Battery cell, battery, and electric device

Abstract

The present application relates to the technical field of batteries, and provides a battery cell, a battery, and an electric device. The battery cell comprises a casing, a plurality of electrode assemblies, and a buffer structure; the electrode assemblies are arranged in the casing; the buffer structure is arranged between the two adjacent electrode assemblies; and / or the buffer structure is arranged between the electrode assemblies and the inner wall of the casing; and the compression volume V of the buffer structure, the compression ratio B of the buffer structure, and the battery cell capacity Cn of the battery cell satisfy the following relational expression: 0.7(mL / Ah)≤V*B / Cn≤1.0(mL / Ah). The deposition layer formed by the negative electrode in the battery cell can be buffered and limited by the buffer structure, so that the probability of micro-short circuit of the electrode assemblies caused by puncturing the separator by a sharp structure formed by growing the deposition layer in any direction is reduced.

Description

Battery cells, batteries and electrical equipment

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on November 30, 2023, with application number 202323261134.2 and invention name “Battery Cell, Battery and Electrical Equipment”, the entire contents of which are incorporated by reference into this application. Technical Field

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

[0003] The volume of the negative electrode of the sodium metal system battery changes significantly during the charge and discharge process. The main reason is that during the charge and discharge process of the battery, the current passes through the negative electrode, and the metal ions on the negative electrode are reduced to metal deposits, or other reaction products are deposited on the surface of the negative electrode, and deposition also occurs on its surface.

[0004] However, the deposition phenomenon occurring on the negative electrode surface can easily puncture the separator of the electrode assembly, eventually leading to a micro-short circuit in the battery. Technical issues

[0005] The purpose of the embodiments of the present application is to provide a battery cell, a battery and an electrical device, aiming to solve the problem of micro-short circuit caused by deposition on the negative electrode of the existing battery cell. Technical Solutions

[0006] To achieve the above objectives, the technical solution adopted in this application is:

[0007] In a first aspect, an embodiment of the present application provides a battery cell, comprising:

[0008] case;

[0009] a plurality of electrode assemblies, each of the electrode assemblies being disposed in the housing;

[0010] a buffer structure, the buffer structure being provided between two adjacent electrode assemblies; and / or the buffer structure being provided between the electrode assembly and the inner wall of the housing;

[0011] Among them, the cumulative volume V of the buffer structure, the compression rate B of the buffer structure and the cell capacity Cn of the battery cell have the following relationship, and the compression rate B of the buffer structure refers to the compression rate of the buffer structure under a pressure of 1 MPa: 0.7 (mL / Ah) ≤ V*B / Cn ≤ 1.0 (mL / Ah).

[0012] Beneficial effects of the present application: The battery cell provided by the present application has a buffer structure provided between two adjacent electrode assemblies; or, a buffer structure provided between an electrode assembly and a shell; or, a buffer structure provided between adjacent electrode assemblies and between an electrode assembly and a shell. In this way, the buffer structure can be used to buffer and limit the deposition layer occurring at the negative electrode in the battery cell, so as to reduce the probability that the deposition layer will puncture the diaphragm and cause a micro-short circuit in the point electrode assembly due to the sharp structure formed by the growth in any direction. In addition, the product of the compressed volume V of the buffer structure and the compression rate B of the buffer structure has the above-mentioned relationship with the cell capacity Cn of the battery cell. V*B / Cn is greater than or equal to 0.7mL / Ah, which means that when the cell capacity Cn of the current battery cell is a certain value, the total volume compression of the buffer structure should meet the minimum volume deformation requirement. Similarly, V*B / Cn is less than or equal to 1.0mL / Ah, which means that when the cell capacity Cn of the current battery cell is a certain value, the total volume compression of the buffer structure should meet the maximum volume deformation requirement.

[0013] In one embodiment, the electrode assembly includes stacked electrode sheets, and the buffer structure is also arranged between the electrode sheets of the same electrode assembly; the electrode assembly includes a positive electrode sheet, a diaphragm and a negative electrode sheet arranged in a stacked manner, and the buffer structure is arranged between the positive electrode sheet and the diaphragm; and / or, the buffer structure is arranged between the negative electrode sheet and the diaphragm.

[0014] In one embodiment, 0.85 (mL / Ah) ≤ V*B / Cn ≤ 0.95 (mL / Ah).

[0015] In one embodiment, a ratio of the cumulative volume of the buffer structure to the effective total volume of the electrode assembly is A, and the range of A is: 2%≤A≤17%.

[0016] In one embodiment, 2%≤A≤12%.

[0017] In one embodiment, the compression rate B of the buffer structure is in the range of 50%≤B≤95%.

[0018] In one embodiment, 70%≤B≤90%.

[0019] In one embodiment, the buffer structure has pores.

[0020] In one embodiment, the battery cell is a sodium metal battery cell;

[0021] The positive electrode of the sodium metal battery cell includes one or more of sodium iron phosphate, layered oxide, sodium iron pyrophosphate, sodium iron sulfate, and sodium vanadium phosphate; and / or,

[0022] The negative electrode of the sodium metal battery cell includes a copper current collector, an aluminum current collector, a copper-aluminum current collector having or containing a carbon-based material coating, and a sodium sheet structure.

[0023] In a second aspect, an embodiment of the present application further provides a battery comprising the battery cell described above.

[0024] In a third aspect, an embodiment of the present application further provides an electrical device comprising the battery described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0026] FIG1 is a schematic diagram of the structure of an electrical device provided in an embodiment of the present application;

[0027] FIG2 is a schematic diagram of the structure of a battery provided in an embodiment of the present application;

[0028] FIG3 is an exploded view of a battery cell provided in an embodiment of the present application;

[0029] FIG4 is a schematic structural diagram of the buffer structure in FIG3 .

[0030] Among them, the reference numerals in the figures are:

[0031] 10000, electrical equipment; 1000, controller; 2000, motor;

[0032] 3000, battery; 3001, battery case; 30011, first part; 30012, second part; 100, battery cell; 101, housing; 102, end cover; 103, electrode assembly; 104, buffer structure. Modes for Carrying Out the Invention

[0033] The following describes in detail embodiments of the present application, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0034] In the description of this application, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0035] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0036] In this application, unless otherwise expressly specified or limited, terms such as "mounted," "connected," "connect," and "fixed" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components or interactions between two components. Those skilled in the art will understand the specific meanings of these terms in this application based on specific circumstances.

[0037] The volume of the negative electrode of the sodium metal system battery changes significantly during the charge and discharge process. The main reason is that during the charge and discharge process of the battery, the current passes through the negative electrode, and the metal ions on the negative electrode are reduced to metal deposits, or other reaction products are deposited on the surface of the negative electrode, and deposition also occurs on its surface.

[0038] This deposition process is irregular, which also leads to a high probability that the deposited layer will form sharp structures on the electrode plates of the electrode assembly. Therefore, during the charge and discharge cycle expansion process of the electrode assembly, the sharp structures of the deposited layer will likely puncture the diaphragm, causing partial or local short circuits between the positive and negative plates of the electrode assembly, ultimately leading to abnormal increase in the internal current of the battery cell and battery overheating.

[0039] In view of this, the present application provides a battery cell, wherein a buffer structure is provided between two adjacent electrode assemblies; alternatively, a buffer structure is provided between an electrode assembly and a housing; alternatively, a buffer structure is provided between two adjacent electrode assemblies and between an electrode assembly and a housing. In this way, the buffer structure is used to limit the expansion of the electrode assembly during charge and discharge cycles, so that the electrode assembly is in a restricted state when it expands to a certain extent. The buffer structure is then used to buffer and squeeze the deposited layer between the electrode pieces of the electrode assembly, thereby reducing the formation of sharp structures in the deposited layer between the electrode pieces of the electrode assembly, and ultimately significantly reducing the probability of micro-short circuits in the electrode assembly of the battery cell. At the same time, the relationship between the compressed volume and compression rate of the buffer structure and the battery capacity of the battery cell is further defined, and by setting corresponding upper and lower limit values, a buffer structure with moderate compressed volume and compression rate is obtained.

[0040] A battery cell includes an electrode assembly and an electrolyte. The electrode assembly consists of a positive electrode sheet, a negative electrode sheet, and a separator. A battery cell primarily operates by the movement of metal ions between the positive and negative electrode sheets. 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 current collector uncoated with the positive active material layer protrudes from the current collector coated with the positive active material layer. The current collectors uncoated with the positive active material layer, after being stacked, serve as the positive electrode tabs. For ease of description, the term "tab" will be used to refer to the positive and / or negative electrode tabs.

[0041] In this application, battery cells include, but are not limited to, lithium-ion secondary battery cells, lithium-ion primary battery cells, lithium-sulfur battery cells, sodium-lithium-ion battery cells, sodium-ion battery cells, or magnesium-ion battery cells. Battery cells may be cylindrical, flat, rectangular, or other shapes. Battery cells are generally categorized into three types based on packaging: cylindrical, prismatic, and soft-pack battery cells.

[0042] The embodiment of the present application provides a device 10000 that uses the battery cell 100 as a power source and can be applied to electrical equipment such as vehicles, mobile phones, portable devices, laptop computers, ships, spacecraft, and power tools. The vehicle can be a fuel vehicle, a gas vehicle, or a new energy vehicle, and the new energy vehicle can be a pure electric vehicle, a hybrid vehicle, or an extended-range vehicle; the spacecraft includes airplanes, rockets, space shuttles, and spacecraft; electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys; and the power tools include metal cutting power tools, grinding power tools, assembly power tools, and iron power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers.

[0043] The battery cell 100 described in the embodiments of the present application is not limited to being applicable to the electrical equipment 10000 described above, but can also be applicable to all devices using the battery cell 100. However, for the sake of simplicity, the following embodiments are described using electric vehicles as an example.

[0044] For example, please refer to Figure 1, which is a structural diagram of a vehicle in an embodiment of the present application. The vehicle can be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 3000, a controller 1000 and a motor 2000 can be set inside the vehicle, and the controller 1000 is used to control the battery 3000 to power the motor 2000. For example, a battery 3000 can be set at the bottom or the front or the rear of the vehicle. The battery 3000 can be used to power the vehicle. For example, the battery 3000 can be used as the operating power supply of the vehicle and used for the circuit system of the vehicle, for example, for the working power requirements during the start-up, navigation and operation of the vehicle. In another embodiment of the present application, the battery 3000 can not only be used as the operating power supply of the vehicle, but also as the driving power supply of the vehicle, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle.

[0045] The battery 3000 mentioned in the embodiments of the present application refers to a single physical module that includes one or more battery cells 100 to provide higher voltage and capacity. Referring to Figure 2, the battery 3000 may include multiple battery cells 100. The number of battery cells 100 and the connection between the battery cells 100 can be set as needed to meet different power requirements. Specifically, multiple battery cells 100 can be connected in series, in parallel, or in hybrid. Hybrid refers to a mixture of series and parallel connections so that the battery 3000 has a larger capacity or power. Optionally, multiple battery cells 100 can first be connected in series, in parallel, or in hybrid to form a battery 3000 module, and multiple battery 3000 modules can then be connected in series, in parallel, or in hybrid to form a battery 3000. That is, multiple battery cells can directly form a battery 3000, or they can first form a battery module, and then the battery module can form a battery 3000.

[0046] The battery 3000 also includes a battery case 3001, which has a storage space inside, and multiple battery cells are stored in the storage space. As shown in the figure, the battery case 3001 can include two parts, which are respectively referred to as the first part 30011 and the second part 30012. Please refer to Figure and Figure, which show the first part 30011 of the battery case 3001. The first part 30011 and the second part 30012 can be connected by snapping, bonding, etc. to form a storage space. Multiple battery cells are connected in parallel, series, or mixed and placed in the case formed by connecting the first part 30011 and the second part 30012. The shapes of the first part 30011 and the second part 30012 can be determined according to the shape of the combination of multiple battery cells.

[0047] The battery case 3001 is used to protect at least one battery cell 100, thereby reducing the impact of liquid or other foreign matter outside the battery 3000 on the charging or discharging of the at least one battery cell 100. The battery cell 100 may be cylindrical, flat, rectangular, or in other shapes. The packaging of the battery cell 100 includes, but is not limited to, cylindrical battery cells, prismatic battery cells, and soft-pack battery cells. Furthermore, each battery cell 100 may be a lithium-ion battery cell, a lithium-sulfur battery cell, a sodium-ion battery cell, or a magnesium-ion battery cell, but is not limited thereto and is not specifically limited in the embodiments of the present application.

[0048] In addition, the battery 3000 may also include other structures, which will not be described in detail here. For example, the battery 3000 may also include a busbar. The busbar is used to achieve electrical connection between multiple battery cells, such as parallel connection, series connection, or mixed connection between multiple battery cells. Specifically, the busbar can achieve electrical connection between battery cells by connecting the electrode terminals of the battery cells. Furthermore, the busbar can be fixedly connected to the electrode terminals of the battery cells by welding. Optionally, the busbar may include a conductive mechanism, and the electrical energy generated by the multiple battery cells can be further led out through the battery case 3001 through the conductive mechanism.

[0049] Please refer to Figure 3, which is a schematic diagram of the exploded structure of a battery cell 100 provided in some embodiments of the present application. A battery cell 100 is the smallest unit that makes up a battery 3000. As shown in Figure 3, a battery cell 100 includes a housing 101, an end cap 102, an electrode assembly 103, electrode terminals, and other functional components.

[0050] The end cap 102 is a component that covers the opening of the housing 101 to isolate the internal environment of the battery cell 100 from the external environment. The shape of the end cap 102 can be adapted to the shape of the housing 101 to fit the housing 101. Optionally, the end cap 102 can be made of a material with a certain degree of hardness and strength (such as an aluminum alloy). This prevents the end cap 102 from deforming when subjected to compression or collision, thereby providing the battery cell 100 with greater structural strength and improved safety. Functional components such as electrode terminals can be provided on the end cap 102. The electrode terminals can be used to connect to the electrode assembly 103 to output or input electrical energy to the battery cell. In some embodiments, the end cap 102 can also be provided with a pressure relief mechanism for relieving internal pressure when the internal pressure or temperature of the battery cell 100 reaches a threshold. The end cap 102 can also be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and this embodiment of the present application does not impose any specific limitations on this. In some embodiments, an insulating member may be provided inside the end cap 102 to isolate the electrical connection components in the housing 101 from the end cap 102 to reduce the risk of short circuit.

[0051] The housing 101 is a component that cooperates with the end cap 102 to form the internal environment of the battery cell 100. This internal environment can be used to accommodate the electrode assembly 103, electrolyte, and other components. The housing 101 and end cap 102 can be separate components. An opening can be provided in the housing 101, and the end cap 102 is placed over the opening to form the internal environment of the battery cell. Alternatively, the end cap 102 and housing 101 can be integrated. Specifically, the end cap 102 and housing 101 can form a common connection surface before other components are inserted into the housing. When the interior of the housing 101 is to be enclosed, the end cap 102 is placed over the housing 101. The housing 101 can have a variety of shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, or a hexagonal prism. Specifically, the shape of the housing 101 can be determined based on the specific shape and size of the electrode assembly. The housing 101 can be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and this embodiment of the present application does not impose any specific limitations on this.

[0052] The electrode assembly 103 is a component in the battery cell 100 where electrochemical reactions occur. One or more electrode assemblies 103 may be contained in the housing 101. The electrode assembly 103 is mainly formed by winding a positive electrode sheet and a negative electrode sheet, and a separator is usually provided between the positive electrode sheet and the negative electrode sheet. The parts of the positive electrode sheet and the negative electrode sheet with active materials constitute the main body of the electrode assembly, and the parts of the positive electrode sheet and the negative electrode sheet without active materials each constitute a tab. The positive electrode tab and the negative electrode tab may be located together at one end of the main body or respectively at both ends of the main body. During the charge and discharge process of the battery, the positive electrode active material and the negative electrode active material react with the electrolyte, and the tabs connect the electrode terminals to form a current loop.

[0053] Referring to FIG. 3 , a battery cell 100 includes a housing 101 , a plurality of electrode assemblies 103 , and a buffer structure 104 .

[0054] Each electrode assembly 103 is disposed in the housing 101; the buffer structure 104 is disposed between two adjacent electrode assemblies 103; and / or, the buffer structure 104 is disposed between the electrode assembly 103 and the inner wall of the housing 101;

[0055] The cumulative volume V of the buffer structure 104 , the compression rate B of the buffer structure 104 , and the cell capacity Cn of the battery cell 100 satisfy the following relationship: 0.7 (mL / Ah) ≤ V*B / Cn ≤ 1.0 (mL / Ah), where the compression rate B of the buffer structure 104 refers to the compression rate of the buffer structure 104 under a pressure of 1 MPa.

[0056] It can be understood that the number of electrode assemblies 103 means that the number of electrode assemblies 103 can be one, or more than two. For example, in a cylindrical battery cell, a columnar electrode assembly is arranged in its shell 101; for another example, in a square battery cell, a plurality of square electrode assemblies can be stacked in a direction perpendicular to its large surface in its shell 101. At the same time, the buffer structure 104 can be adjusted according to the number of electrode assemblies 103. For example, the buffer structure 104 can be arranged between two adjacent electrode assemblies 103; or, the buffer structure 104 can also be arranged between the electrode assembly 103 and the inner wall of the shell 101; or, the buffer structure 104 can also be arranged between two adjacent electrode assemblies 103, and between the electrode assembly 103 and the inner wall of the shell 101.

[0057] Among them, for square battery cells, the large surface of the shell of the square battery cell refers to the end surface with the largest area among the surfaces of the shell, and the large surface of each square electrode assembly refers to the surface corresponding to the large surface of the shell of the square battery cell. Each square electrode assembly is stacked in a direction perpendicular to its large surface. Here, the main expansion direction of the square electrode assembly is perpendicular or approximately perpendicular to the large surface of the square electrode assembly.

[0058] For a cylindrical battery cell, the electrode cell disposed therein is a columnar electrode assembly. Therefore, the main expansion direction of the columnar electrode assembly is a radial direction outward along the radial direction of the columnar electrode assembly with the central axis of the columnar electrode assembly as the center.

[0059] The buffer structure 104 is a structural component having a certain deformation capability, specifically, a certain compression capability. Therefore, the shape and material of the buffer structure 104 can be limited according to actual use requirements.

[0060] Here, the shape of the buffer structure 104 should be adapted to the shape of the electrode assembly 103. For example, the buffer structure 104 arranged between the cylindrical shell 101 and the columnar electrode assembly 103 can be in the shape of a hollow tubular structure or a strip structure; for another example, the buffer structure 104 arranged between the electrode assemblies 103 can be in the shape of a block structure.

[0061] The material of the buffer structure 104 includes but is not limited to foamed polyethylene, polypropylene, polyurethane, silicone rubber, high-density polyethylene, polymethacrylate, polyethylene terephthalate, polytetrafluoroethylene, etc.

[0062] The function of the buffer structure 104 is to limit the expansion of the electrode assembly 103 during charging cycles. This is because the thick electrode deposit layer forms sharp structures in local areas of the electrode assembly 103. Specifically, the buffer structure 104 can squeeze the electrode deposit layer in this area. The cumulative volume V of the buffer structure 104 refers to the sum of the volumes of each buffer structure 104 at 25 degrees Celsius and standard atmospheric pressure. Therefore, the cumulative volume V of the buffer structure 104 is expressed in milliliters or cubic centimeters. The cumulative volume V of the buffer structure 104 is measured by the maximum volume that each buffer structure 104 can recover after being removed from the housing at 25 degrees Celsius and standard atmospheric pressure.

[0063] The compressibility B of the buffer structure 104 refers to the compressibility of the buffer structure 104 under a pressure of 1 MPa.

[0064] The compression ratio B is (the cumulative volume V of the buffer structure 104 - the volume of the buffer structure 104 at 100% SOC) / the cumulative volume V of the buffer structure 104. The volume of the buffer structure 104 at 100% SOC is the volume of each buffer structure 104 after being compressed when the battery cell 100 is charged to 100% SOC (state of charge).

[0065] The cell capacity Cn of the battery cell 100 is the rated capacity of the battery cell 100 . The rated capacity and rated voltage of the battery cell 100 can be obtained from the nameplate on the battery cell 100 . Therefore, the unit of the cell capacity Cn of the battery cell 100 is Ah.

[0066] The product of the cumulative volume V of the buffer structure 104 and the compression rate B refers to the volume compression of the total volume of each buffer structure 104 after being squeezed by the expanded electrode assembly when the battery cell is charged to 100% SOC at 25 degrees Celsius and standard atmospheric pressure.

[0067] The value range of V*B / Cn is 0.7 mL / Ah to 1.0 mL / Ah. It is understandable that the value of V*B / Cn can be 0.7 mL / Ah, 0.75 mL / Ah, 0.8 mL / Ah, 0.85 mL / Ah, 0.95 mL / Ah, 1.0 mL / Ah, etc.

[0068] When the value of V*B / Cn is 0.7 mL / Ah, which means that when the type of the battery cell 100 is determined and the cell capacity Cn of the battery cell 100 is constant, the total volume deformation of the buffer structure 104 should meet the above minimum volume deformation requirement.

[0069] When the value of V*B / Cn is 1.0 mL / Ah, it means that when the type of the battery cell 100 is determined and the cell capacity Cn of the battery cell 100 is a constant value, the total volume compression of the buffer structure 104 should meet the above-mentioned maximum volume deformation requirement.

[0070] It should be noted that, as shown in Figure 4, when performing specific calculations, the volume compression V*B of the buffer structure 104 should be equal to the thickness L of the buffer structure 104*the area M of the large surface N of the buffer structure 104*the compression rate B of the buffer structure 104, wherein the area M of the large surface N of the buffer structure 104 refers to the area parallel to the plane where the large surface of the electrode assembly is located, or refers to the area perpendicular to the main expansion direction of the electrode assembly.

[0071] Then, when the size of the electrode assembly 103 to be buffered and restricted is determined, the area M of the large surface N of the buffer structure 104 should be equal to or nearly equal to the large surface area of ​​the electrode assembly 103. At the same time, the compression rate B of the buffer structure 104 refers to the compression rate of the buffer structure 104 under a pressure of 1 MPa. Therefore, V*B / Cn is converted, V*B / Cn=L*M*B / Cn.

[0072] The battery cell 100 provided in the embodiments of the present application has a buffer structure 104 disposed between two adjacent electrode assemblies 103; or, alternatively, between an electrode assembly 103 and a housing 101; or, alternatively, between two adjacent electrode assemblies 103 and between an electrode assembly 103 and a housing 101. In this manner, the buffer structure 104 limits the expansion of the electrode assembly 103 during charge and discharge cycles, allowing the electrode assembly 103 to be constrained when it expands to a certain extent. The buffer structure 104 then buffers and compresses the deposited layer between the electrode pieces of the electrode assembly 103, thereby reducing the formation of sharp structures in the deposited layer between the electrode pieces of the electrode assembly 103. Ultimately, the probability of micro-short circuits in the electrode assembly 103 of the battery cell 100 is significantly reduced, thereby improving the safety performance of the battery. Furthermore, the relationship between the compressed volume and compression rate of the buffer structure 104 and the battery capacity of the battery cell 100 is further defined, and corresponding upper and lower limits are set to obtain a buffer structure 104 with an appropriate total volume.

[0073] In one embodiment, each electrode assembly 103 is arranged along its own expansion direction, and the buffer structure 104 is arranged between any two adjacent electrode assemblies 103; or, the buffer structure 104 is arranged between the electrode assembly 103 and the inner wall of the shell 101 corresponding to the expansion direction of the electrode assembly 103.

[0074] It is understood that, specifically, the direction of the arrow in FIG3 represents the primary expansion direction of each electrode assembly 103. When the electrode assembly 103 undergoes an electrolytic reaction with the electrolyte, it expands along the stacking direction of its electrode sheets. That is, the expansion direction of the electrode assembly 103 itself is the stacking direction of its electrode sheets. For example, when the electrode assembly 103 is formed by winding a continuous length of electrode sheets, the expansion direction of the electrode assembly 103 is radially outward from the winding center; or, when the electrode assembly 103 is stacked by independent electrode sheets, the expansion direction of the electrode assembly 103 is the thickness direction of the stacked electrode sheets.

[0075] For example, when there is only one electrode assembly 103, the buffer structure 104 is disposed between the electrode assembly 103 and the housing 101 along the expansion direction of the electrode assembly 103. The shape of the buffer structure 104 is adaptively adjusted based on the shape of the electrode assembly 103. If the electrode assembly 103 is a cubic structure, the buffer structure 104 can be a sheet or block structure and located on the circumferential sidewalls of the electrode assembly 103. Alternatively, if the electrode assembly 103 is cylindrical, the buffer structure 104 can be an arc-shaped sheet or strip structure and similarly distributed on the circumferential sidewalls of the electrode assembly 103.

[0076] For example, when there are two or more electrode assemblies 103, similarly, in the expansion direction, the buffer structure 104 may be provided only between the electrode assemblies 103; or, the buffer structure 104 may be provided only between the electrode assembly 103 and the housing 101; or, the buffer structure 104 may be provided between each electrode assembly 103 and between the electrode assembly 103 and the housing 101. Especially when there are a large number of electrode assemblies 103, the buffer structure 104 may be provided between every two adjacent electrode assemblies 103.

[0077] The self-expansion direction of the electrode assembly 103 is the main growth direction of the deposition layer. At the same time, each buffer structure 104 is also arranged along the self-expansion direction of the electrode assembly 103. In this way, the abutment between the buffer structure 104 and the electrode assembly 103 is tighter, the contact area between the two is larger, and the abutment restriction effect of the buffer structure 104 is better.

[0078] Here, when the electrode assemblies 103 are arranged in one or more rows within the housing 101 along their own expansion direction, there are electrode assemblies 103 that are farther away from the housing 101. These electrode assemblies 103 are located in the middle of the current row. Similarly, the electrode assemblies 103 that are closer to the housing 101 are the electrode assemblies 103 closer to the housing 101, and their spatial positions are relative. Furthermore, the number of buffer structures 104 farther away from the housing 101 can be one or more, and the number of buffer structures 104 closer to the housing 101 can also be one or more.

[0079] In one embodiment, the electrode assembly 103 includes stacked electrode sheets, and the buffer structure 104 is further disposed between the electrode sheets of the same electrode assembly 103 .

[0080] It can be understood that the pole pieces of the electrode assembly 103 are the main carriers of the deposition phenomenon. Therefore, setting the buffer structure 104 between the pole pieces of the same electrode assembly 103 can more directly limit the growth and formation process of the deposition layer.

[0081] For example, the buffer structure 104 is disposed between the positive electrode sheets of the electrode assembly 103 ; or, the buffer structure 104 is disposed between the negative electrode sheets of the electrode assembly 103 .

[0082] In one embodiment, the electrode assembly 103 includes a positive electrode sheet, a separator, and a negative electrode sheet stacked together, and the buffer structure 104 is disposed between the positive electrode sheet and the separator; and / or, the buffer structure 104 is disposed between the negative electrode sheet and the separator.

[0083] It can be understood that during the manufacturing process, the electrode assembly 103 is formed by stacking and winding the positive electrode sheet, the separator and the negative electrode sheet, and the buffer structure 104 can be set between the positive electrode sheet and the separator; or, the buffer structure 104 can be set between the negative electrode sheet and the separator; or, the buffer structure 104 can be set between the positive electrode sheet and the separator and between the negative electrode sheet and the separator.

[0084] The buffer structure 104 is set between the pole piece and the diaphragm, and the buffer structure 104 is fixed by the clamping force between the two. In this way, the setting stability of the buffer structure 104 is higher. At the same time, the connection layer structure required for the buffer structure 104 to be set on the side of the pole piece away from the diaphragm can be omitted. For example, through the adhesive connection method, the overall thickness of the buffer structure 104 is thinner, which is also beneficial to improving the energy density of the battery cell 100.

[0085] In terms of layout, the buffer structure 104 can be arranged to fully cover the surface of the positive electrode sheet or the negative electrode sheet, or can be arranged to partially cover the surface of the positive electrode sheet or the negative electrode sheet.

[0086] Exemplarily, the buffer structure 104 is a sheet structure in a wound form, and the width of the buffer structure 104 is the same as the width of the electrode sheet. During the manufacturing process of the electrode assembly 103, the buffer structure 104 is stacked together with the positive electrode sheet, the separator and the negative electrode sheet to form the electrode assembly 103. In this way, the buffer structure 104 completely covers the surface of the positive electrode sheet or the negative electrode sheet.

[0087] Exemplarily, the buffer structure 104 is a layered structure, and the width of the buffer structure 104 can be the same as the width of the electrode. Then, the buffer structure 104 is arranged at intervals along the length direction of the electrode, thereby only covering local areas of the positive electrode and the negative electrode.

[0088] In one embodiment, 0.85 (mL / Ah) ≤ V*B / Cn ≤ 0.95 (mL / Ah).

[0089] It can be understood that the value range of V*B / Cn can also be 0.85mL / Ah, 0.86mL / Ah, 0.87mL / Ah, 0.88mL / Ah, 0.89mL / Ah, 0.90mL / Ah, 0.91mL / Ah, 0.92mL / Ah, 0.93mL / Ah, 0.94mL / Ah, 0.95mL / Ah, etc.

[0090] When the ratio of V*B / Cn is within the above range, the buffer structure 104 can further enhance the limiting effect of the deposited layer in the electrode assembly 103 , thereby reducing the probability of micro-short circuits occurring in the electrode assembly 103 of the battery cell 100 .

[0091] In one embodiment, the ratio of the cumulative volume of the buffer structure 104 to the effective total volume of the electrode assembly 103 is A, and the range of A is: 2%≤A≤17%.

[0092] It can be understood that the cumulative volume of the buffer structure 104 refers to the sum of the volumes of all buffer structures 104 at 25 degrees and standard atmospheric pressure, and the effective total volume of the electrode assembly 103 refers to the sum of the volumes of each electrode assembly 103 in a dry weight state, but does not include the volume of the tabs.

[0093] The significance of the ratio A is to further limit the number of buffer structures 104 used, and thus limit the total volume used by the buffer structures 104, so that more electrode assemblies 103 can be accommodated in the housing 101 without reducing or minimizing the energy density of the battery cell 100.

[0094] For example, the value of A can be 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, etc.

[0095] The test method for the effective total volume of the electrode assembly 103 is as follows:

[0096] If the electrode assembly 103 is a square wound component, the effective total volume of the electrode assembly 103 is equal to or approximately equal to the height of the electrode assembly 103 * the thickness of the electrode assembly 103 * the width of the electrode assembly 103. The length, thickness, and width of the electrode assembly 103 can be measured using a conventional length measuring instrument, such as a vernier caliper.

[0097] If the electrode assembly 103 is a wound cylindrical member, then the effective total volume of the electrode assembly 103 is equal to 0.25*π*the square of the diameter of the electrode assembly 103*the height of the electrode assembly 103; similarly, the diameter and height of the electrode assembly 103 can be measured using a conventional length measuring instrument;

[0098] If the electrode assembly 103 is a laminated piece, then the effective total volume of the electrode assembly 103 is equal to the height of the electrode assembly 103 * the thickness of the electrode assembly 103 * the width of the electrode assembly 103; similarly, the diameter and height of the electrode assembly 103 can be measured by conventional length measuring instruments.

[0099] It should be noted that the electrode assembly 103 is immersed in the electrolyte after leaving the factory. Therefore, the volume of the electrode assembly 103 after leaving the factory can be restored to the volume of the electrode assembly 103 in the laboratory state by the following method:

[0100] First, discharge the battery cell 100 directly to the lower limit nominal voltage after leaving the factory, then disassemble the shell 101 to obtain the electrode assembly 103 soaked in electrolyte, place the electrode assembly 103 in an oven and perform vacuum drying. During the drying process, weigh it multiple times until the weight of the electrode assembly 103 does not change or the change is negligible. The true volume of the electrode assembly 103, that is, the volume of the electrode assembly 103 in the laboratory state, is obtained. Then, the volume parameters of the electrode assembly 103 are obtained through volume measurement methods such as the water displacement method.

[0101] In one embodiment, 2%≤A≤12%.

[0102] It is understood that the value of A can be 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, etc. It is understood that setting the lower limit of A to greater than 2% ensures that the buffer structure 104 can play a corresponding limiting role at this volume ratio; at the same time, setting the value of A to less than or equal to 12% means that an excessively high ratio will cause the buffer structure 104 to compress the internal space of the housing 101, thereby reducing the energy density of the battery cell 100.

[0103] Optionally, in some embodiments, 3%≤A≤7%.

[0104] It can be understood that the value of A can be 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, etc.

[0105] In one embodiment, the compression rate B of the buffer structure 104 is in the range of 50%≤B≤95%.

[0106] It can be understood that the compression rate B of the buffer structure 104 may be 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%.

[0107] The compression rates B of the buffer structures 104 made of different materials are different, and the compression rates B of the buffer structures 104 made of various materials should be within the above range.

[0108] Alternatively, in one embodiment, 70%≤B≤90%.

[0109] It can be understood that the compression rate B of the buffer structure 104 may be 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, etc.

[0110] Alternatively, in one embodiment, 80%≤B≤90%.

[0111] It can be understood that the compression rate B of the buffer structure 104 may be 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, etc.

[0112] In one embodiment, the buffer structure 104 has pores.

[0113] It is understood that the buffer structure 104 having pores means that the buffer structure 104 has a spatial network structure with a certain porosity. Here, the buffer structure 104 may have pores throughout its entire structure, similar to a sponge, or the buffer structure 104 may have pores only partially.

[0114] In this way, the buffer structure 104 having pores can store a certain amount of electrolyte, thereby increasing the reserve amount of electrolyte in the battery cell 100 .

[0115] In one embodiment, the battery cells are sodium metal battery cells;

[0116] The positive electrode of the sodium metal battery cell includes one or more of sodium iron phosphate, layered oxide, sodium iron pyrophosphate, sodium iron sulfate, and sodium vanadium phosphate; and / or,

[0117] The negative electrode of the sodium metal battery cell includes a copper current collector, an aluminum current collector, a copper-aluminum current collector having or containing a carbon-based material coating, and a sodium sheet structure.

[0118] It can be understood that the positive electrode of the sodium metal battery cell can be one or more of a sodium iron phosphate positive electrode, a layered oxide positive electrode, a sodium iron pyrophosphate positive electrode, a sodium iron sulfate positive electrode, and a sodium vanadium phosphate positive electrode.

[0119] Alternatively, the negative electrode of the sodium metal battery cell can be a copper current collector, an aluminum current collector, a copper-aluminum current collector having or including a carbon-based coating, and a sodium sheet structure.

[0120] Alternatively, the positive electrode of the sodium metal battery cell can be one or more of a sodium iron phosphate positive electrode, a layered oxide positive electrode, a sodium iron pyrophosphate positive electrode, a sodium iron sulfate positive electrode, or a sodium vanadium phosphate positive electrode. Meanwhile, the negative electrode of the sodium metal battery cell can be a copper current collector, an aluminum current collector, a copper-aluminum current collector having or including a carbon-based coating, or a sodium sheet structure.

[0121] The following takes sodium metal batteries as an example:

[0122] 1) Preparation of positive electrode slurry

[0123] 95 wt% of sodium battery positive electrode active material (such as common olivine structure sodium iron phosphate, 2.5 wt% of conductive agent (conductive carbon black), 2.0 wt% of binder (polyvinylidene fluoride), and 0.5 wt% of dispersant are mixed, and then N-methylpyrrolidone is added, stirred, and dispersed to prepare a positive electrode slurry.

[0124] 2) Preparation of positive electrode

[0125] The slurry viscosity is adjusted to 8000-20000 mPa.s, and then the first positive electrode slurry is coated on the aluminum foil through a double-sided double-cavity coating device. After the double-sided coating is completed, it is dried, cold pressed, and cut to prepare the positive electrode sheet.

[0126] 3) Preparation of negative electrode sheet

[0127] A negative electrode slurry is prepared by mixing a certain proportion of a negative electrode active material (such as a carbon-based material), 2.0 wt% of a binder (styrene-butadiene rubber (SBR)), and 2.0 wt% of a thickener (sodium carboxymethyl cellulose (CMC)). 0.5 wt% of a dispersant is added and stirred in deionized water. The slurry is then coated on a Cu foil. After both sides are coated, the foil is dried, cold-pressed, slit, and sheeted to produce the negative electrode sheet.

[0128] 4) Battery preparation and design

[0129] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator positioned between the cathode and anode to act as a barrier. The electrode assembly is then wound. The battery consists of four electrode assemblies, and several buffer structures are placed between the electrode assemblies at the locations where the large surfaces contact each other. These structures are then secured and packaged together with the electrode assemblies, placed in an outer package, and the prepared electrolyte is injected. The battery is then packaged, filled, formed, and vented, resulting in a finished product.

[0130] The following examples illustrate the effects of providing a corresponding number of buffer structures 104 in the battery cell 100:

[0131] The experimental objects in each embodiment are sodium metal battery cells of the same specification, so as to ensure the single variable of the buffer structure 104 .

[0132] Table 1 shows the relationship between the compressed volume V and compression ratio B of different buffer structures 104 and the cell capacity Cn of the same battery cell 100. It can be seen that, using the parameters of Example 1 as a standard, when the ratio of the compressed volume V and compression ratio B of the buffer structure 104 to the cell capacity Cn of the battery cell 100 is 0.7, the energy density of the current battery cell 100 is unaffected, and therefore its energy density is 0%. As the V*B value of the buffer structure 104 increases, the energy density of the battery cell 100 also decreases accordingly, indicating that the buffer structure 104 requires a certain amount of internal space in the housing 101 of the battery cell 100. At the same time, as the V*B value of the buffer structure 104 continues to increase, the cycle life of the battery cell 100 also shows a corresponding increasing trend, indicating that the restrictive effect of the buffer structure 104 on the electrode assembly 103 in the battery cell 100 becomes more and more obvious. Therefore, it is necessary to select a compromise ratio between the V*B value of the buffer structure 104 and the current energy density of the battery cell 100, that is, to maximize the cycle life of the battery cell 100, but the energy density of the battery cell 100 cannot be reduced too much. It can be seen from the embodiment that when V*B / Cn=0.95, this buffer structure 104 can meet the above conditions.

[0133] Table 2 shows the relationship between the ratio A of the cumulative volume of different buffer structures 104 to the total volume of the electrode assembly 103, the compression ratio B of the buffer structure 104, and the energy density and cycle life of the same battery cell 100. It can be seen that, using the parameters of Comparative Example 1 as the standard, that is, the current battery cell 100 does not have a buffer structure 104, the values ​​A and B are both 0. In this case, the energy density of the current battery cell 100 is unaffected and, therefore, its energy density is 0%.

[0134] Comparing Examples 1 to 6, when the compression ratio B of the buffer structure 104 remains constant, as the cumulative volume of the buffer structure 104 increases relative to the total volume of the electrode assembly 103, i.e., the value A gradually increases, the energy density of the battery cell 100 decreases accordingly. This indicates that the buffer structure 104 requires a certain amount of internal space within the housing 101 of the battery cell 100. Simultaneously, the cycle life of the battery cell 100 also increases accordingly, indicating that the buffer structure 104 has an increasingly significant restraining effect on the electrode assembly 103 within the battery cell 100. Furthermore, in Examples 3 and 4, the cycle life of the battery cell 100 is highest when the value A is between 6% and 7%.

[0135] Comparing Examples 6 to 10 horizontally, when the A value remains fixed, as the compression rate B of the buffer structure 104 increases, the cycle life of the battery cell 100 shows a trend of first decreasing and then increasing, but the fluctuation amplitude is small, that is, when the cumulative volume of the buffer structure 104 remains unchanged, the compression rate of the buffer structure 104 has a relatively small effect on the cycle life of the battery cell 100.

[0136] A vertical comparison of Example 2 and Example 9 shows that the cumulative volume proportions of the buffer structure 104 in the two embodiments are different, and the compression rates of the buffer structure 104 are also different. However, the cycle life of the corresponding battery cells 100 is not much different, and the energy density is the same, indicating that the overall compression amount of the buffer structure 104 (the degree of restriction on the electrode assembly 103) can be adjusted according to the compression rate B and the volume proportion, so as to obtain a buffer structure 104 with better performance.

[0137] As can be seen from Comparative Examples 2 and 3, only when the compression ratio B and A values ​​of the buffer structure 104 simultaneously satisfy the corresponding ranges can the battery cell 100 have both a longer cycle life and a higher energy density.

[0138] Referring to the figure, in a specific embodiment, a battery cell 100 includes a housing 101 , a plurality of electrode assemblies 103 and a buffer structure 104 .

[0139] Each electrode assembly 103 is arranged along its own expansion direction, and the buffer structure 104 is provided between any two adjacent electrode assemblies 103 .

[0140] The value range of V*B / Cn is 0.85mL / Ah to 0.95mL / Ah.

[0141] The ratio of the cumulative volume of the buffer structure 104 to the effective total volume of the electrode assembly 103 is A, and the range of A is: 3%≤A≤7%.

[0142] The range of the compression rate B of the buffer structure 104 is: 70%≤B≤90%.

[0143] The buffer structure 104 has pores.

[0144] In a second aspect, an embodiment of the present application further provides a battery, comprising the above-mentioned battery cell 100 .

[0145] In a third aspect, an embodiment of the present application further provides an electrical device comprising the above-mentioned battery.

[0146] The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A battery cell, characterized in that: include, case; A plurality of electrode assemblies, each of which is disposed in the housing; A buffer structure, wherein the buffer structure is disposed between two adjacent electrode assemblies; and / or the buffer structure is disposed between the electrode assembly and the inner wall of the housing; The cumulative volume V of the buffer structure, the compression rate B of the buffer structure, and the cell capacity Cn of the battery cell have the following relationship, wherein the compression rate B of the buffer structure refers to the compression rate of the buffer structure under a pressure of 1 MPa: 0.7(mL / Ah)≤V*B / Cn≤1.0(mL / Ah).

2. The battery cell according to claim 1, characterized in that: The electrode assembly includes stacked electrode sheets, and the buffer structure is also arranged between the electrode sheets of the same electrode assembly; the electrode assembly includes stacked positive electrode sheets, diaphragms and negative electrode sheets, and the buffer structure is arranged between the positive electrode sheets and the diaphragms; and / or the buffer structure is arranged between the negative electrode sheets and the diaphragms.

3. The battery cell according to claim 1, characterized in that: 0.85(mL / Ah)≤V*B / Cn≤0.95(mL / Ah).

4. The battery cell according to any one of claims 1 to 3, characterized in that: The ratio of the cumulative volume of the buffer structure to the effective total volume of the electrode assembly is A, and the range of A is: 2%≤A≤17%.

5. The battery cell according to claim 4, characterized in that: 2％≤A≤12％。 6. The battery cell according to any one of claims 1 to 3, characterized in that: The compression rate B of the buffer structure is in the range of 50%≤B≤95%.

7. The battery cell according to claim 6, characterized in that: 70％≤B≤90％。 8. The battery cell according to any one of claims 1 to 3, characterized in that: The buffer structure has pores.

9. The battery cell according to any one of claims 1 to 3, characterized in that: The battery cell is a sodium metal battery cell; The positive electrode of the sodium metal battery cell includes one or more of sodium iron phosphate, layered oxide, sodium iron pyrophosphate, sodium iron sulfate, and sodium vanadium phosphate; and / or, The negative electrode of the sodium metal battery cell includes a copper current collector, an aluminum current collector, a copper-aluminum current collector having or containing a carbon-based material coating, and a sodium sheet structure.

10. A battery, characterized in that: The invention comprises a battery cell as claimed in any one of claims 1 to 9.

11. An electrical equipment, characterized in that: Comprising the battery as claimed in claim 10.

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