Battery cell, manufacturing method therefor, battery, and electric device

Abstract

The present application relates to the technical field of batteries, and provides a battery cell, a manufacturing method therefor, a battery and an electrical apparatus. The battery cell comprises a battery core assembly and an outer package; the battery core assembly comprises a positive electrode sheet, an active material coating being provided on the positive electrode sheet, and the active material coating comprising a sodium-containing copper-based layered oxide; the outer package is used for packaging the battery core assembly. A ventilation member is provided in the outer package, the ventilation rate of the ventilation member being equal to or larger than the maximum required venting capacity of the battery cell in total cycle time per unit, and the maximum required venting capacity of the battery cell in the total cycle time per unit being obtained by converting the volume of carbon dioxide generated by cleavage of Cu-O bonds and oxygen release in the sodium-containing copper-based layered oxide. The battery cell of the present application uses the ventilation member to timely discharge the redundant gas generated by the cleavage of Cu-O bonds in the working process of the battery out of the battery cell, such that the problem of battery cell failure caused by valve opening of a pressure relief mechanism of the battery cell due to the internal gas pressure being too large and reaching a threshold value of the pressure relief mechanism is less likely to occur.

Description

Battery monomer and preparation method thereof, battery and power-using device

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on October 30, 2023, with application number 202311421246.1 and invention name “Battery Cell and Preparation Method Thereof, Battery and Electrical Device”, the entire contents of which are incorporated by reference into this application. Technical Field

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

[0003] In related technologies, the positive electrode active material in the battery can become structurally unstable during operation due to the influence of operating conditions. This instability can cause the active material to release oxygen, increasing gas production within the battery. When the internal pressure reaches the valve opening threshold of the pressure relief mechanism, the valve opens, causing the pressure relief mechanism to fail. Excessive pressure can even cause safety accidents such as explosions, affecting battery safety. Therefore, improving battery safety is a technical issue that needs to be urgently addressed.

[0004] Application Contents

[0005] The purpose of the embodiments of the present application is to provide a battery cell and a method for preparing the same, a battery, and an electrical device, in order to solve the problem of poor battery safety in the related art. Technical Solutions

[0006] The technical solution adopted in the embodiment of this application is:

[0007] In a first aspect, an embodiment of 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 being used to encapsulate the battery cell assembly, the outer packaging being provided with a breathable member, the breathable member having an air permeability equal to or greater than a 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 being obtained by converting the volume of carbon dioxide generated by oxygen release due to the breaking of Cu-O bonds in the sodium-copper-based layered oxide.

[0008] 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 based on 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. Therefore, the breathable piece can timely discharge the excess gas generated by the breaking of the Cu-O bond during the operation of the battery to the outside of the battery cell, so that the pressure relief mechanism of the battery cell is not prone to the problem of the valve opening 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 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 relationship: Among them, V CO2 is the volume of carbon dioxide generated by the rupture of Cu-O bonds in sodium-containing copper-based layered oxides 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 sodium-containing copper-based layered oxides in all gases, and a = 0.45-0.72, P max V is the maximum acceptable threshold of the battery cell internal pressure. 残 is the residual volume of the battery cell, and T is the total cycle time of the battery cell.

[0010] 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 the release of oxygen due to the rupture of Cu-O bonds in the sodium-containing 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 the release of oxygen due to the rupture of Cu-O bonds in the sodium-containing 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 a timely manner through the breathable component, so that the pressure relief mechanism of the battery cell is not prone to the problem of the internal air pressure being too high and reaching the threshold of the pressure relief mechanism, causing it to open the valve, thereby causing the battery cell to fail, thereby improving the safety of the battery.

[0011] 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, mCu is the mass of copper atoms in sodium-containing copper-based layered oxides, Mo is the molar mass of oxygen atoms, and 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.

[0012] In the technical solution of the embodiments of the present application, the volume of carbon dioxide generated by the release of oxygen from the broken Cu-O bonds in the sodium-copper-based layered oxide is calculated using the above formula. The volume of carbon dioxide is related to the mass of the copper atoms in the sodium-copper-based layered oxide. Consequently, different permeability components are used to account for the different masses of copper atoms in the active material. This allows for the timely discharge of excess gas exceeding the internal pressure of the battery cell through the permeability component. This reduces the risk of the pressure relief mechanism of the battery cell opening due to excessive internal pressure reaching the pressure relief mechanism threshold, which could lead to cell failure, thereby improving battery safety.

[0013] In some embodiments, the chemical formula of the sodium copper-containing 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, and 0.03≤y≤0.2.

[0014] 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 O2, wherein 0.03≤y≤0.2. The number of Cu atoms is within the range of 0.03 to 0.2, which can prevent excessive gas production during battery cell operation, reduce electrolyte consumption, and prevent premature termination of battery cell cycles.

[0015] In some embodiments, M includes Ni, Mn, and Fe, and 0.81≤q≤1, 0.8<x+y≤1, and 0.05≤y≤0.2.

[0016] 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 premature termination of the battery cell cycle.

[0017] In some embodiments, the breathable member includes a breathable film, the outer package includes an end cover, and the breathable film is disposed on the end cover.

[0018] In the technical solution of the embodiment of the present application, a breathable membrane is provided on the end cover to promptly discharge excess gas generated by the breakage of Cu-O bonds in the battery cell due to the instability of the copper-based layered oxide to the outside of the battery cell. Since the end cover is located above the battery assembly, the breathable membrane is provided on the end cover, which facilitates the upward discharge of excess gas, thereby making it less likely for the pressure relief mechanism of the battery cell to open its valve due to excessive internal air pressure, which easily reaches its threshold and ultimately causes the battery cell to fail, thereby improving the safety of the battery.

[0019] In some embodiments, the material of the breathable membrane includes at least one of polytetrafluoroethylene, polyethylene, or polypropylene.

[0020] 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.

[0021] In some embodiments, the pore size of the breathable membrane is 0.001 to 0.5 μm.

[0022] In the technical solution of the embodiments of the present application, the breathable membrane within this pore size range exhibits excellent waterproof and breathable properties. Because gas molecules are spaced relatively close together, they can diffuse through the membrane's pores. However, the spacing between liquid molecules is smaller than the pore spacing, and due to surface tension, liquid molecules cannot pass through the membrane, achieving a breathable, but liquid-proof performance.

[0023] In a second aspect, an embodiment of the present application provides a method for preparing a battery cell, comprising the following steps:

[0024] Obtaining a maximum required exhaust volume of a battery cell per unit cycle time, wherein the maximum required exhaust volume of a battery cell per unit cycle time is calculated based on the volume of carbon dioxide generated by oxygen released by breaking Cu-O bonds in a sodium-containing copper-based layered oxide;

[0025] Select a breathable member with an air permeability equal to or greater than the maximum required exhaust volume of the battery cell per unit cycle time;

[0026] The ventilating member is mounted on the outer packaging of the battery cell.

[0027] In some embodiments, the step of obtaining the maximum required exhaust volume of the battery cell per unit cycle time, wherein 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 rupture of Cu-O bonds in the sodium-containing copper-based layered oxide and releasing oxygen, further comprises: obtaining the maximum required exhaust volume of the battery cell based on the following formula:

[0028] Among them, V CO2 is the volume of carbon dioxide generated by the rupture of Cu-O bonds in sodium-containing copper-based layered oxides 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 sodium-containing copper-based layered oxides in all gases, and a = 0.45-0.72, P max V is the maximum acceptable threshold of the battery cell internal pressure. 残 is the residual volume of the battery cell, and T is the total cycle time of the battery cell.

[0029] In some embodiments, the method for preparing the battery cell further includes: 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:

[0030] 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.

[0031] In a third aspect, an embodiment of the present application provides a battery comprising the above-mentioned battery cell.

[0032] In a fourth aspect, an embodiment of the present application provides an electrical device comprising the above-mentioned battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or exemplary technical descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0034] FIG1 is a schematic structural diagram of a vehicle according to some embodiments of the present application;

[0035] FIG2 is a schematic diagram of the exploded structure of a battery according to some embodiments of the present application;

[0036] FIG3 is a schematic diagram of the exploded structure of a battery cell according to some embodiments of the present application;

[0037] Among them, the reference numerals in the figures are:

[0038] Vehicles 1000;

[0039] Battery 100, controller 200, motor 300;

[0040] Box body 10, first part 11, second part 12;

[0041] Battery cell 20 , end cover 21 , electrode terminal 21 a , pressure relief mechanism 21 b , housing 22 , battery core assembly 23 , tab 23 a , and breathable member 24 . DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit this application.

[0043] It should be noted that when a component is referred to as being "fixed on" or "disposed on" another component, it may be directly on the other component or indirectly on the other component. When a component is referred to as being "connected to" another component, it may be directly or indirectly connected to the other component. The terms "upper", "lower", "left", "right", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of 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. Therefore, they cannot be understood as limitations on this application. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances. The terms "first" and "second" are only used for the purpose of convenience of description and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[0044] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0045] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0046] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0047] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", 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 embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0048] In the description of the embodiments of the present application, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0049] In the sodium-ion battery of the related art, the positive electrode is coated with a copper-based layered oxide coating of active material. During the use of the battery and under high-voltage 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 releasing 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, the Cu-O bond 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 the sodium-ion battery.

[0050] Based on the above considerations, a battery cell has been designed to address the issue of increased gas production during battery cell use due to the instability of the copper-based layered oxide material, which ultimately causes the battery cell valve to fail and thus affects the safety of the battery cell. A venting member with a certain air permeability is provided on the battery cell's outer packaging, and the air permeability of the venting member is set to be 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 calculated based on the volume of carbon dioxide generated by the rupture of Cu-O bonds in the sodium-containing copper-based layered oxide. Furthermore, the venting member can promptly discharge excess gas generated by the rupture of Cu-O bonds during battery operation to the exterior of the battery cell, making it less likely that the battery cell's pressure relief mechanism will open its valve due to excessive internal pressure reaching the pressure relief mechanism's threshold, thereby causing the battery cell to fail. This improves battery safety.

[0051] The battery cells 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 include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, battery-powered vehicles, electric vehicles, ships, spacecraft, and the like. Electric toys can include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, and spacecraft can include airplanes, rockets, space shuttles, and spacecraft, among others.

[0052] 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.

[0053] Please refer to Figure 1, which is a schematic structural diagram of a vehicle 1000 provided in some embodiments of the present application. The vehicle 1000 can be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 100 is provided inside the vehicle 1000, and the battery 100 can be provided at the bottom, head or tail of the vehicle 1000. The battery 100 can be used to power the vehicle 1000. For example, the battery 100 can serve as an operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300. 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.

[0054] In some embodiments of the present application, the battery 100 can serve not only as an operating power source for the vehicle 1000, but also 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.

[0055] Please refer to Figure 2, which is an exploded view of a battery 100 provided in some embodiments of the present application. The battery 100 includes a housing 10 and a battery cell 20, with the battery cell 20 housed within the housing 10. The housing 10 provides a storage space for the battery cell 20 and can have various structures. In some embodiments, the housing 10 can include a first portion 11 and a second portion 12, which overlap each other and together define a storage space for the battery cell 20. The second portion 12 can be a hollow structure with one end open. The first portion 11 can be a plate-like structure, with the first portion 11 overlapping the open side of the second portion 12, so that the first portion 11 and the second portion 12 together define a storage space. Alternatively, the first portion 11 and the second portion 12 can each be a hollow structure with one end open, with the open side of the first portion 11 overlapping the open side of the second portion 12. Of course, the housing 10 formed by the first portion 11 and the second portion 12 can have various shapes, such as a cylinder, a rectangular parallelepiped, etc.

[0056] 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 hybrid connection. A hybrid connection refers to a combination of series and parallel connections among the multiple battery cells 20. The multiple battery cells 20 may be directly connected in series, in parallel, or in a hybrid connection, and then the entire battery cell 20 may be housed within the housing 10. Alternatively, the battery 100 may be constructed by first connecting multiple battery cells 20 in series, in parallel, or in a hybrid connection to form a battery module, which is then connected in series, in parallel, or in a hybrid connection to form a complete battery module, and then housed within the housing 10. The battery 100 may also include other structures, such as a busbar assembly for electrically connecting the multiple battery cells 20.

[0057] 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.

[0058] Please refer to Figure 3, which shows an exploded schematic diagram of a battery cell 20 provided in some embodiments of the present application. A battery cell 20 is the smallest unit of a battery. As shown in Figure 3, a battery cell 20 includes an outer packaging, a cell assembly 23, and other functional components. The outer packaging includes an end cap 21 and a housing 22.

[0059] The end cap 21 is a component that covers the opening of the housing 22 to isolate the internal environment of the battery cell 20 from the external environment. The shape of the end cap 21 can be adapted to the shape of the housing 22 to fit the housing 22. Optionally, the end cap 21 can be made of a material with a certain hardness and strength (such as an aluminum alloy). This prevents the end cap 21 from deforming when subjected to compression or collision, giving the battery cell 20 greater structural strength and improved safety. Functional components such as electrode terminals 21a can be provided on the end cap 21. The electrode terminals 21a can be used to electrically connect to the battery cell assembly 23 to output or input electrical energy to the battery cell 20. In some embodiments, the end cap 21 can also be provided with a pressure relief mechanism 21b for relieving internal pressure when the internal pressure or temperature of the battery cell 20 reaches a threshold. The end cap 21 can also be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and this embodiment of the present application does not impose any specific limitations on this. In some embodiments, an insulating member may be provided inside the end cap 21 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 made of plastic, rubber, or the like.

[0060] The housing 22 is a component that cooperates with the end cap 21 to form the internal environment of the battery cell 20. This internal environment can be used to accommodate the battery cell assembly 23, electrolyte, and other components. The housing 22 and end cap 21 can be separate components. An opening can be provided in the housing 22, and the end cap 21 is placed over the opening to form the internal environment of the battery cell 20. Alternatively, the end cap 21 and housing 22 can be integrated. Specifically, the end cap 21 and housing 22 can form a common connection surface before other components are inserted into the housing. When the interior of the housing 22 needs to be enclosed, the end cap 21 is placed over the housing 22. The housing 22 can have a variety of shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shape of the housing 22 can be determined based on the specific shape and size of the battery cell assembly 23. The housing 22 can be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and this embodiment of the present application does not impose any specific limitations on this.

[0061] 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 shell 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 substances constitute the main body of the battery cell assembly, and the parts of the positive and negative electrode sheets without active substances each constitute a tab 23a. The positive and negative electrode tabs 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 substance and the negative active substance react with the electrolyte, and the tabs 23a connect the electrode terminals to form a current loop.

[0062] According to some embodiments of the present application, referring to FIG. 3 , a battery cell 20 is provided. The battery cell 20 includes a cell assembly 23 and an outer packaging. The cell assembly 23 includes a positive electrode sheet provided with an active material coating, the active material coating including a sodium-containing copper-based layered oxide. The outer packaging is used to encapsulate the cell assembly 23 and is provided with a breathable member 24. The breathable member 24 has an air permeability greater than or equal to the maximum required exhaust volume of the battery cell 20 per unit cycle time. The maximum required exhaust volume of the battery cell 20 per unit cycle time is calculated based on the volume of carbon dioxide generated by the release of oxygen from the rupture of Cu-O bonds in the sodium-containing copper-based layered oxide.

[0063] The cell assembly 23 is the portion 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 matrix oxide that reacts with the electrolyte. The breathable member 24 is a leak-proof component that is resistant to electrolyte corrosion and is used to promptly discharge excess gas generated within the battery cell 20. The permeability of the breathable member 24 refers to the amount of gas that can pass through per unit time. The maximum required exhaust volume per unit cycle time for a battery cell is the amount of gas that needs to be discharged per day, calculated from the total cycle time, to avoid failure of the pressure relief valve.

[0064] 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 voltage (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 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, and the maximum required exhaust volume is obtained based on the volume conversion of carbon dioxide generated by the release of oxygen due to the breakage of the Cu-O bond in the sodium-copper-based layered oxide. Therefore, the breathable piece can promptly discharge the excess gas generated by the breakage of the Cu-O bond during the operation of the battery cell to the outside of the battery cell, so that the pressure relief mechanism of the battery cell is not prone to the problem of the valve opening 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.

[0065] In some embodiments of the present application, 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 relationship: Among them, V CO2 is the volume of carbon dioxide generated by the rupture of Cu-O bonds in sodium-containing copper-based layered oxides 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 sodium-containing copper-based layered oxides in all gases, and a = 0.45-0.72, P max V is the maximum acceptable threshold of the battery cell internal pressure. 残 is the residual volume of the battery cell, and T is the total cycle time of the battery cell.

[0066] During the charge and discharge process of a battery cell, when the Cu-O bond of the sodium-copper-based layered oxide, the positive electrode active material, breaks and produces gas, the total amount of carbon dioxide gas produced accounts for 50% to 80% of the total amount of gas. During the cycle, the amount of carbon dioxide released due to the break of the Cu-O bond accounts for more than 90% of the total amount of 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 break of the Cu-O bond in the sodium-copper-based layered oxide during the total cycle time of the battery cell accounts for 45% to 72% of the total amount of gas produced during the total cycle time. The maximum required exhaust volume of the battery cell and the air permeability of the vent are then converted based on the volume of carbon dioxide released due to the break of the Cu-O bond. The air permeability of the selected vent can meet the requirement of promptly discharging excess gas generated inside the battery cell due to the break of the Cu-O bond to the outside of the battery cell.

[0067] "Total cycle time of a battery cell" refers to the total time required for all cycles of the battery cell, that is, the product of the required number of cycles and the time of each cycle. "Maximum acceptable threshold value of internal pressure of the battery cell" refers to the threshold of the pressure relief mechanism 21b, which is also the minimum pressure value at which the pressure relief mechanism 21b opens. "Residual volume of the battery cell" refers to the volume remaining in the battery cell 20 after removing all solid and liquid components (including the positive electrode sheet, negative electrode sheet, separator, mechanical components, electrolyte, etc.), that is, the volume occupied by gas.

[0068] 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 the release of oxygen due to the rupture of Cu-O bonds in the sodium-containing 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 the release of oxygen due to the rupture of Cu-O bonds in the sodium-containing 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 promptly discharged to the outside of the battery cell through the breathable component, so that the pressure relief mechanism of the battery cell is not prone to the problem of the internal air pressure being too high and reaching the threshold of the pressure relief mechanism, causing it to open the valve, thereby causing the battery cell to fail, thereby improving the safety of the battery.

[0069] 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 sodium-containing copper-based layered oxides, 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.

[0070] In the technical solution of the embodiment of the present application, the battery life will end if 5%-10% of the Cu-O bonds in the sodium-copper-based layered oxide break and release oxygen. Therefore, the present application calculates the volume of carbon dioxide generated by the 5%-10% Cu-O bond break and release of oxygen. Therefore, b is set to 0.05-0.1. The volume of carbon dioxide generated by the Cu-O bond break and release of oxygen 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. Therefore, different permeability is used to adapt to the different mass of copper atoms in the active material. This allows the permeability to promptly discharge excess gas that exceeds the gas volume accepted by the internal pressure of the battery cell. This makes it less likely that the pressure relief mechanism of the battery cell will open due to excessive internal pressure reaching the pressure relief mechanism threshold, thereby causing the battery cell to fail, thereby improving battery safety.

[0071] In some embodiments of the present application, the maximum required exhaust volume of a battery cell per unit cycle time can be obtained based on the following method:

[0072] Among them, V t It is the maximum exhaust volume required for the battery cell in the total cycle time, 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 The volume of gas generated by the battery cell when the internal pressure of the battery cell can be accepted at the end of the cycle, in ml.

[0073] 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 CO2 ρ is the mass of carbon dioxide generated by the rupture of Cu-O bonds in sodium-containing copper-based layered oxides, in g. CO2The density of released carbon dioxide gas is 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.

[0074] The mass m of copper atoms in sodium-containing copper-based layered oxides Cu Satisfied: m Cu =m×W Cu , where m is the weight of the sodium copper-based matrix oxide, in g. Cu is the mass fraction of copper element in copper-based layered oxide, in %.

[0075] The volume of gas generated by the battery cell when the battery cell internal pressure reaches the end of the cycle V EOL satisfy: Among them, P max This is the maximum acceptable internal pressure threshold for the battery cell from the moment the cycle is terminated, measured in MPa. When the internal pressure reaches this threshold, the pressure relief mechanism 21b opens. Excessive pressure can cause an explosion or other safety hazard. Vremaining is the residual volume of the battery cell, measured in ml. This refers to the volume remaining in the battery cell 20 after removing all solid and liquid components (including the positive and negative electrodes, separators, mechanical components, and electrolyte), i.e., the volume occupied by gas.

[0076] The total cycle time T of a battery cell satisfies the following: T = X × t, where X is the number of cycles required at 25°C for the cell, for example, 1000 cycles. t is the cycle time per cycle, measured in hours. The total cycle time of a battery cell can be calculated in days, with each day being 24 hours. A single cycle of a battery cell follows the following process: 1) 0.33C cross-current charge to 4.0V (approximately 3 hours); 2) rest for 0.5 hours; 3) 0.33C cross-current discharge to 1.5V (approximately 3 hours); 4) rest for 0.5 hours. Steps 1)-4) are repeated until the cell decays to 80% of its initial capacity. C is the cell capacity. The cell capacity C satisfies the following: C = m × K, where m is the weight of the sodium-copper-based layered oxide, measured in grams. K is the capacity per gram of the active material, the sodium-copper-based layered oxide, measured in mAh / g.

[0077] In some embodiments of the present application, the chemical formula of the sodium copper-based layered oxide is Na q M xCu 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, and 0.03≤y≤0.2.

[0078] 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 O2, wherein 0.03≤y≤0.2. The number of Cu atoms is within the range of 0.03 to 0.2, which can prevent excessive gas production during battery cell operation, reduce electrolyte consumption, and prevent premature termination of battery cell cycles.

[0079] In some embodiments of the present application, the chemical formula of the sodium copper-based layered oxide is Na q M x Cu y O2, wherein M includes Ni, Mn and Fe, and 0.81≤q≤1, 0.8<x+y≤1, 0.05≤y≤0.2.

[0080] 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 premature termination of the battery cell cycle.

[0081] In some embodiments of the present application, referring to FIG. 3 , the breathable member 24 includes a breathable film, the outer package includes an end cap 21 , and the breathable film is disposed on the end cap 21 .

[0082] "A breathable membrane disposed on the end cap 21" means placing the breathable membrane anywhere on the end cap 21, except for the electrode terminals 21a and the pressure relief mechanism 21b, so that it does not interfere with other functional components and can discharge excess gas generated within the battery cell into the outer packaging, thus providing a waterproof and breathable effect. The breathable membrane can be a breathable member with air holes, and its shape can be circular, square, rectangular, diamond-shaped, elliptical, or other irregular. A mounting opening for the breathable membrane can be reserved on the end cap 21. The edge of the breathable membrane and the edge of the mounting opening can be sealed together, for example, by gluing or welding, and the breathable membrane allows gas communication between the interior and exterior of the end cap 21.

[0083] In the technical solution of the embodiment of the present application, a breathable membrane is provided on the end cover 21 to promptly discharge excess gas generated by the rupture of Cu-O bonds 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 its 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.

[0084] 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.

[0085] 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.

[0086] In the technical solution of the embodiment of the present application, the pore size of the breathable membrane is 0.001 to 0.5 um.

[0087] Breathable membranes within this pore size range exhibit excellent waterproof and breathable properties. Because gas molecules are spaced relatively close together, they can diffuse through the membrane's pores. Liquid molecules, however, are spaced closer together, and surface tension prevents them from passing through the membrane, ensuring air permeability without leaking liquids.

[0088] In some embodiments of the present application, the thickness of the breathable membrane is 1 to 5 mm, and can be 2 mm.

[0089] In a second aspect, the present application provides a method for preparing a battery cell, which is used to prepare the above-mentioned battery cell, comprising the following steps:

[0090] Obtaining the maximum required exhaust volume of the battery cell per unit cycle time, wherein the maximum required exhaust volume of the battery cell per unit cycle time is calculated based on 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;

[0091] Select a breathable component with an air permeability equal to or greater than the maximum required exhaust volume of the battery cell per unit cycle time;

[0092] The ventilating member is mounted on the outer packaging of the battery cell.

[0093] 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 breaking 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 a timely manner 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.

[0094] 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 the battery cell per unit cycle time is obtained by converting the volume of carbon dioxide generated by oxygen released by breaking 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:

[0095] Among them, V CO2 is the volume of carbon dioxide generated by the rupture of Cu-O bonds in sodium-containing copper-based layered oxides 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 sodium-containing copper-based layered oxides in all gases, and a = 0.45-0.72, P max is the maximum acceptable threshold of the internal pressure of the battery cell, Vremains is the residual volume of the battery cell, and T is the total cycle time of the battery cell.

[0096] In some embodiments of the present application, the volume of carbon dioxide generated by the release of oxygen by the rupture of Cu-O bonds in the sodium-containing copper-based layered oxide is obtained based on the following formula:

[0097] 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.

[0098] In a third aspect, the present application also provides a battery, which includes the above-mentioned battery cell.

[0099] In a fourth aspect, the present application also provides an electrical device, which includes the above-mentioned battery.

[0100] The following description will be made in conjunction with specific examples. The examples described below are exemplary and are intended only to explain the present application and are not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used without manufacturer's indication are conventional products that can be purchased commercially.

[0101] Example 1:

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

[0103] The chemical formula of the sodium-copper-based layered oxide in Example 1 is: Na 0.9 Cu 0.2 Ni 0.15 Fe 0.25 Mn 0.4 O2, the molar molecular mass is 110.1g / 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 0.2 Ni 0.15 Fe 0.25 Mn 0.4 The mass fraction of copper in O2 in copper-based layered oxides is W cu 11.5%, copper-based layered oxide Na 0.9 Cu 0.2 Ni 0.15 Fe 0.25 Mn 0.4 The mass of a copper atom in O2 m cu =m×W cu 115.4g, copper-based layered oxide Na 0.9 Cu 0.2 Ni 0.15 Fe 0.25 Mn 0.4 The mass m of the oxygen atom bonded to the copper atom in O2 o =m cu ×16 / 63.55 is 28.85g, and the maximum released carbon dioxide mass m Co2 =0.1×m o×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 value. In this embodiment, it is calculated based on b = 0.1) is 4.0g, and the density of carbon dioxide ρ Co2 The maximum volume of carbon dioxide released is 1.977 g / L. 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. The residual volume of the battery cell is Vresidue'=Vresidue / C is 1.2ml / Amh, that is, the space that the gas can occupy per unit volume. The maximum acceptable threshold value Pmax of the internal pressure of the battery cell from the battery cell to the end of the cycle is 0.35MPa. The volume of gas that can be generated in the battery cell from the battery cell to the end of the cycle is VEOL, which is 567ml. The maximum volume of gas that the battery cell needs to discharge is The discharge capacity of the battery cell is 3892ml (a is 0.45), the number of cycles X required at 25℃ is 1000, 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 discharge capacity V of the battery cell within 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 O2, a binder, and conductive carbon are mixed in mass percentages of 94%, 2.5%, and 3.5%, and then NMP is added and stirred to form a positive electrode slurry. The mass ratio of the added NMP to the fixed mixture is 4:6. The binder is PVDF.

[0106] Preparation of negative electrode slurry:

[0107] Hard carbon, binder, 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 ratio of the added stirring solvent NMP to the fixed mixture was 5:5.

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

[0109] The end cap 21 of the battery cell of this embodiment is provided with a breathable membrane. 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 during the total cycle time of the battery cell of this embodiment. 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. The battery cell in this embodiment includes a battery cell assembly 23 and a breathable membrane. The battery cell assembly 23 includes a positive electrode sheet 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 O2, the molar molecular mass is 109.7g / 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 0.1 Ni 0.25 Fe 0.25 Mn 0.4 The mass fraction of copper in O2 in copper-based layered oxides is W cu 5.8%, copper-based layered oxide Na 0.9 Cu 0.1 Ni 0.25 Fe 0.25 Mn 0.4 The mass of a copper atom in O2 m cu 57.95g, copper-based layered oxide Na 0.9 Cu 0.1 Ni 0.25 Fe 0.25 Mn 0.4 The mass m of the oxygen atom bonded to the copper atom in O2 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 ρ Co2The maximum volume of carbon dioxide released is 1.977 g / L. 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, the maximum acceptable threshold value Pmax of the internal pressure of the battery cell from the end of the cycle is 0.35MPa, and the volume V of the gas that can be generated in the battery cell from the end of the cycle is 0.35MPa. EOL The volume of gas that needs to be discharged from the battery cell is 567ml. It is 1672ml (a is taken as 0.45), the battery cell requires 1000 cycles X at 25℃, and the cycle time t is 7h. The total cycle time of the battery cell is 292days. If it is calculated as 24h per day, the maximum required exhaust volume Vt=Vp / T of the battery cell per unit cycle time 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 O2, a binder, and conductive carbon were mixed in 94%, 2.5%, and 3.5% mass percentages, and then NMP was added and stirred to form a positive electrode slurry. The mass ratio of the added stirring solvent NMP to the fixed mixture was 4:6. The binder was PVDF.

[0115] Preparation of negative electrode slurry:

[0116] Hard carbon, binder, 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 ratio of the added stirring solvent NMP to the fixed mixture was 5:5.

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

[0118] The end cap 21 of the battery cell of this embodiment is provided with a breathable membrane. 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 2The air permeability of the selected breathable membrane is 6 ml / day. After testing, the battery cell of this embodiment did 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. The battery cell in this embodiment includes a cell assembly 23 and a breathable membrane. The cell assembly 23 includes a positive electrode sheet coated with a sodium copper-based layered oxide as a positive electrode active material.

[0121] In Example 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 O2, 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 The mass fraction of copper in O2 in copper-based layered oxides is W cu 2.9%, copper-based layered oxide Na 0.9 Cu 0.05 Ni 0.3 Fe 0.25 Mn 0.4 The mass of a copper atom in O2 m cu 29.04g, copper-based layered oxide Na 0.9 Cu 0.05 Ni 0.3 Fe 0.25 Mn 0.4 The mass m of the oxygen atom bonded to the copper atom in O2 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) = 1.0g, the density of carbon dioxide ρ Co2 The maximum volume of carbon dioxide released is 1.977 g / L. 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. The required cycle time X of the battery cell at 25°C is 1000, and the cycle time t is 7 hours. The total cycle time of the battery cell is 291 days. If each day is calculated as 24 hours, 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 O2, a binder, and conductive carbon are mixed in mass percentages of 94%, 2.5%, and 3.5%, and then NMP is added and stirred to form a positive electrode slurry. The mass ratio of the added NMP to the fixed mixture is 4:6. The binder is PVDF.

[0124] Preparation of negative electrode slurry:

[0125] Hard carbon, binder, 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 ratio of the added stirring solvent NMP to the fixed mixture was 5:5.

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

[0127] The end cap 21 of the battery cell of this embodiment is provided with a breathable membrane. 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] Example 4:

[0129] Example 4 As shown in Table 1 below, a battery cell of Example 4 was prepared in the same manner as Example 1 except that the type of sodium-copper-based layered oxide and the mass of copper atoms were adjusted.

[0130] Example 5:

[0131] Example 5 As shown in Table 1 below, a battery cell of Example 5 was prepared in the same manner as Example 1 except that the type of the breathable membrane was adjusted.

[0132] Example 6:

[0133] Example 6 As shown in Table 1 below, a battery cell of Example 6 was prepared in the same manner as Example 1 except that the type of the breathable membrane was adjusted.

[0134] Comparative Example 1:

[0135] 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-containing copper-based layered oxide as a positive electrode active material. The chemical formula of the sodium-containing copper-based layered oxide is: Na 0.9 Cu 0.1 Ni 0.25 Fe 0.25 Mn 0.4 O2, the weight m of the coated positive electrode active material is 1000 g.

[0136] Preparation of positive electrode slurry:

[0137] Sodium-containing copper-based layered oxide Na 0.9 Cu 0.1 Ni 0.25 Fe 0.25 Mn 0.4 O2, a binder, and conductive carbon were mixed in 94%, 2.5%, and 3.5% mass percentages, and then NMP was added and stirred to form a positive electrode slurry. The mass ratio of the added stirring solvent NMP to the fixed mixture was 4:6. The binder was PVDF.

[0138] Preparation of negative electrode slurry:

[0139] Hard carbon, binder, 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 ratio of the added stirring solvent NMP to the fixed mixture was 5:5.

[0140] The battery cell components are then prepared through coating → cold pressing → die cutting → winding → assembly → liquid injection → aging → formation.

[0141] 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 required for the battery cell of this embodiment to reach the valve opening threshold of the pressure relief mechanism is 339.

[0142] Comparative Example 2:

[0143] Comparative Example 2 As shown in Table 1, in Comparative Example 2, the air permeability of the breathable membrane used was adjusted, and otherwise, a battery cell of Comparative Example 2 was prepared in the same manner as in Example 1.

[0144] Table 1: Related parameter results of battery cells of Examples 1 to 6 and Comparative Examples 1-2

[0145] Performance testing:

[0146] 1. Cycle test process: Cycle according to the following process at normal pressure 25±2℃:

[0147] 1) 0.33C cross-current charging to 4.0V;

[0148] 2) rest 0.5h;

[0149] 3) 0.33C cross-current discharge 1.5V;

[0150] 4) rest 0.5h;

[0151] Steps 1-4) were cycled until the capacity of the battery cell decayed to 80% of the initial capacity to test the cycle number of the battery cell, where C=135 Ah is the battery cell capacity. The test results are shown in Table 2 below.

[0152] 2. Battery Cell Valve Opening: By observing the valve opening of the battery cell pressure relief mechanism 21b in real time during the total cycle time, it is determined whether the pressure relief structure valve opening occurs during the total cycle time of the battery cell. The test results are shown in Table 2 below.

[0153] 3. Cycle end maximum internal pressure test: When the battery cell is manufactured, a pressure gauge is connected. 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.

[0154] Table 2 Performance results of battery cells of Examples 1-6 and Comparative Examples 1-2

[0155] The above results show that, compared to Comparative Example 1, which lacked a breathable membrane, Examples 1 to 6, by installing a breathable membrane with a permeability greater than the maximum required exhaust volume per unit cycle time of the battery cell, prevented the maximum internal pressure within the battery cell from reaching the threshold of the pressure relief mechanism. During the battery cell cycle test, no valve failure of the pressure relief mechanism occurred, and the battery cell cycle number met the required number, thereby improving battery safety. However, Comparative Example 1 experienced valve failure at 502 cycles.

[0156] Compared to Comparative Example 2, where the permeability of the breathable membrane was less than the maximum gas release rate of the battery cell, the permeability of the breathable membranes used in Examples 1 to 6 exceeded the maximum required gas release rate of the battery cell per unit cycle time. The maximum internal pressure within the battery cell did not reach the threshold of the pressure relief mechanism. During the battery cell cycle test, no pressure relief mechanism valve failure occurred, and the battery cell cycle count met the required number. In Comparative Example 2, however, the pressure relief mechanism valve opening threshold was reached after 529 cycles, and valve failure occurred at 703 cycles.

[0157] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

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: Wherein, VCO2 is the volume of carbon dioxide released 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 released by the rupture of Cu-O bonds in the sodium-containing copper-based layered oxide in all gases, and a=0.45~0.72, Pmax is the maximum acceptable threshold value of the internal pressure of the battery cell, Vresidual 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.

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