly. In the above technical solution, the buffer can separate the separator from the adjacent electrode assembly or housing. When the electrode assembly expands, the buffer deforms, which to some extent alleviates the stress concentration caused by the end of the separator having a certain thickness and protruding from other parts. This ensures that the two parts with different heights are evenly stressed, thereby improving the service life and reliability of the battery cell.

[0018] In some embodiments, the ratio of the compression rates of the buffer and the separator at 1 MPa is L1 / L3, where 1 ≤ L1 / L3 ≤ 5, and preferably 2 ≤ L1 / L3 ≤ 3.5. In the above technical solution, the buffer not only separates the separator from the adjacent structure, but also effectively deforms when the electrode assembly expands, thereby achieving a buffering effect. This ensures that the two parts with a height difference are evenly stressed, reducing the probability of stress concentration when the electrode assembly expands. At the same time, the buffer can provide effective support, reduce the probability of wrinkling and deformation, and improve the service life and reliability of the battery cell.

[0019] In some embodiments, the thickness ratio of the buffer member to the separator is H1 / H3, 50≤H1 / H3≤700. In the above technical solution, a transient reduction in the volumetric energy density of the battery cell can be prevented, while the probability of stress concentration occurring during expansion of the electrode assembly can be reduced, thereby improving the service life and reliability of the battery cell.

[0020] In some embodiments, the end of the separator, facing the center of the electrode assembly, comprises a viscous material. In the above technical solution, the end of the separator can be directly bonded to an adjacent separator or electrode, thereby securing the electrode and separator, maintaining the overall structure of the electrode assembly, reducing the probability of displacement and deformation, reducing electrode wrinkling, and reducing the probability of internal short circuits.

[0021] In some embodiments, the end of the electrode sheet forms the winding end along the winding direction of the electrode assembly. In the above technical solution, the buffer member deforms when the electrode assembly expands, which to some extent alleviates the stress concentration problem caused by the end of the electrode sheet having a certain thickness and protruding from other parts, so that the two parts with different heights are evenly stressed, thereby improving the service life and reliability of the battery cell.

[0022] In some embodiments, the electrode has a thinned region, and the buffer covers at least a portion of the thinned region. In the above technical solution, the deformation of the buffer alleviates to some extent the stress concentration caused by the height difference in the thinned region of the electrode, ensuring that the stress is evenly distributed between the two portions with the height difference, thereby improving the service life and reliability of the battery cell.

[0023] In some embodiments, the electrode assembly includes a straight region and a bend region connected to the end of the straight region, and the buffer is disposed opposite at least one of the straight region and the bend region. In the above technical solution, the straight region and the buffer are disposed opposite each other, enabling the buffer to provide a buffering effect on the region of the electrode assembly corresponding to the straight region; the bend region and the buffer are disposed opposite each other, such that the region of the buffer facing the bend is generally arc-shaped, allowing the buffer to buffer the expansion force of the bend region, thereby reducing the risk of bridge failure and lithium deposition in the electrode assembly.

[0024] In some embodiments, the end of the electrode is located in the flat region, and the buffer covers the end of the electrode along the stacking direction of the electrode and the separator. This technical solution alleviates to some extent the stress concentration caused by the end of the electrode having a certain thickness and protruding from other parts, ensuring that the two parts with different heights are evenly stressed, thereby improving the service life and reliability of the battery cell.

[0025] In some embodiments, the electrode assembly includes a straight region and a bend region connected to the end of the straight region. The end of the electrode piece is located in the bend region, and the buffer is arranged offset from the end of the electrode piece. This technical solution can reduce the size of the buffer, thereby reducing the probability of stress concentration during expansion of the electrode assembly, reducing manufacturing costs, and facilitating installation of the buffer.

[0026] In some embodiments, the electrode assembly includes a straight region and a bend region connected to the end of the straight region. Along the stacking direction of the buffer and the electrode assembly, the area of ​​the buffer projected onto the outer shell is S3, and the area of ​​the positive electrode active material region of the straight region projected onto the outer shell is S4, where 0.3 ≤ S3 / S4 ≤ 1.1, preferably, 0.5 ≤ S3 / S4 ≤ 0.9. In the above technical solution, the provision of the buffer can reduce the probability of stress concentration when the electrode assembly expands. The buffer is also easy to install and does not occupy excessive space, thereby improving the reliability of the battery cell.

[0027] In some embodiments, the thickness of the buffer member is H1, 0.5mm≤H1≤10mm. In the above technical solution, it can prevent the excessive reduction of the volume energy density of the battery cell, and reduce the probability of stress concentration when the electrode assembly expands, thereby improving the service life and reliability of the battery cell.

[0028] In some embodiments, the compression rate of the buffer at 1 MPa is L1, L1 ≥ 50%, preferably L1 ≥ 60%. In the above technical solution, the buffer can be compressed and deformed as the electrode assembly expands, which can absorb the expansion of the electrode assembly and reduce the probability of stress concentration.

[0029] In some embodiments, the buffer member is made of a porous material. In the above technical solution, by adopting such a porous foam material, the compressibility of the buffer member can be improved while reducing the manufacturing cost.

[0030] In some embodiments, the material of the buffer component includes at least one of polyvinyl chloride, polyethylene-vinyl acetate, polyethylene, polypropylene, polyurethane, polymethylimide, polyimide, polystyrene, and modified silicone rubber. In the above technical solution, by controlling the type of the main material of the buffer component, the material has excellent electrolyte corrosion resistance, compressibility, and resilience, ensuring its reliability throughout the battery cell life cycle.

[0031] In a second aspect, the present application provides a battery comprising the battery cell in the above embodiment.

[0032] In a third aspect, the present application provides an electrical device, which includes the battery in the above embodiment, and the battery is used to provide electrical energy.

[0033] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0035] FIG1 is a schematic diagram of an electric device in the related art;

[0036] FIG2 is a schematic diagram of a battery in the related art;

[0037] FIG3 is a schematic diagram of a battery cell in the related art;

[0038] FIG4 is a partial schematic diagram of a battery cell according to some embodiments of the present application, wherein the ends of the electrode sheets form winding ends;

[0039] FIG5 is a partial schematic diagram of a battery cell according to some other embodiments of the present application, wherein the ends of the pole pieces form winding ends;

[0040] FIG6 is a partial schematic diagram of a battery cell according to some other embodiments of the present application, wherein the ends of the pole pieces form winding ends;

[0041] FIG7 is a partial schematic diagram of a battery cell according to some further embodiments of the present application, wherein the ends of the electrode sheets form winding ends;

[0042] FIG8 is a schematic diagram of the winding structure shown in FIG7 according to some embodiments of the present application;

[0043] FIG9 is a schematic diagram of the winding structure shown in FIG7 provided in other embodiments of the present application;

[0044] FIG10 is a partial schematic diagram of a battery cell according to some embodiments of the present application;

[0045] FIG11 is a schematic diagram of winding the structure shown in FIG10 according to some embodiments of the present application, wherein the end of the isolation film forms the winding end;

[0046] FIG12 is a schematic diagram of winding the structure shown in FIG10 according to other embodiments of the present application, wherein the end of the isolation film forms the winding end;

[0047] FIG13 is a schematic diagram of winding of the structure shown in FIG10 according to some other embodiments of the present application, wherein the end of the pole piece forms the winding end;

[0048] 14-16 are cross-sectional views of battery cells according to some embodiments of the present application.

[0049] Reference numerals:

[0050] Battery 1000, power-consuming device 2000,

[0051] Battery cell 100,

[0052] Shell 10, housing 11, end cover 12,

[0053] Electrode assembly 20, winding end 20a, straight area 201, turning area 202, pole piece 21, pole piece end 211, separator 22, separator end 221, finishing glue 23, first glue segment 231, second glue segment 232,

[0054] Buffer 30. DETAILED DESCRIPTION

[0055] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0056] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order or a primary-secondary relationship.

[0057] References to "embodiments" in this application mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments.

[0058] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connected," and "attached" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to direct connections, indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0059] The term "and / or" in this application simply describes an association between related objects, indicating that three possible relationships exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this application generally indicates that the related objects are in an "or" relationship.

[0060] In the embodiments of this application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components in different embodiments are omitted. It should be understood that the thickness, length, width, and other dimensions of the various components in the embodiments of this application, as well as the overall thickness, length, width, and other dimensions of the integrated device shown in the drawings are merely illustrative and should not constitute any limitation on this application.

[0061] The term "plurality" used in this application refers to two or more (including two).

[0062] In this application, a battery refers to a single physical module that includes one or more battery cells to provide higher voltage and capacity. For example, the batteries mentioned in this application may include battery modules or battery packs. Some batteries may include a casing for enclosing one or more battery cells or multiple battery modules. The casing prevents liquids or other foreign matter from affecting the charging or discharging of the battery cells. Of course, some batteries may not include the above-mentioned casing and are directly installed in the battery installation compartment of the electrical device.

[0063] In this application, battery cells may include lithium-ion secondary batteries, lithium-ion primary batteries, lithium-sulfur batteries, sodium-lithium-ion batteries, sodium-ion batteries, or magnesium-ion batteries, etc., and the embodiments of this application do not limit this. Battery cells may be cylindrical, flat, rectangular, or other shapes, etc., and the embodiments of this application do not limit this. Battery cells are generally divided into three types based on the packaging method: cylindrical battery cells, prismatic battery cells, and soft-pack battery cells, and the embodiments of this application do not limit this.

[0064] For example, a battery cell may include a housing, an electrode assembly, and an electrolyte, wherein the housing is used to contain the electrode assembly and the electrolyte. The electrode assembly is composed of a positive electrode sheet, a negative electrode sheet, and a separator. The battery cell mainly relies on the movement of metal ions between the positive electrode sheet and the negative electrode sheet to work. The positive electrode sheet includes a positive electrode collector and a positive electrode active material layer. The positive electrode active material layer is coated on the surface of the positive electrode collector. The positive electrode collector not coated with the positive electrode active material layer protrudes from the positive electrode collector coated with the positive electrode active material layer, and the positive electrode collector not coated with the positive electrode active material layer serves as the positive electrode tab. Taking lithium-ion batteries as an example, the material of the positive electrode collector can be aluminum, and the positive electrode active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc.

[0065] The negative electrode sheet includes a negative electrode current collector, or includes a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer is coated on the surface of the negative electrode current collector. The negative electrode current collector not coated with the negative electrode active material layer protrudes from the negative electrode current collector coated with the negative electrode active material layer. The negative electrode current collector not coated with the negative electrode active material layer serves as the negative electrode tab. The negative electrode current collector can be made of copper, and the negative electrode active material can be carbon, silicon, or other materials. To ensure that high currents can pass without melting, multiple positive electrode tabs are stacked together, and multiple negative electrode tabs are stacked together.

[0066] The material of the isolation film may be PP (polypropylene) or PE (polyethylene), etc. In addition, the electrode assembly may be a wound structure or a laminated structure, but the embodiments of the present application are not limited thereto.

[0067] Battery cells can be equipped with terminals and other components connected to the tabs, serving as electrical connections. Furthermore, they can have pressure relief features. When the internal pressure in a battery cell becomes excessive (e.g., due to thermal runaway), these features release substances (e.g., gas, liquid, particulate matter, etc.) from the cell to reduce the internal pressure. This prevents excessive internal pressure from causing dangerous accidents such as explosions. For example, these relief features can be explosion-proof valves, explosion-proof discs, and the like.

[0068] For example, as shown in Figures 1 and 2, some electrical devices 2000 are powered by batteries 1000. The battery 1000 includes a housing and a battery cell 100. The housing includes an upper shell and a lower shell. As shown in Figure 3, the battery cell 100 includes an electrode assembly 20 and a housing 10. The housing 10 includes a shell 11 and an end cap 12. In conventional technology, some wound batteries have an electrode assembly 20 that forms an end after winding. This end has a certain thickness and forms a height difference with other positions. During the charge and discharge process of the battery cell 100, the electrode assembly 20 expands. This end contacts the adjacent electrode assembly 20 or the housing 10, causing stress concentration and uneven stress on the adjacent electrode assembly 20 or the housing 10, affecting the reliability and service life of the battery cell 100.

[0069] To this end, the present application proposes a battery cell 100 including: a shell 10, an electrode assembly 20 arranged in the shell 10, and a buffer member 30. The electrode assembly 20 includes a pole piece 21 and an isolation membrane 22. The pole piece 21 and the isolation membrane 22 are stacked and wound to form the electrode assembly 20. Along the winding direction of the electrode assembly 20, the electrode assembly 20 has a winding end 20a. The buffer member 30 is arranged in the shell 10. Along the stacking direction of the pole piece 21 and the isolation membrane 22, the buffer member 30 covers at least a portion of the winding end 20a.

[0070] In the battery cell 100 of the above-mentioned structure, by providing a buffer member 30 at the winding end 20a, the buffer member 30 can cover at least a portion of the winding end 20a. The buffer member 30 can separate the winding end 20a of the electrode assembly 20 from its adjacent structure. When the electrode assembly 20 expands, the buffer member 30 deforms, which to a certain extent alleviates the stress concentration problem caused by the protrusion of the winding end 20a from other parts, so that the two parts with height difference are evenly stressed, thereby improving the reliability and service life of the battery cell 100.

[0071] The battery 1000 with the battery cell 100 disclosed in the embodiment of the present application can be used for, but not limited to, an electrical device 2000 such as a vehicle, ship or aircraft. The power supply system of the electrical device 2000 composed of the battery 1000 disclosed in the present application can ensure the safety and reliability of the electrical device 2000.

[0072] For example, the power-consuming device 2000 disclosed in the embodiments of the present application may be, but is not limited to, a vehicle, a mobile phone, a tablet, a laptop computer, a ship, a spacecraft, an electric toy, an electric tool, etc. A vehicle may be a fuel vehicle, a gas vehicle, a new energy vehicle, or a rail vehicle, and a new energy vehicle may be a pure electric vehicle, a hybrid vehicle, or an extended-range vehicle, etc.; a spacecraft includes an airplane, a rocket, a space shuttle, and a spacecraft, etc.; an electric toy includes a fixed or mobile electric toy, such as a game console, an electric vehicle toy, an electric ship toy, and an electric airplane toy, etc.; an electric tool includes a metal cutting electric tool, a grinding electric tool, an assembly electric tool, and a railway electric tool, such as an electric drill, an electric grinder, an electric wrench, an electric screwdriver, an electric hammer, an impact drill, a concrete vibrator, and an electric planer, etc.

[0073] Hereinafter, a battery cell 100 according to an embodiment of the present application will be described with reference to the accompanying drawings.

[0074] As shown in Figures 4 to 16, Figures 4 to 16 show structural diagrams of battery cells 100 of multiple embodiments. According to the embodiment of the present application, the battery cell 100 includes: a shell 10, an electrode assembly 20 and a buffer 30. The electrode assembly 20 is arranged in the shell 10. The electrode assembly 20 includes a pole piece 21 and an isolation membrane 22. The pole piece 21 and the isolation membrane 22 are stacked and wound to form the electrode assembly 20. Along the winding direction of the electrode assembly 20, the electrode assembly 20 has a winding end 20a. The buffer 30 is arranged in the shell 10. Along the stacking direction of the pole piece 21 and the isolation membrane 22, the buffer 30 covers at least a portion of the winding end 20a.

[0075] The outer shell 10 is the outermost structural component of the battery cell 100 , and contains the electrode assembly 20 and electrolyte.

[0076] The electrode assembly 20 includes a wound electrode sheet 21 and a separator 22, wherein the electrode sheet 21 includes a positive electrode sheet and a negative electrode sheet, wherein the positive electrode sheet includes a positive electrode collector and a positive electrode active material layer, the negative electrode sheet may include a negative electrode collector, or the negative electrode sheet includes a negative electrode collector and a negative electrode active material layer.

[0077] The electrode sheet 21 and the separator 22 are stacked and wound around a winding axis to form an electrode assembly 20. In the winding direction, the electrode assembly 20 has a winding end 20a. The winding end 20a can be the end 211 of the electrode sheet 21 or the end 221 of the separator 22. In some examples, the electrode assembly 20 further includes a finishing glue 23. The finishing glue 23 is provided at the end 211 of the electrode sheet 21 or the end 221 of the separator 22 to fix the electrode sheet 21 and the separator 22. The finishing glue 23 can cover the outside of the end 211 of the electrode sheet 21 or the end 221 of the separator 22, or can be provided on the side of the separator 22 or the end 211 of the electrode sheet 21 facing the center of the electrode assembly 20. Therefore, the winding end 20a can also be the end of the finishing glue 23. The winding end 20a can be arranged opposite to the housing 10 or opposite to another electrode assembly 20, that is, the winding end 20a has an adjacent structure.

[0078] The buffer member 30 is disposed within the housing 10 and can cover the winding end 20a. The buffer member 30 is used to provide a buffer for the winding end 20a of the electrode assembly 20, preventing the electrode assembly 20 from expanding and being squeezed against the housing 10 or adjacent electrode assemblies 20, thereby causing stress concentration. Specifically, the buffer member 30 can provide a buffer space for the expansion of the electrode assembly 20. For example, the buffer member 30 itself can be elastically deformable. When the electrode assembly 20 expands, the buffer member 30 can adaptively contract to provide a buffer space for the electrode assembly 20. For another example, the buffer member 30 itself can have a buffer space, which can accommodate the expanded portion of the electrode assembly 20 when it expands.

[0079] The stacking direction of the pole piece 21 and the isolation film 22 is perpendicular to the outer surface of the electrode assembly 20. The buffer 30 covers at least a portion of the winding end 20a. The buffer 30 is arranged on the outside of the outer surface of the electrode assembly 20. The buffer 30 can separate the winding end 20a from the adjacent electrode assembly 20 or the shell 10. When the electrode assembly 20 expands, the buffer 30 is deformed, which to a certain extent alleviates the stress concentration problem caused by the protrusion of the winding end 20a from other parts, so that the two parts with height difference are evenly stressed, thereby improving the service life and reliability of the battery cell 100.

[0080] In addition, when the battery cell 100 is charged and discharged, the buffer component 30 has a certain supporting effect on the winding end 20a of the electrode assembly 20, which can reduce the deformation of the winding end 20a, thereby improving the wrinkling of the electrode sheet 21 caused by the expansion of the electrode assembly 20, thereby alleviating the problem of lithium or sodium precipitation during the cycle of the battery cell 100.

[0081] As shown in Figure 16, the buffer member 30 can be located between the electrode assembly 20 and the outer shell 10, and the end of the electrode assembly 20 is located between the electrode assembly 20 and the outer shell 10. The buffer member 30 can not only support and cushion the electrode assembly 20, but also separate the electrode assembly 20 from the outer shell 10, so that the electrode assembly 20 is not easily squeezed by the outer shell 10 after expansion.

[0082] Alternatively, as shown in FIG14 , the buffer member 30 may be positioned between two adjacent electrode assemblies 20. There are a plurality of electrode assemblies 20 arranged in the front-to-back direction, and the winding end 20a of at least one electrode assembly 20 is positioned between the two electrode assemblies 20. The buffer member 30 is disposed between the two adjacent electrode assemblies 20. The buffer member 30 may support and cushion the electrode assemblies 20, and may also separate the adjacent electrode assemblies 20 so that the electrode assemblies 20 are not easily squeezed against each other after expansion.

[0083] Of course, the buffer member 30 can also be partially disposed between the electrode assembly 20 and the housing 10, and partially disposed between adjacent electrode assemblies 20, as shown in FIG15 . This is also within the scope of protection of this application. It should be noted that the buffer member 30 disposed between the electrode assembly 20 and the housing 10 and the buffer member 30 disposed between adjacent electrode assemblies 20 can be different parts of the same buffer member 30, or can be independent and different buffer members 30.

[0084] In the technical solution of the present application, a buffer member 30 is provided at the winding end 20a, so that the buffer member 30 can cover at least a portion of the winding end 20a. The buffer member 30 can separate the winding end 20a of the electrode assembly 20 from its adjacent structure. When the electrode assembly 20 expands, the buffer member 30 is deformed, which to a certain extent alleviates the stress concentration problem caused by the protrusion of the winding end 20a from other parts, so that the two parts with height difference are evenly stressed, thereby improving the reliability and service life of the battery cell 100.

[0085] As shown in FIG. 4 to FIG. 9 , along the winding direction of the electrode assembly 20 , the end of the electrode assembly 20 has a finishing glue 23 , and the end of the finishing glue 23 along the winding direction forms a winding end 20 a .

[0086] As shown in Figures 4 to 9, the electrode assembly 20 is wound in a clockwise direction, and has a tail glue 23 at the winding end 20a. The tail glue 23 is provided at the end 211 of the electrode 21 or the end 221 of the isolation membrane 22. The tail glue 23 is used to fix the electrode 21 and the isolation membrane 22. The tail glue 23 can keep the overall structure of the electrode assembly 20 stable, reduce the probability of displacement and deformation, reduce the wrinkling of the electrode 21, reduce the probability of internal short circuit, etc. The tail glue 23 can cover the end 211 of the electrode 21 or the isolation membrane 22. The end 221 of the electrode assembly 20 may be located on the outside of the end 221 of the isolating membrane 22 or the end 211 of the electrode piece 21, and may also be located on the side of the isolating membrane 22 or the end 211 of the electrode piece 21 facing the center of the electrode assembly 20. Specifically, the end glue 23 may be sandwiched between the end 221 of the isolating membrane 22 and the other parts of the isolating membrane 22. The end glue 23 may also be sandwiched between the end 221 of the isolating membrane 22 and the electrode piece 21. The end glue 23 may also be sandwiched between the end 211 of the electrode piece 21 and the other parts of the electrode piece 21. The end glue 23 may also be sandwiched between the end 211 of the electrode piece 21 and the isolating membrane 22.

[0087] The finishing glue 23 has a certain thickness. The thickness of the finishing glue 23 is such as the size of the finishing glue 23 in the third direction (the front-to-back direction as shown in Figure 8). As shown in Figure 8, in the third direction, the finishing glue 23 protrudes from the isolation membrane 22, and there is a height difference between the finishing glue 23 and the isolation membrane 22.

[0088] Along the stacking direction of the electrode 21 and the isolation membrane 22, the buffer 30 covers at least a portion of the finishing glue 23. The buffer 30 can separate the finishing glue 23 from the adjacent electrode assembly 20 or the shell 10. When the electrode assembly 20 expands, the buffer 30 deforms, which to a certain extent alleviates the stress concentration problem caused by the protrusion of the finishing glue 23 from the isolation membrane 22 or the electrode 21, so that the two parts with height difference are evenly stressed, thereby improving the service life and reliability of the battery cell 100.

[0089] As shown in FIG4 , in some embodiments, the finishing glue 23 includes a first glue segment 231 and a second glue segment 232 . The first glue segment 231 covers the end 221 of the isolation membrane 22 or the end 211 of the pole piece 21 . The second glue segment 232 is located on one side of the first glue segment 231 . The buffer member 30 covers at least a portion of the second glue segment 232 .

[0090] As shown in Figure 4, the first glue segment 231 of the finishing glue 23 covers the end 221 of the isolation membrane 22, and the first glue segment 231 is bonded to the end 221 of the isolation membrane 22. The second glue segment 232 exceeds the end 221 of the isolation membrane 22. The second glue segment 232 can be bonded to a part of the isolation membrane 22 or the pole piece 21. The second glue segment 232 protrudes from the isolation membrane 22 or the pole piece 21. The position corresponding to the second glue segment 232 is prone to stress concentration. The buffer component 30 covers the second glue segment 232 or a part of the second glue segment 232. The buffer component 30 absorbs the expansion stress by deformation, which to a certain extent alleviates the stress concentration problem caused by the second glue segment 232 protruding from the isolation membrane 22 or the pole piece 21, so that the two parts with a height difference are evenly stressed, thereby improving the service life and reliability of the battery cell 100.

[0091] As shown in Figure 5, in some embodiments, the finishing glue 23 includes a first glue segment 231 and a second glue segment 232. The first glue segment 231 covers the end 221 of the isolation membrane 22 or the end 211 of the pole piece 21, and the second glue segment 232 is located on one side of the first glue segment 231. The buffer member 30 covers at least a portion of the first glue segment 231.

[0092] As shown in Figure 5, the first glue segment 231 of the finishing glue 23 covers the end 221 of the isolation membrane 22, and the first glue segment 231 is bonded to the end 221 of the isolation membrane 22. The second glue segment 232 exceeds the end 221 of the isolation membrane 22. The second glue segment 232 can be bonded to a part of the isolation membrane 22 or the electrode piece 21. The first glue segment 231 protrudes from the isolation membrane 22. The third direction serves as the height direction of the electrode assembly 20. The height of the electrode assembly 20 at the position of the first glue segment 231 is greater than the height at the position of the second glue segment 232.

[0093] The buffer member 30 covers the first rubber segment 231 or a portion of the first rubber segment 231. The buffer member 30 absorbs the expansion stress by deformation, thereby alleviating to a certain extent the stress concentration problem caused by the first rubber segment 231 protruding from the isolation membrane 22 or the pole piece 21, so that the two parts with a height difference are evenly stressed; and because the first rubber segment 231 is higher than the second rubber segment 232, the second rubber segment 232 can also be separated from the adjacent structure under the action of the buffer member 30, and the stress concentration problem caused by the second rubber segment 232 having a certain thickness protruding from the isolation membrane or the pole piece can also be alleviated, thereby improving the service life and reliability of the battery cell 100.

[0094] As shown in Figures 6 and 7, in some embodiments, the buffer 30 covers at least a portion of the first rubber segment 231, and the buffer 30 covers at least a portion of the second rubber segment 232. As shown in Figure 6, the buffer 30 covers a portion of the first rubber segment 231, and the buffer 30 covers a portion of the second rubber segment 232. Here, the buffer 30 can be two independent buffers 30; as shown in Figure 7, a portion of the buffer 30 covers the first rubber segment 231, and another portion of the buffer 30 covers the second rubber segment 232. Different portions of the same buffer 30 correspond to the two rubber segments, respectively. By covering at least a portion of the first rubber segment 231 and at least a portion of the second rubber segment 232 with the buffer 30, the buffer 30 absorbs the expansion stress through deformation, so that the two parts with height difference are evenly stressed, thereby improving the service life and reliability of the battery cell 100.

[0095] As shown in Figures 4 to 7, in some examples, the pole piece 21 and the isolation membrane 22 are wound around the winding axis. In the extension direction of the winding axis, the finishing glue 23 has a first end and a second end arranged oppositely, and the buffer member 23 covers the first end and / or the second end.

[0096] As shown in Figures 4 to 7, the winding axis extends along a first direction (the up and down direction as shown in Figure 4). In the first direction, the finishing glue 23 has a first end and a second end, and the buffer member 23 covers at least one end, thereby alleviating to a certain extent the stress concentration problem caused by the protrusion of the first end or the second end from the isolation membrane 22 or the pole piece 21, so that the two parts with a height difference are evenly stressed, thereby improving the service life and reliability of the battery cell 100.

[0097] In some examples, in the extension direction of the winding axis, the length of the buffer 30 is not less than the length of the finishing glue 23 .

[0098] As shown in Figures 4 to 7, the winding axis extends along the first direction (the up and down direction as shown in Figure 4), and the length of the buffer 30 in the first direction is greater than the length of the tail glue 23, so that the buffer 30 can cover the end of the tail glue 23 in the first direction, thereby alleviating to a certain extent the stress concentration problem caused by the end of the tail glue 23 protruding from the isolation membrane 22 or the pole piece 21, so that the two parts with a height difference are evenly stressed, thereby improving the service life and reliability of the battery cell 100.

[0099] In some embodiments, the ratio of the compression rates of the buffer 30 and the finishing glue 23 at 1 MPa is L1 / L2, wherein 5≤L1 / L2≤30, preferably, 10≤L1 / L2≤20.

[0100] The buffer member 30 compresses, meaning it deforms when subjected to an external force to reduce its occupied space. When the external force is removed, it at least partially recovers its deformation to provide stable support for the electrode assembly 20. The compressibility of the buffer member 30 refers to the ratio of the volume of the buffer member 30 reduced when compressed to its original volume.

[0101] At 1 MPa, if the ratio of the compression rate of the buffer 30 to the finishing glue 23 is too small, the compression rates of the buffer 30 and the finishing glue 23 are close, the buffering effect of the buffer 30 is not obvious, and stress concentration problems are likely to occur when the electrode assembly 20 expands. If the ratio of the compression rate of the buffer 30 to the finishing glue 23 is too large, the compression rate of the buffer 30 is too large, and it is difficult to play an effective supporting role, and the winding end 20a is prone to wrinkling and deformation.

[0102] To this end, L1 / L2 can be limited to between 5 and 30, and L1 / L2 can be any value among 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 or a range between any two of them.

[0103] As a result, the buffer component 30 can separate the finishing glue 23 from the adjacent structure and can effectively deform when the electrode assembly 20 expands, thereby achieving a buffering effect, so that the two parts with a height difference are evenly stressed, reducing the probability of stress concentration when the electrode assembly 20 expands. At the same time, the buffer component 30 can play an effective supporting role, reduce the probability of wrinkling and deformation, and improve the service life and reliability of the battery cell 100.

[0104] In some embodiments, 10≤L1 / L2≤20, and L1 / L2 can be any value among 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, 20 or any range between two values.

[0105] As a result, the buffer component 30 can separate the finishing glue 23 from the adjacent structure and can effectively deform when the electrode assembly 20 expands, thereby achieving a buffering effect, so that the two parts with a height difference are evenly stressed, reducing the probability of stress concentration when the electrode assembly 20 expands. At the same time, the buffer component 30 can play an effective supporting role, reduce the probability of wrinkling and deformation, and improve the service life and reliability of the battery cell 100.

[0106] As shown in FIG8 and FIG9 , in some embodiments, the thickness ratio of the buffer 30 to the finishing glue 23 is H1 / H2, 10≤H1 / H2≤100, preferably, 10≤H1 / H2≤20.

[0107] As shown in Figures 8 and 9, in some examples, in the third direction, the thickness of the buffer 30 is H1, where the thickness of the buffer 30 is the thickness of the buffer 30 in the free state, and the thickness of the finishing glue 23 is H2. If H1 / H2 is too large, H1 is too large, the thickness of the buffer 30 is too large, and the buffer 30 occupies too much space in the third direction, and the space occupied by the corresponding electrode assembly 20 in the third direction is reduced, which will lead to a decrease in the volume energy density of the battery cell 100. If H1 / H2 is too small, H1 is too small, the thickness of the buffer 30 is too small, and the deformable space of the buffer 30 is too small, so that when the electrode assembly 20 expands, stress concentration is likely to occur at the finishing glue 23.

[0108] To this end, H1 / H2 is limited to between 10-100. H1 / H2 can be any value among 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100 or any range between two values.

[0109] In this way, the volume energy density of the battery cell 100 can be prevented from being excessively reduced, and the probability of stress concentration occurring when the electrode assembly 20 expands can be reduced, thereby improving the service life and reliability of the battery cell 100.

[0110] In some embodiments, 10≤H1 / H2≤20, and H1 / H2 can be any value among 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or a range between any two values.

[0111] This can further prevent the volume energy density of the battery cell 100 from being excessively reduced, reduce the probability of stress concentration occurring when the electrode assembly 20 expands, and improve the service life and reliability of the battery cell 100.

[0112] As shown in FIG. 4 to FIG. 9 , in some embodiments, the ratio of the area of ​​the portion of the buffer 30 covering the finishing glue 23 to the area of ​​the finishing glue 23 is S1 / S2, 0.1≤S1 / S2≤1, preferably, 0.8≤S1 / S2≤1.

[0113] As shown in Figures 4 and 5, the buffer member 30 covers at least a portion of the finishing glue 23. The size of the portion of the buffer member 30 covering the finishing glue 23 in the second direction (the left and right direction as shown in Figure 4) is a, the size of the portion of the buffer member 30 covering the finishing glue 23 in the first direction is j, the area S1 is a*j, the size of the finishing glue 23 in the first direction is c, the size of the finishing glue 23 in the first direction is k, and the area S2 is c*k.

[0114] When S1 / S2 is too small, the portion of the buffer 30 covering the finishing glue 23 is too small, and when the electrode assembly 20 expands, stress concentration is likely to occur at the finishing glue 23 .

[0115] Thus, S1 / S2 can be limited to between 0.1-1. S1 / S2 can be any value among 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or a range of values ​​between any two of them. When S1 / S2 is 1, the buffer 30 can completely cover the finishing glue 23.

[0116] By limiting S1 / S2, the buffer member 30 can effectively cover the finishing glue 23, thereby avoiding to a certain extent the stress concentration problem caused by the protrusion of the finishing glue 23 from the isolation membrane 22 or the pole piece 21, so that the two parts with a height difference are evenly stressed, thereby improving the service life and reliability of the battery cell 100.

[0117] In some embodiments, 0.8≤S1 / S2≤1, S1 / S2 can be any value among 0.8, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1 or any range between two values.

[0118] In this way, the buffer member 30 can cover more of the finishing glue 23, which can avoid the stress concentration problem caused by the protrusion of the finishing glue 23 from the isolation membrane 22 and the pole piece 21 to a certain extent, so that the two parts with height difference are evenly stressed, thereby improving the service life and reliability of the battery cell 100.

[0119] As shown in FIG. 4 to FIG. 9 , in some embodiments, along the stacking direction of the pole piece 21 and the isolation film 22 , the buffer member 30 covers at least a portion of the isolation film 22 and / or at least a portion of the pole piece 21 .

[0120] As shown in FIG8 , in the third direction (the front-to-back direction shown in FIG8 ), the buffer member 30 covers at least a portion of the finishing glue 23 , and the buffer member 30 also covers a portion of the isolation film 22 , thereby making the two parts with a height difference bear force evenly, thereby improving the service life and reliability of the battery cell 100 .

[0121] In other examples, the buffer 30 covers at least a portion of the finishing glue 23, and the buffer 30 also covers a portion of the pole piece 21, or the buffer 30 covers at least a portion of the finishing glue 23, and the buffer 30 also covers a portion of the isolation membrane 22 and a portion of the pole piece 21, thereby making the two parts with a height difference evenly stressed, thereby improving the service life and reliability of the battery cell 100.

[0122] As shown in FIG. 10 to FIG. 12 , in some embodiments, along the winding direction of the electrode assembly 20 , the end 221 of the separator 22 forms a winding end 20 a .

[0123] As shown in FIG. 10 to FIG. 12 , the electrode assembly 20 is wound in a clockwise direction, and the winding end 20 a is the separator 22 , that is, the end 221 of the separator 22 forms the winding end 20 a .

[0124] The isolation membrane 22 has a certain thickness. The thickness of the isolation membrane 22 is such as the size of the isolation membrane 22 in the third direction (the front-to-back direction as shown in Figure 11). As shown in Figure 11, in the third direction, the end 221 of the isolation membrane 22 protrudes from the other parts of the isolation membrane 22, and the end of the isolation membrane 22 and the other parts of the isolation membrane 22 have a height difference.

[0125] Along the stacking direction of the electrode 21 and the isolation membrane 22, the buffer 30 covers at least a portion of the isolation membrane 22. The buffer 30 can separate the isolation membrane 22 from the adjacent electrode assembly 20 or the shell 10. When the electrode assembly 20 expands, the buffer 30 deforms, which to a certain extent alleviates the stress concentration problem caused by the end of the isolation membrane 22 having a certain thickness and protruding from other parts, so that the two parts with a height difference are evenly stressed, thereby improving the service life and reliability of the battery cell 100.

[0126] In some embodiments, the ratio of the compression rates of the buffer member 30 and the isolation membrane 22 at 1 MPa is L1 / L3, wherein 1≤L1 / L3≤5, preferably, 2≤L1 / L3≤3.5.

[0127] At 1 MPa, if the ratio of the compression rate of the buffer component 30 to the isolation membrane 22 is too small, the compression rates of the buffer component 30 and the isolation membrane 22 are close, the buffering effect of the buffer component 30 is not obvious, and stress concentration problems are likely to occur when the electrode assembly 20 expands. If the ratio of the compression rate of the buffer component 30 to the isolation membrane 22 is too large, the compression rate of the buffer component 30 is too large, and it is difficult to play an effective supporting role, and the winding end 20a is prone to wrinkling and deformation.

[0128] To this end, L1 / L3 can be limited to between 1 and 5. L1 / L3 can be any value among 1, 2, 3, 4, and 5, or a range value between any two of them.

[0129] As a result, the buffer member 30 can not only separate the isolation membrane 22 from the adjacent structure, but also effectively deform when the electrode assembly 20 expands, thereby achieving a buffering effect, so that the two parts with a height difference are evenly stressed, reducing the probability of stress concentration when the electrode assembly 20 expands. At the same time, the buffer member 30 can play an effective supporting role, reduce the probability of wrinkling and deformation, and improve the service life and reliability of the battery cell 100.

[0130] In some embodiments, 2≤L1 / L3≤3.5, L1 / L3 can be any value among 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5 or any range between two values.

[0131] As a result, the buffer member 30 can separate the isolation membrane 22 from the adjacent structure and can be effectively deformed when the electrode assembly 20 expands. The buffer member 30 can achieve a buffering effect, so that the two parts with a height difference are evenly stressed, reducing the probability of stress concentration when the electrode assembly 20 expands. At the same time, the buffer member 30 can play an effective supporting role, reduce the probability of wrinkling and deformation, and improve the service life and reliability of the battery cell 100.

[0132] As shown in FIG. 11 , in some embodiments, the thickness ratio of the buffer member 30 to the isolation film 22 is H1 / H3, and 50≤H1 / H3≤700.

[0133] As shown in FIG11 , in some examples, the thickness of the buffer 30 is H1, where the thickness of the buffer 30 is the thickness of the buffer 30 in a free state, and the thickness of each isolation membrane 22 is H3. If H1 / H3 is too large, H1 is too large, the thickness of the buffer 30 is too large, the buffer 30 occupies too much space, and the space occupied by the corresponding electrode assembly 20 is reduced, which will lead to a decrease in the volume energy density of the battery cell 100. If H1 / H3 is too small, H1 is too small, the thickness of the buffer 30 is too small, and the deformable space of the buffer 30 is too small, so that when the electrode assembly 20 expands, stress concentration is likely to occur at the winding end 20a.

[0134] To this end, H1 / H3 is limited to between 50-700. H1 / H3 can be any value among 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700 or any range between two values.

[0135] In this way, the volume energy density of the battery cell 100 can be prevented from being excessively reduced, and the probability of stress concentration occurring when the electrode assembly 20 expands can be reduced, thereby improving the service life and reliability of the battery cell 100.

[0136] In some embodiments, a side of the end 221 of the separator 22 facing the center of the electrode assembly 20 has an adhesive material.

[0137] The end 221 of the isolation membrane 22 has a sticky material, which can be directly formed on the end 221 of the isolation membrane 22. The sticky material can show its characteristics under a specific state, so that the end 221 of the isolation membrane 22 can be directly bonded to the adjacent isolation membrane 22 or the pole piece 21, thereby fixing the pole piece 21 and the isolation membrane 22, so that the overall structure of the electrode assembly 20 remains stable, reducing the probability of displacement and deformation, reducing wrinkling of the pole piece 21, reducing the probability of internal short circuit, etc.

[0138] As shown in FIG. 13 , in some embodiments, along the winding direction of the electrode assembly 20 , the end 211 of the electrode sheet 21 forms a winding end 20 a .

[0139] As shown in FIG13 , the electrode assembly 20 is wound in a clockwise direction, and the electrode piece 21 is formed at the winding end 20 a , that is, the end 211 of the electrode piece 21 forms the winding end 20 a .

[0140] The pole piece 21 has a certain thickness. The thickness of the pole piece 21 is such as the size of the pole piece 21 in the third direction (the front-to-back direction as shown in Figure 13). As shown in Figure 13, in the third direction, the end 211 of the pole piece 21 protrudes from other parts of the pole piece 21, and there is a height difference between the end 211 of the pole piece 21 and the pole piece 21.

[0141] Along the stacking direction of the electrode 21 and the isolation membrane 22, the buffer 30 covers at least a portion of the electrode 21. The buffer 30 can separate the electrode 21 from the adjacent electrode assembly 20 or the shell 10. When the electrode assembly 20 expands, the buffer 30 deforms, which to a certain extent alleviates the stress concentration problem caused by the end 211 of the electrode 21 having a certain thickness and protruding from other parts, so that the two parts with height difference are evenly stressed, thereby improving the service life and reliability of the battery cell 100.

[0142] In some embodiments, the pole piece 21 has a pole piece thinning area, and the buffer 30 covers at least a portion of the pole piece thinning area.

[0143] The end of the pole piece 21 has a pole piece thinning area, and the thickness of the pole piece thinning area is less than the thickness of other positions of the pole piece 21, thereby forming a height difference at the connection between the pole piece thinning area and other positions of the pole piece 21. The buffer part 30 covers the end 211 of the pole piece 21 and extends to the pole piece thinning area. The deformation of the buffer part 30 alleviates the stress concentration problem caused by the height difference in the pole piece thinning area to a certain extent, so that the two parts with the height difference are evenly stressed, thereby improving the service life and reliability of the battery cell 100.

[0144] As shown in Figures 8, 9, 11-13, in some embodiments, the electrode assembly 20 includes a straight area 201 and a turning area 202 connected to the end of the straight area 201, and the buffer member 30 is arranged relative to at least one of the straight area 201 and the turning area 202.

[0145] As shown in Figure 8, the electrode 21 and the isolation membrane 22 are stacked and wound to form a straight area 201. The straight area 201 refers to the portion extending along the plane after winding; the turning area 202 refers to the portion extending along the arc surface after winding. For example, as shown in Figure 8, the portion between the front side surface and the rear side surface of the electrode assembly 20 is formed as the straight area 201. The extension direction of the electrode 21 in the straight area 201 is the length direction of the straight area 201. In the second direction shown in Figure 8, the left and right ends of the straight area 201 are the turning areas 202.

[0146] The straight area 201 is arranged opposite to the buffer member 30, so that the buffer member 30 can play a buffering role on the area of ​​the electrode assembly 20 corresponding to the straight area 201; the bend portion is arranged opposite to the buffer member 30, so that the area of ​​the buffer member 30 facing the bend portion is generally formed into an arc shape, so that the buffer member 30 can buffer the expansion force of the bend portion and reduce the risk of bridge breakage and lithium deposition of the electrode assembly 20.

[0147] As shown in FIG8 and FIG9 , in some embodiments, the end 211 of the pole piece 21 is located in the straight region 201 , and the buffer 30 covers the end 211 of the pole piece 21 along the stacking direction of the pole piece 21 and the isolation film 22 .

[0148] As shown in Figures 8 and 9, the buffer member 30 covers at least a portion of the finishing glue 23. The buffer member 30 also covers a portion of the isolation membrane 22 and a portion of the pole piece 21. This alleviates to a certain extent the stress concentration problem caused by the end of the pole piece 21 having a certain thickness and protruding from other parts, so that the two parts with a height difference are evenly stressed, thereby improving the service life and reliability of the battery cell 100.

[0149] As shown in Figure 13, in some embodiments, the electrode assembly 20 includes a straight area 201 and a turning area 202 connected to the end of the straight area 201, the end 211 of the pole piece 21 is located in the turning area 202, and the buffer member 30 is staggered with the end 211 of the pole piece 21.

[0150] As shown in Figure 13, the electrode 21 and the isolation membrane 22 are stacked and wound to form a straight area 201. The straight area 201 refers to the portion extending along the plane after winding; the turning area 202 refers to the portion extending along the arc surface after winding. For example, as shown in Figure 13, the portion between the front side surface and the rear side surface of the electrode assembly 20 is formed as the straight area 201. The extension direction of the electrode 21 in the straight area 201 is the length direction of the straight area 201. In the second direction shown in Figure 13, the left and right ends of the straight area 201 are the turning areas 202.

[0151] As shown in Figure 13, the end 211 of the electrode 21 is located at the right side of the turning area 202. Since there is a certain gap between the turning area 202 and the adjacent electrode assembly 20 or the shell 10, the electrode assembly 20 has a buffer space when it expands. The right end of the buffer 30 is located on the left side of the end of the electrode 21, so that the buffer 30 and the end 211 of the electrode 21 are staggered.

[0152] This can reduce the size of the buffer member 30 , thereby reducing the probability of stress concentration occurring when the electrode assembly 20 expands, reducing manufacturing costs, and facilitating installation of the buffer member 30 .

[0153] In some embodiments, the electrode assembly 20 includes a straight region 201 and a turning region 202 connected to the end of the straight region 201. Along the stacking direction of the buffer member 30 and the electrode assembly 20, the area of ​​the buffer member 30 projected on the outer shell 10 is S3, and the area of ​​the positive electrode active material region of the straight region 201 projected on the outer shell 10 is S4, wherein 0.3≤S3 / S4≤1.1, preferably, 0.5≤S3 / S4≤0.9.

[0154] As shown in Figure 8, the electrode 21 and the isolation film 22 are stacked and wound to form a straight area 201. The straight area 201 refers to the part extending along the plane after winding; the turning area 202 refers to the part extending along the arc surface after winding. For example, as shown in Figure 8, the part between the front side surface and the rear side surface of the electrode assembly 20 is formed as the straight area 201. The extension direction of the electrode 21 in the straight area 201 is the length direction of the straight area 201. In the second direction shown in Figure 8, the left and right ends of the straight area 201 are the turning areas 202. The length dimension of the straight area 201 in the second direction is B, and B is the distance between the corners on both sides of the innermost circle of the winding. The height dimension of the positive active material layer in the straight area 201 in the first direction is D, and the area of ​​the positive active material area of ​​the straight area 201 projected on the outer shell 10 is S4, S4=B*D.

[0155] As shown in FIG6 , the buffer member 30 is projected onto the housing 10 , with a length dimension e in the second direction and a height dimension f in the first direction. The area of ​​the buffer member 30 projected onto the housing 10 is S3 , where S3 = e*f.

[0156] If S3 / S4 is too small, the portion of the buffer 30 covering the flat area 201 is too small. When the electrode assembly 20 expands, the electrode assembly 20 is still easily squeezed into the adjacent structure, thereby causing stress concentration problems. If S3 / S4 is too large, the buffer 30 is too large, and the buffer 30 is inconvenient to install in the battery cell 100. The buffer 30 occupies too much space and easily affects the exhaust space inside the battery cell 100.

[0157] Therefore, S3 / S4 is limited to between 0.3-1.1, and S3 / S4 can be any value among 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1 or any range between two values.

[0158] Therefore, the provision of the buffer member 30 can reduce the probability of stress concentration occurring when the electrode assembly 20 expands. At the same time, the buffer member 30 is easy to install and does not occupy too much space, thereby improving the reliability of the battery cell 100.

[0159] In some embodiments, 0.5≤S3 / S4≤0.9, and S3 / S4 can be any value among 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, or any range between any two values.

[0160] This can further reduce the probability of stress concentration occurring when the electrode assembly 20 expands. At the same time, the buffer member 30 is easy to install and does not occupy too much space, thereby improving the reliability of the battery cell 100.

[0161] In some embodiments, 0.6≤S3 / S4≤0.85, and S3 / S4 can be any value among 0.6, 0.66, 0.7, 0.76, 0.8, 0.85, or a range of values ​​between any two of them.

[0162] This can further reduce the probability of stress concentration occurring when the electrode assembly 20 expands. At the same time, the buffer member 30 is easy to install and does not occupy too much space, thereby improving the reliability of the battery cell 100.

[0163] As shown in FIG. 8 , in some embodiments, the buffer member 30 has a thickness H1 , where 0.5 mm ≤ H1 ≤ 10 mm.

[0164] If H1 is too large, the buffer component 30 occupies too much space, and the space occupied by the corresponding electrode assembly 20 is reduced, which will lead to a decrease in the volume energy density of the battery cell 100. If H1 is too small, the deformable space of the buffer component 30 is small. When the electrode assembly 20 expands, the winding end 20a squeezes the adjacent structure, which is likely to cause stress concentration.

[0165] The thickness H1 of the buffer member 30 is limited to between 0.5 and 10 mm. H1 can be any value among 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, and 10 mm, or a range of values ​​between any two of them.

[0166] In this way, the volume energy density of the battery cell 100 can be prevented from being excessively reduced, and the probability of stress concentration occurring when the electrode assembly 20 expands can be reduced, thereby improving the service life and reliability of the battery cell 100.

[0167] In some embodiments, 1≤H1≤2.5mm, and H1 can be any value among 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, 2mm, 2.1mm, 2.2mm, 2.3mm, 2.4mm, and 2.5mm, or any range therebetween. This can further prevent a transient decrease in the volumetric energy density of the battery cell 100, reduce the probability of stress concentration during expansion of the electrode assembly 20, and improve the service life and reliability of the battery cell 100.

[0168] In some embodiments, the compression rate of the buffer 30 at 1 MPa is L1, L1 ≥ 50%, preferably, L1 ≥ 60%.

[0169] When the compression rate of the buffer 30 is too small, the compressible amount of the buffer 30 is small, and it is difficult to absorb the deformation of the electrode assembly 20. At the same time, the expansion force of the electrode assembly 20 is easily applied to the adjacent structure, resulting in stress concentration. For this reason, the compression rate L1 of the buffer 30 at 1 MPa is greater than or equal to 50%. L1 can be 50%, or 60%, 70%, 80%, or 90%. In this way, the buffer 30 can be compressed and deformed as the electrode assembly 20 expands, and can absorb the expansion of the electrode assembly 20, thereby reducing the probability of stress concentration.

[0170] In some examples, L1 ≥ 60%, L1 can be 60%, 65%, 70%, 80%, or 90%. More preferably, L1 ≥ 80%, L1 can be 80%, 85%, 90%, or 95%. This allows the buffer 30 to compress and deform as the electrode assembly 20 expands, thereby absorbing the expansion of the electrode assembly 20 as much as possible and reducing the probability of stress concentration.

[0171] The compression rate test method of the buffer 30 is as follows:

[0172] 1) Take samples with a size of 46*50mm for testing, and perform two sets of parallel samples each time.

[0173] 2) Confirm that there is only an empty pad in the sample chamber and no sample, close the protective door, open the MISS software, and select the channel to be tested in the channel information; click back to the origin, reset the pressure, and reset the thickness.

[0174] 3) Place the sample in the sample chamber of the in-situ expansion analyzer so that the center of the sample and the center of the pad correspond to the centers of the two lasers. Close the protective door and fasten the explosion-proof buckle, making sure that the upper and lower pads are aligned. Enter the sample length and width values ​​in the MISS system and click Start Experiment to conduct the test.

[0175] 4) Perform compression testing at 0.5 mm / min and record the thickness change in real time until the recorded value reaches 1 MPa. The change in compressibility is obtained, and the compression rate of the sample can be obtained.

[0176] In some embodiments, the buffer member 30 is a porous material.

[0177] The porous material can be made through a foaming process. By using such a porous foam material, the compressibility of the buffer component 30 can be improved while reducing the manufacturing cost.

[0178] In some embodiments, the material of the buffer 30 includes at least one of polyvinyl chloride, polyethylene vinyl acetate, polyethylene, polypropylene, polyurethane, polymethylimide, polyimide, polystyrene, and modified silicone rubber.

[0179] By controlling the type of the main material of the buffer member 30 , the material is made to have good electrolyte corrosion resistance, compressibility, and resilience, thereby ensuring its reliability throughout the entire life cycle of the battery cell 100 .

[0180] The battery 1000 according to the embodiment of the second aspect of the present application includes the battery cell 100 according to the embodiment of the first aspect of the present application.

[0181] According to the third embodiment of the present application, the power device 2000 includes the battery 1000 according to the second embodiment of the present application, and the battery 1000 is used to provide power to the power device 2000. Therefore, by using the above-mentioned battery 1000, the safety and reliability of the power device 2000 are improved.

[0182] Optionally, as shown in FIG1 , when battery 1000 is used in a vehicle, it can be located at the bottom, front, or rear of the vehicle. Battery 1000 can be used to power the vehicle, for example, as an operating power source for the vehicle. The vehicle can also include a controller and a motor, with the controller controlling battery 1000 to power the motor, for example, to meet the vehicle's starting, navigation, and operating power requirements during driving.

[0183] A battery 1000 and a vehicle having the same according to a specific embodiment of the present application will be described below with reference to the accompanying drawings.

[0184] As shown in Figure 1, the battery 1000 is arranged at the bottom of the vehicle, and as shown in Figures 2 and 3, the battery 1000 includes a plurality of battery cells 100. As shown in Figures 7 and 8, the battery cell 100 includes a shell 10, an electrode assembly 20 and a buffer 30. The electrode assembly 20 and the buffer 30 are arranged in the shell 10. The electrode assembly 20 includes a wound pole piece 21 and an isolation film 22. The pole piece 21 and the isolation film 22 are stacked and wound around a winding axis to form an electrode assembly 20. After winding, the outermost side is the isolation film 22. In the winding direction, the end 221 of the isolation film 22 has a finishing glue 23. The finishing glue 23 includes a first glue segment 231 and a second glue segment 232. The first glue segment 231 covers the end 221 of the isolation membrane 22. The second glue segment 232 is located on one side of the first glue segment 231. The second glue segment 232 protrudes from the isolation membrane 22. Therefore, the finishing glue 23 can fix the electrode 21 and the isolation membrane 22, so that the overall structure of the electrode assembly 20 remains stable, reducing the probability of displacement and deformation, reducing wrinkling of the electrode 21, and reducing the probability of internal short circuit.

[0185] In the stacking direction of the pole piece 21 and the isolation film 22 (the front-to-back direction as shown in FIG. 8 ), the buffer member 30 covers the finishing glue 23 and the isolation film 22 .

[0186] The compression rate of the buffer 30 at 1 MPa is L1, L1 ≥ 50%, and the ratio of the compression rates of the buffer 30 and the finishing glue 23 at 1 MPa is L1 / L2, where 5≤L1 / L2≤30.

[0187] The thickness of the buffer member 30 is H1, 0.5 mm ≤ H1 ≤ 10 mm, and the thickness ratio of the buffer member 30 to the finishing glue 23 is H1 / H2, 10 ≤ H1 / H2 ≤ 100.

[0188] The ratio of the area of ​​the portion of the buffer 30 covering the finishing glue 23 to the area of ​​the finishing glue 23 is S1 / S2, and S1 / S2 is equal to 1.

[0189] The buffer member 30 can separate the finishing glue 23 and the isolation film 22 from the adjacent electrode assembly 20 or the outer shell 10. When the electrode assembly 20 expands, the buffer member 30 deforms, which to a certain extent alleviates the stress concentration problem caused by the protrusion of other parts due to the certain thickness of the finishing glue 23, so that the two parts with height difference are evenly stressed, thereby improving the service life and reliability of the battery cell 100.

[0190] In addition, when the battery cell 100 is charged and discharged, the buffer member 30 has a certain supporting effect on the electrode assembly 20, which can reduce deformation, thereby improving the wrinkling of the electrode sheet 21 caused by the expansion of the electrode assembly 20, thereby alleviating the problem of lithium or sodium precipitation during the cycle of the battery cell 100.

[0191] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A battery cell, characterized in that, Comprising: A housing; An electrode assembly disposed within the housing, the electrode assembly including electrode sheets and a separator membrane, the electrode sheets and the separator membrane being wound after being stacked to form the electrode assembly, and along the winding direction of the electrode assembly, the electrode assembly having a winding end; A buffer member disposed within the housing, and along the stacking direction of the electrode sheets and the separator membrane, the buffer member covering at least a portion of the winding end.

2. The battery cell according to claim 1, wherein Along the winding direction of the electrode assembly, the end of the electrode assembly has a finishing adhesive, and the end of the finishing adhesive along the winding direction forms the winding end.

3. The battery cell according to claim 2, wherein The finishing adhesive includes a first adhesive segment and a second adhesive segment, the first adhesive segment covering the end of the separator membrane or the end of the electrode sheet, the second adhesive segment being located on one side of the first adhesive segment, and the buffer member covering at least a portion of the second adhesive segment.

4. The battery cell according to claim 2 or 3, wherein The finishing adhesive includes a first adhesive segment and a second adhesive segment, the first adhesive segment covering the end of the separator membrane or the end of the electrode sheet, the second adhesive segment being located on one side of the first adhesive segment, and the buffer member covering at least a portion of the first adhesive segment.

5. The battery cell according to any one of claims 2-4, characterized in that, The electrode sheets and the separator membrane are wound around a winding axis, and along the extending direction of the winding axis, the finishing adhesive has a first end portion and a second end portion arranged oppositely, and the buffer member covers the first end portion and / or the second end portion.

6. The battery cell according to claim 5, characterized in that, Along the extending direction of the winding axis, the length dimension of the buffer member is not less than the length dimension of the finishing adhesive.

7. The battery cell according to any one of claims 2-6, characterized in that, The thickness ratio of the buffer member to the finishing adhesive is H1 / H2, 10 ≤ H1 / H2 ≤ 100, preferably, 10 ≤ H1 / H2 ≤ 20.

8. The battery cell according to any one of claims 2-7, characterized in that, The area ratio of the portion of the buffer member covering the finishing adhesive to the area of the finishing adhesive is S1 / S2, 0.1 ≤ S1 / S2 ≤ 1, preferably, 0.8 ≤ S1 / S2 ≤ 1.

9. The battery cell according to any one of claims 2-8, characterized in that, Along the stacking direction of the electrode sheets and the separator membrane, the buffer member covers at least a portion of the separator membrane and / or at least a portion of the electrode sheets.

10. The battery cell according to any one of claims 2-9, characterized in that, The compression ratio ratio of the buffer member to the finishing adhesive under 1 MPa is L1 / L2, wherein, 5 ≤ L1 / L2 ≤ 30, preferably, 10 ≤ L1 / L2 ≤ 20.

11. The battery cell according to any one of claims 1-10, characterized in that, Along the winding direction of the electrode assembly, the end of the separator membrane forms the winding end.

12. The battery cell according to claim 11, characterized in that, The compression ratio ratio of the buffer member to the separator membrane under 1 MPa is L1 / L3, wherein, 1 ≤ L1 / L3 ≤ 5, preferably, 2 ≤ L1 / L3 ≤ 3.

5.

13. The battery cell according to claim 10, characterized in that, The thickness ratio of the buffer member to the separator membrane is H1 / H3, 50 ≤ H1 / H3 ≤ 700.

14. The battery cell according to claim 13, wherein One side of the end of the separator membrane facing the center of the electrode assembly has an adhesive material.

15. The battery cell according to any one of claims 1 - 14, wherein Along the winding direction of the electrode assembly, the end of the electrode sheet forms the winding end.

16. The battery cell according to claim 15, wherein the electrode sheet has an electrode sheet thinning area, and the buffer member covers at least a part of the electrode sheet thinning area.

17. The battery cell according to any one of claims 1-16, wherein the electrode assembly includes a straight area and a turning area connected to an end of the straight area, and the buffer member is disposed opposite to at least one of the straight area and the turning area.

18. The battery cell according to claim 17, wherein the end of the electrode sheet is located in the straight area, and along the stacking direction of the electrode sheet and the separator, the buffer member covers the end of the electrode sheet.

19. The battery cell according to any one of claims 1-14, characterized in that, The electrode assembly includes a straight area and a turning area connected to an end of the straight area, the end of the electrode sheet is located in the turning area, and the buffer member is arranged in a staggered manner with respect to the end of the electrode sheet.

20. The battery cell according to any one of claims 1-19, characterized in that, The electrode assembly includes a straight area and a turning area connected to an end of the straight area, along the stacking direction of the buffer member and the electrode assembly, the area of the buffer member projected on the housing is S3, and the area of the positive electrode active material area of the straight area projected on the housing is S4, wherein 0.3 ≤ S3 / S4 ≤ 1.1, preferably, 0.5 ≤ S3 / S4 ≤ 0.

9.

21. The battery cell according to any one of claims 1-20, characterized in that, The thickness of the buffer member is H1, and 0.5 mm ≤ H1 ≤ 10 mm.

22. The battery cell according to any one of claims 1-21, characterized in that, The compression ratio of the buffer member under 1 MPa is L1, and L1 ≥ 50%, preferably, L1 ≥ 60%.

23. The battery cell according to any one of claims 1-22, characterized in that, The buffer member is a porous material member.

24. The battery cell according to any one of claims 1-23, characterized in that, The material of the buffer member includes at least one of polyvinyl chloride, ethylene-vinyl acetate, polyethylene, polypropylene, polyurethane, polymethylimide, polyimide, polystyrene, and modified silicone rubber.

25. A battery, characterized in that, including the battery cell according to any one of claims 1-24.

26. An electrical device, characterized in that, including the battery according to claim 25, the battery being used to provide electrical energy.

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