Sodium battery and preparation method therefor, battery device, and electric device

Abstract

A sodium battery and a preparation method therefor, a battery device, and an electric device. The sodium battery comprises a gel electrolyte, the gel electrolyte comprises a polymer and a free radical scavenger, and in the gel electrolyte, the mass ratio of the free radical scavenger to the polymer is 1:(10-75).

Description

Sodium batteries and their preparation methods, battery devices, and electrical devices

[0001] Priority information

[0002] This application is based on and claims priority to Chinese Patent Application No. 202411906811.8, filed on December 23, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of sodium batteries, specifically to sodium batteries and their preparation methods, battery devices, and electrical devices. Background Technology

[0004] As the application of lithium-ion batteries expands in consumer electronics, electric vehicles, and energy storage, they also face significant challenges, such as the increasing scarcity of lithium resources, rising prices of upstream materials, and lagging development of recycling technologies. Sodium batteries, due to the high abundance of sodium on Earth, are gaining attention. They utilize the intercalation / deposition / stripping of sodium ions between the positive and negative electrodes to achieve charging and discharging. Furthermore, sodium resources are more widely distributed and significantly cheaper than lithium, giving them a strategically important position in cost-sensitive applications such as energy storage. However, many issues regarding the application of sodium batteries still remain to be resolved.

[0005] It should be noted that the above statements are only used to provide background information related to this application and do not necessarily constitute prior art.

[0006] Application content

[0007] In a first aspect of this application, a sodium battery is proposed, comprising: a gel electrolyte, the gel electrolyte comprising: a polymer; and a free radical scavenger, wherein the mass ratio of the free radical scavenger to the polymer in the gel electrolyte is 1:(10-75). Thus, the addition of the free radical scavenger can capture free radicals, suppressing the reaction between free radicals generated after the polymer decomposes in the electrolyte solvent and sodium metal, thereby improving the interfacial stability between the gel electrolyte and sodium metal, reducing the occurrence of gas generation in the battery, and improving the high-temperature performance of the battery.

[0008] In some embodiments, the polymer comprises at least one of polyethylene oxide, polyethylene glycol, polyvinylidene fluoride, polyethylene glycol diacrylate, polymethyl methacrylate, polycaprolactone triacrylate, polyacrylonitrile, polyvinylpyrrolidone, sodium perfluorosulfonate, sodium poly(tartaric acid)borate, polypentylmalonic acid, polyurethane, trimethylsilyl cage polysilsesquioxane, polyvinylidene fluoride-hexafluoropropylene copolymer, and methyl vinyl ether maleic anhydride copolymer. Therefore, the polymer exhibits superior electrochemical stability and possesses numerous polar groups that can interact with electrolyte salts to form coordination bonds, thereby promoting the dissociation and migration of sodium ions.

[0009] In some embodiments, at least one of the following conditions is met: (1) the polymer comprises polyacrylonitrile, wherein the relative molecular mass of the polyacrylonitrile is 50,000 to 150,000; (2) the polymer comprises polyvinylidene fluoride-hexafluoropropylene copolymer, wherein the relative molecular mass of the polyvinylidene fluoride-hexafluoropropylene copolymer is 200,000 to 500,000; (3) the polymer comprises methyl vinyl ether maleic anhydride copolymer, wherein the relative molecular mass of the methyl vinyl ether maleic anhydride copolymer is 200,000 to 1,000,000; (4) the polymer comprises polyethylene oxide, wherein the relative molecular mass of the polyethylene oxide is 400,000 to 1,000,000. Thus, the polymer possesses superior mechanical strength, elastic modulus, and ionic conductivity.

[0010] In some embodiments, the free radical scavenger includes at least one of benzophenone, β-diketone, glyceryl triglycidyl ether, 4-benzoyl-2,2,6,6-tetramethylpiperidine, benzotriazole, tris(2,4-di-tert-butylphenyl) phosphite, octadecyl β-(4-hydroxyphenyl-3,5-di-tert-butyl)propionate, lead stearate, basic lead carbonate, calcium stearate, zinc glycerol, cerium carbonate, lanthanum stearate, praseodymium stearate, nickel 3,5-di-tert-butyl-4-hydroxybenzyl phosphate monoethyl ester, butyltin dimethylsilicate, dioctyltin monoethyl maleate, and antimony isooctyl trithioacetate. Thus, the free radical scavenger can efficiently coordinate and capture free radicals in the gel electrolyte, reducing the reaction between free radicals generated after polymer decomposition in the electrolyte solvent and sodium metal.

[0011] In some embodiments, the free radical scavenger includes at least one selected from benzophenone, 4-benzoyl-2,2,6,6-tetramethylpiperidine, lead stearate, and butyltin dimethylsilylsilicate. Thus, the free radical scavenger possesses both strong free radical coordination and scavenging capabilities and high intrinsic stability, contributing to its long-lasting effectiveness.

[0012] In some embodiments, at least one of the following conditions is met: (1) the mass fraction of the polymer in the gel electrolyte is 20%-60%; (2) the mass fraction of the free radical scavenger in the gel electrolyte is 0.5%-4%. Thus, the high proportion of polymer in the gel electrolyte results in higher viscosity and semi-solid properties, reducing the risk of leakage caused by gel electrolyte when the battery is subjected to physical impact or puncture.

[0013] In some embodiments, the gel electrolyte further comprises an inorganic material filled within the polymer, the inorganic material including at least one of alumina, silica, sodium carbonate, sodium fluoride, β-alumina solid electrolyte, and NASICON solid electrolyte. This improves the polymer's mechanical strength, thermal stability, ionic conductivity, and other properties.

[0014] In some embodiments, the sodium battery is a negative electrode-less sodium battery. Therefore, this sodium battery has a high energy density.

[0015] In a second aspect of this application, a method for preparing a sodium battery is proposed, comprising: mixing a polymer, a free radical scavenger, and a first electrolyte salt in a solvent to obtain a sol, wherein the solvent includes at least one selected from acetonitrile, N-methylpyrrolidone, and acetone; heating the sol to obtain a pre-formed polymer electrolyte; and immersing the pre-formed polymer electrolyte in an electrolyte solution to obtain a gel electrolyte, thereby obtaining the sodium battery, wherein the electrolyte solution includes an electrolyte solvent and a second electrolyte salt, the immersion time is 8-50 hours, and the immersion temperature is 30°C-60°C. Thus, by first preparing a pre-formed polymer electrolyte film and then performing swelling in the electrolyte solution, excessive swelling of the polymer in the electrolyte solvent is suppressed, thereby reducing polymer decomposition, improving the chemical stability of the polymer and the free radical scavenger during the immersion process, and forming a gel electrolyte by swelling without damaging the main polymer structure as much as possible.

[0016] In some embodiments, the first electrolyte salt is the same as the second electrolyte salt. This effectively reduces the leaching of the first electrolyte salt from the preformed polymer electrolyte during the soaking process.

[0017] In some embodiments, at least one of the following conditions is met: (1) in the mixing process, the mass ratio of the polymer, the free radical scavenger, and the first electrolyte salt is (50-75):(1-5):(25-50); (2) the temperature of the mixing process is 60°C-90°C, and the time of the mixing process is 8h-24h. This helps to form a uniformly dispersed sol.

[0018] In some embodiments, the solid content of the sol is 5%-15%. This gives the sol good flowability, which facilitates coating on flat surfaces.

[0019] In some embodiments, the heat treatment includes coating the sol onto a flat plate surface to form a coating layer with a thickness of 150 μm to 1000 μm; and subjecting the coating layer to vacuum drying at a temperature of 50°C to 120°C. This facilitates the complete evaporation of the solvent in the sol.

[0020] In some embodiments, the molar concentration of the second electrolyte salt in the electrolyte is 0.5 mol / L to 2.5 mol / L. This suppresses the diffusion of anions and cations from the preformed polymer electrolyte into the electrolyte solvent and their recoordination with solvent molecules.

[0021] In a third aspect, this application proposes a battery device comprising at least one of the aforementioned sodium battery and a sodium battery prepared by the aforementioned method. Thus, this battery device possesses all the features and advantages of the aforementioned sodium battery and the method for preparing the sodium battery, which will not be repeated here.

[0022] In a fourth aspect, this application proposes an electrical device comprising at least one of the aforementioned sodium battery and a sodium battery prepared by the aforementioned method. Thus, the electrical device possesses all the features and advantages of the aforementioned sodium battery and the method for preparing the sodium battery, which will not be repeated here. Attached Figure Description

[0023] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0024] Figure 1 is a schematic diagram of a battery cell according to an embodiment of this application;

[0025] Figure 2 is an exploded view of a battery cell according to an embodiment of this application shown in Figure 1;

[0026] Figure 3 is a schematic diagram of a battery module according to an embodiment of this application;

[0027] Figure 4 is a schematic diagram of a battery pack according to an embodiment of this application;

[0028] Figure 5 is an exploded view of a battery pack according to an embodiment of this application shown in Figure 4;

[0029] Figure 6 is a schematic diagram of an electrical device in which a battery is used as a power source according to an embodiment of this application.

[0030] Explanation of reference numerals in the attached drawings: 1 Battery pack; 2 Upper casing; 3 Lower casing; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0031] The embodiments of this application are described in detail below, with examples of these embodiments shown in the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0032] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit the application; unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0033] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are open-ended expressions, meaning they include what is specified in this application but do not exclude other aspects.

[0034] In the description of this application, all figures disclosed herein, whether or not the words "approximately" or "about" are used, are approximate values. Each figure may vary by less than 10% or by a difference that is considered reasonable by one of the art, such as 1%, 2%, 3%, 4%, or 5%.

[0035] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, 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 specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0036] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. "First feature" and "second feature" may include one or more of the indicated feature.

[0037] In the description of this application, "multiple" means two or more.

[0038] In the description of this application, "A and / or B" can include any of the cases of A alone, B alone, or A and B, where A and B are merely examples and can be any technical feature connected by "and / or" in this application.

[0039] In this application, the order in which the steps are written does not imply a strict execution order and does not constitute any limitation on the implementation process. The specific execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0040] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0041] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0042] Electrodeless sodium batteries offer advantages such as high energy density and low cost. Specifically, an electrodeless sodium battery refers to a battery in which no negative electrode active material layer is actively deposited on the negative electrode side during the manufacturing process of the battery cell. For example, no negative electrode active material layer is formed on the surface of the negative electrode current collector through coating or deposition processes during the manufacturing of the battery cell. During battery charging, sodium ions in the positive electrode active material layer migrate to the surface of the negative electrode current collector and deposit to form a sodium metal layer. During battery discharge, the metallic sodium in the sodium metal layer can be converted into sodium ions and re-intercalated into the positive electrode, thus achieving cyclic charging and discharging. Compared to other sodium batteries, electrodeless sodium batteries, due to the absence of a pre-set negative electrode active material layer, have higher volumetric energy density and gravimetric energy density. However, when a sodium-ion battery without a negative electrode is charged, the surface of the negative electrode current collector has a sodium metal layer with high chemical reactivity. During the high-temperature storage and cycling process of the battery (e.g., above 45°C), the sodium metal will undergo a side reaction with the electrolyte solvent to produce a large amount of gas, and more than 90% of the gas produced is hydrogen. The extra consumption of electrolyte makes the battery's cycle performance and storage performance poor, and may even seriously deteriorate the battery's safety performance.

[0043] Replacing the electrolyte, which consists of an electrolyte solvent containing dissolved electrolyte salts, with a semi-solid gel electrolyte can mitigate side reactions between sodium metal and the electrolyte solvent to some extent, thanks to the higher chemical stability of gel electrolytes. However, other problems remain to be solved. Specifically, gel electrolytes typically consist of polymers, electrolyte solvents, and electrolyte salts. When preparing gel electrolytes by swelling a polymer containing electrolyte salts in an electrolyte solvent, the polymer, with its relatively high molecular weight, absorbs too much electrolyte solvent, causing the polymer chains to loosen. These polymer chains then gradually disperse and dissolve into the electrolyte solvent from the surface, forming free radicals and hydroxyl-containing small molecules. These free radicals react with sodium metal, further deteriorating the battery's high-temperature performance and safety. When using polymers without electrolyte solvents directly as polymer solid electrolytes, the problem of excessive polymer swelling in the electrolyte solvent can be mitigated, side reaction kinetics can be suppressed, and the stability of the sodium metal interface can be improved. However, this results in extremely low ionic conductivity of the gel electrolyte (approximately 10). -7 s·cm -1 -10 -5 s·cm-1 Furthermore, the interfacial resistance when in contact with the positive and negative electrodes is too high (above 200 Ω·cm). 2 This results in higher internal resistance and poorer cycle performance in the battery.

[0044] In this application, after the polymer swells and absorbs a significant amount of electrolyte solvent, it dissolves in the electrolyte solvent and further decomposes to generate free radicals. By adding a free radical scavenger to the gel electrolyte, the free radical scavenger can undergo a coordination reaction with the free radicals to form stable coordination compounds, efficiently capturing free radicals and effectively suppressing side reactions between free radicals and sodium metal. This improves the interfacial stability between the gel electrolyte and the sodium metal layer, reduces high-temperature gas generation in sodium batteries, and significantly enhances the high-temperature performance and safety performance of the battery. Simultaneously, after the polymer fully swells and absorbs the electrolyte solvent, it can significantly increase the ionic conductivity of the gel electrolyte (ionic conductivity higher than 1×10⁻⁶ at 25°C). -4 S·cm -1 And reduce the interfacial resistance between the gel electrolyte and the positive and negative electrodes (less than 100 Ω·cm). 2 The battery has low internal resistance and excellent cycle performance.

[0045] In summary, by using a combination of free radical scavengers and polymers, the polymers, after swelling and absorbing a large amount of solvent, not only achieve high ionic conductivity and low interfacial resistance in the gel electrolyte, but also maintain high interfacial stability with the sodium metal layer. This reduces the occurrence of high-temperature gas generation side reactions in the negative electrode-less sodium battery, thereby improving the battery's high-temperature storage performance and high-temperature cycling performance.

[0046] In a first aspect, this application proposes a sodium battery comprising: a gel electrolyte, the gel electrolyte comprising: a polymer; and a free radical scavenger, wherein the mass ratio of the free radical scavenger to the polymer in the gel electrolyte is 1:(10-75). Thus, the addition of the free radical scavenger can capture free radicals, suppressing the side reactions between free radicals generated after the polymer decomposes in the electrolyte solvent and sodium metal. The polymer has high chemical stability, thereby improving the interfacial stability between the gel electrolyte and the sodium metal on the surface of the negative electrode current collector, reducing the occurrence of gas generation in the battery, and improving the high-temperature performance of the battery.

[0047] As an example, the mass ratio of the free radical scavenger to the polymer in the gel electrolyte can be 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45, 1:50, 1:55, 1:60, 1:65, or 1:70.

[0048] When the mass ratio of the free radical scavenger to the polymer in the gel electrolyte is within the aforementioned range, the addition of a small amount of free radical scavenger can efficiently capture free radicals, suppress the side reactions between free radicals generated by the decomposition of the polymer in the electrolyte solvent and sodium metal, improve the interfacial stability between the gel electrolyte and the sodium metal on the surface of the negative electrode current collector, and reduce the occurrence of high-temperature gas generation.

[0049] As an example, the mass fraction of free radical scavengers in gel electrolytes can be determined by the following method: molecules of different sizes, including solvent molecules, free radical scavenger molecules, and polymers, in gel electrolytes can be separated by gel chromatography, and their different molecular weights and distributions can be determined to deduce the mass fraction of free radical scavengers.

[0050] As an example, the mass fraction of polymers in gel electrolytes can be determined by the following method: molecules of different sizes, including solvent molecules, free radical scavenger molecules, and polymers, in gel electrolytes can be separated by gel chromatography to determine their different molecular weights and distributions, thereby deriving the mass fraction of polymers.

[0051] In some embodiments, the polymer comprises at least one of polyethylene oxide, polyethylene glycol, polyvinylidene fluoride, polyethylene glycol diacrylate, polymethyl methacrylate, polycaprolactone triacrylate, polyacrylonitrile, polyvinylpyrrolidone, sodium perfluorosulfonate, sodium poly(tartaric acid)borate, polypentylmalonic acid, polyurethane, trimethylsilyl cage polysilsesquioxane, polyvinylidene fluoride-hexafluoropropylene copolymer, and methyl vinyl ether maleic anhydride copolymer. Therefore, the polymer exhibits superior electrochemical stability and possesses numerous polar groups that can interact with electrolyte salts to form coordination bonds, thereby promoting the dissociation and migration of sodium ions.

[0052] In some embodiments, the polymer comprises polyacrylonitrile, wherein the polyacrylonitrile has a relative molecular mass of 50,000 to 150,000. This results in a polymer with high mechanical strength, which helps improve the stability of the gel electrolyte; it also maintains stability over a wide temperature range, making it suitable for high-temperature applications.

[0053] In some embodiments, the polymer comprises a polyvinylidene fluoride-hexafluoropropylene copolymer with a relative molecular mass of 200,000 to 500,000. Therefore, the polymer exhibits superior flexibility, effectively reducing the formation of gel electrolyte cracks, and demonstrates good compatibility with various electrolyte solvents, which is beneficial for forming a uniform gel structure.

[0054] In some embodiments, the polymer comprises a methyl vinyl ether maleic anhydride copolymer having a relative molecular mass of 200,000 to 1,000,000. Thus, the anhydride groups in the polymer can react with the electrolyte salt, increasing the ionic conductivity of the gel electrolyte and simultaneously improving the interfacial compatibility between the gel electrolyte and the positive and negative electrodes.

[0055] In some embodiments, the polymer comprises polyethylene oxide with a relative molecular mass of 400,000 to 1,000,000. Thus, the polymer can form a complex with the electrolyte salt, resulting in a gel electrolyte with high ionic conductivity and high thermoplasticity, facilitating processing.

[0056] In some embodiments, the free radical scavenger includes at least one of benzophenone, β-diketone, glyceryl triglycidyl ether, 4-benzoyl-2,2,6,6-tetramethylpiperidine, benzotriazole, tris(2,4-di-tert-butylphenyl) phosphite, octadecyl β-(4-hydroxyphenyl-3,5-di-tert-butyl)propionate, lead stearate, basic lead carbonate, calcium stearate, zinc glycerol, cerium carbonate, lanthanum stearate, praseodymium stearate, nickel 3,5-di-tert-butyl-4-hydroxybenzyl phosphate monoethyl ester, butyltin dimethylsilicate, dioctyltin monoethyl maleate, and antimony isooctyl trithioacetate. Thus, the free radical scavenger can efficiently coordinate and capture free radicals in the gel electrolyte, reducing polymer decomposition in the electrolyte solvent and improving the polymer's chemical stability.

[0057] The aforementioned free radical scavenger can coordinate with free radicals to form stable coordination compounds, thereby achieving free radical capture. This suppresses the side reactions between free radicals generated after the polymer decomposes in the electrolyte solvent and sodium metal, improves the interfacial stability of the gel electrolyte, and reduces the high-temperature gas generation phenomenon in sodium batteries.

[0058] In some embodiments, the free radical scavenger includes at least one selected from benzophenone, 4-benzoyl-2,2,6,6-tetramethylpiperidine, lead stearate, and butyltin dimethylsilylsilicate. Thus, the free radical scavenger possesses both strong free radical coordination and scavenging capabilities and high intrinsic stability, contributing to its long-lasting effectiveness.

[0059] In some embodiments, the polymer in the gel electrolyte comprises 20%-60% by mass; and / or, the free radical scavenger in the gel electrolyte comprises 0.5%-4% by mass. Thus, the higher proportion of polymer in the gel electrolyte results in higher viscosity and semi-solid properties, reducing the risk of gel electrolyte leakage when the battery is subjected to physical impact or puncture.

[0060] In some embodiments, the gel electrolyte further comprises an inorganic material filled within the polymer, the inorganic material including at least one of alumina, silica, sodium carbonate, sodium fluoride, β-alumina solid electrolyte, and NASICON solid electrolyte. This improves the polymer's mechanical strength, thermal stability, ionic conductivity, and other properties.

[0061] As an example, when inorganic materials include alumina and silicon dioxide, they can improve the mechanical strength and thermal stability of polymers.

[0062] As an example, when inorganic materials include β-alumina solid electrolytes and NASICON solid electrolytes, the ionic conductivity of the polymer can be significantly improved, and the high-temperature performance of the battery can be further improved.

[0063] In some embodiments, the sodium battery is a negative electrode-less sodium battery. Therefore, this sodium battery has a high energy density.

[0064] In some embodiments, the gel electrolyte further comprises an electrolyte solvent, which includes at least one selected from ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene carbonate, propylene carbonate, butenyl carbonate, vinylene carbonate, fluoroethylene carbonate, methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, and dimethyl sulfoxide. This helps to promote the dissociation of the electrolyte salt and improve the ionic conductivity of the gel electrolyte.

[0065] Electrolyte salts can be dissolved in the electrolyte solvent, so that during the process of the polymer absorbing and swelling the electrolyte solvent, the electrolyte salts can also be carried into the polymer to form freely moving sodium ions, which improves the ionic conductivity of the polymer and alleviates the internal polarization of the sodium battery.

[0066] As an example, the electrolyte solvent includes at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

[0067] The aforementioned electrolyte solvent is relatively stable with sodium metal and can enter the cross-linking backbone of the polymer without dissolving it.

[0068] In some embodiments, the mass fraction of the electrolyte solvent in the gel electrolyte is 20%-50%. This helps to further improve the ionic conductivity of the gel electrolyte.

[0069] In some embodiments, the gel electrolyte further comprises an electrolyte salt, which includes at least one selected from sodium hexafluorophosphate, sodium nitrate, sodium perchlorate, sodium acetate, sodium trifluoroacetate, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide. Thus, the electrolyte salt can dissociate in the electrolyte solvent to generate sodium ions, providing a conductive medium.

[0070] As an example, the electrolyte salt includes at least one of sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, and sodium bis(trifluoromethylsulfonyl)imide.

[0071] The aforementioned electrolyte salt can inhibit the decomposition of polymers in electrolyte solvents, while having good solubility in both polymers and electrolyte solvents.

[0072] In some embodiments, the mass fraction of the electrolyte salt in the gel electrolyte is 12.5%-40%. Thus, an appropriate electrolyte salt concentration ensures sufficient ion concentration, thereby improving the ionic conductivity of the gel electrolyte.

[0073] [Positive electrode plate]

[0074] In some embodiments, the sodium battery includes a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive active material layer located on at least one side of the positive current collector, the positive active material layer including a positive active material.

[0075] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0076] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0077] As an example, the positive electrode active material may include at least one of the following materials: sodium transition metal oxides, polyanionic compounds, and Prussian blue sodium compounds, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. The modified compounds of the above materials may be for doping modification and / or surface coating modification of the materials.

[0078] In some embodiments, the transition metal in the sodium transition metal oxide can be at least one selected from Ti, V, Mn, Co, Ni, Fe, Zn, V, Zr, Ce, Cr, and Cu. The chemical formula of the sodium transition metal oxide can satisfy Na x MO2, wherein M includes at least one of Ti, V, Mn, Co, Ni, Fe, Zn, V, Zr, Ce, Cr, and Cu, and 0 < x ≤ 1.

[0079] In some embodiments, the polyanionic compound may be a sodium ion, a transition metal ion, or a tetrahedral (YO4) compound. n- A class of compounds with anionic units. The transition metal may include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may include at least one of P, S, and Si; n represents (YO4). n- The price state.

[0080] In some embodiments, the polyanionic compound may also have sodium ions, transition metal ions, or a tetrahedral (YO4) structure. n- A class of compounds containing anionic units and halide anions. Transition metals may include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may include at least one of P, S, and Si, where n represents (YO4). n- The valence state of halogens can include at least one of F, Cl, and Br.

[0081] In some embodiments, the polyanionic compound may also be a tetrahedral compound containing sodium ions (YO4). n- Anionic unit, polyhedral unit (ZO) y ) m+ And a class of compounds with optional halide anions. M may include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, Y may include at least one of P, S and Si, and n represents (YO4). n- The valence state, Z represents transition metal, m represents (ZO) y ) m+ The valence state of halogens can include at least one of F, Cl, and Br.

[0082] As an example, polyanionic compounds can satisfy the chemical formulas NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7), NaM'PO4F (M' includes at least one of V, Fe, Mn and Ni), and Na3(VO y )2(PO4)2F 3-2yAt least one of (0≤y≤1).

[0083] In some embodiments, Prussian blue compounds may contain sodium ions, transition metal ions, and cyanide ions (CN). - A class of compounds. Transition metals may include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce.

[0084] As an example, Prussian blue compounds can satisfy the chemical formula Na a Me b Me' c (CN)6, wherein Me and Me' each independently include at least one of Ni, Cu, Fe, Mn, Co, and Zn, 0 < a ≤ 2, 0 < b < 1, and 0 < c < 1.

[0085] As an example, the positive electrode active material includes Na8Fe4(P2O7)5 and NaNi. 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, Na(Cu) 1 / 9 Ni 2 / 9 Fe 1 / 3 Mn 1 / 3 O2, Na 2 / 3 Ni 1 / 6 Mn 2 / 3 Cu 1 / 9 Mg 1 / 18 O2, NaFePO4, Na3V2(PO4)3, Na 1.9 At least one of CoFe(CN)6, Na2NiFe(CN)6, and NaMnFe(CN)6.

[0086] In some embodiments, the surface of the positive electrode active material has a coating layer that at least partially covers the surface of the aforementioned positive electrode active material. The coating layer includes one or more of carbon materials, polyaniline, polypyrrole, poly(3,4-ethylenedioxythiophene), alumina, zinc oxide, titanium oxide, zirconium oxide, magnesium oxide, silicon oxide, lanthanum oxide, sodium fluoride, lithium fluoride, and aluminum fluoride. The carbon material includes one or more of amorphous carbon, graphite, and graphene.

[0087] During the charging and discharging process of a battery, sodium (Na) undergoes insertion / extraction and consumption, resulting in varying molar Na content at different discharge states. In the examples of positive electrode active materials in this application, the molar Na content refers to the initial state of the material, i.e., the state before material addition. After charge-discharge cycles, the molar Na content changes when the positive electrode active material is applied to the battery system.

[0088] In the enumeration of positive electrode active materials for sodium batteries in this application, the molar content of O is only a theoretical state value. Oxygen release from the crystal lattice will cause changes in the molar content of oxygen, and the actual molar content of O will fluctuate.

[0089] In some embodiments, the positive electrode active material layer may optionally include a binder.

[0090] As an example, the adhesive may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0091] In some embodiments, the positive electrode active material layer may optionally include a conductive agent.

[0092] As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0093] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0094] [Negative electrode plate]

[0095] In some embodiments, the negative electrode may include a negative current collector, which may be a metal foil, a foamed metal, or a composite current collector. For example, as a metal foil, silver-treated aluminum or stainless steel, stainless steel, copper, aluminum, nickel, carbon electrodes, carbon, nickel, or titanium may be used. The foamed metal may be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, etc. The composite current collector may include a polymeric material substrate and a metal layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymeric material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0096] In some embodiments, in order to improve the performance of a single battery cell, the negative electrode sheet may include a negative current collector and a functional coating disposed on at least one side of the surface of the negative current collector. The functional coating may include a carbon material coating (carbon materials include single-walled conductive carbon nanotubes, multi-walled conductive carbon nanotubes, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers, soft carbon and hard carbon, etc.), a lithium-loving / sodium-loving metal composite coating, etc.

[0097] In some embodiments, the negative electrode current collector can be a composite current collector. For example, the composite current collector may include at least one of carbon cloth, carbon film, carbonaceous material, porous current collector, alloyed modified current collector, and lithium-philic / sodium-modified current collector.

[0098] As an example, the thickness of the functional coating can range from 2μm to 100μm.

[0099] As an example, the thickness of the negative electrode current collector can be 10μm-100μm.

[0100] [Isolation membrane]

[0101] In some embodiments, the sodium battery also includes a separator. This application does not impose any particular limitation on the type of separator; any porous separator with good chemical and mechanical stability can be selected.

[0102] In some embodiments, the material of the separator includes at least one selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0103] In a second aspect, this application proposes a method for preparing a sodium battery. The method involves first preparing a pre-formed polymer electrolyte without an electrolyte solvent, then immersing the pre-formed polymer electrolyte in an electrolyte solvent containing an electrolyte salt to allow it to fully swell, thereby obtaining a gel electrolyte. This method helps to suppress excessive swelling of the polymer in the electrolyte solvent, reduces polymer decomposition, and effectively improves the chemical stability of the polymer and free radical scavengers during the immersion process, allowing for sufficient swelling to form a gel electrolyte while minimizing damage to the polymer's main structure. Specifically, the method includes:

[0104] S1: The polymer, free radical scavenger, and first electrolyte salt are mixed in a solvent.

[0105] In some embodiments, in this step, the polymer, free radical scavenger, and first electrolyte salt are mixed in a solvent to obtain a sol, wherein the solvent includes at least one of acetonitrile, N-methylpyrrolidone, and acetone.

[0106] Using the aforementioned solvent helps to uniformly diffuse the polymer, free radical scavenger, and first electrolyte salt in the solvent, which in turn helps to form a uniformly dispersed gel.

[0107] By using a solvent with good solubility for the free radical scavenger, the polymer and free radical scavenger can be uniformly mixed while reducing polymer dissolution and further decomposition. Furthermore, swelling is a process where solvent molecules penetrate into the polymer. Immersing the pre-formed polymer electrolyte in an electrolyte solution facilitates the entry of electrolyte salts. However, the diffusion process of anions and cations during immersion cannot be precisely controlled. Therefore, the amount of electrolyte that can enter the polymer through subsequent immersion in the electrolyte solution alone may be very small. Adding electrolyte salts during gel preparation can effectively compensate for the high concentration of electrolyte salts in the gel electrolyte that cannot be achieved through immersion alone.

[0108] In some embodiments, during the mixing process, the mass ratio of the polymer, the free radical scavenger, and the first electrolyte salt is (50-75):(1-5):(25-50). This helps to obtain a polymer with a high electrolyte salt content and high stability.

[0109] As an example, in the mixing process, the mass ratio of the polymer, the free radical scavenger, and the first electrolyte salt can be 50:1:25, 50:1:50, 75:1:25, 75:1:50, 50:5:25, 50:5:50, 75:5:25, 75:5:50, etc.

[0110] In some embodiments, the mixing process is carried out at a temperature of 60°C-90°C for 8 hours to 24 hours. This helps to form a uniform and stable sol.

[0111] As an example, the temperature for the mixing process can be 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, or 90℃.

[0112] For example, the mixed processing time can be 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h or 24h.

[0113] In some embodiments, the solid content of the sol is 5%-15%. This gives the sol good flowability, which facilitates the coating and formation of a polymer film on a flat surface.

[0114] The solid content of a sol refers to the percentage of the total mass of the polymer, free radical scavenger, and first electrolyte salt in the sol, based on the total mass of the sol.

[0115] As an example, the solid content of the sol can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%.

[0116] It should be noted that, for the free radical scavenger added to the aforementioned sol, if the free radical scavenger is soluble in the electrolyte solvent and can still maintain its corresponding function after being dissolved in the electrolyte solvent, the step of adding the free radical scavenger during the sol preparation process can be omitted, and it can be added to the electrolyte. Alternatively, the aforementioned free radical scavenger can be added during both the sol preparation process and the electrolyte.

[0117] S2: Heat treatment of the sol

[0118] In some embodiments, the sol is heated in this step to remove the solvent, thereby obtaining a pre-formed polymer electrolyte. By preparing a pre-formed polymer electrolyte film and then immersing it in the electrolyte, excessive swelling of the polymer in the electrolyte solvent can be effectively suppressed, thus reducing polymer decomposition, compared to directly immersing the polymer in the electrolyte.

[0119] In some embodiments, the heat treatment includes coating the sol onto the surface of a plate to form a coating layer with a thickness of 150 μm to 1000 μm.

[0120] Forming a coating layer by coating the sol onto the surface of a plate helps to increase the surface area of ​​the sol, and the combination of a thinner coating layer thickness helps the solvent to evaporate fully and quickly.

[0121] As an example, the casting method can be used to prepare the coating layer. The casting method is simple and efficient, and can produce a coating layer with uniform thickness and smooth surface.

[0122] In some embodiments, the coating layer is subjected to vacuum drying at a temperature of 50°C-120°C. This facilitates the complete evaporation of the solvent in the sol.

[0123] The boiling point of liquids is lowered in a vacuum environment, and vacuum drying can be carried out at a lower temperature, which helps to reduce the thermal degradation or denaturation of polymers and free radical scavengers under high temperature conditions.

[0124] S3: Immerse the pre-formed polymer electrolyte in the electrolyte solution.

[0125] In some embodiments, in this step, the dried pre-formed polymer electrolyte is immersed in an electrolyte solution to swell and obtain a gel electrolyte to obtain the sodium battery, wherein the electrolyte solution includes an electrolyte solvent and a second electrolyte salt, the immersion time is 8h-50h, and the immersion temperature is 30℃-60℃.

[0126] As an example, the soaking time can be 8h, 12h, 16h, 20h, 24h, 28h, 32h, 36h, 40h, 44h, 48h or 50h.

[0127] As an example, the soaking temperature can be 30℃, 35℃, 40℃, 45℃, 50℃, 55℃ or 60℃. By controlling the soaking time and soaking temperature, the swelling amount of the electrolyte can be controlled. When the soaking time and soaking temperature are within the aforementioned range, the mass ratio of the gel electrolyte to the preformed polymer electrolyte can reach (1.2-1.5):1, that is, the mass of the preformed polymer electrolyte increases by 20%-50% after soaking, and the gel electrolyte obtained after soaking contains more electrolyte.

[0128] In some embodiments, the molar concentration of the second electrolyte salt in the electrolyte is 0.5 mol / L to 2.5 mol / L. This suppresses the diffusion of anions and cations from the preformed polymer electrolyte into the electrolyte solvent and their recoordination with solvent molecules.

[0129] In some embodiments, the first electrolyte salt is the same as the second electrolyte salt. This effectively reduces the leaching of the first electrolyte salt from the preformed polymer electrolyte during the soaking process.

[0130] It should be noted that the descriptions of the various embodiments above tend to emphasize the differences between them, while their similarities or commonalities can be referred to each other. Parts not described in the above embodiments can also be referred to in the foregoing embodiments. For the sake of brevity, they will not be repeated here.

[0131] In a third aspect, this application proposes a battery device comprising the aforementioned sodium battery, and / or a sodium battery prepared using the aforementioned method. Thus, the battery device possesses all the features and advantages of the aforementioned sodium battery and the method for preparing the sodium battery, which will not be repeated here.

[0132] The battery device of this application includes battery cell form, battery module form, and battery pack form. The battery cell, battery module, and battery pack of this application will be described below with appropriate reference to the accompanying drawings.

[0133] In some embodiments, the aforementioned sodium battery can be used as a battery cell. This application does not impose any particular limitation on the shape of the battery cell 5, which can be cylindrical, square, or other arbitrary shapes. For example, Figure 1 shows a square-structured battery cell 5 as an example.

[0134] In some embodiments, referring to FIG2, the outer packaging may include a housing 51 and a top cover assembly 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the top cover assembly 53 can cover the opening to close the receiving cavity. A positive electrode sheet, a negative electrode sheet, and a separator can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in a single battery cell can be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0135] In some embodiments, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process. Specifically, the gel electrolyte can be pre-attached to both sides of the separator before the aforementioned winding or stacking process is performed.

[0136] In some embodiments, a single battery cell may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0137] In some embodiments, the outer packaging of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0138] In some embodiments, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0139] Figure 3 shows a battery module 4 as an example. Referring to Figure 3, in battery module 4, multiple battery cells can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells can be fixed in place using fasteners.

[0140] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells are housed.

[0141] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0142] Figures 4 and 5 show a battery pack 1 as an example. Referring to Figures 4 and 5, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0143] In a fourth aspect, this application proposes an electrical device comprising the aforementioned sodium battery, and / or a sodium battery prepared using the aforementioned method. Thus, the electrical device possesses all the features and advantages of the aforementioned sodium battery and the method for preparing the sodium battery, which will not be repeated here.

[0144] Battery cells, battery modules, and battery packs can be used as power sources for electrical devices or as energy storage units for electrical devices. Electrical devices can include, but are not limited to, mobile devices (such as mobile phones, laptops, 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.

[0145] As an electrical device, batteries, battery modules, or battery packs can be selected according to their usage requirements.

[0146] Figure 6 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of this device, a battery pack or battery module can be used.

[0147] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0148] The following specific embodiments illustrate the solution of this application. It should be noted that these embodiments are for illustrative purposes only and should not be considered as limiting the scope of this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0149] Example 1

[0150] Preparation of positive electrode sheet: The positive electrode active material is carbon-coated sodium iron pyrophosphate. The positive electrode active material, conductive carbon black and polyvinylidene fluoride are mixed in a mass ratio of 95:3:2 and then N-methylpyrrolidone solvent is added to prepare a positive electrode slurry with a solid content of 5%. The slurry is coated on one side of aluminum foil and then cold-pressed and cut to obtain the positive electrode sheet.

[0151] Preparation of the negative electrode sheet: Aluminum foil coated with single-walled carbon nanotubes was used. Single-walled carbon nanotubes and sodium carboxymethyl cellulose were mixed at a mass ratio of 99:1 and then added to a deionized water solvent to prepare a functional coating slurry with a solid content of 4‰. The slurry was coated on one side of the aluminum foil with a thickness of 2μm. After cold pressing and cutting, the negative electrode sheet was obtained.

[0152] Separator: A polyethylene film with a thickness of 7μm is used as the separator.

[0153] Preparation of the gel electrolyte: Polyethylene oxide, benzophenone, and sodium hexafluorophosphate with an average relative molecular mass of 600,000 were mixed in a mass ratio of 60:3:40 in acetonitrile (solvent) at 70°C to form a sol with a solid content of 8%. The sol was uniformly coated onto a glass plate to a thickness of 300 μm, and then vacuum dried at 60°C for 8 h to obtain a pre-formed polymer electrolyte. The obtained pre-formed polymer electrolyte was immersed in 1 mol / L sodium hexafluorophosphate in ethylene glycol dimethyl ether at 40°C for 20 h to obtain the gel electrolyte. The mass of the pre-formed polymer electrolyte was m1, the mass of the gel electrolyte was m2, and the liquid absorption was (m2-m1) / m1.

[0154] Battery assembly:

[0155] Sodium battery assembly: The tabs are welded to the positive and negative electrode plates by electric welding. The gel electrolyte is attached to the front and back of the 7μm polyethylene separator. The plates are stacked in the order of negative electrode plate-separator-positive electrode plate and encapsulated with aluminum-plastic film. After standing for 4 hours, the sodium battery is formed with a current of 0.1C and a charge / discharge cutoff voltage of 1.5V-3.6V.

[0156] For the differences between the other examples and comparative examples and Example 1, please refer to Tables 1-1 and 1-2. In Comparative Example 1, no free radical scavenger was added when preparing the gel electrolyte, while in Example 9, NASICON solid electrolyte was added to the sol when preparing the gel electrolyte.

[0157] Table 1-1

[0158] Table 1-2

[0159] The mass fractions of each substance in the gel electrolyte prepared above are shown in Table 1-3:

[0160] Table 1-3

[0161] The batteries in the aforementioned embodiments and comparative examples were subjected to the following performance tests, and the test results are shown in Table 2.

[0162] High-temperature cycling performance: ① Let the battery stand for 4 hours and test its volume V1 (ml). ② Charge the battery at a constant current of 0.1C to 3.65V, then charge it at a constant voltage of 3.65V to a current of 0.02C and let it stand for 5 minutes. ③ Discharge the battery at a current of 0.1C to 1.5V, then let it stand for 5 minutes and then discharge it to 1.5V at a current of 0.02C. ④ Charge the battery at a constant current of 1C to 3.65V, then charge it at a constant voltage of 3.65V to a current of 0.02C and let it stand for 5 minutes. ⑤ Discharge the battery at a current of 1C to 1.5V, then let it stand for 5 minutes and then discharge it to 1.5V at a current of 0.02C. ⑥ Place the battery in silicone oil at a temperature controlled at 60℃ and repeat steps ④ and ⑤ above. After 200 cycles, test the battery volume V3 (ml). Gas production (ml) after 200 cycles = V3 - V1.

[0163] High-Temperature Storage Gas Production Test: ① Let the battery stand for 4 hours and measure its volume V1 (ml). ② Charge the battery at a constant current of 0.1C to 3.65V, then charge it at a constant voltage of 3.65V to a current of 0.02C, and let it stand for 5 minutes. ③ Discharge the battery at a current of 0.1C to 1.5V, then let it stand for 5 minutes, and then discharge it again at a current of 0.02C to 1.5V. ④ Charge the battery at a constant current of 1C to 3.65V, then charge it at a constant voltage of 3.65V to a current of 0.02C, and let it stand for 5 minutes. ⑤ Store the battery in a 60℃ constant temperature chamber for 10 days and measure its volume V2 (ml). Gas production (ml) after 10 days of storage = V2 - V1.

[0164] Table 2

[0165] Table 2 shows that for polymers with different relative molecular masses in Examples 1-3 and different types of polymers in Examples 4-6, the addition of free radical scavengers can suppress the side reactions between free radicals formed by polymer decomposition and sodium metal, effectively improving the high-temperature performance of the battery. Examples 7 and 8 show that different free radical scavengers can capture free radicals and suppress the side reactions between free radicals formed by polymer decomposition and sodium metal. Example 9 shows that the ionic conductivity of the polymer is improved after filling with inorganic materials, and the high-temperature performance of the battery is further improved. Example 10 shows that different electrolyte salts can be used in the gel electrolyte system of this application. Examples 11-20 show that the mass ratio of free radical scavengers to polymers in the gel electrolyte can be controlled by adjusting the mass ratio between the substances in the sol, the soaking time and temperature, and the molar concentration of the second electrolyte salt in the electrolyte, thereby improving the performance of the gel electrolyte. Among them, Example 16 shows that using the same first electrolyte salt and second electrolyte salt helps to reduce the dissolution of the first electrolyte salt during the soaking process, improve the ionic conductivity of the polymer, and improve the high-temperature performance of the battery. Comparative Example 1 shows that without the addition of a free radical scavenger, the side reaction between the free radicals formed by polymer decomposition and sodium metal cannot be effectively suppressed, resulting in poor high-temperature performance of the battery.

[0166] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. Sodium batteries, among which, include: Gel electrolyte, the gel electrolyte comprising: polymer; Free radical scavenger, wherein the mass ratio of the free radical scavenger to the polymer in the gel electrolyte is 1:(10-75).

2. The sodium battery according to claim 1, wherein, The polymer includes at least one of the following: polyethylene oxide, polyethylene glycol, polyvinylidene fluoride, polyethylene glycol diacrylate, polymethyl methacrylate, polycaprolactone triacrylate, polyacrylonitrile, polyvinylpyrrolidone, sodium perfluorosulfonate, sodium poly(tartaric acid)borate, polypentylmalonic acid, polyurethane, trimethylsilyl cage polysilsesquioxane, polyvinylidene fluoride-hexafluoropropylene copolymer, and methyl vinyl ether maleic anhydride copolymer.

3. The sodium battery according to claim 2, wherein, At least one of the following conditions must be met: (1) The polymer includes polyacrylonitrile, wherein the relative molecular mass of the polyacrylonitrile is 50,000 to 150,000; (2) The polymer includes polyvinylidene fluoride-hexafluoropropylene copolymer, wherein the relative molecular mass of the polyvinylidene fluoride-hexafluoropropylene copolymer is 200,000 to 500,000; (3) The polymer includes a methyl vinyl ether maleic anhydride copolymer, wherein the relative molecular mass of the methyl vinyl ether maleic anhydride copolymer is 200,000 to 1,000,000; (4) The polymer includes polyethylene oxide, the relative molecular mass of which is 400,000 to 1,000,000.

4. The sodium battery according to any one of claims 1-3, wherein, The free radical scavenger includes at least one of benzophenone, β-diketone, glyceryl triglycidyl ether, 4-benzoyl-2,2,6,6-tetramethylpiperidine, benzotriazole, tris(2,4-di-tert-butylphenyl) phosphite, octadecyl β-(4-hydroxyphenyl-3,5-di-tert-butyl)propionate, lead stearate, basic lead carbonate, calcium stearate, zinc glycerol, cerium carbonate, lanthanum stearate, praseodymium stearate, nickel 3,5-di-tert-butyl-4-hydroxybenzyl phosphate monoethyl ester, butyltin dimethylsiloxane, dioctyltin monoethyl maleate, and antimony isooctyl trithioacetate.

5. The sodium battery according to claim 4, wherein, The free radical scavenger includes at least one of benzophenone, 4-benzoyl-2,2,6,6-tetramethylpiperidine, lead stearate, and butyltin disterite.

6. The sodium battery according to any one of claims 1-5, wherein, At least one of the following conditions must be met: (1) The mass fraction of the polymer in the gel electrolyte is 20%-60%; (2) The mass fraction of the free radical scavenger in the gel electrolyte is 0.5%-4%.

7. The sodium battery according to any one of claims 1-6, wherein, The gel electrolyte further comprises an inorganic material filled in the polymer, the inorganic material including at least one of alumina, silicon dioxide, sodium carbonate, sodium fluoride, β-alumina solid electrolyte, and NASICON solid electrolyte.

8. The sodium battery according to any one of claims 1-7, wherein, The sodium battery is a negative electrode-less sodium battery.

9. A method for preparing a sodium battery, wherein, include: The polymer, free radical scavenger, and first electrolyte salt are mixed in a solvent to obtain a sol, wherein the solvent includes at least one of acetonitrile, N-methylpyrrolidone, and acetone. The sol is heated to obtain a pre-formed polymer electrolyte; The preformed polymer electrolyte is immersed in an electrolyte solution to obtain a gel electrolyte, thereby obtaining the sodium battery. The electrolyte solution includes an electrolyte solvent and a second electrolyte salt. The immersion time is 8-50 hours, and the immersion temperature is 30°C-60°C.

10. The method according to claim 9, wherein, The first electrolyte salt is the same as the second electrolyte salt.

11. The method according to claim 9 or 10, wherein, At least one of the following conditions must be met: (1) In the mixing process, the mass ratio of the polymer, the free radical scavenger, and the first electrolyte salt is (50-75):(1-5):(25-50). (2) The temperature of the mixing treatment is 60℃-90℃ and the time of the mixing treatment is 8h-24h.

12. The method according to any one of claims 9-11, wherein, The solid content of the sol is 5%-15%.

13. The method according to any one of claims 9-12, wherein, The heat treatment includes coating the sol onto the surface of a flat plate to form a coating layer with a thickness of 150 μm-1000 μm; The coating layer is subjected to vacuum drying treatment at a temperature of 50℃-120℃.

14. The method according to claim 9, wherein, The molar concentration of the second electrolyte salt in the electrolyte is 0.5 mol / L to 2.5 mol / L.

15. Battery device, wherein, The sodium battery includes at least one of the sodium batteries according to any one of claims 1-8, and sodium batteries prepared by the method according to any one of claims 9-14.

16. Electrical appliances, of which, The sodium battery includes at least one of the sodium batteries according to any one of claims 1-8, and sodium batteries prepared by the method according to any one of claims 9-14.

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