Battery cell, battery, and electric device

Abstract

The application discloses a battery monomer, a battery and a power utilization device. The battery monomer comprises a shell, an electrode assembly and a buffer. The electrode assembly is accommodated in the shell. The buffer is accommodated in the shell and is stacked with the electrode assembly along a first direction, and the first direction is parallel to a thickness direction of the battery monomer. The electrode assembly comprises a flat area and two bending areas, and the two bending areas are respectively located on both sides of the flat area along a third direction, and the third direction is perpendicular to the first direction. A part of the buffer overlaps the flat area in the first direction. In the third direction, at least one end of the buffer exceeds the flat area.

Description

[0001] This application is a divisional application based on application number 202210379965.0, filed on April 12, 2022, by CATL (Contemporary Amperex Technology Co., Limited), entitled "Battery Cells, Batteries and Electrical Devices". Technical Field

[0002] This application relates to the field of batteries, and in particular to a battery cell, a battery, and an electrical device. Background Technology

[0003] Battery cells are widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and power tools. Battery cells can include nickel-cadmium battery cells, nickel-metal hydride battery cells, lithium-ion battery cells, and rechargeable alkaline zinc-manganese battery cells, among others.

[0004] In the development of battery technology, improving the cycle performance of individual battery cells is an important research direction. Summary of the Invention

[0005] This application provides a battery cell, a battery, and an electrical device that can improve the cycle performance of the battery cell.

[0006] In a first aspect, this application provides a battery cell including a housing, an electrode assembly, and a buffer. The electrode assembly is housed within the housing. The buffer is housed within the housing and stacked with the electrode assembly along a first direction parallel to the thickness direction of the battery cell. The electrode assembly includes a flat region and two bent regions, respectively located on either side of the flat region along a third direction perpendicular to the first direction. A portion of the buffer overlaps with the flat region in the first direction. In the third direction, at least one end of the buffer extends beyond the flat region.

[0007] In the above technical solution, during the cycling process of a battery cell, the buffer is compressed when subjected to pressure from the electrode assembly to provide space for the expansion of the electrode assembly, reduce the force between the casing and the electrode assembly, and improve the cycling performance of the electrode assembly. At least one end of the buffer extends beyond the flat region so that the buffer can effectively absorb the expansion of the flat region and improve the cycling performance of the flat region.

[0008] In some implementations, in the third direction, both ends of the buffer extend beyond the flat region. The buffer can effectively absorb the expansion of the flat region, improving the circulation performance of the flat region.

[0009] In some implementations, in the third direction, the end of the bending area away from the straight area extends beyond the buffer.

[0010] Because the gap between the bending area of ​​the electrode assembly and the outer casing is relatively large, the expansion force generated in the bending area is small; correspondingly, the need for buffer components in the bending area is smaller. The above technical solution can reduce the amount of buffer components used, reduce the volume and weight occupied by the buffer components, and improve the energy density of the battery cell.

[0011] In some embodiments, the electrode assembly includes a first electrode plate, which includes a first body and a first tab extending from one end of the first body along a second direction perpendicular to the first direction. The buffer has a dimension H1 along the second direction; the first body has a first active material layer with a dimension H2 along the second direction. H1 and H2 satisfy: H1 ≥ 0.85·H2.

[0012] The main reason for the expansion of the electrode assembly is the expansion of the active material layer during charging. The above technical solution limits the value of H1 to greater than or equal to 0.85·H2, so that the expansion of more than 85% of the first active material layer in the second direction can be absorbed by the buffer, thereby reducing the pressure on the first active material layer and improving the cycle performance of the electrode assembly.

[0013] In some embodiments, the first active material layer includes a substrate region and a thinned region connected to the substrate region, the thickness of the thinned region being less than the thickness of the substrate region. In a second direction, the thinned region is located on the side of the substrate region closer to the first tab. In the second direction, both ends of the buffer extend beyond the substrate region.

[0014] Compared to the thinned area, the expansion force generated when the substrate expands is greater. Therefore, the above technical solution makes the two ends of the buffer extend beyond the substrate area along the second direction to effectively absorb the expansion of the substrate area and improve the cycle performance of the electrode assembly.

[0015] In some embodiments, the electrode assembly further includes a spacer, which is stacked with the first main body. The spacer has a dimension H3 along the second direction. H1 and H3 satisfy: H1 ≤ 1.1·H3. In the second direction, the portion of the buffer extending beyond the spacer will not absorb the expansion of the electrode assembly, but will instead increase the volume and weight of the buffer. The above technical solution makes the value of H1 less than or equal to 1.1·H3, so as to reduce the amount of buffer used and improve the energy density of the battery cell.

[0016] In some implementations, in the second direction, neither end of the buffer extends beyond the separator, thereby reducing the amount of buffer used, lowering the risk of interference between the buffer and other components, and increasing the energy density of the battery cell.

[0017] In some embodiments, the housing includes two first sidewalls disposed opposite each other along a first direction, the distance between the two first sidewalls along the first direction being D1. There are M electrode assemblies, and in the fully charged state, the sum of the dimensions of the M electrode assemblies along the first direction is D2, where M is a positive integer greater than 0. There are N buffers, and the N buffers are stacked with the M electrode assemblies along the first direction; the buffers are configured to be compressible, and in the uncompressed state, the sum of the dimensions of the N buffers along the first direction is D3, where N is a positive integer greater than 0. D1, D2, and D3 satisfy: 0.9 ≤ (D2 + D3) / D1 ≤ 1.5.

[0018] In the above technical solution, the buffer can, to a certain extent, limit the deformation of the electrode assembly during the initial charging of the battery cell, improve the uniformity of the force distribution on the electrode assembly, reduce the risk of wrinkling of the electrode plates, and extend the life of the electrode assembly. During the cycling process of the battery cell, the buffer is compressed when subjected to pressure from the electrode assembly, providing space for the expansion of the electrode assembly, reducing the force between the casing and the electrode assembly, and improving the cycle performance of the electrode assembly. The above technical solution limits the value of (D2+D3) / D1 to 0.9-1.5, which can reduce the risk of wrinkling of the electrode plates, save the amount of buffer used, increase the energy density of the battery cell, reduce the expansion force of the electrode assembly, and improve the cycle performance of the electrode assembly.

[0019] In some implementations, D1, D2, and D3 satisfy: 0.98 ≤ (D2 + D3) / D1 ≤ 1.25.

[0020] In some implementations, D2 and D3 satisfy: D3 ≤ 0.25·D2. The above technical solution can reduce the amount of buffer components, increase the energy density of individual battery cells, and improve the cycle performance of electrode assemblies.

[0021] In some embodiments, the dimension of the buffer in the third direction is L1, the dimension of the electrode assembly in the third direction when fully charged is L2, and the dimension of an electrode assembly in the first direction when fully charged is D4. L1, L2, and D4 satisfy: L1 ≥ 0.85(L2 - D4).

[0022] The above technical solution limits the value of L1 to greater than or equal to 0.85(L2-D4), so that the expansion of more than 85% of the flat area in the third direction can be absorbed by the buffer to ensure the circulation performance of the flat area.

[0023] In some embodiments, the housing includes two first sidewalls disposed opposite each other along a first direction. The area of ​​the buffer member projected onto the inner surface of the first sidewall along the first direction is S1, and the area of ​​the inner surface of the first sidewall is S2, wherein S1 and S2 satisfy: S1 ≤ 0.95·S2.

[0024] The above technical solution can reduce the overall amount of buffer components used, provide more space for other components inside the casing, and improve the energy density and service life of individual battery cells.

[0025] In some embodiments, the dimension of each buffer member in the uncompressed state along the first direction is D5, where D5 satisfies: 0.1mm≤D5≤10mm.

[0026] In some implementations, the compression ratio f of the buffer under a pressure of 2 MPa satisfies: 1% ≤ f ≤ 99%.

[0027] In some implementations, the buffer is attached to the electrode assembly. The buffer attached to the electrode assembly can be housed together with the electrode assembly to simplify the assembly process. The electrode assembly can also limit the movement of the buffer when the battery cell is subjected to external impact, thereby reducing the risk of buffer displacement.

[0028] In some embodiments, there are multiple electrode assemblies. A buffer is provided between at least two adjacent electrode assemblies. Placing the buffer between two adjacent electrode assemblies can reduce the risk of the buffer shaking when the battery cell is subjected to external impact.

[0029] In some implementations, the buffer is a flat plate structure. Flat plate structures are easy to mold and can improve the uniformity of force distribution on the electrode assembly when the electrode assembly expands.

[0030] In some embodiments, the buffer has a porous structure. The micropores in the buffer can be used to store electrolyte, and when the electrode assembly expands and squeezes the buffer, the electrolyte in the buffer can be squeezed out, thereby improving the wettability of the electrolyte.

[0031] Secondly, embodiments of this application provide a battery comprising a plurality of battery cells according to any of the embodiments of the first aspect.

[0032] Thirdly, embodiments of this application provide an electrical device that includes a battery cell according to any embodiment of the first aspect, the battery cell being used to provide electrical energy. Attached Figure Description

[0033] The features, advantages, and technical effects of exemplary embodiments of this application will now be described with reference to the accompanying drawings.

[0034] Figure 1 This application provides structural schematic diagrams of vehicles for some embodiments;

[0035] Figure 2 Explosion diagrams of batteries provided for some embodiments of this application;

[0036] Figure 3 for Figure 2An exploded view of the battery module shown.

[0037] Figure 4 This is an exploded schematic diagram of a battery cell provided in some embodiments of this application;

[0038] Figure 5 This is a schematic diagram of the structure of a battery cell provided in some embodiments of this application;

[0039] Figure 6 This is a cross-sectional schematic diagram of the electrode assembly of a battery cell provided in some embodiments of this application;

[0040] Figure 7 A cross-sectional schematic diagram of a battery cell provided in some embodiments of this application;

[0041] Figure 8 A partial cross-sectional schematic diagram of the electrode assembly and buffer of a battery cell provided in some embodiments of this application;

[0042] Figure 9 This is a schematic diagram of the structure of a battery cell provided in some other embodiments of this application;

[0043] Figure 10 This is a schematic diagram of the structure of a battery cell provided in some embodiments of this application;

[0044] Figure 11 This is a schematic diagram of the structure of a battery cell provided in some embodiments of this application;

[0045] Figure 12 A schematic flowchart illustrating a method for manufacturing a single battery cell according to some embodiments of this application;

[0046] Figure 13 A schematic block diagram of a battery cell manufacturing system provided for some embodiments of this application;

[0047] Figure 14 The diagram shows the structure of a single battery cell provided in some embodiments of this application.

[0048] The reference numerals in the accompanying drawings for the specific embodiments are as follows:

[0049] 1. Vehicle; 2. Battery; 3. Controller; 4. Motor; 5. Housing; 5a. First housing section; 5b. Second housing section; 5c. Storage space; 6. Battery module; 7. Battery cell;

[0050] 10. Electrode assembly; 11. First electrode; 111. First body; 112. First active material layer; 112a. Substrate region; 112b. Thinned region; 12. Second electrode; 13. Spacer; 14. Body portion; 15. First tab; 16. Second tab; 10a. Straight region; 10b. Bending region;

[0051] 20. Outer shell; 21. Housing; 211. First sidewall; 212. Second sidewall; 22. End cap;

[0052] 30. Buffer component; 40. Electrode terminal;

[0053] 90. Manufacturing system; 91. First supply device; 92. Second supply device; 93. Assembly device;

[0054] X, first direction; Y, second direction; Z, third direction. Detailed Implementation

[0055] 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 described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort 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 meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the description of this application is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms "comprising" and "having," and any variations thereof, in the description, claims, and accompanying drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the description, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or hierarchy.

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

[0058] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "attachment" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0059] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

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

[0061] In this application, "multiple" means two or more (including two).

[0062] In this application, the battery cell may include a lithium-ion secondary battery cell, a lithium-ion primary battery cell, a lithium-sulfur battery cell, a sodium-lithium-ion battery cell, a sodium-ion battery cell, or a magnesium-ion battery cell, etc., and the embodiments of this application are not limited thereto. The battery cell may be cylindrical, flat, cuboid, or other shapes, etc., and the embodiments of this application are not limited thereto.

[0063] The battery mentioned in the embodiments of this application refers to a single physical module comprising one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in this application may include a battery module or a battery pack. A battery generally includes a housing for encapsulating one or more battery cells. The housing prevents liquids or other foreign matter from affecting the charging or discharging of the battery cells.

[0064] A single battery cell includes electrode components and an electrolyte. The electrode components include a positive electrode, a negative electrode, and a separator. The battery cell primarily functions by the movement of metal ions between the positive and negative electrodes. The positive electrode includes a positive current collector and a positive active material layer, which is coated on the surface of the positive current collector. The positive current collector includes a positive electrode coating area and a positive electrode tab connected to the coating area. The coating area is coated with the positive active material layer, while the tab is not. Taking a lithium-ion battery cell as an example, the positive current collector can be made of aluminum, and the positive active material layer includes the positive active material, which can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc. The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer being coated on the surface of the negative electrode current collector. The negative electrode current collector includes a negative electrode coating area and a negative electrode tab connected to the negative electrode coating area. The negative electrode coating area is coated with the negative electrode active material layer, while the negative electrode tab is not coated with the negative electrode active material layer. The material of the negative electrode current collector can be copper, and the negative electrode active material layer includes negative electrode active material, which can be carbon or silicon, etc. The material of the separator can be PP (polypropylene) or PE (polyethylene), etc.

[0065] The battery cell also includes a casing, inside which a cavity is formed to house the electrode assembly. The casing protects the electrode assembly from external contaminants to prevent them from being affected by external objects during charging or discharging.

[0066] During charging, the electrode assembly expands; the expanding electrode assembly compresses the outer casing, and correspondingly, the outer casing exerts a reaction force on the electrode assembly to limit its expansion. If the force between the electrode assembly and the outer casing is too large, the electrolyte between the electrodes may be forced out, affecting the cycle performance of the electrode assembly.

[0067] The inventors attempted to incorporate a gap between the electrode assembly and the housing. This gap allows space for the expansion of the electrode assembly, thereby reducing the interaction force between the housing and the electrode assembly and improving its cycle performance. However, the inventors discovered that during the initial charging of the electrode assembly, the presence of this gap results in the electrode assembly being less constrained by the housing, leading to poor uniformity of stress and increasing the risk of electrode wrinkling. If wrinkling occurs, metal ion deposition may occur during subsequent cycles, reducing the cycle life of the electrode assembly and potentially causing it to fail.

[0068] In view of this, the inventors incorporated a buffer component within the casing. This buffer component can, to some extent, limit the deformation of the electrode assembly during the initial charging of the battery cell, improve the uniformity of stress distribution on the electrode assembly, reduce the risk of wrinkling of the electrode plates, and extend the lifespan of the electrode assembly. During the cycling process of the battery cell, the buffer component compresses under the pressure of the electrode assembly, providing space for the expansion of the electrode assembly, reducing the interaction force between the casing and the electrode assembly, and improving the cycle performance of the electrode assembly. Through calculation and experimentation, the inventors determined the size of the buffer component based on the dimensions of the electrode assembly and the casing to improve the cycle performance of the electrode assembly.

[0069] The battery cells described in the embodiments of this application are applicable to batteries and electrical devices that use battery cells.

[0070] Electrical devices can include vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and power tools, etc. Vehicles can be gasoline-powered cars, natural gas-powered cars, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose any special limitations on the above-mentioned electrical devices.

[0071] For ease of explanation, the following embodiments will use a vehicle as an example of an electrical device.

[0072] Figure 1 The diagram shows the structural features of a vehicle provided in some embodiments of this application.

[0073] like Figure 1 As shown, a battery 2 is installed inside the vehicle 1. The battery 2 can be located at the bottom, front, or rear of the vehicle 1. The battery 2 can be used to power the vehicle 1; for example, the battery 2 can serve as the operating power source for the vehicle 1.

[0074] Vehicle 1 may also include controller 3 and motor 4. Controller 3 is used to control battery 2 to supply power to motor 4, for example, for the power needs of vehicle 1 during start-up, navigation and driving.

[0075] In some embodiments of this application, the battery 2 can not only serve as the operating power source for the vehicle 1, but also as the driving power source for the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

[0076] Figure 2This is an exploded schematic diagram of a battery provided for some embodiments of this application.

[0077] like Figure 2 As shown, battery 2 includes a housing 5 and battery cells (not shown), with the battery cells housed within the housing 5.

[0078] The housing 5 is used to house individual battery cells, and the housing 5 can have various structures. In some embodiments, the housing 5 may include a first housing portion 5a and a second housing portion 5b, which overlap each other, and together define a housing space 5c for housing the individual battery cells. The second housing portion 5b may be a hollow structure with one end open, and the first housing portion 5a may be a plate-like structure, with the first housing portion 5a covering the open side of the second housing portion 5b to form a housing 5 with the housing space 5c; alternatively, both the first housing portion 5a and the second housing portion 5b may be hollow structures with one side open, with the open side of the first housing portion 5a covering the open side of the second housing portion 5b to form a housing 5 with the housing space 5c. Of course, the first housing portion 5a and the second housing portion 5b can have various shapes, such as cylinders, cuboids, etc.

[0079] To improve the sealing performance after the first housing part 5a and the second housing part 5b are connected, a sealing element, such as sealant or sealing ring, can also be provided between the first housing part 5a and the second housing part 5b.

[0080] Assuming that the first box section 5a covers the top of the second box section 5b, the first box section 5a can also be called the upper box cover, and the second box section 5b can also be called the lower box.

[0081] In battery 2, there can be one or more individual battery cells. If there are multiple individual battery cells, they can be connected in series, parallel, or in a mixed configuration. A mixed configuration means that multiple individual battery cells are connected in both series and parallel configurations. Multiple individual battery cells can be directly connected in series, parallel, or in a mixed configuration and then housed within housing 5. Alternatively, multiple individual battery cells can first be connected in series, parallel, or in a mixed configuration to form battery module 6, and then multiple battery modules 6 can be connected in series, parallel, or in a mixed configuration to form a whole and housed within housing 5.

[0082] Figure 3 for Figure 2 The diagram shows an exploded view of the battery module.

[0083] In some embodiments, such as Figure 3 As shown, there are multiple battery cells 7, which are first connected in series, parallel, or a combination of both to form a battery module 6. These battery modules 6 are then connected in series, parallel, or a combination of both to form a whole, which is housed within the casing.

[0084] Multiple battery cells 7 in battery module 6 can be electrically connected through a busbar component to achieve parallel, series, or mixed connection of multiple battery cells 7 in battery module 6.

[0085] Figure 4 This is an exploded schematic diagram of a battery cell provided in some embodiments of this application; Figure 5 This is a schematic diagram of the structure of a battery cell provided in some embodiments of this application, wherein the end cap is omitted; Figure 6 This is a cross-sectional schematic diagram of the electrode assembly of a battery cell provided in some embodiments of this application.

[0086] like Figures 4 to 6 As shown, the battery cell 7 in this embodiment includes a housing 20, electrode assemblies 10, and buffer members 30. The housing 20 includes two first sidewalls 211 disposed opposite each other along a first direction X, with a distance D1 between the two first sidewalls 211 along the first direction X. M electrode assemblies 10 are provided, housed within the housing 20. In a fully charged state, the sum of the dimensions of the M electrode assemblies 10 along the first direction X is D2, where M is a positive integer greater than 0. N buffer members 30 are provided, housed within the housing 20, and stacked with the M electrode assemblies 10 along the first direction X. The buffer members 30 are configured to be compressible, with the sum of the dimensions of the N buffer members 30 along the first direction X in an uncompressed state being D3, where N is a positive integer greater than 0. D1, D2, and D3 satisfy: 0.9 ≤ (D2 + D3) / D1 ≤ 1.5.

[0087] The outer shell 20 is a hollow structure, with an internal cavity for accommodating the electrode assembly 10 and the electrolyte. The outer shell 20 can be of various shapes, such as a cuboid. The shape of the outer shell 20 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 is a cuboid structure, a cuboid outer shell can be selected.

[0088] This embodiment does not limit the material of the outer shell 20. For example, the outer shell 20 can be made of rigid materials such as aluminum, steel, or plastic, or it can be made of aluminum-plastic film, steel-plastic film, or other soft materials.

[0089] Two first sidewalls 211 are located on opposite sides of the receiving cavity along the first direction X. For example, the dimension of the receiving cavity along the first direction X is D1.

[0090] The value of D1 can be measured in a variety of ways. For example, D1 can be measured using vernier calipers or by microscopic marking such as mechanical cross-section / surface analysis.

[0091] The electrode assembly 10 includes a first electrode 11 and a second electrode 12. The electrode assembly 10 mainly operates by the movement of metal ions between the first electrode 11 and the second electrode 12. Exemplarily, the electrode assembly 10 also includes a spacer 13 for insulating and isolating the first electrode 11 and the second electrode 12.

[0092] The polarity of the first electrode 11 is opposite to that of the second electrode 12. Specifically, one of the first electrode 11 and the second electrode 12 is a positive electrode, and the other is a negative electrode.

[0093] M is a positive integer greater than 0, meaning that there can be one or more electrode components 10. When there are multiple electrode components 10, they can be stacked along the first direction X.

[0094] When fully charged, the electrode assembly 10 will expand. For example, after the battery cell 7 is manufactured, it is charged at a rate of 0.33C at room temperature until fully charged. After the battery cell 7 is fully charged, it is disassembled, and the dimension D4 of each electrode assembly 10 along the first direction X is measured using calipers when fully charged.

[0095] When only one electrode assembly 10 is provided inside the battery cell 7, the value of D2 is equal to D4. When multiple electrode assemblies 10 are provided inside the battery cell 7, the value of D2 is equal to the sum of the dimensions D4 of the multiple electrode assemblies 10 along the first direction X.

[0096] When multiple electrode assemblies 10 are provided, the dimensions D4 of different electrode assemblies 10 along the first direction X can be the same or different.

[0097] N is a positive integer greater than 0, meaning that there can be one or more buffers 30.

[0098] N buffer components 30 and M electrode assemblies 10 are stacked along the first direction X. The embodiments of this application do not limit the stacking order of the buffer components 30 and the electrode assemblies 10 along the first direction X.

[0099] In some examples, there is one buffer 30 and multiple electrode assemblies 10. Multiple electrode assemblies 10 can be sequentially arranged along a first direction X to form an electrode unit, and the buffer 30 can be disposed on one side of the electrode unit along the first direction X. Alternatively, the buffer 30 can also be disposed between two adjacent electrode assemblies 10.

[0100] In other examples, there are multiple buffer elements 30 and one electrode assembly 10. Multiple buffer elements 30 can be sequentially arranged along a first direction X to form a buffer unit, and the electrode assembly 10 can be disposed on one side of the buffer unit along the first direction X. Alternatively, the electrode assembly 10 can also be disposed between two adjacent buffer elements 30.

[0101] In some other examples, there are multiple buffer elements 30 and multiple electrode assemblies 10. The stacking order of the multiple buffer elements 30 and multiple electrode assemblies 10 along the first direction X can be freely set according to requirements. For example, each buffer element 30 can be adjacent to an electrode assembly 10 or to another buffer element 30.

[0102] The buffer 30 can be compressed when it is squeezed by the electrode assembly 10, so as to provide space for the expansion of the electrode assembly 10 and reduce the force between the first sidewall 211 and the electrode assembly 10.

[0103] For example, the buffer 30 has a certain elastic deformation capability. When the electrode assembly 10 is fully charged, the buffer 30 can be compressed by the electrode assembly 10. When the electrode assembly 10 is fully discharged, the buffer 30 can recover at least part of its deformation to ensure that the buffer 30 can resist the electrode assembly 10, improve the uniformity of the force distribution of the electrode assembly 10, and reduce the risk of wrinkles on the electrode sheet of the electrode assembly 10.

[0104] This application does not limit the specific material of the buffer member 30, but it needs to have a certain ability to deform and be able to recover at least part of its deformation when the external force is removed. For example, when it is necessary to measure the dimension of each buffer member 30 in the uncompressed state along the first direction X, the battery cell 7 can be disassembled and the buffer member 30 removed, and then the dimension D5 of each buffer member 30 in the uncompressed state along the first direction X can be measured using vernier calipers. Alternatively, during the manufacturing process of the battery cell 7, the dimension D5 of the buffer member 30 in the uncompressed state along the first direction X can be measured before the buffer member 30 is inserted into the casing.

[0105] When only one buffer element 30 is provided inside the battery cell 7, the value of D3 is equal to the value of D5. When multiple buffer elements 30 are provided inside the battery cell 7, the value of D3 is equal to the sum of the dimensions D5 of the multiple buffer elements 30 along the first direction X.

[0106] When multiple buffers 30 are provided, the dimensions D5 of different buffers 30 along the first direction X in the uncompressed state can be the same or different.

[0107] The shape of the buffer 30 is not limited in this embodiment; it can be plate-shaped, block-shaped, or other irregular shapes.

[0108] The buffer 30 can limit the deformation of the electrode assembly 10 to a certain extent during the initial charging of the battery cell 7, improve the uniformity of the force distribution on the electrode assembly 10, reduce the risk of wrinkling of the electrode sheets of the electrode assembly 10, and extend the life of the electrode assembly 10. During the cycling process of the battery cell 7, the buffer 30 is compressed when squeezed by the electrode assembly 10, providing space for the expansion of the electrode assembly 10, reducing the interaction force between the outer casing 20 and the electrode assembly 10, and improving the cycle performance of the electrode assembly 10.

[0109] The smaller the value of (D2+D3) / D1, the lower the utilization rate of the internal space of the casing 20, the less binding force the electrode assembly 10 experiences from the first sidewall 211 during charging, and the higher the risk of wrinkles appearing on the electrode sheets of the electrode assembly 10. Although the buffer 30 can limit the deformation of the electrode assembly 10 to some extent during the initial charging of the battery cell 7, if the value of (D2+D3) / D1 is too small, the buffer 30 may not be able to effectively limit the wrinkles of the electrode sheets. In view of this, the inventors made (D2+D3) / D1 greater than or equal to 0.9 to improve space utilization and effectively reduce the risk of wrinkles appearing on the electrode sheets.

[0110] The larger the value of (D2+D3) / D1, the better the buffer 30 can limit the deformation of the electrode assembly 10 during the initial charging of the battery cell 7. However, a larger value of (D2+D3) / D1 also means a larger space and weight occupied by the buffer 30, and a greater compression of the buffer 30 during the cycling process of the battery cell 7. If the value of (D2+D3) / D1 is too large, it may result in a smaller compressibility of the buffer 30 after it is installed in the casing, leading to insufficient absorption of expansion and excessive expansion force of the electrode assembly 10. Therefore, the inventors have made (D2+D3) / D1 less than or equal to 1.5 to save on the amount of buffer 30 used, increase the energy density of the battery cell 7, reduce the expansion force of the electrode assembly 10, and improve the cycle performance of the electrode assembly 10.

[0111] Optionally, the value of (D2+D3) / D1 can be 0.9, 0.95, 0.98, 1, 1.1, 1.2, 1.25, 1.3, 1.4 or 1.5.

[0112] In some embodiments, D1, D2, and D3 satisfy: 0.98 ≤ (D2 + D3) / D1 ≤ 1.25.

[0113] In some embodiments, the electrode assembly 10 includes a main body 14 and a first tab 15 and a second tab 16 extending from the main body 14. The main body 14 includes a positive electrode coating region, a positive electrode active material layer, a negative electrode coating region, a negative electrode active material layer, and a separator 13. One of the first tab 15 and the second tab 16 is a positive tab, and the other is a negative tab.

[0114] In this application, when fully charged, the dimension of the main body 14 along the first direction X is D4.

[0115] In some embodiments, the housing 20 includes a housing 21 and an end cap 22, the housing 21 having an opening and the end cap 22 closing the opening. Exemplarily, the housing 21 includes two first sidewalls 211.

[0116] The housing 21 may have an opening on one side, and the end cap 22 may be one that covers the opening of the housing 21. Alternatively, the housing 21 may have an opening on both sides, and the end caps 22 may be two, with the two end caps 22 respectively covering the two openings of the housing 21.

[0117] For example, the end cap 22 is attached to the housing 21 by welding, bonding, snap-fitting or other means.

[0118] In some embodiments, the first sidewall 211 is a flat plate structure.

[0119] In some embodiments, the housing 21 has an opening at one end along the second direction Y. Optionally, the first direction X is perpendicular to the second direction Y.

[0120] In some embodiments, the housing 21 includes two second sidewalls 212, which are disposed opposite each other along a third direction Z. Optionally, the third direction Z is perpendicular to the first direction X and the second direction Y.

[0121] Two first sidewalls 211 and two second sidewalls 212 are alternately arranged along the circumference of the opening. The two ends of the first sidewalls 211 along the third direction Z are respectively connected to the two second sidewalls 212.

[0122] In some embodiments, adjacent first sidewalls 211 and second sidewalls 212 are connected by an arcuate wall.

[0123] In some embodiments, the value of D1 can be measured by the following method: measuring the dimension D6 of the housing 21 along the first direction X using a vernier caliper; measuring the wall thickness D7 of the first sidewall 211 using a vernier caliper; D1 = D6 - 2·D7.

[0124] During the cycling process of the battery cell 7, the first sidewall 211 may deform due to the expansion of the electrode assembly 10. Since the deformation at the end of the first sidewall 211 near the second sidewall 212 is smaller, the vernier caliper can clamp the ends of the two first sidewalls 211 near the second sidewall 212 and take the measured value as D6.

[0125] In some embodiments, the battery cell 7 further includes two electrode terminals 40, which may be disposed on the end cap 22. One electrode terminal 40 is used to electrically connect to the first electrode 11 of the electrode assembly 10, and the other electrode terminal 40 is used to electrically connect to the second electrode 12, so as to lead the electrical energy generated by the electrode assembly 10 out of the housing 20.

[0126] In some embodiments, the buffer 30 may be a porous structure. The micropores in the buffer 30 can be used to store electrolyte, which can be squeezed out when the electrode assembly 10 expands and compresses the buffer 30.

[0127] In some embodiments, the cushioning element 30 may be made of foam.

[0128] In some embodiments, the first direction X is parallel to the thickness direction of the battery cell 7. In the battery, multiple battery cells 7 can be stacked along the first direction X.

[0129] In some embodiments, D2 and D3 satisfy: D3≤0.25·D2.

[0130] With a fixed value for D2, the larger the value of D3, the larger the volume and weight of the buffer 30, and the lower the gravimetric energy density of the battery cell 7. The inventors discovered that when the value of D3 exceeds a certain range, the effect of the buffer 30 in improving the cycle performance of the electrode assembly 10 does not further increase with the increase of D3. Through experiments, the inventors found that limiting the value of D3 to less than or equal to 0.25·D2 can reduce the amount of buffer 30 used, increase the energy density of the battery cell 7, and improve the cycle performance of the electrode assembly 10.

[0131] In some embodiments, the buffer 30 is a flat plate structure. The flat plate structure is easy to form and can improve the uniformity of the force distribution on the electrode assembly 10 when the electrode assembly 10 expands.

[0132] In some embodiments, the buffer 30 may be rectangular, circular, elliptical, or otherwise shaped. Optionally, the buffer 30 may be a rectangular plate.

[0133] In some embodiments, the buffer 30 is attached to the electrode assembly 10.

[0134] Attachment refers to the cushioning member 30 being attached to and connected to the surface of the electrode assembly 10. For example, the cushioning member 30 can be bonded to the electrode assembly 10 with an adhesive.

[0135] The buffer 30 attached to the electrode assembly 10 can be installed together with the electrode assembly 10 into the housing 21 to simplify the assembly process. The electrode assembly 10 can also limit the shaking of the buffer 30 when the battery cell 7 is subjected to external impact, thereby reducing the risk of the buffer 30 shifting.

[0136] In some embodiments, the compression ratio f of the buffer 30 under a pressure of 2 MPa satisfies: 1% ≤ f ≤ 99%. Optionally, the compression ratio f of the buffer 30 under a pressure of 2 MPa satisfies: 40% ≤ f ≤ 99%.

[0137] In some embodiments, the electrode assembly 10 includes a straight region 10a and two bent regions 10b, which are located on opposite sides of the straight region 10a along a third direction Z, which is perpendicular to the first direction X. The buffer 30 has a dimension L1 along the third direction Z, the electrode assembly 10 has a dimension L2 along the third direction Z when fully charged, and the electrode assembly 10 has a dimension D4 along the first direction X when fully charged. L1, L2, and D4 satisfy: L1 ≥ 0.85(L2 - D4).

[0138] The flat region 10a is a region of the electrode assembly 10 with a flat structure, and the portion of the electrode sheet located in the flat region 10a is generally flat. The bending region 10b is a region of the electrode assembly 10 with a bending structure, and the portion of the electrode sheet located in the bending region 10b is generally bent. For example, the portion of the electrode sheet located in the bending region 10b is generally bent into an arc shape.

[0139] In the fully charged state, the dimension of the bending region 10b along the third direction Z is approximately half of D4, and L2-D4 is approximately the dimension of the straight region 10a along the third direction Z.

[0140] Because the gap between the bending region 10b of the electrode assembly 10 and the first sidewall 211 is relatively large, the expansion force generated by the bending region 10b is relatively small. Conversely, the gap between the straight region 10a of the electrode assembly 10 and the first sidewall 211 is relatively small, resulting in a larger expansion force generated by the straight region 10a. In this embodiment, the value of L1 is limited to greater than or equal to 0.85(L2-D4), ensuring that the expansion of more than 85% of the straight region 10a in the third direction Z can be absorbed by the buffer 30, thereby guaranteeing the cycle performance of the straight region 10a.

[0141] In some embodiments, in the third direction Z, the two ends of the buffer 30 extend beyond the flat region 10a. The buffer 30 can effectively absorb the expansion of the flat region 10a and improve the cycling performance of the flat region 10a.

[0142] In some embodiments, L1 and L2 satisfy: L1 ≤ 1.1·L2. In the third direction Z, the portion of the buffer 30 exceeding the electrode assembly 10 will not absorb the expansion of the electrode assembly 10, but will instead increase the volume and weight of the buffer 30. This embodiment makes the value of L1 less than or equal to 1.1·L2 to reduce the amount of buffer 30 used and increase the energy density of the battery cell 7.

[0143] In some embodiments, the area of ​​the projection of the buffer 30 onto the inner surface of the first sidewall 211 along the first direction X is S1, and the area of ​​the inner surface of the first sidewall 211 is S2. S1 and S2 satisfy: S1≤0.95·S2.

[0144] The inner surface of the first sidewall 211 will compress the electrode assembly 10 when it expands, thus limiting the expansion and deformation of the electrode assembly 10. In addition to housing the electrode assembly 10, the housing 20 also needs to accommodate other functional components, so a portion of the inner surface of the first sidewall 211 will not compress the electrode assembly 10. In this embodiment, S1 ≤ 0.95·S2, thereby reducing the overall amount of buffer 30 used, providing more space for other components within the housing 20, and improving the energy density and lifespan of the battery cell 7.

[0145] In some embodiments, the dimension of each buffer 30 in the uncompressed state along the first direction X is D5, where D5 satisfies: 0.1mm ≤ D5 ≤ 10mm. Optionally, the value of D5 is 0.1mm, 0.5mm, 1mm, 2mm, 4mm, 5mm, 8mm, or 10mm.

[0146] If D5 is too small, more buffers 30 need to be placed inside the battery cell 7 to meet the requirements, resulting in a complex structure and low assembly efficiency for the battery cell 7. Therefore, in this embodiment, the value of D5 is limited to greater than or equal to 0.1 mm.

[0147] If D5 is too large, the weight of the buffer 30 will be too large, and the space it occupies will be too large, resulting in a lower energy density of the battery cell 7. Therefore, in this embodiment, the value of D5 is limited to less than or equal to 10 mm.

[0148] In some embodiments, D5 satisfies: 0.5mm≤D5≤4mm.

[0149] Figure 7 A cross-sectional schematic diagram of a battery cell provided in some embodiments of this application; Figure 8 This is a partial cross-sectional schematic diagram of the electrode assembly and buffer of a battery cell provided in some embodiments of this application.

[0150] like Figure 7 and Figure 8 As shown, in some embodiments, the electrode assembly 10 includes a first electrode 11, which includes a first body 111 and a first tab 15 extending from one end of the first body 111 along a second direction Y, where the second direction Y is perpendicular to the first direction X. The buffer 30 has a dimension H1 along the second direction Y; the first body 111 is provided with a first active material layer 112, which has a dimension H2 along the second direction Y. H1 and H2 satisfy: H1 ≥ 0.85·H2.

[0151] The main reason for the expansion of the electrode assembly 10 is the expansion of the active material layer during charging. In this embodiment, the value of H1 is limited to be greater than or equal to 0.85·H2, so that the expansion of more than 85% of the region of the first active material layer 112 in the second direction Y can be absorbed by the buffer 30, thereby reducing the pressure on the first active material layer 112 and improving the cycle performance of the electrode assembly 10.

[0152] The first electrode 11 can be either a positive electrode or a negative electrode. For example, the first electrode 11 is a negative electrode, and the first active material layer 112 is a negative active material layer. The first body 111 also includes a negative electrode coating region for a negative current collector.

[0153] In some embodiments, the first active material layer 112 includes a substrate region 112a and a thinned region 112b connected to the substrate region 112a, wherein the thickness of the thinned region 112b is less than the thickness of the substrate region 112a. In the second direction Y, the thinned region 112b is located on the side of the substrate region 112a closest to the first tab 15. In the second direction Y, both ends of the buffer member 30 extend beyond the substrate region 112a.

[0154] During the forming process of the first electrode 11, the first active material layer 112 needs to be rolled to increase the compaction density of the first active material layer 112. In this embodiment, the thickness of the thinning region 112b is reduced to reduce stress concentration at the junction of the first body 111 and the first electrode tab 15 during the rolling process, thereby reducing the risk of cracking of the first electrode tab 15.

[0155] Compared to the thinned region 112b, the expansion force generated when the substrate region 112a expands is greater. Therefore, in this embodiment, the buffer member 30 extends beyond the substrate region 112a at both ends along the second direction Y to effectively absorb the expansion of the substrate region 112a and improve the cycle performance of the electrode assembly 10.

[0156] In some embodiments, the electrode assembly 10 further includes a spacer 13, which is stacked on top of the first body 111. The spacer 13 has a dimension H3 along the second direction Y; H1 and H3 satisfy: H1≤1.1·H3.

[0157] The insulating element 13 is used to insulate and isolate the first body 111 from the second electrode 12.

[0158] In the second direction Y, the portion of the separator 13 extending beyond the separator 13 will not absorb the expansion of the electrode assembly 10, but will instead increase the volume and weight of the buffer 30. In this embodiment, the value of H1 is less than or equal to 1.1·H3 to reduce the amount of buffer 30 used and increase the energy density of the battery cell 7.

[0159] In some embodiments, in the second direction Y, neither end of the buffer 30 extends beyond the separator 13, so as to reduce the amount of buffer 30 used, reduce the risk of interference between the buffer 30 and other components, and improve the energy density of the battery cell 7.

[0160] Figure 9 The diagram shows the structure of a battery cell provided in some other embodiments of this application.

[0161] like Figure 9 As shown, in some embodiments, there are multiple electrode assemblies 10. A buffer 30 is provided between at least two adjacent electrode assemblies 10.

[0162] By placing the buffer 30 between two adjacent electrode assemblies 10, the risk of the buffer 30 shaking can be reduced when the battery cell 7 is subjected to external impact.

[0163] Figure 10 This is a schematic diagram of the structure of a battery cell provided in some embodiments of this application. For example... Figure 10 As shown, in some embodiments, there are multiple electrode assemblies 10 and multiple buffers 30.

[0164] For example, there are two electrode assemblies 10 and two buffer members 30. The two electrode assemblies 10 are arranged adjacently to form an electrode unit, and the two buffer members 30 are respectively located on both sides of the electrode unit along the first direction X.

[0165] Figure 11 This is a schematic diagram of the structure of a battery cell provided in some embodiments of this application. For example... Figure 11 As shown, in some embodiments, there are four electrode assemblies 10 and two buffer members 30. The four electrode assemblies 10 are arranged adjacently to form an electrode unit, and the two buffer members 30 are respectively located on both sides of the electrode unit along the first direction X.

[0166] According to some embodiments of this application, this application also provides a battery comprising a plurality of battery cells provided in any of the above embodiments.

[0167] According to some embodiments of this application, this application also provides an electrical device, which includes a battery cell provided in any of the above embodiments, the battery cell being used to provide electrical energy to the electrical device.

[0168] According to some embodiments of this application, refer to Figure 10The battery cell 7 in this embodiment includes a housing 20, two electrode assemblies 10, and two buffer members 30. The housing 20 includes two first sidewalls 211 disposed opposite each other along a first direction X, with a distance D1 between the two first sidewalls 211 along the first direction X. The two electrode assemblies 10 are housed within the housing 20, and in a fully charged state, the sum of the dimensions of the two electrode assemblies 10 along the first direction X is D2. The two electrode assemblies 10 constitute an electrode unit, and the two buffer members 30 are respectively located on both sides of the electrode unit along the first direction X. The buffer members 30 are configured to be compressible, and each buffer member 30 in its uncompressed state has a dimension D5 along the first direction X, and the sum of the dimensions of the two buffer members 30 in their uncompressed state along the first direction X is D3. D1, D2, and D3 satisfy: 0.9 ≤ (D2 + D3) / D1 ≤ 1.5.

[0169] Figure 12 This is a schematic flowchart illustrating a method for manufacturing a battery cell according to some embodiments of this application.

[0170] like Figure 12 As shown in the figure, this application provides a method for manufacturing a single battery cell, which includes:

[0171] S100, providing a housing, the housing including two first sidewalls disposed opposite to each other along a first direction;

[0172] S200, provides electrode assemblies and buffer components;

[0173] S300, Install the electrode assembly and buffer into the housing.

[0174] The distance between the two first sidewalls along the first direction is D1. There are M electrode assemblies, where M is a positive integer greater than 0. In the fully charged state, the sum of the dimensions of the M electrode assemblies along the first direction is D2. There are N buffers, where N is a positive integer greater than 0; the N buffers are stacked with the M electrode assemblies along the first direction. The buffers are configured to be compressible, and the sum of the dimensions of the N buffers in the uncompressed state along the first direction is D3. D1, D2, and D3 satisfy: 0.9 ≤ (D2 + D3) / D1 ≤ 1.5.

[0175] It should be noted that the relevant structure of the battery cell manufactured by the above-described battery cell manufacturing method can be found in the battery cells provided in the above embodiments.

[0176] When manufacturing a battery cell based on the above-described method, the steps do not necessarily need to be performed sequentially. That is, the steps can be performed in the order mentioned in the embodiments, or in a different order, or several steps can be performed simultaneously. For example, steps S100 and S200 can be performed concurrently without any order.

[0177] Figure 13 This is a schematic block diagram of a battery cell manufacturing system provided for some embodiments of this application.

[0178] like Figure 13 As shown, this application embodiment provides a battery cell manufacturing system 90, which includes a first providing device 91, a second providing device 92, and an assembly device 93. The first providing device 91 provides a housing, the housing including two first sidewalls disposed opposite each other along a first direction. The second providing device 92 provides electrode assemblies and buffers. The assembly device 93 installs the electrode assemblies and buffers into the housing. The distance between the two first sidewalls along the first direction is D1. There are M electrode assemblies, where M is a positive integer greater than 0. In a fully charged state, the sum of the dimensions of the M electrode assemblies along the first direction is D2. There are N buffers, where N is a positive integer greater than 0; the N buffers are stacked with the M electrode assemblies along the first direction. The buffers are configured to be compressible, and the sum of the dimensions of the N buffers in an uncompressed state along the first direction is D3. D1, D2, and D3 satisfy: 0.9 ≤ (D2 + D3) / D1 ≤ 1.5.

[0179] The present application is further illustrated below with reference to the embodiments.

[0180] To make the inventive purpose, technical solution, and beneficial technical effects of this application clearer, the following describes this application in further detail with reference to embodiments. However, it should be understood that the embodiments of this application are merely for explaining this application and are not intended to limit this application, and the embodiments of this application are not limited to the embodiments given in the specification. Unless otherwise specified, specific experimental or operating conditions in the embodiments are prepared under conventional conditions or according to the conditions recommended by the material supplier.

[0181] Example 1 can be prepared according to the following steps:

[0182] (i) The positive electrode active material NCM523, the conductive agent acetylene black, and the binder PVDF are mixed at a mass ratio of 96:2:2. The solvent NMP is added and the mixture is stirred under vacuum until the system is homogeneous to obtain the positive electrode slurry. The positive electrode slurry is uniformly coated on aluminum foil, dried at room temperature, and then transferred to an oven for further drying. The positive electrode sheet is then obtained by cold pressing, slitting, and cutting.

[0183] (ii) The negative electrode active material graphite or a mixture of graphite and other active materials in different mass ratios, the conductive agent acetylene black, the thickener CMC, and the binder SBR are mixed in a mass ratio of 96.4:1:1.2:1.4. Deionized water is added as a solvent, and the mixture is stirred in a vacuum mixer until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on copper foil, dried at room temperature, and then transferred to an oven for further drying. After cold pressing, slitting, and cutting, the negative electrode sheet is obtained.

[0184] (iii) Ethyl carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 is dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0185] (iv) Use a 12μm thick polypropylene film as a separator.

[0186] (v) The positive electrode, the separator and the negative electrode are stacked together and wound into multiple turns, and then flattened into a flat shape to prepare the electrode assembly.

[0187] (VI) The two electrode assemblies and two buffer components are stacked and installed into the housing. Then the end caps and housing are welded together, and the battery cell is obtained through processes such as liquid injection, settling, formation and shaping.

[0188] In step (VI), as Figure 14 As shown, two buffer members 30 and two electrode assemblies 10 are stacked along the first direction X. The housing 21 includes two first sidewalls 211 disposed opposite each other along the first direction X. Using calipers, the distance D1 between the two first sidewalls 211 along the first direction X is measured to be 27 mm. Before the buffer members 30 are installed into the housing 21, the thickness D5 of the buffer members 30 is measured to be 0.45 mm using calipers; correspondingly, the sum of the dimensions of the two buffer members 30 in the compressed state along the first direction X is D3, and D3 is 0.9 mm.

[0189] Two battery cells 7 were prepared according to the above preparation steps, and interface detection and cycle performance testing were performed on them respectively.

[0190] Interface testing:

[0191] Under normal temperature conditions, a single battery cell 7 is charged at a rate of 0.33C until fully charged. After the battery cell 7 is fully charged, it is disassembled, and the dimensions of each electrode assembly 10 along the first direction X are measured using vernier calipers under full charge conditions. After completing the dimensional measurements, the electrode assembly 10 is further disassembled, and the interface state of the negative electrode is observed.

[0192] After measurement and calculation, the sum of the dimensions D2 of the two electrode assemblies 10 along the first direction X is 25.6 mm.

[0193] Cyclic performance testing:

[0194] Another battery cell 7 is fixed to the clamp, which clamps the two first sidewalls 211 of the battery cell 7 from both sides and applies a clamping force of 3000N to the first sidewalls 211. The clamp is equipped with a pressure sensor to detect the pressure F between the first sidewalls 211 and the clamp in real time.

[0195] Under normal temperature conditions, battery cell 7 was charged at a 1C rate and discharged at a 1C rate to perform a full charge and discharge cycle test until the capacity of battery cell 7 decreased to 90% of its initial capacity.

[0196] During the cycling process, the status of the battery cell 7 is monitored in real time. When the capacity of the battery cell 7 decreases to 90% of its initial capacity, the number of cycles of the battery cell 7 is recorded, and the increase in the expansion force of the battery cell 7, ΔF, is calculated, where ΔF = F - 3000N.

[0197] For example, the clamp includes two clamping plates that clamp the battery cell 7 from both sides and are respectively opposite to two first sidewalls 211. A buffer pad may be provided between the clamping plates and the corresponding first sidewalls 211.

[0198] Example 2: The preparation and testing methods of the battery cell in Example 2 are the same as those in Example 1, except that D3 is 1.4 mm.

[0199] Example 3: The preparation and testing methods of the battery cell in Example 3 are the same as those in Example 1, except that D3 is 4.1 mm.

[0200] Example 4: The preparation and testing methods of the battery cell in Example 4 are the same as those in Example 1, except that D3 is 8.15mm.

[0201] Example 5: The preparation and testing methods of the battery cell in Example 5 are the same as those in Example 1, except that D3 is 12.2 mm.

[0202] Example 6: The preparation and testing methods of the battery cell in Example 6 are the same as those in Example 1, except that D3 is 14.9 mm.

[0203] Example 7: The preparation and testing methods of the battery cell in Example 7 are the same as those in Example 1, except that D3 is 0.7 mm and D2 is 23.6 mm.

[0204] Example 8: The preparation and testing methods of the battery cell in Example 8 are the same as those in Example 1, except that D3 is 2.1 mm and D2 is 23.6 mm.

[0205] Comparative Example 1: The preparation and testing methods of the battery cell in Comparative Example 1 are the same as those in Example 1, except that D2 is 24.3 mm and there is no buffer inside Comparative Example 1 (i.e., D3 is 0).

[0206] Comparative Example 2: The preparation and testing methods of the battery cell of Comparative Example 1 are the same as those of Example 1, except that D2 is 25.6 mm and there is no buffer inside Comparative Example 1 (i.e., D3 is 0).

[0207] Comparative Example 3: The preparation and testing methods of the battery cell of Comparative Example 1 are the same as those of Example 1, except that D2 is 26.4 mm and there is no buffer inside Comparative Example 1 (i.e., D3 is 0).

[0208] Comparative Example 4: The preparation and testing methods of the battery cells in Comparative Example 4 are the same as those in Example 1, except that D3 is 0.6 mm and D2 is 21 mm.

[0209] Comparative Example 5: The preparation and testing methods of the battery cell in Comparative Example 5 are the same as those in Example 1, except that D3 is 17.6 mm.

[0210] The evaluation results of Examples 1-8 and Comparative Examples 1-5 are shown in Table 1.

[0211] Table 1

[0212]

[0213] It should be noted that, along the axial direction of the electrode assembly winding, if the ratio of the size of the fold to the size of the electrode sheet is less than 5%, it is considered as no folds; if the ratio of the size of the fold to the size of the electrode sheet is 5%-30%, it is considered as slight folds; and if the ratio of the size of the fold to the size of the electrode sheet is greater than 30%, it is considered as severe folds.

[0214] Referring to Examples 1-8 and Comparative Examples 1-3, the embodiments of this application, by setting a buffer, can reduce the risk of the electrode sheet wrinkling during the first charging of the battery cell, reduce the expansion force generated by the battery cell during cycling, extend the number of cycles of the battery cell, and improve the cycle performance of the battery cell.

[0215] Referring to Examples 1-8 and Comparative Examples 4-5, the embodiments of this application limit the value of (D2+D3) / D1 to between 0.9 and 1.5, which can reduce the risk of the electrode sheet wrinkling during the first charging of the battery cell, reduce the expansion force generated by the battery cell during the cycle, extend the number of cycles of the battery cell, and improve the cycle performance of the battery cell.

[0216] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, characterized in that, include: shell; An electrode assembly is housed within the housing. The electrode assembly includes a first electrode, a second electrode, and a separator, wherein the separator is used to insulate and isolate the first electrode and the second electrode. A buffer element is housed within the outer casing and stacked with the electrode assembly along a first direction parallel to the thickness direction of the battery cell. The buffer element has a porous structure. In the second direction, neither end of the buffer extends beyond the isolator, and the size of the buffer is smaller than the size of the isolator; the electrode assembly includes a straight region and two bent regions, the two bent regions being located on both sides of the straight region along a third direction, the third direction, the second direction, and the first direction being perpendicular to each other; a portion of the buffer overlaps with the straight region in the first direction; In the third direction, at least one end of the buffer extends beyond the flat area.

2. The battery cell according to claim 1, characterized in that, In the third direction, both ends of the buffer extend beyond the flat area.

3. The battery cell according to claim 1 or 2, characterized in that, In the third direction, the end of the bending area away from the straight area extends beyond the buffer.

4. The battery cell according to claim 1, characterized in that, The electrode assembly includes a first electrode plate, the first electrode plate including a first body and a first electrode tab extending from one end of the first body along the second direction; The buffer has a dimension of H1 along the second direction; the first body is provided with a first active material layer, and the dimension of the first active material layer along the second direction is H2; H1 and H2 satisfy: H1≥0.85•H2.

5. The battery cell according to claim 4, characterized in that, The first active material layer includes a matrix region and a thinned region connected to the matrix region, wherein the thickness of the thinned region is less than the thickness of the matrix region; In the second direction, the thinned area is located on the side of the substrate region closer to the first tab; In the second direction, both ends of the buffer extend beyond the base region.

6. The battery cell according to claim 1, characterized in that, The outer shell includes two first sidewalls disposed opposite each other along the first direction, and the distance between the two first sidewalls along the first direction is D1; The number of electrode assemblies is M. In the fully charged state, the sum of the dimensions of the M electrode assemblies along the first direction is D2, where M is a positive integer greater than 0. There are N buffer elements, and the N buffer elements are stacked with M electrode assemblies along the first direction; the buffer elements are configured to be compressible, and the sum of the dimensions of the N buffer elements along the first direction in the uncompressed state is D3, where N is a positive integer greater than 0; Among them, D1, D2 and D3 satisfy: 0.9≤(D2+D3) / D1≤1.

5.

7. The battery cell according to claim 6, characterized in that, D1, D2, and D3 satisfy: 0.98 ≤ (D2 + D3) / D1 ≤ 1.

25.

8. The battery cell according to claim 7, characterized in that, D2 and D3 satisfy: D3≤0.25•D2.

9. The battery cell according to claim 1, characterized in that, The buffer has a dimension of L1 in the third direction, the electrode assembly has a dimension of L2 in the third direction when fully charged, and the electrode assembly has a dimension of D4 in the first direction when fully charged. L1, L2, and D4 satisfy: L1 ≥ 0.85 (L2 - D4).

10. The battery cell according to claim 1, characterized in that, The outer casing includes two first sidewalls disposed opposite to each other along the first direction; The area of ​​the buffer component projected onto the inner surface of the first sidewall along the first direction is S1, and the area of ​​the inner surface of the first sidewall is S2. S1 and S2 satisfy: S1≤0.95•S2.

11. The battery cell according to claim 1, characterized in that, The dimension of each buffer member in the first direction when it is not compressed is D5, and D5 satisfies: 0.1mm≤D5≤10mm.

12. The battery cell according to claim 1, characterized in that, The compression ratio f of the buffer under a pressure of 2 MPa satisfies: 1% ≤ f ≤ 99%.

13. The battery cell according to claim 1, characterized in that, The buffer is attached to the electrode assembly.

14. The battery cell according to claim 1, characterized in that, The electrode assembly comprises multiple components; The buffer is provided between at least two adjacent electrode assemblies.

15. The battery cell according to claim 1, characterized in that, The buffer component has a flat plate structure.

16. A battery, characterized in that, It includes multiple battery cells according to any one of claims 1-15.

17. An electrical appliance, characterized in that, Includes a battery cell according to any one of claims 1-15, the battery cell being used to provide electrical energy.

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