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

Abstract

The invention provides a battery monomer and a preparation method thereof, a battery and a power utilization device, the battery monomer comprises an electrode assembly and an outer package, the electrode assembly comprises a positive pole piece, the positive pole piece is provided with a positive active material layer, and the positive active material layer comprises a transition metal oxide; the outer package is used for packaging the electrode assembly, and an exhaust device is arranged on the outer package and comprises a breathable film. The exhaust device is mounted on the outer package of the battery monomer, so that excessive gas generated due to instability of transition metal in the use process of the battery monomer is exhausted out of the battery monomer in time through the breathable film of the exhaust device, and the situation that the explosion-proof valve of the battery monomer is opened abnormally due to excessive internal air pressure is not easy to occur; and the reliability and the service life of the battery are improved.

Description

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 the related art, 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 gas 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 gas pressure may even cause accidents such as explosions, affecting the reliability of the battery cell. Summary of the invention

[0003] 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, so as to solve the technical problem of poor battery reliability in the prior art.

[0004] To achieve the above purpose, the technical solution adopted in this application is:

[0005] 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.

[0006] 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 catalytic oxidation electrolyte decomposition, or promotion of 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 opening due to excessive internal air pressure, thereby improving the reliability and service life of the battery.

[0007] In some embodiments, the exhaust device further includes a connector having at least one through hole, and the breathable membrane is disposed on a side of the connector facing the interior of the battery cell, and the breathable membrane covers all the through holes.

[0008] In the technical solution of the embodiment of the present application, the exhaust device includes a connector, the connector is provided with at least one through hole, the breathable membrane is arranged on the side of the connector facing the inside 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, and while ensuring that there is sufficient exhaust area, it is not easy to cause the breathable membrane to deform or shift 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 arranged on the side of the connector facing the inside 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 inner and outer sides of the breathable membrane, so that the excess gas inside the battery cell can pass through the breathable membrane to discharge the gas inside the battery cell through the through hole to the outside of the battery cell, thereby improving the reliability of the battery cell.

[0009] In some embodiments, the breathable membrane is sealingly connected to a contact surface of the connector.

[0010] In the technical solution of the embodiment of the present application, the contact surface between the breathable membrane and the connecting piece is sealed to keep the contact surface between the breathable membrane and the connecting piece sealed, and the connecting piece provides support force for the breathable membrane to improve the reliability of the exhaust device.

[0011] 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.

[0012] 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, so as to ensure the reliability of the breathable membrane and thus improve the service life of the battery cell.

[0013] In some embodiments, along the axial direction of the through holes, the orthographic projection area of ​​all through holes is 10 mm. 2 ~50mm 2 .

[0014] 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 time.

[0015] 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.

[0016] 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, the thickness is 0.2 mm to 0.8 mm, so that the breathable membrane maintains a certain air permeability rate within the thickness range.

[0017] In some embodiments, the exhaust device further includes a backing member, which 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.

[0018] In the technical solution of the embodiment of the present application, the exhaust device also includes a backing member, which is arranged between the connector and the breathable membrane, and the breathable membrane covers the backing member, and the backing member covers all through holes. The gas inside the battery cell passes through the breathable membrane and the backing member in sequence and then is discharged from the outside of the battery cell through the through holes. The backing member can support the breathable membrane, and while ensuring that there is sufficient exhaust area, it is not easy to cause the breathable membrane to deform or shift due to excessive pressure inside the battery cell, thereby ensuring the integrity of the breathable membrane. In addition, the backing member can isolate the breathable membrane from contact with external substances of the battery cell, thereby extending the service life.

[0019] 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 gas permeable membrane and / or the backing member.

[0020] 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.

[0021] In some embodiments, the air permeability of the backing member is greater than the air permeability of the breathable film.

[0022] 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 from the outside of the battery cell in time through the breathable membrane, the backing member and the through hole.

[0023] In some embodiments, the melting point of the backing member is greater than the melting point of the breathable membrane.

[0024] In the technical solution of the embodiment of the present application, the melting point of the backing member is greater than the melting point of the breathable film, so that the high temperature resistance of the backing member is better than that of the breathable film. The temperature of the breathable film when it is fused with the connecting member such as an aluminum sheet is greater than the melting point of the breathable film itself. In order to prevent the breathable film from being fused with the backing member during the fusion process and the backing member from changing its air permeability due to melting, the melting point of the backing member is set to be higher than the melting point of the breathable film. It is not easy for the backing member and the breathable film to adhere to each other, thereby blocking the breathable film. At the same time, the air permeability of the backing member will not be affected by melting due to temperature.

[0025] In some embodiments, the air permeability area of ​​the backing member is 50 mm 2 ~200mm 2 .

[0026] 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.

[0027] In some embodiments, the outer package includes an end cover, the exhaust device is arranged 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.

[0028] 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.

[0029] 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 with the exhaust hole through the air guide channel, and the exhaust hole and the through hole are staggered.

[0030] In the technical solution of the embodiment of the present application, an air guide channel is provided so that the gas can be discharged from the battery cell from the exhaust hole after a short buffer after being discharged through the through hole of the exhaust device. The exhaust hole and the through hole are staggered, so that the exhaust device can be protected and external impurities are not easily allowed to enter the exhaust hole to affect the ventilation effect of the exhaust device.

[0031] In some embodiments, an insulating member is provided inside the end cover, and an air vent is provided on the insulating member, and the gas inside the battery cell is discharged to the outside of the battery cell through the air vent, the exhaust device, the air guide channel and the exhaust vent.

[0032] 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.

[0033] In some embodiments, in the thickness direction of the end cap, the orthographic projection of the vent hole covers the orthographic projections of all the through holes.

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

[0035] In some embodiments, the chemical formula of the transition metal oxide is AMOs, 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 a positive electrode active material for lithium battery, sodium battery, potassium battery or magnesium battery. The transition metal oxide in the positive electrode active material contains transition metal elements. As a 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 ) 2 , 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 ) 2 , 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, 0.81≤x+y+z<1. The battery can 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 single-sided thickness 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%, optionally, the porosity is 8%-50%.

[0042] 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.

[0043] 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.

[0044] In the technical solution of the embodiment of the present application, when the material specific surface area BET is smaller, the contact area and interactive interface with the electrolyte are often smaller, and the gas production is smaller; but a specific surface area BET that is too small is often prone 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 less, and the stability of the positive electrode active material structure is maintained.

[0045] In some embodiments, the average particle size of the transition metal oxide satisfies: 2 μm≤Dv50≤12 μm, optionally, 3 μm≤Dv50≤10 μm.

[0046] In the technical solution of the embodiment of the present application, when the particle size of the material is larger, the contact area and the interactive interface with the electrolyte are smaller, and the gas production is smaller; 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 gas production of the battery is small, while maintaining the stability of the positive electrode active material structure.

[0047] In some embodiments, 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.

[0048] 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 the stability and safety of the battery are better guaranteed.

[0049] In some embodiments, 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] In some embodiments, the air permeability of the breathable membrane is 0.1 to 5 mL / D, optionally, 0.2 to 4 mL / D, and more optionally, 0.2 to 0.7 mL / D.

[0054] 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 the excess gas generated inside the battery cell out of the battery cell.

[0055] In some embodiments, the air permeability rate v of the air permeable membrane and the gas generation rate V inside the battery cell satisfy: 0.9≤v / V≤5, optionally, 1≤v / V≤4.

[0056] 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 air permeability effect, so that the gas produced inside the battery cell can be discharged from the breathable membrane in time. When the ratio is too small, the air permeability of the breathable membrane is poor. When the ratio is too large, the breathable membrane is easy to penetrate moisture in the air and its life is shortened.

[0057] In some embodiments, the transition metal oxide Na p (Ni x Fe y Mn z Me q ) 2 The stoichiometric ratio z of the Mn element and the air permeability v of the breathable membrane satisfy: 0.1≤z / v≤2, optionally, 0.25≤z / v≤1.7.

[0058] In the technical solution of the embodiment of the present application, due to the existence of the Jan-Taylor 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 gas permeability 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 is easily infiltrated with moisture in the air and its life is deteriorated.

[0059] In some embodiments, an explosion-proof valve is also provided on the outer packaging.

[0060] 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 internal pressure of the battery cell, and prevent the battery from exploding in thermal runaway.

[0061] In a second aspect, the present application also provides a method for preparing a battery cell, comprising:

[0062] An electrode assembly is provided, the electrode assembly comprising a positive electrode plate, a positive electrode active material layer is provided on the positive electrode plate, and the positive electrode active material layer comprises a transition metal oxide;

[0063] An outer package is provided, on which an exhaust device is arranged, and the outer package is sealed on the outside of the electrode assembly, and the exhaust device includes a breathable film.

[0064] In a third aspect, the present application also provides a battery, the battery comprising the aforementioned battery cell.

[0065] In a fourth aspect, the present application also provides an electrical device, which includes the aforementioned battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0067] Figure 1 A schematic diagram of the structure of a vehicle according to some embodiments of the present application;

[0068] Figure 2 A schematic diagram of the exploded structure of a battery according to some embodiments of the present application;

[0069] Figure 3 A schematic diagram of the exploded structure of a battery cell according to some embodiments of the present application;

[0070] Figure 4 A schematic diagram of the structure of an exhaust device in some embodiments of the present application;

[0071] Figure 5 for Figure 4 A schematic diagram of the cross-sectional structure of the exhaust device in FIG.

[0072] Figure 6 for Figure 4 A schematic cross-sectional structure diagram of the matching installation method of the exhaust device and the end cover;

[0073] Figure 7 Schematic diagram of the structure of the exhaust device of other embodiments of the present application;

[0074] Figure 8 for Figure 7 Schematic diagram of the exploded structure of the exhaust device;

[0075] Fig. 9 for Figure 7 A schematic diagram of the cross-sectional structure of the exhaust device in FIG.

[0076] Fig.10 for Figure 7 A schematic cross-sectional structure diagram of the coordinated installation method of the exhaust device and the end cover.

[0077] Among them, in the figure: 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-housing; 23-electrode assembly; 23a-ear; 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-vent. DETAILED DESCRIPTION

[0078] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0079] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can 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 can be directly connected to the other element or indirectly connected to the other element.

[0080] 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 drawings, and are only for the convenience of describing 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 should not be understood as a limitation on the present application.

[0081] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0082] In lithium, sodium, potassium and other types of batteries, layered oxide-based positive electrode active materials contain active elements of transition metals, which often cause problems such as material structure phase change oxygen release, transition metal dissolution catalytic oxidation electrolyte decomposition, and promotion of fixed electrolyte interface (SEI) decomposition and repair during high temperature or high pressure use. This ultimately 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 and cause battery failure. Excessive gas pressure may even cause explosions and other accidents, affecting the reliability and service life of the battery.

[0083] Based on the above considerations, in order to solve the problem that the presence of transition metal elements in the positive electrode active material of the battery cell during use leads to increased gas production, which will eventually cause the battery cell to abnormally open 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. 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 exhaust device, so that the explosion-proof valve of the battery cell is not prone to abnormal opening due to excessive internal air pressure, thereby improving the reliability and service life of the battery.

[0084] The battery cell disclosed in the embodiments of the present application can be used in electrical devices that use batteries as power sources or various energy storage systems that use batteries as energy storage elements. Electrical devices can be, but are not limited to, mobile phones, tablets, laptops, electric toys, electric tools, battery cars, electric cars, ships, spacecraft, etc. Among them, electric toys can include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., and spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0085] 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.

[0086] Please refer to Figure 1 , Figure 1 A schematic diagram of the structure of a vehicle 1000 provided for some embodiments of the present application. The vehicle 1000 may be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 100 is provided inside the vehicle 1000, and the battery 100 may be provided at the bottom, head or tail of the vehicle 1000. The battery 100 may be used to power the vehicle 1000, for example, the battery 100 may be used as an operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300, and the controller 200 is used to control the battery 100 to power the motor 300, for example, for starting, navigating and driving the vehicle 1000.

[0087] In some embodiments of the present application, the battery 100 can be used 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, which includes an energy storage container or an energy storage cabinet.

[0088] Please refer to Figure 2 , Figure 2An exploded view of a battery 100 provided in some embodiments of the present application. The battery 100 includes a box 10 and a battery cell 20, and the battery cell 20 is contained in the box 10. Among them, the box 10 is used to provide a storage space for the battery cell 20, and the box 10 can adopt a variety of structures. In some embodiments, the box 10 may include a first part 11 and a second part 12, the first part 11 and the second part 12 cover each other, and the first part 11 and the second part 12 jointly define a storage space for accommodating the battery cell 20. The second part 12 may be a hollow structure with one end open, the first part 11 may be a plate-like structure, and the first part 11 covers the open side of the second part 12, so that the first part 11 and the second part 12 jointly define a storage space; the first part 11 and the second part 12 may also be hollow structures with one side open, and the open side of the first part 11 covers the open side of the second part 12. Of course, the box 10 formed by the first part 11 and the second part 12 may be in a variety of shapes, such as a cylinder, a cuboid, etc.

[0089] In the battery 100, there may be multiple battery cells 20, and the multiple battery cells 20 may be connected in series, in parallel, or in a mixed connection. A mixed connection means that the multiple battery cells 20 are both connected in series and in parallel. The multiple battery cells 20 may be directly connected in series, in parallel, or in a mixed connection, and then the whole formed by the multiple battery cells 20 is accommodated in the box 10; of course, the battery 100 may also be a battery module formed by connecting multiple battery cells 20 in series, in parallel, or in a mixed connection, and then the multiple battery modules are connected in series, in parallel, or in a mixed connection to form a whole, and accommodated in the box 10. The battery 100 may also include other structures, for example, the battery 100 may also include a busbar component for realizing electrical connection between the multiple battery cells 20.

[0090] 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.

[0091] Please refer to Figure 3 , Figure 3 The schematic diagram of the exploded structure of the battery cell 20 provided in some embodiments of the present application. The battery cell 20 refers to the smallest unit that constitutes the battery. Figure 3 The battery cell 20 includes an outer package, an electrode assembly 23 and an electrolyte, wherein the outer package includes an end cover 21 and a shell 22 .

[0092] The end cap 21 refers to a component that covers the opening of the shell 22 to isolate the internal environment of the battery cell 20 from the external environment. Without limitation, the shape of the end cap 21 can be adapted to the shape of the shell 22 to match the shell 22. Optionally, the end cap 21 can be made of a material with a certain hardness and strength (such as aluminum alloy), so that the end cap 21 is not easily deformed when squeezed and collided, so that the battery cell 20 can have a higher structural strength and the safety performance can also be improved. Functional components such as electrode terminals 21a can be provided on the end cap 21. The electrode terminal 21a can be used to electrically connect to the electrode assembly 23 for outputting or inputting electrical energy of the battery cell 20. In some embodiments, the end cap 21 can also be provided with an explosion-proof valve 21b for releasing the internal pressure when the internal pressure or temperature of the battery cell 20 reaches a threshold. The material of the end cap 21 can also be a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiment of the present application does not impose any special restrictions on this. In some embodiments, an insulating member 25 may be provided inside the end cap 21, and the insulating member 25 may be used to isolate the electrical connection components in the housing 22 from the end cap 21 to reduce the risk of short circuit. For example, the insulating member 25 may be plastic, rubber, or the like.

[0093] The shell 22 is a component used to cooperate with the end cap 21 to form the internal environment of the battery cell 20, wherein the formed internal environment can be used to accommodate the electrode assembly 23, the electrolyte and other components. The shell 22 and the end cap 21 can be independent components, and an opening can be set on the shell 22, and the internal environment of the battery cell 20 is formed by covering the opening with the end cap 21 at the opening. Without limitation, the end cap 21 and the shell 22 can also be integrated. Specifically, the end cap 21 and the shell 22 can form a common connection surface before other components are put into the shell, and when the interior of the shell 22 needs to be encapsulated, the end cap 21 covers the shell 22. The shell 22 can be of various shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shape of the shell 22 can be determined according to the specific shape and size of the electrode assembly 23. The material of the shell 22 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiment of the present application does not impose any special restrictions on this.

[0094] The electrode assembly 23 is a component in the battery cell 20 where an electrochemical reaction occurs. One or more electrode assemblies 23 may be included in the housing 22. The electrode assembly 23 is mainly formed by winding or stacking a positive electrode sheet and a negative electrode sheet, and a separator is usually provided between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet may include a positive electrode current collector and a positive electrode active material layer coated on opposite sides of the positive electrode current collector. The negative electrode sheet may include a negative electrode current collector and a negative electrode active material layer coated on opposite sides of the negative electrode current collector. The parts of the positive electrode sheet and the negative electrode sheet with active materials constitute the main body of the electrode assembly, and the parts of the positive electrode sheet and the negative electrode sheet without active materials each constitute a tab 23a. The positive tab and the negative tab may be located together at one end of the main body or at both ends of the main body. During the charge and discharge process of the battery, the positive electrode active material and the negative electrode active material react with the electrolyte, and the tab 23a connects the electrode terminal to form a current loop.

[0095] In the technical solution of the 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 the outer packaging 26 is provided with an exhaust device 24, and the exhaust device 24 includes a breathable membrane 240.

[0096] The exhaust device 24 is a component for exhausting the gas inside 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 production, 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.

[0097] 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 catalytic oxidation electrolyte decomposition, or promotion of 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.

[0098] Please refer to Figure 4 and Figure 5 or Figure 7 , Figure 8 and Fig. 9In some embodiments, the exhaust device 24 includes a connector 242, which is provided with at least one through hole 241, and a breathable membrane 240 is disposed on a side of the connector 242 facing the inside of the battery cell 20. The breathable membrane 240 covers all the through holes 241.

[0099] The connector 242 may be a component connected to the outer packaging 26, and may be a split structure. Alternatively, the connector 242 may be a part of the outer packaging 26, that is, an integral structure with the outer packaging 26. The connection between the connector 242 and the outer packaging may be a fixed connection such as welding.

[0100] 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 hole 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.

[0101] Through the above arrangement, the breathable membrane 240 is arranged on the side of the connector 242 facing the inside of the battery cell 20. During the exhaust process, the connector 242 can provide support for the breathable membrane 240. While ensuring that there is sufficient exhaust area, it is not easy to cause the breathable membrane 240 to deform or shift due to excessive internal pressure of the battery cell, thereby ensuring the integrity of the breathable membrane 240 and improving safety. At the same time, the breathable membrane 240 is arranged on the side of the connector 242 facing the inside 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 20 increases and reaches a certain pressure, a pressure difference is generated between the inner and outer sides of the breathable membrane 240. Then, the excess gas inside the battery cell 20 can pass through the breathable membrane 240 to discharge the gas inside the battery cell through the through hole 241 to the outside of the battery cell, thereby improving the reliability of the battery cell.

[0102] Please refer to the above settings Figure 4 and Figure 5 In some embodiments, the contact surface of the breathable membrane 240 and the connecting member 242 is sealed and connected.

[0103] In some embodiments, the material of the breathable membrane may be polyolefin or polyurethane, and polyolefin may be polypropylene, polyethylene or polypropylene. The contact surface of the breathable membrane 240 and the connecting member 242 may be sealed and connected by fusion bonding.

[0104] Through the above arrangement, the contact surface between the breathable membrane 240 and the connecting member 242 is sealed to keep the contact surface between the breathable membrane 240 and the connecting member 242 sealed. The connecting member 242 provides support force for the breathable membrane 240, thereby improving the reliability of the exhaust device.

[0105] Please refer to Figure 4 and Figure 5 In some embodiments, a plurality of through holes 241 are provided on the connecting member 242, and the aperture of each through hole is less than or equal to 3 mm.

[0106] The plurality may be two, three or more. The through hole may be a circular hole.

[0107] Through the above arrangement, the through hole 241 is arranged to include a plurality of through holes, each of which has an aperture less than or equal to 3 mm. In the example, the aperture of each through hole can be a typical but non-restrictive aperture such as 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm or 3 mm, or a range between any two apertures, so that the breathable membrane 240 is not easily deformed or shifted due to excessive internal pressure of the battery cell, so as to ensure the reliability of the breathable membrane 240 and thereby improve the service life of the battery cell.

[0108] 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 the 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 , 50mm 2 The orthographic projection area of ​​all through holes is set to the above range, so that the gas inside the battery cell 20 can be discharged to the outside of the battery cell 20 through the breathable membrane 240 and the through hole 241 in time.

[0109] In some embodiments, the thickness of the breathable film 240 is 0.1 mm to 3 mm, and optionally, the thickness is 0.2 mm to 0.8 mm. In the example, the thickness of the breathable film 240 can be 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, etc., which are typical but non-limiting thicknesses, or a range between two thicknesses, so that the breathable film maintains a certain air permeability within the thickness range.

[0110] 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 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.

[0111] Please refer to Figure 6 , Figure 6 Shows Figure 4 A schematic cross-sectional view of the exhaust device and the end cover in some embodiments of the cooperative installation method. Figure 6 In the installation method shown, the exhaust device 24 is installed on the side of the end cover 21 facing the inside of the battery cell. A receiving groove for receiving the exhaust device 24 is provided on the side of the end cover 21 facing the inside of the battery cell 20, so that the exhaust device 24 is installed in the receiving groove of the end cover 21. In some embodiments, a vent hole 251 is provided on the insulating member 25 located on the inner side of the end cover 21, and an exhaust hole 211 is provided on the outer side of the end cover 21. The gas inside the battery cell 20 passes through the vent hole 251, the breathable membrane 240 of the exhaust device 24, and the through hole 241 and the exhaust hole 211 to be discharged to the outside of the battery cell 20.

[0112] 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 temporarily buffer the gas after it is discharged through the through hole 241 before being discharged from the exhaust hole 211.

[0113] 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 .

[0114] In some embodiments, in the thickness direction of the end cover 21 , the orthographic projection of the vent hole 251 of the insulating member 25 covers the orthographic projection of all through holes 241 , so that the gas inside the battery cell can freely pass through the vent hole 251 and be discharged to the outside of the battery cell by the exhaust device 24 in time.

[0115] Please refer to Figure 7 , Figure 8 and Fig. 9 In some embodiments, the exhaust device 24 further includes a backing member 244 , which is disposed between the connecting member 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 .

[0116] In some embodiments, the backing member 244 may refer to a component in the exhaust device 24 that supports the breathable membrane 240, so that the breathable membrane 240 is not easily deformed. The backing member 244 may be a porous polymer such as polypropylene, polyamide, polytetrafluoroethylene, polyperfluoroethylene propylene, etc., or a metal organic framework porous material, as well as a carbon film and a ceramic porous material.

[0117] Through the above arrangement, the gas inside the battery cell 20 can pass through the breathable membrane 240 and the backing member 244 in sequence and then be discharged from the battery cell 20 through the through hole 241. The area of ​​the backing member 244 is the breathable area. The backing member 244 can support the breathable membrane 240. While ensuring sufficient exhaust area, it is not easy to cause the breathable membrane 240 to deform or shift due to excessive pressure inside the battery cell, thereby ensuring the integrity of the breathable membrane 240. In addition, the backing member 244 can isolate the breathable membrane 240 from contacting the external substances of the battery cell 20, thereby extending the service life.

[0118] Please refer to Fig. 9 In some embodiments, a recess 245 is provided on a side of the connector 242 facing the interior of the battery cell, and the recess 245 is used to accommodate the breathable membrane 240 and / or the backing member 244 .

[0119] In some embodiments, the recess 245 is used to accommodate the backing member 244 .

[0120] The recess 245 is formed by being recessed on a side of the connector 242 facing the inside of the battery cell.

[0121] Through the above configuration, a recess 245 is provided on the side of the connector 242 facing 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 .

[0122] In some embodiments, the air permeability of the backing member 244 is greater than that of the breathable membrane 240. With the above configuration, the backing member 244 does not hinder the ventilation effect of the breathable membrane 240, so that the gas inside the battery cell 20 can be discharged to the outside of the battery cell through the breathable membrane 240, the backing member 244 and the through hole 241 in a timely manner.

[0123] 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 may be 50 mm 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 air permeability areas or ranges between any two air permeability areas. Exemplarily, the air permeability area of ​​the backing member 244 is 94.98 mm 2 , or 167.1mm 2 .

[0124] 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 through the air permeable membrane 240 and the backing member 244 in time.

[0125] In some embodiments, the melting point of the backing member 244 is greater than the melting point of the breathable membrane 240. Exemplarily, the melting point of the backing member 244 is between 160 and 260°C. Exemplarily, the melting point of the backing member 244 is 10°C, 15°C, 20°C, 25°C, 30°C, or any other typical non-limiting ranges greater than the melting point of the breathable membrane 240, or a range between any two ranges. The high temperature resistance of the backing member 244 is better than that of the breathable membrane 240, and it is not easy for the backing member 244 and the breathable membrane 240 to adhere to each other, thereby blocking the breathable membrane 240. At the same time, the backing member 244 will not be affected by melting due to temperature and its air permeability. 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 melted together with the backing member 244 during the fusion process, and to prevent the backing member 244 from changing its breathability properties due to melting 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.

[0126] Please refer to Fig.10 , Fig.10 Shows Figure 7 A schematic cross-sectional view of the exhaust device and the end cover in some embodiments of the cooperative installation method. Fig.10In the installation method shown, the exhaust device 24 is installed on the side of the end cover 21 facing the inside of the battery cell. A receiving groove for receiving the exhaust device 24 is provided on the side of the end cover 21 facing the inside of the battery cell 20, so that the exhaust device 24 is installed in the receiving groove of the end cover 21. In some embodiments, a vent hole 251 is provided on the insulating member 25 located on the inner side of the end cover 21, and an exhaust hole 211 is provided on the outer side of the end cover 21. The 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 exhaust hole 211. 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 and the exhaust hole 211. The air guide channel 212 can be used to discharge the gas from the exhaust hole 211 after a short buffer after the gas is discharged through the through hole 241. In some embodiments, the orthographic projection area of ​​the vent holes 251 of the insulating member 25 is not less than the vent area of ​​the backing member 244 , so that the gas inside the battery cell can freely pass through the vent holes 251 and be promptly discharged from the battery cell by the exhaust device 24 .

[0127] 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.

[0128] In the technical solution of the embodiment of the present application, the transition metal oxide can be a positive electrode active material for lithium battery, sodium battery, potassium battery or magnesium battery. The transition metal oxide in the positive electrode active material contains transition metal elements. As a positive electrode active material of the battery, it can make the battery have higher energy and power density.

[0129] In some embodiments, the transition metal oxide is Na p (Ni x Fe y Mn z Me q ) 2 , 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.

[0130] 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) 2 , 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, 0.81≤x+y+z<1. The battery can have higher energy and power density.

[0131] In some embodiments, 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. Exemplarily, the single-sided thickness 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, etc., typical non-limiting thicknesses or ranges between any two thicknesses.

[0132] 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 make the battery have a higher energy density.

[0133] In some embodiments, the porosity of the positive electrode active material layer is 1%-70%, and 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%, etc., typical non-limiting porosity or the range between any two porosities.

[0134] The porosity test of the positive electrode plate refers to GB / T24586-2009 and is tested 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 real volume of the material to be 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, cm3 ; V2 - apparent volume of the sample, cm 3 ; α—porosity of the sample, %.

[0135] 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.

[0136] 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. Exemplarily, the specific surface area of ​​the transition metal oxide BET may 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 / g etc. or the range between any two specific surface areas.

[0137] The specific surface area BET is the total area per unit mass of a material. The specific surface area BET is well known in the art and can be measured using instruments and methods well known in the art. For example, the GB / T19587-2017 standard can be referred to.

[0138] In the technical solution of the embodiment of the present application, when the material specific surface area BET is smaller, the contact area and interactive interface with the electrolyte are often smaller, and the gas production is smaller; but a specific surface area BET that is too small is often prone 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 less, and the stability of the positive electrode active material structure is maintained.

[0139] In some embodiments, the average particle size of the transition metal oxide satisfies: 2μm≤Dv50≤12μm, optionally, 3μm≤Dv50≤10μm. Exemplarily, the average particle size Dv50 of the transition metal oxide can be 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 5.8μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, 10μm, 10.5μm, 11μm, 11.5μm, 12μm, etc., typical non-limiting particle sizes or ranges between any two particle sizes.

[0140] Dv50, also known as median diameter or median particle size, means that 50% of the particles in a particle group have a particle size smaller than this value, and 50% of the particles have a particle size larger than this value. The median particle size Dv50 is well known in the art and can be measured using instruments and methods well known in the art. For example, the particle size distribution-laser diffraction method can be used, and the GB / T19077-2016 standard can be referred to.

[0141] In the technical solution of the embodiment of the present application, when the particle size of the material is larger, the contact area and the interactive interface with the electrolyte are smaller, and the gas production is smaller; 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 gas production of the battery is small, while maintaining the stability of the positive electrode active material structure.

[0142] In some embodiments, the battery cell 20 further includes an electrolyte, and the conductivity of the electrolyte is 5mS / cm to 18mS / cm, and optionally, the conductivity is 6mS / cm to 12mS / cm. Exemplarily, the conductivity of the electrolyte can be 5mS / cm, 6mS / cm, 7mS / cm, 8mS / cm, 9mS / cm, 10mS / cm, 11mS / cm, 12mS / cm, 13mS / cm, 14mS / cm, 15mS / cm, 16mS / cm, 17mS / cm, 18mS / cm, or other typical non-limiting conductivity or a range between any two conductivity values.

[0143] 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).

[0144] The solvent may include at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl 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.

[0145] 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 can better ensure the stability and safety of the battery.

[0146] In some embodiments, 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. Exemplarily, 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, and other typical non-limiting concentrations or ranges between any two concentrations.

[0147] The solute concentration is also the sodium salt concentration. 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.

[0148] In some embodiments, the residual space coefficient of the battery cell is 0.02-1 mL / Ah, and optionally, 0.2-0.8 mL / Ah. Exemplarily, 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.

[0149] 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 (including positive electrode plates, negative electrode plates, isolation membranes, mechanical parts, electrolytes, etc.) from the battery cell 20. The residual volume can be measured by calculating the volume by injecting liquid to fill the residual space under the condition that the shell remains unchanged, or by using laser scanning / nuclear magnetic resonance technology and other methods. For example, after the battery cell 20 is finished, the electrolyte is injected into the shell until the entire containing cavity is filled, and the volume of the electrolyte injected later.

[0150] 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.

[0151] In some embodiments, the permeability rate of the breathable 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. Exemplarily, the permeability rate of the breathable 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, etc., or a range between any two permeability rates. The permeability rate of the breathable membrane is set within the above range so that the breathable membrane can discharge the excess gas generated inside the battery cell out of the battery cell.

[0152] The test method of air permeability can refer to GB / T1038-2000.

[0153] In some embodiments, the air permeability v of the air permeable membrane 240 and the gas production rate V inside the battery cell 20 satisfy: 0.9≤v / V≤5, optionally, 1≤v / V≤4. Exemplarily, the ratio between the air permeability v of the air permeable membrane 240 and the gas production rate V inside the battery cell 20 can 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 and 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. When the ratio is too large, the breathable membrane is easy to penetrate moisture in the air and shorten its life.

[0154] The gas production rate can be tested using an infrared flowmeter. The gas production pin is welded to the 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.

[0155] In some embodiments, the transition metal oxide Na p (Ni x Fe y Mn z Me q ) 2 The stoichiometric ratio z of the Mn element in the gas permeable membrane and the gas permeability v satisfy: 0.1≤z / v≤2, optionally, 0.25≤z / v≤1.7. p (Ni x Fe y Mn z Me q ) 2 The ratios between the stoichiometric ratio z of the Mn element and the air 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.

[0156] In the technical solution of the embodiment of the present application, due to the existence of the Jan-Taylor 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 gas permeability 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 is easily infiltrated with moisture in the air and its life is deteriorated.

[0157] In the embodiment of the present application, an inductively coupled plasma spectrometer (ICP) can be used to test and detect the transition metal oxide AMO of the positive electrode active material. 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.

[0158] Please refer to Figure 3 In some embodiments, an explosion-proof valve 21b is also provided on the outer packaging 26.

[0159] In some embodiments, the explosion-proof valve 21 b is disposed on the end cover 21 .

[0160] 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.

[0161] Example 1

[0162] This embodiment provides a battery cell, including: an electrode assembly 23 and an outer package 26, wherein the electrode assembly 23 includes a positive electrode plate, on which a positive electrode active material layer is provided, and 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 ) 2 The positive electrode sheet may include a positive electrode current collector and a positive electrode active material layer coated on two opposite sides of the positive electrode current collector, and the single-sided thickness of the positive electrode active material layer on the positive electrode sheet is 65 μm. 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 0.53 m 2 / g. The average particle size of the transition metal layered oxide satisfies: Dv50 is 5.8 μm.

[0163] Preparation of positive electrode slurry:

[0164] Transition metal layered oxides Na 0.9 (Ni 0.3 Fe 0.3 Mn 0.3 Ca 0.1 ) 2 , a binder and conductive carbon are mixed in 94%, 2.5% and 3.5% by mass, and then a stirring solvent NMP is added and stirred to obtain a positive electrode slurry, and the mass ratio of the added stirring solvent NMP to the fixed mixture is 4:6. Among them, the binder is PVDF.

[0165] Preparation of negative electrode slurry:

[0166] Hard carbon, a binder, a thickener and conductive carbon were mixed in a mass percentage of 94%, 4%, 1% and 1%, and then a stirring solvent NMP was added and stirred to obtain a negative electrode slurry. The mass of the added stirring solvent NMP and the fixed mixture was 5:5.

[0167] The battery cell 20 also includes an electrolyte, which is an ethylene carbonate solvent and a fluorocarbonate additive, and the conductivity of the electrolyte is 8.4 mS / cm. The sodium salt concentration of the electrolyte is 0.9 mol / L. The residual space coefficient of the battery cell is 0.4 mL / Ah.

[0168] Then the electrode assembly is prepared through coating → cold pressing → die cutting → winding → assembly → liquid injection → aging → formation.

[0169] Install the exhaust device 24 on the end cover 21 of the battery cell, please refer to 4 and Figure 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 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.

[0170] like Figure 6As shown, the exhaust device 24 is installed on the side of the end cover 21 facing the inside of the battery cell 20. A receiving groove for accommodating the exhaust device 24 is provided on the side of the end cover 21 facing the inside of the battery cell 20, a vent hole 251 is provided on the insulating member 25, and an exhaust hole 211 is provided on the outside of the end cover 21. The gas inside the battery cell 20 passes through the vent hole 251, the breathable 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 vent hole 211. 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 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 assembled into a battery cell.

[0171] Examples 2 to 5 are shown in Table 1 below. In Examples 2, 4 and 5, the battery cells of Examples 2, 4 and 5 were prepared in the same manner as in Example 1, except that the air permeability of the air permeable membrane was adjusted. In Example 3, the battery cell of Example 3 was prepared in the same manner as in Example 1, except that the stoichiometric ratio of the Mn element in the transition metal oxide and the air permeability of the air permeable membrane were adjusted. In Comparative Example 1, the air permeability of the air permeable membrane was adjusted, and the battery cell of Comparative Example 1 was prepared in the same manner as in Example 1. In Comparative Example 2, the battery cell of Comparative Example 1 was prepared in the same manner as in Example 1, except that the stoichiometric ratio of the Mn element in the transition metal oxide and the air permeability of the air permeable membrane were adjusted. In Comparative Example 3, no air permeable membrane was provided.

[0172] Table 1 Results of relevant parameters of battery cells of Examples 1 to 5 and Comparative Examples 1-3

[0173]

[0174] Performance Testing:

[0175] (1) Cycle rate test: Cycle according to the following process at normal pressure and 25±2℃:

[0176] 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.

[0177] (2) Cycle end maximum internal pressure test: When the battery cell is manufactured, a pressure gauge is connected, and the pressure gauge is connected to a pressure receiving sensor to monitor the internal pressure of the battery cell, and the maximum internal pressure of the battery cell at the end of the cycle is recorded. The test results are shown in Table 2 below.

[0178] Table 2 Performance results of battery cells of Examples 1-5 and Comparative Examples 1-3

[0179]

[0180]

[0181] According to the above results, it can be seen that compared with comparative example 3 in which no breathable membrane is provided, embodiments 1 to 5 provide breathable membranes, and the cycle performance of the battery cells is significantly improved, and the internal pressure inside the battery cells will not be too high, thereby improving the reliability of the battery. However, in comparative example 3 in which no breathable membrane is provided, the internal pressure inside the battery cells is too high, which easily leads to abnormal opening of the explosion-proof valve.

[0182] Compared with Comparative Examples 1 and 2, in which the ratio of the air permeability rate of the breathable membrane to the gas production rate of the battery cell is not within the appropriate range, and the stoichiometric ratio of the Mn element to the air permeability rate of the breathable membrane is not within the appropriate range, in Examples 1 to 5, the stoichiometric ratio of the Mn element to the air permeability rate of the breathable membrane is set within the appropriate range, the air permeability rate of the breathable membrane and the gas production rate of the battery cell are set within the appropriate range, the cycle performance of the battery cell is significantly improved, and the internal pressure inside the battery cell is not too large, thereby improving the reliability of the battery. In Comparative Example 1, z / v is too small, and the breathable membrane is easy to penetrate moisture in the air, so the life of the battery cell in Comparative Example 1 is seriously deteriorated. In Comparative Example 2, z / v is too large, resulting in poor air permeability of the breathable membrane, and the internal pressure inside the battery cell will be relatively increased.

[0183] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A battery cell, It is characterized in that The battery cell comprises: An electrode assembly, 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 package the electrode assembly. The outer packaging is provided with an exhaust device, and the exhaust device includes a breathable film.

2. The battery cell according to claim 1, It is characterized in that The exhaust device further comprises a connecting member, the connecting member is provided with at least one through hole, the breathable membrane is arranged 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, It is characterized in that The air-permeable membrane is sealed and connected to a contact surface of the connecting piece.

4. The battery cell according to claim 2 or 3, It is characterized in that The connecting member is provided with a plurality of through holes, and the diameter 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, It is characterized in that Along the axial direction of the through hole, the orthographic projection area of ​​all the through holes is 10 mm 2 ~50mm 2 .

6. The battery cell according to any one of claims 1 to 5, It is characterized in that 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.

7. The battery cell according to any one of claims 2 to 6, It is characterized in that The exhaust device further comprises a backing member, wherein the backing member is arranged 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, It is characterized in that 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.

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

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

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

12. The battery cell according to any one of claims 2 to 11, It is characterized in that The outer package includes an end cover, the exhaust device is arranged on a side of the end cover facing the interior of the battery cell, and the end cover is provided with an exhaust hole connected to the through hole of the exhaust device.

13. The battery cell according to claim 12, It is characterized in that A receiving groove for receiving 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 with the exhaust hole through the air guide channel, and the exhaust hole is staggered with the through hole.

14. The battery cell according to claim 13, It is characterized in that An insulating member is provided inside the end cover, and an air vent is provided on the insulating member. Gas inside the battery cell is discharged to the outside of the battery cell through the air vent, the exhaust device, the air guide channel and the exhaust vent.

15. The battery cell according to claim 14, It is characterized in that In the thickness direction of the end cover, the orthographic projection of the vent hole covers the orthographic projections of all the through holes.

16. The battery cell according to any one of claims 1 to 15, It is characterized in that The chemical formula of the transition metal oxide is AMOs, 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.

17. The battery cell according to any one of claims 1 to 16, It is characterized in that The transition metal oxide is Na p (Ni x Fe y Mn z Me q ) 2 , 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.

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

19. The battery cell according to any one of claims 1 to 18, It is characterized in that 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, It is characterized in that The specific surface area of ​​the transition metal oxide in the positive electrode active material layer satisfies the BET: 0.2 m 2 / g≤BET≤1.5m 2 / g, optionally, 0.4m 2 / g≤BET≤1.2m 2 / g.

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

22. The battery cell according to any one of claims 1 to 21, It is characterized in that The battery cell further includes an electrolyte, 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, It is characterized in that 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, It is characterized in that The residual space coefficient of the battery cell is 0.02 to 1 mL / Ah, and optionally, 0.2 to 0.8 mL / Ah.

25. The battery cell according to any one of claims 1 to 24, It is characterized in that The air permeability rate of the air permeable membrane is 0.1 to 5 mL / D, optionally, 0.2 to 4 mL / D, and more optionally, 0.2 to 0.7 mL / D. 26 . The battery cell according to claim 1 , wherein the air permeability rate v of the air permeable membrane and the gas generation rate V inside the battery cell satisfy: 0.9≤v / V≤5, optionally, 1≤v / V≤4.

27. The battery cell according to any one of claims 17 to 26, It is characterized in that The transition metal oxide Na p (Ni x Fe y Mn z Me q ) 2 The stoichiometric ratio z of the Mn element and the air permeability v of the breathable membrane satisfy: 0.1≤z / v≤2, optionally, 0.25≤z / v≤1.

7.

28. The battery cell according to any one of claims 1 to 27, It is characterized in that The outer package is also provided with an explosion-proof valve.

29. A method for preparing a battery cell, It is characterized in that include: Providing an electrode assembly, 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; An outer package is provided, on which an exhaust device is arranged, and the outer package is sealed on the outside of the electrode assembly, and the exhaust device includes a breathable film.

30. A battery, It is characterized in that The battery comprises the battery cell according to any one of claims 1 to 28.

31. An electrical device, It is characterized in that The electrical device comprises the battery according to claim 30.

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