Sodium metal battery and preparation method therefor, and electrical apparatus

Abstract

The present application belongs to the technical field of batteries, and specifically relates to a sodium metal battery and a preparation method therefor, and an electrical apparatus. The sodium metal battery comprises a positive electrode sheet and a negative electrode sheet. The negative electrode sheet comprises a negative current collector, and a sodium metal layer located on at least one side surface of the negative current collector. A separator film is located between the positive electrode sheet and the negative electrode sheet. The separator film comprises a base film, and a first coating layer located on at least one side surface of the base film, and at least a part of the first coating layer faces the sodium metal layer. The first coating layer has a 20%-80% compression deformation in the sodium metal battery. The design method provided in the present application is beneficial to improving the safety of a battery.

Description

Sodium metal battery, preparation method thereof and electric device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application with the title of “Sodium metal battery, preparation method thereof and electric device”, application number: 202411280845.0, filed on September 12, 2024, the entire content of which is incorporated herein by reference. TECHNICAL FIELD

[0003] The present application relates to the field of batteries, in particular to a sodium metal battery, a preparation method thereof and an electric device. BACKGROUND

[0004] Secondary batteries are widely used in various consumer electronic products and electric vehicles due to their light weight, no pollution, no memory effect and other outstanding characteristics. Among them, lithium ion batteries have very wide applications in portable electronic devices, electric vehicles and other fields.

[0005] With the increasingly wide range of applications of secondary batteries, the requirements for battery performance are also becoming higher and higher. SUMMARY

[0006] In view of the above problems, the present application provides a sodium metal battery, a preparation method thereof and an electric device. The isolation film in the sodium metal battery can provide a buffer for the deposition of the sodium metal layer of the negative electrode sheet, thereby reducing the generation amount of sodium dendrites to improve the safety of the sodium metal battery.

[0007] In a first aspect, the present application provides a sodium metal battery, which comprises a positive electrode sheet and a negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a sodium metal layer located on at least one side surface of the negative electrode current collector;

[0008] The sodium metal battery further comprises an isolation film located between the positive electrode sheet and the negative electrode sheet;

[0009] The isolation film comprises a base film and a first coating layer located on at least one side surface of the base film, at least part of the first coating layer facing the sodium metal layer;

[0010] The first coating layer has a compression deformation amount of 20% to 80% in the sodium metal battery.

[0011] In some embodiments of the present application, the porosity of the first coating layer without compression deformation amount is A1;

[0012] The porosity of the first coating layer under a compression deformation amount of 20% to 80% is A2;

[0013] The porosity of the base film is A0;

[0014] A2≤A0<A1 is satisfied.

[0015] In some embodiments of the present application, the porosity A1 of the first coating layer at a compression deformation amount of 0% is 40% to 90%;

[0016] The porosity A2 of the first coating layer at a compression deformation amount of 20% to 80% is 20% to 45%;

[0017] The porosity A0 of the base film is 30% to 50%.

[0018] In some embodiments of the present application, the air permeability of the separation film is ≤350 s / 100cc.

[0019] In some embodiments of the present application, the air permeability of the separation film is 200 s / 100cc to 350 s / 100cc.

[0020] In some embodiments of the present application, the air permeability of the separation film is 200 s / 100cc to 300 s / 100cc.

[0021] In some embodiments of the present application, the material of the first coating layer includes any one or more of thermoplastic polyester elastomer, thermoplastic dynamic vulcanized rubber, and thermoplastic polyurethane rubber.

[0022] In some embodiments of the present application, the average relative molecular mass of the thermoplastic polyester elastomer is 100,000 to 1,500,000 g / mol;

[0023] and / or;

[0024] The average relative molecular mass of the thermoplastic dynamic vulcanized rubber is 50,000 to 1,000,000 g / mol;

[0025] and / or;

[0026] The average relative molecular mass of the thermoplastic polyurethane rubber is 50,000 to 1,000,000 g / mol.

[0027] In some embodiments of the present application, the thermoplastic polyester elastomer includes a first hard segment and a first soft segment, and the mass ratio of the first hard segment to the first soft segment is (5 to 70):(30 to 95); the first hard segment includes any one or more of polybutylene terephthalate, polyethylene terephthalate, polyethylene naphthalate, polylactic acid, and polybutylene adipate, and the first soft segment includes any one or more of polyethylene glycol ether, polypropylene glycol ether, polybutylene glycol ether, polylactide, polyglycolide, polycaprolactone, polyethylene oxide, polypropylene oxide, polytetrahydrofuran, polybutylene oxide, and polyepichlorohydrin.

[0028] and / or;

[0029] The thermoplastic dynamic vulcanizate comprises a thermoplastic resin and a rubber, the mass ratio of the thermoplastic resin to the rubber being (10-80):(20-90); the thermoplastic resin comprises any one or more of polypropylene, polyethylene, polystyrene, polyvinyl chloride, thermoplastic elastomer, polybutylene terephthalate, nylon, polyphenylene ether, polycarbonate; the rubber comprises any one or more of ethylene-propylene-diene monomer rubber, natural rubber, nitrile rubber, styrene butadiene rubber, isoprene rubber, butyl rubber, ethylene-propylene rubber, ethylene-vinyl acetate copolymer, acrylate rubber, ethylene-acrylate copolymer;

[0030] and / or;

[0031] The thermoplastic polyurethane rubber comprises a second hard segment and a second soft segment, the mass ratio of the second hard segment to the second soft segment being (10-80):(20-90); the second hard segment comprises any one or more of polyterephthalate glycol, polyadipate glycol, polyether polyurethane, polycarbonate polyurethane, polyether ester polyurethane; the second soft segment comprises any one or more of polytetrahydrofuran, polypropylene oxide, polyethylene glycol, polypropylene glycol, polybutylene glycol.

[0032] In some embodiments of the present application, the first coating layer comprises a binder, the mass percentage content of the binder in the coating layer being 5%-40%.

[0033] In some embodiments of the present application, at least part of the first coating layer faces the positive electrode tab.

[0034] In some embodiments of the present application, the separator film comprises a second coating layer, the second coating layer facing the positive electrode tab;

[0035] The second coating layer comprises an inorganic filler, the inorganic filler comprising any one or more of boehmite, aluminum oxide, barium sulfate, magnesium oxide, magnesium hydroxide, silicon oxide compound, tin dioxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, hafnium dioxide, cerium oxide, zirconium titanate, barium titanate and magnesium fluoride.

[0036] In some embodiments of the present application, the thickness of the sodium metal layer is 5-100 μm.

[0037] In some embodiments of the present application, an electrically conductive layer is provided between the negative electrode current collector and the sodium metal layer;

[0038] The electrically conductive layer comprises one or more of carbon-based conductive material and conductive polymer material;

[0039] The carbon-based conductive material includes any one or more of graphite, superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0040] The conductive polymer material includes any one or more of polyaniline, polypyrrole, polyacetylene, polyphenyl, polythiophene, and polypyridine.

[0041] In some embodiments of the present application, the negative electrode tab includes a negative current collector, a conductive layer, and a sodium metal layer, wherein the conductive layer is disposed close to the negative current collector, and the sodium metal layer is disposed away from the negative current collector.

[0042] In some embodiments of the present application, the thickness of the negative current collector is 5 μm to 60 μm.

[0043] A second aspect of the present application is to provide a method for preparing a sodium metal battery, including the following processes:

[0044] Preparation of the isolation film: disperse the elastomer particles and the binder into an organic solvent to form a slurry, coat the slurry on at least one side surface of the base film, and form a first coating layer after drying;

[0045] Assemble the isolation film, the positive electrode tab, and the negative electrode tab together to form the sodium metal battery.

[0046] In some embodiments of the present application, the elastomer particles have any one or more of a spherical shape, a spherical-like shape, a regular polygonal shape, or an irregular polygonal shape.

[0047] In some embodiments of the present application, the volume particle size distribution Dv50 of the elastomer particles is 3 μm to 50 μm.

[0048] In some embodiments of the present application, the specific surface area BET of the elastomer particles is 0.5 m 2 / g to 15 m 2 / g.

[0049] In some embodiments of the present application, the elastomer particles include any one or more of a thermoplastic polyester elastomer, a thermoplastic dynamic vulcanized rubber, and a thermoplastic polyurethane rubber.

[0050] In some embodiments of the present application, the elastomer particles have a porous structure, and the porous structure includes mesopores with an average pore size of 2 nm to 50 nm.

[0051] In some embodiments of the present application, the mass ratio between the elastomer particles and the binder is (60% to 95%) : (5% to 40%).

[0052] In some embodiments of the present application, the above-mentioned binder includes any one or more of a methyl methacrylate monomer copolymer and / or homopolymer, a saccharide monomer copolymer and / or homopolymer, an acrylic acid monomer copolymer and / or homopolymer, a styrene monomer copolymer and / or homopolymer, a butadiene monomer copolymer and / or homopolymer, a phenol monomer copolymer and / or homopolymer, an aldehyde monomer copolymer and / or homopolymer, a diatomic amine monomer copolymer and / or homopolymer, a diatomic anhydride monomer copolymer and / or homopolymer, a benzene ring monomer copolymer and / or homopolymer, or a derivative thereof, a modification thereof.

[0053] A third aspect of the present application is to provide a power utilization device, which includes the sodium metal battery of the first aspect or the sodium metal battery prepared by the preparation method of the second aspect.

[0054] The above description is only a summary of the technical solutions of the present application. In order to enable one of ordinary skill in the art to better understand the technical means of the present application and implement it according to the content of the description, and in order to enable the above and other purposes, characteristics and advantages of the present application to be more apparent and easy to understand, the following specific embodiments of the present application are described. BRIEF DESCRIPTION OF DRAWINGS

[0055] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The accompanying drawings are included to provide a description of the preferred embodiments and are not meant to limit the present application. Moreover, the same reference numerals in the accompanying drawings indicate the same or similar components. In the drawings:

[0056] FIG. 1 is a schematic diagram of a battery structure according to some embodiments of the present application;

[0057] FIG. 2 is a schematic diagram of an exploded structure of a battery according to some embodiments of the present application;

[0058] FIG. 3 is a schematic diagram of a vehicle structure according to some embodiments of the present application;

[0059] FIG. 4 is a schematic diagram of a battery pack structure according to some embodiments of the present application;

[0060] FIG. 5 is a schematic diagram of one of the sodium metal batteries according to some embodiments of the present application;

[0061] FIG. 6 is a schematic diagram of a separator film according to some embodiments of the present application;

[0062] FIGS. 7A, 7B and 8 are schematic diagrams of a sodium metal battery according to some embodiments of the present application;

[0063] FIG. 9 is a schematic diagram of a negative electrode sheet according to some embodiments of the present application;

[0064] The reference signs in the detailed description are as follows: 10000, vehicle; 1000, battery; 2000, controller; 3000, motor; 100, battery cell; 200, case; 210, first part; 220, second part; 10, secondary battery; 101, shell; 102, electrode assembly; 103, cover plate; 1, negative electrode sheet; 11, negative electrode current collector; 12, sodium metal layer; 13, conductive layer; 2, positive electrode sheet; 3, separator; 31, base film; 32, first coating layer; 33, second coating layer; first direction: coordinate axis x direction, which can also be the stacking direction or the separator thickness direction; coordinate axis y direction: separator length or width direction. DETAILED DESCRIPTION

[0065] Hereinafter, embodiments of the sodium metal battery and the method for manufacturing the same and the electric device according to the present application will be described in detail with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed description is omitted. For example, there will be cases where detailed description of matters known well and repeated description of substantially the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the accompanying drawings and the following description are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0066] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a specific range. The range defined in this way can include or not include the end value, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present application, unless otherwise stated, a numerical range "a-b" represents a shorthand notation for any integer combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed herein, and "0-5" is just a shorthand notation for these numerical combinations. In addition, when it is stated that a parameter is an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0067] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0068] If there is no special indication, all the technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0069] If there is no special indication, all the steps of the present application can be performed in sequence or randomly, preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method also comprises step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0070] If there is no special indication, the "includes" and "contains" mentioned in the present application are open-ended, and can also be closed. For example, "includes" and "contains" can mean that other components not listed can also be included or contained, or only the listed components can be included or contained.

[0071] If there is no special indication, in the present application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any one of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or A and B are both true (or exist).

[0072] If there is no special indication, in the present application, the terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0073] If there is no special indication, in the present application, the term "multiple" refers to more than two (including two), and similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0074] If there is no special indication, the technical terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the embodiments of the present application and simplifying the description, and does not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0075] Sodium metal batteries have the advantage of high energy density, but short circuits are prone to occur during repeated charging and discharging of the sodium metal battery. The reason may be that the sodium metal negative electrode changes in volume during repeated sodium extraction and embedding, which easily causes sodium dendrites, the sodium dendrites easily pierce or "overflow" the separator, causing the positive and negative electrode plates to overlap, and thus causing the positive and negative electrodes to come into contact and short circuit. Such short circuits are prone to occur when the battery is overcharged, which can cause the battery to catch fire or even explode, posing a great safety risk.

[0076] To solve the above technical problems, the present application provides a sodium metal battery, which comprises a positive electrode plate and a negative electrode plate, the negative electrode plate comprising a negative electrode current collector and a sodium metal layer located on at least one side surface of the negative electrode current collector; the sodium metal battery further comprises a separator located between the positive electrode plate and the negative electrode plate; the separator comprises a base film and a first coating layer located on at least one side surface of the base film, at least part of the first coating layer facing the sodium metal layer; the first coating layer has a compression deformation of 20% to 80% in the sodium metal battery.

[0077] The separator in the sodium metal battery of the present application can provide a buffer for the deposition of the sodium metal layer of the negative electrode plate, thereby reducing the number of sodium dendrites generated to improve the safety of the sodium metal battery. At the same time, the pressure exerted by the generated sodium dendrites on the coating layer at a certain position of the separator is also easily dispersed to other positions, reducing the probability of piercing the separator and further improving the safety of the sodium metal battery.

[0078] Therefore, the sodium metal battery provided by the present application is beneficial to improve the safety of the battery, and at the same time, the sodium metal battery has a relatively high energy density, and safe use at this energy density is beneficial to ensure the stability of the cycle capacity retention rate of the battery. Therefore, the sodium metal battery provided by the present application is beneficial to increase the user experience. The sodium metal battery can comprise an outer package. The outer package can be used to package the electrode assembly and the electrolyte composed of the above-mentioned sodium metal battery. The outer package of the sodium metal battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the sodium metal battery can also be a soft package, such as a bag-type soft package. The material of the soft package can be plastic, including but not limited to polypropylene, polybutylene terephthalate, and polybutylene succinate, etc.

[0079] The shape of the sodium metal battery of the present application is not particularly limited, which can be cylindrical, square or any other shape. For example, FIG. 1 is a square structure of a sodium metal battery (secondary battery 10) as an example.

[0080] According to some embodiments of the present application, referring to FIG. 2, the outer package can include a shell 101 and a cover plate 103. The shell 101 can include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 101 has an opening communicating with the receiving cavity, and the cover plate 103 can be arranged on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the separator film can form an electrode assembly 102 through a winding process or a stacking process. The electrode assembly 102 is packaged in the receiving cavity. The electrolyte is impregnated in the electrode assembly 102. The number of electrode assemblies 102 contained in the secondary battery 10 can be one or more, which can be selected by those skilled in the art according to specific actual needs.

[0081] The electrode assembly 102 provided by the present application is applied to the secondary battery, which is beneficial to improve the performance of the secondary battery, and can be used as a power supply of an electric device or an energy storage unit of an electric device. The electric device is applied to the power field, such as a mobile device (for example, a mobile phone, a notebook computer, etc.), an electric vehicle (for example, a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc. The energy storage system can store electric energy as needed and output electric energy at appropriate times. For example, the energy storage system includes one or more batteries, and the energy storage system can store electric energy during the off-peak period of electricity consumption, and provide electric energy for related users or electric devices during the peak period of electricity consumption. The energy storage system provided by the embodiments of the present application can be any power system that needs to use an energy storage device.

[0082] Some embodiments of the present application take a vehicle as an example for convenience of description.

[0083] Please refer to FIG. 3, which is a structural schematic diagram of a vehicle 10000 provided by some embodiments of the present application. The vehicle 10000 can be a fuel automobile, a gas automobile or a new energy automobile, and the new energy automobile can be a pure electric vehicle, a hybrid electric vehicle or a range extended vehicle, etc. The vehicle 10000 is internally provided with a battery 1000, which can be arranged at the bottom, the head or the tail of the vehicle 10000. The battery 1000 can be used for power supply of the vehicle 10000, for example, the battery 1000 can be used as an operating power supply of the vehicle 10000. The vehicle 10000 can further include a controller 2000 and a motor 3000, and the controller 2000 is used to control the battery 1000 to supply power to the motor 3000, for example, to meet the working power demand of the vehicle 10000 during starting, navigation and driving.

[0084] In some embodiments of the present application, the battery 1000 can not only serve as the operating power source of the vehicle 10000, but also serve as the driving power source of the vehicle 10000, replacing or partially replacing the fuel or natural gas to provide driving power for the vehicle 10000.

[0085] Please refer to FIG. 4, which is an exploded view of the battery 1000 provided by some embodiments of the present application. The battery 1000 includes a box body 200 and a battery cell 100, which is a primary battery or a secondary battery. The present application specifically protects the secondary battery 100, which is accommodated in the box body 200. Among them, the box body 200 is used to provide an accommodation space for the battery cell 100, and the box body 200 can adopt various structures.

[0086] In some embodiments, the box body 200 can include a first part 210 and a second part 220, the first part 210 and the second part 220 are covered with each other, and the first part 210 and the second part 220 jointly define an accommodation space for accommodating the secondary battery 100. The second part 220 can be a hollow structure with one end open, and the first part 210 can be a plate structure, which is covered on the open side of the second part 220 to jointly define the accommodation space with the second part 220; the first part 210 and the second part 220 can also be hollow structures with one side open, and the open side of the first part 210 is covered on the open side of the second part 220. Of course, the box body 200 formed by the first part 210 and the second part 220 can have various shapes, such as a cylinder, a cuboid, etc.

[0087] In the battery 1000, the battery cell 100 can be multiple, and the multiple battery cells 100 can be connected in series, in parallel, or in a mixed manner. The mixed manner means that the multiple battery cells 100 are connected in series and in parallel. The multiple battery cells 100 can be directly connected in series, in parallel, or in a mixed manner, and then the whole of the multiple battery cells 100 is accommodated in the box body 200; of course, the battery 1000 can also be that the multiple battery cells 100 are first connected in series, in parallel, or in a mixed manner to form a battery 1000 module, and then the multiple battery 1000 modules are connected in series, in parallel, or in a mixed manner to form a whole, which is accommodated in the box body 200. The battery 1000 can also include other structures, for example, the battery 1000 can also include a busbar component for realizing the electrical connection between the multiple battery cells 100.

[0088] Sodium metal battery

[0089] The application discloses a sodium metal battery in some embodiments, which comprises a positive electrode sheet and a negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a sodium metal layer on at least one side surface of the negative electrode current collector; the sodium metal battery further comprises a separator between the positive electrode sheet and the negative electrode sheet; the separator comprises a base film and a first coating layer on at least one side surface of the base film, at least part of the first coating layer facing the sodium metal layer; the first coating layer has a compression deformation amount of 20% to 80% in the sodium metal battery.

[0090] The positive electrode sheet, the separator and the negative electrode sheet in the application can be formed into a sodium metal battery by winding or stacking process. Specifically, the application illustrates a secondary battery 10 (sodium metal battery) formed by a stacking method in FIG. 5. As shown in FIG. 5, the negative electrode sheet 1 or the positive electrode sheet 2 is placed between two adjacent separators 3, and the negative electrode sheet 1 and the positive electrode sheet 2 are arranged alternately along the stacking direction (coordinate axis x direction). The number and size of the negative electrode sheet 1 and / or the positive electrode sheet 2 can be selected according to the actual situation, and the application will not be described here. In addition, the application only illustrates one stacking method in FIG. 5, and other stacking or winding methods are also within the protection scope of the application.

[0091] The application illustrates that the separator 3 comprises a base film 31 and a first coating layer 32 on at least one side surface of the base film 31 in FIG. 6. The application only illustrates that the first coating layer 32 is arranged on one side surface of the base film 31 in FIG. 6.

[0092] The deformation amount of the first coating layer in the application refers to the thickness of the coating layer before compression deformation h1, the thickness of the coating layer after compression deformation h2, and the calculation value of (h1-h2) / h1*100%. The thickness of the coating layer refers to the distance between the two end surfaces of the coating layer along the stacking direction of the battery, which can be measured by a conventional laser thickness gauge in the art.

[0093] The separator in the sodium metal battery of the application can provide a buffer for the deposition of the sodium metal layer of the negative electrode sheet, thereby reducing the generation amount of sodium dendrites to improve the safety of the sodium metal battery. At the same time, even if sodium dendrites are generated, the pressure exerted by the sodium dendrites on the coating layer at a certain position of the separator can be easily dispersed to other positions, reducing the probability of piercing the separator and further improving the safety of the sodium metal battery.

[0094] In some embodiments of the application, the porosity of the first coating layer without compression deformation amount is A1;

[0095] The porosity of the first coating layer under a compression deformation amount of 20% to 80% is A2;

[0096] The porosity of the base film is A0; and A2≤A0 A1.

[0097] The first coating layer in the separator of the present application has a certain porosity to realize the normal conduction of ions in the battery. Meanwhile, the first coating layer with a certain porosity can also disperse the pressure exerted by sodium dendrites on the coating at a certain position, thereby reducing the probability of puncturing the separator.

[0098] In some embodiments, the first coating layer has a porosity A1 of 40% to 90% without compression deformation.

[0099] The first coating layer has a porosity A2 of 20% to 45% under a compression deformation of 20% to 80%.

[0100] The base film has a porosity A0 of 30% to 50%.

[0101] The measurement method of the porosity of the separator of the present application includes various methods in the art, such as the weighing method: the volume of the base film or coating layer is tested, and the volume of the internal pores is calculated by the true density of the base film or coating material to obtain the porosity; the mercury intrusion method, the standard reference is GB / T21650.2-2008 "Determination of Pore Size Distribution and Porosity of Solid Materials by Mercury Porosimetry and Gas Adsorption Part 2: Analysis of Mesopores and Macropores by Gas Adsorption", and in addition, the following methods are used to measure or calculate:

[0102] For example, the coating sample or base film sample after drying treatment is cut into a square sample of about 20 mm x 20 mm, the thickness and actual side length are measured by a digital screw micrometer and a vernier caliper, the volume is calculated as V, and the weight M0 is measured, then the square sample is immersed in an electrolyte, taken out after soaking at room temperature and in air for 2 hours, the surface adsorbed electrolyte is absorbed, and then the weight M is measured. t The porosity of the coating sample or base film sample satisfies the following mathematical relationship:

[0103] Porosity = (M t -M0) / p x V x 100%;

[0104] In the above mathematical relationship, p is the density of the electrolyte, mm 3 / g, V is the volume of the square sample of the coating sample or base film sample, mm 3 , the weights M0 and M t are in units of g, the weight measuring instrument is a thousandth balance, and the model of the thousandth balance, the digital screw micrometer, and the vernier caliper includes but is not limited to any model in the art.

[0105] The application discloses a method for measuring the porosity of the first coating layer with a compression deformation variable of 20-80%, which comprises the following steps: applying pressure to the coating layer to form a coating sample with a compression deformation variable of 20-80%, and then measuring the coating sample by using the same method as described above.

[0106] In the embodiments, the first coating layer has a porosity A1 of any one of 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90% or any one of the range values described above without a compression deformation variable.

[0107] In the embodiments, the first coating layer has a porosity A2 of any one of 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45% or any one of the range values described above under a compression deformation variable of 20-80%.

[0108] In the embodiments, the base film has a porosity A0 of any one of 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50% or any one of the range values described above.

[0109] In the embodiments, the first coating layer of the separator film has a compression deformation variable in the battery, so that the porosity changes, while the base film has almost no compression variable in the battery, and the porosity does not change. Under the premise of meeting the porosity described above, the first coating layer and the base film of the separator film can not only ensure the normal conduction of ions in the battery, but also disperse the pressure applied by the sodium dendrite at a certain position to the coating layer at the position, which is beneficial to reducing the probability of puncturing the separator film.

[0110] In some embodiments, the separator film has an air permeability of ≤350 s / 100cc.

[0111] The application discloses, in some embodiments, that the air permeability of the isolation film is 200 s / 100cc-350 s / 100cc.

[0112] The application discloses, in some embodiments, that the air permeability of the isolation film is 200 s / 100cc-300 s / 100cc.

[0113] The air permeability of the isolation film of the application refers to the amount of gas permeated by the isolation film under a certain time pressure, and the industry is used to express it by the Gurley value, which means the time required for 100 mL of oxygen to permeate 1 square inch (which can be converted into 1 square centimeter) of the isolation film under the pressure of 1.22 KPa. Generally speaking, the air permeability of the isolation film is related to its thickness, pore size, porosity and pore tortuosity, etc. By selecting the appropriate air permeability of the isolation film, the probability of sodium dendrite piercing the isolation film can be reduced under the premise of ensuring the normal conduction of ions in the battery.

[0114] The application discloses, in some embodiments, that the material of the first coating layer comprises any one or more of thermoplastic polyester elastomer, thermoplastic dynamic vulcanized rubber and thermoplastic polyurethane rubber.

[0115] The thermoplastic polyester elastomer (TPEE) in the application is a block copolymer, which comprises high-melting-point, high-hardness crystalline polyester hard segments and low-glass-transition-temperature amorphous polyether or polyester soft segments. The crystalline polyester hard segments have a physical crosslinking effect, and the amorphous polyether or polyester soft segments impart high resilience to the block copolymer.

[0116] The application discloses, in these embodiments, that the average relative molecular mass of the thermoplastic polyester elastomer is 100,000-1,500,000, in units of g / mol.

[0117] The average relative molecular mass of the application refers to the average relative molar mass for a single component, and refers to the ratio between the mass and the molar mass of the mixed components for mixed components. The average relative molecular mass of the thermoplastic polyester elastomer is any one of 100,000, 200,000, 300,000, 400,000, 500,000, 600,000, 700,000, 800,000, 900,000, 1,000,000, 1,100,000, 1,200,000, 1,300,000, 1,400,000 and 1,500,000.

[0118] The thermoplastic polyester elastomer disclosed in the embodiments of the present application comprises a first hard segment and a first soft segment, the mass ratio of the first hard segment and the first soft segment being (5-70):(30-95); the first hard segment comprises any one or more of polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polylactic acid (PLA), and polybutylene adipate (PBAT), and the first soft segment comprises any one or more of polyethylene glycol ether, polypropylene glycol ether, polybutylene glycol ether, polylactide, polyglycolide, polycaprolactone, polyethylene oxide (PEO), polypropylene oxide (PPG), polytetrahydrofuran (PTMEG), polybutylene oxide (PEB), and polyepichlorohydrin (PEC).

[0119] The thermoplastic polyester elastomer disclosed in the embodiments of the present application further comprises a first hard segment and a first soft segment, the mass ratio of the first hard segment and the first soft segment being any one of 5:95, 10:90, 20:80, 30:70, 40:60, 50:50, 60:40, and 70:30.

[0120] The thermoplastic dynamic vulcanized rubber (TPV) of the present application refers to a blended material prepared by dynamic vulcanization technology, which has high elasticity of rubber at room temperature and can be melt plasticized at high temperature, and has excellent properties of both rubber and thermoplastic resin. Therefore, the thermoplastic dynamic vulcanized rubber (TPV) mainly consists of two parts: one is a thermoplastic resin as a continuous phase, and the other is a rubber as a dispersed phase. The average relative molecular mass of the thermoplastic dynamic vulcanized rubber disclosed in the embodiments of the present application is 50,000-1,000,000, and the unit is g / mol, and the meaning of the average relative molecular mass here is the same as above. The average relative molecular mass of the thermoplastic dynamic vulcanized rubber is any one of 50,000, 100,000, 200,000, 300,000, 400,000, 500,000, 600,000, 700,000, 800,000, 900,000, and 1,000,000.

[0121] The application discloses in these embodiments that the thermoplastic dynamically vulcanized rubber comprises a thermoplastic resin and a rubber, the mass ratio of the thermoplastic resin and the rubber is (10-80):(20-90), the thermoplastic resin comprises any one or more of polypropylene (PP), polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC), thermoplastic elastomer (TPE), polybutylene terephthalate (PBT), nylon, polyphenylene ether, polycarbonate; the rubber comprises any one or more of ethylene-propylene-diene monomer rubber (EPDM), natural rubber (NR), nitrile rubber (NBR), styrene butadiene rubber (SBR), isoprene rubber, butyl rubber, ethylene-propylene rubber, ethylene-vinyl acetate copolymer, acrylate rubber, ethylene-acrylate copolymer. The application discloses in these embodiments that the mass ratio of the thermoplastic resin and the rubber is any one of 10:90, 20:80, 30:70, 40:60, 50:50, 60:40, 70:30, 80:20.

[0122] The thermoplastic polyurethane rubber (TPU) of the application is a kind of elastomer that can be plasticized by heating and can be dissolved by solvent, which is a (AB) n linear block polymer, A is a polyester or polyether with a high molecular weight (1000-6000), B is a diol containing 2-12 linear carbon atoms, and the chemical structure between AB segments is diisocyanate. The application discloses in these embodiments that the average relative molecular weight of the thermoplastic polyurethane rubber is 500,000-1,000,000, unit: g / mol. The average relative molecular weight of the thermoplastic polyurethane rubber of the application is any one of 500,000, 1,000,000, 2,000,000, 3,000,000, 4,000,000, 5,000,000, 6,000,000, 7,000,000, 8,000,000, 9,000,000, 10,000,000.

[0123] The application also discloses that the thermoplastic polyurethane rubber comprises a second hard segment and a second soft segment, the mass ratio of the second hard segment and the second soft segment is (10-80):(20-90); the second hard segment comprises any one or more of polybutylene terephthalate (PBT), polydiol adipate (PTT), polyether type polyurethane (hard segment formed by reaction of polyether diol and isocyanate), polycarbonate type polyurethane (hard segment formed by reaction of polycarbonate diol and isocyanate), polyether ester type polyurethane; the second soft segment comprises any one or more of polytetrahydrofuran (PTMG), polypropylene oxide (PPG), polyethylene glycol (PEG), polypropylene glycol (PPG), polybutylene glycol (PBG). The application discloses in these embodiments that the mass ratio of the second hard segment and the second soft segment is any one of 10:90, 20:80, 30:70, 40:60, 50:50, 60:40, 70:30, 80:20.

[0124] The present application discloses, in some embodiments, that the first coating layer contains a binder, and the mass percentage content of the binder in the first coating layer is 5% to 40%.

[0125] The present application discloses, in the above embodiments, that the first coating layer material contains any one or more of thermoplastic polyester elastomer, thermoplastic dynamic vulcanized rubber and thermoplastic polyurethane rubber, in addition to which, a binder is contained, which is used for the adhesion between the first coating layer materials, and the adhesion of the first coating layer materials to the base film. The present application discloses, in these embodiments, that the mass percentage content of the binder in the first coating layer is any one of 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40% or any one of the above range values.

[0126] The present application also discloses, in these embodiments, specific types of the binder, which include at least one of acrylic monomer copolymer and / or homopolymer, polyvinyl alcohol, vinylidene fluoride polymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-pentafluoropropylene copolymer, vinylidene fluoride-tetrafluoropropylene copolymer, vinylidene fluoride-trifluoropropylene copolymer, vinylidene fluoride-perfluorobutylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-trifluorochloroethylene copolymer or vinylidene fluoride-fluoroethylene copolymer, saccharide monomer copolymer and / or homopolymer, acrylic monomer copolymer and / or homopolymer, styrene monomer copolymer and / or homopolymer, butadiene monomer copolymer and / or homopolymer, phenol monomer copolymer and / or homopolymer, aldehyde monomer copolymer and / or homopolymer, dibasic amine monomer copolymer and / or homopolymer, dibasic anhydride monomer copolymer and / or homopolymer, benzene ring monomer copolymer and / or homopolymer, or derivatives thereof, modified products thereof.

[0127] Among them, the monomers in the acrylic monomer copolymer and / or homopolymer of the present application include any one or more of methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-propyl acrylate, cyclohexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate and 2-hydroxypropyl methacrylate.

[0128] The saccharide monomer copolymer and / or homopolymer of the present application includes carboxymethyl cellulose, sodium alginate. The acrylic acid monomer copolymer and / or homopolymer of the present application includes polyacrylic acid. The styrene monomer copolymer and / or homopolymer of the present application includes butadiene styrene rubber, styrene monomer-butadiene monomer-styrene monomer block copolymer. The aldehyde monomer copolymer and / or homopolymer of the present application includes phenolic resin. The diamine monomer copolymer and / or homopolymer of the present application includes polyimide.

[0129] In some embodiments, the first coating layer 32 of the separator film 3 is arranged towards the sodium metal layer 12 of the negative electrode tab 1, as shown in FIG. 7A.

[0130] In some embodiments, the first coating layer 32 of the separator film 3 is arranged towards the sodium metal layer 12 of the negative electrode tab 1, and the first coating layer 32 is also arranged towards the positive electrode tab 2, as shown in FIG. 7B.

[0131] As shown in FIGS. 7A and 7B, the first coating layer 32 of the separator film 3 is attached to the sodium metal layer 12 of the negative electrode tab 1, and the first coating layer 32 has a certain compression deformation in the sodium metal battery, that is, there is stress between the sodium metal layer 12 and the first coating layer 32 of the separator film 3. Under the guidance of the stress, the deposition and peeling process of the sodium metal layer 12 mainly occurs along the interface, thereby reducing the generation amount of sodium dendrites to improve the safety of the sodium metal battery.

[0132] In some embodiments, the separator film 3 comprises a second coating layer 33 arranged towards the positive electrode tab 2. As shown in FIG. 8, the separator film 3 comprises a base film 31, a first coating layer 32 arranged on one side surface of the base film 31, and a second coating layer 33 arranged on the other side surface of the base film 31. The first coating layer 32 is arranged towards the sodium metal layer 12 of the negative electrode tab 1, and the second coating layer 33 is arranged towards the positive electrode tab 2. The material of the second coating layer 33 is different from that of the first coating layer 32. Specifically, the second coating layer 33 comprises inorganic fillers in these embodiments, and the inorganic fillers include any one or more of boehmite, aluminum oxide, barium sulfate, magnesium oxide, magnesium hydroxide, silicon oxide compounds, tin dioxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, hafnium dioxide, cerium oxide, zirconium titanate, barium titanate, and magnesium fluoride.

[0133] The above design is adopted, which is convenient to reduce the generation amount of sodium dendrites of the negative electrode tab of the battery, is also conducive to improving the thermal stability and mechanical strength of the separator film, and further reduces the probability of sodium dendrites piercing the separator film.

[0134] In some embodiments, the application discloses that the negative current collector 11 is provided with an electrically conductive layer 13 between the negative current collector 11 and the sodium metal layer 12, which can be shown in FIG. 9. FIG. 9 shows that the electrically conductive layer 13 is arranged on one side surface of the negative current collector 11. The application also includes that the electrically conductive layer 13 is arranged on both side surfaces of the negative current collector 11. The electrically conductive layer 13 can be arranged on the surface of the negative current collector 11 in a full formation or a partial formation. In the following embodiments, the electrically conductive layer 13 is mainly discussed in the full formation on both side surfaces of the negative current collector 11. The formation of the electrically conductive layer 13 on the surface of the negative current collector 11 includes any conventional method in the art, such as coating, deposition, etc.

[0135] In some embodiments, the application discloses that the electrically conductive layer includes one or more of carbon-based conductive materials and conductive polymer materials. The carbon-based conductive materials include any one or more of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The conductive polymer materials include any one or more of polyaniline, polyacetylene, polypyrrole, polythiophene, and polypyridine.

[0136] The electrically conductive layer provided by the application can effectively reduce the overpotential of the sodium metal layer during deposition, thereby relieving the non-uniform metal deposition of the negative electrode interface or reducing the number of sodium dendrites. That is, the application is beneficial to reduce the probability of sodium dendrites by arranging the electrically conductive layer on the surface of the negative current collector.

[0137] In some embodiments, the application discloses that the thickness of the negative current collector is 5 μm to 60 μm. The thickness of the negative current collector in the application includes the distance between the opposite two end surfaces of the negative current collector along a certain direction, such as the x-axis direction in FIG. 9. The measurement method includes any conventional measurement method in the art, such as direct measurement or calculation after taking a picture. In some embodiments, the application discloses that the thickness of the negative current collector is any one of 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, and 60 μm.

[0138] In some embodiments, the application discloses that the thickness of the sodium metal layer is 5 μm to 100 μm.

[0139] The sodium metal battery provided in the application can form a sodium metal layer on the surface of the negative current collector during the first charging, which can be obtained by taking a picture, such as scanning the negative electrode sheet of the sodium metal battery by using a transmission electron microscope (TEM), and then measuring the distance between the opposite two end faces of the sodium metal layer along the x-axis direction in FIG. 9, that is, the thickness value. In some embodiments, the thickness of the conductive layer is 100 nm to 7 μm. As described above, the thickness of the conductive layer of the application includes the distance between the opposite two end faces of the conductive layer along a certain direction, such as the x-axis direction in FIG. 9, and the measurement method includes the conventional measurement method in the art, such as direct measurement or calculation after taking a picture.

[0140] Method for preparing a sodium metal battery

[0141] In some embodiments, the application discloses a method for preparing a sodium metal battery, which comprises the following processes:

[0142] Preparation of the isolation film: disperse the elastomer particles and the binder into an organic solvent to form a slurry, coat the slurry on at least one side surface of the base film, and dry to form a first coating layer;

[0143] Assemble the isolation film, the positive electrode sheet and the negative electrode sheet together to form a sodium metal battery.

[0144] In some embodiments, the application discloses that the elastomer particles have any one or more of the following morphologies: spherical, spherical-like, regular or irregular polygonal. The elastomer particles of the application have these morphologies, which are convenient for preparing the coating layer.

[0145] In some embodiments, the application discloses that the volume particle size distribution Dv50 of the elastomer particles is 3 μm to 50 μm.

[0146] The measurement method of the volume particle size distribution Dv50 of the elastomer particles of the application includes: referring to GB / T19077 2016, obtaining the volume particle size distribution curve of the particles, and taking the particle size corresponding to the cumulative volume distribution percentage of 50% as the average particle size Dv50. The test instrument can be a Mastersizer 3000 type laser particle size analyzer of Malvern Instruments Ltd., UK. The solvent used is deionized water, and the particles are ultrasonically treated for about 5 min before testing.

[0147] The present application discloses in these embodiments that the volume particle size distribution Dv50 of the elastomer particles is any one of 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, 35 μm, 36 μm, 37 μm, 38 μm, 39 μm, 40 μm, 41 μm, 42 μm, 43 μm, 44 μm, 45 μm, 46 μm, 47 μm, 48 μm, 49 μm, 50 μm or meets any one of the above range values.

[0148] The present application discloses in some embodiments that the specific surface area BET of the elastomer particles is 0.5 m 2 / g to 15 m 2 / g.

[0149] The measurement method of the specific surface area BET of the elastomer particles of the present application includes: referring to GB / T 195872004, using the nitrogen adsorption specific surface area analysis test method for testing, and using the BET (Brunauer Emmett Teller) method to calculate the specific surface area of the particles. The testing instrument can be a TRISTAR II 3020 type specific surface area and porosity analyzer of the Micromeritics company in the United States.

[0150] The present application discloses in these embodiments that the specific surface area BET of the elastomer particles is 0.5 m 2 / g, 1 m 2 / g, 1.5 m 2 / g, 2 m 2 / g, 2.5 m 2 / g, 3 m 2 / g, 3.5 m 2 / g, 4 m 2 / g, 4.5 m 2 / g, 5 m 2 / g, 5.5 m 2 / g, 6 m 2 / g, 6.5 m 2 / g, 7 m 2 / g, 7.5 m 2 / g, 8 m 2 / g, 8.5 m 2 / g, 9 m 2 / g, 9.5 m 2 / g, 10 m 2 / g, 10.5 m2 / g, 11 m 2 / g, 11.5 m 2 / g, 12 m 2 / g, 12.5 m 2 / g, 13 m 2 / g, 13.5 m 2 / g, 14 m 2 / g, 14.5 m 2 / g, 15 m 2 / g, 15 m

[0151] In some embodiments, the elastomer particles include any one or more of a thermoplastic polyester elastomer, a thermoplastic dynamic vulcanizate, and a thermoplastic polyurethane elastomer.

[0152] In the above embodiments, the material of the first coating layer is discussed, and is not repeated here.

[0153] In some embodiments, the elastomer particles have a porous structure, and the porous structure includes mesopores with an average pore size of 2 nm to 50 nm.

[0154] In these embodiments, the average pore size of the mesopores in the porous structure of the elastomer particles is measured by any method in the art. For example, the distribution of each pore is measured by a test instrument in the art, and the number of each pore is counted, and then the average pore size is calculated by a mathematical function. The pore volume and specific surface area of the porous structure can also be obtained by adsorption and desorption isotherms, and the average pore size is obtained by dividing the pore volume by the specific surface area and multiplying the model coefficient according to the relevant pore model. For example, the test instrument is ASAP2460-physical adsorption analyzer, the elastomer particle sample after drying and degassing treatment is placed in liquid nitrogen, different test pressures are adjusted, the adsorption amount of nitrogen is measured respectively, and the adsorption and desorption isotherms are drawn, then the pore volume and specific surface area of the elastomer particles are obtained according to the adsorption and desorption isotherms, and the average pore size of the elastomer particles is calculated.

[0155] In these embodiments, the elastomer particles have a porous structure, so that the first coating layer formed under the premise of the above compression deformation amount can also meet the above porosity requirement.

[0156] The present application also discloses in some embodiments that the elastomer particles have a solid structure, and the elastomer particles with the solid structure are added with a pore-forming agent in the process of preparing the first coating layer. The pore-forming agent includes any one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, vinylene carbonate, diethylene glycol dimethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, and dipropylene glycol dimethyl ether. The pore-forming agent is added in an amount of 100% to 1000% of the weight of the adhesive, so that the first coating layer formed can meet the porosity requirement.

[0157] The present application discloses in some embodiments that the mass ratio of the elastomer particles to the adhesive is (60% to 95%):(5% to 40%).

[0158] The present application discloses in these embodiments that the first coating layer contains the elastomer particles and the adhesive, and the mass ratio of the elastomer particles to the adhesive is any one of 60%:40%, 70%:30%, 80%:20%, 90%:10%, 95%:5% or meets any one of the above range values.

[0159] The present application discloses in some embodiments that the adhesive includes any one or more of an acrylic monomer copolymer and / or homopolymer, polyvinyl alcohol, a vinylidene fluoride polymer, a vinylidene fluoride-hexafluoropropylene copolymer, a vinylidene fluoride-pentafluoropropylene copolymer, a vinylidene fluoride-tetrafluoropropylene copolymer, a vinylidene fluoride-trifluoropropylene copolymer, a vinylidene fluoride-perfluorobutene copolymer, a vinylidene fluoride-tetrafluoroethylene copolymer, a vinylidene fluoride-trifluoroethylene copolymer, a vinylidene fluoride-trifluorochloroethylene copolymer, or a vinylidene fluoride-fluoroethylene copolymer, a saccharide monomer copolymer and / or homopolymer, an acrylic monomer copolymer and / or homopolymer, a styrene monomer copolymer and / or homopolymer, a butadiene monomer copolymer and / or homopolymer, a phenol monomer copolymer and / or homopolymer, an aldehyde monomer copolymer and / or homopolymer, a diatomic amine monomer copolymer and / or homopolymer, a diatomic anhydride monomer copolymer and / or homopolymer, a benzene ring monomer copolymer and / or homopolymer, or any derivative or modification thereof.

[0160] The present application discloses in these embodiments that the second coating layer contains an inorganic filler and an adhesive. The inorganic filler is as described above, and the adhesive in the second coating layer is as described above. The mass ratio of the inorganic filler to the adhesive is (75% to 95%):(5% to 25%). The second coating layer is formed by dispersing the inorganic filler and the adhesive in an organic solvent and then coating one side surface of the base film, and then dried to form the second coating layer.

[0161] [Separation film]

[0162] According to some embodiments of the present application, the separator film comprises a base film and a first coating layer on at least one surface of the base film, and the first coating layer has a compression deformation of 20% to 80% under a positive pressure of 1 MPa to 3 MPa.

[0163] The deformation of the first coating layer of the present application refers to the thickness of the coating layer before compression deformation as h1, and the thickness of the coating layer after compression deformation as h2, and the calculation value of (h1-h2) / h1*100%. The thickness of the coating layer refers to the difference between the two end surfaces of the coating layer in the direction of the battery stack, which can be measured by a laser thickness gauge commonly used in the art.

[0164] According to some embodiments of the present application, the porosity of the first coating layer without compression deformation is A1, the porosity of the first coating layer under a compression deformation of 20% to 80% is A2, and the porosity of the base film is A0; A2≤A0<A1 is satisfied.

[0165] According to some embodiments of the present application, the porosity A1 of the first coating layer without compression deformation is 40% to 90%.

[0166] The porosity A2 of the first coating layer under a compression deformation of 20% to 80% is 20% to 45%.

[0167] The porosity A0 of the base film is 30% to 50%.

[0168] The measurement method of the porosity of the separator film of the present application includes various methods commonly used in the art, such as the weighing method: the volume of the separator film is tested, and the volume of the pores in the separator film is calculated by the true density of the separator film material to obtain the porosity; the mercury injection method, the standard reference is GB / T21650.2-2008 "Determination of Pore Size Distribution and Porosity of Solid Materials by Mercury Porosimetry and Gas Adsorption Part 2: Analysis of Mesopores and Macropores by Gas Adsorption", and in addition, the following methods are used to measure or calculate:

[0169] For example, the coating sample or base film sample after drying treatment is cut into a square sample of about 20 mm x 20 mm, the thickness and actual side length are measured by a digital screw micrometer and a vernier caliper, the volume V is calculated, and the weight M0 is measured, then the square sample is immersed in an electrolyte, taken out after soaking for 2 hours at room temperature and in air, and the surface adsorbed electrolyte is absorbed, and then the weight M is measured. t The porosity of the coating sample or base film sample satisfies the following mathematical relationship:

[0170] Porosity=(M t -M0) / p*V*100%;

[0171] The ρ in the above mathematical relationship is the density of the electrolyte, in mm 3 / g, V is the volume of the square sample of the coating sample or the base film sample, in mm 3 , the weight M0 and M t The weight measuring instrument is a thousandth scale, and the model of the thousandth scale, the digital screw micrometer, and the vernier caliper includes but is not limited to any model in the art.

[0172] The application discloses a method for measuring the porosity of the first coating with a compression deformation amount of 20% to 80%, which comprises: applying pressure to the coating to form a coating sample with a compression deformation amount of 20% to 80%, and then taking the same measurement method as above for the coating sample.

[0173] The application discloses that the porosity A1 of the first coating without a compression deformation amount is any one of 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90% or any one of the above range values in some embodiments.

[0174] The application discloses that the porosity A2 of the first coating with a compression deformation amount of 20% to 80% is any one of 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45% or any one of the above range values in some embodiments.

[0175] The application discloses that the air permeability of the separation film is ≤350 s / 100cc in some embodiments.

[0176] The application discloses that the air permeability of the separation film is 200 s / 100cc to 350 s / 100cc in some embodiments.

[0177] The application discloses that the air permeability of the separation film is 200 s / 100cc to 300 s / 100cc in some embodiments.

[0178] The air permeability of the isolation film of the present application refers to the amount of gas permeated by the isolation film under a certain time pressure, and the industry is used to express it by the Gurley value, which means the time required for 100 mL of oxygen to permeate through 1 square inch (which can be converted into 1 square centimeter) of the isolation film under a pressure of 1.22 KPa. Generally speaking, the air permeability of the isolation film is related to various parameters such as its thickness, pore size, porosity and pore tortuosity. By selecting an appropriate air permeability of the isolation film, the probability of sodium dendrite piercing the isolation film can be reduced under the premise of ensuring the normal conduction of ions in the battery.

[0179] The present application discloses, in some embodiments, that the material of the first coating layer includes any one or more of thermoplastic polyester elastomer, thermoplastic dynamic vulcanized rubber and thermoplastic polyurethane rubber.

[0180] The thermoplastic polyester elastomer (TPEE) in the present application is a block copolymer, which includes high-melting-point, high-hardness crystalline polyester hard segments and low-glass-transition-temperature amorphous polyether or polyester soft segments. The crystalline polyester hard segments play a physical crosslinking role, and the amorphous polyether or polyester soft segments impart high resilience to the block copolymer.

[0181] The present application discloses, in these embodiments, that the average relative molecular mass of the thermoplastic polyester elastomer is 100,000-150,000 g / mol.

[0182] The average relative molecular mass of the present application refers to the average relative molar mass for a single component, and refers to the ratio between the mass and molar mass of the mixed components for mixed components. The average relative molecular mass of the thermoplastic polyester elastomer is any one of 100,000, 200,000, 300,000, 400,000, 500,000, 600,000, 700,000, 800,000, 900,000, 1,000,000, 1,100,000, 1,200,000, 1,300,000, 1,400,000 and 1,500,000.

[0183] The present application discloses, in these embodiments, that the thermoplastic polyester elastomer includes first hard segments and first soft segments, and the mass ratio of the first hard segments to the first soft segments is (5-70):(30-95); the first hard segments include any one or more of polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polylactic acid (PLA) and polybutylene adipate (PBAT), and the first soft segments include any one or more of polyethylene glycol ether, polypropylene glycol ether, polybutylene glycol ether, polylactide, polyglycolide, polycaprolactone, polyethylene oxide (PEO), polypropylene oxide (PPG), polytetrahydrofuran (PTMEG), polybutylene oxide (PEB) and polyepichlorohydrin (PEC).

[0184] The application also discloses in these embodiments that the mass ratio of the first hard segment to the first soft segment in the thermoplastic polyester elastomer is any one of 5:95, 10:90, 20:80, 30:70, 40:60, 50:50, 60:40, 70:30.

[0185] The thermoplastic dynamic vulcanization rubber (TPV) of the application refers to a blended material prepared by a dynamic vulcanization technology, which has high elasticity of rubber at room temperature and can be melt plasticized at high temperature, and has excellent properties of both rubber and thermoplastic resin. Therefore, the thermoplastic dynamic vulcanization rubber (TPV) mainly consists of two parts: one is a thermoplastic resin as a continuous phase, and the other is a rubber as a dispersed phase. The application discloses in these embodiments that the average relative molecular mass of the thermoplastic dynamic vulcanization rubber is 50,000-1,000,000 g / mol, and the meaning of the average relative molecular mass herein is the same as above. The average relative molecular mass of the thermoplastic dynamic vulcanization rubber is any one of 50,000, 100,000, 200,000, 300,000, 400,000, 500,000, 600,000, 700,000, 800,000, 900,000, 1,000,000.

[0186] The application discloses in these embodiments that the thermoplastic dynamic vulcanization rubber comprises a thermoplastic resin and a rubber, and the mass ratio of the thermoplastic resin to the rubber is (10-80):(20-90). The thermoplastic resin comprises any one or more of polypropylene (PP), polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC), thermoplastic elastomer (TPE), polybutylene terephthalate (PBT), nylon, polyphenyl ether and polycarbonate; and the rubber comprises any one or more of ethylene-propylene-diene monomer rubber (EPDM), natural rubber (NR), nitrile rubber (NBR), styrene butadiene rubber (SBR), isoprene rubber, butyl rubber, ethylene-propylene rubber, ethylene-vinyl acetate copolymer, acrylate rubber and ethylene-acrylate copolymer. The application also discloses in these embodiments that the mass ratio of the thermoplastic resin to the rubber is any one of 10:90, 20:80, 30:70, 40:60, 50:50, 60:40, 70:30, 80:20.

[0187] The thermoplastic polyurethane rubber (TPU) of the application is a kind of elastomer which can be plasticized by heating and dissolved by solvent, and is a kind of (AB) nThe thermoplastic polyurethane rubber disclosed in the present application is a segmented linear polymer, A is a polyester or a polyether with a high molecular weight (1000-6000), B is a diol containing 2-12 linear carbon atoms, and the chemical structure between AB segments is diisocyanate. The present application discloses that the average relative molecular weight of the thermoplastic polyurethane rubber in these embodiments is 500,000-1,000,000, and the unit is g / mol. The average relative molecular weight of the thermoplastic polyurethane rubber disclosed in the present application is any one of 500,000, 1,000,000, 2,000,000, 3,000,000, 4,000,000, 5,000,000, 6,000,000, 7,000,000, 8,000,000, 9,000,000, and 10,000,000.

[0188] The present application also discloses that the thermoplastic polyurethane rubber comprises a second hard segment and a second soft segment, the mass ratio of the second hard segment to the second soft segment is (10-80):(20-90); the second hard segment comprises any one or more of polybutylene terephthalate (PBT), polydiol adipate (PTT), polyether-based polyurethane (a hard segment formed by the reaction of a polyether diol and an isocyanate), polycarbonate-based polyurethane (a hard segment formed by the reaction of a polycarbonate diol and an isocyanate), and polyether ester-based polyurethane; and the second soft segment comprises any one or more of polytetrahydrofuran (PTMG), polypropylene oxide (PPG), polyethylene glycol (PEG), polypropylene glycol (PPG), and polybutylene glycol (PBG). The present application discloses that the mass ratio of the second hard segment to the second soft segment in these embodiments is any one of 10:90, 20:80, 30:70, 40:60, 50:50, 60:40, 70:30, and 80:20.

[0189] The present application discloses in some embodiments that the first coating layer contains a bonding agent, and the mass percentage content of the bonding agent in the above-mentioned first coating layer is 5%-40%.

[0190] The present application discloses in the above-mentioned embodiments that the material of the first coating layer contains any one or more of a thermoplastic polyester elastomer, a thermoplastic dynamic vulcanized rubber, and a thermoplastic polyurethane rubber, and in addition to the above, a bonding agent is also contained, which is used for bonding between the materials of the first coating layer and bonding the materials of the first coating layer to the base film. The present application discloses in these embodiments that the mass percentage content of the bonding agent in the above-mentioned first coating layer is any one of 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, and 40%, or any one of the above-mentioned range values.

[0191] The present application also discloses specific types of binders in these embodiments, including at least one of an acrylic monomer copolymer and / or homopolymer, a polyvinyl alcohol, a vinylidene fluoride polymer, a vinylidene fluoride-hexafluoropropylene copolymer, a vinylidene fluoride-pentafluoropropylene copolymer, a vinylidene fluoride-tetrafluoropropylene copolymer, a vinylidene fluoride-trifluoropropylene copolymer, a vinylidene fluoride-perfluorobutylene copolymer, a vinylidene fluoride-tetrafluoroethylene copolymer, a vinylidene fluoride-trifluoroethylene copolymer, a vinylidene fluoride-trifluorochloroethylene copolymer, or a vinylidene fluoride-vinyl fluoride copolymer, a saccharide monomer copolymer and / or homopolymer, an acrylic monomer copolymer and / or homopolymer, a styrene monomer copolymer and / or homopolymer, a butadiene monomer copolymer and / or homopolymer, a phenol monomer copolymer and / or homopolymer, an aldehyde monomer copolymer and / or homopolymer, a diatomic amine monomer copolymer and / or homopolymer, a diatomic anhydride monomer copolymer and / or homopolymer, a benzene ring monomer copolymer and / or homopolymer, or a derivative thereof, a modified product thereof.

[0192] In the present application, the monomers in the acrylic monomer copolymer and / or homopolymer include any one or more of methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, t-butyl acrylate, n-propyl acrylate, cyclohexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate.

[0193] The saccharide monomer copolymer and / or homopolymer in the present application includes carboxymethyl cellulose, sodium alginate. The acrylic monomer copolymer and / or homopolymer in the present application includes polyacrylic acid. The styrene monomer copolymer and / or homopolymer in the present application includes butadiene styrene rubber, a styrene monomer-butadiene monomer-styrene monomer block copolymer. The aldehyde monomer copolymer and / or homopolymer in the present application includes phenolic resin. The diatomic amine monomer copolymer and / or homopolymer in the present application includes polyimide.

[0194] The present application discloses, in some embodiments, that the material of the base film includes one or more of polyethylene, polypropylene, poly-p-phenyleneterephthalamide, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, and polyamide.

[0195] The present application discloses, in some embodiments, that the release film includes a base film, and a first coating layer on both sides of the base film.

[0196] The present application discloses, in some embodiments, that the release film includes a base film, a first coating layer on one side of the base film, and a second coating layer on the other side of the base film.

[0197] In some embodiments, the second coating layer comprises an inorganic filler, which includes any one or more of boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon oxide compound, tin dioxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, hafnium dioxide, cerium oxide, zirconium titanate, barium titanate, and magnesium fluoride.

[0198] In some embodiments, the second coating layer further comprises a binder, which is of the same kind as the binder in the first coating layer.

[0199] In some embodiments, the second coating layer comprises a binder in a mass percentage of 5% to 25%. In these embodiments, the second coating layer comprises a binder in a mass percentage of any one of 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, or any range thereof.

[0200] [Negative electrode tab]

[0201] According to some embodiments of the present application, as described above, the negative electrode tab comprises a negative electrode current collector and a sodium metal layer on at least one side surface of the negative electrode current collector.

[0202] According to some embodiments of the present application, an electrically conductive layer is arranged between the negative electrode current collector and the sodium metal layer.

[0203] According to some embodiments of the present application, the material of the negative electrode current collector comprises at least one of a metal foil, a metal foam current collector, a metal mesh current collector, a carbon felt current collector, a carbon cloth current collector, a carbon paper current collector, and a composite current collector. In these embodiments, the metal foil comprises copper foil, aluminum foil, stainless steel foil, iron foil, zinc foil, titanium foil, etc. In these embodiments, the metal foam current collector comprises copper foam, aluminum foam, zinc foam, etc. In these embodiments, the metal mesh current collector comprises copper mesh, aluminum mesh, etc. Meanwhile, the negative electrode current collector can also be a composite current collector formed by combining a metal foil and a metal foam, or a composite current collector formed by combining a metal foil and a metal mesh, or a composite current collector formed by combining a metal foil and a polymer-based film, which is not particularly limited by the present application.

[0204] According to some embodiments of the present application, the conductive layer comprises one or more of carbon-based conductive materials and conductive polymer materials; wherein the carbon-based conductive materials comprise any one or more of graphite, superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers; and the conductive polymer materials comprise any one or more of polyaniline, polypyrrole, polyacetylene, polyphenyl, polythiophene, and polypyridine.

[0205] According to some embodiments of the present application, the thickness of the negative current collector is 5 μm to 60 μm; the thickness of the negative current collector in the present application includes the distance between the opposite two end surfaces of the negative current collector along a certain direction, such as the x-axis direction in FIG. 9 of the specification, and the measurement method includes the conventional measurement method in the art, such as direct measurement or calculation after taking a photo. The present application discloses in these embodiments that the thickness of the negative current collector is any one of 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, and 60 μm.

[0206] According to some embodiments of the present application, the thickness of the sodium metal layer is 5 μm to 100 μm. The sodium metal battery provided by the present application can form a sodium metal layer on the surface of the negative current collector during the first charging, which can be taken by a photo shooting method, such as scanning the negative electrode sheet of the sodium metal battery by using a transmission electron microscope (TEM) to obtain the microstructure of the sodium metal layer, and then measuring to obtain the distance between the opposite two end surfaces of the sodium metal layer along the x-axis direction in FIG. 9, that is, the thickness value. The present application discloses in these embodiments that the thickness of the sodium metal layer is any one of 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, and 100 μm. According to some embodiments of the present application, the thickness of the conductive layer is 100 nm to 7 μm. As described above, the thickness of the conductive layer in the present application includes the distance between the opposite two end surfaces of the conductive layer along a certain direction, such as the x-axis direction in FIG. 9 of the specification, and the measurement method includes the conventional measurement method in the art, such as direct measurement or calculation after taking a photo.

[0207] [Positive electrode sheet]

[0208] According to some embodiments of the present application, the positive electrode sheet comprises a positive current collector and a positive film layer located on at least one side surface of the positive current collector. Wherein the positive electrode sheet comprises a positive current collector and a positive film layer located on at least one side surface of the positive current collector, and the positive film layer comprises a sodium ion positive active material.

[0209] According to some embodiments of the present application, the sodium-ion positive electrode active material comprises, but is not limited to, at least one of sodium transition metal oxides, polyanionic compounds, Prussian blue type compounds. However, the present application is not limited to these materials, and other conventionally known materials that can be used as sodium-ion battery positive electrode active materials can also be used.

[0210] In the present application, the transition metal in the sodium transition metal oxide can be one or more than two of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce.

[0211] The sodium transition metal oxide in the present application can be a layered transition metal oxide, and the chemical formula of the layered transition metal oxide is Na x M y O z , wherein M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, 0

[0212] The polyanionic compound in the present application can be a compound having sodium ions, transition metal ions, tetrahedral (YO4) n- valence. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce; Y can be at least one of P, S and Si, and n represents the valence of (YO4) n- .

[0213] The polyanionic compound in the present application can also be a compound having sodium ions, tetrahedral (YO4) n- anion unit, polyhedral unit (ZO y ) m+ and optional halogen anion. Y can be at least one of P, S and Si, and n represents the valence of (YO4) n- ; Z represents a transition metal, which can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, and m represents the valence of (ZO y ) m+ ; halogen can be at least one of F, Cl and Br.

[0214] The polyanionic compound in the present application comprises at least one of sodium iron pyrophosphate (NaFePO4), sodium vanadium phosphate (Na3V2(PO4)3), NaM’PO4F (M’ is one or more of V, Fe, Mn and Ni) and Na3(VO y )2(PO4)2F 3-2y (0≤y≤1).

[0215] The polyanionic compound in the present application includes any one or more of sodium vanadophosphate, sodium vanadofluorophosphate, sodium vanadophosphate, sodium iron pyrophosphate, and sodium iron pyrophosphate.

[0216] The Prussian blue compound in the present application can be a compound having sodium ions, transition metal ions, and cyanide ions (CN - ). The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The Prussian blue compound is, for example, Na a Me b Me’ c (CN)6, wherein Me and Me’ are each independently at least one of Ni, Cu, Fe, Mn, Co, and Zn, 0 < a < 2, 0 < b < 1, and 0 < c < 1.

[0217] The positive electrode film layer in some embodiments of the present application can further include a conductive agent to improve the conductivity of the positive electrode. The type of conductive agent is not specifically limited in the present application and can be selected according to actual needs. As an example, the conductive agent can be one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphite, graphene, and carbon nanofibers.

[0218] The positive electrode film layer in some embodiments of the present application can further include a binder to firmly bond the sodium-ion positive electrode active material and the optional conductive agent to the positive electrode current collector. The type of binder is not specifically limited in the present application and can be selected according to actual needs. As an example, the binder can include, but is not limited to, one or a combination of two or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, a fluorine-containing acrylate resin, a styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, carboxymethyl chitosan, and the like.

[0219] The positive electrode current collector in some embodiments of the present application can be a conductive carbon sheet, a metal foil, a carbon-coated metal foil, a porous metal plate, or a composite current collector. The conductive carbon material of the conductive carbon sheet can be one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphite, graphene, and carbon nanofibers. The metal material of the metal foil, the carbon-coated metal foil, and the porous metal plate can each independently be at least one of copper, aluminum, nickel, and stainless steel. The composite current collector can be a composite current collector formed by combining a metal foil and a polymer-based film.

[0220] The positive current collector is, for example, one or more of a copper foil, an aluminum foil, a nickel foil, a stainless steel foil, a stainless steel mesh, and a carbon-coated aluminum foil, and preferably an aluminum foil.

[0221] The positive electrode tab can be prepared according to conventional methods in the art. Typically, the sodium-ion positive active material and optionally the conductive agent and the binder are dispersed in a solvent (e.g., N-methylpyrrolidone, abbreviated as NMP) to form a uniform positive electrode slurry, the positive electrode slurry is coated on both sides of the positive current collector, and the positive electrode tab is obtained after drying, cold pressing, etc.

[0222] [Electrolyte]

[0223] In some embodiments of the present application, the sodium metal battery further comprises an electrolyte, which can be in a liquid state, a solid state, or a gel state. Among them, the solid state is a solid electrolyte, the liquid state is a liquid electrolyte, and the gel state is a gel electrolyte. The sodium metal battery of the present application uses a liquid electrolyte, that is, an electrolyte. The electrolyte comprises an electrolyte salt and an organic solvent. Among them, the type of electrolyte salt comprises any type of conventional in the art, such as, including but not limited to inorganic metal salts, such as NaClO4, NaAsF6, NaPF6, NaBF4, NaSbF6, NaSO3F, NaN(FSO2)2, etc.; fluorine-containing organic metal salts, such as NaCF3SO3, NaN(FSO2)(CF3SO2), NaN(CF3SO2)2, NaN(C2F5SO2)2, sodium cyclic 1,3-hexafluoropropylene disulfonimide, sodium cyclic 1,2-tetrafluoroethane disulfonimide, NaN(CF3SO2)(C4F9SO2), NaC(CF3SO2)3, NaPF4(CF3)2, NaPF4(C2F5)2, NaPF4(CF3SO2)2, NaPF4(C2F5SO2)2, NaBF2(CF3)2, NaBF2(C2F5)2, NaBF2(CF3SO2)2, NaBF2(C2F5SO2)2, etc.; and dicarboxylic acid complex metal salts, such as sodium bis(oxalato)borate, sodium difluoro(oxalato)borate, sodium tris(oxalato)phosphate, sodium difluoro bis(oxalato)phosphate, sodium tetrafluoro(oxalato)phosphate, etc.

[0224] According to some embodiments of the present application, the electrolyte salt has a concentration of 0.1 mol / L to 4 mol / L in the electrolyte. The present application discloses any one of the concentration of the electrolyte salt of 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L, 2.2 mol / L, 2.5 mol / L, 2.8 mol / L, 3 mol / L, 3.2 mol / L, 3.5 mol / L, 3.8 mol / L, 4 mol / L or satisfies any one of the above range values.

[0225] As described above, the organic solvent includes any one or more of carboxylic acid ester compounds, carbonate compounds, and ether compounds. Among them, the carboxylic acid ester compounds include one or more of ethyl acetate (EA), methyl acetate (MA), ethyl propionate (EP), propyl acetate (PA), methyl propionate (MP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL); the carbonate compounds include one or more of ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl ethyl carbonate (EMC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC); and the ether compounds include at least one of tetrahydrofuran, dimethyl tetrahydrofuran, tetrahydropyran, dimethyl tetrahydropyran, 1,2-dimethoxyethane, dipropylene glycol dimethyl ether, or dimethyl phthalate. The organic solvent of the present application further includes one or both of a nitrile solvent and a sulfone solvent, the nitrile solvent including one or more of acetonitrile (AN), glutaronitrile (GLN), and adiponitrile (ADN); and the sulfone solvent including at least one or a combination of two of sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0226] According to some embodiments of the present application, the electrolyte further comprises a film-forming stabilizer, which comprises a positive electrode film-forming stabilizer and a negative electrode film-forming stabilizer. The positive electrode film-forming stabilizer comprises a carbonate additive and / or a sulfate additive. The carbonate additive comprises one or more of vinylene carbonate (VC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), vinyl ethylene carbonate (VEC), and dioctyl carbonate (CC). The sulfate additive comprises a cyclic sulfonate additive and / or a hydrocarbon sulfonate additive. The cyclic sulfonate additive comprises one or more of 1,3-propane sultone (PS), propene sultone (PES), and 3-fluoro-1,3-propane sultone (FPS). The hydrocarbon sulfonate additive comprises one or more of vinyl sulfonate (DTD), diethyl sulfonate (DES), and dimethyl sulfonate (DMS). The negative electrode film-forming stabilizer comprises one or more of a boron-containing sodium salt, a phosphorus-containing sodium salt, and a sulfur-containing sodium salt. The boron-containing sodium salt comprises one or more of sodium tetrafluoroborate (NaBF4), sodium bis(oxalato)borate (NaBOB), and sodium bis(fluoro oxalato)borate (NaDFOB). The phosphorus-containing sodium salt comprises one or more of sodium difluorophosphate (NaPO2F2), sodium fluorophosphate (Na2PO3F), and sodium phosphate (Na3PO4). The sulfur-containing sodium salt comprises one or more of sodium fluorosulfonate (NaFSO3), sodium sulfate (Na2SO4), and sodium sulfamate (NaSO3NH2).

[0227] The secondary battery according to the present application will be described in detail below with reference to specific examples.

[0228] The experimental methods used in the following examples are conventional methods unless otherwise specified.

[0229] The materials, reagents, etc. used in the following examples can be obtained commercially unless otherwise specified.

[0230] The present application can employ conventional techniques of inorganic chemistry within the skill of the art. In the following examples, efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.) but some experimental errors and deviations should be accounted for. Temperatures used in the following examples are in degrees Celsius, and pressures are at or near atmospheric pressure. All reagents were obtained commercially at AR grade, and all reactions were performed under an argon atmosphere. Unless otherwise indicated, all reagents were obtained from commercial sources.

[0231] The experimental materials are specifically indicated in the following table.

[0232] Table 1 Solid elastomer particles

[0233] Table 2 Porous structure elastomer particles

[0234] Example 1-1

[0235] A sodium metal battery is provided, which comprises a positive electrode sheet, a separator film and a negative electrode sheet which are sequentially stacked, and further comprises an electrolyte.

[0236] The separator film is prepared as follows:

[0237] A polyethylene separator film with a thickness of 7 μm is taken as a base film (porosity A0 is 40%);

[0238] The thermoplastic polyester elastomer particles with serial number I-1 in Table 1 above and the adhesive (PVDF) are uniformly mixed in a mass ratio of 80%:20%, and then dispersed in an organic solvent NMP to form a slurry, and then a pore-forming agent (diethyl carbonate) is added to the slurry, and the amount of the pore-forming agent added is 500% of the weight of the adhesive.

[0239] The above slurry is coated on both sides of the base film, and after drying, a first coating layer with a thickness of 31.5 μm is formed.

[0240] The electrolyte is prepared as follows:

[0241] In an environment with a water content of less than 10 ppm, non-aqueous organic solvents ethylene carbonate, diethyl carbonate and dimethyl carbonate are mixed in a volume ratio of 1:1:1 to obtain a solvent, and sodium hexafluorophosphate is added to the solvent to form an electrolyte with a sodium hexafluorophosphate concentration of 1 mol / L.

[0242] The positive electrode sheet is prepared as follows:

[0243] Na3V2(PO4)3 (93.8 w%), conductive carbon black (3.0 wt%), PVDF (2.5 wt%), dispersant (hydrogenated butyl nitrile rubber, 0.3 wt%) and residual alkali removing agent (0.4 wt%) are mixed, and the residual alkali removing agent includes any one or more of some weak acids commonly used in the art, such as maleic anhydride, benzoic acid, salicylic acid, etc., and maleic anhydride is selected in this embodiment. Then, N-methyl pyrrolidone (NMP) is added and stirred to disperse, and a positive electrode slurry is prepared. After the prepared oil-based positive electrode slurry is stirred, the slurry viscosity is adjusted to 10000 mPa.s, and the prepared slurry is not stratified, and then the slurry is coated on an Al foil by a double-sided double-cavity coating device, with a coating weight controlled at 200 mg / 1540.25 cm 2 After the double-sided coating is completed, drying, cold pressing, and cutting are performed to prepare the positive electrode sheet.

[0244] The negative electrode sheet is prepared as follows:

[0245] Single-walled carbon nanotubes (tube diameter 1-3 nm, BET 1000 m 2A dispersion of the above prepared positive electrode sheet, separator, and negative electrode sheet is dispersed in a binder (polyacrylic acid) into NMP to form a uniform slurry, and the slurry is coated on both sides of a copper foil (thickness: 8 μm) to form a negative electrode sheet, wherein the thickness of the conductive layer is 2 μm.

[0246] A sodium metal battery is prepared as follows:

[0247] A sodium metal battery is prepared as follows:

[0248] Example 1-2

[0249] A sodium metal battery is provided, which is different from Example 1-1 in that the material of the first coating layer in the separator is different, which is serial number I-2 in Table 1, and the other aspects are the same as Example 1-1.

[0250] Example 1-3

[0251] A sodium metal battery is provided, which is different from Example 1-1 in that the material of the first coating layer in the separator is different, which is serial number I-3 in Table 1, and the other aspects are the same as Example 1-1.

[0252] Comparative Example 1

[0253] A sodium metal battery is provided, which is different from Example 1-1 in that the thickness of the polyethylene separator is 7 μm. The other aspects are the same as Example 1-1.

[0254] Example 2-1

[0255] A sodium metal battery is provided, which is different from Example 1-1 in that the material of the first coating layer in the separator is different, which is serial number II-1 in Table 1, and the other aspects are the same as Example 1-1.

[0256] Example 2-2

[0257] A sodium metal battery is provided, which is different from Example 1-1 in that the material of the first coating layer in the separator is different, which is serial number III-1 in Table 1, and the other aspects are the same as Example 1-1.

[0258] Example 3-1

[0259] A sodium metal battery is provided, which is different from Example 1-1 in that the material of the first coating layer in the separator is different, which is serial number IV-1 in Table 2, and no pore-forming agent is added in the slurry during the preparation of the separator, and the other aspects are the same as Example 1-1.

[0260] Example 4-1

[0261] A sodium metal battery is provided, which differs from Example 1-1 in that a first coating layer is formed on one side of the separator film and a second coating layer is formed on the other side. The specific steps are as follows: a polyethylene separator film with a thickness of 7 μm is provided as a base film (porosity A0 is 35%);

[0262] Preparation of the first slurry: the thermoplastic polyester elastomer particles of No. I-1 in Table 1 above and the binder (PVDF) are mixed in a mass ratio of 80%:20% and then dispersed in the organic solvent NMP to form a slurry, and then the pore-forming agent (diethyl carbonate) is added to the slurry, and the amount of the pore-forming agent added is 500% of the weight of the binder, to form the first slurry;

[0263] Preparation of the second slurry: the silica (Dv50 is 3.2 μm) and the binder (PVDF) are mixed in a mass ratio of 90%:10% and then dispersed in the organic solvent NMP to form a second slurry;

[0264] The first slurry is coated on one side of the base film, and the second slurry is coated on the other side of the base film. After drying, the thickness of the first coating layer is 31.5 μm, and the thickness of the second coating layer is 2 μm.

[0265] Example 5-1

[0266] A sodium metal battery is provided, which differs from Example 1-1 in that the porous structure elastomer particles and the binder are mixed in a mass ratio of 95%:5% and then dispersed in the organic solvent NMP to form a slurry; the other aspects remain the same as in Example 1-1.

[0267] Example 6-1

[0268] A sodium metal battery is provided, which differs from Example 1-1 in that the negative electrode tab is made of a copper foil with a thickness of 8 μm, and the other aspects remain the same as in Example 1-1.

[0269] [Performance Test]

[0270] ① Test the compression deformation of the coating layer:

[0271] A universal testing machine (MDTC-EQ-M12-01) is used for testing. The coating layer sample is placed on the sample testing table, and a load is applied to the coating layer. The specific testing steps are as follows:

[0272] Step 1, select the separator film to be tested: through multi-layer stacking test, the thickness of the coating layer sample is controlled to be ≥1 mm, and the error accuracy is controlled;

[0273] Step 2, initial thickness collection: apply an initial pressure (try initial value ≥ 0.05 MPa) to the coating sample to obtain the initial thickness of the release film sample under this constant pressure;

[0274] Step 3, compression modulus collection: continuously apply pressure to the coating sample until the thickness is constant, and the pressure / pressure appears an exponential rising inflection point, then it is considered that the data collection has been completed, the initial segment slope of the stress-strain curve corresponds to the compression modulus of this coating sample, and thus the compression modulus of different target samples is obtained, and the stress-strain curve is analyzed,

[0275] Step 4, read the compression ratio and rebound ratio corresponding to the target pressure from the stress-strain curve; the compression ratio and rebound ratio corresponding to 1 MPa-3 MPa are selected in this application.

[0276] ②Test the porosity of the coating:

[0277] The coating sample after drying treatment is cut into a square sample of about 20 mm x 20 mm, the thickness and actual side length are measured by a digital screw micrometer and a vernier caliper, the volume V is calculated, and the weight M0 is measured, then the square sample is immersed in an electrolyte, taken out after 2 hours of immersion at room temperature and in air atmosphere, and the electrolyte liquid adsorbed on the surface is absorbed, then the weight M is measured. t The porosity of the coating sample satisfies the following mathematical relationship:

[0278] Porosity = (M t -M0) / p x V x 100%;

[0279] In the above mathematical relationship, p is the density of the electrolyte in Example 1-1, the unit is mm 3 / g, V is the volume of the square sample of the coating sample, the unit is mm 3 , the weight M0 and M t are in units of g, the weight measuring instrument is a thousandth balance, and the model of the thousandth balance, the digital screw micrometer, and the vernier caliper includes but is not limited to any model in the conventional art.

[0280] The application provides a method for measuring the porosity of a first coating with a compression deformation of 20%-80%, which comprises: applying pressure to the coating to form a coating sample with a compression deformation of 20%-80%, and then taking the same measurement method as described above for the coating sample.

[0281] ③Test the air permeability of the release film:

[0282] Specifically, the MP010 Gurley method for air permeability analysis disclosed in GB / T 458-2008 is referred to. The test unit of air permeability is s / 100 mL (time of 100 mL of gas permeation).

[0283] 4. Test the thickness of the sodium metal layer:

[0284] Dismantle the glove box to obtain the negative electrode sheet of the battery prepared in the above examples and comparative examples, and prepare samples. Transfer using a vacuum transfer box, and cut into appropriate size samples. Fix the samples on the sample stage with conductive glue, and ensure that the samples are flat and well conductive. Turn on the Zeiss Sigma300 ion polishing system, preheat the equipment, and set the initial working parameters, including ion beam energy, tilt angle, polishing time, etc. Use lower ion beam energy for initial cutting to quickly remove impurities on the surface of the sample. Adjust the tilt angle of the sample stage, use the ion beam to cut the sample cross section at an angle to form a suitable cross section for observation, gradually reduce the ion beam energy, and polish the sample surface carefully to reduce surface damage. Perform final polishing at a lower energy until the sample surface reaches the desired smoothness and clarity. After polishing, wash the sample surface with an appropriate solvent to remove residual polishing liquid, dry the sample, and prepare for SEM observation. Take the polished sample out of the ion polishing system and transfer it to the sample chamber of the scanning electron microscope (SEM). Observe the sample under the SEM, use the device's built-in function ruler to measure the thickness of the deposited metal layer, and analyze the thickness distribution of the metal cross section (generally test 2-3 samples at different positions, test one thickness at an interval of 50 um for each sample, and take the average thickness of the tested samples as the average thickness output. Due to consistency and test error, the thickness average output is rounded to 0.5 decimal places).

[0285] 5. Test the capacity retention rate of the battery after 200 cycles at 25°C:

[0286] Place the batteries prepared in the examples and comparative examples in a constant temperature oven at 25°C, and test the cycle life according to the process:

[0287] 1) Stand for 10h;

[0288] 2) 0.1C constant current charging to 3.65V, 3.65V constant voltage charging to 0.05C0;

[0289] 3) Stand for 30min;

[0290] 4) 0.1C constant current discharging to 1.5V;

[0291] 5) Stand for 30min;

[0292] 6) 0.33C constant current charging to 3.65V, 3.65V constant voltage charging to 0.05C0;

[0293] 7) Stand for 30min;

[0294] 8) 0.33C constant current discharging to 1.5V;

[0295] 9) rest for 30 min;

[0296] 10) repeat step 6) to step 9) for 3 times;

[0297] 11) 1C constant current charge to 3.65V, 3.65V constant voltage charge to 0.05C0;

[0298] 12) rest for 30 min;

[0299] 13) 1C constant current discharge to 1.5V;

[0300] 14) rest for 30 min;

[0301] Record the discharge capacity at this time, which is the initial discharge capacity.

[0302] Repeat steps 11) to 14) for 200 times, and record the discharge capacity of the 200th time, which is the terminal discharge capacity.

[0303] The capacity retention rate after 200 cycles is the terminal discharge capacity / initial discharge capacity x 100%.

[0304] (6) 25℃, detect the internal short circuit of the battery after 200 cycles:

[0305] According to the detection method of the above (5), the battery is subjected to cyclic charging and discharging:

[0306] 1) rest for 10h;

[0307] 2) 0.1C constant current charge to 3.65V, 3.65V constant voltage charge to 0.05C0;

[0308] 3) rest for 30 min;

[0309] 4) 0.1C constant current discharge to 1.5V;

[0310] 5) rest for 30 min;

[0311] 6) 0.33C constant current charge to 3.65V, 3.65V constant voltage charge to 0.05C0; record the charge capacity

[0312] 7) rest for 30 min;

[0313] 8) 0.33C constant current discharge to 1.5V; record the discharge capacity;

[0314] 9) rest for 30 min;

[0315] Coulomb efficiency = charge capacity / discharge capacity;

[0316] 10) Repeat step 6) to step 9) for 3 times, and calculate the coulombic efficiency according to the above formula each time;

[0317] 11) 1C constant current charging to 3.65V, 3.65V constant voltage charging to 0.05C0;

[0318] 12) Stand for 30 min;

[0319] 13) 1C constant current discharging to 1.5V;

[0320] 14) Stand for 30 min;

[0321] Repeat steps 11) to 14) for 200 times.

[0322] If the coulombic efficiency is greater than or equal to 1.1 for 3 times, it is judged that the battery cell is short-circuited.

[0323] Table 3 Performance of the separator

[0324] Table 4 Performance of the battery (I)

[0325] Table 5 Performance of the battery (II)

[0326] As can be seen from the above list, the design provided by the present application can provide a buffer for the deposition of the sodium metal layer of the negative pole piece, and the number of sodium dendrites generated is reduced to improve the safety of the sodium metal battery. At the same time, the pressure exerted by the generated sodium dendrites on the coating at a certain position of the separator is also easily dispersed to other positions, reducing the probability of piercing the separator, further improving the safety of the sodium metal battery, and at the same time, under safe use, it is also conducive to ensuring the stability of the cycle capacity retention rate of the battery.

[0327] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should be covered in the scope of the claims and the specification of the present application. Especially, as long as there is no structural conflict, each technical feature mentioned in each embodiment can be combined in any way. The present application is not limited to the specific embodiments disclosed in the text, but includes all technical solutions falling within the scope of the claims.

Claims

1. A sodium metal battery, wherein: The sodium metal battery comprises a positive electrode sheet and a negative electrode sheet, the negative electrode sheet comprises a negative electrode current collector and a sodium metal layer on at least one side surface of the negative electrode current collector; The sodium metal battery further comprises a separator membrane between the positive electrode sheet and the negative electrode sheet; The separator membrane comprises a base film and a first coating layer on at least one side surface of the base film, at least part of the first coating layer faces the sodium metal layer; The first coating layer has a compression deformation amount of 20% to 80% in the sodium metal battery.

2. The sodium metal battery of claim 1, wherein: The porosity of the first coating layer without compression deformation amount is A1; The porosity of the first coating layer with a compression deformation amount of 20% to 80% is A2; The porosity of the base film is A0; A2≤A0<A1 is satisfied.

3. The sodium metal battery of claim 2, wherein: The porosity A1 of the first coating layer without compression deformation amount is 40% to 90%; The porosity A2 of the first coating layer with a compression deformation amount of 20% to 80% is 20% to 45%; The porosity A0 of the base film is 30% to 50%.

4. The sodium metal battery of any one of claims 1-3, wherein: The air permeability of the separator membrane is ≤350 s / 100cc.

5. The sodium metal battery of any one of claims 1-4, wherein: The air permeability of the separator membrane is 200 s / 100cc to 350 s / 100cc.

6. The sodium metal battery of any one of claims 1-5, wherein: The material of the first coating layer comprises any one or more of thermoplastic polyester elastomer, thermoplastic dynamic vulcanized rubber and thermoplastic polyurethane rubber.

7. The sodium metal battery of claim 6, wherein: The average relative molecular mass of the thermoplastic polyester elastomer is 100,000 to 1,500,000 g / mol; and / or; The average relative molecular mass of the thermoplastic dynamic vulcanized rubber is 50,000 to 1,000,000 g / mol; and / or; The average relative molecular mass of the thermoplastic polyurethane rubber is 50,000 to 1,000,000 g / mol.

8. The sodium metal battery of any one of claims 6-7, wherein: The thermoplastic polyester elastomer comprises a first hard segment and a first soft segment, the mass ratio of the first hard segment to the first soft segment is (5 to 70):(30 to 95), the first hard segment comprises any one or more of polybutylene terephthalate, polyethylene terephthalate, polyethylene naphthalate, polylactic acid and polybutylene adipate, and the first soft segment comprises any one or more of polyethylene glycol ether, polypropylene glycol ether, polybutylene glycol ether, polylactide, polyglycolide, polycaprolactone, polyethylene oxide, polypropylene oxide, polytetrahydrofuran, polybutylene oxide and polyepichlorohydrin; and / or; The thermoplastic dynamic vulcanized rubber comprises a thermoplastic resin and a rubber, the mass ratio of the thermoplastic resin to the rubber is (10 to 80):(20 to 90), the thermoplastic resin comprises any one or more of polypropylene, polyethylene, polystyrene, polyvinyl chloride, thermoplastic elastomer, polybutylene terephthalate, nylon, polyphenylene ether and polycarbonate, and the rubber comprises any one or more of ethylene-propylene-diene monomer rubber, natural rubber, nitrile rubber, styrene butadiene rubber, isoprene rubber, butyl rubber, ethylene-propylene rubber, ethylene-vinyl acetate copolymer, acrylate rubber and ethylene-acrylate copolymer; and / or; The thermoplastic polyurethane rubber comprises a second hard segment and a second soft segment, the mass ratio of the second hard segment to the second soft segment is (10-80):(20-90); the second hard segment comprises any one or more of polyalkylene terephthalate, polyalkylene adipate, polyether-based polyurethane, polycarbonate-based polyurethane, and polyether ester-based polyurethane; the second soft segment comprises any one or more of polytetrahydrofuran, polypropylene oxide, polyethylene glycol, polypropylene glycol, and polybutylene glycol.

9. The sodium metal battery of any one of claims 1-8, wherein: The first coating layer comprises a binder, and the mass percentage content of the binder in the first coating layer is 5%-40%.

10. The sodium metal battery of any one of claims 1-9, wherein: At least part of the first coating layer faces the positive electrode tab.

11. The sodium metal battery of any one of claims 1-9, wherein: The separator film comprises a second coating layer, and the second coating layer faces the positive electrode tab. The second coating layer comprises an inorganic filler, and the inorganic filler comprises any one or more of boehmite, aluminum oxide, barium sulfate, magnesium oxide, magnesium hydroxide, silicon oxide compounds, tin dioxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, hafnium dioxide, cerium oxide, zirconium titanate, barium titanate, and magnesium fluoride.

12. The sodium metal battery of any one of claims 1-11, wherein: The thickness of the sodium metal layer is 5 μm-100 μm.

13. The sodium metal battery of any one of claims 1-12, wherein: An electrically conductive layer is arranged between the negative electrode current collector and the sodium metal layer. The electrically conductive layer comprises one or more of a carbon-based conductive material and an electrically conductive polymer material. The carbon-based conductive material comprises any one or more of graphite, superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The electrically conductive polymer material comprises any one or more of polystyrene, polypyrrole, polyacetylene, polyaniline, polythiophene, and polypyridine.

14. The sodium metal battery of any one of claims 1-13, wherein: The thickness of the negative electrode current collector is 5 μm-60 μm.

15. A method of making a sodium metal battery, wherein: The process comprises the following steps: Preparation of a separator film: dispersing elastomer particles and a binder in an organic solvent to form a slurry, coating the slurry on at least one side surface of a base film, and drying to form a first coating layer; Assembling the separator film, the positive electrode tab, and the negative electrode tab together to form a sodium metal battery.

16. The method of making according to claim 15, wherein: The elastomer particles have any one or more of a spherical shape, a spherical-like shape, a regular or irregular polygonal shape. And / or The volume particle size distribution Dv50 of the elastomer particles is 3 μm-50 μm. And / or The specific surface area BET of the elastomeric particulate is comprised between 0.5 m 2 / g and 15 m 2 / g; And / or The elastomer particles comprise any one or more of a thermoplastic polyester elastomer, a thermoplastic dynamically vulcanized rubber, and a thermoplastic polyurethane rubber.

17. The method of making according to any one of claims 15-16, wherein: The elastomer particles have a porous structure, and the porous structure comprises mesopores with an average pore size of 2 nm-50 nm.

18. The method of making according to any one of claims 15-17, wherein: The mass ratio of the elastomer particles to the binder is (60%-95%):(5%-40%).

19. The method of making according to any one of claims 15-18, wherein: The binder includes any one or more of an acrylate monomer copolymer and / or homopolymer, a polyvinyl alcohol, a vinylidene fluoride polymer, a vinylidene fluoride-hexafluoropropylene copolymer, a vinylidene fluoride-pentafluoropropylene copolymer, a vinylidene fluoride-tetrafluoropropylene copolymer, a vinylidene fluoride-trifluoropropylene copolymer, a vinylidene fluoride-perfluorobutylene copolymer, a vinylidene fluoride-tetrafluoroethylene copolymer, a vinylidene fluoride-trifluoroethylene copolymer, a vinylidene fluoride-trifluorochloroethylene copolymer, or a vinylidene fluoride-vinyl fluoride copolymer, a saccharide monomer copolymer and / or homopolymer, an acrylic monomer copolymer and / or homopolymer, a styrene monomer copolymer and / or homopolymer, a butadiene monomer copolymer and / or homopolymer, a phenol monomer copolymer and / or homopolymer, an aldehyde monomer copolymer and / or homopolymer, a diatomic amine monomer copolymer and / or homopolymer, a diatomic anhydride monomer copolymer and / or homopolymer, a benzene ring monomer copolymer and / or homopolymer, or a derivative thereof, a modification thereof.

20. An electrical device, comprising: A sodium metal battery including the sodium metal battery of any one of claims 1-14 or the sodium metal battery prepared by the method of any one of claims 15-19.

Images