Battery monomer, battery and electric equipment

Abstract

The utility model relates to the technical field of batteries, and provides a single battery, a battery and electric equipment, the single battery comprises a shell, a plurality of electrode assemblies and a buffer structure, and each electrode assembly is arranged in the shell; the buffer structure is arranged between two adjacent electrode assemblies; and / or the buffer structure is arranged between the electrode assembly and the inner wall of the shell; wherein the compression volume V of the buffer structure, the compression ratio B of the buffer structure and the cell capacity Cn of the single battery have the following relational expression: 0.7 (mL / Ah) < = V * B / Cn < = 1.0 (mL / Ah). The buffer structure can be used for buffering and limiting the deposition layer formed by the negative electrode in the battery monomer so as to reduce the probability of micro short circuit of the electrode assembly caused by the fact that the deposition layer grows in any direction to form a sharp structure to pierce the diaphragm.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, and in particular provides a battery monomer, a battery and an electrical device. Background Art

[0002] 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.

[0003] 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. Utility Model Content

[0004] The utility model aims 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.

[0005] In order to achieve the above purpose, the technical solution adopted by the utility model is:

[0006] In a first aspect, an embodiment of the present application provides a battery cell, comprising:

[0007] case;

[0008] A plurality of electrode assemblies, each of which is disposed in the housing;

[0009] 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;

[0010] 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:

[0011] 0.7(mL / Ah)≤V*B / Cn≤1.0(mL / Ah).

[0012] Beneficial effects of the utility model: The battery cell provided by the utility model has a buffer structure between two adjacent electrode assemblies; or, a buffer structure is provided between the electrode assembly and the shell; or, a buffer structure is provided between adjacent electrode assemblies and between the electrode assembly and the 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 punctures the diaphragm due to the sharp structure formed by the growth in any direction, causing a micro-short circuit in the point electrode assembly. In addition, the product of the compression volume V of the buffer structure and the compression rate B of the buffer structure and the battery cell capacity Cn of the battery cell have the above relationship. V*B / Cn is greater than or equal to 0.7mL / Ah, which means that when the battery 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 battery 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 separator and a negative electrode sheet that are stacked, and the buffer structure is arranged between the positive electrode sheet and the separator; and / or the buffer structure is arranged between the negative electrode sheet and the separator.

[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 comprises one 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 invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 A schematic diagram of the structure of an electrical device provided in an embodiment of the utility model;

[0027] Figure 2 A schematic diagram of the structure of a battery provided in an embodiment of the utility model;

[0028] Figure 3 An exploded view of a battery cell provided in an embodiment of the utility model;

[0029] Figure 4 for Figure 3 Structural diagram of the buffer structure.

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

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

[0032] 3000, battery; 3001, battery box; 30011, first part; 30012, second part;

[0033] 100. Battery cell; 101. Shell; 102. End cover; 103. Electrode assembly; 104. Buffer structure. DETAILED DESCRIPTION

[0034] The embodiments of the present invention are described in detail below, and examples of the embodiments 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 invention, and should not be construed as limiting the present invention.

[0035] In the description of the present invention, 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 the present invention 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 the present invention.

[0036] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present utility model, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0037] In the present invention, unless otherwise clearly specified and limited, the terms "install", "connect", "connect", "fix" and the like 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 mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0038] 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.

[0039] This deposition process is irregular, which also leads to a high probability that the deposition layer will form sharp structures on the electrode plates of the electrode assembly. As a result, during the charge and discharge cycle expansion process of the electrode assembly, the sharp structures of the deposition layer will likely puncture the diaphragm, causing a partial or local short circuit between the positive and negative plates of the electrode assembly, ultimately leading to an abnormal increase in the internal current of the battery cell and battery overheating.

[0040] In view of this, the present application provides a battery cell, wherein a buffer structure is provided between two adjacent electrode assemblies; or, a buffer structure is provided between an electrode assembly and a shell; or, a buffer structure is provided between two adjacent electrode assemblies and between an electrode assembly and a shell, so that the expansion of the electrode assembly during charge and discharge cycles is limited by the buffer structure, so that the electrode assembly is in a restricted state when it expands to a certain extent, thereby utilizing the buffer structure to buffer and squeeze the deposited layer between the pole pieces of the electrode assembly, so as to reduce the formation of a sharp structure of the deposited layer between the pole pieces of the electrode assembly, and ultimately, greatly reduce 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.

[0041] A battery cell includes an electrode assembly and an electrolyte. The electrode assembly is composed of 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 electrode collector and a positive electrode active material layer. The positive electrode active material layer is coated on the surface of the positive electrode collector. The current collector not coated with the positive electrode active material layer protrudes from the current collector coated with the positive electrode active material layer. The current collector not coated with the positive electrode active material layer is stacked as a positive electrode tab. For the convenience of description, the term "tab" is used below to refer to the positive electrode tab and / or the negative electrode tab.

[0042] In the present 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 can be cylindrical, flat, rectangular or other shapes. Battery cells are generally divided into three types according to the packaging method: cylindrical battery cells, square battery cells and soft-pack battery cells.

[0043] The embodiment of the present application provides a kind of electric equipment 10000 which can be applied to vehicles, mobile phones, portable devices, laptops, ships, spacecrafts, electric tools, etc. using the above-mentioned battery cell 100 as a power source. Among them, 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, etc.; the spacecraft includes airplanes, rockets, space shuttles and spacecrafts, etc.; the electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, electric airplane toys, etc.; the electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools and iron electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators and electric planers, etc.

[0044] The battery cell 100 described in the embodiment of the present application is not limited to the above-described electrical equipment 10000, but can also be applied 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.

[0045] For example, see Figure 1 , Figure 1 This is a schematic diagram of the structure of a vehicle according to an embodiment of the present application. The vehicle may be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 3000, a controller 1000 and a motor 2000 may be provided inside the vehicle, and the controller 1000 is used to control the battery 3000 to supply power to the motor 2000. For example, a battery 3000 may be provided at the bottom, front or rear of the vehicle. The battery 3000 may be used to power the vehicle. For example, the battery 3000 may be used as an operating power source for the vehicle, 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 may be used not only as an operating power source for the vehicle, but also as a driving power source for the vehicle, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle.

[0046] The battery 3000 mentioned in the embodiment of the present application refers to a single physical module including one or more battery cells 100 to provide higher voltage and capacity. Figure 2 , the battery 3000 may include a plurality of battery cells 100. The number of battery cells 100 and the connection between the battery cells 100 can be set as required to meet different power requirements. Specifically, a plurality of battery cells 100 can be connected in series, in parallel, or in mixed connection, and mixed connection refers to a mixture of series connection and parallel connection so that the battery 3000 has a larger capacity or power. Optionally, a plurality of battery cells 100 can be connected in series, in parallel, or in mixed connection to form a battery 3000 module, and a plurality of battery 3000 modules can be connected in series, in parallel, or in mixed connection to form a battery 3000. In other words, a plurality of 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.

[0047] The battery 3000 also includes a battery case 3001, and the battery case 3001 has a storage space inside, and multiple battery cells are stored in the storage space. As shown in the figure, the battery case 3001 may 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 are the first part 30011 of a 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 box formed by connecting the first part 30011 and the second part 30012. Among them, the shapes of the first part 30011 and the second part 30012 can be determined according to the shape formed by the combination of multiple battery cells.

[0048] The battery case 3001 is used to protect at least one battery cell 100, thereby reducing the influence of liquid or other foreign matter outside the battery 3000 on the charging or discharging of at least one battery cell 100. The battery cell 100 may be cylindrical, flat, rectangular or other shapes. The packaging methods of the battery cell 100 include but are not limited to cylindrical battery cells, square battery cells and soft-pack battery cells, and 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 the embodiments of the present application do not specifically limit this.

[0049] In addition, the battery 3000 may also include other structures, which are not described one by one 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. Further, 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 electric energy generated by the multiple battery cells can be further led out through the battery case 3001 through the conductive mechanism.

[0050] Please refer to Figure 3 , Figure 3 The schematic diagram of the exploded structure of the battery cell 100 provided in some embodiments of the present application. The battery cell 100 refers to the smallest unit constituting the battery 3000. Figure 3 The battery cell 100 includes a shell 101, an end cover 102, an electrode assembly 103, electrode terminals and other functional components.

[0051] The end cap 102 refers to a component that covers the opening of the shell 101 to isolate the internal environment of the battery cell 100 from the external environment. Without limitation, the shape of the end cap 102 can be adapted to the shape of the shell 101 to match the shell 101. Optionally, the end cap 102 can be made of a material with a certain hardness and strength (such as aluminum alloy), so that the end cap 102 is not easy to deform when it is squeezed and collided, so that the battery cell 100 can have a higher structural strength and the safety performance can also be improved. Functional components such as electrode terminals can be provided on the end cap 102. The electrode terminal can be used to connect with the electrode assembly 103 for outputting or inputting the electrical energy of the battery cell. In some embodiments, the end cap 102 can also be provided with a pressure relief mechanism for releasing the internal pressure when the internal pressure or temperature of the battery cell 100 reaches a threshold. The material of the end cap 102 can also be a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiment of the present application does not impose any special restrictions 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. For example, the insulating member may be plastic, rubber, or the like.

[0052] The shell 101 is a component used to cooperate with the end cap 102 to form the internal environment of the battery cell 100, wherein the formed internal environment can be used to accommodate the electrode assembly 103, the electrolyte and other components. The shell 101 and the end cap 102 can be independent components, and an opening can be set on the shell 101, and the internal environment of the battery cell is formed by covering the opening with the end cap 102 at the opening. Without limitation, the end cap 102 and the shell 101 can also be integrated. Specifically, the end cap 102 and the shell 101 can form a common connection surface before other components are put into the shell, and when the interior of the shell 101 needs to be encapsulated, the end cap 102 covers the shell 101. The shell 101 can be of various shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shape of the shell 101 can be determined according to the specific shape and size of the electrode assembly. The material of the shell 101 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiment of the present application does not impose any special restrictions on this.

[0053] The electrode assembly 103 is a component in the battery cell 100 where electrochemical reactions occur. One or more electrode assemblies 103 may be included 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 at both ends of the main body respectively. 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.

[0054] Please refer to Figure 3 The battery cell 100 includes a shell 101 , a plurality of electrode assemblies 103 and a buffer structure 104 .

[0055] 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;

[0056] Among them, 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 have the following relationship: 0.7 (mL / Ah) ≤ V*B / Cn ≤ 1.0 (mL / Ah), wherein 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.

[0057] 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.

[0058] Among them, for a square battery cell, the large surface of the shell of the square battery cell refers to the end surface with the largest area among all 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.

[0059] 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.

[0060] The buffer structure 104 refers to a structural member 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.

[0061] 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 columnar shell 101 and the columnar electrode assembly 103 may 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 may be in the shape of a block structure.

[0062] 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.

[0063] The function of the buffer structure 104 is to limit the expansion of the electrode assembly 103 during the charging cycle. The local area of ​​the electrode assembly 103 forms a sharp structure due to the thick electrode deposition layer. That is, the buffer structure 104 can squeeze and limit the electrode deposition layer in this area.

[0064] The cumulative volume V of the buffer structure 104 refers to the sum of the volumes of each buffer structure 104 at 25 degrees and standard atmospheric pressure, and thus the cumulative volume V of the buffer structure 104 is in milliliters or cubic centimeters. The cumulative volume V of the buffer structure 104 is measured by taking each buffer structure 104 out of the housing and then restoring the maximum volume of each buffer structure 104 at 25 degrees and standard atmospheric pressure.

[0065] The compressibility B of the buffer structure 104 refers to the compressibility of the buffer structure 104 under a pressure of 1 MPa.

[0066] The compression ratio B is (cumulative volume V of the buffer structure 104 - volume of the buffer structure 104 at 100% SOC) / 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).

[0067] 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.

[0068] The product of the cumulative volume V of the buffer structure 104 and the compression rate B refers to the volume compression amount 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 and standard atmospheric pressure.

[0069] The value range of V*B / Cn is 0.7mL / Ah to 1.0mL / Ah. It can be understood that the value of V*B / Cn can be 0.7mL / Ah, 0.75mL / Ah, 0.8mL / Ah, 0.85mL / Ah, 0.95mL / Ah, 1.0mL / Ah, etc.

[0070] When the value of V*B / Cn is 0.7 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 deformation of the buffer structure 104 should meet the above minimum volume deformation requirement.

[0071] 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 total volume compression requirement of its maximum volume deformation.

[0072] It should be noted that if Figure 4 As shown, 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.

[0073] Then, when the size of the electrode assembly 103 to be buffered 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.

[0074] The battery cell 100 provided by the embodiment of the utility model has a buffer structure 104 disposed between two adjacent electrode assemblies 103; or, a buffer structure 104 is disposed between the electrode assembly 103 and the shell 101; or, a buffer structure 104 is disposed between two adjacent electrode assemblies 103 and between the electrode assembly 103 and the shell 101. In this way, the buffer structure 104 is used to limit the expansion of the electrode assembly 103 during charge and discharge cycles, so that the electrode assembly 103 can be in a restricted state when it expands to a certain extent, so that the buffer structure 104 is used to buffer and squeeze the deposited layer between the pole pieces of the electrode assembly 103, so as to reduce the formation of a sharp structure of the deposited layer between the pole pieces of the electrode assembly 103, and finally, the probability of micro-short circuit of the electrode assembly 103 of the battery cell 100 is greatly reduced, so as to improve the safety performance of the battery. At the same time, 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 limited, and the buffer structure 104 with a suitable total volume is obtained by setting the corresponding upper and lower limit values.

[0075] 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.

[0076] Understandably, specifically, Figure 3 The direction of the middle arrow is the main expansion direction of each electrode assembly 103. When the electrode assembly 103 undergoes electrolysis reaction with the electrolyte, it will expand along the stacking direction of each electrode sheet, that is, the expansion direction of the electrode assembly 103 itself is the stacking direction of each electrode sheet. 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 the radial direction from the winding center to the outside; or, when the electrode assembly 103 is stacked by each independent electrode sheet, the expansion direction of the electrode assembly 103 is the thickness direction of each stacked electrode sheet.

[0077] For example, when the number of electrode assemblies 103 is one, the buffer structure 104 is arranged between the electrode assembly 103 and the shell 101 along the expansion direction of the electrode assembly 103. At the same time, the shape and structure of the buffer structure 104 are adaptively adjusted according to the shape and structure of the electrode assembly 103. If the electrode assembly 103 is a cubic structure, the buffer structure 104 can be a sheet structure or a block structure, and is located on the peripheral side wall of the electrode assembly 103. Alternatively, if the electrode assembly 103 is in a cylindrical state, the buffer structure 104 can be an arc-shaped sheet or a strip structure, and is similarly distributed on the peripheral side wall of the electrode assembly 103.

[0078] For example, when there are more than two electrode assemblies 103, similarly, in the expansion direction thereof, 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 assemblies 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. In particular, when there are a large number of electrode assemblies 103, the buffer structure 104 may be provided between each two adjacent electrode assemblies 103.

[0079] 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 limiting effect of the buffer structure 104 is better.

[0080] Here, when the electrode assemblies 103 are arranged in one or more rows in the shell 101 along the direction of their own expansion, there are electrode assemblies 103 far away from the shell 101, and these electrode assemblies 103 are located in the middle of the current row. Similarly, the electrode assemblies 103 closer to the shell 101 are the electrode assemblies 103 close to the shell 101, and the spatial positions of the two are relative. At the same time, the number of buffer structures 104 far away from the shell 101 can be one or more, and the number of buffer structures 104 close to the shell 101 can also be one or more.

[0081] In one embodiment, the electrode assembly 103 includes stacked pole pieces, and the buffer structure 104 is also disposed between the pole pieces of the same electrode assembly 103 .

[0082] It can be understood that the pole pieces of the electrode assembly 103 are the main carriers of the deposition phenomenon. Therefore, disposing 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.

[0083] 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 .

[0084] In one embodiment, the electrode assembly 103 includes a positive electrode sheet, a separator and a negative electrode sheet which are stacked, 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.

[0085] 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.

[0086] The buffer structure 104 is arranged 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 buffer structure 104 is arranged more stably. At the same time, the connection layer structure required for the buffer structure 104 to be arranged 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.

[0087] In terms of layout, the buffer structure 104 can be arranged to completely 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.

[0088] 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.

[0089] 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 sheet. Then, the buffer structure 104 is arranged at intervals along the length direction of the electrode sheet, thereby only covering partial areas of the positive electrode sheet and the negative electrode sheet.

[0090] In one embodiment, 0.85 (mL / Ah) ≤ V*B / Cn ≤ 0.95 (mL / Ah).

[0091] 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.

[0092] When the ratio of V*B / Cn is within the above range, the limiting effect of the buffer structure 104 on the deposition layer in the electrode assembly 103 can be further enhanced, thereby reducing the probability of micro-short circuits occurring in the electrode assembly 103 of the battery cell 100 .

[0093] 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%.

[0094] 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.

[0095] The significance of the ratio A is to further limit the number of buffer structures 104 used, and further 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 less reducing the energy density of the battery cell 100.

[0096] 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.

[0097] The test method of the effective total volume of the electrode assembly 103 is as follows:

[0098] If the electrode assembly 103 is a square winding, 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, and the length, thickness and width can be measured by a conventional length measuring instrument, such as a vernier caliper.

[0099] 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 by a conventional length measuring instrument;

[0100] 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.

[0101] It should be noted that the electrode assembly 103 after leaving the factory is immersed in the electrolyte. 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:

[0102] First, the battery cell 100 is discharged to the lower limit nominal voltage after leaving the factory, and then the shell 101 is disassembled to obtain the electrode assembly 103 soaked in electrolyte, and the electrode assembly 103 is placed in an oven for vacuum drying. The electrode assembly 103 is weighed several times during the drying process until the weight of the electrode assembly 103 does not change or the change is negligible. The real volume of the electrode assembly 103, that is, the volume of the electrode assembly 103 in the laboratory state, is obtained, and then the volume parameters of the electrode assembly 103 are obtained through volume measurement methods such as the water displacement method.

[0103] In one embodiment, 2%≤A≤12%.

[0104] It is understandable that the value of A can be 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, etc. It is understandable that setting the lower limit of A to be greater than 2% means that the buffer structure 104 can play a corresponding limiting role under this volume ratio; at the same time, the value of A is less than or equal to 12% means that too high a ratio will cause the buffer structure 104 to compress the internal space of the shell 101, thereby reducing the energy density of the battery cell 100.

[0105] Optionally, in some embodiments, 3%≤A≤7%.

[0106] 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.

[0107] In one embodiment, the compression rate B of the buffer structure 104 is in the range of 50%≤B≤95%.

[0108] 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%.

[0109] 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.

[0110] Optionally, in one embodiment, 70%≤B≤90%.

[0111] 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.

[0112] Optionally, in one embodiment, 80%≤B≤90%.

[0113] 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.

[0114] In one embodiment, the buffer structure 104 has pores.

[0115] It can be understood that the buffer structure 104 has pores means that the buffer structure 104 has a spatial network structure with a certain porosity. Here, the buffer structure 104 may have pores in the entire structure, similar to a sponge, or the buffer structure 104 may have pores only in a local structure.

[0116] 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 .

[0117] In one embodiment, the battery cells are sodium metal battery cells;

[0118] The positive electrode of the sodium metal battery monomer includes one of sodium iron phosphate, layered oxide, sodium iron pyrophosphate, sodium iron sulfate, and sodium vanadium phosphate; and / or,

[0119] 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.

[0120] It can be understood that the positive electrode of the sodium metal battery cell can be one 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.

[0121] 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 substance coating, and a sodium sheet structure.

[0122] 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, and 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 material coating, and a sodium sheet structure.

[0123] The following takes sodium metal battery as an example:

[0124] 1) Preparation of positive electrode slurry

[0125] 95wt% of sodium positive electrode active material (such as common olivine structure sodium iron phosphate, 2.5wt% of conductive agent (conductive carbon black), 2.0wt% of binder (polyvinylidene fluoride), and 0.5wt% of dispersant are mixed, and then N-methylpyrrolidone is added, stirred, and dispersed to prepare positive electrode slurry.

[0126] 2) Preparation of positive electrode

[0127] The viscosity of the slurry 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, cut, and prepared to obtain the positive electrode sheet.

[0128] 3) Preparation of negative electrode

[0129] A certain proportion of negative electrode active material (such as carbon-based material), 2.0wt% binder (styrene-butadiene rubber (SBR)) and 2.0wt% thickener (sodium carboxymethyl cellulose (CMC)) are mixed, and 0.5wt% dispersant is added to deionized water and stirred to disperse to form negative electrode slurry. Then the negative electrode slurry is coated on Cu foil. After both sides are completed, it is dried, cold pressed, cut and sliced ​​to prepare the negative electrode sheet.

[0130] 4) Preparation and design of batteries

[0131] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, so that the separator is placed between the cathode and the anode to play a role of isolation, and then wound to obtain the electrode assembly. The battery consists of four electrode assemblies, and several buffer structures are placed in the large surface contact position between the electrode assemblies, and fixed and packaged together with the electrode assemblies, placed in an outer package, injected with the prepared electrolyte, and packaged, injected, formed, vented, and other processes to obtain a finished battery.

[0132] The following uses various examples to illustrate the effects of providing a corresponding number of buffer structures 104 in the battery cell 100:

[0133] The experimental objects in each embodiment are sodium metal battery cells of the same specification to ensure the single variable of the buffer structure 104 .

[0134]

[0135] Table 1 shows the relationship between the compression volume V and compression rate B of different buffer structures 104 and the cell capacity Cn of the same battery cell 100. It can be concluded that, taking the parameters of Example 1 as the standard, that is, when the ratio of the compression volume V and compression rate 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 not affected, and therefore, its energy density is 0%. As the V*B value of the buffer structure 104 continues to increase, the energy density of the battery cell 100 also decreases accordingly, which indicates that the buffer structure 104 needs to occupy a certain internal space of the shell 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 limiting 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 energy density of the current 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.

[0136]

[0137] Table 2 shows the relationship between the cumulative volume ratio A of different buffer structures 104 to the total volume of the electrode assembly 103, the compression rate B of the buffer structure 104, and the energy density and cycle life of the same battery cell 100. It can be concluded that the parameters of Comparative Example 1 are used as the standard, that is, the buffer structure 104 is not provided in the current battery cell 100, therefore, the A value and the B value are both 0, at this time, the energy density of the current battery cell 100 is not affected, therefore, its energy density is 0%.

[0138] Comparing Examples 1 to 6 horizontally, when the compression rate B of the buffer structure 104 is a fixed value and remains unchanged, as the cumulative volume of the buffer structure 104 increases in the total volume of the electrode assembly 103, that is, the A value gradually increases, the energy density of the battery cell 100 also shows a decreasing trend accordingly, which indicates that the buffer structure 104 needs to occupy a certain internal space of the shell 101 of the battery cell 100. At the same time, 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 is more obvious, and in Examples 3 and 4, when the A value is 6% to 7%, the cycle life of the battery cell 100 is the highest.

[0139] 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 range 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.

[0140] A vertical comparison of Example 2 and Example 9 shows that the cumulative volume percentages of the buffer structures 104 in the two embodiments are different, and the compression rates of the buffer structures 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 percentage, so as to obtain a buffer structure 104 with better performance.

[0141] It can be seen from Comparative Examples 2 and 3 that 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 higher cycle life and a higher energy density.

[0142] 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 .

[0143] 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 .

[0144] The value range of V*B / Cn is 0.85mL / Ah~0.95mL / Ah.

[0145] 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%.

[0146] The range of the compression rate B of the buffer structure 104 is: 70%≤B≤90%.

[0147] The buffer structure 104 has pores.

[0148] In a second aspect, an embodiment of the present application further provides a battery, comprising the above-mentioned battery cell 100 .

[0149] In a third aspect, an embodiment of the present application further provides an electrical device, comprising the above-mentioned battery.

[0150] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

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 comprises one 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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