Battery cell, battery and electric device

Abstract

The invention discloses a battery monomer, a battery and a power utilization device. A battery cell includes a housing, an electrode assembly, and a buffer. The electrode assembly is housed within the housing. The electrode assembly comprises a first pole piece and a second pole piece, and the polarity of the first pole piece is opposite to that of the second pole piece. The first pole piece comprises a first main body and a first tab led out from the first main body, the first main body is provided with a first active substance layer, the first active substance layer comprises a base body area and a thinned area connected to the base body area, the thinned area is located on one side of the base body area, and the thickness of the thinned area is smaller than that of the base body area. The buffer is accommodated in the case and stacked with the electrode assembly in a first direction parallel to a thickness direction of the battery cells. In the first direction, a portion of the base region overlaps the buffer. The buffer part exceeds the base body area in the direction from the base body area to the thinned area.

Description

[0001] This application is a divisional application based on the application number 202210379965.0, the application date April 12, 2022, the applicant is Contemporary Amperex Technology Co., Ltd., and the application name is "Battery Cells, Batteries and Electrical Devices". Technical Field

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

[0003] Battery cells are widely used in electronic devices, such as mobile phones, laptop computers, electric vehicles, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and electric tools, etc. Battery cells can include nickel-cadmium battery cells, nickel-hydrogen battery cells, lithium-ion battery cells, and secondary alkaline zinc-manganese battery cells, etc.

[0004] In the development of battery technology, how to improve the cycle performance of battery cells is an important research direction in battery technology. Summary of the invention

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

[0006] In a first aspect, the present application provides a battery cell, which includes a housing, an electrode assembly and a buffer. The electrode assembly is accommodated in the housing. The electrode assembly includes a first pole piece and a second pole piece, and the first pole piece and the second pole piece have opposite polarities. The first pole piece includes a first main body and a first pole ear led out from the first main body, and the first main body is provided with a first active material layer, and the first active material layer includes a substrate area and a thinning area connected to the substrate area, and the thinning area is located on one side of the substrate area, and the thickness of the thinning area is less than the thickness of the substrate area. The buffer is accommodated in the housing and is stacked with the electrode assembly along a first direction, and the first direction is parallel to the thickness direction of the battery cell. In the first direction, a portion of the substrate area overlaps with the buffer; in the direction from the substrate area to the thinning area, the buffer exceeds the substrate area.

[0007] In the above technical solution, the buffer can limit the deformation of the electrode assembly to a certain extent when the battery cell is charged for the first time, improve the uniformity of the force distribution of the electrode assembly, reduce the risk of wrinkles on the electrode sheet of the electrode assembly, and extend the life of the electrode assembly. During the cycle of the battery cell, the buffer is compressed when squeezed by the electrode assembly to provide space for the expansion of the electrode assembly, reduce the force between the shell and the electrode assembly, and improve the cycle performance of the electrode assembly. The expansion force generated when the substrate area expands is large, so that the buffer exceeds the substrate area, which can effectively absorb the expansion of the substrate area and improve the cycle performance of the electrode assembly.

[0008] In some embodiments, the thinned region is located on one side of the base region along a second direction, and the second direction is perpendicular to the first direction.

[0009] In some embodiments, the first electrode tab is led out from one end of the first body along a second direction, and the second direction is perpendicular to the first direction. In the second direction, the thinned region is located on a side of the base region close to the first electrode tab.

[0010] In some embodiments, both ends of the buffer member extend beyond the substrate region in the second direction. Both ends of the buffer member extend beyond the substrate region in the second direction. Compared with the thinned region, the expansion force generated when the substrate region expands is greater. Therefore, the above technical solution enables both ends of the buffer member along the second direction to extend beyond the substrate region, so as to effectively absorb the expansion of the substrate region and improve the cycle performance of the electrode assembly.

[0011] In some embodiments, the thinned area is located on one side of the substrate area along the second direction, and the second direction is perpendicular to the first direction. The size of the buffer along the second direction is H1, and the size of the first active material layer along the second direction is H2. 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 be greater than or equal to 0.85·H2, so that the expansion of more than 85% of the area 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 housing includes two first side walls arranged opposite to each other along a first direction, and the spacing between the two first side walls along the first direction is D1. There are M electrode assemblies, and in a fully charged state, the sum of the dimensions of the M electrode assemblies along the first direction is D2, and 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 the sum of the dimensions of the N buffers along the first direction in an uncompressed state is D3, and N is a positive integer greater than 0. D1, D2, and D3 satisfy: 0.9≤(D2+D3) / D1≤1.5.

[0014] The above technical solution limits the value of (D2+D3) / D1 to 0.9-1.5, which can reduce the risk of wrinkles on the pole piece, save the amount of buffer components, 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.

[0015] In some embodiments, D1, D2, and D3 satisfy: 0.98≤(D2+D3) / D1≤1.25.

[0016] In some embodiments, D2 and D3 satisfy: D3≤0.25·D2. The above technical solution can reduce the amount of buffer components, increase the energy density of the battery cell, and improve the cycle performance of the electrode assembly.

[0017] In some embodiments, the electrode assembly further includes a separator, which is used to insulate and isolate the first pole piece from the second pole piece. The separator is stacked with the first body. The first pole ear is led out from one end of the first body along the second direction, and the second direction is perpendicular to the first direction. The size of the buffer along the second direction is H1, and the size of the separator along the second direction is H3. H1 and H3 satisfy: H1≤1.1·H3.

[0018] In the second direction, the portion of the separator that exceeds the separator will not absorb the expansion of the electrode assembly, but will 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 the buffer and improve the energy density of the battery cell.

[0019] In some embodiments, in the second direction, both ends of the buffer do not extend beyond the isolation member, so as to reduce the amount of the buffer, reduce the risk of interference between the buffer and other components, and improve the energy density of the battery cell.

[0020] In some embodiments, the electrode assembly includes a straight region and two bending regions, the two bending regions are respectively located on both sides of the straight region along a third direction, and the third direction is perpendicular to the first direction. A portion of the buffer overlaps the straight region in the first direction; in the third direction, at least one end of the buffer exceeds the straight region, so that the buffer can effectively absorb the expansion of the straight region and improve the cycle performance of the straight region.

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

[0022] Since the gap between the bending area of ​​the electrode assembly and the first side wall is large, the expansion force generated in the bending area is small. The gap between the straight area of ​​the electrode assembly and the first side wall is small, so the expansion force generated in the straight area is large. The above technical solution limits the value of L1 to be greater than or equal to 0.85 (L2-D4), so that the expansion of more than 85% of the area of ​​the straight area in the third direction can be absorbed by the buffer to ensure the cycle performance of the straight area.

[0023] In some embodiments, L1 and L2 satisfy: L1≤1.1·L2.

[0024] In some embodiments, in the third direction, both ends of the buffer member extend beyond the straight region. The buffer member can effectively absorb the expansion of the straight region and improve the cycle performance of the straight region.

[0025] In some embodiments, in the third direction, the end of the bending area away from the straight area exceeds the buffer. Since the gap between the bending area of ​​the electrode assembly and the shell is large, the expansion force generated by the bending area is small; correspondingly, the bending area has a small demand for the buffer. The above technical solution can reduce the amount of buffer, reduce the volume and weight occupied by the buffer, and improve the energy density of the battery cell.

[0026] In some embodiments, the housing includes two first side walls arranged opposite to each other along a first direction. The area of ​​the projection of the buffer on the inner surface of the first side wall along the first direction is S1, and the area of ​​the inner surface of the first side wall is S2, and S1 and S2 satisfy: S1≤0.95·S2. The above technical solution can reduce the overall usage of the buffer, provide more space for other components in the housing, and improve the energy density and service life of the battery cell.

[0027] In some embodiments, a dimension of each buffer member along the first direction in an uncompressed state is D5, and D5 satisfies: 0.1 mm≤D5≤10 mm.

[0028] In some embodiments, the compression rate f of the buffer under a pressure of 2 MPa satisfies: 1%≤f≤99%.

[0029] In some embodiments, the buffer is attached to the electrode assembly. The buffer attached to the electrode assembly can be installed in the housing together with the electrode assembly to simplify the assembly process. The electrode assembly can also limit the shaking of the buffer when the battery cell is subjected to external impact to reduce the risk of the buffer shifting.

[0030] In some embodiments, there are multiple electrode assemblies. A buffer is provided between at least two adjacent electrode assemblies. The buffer is provided between two adjacent electrode assemblies to reduce the risk of the buffer shaking when the battery cell is subjected to external impact.

[0031] In some embodiments, the buffer is a flat plate structure, which is easy to shape and can improve the uniformity of force distribution of the electrode assembly when the electrode assembly expands.

[0032] In some embodiments, the buffer is a porous structure. The micropores in the buffer can be used to store electrolyte, and when the electrode assembly expands and presses the buffer, the electrolyte in the buffer can be squeezed out, thereby improving the wettability of the electrolyte.

[0033] In a second aspect, an embodiment of the present application provides a battery comprising a plurality of battery cells according to any embodiment of the first aspect.

[0034] In a third aspect, an embodiment of the present application provides an electrical device, which includes a battery cell according to any embodiment of the first aspect, and the battery cell is used to provide electrical energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The features, advantages and technical effects of exemplary embodiments of the present application will be described below with reference to the accompanying drawings.

[0036] Figure 1 A schematic diagram of the structure of a vehicle provided in some embodiments of the present application;

[0037] Figure 2 An exploded schematic diagram of a battery provided in some embodiments of the present application;

[0038] Figure 3 for Figure 2 An exploded schematic diagram of a battery module is shown;

[0039] Figure 4 An exploded schematic diagram of a battery cell provided in some embodiments of the present application;

[0040] Figure 5 A schematic diagram of the structure of a battery cell provided in some embodiments of the present application;

[0041] Figure 6 A schematic cross-sectional view of an electrode assembly of a battery cell provided in some embodiments of the present application;

[0042] Figure 7 A schematic cross-sectional view of a battery cell provided in some embodiments of the present application;

[0043] Figure 8 A partial cross-sectional schematic diagram of an electrode assembly and a buffer member of a battery cell provided in some embodiments of the present application;

[0044] Fig. 9 A schematic diagram of the structure of a battery cell provided in some other embodiments of the present application;

[0045] Fig.10 A schematic diagram of the structure of a battery cell provided in some other embodiments of the present application;

[0046] Fig.11 A schematic diagram of the structure of a battery cell provided in some other embodiments of the present application;

[0047] Fig.12 A schematic diagram of a process for manufacturing a battery cell provided in some embodiments of the present application;

[0048] Fig.13 A schematic block diagram of a battery cell manufacturing system provided for some embodiments of the present application;

[0049] Fig.14 A schematic diagram of the structure of a battery cell provided in some embodiments of the present application.

[0050] The reference numerals of the specific embodiments are as follows:

[0051] 1. Vehicle; 2. Battery; 3. Controller; 4. Motor; 5. Box; 5a. First box portion; 5b. Second box portion; 5c. Accommodation space; 6. Battery module; 7. Battery cell;

[0052] 10. electrode assembly; 11. first pole piece; 111. first main body; 112. first active material layer; 112a. substrate area; 112b. thinning area; 12. second pole piece; 13. separator; 14. main body; 15. first pole ear; 16. second pole ear; 10a. straight area; 10b. bending area;

[0053] 20. housing; 21. shell; 211. first side wall; 212. second side wall; 22. end cover;

[0054] 30. Buffer; 40. Electrode terminal;

[0055] 90. Manufacturing system; 91. First providing device; 92. Second providing device; 93. Assembling device;

[0056] X, first direction; Y, second direction; Z, third direction. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0058] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by technicians in the technical field of this application; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned drawings and any variations thereof 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 and secondary relationship.

[0059] Reference to "embodiment" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiment may be included in at least one embodiment of the present application. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments.

[0060] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "attached" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0061] The term "and / or" in this application is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this application generally indicates that the associated objects before and after are in an "or" relationship.

[0062] In the embodiments of the present application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width and other dimensions of various components in the embodiments of the present application shown in the drawings, as well as the overall thickness, length, width and other dimensions of the integrated device are only exemplary descriptions and should not constitute any limitation to the present application.

[0063] The term "plurality" used in the present application refers to two or more (including two).

[0064] In the present 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 the present application do not limit this. The battery cell may be cylindrical, flat, rectangular or other shapes, etc., and the embodiments of the present application do not limit this.

[0065] The battery mentioned in the embodiments of the present application refers to a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in the present application may include a battery module or a battery pack. The battery generally includes a box for encapsulating one or more battery cells. The box can prevent liquid or other foreign matter from affecting the charging or discharging of the battery cells.

[0066] A battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separator. A 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 current collector and a positive active material layer. The positive active material layer is coated on the surface of the positive current collector. The positive current collector includes a positive coating area and a positive electrode ear connected to the positive coating area. The positive coating area is coated with a positive active material layer, and the positive electrode ear is not coated with a positive active material layer. Taking a lithium-ion battery cell as an example, the material of the positive current collector can be aluminum, and the positive active material layer includes a positive active material. The positive active material 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, and the negative electrode active material layer is 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 a negative electrode active material layer, and the negative electrode tab is not coated with a negative electrode active material layer. The material of the negative electrode current collector can be copper, and the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material can be carbon or silicon, etc. The material of the separator can be PP (polypropylene) or PE (polyethylene), etc.

[0067] The battery cell further includes a housing, and a housing is formed inside the housing to accommodate the electrode assembly. The housing can protect the electrode assembly from the outside to prevent external foreign matter from affecting the charging or discharging of the electrode assembly.

[0068] During the charging process, the electrode assembly will expand; the expanded electrode assembly will squeeze the outer shell, and correspondingly, the outer shell will exert a reaction force on the electrode assembly to limit the expansion of the electrode assembly. If the force between the electrode assembly and the outer shell is too large, the electrolyte between the pole pieces may be squeezed out, affecting the cycle performance of the electrode assembly.

[0069] The inventors tried to set a gap between the electrode assembly and the shell, which can reserve space for the expansion of the electrode assembly, thereby reducing the force between the shell and the electrode assembly and improving the cycle performance of the electrode assembly. However, the inventors found that when the electrode assembly was first charged, due to the existence of the gap, the electrode assembly was not restrained by the shell or the restraining force of the shell was small, resulting in poor force uniformity of the electrode assembly and the risk of wrinkling the pole piece. If the pole piece is wrinkled, then in the subsequent cycle process, metal ions may precipitate from the pole piece, reducing the cycle life of the electrode assembly and even causing the electrode assembly to fail.

[0070] In view of this, the inventors set a buffer inside the shell, which can limit the deformation of the electrode assembly to a certain extent when the battery cell is charged for the first time, improve the uniformity of the force distribution of the electrode assembly, reduce the risk of wrinkles on the electrode sheet of the electrode assembly, and extend the life of the electrode assembly. During the cycle of the battery cell, the buffer is compressed when squeezed by the electrode assembly to provide space for the expansion of the electrode assembly, reduce the force between the shell and the electrode assembly, and improve the cycle performance of the electrode assembly. After calculation and experiment, the inventors set the size of the buffer according to the size of the electrode assembly and the size of the shell to improve the cycle performance of the electrode assembly.

[0071] The battery cells described in the embodiments of the present application are suitable for use in batteries and electrical devices using the battery cells.

[0072] The electrical device may be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, an electric tool, and the like. The vehicle may be a fuel vehicle, a gas vehicle, or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle, or an extended-range vehicle, and the like; the spacecraft may include an airplane, a rocket, a space shuttle, and a spacecraft, and the like; the electric toy may include a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy, and an electric airplane toy, and the like; the electric tool may include a metal cutting electric tool, a grinding electric tool, an assembly electric tool, and an electric tool for railways, 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, and the like. The embodiments of the present application do not impose any special restrictions on the above-mentioned electrical devices.

[0073] For the convenience of description, the following embodiments are described by taking the electric device as a vehicle as an example.

[0074] Figure 1 A schematic diagram of the structure of a vehicle provided for some embodiments of the present application.

[0075] like Figure 1 As shown, a battery 2 is disposed inside the vehicle 1, and the battery 2 may be disposed at the bottom, head, or tail of the vehicle 1. The battery 2 may be used to power the vehicle 1, for example, the battery 2 may be used as an operating power source for the vehicle 1.

[0076] The vehicle 1 may further include a controller 3 and a motor 4 , wherein the controller 3 is used to control the battery 2 to supply power to the motor 4 , for example, to meet the power requirements of starting, navigating, and driving the vehicle 1 .

[0077] In some embodiments of the present application, the battery 2 can not only serve as an operating power source for the vehicle 1, but also serve as a driving power source for the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

[0078] Figure 2An exploded schematic diagram of a battery provided for some embodiments of the present application.

[0079] like Figure 2 As shown, the battery 2 includes a housing 5 and a battery cell (not shown), and the battery cell is accommodated in the housing 5 .

[0080] The box 5 is used to accommodate the battery cells, and the box 5 can be of various structures. In some embodiments, the box 5 can include a first box portion 5a and a second box portion 5b, the first box portion 5a and the second box portion 5b cover each other, and the first box portion 5a and the second box portion 5b jointly define a storage space 5c for accommodating the battery cells. The second box portion 5b can be a hollow structure with one end open, the first box portion 5a is a plate-like structure, and the first box portion 5a covers the open side of the second box portion 5b to form a box 5 with a storage space 5c; the first box portion 5a and the second box portion 5b can also be hollow structures with one side open, and the open side of the first box portion 5a covers the open side of the second box portion 5b to form a box 5 with a storage space 5c. Of course, the first box portion 5a and the second box portion 5b can be of various shapes, such as a cylinder, a cuboid, etc.

[0081] In order to improve the sealing performance after the first box body part 5a and the second box body part 5b are connected, a sealing member, such as a sealant, a sealing ring, etc., may also be provided between the first box body part 5a and the second box body part 5b.

[0082] Assuming that the first box body portion 5a covers the top of the second box body portion 5b, the first box body portion 5a can also be called an upper box cover, and the second box body portion 5b can also be called a lower box.

[0083] In the battery 2, there can be one or more battery cells. If there are multiple battery cells, the multiple battery cells can be connected in series, in parallel, or in mixed connection. Mixed connection means that the multiple battery cells are both connected in series and in parallel. The multiple battery cells can be directly connected in series, in parallel, or in mixed connection, and then the whole formed by the multiple battery cells is accommodated in the box 5; of course, multiple battery cells can also be connected in series, in parallel, or in mixed connection to form a battery module 6, and the multiple battery modules 6 are then connected in series, in parallel, or in mixed connection to form a whole, and accommodated in the box 5.

[0084] Figure 3 for Figure 2 An exploded schematic diagram of the battery module is shown.

[0085] In some embodiments, Figure 3 As shown, there are multiple battery cells 7, and the multiple battery cells 7 are first connected in series, in parallel, or in mixed connection to form a battery module 6. The multiple battery modules 6 are then connected in series, in parallel, or in mixed connection to form a whole, and are accommodated in a box.

[0086] The multiple battery cells 7 in the battery module 6 can be electrically connected through a busbar component to achieve parallel connection, series connection or mixed connection of the multiple battery cells 7 in the battery module 6 .

[0087] Figure 4 An exploded schematic diagram of a battery cell provided in some embodiments of the present application; Figure 5 A schematic diagram of the structure of a battery cell provided in some embodiments of the present application, wherein the end cover is omitted; Figure 6 A schematic cross-sectional view of an electrode assembly of a battery cell provided in some embodiments of the present application.

[0088] like Figures 4 to 6 As shown, the battery cell 7 of the embodiment of the present application includes a shell 20, an electrode assembly 10 and a buffer 30. The shell 20 includes two first side walls 211 arranged opposite to each other along a first direction X, and the spacing between the two first side walls 211 along the first direction X is D1. The electrode assemblies 10 are provided in M ​​numbers, and the M electrode assemblies 10 are accommodated in the shell 20. In the fully charged state, the sum of the dimensions of the M electrode assemblies 10 along the first direction X is D2, and M is a positive integer greater than 0. The buffer 30 is provided in N numbers, and the N buffers 30 are accommodated in the shell 20 and stacked with the M electrode assemblies 10 along the first direction X. The buffer 30 is configured to be compressible, and the sum of the dimensions of the N buffers 30 along the first direction X in an uncompressed state is D3, and N is a positive integer greater than 0. D1, D2 and D3 satisfy: 0.9≤(D2+D3) / D1≤1.5.

[0089] The housing 20 is a hollow structure, and a cavity for accommodating the electrode assembly 10 and the electrolyte is formed therein. The housing 20 can be in various shapes, such as a rectangular parallelepiped. The shape of the housing 20 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 is a rectangular parallelepiped structure, a rectangular housing can be selected.

[0090] This embodiment does not limit the material of the housing 20. For example, the housing 20 can be made of hard materials such as aluminum, steel, and plastic, or can be made of aluminum-plastic film, steel-plastic film, or other soft materials.

[0091] The two first side walls 211 are respectively located at two sides of the accommodation cavity along the first direction X. Exemplarily, the size of the accommodation cavity along the first direction X is D1.

[0092] The value of D1 can be measured in a variety of ways. For example, the value of D1 can be measured using a vernier caliper, or by microscopic point measurement such as mechanical section / surface analysis.

[0093] The electrode assembly 10 includes a first electrode piece 11 and a second electrode piece 12. The electrode assembly 10 mainly works by the movement of metal ions between the first electrode piece 11 and the second electrode piece 12. Exemplarily, the electrode assembly 10 also includes an isolator 13, which is used to insulate and isolate the first electrode piece 11 and the second electrode piece 12.

[0094] The polarity of the first pole piece 11 is opposite to the polarity of the second pole piece 12. Specifically, one of the first pole piece 11 and the second pole piece 12 is a positive pole piece, and the other is a negative pole piece.

[0095] M is a positive integer greater than 0, that is, there may be one or more electrode assemblies 10. When there are more than one electrode assemblies 10, the plurality of electrode assemblies 10 may be stacked along the first direction X.

[0096] In a fully charged state, the electrode assembly 10 will expand. Exemplarily, after the battery cell 7 is prepared, the battery cell 7 is charged at a rate of 0.33C at room temperature until it is fully charged. After the battery cell 7 is fully charged, the battery cell 7 is disassembled, and a vernier caliper is used to measure the dimension D4 of each electrode assembly 10 along the first direction X in the fully charged state.

[0097] When only one electrode assembly 10 is disposed inside the battery cell 7 , the value of D2 is equal to D4 . When multiple electrode assemblies 10 are disposed 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.

[0098] When a plurality of electrode assemblies 10 are provided, the dimensions D4 of different electrode assemblies 10 along the first direction X may be the same or different.

[0099] N is a positive integer greater than 0, that is, the number of the buffer member 30 may be one or more.

[0100] The N buffer members 30 and the M electrode assemblies 10 are stacked along the first direction X. The embodiment of the present application does not limit the order in which the buffer members 30 and the electrode assemblies 10 are stacked along the first direction X.

[0101] In some examples, there is one buffer 30 and there are multiple electrode assemblies 10. Multiple electrode assemblies 10 may be sequentially arranged along the first direction X to form an electrode unit, and the buffer 30 may be arranged on one side of the electrode unit along the first direction X. Alternatively, the buffer 30 may also be arranged between two adjacent electrode assemblies 10.

[0102] In other examples, there are multiple buffer members 30 and one electrode assembly 10. Multiple buffer members 30 may be sequentially arranged along the first direction X to form a buffer unit, and the electrode assembly 10 may be arranged on one side of the buffer unit along the first direction X. Alternatively, the electrode assembly 10 may also be arranged between two adjacent buffer members 30.

[0103] In some other examples, there are multiple buffer members 30 and multiple electrode assemblies 10. The order in which the multiple buffer members 30 and the multiple electrode assemblies 10 are stacked along the first direction X can be freely set according to needs. For example, each buffer member 30 can be adjacent to the electrode assembly 10, or can be adjacent to another buffer member 30.

[0104] When the buffer member 30 is squeezed by the electrode assembly 10 , it can be compressed to provide space for the expansion of the electrode assembly 10 and reduce the force between the first side wall 211 and the electrode assembly 10 .

[0105] Exemplarily, the buffer 30 has a certain elastic deformation ability. 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 restore at least part of its deformation to ensure that the buffer 30 can offset 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 sheets of the electrode assembly 10.

[0106] The embodiment of the present application does not limit the specific material of the buffer 30, which needs to have a certain ability to produce deformation and be able to restore at least part of the deformation when the external force is removed. Exemplarily, when it is necessary to measure the size of each buffer 30 along the first direction X in an uncompressed state, the battery cell 7 can be disassembled and the buffer 30 can be taken out, and then the size D5 of each buffer 30 along the first direction X in an uncompressed state can be measured using a vernier caliper. Alternatively, during the preparation process of the battery cell 7, the size D5 of the buffer 30 along the first direction X in an uncompressed state can be measured before the buffer 30 is put into the shell.

[0107] When only one buffer 30 is disposed inside the battery cell 7 , the value of D3 is equal to the value of D5 . When multiple buffers 30 are disposed inside the battery cell 7 , the value of D3 is equal to the sum of the dimensions D5 of the multiple buffers 30 along the first direction X.

[0108] When a plurality of buffer members 30 are provided, the dimensions D5 of different buffer members 30 along the first direction X in an uncompressed state may be the same or different.

[0109] The embodiment of the present application does not limit the shape of the buffer member 30 , which may be in the shape of a plate, a block, or other irregular shapes.

[0110] The buffer 30 can limit the deformation of the electrode assembly 10 to a certain extent when the battery cell 7 is charged for the first time, improve the uniformity of the force distribution of the electrode assembly 10, reduce the risk of wrinkles on the pole piece of the electrode assembly 10, and extend the life of the electrode assembly 10. During the cycle of the battery cell 7, the buffer 30 is compressed when squeezed by the electrode assembly 10 to provide space for the expansion of the electrode assembly 10, reduce the force between the housing 20 and the electrode assembly 10, and improve the cycle performance of the electrode assembly 10.

[0111] The smaller the value of (D2+D3) / D1, the lower the utilization rate of the internal space of the housing 20, the smaller the restraining force from the first side wall 211 on the electrode assembly 10 during charging, and the higher the risk of wrinkles on the pole piece of the electrode assembly 10. Although the buffer 30 can limit the deformation of the electrode assembly 10 to a certain extent when the battery cell 7 is initially charged, if the value of (D2+D3) / D1 is too small, it may be difficult for the buffer 30 to effectively limit the wrinkles on the pole piece. In view of this, the inventor makes (D2+D3) / D1 greater than or equal to 0.9 to improve the space utilization rate and effectively reduce the risk of wrinkles on the pole piece.

[0112] The larger the value of (D2+D3) / D1 is, the better the buffer 30 can limit the deformation of the electrode assembly 10 when the battery cell 7 is initially charged. Of course, the larger the value of (D2+D3) / D1 is, the larger the space and weight occupied by the buffer 30 is, and the greater the compression of the buffer 30 during the cycle of the battery cell 7 is. If the value of (D2+D3) / D1 is too large, the compressibility of the buffer 30 after entering the shell may be too small, resulting in insufficient expansion that can be absorbed by the buffer 30, resulting in excessive expansion force of the electrode assembly 10. In view of this, the inventor makes (D2+D3) / D1 less than or equal to 1.5 to save the amount of buffer 30, 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.

[0113] Alternatively, the value of (D2+D3) / D1 may be 0.9, 0.95, 0.98, 1, 1.1, 1.2, 1.25, 1.3, 1.4 or 1.5.

[0114] In some embodiments, D1, D2, and D3 satisfy: 0.98≤(D2+D3) / D1≤1.25.

[0115] In some embodiments, the electrode assembly 10 includes a main body 14 and a first electrode tab 15 and a second electrode 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 electrode tab 15 and the second electrode tab 16 is a positive electrode tab, and the other is a negative electrode tab.

[0116] In the present application, in the fully charged state, the dimension of the main body 14 along the first direction X is D4.

[0117] In some embodiments, the housing 20 includes a shell 21 and an end cover 22 , wherein the shell 21 has an opening and the end cover 22 covers the opening. Exemplarily, the shell 21 includes two first side walls 211 .

[0118] The housing 21 may be a structure with one side open, and one end cap 22 is provided to cover the opening of the housing 21. Alternatively, the housing 21 may be a structure with two sides open, and two end caps 22 are provided, and the two end caps 22 cover the two openings of the housing 21 respectively.

[0119] Exemplarily, the end cover 22 is connected to the housing 21 by welding, bonding, clamping or other methods.

[0120] In some embodiments, the first side wall 211 is a flat plate structure.

[0121] In some embodiments, an opening is provided at one end of the housing 21 along the second direction Y. Optionally, the first direction X is perpendicular to the second direction Y.

[0122] In some embodiments, the housing 21 includes two second side walls 212 , and the two second side walls 212 are arranged opposite to each other along a third direction Z. Optionally, the third direction Z is perpendicular to the first direction X and the second direction Y.

[0123] The two first side walls 211 and the two second side walls 212 are alternately arranged along the circumference of the opening. Both ends of the first side wall 211 along the third direction Z are connected to the two second side walls 212 respectively.

[0124] In some embodiments, adjacent first side walls 211 and second side walls 212 are connected by an arc-shaped wall.

[0125] In some embodiments, the value of D1 can be measured by the following method: using a vernier caliper to measure the dimension D6 of the housing 21 along the first direction X; using a vernier caliper to measure the wall thickness D7 of the first side wall 211; D1 = D6 - 2·D7.

[0126] During the cycle of the battery cell 7, the first side wall 211 may be deformed due to the expansion of the electrode assembly 10. Since the deformation of the end of the first side wall 211 close to the second side wall 212 is small, the vernier caliper can clamp the ends of the two first side walls 211 close to the second side wall 212, and the measured value is used as D6.

[0127] In some embodiments, the battery cell 7 further includes two electrode terminals 40, which can be disposed on the end cap 22. One electrode terminal 40 is used to be electrically connected to the first electrode sheet 11 of the electrode assembly 10, and the other electrode terminal 40 is used to be electrically connected to the second electrode sheet 12, so as to lead the electric energy generated by the electrode assembly 10 out of the housing 20.

[0128] In some embodiments, the buffer member 30 may be a porous structure. The micropores in the buffer member 30 may be used to store electrolyte, and when the electrode assembly 10 expands and presses the buffer member 30, the electrolyte in the buffer member 30 may be squeezed out.

[0129] In some embodiments, the cushioning member 30 may be made of foam.

[0130] In some embodiments, the first direction X is parallel to a thickness direction of the battery cell 7. In the battery, a plurality of battery cells 7 may be stacked along the first direction X.

[0131] In some embodiments, D2 and D3 satisfy: D3≤0.25·D2.

[0132] When the value of D2 is constant, the larger the value of D3 is, the larger the volume and weight of the buffer 30 is, and the lower the weight energy density of the battery cell 7 is. The inventors found that when the value of D3 exceeds a certain range, the effect of the buffer 30 on improving the cycle performance of the electrode assembly 10 will not be further improved as D3 increases; after experiments, the inventors limited the value of D3 to less than or equal to 0.25·D2, which can reduce the amount of the buffer 30, increase the energy density of the battery cell 7, and improve the cycle performance of the electrode assembly 10.

[0133] In some embodiments, the buffer member 30 is a flat plate structure, which is easy to shape and can improve the uniformity of force distribution of the electrode assembly 10 when the electrode assembly 10 expands.

[0134] In some embodiments, the buffer member 30 may be rectangular, circular, oval or other shapes. Optionally, the buffer member 30 is a rectangular flat plate.

[0135] In some embodiments, the buffer 30 is attached to the electrode assembly 10 .

[0136] Attachment means that the buffer member 30 is attached to and connected to the surface of the electrode assembly 10. For example, the buffer member 30 may be bonded to the electrode assembly 10 by an adhesive.

[0137] The buffer member 30 attached to the electrode assembly 10 can be installed in the housing 21 together with the electrode assembly 10 to simplify the assembly process. The electrode assembly 10 can also limit the shaking of the buffer member 30 when the battery cell 7 is subjected to external impact to reduce the risk of the buffer member 30 shifting.

[0138] In some embodiments, the compression rate f of the buffer member 30 under a pressure of 2 MPa satisfies: 1%≤f≤99%. Optionally, the compression rate f of the buffer member 30 under a pressure of 2 MPa satisfies: 40%≤f≤99%.

[0139] In some embodiments, the electrode assembly 10 includes a straight region 10a and two bending regions 10b, the two bending regions 10b are respectively located on both sides of the straight region 10a along the third direction Z, and the third direction Z is perpendicular to the first direction X. The size of the buffer 30 in the third direction Z is L1, the size of the electrode assembly 10 in the fully charged state along the third direction Z is L2, and the size of one electrode assembly 10 in the fully charged state along the first direction X is D4. L1, L2 and D4 satisfy: L1 ≥ 0.85 (L2-D4).

[0140] The straight region 10a is a region of the electrode assembly 10 having a straight structure, and the portion of the electrode piece located in the straight region 10a is generally in a straight state. The bending region 10b is a region of the electrode assembly 10 having a bent structure, and the portion of the electrode piece located in the bending region 10b is generally in a bent state. Exemplarily, the portion of the electrode piece located in the bending region 10b is generally bent into an arc shape.

[0141] In the fully charged state, the dimension of the bending area 10b along the third direction Z is substantially equal to half of D4, and L2-D4 is substantially the dimension of the straight area 10a along the third direction Z.

[0142] Since the gap between the bending area 10b of the electrode assembly 10 and the first side wall 211 is large, the expansion force generated by the bending area 10b is small. The gap between the straight area 10a of the electrode assembly 10 and the first side wall 211 is small, so the expansion force generated by the straight area 10a is large. In this embodiment, the value of L1 is limited to be greater than or equal to 0.85 (L2-D4), so that the expansion of more than 85% of the area of ​​the straight area 10a in the third direction Z can be absorbed by the buffer 30 to ensure the cycle performance of the straight area 10a.

[0143] In some embodiments, both ends of the buffer member 30 extend beyond the straight region 10 a in the third direction Z. The buffer member 30 can effectively absorb the expansion of the straight region 10 a and improve the cycle performance of the straight region 10 a.

[0144] In some embodiments, L1 and L2 satisfy: L1≤1.1·L2. In the third direction Z, the portion of the buffer 30 that exceeds the electrode assembly 10 will not absorb the expansion of the electrode assembly 10, but will increase the volume and weight of the buffer 30. In this embodiment, the value of L1 is less than or equal to 1.1·L2 to reduce the amount of the buffer 30 and improve the energy density of the battery cell 7.

[0145] In some embodiments, the projection area of ​​the buffer member 30 on the inner surface of the first side wall 211 along the first direction X is S1, the area of ​​the inner surface of the first side wall 211 is S2, and S1 and S2 satisfy: S1≤0.95·S2.

[0146] The inner surface of the first side wall 211 will squeeze the electrode assembly 10 when the electrode assembly 10 expands to limit the expansion deformation of the electrode assembly 10. In addition to accommodating the electrode assembly 10, the outer shell 20 also needs to accommodate other functional components, so a portion of the inner surface of the first side wall 211 will not squeeze the electrode assembly 10. In the embodiment of the present application, S1≤0.95·S2 is set to reduce the overall usage of the buffer 30, provide more space for other components in the outer shell 20, and improve the energy density and service life of the battery cell 7.

[0147] In some embodiments, the dimension of each buffer 30 along the first direction X in an uncompressed state is D5, and D5 satisfies: 0.1 mm≤D5≤10 mm. Optionally, the value of D5 is 0.1 mm, 0.5 mm, 1 mm, 2 mm, 4 mm, 5 mm, 8 mm or 10 mm.

[0148] If D5 is too small, more buffers 30 need to be provided in the battery cell 7 to meet the requirements, which results in a complex structure of the battery cell 7 and low assembly efficiency. Therefore, the embodiment of the present application limits the value of D5 to be greater than or equal to 0.1 mm.

[0149] If D5 is too large, the weight of the buffer 30 is too large and the space occupied is too large, resulting in a low energy density of the battery cell 7. Therefore, the embodiment of the present application limits the value of D5 to less than or equal to 10 mm.

[0150] In some embodiments, D5 satisfies: 0.5 mm ≤ D5 ≤ 4 mm.

[0151] Figure 7 A schematic cross-sectional view of a battery cell provided in some embodiments of the present application; Figure 8 A partial cross-sectional schematic diagram of an electrode assembly and a buffer component of a battery cell provided in some embodiments of the present application.

[0152] like Figure 7 and Figure 8 As shown, in some embodiments, the electrode assembly 10 includes a first electrode sheet 11, the first electrode sheet 11 includes a first body 111 and a first electrode ear 15 extending from one end of the first body 111 along a second direction Y, and the second direction Y is perpendicular to the first direction X. The size of the buffer 30 along the second direction Y is H1; the first body 111 is provided with a first active material layer 112, and the size of the first active material layer 112 along the second direction Y is H2. H1 and H2 satisfy: H1≥0.85·H2.

[0153] The main reason for the expansion of the electrode assembly 10 is the expansion of the active material layer during charging. In the embodiment of the present application, 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 area of ​​the first active material layer 112 in the second direction Y can be absorbed by the buffer 30, so as to reduce the pressure on the first active material layer 112 and improve the cycle performance of the electrode assembly 10.

[0154] The first electrode sheet 11 may be a positive electrode sheet or a negative electrode sheet. Exemplarily, the first electrode sheet 11 is a negative electrode sheet, and the first active material layer 112 is a negative active material layer. The first body 111 also includes a negative electrode coating region of a negative electrode current collector.

[0155] In some embodiments, the first active material layer 112 includes a base region 112a and a thinned region 112b connected to the base region 112a, and the thickness of the thinned region 112b is less than the thickness of the base region 112a. In the second direction Y, the thinned region 112b is located on a side of the base region 112a close to the first electrode tab 15. In the second direction Y, both ends of the buffer 30 exceed the base region 112a.

[0156] During the molding process of the first electrode sheet 11, the first active material layer 112 needs to be rolled to increase the compaction density of the first active material layer 112. The embodiment of the present application reduces the thickness of the thinned area 112b to reduce the stress concentration at the junction of the first body 111 and the first pole tab 15 during the rolling process, thereby reducing the risk of cracking of the first pole tab 15.

[0157] Compared with the thinned area 112b, the expansion force generated by the base area 112a during expansion is greater. Therefore, in the embodiment of the present application, both ends of the buffer member 30 along the second direction Y extend beyond the base area 112a to effectively absorb the expansion of the base area 112a and improve the cycle performance of the electrode assembly 10.

[0158] In some embodiments, the electrode assembly 10 further includes a separator 13, and the separator 13 is stacked with the first body 111. The size of the separator 13 along the second direction Y is H3; H1 and H3 satisfy: H1≤1.1·H3.

[0159] The isolation member 13 is used to insulate and isolate the first body 111 from the second pole piece 12 .

[0160] In the second direction Y, the portion of the separator 13 that exceeds the separator 13 will not absorb the expansion of the electrode assembly 10, but will 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 the buffer 30 and improve the energy density of the battery cell 7.

[0161] In some embodiments, in the second direction Y, both ends of the buffer 30 do not extend beyond the isolation member 13 , so as to reduce the amount of the 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 .

[0162] Fig. 9 Schematic diagram of the structure of battery cells provided in other embodiments of the present application.

[0163] like Fig. 9 As shown, in some embodiments, there are multiple electrode assemblies 10. A buffer 30 is disposed between at least two adjacent electrode assemblies 10.

[0164] The buffer member 30 is disposed between two adjacent electrode assemblies 10 to reduce the risk of the buffer member 30 shaking when the battery cell 7 is subjected to external impact.

[0165] Fig.10 This is a schematic diagram of the structure of a battery cell provided in some embodiments of the present application. Fig.10 As shown, in some embodiments, there are multiple electrode assemblies 10 and multiple buffer members 30.

[0166] Exemplarily, there are two electrode assemblies 10 and two buffer members 30. The two electrode assemblies 10 are disposed adjacent to each other and constitute an electrode unit, and the two buffer members 30 are located at two sides of the electrode unit along the first direction X, respectively.

[0167] Fig.11 This is a schematic diagram of the structure of a battery cell provided in some embodiments of the present application. Fig.11 As shown, in some embodiments, there are four electrode assemblies 10 and two buffer members 30. The four electrode assemblies 10 are adjacently arranged 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.

[0168] According to some embodiments of the present application, the present application also provides a battery, which includes a plurality of battery cells provided by any of the above embodiments.

[0169] According to some embodiments of the present application, the present application further provides an electrical device, which includes a battery cell provided by any of the above embodiments, and the battery cell is used to provide electrical energy to the electrical device.

[0170] According to some embodiments of the present application, referring to Fig.10, the battery cell 7 of the embodiment of the present application includes a shell 20, two electrode assemblies 10 and two buffers 30. The shell 20 includes two first side walls 211 arranged opposite to each other along the first direction X, and the spacing between the two first side walls 211 along the first direction X is D1. The two electrode assemblies 10 are accommodated in the shell 20, and in the 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 buffers 30 are respectively located on both sides of the electrode unit along the first direction X. The buffer 30 is configured to be compressible, and the dimension of each buffer 30 along the first direction X in the uncompressed state is D5, and the sum of the dimensions of the two buffers 30 along the first direction X in the uncompressed state is D3. D1, D2 and D3 satisfy: 0.9≤(D2+D3) / D1≤1.5.

[0171] Fig.12 A schematic flow chart of a method for manufacturing a battery cell provided in some embodiments of the present application.

[0172] like Fig.12 As shown, the embodiment of the present application provides a method for manufacturing a battery cell, which includes:

[0173] S100, providing a housing, wherein the housing comprises two first side walls arranged opposite to each other along a first direction;

[0174] S200, providing an electrode assembly and a buffer;

[0175] S300, installing the electrode assembly and the buffer into the housing.

[0176] The spacing between the two first side walls along the first direction is D1. The number of electrode assemblies is M, 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. The number of buffers is N, where N is a positive integer greater than 0; the N buffers are stacked with the M electrode assemblies along the first direction. The buffer is configured to be compressible, and the sum of the dimensions of the N buffers along the first direction in an uncompressed state is D3. D1, D2, and D3 satisfy: 0.9≤(D2+D3) / D1≤1.5.

[0177] It should be noted that the relevant structure of the battery cell manufactured by the above-mentioned method for manufacturing the battery cell can refer to the battery cell provided in the above-mentioned embodiments.

[0178] When manufacturing a battery cell based on the above-mentioned method for manufacturing a battery cell, it is not necessary to perform the above-mentioned steps in sequence, that is, the steps can be performed in the order mentioned in the embodiment, or in a different order from the order mentioned in the embodiment, or several steps can be performed simultaneously. For example, the execution of steps S100 and S200 is not in order, and can also be performed simultaneously.

[0179] Fig.13 A schematic block diagram of a battery cell manufacturing system provided for some embodiments of the present application.

[0180] like Fig.13 As shown, an embodiment of the present application provides a manufacturing system 90 for a battery cell, which includes a first providing device 91, a second providing device 92 and an assembling device 93. The first providing device 91 is used to provide a shell, and the shell includes two first side walls arranged opposite to each other along a first direction. The second providing device 92 is used to provide an electrode assembly and a buffer. The assembling device 93 is used to install the electrode assembly and the buffer into the shell. The spacing between the two first side walls along the first direction is D1. The electrode assembly is set to M, and 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, and N is a positive integer greater than 0; N buffers are stacked with the M electrode assemblies along the first direction. The buffer is configured to be compressible, and the sum of the dimensions of the N buffers along the first direction in an uncompressed state is D3. D1, D2 and D3 satisfy: 0.9≤(D2+D3) / D1≤1.5.

[0181] The present application is further described below with reference to embodiments.

[0182] In order to make the invention purpose, technical scheme and beneficial technical effect of the present application clearer, the present application is further described in detail below in conjunction with the examples. However, it should be understood that the examples of the present application are only for explaining the present application, not for limiting the present application, and the examples of the present application are not limited to the examples given in the specification. The specific experimental conditions or operating conditions not specified in the examples are made under conventional conditions, or are made under the conditions recommended by the material supplier.

[0183] Example 1 can be prepared according to the following steps:

[0184] (i) The positive electrode active material NCM523, the conductive agent acetylene black, and the binder PVDF are mixed in a mass ratio of 96:2:2, and the solvent NMP is added, and the mixture is stirred under the action of a vacuum mixer until the system becomes uniform to obtain a positive electrode slurry; the positive electrode slurry is evenly coated on an aluminum foil, dried at room temperature, and then transferred to an oven for further drying, and then cold pressed, slit, and cut into pieces to obtain a positive electrode sheet.

[0185] (ii) Mixing 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 in a mass ratio of 96.4:1:1.2:1.4, adding deionized water as a solvent, and stirring the mixture under the action of a vacuum stirrer until the system becomes uniform to obtain a negative electrode slurry; coating the negative electrode slurry evenly on a copper foil, drying it at room temperature, and then transferring it to an oven for further drying, and then cold pressing, slitting, and cutting to obtain a negative electrode sheet.

[0186] (iii) Ethylene 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, and then fully dried lithium salt Li PF6 is dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0187] (iv) A 12 μm thick polypropylene film was used as the separator.

[0188] (v) The positive electrode sheet, the separator and the negative electrode sheet are stacked together and wound into multiple turns, and then flattened into a flat shape after winding to prepare an electrode assembly.

[0189] (VI) The two electrode assemblies and the two buffer members are stacked and installed in a shell, and then the end caps and the shell are welded. After the processes of liquid injection, standing, forming, shaping, etc., a battery cell is obtained.

[0190] In step (VI), if Fig.14 As shown, two buffer members 30 and two electrode assemblies 10 are stacked along the first direction X, and the housing 21 includes two first side walls 211 arranged opposite to each other along the first direction X. Using a vernier caliper, the distance D1 between the two first side walls 211 along the first direction X is measured to be 27 mm. Before the buffer member 30 is installed into the housing 21, the thickness D5 of the buffer member 30 is measured to be 0.45 mm using a vernier caliper; correspondingly, the sum of the dimensions of the two buffer members 30 along the first direction X in a compressed state is D3, and D3 is 0.9 mm.

[0191] According to the above preparation steps, two battery cells 7 are prepared, and interface testing and cycle performance testing are performed respectively.

[0192] Interface detection:

[0193] Under normal temperature, a battery cell 7 is charged at a rate of 0.33C until it is fully charged. After the battery cell 7 is fully charged, the battery cell 7 is disassembled, and a vernier caliper is used to measure the size of each electrode assembly 10 along the first direction X in the fully charged state. After the size measurement is completed, the electrode assembly 10 is further disassembled, and the interface state of the negative electrode sheet is observed.

[0194] After measurement and calculation, the sum D2 of the dimensions of the two electrode assemblies 10 along the first direction X is 25.6 mm.

[0195] Cycle performance test:

[0196] Another battery cell 7 is fixed on the clamp, and the clamp clamps the two first side walls 211 of the battery cell 7 from both sides and applies a clamping force of 3000 N to the first side walls 211. The clamp is provided with a pressure sensor to detect the pressure F between the first side wall 211 and the clamp in real time.

[0197] Under normal temperature, the battery cell 7 is charged at a 1C rate and discharged at a 1C rate to perform a full charge-discharge cycle test until the capacity of the battery cell 7 decays to 90% of the initial capacity.

[0198] During the cycle, the state of the battery cell 7 is monitored in real time. When the capacity of the battery cell 7 decays to 90% of the initial capacity, the number of cycles of the battery cell 7 is recorded, and the increase ΔF of the expansion force of the battery cell 7 is calculated, ΔF=F-3000N.

[0199] Exemplarily, the clamp includes two clamping plates, which clamp the battery cell 7 from two sides and are respectively opposite to the two first side walls 211 , and a buffer pad may be provided between the clamping plates and the corresponding first side walls 211 .

[0200] Example 2: The preparation method and detection method of the battery cell of Example 2 refer to Example 1, except that D3 is 1.4 mm.

[0201] Example 3: The preparation method and detection method of the battery cell of Example 3 refer to Example 1, except that D3 is 4.1 mm.

[0202] Example 4: The preparation method and detection method of the battery cell of Example 4 refer to Example 1, except that D3 is 8.15 mm.

[0203] Example 5: The preparation method and detection method of the battery cell of Example 5 refer to Example 1, except that D3 is 12.2 mm.

[0204] Example 6: The preparation method and detection method of the battery cell of Example 6 refer to Example 1, except that D3 is 14.9 mm.

[0205] Example 7: The preparation method and detection method of the battery cell of Example 7 refer to Example 1, except that D3 is 0.7 mm and D2 is 23.6 mm.

[0206] Example 8: The preparation method and detection method of the battery cell of Example 8 refer to Example 1, except that D3 is 2.1 mm and D2 is 23.6 mm.

[0207] Comparative Example 1: The preparation method and detection method of the battery cell of Comparative Example 1 refer to Example 1, except that D2 is 24.3 mm, and no buffer is provided inside Comparative Example 1 (ie, D3 is 0).

[0208] Comparative Example 2: The preparation method and detection method of the battery cell of Comparative Example 1 refer to Example 1, except that D2 is 25.6 mm, and no buffer is provided inside Comparative Example 1 (ie, D3 is 0).

[0209] Comparative Example 3: The preparation method and detection method of the battery cell of Comparative Example 1 refer to Example 1, except that D2 is 26.4 mm, and no buffer is provided inside Comparative Example 1 (ie, D3 is 0).

[0210] Comparative Example 4: The preparation method and detection method of the battery cell of Comparative Example 4 refer to those of Example 1, except that D3 is 0.6 mm and D2 is 21 mm.

[0211] Comparative Example 5: The preparation method and detection method of the battery cell of Comparative Example 5 refer to those of Example 1, except that D3 is 17.6 mm.

[0212] The evaluation results of Examples 1 to 8 and Comparative Examples 1 to 5 are shown in Table 1.

[0213] Table 1

[0214]

[0215] It should be noted that along the axial direction of the winding of the electrode assembly, if the ratio of the size of the wrinkles to the size of the pole piece is less than 5%, it is regarded as no wrinkles; if the ratio of the size of the wrinkles to the size of the pole piece is 5%-30%, it is regarded as slight wrinkles; if the ratio of the size of the wrinkles to the size of the pole piece is greater than 30%, it is regarded as severe wrinkles.

[0216] With reference to Examples 1-8 and Comparative Examples 1-3, the embodiments of the present application can reduce the risk of wrinkles on the pole pieces during the initial charging of the battery cells by providing a buffer, reduce the expansion force generated by the battery cells during the cycle, extend the number of cycles of the battery cells, and improve the cycle performance of the battery cells.

[0217] Referring to Examples 1-8 and Comparative Examples 4-5, the examples of the present application limit the value of (D2+D3) / D1 to between 0.9 and 1.5, which can reduce the risk of wrinkles on the electrode during the initial 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.

[0218] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and parts thereof may be replaced with equivalents without departing from the scope of the present application. In particular, the various technical features mentioned in the various embodiments may be combined in any manner as long as there is no structural conflict. The present 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, contained in the housing, the electrode assembly comprising a first pole piece and a second pole piece, the first pole piece and the second pole piece having opposite polarities, the first pole piece comprising a first body and a first pole ear extending from the first body, the first body being provided with a first active material layer, the first active material layer comprising a substrate region and a thinned region connected to the substrate region, the thinned region being located at one side of the substrate region, and the thickness of the thinned region being less than the thickness of the substrate region; a buffer member, contained in the housing and stacked with the electrode assembly along the first direction, wherein the first direction is parallel to the thickness direction of the battery cell; Wherein, in the first direction, a portion of the base area overlaps with the buffer component; and in the direction from the base area to the thinning area, the buffer component exceeds the base area.

2. The battery cell according to claim 1, characterized in that: The thinning area is located on one side of the base area along a second direction, and the second direction is perpendicular to the first direction; In the second direction, both ends of the buffer member extend beyond the base region.

3. The battery cell according to claim 1, characterized in that: The first electrode tab is led out from one end of the first body along a second direction, and the second direction is perpendicular to the first direction; In the second direction, the thinned region is located on a side of the base region close to the first electrode tab.

4. The battery cell according to claim 3, characterized in that: In the second direction, both ends of the buffer member extend beyond the base region.

5. The battery cell according to claim 1, characterized in that: The thinning area is located on one side of the base area along a second direction, and the second direction is perpendicular to the first direction; The size of the buffer member along the second direction is H1, and the size of the first active material layer along the second direction is H2; H1 and H2 satisfy: H1 ≥ 0.85·H2.

6. The battery cell according to claim 1, characterized in that: The housing comprises two first side walls arranged opposite to each other along the first direction, and a distance D1 between the two first side walls along the first direction; There are M electrode assemblies, and in a fully charged state, the sum of the dimensions of the M electrode assemblies along the first direction is D2, and M is a positive integer greater than 0; The buffer members are N in number, and the N buffer members and the M electrode assemblies are stacked along the first direction; the buffer member is configured to be compressible, and the sum of the dimensions of the N buffer members along the first direction in an uncompressed state is D3, and 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 6 or 7, characterized in that: D2 and D3 satisfy: D3≤0.25·D2.

9. The battery cell according to claim 1, characterized in that: The electrode assembly further includes a separator, which is used to insulate and isolate the first pole piece from the second pole piece; The isolating member is stacked with the first main body; The first electrode tab is led out from one end of the first body along a second direction, and the second direction is perpendicular to the first direction; The dimension of the buffer member along the second direction is H1, and the dimension of the isolation member along the second direction is H3; H1 and H3 satisfy: H1≤1.1·H3.

10. The battery cell according to claim 9, characterized in that: In the second direction, both ends of the buffer member do not exceed the isolation member.

11. The battery cell according to claim 1, characterized in that: The electrode assembly comprises a straight region and two bending regions, wherein the two bending regions are respectively located on both sides of the straight region along a third direction, and the third direction is perpendicular to the first direction; A portion of the buffer overlaps the straight area in the first direction; In the third direction, at least one end of the buffer member exceeds the straight area.

12. The battery cell according to claim 11, characterized in that: The buffer member has a dimension L1 in the third direction, the electrode assembly has a dimension L2 in the third direction in a fully charged state, and one electrode assembly has a dimension D4 in the first direction in a fully charged state; L1, L2 and D4 satisfy: L1 ≥ 0.85 (L2-D4).

13. The battery cell according to claim 12, characterized in that: L1 and L2 satisfy: L1≤1.1·L2.

14. The battery cell according to claim 11, characterized in that: In the third direction, both ends of the buffer member exceed the straight area.

15. The battery cell according to claim 11, characterized in that: In the third direction, an end of the bending area away from the straight area exceeds the buffer.

16. The battery cell according to claim 1, characterized in that: The housing comprises two first side walls arranged opposite to each other along the first direction; The area of ​​the projection of the buffer member on the inner surface of the first side wall along the first direction is S1, the area of ​​the inner surface of the first side wall is S2, and S1 and S2 satisfy: S1≤0.95·S2.

17. The battery cell according to claim 1, characterized in that: The dimension of each buffer member along the first direction in an uncompressed state is D5, and D5 satisfies: 0.1 mm≤D5≤10 mm.

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

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

20. The battery cell according to claim 1, characterized in that: There are multiple electrode assemblies; The buffer member is disposed between at least two adjacent electrode assemblies.

21. The battery cell according to claim 1, characterized in that: The buffer member is a flat plate structure.

22. The battery cell according to claim 1, characterized in that: The buffer component is a porous structure.

23. A battery, characterized in that: The invention comprises a plurality of battery cells according to any one of claims 1 to 22.

24. An electrical device, characterized in that: The invention comprises a battery cell according to any one of claims 1 to 22, wherein the battery cell is used to provide electrical energy.

Images