Sodium-ion battery and electric device

Abstract

The present application belongs to the technical field of batteries, and specifically discloses a sodium-ion battery and an electric device. The present application discloses a sodium-ion battery, which comprises a positive electrode sheet and a negative electrode sheet. The battery further comprises a gel electrolyte, part of the surface of which faces the negative electrode sheet and forms an interface layer, wherein the interface layer comprises sodium fluoride. The gel electrolyte comprises a polymer, an ether component, and a sodium salt. The design provided in the present application is used for improving the cycling performance of a battery.

Description

Sodium-ion battery and electric device

[0001] Cross-reference to Related Applications

[0002] The present application claims priority to Chinese Patent Application No. 202411066709.1, filed on August 5, 2024, entitled “Sodium-ion battery and electric device”, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present application relates to the field of batteries, in particular to a sodium-ion battery 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-ion battery and an electric device, which reduces the non-uniform sodium metal deposition or sodium dendrite of the negative electrode interface of the sodium-ion battery, reduces the electrode / electrolyte interface impedance, improves the interface compatibility, and ultimately improves the cycle performance and storage life of the battery.

[0007] In a first aspect, the present application provides a sodium-ion battery, which comprises a positive electrode sheet and a negative electrode sheet arranged in layers; further comprising a gel electrolyte, part of the surface of the gel electrolyte faces the negative electrode sheet and forms an interface layer, the interface layer comprises sodium fluoride; and the gel electrolyte comprises a polymer, an ether component and a sodium salt.

[0008] In some embodiments of the present application, the compressive strength σ of the gel electrolyte satisfies: σ≥0.6MPa, preferably 0.6MPa≤σ≤1.2MPa;

[0009] and / or;

[0010] The ionic conductivity λ of the gel electrolyte satisfies: λ≥1.5×10 -3 S / cm, preferably 1.5×10 -3 S / cm≤λ≤9.35×10 -3 S / cm.

[0011] In some embodiments of the present application, the ether component includes one or more of a chain ether and a cyclic ether; the chain ether includes any one or more of ethylene glycol dimethyl ether, dimethoxymethane, 1,2-dimethoxypropane, triethylene glycol dimethyl ether;

[0012] and / or;

[0013] The cyclic ether includes any one or more of 1,3-dioxolane, 4-methyl-1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran.

[0014] In some embodiments of the present application, the mass percentage content of the ether component in the above-mentioned gel electrolyte is 50% to 80%.

[0015] In some embodiments of the present application, the polymer includes any one or more of an organic polymer and a modified organic polymer;

[0016] and / or;

[0017] The material of the organic polymer includes any one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyethylene oxide, polyacrylonitrile, polyacrylic acid, polymethacrylate, polycarbonate, polyimide, a polymer of cyclic amide, starch, cellulose, chitosan, lignin, chitin;

[0018] and / or;

[0019] The modified organic polymer includes an organic polymer modified by an inorganic filler.

[0020] In some embodiments of the present application, the material of the organic polymer includes any one or more of polyethylene oxide, polyacrylic acid, and polyimide;

[0021] The number average molecular weight of the polyethylene oxide is 500,000 to 600,000; and the ratio between the weight average molecular weight and the number average molecular weight of the polyethylene oxide is 15 to 20;

[0022] The number average molecular weight of the polyacrylic acid is 10,000 to 50,000;

[0023] The polyimide includes an aromatic polyimide.

[0024] In some embodiments of the present application, the mass percentage content of the inorganic filler in the above-mentioned modified organic polymer is 5% to 20%;

[0025] and / or;

[0026] The inorganic filler includes one or more of silicon oxide, aluminum oxide, silicon nitride, and boron nitride.

[0027] In some embodiments of the present application, the negative electrode tab comprises a negative current collector and a conductive layer located on at least one side surface of the negative current collector.

[0028] or;

[0029] The negative electrode tab comprises a negative current collector and a conductive layer and a sodium metal layer arranged in sequence along at least one side surface of the negative current collector.

[0030] In some embodiments of the present application, the conductive layer comprises one or more of a carbon-based conductive material and a conductive polymer material.

[0031] 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.

[0032] The conductive polymer material comprises any one or more of polyethylene, polyphenyl, polypyrrole, polyacetylene, polyphenyl glue, polythiophene and polypyridine.

[0033] In some embodiments of the present application, the thickness of the negative electrode tab is 8 μm to 27 μm.

[0034] and / or;

[0035] The thickness of the conductive layer is 100 nm to 7 μm.

[0036] In some embodiments of the present application, the separator film comprises a base film and a coating layer located on at least one side surface of the base film, the coating layer comprising one or more of a ceramic adhesive layer or a polymer adhesive layer.

[0037] A second aspect of the present application is to provide a preparation method of a sodium ion battery, comprising:

[0038] Mixing a sodium salt, an ether component, a polymer monomer and an initiator to form an uncured electrolyte;

[0039] Placing a positive electrode tab, a negative electrode tab and a separator film in an outer package, injecting the above-mentioned uncured electrolyte into the outer package, and then performing a curing treatment to obtain a sodium ion battery.

[0040] In some embodiments of the present application, the curing treatment is performed in an oxygen-free atmosphere.

[0041] and / or;

[0042] The curing treatment temperature is 45°C to 70°C.

[0043] and / or;

[0044] The curing treatment time is 10 h to 15 h.

[0045] In some embodiments of the present application, the molar concentration of the sodium salt in the mixture of the sodium salt and the ether component is 0.8 mol / L to 4 mol / L.

[0046] A third aspect of the present application provides a power utilization device comprising the sodium ion battery of the first aspect or the sodium ion battery prepared by the preparation method of the second aspect.

[0047] The above description is only a summary of the technical solutions of the present application. In order to enable one skilled in the art to better understand the technical means of the present application and to implement the same according to the content of the description, and in order to make the above and other purposes, characteristics and advantages of the present application more apparent and easy to understand, the following specific embodiments of the present application are described. BRIEF DESCRIPTION OF DRAWINGS

[0048] 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. Furthermore, the same reference numerals are used throughout the several views to denote the same or similar parts. In the drawings:

[0049] FIG. 1 is a schematic diagram of a battery structure according to some embodiments of the present application;

[0050] FIG. 2 is a schematic diagram of an exploded structure of a battery according to some embodiments of the present application;

[0051] FIG. 3 is a schematic diagram of a vehicle structure according to some embodiments of the present application;

[0052] FIG. 4 is a schematic diagram of a battery pack structure according to some embodiments of the present application;

[0053] FIG. 5 is a schematic diagram of a secondary battery structure according to some embodiments of the present application;

[0054] FIG. 6A is a schematic diagram of one structure of a negative electrode sheet according to some embodiments of the present application;

[0055] FIG. 6B is a schematic diagram of another structure of a negative electrode sheet according to some embodiments of the present application;

[0056] FIG. 7 is a schematic diagram of another structure of a negative electrode sheet according to some embodiments of the present application;

[0057] In the detailed description, the following reference signs are used: 10000, vehicle; 1000, battery; 2000, controller; 3000, motor; 100, battery cell; 200, case; 210, first portion; 220, second portion; 10, secondary battery; 101, housing; 102, electrode assembly; 103, cover plate; 1, negative electrode sheet; 11, negative electrode current collector; 12, conductive layer; 13, sodium metal layer; 2, positive electrode sheet; 3, separator. Coordinate axis x direction: first direction; coordinate axis z direction: second direction (sheet thickness direction or stacking direction of the battery cell). DETAILED DESCRIPTION

[0058] Hereinafter, embodiments of the negative electrode sheet, the secondary battery, and the electric device of the present application are specifically disclosed with appropriate reference to the accompanying drawings. However, there are cases where unnecessary detailed description is omitted. For example, there are cases where detailed description of matters that are already well known, and repeated description of actually identical structures 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 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.

[0059] The "ranges" disclosed in the present application are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The ranges defined in this way can be inclusive or exclusive of the end values, 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 a minimum range value of 1 and 2 is listed, and if a maximum range value of 3, 4, and 5 is listed, then 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 manner of describing any integer combination of the range 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 of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0060] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0061] If there is no special indication, all the technical features in the present application and the optional technical features can be combined with each other to form new technical solutions.

[0062] If there is no special indication, all the steps in the present application can be performed in sequence or randomly, and preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed 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.

[0063] 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.

[0064] 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).

[0065] 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.

[0066] 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).

[0067] 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 specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0068] Secondary batteries have been widely used in various products due to their high energy density, long cycle life, safety and reliability. In recent years, with the significant increase in demand for secondary batteries as energy sources, higher requirements have been placed on the performance of secondary batteries such as energy density, cycle performance, etc.

[0069] For example, the negative active material of lithium ion battery contains carbonaceous material such as graphite, but the mass specific capacity of graphite is limited, and the volume specific capacity has little room for improvement, which seriously limits the further improvement of the weight energy density and volume energy density of lithium ion battery. With the development of current consumer electronics and electric vehicle technology, it is urgent to develop a battery system with higher energy density.

[0070] Sodium metal has very high mass energy density and volume energy density, so it is often used as the negative electrode of metal batteries. In order to further obtain higher battery energy density, sodium ion batteries by in-situ deposition of sodium ions from the positive electrode material to the negative electrode current collector have also been studied. However, the deposition of sodium ions on the surface of the negative electrode current collector requires a higher overpotential, which can also cause uneven metal deposition or sodium dendrite problems at the negative electrode interface. The instability of the interface further exacerbates the side reactions with the liquid electrolyte (such as increased gas production), which greatly consumes active sodium, ultimately affecting the cycle performance and storage life of the battery.

[0071] Based on the above considerations, in order to solve the problem of uneven metal deposition or sodium dendrite at the negative electrode interface of sodium ion battery, according to the above design concept and related experimental exploration, a sodium ion battery and an electric device are obtained.

[0072] Firstly, the present application discloses a sodium ion battery, which comprises a positive electrode sheet, a separator and a negative electrode sheet, wherein the positive electrode sheet, the separator and the negative electrode sheet are sequentially stacked to form a wound cell or a stacked cell. At the same time, the sodium ion battery also comprises a gel electrolyte, part of the surface of the gel electrolyte faces the negative electrode sheet and forms an interface layer, and the interface layer comprises sodium fluoride; the gel electrolyte comprises a polymer, an ether component and a sodium salt.

[0073] The gel electrolyte of the present application comprises a polymer skeleton, an ether component and a sodium salt. Some of the components in these components are easy to generate sodium fluoride in the interface layer formed between the gel electrolyte and the negative electrode sheet. Sodium fluoride can not only induce uniform deposition of sodium ions at the negative electrode interface, but also reduce the number of sodium dendrites. Therefore, the compatibility between the gel electrolyte and the negative electrode interface is improved, and finally the cycle performance and storage life of the battery are improved.

[0074] Therefore, the sodium-ion battery provided by the application as a secondary battery is beneficial to improve the cycle stability of the battery and prolong the storage life of the battery, so as to meet the increasingly strict requirements and increase the user experience. The secondary battery can include an outer package. The outer package can be used to package the electrode assembly and the electrolyte composed of the above-mentioned secondary battery. The outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery can also be a soft package, such as a bag-type soft package. The material of the soft package can be plastic, and as plastic, it includes but is not limited to polypropylene, polybutylene terephthalate, and polybutylene succinate, etc.

[0075] The shape of the secondary battery containing the sodium-ion battery is not particularly limited in the application, which can be cylindrical, square or any other shape. For example, FIG. 1 is a square structure of a secondary battery 10 as an example.

[0076] According to some embodiments of the 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 form an accommodation cavity. The shell 101 has an opening communicating with the accommodation cavity, and the cover plate 103 can be arranged on the opening to close the accommodation cavity. The positive electrode sheet, the negative electrode sheet and the separator can form an electrode assembly 102 through a winding process or a stacking process. The electrode assembly 102 is packaged in the accommodation 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.

[0077] The electrode assembly 102 provided by the application applied to the secondary battery is beneficial to improve the performance of the secondary battery, which can be used as a power supply of an electric device or an energy storage unit of an electric device, and the electric device is applied to the field of power, such as mobile devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited to the above-mentioned fields.

[0078] Some embodiments of the application take a vehicle as an example for convenience of illustration.

[0079] Please refer to FIG. 3, which is a structural schematic diagram of a vehicle 10000 according to 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 automobile, a hybrid automobile, or a range extended automobile, 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 source 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.

[0080] In some embodiments of the present application, the battery 1000 can not only be used as an operating power source of the vehicle 10000, but also be used as a driving power source of the vehicle 10000, to replace or partially replace fuel or natural gas to provide driving power for the vehicle 10000.

[0081] Please refer to FIG. 4, which is an exploded view of the battery 1000 according to some embodiments of the present application. The battery 1000 includes a box body 200 and a battery cell 100. A conventional battery cell includes a primary battery or a secondary battery, and the present application specifically protects a secondary battery 100, which is accommodated in the box body 200. 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.

[0082] In some embodiments, the box body 200 can include a first part 210 and a second part 220, and the first part 210 and the second part 220 are mutually covered. 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-shaped structure, which is covered on the open side of the second part 220 to jointly define the accommodation space with the second part 220. Alternatively, the first part 210 and the second part 220 can both 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.

[0083] In the battery 1000, the battery monomer 100 can be multiple, and the multiple battery monomers 100 can be connected in series or in parallel or in a mixed connection, and the mixed connection means that there are both series and parallel connections among the multiple battery monomers 100. The multiple battery monomers 100 can be directly connected in series or in parallel or in a mixed connection together, and then the whole formed by the multiple battery monomers 100 is accommodated in the box body 200; of course, the battery 1000 can also be that the multiple battery monomers 100 are first connected in series or in parallel or in a mixed connection to form a battery 1000 module form, and then multiple batteries 1000 modules are connected in series or in parallel or in a mixed connection to form a whole and are accommodated in the box body 200. The battery 1000 can also include other structures, for example, the battery 1000 can also include a current collecting component for realizing the electrical connection between the multiple battery monomers 100.

[0084] Sodium ion battery

[0085] The present application discloses a sodium ion battery in some embodiments, which comprises a positive electrode sheet, a separator film and a negative electrode sheet, wherein the positive electrode sheet, the separator film and the negative electrode sheet are sequentially stacked to form a wound cell or a stacked cell. At the same time, the sodium ion battery also comprises a gel electrolyte, part of the surface of the gel electrolyte faces the negative electrode sheet and forms an interface layer, the interface layer comprises sodium fluoride; the gel electrolyte comprises a polymer, an ether component and a sodium salt.

[0086] The positive electrode sheet, the separator film and the negative electrode sheet of the present application can be formed into a sodium ion battery by winding or stacking process. Specifically, the present application shows a sodium ion battery (secondary battery 10) formed by a winding method in Figure 5. As shown in Figure 5, the negative electrode sheet 1 or the positive electrode sheet 2 is placed between the two adjacent separator films 3, and the negative electrode sheet 1 and the positive electrode sheet 2 are sequentially and alternately arranged along the stacking direction (z-axis 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 present application will not be described here. In addition, the present application only shows one winding method in Figure 5, and other winding or stacking methods are also within the scope of the present application.

[0087] The gel electrolyte of the present application belongs to one kind of polymer electrolyte, which has the functions of conducting electricity and diaphragm. The polymer of the present application is mainly used to load the ether component and the sodium salt as the polymer skeleton. Some components in the gel electrolyte of the present application are easy to generate sodium fluoride in the interface layer formed between the gel electrolyte and the negative electrode sheet. Sodium fluoride can not only induce the uniform deposition of sodium ions at the negative electrode interface, but also reduce the number of sodium dendrites. Therefore, the compatibility between the gel electrolyte and the negative electrode interface is improved, and finally the cycle performance and storage life of the battery are improved.

[0088] In some embodiments of the present application, the compressive strength σ of the gel electrolyte satisfies: σ≥0.6MPa.

[0089] In some embodiments of the present application, the compressive strength σ of the gel electrolyte satisfies: 0.6 MPa≤σ≤1.2 MPa.

[0090] The compressive strength of the gel electrolyte of the present application is mainly used to represent the mechanical strength of the gel electrolyte, and the measurement method comprises the conventional method in the art. With the certain mechanical properties of the gel electrolyte itself, the present application can promote the uniform deposition of metallic sodium along the negative electrode interface, while also reducing the probability of sodium dendrite.

[0091] In some embodiments of the present application, the compressive strength σ of the gel electrolyte satisfies any one of 0.6 MPa, 0.62 MPa, 0.65 MPa, 0.7 MPa, 0.75 MPa, 0.76 MPa, 0.79 MPa, 0.80 MPa, 0.85 MPa, 0.9 MPa, 0.93 MPa, 0.95 MPa, 1.0 MPa, 1.05 MPa, 1.1 MPa, 1.12 MPa, 1.2 MPa or satisfies any one of the above range values.

[0092] In some embodiments of the present application, the ionic conductivity λ of the gel electrolyte satisfies: λ≥1.5×10 -3 S / cm.

[0093] In some embodiments of the present application, the ionic conductivity λ of the gel electrolyte satisfies: 1.5×10 -3 S / cm≤λ≤9.35×10 -3 S / cm.

[0094] The ionic conductivity of the gel electrolyte of the present application is mainly used to represent the ability of the gel electrolyte to conduct ions, and the actual test method comprises placing the gel electrolyte in an electrolyte and testing with a conductivity meter. The gel electrolyte of the present application has a suitable ionic conductivity, which is conducive to the rapid extraction of sodium ions in the positive electrode sheet and the rapid embedding of sodium ions in the negative electrode sheet, thereby reducing the interface impedance between the negative electrode and the gel electrolyte interface, improving the interface compatibility, and further promoting the uniform deposition of metallic sodium along the negative electrode interface.

[0095] In some embodiments of the present application, the ionic conductivity λ of the gel electrolyte satisfies any one of 1.5×10 -3 , 2.0×10 -3 , 2.5×10 -3 , 3.0×10 -3 , 3.5×10 -3 , 4.0×10 -3 , 4.1×10 -3 , 4.3×10 -3 , 4.5×10 -3 , 5.0×10 -3, 5.05 x 10 -3 , 5.5 x 10 -3 , 5.7 x 10 -3 , 5.85 x 10 -3 , 6.0 x 10 -3 , 6.5 x 10 -3 , 7.0 x 10 -3 , 7.08 x 10 -3 , 7.5 x 10 -3 , 8.0 x 10 -3 , 8.05 x 10 -3 , 8.2 x 10 -3 , 8.5 x 10 -3 , 9.0 x 10 -3 , 9.27 x 10 -3 , 9.35 x 10 -3 , any one of the above, all in S / cm.

[0096] In some embodiments of the present application, the ether component includes one or more of linear ethers and cyclic ethers; the linear ethers include any one or more of ethylene glycol dimethyl ether (DME), dimethoxymethane (DMM), 1,2-dimethoxypropane (DMP), triethylene glycol dimethyl ether (DG).

[0097] In some embodiments of the present application, the cyclic ethers include any one or more of 1,3-dioxolane (DOL), 4-methyl-1,3-dioxolane (4MeDOL), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2MeTIF).

[0098] The linear ether of the present application refers to an ether compound with a linear alkane, containing a certain number of carbon atoms, and a certain chain length. The cyclic ether of the present application refers to an ether compound with a certain number of carbon atoms and a ring structure formed by the combination of the head and tail, such as a three-membered ring or more. Whether it is a linear ether or a cyclic ether, it is all wrapped inside the skeleton formed by the polymer in the gel electrolyte, which mainly provides a continuous amorphous phase conductive channel for sodium ion conduction. At the same time, when preparing a secondary battery, the linear ether and / or cyclic ether has good compatibility with organic polymers, negative electrode sheets, etc.

[0099] In some embodiments of the present application, the mass percentage content of the ether component in the above gel electrolyte is 50% to 80%.

[0100] The measurement method of the mass percentage content of the ether solvent in the gel electrolyte of the present application comprises: taking a gel electrolyte film with a certain size, measuring its weight as m1, drying it until all the solvent is volatilized, measuring its weight as m2, then the mass of the ether solvent is m1-m2, and the mass percentage content is: (m1-m2) / m1x100%. Repeat the experiment 5 times, and take the average value as the mass percentage content of the ether solvent in the gel electrolyte.

[0101] The present application discloses in these embodiments that the mass percentage content of the ether solvent in the gel electrolyte is any one of 50%-80%, 50%-70%, 50%-60%, 50%-55%, 60%-65%, 60%-70%, 70%-75%, 70%-80% or meets any one of the above range values.

[0102] The present application discloses in these embodiments that the mass percentage content of the ether solvent in the gel electrolyte is any one of 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% or meets any one of the above range values.

[0103] In some embodiments of the present application, the polymer comprises any one or more of organic polymers and modified organic polymers.

[0104] The polymer of the present application is used to wrap the ether component and sodium salt, wherein the polymer comprises a three-dimensional network structure, and the three-dimensional network structure comprises channels for facilitating the movement and transmission of sodium ions.

[0105] In some embodiments of the present application, the material of the organic polymer comprises any one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyethylene oxide, polyacrylonitrile, polyacrylic acid, polymethacrylate, polycarbonate, polyimide, polymeric ring amide, starch, cellulose, chitosan, lignin, and chitin.

[0106] The polyvinylidene fluoride (PVDF) in the present application mainly refers to polyvinylidene fluoride homopolymer or copolymer of polyvinylidene fluoride and other small amount of fluorine-containing vinyl monomers. The copolymer is a crystalline polymer.

[0107] The polyvinylidene fluoride-hexafluoropropylene in the present application refers to a copolymer of vinylidene fluoride and hexafluoropropylene. The addition of hexafluoropropylene in the copolymer can reduce the crystallinity, so the mass percentage content of hexafluoropropylene in the polyvinylidene fluoride-hexafluoropropylene is 8% to 25%, at this time, the better the swelling and wetting properties of the polymer, and the lower the crystallinity of the polymer, the greater the solubility and swelling.

[0108] The polyacrylonitrile in the present application refers to a compound containing a cyano group in the polymer molecular chain, and the properties of polyacrylonitrile and its excellent performance depend largely on the relative molecular mass of the product and its distribution. Generally speaking, when the relative molecular mass is less than 10000, it is often impossible to form fibers, and the more the relative molecular mass, the greater the dispersibility. The relative molecular mass of the polyacrylonitrile of the present application is 2.5x10 4 ~8x10 4 .

[0109] The polyacrylic acid in the present application is obtained by polymerization of acrylic acid monomers such as acrylic acid under certain conditions, and its preparation method includes conventional methods in the art, such as emulsion polymerization, and after drying, a film of polyacrylic acid is formed.

[0110] The polymethyl methacrylate in the present application is obtained by polymerization of methacrylate monomers such as alkyl methacrylate under certain conditions, and its preparation method includes conventional methods in the art.

[0111] The polyethylene oxide in the present application, also known as polyethylene oxide, is a crystalline water-soluble polymer with a molecular formula of When the relative molecular mass is less than 5000, it has amphiphilic properties of dissolving in organic solvents and aqueous solutions. The relative molecular mass here and the relative molecular mass described above both refer to the relative molecular mass, which refers to the sum of the relative atomic mass (Ar) of each atom in the chemical formula, with the unit being 1.

[0112] The polycarbonate in the present application refers to a general assembly of a class of high molecular compounds containing carbonate chains in the molecular chain, which belongs to thermoplastic materials.

[0113] The polyimide in the present application refers to a class of polymer materials containing imide functional groups in the molecular backbone. This highly conjugated backbone structure endows polyimide fibers with good mechanical properties, excellent heat resistance and stability, solvent corrosion resistance, and excellent light stability.

[0114] The polymer of cyclic amide in the present application refers to a polymer formed by initiation and polymerization of an initiator such as caprolactam.

[0115] The starch in the present application is the largest natural polymer carbohydrate in the nature. In the industry, it is mainly produced by using cereal crops (such as corn, wheat) and potato crops (such as potato, cassava, etc.) as raw materials. If the obtained starch product is not denatured, its chemical structure and properties are the same as those in the raw material, and no change occurs during the production process, which is called raw starch, otherwise it is called modified starch. The present application refers to the polymer skeleton of starch material prepared by modifying starch by conventional methods in the art.

[0116] The cellulose in the present application is the most common organic biopolymer in the nature. Cellulose can be extracted from different sources, such as crops, biomass residues, algae, tunicates, fungi and bacteria. The cellulose in the present application is modified and can be used to prepare a polymer skeleton of cellulose material.

[0117] The chitosan in the present application is a copolymer of N-acetylglucosamine and glucosamine. Chitosan is formed by removing acetyl groups from natural chitin under certain conditions. The chitosan in the present application is modified and can be used to prepare a polymer skeleton of chitosan material.

[0118] The lignin in the present application is the second largest natural organic polymer in the nature, which enables plants to build rigid chemical structures. As a highly complex natural polymer, lignin itself contains a large number of functional groups, such as hydroxyl, carboxyl, ether, etc. These functional groups provide multiple possibilities for modification. The lignin in the present application is modified and can be used to prepare a polymer skeleton of lignin material.

[0119] The chitin in the present application is the second largest renewable natural polysaccharide in the nature after cellulose, with a relative molecular mass ranging from hundreds of thousands to millions of Daltons. The chitin in the present application is modified and can be used to prepare a polymer skeleton of chitin material.

[0120] In some embodiments of the present application, the material of the organic polymer skeleton includes any one or more of polyethylene oxide, polyacrylic acid, and polyimide.

[0121] The polyethylene oxide in the present application has a number average molecular weight of 500,000-600,000, and a ratio between the weight average molecular weight and the number average molecular weight of the polyethylene oxide of 15-20. The number average molecular weight in the present application includes any meaning in the conventional art, and the weight average molecular weight in the present application also includes any meaning in the conventional art, which is mainly the average molecular weight obtained by mass statistics. The measurement method of the weight average molecular weight and the number average molecular weight includes direct measurement by experimental techniques such as gel permeation chromatography (GPC) or physical methods such as light scattering, etc.

[0122] The ratio between the weight average molecular weight and the number average molecular weight of the polyethylene oxide is selected to be 15-20 in the present application, so that the molecular weight distribution of the polyethylene oxide is moderate, and the influence on ion conduction and electron conduction is small.

[0123] The present application discloses a method for measuring the weight average molecular weight and the number average molecular weight in some embodiments, which comprises referring to GB / T 21863-2008 gel permeation chromatography, using an ultra-high performance polymer chromatograph: ACQUITY APC; and a detector: ACQUITY differential refractometer. The test steps are as follows: (1) preheating after starting: after installing the chromatographic column and the pipeline, turn on the console, the test power supply and the like in sequence, and open the test software Empower; (2) parameter setting: sample volume: 0 μL to 50 μL (determined according to the sample concentration); pump flow rate: 0.2 mL / min; mobile phase: 30 mol / L LiBr NMP solution; sealing cleaning liquid: isopropyl alcohol; pre-column: PL gel 10 μm MiniMIX-B Guard (size: 50 mm*4.6 mm*2); analysis phase: PL gel 10 μm MiniMIX-B (size: 250 mm*4.6 mm); standard: polystyrene kit; running time: 30 min; detector: ACQUITY differential refractometer (RI) detector; column oven temperature: 90℃; detector temperature: 55℃. (3) sample test: a. standard sample and test sample configuration: respectively take 0.002 g to 0.004 g of the standard sample / test sample and add 2 mL of the mobile phase liquid to prepare 0.1% to 0.5% of the mixed standard, and store in the refrigerator for >8 h; b. standard solution / sample test: edit the sample group to be tested, select the established sample group method, and after the baseline is stable, click to run the queue to start the test sample; (4) data processing: according to the relationship between the retention time and the molecular weight, the calibration curve is established by using the chemical workstation, the sample spectrum is quantitatively integrated, and the molecular weight and the molecular weight distribution results are automatically generated by the chemical workstation.

[0124] The number average molecular weight of the polyacrylic acid is 10000-50000 in the present application, so as to facilitate the formation of a polymer with a skeleton structure.

[0125] The polyimide of the present application mainly comprises an aromatic polyimide, which is a thermoplastic material, such as comprising a raw material aromatic dianhydride and an aromatic diamine.

[0126] In some embodiments of the present application, the modified organic polymer comprises an inorganic filler modified organic polymer skeleton.

[0127] In the present application, the inorganic filler is used to modify the organic polymer, wherein the inorganic filler can absorb a large amount of anions to promote the dissociation of sodium salt, thereby improving the ion conduction capacity.

[0128] The organic polymer and the modified organic polymer provided by the application are ion-conducting polymers. The movement of ions and / or functional groups on the surface of the ion-conducting polymers provides activation energy for sodium ions to pass through the polymer skeleton channel of the gel electrolyte, thereby reducing the interfacial impedance between the negative electrode and the electrolyte, improving the interfacial compatibility, and promoting the uniform deposition of metallic sodium along the negative electrode interface. In addition, the functional groups on the surface of the organic polymer can interact with the ether component, change the solvation sheath structure, weaken the interaction between the ether component and the cation, form more anion-dominated aggregates, reduce the desolvation energy of the negative electrode interface, and be beneficial to further improve the interfacial compatibility.

[0129] In some embodiments of the application, the material of the organic polymer includes any one or more of polyethylene oxide, polyacrylic acid, and polyimide.

[0130] In some embodiments of the application, the material of the organic polymer includes any one or more of polyethylene oxide, polyacrylic acid, and polyimide. These materials are more conducive to forming a polymer skeleton with a network channel, and at the same time, the polymer skeleton can better wrap the ether component and the sodium salt inside it.

[0131] In some embodiments of the application, the mass percentage content of the inorganic filler in the modified organic polymer described above is 5% to 20%.

[0132] In some embodiments of the application, the inorganic filler includes one or more of silicon oxide, aluminum oxide, silicon nitride, and boron nitride.

[0133] The inorganic fillers listed in the above embodiments also include a three-dimensional spatial structure, which is conducive to further enhancing the transmission of lithium ions.

[0134] In these embodiments, the application discloses that the mass percentage content of the inorganic filler in the modified organic polymer skeleton described above is any one of 5% to 20%, 5% to 15%, 5% to 10%, 10% to 15%, 10% to 20%, and 15% to 20%, or satisfies any one of the above range values.

[0135] In these embodiments, the application discloses that the mass percentage content of the inorganic filler in the modified organic polymer skeleton described above is any one of 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 19.6%, and 20%, or satisfies any one of the above range values.

[0136] In some embodiments of the application, the negative electrode tab includes a negative electrode current collector and a conductive layer located on at least one side surface of the negative electrode current collector.

[0137] In some embodiments of the present application, the negative electrode tab comprises a negative current collector and, sequentially arranged along at least one side surface of the negative current collector, an electrically conductive layer and a sodium metal layer.

[0138] As shown in FIGS. 6A and 6B, the negative electrode tab 1 comprises a negative current collector 11 and an electrically conductive layer 12 formed on at least part of the surface of the negative current collector 11, wherein FIG. 6A shows that the electrically conductive layer 12 is arranged on one side surface of the negative current collector 11, and FIG. 6B shows that the electrically conductive layer 12 is arranged on both side surfaces of the negative current collector 11. The electrically conductive layer 12 can be formed on the entire surface of the negative current collector 11 or part of the surface of the negative current collector 11, and the present application focuses on the electrically conductive layer 12 being arranged on both side surfaces of the negative current collector 11 in the following embodiments. The electrically conductive layer 12 can be formed on the surface of the negative current collector 11 in any manner known in the art, such as coating, deposition, etc.

[0139] The negative electrode tab provided by the present application is a negative electrode tab without negative active material. During the first charging, a sodium metal layer is deposited on the surface of the negative current collector. The sodium metal layer can be attached to the electrically conductive layer. The electrically conductive layer can effectively reduce the overpotential during the deposition of the sodium metal layer and inhibit the formation of sodium dendrites. During the discharging process, the metal sodium in the sodium metal layer can be converted into sodium ions and returned to the positive electrode, realizing the cyclic charging and discharging. At the same time, the battery provided by the present application can only deposit and convert metal sodium during the cyclic use, so it has good storage performance and is conducive to long storage.

[0140] In some embodiments of the present application, the electrically conductive layer comprises one or more of carbon-based conductive materials and conductive polymer materials.

[0141] In some embodiments of the present application, 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.

[0142] In some embodiments of the present application, the conductive polymer material comprises any one or more of polyaniline, polypyrrole, polyacetylene, polyphenyl, polythiophene and polypyridine. In addition, the electron delocalization of the conductive polymer material can be increased by doping and the like to improve the electrical conductivity.

[0143] The electrically conductive layer provided by the present application can effectively reduce the overpotential during the deposition of the sodium metal layer, thereby alleviating the phenomenon of non-uniform metal deposition or sodium dendrites at the negative electrode interface. That is, the present application is conducive to reducing the probability of sodium dendrites by arranging the electrically conductive layer on the surface of the negative current collector.

[0144] In some embodiments of the present application, the thickness of the negative electrode tab is 8 μm to 27 μm.

[0145] In some embodiments of the present application, the thickness of the conductive layer is 100 nm to 7 μm.

[0146] In some embodiments of the present application, the thickness of the sodium metal layer is 100 nm to 1 μm.

[0147] The thickness of the negative electrode tab in the present application includes the distance between the opposite two end surfaces of the negative electrode tab along a certain direction, such as the coordinate axis Z direction in FIG. 5 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.

[0148] In some embodiments of the present application, the negative electrode tab of the present application includes the negative electrode current collector and the conductive layer, and the thickness of the conductive layer is the difference between the thickness of the negative electrode tab and the thickness of the negative electrode current collector.

[0149] In these embodiments, the present application discloses that the thickness of the negative electrode tab is any one of 8 μm to 27 μm, 8 μm to 20 μm, 8 μm to 15 μm, 8 μm to 13 μm, 8 μm to 10 μm, 10 μm to 15 μm, 10 μm to 18 μm, 15 μm to 18 μm, 18 μm to 27 μm or satisfies any one of the above range values.

[0150] In these embodiments, the present application discloses that the thickness of the negative electrode tab is any one of 8 μm, 8.5 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, 25.8 μm, 26 μm, 27 μm or satisfies any one of the above range values.

[0151] In some embodiments of the present application, the thickness of the conductive layer is 300 nm to 10 μm. As described above, the thickness of the conductive layer includes the distance between the opposite two end surfaces of the conductive layer along a certain direction, such as the coordinate axis Z direction in FIG. 5 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.

[0152] In these embodiments, the present application discloses that the thickness of the conductive layer is any one of 100 nm to 7 μm, 500 nm to 7 μm, 1 μm to 7 μm, 2 μm to 7 μm, 3 μm to 7 μm, 4 μm to 7 μm, 5 μm to 7 μm, 6 μm to 7 μm or satisfies any one of the above range values.

[0153] The present application discloses in these embodiments that the thickness of the conductive layer is any one of 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 680 nm, 700 nm, 800 nm, 900 nm, 1000 nm (1 μm), 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 6.8 μm, 7 μm or satisfies any one of the above range values.

[0154] The present application discloses in these embodiments that the thickness of the sodium metal layer is any one of 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm or satisfies any one of the above range values.

[0155] In some embodiments of the present application, the separation film comprises a base film and a coating layer on at least one side surface of the base film, and the coating layer comprises one or more of a ceramic bonding layer or a polymer bonding layer.

[0156] The material of the base film in the present application comprises one or more of polyethylene, polypropylene, poly-p-phenylene terephthalamide, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide and polyamide; wherein the base film has good permeability to lithium ions, which is conducive to the migration of lithium ions.

[0157] The ceramic bonding layer in the present application comprises a ceramic material selected from one or more of silicon oxide (such as SiO2), titanium oxide (such as TiO2), zirconium oxide (such as ZrO2), aluminum oxide (such as Al2O3), magnesium oxide (such as MgO) and silicon carbide (such as SiC). In some embodiments, the ceramic bonding layer optionally further comprises a binder selected from one or more of polyvinylidene fluoride (PVDF), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, polyurethane (PU) and styrene-acrylic latex (SA).

[0158] The polymer bonding layer in the present application refers to a coating layer comprising a polymer adhesive selected from one or more of polyvinylidene fluoride (PVDF), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, polyurethane (PU) and styrene-acrylic latex (SA).

[0159] [Negative electrode tab]

[0160] The present application provides in some embodiments a negative electrode tab, which comprises a negative electrode current collector and a conductive layer formed on at least part of the surface of the negative electrode current collector.

[0161] The application provides, in some embodiments, a negative electrode tab, which comprises a negative electrode current collector and, in sequence along at least one side surface of the negative electrode current collector, an electrically conductive layer and a sodium metal layer.

[0162] The sodium ion battery provided by the application can deposit metal sodium on the surface of the negative electrode current collector and form a sodium metal layer during the first charging, and the sodium metal layer can be attached to the electrically conductive layer on the surface of the negative electrode current collector. As shown in FIG. 7, the sodium metal layer has a low potential barrier, which can reduce the sodium embedding overpotential of the electrically conductive layer and the overpotential of the entire negative electrode tab. The sodium metal layer can completely cover the surface of the electrically conductive layer or partially cover the surface of the electrically conductive layer.

[0163] In some embodiments of the application, the electrically conductive layer can further comprise at least one of a binder, such as sodium cellulose, sodium carboxymethyl cellulose, hydroxypropyl cellulose, sodium hydroxymethyl cellulose, potassium hydroxymethyl cellulose, diacetyl cellulose, polyacrylic acid, sodium alginate, butadiene styrene rubber, butadiene acrylonitrile rubber, polypyrrole, polyaniline, epoxy resin and guar gum. The binder has high viscosity and mechanical strength, which can ensure the integrity of the contact interface between the electrically conductive layer and the negative electrode current collector, inhibit dendrite growth and improve the cycle performance.

[0164] In some embodiments of the application, a preparation method of the negative electrode tab is disclosed, which comprises: adding an electrically conductive material and a binder into a solvent such as NMP to stir a uniform slurry, coating the slurry on a negative electrode current collector (copper foil), and drying to obtain the negative electrode tab.

[0165] In these embodiments of the 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 of the application, the metal foil comprises a copper foil, an aluminum foil, a stainless steel foil, an iron foil, a zinc foil, a titanium foil and the like. In these embodiments of the application, the metal foam current collector comprises a copper foam, an aluminum foam, a zinc foam and the like. In these embodiments of the application, the metal mesh current collector comprises a copper mesh, an aluminum mesh and the like. Meanwhile, the negative electrode current collector can also be a composite current collector formed by compounding a metal foil and a metal foam, or a composite current collector formed by compounding a metal foil and a metal mesh, or a composite current collector formed by compounding a metal foil and a polymer-based film, which is not particularly limited in the application.

[0166] The sodium ion battery provided in the application can form metal sodium on the surface of the negative current collector during the first charging, so that the metal sodium can be attached to the conductive layer on the surface of the negative current collector, the conductive layer can effectively reduce the overpotential of sodium metal deposition, inhibit the formation of sodium dendrites, and be beneficial to improve the cycle performance of the battery. During the discharging process, the metal sodium can be converted into sodium ions to return to the positive electrode to realize the cycle charging and discharging.

[0167] [Positive electrode sheet]

[0168] The application provides a positive electrode sheet in some embodiments, the positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer located on at least one side surface of the positive electrode current collector, wherein the positive electrode film layer comprises a positive electrode active material.

[0169] According to some embodiments of the application, the positive electrode active material comprises at least one of sodium transition metal oxide, polyanion compound and prussian blue compound, but the application is not limited to these materials, and other conventional and well-known materials that can be used as positive electrode active materials of sodium ion batteries can also be used.

[0170] In the application, in the sodium transition metal oxide, the transition metal can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, and the sodium transition metal oxide is, for example, Na x MO2, wherein M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0 < x ≤ 1. The polyanion compound 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- .

[0171] The polyanion compound of the application can also be a compound having sodium ions, tetrahedral (YO4) n- anion unit, polyhedral unit (ZO y ) m+ and optional halide 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+ . The halogen can be at least one of F, Cl and Br.

[0172] The polyanionic compound of the present application includes at least one of sodium iron pyrophosphate (NaFeP04), sodium vanadium phosphate (Na3V2(P04)3), NaM’P04F (M’ is one or more of V, Fe, Mn, and Ni), and Na3(V02(P04)2F y )2(P04)2F 3-2y (0≤y≤1).

[0173] The polyanionic compound of the present application includes any one or more of sodium vanadotrifluorophosphate, sodium vanadium fluorophosphate, sodium vanadium phosphate, sodium iron pyrophosphate, and sodium iron pyrophosphate.

[0174] The Prussian blue compound of the present application can be a compound having sodium ions, transition metal ions, and cyanide ions (CN - )6, wherein Me and Me’ are each independently at least one of Ni, Cu, Fe, Mn, Co, and Zn, 0 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

[0175] The positive electrode active material layer can further include a conductive agent to improve the conductivity of the positive electrode in some embodiments of the present application. 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 super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphite, graphene, and carbon nanofibers.

[0176] The positive electrode active material layer can further include a binder to firmly bind the positive electrode active material and the optional conductive agent to the positive electrode current collector in some embodiments of the present application. 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 more than two combinations of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorine-containing acrylate resin, styrene butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, carboxymethyl chitosan, and the like.

[0177] In some embodiments, the positive electrode current collector can be made of conductive carbon sheet, metal foil, carbon-coated metal foil, porous metal plate, or 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, carbon-coated metal foil, and porous metal plate can be independently selected from 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.

[0178] The positive electrode current collector can be, for example, one or more of copper foil, aluminum foil, nickel foil, stainless steel foil, stainless steel mesh, and carbon-coated aluminum foil, and preferably aluminum foil.

[0179] The positive electrode tab can be prepared according to conventional methods in the art. Typically, the positive electrode active material and optional conductive agent and binder are dispersed in a solvent (e.g., N-methylpyrrolidone, abbreviated as NMP) to form a uniform positive electrode slurry, which is coated on both sides of the positive electrode current collector, dried, and cold-pressed to obtain the positive electrode tab.

[0180] [Separator]

[0181] In some embodiments, the present application discloses a separator. The type of the separator is not particularly limited in the present application, and any known porous structure separator having good chemical stability and mechanical stability can be selected.

[0182] In some embodiments, the separator includes a base film (or base material layer) and a coating layer disposed on the surface of the base film.

[0183] The base film of the present application is made of a base material, which includes one or more of polyethylene, polypropylene, poly-p-phenylene terephthalamide, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, and polyamide. The base film can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the base film is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited. The base film provided by the present application has good permeability to sodium ions, which is beneficial to the migration of sodium ions.

[0184] In other embodiments of the present application, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited.

[0185] [Preparation of sodium ion battery]

[0186] The application discloses a preparation method of a sodium ion battery in some embodiments, including the following processes:

[0187] The positive electrode sheet, the isolation film and the negative electrode sheet are stacked in sequence, the isolation film is between the cathode and the anode to play a role of isolation, and a bare battery is obtained by winding.

[0188] The sodium salt is dispersed into the ether component to form a mixture, the molar concentration of the sodium salt is controlled to be 0.8 mol / L-4 mol / L, the initiator is added into the mixture, the monomer is added after complete dissolution, and the un-solidified electrolyte is obtained by stirring until complete dissolution.

[0189] The electrolyte is injected into the bare battery, and then solidification treatment is performed in an oxygen-free atmosphere, the solidification temperature is controlled to be 45 DEG C-70 DEG C, the solidification / immersion time is controlled to be 10 h-15 h, a gel electrolyte is obtained, and finally the sodium ion battery is obtained after subsequent processes such as formation and exhaust.

[0190] The monomer of the application includes a polymer monomer, which includes but is not limited to one or more of vinylidene fluoride, hexafluoropropylene, acrylonitrile, acrylic acid, acrylate, oxirane, etc.

[0191] The initiator of the application includes one or both of organic peroxide or inorganic peroxide.

[0192] The initiator of the application includes but is not limited to at least one of ammonium persulfate, potassium persulfate, sodium persulfate, benzoyl peroxide BPO, dodecanoyl peroxide LPO, lauryl peroxide, dicumyl peroxide, tert-butyl peroxybenzoate or tert-butyl peroxy-2-ethylhexanoate, preferably at least one of ammonium persulfate, potassium persulfate and sodium persulfate.

[0193] The sodium salt, the ether component and the polymer monomer of the application have good compatibility, which is manifested as not easy to settle. The gel electrolyte formed by compounding the components is distributed around the negative electrode sheet, and directly contacts the negative electrode sheet, wherein part of the surface of the gel electrolyte faces the negative electrode sheet and forms an interface layer, the interface layer includes sodium fluoride, the sodium fluoride can induce sodium ions to be uniformly deposited on the negative electrode interface, and can also reduce the number of sodium dendrites. Therefore, the compatibility between the gel electrolyte and the negative electrode interface is improved, and finally the cycle performance and storage life of the battery are improved.

[0194] The sodium ion battery of the application will be emphatically described below in combination with specific embodiments.

[0195] The experimental methods used in the following examples are conventional methods unless otherwise specified.

[0196] The materials, reagents and the like used in the following examples, unless otherwise specified, can be obtained commercially.

[0197] 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 (amounts, temperature, reaction times, 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 reagent chemicals were obtained in AR grade, and all reactions were carried out under an argon atmosphere. Unless otherwise indicated, all reagents were obtained from commercial sources.

[0198] Example 1

[0199] A sodium-ion battery is provided, which includes a positive electrode sheet, a separator film and a negative electrode sheet which are sequentially stacked, and further includes a gel electrolyte.

[0200] Preparation of the negative electrode sheet:

[0201] A dispersion liquid of single-walled carbon nanotubes (tube diameter 1-3 nm, BET 1000 m 2 / g) and a binder (polyacrylic acid) are dispersed into NMP to form a uniform slurry, which is coated on both sides of a copper foil to form a negative electrode sheet with a thickness of 10 μm, wherein the thickness of the conductive layer is 2 μm.

[0202] In this embodiment, the present application does not provide a sodium metal layer on the surface of the conductive layer, and the sodium metal layer is actually generated during the formation stage of the battery. The sodium metal layer can be attached to the conductive layer, which can effectively reduce the overpotential during the deposition of the sodium metal layer and inhibit the formation of sodium dendrites. During the discharge process, the metal sodium in the sodium metal layer can be converted into sodium ions to return to the positive electrode, realizing the cycle charging and discharging. At the same time, the battery provided by the present application will only deposit and convert metal sodium during the cycle use, so it has good storage performance and is beneficial to long storage.

[0203] Preparation of the positive electrode sheet:

[0204] Na3V2(PO4)3(93.8 w%), conductive carbon black (3.0 wt%), PVDF (2.5 wt%), dispersant (hydrogenated butyl rubber, 0.3 wt%) and residual alkali removing agent (0.4 wt%) are mixed, wherein 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, to prepare a positive electrode slurry. After the prepared oil-based slurry is stirred to end, the viscosity of the slurry is adjusted to 10000 mPa.s, and the prepared slurry is not stratified, and then the slurry is coated by a double-sided double-cavity coating device to control the weight at 200 mg / 1540.25 cm2 The positive electrode sheet is prepared by coating on an Al foil, drying, cold pressing, slitting, and the like after coating on both sides.

[0205] A separator film is provided.

[0206] A porous polyethylene (PE) film having a thickness of 13 μm is used as the separator film, and a ceramic adhesive layer (SiO2) of 500 nm and a polymer adhesive layer (polyvinylidene fluoride) of 500 nm are sequentially formed on one surface of the porous polyethylene (PE) film.

[0207] A sodium ion battery is prepared.

[0208] Sodium hexafluorophosphate is dispersed into ethylene glycol dimethyl ether to form a solution having a concentration of 1 mol / L, and an initiator, potassium persulfate (1 wt%), is added into the mixture, and after complete dissolution, monomers, pyromellitic dianhydride and p-phenylenediamine in a molar ratio of 1:1.2, are added and stirred until complete dissolution to obtain an uncured electrolyte.

[0209] The positive electrode sheet, the separator film, and the negative electrode sheet prepared above are sequentially stacked with the separator film between the anode and the cathode to play a role of separation, and are wound to obtain a bare battery cell. The bare battery cell is placed in an outer package, dried, and then the uncured electrolyte is injected, and then curing treatment is performed in an oxygen-free atmosphere, the curing temperature is controlled to be 50°C, the curing / impregnation time is 12 h, to obtain a gel electrolyte, and then formation, exhaust, and the like are performed to obtain a sodium ion battery.

[0210] Embodiments 2 to 4 provide a sodium ion battery.

[0211] In the sodium ion batteries provided in embodiments 2 to 4, the types of ether components are different, and other aspects are the same as those in embodiment 1.

[0212] Embodiments 5 to 6 provide a sodium ion battery.

[0213] In the sodium ion batteries provided in embodiments 5 to 6, the contents of the ether components are different, the concentrations of the mixed solutions formed when the sodium salt is dispersed in the ether components are different, the thicknesses of the conductive layers are different, and the thicknesses of the negative electrode sheets are also different, and other aspects are the same as those in embodiment 1.

[0214] Embodiments 7 to 10 provide a sodium ion battery.

[0215] In the sodium ion batteries provided in embodiments 7 to 10, the types of organic polymers are different, the contents of the inorganic fillers in the organic polymers are different, the concentrations of the mixed solutions formed when the sodium salt is dispersed in the ether components are different, the thicknesses of the conductive layers are different, and the thicknesses of the negative electrode sheets are also different, and other aspects are the same as those in embodiment 1.

[0216] Comparative Example 1

[0217] A sodium ion battery is provided, which is different from Example 1 in that sodium salt sodium hexafluorophosphate is dispersed into ester solvents, such as ethylene carbonate, diethyl carbonate, dimethyl carbonate mixed in a volume ratio of 1:1:1 to obtain a solvent, and then monomers and initiators are added to prepare a sodium ion battery.

[0218] Comparative Example 2

[0219] Replace the gel electrolyte with electrolyte:

[0220] In an environment with water content less than 10 ppm, non-aqueous organic solvents ethylene carbonate, diethyl carbonate, dimethyl carbonate are mixed in a volume ratio of 1:1:1 to obtain a solvent, sodium salt sodium hexafluorophosphate is added to the solvent, and an electrolyte with a sodium hexafluorophosphate concentration of 1 mol / L is configured.

[0221] Table 1-1 Raw Material List

[0222] Table 1-2 Raw Material List

[0223] Table 1-3 Raw Material List

[0224] Table 2

[0225] [Performance Test]

[0226] ①Test sodium fluoride:

[0227] The sodium ion battery is cycled 100 times at 25°C, and each cycle process is as follows:

[0228] 1) Rest 30min;

[0229] 2) 0.33C DC 1.5V;

[0230] 3) Rest 30min 25℃;

[0231] 4) 0.33C CC 3.65V CV 0.05C;

[0232] 5) Rest 30min;

[0233] 6) 0.33C DC 1.5V, recorded as 1 cycle, repeated 100 times, and the battery was disassembled. High magnification was used, and X-ray diffraction spectroscopy was used to observe whether sodium fluoride was present in the interface layer formed by the gel electrolyte and the negative electrode plate. In addition, it was observed under an electron microscope that the negative electrode surface in the example was more uniform than that of the comparative example, and the number of sodium dendrites decreased.

[0234] The following list was obtained:

[0235] Table 3

[0236] 2. Test the compression strength of the gel electrolyte:

[0237] During testing, the gel electrolyte sample was placed in a compression testing machine, and a uniform load was applied at a certain speed until the sample failed. The failure load was recorded, and the compression strength was calculated. The formula for calculating the compression strength is σ = P / A, where σ is the compression strength, P is the applied pressure, and A is the cross-sectional area.

[0238] 3. Test the ionic conductivity of the gel electrolyte:

[0239] According to GB / T 21961-2008, the actual test used a conductivity meter to test the conductivity of the electrolyte:

[0240] Measurement principle: A conductivity meter usually consists of two parallel electrodes that are immersed in the electrolyte. The distance between the electrodes is fixed, and their surface area is also known.

[0241] Applied voltage: The conductivity meter applies a small alternating voltage (AC voltage) to the electrodes, rather than a direct current, to avoid polarization of the electrode surface.

[0242] Calculate the conductivity: Using the following formula, the conductivity is calculated based on the measured current and the known distance and area between the electrodes: λ = I / V*A*L, where I is the current, V is the voltage, A is the cross-sectional area of the electrode, and L is the distance between the electrodes.

[0243] Table 4

[0244] 4. Test the liquid retention of the battery after formation:

[0245] Weighing method: Record the weight of the battery before and after injection, and after formation

[0246] The amount of electrolyte retained M = the weight of the battery after formation M1 - the weight of the battery before injection M2.

[0247] 5. Test the gas production of the battery:

[0248] The gas production of the battery cell was tested using an infrared flow meter, specifically by measuring the flow rate through infrared sensors that emit infrared signals and receive infrared signals scattered by moving fluids.

[0249] (6) The cycle number of the battery at 25°C, with a capacity retention of 80%:

[0250] Capacity CO calibration: One charge-discharge cycle before cycling was performed as a capacity reference;

[0251] 1) Rest 30min;

[0252] 2) 0.33C DC 1.5V;

[0253] 3) Rest 30min 25°C;

[0254] 4) 0.33C CC 3.65V CV 0.05C;

[0255] 5) Rest 30min;

[0256] 6) 0.33C DC 1.5V (this step is recorded as actual capacity CO);

[0257] 7) Rest 30min;

[0258] Cycle steps:

[0259] 1) Rest 30min;

[0260] 2) 0.33Cn DC 1.5V;

[0261] 3) 1Cn CC 3.65V CV 0.05Cn cycle section;

[0262] 4) Rest 30min;

[0263] 5) 1Cn DC 1.5V F (this step calculates Fading);

[0264] 6) Rest 30min;

[0265] 8) Cycle steps 3-6 until the cutoff condition ≤80% SOH is met.

[0266] (6) The cycle number of the battery at 25°C, with a capacity retention of 80%:

[0267] The measurement method is the same as above at 25°C, except that the test temperature is -20°C.

[0268] Table 5

[0269] From the above list, it can be seen that the sodium fluoride generated in the interface layer of the application is beneficial to improve the cycle performance of the battery at low temperature, at the same time, it is beneficial to the battery to have high liquid retention after formation, and to have less gas generation when placed at room temperature, so it is also beneficial to improve the storage performance.

[0270] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the application, but not to limit them; although the 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 application, and they should be covered in the scope of the claims and the specification of the application. Especially, as long as there is no structural conflict, each technical feature mentioned in each embodiment can be combined in any way. The 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-ion battery, characterized in that, The positive electrode sheet and the negative electrode sheet are arranged in a stack; The sodium-ion battery further comprises a gel electrolyte, part of a surface of the gel electrolyte faces the negative electrode sheet and forms an interface layer, and the interface layer comprises sodium fluoride; The gel electrolyte comprises a polymer, an ether component, and a sodium salt.

2. The sodium-ion battery of claim 1, wherein, The compressive strength σ of the gel electrolyte satisfies: σ≥0.6 MPa, preferably 0.6 MPa≤σ≤1.2 MPa; And / or; The ionic conductivity λ of the gel electrolyte satisfies: λ≥1.5×10 -3 S / cm, preferably 1.5×10 -3 S / cm≤λ≤9.35×10 -3 S / cm.

3. The sodium-ion battery of any one of claims 1-2, wherein, The ether component comprises one or more of a chain ether and a cyclic ether; The chain ether comprises any one or more of ethylene glycol dimethyl ether, dimethoxymethane, 1,2-dimethoxypropane, and triethylene glycol dimethyl ether; And / or; The cyclic ether comprises any one or more of 1,3-dioxolane, 4-methyl-1,3-dioxolane, tetrahydrofuran, and 2-methyltetrahydrofuran.

4. The sodium-ion battery according to any one of claims 1-3, wherein, The mass percentage content of the ether component in the gel electrolyte is 50% to 80%.

5. The sodium-ion battery according to any one of claims 1-4, wherein, The polymer comprises any one or more of an organic polymer and a modified organic polymer; And / or; The material of the organic polymer comprises any one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyethylene oxide, polyacrylonitrile, polyacrylic acid, polymethacrylate, polycarbonate, polyimide, a polymer of cyclic amide, starch, cellulose, chitosan, lignin, and chitin; And / or; The modified organic polymer comprises an inorganic filler modified organic polymer.

6. The sodium-ion battery according to any one of claims 1-5, wherein, The material of the organic polymer comprises any one or more of polyethylene oxide, polyacrylic acid, and polyimide; The number average molecular weight of the polyethylene oxide is 500,000 to 600,000; and the ratio between the weight average molecular weight and the number average molecular weight of the polyethylene oxide is 15 to 20; The number average molecular weight of the polyacrylic acid is 10,000 to 50,000; The polyimide comprises an aromatic polyimide.

7. The sodium-ion battery of claim 5, wherein, The mass percentage content of the inorganic filler in the modified organic polymer is 5% to 20%; And / or; The inorganic filler comprises any one or more of silicon oxide, aluminum oxide, silicon nitride, and boron nitride.

8. The sodium-ion battery of any one of claims 1-7, wherein, The negative electrode sheet comprises a negative electrode current collector and a conductive layer located on at least one side surface of the negative electrode current collector; Or; The negative electrode sheet comprises a negative electrode current collector and a sodium metal layer arranged in sequence along at least one side surface of the negative electrode current collector.

9. The sodium-ion battery of claim 8, wherein, The conductive layer comprises any one or more of a carbon-based conductive material and a 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 conductive polymer material comprises any one or more of polyaniline, polyacetylene, polypyrrole, polythiophene, and polypyridine.

10. The sodium-ion battery of any one of claims 8-9, wherein, The thickness of the negative electrode sheet is 8 μm to 27 μm; And / or; The thickness of the conductive layer is 100 nm to 7 μm.

11. The sodium-ion battery of any one of claims 1-10, wherein, The separator film comprises a base film and a coating layer located on at least one side surface of the base film, and the coating layer comprises any one or more of a ceramic adhesive layer or a polymer adhesive layer.

12. A method of preparing a sodium-ion battery, characterized by: Comprising: Mixing a sodium salt, an ether component, a polymer monomer, and an initiator to form an uncured electrolyte; The positive electrode sheet, the negative electrode sheet and the separator are placed in an outer package, the above-mentioned uncured electrolyte is injected into the outer package, and then a curing treatment is performed to obtain a sodium ion battery.

13. The method of claim 12, wherein: The curing treatment is performed in an oxygen-free atmosphere; and / or; The curing treatment temperature is 45 DEG C to 70 DEG C; and / or; The curing treatment time is 10 h to 15 h.

14. The method of any one of claims 12-13, wherein: The molar concentration of the sodium salt in the mixture of the sodium salt and the ether component is 0.8 mol / L to 4 mol / L.

15. An electrical device, comprising: The sodium ion battery prepared by the preparation method of any one of claims 1 to 14.

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