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

Abstract

The present application provides a battery cell and a preparation method therefor, a battery, and an electric device. The battery cell comprises: an electrode assembly and an outer package, the electrode assembly comprises a positive electrode sheet, a positive electrode active material layer is provided on the positive electrode sheet, and the positive active material layer comprises a transition metal oxide; the outer package is used for packaging the electrode assembly, a venting device is arranged on the outer package, and the venting device comprises a breathable membrane. The venting device is mounted on the outer package of the battery cell, and excess gas generated due to the instability of transition metals during use of the battery cell is discharged out of the battery cell in time by means of the breathable membrane of the venting device, so that the explosion-proof valve of the battery cell is not prone to abnormal valve opening due to excessively large internal air pressure, improving the reliability of the battery and prolonging the service life thereof.

Description

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

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

[0002] In related technologies, since the positive electrode material of the battery contains active elements, the instability of the active elements will cause the gas production inside the battery cell to increase during use. When the internal air pressure of the battery reaches the valve opening threshold of the battery explosion-proof valve, the battery cell explosion-proof valve will open abnormally and cause battery failure. Excessive air pressure may even cause explosions and other accidents, affecting the reliability of the battery cell.

[0003] Summary of the Invention

[0004] 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 to solve the technical problem of poor battery reliability in the prior art.

[0005] To achieve the above objectives, the technical solution adopted in this application is:

[0006] In a first aspect, the present application provides a battery cell comprising: an electrode assembly and an outer packaging, the electrode assembly comprising a positive electrode plate, the positive electrode plate being provided with a positive electrode active material layer, the positive electrode active material layer comprising a transition metal oxide; the outer packaging is used to encapsulate the electrode assembly, the outer packaging being provided with an exhaust device, the exhaust device comprising a breathable membrane.

[0007] In the technical solution of the embodiment of the present application, when the positive electrode active material layer includes transition metal oxides, problems such as structural phase change oxygen release, transition metal dissolution catalyzing oxidative electrolyte decomposition, or promoting SEI decomposition and repair are likely to occur during high temperature or high pressure use, which increases the gas production inside the battery cell. By installing an exhaust device on the outer packaging of the battery cell, the exhaust device includes a breathable membrane, and then the excess gas generated by the instability of the transition metal during the use of the battery is discharged to the outside of the battery cell in time through the breathable membrane of the exhaust device, so that the explosion-proof valve of the battery cell is not prone to abnormal valve opening due to excessive internal air pressure, thereby improving the reliability and service life of the battery.

[0008] In some embodiments, the exhaust device further includes a connector having at least one through hole formed therein, and a breathable membrane is disposed on a side of the connector facing the interior of the battery cell, with the breathable membrane covering all the through holes.

[0009] In the technical solution of the embodiment of the present application, the exhaust device includes a connector, which is provided with at least one through-hole. A breathable membrane is provided on the side of the connector facing the interior of the battery cell, and the breathable membrane covers all the through-holes. During the exhaust process, the connector can provide support for the breathable membrane, ensuring sufficient exhaust area while not easily causing deformation or displacement of the breathable membrane due to excessive pressure inside the battery cell, thereby ensuring the integrity of the breathable membrane and improving safety and reliability. At the same time, the breathable membrane is provided on the side of the connector facing the interior of the battery cell. This arrangement can improve the utilization rate of the external space of the outer packaging and facilitate the placement of other components. When the gas production inside the battery cell increases and reaches a certain pressure, a pressure difference is generated between the inside and outside of the breathable membrane. Then, the excess gas inside the battery cell can be discharged from the battery cell through the through-hole through the breathable membrane to the outside of the battery cell, thereby improving the reliability of the battery cell.

[0010] In some embodiments, the breathable membrane is sealingly connected to the contact surface of the connector.

[0011] In the technical solution of the embodiment of the present application, the contact surface between the breathable membrane and the connector is sealed to keep the contact surface between the breathable membrane and the connector sealed. The connector provides support force for the breathable membrane, thereby improving the reliability of the exhaust device.

[0012] In some embodiments, the connector is provided with a plurality of through holes, and the diameter of each through hole is less than or equal to 3 mm.

[0013] In the technical solution of the embodiment of the present application, a plurality of through holes are provided, and the aperture of each through hole is less than or equal to 3 mm, so that the breathable membrane is not easily deformed or shifted due to excessive internal pressure of the battery cell, thereby ensuring the reliability of the breathable membrane and thereby improving the service life of the battery cell.

[0014] In some embodiments, the orthographic projection area of ​​all through holes along the axial direction of the through holes is 10 mm. 2 ~50mm 2 .

[0015] In the technical solution of the embodiment of the present application, the orthographic projection area of ​​all through holes is set to the above range, so that the gas inside the battery cell can be discharged to the outside of the battery cell through the breathable membrane and the through holes in a timely manner.

[0016] In some embodiments, the breathable membrane has a thickness of 0.1 mm to 3 mm, and optionally, a thickness of 0.2 mm to 0.8 mm.

[0017] In the technical solution of the embodiment of the present application, the thickness of the breathable membrane is 0.1 mm to 3 mm, and optionally, 0.2 mm to 0.8 mm, so that the breathable membrane maintains a certain air permeability within this thickness range.

[0018] In some embodiments, the exhaust device further includes a backing member, which is disposed between the connector and the breathable membrane, and the breathable membrane covers the backing member, and the backing member covers all the through holes.

[0019] In the technical solution of the embodiment of this application, the exhaust device also includes a backing member, which is disposed between the connector and the breathable membrane. The breathable membrane covers the backing member, and the backing member covers all through-holes. Gas inside the battery cell passes through the breathable membrane and the backing member in sequence before being discharged from the battery cell through the through-holes. The backing member supports the breathable membrane, ensuring sufficient exhaust area while preventing deformation or displacement of the breathable membrane due to excessive internal pressure in the battery cell, thereby ensuring the integrity of the breathable membrane. Furthermore, the backing member isolates the breathable membrane from contact with materials outside the battery cell, thereby extending its service life.

[0020] In some embodiments, a recess is provided on a side of the connector facing the interior of the battery cell, and the recess is used to accommodate the breathable membrane and / or the backing member.

[0021] In the technical solution of the embodiment of the present application, a recess is provided on the side of the connector facing the inside of the battery, and the recess is used to accommodate the breathable membrane and / or the backing member, so as to reduce the space occupied by the backing member or the breathable membrane.

[0022] In some embodiments, the backing member has an air permeability greater than the air permeability of the breathable film.

[0023] In the technical solution of the embodiment of the present application, the air permeability of the backing member is greater than that of the breathable membrane, so that the backing member will not hinder the air permeability of the breathable membrane, so that the gas inside the battery cell can be discharged to the outside of the battery cell in time through the breathable membrane, the backing member and the through hole.

[0024] In some embodiments, the backing member has a melting point greater than the melting point of the breathable film.

[0025] In the technical solution of the embodiments of the present application, the melting point of the backing member is higher than that of the breathable membrane, making the backing member more resistant to high temperatures than the breathable membrane. The temperature at which the breathable membrane is fused to the connecting member, such as an aluminum sheet, is higher than the melting point of the breathable membrane itself. To prevent the breathable membrane from fusing to the backing member during the fusion process and to prevent the backing member from melting and altering its permeability due to temperature, the melting point of the backing member is set higher than that of the breathable membrane. This prevents the backing member and the breathable membrane from adhering to each other, thereby clogging the breathable membrane. Furthermore, the backing member's permeability is not affected by melting and thus its permeability.

[0026] In some embodiments, the air permeability area of ​​the backing member is 50 mm 2 ~200mm 2 .

[0027] In the technical solution of the embodiment of the present application, the air permeability area of ​​the backing member is set within the above range, so that the gas inside the battery cell can be discharged to the outside of the battery cell through the air permeable membrane and the backing member in time.

[0028] In some embodiments, the outer package includes an end cover, the exhaust device is provided on a side of the end cover facing the battery cell, and an exhaust hole connected to the through hole of the exhaust device is provided on the end cover.

[0029] In the technical solution of the embodiment of the present application, the exhaust device is arranged on the side of the end cover facing the battery cell, and the end cover is provided with an exhaust hole connected to the through hole of the exhaust device, so that the gas gathered above the inside of the battery cell can be quickly discharged from the battery cell through the exhaust device and the exhaust hole.

[0030] In some embodiments, a receiving groove for accommodating the exhaust device is provided on the side of the end cover facing the interior of the battery cell. When the exhaust device is installed in the receiving groove, an air guide channel is provided above the through hole of the exhaust device. The through hole is connected to the exhaust hole through the air guide channel, and the exhaust hole and the through hole are staggered.

[0031] In the technical solution of the embodiment of the present application, an air guide channel is provided so that the gas can be briefly buffered after being discharged through the through hole of the exhaust device and then discharged from the battery cell from the exhaust hole. The exhaust hole and the through hole are staggered, thereby protecting the exhaust device and preventing external impurities from entering the exhaust hole and affecting the ventilation effect of the exhaust device.

[0032] In some embodiments, an insulating member is provided inside the end cover, and a vent is provided on the insulating member. The gas inside the battery cell is discharged to the outside of the battery cell through the vent, the exhaust device, the air guide channel and the vent.

[0033] In the technical solution of the embodiment of the present application, the above arrangement allows the gas inside the battery cell to freely pass through the vent holes and be discharged to the outside of the battery cell in a timely manner by the exhaust device.

[0034] In some embodiments, the orthographic projection of the vent holes covers the orthographic projections of all the through holes in the thickness direction of the end cap. In the technical solution of the embodiment of the present application, the orthographic projection of the vent holes can cover the orthographic projections of all the through holes in the thickness direction of the end cap, so that the gas inside the battery cell can freely pass through the vent holes and be promptly discharged to the outside of the battery cell by the exhaust device, without affecting the ventilation effect of the exhaust device.

[0035] In some embodiments, the transition metal oxide has the formula AMO s , wherein 1≤s≤2, the A element includes at least one of Li, Na, K or Mg, and the M element includes a transition metal element.

[0036] In the technical solution of the embodiment of the present application, the transition metal oxide can be the positive electrode active material of lithium battery, sodium battery, potassium battery or magnesium battery. The transition metal oxide in the positive electrode active material contains transition metal elements. As the positive electrode active material of the battery, it can make the battery have higher energy and power density.

[0037] In some embodiments, the transition metal oxide is Na p (Ni x Fe y Mn z Me q )O2, wherein the Me element includes any one or more of Zn, Ti, Zr, Mg, La, Y, Co, Cr, Al, K, V, Mo, W, Sr, Ta, Nb or Ca, and 0.8≤p<1, 0.01≤x<0.35, 0.01≤y<0.35, 0.01≤z<0.5, 0.01≤q<0.3, and 0.81≤x+y+z<1.

[0038] In the technical solution of the embodiment of the present application, the transition metal oxide is Na p (Ni x Fe y Mn z Me q )O2, wherein the Me element includes any one or more of Zn, Ti, Zr, Mg, La, Y, Co, Cr, Al, K, V, Mo, W, Sr, Ta, Nb, or Ca, and 0.8≤p<1, 0.01≤x<0.35, 0.01≤y<0.35, 0.01≤z<0.5, 0.01≤q<0.3, and 0.81≤x+y+z<1. This can enable the battery to have higher energy and power density.

[0039] In some embodiments, the thickness of a single side of the positive electrode active material layer is 50 μm to 150 μm, and optionally, the thickness of a single side is 55 μm to 130 μm.

[0040] In the technical solution of the embodiment of the present application, the thickness of the single side of the positive electrode active material is set within the above range, so as to reduce the ion transmission path and make the battery have a higher energy density.

[0041] In some embodiments, the porosity of the positive electrode active material layer is 1%-70%, and optionally, the porosity is 8%-50%. In the technical solutions of the embodiments of the present application, the porosity of the positive electrode active material layer is set within the above range. The smaller the porosity, the smaller the contact area and interaction interface between the transition metal oxide of the positive electrode active material and the electrolyte, which reduces side reactions and gas production, while also ensuring that the battery has a good capacity and cycle life.

[0042] In some embodiments, the specific surface area of ​​the transition metal oxide in the positive electrode active material layer satisfies the following BET: 0.2 m 2 / g≤BET≤1.5m 2 / g, optionally, 0.4m 2 / g≤BET≤1.2m 2 / g.

[0043] In the technical solution of the embodiment of the present application, the smaller the material specific surface area BET, the smaller the contact area and interactive interface with the electrolyte, and the smaller the gas production; but a specific surface area BET that is too small often easily leads to insufficient structural stability and easy collapse and breakage, resulting in aggravated side reactions; therefore, the specific surface area of ​​the transition metal oxide in the positive electrode active material layer is controlled to meet the above range, so that the battery gas production is smaller, the side reactions are fewer, and the stability of the positive electrode active material structure is maintained.

[0044] In some embodiments, the average particle size of the transition metal oxide satisfies: 2 μm≤Dv50≤12 μm, optionally, 3 μm≤Dv50≤10 μm.

[0045] In the technical solution of the embodiment of the present application, the larger the material particle size, the smaller the contact area and interactive interface with the electrolyte, and the smaller the gas production; but if the particle size is too large, it is easy to break and the structural stability is insufficient; therefore, the average particle size of the transition metal oxide is set to meet the above range, so that the battery gas production is small while maintaining the stability of the positive electrode active material structure.

[0046] In some embodiments, the battery cell further includes an electrolyte, and the conductivity of the electrolyte is 5 mS / cm to 18 mS / cm, optionally, the conductivity is 6 mS / cm to 12 mS / cm.

[0047] In the technical solution of the embodiment of the present application, the conductivity of the electrolyte is set to the above range, so that the battery has good efficiency and energy density, and better ensures the stability and safety of the battery.

[0048] In some embodiments, the solute concentration of the electrolyte is 0.7 to 1.2 mol / L, optionally, the solute concentration is 0.85 to 1.1 mol / L.

[0049] In the technical solution of the embodiment of the present application, the solute concentration of the electrolyte is set within the above range so that the battery has good charge and discharge efficiency and better ensures the stability and safety of the battery.

[0050] In some embodiments, the residual space coefficient of the battery cell is 0.02 to 1 mL / Ah, and optionally 0.2 to 0.8 mL / Ah. In the technical solutions of the embodiments of the present application, the residual space coefficient of the battery cell is set within the above range so that there is a certain amount of gas accommodation space inside the battery cell, and excess gas can be discharged to the outside of the battery cell through the exhaust device, thereby improving the safety of the battery.

[0051] In some embodiments, the breathable membrane has a breathability rate of 0.1 to 5 mL / D, optionally 0.2 to 4 mL / D, and more optionally 0.2 to 0.7 mL / D.

[0052] In the technical solution of the embodiment of the present application, the air permeability of the breathable membrane is set within the above range so that the breathable membrane can discharge excess gas generated inside the battery cell out of the battery cell.

[0053] In some embodiments, the air permeability rate v of the breathable membrane and the gas generation rate V inside the battery cell satisfy the following relationship: 0.9≤v / V≤5, optionally, 1≤v / V≤4.

[0054] In the technical solution of the embodiment of the present application, the ratio between the air permeability rate v of the breathable membrane and the gas production rate V inside the battery cell satisfies the above relationship, so that the breathable membrane has a suitable breathable effect, so that the gas produced inside the battery cell can be discharged from the breathable membrane in time. If the ratio is too small, the breathable effect of the breathable membrane is poor. When the ratio is too large, the breathable membrane is easily infiltrated with moisture in the air, which shortens its life.

[0055] In some embodiments, the transition metal oxide Na p (Ni x Fe y Mn z Me q )The stoichiometric ratio z of the Mn element in O2 and the permeability v of the breathable membrane satisfy: 0.1≤z / v≤2, optionally, 0.25≤z / v≤1.7.

[0056] In the technical solution of the embodiment of the present application, due to the existence of the Jan-Teller effect of the Mn element, and the occurrence of element valence change and bulk phase distortion, the Mn element will escape from the lattice and deposit on the negative electrode, catalyze the decomposition of the fixed electrolyte interface (SEI) and produce gas. The larger the stoichiometric ratio z of the Mn element, the greater the gas production rate, and the greater the required gas permeability v of the breathable membrane. By making the stoichiometric ratio of the Mn element in the transition metal oxide and the gas permeability v of the breathable membrane satisfy the above relationship, the gas permeability rate of the breathable membrane can meet the gas production rate affected by the Mn element, and the battery cell has a suitable ventilation effect. When the ratio is too large, the gas permeability rate of the breathable membrane of the battery cell will be insufficient and the effect will be poor. When the ratio is too small, the breathable membrane will easily penetrate moisture in the air and its life will be shortened.

[0057] In some embodiments, an explosion-proof valve is also provided on the outer packaging.

[0058] In the technical solution of the embodiment of the present application, an explosion-proof valve is also provided on the outer packaging. The setting of the explosion-proof valve can open the explosion-proof valve in time when the internal pressure of the battery cell is too high, release the pressure inside the battery cell, and prevent the battery from exploding during thermal runaway.

[0059] In a second aspect, the present application also provides a method for preparing a battery cell, comprising:

[0060] Providing an electrode assembly, the electrode assembly includes a positive electrode plate, a positive electrode active material layer is provided on the positive electrode plate, and the positive electrode active material layer includes a transition metal oxide;

[0061] An outer package is provided, on which an exhaust device is provided, and the outer package is sealed on the outside of the electrode assembly, wherein the exhaust device includes a breathable film.

[0062] In a third aspect, the present application also provides a battery, which includes the aforementioned battery cell.

[0063] In a fourth aspect, the present application further provides an electrical device, which includes the aforementioned battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0065] FIG1 is a schematic structural diagram of a vehicle according to some embodiments of the present application;

[0066] FIG2 is a schematic diagram of the exploded structure of a battery according to some embodiments of the present application;

[0067] FIG3 is a schematic diagram of the exploded structure of a battery cell according to some embodiments of the present application;

[0068] FIG4 is a schematic structural diagram of an exhaust device according to some embodiments of the present application;

[0069] FIG5 is a schematic cross-sectional view of the exhaust device in FIG4 ;

[0070] FIG6 is a schematic cross-sectional view of the exhaust device and the end cover in FIG4 ;

[0071] FIG7 is a schematic structural diagram of an exhaust device according to another embodiment of the present application;

[0072] FIG8 is a schematic diagram of the exploded structure of the exhaust device in FIG7 ;

[0073] FIG9 is a schematic cross-sectional view of the exhaust device in FIG7 ;

[0074] FIG10 is a schematic cross-sectional view of the coordinated installation of the exhaust device and the end cover in FIG7 .

[0075] Among them, the figure marks in the figure are: 1000, vehicle; 100, battery; 200, controller; 300, motor; 10, housing; 11, first part; 12, second part; 20, battery cell; 21, end cover; 21a, electrode terminal; 21b, explosion-proof valve; 22, shell; 23, electrode assembly; 23a, tab; 24, exhaust device; 25, insulating member; 26, outer packaging; 211, exhaust hole; 212, air guide channel; 240, breathable membrane; 241, through hole; 242, connector; 244, backing member; 245, recess; 251, breathable hole. DETAILED DESCRIPTION

[0076] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, this 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 this application and are not intended to limit this application.

[0077] It should be noted that when an element is referred to as being “fixed on” or “disposed on” another element, it may be directly on the other element or indirectly on the other element. When an element is referred to as being “connected to” another element, it may be directly connected to the other element or indirectly connected to the other element.

[0078] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0079] In addition, the terms "first", "second", "third", "fourth", "fifth", "sixth", and "seventh" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, a feature defined as "first", "second", "third", "fourth", "fifth", "sixth", and "seventh" may explicitly or implicitly include one or more of the features. In the description of this application, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0080] In lithium, sodium, potassium and other types of batteries, the layered oxide-type positive electrode active materials contain active elements of transition metals, which often cause problems such as material structure phase change and oxygen release, transition metal dissolution catalyzing oxidation electrolyte decomposition, and promoting the decomposition and repair of the fixed electrolyte interface (SEI) during high temperature or high pressure use. Ultimately, this leads to increased gas production inside the battery cell. When the internal gas pressure of the battery cell reaches the opening threshold of the battery explosion-proof valve, the battery explosion-proof valve will open abnormally, causing battery failure. Excessive gas pressure may even cause explosions and other accidents, affecting the reliability and service life of the battery.

[0081] Based on the above considerations, in order to solve the problem that the presence of transition metal elements in the positive electrode active material during the use of the battery cell leads to increased gas production and eventually causes the battery cell to abnormally open the valve and fail, thereby affecting the reliability of the battery cell, a battery cell is designed. An exhaust device is installed on the outer packaging of the battery cell, and the exhaust device includes a breathable membrane. The exhaust device then discharges excess gas generated by the instability of the transition metal during the use of the battery to the outside of the battery cell in a timely manner, so that the explosion-proof valve of the battery cell is not prone to abnormal opening of the valve due to excessive internal air pressure, thereby improving the reliability and service life of the battery.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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. The battery 100 can also be an energy storage device, including an energy storage container or an energy storage cabinet.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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, an electrode assembly 23, and an electrolyte. The outer packaging includes an end cap 21 and a housing 22.

[0090] 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 degree of hardness and strength (such as an aluminum alloy). This prevents the end cap 21 from deforming when subjected to compression or collision, thereby enhancing the structural strength and safety of the battery cell 20. The end cap 21 can be provided with functional components such as electrode terminals 21a. The electrode terminals 21a can be used to electrically connect to the electrode assembly 23 to transmit or receive electrical energy from the battery cell 20. In some embodiments, the end cap 21 can also be provided with an explosion-proof valve 21b to release 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 25 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 25 may be made of plastic, rubber, or the like.

[0091] 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 electrode 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, or a hexagonal prism. Specifically, the shape of the housing 22 can be determined based on the specific shape and size of the electrode 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 particular limitations on this.

[0092] The electrode assembly 23 is the component within the battery cell 20 where the electrochemical reaction occurs. The housing 22 may contain one or more electrode assemblies 23. The electrode assembly 23 is primarily formed by winding or stacking positive and negative electrode sheets, typically with a separator between the positive and negative electrode sheets. A positive electrode sheet may include a positive current collector and a positive active material layer applied to opposite sides of the positive current collector. A negative electrode sheet may include a negative current collector and a negative active material layer applied to opposite sides of the negative current collector. The portions of the positive and negative electrode sheets containing active material constitute the main body of the electrode assembly, while the portions of the positive and negative electrode sheets without active material each constitute a tab 23a. The positive and negative tabs may be located together at one end of the main body or separately at opposite ends. During the battery's charge and discharge processes, the positive and negative active materials react with the electrolyte, and the tabs 23a connect to the electrode terminals to form a current circuit.

[0093] In the technical solution of an embodiment of the present application, a battery cell is provided, including: an electrode assembly 23 and an outer packaging 26, the electrode assembly 23 includes a positive electrode plate, the positive electrode plate is provided with a positive electrode active material layer, and the positive electrode active material layer includes a transition metal oxide; the outer packaging 26 is used to encapsulate the electrode assembly 23, and an exhaust device 24 is provided on the outer packaging 26, and the exhaust device 24 includes a breathable membrane 240.

[0094] The exhaust device 24 is a component used to exhaust gas from the battery cell 20. When the gas production inside the battery cell increases and the internal space of the battery cell 20 cannot accommodate the excess gas, the gas inside the battery cell 20 is promptly exhausted through the exhaust device 24. The breathable membrane 240 can be a component with a breathable function.

[0095] In the technical solution of the embodiment of the present application, when the positive electrode active material layer includes a transition metal oxide, problems such as structural phase change oxygen release, transition metal dissolution catalyzing oxidative electrolyte decomposition, or promoting SEI decomposition and repair are likely to occur during high-temperature or high-pressure use, which increases the gas production inside the battery cell 20. By installing an exhaust device 24 on the outer packaging 26 of the battery cell, the exhaust device 24 includes a breathable membrane 240, and then the excess gas generated by the instability of the transition metal during the use of the battery is discharged to the outside of the battery cell in time through the breathable membrane 240 of the exhaust device 24, so that the air pressure inside the battery cell 20 is not easy to reach the valve opening threshold of the explosion-proof valve 21b, and it is not easy for the internal air pressure of the battery cell to be too high, resulting in abnormal opening of the explosion-proof valve 21b, thereby improving the reliability and service life of the battery.

[0096] 4 and 5 or 7, 8, and 9, in some embodiments, the exhaust device 24 includes a connector 242 having at least one through hole 241 formed therein, and a breathable membrane 240 disposed on a side of the connector 242 facing the interior of the battery cell 20. The breathable membrane 240 covers all through holes 241.

[0097] The connector 242 can be a component connected to the outer packaging 26 and can be a split structure. Alternatively, the connector 242 can be a part of the outer packaging 26, that is, a one-piece structure with the outer packaging 26. The connection between the connector 242 and the outer packaging can be a fixed connection such as welding.

[0098] In some embodiments, the connector 242 may be a metal aluminum sheet. The number of through holes 241 on the connector 242 may be one, two, three, or more. The shape of the through holes 241 may be a regular geometric shape, such as a circle, an ellipse, a regular polygon, etc. Of course, it may also be an irregular geometric shape.

[0099] Through the above arrangement, the breathable membrane 240 is positioned on the side of the connector 242 facing the interior of the battery cell 20. During the exhaust process, the connector 242 can provide support for the breathable membrane 240, ensuring sufficient exhaust area while preventing deformation or displacement of the breathable membrane 240 due to excessive internal pressure in the battery cell. This ensures the integrity of the breathable membrane 240 and improves safety. Furthermore, positioning the breathable membrane 240 on the side of the connector 242 facing the interior of the battery cell improves the utilization of the external space of the outer packaging, making it easier to place other components. When the gas production inside the battery cell 20 increases and reaches a certain pressure, a pressure difference is generated between the inside and outside of the breathable membrane 240. Excess gas inside the battery cell 20 can then be discharged from the battery cell through the breathable membrane 240 and discharged to the outside of the battery cell through the through hole 241, thereby improving the reliability of the battery cell.

[0100] 4 and 5 , in some embodiments, the contact surface of the breathable membrane 240 and the connecting member 242 is sealed.

[0101] In some embodiments, the material of the breathable membrane can be polyolefin or polyurethane, and polyolefin can be polypropylene, polyethylene or polypropylene. The contact surface of the breathable membrane 240 and the connecting member 242 can be sealed by fusion bonding.

[0102] Through the above arrangement, the contact surface between the breathable membrane 240 and the connecting member 242 is sealed, so that the contact surface between the breathable membrane 240 and the connecting member 242 remains sealed. The connecting member 242 provides support for the breathable membrane 240, thereby improving the reliability of the exhaust device.

[0103] 4 and 5 , in some embodiments, a plurality of through holes 241 are provided on the connecting member 242 , and the diameter of each through hole is less than or equal to 3 mm.

[0104] The plurality may be two, three or more. The through hole may be a circular hole.

[0105] Through the above setting, the through hole 241 is set to include multiple, and the pore size of each through hole is less than or equal to 3 mm. In the example, the pore size of each through hole can be 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm or 3 mm, etc., which is typical but not restrictive, or a range between any two pore sizes. This makes it difficult for the breathable membrane 240 to be deformed or shifted due to excessive internal pressure of the battery cell, thereby ensuring the reliability of the breathable membrane 240 and improving the service life of the battery cell.

[0106] In some embodiments, along the axial direction of the through holes 241, the orthographic projection area of ​​all the through holes 241 is 10 mm. 2 ~50mm 2 In this example, the orthographic projection area of ​​all through holes 241 may be 10 mm 2 , 13mm 2 , 15mm 2 , 18mm 2 , 20mm 2 , 22mm 2 , 25mm 2 , 27mm 2 , 30mm 2 , 33mm 2 , 35mm 2 , 37mm 2 , 40mm 2 , 42mm 2 , 45mm 2 , 48mm 2 , 50mm2 The orthographic projection areas of all through holes are set to the above ranges so that the gas inside the battery cell 20 can be discharged from the battery cell 20 through the breathable membrane 240 and the through hole 241 in a timely manner.

[0107] In some embodiments, the breathable membrane 240 has a thickness of 0.1 mm to 3 mm, and optionally, a thickness of 0.2 mm to 0.8 mm. In this example, the breathable membrane 240 can have a thickness of 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 3 mm, or other typical but non-limiting thicknesses, or a range therebetween, so that the breathable membrane maintains a certain air permeability within this thickness range.

[0108] In some embodiments, the exhaust device 24 can be installed on the side of the end cover 21 facing the interior of the battery cell, or it can be installed on the side of the end cover 21 facing away from the interior of the battery cell, and an exhaust hole 211 connected to the through hole 241 of the exhaust device 24 is provided on the end cover 21. As long as the exhaust device 24 can discharge the gas inside the battery cell 20 to the outside of the battery cell 20, it can be sufficient.

[0109] Please refer to Figure 6, which shows a cross-sectional structural diagram of some embodiments of the coordinated installation of the exhaust device and the end cover in Figure 4. In the installation method shown in Figure 6, the exhaust device 24 is installed on the side of the end cover 21 facing the interior of the battery cell. A receiving groove for accommodating the exhaust device 24 is provided on the side of the end cover 21 facing the interior of the battery cell 20, so that the exhaust device 24 can be installed in the receiving groove of the end cover 21. In some embodiments, an air vent 251 is provided on the insulating member 25 located on the inner side of the end cover 21, and an exhaust vent 211 is provided on the outer side of the end cover 21. The gas inside the battery cell 20 passes through the air vent 251, the air permeable membrane 240 of the exhaust device 24, and the through hole 241 and is discharged from the outside of the battery cell 20 through the exhaust vent 211.

[0110] In some embodiments, after the exhaust device 24 is installed in the receiving groove of the end cover 21, an air guide channel 212 can be formed between the through hole 241 of the exhaust device 24 and the exhaust hole 211. The air guide channel 212 can be used to provide a short buffer for the gas after it is discharged through the through hole 241 before being discharged from the exhaust hole 211.

[0111] In some embodiments, the exhaust hole 211 and the through hole 241 are staggered to protect the breathable membrane 240 of the exhaust device 24 and prevent external impurities from entering the exhaust hole 211 and affecting the ventilation effect of the breathable membrane 240.

[0112] In some embodiments, in the thickness direction of the end cover 21 , the orthographic projection of the vent holes 251 of the insulating member 25 covers the orthographic projections of all through holes 241 , so that the gas inside the battery cell can freely pass through the vent holes 251 and be discharged to the outside of the battery cell in a timely manner by the exhaust device 24 .

[0113] 7 , 8 and 9 , in some embodiments, the exhaust device 24 further includes a backing member 244 , which is disposed between the connector 242 and the breathable membrane 240 , and the breathable membrane 240 covers the backing member 244 , and the backing member 244 covers all the through holes 241 .

[0114] In some embodiments, the backing member 244 may be a component within the exhaust device 24 that supports the breathable membrane 240, thereby preventing deformation of the breathable membrane 240. The backing member 244 may be a porous polymer such as polypropylene, polyamide, polytetrafluoroethylene, or polyperfluoroethylene propylene, or a porous metal organic framework, carbon membrane, or ceramic.

[0115] With this arrangement, gas inside the battery cell 20 can sequentially pass through the breathable membrane 240 and backing member 244 before being discharged from the battery cell 20 through the through-hole 241. The area of ​​the backing member 244 is the ventilation area, and the backing member 244 supports the breathable membrane 240. While ensuring sufficient exhaust area, it also prevents deformation or displacement of the breathable membrane 240 due to excessive internal pressure in the battery cell, thereby ensuring the integrity of the breathable membrane 240. Furthermore, the backing member 244 isolates the breathable membrane 240 from contact with materials outside the battery cell 20, thereby extending its service life.

[0116] 9 , in some embodiments, a recess 245 is provided on a side of the connector 242 facing the interior of the battery cell. The recess 245 is used to accommodate the breathable membrane 240 and / or the backing member 244 .

[0117] In some embodiments, the recess 245 is used to accommodate the backing member 244 .

[0118] The recess 245 is formed by being recessed on a side of the connector 242 facing the interior of the battery cell.

[0119] Through the above configuration, a recess 245 is provided on the side of the connector 242 facing the inside of the battery cell 20 , and the recess is used to accommodate the breathable membrane 240 and / or the backing member 244 , so as to reduce the space occupied by the breathable membrane 240 and / or the backing member 244 .

[0120] In some embodiments, the air permeability of the backing member 244 is greater than that of the breathable membrane 240. With this arrangement, the backing member 244 does not hinder the ventilation of the breathable membrane 240, allowing the gas inside the battery cell 20 to be promptly discharged outside the battery cell through the breathable membrane 240, the backing member 244, and the through-holes 241.

[0121] In some embodiments, the air permeability area of ​​the backing member 244 is 50 mm 2 ~200mm 2 For example, the air permeability area of ​​the backing member 244 can be 50mm 2 , 60mm 2 , 70mm 2 , 80mm 2 , 90mm 2 , 100mm 2 , 110mm 2 , 120mm 2 , 130mm 2 , 140mm 2 , 150mm 2 , 160mm 2 , 170mm 2 , 180mm 2 , 190mm 2 , 200mm 2 Typical non-limiting breathable areas or any range between two breathable areas. For example, the breathable area of ​​the backing member 244 is 94.98 mm 2 , or 167.1mm 2 .

[0122] In the technical solution of the embodiment of the present application, the air permeability area of ​​the backing member 244 is set within the above range so that the gas inside the battery cell 20 can be discharged to the outside of the battery cell in time through the air permeable membrane 240 and the backing member 244.

[0123] In some embodiments, the melting point of the backing member 244 is greater than that of the breathable membrane 240. Exemplarily, the melting point of the backing member 244 is between 160°C and 260°C. Exemplarily, the melting point of the backing member 244 is greater than that of the breathable membrane 240 by a typical, non-limiting range such as 10°C, 15°C, 20°C, 25°C, or 30°C, or any range between any two ranges. This allows the backing member 244 to have better high-temperature resistance than the breathable membrane 240, preventing adhesion between the backing member 244 and the breathable membrane 240, thereby clogging the membrane 240. Furthermore, the backing member 244 will not melt due to high temperatures, thereby affecting its breathability. In addition, the temperature at which the breathable membrane 240 is fused and compounded with the connecting member 242, such as an aluminum sheet, is greater than the melting point of the breathable membrane 240 itself. In order to prevent the breathable membrane 240 from being welded together with the backing member 244 during the fusion process, and to prevent the backing member 244 from melting and changing its breathability due to the temperature, the melting point of the backing member 244 is set to be higher than the melting point of the breathable membrane 240.

[0124] Please refer to Figure 10, which shows a cross-sectional schematic diagram of the mounting arrangement of the exhaust device and end cap in Figure 7 in some embodiments. In the mounting arrangement shown in Figure 10, the exhaust device 24 is mounted on the side of the end cap 21 facing the interior of the battery cell. A receiving groove for accommodating the exhaust device 24 is provided on the side of the end cap 21 facing the interior of the battery cell 20, allowing the exhaust device 24 to be installed within the receiving groove of the end cap 21. In some embodiments, the insulating member 25 located on the inner side of the end cap 21 is provided with a vent hole 251, and the outer side of the end cap 21 is provided with a vent hole 211. Gas inside the battery cell 20 passes through the vent hole 251, the breathable membrane 240 of the exhaust device 24, the backing member 244, and the through hole 241, and is discharged from the battery cell 20 through the vent hole 211. In some embodiments, after the exhaust device 24 is installed in the receiving groove of the end cap 21, an air guide channel 212 can be formed between the through hole 241 and the vent hole 211. The air guide channel 212 can be used to provide a short buffer for the gas after it is discharged through the through hole 241 before being discharged from the exhaust hole 211. In some embodiments, the orthographic projection area of ​​the air holes 251 of the insulating member 25 is not less than the air permeability area of ​​the backing member 244, so that the gas inside the battery cell can freely pass through the air holes 251 and be promptly discharged from the battery cell by the exhaust device 24.

[0125] In some embodiments, the transition metal oxide has the formula AMO s , wherein 1≤s≤2, wherein the A element includes at least one of Li, Na, K or Mg, and the M element includes a transition metal element.

[0126] In the technical solution of the embodiment of the present application, the transition metal oxide can be the positive electrode active material of lithium battery, sodium battery, potassium battery or magnesium battery. The transition metal oxide in the positive electrode active material contains transition metal elements. As the positive electrode active material of the battery, it can make the battery have higher energy and power density.

[0127] In some embodiments, the transition metal oxide is Na p (Ni x Fe y Mn z Me q )O2, wherein the Me element includes any one or more of Zn, Ti, Zr, Mg, La, Y, Co, Cr, Al, K, V, Mo, W, Sr, Ta, Nb or Ca, and 0.8≤p<1, 0.01≤x<0.35, 0.01≤y<0.35, 0.01≤z<0.5, 0.01≤q<0.3, and 0.81≤x+y+z<1.

[0128] In the technical solution of the embodiment of the present application, the transition metal oxide is Na p (Ni x Fe y Mn z Me q )O2, wherein the Me element includes any one or more of Zn, Ti, Zr, Mg, La, Y, Co, Cr, Al, K, V, Mo, W, Sr, Ta, Nb, or Ca, and 0.8≤p<1, 0.01≤x<0.35, 0.01≤y<0.35, 0.01≤z<0.5, 0.01≤q<0.3, and 0.81≤x+y+z<1. This can enable the battery to have higher energy and power density.

[0129] In some embodiments, the thickness of a single side of the positive electrode active material layer is 50 μm to 150 μm, and optionally, the thickness of a single side is 55 μm to 130 μm. For example, the thickness of a single side of the positive electrode active material layer can be 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, 115 μm, 120 μm, 125 μm, 130 μm, 135 μm, 140 μm, 145 μm, 150 μm, or other typical non-limiting thicknesses, or a range between any two thicknesses.

[0130] The single-sided thickness refers to the thickness of the positive electrode active material layer coated on one side of the positive electrode current collector. In the technical solution of the embodiment of the present application, the single-sided thickness of the positive electrode active material is set within the above range to reduce the ion transmission path and enable the battery to have a higher energy density.

[0131] In some embodiments, the porosity of the positive electrode active material layer is 1%-70%, optionally, the porosity is 8%-50%. Exemplarily, the porosity of the positive electrode active material layer can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 14%, 18%, 20%, 22%, 25%, 29%, 30%, 33%, 35%, 39%, 43%, 46%, 50%, 52%, 56%, 58%, 60%, 64%, 68%, 70%, or other typical non-limiting porosities or ranges between any two porosities.

[0132] The porosity test of the positive electrode plate is carried out in accordance with GB / T24586-2009 and is performed using a true density meter (equipment model: AccuPycII1340). Test principle: Using the inert gas (helium) displacement method with a small molecular diameter, combined with Archimedes' principle and Bohr's law (PV=nRT), the true volume of the material being tested is accurately measured to obtain the porosity of the sample to be tested. Calculation formula: Apparent volume V2=S×H×A; Porosity α=(V2-V1) / V2×100%, where: S-sample area, cm 2 ; H – sample thickness, cm; A – sample number, EA; V1 – true volume of the sample, cm 3 ; V2 - apparent volume of the sample, cm 3 ;α—porosity of the sample, %.

[0133] In the technical solution of the embodiment of the present application, the porosity of the positive electrode active material layer is set within the above range. The smaller the porosity, the smaller the contact area and interaction interface between the transition metal oxide of the positive electrode active material and the electrolyte, the smaller the side reaction and gas production, and the battery has good capacity and cycle life.

[0134] In some embodiments, the BET specific surface area of ​​the transition metal oxide in the positive electrode active material layer satisfies: 0.2 m 2 / g≤BET≤1.5m 2 / g, optionally, 0.4m 2 / g≤BET≤1.2m 2 / g. For example, the specific surface area BET of the transition metal oxide can be 0.2 m 2 / g, 0.3m 2 / g, 0.4m 2 / g, 0.5m 2 / g, 0.6m 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1.0m 2 / g, 1.1m 2 / g, 1.2m 2 / g, 1.3m 2 / g, 1.4m 2 / g, 1.5m 2 Typical non-limiting specific surface areas such as 1,4-dimethyl-1,4-dioxane, 1,4-dimethyl-1,4-dioxane, 1,4-dihydro ...

[0135] The BET surface area is the total surface area per unit mass of a material. BET surface area is well known in the art and can be measured using instruments and methods known in the art. For example, reference can be made to GB / T 19587-2017.

[0136] In the technical solution of the embodiment of the present application, the smaller the material specific surface area BET, the smaller the contact area and interactive interface with the electrolyte, and the smaller the gas production; but a specific surface area BET that is too small often easily leads to insufficient structural stability and easy collapse and breakage, resulting in aggravated side reactions; therefore, the specific surface area of ​​the transition metal oxide in the positive electrode active material layer is controlled to meet the above range, so that the battery gas production is smaller, the side reactions are fewer, and the stability of the positive electrode active material structure is maintained.

[0137] In some embodiments, the average particle size of the transition metal oxide satisfies: 2 μm ≤ Dv50 ≤ 12 μm, optionally, 3 μm ≤ Dv50 ≤ 10 μm. For example, the average particle size Dv50 of the transition metal oxide can be 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 5.8 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, or other typical, non-limiting particle sizes, or a range between any two particle sizes.

[0138] Dv50, also known as the median diameter or median particle size, refers to the particle size at which 50% of the particles in a population have a diameter smaller than this value and 50% of the particles have a diameter larger than this value. The median particle size Dv50 is well known in the art and can be measured using instruments and methods known in the art. For example, the particle size distribution laser diffraction method can be used in accordance with the GB / T19077-2016 standard.

[0139] In the technical solution of the embodiment of the present application, the larger the material particle size, the smaller the contact area and interactive interface with the electrolyte, and the smaller the gas production; but if the particle size is too large, it is easy to break and the structural stability is insufficient; therefore, the average particle size of the transition metal oxide is set to meet the above range, so that the battery gas production is small while maintaining the stability of the positive electrode active material structure.

[0140] In some embodiments, the battery cell 20 further includes an electrolyte having a conductivity of 5 mS / cm to 18 mS / cm, and optionally, a conductivity of 6 mS / cm to 12 mS / cm. For example, the conductivity of the electrolyte may be 5 mS / cm, 6 mS / cm, 7 mS / cm, 8 mS / cm, 9 mS / cm, 10 mS / cm, 11 mS / cm, 12 mS / cm, 13 mS / cm, 14 mS / cm, 15 mS / cm, 16 mS / cm, 17 mS / cm, 18 mS / cm, or any other typical, non-limiting conductivity values, or a range between any two conductivity values.

[0141] The electrolyte includes an electrolyte sodium salt and a solvent. The electrolyte sodium salt may be an inorganic sodium salt, including at least one of sodium perchlorate, sodium tetrafluoroborate, sodium hexafluoroarsenate, and sodium hexafluorophosphate; or an organic sodium salt, including at least one of sodium bis(oxalatoborate), sodium difluorooxalatoborate, sodium bis(difluorosulfonylimide), and sodium bis(trifluoromethylsulfonylimide).

[0142] The solvent may include at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, ethylene carbonate, propylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone, diethyl sulfone, 1,3-dioxolane, tetrahydrofuran, ethylene glycol dimethyl ether, and acetonitrile.

[0143] In the technical solution of the embodiment of the present application, the ester electrolyte has low volatility, good solubility and stability, and can provide good ionic conductivity for the electrolyte. Setting the conductivity of the electrolyte to the above range can improve the efficiency and energy density of the battery, and better ensure the stability and safety of the battery.

[0144] In some embodiments, the solute concentration of the electrolyte is 0.7 to 1.2 mol / L, optionally, the solute concentration is 0.85 to 1.1 mol / L. For example, the solute concentration of the electrolyte can be 0.7 mol / L, 0.72 mol / L, 0.77 mol / L, 0.79 mol / L, 0.81 mol / L, 0.82 mol / L, 0.85 mol / L, 0.89 mol / L, 0.90 mol / L, 0.92 mol / L, 0.96 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, or other typical non-limiting concentrations or ranges between any two concentrations.

[0145] The solute concentration is also the sodium salt concentration. Setting the solute concentration of the electrolyte within the above range can enable the battery to have good charge and discharge efficiency and better ensure the stability and safety of the battery.

[0146] In some embodiments, the residual space coefficient of the battery cell is 0.02 to 1 mL / Ah, and optionally, 0.2 to 0.8 mL / Ah. For example, the residual space coefficient of the battery cell can be 0.02 mL / Ah, 0.03 mL / Ah, 0.04 mL / Ah, 0.05 mL / Ah, 0.06 mL / Ah, 0.07 mL / Ah, 0.08 mL / Ah, 0.09 mL / Ah, 0.1 mL / Ah, 0.2 mL / Ah, 0.3 mL / Ah, 0.4 mL / Ah, 0.5 mL / Ah, 0.6 mL / Ah, 0.7 mL / Ah, 0.8 mL / Ah, 0.9 mL / Ah, 1 mL / Ah, or other typical non-limiting residual space coefficients, or a range between any two residual space coefficients.

[0147] The residual space coefficient of the battery cell 20 is the ratio of the residual volume to the rated capacity of the battery cell. The residual volume can be the volume remaining after removing all solid and liquid components (including positive electrode sheets, negative electrode sheets, separators, mechanical components, electrolyte, etc.) from the battery cell 20. The residual volume can be measured by injecting liquid to fill the residual space while the shell remains unchanged, or by using laser scanning / nuclear magnetic resonance technology. For example, after the battery cell 20 is completed, the electrolyte is injected into the shell until the entire holding cavity is filled. The volume of the electrolyte injected later is the volume of the electrolyte.

[0148] In the technical solution of the embodiment of the present application, the residual space coefficient of the battery cell is set within the above range so that there is a certain gas accommodating space inside the battery cell, and the excess gas can be discharged to the outside of the battery cell through the exhaust device, thereby improving the safety of the battery.

[0149] In some embodiments, the permeability rate of the breather membrane 240 is 0.1 to 5 mL / D, optionally 0.2 to 4 mL / D, and more optionally 0.2 to 0.7 mL / D. For example, the permeability rate of the breather membrane 240 can be 0.1 mL / D, 0.15 mL / D, 0.2 mL / D, 0.3 mL / D, 0.4 mL / D, 0.5 mL / D, 0.6 mL / D, 0.7 mL / D, 0.8 mL / D, 0.9 mL / D, 1.0 mL / D, 1.5 mL / D, 2 mL / D, 2.5 mL / D, 3 mL / D, 3.5 mL / D, 4 mL / D, 4.5 mL / D, 5 mL / D, or any range between any two permeability rates. The permeability rate of the breather membrane is set within the above range so that the breather membrane can discharge excess gas generated inside the battery cell out of the battery cell.

[0150] The test method of air permeability can refer to GB / T1038-2000.

[0151] In some embodiments, the air permeability rate v of the breathable membrane 240 and the gas production rate V inside the battery cell 20 satisfy the following relationship: 0.9≤v / V≤5, optionally, 1≤v / V≤4. For example, the ratio between the air permeability rate v of the breathable membrane 240 and the gas production rate V inside the battery cell 20 may be: 0.9, 0.95, 1, 1.2, 1.5, 1.6, 1.8, 2, 2.2, 2.5, 2.8, 2.9, 3, 3.2, 3.5, 3.6, 3.8, 4, 4.6, 5, or other typical, non-limiting ratios or ranges between any two ratios. The ratio between the gas production rate v inside the battery cell and the gas permeability rate V of the breathable membrane satisfies the above relationship, so that the breathable membrane has a suitable ventilation effect, so that the gas produced inside the battery cell can be discharged from the breathable membrane in time. If the ratio is too small, the ventilation effect of the breathable membrane is poor. If the ratio is too large, the breathable membrane is easily penetrated by moisture in the air, which shortens its life.

[0152] The gas production rate can be tested using an infrared flowmeter. A gas production pin is welded to the liquid injection hole of the battery cell and connected to the flowmeter with a hose. The electrode assembly is cycled at a rate of 1C / 1C and 100% DOD. The gas production of the flowmeter is monitored within 100cls and the rate v, mL / D, is calculated.

[0153] In some embodiments, the transition metal oxide Na p (Ni x Fe y Mn z Me q ) The stoichiometric ratio z of the Mn element in O2 and the permeability v of the breathable membrane satisfy: 0.1≤z / v≤2, optionally, 0.25≤z / v≤1.7. For example, the transition metal oxide Na p (Ni x Fe y Mn z Me q )The ratios between the stoichiometric ratio z of the Mn element in )O2 and the permeability v of the breathable membrane are: 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.5, 1.7, and 2.

[0154] In the technical solution of the embodiment of the present application, due to the existence of the Jan-Teller effect of the Mn element, and the occurrence of element valence change and bulk phase distortion, the Mn element will escape from the lattice and deposit on the negative electrode, catalyze the decomposition of the fixed electrolyte interface (SEI) and produce gas. The larger the stoichiometric ratio z of the Mn element, the greater the gas production rate, and the greater the required gas permeability v of the breathable membrane. By making the stoichiometric ratio of the Mn element in the transition metal oxide and the gas permeability v of the breathable membrane satisfy the above relationship, the gas permeability rate of the breathable membrane can meet the gas production rate affected by the Mn element, and the battery cell has a suitable ventilation effect. When the ratio is too large, the gas permeability rate of the breathable membrane of the battery cell will be insufficient and the effect will be poor. When the ratio is too small, the breathable membrane will easily penetrate moisture in the air and its life will be shortened.

[0155] The embodiment of the present application can use inductively coupled plasma spectrometer (ICP) to test the positive electrode active material transition metal oxide AMO s The stoichiometric ratio z of the Mn element can be calculated by removing the non-M elements and confirming the molar ratio of each element according to the molar mass of each M element and converting the chemical formula.

[0156] Referring to FIG. 3 , in some embodiments, an explosion-proof valve 21 b is further provided on the outer packaging 26 .

[0157] In some embodiments, an explosion-proof valve 21 b is provided on the end cover 21 .

[0158] In the technical solution of the embodiment of the present application, an explosion-proof valve 21b is provided on the end cover 21. The setting of the explosion-proof valve 21b can open the explosion-proof valve in time when the internal pressure of the battery cell is too high, release the pressure inside the battery cell, and prevent the battery from exploding during thermal runaway.

[0159] Example 1

[0160] This embodiment provides a battery cell, including: an electrode assembly 23 and an outer package 26. The electrode assembly 23 includes a positive electrode plate, on which a positive electrode active material layer is provided. The positive electrode active material layer includes a transition metal layered oxide. The transition metal layered oxide is Na 0.9 (Ni 0.3 Fe 0.3 Mn 0.3 Ca 0.1 )O2, wherein the positive electrode plate may include a positive electrode current collector and a positive electrode active material layer coated on opposite sides of the positive electrode current collector, and the thickness of the positive electrode active material layer on the positive electrode plate is 65μm. The porosity of the positive electrode active material layer is 10%. The specific surface area BET in the positive electrode active material layer satisfies: BET is 0.53m 2 The average particle size of the transition metal layered oxide satisfies the following conditions: Dv50 is 5.8 μm.

[0161] Preparation of positive electrode slurry:

[0162] Transition metal layered oxides Na 0.9 (Ni 0.3 Fe 0.3 Mn 0.3 Ca 0.1 )O2, a binder, and conductive carbon are mixed in weight percentages of 94%, 2.5%, and 3.5%, and then a stirring solvent, NMP, is added and stirred to obtain a positive electrode slurry. The mass ratio of the added stirring solvent, NMP, to the fixed mixture is 4:6. The binder is PVDF.

[0163] Preparation of negative electrode slurry:

[0164] 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.

[0165] The battery cell 20 also includes an electrolyte solution containing ethylene carbonate as a solvent and a fluorocarbonate additive. The electrolyte has a conductivity of 8.4 mS / cm, a sodium salt concentration of 0.9 mol / L, and a residual space coefficient of 0.4 mL / Ah.

[0166] The electrode assembly is then prepared through coating → cold pressing → die cutting → winding → assembly → liquid injection → aging → formation.

[0167] An exhaust device 24 is installed on the end cap 21 of the battery cell. Please refer to Figures 4 and 5. The exhaust device 24 includes a metal aluminum sheet and a breathable membrane 240. The breathable membrane 240 is sealed and fused to the side of the metal aluminum sheet facing the inside of the battery cell. The metal aluminum sheet is provided with 7 through holes 241. The through holes 241 are small circular holes. The aperture of each through hole is 2 mm, and the total area of ​​the through holes is 21.98 mm. 2 The thickness of the breathable membrane 240 is 0.4 mm.

[0168] As shown in Figure 6, the exhaust device 24 is installed on the side of the end cap 21 facing the interior of the battery cell 20. A receiving groove for accommodating the exhaust device 24 is provided on the side of the end cap 21 facing the interior of the battery cell 20. A vent 251 is provided on the insulating member 25, and an exhaust hole 211 is provided on the outer side of the end cap 21. The gas inside the battery cell 20 passes through the vent 251, the breathable membrane 240 of the exhaust device 24, and the through hole 241, and is discharged from the battery cell 20 through the exhaust hole 211. After the exhaust device 24 is installed in the receiving groove of the end cap 21, an air guide channel 212 can be formed between the through hole 241 and the exhaust hole 211. The orthographic projection area of ​​the air hole 251 of the insulating member 25 is not less than the orthographic projection area of ​​all the through holes 241. The exhaust hole 211 and the through hole 241 are staggered. Then, the battery cell is assembled.

[0169] Examples 2 to 5 are shown in Table 1 below. Battery cells for Examples 2, 4, and 5 were prepared in the same manner as for Example 1, except that the permeability of the breathable membrane was adjusted. The battery cell for Example 3 was prepared in the same manner as for Example 1, except that the stoichiometric ratio of the Mn element in the transition metal oxide and the permeability of the breathable membrane were adjusted. For Comparative Example 1, the battery cell for Comparative Example 1 was prepared in the same manner as for Example 1, except that the permeability of the breathable membrane was adjusted. For Comparative Example 2, the battery cell for Comparative Example 1 was prepared in the same manner as for Example 1, except that the stoichiometric ratio of the Mn element in the transition metal oxide and the permeability of the breathable membrane were adjusted. In Comparative Example 3, no breathable membrane was provided.

[0170] Table 1 Results of relevant parameters of battery cells of Examples 1 to 5 and Comparative Examples 1-3

[0171] Performance testing:

[0172] (1) Cycle rate test: Cycle according to the following process at normal pressure and 25±2℃:

[0173] Charge at 0.33C to 100% SOC, then CV (constant voltage 4.2V) to 0.05C; discharge at 0.5C, and record the number of cycles and internal pressure of the battery cell when the cycle reaches 85% SOH.

[0174] (2) Cycle-End Maximum Internal Pressure Test: During battery cell fabrication, a pressure gauge was connected to a pressure receiving sensor to monitor the internal pressure of the battery cell. The maximum internal pressure at the end of the cycle was recorded. The test results are shown in Table 2.

[0175] Table 2 Performance results of battery cells of Examples 1-5 and Comparative Examples 1-3

[0176] The above results show that compared to Comparative Example 3, which lacks a breathable membrane, Examples 1 to 5 significantly improve the cycling performance of the battery cells by providing a breathable membrane, while also minimizing excessive internal pressure within the battery cells, thereby enhancing battery reliability. In contrast, in Comparative Example 3, which lacks a breathable membrane, excessive internal pressure within the battery cells can easily lead to abnormal opening of the explosion-proof valve.

[0177] Compared to Comparative Examples 1 and 2, where the ratio of the breathable membrane's air permeability rate to the battery cell's gas production rate fell outside the appropriate range, and where the stoichiometric ratio of the Mn element fell outside the appropriate range, Examples 1 through 5 set the stoichiometric ratio of the Mn element to the breathable membrane's air permeability rate within an appropriate range, and the breathable membrane's air permeability rate and battery cell's gas production rate within an appropriate range. This significantly improved the battery cell's cycling performance, while also minimizing excessive internal pressure within the battery cell, thereby enhancing battery reliability. In Comparative Example 1, the z / v ratio was too low, allowing the breathable membrane to easily absorb moisture from the air, significantly shortening the battery cell's lifespan. In Comparative Example 2, the z / v ratio was too high, resulting in poor breathable membrane air permeability and a relatively high internal pressure within the battery cell.

[0178] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A battery cell, characterized in that, the battery cell comprises: an electrode assembly, the electrode assembly includes a positive electrode tab, a positive electrode active material layer is provided on the positive electrode tab, and the positive electrode active material layer includes a transition metal oxide; an outer package for encapsulating the electrode assembly, an exhaust device is provided on the outer package, and the exhaust device includes a breathable membrane.

2. The battery cell according to claim 1, characterized in that, the exhaust device further includes a connecting member, at least one through hole is provided on the connecting member, the breathable membrane is disposed on a side of the connecting member facing the inside of the battery cell, and the breathable membrane covers all the through holes.

3. The battery cell according to claim 2, characterized in that, the contact surface between the breathable membrane and the connecting member is sealingly connected.

4. The battery cell according to claim 2 or 3, characterized in that, the connecting member is provided with a plurality of the through holes, and the aperture of each through hole is less than or equal to 3 mm.

5. The battery cell according to any one of claims 2 to 4, characterized in that, In the axial direction of the through holes, the orthographic projection area of all the through holes is 10 mm 2 ~50 mm 2 .

6. The battery cell according to any one of claims 1 to 5, characterized in that, the thickness of the breathable membrane is 0.1 mm to 3 mm, optionally, the thickness is 0.2 mm to 0.8 mm.

7. The battery cell according to any one of claims 2 to 6, characterized in that, the exhaust device further includes a backing member, the backing member is disposed between the connecting member and the breathable membrane and the breathable membrane covers the backing member, and the backing member covers all the through holes.

8. The battery cell according to claim 7, characterized in that, a recess is provided on a side of the connecting member facing the inside of the battery cell, and the recess is used for accommodating the breathable membrane and / or the backing member.

9. The battery cell according to claim 7 or 8, characterized in that, the air permeability of the backing member is greater than the air permeability of the breathable membrane.

10. The battery cell according to any one of claims 7 to 9, characterized in that, the melting point of the backing member is greater than the melting point of the breathable membrane.

11. The battery cell according to any one of claims 7 to 10, characterized in that, The breathable area of the backing member is 50 mm 2 to 200 mm 2 .

12. The battery cell according to any one of claims 2 to 11, characterized in that, the outer package includes an end cap, the exhaust device is disposed on a side of the end cap facing the inside of the battery cell, and an exhaust hole communicating with the through hole of the exhaust device is provided on the end cap.

13. The battery cell according to claim 12, characterized in that, a receiving groove for accommodating the exhaust device is provided on a side of the end cap facing the inside of the battery cell. When the exhaust device is installed in the receiving groove, a gas guiding channel is provided above the through hole of the exhaust device, the through hole is connected to the exhaust hole through the gas guiding channel, and the exhaust hole and the through hole are disposed in a staggered manner.

14. The battery cell according to claim 13, characterized in that, An insulating member is provided inside the end cap. The insulating member is provided with ventilation holes. The gas inside the battery cell is discharged to the outside of the battery cell through the ventilation holes, the exhaust device, the air guide channel and the exhaust holes.

15. The battery cell according to claim 14, wherein, in the thickness direction of the end cap, the orthographic projection of the ventilation holes covers the orthographic projection of all the through holes.

16. The battery cell according to any one of claims 1 to 15, wherein, The chemical formula of the transition metal oxide is AMO s , where 1 ≤ s ≤ 2, element A includes at least one of Li, Na, K or Mg, and element M includes transition metal elements.

17. The battery cell according to any one of claims 1 to 16, wherein, The transition metal oxide is Na p (Ni x Fe y Mn z Me q )O 2 , where the Me element includes any one or more of Zn, Ti, Zr, Mg, La, Y, Co, Cr, Al, K, V, Mo, W, Sr, Ta, Nb or Ca, and 0.8 ≤ p < 1, 0.01 ≤ x < 0.35, 0.01 ≤ y < 0.35, 0.01 ≤ z < 0.5, 0.01 ≤ q < 0.3, 0.81 ≤ x + y + z < 1.

18. The battery cell according to any one of claims 1 to 17, wherein, the single-sided thickness of the positive electrode active material layer is 50 μm to 150 μm, and optionally, the single-sided thickness is 55 μm to 130 μm.

19. The battery cell according to any one of claims 1 to 18, wherein, the porosity of the positive electrode active material layer is 1% - 70%, and optionally, the porosity is 8% - 50%.

20. The battery cell according to any one of claims 1 to 19, wherein, The specific surface area BET of the transition metal oxide in the positive electrode active material layer satisfies: 0.2 m 2 / g ≤ BET ≤ 1.5 m 2 / g. Optionally, 0.4 m 2 / g ≤ BET ≤ 1.2 m 2 / g.

21. The battery cell according to any one of claims 1 to 20, wherein, the average particle size of the transition metal oxide satisfies: 2 μm ≤ Dv50 ≤ 12 μm, and optionally, 3 μm ≤ Dv50 ≤ 10 μm.

22. The battery cell according to any one of claims 1 to 21, wherein, the battery cell further includes an electrolyte, and the conductivity of the electrolyte is 5 mS / cm to 18 mS / cm, and optionally, the conductivity is 6 mS / cm to 12 mS / cm.

23. The battery cell according to claim 22, wherein, the solute concentration of the electrolyte is 0.7 to 1.2 mol / L, and optionally, the solute concentration is 0.85 to 1.1 mol / L.

24. The battery cell according to any one of claims 1 to 23, wherein, the residual space coefficient of the battery cell is 0.02 to 1 mL / Ah, and optionally, it is 0.2 to 0.8 mL / Ah.

25. The battery cell according to any one of claims 1 to 24, wherein, the gas permeability rate of the gas permeable membrane is 0.1 to 5 mL / D, and optionally, it is 0.2 to 4 mL / D, and more optionally, it is 0.2 to 0.7 mL / D.

26. For the battery cell according to any one of claims 1 to 25, the gas permeability rate v of the gas permeable membrane and the gas generation rate V inside the battery cell satisfy: 0.9 ≤ v / V ≤ 5, and optionally, 1 ≤ v / V ≤ 4.

27. The battery cell according to any one of claims 17 to 26, wherein, The transition metal oxide Na p (Ni x Fe y Mn z Me q )O 2 satisfies 0.1 ≤ z / v ≤ 2, optionally 0.25 ≤ z / v ≤ 1.7, between the stoichiometric ratio z of the Mn element in it and the gas permeability rate v of the gas permeable membrane.

28. The battery cell according to any one of claims 1 to 27, wherein, an explosion-proof valve is further provided on the outer package.

29. A method for preparing a battery cell, wherein, comprising: providing an electrode assembly, the electrode assembly includes a positive electrode plate, and a positive electrode active material layer is provided on the positive electrode plate, and the positive electrode active material layer includes a transition metal oxide; Provide an outer package, on which an exhaust device is provided. The outer package is encapsulated outside the electrode assembly, and the exhaust device includes a breathable membrane.

30. A battery, characterized in that the battery includes the battery cell according to any one of claims 1 to 28.

31. An electrical device, characterized in that the electrical device includes the battery according to claim 30.

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