Battery monomer and preparation method thereof, battery and power utilization device

Abstract

The invention relates to the technical field of batteries, and provides a battery monomer, which comprises a battery cell assembly and an outer package, the battery cell assembly comprises a positive plate, the positive plate is provided with an active material coating, and the active material coating comprises a sodium-containing copper-based layered oxide; the outer package is used for packaging the battery cell assembly, a ventilation piece is arranged on the outer package, and the air permeability of the ventilation piece is equal to or greater than the maximum required air displacement of the battery monomers in the total unit cycle time; and the maximum required gas displacement of the battery monomer in the unit cycle total time is obtained by converting the volume of carbon dioxide generated by Cu-O bond breakage oxygen release in the sodium-containing copper-based layered oxide. According to the battery monomer disclosed by the invention, redundant gas generated due to Cu-O bond fracture in the working process of the battery is timely discharged out of the battery monomer through the ventilation piece, so that the problem that the valve of the pressure relief mechanism of the battery monomer is opened due to the fact that internal air pressure is too large and reaches a threshold value of the pressure relief mechanism, and the battery monomer fails is solved; therefore, the safety of the battery is improved.

Description

Technical Field

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

[0002] In the related art, the positive electrode active material in the battery will become unstable due to the influence of working conditions during operation. The instability of the active material will cause the active material to release oxygen to a certain extent, increasing the gas production inside the battery. When the internal gas pressure of the battery reaches the valve opening threshold of the pressure relief mechanism in the battery, the pressure relief mechanism of the battery will open and fail. Excessive gas pressure may even cause safety accidents such as explosions, affecting the safety of the battery. It can be seen that how to improve the safety of the battery is a technical problem that needs to be solved urgently. Summary of the invention

[0003] The purpose of the present application is to provide a battery cell and a method for preparing the same, a battery and an electrical device, aiming to solve the problem of poor battery safety in the related art.

[0004] In order to achieve the above application purpose, the technical solution adopted in this application is as follows:

[0005] In a first aspect, the present application provides a battery cell, comprising: a battery cell assembly and an outer packaging, the battery cell assembly comprising a positive electrode sheet, the positive electrode sheet being provided with an active material coating, the active material coating comprising a sodium-copper-based layered oxide; the outer packaging is used to encapsulate the battery cell assembly, a breathable member is provided on the outer packaging, the air permeability of the breathable member is equal to or greater than the maximum required exhaust volume of the battery cell per unit cycle time, the maximum required exhaust volume of the battery cell per unit cycle time is obtained by converting the volume of carbon dioxide generated by oxygen release due to the breakage of Cu-O bonds in the sodium-copper-based layered oxide.

[0006] During the operation of the battery cell, the sodium-copper-based layered oxide as the positive electrode material is structurally unstable under high pressure, which will expose more active sites on the surface of the active material coating to the electrolyte, causing copper to dissolve, resulting in the breaking of the Cu-O bond, and the increase in oxygen release, which ultimately leads to an increase in gas production. In the technical solution of the embodiment of the present application, a breathable piece is provided on the outer packaging of the battery cell, and the selected breathable piece has an air permeability equal to or greater than the maximum required exhaust volume of the battery cell per unit cycle time. The maximum required exhaust volume of the battery cell per unit cycle time is obtained by converting the volume of carbon dioxide generated by the oxygen release due to the breaking of the Cu-O bond in the sodium-copper-based layered oxide. Then, the excess gas generated by the breaking of the Cu-O bond during the operation of the battery can be discharged to the outside of the battery cell in time through the breathable piece, so that the pressure relief mechanism of the battery cell is not prone to the problem of opening the valve due to excessive internal air pressure reaching the threshold of the pressure relief mechanism, thereby causing the battery cell to fail, thereby improving the safety of the battery.

[0007] In some embodiments, the maximum required exhaust volume of the battery cell per unit cycle time and the volume of carbon dioxide generated by the breakage of Cu-O bonds in the sodium-containing copper-based layered oxide satisfy the following conditions: Among them, V CO2 is the volume of carbon dioxide generated by the rupture of Cu-O bonds in the sodium-containing copper-based layered oxide during the total cycle time of the battery cell, a is the proportion of carbon dioxide generated by the rupture of Cu-O bonds in the sodium-containing copper-based layered oxide in all gases, and a = 0.45 ~ 0.72, P max is the maximum acceptable threshold of the battery cell internal pressure, V 残 is the residual volume of the battery cell, and T is the total cycle time of the battery cell.

[0008] In the technical solution of the embodiment of the present application, the above-mentioned relationship is satisfied between the maximum required exhaust volume of the battery cell per unit cycle time and the volume of carbon dioxide generated by oxygen release due to the rupture of Cu-O bonds in the sodium-copper-based layered oxide, so that the maximum required exhaust volume per unit cycle time of the battery cell can be converted based on the carbon dioxide generated by oxygen release due to the rupture of Cu-O bonds in the sodium-copper-based layered oxide, and then a breathable component with a certain air permeability is selected according to the exhaust volume of the battery cell within the total cycle time. The excess gas generated by the rupture of Cu-O bonds during the operation of the battery is discharged to the outside of the battery cell in time through the breathable component, so that the pressure relief mechanism of the battery cell is not prone to the problem of opening the valve due to excessive internal air pressure reaching the threshold of the pressure relief mechanism, thereby causing the battery cell to fail, thereby improving the safety of the battery.

[0009] In some embodiments, the volume of carbon dioxide generated by the rupture of Cu-O bonds in the sodium-containing copper-based layered oxide and the release of oxygen satisfies: Where b = 0.05 to 0.1, m Cu is the mass of copper atoms in the sodium-containing copper-based layered oxide, M o is the molar mass of oxygen atom, M Co2 is the molar mass of carbon dioxide, M Cu is the molar mass of the copper atom, M O2 is the molar mass of oxygen, ρ Co2 is the density of carbon dioxide.

[0010] In the technical solution of the embodiment of the present application, the volume of carbon dioxide generated by the breakage of Cu-O bonds in the sodium-containing copper-based layered oxide and the oxygen release is obtained by the above formula. The volume of carbon dioxide is related to the mass of copper atoms in the sodium-containing copper-based layered oxide, and then the permeable parts with different air permeabilities are used according to the different masses of copper atoms in the active material. In order to timely discharge the excess gas exceeding the gas volume accepted by the internal pressure of the battery cell through the permeable parts, the pressure relief mechanism of the battery cell is not likely to open the valve due to excessive internal air pressure reaching the threshold of the pressure relief mechanism, thereby causing the battery cell to fail, thereby improving the safety of the battery.

[0011] In some embodiments, the chemical formula of the sodium copper-containing layered oxide is Na q M x Cu y O 2 , wherein M includes two or more elements selected from Ti, V, Cr, Mn, Fe, Co, Ni or Zn, and 0.81≤q≤1, 0.8<x+y≤1, 0.03≤y≤0.2.

[0012] In the technical solution of the embodiment of the present application, the chemical formula of the sodium copper-containing layered oxide is Na q M x Cu y O 2 , where 0.03≤y≤0.2. The number of Cu atoms is in the range of 0.03 to 0.2, which can prevent excessive gas production during the operation of the battery cell, prevent excessive consumption of the electrolyte, and prevent premature termination of the battery cell cycle.

[0013] In some embodiments, M includes Ni, Mn, and Fe, and 0.81≤q≤1, 0.8<x+y≤1, 0.05≤y≤0.2.

[0014] In the technical solution of the embodiment of the present application, the sodium-copper-based layered oxide selects a layered oxide containing active elements of Cu, Ni, Mn and Fe as the positive electrode active material, so that the stability of the sodium-copper-based layered oxide is improved compared with other active elements, and the cost is relatively low. When the number of Cu atoms is in the range of 0.05 to 0.2, the gas production during the operation of the battery cell will not be too large, the consumption of the electrolyte will not be too much, and it is not easy to cause the premature termination of the battery cell cycle.

[0015] In some embodiments, the breathable member includes a breathable film, the outer package includes an end cap, and the breathable film is disposed on the end cap.

[0016] In the technical solution of the embodiment of the present application, a breathable membrane is arranged on the end cover to discharge the excess gas generated by the breakage of the Cu-O bond in the battery cell due to the instability of the copper-based layered oxide in the battery cell to the outside of the battery cell in time. Since the end cover is located above the battery assembly and the breathable membrane is arranged on the end cover, it is easy for the excess gas to be discharged upward, thereby making it less likely for the pressure relief mechanism of the battery cell to open the valve due to excessive internal air pressure, which easily reaches its threshold and eventually causes the battery cell to fail, thereby improving the safety of the battery.

[0017] In some embodiments, the material of the breathable membrane includes at least one of polytetrafluoroethylene, polyethylene or polypropylene.

[0018] In the technical solution of the embodiment of the present application, the material of the breathable membrane can be at least one of polytetrafluoroethylene, polyethylene or polypropylene, so that the selected breathable membrane has good waterproof and breathable properties.

[0019] In some embodiments, the pore size of the breathable membrane is 0.001-0.5 um.

[0020] In the technical solution of the embodiment of the present application, the breathable membrane within the pore size range has good waterproof and breathable performance. Since the distance between gas molecules is large, they can pass through the pores of the breathable membrane during diffusion movement, while the distance between liquid molecules is smaller than the distance between the pores, and under the action of surface tension, the liquid molecules cannot pass through the breathable membrane, thus achieving the effect of air permeability without liquid leakage.

[0021] In a second aspect, the present application also provides a method for preparing a battery monomer, which is used to prepare the above-mentioned battery monomer, comprising the following steps:

[0022] Obtaining the maximum required exhaust volume of the battery cell in the total unit cycle time, wherein the maximum required exhaust volume of the battery cell in the total unit cycle time is converted based on the volume of carbon dioxide generated by the release of oxygen due to the breakage of Cu-O bonds in the sodium-containing copper-based layered oxide;

[0023] Select a venting component with an air permeability equal to or greater than the maximum required exhaust volume of the battery cell per unit cycle time;

[0024] Install the venting member onto the outer packaging of the battery cell.

[0025] In some embodiments, the step of obtaining the maximum required exhaust volume of the battery monomer per unit cycle time, wherein the maximum required exhaust volume of the battery monomer per unit cycle time is obtained by converting the volume of carbon dioxide generated by the oxygen released by the breaking of Cu-O bonds in the sodium-containing copper-based layered oxide; further includes: obtaining the maximum required exhaust volume of the battery monomer based on the following formula:

[0026] The maximum required time of a battery cell per unit cycle Among them, V CO2 is the volume of carbon dioxide generated by the rupture of Cu-O bonds in the sodium-containing copper-based layered oxide during the total cycle time of the battery cell, a is the proportion of carbon dioxide generated by the rupture of Cu-O bonds in the sodium-containing copper-based layered oxide in all gases, and a = 0.45 ~ 0.72, P max is the maximum acceptable threshold of the battery cell internal pressure, V 残 is the residual volume of the battery cell, and T is the total cycle time of the battery cell.

[0027] In some embodiments, the method further comprises: obtaining the volume of carbon dioxide generated by the rupture of Cu-O bonds in the sodium-containing copper-based layered oxide based on the following formula:

[0028] Where b = 0.05 to 0.1, m Cu is the mass of copper atoms in the sodium-containing copper-based layered oxide, M o is the molar mass of oxygen atom, M Co2 is the molar mass of carbon dioxide, M Cu is the molar mass of the copper atom, M O2 is the molar mass of oxygen, ρ Co2 is the density of carbon dioxide.

[0029] In a third aspect, the present application also provides a battery, which includes the above-mentioned battery cell.

[0030] In a fourth aspect, the present application also provides an electrical device, which includes the above-mentioned battery.

[0031] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application, 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 application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0033] Figure 1 A schematic diagram of the structure of a vehicle according to some embodiments of the present application;

[0034] Figure 2A schematic diagram of the exploded structure of a battery according to some embodiments of the present application;

[0035] Figure 3 This is a schematic diagram of the exploded structure of a battery cell according to some embodiments of the present application.

[0036] Among them, the reference numerals in the figure are:

[0037] Vehicles 1000;

[0038] Battery 100, controller 200, motor 300;

[0039] Box body 10, first part 11, second part 12;

[0040] Battery cell 20 , end cover 21 , electrode terminal 21 a , pressure relief mechanism 21 b , shell 22 , battery core assembly 23 , pole tab 23 a , and air permeable member 24 . DETAILED DESCRIPTION

[0041] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0042] In this application, the term "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0043] In the present application, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple, respectively.

[0044] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0045] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0046] The weight of the relevant components mentioned in the embodiment description of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the embodiment description of the present application, it is within the scope disclosed in the embodiment description of the present application. Specifically, the mass described in the embodiment description of the present application can be a mass unit known in the chemical industry such as μg, mg, g, kg, etc.

[0047] The terms "first" and "second" are used only for descriptive purposes to distinguish objects such as substances from each other, and should not be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX may also be referred to as the second XX, and similarly, the second XX may also be referred to as the first XX. Thus, features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0048] In the sodium-ion battery of the related art, the positive electrode is coated with an active material copper-based layered oxide coating. During the use of the battery and under high pressure conditions, the structure of the copper-based layered oxide is unstable. The copper-based layered oxide will convert between +2 and +3 valences during the cycle. The +3 valence copper has extremely strong oxidizing properties and is prone to release oxygen to form more stable divalent copper, which will expose more active sites on the surface of the material to the electrolyte. Copper will dissolve, Cu-O bonds will break, and the amount of oxygen released will increase, ultimately leading to an increase in gas production inside the battery cell. The increase in gas production inside the battery cell will easily increase the internal air pressure. When the internal air pressure of the battery cell is too high and reaches the valve opening threshold of the pressure relief mechanism, the pressure relief mechanism will open the valve and cause the battery cell to fail. Excessive air pressure will cause safety accidents such as explosions, affecting the safety of sodium-ion batteries.

[0049] Based on the above considerations, in order to solve the problem that the instability of copper-based layered oxide materials during the use of battery cells leads to increased gas production and eventually causes the battery cell valve to fail, affecting the safety of the battery cell, a battery cell is designed. A gas-permeable member with a certain gas permeability is provided on the outer packaging of the battery cell, and the gas permeability of the gas-permeable member is equal to or greater than the maximum required exhaust volume of the battery cell in the total unit cycle time. The maximum required exhaust volume of the battery cell in the total unit cycle time is obtained by converting the volume of carbon dioxide generated by the breakage of Cu-O bonds in the sodium-containing copper-based layered oxide. Then, the excess gas generated by the breakage of Cu-O bonds during the operation of the battery can be discharged to the outside of the battery cell in time through the gas-permeable member, so that the pressure relief mechanism of the battery cell is not likely to open the valve due to excessive internal gas pressure reaching the threshold of the pressure relief mechanism, thereby causing the battery cell to fail, thereby improving the safety of the battery.

[0050] The battery cell disclosed in the embodiments of the present application can be used in electrical devices that use batteries as power sources or various energy storage systems that use batteries as energy storage elements. Electrical devices can be, but are not limited to, mobile phones, tablets, laptops, electric toys, electric tools, battery cars, electric cars, ships, spacecraft, etc. Among them, electric toys can include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., and spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0051] For the convenience of description, the following embodiments are described by taking a vehicle 1000 as an example of an electrical device according to an embodiment of the present application.

[0052] Please refer to Figure 1 , Figure 1 A schematic diagram of the structure of a vehicle 1000 provided for some embodiments of the present application. The vehicle 1000 may be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 100 is provided inside the vehicle 1000, and the battery 100 may be provided at the bottom, head or tail of the vehicle 1000. The battery 100 may be used to power the vehicle 1000, for example, the battery 100 may be used as an operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300, and the controller 200 is used to control the battery 100 to power the motor 300, for example, for starting, navigating and driving the vehicle 1000.

[0053] In some embodiments of the present application, the battery 100 can not only serve as an operating power source for the vehicle 1000, but also serve as a driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0054] Please refer to Figure 2 , Figure 2 An exploded view of a battery 100 provided in some embodiments of the present application. The battery 100 includes a box 10 and a battery cell 20, and the battery cell 20 is contained in the box 10. Among them, the box 10 is used to provide a storage space for the battery cell 20, and the box 10 can adopt a variety of structures. In some embodiments, the box 10 may include a first part 11 and a second part 12, the first part 11 and the second part 12 cover each other, and the first part 11 and the second part 12 jointly define a storage space for accommodating the battery cell 20. The second part 12 may be a hollow structure with one end open, the first part 11 may be a plate-like structure, and the first part 11 covers the open side of the second part 12, so that the first part 11 and the second part 12 jointly define a storage space; the first part 11 and the second part 12 may also be hollow structures with one side open, and the open side of the first part 11 covers the open side of the second part 12. Of course, the box 10 formed by the first part 11 and the second part 12 may be in a variety of shapes, such as a cylinder, a cuboid, etc.

[0055] In the battery 100, there may be multiple battery cells 20, and the multiple battery cells 20 may be connected in series, in parallel, or in a mixed connection. A mixed connection means that the multiple battery cells 20 are both connected in series and in parallel. The multiple battery cells 20 may be directly connected in series, in parallel, or in a mixed connection, and then the whole formed by the multiple battery cells 20 is accommodated in the box 10; of course, the battery 100 may also be a battery module formed by connecting multiple battery cells 20 in series, in parallel, or in a mixed connection, and then the multiple battery modules are connected in series, in parallel, or in a mixed connection to form a whole, and accommodated in the box 10. The battery 100 may also include other structures, for example, the battery 100 may also include a busbar component for realizing electrical connection between the multiple battery cells 20.

[0056] Each battery cell 20 may be a secondary battery or a primary battery, but is not limited thereto. The battery cell 20 may be cylindrical, flat, rectangular or in other shapes.

[0057] Please refer to Figure 3 , Figure 3 The schematic diagram of the exploded structure of the battery cell 20 provided in some embodiments of the present application. The battery cell 20 refers to the smallest unit that constitutes the battery. Figure 3 The battery cell 20 includes an outer package, a battery cell assembly 23 and other functional components, wherein the outer package includes an end cover 21 and a shell 22 .

[0058] The end cap 21 refers to a component that covers the opening of the shell 22 to isolate the internal environment of the battery cell 20 from the external environment. Without limitation, the shape of the end cap 21 can be adapted to the shape of the shell 22 to match the shell 22. Optionally, the end cap 21 can be made of a material with a certain hardness and strength (such as aluminum alloy), so that the end cap 21 is not easily deformed when squeezed and collided, so that the battery cell 20 can have a higher structural strength and the safety performance can also be improved. Functional components such as electrode terminals 21a can be provided on the end cap 21. The electrode terminal 21a can be used to electrically connect to the battery cell assembly 23 for outputting or inputting electrical energy of the battery cell 20. In some embodiments, the end cap 21 can also be provided with a pressure relief mechanism 21b for releasing the internal pressure when the internal pressure or temperature of the battery cell 20 reaches a threshold. The material of the end cap 21 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 21, and the insulating member may be used to isolate the electrical connection components in the housing 22 from the end cap 21 to reduce the risk of short circuit. For example, the insulating member may be plastic, rubber, or the like.

[0059] The shell 22 is a component used to cooperate with the end cover 21 to form the internal environment of the battery cell 20, wherein the formed internal environment can be used to accommodate the battery cell assembly 23, electrolyte and other components. The shell 22 and the end cover 21 can be independent components, and an opening can be set on the shell 22, and the internal environment of the battery cell 20 is formed by covering the opening with the end cover 21 at the opening. Without limitation, the end cover 21 and the shell 22 can also be integrated. Specifically, the end cover 21 and the shell 22 can form a common connection surface before other components are put into the shell, and when the interior of the shell 22 needs to be encapsulated, the end cover 21 covers the shell 22. The shell 22 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 22 can be determined according to the specific shape and size of the battery cell assembly 23. The material of the shell 22 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.

[0060] The battery cell assembly 23 is a component in the battery cell 100 where electrochemical reactions occur. One or more battery cell assemblies 23 may be contained in the housing 22. The battery cell assembly 23 is mainly formed by winding or stacking positive and negative electrode sheets, and a separator is usually provided between the positive and negative electrode sheets. The parts of the positive and negative electrode sheets with active materials constitute the main body of the battery cell assembly, and the parts of the positive and negative electrode sheets without active materials each constitute a tab 23a. The positive tab and the negative 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 active material and the negative active material react with the electrolyte, and the tab 23a connects the electrode terminals to form a current loop.

[0061] According to some embodiments of this application, please refer to Figure 3 The embodiment of the present application provides a battery cell, wherein the battery cell 20 comprises: a battery cell assembly 23 and an outer package, wherein the battery cell assembly 23 comprises a positive electrode sheet, wherein an active material coating is provided on the positive electrode sheet, wherein the active material coating comprises a sodium-containing copper-based layered oxide. The outer package is used to encapsulate the battery cell assembly 23, and a breathable member 24 is provided on the outer package, wherein the air permeability of the breathable member 24 is greater than or equal to the maximum required exhaust volume of the battery cell 20 per unit cycle time, and the maximum required exhaust volume of the battery cell 20 per unit cycle time is obtained by converting the volume of carbon dioxide generated by the oxygen released by the breaking of Cu-O bonds in the sodium-containing copper-based layered oxide.

[0062] The cell assembly 23 is the part of the battery cell where the electrochemical reaction occurs. The positive electrode of the cell assembly 23 is coated with an active material coating, which includes a sodium-copper-based layered oxide for reacting with the electrolyte. The air-permeable member 24 is a component that is air-permeable without leaking and resistant to electrolyte corrosion, and is used to discharge the excess gas generated inside the battery cell 20 from the battery cell in a timely manner. The air permeability of the air-permeable member 24 refers to the amount of gas that permeates per unit time. The maximum required exhaust volume of a battery cell per unit total cycle time refers to the amount of gas that needs to be discharged by the battery cell in each day calculated from the total cycle time in order not to cause the pressure relief mechanism to fail to open the valve.

[0063] In the technical solution of the embodiment of the present application, during the operation of the battery cell, the sodium-copper-based layered oxide as the positive electrode material is structurally unstable under high pressure (greater than or equal to 4.0V), which will expose more active sites on the surface of the active material coating to the electrolyte, causing copper to dissolve, resulting in the breakage of the Cu-O bond, and the increase in oxygen release, which ultimately leads to an increase in gas production. In the technical solution of the embodiment of the present application, a breathable piece is provided on the outer packaging of the battery cell, and the air permeability of the selected breathable piece is equal to or greater than the maximum required exhaust volume of the battery cell per unit cycle time, and the maximum required exhaust volume is obtained by converting the volume of carbon dioxide generated by the oxygen release due to the breakage of the Cu-O bond in the sodium-copper-based layered oxide. Therefore, the excess gas generated by the breakage of the Cu-O bond in the operation of the battery cell can be discharged to the outside of the battery cell in time through the breathable piece, so that the pressure relief mechanism of the battery cell is not prone to the problem of opening the valve due to excessive internal air pressure reaching the threshold of the pressure relief mechanism, thereby causing the battery cell to fail, thereby improving the safety of the battery.

[0064] In some embodiments of the present application, the maximum required exhaust volume of the battery cell in the total unit cycle time and the volume of carbon dioxide generated by the breakage of Cu-O bonds in the sodium-containing copper-based layered oxide satisfy the following conditions: Among them, V CO2 is the volume of carbon dioxide generated by the rupture of Cu-O bonds in the sodium-containing copper-based layered oxide during the total cycle time of the battery cell, a is the proportion of carbon dioxide generated by the rupture of Cu-O bonds in the sodium-containing copper-based layered oxide in all gases, and a = 0.45 ~ 0.72, P max is the maximum acceptable threshold of the battery cell internal pressure, V 残 is the residual volume of the battery cell, and T is the total cycle time of the battery cell.

[0065] During the charge and discharge process of the battery cell, when the sodium copper-based layered oxide as the positive electrode active material generates gas due to the breaking of the Cu-O bond, the amount of all carbon dioxide gas generated accounts for 50% to 80% of the total gas volume, and the amount of carbon dioxide released due to the breaking of the Cu-O bond during the cycle accounts for more than 90% of all carbon dioxide gas. Therefore, the value of a in this application is 0.45 to 0.72, that is, the carbon dioxide generated by the breaking of the Cu-O bond in the sodium copper-based layered oxide during the total cycle time accounts for 45% to 72% of all gas generated during the total cycle time. Then, the maximum required exhaust volume of the battery cell and the air permeability of the air permeable member are converted by the volume of carbon dioxide released by the breaking of the Cu-O bond. The air permeability of the selected air permeable member can meet the requirement of timely discharging the excess gas generated by the breaking of the Cu-O bond inside the battery cell to the outside of the battery cell.

[0066] "Total cycle time of battery cell" refers to the total time of all cycles required by the battery cell, that is, the product of the required number of cycles of the battery cell and the time of each cycle. "Maximum acceptable threshold value of internal pressure of battery cell" refers to the threshold value of pressure relief mechanism 21b, which is also the minimum pressure value for opening the valve of pressure relief mechanism 21b. "Residual volume of battery cell" refers to the volume remaining after removing all solid and liquid (including positive electrode sheet, negative electrode sheet, isolation membrane, mechanical parts, electrolyte, etc.) from the battery cell 20, that is, the volume occupied by gas.

[0067] In the technical solution of the embodiment of the present application, the above-mentioned relationship is satisfied between the maximum required exhaust volume of the battery cell per unit cycle time and the volume of carbon dioxide generated by oxygen release due to the rupture of Cu-O bonds in the sodium-copper-based layered oxide, so that the maximum required exhaust volume per unit cycle time of the battery cell can be converted based on the volume of carbon dioxide generated by oxygen release due to the rupture of Cu-O bonds in the sodium-copper-based layered oxide, and then a breathable component with a certain air permeability is selected according to the maximum required exhaust volume of the battery cell per unit cycle time, and then the excess gas generated by the rupture of Cu-O bonds during the operation of the battery cell is discharged to the outside of the battery cell in time through the breathable component, so that the pressure relief mechanism of the battery cell is not prone to the problem of opening the valve due to excessive internal air pressure reaching the threshold of the pressure relief mechanism, thereby causing the battery cell to fail, thereby improving the safety of the battery.

[0068] In some embodiments of the present application, the volume of carbon dioxide generated by the rupture of Cu-O bonds in the sodium-containing copper-based layered oxide and the release of oxygen satisfies: Where b = 0.05 to 0.1, m Cu is the mass of copper atoms in the sodium-containing copper-based layered oxide, M o is the molar mass of oxygen atom, M Co2 is the molar mass of carbon dioxide, M Cu is the molar mass of the copper atom, M O2 is the molar mass of oxygen, ρ Co2 is the density of carbon dioxide.

[0069] In the technical solution of the embodiment of the present application, since the battery life will be terminated when 5%-10% of the Cu-O bonds in the sodium-copper-based layered oxide break and release oxygen, the volume of carbon dioxide generated by the break and release of 5%-10% of the Cu-O bonds in the present application is calculated, so b is taken as 0.05-0.1, and the volume of carbon dioxide generated by the break and release of Cu-O bonds in the sodium-copper-based layered oxide is obtained by the above formula. The volume of carbon dioxide is related to the mass of copper atoms in the sodium-copper-based layered oxide, and then different air permeability components are used for different masses of copper atoms in the active material. In order to timely discharge excess gas that exceeds the amount of gas accepted by the internal pressure of the battery cell through the air permeable component, the pressure relief mechanism of the battery cell is not likely to open the valve due to excessive internal air pressure reaching the threshold of the pressure relief mechanism, thereby causing the battery cell to fail, thereby improving the safety of the battery.

[0070] In some embodiments of the present application, the maximum required exhaust volume of the battery cell per unit cycle time can be obtained based on the following method:

[0071] The maximum required exhaust volume of the battery cell in the total unit cycle time meets: V t =V p / T, -V EOL , where V t It is the maximum exhaust volume required for the battery cell in the total cycle time per unit, in ml / day. p V is the maximum volume of gas that needs to be discharged from the battery cell to the end of the cycle, in ml. T is the total cycle time of the battery cell, in day (calculated as 24 hours per day). CO2 V is the volume of carbon dioxide generated by the rupture of Cu-O bonds in sodium-containing copper-based layered oxides, in ml. EOL It is the volume of gas that can be generated by the internal pressure of the battery cell when the cycle is terminated, in ml.

[0072] The volume of carbon dioxide V generated by the rupture of Cu-O bonds in the sodium-containing copper-based layered oxide of the battery cell CO2 The relationship between the mass of copper atoms in the sodium-containing copper-based layered oxide satisfies: V CO2 =m CO2 / ρ CO2 , m CO2 =b×m o ×M CO2 / M O2 , m o =m Cu ×M o / M Cu Wherein, b = 0.05 ~ 0.1, m CO2ρ is the mass of carbon dioxide generated by the rupture of Cu-O bonds in sodium-containing copper-based layered oxides, in g. CO2 The density of released carbon dioxide gas is expressed in g / L. The density of carbon dioxide is 1.997 g / L. o is the mass of oxygen atoms bonded to copper atoms in sodium-containing copper-based layered oxides, in g, m Cu is the mass of copper atoms in sodium-containing copper-based layered oxides, in g, M CO2 is the molar mass of carbon dioxide, in g / mol, M O2 is the molar mass of oxygen in g / mol.

[0073] The mass m of copper atoms in sodium-containing copper-based layered oxides Cu Satisfaction: m Cu =m×W Cu , where m is the weight of the sodium copper-containing layered oxide in grams. Cu It is the mass fraction of copper element in copper-based layered oxide, in %.

[0074] The internal pressure of the battery cell can accept the volume of gas generated when the cycle ends. EOL satisfy: Among them, P max The maximum acceptable threshold of the internal pressure of the battery cell from the battery cell to the end of the cycle, in MPa. When the internal pressure of the battery cell reaches the threshold, the pressure relief mechanism 21b will open the valve. If the pressure is too high, it will cause safety accidents such as explosions. 残 The residual volume of the battery cell is expressed in ml. The residual volume of the battery cell refers to the volume remaining after removing all solid and liquid (including positive electrode sheet, negative electrode sheet, separator, mechanical parts, electrolyte, etc.) from the battery cell 20, that is, the volume occupied by gas.

[0075] The total cycle time T of the battery cell satisfies: T = X × t, where X is the number of cycles required at 25°C for the battery cell, for example, 1000 cycles. t refers to the cycle time for one cycle, in h. The total cycle time of the battery cell can be calculated in units of "days", with each day calculated as 24 hours. The battery cell is cycled once according to the following process: 1) 0.33C cross-current charging to 4.0V (about 3h); 2) rest 0.5h; 3) 0.33C cross-current discharge 1.5V (about 3h); 4) rest 0.5h. The above steps 1)-4) are repeated until the battery cell decays to 80% of the initial capacity, where C refers to the battery cell capacity. The battery cell capacity C satisfies: C = m × K, where m refers to the weight of the sodium copper-based layered oxide, in g. K refers to the capacity that can be exerted per gram of the active material, i.e., the sodium copper-based layered oxide, in mAh / g.

[0076] In some embodiments of the present application, the chemical formula of the sodium copper-containing layered oxide is Na q M x Cu y O 2 , wherein M includes two or more elements selected from Ti, V, Cr, Mn, Fe, Co, Ni or Zn, and 0.81≤q≤1, 0.8<x+y≤1, 0.03≤y≤0.2.

[0077] In the technical solution of the embodiment of the present application, the chemical formula of the sodium copper-containing layered oxide is Na q M x Cu y O 2 , where 0.03≤y≤0.2. The number of Cu atoms is in the range of 0.03 to 0.2, which can prevent excessive gas production during the operation of the battery cell, prevent excessive consumption of the electrolyte, and prevent premature termination of the battery cell cycle.

[0078] In some embodiments of the present application, the chemical formula of the sodium copper-containing layered oxide is Na q M x Cu y O 2 , wherein M includes Ni, Mn and Fe, and 0.81≤q≤1, 0.8<x+y≤1, 0.05≤y≤0.2.

[0079] In the technical solution of the embodiment of the present application, the sodium-copper-based layered oxide selects a layered oxide containing active elements of Cu, Ni, Mn and Fe as the positive electrode active material, so that the stability of the copper-based layered oxide is improved compared with other active elements, and the cost is relatively low. When the number of Cu atoms is in the range of 0.05 to 0.2, the gas production during the operation of the battery cell will not be too large, the consumption of the electrolyte will not be too much, and it is not easy to cause the premature termination of the battery cell cycle.

[0080] In some embodiments of this application, please refer to Figure 3 The breathable member 24 includes a breathable film, the outer package includes an end cover 21, and the breathable film is arranged on the end cover 21.

[0081] “The breathable membrane is disposed on the end cap 21” means placing the breathable membrane at any position of the end cap 21 except the electrode terminal 21a and the pressure relief mechanism 21b, so that it does not affect other functional components and can discharge the excess gas generated inside the battery cell to the outer packaging, thereby playing a waterproof and breathable role. The breathable membrane can be a breathable part with air holes, and its shape can be circular, square, rectangular, diamond, elliptical or other irregular shapes. An installation opening for the breathable membrane can be reserved on the end cap 21, and the edge of the breathable membrane and the edge of the installation opening can be sealed by, for example, gluing or welding, and the gas inside and outside the end cap 21 can be connected through the breathable membrane.

[0082] In the technical solution of the embodiment of the present application, a breathable membrane is arranged on the end cover 21 to promptly discharge the excess gas generated by the breakage of the Cu-O bond in the battery cell due to the instability of the copper-based layered oxide in the battery cell, thereby making it less likely for the pressure relief mechanism of the battery cell to open the valve due to excessive internal air pressure reaching the threshold of the pressure relief mechanism, ultimately leading to failure of the battery cell, thereby improving the safety of the battery.

[0083] In some embodiments of the present application, the material of the breathable membrane includes at least one of polytetrafluoroethylene (PTFE), polyethylene (UHMWPE) or polypropylene (PP), and polytetrafluoroethylene (PTFE) can be selected.

[0084] In the technical solution of the embodiment of the present application, the material of the breathable membrane can be at least one of PTFE, UHMWPE or PP, so that the selected breathable membrane has good waterproof and breathable properties.

[0085] In the technical solution of the embodiment of the present application, the pore size of the breathable membrane is 0.001-0.5 um.

[0086] The breathable membrane within this pore size range has good waterproof and breathable properties. Since the distance between gas molecules is large, they can pass through the pores of the breathable membrane during diffusion, while the distance between liquid molecules is smaller than the distance between the pores, and under the action of surface tension, liquid molecules cannot pass through the breathable membrane, achieving the effect of air permeability without leakage.

[0087] In some embodiments of the present application, the thickness of the breathable membrane is 1 to 5 mm, and can be 2 mm.

[0088] In a second aspect, the present application provides a method for preparing a battery monomer, which is used to prepare the above-mentioned battery monomer, comprising the following steps:

[0089] Obtaining the maximum required exhaust volume of the battery cell in the total unit cycle time, wherein the maximum required exhaust volume of the battery cell in the total unit cycle time is converted based on the volume of carbon dioxide generated by the release of oxygen due to the breakage of Cu-O bonds in the sodium-containing copper-based layered oxide;

[0090] Select a venting component with an air permeability equal to or greater than the maximum required exhaust volume of the battery cell per unit cycle time;

[0091] The air-permeable member is mounted on the outer packaging of the battery cell.

[0092] The preparation method of the present application obtains the maximum required exhaust volume of the battery cell per unit cycle time by converting the volume of carbon dioxide generated by the breakage of Cu-O bonds in the sodium-copper-based layered oxide in the positive electrode material coating and releasing oxygen. Based on the maximum required exhaust volume of the battery cell per unit cycle time, a breathable component with an air permeability equal to or greater than the maximum required exhaust volume is selected, and then the breathable component is installed on the outer packaging of the battery cell. The excess gas generated during the operation of the battery can be discharged to the outside of the battery cell in time through the breathable component, so that the pressure relief mechanism of the battery cell is not prone to the problem of opening the valve due to excessive internal air pressure reaching the threshold of the pressure relief mechanism, thereby causing the battery cell to fail, thereby improving the safety of the battery.

[0093] In some embodiments of the present application, the maximum required exhaust volume of a battery cell per unit cycle time is obtained, wherein the maximum required exhaust volume of a battery cell per unit cycle time is obtained by converting the volume of carbon dioxide generated by the oxygen released by the breaking of Cu-O bonds in a sodium-containing copper-based layered oxide; and further comprising: obtaining the maximum required exhaust volume of the battery cell based on the following formula:

[0094] The maximum required time of a battery cell per unit cycle Among them, V CO2 is the volume of carbon dioxide generated by the rupture of Cu-O bonds in the sodium-containing copper-based layered oxide during the total cycle time of the battery cell, a is the proportion of carbon dioxide generated by the rupture of Cu-O bonds in the sodium-containing copper-based layered oxide in all gases, and a = 0.45 ~ 0.72, P max is the maximum acceptable threshold of the battery cell internal pressure, V 残 is the residual volume of the battery cell, and T is the total cycle time of the battery cell.

[0095] In some embodiments of the present application, the volume of carbon dioxide generated by the rupture of Cu-O bonds in the sodium-containing copper-based layered oxide is obtained based on the following formula:

[0096] Where b = 0.05 to 0.1, m Cu is the mass of copper atoms in the sodium-containing copper-based layered oxide, Mo is the molar mass of oxygen atom, M Co2 is the molar mass of carbon dioxide, M Cu is the molar mass of the copper atom, M O2 is the molar mass of oxygen, ρ Co2 is the density of carbon dioxide.

[0097] In a third aspect, the present application also provides a battery, which includes the above-mentioned battery cell.

[0098] In a fourth aspect, the present application also provides an electrical device, which includes the above-mentioned battery.

[0099] Example

[0100] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0101] Example 1

[0102] This embodiment provides a battery cell, in which the battery cell includes a battery cell assembly 23 and a breathable membrane. The battery cell assembly 23 includes a positive electrode sheet, on which a sodium copper-based layered oxide is coated as a positive electrode active material.

[0103] The chemical formula of the sodium-copper-based layered oxide in Example 1 is: 0.9 Cu 0.2 Ni 0.15 Fe 0.25 Mn 0.4 O 2 , the molar molecular mass is 110.1 g / mol, the weight m of the coated positive electrode active material is 1000 g, the gram capacity K of the active material is 135 mAh / g, and the capacity C = m × K of the positive electrode active material is 135000 mAh. 0.9 Cu 0.2 Ni 0.15 Fe 0.25 Mn 0.4 O 2 The mass fraction of copper in copper-based layered oxides W cu 11.5%, copper-based layered oxide Na 0.9 Cu 0.2 Ni 0.15 Fe 0.25 Mn 0.4 O 2The mass of the copper atom in cu =m×W cu 115.4 g, copper-based layered oxide Na 0.9 Cu 0.2 Ni 0.15 Fe 0.25 Mn 0.4 O 2 The mass of the oxygen atom bonded to the copper atom is m o =m cu ×16 / 63.55 is 28.85g, and the maximum mass of carbon dioxide released is m Co2 =0.1×mo×44 / 32 (when 5% to 10% of the copper-oxygen bonds are broken, the copper-based layered oxide will experience a severe collapse cycle and a sharp drop in water. In this embodiment, it is calculated according to b=0.1) is 4.0g, and the density of carbon dioxide ρ Co2 is 1.977 g / L, and the maximum volume of carbon dioxide released is V Co2 =m Co2 / ρ Co2 The volume of all released gas is 2006ml Battery cell residual volume V 残 The residual volume of the battery cell is 162ml. 残’ =V 残 / C is 1.2ml / Amh, that is, the space that gas can occupy per unit volume, and the maximum acceptable threshold value P of the internal pressure of the battery cell to the end of the cycle max The volume V of the battery cell that can accept the gas generated by the battery cell until the cycle ends is 0.35MPa. EOL The maximum gas volume that the battery cell needs to discharge is 567ml. is 3892ml (a is 0.45), the cell requires 1000 cycles at 25℃, and the cycle time t is 7h. The total cycle time of the battery cell is 292days, and each day is calculated as 24h. Then the maximum required discharge volume V of the battery cell in the total cycle time is t =V p / T is 13.3ml / day.

[0104] Preparation of positive electrode slurry:

[0105] Sodium-containing copper-based layered oxide Na 0.9 Cu 0.2 Ni 0.15 Fe 0.25 Mn 0.4 O 2, a binder and conductive carbon are mixed in 94%, 2.5% and 3.5% by mass, and then a stirring solvent NMP is added and stirred to obtain a positive electrode slurry, and the mass ratio of the added stirring solvent NMP to the fixed mixture is 4:6. Among them, the binder is PVDF.

[0106] Preparation of negative electrode slurry:

[0107] Hard carbon, a binder, a thickener and conductive carbon were mixed in a mass percentage of 94%, 4%, 1% and 1%, and then a stirring solvent NMP was added and stirred to obtain a negative electrode slurry. The mass of the added stirring solvent NMP and the fixed mixture was 5:5.

[0108] Then the battery cell components are prepared through coating → cold pressing → die cutting → winding → assembly → liquid injection → aging → formation.

[0109] In this embodiment, a breathable membrane is provided on the end cap 21 of the battery cell. The selected breathable membrane material is PTFE. The thickness of the breathable membrane is 2 mm and the area of ​​the breathable membrane is 19.63 mm. 2 The pore size of the breathable membrane is 0.45um and the total breathable area is 5mm 2 The air permeability of the selected breathable membrane is 15 ml / day. After testing, the pressure relief mechanism does not open the valve during the total cycle time of the battery cell of this embodiment, and the number of cycles of the battery cell of this embodiment can reach the required 1000 cycles.

[0110] Example 2

[0111] This embodiment provides another battery cell. In the battery cell of this embodiment, a battery cell assembly 23 and a breathable membrane are included. The battery cell assembly 23 includes a positive electrode sheet, and the positive electrode sheet is coated with a sodium copper-based layered oxide as a positive electrode active material.

[0112] In Example 2, the chemical formula of the sodium-copper-based layered oxide is: Na 0.9 Cu 0.1 Ni 0.25 Fe 0.25 Mn 0.4 O 2 , the molar molecular mass is 109.7 g / mol, the weight m of the coated positive electrode active material is 1000 g, the gram capacity K of the active material is 135 mAh / g, and the capacity C = m × K of the positive electrode active material is 135000 mAh. 0.9 Cu 0.1 Ni 0.25 Fe 0.25 Mn 0.4 O 2 The mass fraction of copper in copper-based layered oxides W cu5.8%, copper-based layered oxide Na 0.9 Cu 0.1 Ni 0.25 Fe 0.25 Mn 0.4 O 2 The mass of the copper atom in cu 57.95 g, copper-based layered oxide Na 0.9 Cu 0.1 Ni 0.25 Fe 0.25 Mn 0.4 O 2 The mass of the oxygen atom bonded to the copper atom is m o =m cu ×16 / 63.55 is 14.49g, and the maximum mass of carbon dioxide released is m Co2 =0.1×mo×44 / 32 (b is 0.1) is 2.0g, the density of carbon dioxide is ρ Co2 is 1.977 g / L, and the maximum volume of carbon dioxide released is V Co2 =m Co2 / ρ Co2 The volume of all released gas is 1008ml Battery cell residual volume V 残 The residual volume of the battery cell is 162ml. 残’ =V 残 / C is 1.2ml / Amh, that is, the space that gas can occupy per unit volume, and the maximum acceptable threshold value P of the internal pressure of the battery cell to the end of the cycle max The volume V of the battery cell that can accept the gas generated by the battery cell until the cycle ends is 0.35MPa. EOL is 567ml, then the volume of gas that needs to be discharged from the battery cell is 1672ml (a is 0.45), the battery cell requires 1000 cycles at 25℃, and the cycle time t is 7h. The total cycle time of the battery cell is 292days. If each day is calculated as 24h, then the maximum required exhaust volume V of the battery cell per unit cycle time is t =V p / T is 5.7ml / day.

[0113] Preparation of positive electrode slurry:

[0114] Sodium-containing copper-based layered oxide Na 0.9 Cu 0.1 Ni 0.25 Fe 0.25 Mn 0.4 O 2, a binder and conductive carbon are mixed in 94%, 2.5% and 3.5% by mass, and then a stirring solvent NMP is added and stirred to obtain a positive electrode slurry, and the mass ratio of the added stirring solvent NMP to the fixed mixture is 4:6. Among them, the binder is PVDF.

[0115] Preparation of negative electrode slurry:

[0116] Hard carbon, a binder, a thickener and conductive carbon were mixed in a mass percentage of 94%, 4%, 1% and 1%, and then a stirring solvent NMP was added and stirred to obtain a negative electrode slurry. The mass of the added stirring solvent NMP and the fixed mixture was 5:5.

[0117] Then the battery cell components are prepared through coating → cold pressing → die cutting → winding → assembly → liquid injection → aging → formation.

[0118] In this embodiment, a breathable membrane is provided on the end cap 21 of the battery cell. The breathable membrane material is PTFE. The thickness of the breathable membrane is 2 mm and the area of ​​the breathable membrane is 19.63 mm. 2 The pore size of the breathable membrane is 0.19um and the total breathable area is 2.15mm 2 The air permeability of the selected breathable membrane is 6 ml / day. After testing, the battery cell of this embodiment does not have the situation of the pressure relief mechanism opening the valve within the total cycle time. The number of cycles of the battery cell of this embodiment can reach 1000 cycles.

[0119] Example 3

[0120] This embodiment provides another battery cell. In the battery cell of this embodiment, a battery cell assembly 23 and a breathable membrane are included. The battery cell assembly 23 includes a positive electrode sheet, and the positive electrode sheet is coated with a sodium copper-based layered oxide as a positive electrode active material.

[0121] In this embodiment 3, the chemical formula of the sodium-copper-based layered oxide is: Na 0.9 Cu 0.05 Ni 0.3 Fe 0.25 Mn 0.4 O 2 , the molar molecular mass is 109.4g / mol, the weight m of the coated positive electrode active material is 1000g, the gram capacity K of the active material is 135mAh / g, and the capacity C=m×K of the positive electrode active material is 135000mAh. 0.9 Cu 0.05 Ni 0.3 Fe 0.25 Mn 0.4 O 2 The mass fraction of copper in copper-based layered oxides W cu2.9%, copper-based layered oxide Na 0.9 Cu 0.05 Ni 0.3 Fe 0.25 Mn 0.4 O 2 The mass of the copper atom in cu 29.04 g, copper-based layered oxide Na 0.9 Cu 0.05 Ni 0.3 Fe 0.25 Mn 0.4 O 2 The mass of the oxygen atom bonded to the copper atom is m o =m cu ×16 / 63.55 is 7.26g, and the maximum mass of carbon dioxide released is m Co2 =0.1×mo×44 / 32 (b is 0.1) is 1.0g, the density of carbon dioxide is ρ Co2 is 1.977 g / L, and the maximum volume of carbon dioxide released is V Co2 =m Co2 / ρ Co2 The volume of all released gas is 505ml Battery cell residual volume V 残 The residual volume of the battery cell is 162ml. 残’ =V 残 / C is 1.2ml / Amh, that is, the space that gas can occupy per unit volume, and the maximum acceptable threshold value P of the internal pressure of the battery cell to the end of the cycle max The volume V of the battery cell that can accept the gas generated by the battery cell until the cycle ends is 0.35MPa. EOL The maximum gas volume that the battery cell needs to discharge is 567ml. is 555ml (a is 0.45), the cell requires 1000 cycles at 25℃, and the cycle time t is 7h. The total cycle time of the battery cell is 291days, and each day is calculated as 24h. Then the maximum required exhaust volume V of the battery cell per unit cycle time is t =V p / T is 1.9ml / day.

[0122] Preparation of positive electrode slurry:

[0123] Sodium-containing copper-based layered oxide Na 0.9 Cu 0.05 Ni 0.3 Fe 0.25 Mn 0.4 O 2, a binder and conductive carbon are mixed in 94%, 2.5% and 3.5% by mass, and then a stirring solvent NMP is added and stirred to obtain a positive electrode slurry, and the mass ratio of the added stirring solvent NMP to the fixed mixture is 4:6. Among them, the binder is PVDF.

[0124] Preparation of negative electrode slurry:

[0125] Hard carbon, a binder, a thickener and conductive carbon were mixed in a mass percentage of 94%, 4%, 1% and 1%, and then a stirring solvent NMP was added and stirred to obtain a negative electrode slurry. The mass of the added stirring solvent NMP and the fixed mixture was 5:5.

[0126] Then the battery cell components are prepared through coating → cold pressing → die cutting → winding → assembly → liquid injection → aging → formation.

[0127] In this embodiment, a breathable membrane is provided on the end cap 21 of the battery cell. The breathable membrane material is PTFE. The thickness of the breathable membrane is 2 mm and the area of ​​the breathable membrane is 19.63 mm. 2 The pore size of the breathable membrane is 0.06um, and the total breathable area is 0.71mm 2 The air permeability of the breathable membrane is 2 ml / day. After testing, the battery cell of this embodiment does not have the situation of the pressure relief mechanism opening the valve within the total cycle time. The number of cycles of the battery cell of this embodiment can reach the required 1000 cycles.

[0128] As shown in Table 1 below, Example 4 prepared a battery cell in the same manner as Example 1 except that the type of sodium copper-containing layered oxide and the mass of copper atoms were adjusted. As shown in Table 1 below, Example 5 and Example 6 prepared a battery cell in the same manner as Example 1 except that the type of breathable membrane was adjusted.

[0129] Comparative Example 1

[0130] This embodiment provides a battery cell. In this embodiment, no breathable film is provided on the outer packaging of the battery cell. The battery cell includes a battery cell assembly 23. The battery cell assembly 23 includes a positive electrode sheet. The positive electrode sheet is coated with a sodium-copper-based layered oxide as a positive electrode active material. The chemical formula of the sodium-copper-based layered oxide is: Na 0.9 Cu 0.1 Ni 0.25 Fe 0.25 Mn 0.4 O 2 , the weight m of the coated positive electrode active material is 1000 g.

[0131] Preparation of positive electrode slurry:

[0132] Sodium-containing copper-based layered oxide Na0.9 Cu 0.1 Ni 0.25 Fe 0.25 Mn 0.4 O 2 , a binder and conductive carbon are mixed in 94%, 2.5% and 3.5% by mass, and then a stirring solvent NMP is added and stirred to obtain a positive electrode slurry, and the mass ratio of the added stirring solvent NMP to the fixed mixture is 4:6. Among them, the binder is PVDF.

[0133] Preparation of negative electrode slurry:

[0134] Hard carbon, a binder, a thickener and conductive carbon were mixed in a mass percentage of 94%, 4%, 1% and 1%, and then a stirring solvent NMP was added and stirred to obtain a negative electrode slurry. The mass of the added stirring solvent NMP and the fixed mixture was 5:5.

[0135] Then the battery cell components are prepared through coating → cold pressing → die cutting → winding → assembly → liquid injection → aging → formation.

[0136] In this embodiment, no breathable membrane is provided on the end cover 21 of the battery cell. According to the test, the number of cycles for the battery cell of this embodiment to reach the valve opening threshold of the pressure relief mechanism is 339.

[0137] Comparative Example 2 As shown in Table 1, in Comparative Example 2, the air permeability of the air permeable membrane used was adjusted, and the battery cell of Comparative Example 2 was prepared in the same manner as in Example 1.

[0138] Table 1: Related parameter results of battery cells of Examples 1 to 6 and Comparative Examples 1-2

[0139]

[0140]

[0141] Performance Testing:

[0142] 1. Cycle test process: Cycle according to the following process at normal pressure 25±2℃:

[0143] 1) 0.33C cross-current charging to 4.0V;

[0144] 2) rest 0.5h;

[0145] 3) 0.33C cross-current discharge 1.5V;

[0146] 4) rest 0.5h;

[0147] The cycle steps 1-4) are repeated until the capacity of the battery cell decays to 80% of the initial capacity to test the cycle number of the battery cell, wherein C=135Ah is the battery cell capacity. The test results are shown in Table 2 below.

[0148] 2. Valve opening of battery cells: By observing the valve opening of the pressure relief mechanism 21b of the battery cells in real time during the total cycle time, it is determined whether the valve opening of the pressure relief structure occurs during the total cycle time of the battery cells. The test results are shown in Table 2 below.

[0149] 3. Cycle end maximum internal pressure test: When the battery cell is made, a pressure gauge is connected, and the pressure gauge is connected to a pressure receiving sensor to monitor the internal pressure of the battery cell. The maximum internal pressure of the battery cell during the cycle test time is recorded. The test results are shown in Table 2 below.

[0150] Table 2 Performance results of battery cells of Examples 1-6 and Comparative Examples 1-2

[0151]

[0152]

[0153] According to the above results, compared with comparative example 1 in which no breathable membrane is provided, embodiments 1 to 6 provide breathable membranes, and the selected breathable membranes have a permeability greater than the maximum required exhaust volume of the battery cell per unit cycle time. The maximum internal pressure in the battery cell will not reach the threshold of the pressure relief mechanism, and the pressure relief mechanism does not fail to open the valve during the battery cell cycle test, and the number of cycles of the battery cell can meet the requirements, thereby improving the safety of the battery. However, in comparative example 1, the valve failure occurred at 502 cycles.

[0154] Compared with the air permeability of the breathable membrane set in Comparative Example 2, which is less than the maximum gas release of the battery cell, the air permeability of the breathable membrane selected in Examples 1 to 6 is greater than the maximum required gas release of the battery cell per unit cycle time, and the maximum internal pressure in the battery cell will not reach the threshold of the pressure relief mechanism. During the battery cell cycle test, there is no failure of the pressure relief mechanism to open the valve, and the number of cycles of the battery cell can meet the requirements. In Comparative Example 2, the number of cycles to reach the threshold of the pressure relief mechanism to open the valve is 529, and the valve failure occurs at 703 cycles.

[0155] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A battery cell, characterized in that: The battery cell comprises: A battery cell assembly, the battery cell assembly comprising a positive electrode sheet, the positive electrode sheet being provided with an active material coating, the active material coating comprising a sodium-copper-based layered oxide; The outer packaging is used to encapsulate the battery cell assembly, and a breathable member is provided on the outer packaging, and the air permeability of the breathable member is equal to or greater than the maximum required exhaust volume of the battery cell in a unit cycle time. The maximum required exhaust volume of the battery cell in a unit cycle time is obtained by converting the volume of carbon dioxide generated by the release of oxygen due to the rupture of Cu-O bonds in the sodium-containing copper-based layered oxide.

2. The battery cell according to claim 1, characterized in that: The maximum required exhaust volume of the battery cell per unit cycle time and the volume of carbon dioxide generated by the rupture of Cu-O bonds in the sodium-containing copper-based layered oxide satisfy the following: Among them, V CO2 is the volume of carbon dioxide generated by the rupture of Cu-O bonds in the sodium-containing copper-based layered oxide during the total cycle time of the battery cell, a is the proportion of carbon dioxide generated by the rupture of Cu-O bonds in the sodium-containing copper-based layered oxide in all gases, and a = 0.45 ~ 0.72, P max is the maximum acceptable threshold of the battery cell internal pressure, V 残 is the residual volume of the battery cell, and T is the total cycle time of the battery cell.

3. The battery cell according to claim 2, characterized in that: The volume of carbon dioxide generated by the rupture of Cu-O bonds in the sodium-containing copper-based layered oxide and the release of oxygen satisfies: Where b = 0.05 to 0.1, m Cu is the mass of copper atoms in the sodium-containing copper-based layered oxide, M o is the molar mass of oxygen atom, M Co2 is the molar mass of carbon dioxide, M Cu is the molar mass of the copper atom, M O2 is the molar mass of oxygen, ρ Co2 is the density of carbon dioxide.

4. The battery cell according to any one of claims 1 to 3, characterized in that: The chemical formula of the sodium-copper-based layered oxide is Na q M x Cu y O2, wherein M includes two or more elements selected from Ti, V, Cr, Mn, Fe, Co, Ni or Zn, and 0.81≤q≤1, 0.8<x+y≤1, 0.03≤y≤0.

2.

5. The battery cell according to claim 4, characterized in that: The M includes Ni, Mn and Fe, and 0.81≤q≤1, 0.8<x+y≤1, and 0.05≤y≤0.

2.

6. The battery cell according to any one of claims 1 to 5, characterized in that: The breathable member comprises a breathable film, the outer package comprises an end cover, and the breathable film is arranged on the end cover.

7. The battery cell according to claim 6, characterized in that: The material of the breathable membrane includes at least one of polytetrafluoroethylene, polyethylene or polypropylene.

8. The battery cell according to claim 6, characterized in that: The pore size of the breathable membrane is 0.001-0.5 um.

9. A method for preparing a battery monomer, characterized in that: The steps include: Obtaining the maximum required exhaust volume of the battery cell in the total unit cycle time, wherein the maximum required exhaust volume of the battery cell in the total unit cycle time is converted based on the volume of carbon dioxide generated by the release of oxygen from the breakage of Cu-O bonds in the sodium-containing copper-based layered oxide; Select a breathable member with a permeability equal to or greater than the maximum required exhaust volume of the battery cell per unit cycle time; The air-permeable member is mounted on the outer packaging of the battery cell.

10. The preparation method according to claim 9, characterized in that: The step of obtaining the maximum required exhaust volume of the battery monomer in the total unit cycle time, wherein the maximum required exhaust volume of the battery monomer in the total unit cycle time is obtained by converting the volume of carbon dioxide generated by the rupture of Cu-O bonds in the sodium-containing copper-based layered oxide and releasing oxygen; also includes: obtaining the maximum required exhaust volume of the battery monomer based on the following formula: Among them, V CO2 is the volume of carbon dioxide generated by the rupture of Cu-O bonds in the sodium-containing copper-based layered oxide during the total cycle time of the battery cell, a is the proportion of carbon dioxide generated by the rupture of Cu-O bonds in the sodium-containing copper-based layered oxide in all gases, and a = 0.45 ~ 0.72, P max is the maximum acceptable threshold of the battery cell internal pressure, V 残 is the residual volume of the battery cell, and T is the total cycle time of the battery cell.

11. The preparation method according to claim 10, characterized in that: Also includes: The volume of carbon dioxide generated by the rupture of Cu-O bonds in sodium-containing copper-based layered oxides is obtained based on the following formula: Where b = 0.05 to 0.1, m Cu is the mass of copper atoms in the sodium-containing copper-based layered oxide, M o is the molar mass of oxygen atom, M Co2 is the molar mass of carbon dioxide, M Cu is the molar mass of the copper atom, M O2 is the molar mass of oxygen, ρ Co2 is the density of carbon dioxide.

12. A battery, characterized in that: The battery comprises the battery cell according to any one of claims 1 to 8.

13. An electrical device, characterized in that: The electrical device comprises the battery according to claim 12.

Images