Electrochemical method for realizing room-temperature reversible phase transition of sodium chloride and metal sodium

Abstract

The invention provides an electrochemical method for realizing reversible phase transition of sodium chloride and metal sodium at room temperature. A chloride material is used as a cathode material, and metal sodium is used as an anode material, or a non-chloride material is used as the cathode material, and sodium chloride is used as the anode material; the electrolyte containing organic chlorine salt is adopted; and then, at normal temperature and normal pressure, chloride ions are driven to shuttle between the cathode and the anode through constant-current charging and discharging, and reversible phase transformation between sodium chloride and metal sodium is realized at room temperature through a discharging-charging process. By constructing an electrochemical system, reversible phase transformation between sodium chloride and metal sodium is realized at room temperature, and a technical support is provided for realizing low-carbon sodium preparation.

Description

Technical Field

[0001] The present invention relates to the technical field of metallic sodium preparation, and in particular to an electrochemical method for achieving room-temperature reversible phase transformation between sodium chloride and metallic sodium. Background Art

[0002] Sodium metal (Na) has been widely used in various fields, including energy storage, catalytic reactions, and chemical synthesis, due to its high energy density and excellent electrochemical properties. In recent years, due to its abundant resources and low cost, sodium metal has gradually become a key candidate material for next-generation energy storage technologies, especially in the field of secondary battery energy storage, where its demand continues to grow.

[0003] Currently, the main industrial processes for producing sodium metal include molten salt electrolysis, caustic soda electrolysis, and chemical reduction. Molten salt electrolysis, in particular, has become the mainstream process for producing sodium metal worldwide. This process typically uses graphite as the anode, nickel or iron as the cathode, and molten sodium chloride as the electrolyte for electrolysis. Sodium chloride, a raw material widely found in seawater and salt mines, is abundant, readily available, and relatively low in cost, offering significant resource advantages. Therefore, using sodium chloride to produce sodium metal has become a highly promising and sustainable production solution.

[0004] However, despite the abundance and low cost of sodium chloride, traditional electrolysis still faces several challenges. Sodium chloride has a high melting point of 801°C, requiring significant energy consumption for molten electrolysis. Furthermore, the complex electrolysis equipment makes it difficult to meet the demands of large-scale industrial production. To lower the temperature of the electrolysis reaction, existing technologies often use binary or ternary eutectics (such as mixtures of sodium chloride with potassium chloride and calcium chloride) to reduce the reaction temperature to around 600°C, thereby reducing energy consumption.

[0005] Despite this, these traditional methods still require electrolytic melting at extremely high temperatures to convert sodium chloride into metallic sodium, resulting in significant energy consumption and potential safety risks. Furthermore, the conversion of sodium chloride into metallic sodium often involves the production of chlorine gas, posing potential environmental and safety risks.

[0006] However, there is no method in the existing technology that can achieve the phase transformation of sodium chloride to metallic sodium at room temperature, thus failing to provide technical support for low-carbon sodium production. Summary of the Invention

[0007] The present invention aims to address the deficiencies in the existing technology and provide an electrochemical method for achieving reversible phase transformation of sodium chloride and metallic sodium at room temperature. Under normal temperature and pressure conditions, the phase transformation path from sodium chloride to metallic sodium is achieved through electrochemical reaction, providing technical support for the realization of low-carbon sodium production.

[0008] According to a first aspect of the present invention, there is provided an electrochemical method for achieving a reversible phase transition between sodium chloride and metallic sodium at room temperature, the method comprising:

[0009] A chloride material is used as a cathode material, metallic sodium is used as an anode material, and an electrolyte containing an organic chloride salt is used;

[0010] Afterwards, at room temperature and pressure, constant current charging and discharging drives chloride ions to shuttle between the cathode and the anode. After the discharge-charge process, a reversible phase transition between sodium chloride and metallic sodium is achieved at room temperature.

[0011] During the discharge process, chloride ions are transferred from the cathode to the anode, and sodium chloride is obtained on the anode side; during the charging process, chloride ions are transferred from the anode to the cathode, and the sodium chloride on the anode side is electrochemically reduced to metallic sodium.

[0012] According to a second aspect of the present invention, there is provided an electrochemical method for achieving a reversible phase transition between sodium chloride and metallic sodium at room temperature, the method comprising:

[0013] Using a non-chloride material as the cathode material and sodium chloride as the anode material; and using an electrolyte containing an organic chloride salt;

[0014] Afterwards, at room temperature and pressure, constant current charging and discharging drives chloride ions to shuttle between the cathode and the anode. After the discharge-charge process, a reversible phase transition between sodium chloride and metallic sodium is achieved at room temperature.

[0015] During the discharge process, chloride ions are transferred from the cathode to the anode, and sodium chloride is obtained on the anode side; during the charging process, chloride ions are transferred from the anode to the cathode, and the sodium chloride on the anode side is electrochemically reduced to metallic sodium.

[0016] As an optional embodiment, the electrolyte is in liquid, gel or solid state.

[0017] As an optional embodiment, when the electrolyte is in a liquid or gel state, the electrolyte comprises an organic chloride salt and an organic solvent, and the organic solvent comprises an ether solvent and / or an ester solvent.

[0018] As an optional embodiment, the ether solvent includes 1,3-dioxolane and / or 1,4-dioxane, and the ester solvent includes propylene carbonate.

[0019] As an alternative embodiment, when the electrolyte is in a solid state, the electrolyte comprises an organic chloride salt and a hydrogen bond donor, and the hydrogen bond donor comprises ethylene carbonate.

[0020] As an optional embodiment, the organic chloride salt includes one or more of pyrrolidine chloride salt, piperidine chloride salt, imidazole chloride salt and quaternary ammonium chloride salt.

[0021] As an optional embodiment, the chloride material includes one or more of transition metal chlorides, transition metal oxychlorides, main group metal chlorides, main group metal oxychlorides, and organic chlorides.

[0022] As an optional embodiment, the non-chloride material includes one or more of the discharge products of transition metal chlorides, the discharge products of transition metal chloride oxides, the discharge products of main group metal chlorides, the discharge products of main group metal chloride oxides, the discharge products of organic chlorides, and carbon materials.

[0023] As an optional embodiment, the organic chloride includes one or more of chlorine-doped polythiophene, chlorine-doped polyaniline, chlorine-doped polypyrrole, chlorine-doped polycyanonitrile, and chlorine-doped polyphenazine.

[0024] As can be seen from the above technical solutions of the present invention, the electrochemical method for achieving room-temperature reversible phase transformation between sodium chloride and metallic sodium proposed in the present invention realizes the reversible phase transformation between sodium chloride and metallic sodium at room temperature by constructing an electrochemical system. Compared with the traditional method that requires such phase transformation to be carried out at high temperature (>800°C), it has important technical breakthrough significance.

[0025] The method of the present invention can provide important technical support for utilizing sodium chloride resources that are widely available and low in cost to achieve phase conversion of sodium chloride into metallic sodium through an electrochemical reaction at room temperature, thereby achieving efficient and safe preparation of metallic sodium and overcoming the problems of high energy consumption and poor operational safety in traditional high-temperature electrolysis methods. Compared with existing industrial technologies, the method significantly reduces energy consumption, improves energy efficiency, and avoids the generation of chlorine gas, thereby improving safety and reducing environmental risks, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The present invention is a schematic diagram of the process of the electrochemical method for achieving room temperature reversible phase transformation of sodium chloride and metallic sodium.

[0027] Figure 2 1 is the charge and discharge curve of Example 1 of the present invention in constant current mode.

[0028] Figure 3 1 is an XRD pattern of the anode in Example 1 of the present invention after constant current charge and discharge.

[0029] Figure 4 This is a scanning electron microscope (SEM) image of sodium chloride obtained after the anode discharge process in Example 1 of the present invention.

[0030] Figure 5 1 is the charge and discharge curve of Example 2 of the present invention under constant current mode.

[0031] Figure 6 3 is the charge and discharge curve of Example 3 of the present invention in constant current mode.

[0032] Figure 7 1 is the charge and discharge curve of Example 4 of the present invention under constant current mode.

[0033] Figure 8 1 is the charge and discharge curve of Example 5 of the present invention in constant current mode.

[0034] Figure 9 1 is the charge and discharge curve of Example 6 of the present invention in constant current mode.

[0035] Figure 10 1 is the charge and discharge curve of Example 7 of the present invention in constant current mode.

[0036] Figure 11 1 is the charge and discharge curve of Example 8 of the present invention in constant current mode. DETAILED DESCRIPTION

[0037] In order to better understand the technical content of the present invention, specific embodiments are given and described below with reference to the accompanying drawings.

[0038] Various aspects of the present invention are described in this disclosure with reference to the accompanying drawings, in which a number of illustrative embodiments are shown. The embodiments of the present disclosure are not necessarily intended to be comprehensive. It should be understood that the various concepts and embodiments described above, as well as those described in more detail below, can be implemented in any of a number of ways.

[0039] The present invention realizes the reversible phase transition between sodium chloride (NaCl) and metallic sodium (Na) at room temperature by constructing a special electrochemical system, providing important technical support for the direct use of sodium chloride to prepare metallic sodium at room temperature.

[0040] In one exemplary embodiment of the present invention, the electrochemical method for achieving a reversible phase transition between sodium chloride and metallic sodium at room temperature includes:

[0041] A chloride material is used as a cathode material, metallic sodium is used as an anode material, and an electrolyte containing an organic chloride salt is used;

[0042] Afterwards, at room temperature and pressure, constant current charging and discharging drives chloride ions to shuttle between the cathode and the anode. After the discharge-charge process, a reversible phase transition between sodium chloride and metallic sodium is achieved at room temperature.

[0043] During the discharge process, chloride ions are transferred from the cathode to the anode, and sodium chloride is obtained on the anode side; during the charging process, chloride ions are transferred from the anode to the cathode, and the sodium chloride on the anode side is electrochemically reduced to metallic sodium.

[0044] In another exemplary embodiment of the present invention, the electrochemical method for achieving a reversible phase transition between sodium chloride and metallic sodium at room temperature comprises:

[0045] Using a non-chloride material as the cathode material and sodium chloride as the anode material; and using an electrolyte containing an organic chloride salt;

[0046] Afterwards, at room temperature and pressure, constant current charging and discharging drives chloride ions to shuttle between the cathode and the anode. After the discharge-charge process, a reversible phase transition between sodium chloride and metallic sodium is achieved at room temperature.

[0047] During the discharge process, chloride ions are transferred from the cathode to the anode, and sodium chloride is obtained on the anode side; during the charging process, chloride ions are transferred from the anode to the cathode, and the sodium chloride on the anode side is electrochemically reduced to metallic sodium.

[0048] As optional examples, the electrolyte is in liquid, gel or solid state.

[0049] In one example, the electrolyte is a liquid and is composed of an organic chloride salt and an organic solvent.

[0050] In another example, the electrolyte is in a gel state, and the electrolyte is formed by compounding a liquid system consisting of an organic chloride salt and an organic solvent with a corresponding polymer.

[0051] When the electrolyte is in liquid or gel state, the organic solvent used includes ether solvents and / or ester solvents; wherein,

[0052] Ether solvents include 1,3-dioxolane (DOL) and / or 1,4-dioxane (DX);

[0053] Ester solvents include propylene carbonate (PC);

[0054] Specific organic solvents are used to promote the dissociation of chloride salts and provide fast ion transport channels. Through solvation and preferential decomposition of salts, a thin and stable sodium passivation solution is formed on the sodium surface, realizing the phase transition from sodium chloride to metallic sodium at room temperature.

[0055] In another preferred example, a trace amount of additives is added to the organic solvent, for example, one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylene carbonate (EC), tetrahydrofuran (THF), acetonitrile (AN) and sulfolane (TMS);

[0056] By adding the above substances, a more stable SEI layer is generated, making the phase transition between sodium chloride and metallic sodium more stable.

[0057] In other preferred examples, the amount of the additive added is 0.1-5% of the total mass of the electrolyte, and particularly preferably, the amount added is 0.1-3 vol% of the total volume of the electrolyte.

[0058] It is understandable that the types of additives include but are not limited to the above materials, and the principle of selection is that they can promote the formation of a denser and more stable solid electrolyte interface film (SEI) on the sodium surface.

[0059] In a further example, a liquid system consisting of an organic chloride salt and an organic solvent is compounded with a polymer, and a gel electrolyte can be prepared using a method for preparing a gel electrolyte in the prior art.

[0060] In another example, the electrolyte is solid and is formed by a deep eutectic solvent system consisting of an organic chloride salt and a hydrogen bond donor and a corresponding polymer.

[0061] In another preferred example, the hydrogen bond donor includes ethylene carbonate (EC), which forms a stable deep eutectic solvent system with the organic chloride salt through hydrogen bond interaction, promotes the dissociation of the chloride salt and provides a fast ion transport channel, and forms a thin and stable solution for sodium negative electrode passivation on the sodium surface through solvation and preferential decomposition of the salt, thereby realizing the phase transition from sodium chloride to metallic sodium at room temperature.

[0062] It should be understood that hydrogen bond donors include but are not limited to the above materials, and their selection only needs to follow the following basic characteristics:

[0063] (1) It has obvious hydrogen bond donor properties and can form stable hydrogen bond complexes;

[0064] (2) It can effectively lower the melting point of the blend system and form a stable deep eutectic solvent;

[0065] (3) Have good chemical and electrochemical stability and do not interfere with electrode reactions;

[0066] (4) It has a certain ability to dissolve and transport ions to ensure electrolyte conductivity and interface stability.

[0067] In a further example, a deep eutectic solvent system consisting of an organic chloride salt and a hydrogen bond donor is compounded with a corresponding polymer, and a solid electrolyte can be prepared using a method for preparing a solid electrolyte in the prior art.

[0068] It can be understood that the polymer used in preparing the gel or solid electrolyte can also be selected according to the existing technology.

[0069] In one preferred example, the polymer includes one or more of a linear polymer, a network polymer, and a cyclic polymer electrolyte matrix; for example,

[0070] In a preferred example, the linear polymer matrix includes polyethylene oxide, polyvinylidene fluoride, polyethylene glycol diacrylate; the network polymer matrix includes three-dimensional cross-linked polyether, composite cross-linked PEO; and the cyclic polymer matrix includes cyclic carbonate-based polymer, poly 1,3-dioxane.

[0071] In other optional examples, the preparation of gel-state and solid-state electrolytes may adopt thermal polymerization, photopolymerization, or electropolymerization in the prior art.

[0072] In a further preferred embodiment of the present invention, gel and solid electrolytes are prepared by thermally initiated polymerization, for example,

[0073] A polymerizable polymer (such as the aforementioned polymer) and a thermal initiator (such as azobisisobutyronitrile AIBN) are added to a liquid electrolyte formed by dissolving an organic chloride salt in an organic solvent. After stirring evenly, the mixture is heated in an inert atmosphere for several hours to achieve in-situ polymerization of the monomers and obtain a gel electrolyte with a uniform structure.

[0074] In a deep eutectic solvent system composed of an organic chloride salt and a hydrogen bond donor, a polymerizable polymer (such as the aforementioned polymer) and a thermal initiator (such as azobisisobutyronitrile AIBN) are added. After stirring evenly, the mixture is heated in an inert atmosphere for several hours to achieve in-situ polymerization of the monomer and obtain a solid electrolyte with uniform structure.

[0075] It can be understood that in the above-mentioned electrochemical system, if a liquid electrolyte is used as the electrolyte, a diaphragm is required to prevent direct contact between the anode and the cathode. At the same time, the diaphragm can absorb the electrolyte and keep the ions in the electrolyte from being transmitted between the cathode and cathode or the positive and negative electrodes. If a gel or solid electrolyte is used, the gel or solid electrolyte itself has rigidity and can avoid contact between the cathode and cathode, so no diaphragm is required.

[0076] For example, Figure 1 Schematic diagram of an electrochemical system using chloride material as cathode material, metallic sodium as anode material, and a liquid electrolyte composed of an organic chloride salt and an organic solvent as the electrolyte.

[0077] In an optional example, the chloride material includes one or more of transition metal chlorides, transition metal oxychlorides, main group metal chlorides, main group metal oxychlorides, and organic chlorides.

[0078] It should be understood that chloride materials include but are not limited to the above materials, and their selection only needs to follow the following basic characteristics:

[0079] (1) It has low solubility or is insoluble in the organic solvent or electrolyte system used, and can maintain structural stability during the electrochemical cycle;

[0080] (2) Its metal center has reversible redox activity. During the battery discharge process, it can be reduced from a high-valent state to a low-valent state (i.e., from a metal chloride to a corresponding metal compound or metal element). During the charging process, it can be reoxidized to a high-valent metal chloride, achieving a reversible phase transformation.

[0081] (3) The above redox reaction should be carried out within the system operating voltage range and have good cycle stability and capacity retention.

[0082] In other words, the chloride material suitable for the cathode should be a material with good electrochemical reversibility, stable in the electrolyte, capable of undergoing valence state transformation and realizing reversible transformation between chloride and metal (or low-valent compound).

[0083] It will be appreciated that the chloride material can be purchased directly or prepared according to existing techniques.

[0084] In an optional example, the non-chloride material includes one or more of discharge products of transition metal chlorides, discharge products of transition metal oxychlorides, discharge products of main group metal chlorides, discharge products of main group metal oxychlorides, discharge products of organic chlorides, and carbon materials.

[0085] It can be understood that the discharge products of the above substances refer to the products after dechlorination of these substances. For example, the discharge product of BiCl3 actually refers to BiCl3 becoming Bi after discharge, and Bi is the discharge product of BiCl3.

[0086] The non-chloride of the discharge product is generally prepared according to the following steps: chloride or chloride oxide is used as the cathode, metallic sodium is used as the anode, and the non-chloride is obtained by constant current discharge; for example, the corresponding non-chloride is obtained by using the aforementioned system of the present invention using chloride material as the cathode material, metallic sodium as the anode material, and using an electrolyte containing an organic chloride salt.

[0087] Of course, non-chloride materials include but are not limited to these discharge products, and can also be directly synthesized and prepared according to existing technologies.

[0088] It can be understood that the selection of the type of non-chloride material corresponds to the above-mentioned principle of selecting the type of chloride.

[0089] In an optional example, the organic chloride includes one or more of chlorine-doped polythiophene, chlorine-doped polyaniline, chlorine-doped polypyrrole, chlorine-doped polycyanonitrile, and chlorine-doped polyphenazine.

[0090] It should be understood that the organic chloride includes but is not limited to the above materials. The selected organic chloride is a conductive polymer material, which, after chlorine doping, must have the following key properties:

[0091] (1) It can provide reversible redox sites in the established electrochemical system to achieve reversible insertion and removal of chloride ions;

[0092] (2) The material itself has good electrical conductivity and structural stability, and can maintain high electron and ion transmission efficiency during multiple charge and discharge cycles;

[0093] (3) The chlorine-doped polymer exhibits certain electrochemical activity, its redox potential is within the operating voltage range of the system, and the conversion process between the doped and dedoped states is reversible;

[0094] (4) The material has good chemical stability and low solubility in the electrolyte.

[0095] In an optional example, the organic chloride salt includes one or more of pyrrolidine chloride salt, piperidine chloride salt, imidazole chloride salt and quaternary ammonium chloride salt; for example, in a preferred example, the pyrrolidine chloride salt includes N-alkyl-N-methylpyrrolidine chloride salt, the piperidine chloride salt includes 1-butyl-1-methylpiperidinium chloride salt, the imidazole chloride salt includes 1-ethyl-3-methylimidazolium chloride salt (PP 14 Cl) and / or 1-octyl-3-methylimidazolium chloride [OMIM][Cl], the quaternary ammonium chloride salt includes at least one of tributylammonium chloride (TBMACl), choline chloride and tetraethyl chloride.

[0096] It should be understood that organic chloride salts include but are not limited to the above materials, and their selection only needs to follow the following principles:

[0097] (1) It has good ionic conductivity and electrochemical stability, and can form a stable deep eutectic electrolyte system with the selected hydrogen bond donor as a hydrogen bond acceptor;

[0098] (2) Its cationic structure should be thermally stable and chemically inert to ensure that no obvious decomposition reaction occurs within the operating voltage range of the system.

[0099] (3) In addition, to be suitable for industrial applications, organochlorine salts should have clear synthesis routes, a wide range of raw material sources, and controllable costs.

[0100] In an optional example, the charging and discharging processes are both performed under an inert atmosphere.

[0101] It is understood that in an electrochemical system using a non-chloride material as a cathode and sodium chloride as an anode, the sodium chloride used as the anode includes the sodium chloride obtained after the discharge of the metallic sodium in the electrochemical system using a chloride material as a cathode and metallic sodium as an anode; and

[0102] The parameters used in constant current charge and discharge can be adjusted according to actual conditions; in practical applications, the current density can be flexibly set according to factors such as the specific capacity, rate performance and reaction kinetics of the electrode material; the cut-off voltage range for charge and discharge is determined based on the electrode potential of the anode and cathode materials and the potential range of the redox reaction, and should be within the electrochemical stability window of the material to ensure the smooth progress of the reversible reaction.

[0103] For better understanding, the present invention is further described below with reference to several specific examples, but the preparation process is not limited thereto, and the content of the present invention is not limited thereto.

[0104] Unless otherwise specified, the materials in the examples were prepared according to existing methods or directly purchased from the market.

[0105] [Using chloride material as cathode material and metallic sodium as anode material]

[0106] Example 1

[0107] The chlorine oxide FeOCl was used as cathode, glass fiber membrane (GF / D, Whatman) was used as separator, metal Na was used as anode, and PP was used as electrolyte. 14 Cl / PC is a liquid electrolyte.

[0108] Preparation process of cathode material FeOCl: FeCl3·6H2O was vacuum heat-treated at 180℃ for 10h, then washed with acetone and dried in a vacuum oven at 120℃ to obtain FeOCl cathode material.

[0109] Using NMP as solvent, a mixture of active material (FeOCl, 60 wt.%), polyvinylidene fluoride (PVDF, 10 wt.%) and carbon black (30 wt.%) was ground for 30 min, and then the obtained slurry was coated on carbon paper and dried at 80 ° C under vacuum overnight to prepare the cathode electrode material.

[0110] Preparation process of electrolyte: PP 14 Cl was vacuum dried at 80 °C for 48 h before use. 14 Cl was dissolved in PC and stirred at 450 rpm for 12 h at room temperature to obtain a liquid electrolyte with a concentration of 0.5 M. All steps were carried out in a controlled atmosphere of H2O and O2 (<0.01 ppm).

[0111] In a glove box filled with high-purity argon (H2O and O2 < 0.01ppm), FeOCl was used as cathode, metallic sodium was used as anode, and 0.5M PP 14 Cl / PC was used as the electrolyte and glass fiber membrane (GF / D, Whatman) was used as the separator to assemble CR2032 button cells.

[0112] Afterwards, constant current mode was adopted for charging and discharging, with a current density of 5 mA / g and a charge and discharge cut-off voltage range of 1.5 to 3.6 V. After the discharge-charge process, high-purity metallic sodium was obtained on the anode side.

[0113] Figure 2 The constant current charge-discharge curve is shown, indicating that the electrochemical system constructed by the present invention undergoes a reversible charge-discharge reaction, thereby verifying the reversible electrochemical conversion behavior between NaCl and Na.

[0114] The specific phase change is determined by Figure 3 The XRD results shown in the figure verify that, during discharge, sodium chloride is obtained on the anode side; during charging, the sodium chloride on the anode side is electrolytically reduced to metallic sodium, realizing the phase transition between sodium chloride and metallic sodium at room temperature, and obtaining high-purity metallic sodium.

[0115] Figure 4 This is a scanning electron microscope (SEM) image of sodium chloride obtained after the anode discharge process. The deposition morphology of sodium chloride on the electrode surface can be observed, indicating that the system successfully generated sodium chloride during the discharge process. Figure 2 The structural information confirmed by XRD confirms each other, further verifying that the electrochemical system constructed by the present invention can realize the reversible phase transition process between Na and NaCl at room temperature.

[0116] Example 2

[0117] The chloride CuCl was used as the cathode, the glass fiber membrane (GF / D, Whatman) was used as the separator, the metal Na was used as the anode, and the TBMACl / PC-EC was used as the liquid electrolyte.

[0118] Preparation process of cathode material CuCl: Carbon black was dried under vacuum at 80°C overnight, and then a mixture of CuCl powder (80 wt.%) and carbon black (20 wt.%) was ball-milled at 200 rpm for 2 h in an argon atmosphere to prepare the CuCl cathode material.

[0119] A mixture of active material (CuCl, 70 wt.%), polyvinylidene fluoride (PVDF, 10 wt.%), and carbon black (20 wt.%) was ground for 30 min using NMP as solvent. The obtained slurry was then dropped onto stainless steel and dried at 80 °C under vacuum overnight to prepare the cathode electrode material.

[0120] Electrolyte preparation: TBMACl was vacuum-dried at 80°C for 24 hours before use. TBMACl was then dissolved in PC-EC (EC added at 5% of the total liquid mass) and stirred at 450 rpm for 12 hours at room temperature to obtain a 0.5 M liquid electrolyte. All steps were performed in a controlled atmosphere of H2O and O2 (<0.01 ppm).

[0121] In a glove box filled with high-purity argon (H2O and O2 <0.01ppm), CR2032 button cells were assembled with CuCl as cathode, metallic sodium as anode, 0.5M TBMACl / PC-EC as electrolyte, and glass fiber membrane (GF / D, Whatman) as separator.

[0122] Afterwards, constant current mode was adopted for charging and discharging, with a current density of 5 mA / g and a charge and discharge cut-off voltage range of 1.0 to 2.0 V. After the discharge-charge process, high-purity metallic sodium was obtained on the anode side.

[0123] Figure 5 This is the constant current charge-discharge curve of this embodiment, which shows that the electrochemical system constructed by the present invention undergoes a reversible charge-discharge reaction, thereby verifying the reversible electrochemical conversion behavior between NaCl and Na.

[0124] Example 3

[0125] The organic chloride PPyCl is used as the cathode, the metal Na is used as the anode, and the electrolyte is a solid electrolyte composed of an organic chloride salt, a hydrogen bond donor and a polymer.

[0126] The preparation process of the cathode material PPyCl: 3.35g of FeCl3·H2O was added to 42mL of deionized water to prepare a 0.29mol / L FeCl3·6H2O solution. Under ultrasonic argon protection at 0°C, 0.36mL of pyrrole monomer was added to the dispersed carbon nanotube aqueous solution to ensure uniform dispersion. The entire FeCl3·H2O solution was then slowly added dropwise over a reaction time of 4h. After the reaction was completed, the filtrate was filtered through 0.22μm filter paper. After the filtrate became neutral, it was dried under vacuum at 90°C for 24h to prepare the PPyCl cathode material.

[0127] A mixture of active material (PPyCl, 60 wt.%), polyvinylidene fluoride (PVDF, 10 wt.%), and carbon black (30 wt.%) was ground for 30 min using NMP as solvent. The obtained slurry was then coated on carbon paper and dried at 80 °C under vacuum overnight to prepare the cathode electrode material.

[0128] Preparation process of the electrolyte: PEGDA, [OMIM][Cl] and EC are weighed in a mass ratio of 10:5:5, and stirred at 350 rpm on a magnetic stirrer for 5 hours until the solution is evenly mixed; after the solution is evenly distributed, 0.5 wt% of the thermal curing agent AIBN is weighed using an analytical balance and placed in a bottle, and stirred at 350 rpm until AIBN is dissolved in the solution, and then thermally cured at 60°C for 10 hours to obtain a solid electrolyte membrane.

[0129] In a glove box filled with high-purity argon (H2O and O2 <0.01ppm), a CR2032 button cell was assembled using PPyCl as the cathode, metallic sodium as the anode, and a solid electrolyte composed of an organic chloride salt and a polymer composite.

[0130] Afterwards, constant current mode was adopted for charging and discharging, with a current density of 5 mA / g and a charge and discharge cut-off voltage range of 1.2 to 3.0 V. After the discharge-charge process, high-purity metallic sodium was obtained on the anode side.

[0131] Figure 6 This is the constant current charge-discharge curve of this embodiment, which shows that the electrochemical system constructed by the present invention undergoes a reversible charge-discharge reaction, thereby verifying the reversible electrochemical conversion behavior between NaCl and Na.

[0132] Example 4

[0133] The organic chloride PPyCl is used as the cathode, the metal Na is used as the anode, and the electrolyte is a liquid electrolyte composed of an organic chloride salt and an organic solvent and a gel electrolyte composited with a polymer.

[0134] Preparation process of cathode material PPyCl: prepared according to the method in Example 3.

[0135] Preparation process of the electrolyte: A precursor containing 1.5 wt% PETEA and 0.1 wt% AIBN was dissolved in 1 M [OMIM][Cl] / PC electrolyte, and then the precursor solution was in situ polymerized at 60 ° C for 30 min in an Ar-filled glove box (H2O and O2 <0.1 ppm) to obtain a gel electrolyte.

[0136] In a glove box filled with high-purity argon (H2O and O2 <0.01ppm), PPyCl was used as the cathode, metallic sodium was used as the anode, and the electrolyte was a liquid electrolyte composed of an organic chloride salt and an organic solvent and a polymer composite gel electrolyte to assemble a CR2032 button cell.

[0137] Afterwards, constant current mode was adopted for charging and discharging, with a current density of 5 mA / g and a charge and discharge cut-off voltage range of 1.2 to 3.0 V. After the discharge-charge process, high-purity metallic sodium was obtained on the anode side.

[0138] Figure 7 This is the constant current charge-discharge curve of this embodiment, which shows that the electrochemical system constructed by the present invention undergoes a reversible charge-discharge reaction, thereby verifying the reversible electrochemical conversion behavior between NaCl and Na.

[0139] [Using non-chloride materials as cathode materials and sodium chloride as anode materials]

[0140] Example 5

[0141] Non-chloride TPT was used as cathode, glass fiber membrane (GF / D, Whatman) as separator, NaCl as anode, and TBMACl / DOL as liquid electrolyte.

[0142] Preparation of the TPT cathode material: 29.98 g of 4-cyanopyridine was heated to 150°C until molten, followed by the addition of 1.15 g of NaOH powder and reflux at 150°C with stirring for 24 hours. The resulting pale yellow solid was washed three times with acetone, dissolved in HCl solution, and then sonicated for 2 hours with 10.0 g of activated carbon to adsorb impurities. Finally, the suspension was filtered through celite, and the filtrate was neutralized with NaOH solution. The precipitated white solid was washed several times with water, filtered, and dried in vacuo at 80°C for 12 hours to produce the TPT cathode material.

[0143] Using NMP as solvent, a mixture of active material (TPT, 80 wt.%), polyvinylidene fluoride (PVDF, 10 wt.%) and carbon black (10 wt.%) was ground for 30 min, and then the obtained slurry was coated on carbon paper and dried at 80°C under vacuum overnight to prepare the cathode electrode material.

[0144] Electrolyte preparation: TBMACl was vacuum-dried at 80°C for 24 hours before use. TBMACl was then dissolved in DOL and stirred at 450 rpm for 12 hours at room temperature to obtain a 0.5 M liquid electrolyte. All steps were performed in a controlled atmosphere of H2O and O2 (<0.01 ppm).

[0145] In a glove box filled with high-purity argon (H2O and O2 < 0.01ppm), TPT was used as cathode, sodium chloride was used as anode, and 0.5M PP 14 Cl / PP 14 TFSI was used as the electrolyte and glass fiber membrane (GF / D, Whatman) was used as the separator to assemble into CR2032 button cells.

[0146] Afterwards, constant current mode was adopted for charging and discharging, with a current density of 5 mA / g and a charge and discharge cut-off voltage range of 0.1 to 3.5 V. After the charging process, the sodium chloride on the anode side was reduced to metallic sodium.

[0147] Figure 8 This is the constant current charge-discharge curve of this embodiment, which shows that the electrochemical system constructed by the present invention undergoes a reversible charge-discharge reaction, thereby verifying the reversible electrochemical conversion behavior between NaCl and Na.

[0148] Example 6

[0149] Non-chloride PPy was used as the cathode, glass fiber membrane (GF / D, Whatman) as the separator, NaCl as the anode, and [OMIM][Cl] / PC as the liquid electrolyte.

[0150] The cathode material, PPy, is a discharge product of PPyCl. The preparation process is as follows: CR2032 button cells are assembled using the organic chloride PPyCl as the cathode, metallic Na as the anode, and 0.5M [OMIM][Cl] / PC as the electrolyte. Subsequently, the cells are discharged in constant current mode at a current density of 5 mA / g and a discharge cutoff voltage adjusted to 1.2 V. During the discharge process, chloride ions are transferred from the cathode to the anode, and the discharge product PPy of PPyCl is obtained on the cathode side.

[0151] Electrolyte preparation: [OMIM][Cl] was vacuum-dried at 80°C for 24 hours before use. [OMIM][Cl] was then dissolved in PC and stirred at 450 rpm for 12 hours at room temperature to obtain a 0.5 M liquid electrolyte. All steps were performed in a controlled atmosphere of H2O and O2 (<0.01 ppm).

[0152] In a glove box filled with high-purity argon (H2O and O2 <0.01ppm), CR2032 button cells were assembled with PPy as cathode, sodium chloride as anode, 0.5M [OMIM][Cl] / PC as electrolyte, and glass fiber membrane (GF / D, Whatman) as separator.

[0153] Afterwards, constant current mode was adopted for charging and discharging, with a current density of 5 mA / g and a charge and discharge cut-off voltage range of 1.2 to 3.0 V. After the charging process, the sodium chloride on the anode side was reduced to metallic sodium.

[0154] Figure 9 This is the constant current charge-discharge curve of this embodiment, which shows that the electrochemical system constructed by the present invention undergoes a reversible charge-discharge reaction, thereby verifying the reversible electrochemical conversion behavior between NaCl and Na.

[0155] Example 7

[0156] Non-chloride PANI is used as cathode, NaCl is used as anode, and the electrolyte is a solid electrolyte composed of organic chloride salt, hydrogen bond donor and polymer.

[0157] The cathode material, PANI, is the discharge product of PANI-Cl. The preparation process is as follows: organic chloride PANI-Cl is used as the cathode, metallic Na is used as the anode, and 0.5M TBMACI / DX is used as the electrolyte to assemble a CR2032 button cell. Subsequently, the battery is discharged in constant current mode with a current density of 5 mA / g and a discharge cutoff voltage adjusted to 1.0 V. During the discharge process, chloride ions are transferred from the cathode to the anode, and the discharge product of PANI-Cl, PANI, is obtained on the cathode side.

[0158] Preparation process of the electrolyte: PEGDA, PEGDMA, TBMACl, and EC are weighed in a mass ratio of 5:5:4:4 and stirred until the solution is evenly mixed; after the solution is evenly distributed, 0.5wt% of the thermal curing agent AIBN is weighed and placed in a bottle, and then thermally cured at 60°C for 10 hours to obtain a solid electrolyte membrane.

[0159] In a glove box filled with high-purity argon (H2O and O2 <0.01ppm), a CR2032 button battery was assembled with PANI as the cathode, metallic sodium as the anode, and a solid electrolyte composed of an organic chloride salt and a polymer composite.

[0160] Afterwards, constant current mode was adopted for charging and discharging, with a current density of 5 mA / g and a charge and discharge cut-off voltage range of 1.6 to 3.1 V. After the charging process, high-purity metallic sodium was obtained on the anode side.

[0161] Figure 10 This is the constant current charge-discharge curve of this embodiment, which shows that the electrochemical system constructed by the present invention undergoes a reversible charge-discharge reaction, thereby verifying the reversible electrochemical conversion behavior between NaCl and Na.

[0162] Example 8

[0163] Non-chloride PANI is used as cathode, NaCl is used as anode, and the electrolyte is a liquid electrolyte composed of organic chloride salt and organic solvent and a gel electrolyte composited with a polymer.

[0164] Preparation process of cathode material PANI: prepared according to the method in Example 5.

[0165] Electrolyte preparation: A precursor containing 1.5 wt% PETEA and 0.1 wt% AIBN was dissolved in a 1 M TBMACl / DX electrolyte. The precursor solution was then in situ polymerized at 60°C for 30 min in an Ar2-filled glove box (H2O and O2 <0.1 ppm) to produce a gel electrolyte.

[0166] In a glove box filled with high-purity argon (H2O and O2 <0.01ppm), PANI was used as the cathode, NaCl was used as the anode, and the electrolyte was a liquid electrolyte composed of organic chloride salts and organic solvents and a gel electrolyte composited with a polymer to assemble a CR2032 button battery.

[0167] Afterwards, constant current mode was adopted for charging and discharging, with a current density of 5 mA / g and a charge and discharge cut-off voltage range of 1.6 to 3.1 V. After the charging process, high-purity metallic sodium was obtained on the anode side.

[0168] Figure 11 This is the constant current charge-discharge curve of this embodiment, which shows that the electrochemical system constructed by the present invention undergoes a reversible charge-discharge reaction, thereby verifying the reversible electrochemical conversion behavior between NaCl and Na.

[0169] As can be seen from the above, the electrochemical system constructed using the present invention can achieve reversible phase transition between sodium chloride and metallic sodium at room temperature.

[0170] While the present invention has been disclosed above with reference to preferred embodiments, this is not intended to limit the present invention. Persons skilled in the art will readily appreciate that various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. An electrochemical method for achieving a reversible phase transition between sodium chloride and metallic sodium at room temperature, characterized in that: The method includes: A chloride material is used as a cathode material, metallic sodium is used as an anode material, and an electrolyte containing an organic chloride salt is used; Afterwards, at room temperature and pressure, constant current charging and discharging drives chloride ions to shuttle between the cathode and the anode. After the discharge-charge process, a reversible phase transition between sodium chloride and metallic sodium is achieved at room temperature. During the discharge process, chloride ions are transferred from the cathode to the anode, and sodium chloride is obtained on the anode side; during the charging process, chloride ions are transferred from the anode to the cathode, and the sodium chloride on the anode side is electrochemically reduced to metallic sodium.

2. An electrochemical method for achieving a reversible phase transition between sodium chloride and metallic sodium at room temperature, characterized in that: The method includes: Using a non-chloride material as the cathode material and sodium chloride as the anode material; and using an electrolyte containing an organic chloride salt; Afterwards, at room temperature and pressure, constant current charging and discharging drives chloride ions to shuttle between the cathode and the anode. After the discharge-charge process, a reversible phase transition between sodium chloride and metallic sodium is achieved at room temperature. During the discharge process, chloride ions are transferred from the cathode to the anode, and sodium chloride is obtained on the anode side; during the charging process, chloride ions are transferred from the anode to the cathode, and the sodium chloride on the anode side is electrochemically reduced to metallic sodium.

3. The electrochemical method for achieving room temperature reversible phase transition between sodium chloride and metallic sodium according to claim 1 or 2, characterized in that: The electrolyte is in liquid, gel or solid state.

4. The electrochemical method for achieving room temperature reversible phase transition between sodium chloride and metallic sodium according to claim 3, characterized in that: When the electrolyte is in a liquid or gel state, the electrolyte comprises an organic chloride salt and an organic solvent, and the organic solvent comprises an ether solvent and / or an ester solvent.

5. The electrochemical method for achieving room temperature reversible phase transition between sodium chloride and metallic sodium according to claim 4, characterized in that: The ether solvent includes 1,3-dioxolane and / or 1,4-dioxane, and the ester solvent includes propylene carbonate.

6. The electrochemical method for achieving room temperature reversible phase transition between sodium chloride and metallic sodium according to claim 3, characterized in that: When the electrolyte is in a solid state, the electrolyte comprises an organic chloride salt and a hydrogen bond donor, and the hydrogen bond donor comprises ethylene carbonate.

7. The electrochemical method for achieving room temperature reversible phase transition between sodium chloride and metallic sodium according to claim 1 or 2, characterized in that: The organic chloride salt includes one or more of pyrrolidine chloride salt, piperidine chloride salt, imidazole chloride salt and quaternary ammonium chloride salt.

8. The electrochemical method for achieving room temperature reversible phase transition between sodium chloride and metallic sodium according to claim 1, characterized in that: The chloride material includes one or more of transition metal chlorides, transition metal oxychlorides, main group metal chlorides, main group metal oxychlorides, and organic chlorides.

9. The electrochemical method for achieving room temperature reversible phase transition between sodium chloride and metallic sodium according to claim 2, characterized in that: The non-chloride material includes one or more of the discharge products of transition metal chlorides, discharge products of transition metal chloride oxides, discharge products of main group metal chlorides, discharge products of main group metal chloride oxides, discharge products of organic chlorides, and carbon materials.

10. The electrochemical method for achieving room temperature reversible phase transformation of sodium chloride and metallic sodium according to claim 8 or 9, characterized in that: The organic chloride includes one or more of chlorine-doped polythiophene, chlorine-doped polyaniline, chlorine-doped polypyrrole, chlorine-doped polycyanonitrile, and chlorine-doped polyphenazine.

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