A sodium battery based on sodium chloride positive electrode active material

Abstract

This invention belongs to the field of sodium-based battery technology and provides a sodium battery based on sodium chloride as the positive electrode active material. The positive electrode of this sodium battery primarily uses sodium chloride as the positive electrode material, and the electrolyte is a sodium chloride-containing aluminochloride-based electrolyte. This invention demonstrates for the first time the application of sodium chloride as a conversion-type positive electrode active material in a battery, achieved through a luminochloride-based electrolyte. This electrolyte reduces the chloride content... – Simultaneously with activating the positive electrode oxidation reaction, a stable SEI layer is established on the negative electrode side. This strategy allows for the full release of the reversible sodium chloride to chlorine redox reaction, which also enables highly reversible sodium metal deposition and stripping processes, thereby achieving excellent battery performance. The sodium battery provided by this invention features low cost, high sustainability, and superior electrochemical performance, making it a highly promising candidate battery system for next-generation energy storage applications.

Description

Technical Field

[0001] This invention belongs to the field of sodium-based battery technology and relates to a sodium battery based on sodium chloride as the positive electrode active material. This sodium battery uses sodium chloride (NaCl) as the positive electrode material and can be applied to the field of energy storage. Background Technology

[0002] Lithium-ion batteries (LIBs) are now widely used in portable electronic devices and electric vehicles. However, concerns about safety, cost, and raw material availability limit the large-scale application of LIBs in grid energy storage. Therefore, developing targeted novel electrochemical systems based on inexpensive and safe electrode materials is crucial, but challenging, for large-scale energy storage.

[0003] Given the abundance and widespread distribution of sodium reserves, sodium-ion batteries (SIBs) are widely recognized as one of the most promising candidates for the efficient storage and regulation of renewable energy. However, the practical application of SIBs in grid energy storage remains limited by several factors. For example, the energy density of traditional cathode materials based on intercalation / deintercalation mechanisms, such as Prussian blue analogues, polyanionic electrode materials, and layered transition metal oxides, is difficult to achieve, and the complex preparation process further weakens the cost advantage of SIBs. Furthermore, the widespread use of flammable organic electrolytes has raised safety concerns. Therefore, developing a safe, low-cost, and high-energy-density novel electrochemical system is a key objective for expanding the scale of grid energy storage systems, and also a challenging one.

[0004] Sodium chloride (NaCl) is the most common alkali metal salt, utilized throughout almost the entire history of human civilization. With the development of modern chemical engineering, sodium chloride has become the cheapest and most abundant chemical raw material, with an annual production exceeding 290 million tons. A few published studies have explored its application in batteries. For example, Chung et al. achieved a metallization phase transition of sodium chloride at atmospheric pressure through an electrochemical activation process, enabling Na... +Reversible insertion-extraction in sodium chloride (Moeez, I. et al. Enhanced cycle stability of low-cost Na-rich metallic NaClelectrode for advanced Na-ion batteries. Adv. Funct. Mater. 33, 2210370(2023); Moeez, I. et al. Electrochemically induced metallization of NaCl: use of the main component of salt as a cost-effective electrode material for sodium-ion batteries. ACS Energy Lett. 4, 2060-2068 (2019).). However, excessively high overpotentials (above 2.5 V) and poor cycling performance (≤ 100 cycles) have kept this strategy at the theoretical research level. Wang et al. constructed a reversible chlorine redox flow battery by electrolyzing an aqueous sodium chloride solution, extracting the generated chlorine gas, and storing it in carbon tetrachloride. However, the complex battery structure limits its application prospects (Hou, S. et al. High-energy and low-cost membrane-free chlorine flow battery. Nat. Commun. 13,1281 (2022)). In 2021, US researchers used the reduction reaction of thionyl chloride to generate sodium chloride in situ at the positive electrode during the first discharge of the battery, and then converted it into chlorine gas for energy storage during the charging process (Zhu, G. et al. Rechargeable Na / Cl2 and Li / Cl2 batteries. Nature 596, 525-530 (2021)). However, this method cannot control the distribution and loading of sodium chloride, resulting in a sodium chloride utilization rate of less than 20%, a battery energy density of only 20% of current sodium-ion batteries, and a cycle life that is one to two orders of magnitude lower (Ma, C. et al. Confinement-induced in situ Cl2). –Cl2 conversion in a cathode enables a lean electrolyte sodium-chlorine battery. ACS Nano 19, 31213-31223 (2025). Furthermore, this system relies on highly corrosive thionyl chloride and produces highly toxic chlorine gas and sulfur dioxide, posing significant safety hazards and environmental risks, and thus lacks application potential. Summary of the Invention

[0005] In view of the shortcomings of existing technologies, this invention provides a sodium battery based on sodium chloride as a positive electrode active material, demonstrating for the first time the application of sodium chloride as a conversion-type positive electrode active material in batteries, achieved based on a chloroaluminate-based electrolyte. This electrolyte reduces the chloride content... – Simultaneously with activating the positive electrode oxidation reaction, a stable SEI layer is established on the negative electrode side. This strategy allows for the full release of the reversible sodium chloride-to-chlorine redox reaction, which also enables highly reversible sodium metal deposition and stripping processes, resulting in excellent battery performance. Furthermore, the non-flammable electrolyte and the option to construct a negative electrodeless sodium battery provide outstanding safety. The sodium battery provided by this invention features low cost, high sustainability, and superior electrochemical performance, making it a highly promising candidate battery system for next-generation energy storage applications.

[0006] To achieve the above objectives, the present invention employs a technical solution consisting of the following technical measures.

[0007] In one aspect, the present invention provides a sodium battery based on a sodium chloride positive electrode active material, wherein the positive electrode is composed of a positive electrode current collector and a NaCl-containing conductive coating on its surface, or is directly composed of a NaCl-containing composite conductive material; the NaCl content in the NaCl-containing conductive coating and the NaCl-containing composite conductive material is 45~90 wt%.

[0008] Its electrolyte is a chloroaluminate-based electrolyte prepared by using NaCl and AlCl3 as electrolytes; wherein the molar ratio of NaCl to AlCl3 is 0.1~1.1:1.1~2; The AlCl3 in the electrolyte is used to form a chloroaluminate complex system. This chloroaluminate complex system causes the NaCl on the positive electrode to be oxidized to generate chlorine gas during the charging process. It also causes the chlorine gas to be reduced to NaCl and deposited on the positive electrode during the discharging process, thereby achieving a reversible relationship between NaCl and chlorine gas on the positive electrode.

[0009] In this document, the sodium battery based on sodium chloride positive electrode active material, based on common knowledge of sodium-based batteries in the prior art, also includes a negative electrode and / or a negative electrode current collector, and the material selection, material ratio, and preparation process of the negative electrode and / or negative electrode current collector follow conventional sodium-based battery processes. Preferably, it refers to a sodium-based battery without a negative electrode that only uses a negative electrode current collector. Those skilled in the art can select a suitable process to prepare a sodium battery based on sodium chloride positive electrode active material according to the conventional preparation process of sodium-based batteries or the required battery type, based on the prior art.

[0010] To better illustrate the present invention, and to provide an example of a sodium battery based on sodium chloride positive electrode active material provided by the present invention, specifically, the sodium battery is composed of a positive electrode, an electrolyte, and a negative electrode and / or a negative electrode current collector.

[0011] The positive electrode is one of the components commonly known in batteries. The positive electrode used in this invention is the positive electrode as described in this invention: the positive electrode is composed of a positive electrode current collector and a NaCl-containing conductive coating on its surface, or directly composed of a NaCl-containing composite conductive material. Typically, the positive electrode is composed of a positive electrode current collector and a NaCl-containing conductive coating on its surface. The NaCl-containing conductive coating is composed of conventional conductive coatings used in the field of sodium-based batteries with the addition of NaCl. That is, it is composed of conductive materials, binder materials, and NaCl. It may also include functional additives that are commonly known in the art or described in existing technical documents and can be applied to sodium-based batteries. For example, the conductive coating is formed by mixing carbon-based materials, NaCl, and binder as raw material components and coating them onto the surface of the positive electrode current collector. Typically, the positive electrode is directly composed of a NaCl-containing composite conductive material. The NaCl-containing composite conductive material is formed by adding NaCl to a conventional conductive coating used in the field of sodium-based batteries and then drying it. That is, it is composed of conductive materials, binders and NaCl. It may also include functional additives that are common knowledge in the art or described in existing technical literature and can be applied to sodium-based batteries. For example, the positive electrode is formed by drying and shaping carbon-based materials, NaCl and binders as raw material components for the conductive coating.

[0012] Furthermore, the conductive material includes carbon-based materials for conductive coatings, such as at least one of Ketjen black, graphite, conductive carbon black, carbon nanotubes, activated carbon, and metal-organic framework materials (such as UiO-66).

[0013] The bonding material includes any one of aqueous adhesives and non-aqueous adhesives; the aqueous adhesive is a conventional aqueous adhesive described in the prior art that is suitable for use in the positive electrode of a battery, and uses water as the main solvent during use, such as any one of sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), sodium alginate, polyacrylic acid, polyacrylates (such as LA133), natural polymers (such as chitosan, starch, etc.), and conductive polymers (such as PEDOT:PSS); the non-aqueous adhesive is a conventional non-aqueous adhesive described in the prior art that is suitable for use in the positive electrode of a battery, and uses conventional organic reagents (such as N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), tetrahydrofuran (THF), acetone, cyclohexanone, chloroform, dichloromethane, ethyl acetate) as the main solvent during use, such as any one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyurethane (PU), perfluorosulfonic acid-polytetrafluoroethylene copolymer (Nafion), and epoxy resin;

[0014] The positive current collector includes any one of the following: nickel foil, nickel foam, stainless steel foil, stainless steel mesh, aluminum foil, carbon-coated aluminum foil, aluminum foam, titanium foil, carbon-based materials, and metal-organic polymer composites;

[0015] Typically, in the NaCl-containing conductive coating and the NaCl-containing composite conductive material, the ratio of conductive material, binder, and optional functional additives follows the specifications for the positive electrode material of conventional sodium-based batteries.

[0016] In one preferred embodiment, the NaCl loading in the positive electrode is 2-36 mg / cm³. -2 .

[0017] In one preferred embodiment, the NaCl-containing conductive coating and the NaCl-containing composite conductive material further include halogen elements (e.g., elemental iodine, bromine) and / or chalcogen elements (e.g., elemental tellurium, selenium, sulfur) as functional additives. These additives mediate the conversion of chlorine gas into a more stable chlorine-containing active material. Specifically, during battery charging, NaCl on the positive electrode is oxidized to chlorine gas, which is then converted into a chlorine-containing active material. Furthermore, during battery discharging, the chlorine-containing active material is reduced to NaCl and deposited on the positive electrode, thus achieving a reversible conversion between NaCl and the chlorine-containing active material on the positive electrode. The amount of halogen elements and / or chalcogen elements added is 0-50 wt% of the NaCl content.

[0018] More preferably, the NaCl-containing conductive coating and the NaCl-containing composite conductive material further contain elemental sulfur as a functional additive, wherein the amount of elemental sulfur added is 0 to 50 wt% of the NaCl content.

[0019] The negative electrode and / or negative electrode current collector are components commonly known in batteries. In sodium batteries without a negative electrode, only the negative electrode current collector is used. Both the negative electrode and / or the negative electrode current collector can be obtained commercially or prepared according to existing technical literature and conventional processes for sodium-based batteries. For example, the negative electrode can be made directly from elemental metallic sodium, or it can be made directly from conventional carbon-containing materials or alloy-type negative electrodes. Another example is that the negative electrode is formed by loading sodium foil onto the surface of the negative electrode current collector. It may also include functional additives that are commonly known in the art or described in existing technical literature and can be applied to sodium-based batteries.

[0020] Furthermore, the negative electrode current collector includes any one of nickel foil, nickel foam, stainless steel foil, stainless steel mesh, aluminum foil, carbon-coated aluminum foil, aluminum foam, titanium foil, carbon-based materials, and metal-organic polymer composites;

[0021] The process of loading the sodium foil onto the surface of the negative electrode current collector includes any one of direct rolling, electrochemical deposition, mechanical coating, and melt impregnation.

[0022] The electrolyte is a known component in batteries. The electrolyte used in this invention is the electrolyte described in this invention: an aluminochloride-based electrolyte prepared by including NaCl and AlCl3 as electrolytes.

[0023] Typically, the electrolyte is a chloroaluminate-based electrolyte, and the solvent used can refer to the solvents commonly used in chloroaluminate-based electrolytes as described in the prior art. Preferably, it is suitable for solvents commonly used in sodium-based battery systems, such as at least one of imidazole ionic liquids, pyrrolidine ionic liquids, hydrogen bond donors constituting deep eutectic solvents, and solvents for chlorine-based electrolytes.

[0024] Further, the imidazole ionic liquid includes any one of 1-ethyl-3-methylimidazolium chloride (EMImCl), 1-propyl-3-methylimidazolium chloride (PMImCl), 1-butyl-3-methylimidazolium chloride (BMImCl), and 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMIFSI);

[0025] The pyrrolidine ionic liquid includes N-ethyl-N-methylpyrrolidine chloride (Py 12 Cl), N-propyl-N-methylpyrrolidone chloride (Py) 13 Cl) any one of them;

[0026] The hydrogen bond donors constituting the deep eutectic solvent include either urea or acetamide.

[0027] The solvent used in the chlorine-based electrolyte includes any one of thionyl chloride (SOCl2), sulfonyl chloride (SO2Cl2), and chloroacetyl chloride (C2H2Cl2O).

[0028] In one preferred embodiment, the electrolyte is a chloroaluminate-based electrolyte prepared by including sodium salt and AlCl3 as electrolytes, and the solvent is thionyl chloride.

[0029] Generally, the solvent selection mentioned above follows conventional preparation amounts. For example, when the solvent is an imidazole ionic liquid, the molar ratio of NaCl, AlCl3 to the imidazole ionic liquid is 0.1~1.1:1.1~2:1.

[0030] Typically, the electrolyte also includes other conventional electrolyte additives, such as those inherent in commercial chlorine-based electrolyte compositions, especially functional additives, which can be selected and added according to the required functional needs by those skilled in the art. It should be emphasized that the electrolyte in the present invention may or may not contain other conventional electrolyte additives.

[0031] It should be noted that when two or more solvents are selected, one of the solvents can also be added as an additive, and the amount added should conform to the conventional ratio when it is used as an additive, for example, 2 to 10% of the electrolyte volume percentage.

[0032] It should be noted that when preparing the electrolyte, imidazole ionic liquids may mix with AlCl3 to generate heat. Those skilled in the art can reasonably prepare the mixture based on common knowledge, such as by adding solid components in small amounts multiple times or by stirring slowly.

[0033] In one preferred technical solution, in order to make Cl – During the Cl2 oxidation-reduction process, the electrolyte does not produce reactive Al2Cl7. – The concentration of NaCl in the electrolyte reaches saturation.

[0034] Typically, based on common knowledge about batteries in the prior art, the sodium battery may also include a conventional negative electrode shell, gasket, spring, separator for loading electrolyte, positive electrode shell, and other conventional structures / components / parts. Those skilled in the art can select a suitable process to prepare the sodium battery based on the conventional manufacturing process of sodium-based batteries or the required battery type, and on the basis of the prior art.

[0035] Furthermore, based on common knowledge in the prior art regarding sodium-based batteries, in addition to the technical contents already described above, the specifications and assembly ratios of the positive electrode, electrolyte, negative electrode and / or negative electrode current collector in the sodium battery all follow conventional sodium-based battery processes. Those skilled in the art can select a suitable process to prepare the sodium battery product based on the conventional preparation process of sodium-based batteries or the required battery model, and on the basis of the prior art.

[0036] The present invention has the following beneficial effects:

[0037] 1. This invention provides a sodium battery based on sodium chloride as the positive electrode active material, demonstrating for the first time the application of NaCl as a conversion-type positive electrode active material in batteries, achieved using a chloroaluminate-based electrolyte. This electrolyte effectively reduces Cl... – While activating the positive electrode oxidation reaction, a stable solid electrolyte interface (SEI) layer is established on the negative electrode side. Using this strategy, the reversible sodium chloride to chlorine redox reaction can be fully released, which also allows for highly reversible sodium metal deposition and stripping processes, thereby achieving excellent battery performance.

[0038] 2. By utilizing sodium chloride as a low-cost and high-performance cathode material for sodium batteries, the material cost is extremely low, at only $0.04 per kilogram, due to the significant sustainability of sodium chloride in nature. This is two to three orders of magnitude lower than the cathode materials currently used in sodium-ion batteries.

[0039] 3. In the preferred technical solution, on the one hand, the battery performance is significantly improved by using a reasonably proportioned chloroaluminate-based ionic liquid as the electrolyte and by adding additives containing acyl chloride or sulfuryl chloride. For example, the negative electrode-free sodium battery shown in the embodiment has a maximum discharge capacity of 426 mAh g at a high discharge voltage of approximately 3.1 V. -1 At a current density of 3 mA cm⁻¹ -2 At that time, the capacity retention rate was 96.6% after 500 cycles.

[0040] 4. The non-flammable electrolyte and the option to construct a negative electrode-free sodium battery provide excellent safety. The sodium battery provided by this invention features low cost, high sustainability, and excellent electrochemical performance, making it a highly promising candidate battery system for next-generation energy storage applications. Attached Figure Description

[0041] Figure 1 This is a schematic diagram illustrating the structural concept of the sodium-free battery without a negative electrode provided in Embodiment 1 of the present invention.

[0042] Figure 2This is a summary diagram of the redox mechanism on the positive electrode side of the sodium-ion battery without a negative electrode provided in Example 1 of the present invention. Figure a shows the change in the NaCl mass loading on the positive electrode after immersion in NEAS electrolyte for 12 hours in the battery sample prepared in Example 1 of the present invention. The initial NaCl mass loadings on the positive electrode were 3.9 and 7.8 mg cm⁻¹, respectively. -2 The bar chart data represents the average of three battery samples, and the error bars represent the standard deviation. Figure b shows the constant current charge-discharge curve of the NaCl cathode prepared in Example 1 of this invention. The inset shows the SEM images of the NaCl cathode under three representative charge-discharge states: initial charge, after charging, and after complete discharge. The charging capacity is 459 mAh g. -1 This is equivalent to the theoretical capacity of NaCl; Figure c shows the battery sample prepared in Example 1 of this invention with a charging capacity and current density of 3 mAh cm⁻¹. -2 and 2mA cm -2 The initial charge-discharge curves and corresponding in-situ XRD spectra of the NaCl cathode are shown in Figures d and e, respectively, under fully charged and discharged conditions, representing the high-resolution XPS Cl 2p spectra of the NaCl cathode of the battery sample prepared in Example 1 of this invention, with a charging capacity of 2 mAh / cm³. -2 Figure f shows the DEMS measurement results of the negative electrode-free sodium battery prepared in Example 1 of this invention. Argon gas was used as the purge gas, with a concentration of 1 ml / min. -1 The sample was pre-purged for 2.5 hours at a flow rate of 1.25 mA cm⁻¹. -2 Figure g shows the Cl K-edge non-in-situ XANES spectra of the NaCl cathode of the battery sample prepared in Example 1 of the present invention under different charge and discharge states; Figures h and i show the three-dimensional distribution of secondary ion fragments of C, NaCl, and Cl2 obtained by TOF-SIMS based on the fully charged and discharged NaCl cathode of the battery sample prepared in Example 1 of the present invention, with a charging capacity of 2 mAh cm⁻¹. -2 .

[0043] Figure 3 Figure 1 is a summary diagram of the negative electrode chemical tests of the battery samples provided in Verification Examples 1-4 of this invention. Specifically, Figure 1a is a schematic diagram of the Na / Al battery prepared in Verification Example 1 of this invention used to evaluate Na deposition / stripping performance; Figure 2b shows the Na / Al batteries in Verification Examples 1-2 of this invention using NEA and NEAS electrolytes respectively at 3 mA cm⁻¹. –2 and 0.3 mAh cm –2Electrochemical reversibility under certain conditions; Figures c and d are top views and cross-sectional SEM images of the Na deposited layer on the Al foil when using NEA and NEAS electrolytes, respectively, in the Na / Al batteries obtained in Verification Examples 1-2 of this invention. The current density and deposition capacity are 1 mA cm⁻¹, respectively. –2 and 1mAh cm –2 Figure e shows the Cl 2p and Al 2p XPS spectra of the Na deposited layer in Na / Ni batteries using NEA and NEAS electrolytes, respectively, in Verification Examples 3-4 of this invention. The current density and deposition capacity are 2 mA cm⁻¹. –2 and 2 mAh cm –2 Figure f is a cryogenic transmission electron microscope image of the passivation layer formed on the surface of deposited Na metal in NEAS electrolyte of the battery sample prepared in Verification Example 1 of the present invention; Figures g and h are the fast Fourier transform diagrams and corresponding lattice fringe images of deposited Na metal in the battery sample prepared in Verification Example 1 of the present invention, respectively; Figure i is the XRD pattern of Al foil in the initial state, deposited state and peeled state of the battery sample prepared in Verification Example 1 of the present invention, with current density and deposition capacity of 2 mA cm⁻¹, respectively. –2 and 2 mAh cm –2 Figures j and k show the rate performance and corresponding constant current deposition / stripping curves of the Na / Al battery obtained in Verification Example 1 of this invention, respectively, with a deposition capacity of 0.5 mAh cm⁻¹. –2 .

[0044] Figure 4 This is a summary diagram of the positive electrode chemical tests of the sodium-ion batteries without negative electrodes provided in Examples 1, 3-4, and 7 of this invention. Figure a shows the constant current charge-discharge curves of the Na / NaCl half-cells based on different electrolytes in Examples 3-4 of this invention; Figure b shows the cycle performance of the Na / NaCl half-cells based on different electrolytes in Examples 3-4 of this invention. The charging capacity and current density in Figures a and b are 459 mAh g⁻¹, respectively. –1 (Theoretical capacity of NaCl) and 500 mA g –1 Figure c is a comparison of the energy density of NaCl in the battery sample prepared in Example 3 of the present invention with that of previously reported excellent sodium battery cathode materials; Figure d is a Gibbs free energy diagram of the oxidation reaction of NaCl in different electrolytes obtained from the battery samples obtained in Examples 3-4 of the present invention; Figure e is a differential charge density distribution diagram of the adsorption reaction intermediates in the electrolyte (top) of the battery sample obtained in Example 4 of the present invention and the electrolyte (bottom) of the battery sample obtained in Example 3 of the present invention, where the blue and green areas represent the charge depletion region and the charge accumulation region, respectively; Figure f is a diagram of the energy density of Na / Ni batteries using NEA and NEAS electrolytes in Verification Examples 3-4 of the present invention at 1.0 mV s. –1The linear scan voltammetry curves at the scan rate are shown, with Ni foil as the working electrode and Na metal foil serving as both the counter electrode and the reference electrode. Figure g shows the negative electrode-free sodium battery prepared in Example 1 of this invention at a charging capacity of 459 mAh g. –1 Current density from 1 Ag –1 Increased to 3 A g –1 The constant current charge-discharge curves at that time, calculated based on the total mass of the positive and negative electrodes, show that the maximum energy density and power density reach 780 Wh / kg, respectively. –1 and 5,346 W kg –1 Figure h is a comparison of the energy density and power density of the anode-free sodium battery prepared in Example 1 of the present invention with previously reported anode-free Na and Li metal batteries and conventional Na-ion and Li-ion batteries; Figure i is a constant current charge-discharge curve of the battery samples prepared in Example 1 and Comparative Example 1 under conditions with and without NaCl at the positive electrode. The charging capacity of the battery obtained in Example 1 is 459 mAh / g. The same areal capacity was applied to the battery in Comparative Example 1 with no NaCl at the positive electrode; Figure j is a constant current charge-discharge curve of the anode-free sodium battery prepared in Example 1 of the present invention when the charging capacity increases from 459 mAh / g to 600 mAh / g; Figure k is a constant current charge-discharge curve of the anode-free sodium battery based on an optimized NaCl positive electrode obtained in Example 7 of the present invention. The current density in Figures i–k is 2 A g. –1 .

[0045] Figure 5 Figure 1 is a summary diagram of the practical application demonstrations of the battery samples provided in Examples 5, 6, 10, and 17 of this invention. Specifically, Figure 1a is a schematic diagram of the structure of the 135 mAh pouch battery prepared in Example 6 of this invention; Figure 2b shows the 135 mAh pouch battery prepared in Example 6 of this invention at 2 mA cm⁻¹. –2The circuit performance diagrams at current density are shown in Figure 6. The inset shows a photograph of the flammability test of the glass fiber separator immersed in a conventional organic electrolyte (1M NaPF6 dissolved in diethylene glycol dimethyl ether) and a NEAS electrolyte. Figure c shows the temperature and voltage changes during needle penetration of the 135 mAh pouch battery prepared in Example 6 of this invention and the Na / Na3V2(PO4)3 pouch battery using a conventional organic electrolyte. The inset shows the corresponding temperature distribution of the two pouch batteries after needle penetration. Figure d is a schematic diagram of NaCl preparation, negative electrode-free sodium battery production, and grid energy storage application in Example 6 of this invention. Figures e and f are photographs of the 1.1 Ah negative electrode-free sodium battery prepared in Example 5 of this invention and their constant current charge-discharge curves, respectively. At a charge-discharge rate of 1 C, the charging capacity is 1200 mAh. Figure g shows the circuit performance of the negative electrode-free sodium battery using the sea salt positive electrode of Example 10 of this invention (top) and the urea-based electrolyte of Example 17 of this invention (bottom), with a charging capacity of 0.3 mAh / cm³. –2 Figure h shows a comparison of the material costs of a sodium-free negative electrode battery with those of previously reported superior batteries.

[0046] Figure 6 These are constant current charge-discharge curves of the sodium-free batteries without negative electrodes provided in Comparative Examples 2-4 of this invention. Specifically, Figure a shows the constant current charge-discharge curve of the sodium-free battery without negative electrodes provided in Comparative Example 2; Figure b shows the constant current charge-discharge curve of the sodium-free battery without negative electrodes provided in Comparative Example 3; and Figure c shows the constant current charge-discharge curve of the sodium-free battery without negative electrodes provided in Comparative Example 4. The current density and charging capacity tested above are 2 mA cm⁻¹. –2 and 0.3 mAh cm –2 .

[0047] Figure 7 This is the Raman spectrum of the electrolyte in Example 1 of the present invention. The unneutralized ionic liquid corresponds to the mixture prepared by mixing 1-ethyl-3-methylimidazolium chloride and AlCl3 in Example 1. The NaCl neutralized ionic liquid (NEA) corresponds to the mixture after adding NaCl. The NaCl neutralized ionic liquid + 5 wt% SOCl2 (NEAS) corresponds to the electrolyte in Example 1, where pure SOCl2 is thionyl chloride (SOCl2).

[0048] Figure 8This is a comparison of the cycle performance of batteries prepared with the electrolyte of the present invention under different additives and additive amounts. Figure a shows the cycle performance comparison of batteries obtained in Example 2 (NEA + 5% SOCl2), Example 8 (NEA + 5% CAC), and Example 9 (NEA); Figure b shows the cycle performance comparison of batteries obtained in Example 2 (NEA + 5% SOCl2), Example 11 (NEA + 2% SOCl2), and Example 12 (NEA + 10% SOCl2). The current density and charging capacity tested above are 2 mA cm⁻¹. –2 and 0.3 mAh cm –2 .

[0049] Figure 9 Figure a shows the cycle performance of the batteries provided in Examples 13 and 14 of this invention under electrolyte-deficient conditions, and a comparison of the long-term constant current charge-discharge curves of the battery provided in Example 2. Specifically, Figure a shows the cycle performance of the battery obtained in Example 13; Figure b shows the cycle performance of the battery obtained in Example 14; and Figure c shows a comparison of the constant current charge-discharge curves of the battery obtained in Example 2 at the beginning and after 1000 hours of maintenance. The current density tested was 2 mA cm⁻¹. –2 .

[0050] Figure 10 Figure 1 shows a comparison of the cycle performance and constant current charge-discharge curves of the batteries provided in Embodiments 1 and 15 of this invention. Specifically, Figure 1a is a comparison of the cycle performance of the batteries provided in Embodiment 1 (including S) and Embodiment 15 (excluding S); Figure 1b is a constant current charge-discharge curve of the battery provided in Embodiment 1; and Figure 1c is a constant current charge-discharge curve of the battery provided in Embodiment 15. The current density and charging capacity tested above are 1.5 mA g. –1 and 200 mAh g –1 .

[0051] Figure 11 This is a constant current charge-discharge curve of the battery provided in Embodiment 16 of the present invention. The current density and charging capacity are 1.5 mA g. –1 and 200 mAh g –1 The numbers labeled on the corresponding curves represent the number of cycles.

[0052] Figure 12 This is a constant current charge-discharge curve of the battery provided in Embodiment 17 of the present invention. The current density and charging capacity are 1.5 mA cm⁻¹. –2 and 0.3 mAh cm –2 The numbers labeled on the corresponding curves represent the number of cycles.

[0053] Figure 13This is a constant current charge-discharge curve of the battery provided in Embodiment 18 of the present invention. The current density and charging capacity are 1.5 mA g. –1 and 200 mAh g –1 The numbers labeled on the corresponding curves represent the number of cycles.

[0054] Figure 14 This is a constant current charge-discharge curve of the battery provided in Embodiment 19 of the present invention. The current density and charging capacity are 1.5 mA g. –1 and 200 mAh g –1 The numbers labeled on the corresponding curves represent the number of cycles.

[0055] Figure 15 This is a constant current charge-discharge curve of the battery provided in Embodiment 20 of the present invention. The current density and charging capacity are 1.5 mA g. –1 and 200 mAh g –1 .

[0056] Figure 16 This is a constant current charge-discharge curve of the battery provided in Embodiment 21 of the present invention. The current density and charging capacity are 1.5 mA g. –1 and 200 mAh g –1 .

[0057] Figure 17 This is a diagram showing the electrode reaction of the negative electrode-free sodium battery provided in Embodiment 1 of the present invention during cycling. Detailed Implementation

[0058] To further understand the present invention, preferred embodiments are described below with reference to examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims. Those skilled in the art can refer to the content of this document to appropriately improve the process parameters. In particular, it should be noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the scope of the present invention. The methods and applications of the present invention have been described through preferred embodiments, and those skilled in the art can obviously make modifications or appropriate changes and combinations to the methods and applications described herein without departing from the content, spirit and scope of the present invention to realize and apply the technology of the present invention. Although it is believed that those skilled in the art will fully understand the following terms, the following definitions are set forth to help illustrate the subject matter disclosed in the present invention.

[0059] In one aspect, the present invention provides a sodium battery based on sodium chloride positive electrode active material, wherein the positive electrode is composed of a positive electrode current collector and a NaCl-containing conductive coating on its surface, or is directly composed of a NaCl-containing composite conductive material; the NaCl content in the NaCl-containing conductive coating and the NaCl-containing composite conductive material is 45~90 wt%.

[0060] Its electrolyte is a chloroaluminate-based electrolyte prepared by using NaCl and AlCl3 as electrolytes; wherein the molar ratio of NaCl to AlCl3 is 0.1~1.1:1.1~2; The AlCl3 in the electrolyte is used to form a chloroaluminate complex system. This chloroaluminate complex system causes the NaCl on the positive electrode to be oxidized to generate chlorine gas during the charging process. It also causes the chlorine gas to be reduced to NaCl and deposited on the positive electrode during the discharging process, thereby achieving a reversible relationship between NaCl and chlorine gas on the positive electrode.

[0061] In this document, the sodium battery based on sodium chloride positive electrode active material, based on common knowledge of sodium-based batteries in the prior art, also includes a negative electrode and / or a negative electrode current collector, and the material selection, material ratio, and preparation process of the negative electrode and / or negative electrode current collector follow conventional sodium-based battery processes. Preferably, it refers to a sodium-based battery without a negative electrode that only uses a negative electrode current collector. Those skilled in the art can select a suitable process to prepare a sodium battery based on sodium chloride positive electrode active material according to the conventional preparation process of sodium-based batteries or the required battery type, based on the prior art.

[0062] To better illustrate the present invention, and to provide an example of a sodium battery based on sodium chloride positive electrode active material provided by the present invention, specifically, the sodium battery is composed of a positive electrode, an electrolyte, and a negative electrode and / or a negative electrode current collector.

[0063] The positive electrode is one of the components commonly known in batteries. The positive electrode used in this invention is the positive electrode as described in this invention: the positive electrode is composed of a positive electrode current collector and a NaCl-containing conductive coating on its surface, or directly composed of a NaCl-containing composite conductive material. Typically, the positive electrode is composed of a positive electrode current collector and a NaCl-containing conductive coating on its surface. The NaCl-containing conductive coating is composed of conventional conductive coatings used in the field of sodium-based batteries with the addition of NaCl. That is, it is composed of conductive materials, binder materials, and NaCl. It may also include functional additives that are commonly known in the art or described in existing technical documents and can be applied to sodium-based batteries. For example, the conductive coating is formed by mixing carbon-based materials, NaCl, and binder as raw material components and coating them onto the surface of the positive electrode current collector. Typically, the positive electrode is directly composed of a NaCl-containing composite conductive material. The NaCl-containing composite conductive material is formed by adding NaCl to a conventional conductive coating used in the field of sodium-based batteries and then drying it. That is, it is composed of conductive materials, binders and NaCl. It may also include functional additives that are common knowledge in the art or described in existing technical literature and can be applied to sodium-based batteries. For example, the positive electrode is formed by drying and shaping carbon-based materials, NaCl and binders as raw material components for the conductive coating.

[0064] Furthermore, in one embodiment, the conductive material includes a carbon-based material for conductive coating, such as at least one of Ketjen black, graphite, conductive carbon black, carbon nanotubes, activated carbon, and metal-organic framework materials (such as UiO-66).

[0065] In one embodiment, the bonding material includes any one of aqueous binders and non-aqueous binders; the aqueous binder is a conventional aqueous binder described in the prior art that is suitable for use in battery positive electrodes, and uses water as the main solvent during use, such as any one of sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), sodium alginate, polyacrylic acid, polyacrylates (such as LA133), natural polymers (such as chitosan, starch, etc.), and conductive polymers (such as PEDOT:PSS); the non-aqueous binder is... The prior art describes conventional non-aqueous binders suitable for use in battery positive electrodes, which use conventional organic reagents (such as N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), tetrahydrofuran (THF), acetone, cyclohexanone, chloroform, dichloromethane, ethyl acetate) as the main solvent, including any one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyurethane (PU), perfluorosulfonic acid-polytetrafluoroethylene copolymer (Nafion), and epoxy resin;

[0066] In one embodiment, the positive current collector includes any one of nickel foil, nickel foam, stainless steel foil, stainless steel mesh, aluminum foil, carbon-coated aluminum foil, aluminum foam, titanium foil, carbon-based materials, and metal-organic polymer composites;

[0067] Typically, in the NaCl-containing conductive coating and the NaCl-containing composite conductive material, the ratio of conductive material, binder, and optional functional additives follows the specifications for the positive electrode material of conventional sodium-based batteries.

[0068] In one embodiment, the NaCl content in the NaCl-containing conductive coating and the NaCl-containing composite conductive material is 45-90 wt%, for example, 45 wt%, 46 wt%, 47 wt%, 48 wt%, 49 wt%, 50 wt%, 51 wt%, 52 wt%, 53 wt%, 54 wt%, 55 wt%, 56 wt%, 57 wt%, 58 wt%, 59 wt%, 60 wt%, 61 wt%, 62 wt%, 63 wt%, 64 wt%, 65 wt%, 66 wt%, 67 wt%, 68 wt%, 69 wt%, 70 wt%, 71 wt%, 72 wt%, 73 wt%, 74 wt%, 75 wt%, 76 wt%, 77 wt%, 78 wt%, 79 wt%, 80 wt%, 81 wt%, 82 wt%, 83 wt%, 84 wt%, 85 wt%, 86 wt%, 87 wt%, 88 wt%, 89 wt%, 90 wt%, or any range or point value between them.

[0069] In one preferred embodiment, the NaCl loading in the positive electrode is 2~36 mg cm⁻¹. -2 For example, 2mg cm -2 3 mg cm -2 4 mg cm -2 5 mg cm -2 6 mg cm -2 7 mg cm -2 8 mg cm -2 9 mg cm -2 10mg cm -2 11 mg cm -2 12 mg cm -2 13 mg cm -2 14 mg cm -2 15 mg cm -2 16 mg cm -2 17 mgcm-2 18 mg cm -2 19 mg cm -2 20 mg cm -2 21 mg cm -2 22 mg cm -2 23 mg cm -2 24 mg cm -2 25 mg cm -2 26 mg cm -2 27 mg cm -2 28 mg cm -2 29 mg cm -2 30 mg cm -2 31 mg cm -2 32 mgcm -2 33 mg cm -2 34 mg cm -2 35 mg cm -2 36 mg cm -2 Or any range or point value between them.

[0070] In one preferred embodiment, the NaCl-containing conductive coating and the NaCl-containing composite conductive material further include halogen elements (e.g., elemental iodine, bromine) and / or chalcogen elements (e.g., elemental tellurium, selenium, sulfur) as functional additives. These additives mediate the conversion of chlorine gas into a more stable chlorine-containing active material. Specifically, during battery charging, NaCl on the positive electrode is oxidized to chlorine gas, and the additive mediates the generation of the chlorine-containing active material. Furthermore, during battery discharging, the chlorine-containing active material is reduced to NaCl and deposited on the positive electrode, thus achieving reversible conversion between NaCl and the chlorine-containing active material on the positive electrode. The amount of halogen elements and / or chalcogen elements added is 0-50 wt% of the NaCl content, for example, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%. wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, 35 wt%, 36 wt%, 37 wt%, 38 wt%, 39 wt%, 40 wt%, 41 wt%, 42 wt%, 43 wt%, 44 wt%, 45 wt%, 46 wt%, 47 wt%, 48 wt%, 49 wt%, 50 wt% or any range or point value therebetween.

[0071] More preferably, the NaCl-containing conductive coating and the NaCl-containing composite conductive material further contain elemental sulfur as a functional additive, wherein the amount of elemental sulfur added is 0 to 50 wt% of the NaCl content.

[0072] The negative electrode and / or negative electrode current collector are components commonly known in batteries. In sodium batteries without a negative electrode, only the negative electrode current collector is used. Both the negative electrode and / or the negative electrode current collector can be obtained commercially or prepared according to existing technical literature and conventional processes for sodium-based batteries. For example, the negative electrode can be made directly from elemental metallic sodium, or it can be made directly from conventional carbon-containing materials or alloy-type negative electrodes. Another example is that the negative electrode is formed by loading sodium foil onto the surface of the negative electrode current collector. It may also include functional additives that are commonly known in the art or described in existing technical literature and can be applied to sodium-based batteries.

[0073] Furthermore, in one embodiment, the negative electrode current collector includes any one of nickel foil, nickel foam, stainless steel foil, stainless steel mesh, aluminum foil, carbon-coated aluminum foil, aluminum foam, titanium foil, carbon-based materials, and metal-organic polymer composites;

[0074] In one embodiment, the process of loading the sodium foil onto the surface of the negative electrode current collector includes any one of direct rolling, electrochemical deposition, mechanical coating, and melt impregnation.

[0075] The electrolyte is a known component in batteries. The electrolyte used in this invention is the electrolyte described in this invention: an aluminochloride-based electrolyte prepared by including NaCl and AlCl3 as electrolytes.

[0076] In one embodiment, the molar ratio of NaCl to AlCl3 is 0.1~1.1:1.1~2, for example 0.1:1.1, 0.2:1.1, 0.3:1.1, 0.4:1.1, 0.5:1.1, 0.6:1.1, 0.7:1.1, 0.8:1.1, 0.9:1.1, 1:1.1, 1.1:1.1, 0.1:1.2, 0.2:1.2, 0.3:1.2, 0.4:1.2, 0.5:1.2, 0.6:1.2, 0.7:1.2, 0.8:1.2, 0.9:1.2, 1:1.2, 1.1:1.2, 0.1:1. 3, 0.2:1.3, 0.3:1.3, 0.4:1.3, 0.5:1.3, 0.6:1.3, 0.7:1.3, 0.8:1.3, 0.9:1.3, 1:1.3, 1.1:1.3, 0.1:1.4, 0.2:1.4, 0.3:1.4, 0.4:1.4, 0.5:1.4, 0.6:1.4, 0.7:1.4, 0.8:1.4, 0.9:1.4, 1:1.4, 1.1:1.4, 0.1:1.5, 0.2:1.5, 0.3:1.5, 0.4:1.5, 0.5:1.5, 0.6:1.5, 0.7:1.5, 0. 8:1.5, 0.9:1.5, 1:1.5, 1.1:1.5, 0.1:1.6, 0.2:1.6, 0.3:1.6, 0.4:1.6, 0.5:1.6, 0.6:1.6, 0.7:1.6, 0.8:1.6, 0.9:1.6, 1:1.6, 1.1:1.6, 0.1:1.7, 0.2:1.7, 0.3:1.7, 0.4:1.7, 0.5:1.7, 0.6:1.7, 0.7:1.7, 0.8:1.7, 0.9:1.7, 1:1.7, 1.1:1.7, 0.1:1.8, 0.2:1.8, 0.3:1.8 0.4:1.8, 0.5:1.8, 0.6:1.8, 0.7:1.8, 0.8:1.8, 0.9:1.8, 1:1.8, 1.1:1.8, 0.1:1.9, 0.2:1.9, 0.3:1.9, 0.4:1.9, 0.5:1.9, 0.6:1.9, 0.7:1.9, 0.8:1.9, 0.9:1.9, 1:1.9, 1.1:1.9, 0.1:2, 0.2:2, 0.3:2, 0.4:2, 0.5:2, 0.6:2, 0.7:2, 0.8:2, 0.9:2, 1:2, 1.1:2, or any range or point value between them.

[0077] Typically, the electrolyte is a chloroaluminate-based electrolyte, and the solvent used can refer to the solvents commonly used in chloroaluminate-based electrolytes as described in the prior art. Preferably, it is suitable for solvents commonly used in sodium-based battery systems, such as at least one of imidazole ionic liquids, pyrrolidine ionic liquids, hydrogen bond donors constituting deep eutectic solvents, and solvents for chlorine-based electrolytes.

[0078] Further, in one embodiment, the imidazole ionic liquid includes any one of 1-ethyl-3-methylimidazolium chloride (EMImCl), 1-propyl-3-methylimidazolium chloride (PMImCl), 1-butyl-3-methylimidazolium chloride (BMImCl), and 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMIFSI);

[0079] The pyrrolidine ionic liquid includes N-ethyl-N-methylpyrrolidine chloride (Py 12 Cl), N-propyl-N-methylpyrrolidone chloride (Py) 13 Cl) any one of them;

[0080] The hydrogen bond donors constituting the deep eutectic solvent include either urea or acetamide.

[0081] The solvent used in the chlorine-based electrolyte includes any one of thionyl chloride (SOCl2), sulfonyl chloride (SO2Cl2), and chloroacetyl chloride (C2H2Cl2O).

[0082] In one preferred embodiment, the electrolyte is a chloroaluminate-based electrolyte prepared by including sodium salt and AlCl3 as electrolytes, and the solvent is thionyl chloride.

[0083] Generally, the solvent selection mentioned above follows conventional preparation amounts. For example, when the solvent is an imidazole ionic liquid, the molar ratio of NaCl, AlCl3 to the imidazole ionic liquid is 0.1~1.1:1.1~2:1.

[0084] Typically, the electrolyte also includes other conventional electrolyte additives, such as those inherent in commercial chlorine-based electrolyte compositions, especially functional additives, which can be selected and added according to the required functional needs by those skilled in the art. It should be emphasized that the electrolyte in the present invention may or may not contain other conventional electrolyte additives.

[0085] It should be noted that when two or more solvents are selected, one of the solvents can also be added as an additive, and the amount added should conform to the conventional ratio when it is used as an additive, such as 2 to 10% of the electrolyte volume percentage, such as 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or any range or point value between them.

[0086] It should be noted that when preparing the electrolyte, imidazole ionic liquids may mix with AlCl3 to generate heat. Those skilled in the art can reasonably prepare the mixture based on common knowledge, such as by adding solid components in small amounts multiple times or by stirring slowly.

[0087] In one preferred embodiment, so that Cl – During the Cl2 oxidation-reduction process, the electrolyte does not produce reactive Al2Cl7. – The concentration of NaCl in the electrolyte reaches saturation.

[0088] Typically, based on common knowledge about batteries in the prior art, the sodium battery may also include a conventional negative electrode shell, gasket, spring, separator for loading electrolyte, positive electrode shell, and other conventional structures / components / parts. Those skilled in the art can select a suitable process to prepare the sodium battery based on the conventional manufacturing process of sodium-based batteries or the required battery type, and on the basis of the prior art.

[0089] Furthermore, based on common knowledge in the prior art regarding sodium-based batteries, in addition to the technical contents already described above, the specifications and assembly ratios of the positive electrode, electrolyte, negative electrode and / or negative electrode current collector in the sodium battery all follow conventional sodium-based battery processes. Those skilled in the art can select a suitable process to prepare the sodium battery product based on the conventional preparation process of sodium-based batteries or the required battery model, and on the basis of the prior art.

[0090] The present application will be further explained in detail below with reference to embodiments. However, those skilled in the art should understand that these embodiments are provided for illustrative purposes only and are not intended to limit the present application.

[0091] Example

[0092] The embodiments of this application will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be construed as limiting the scope of this application. Where specific conditions are not specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Where the manufacturers of reagents or instruments are not specified, they are all commercially available conventional products. This application should not be construed as being limited to the specific embodiments described.

[0093] raw material:

[0094] EMImCl (99.9%, moisture content less than 200 ppm, Monils Chemical) and NaCl (99.99%, Adamas) were dried under vacuum at 80 °C for 24 hours to remove residual moisture. SOCl2 (99%, Aladdin), AlCl3 (98.0%, TCI), and S (99.99%, Rhawn) were used without further purification. PTFE emulsion binder (60 wt%, D–210C) and Ketjen Black (KJ, ECP–600JD) were purchased from Cyber ​​Electrochemical Materials. Porous aluminum foil (20 μm thick, pore size 10–20 μm) was purchased from Shandong Xinxin Electronic Materials Co., Ltd.

[0095] Example 1

[0096] In this embodiment, a sodium-ion battery without a negative electrode is assembled as a test sample.

[0097] Electrolyte: The electrolyte was prepared in an argon-protected glove box with water and oxygen content below 2 ppm. 2.93 g of 1-ethyl-3-methylimidazolium chloride (EMImCl) and 3.47 g of AlCl3 were weighed and mixed to prepare an ionic liquid. AlCl3 was added in small amounts multiple times and stirred slowly to avoid violent heating. 1 g of ionic liquid was added to 0.06 g of NaCl and stirred for 24 hours. The supernatant was collected, and 5 vol% of thionyl chloride (SOCl2) was added to the supernatant. Stirring was continued for 4 hours to prepare the electrolyte, which was denoted as NEAS electrolyte.

[0098] Positive electrode: 0.2 g Ketjen Black, 0.4 g S, 1.2 g NaCl and 8 g anhydrous ethanol were mixed and ball-milled at 500 rpm for 5 hours, then dried at 80 ℃, and ball-milled again at 500 rpm for 2 hours. Then, it was mixed with polytetrafluoroethylene (PTFE, aqueous dispersion, solids content 0.83 g / mL) –1 The NaCl and Ni were mixed at a mass ratio of 9.5:0.5 and dispersed in ethanol by ultrasonic treatment. The resulting slurry was coated onto Ni foam (12 mm in diameter) and dried at 90 °C to remove the ethanol, thus preparing a low-load NaCl cathode. The NaCl loading was 1.5–2 mg / cm³. 2 .

[0099] The batteries were assembled in an argon-filled glove box, where water and oxygen content were below 2 ppm. In a button cell (type 2032), 120 μL of electrolyte was added to a glass fiber separator (GF / D, Whatman) to prepare a negative electrode-free sodium battery, using aluminum foil and a prepared NaCl positive electrode. The battery casing was made of 316 stainless steel.

[0100] Example 2

[0101] In this embodiment, a sodium-ion battery without a negative electrode is assembled as a test sample.

[0102] Positive electrode: 0.2 g Ketjen Black, 0.4 g S, 4 g NaCl and 8 g anhydrous ethanol were mixed and ball-milled at 500 rpm for 5 hours, then dried at 80 ℃, and ball-milled again at 500 rpm for 2 hours. Then, it was mixed with polytetrafluoroethylene (PTFE, aqueous dispersion, solids content 0.83 g / mL) –1 The NaCl and Ni were mixed at a mass ratio of 9.5:0.5 and dispersed in ethanol by ultrasonic treatment. The resulting slurry was coated onto Ni foam (12 mm in diameter) and dried at 90 °C to remove the ethanol, thus preparing a high-load NaCl cathode. The NaCl loading was 10–15 mg / cm³. 2 .

[0103] Example 2 adopts a similar implementation method to Example 1, but uses the above-mentioned high-load NaCl positive electrode to assemble a sodium battery without a negative electrode.

[0104] Verification Example 1

[0105] This verification example assembles a Na / Al battery as a test sample.

[0106] Verification Example 1 used the same electrolyte as in Example 1. The battery was assembled in an argon-filled glove box with water and oxygen content below 2 ppm. In the button cell (Type 2032), a Na foil (12 mm in diameter) and an Al foil (14 mm in diameter) were separated by a glass fiber separator (GF / D, Whatman), and 120 μL of electrolyte was added.

[0107] Verification Example 2

[0108] This verification example assembles a Na / Al battery as a test sample.

[0109] Verification Example 2 adopts a similar implementation method to Verification Example 1, but thionyl chloride (SOCl2) is not added to the electrolyte. This electrolyte is referred to as NEA electrolyte.

[0110] Verification Example 3

[0111] This verification example assembles a Na / Ni battery as a test sample.

[0112] Verification Example 3 used the same electrolyte as in Example 1. The battery was assembled in an argon-filled glove box with water and oxygen content below 2 ppm. In the button cell (Type 2032), a Na foil (12 mm in diameter) and a Ni foil (14 mm in diameter) were separated by a glass fiber separator (GF / D, Whatman), and 120 μL of electrolyte was added.

[0113] Verification Example 4

[0114] This verification example assembles a Na / Ni battery as a test sample.

[0115] Verification Example 4 adopts a similar implementation method to Verification Example 3, but thionyl chloride (SOCl2) is not added to the electrolyte. This electrolyte is referred to as NEA electrolyte.

[0116] Example 3

[0117] In this embodiment, a Na / NaCl half-cell was assembled as a test sample.

[0118] Electrolyte: The electrolyte was prepared in an argon-protected glove box with water and oxygen content below 2 ppm. 2.93 g of 1-ethyl-3-methylimidazolium chloride (EMImCl) and 3.47 g of AlCl3 were weighed and mixed to prepare an ionic liquid. AlCl3 was added in small amounts multiple times and stirred slowly to avoid violent heating. 1 g of ionic liquid was added to 0.06 g of NaCl and stirred for 24 hours. The supernatant was collected, and 10 vol% of thionyl chloride (SOCl2) was added to the supernatant. Stirring was continued for 4 hours to prepare the electrolyte.

[0119] Example 3 employs a similar implementation method to Example 1, but uses the aforementioned electrolyte. The battery is assembled in an argon-filled glove box, where the water and oxygen content is below 2 ppm. In a button cell (type 2032), a NaCl positive electrode (12 mm in diameter) is paired with a Na foil (14 mm in diameter), separated by a glass fiber separator (GF / D, Whatman), and 120 μL of electrolyte is added.

[0120] Example 4

[0121] In this embodiment, a Na / NaCl half-cell was assembled as a test sample.

[0122] Example 4 adopts a similar implementation method to Example 3, but thionyl chloride (SOCl2) is not added to the electrolyte. This electrolyte is referred to as NEA electrolyte.

[0123] Example 5

[0124] In this embodiment, a 1.1 Ah sodium-free negative electrode battery was assembled as a test sample.

[0125] Positive electrode: 0.2 g Ketjen Black, 0.4 g S, 4 g NaCl and 8 g anhydrous ethanol were mixed and ball-milled at 500 rpm for 5 hours, then dried at 80 ℃, and ball-milled again at 500 rpm for 2 hours. Then, it was mixed with polytetrafluoroethylene (PTFE, aqueous dispersion, solids content 0.83 g / mL) –1 The NaCl and Ni were mixed at a mass ratio of 9.5:0.5 and dispersed in ethanol by ultrasonic treatment. The resulting slurry was coated onto Ni foam and dried at 90 °C to remove the ethanol, thus preparing a high-load NaCl cathode. The NaCl loading was 10–15 mg / cm³. 2 .

[0126] Example 5 used the same electrolyte as in Example 1. The battery was assembled in an argon-filled glove box with water and oxygen content below 2 ppm. To prepare the 1.1 Ah negative electrode-free sodium battery, five high-capacity bilayer NaCl positive electrodes (10.5 × 11.5 cm) were paired with six Al foils (11 × 11.5 cm), separated by ten GF / A separators (12 × 12 cm). Approximately 42 mL of NEAS electrolyte was added to a self-made glass container (internal dimensions: 12 × 12 × 1 cm). Excess volume in the mold was filled with polytetrafluoroethylene plates. Both the positive and negative electrodes were led out using nickel tabs (1 cm wide).

[0127] Example 6

[0128] In this embodiment, a 135 mAh pouch battery was assembled as a test sample.

[0129] Positive electrode: 0.2 g Ketjen Black, 0.4 g S, 4 g NaCl and 8 g anhydrous ethanol were mixed and ball-milled at 500 rpm for 5 hours, then dried at 80 ℃, and ball-milled again at 500 rpm for 2 hours. Then, it was mixed with polytetrafluoroethylene (PTFE, aqueous dispersion, solids content 0.83 g / mL) –1 The NaCl and Ni were mixed at a mass ratio of 9.5:0.5 and dispersed in ethanol by ultrasonic treatment. The resulting slurry was coated onto Ni foam and dried at 90 °C to remove the ethanol, thus preparing a high-load NaCl cathode. The NaCl loading was 10–15 mg / cm³. 2 .

[0130] Example 6 used the same electrolyte as in Example 1. The battery was assembled in an argon-filled glove box with water and oxygen content below 2 ppm. For the preparation of the 135 mAh pouch battery, five Al foils (86 × 67 mm) were paired with four high-capacity NaCl positive electrodes (83 × 65 mm), separated by eight GF / D separators (90 × 70 mm). The multilayer electrodes were ultrasonically welded and led out using nickel tabs (15 mm wide, Kelude), and encapsulated using an aluminum-plastic film (Kelude, DM-L086N). 20 mL of electrolyte was injected before heat sealing and electrochemical testing.

[0131] Example 7

[0132] In this embodiment, a sodium-based battery without a negative electrode, based on an optimized NaCl positive electrode, was assembled as a test sample.

[0133] Positive electrode: Using 800 mg guanine (99%, Sigma Aldrich) as a precursor, 2.852 g potassium chloride (99.8%, Sigma Aldrich) and 5 g zinc chloride (98%, Sigma Aldrich) were ball-milled together with the precursor for 30 minutes. The mixture was then transferred to a ceramic crucible and heat-treated in a tube furnace under an argon atmosphere. All samples were heated to 1000 °C at a heating rate of 1 °C / min and held for 2 hours. After cooling to room temperature, the approximately black, blocky structure was ground and washed twice with 1 L of deionized water, then vacuum-dried overnight at 60 °C to obtain nitrogen-doped porous carbon.

[0134] 0.2 g of nitrogen-doped porous carbon, 0.4 g of S, 1.2 g of NaCl, and 8 g of anhydrous ethanol were mixed and ball-milled at 500 rpm for 5 hours. The mixture was then dried at 80 °C and ball-milled again at 500 rpm for 2 hours. Finally, it was mixed with polytetrafluoroethylene (PTFE) in an aqueous dispersion with a solid content of 0.83 g / mL. –1 The NaCl and NiCl were mixed at a mass ratio of 9.5:0.5 and dispersed in ethanol by ultrasonic treatment. The resulting slurry was coated onto Ni foam (12 mm in diameter) and dried at 90 °C to remove the ethanol, thus preparing the optimized NaCl cathode. The NaCl loading was 1.5–2 mg / cm³. 2 .

[0135] Example 7 uses the same electrolyte as Example 1, but uses the above-described optimized NaCl positive electrode to assemble a sodium-free negative electrode battery.

[0136] Example 8

[0137] In this embodiment, a sodium-ion battery without a negative electrode is assembled as a test sample.

[0138] Example 8 adopts a similar implementation method to Example 2, but the thionyl chloride (SOCl2) is replaced with chloroacetyl chloride (C2H2Cl2O) in the electrolyte.

[0139] Example 9

[0140] In this embodiment, a sodium-ion battery without a negative electrode is assembled as a test sample.

[0141] Example 9 adopts a similar implementation method to Example 2, but thionyl chloride (SOCl2) is not added to the electrolyte, and this electrolyte is referred to as NEA electrolyte.

[0142] Example 10

[0143] In this embodiment, a sodium-ion battery without a negative electrode is assembled as a test sample.

[0144] Example 10 adopts a similar implementation method to Example 2, but the NaCl used in the positive electrode is replaced with sea salt containing about 92% NaCl.

[0145] Example 11

[0146] In this embodiment, a sodium-ion battery without a negative electrode is assembled as a test sample.

[0147] Example 11 adopts a similar implementation method to Example 2, but the amount of thionyl chloride (SOCl2) added to the electrolyte is 2 vol of the supernatant.

[0148] Example 12

[0149] In this embodiment, a sodium-ion battery without a negative electrode is assembled as a test sample.

[0150] Example 12 adopts a similar implementation method to Example 2, but the amount of thionyl chloride (SOCl2) added to the electrolyte is 10 vol of the supernatant.

[0151] Example 13

[0152] In this embodiment, a sodium-ion battery without a negative electrode is assembled as a test sample.

[0153] Example 13 adopts a similar implementation method to Example 2, but when assembling the battery, 1.5 μL of electrolyte is added per mg NaCl in the positive electrode.

[0154] Example 14

[0155] In this embodiment, a sodium-ion battery without a negative electrode is assembled as a test sample.

[0156] Example 14 adopts a similar implementation method to Example 2, but when assembling the battery, 2.5 μL of electrolyte is added per mg of NaCl in the positive electrode.

[0157] Example 15

[0158] In this embodiment, a sodium-ion battery without a negative electrode is assembled as a test sample.

[0159] Example 15 adopts a similar implementation method to Example 1, but S is not added to the positive electrode.

[0160] Example 16

[0161] In this embodiment, a sodium-ion battery without a negative electrode is assembled as a test sample.

[0162] Example 16 employs a similar implementation method to Example 1, but replaces thionyl chloride (SOCl2) in the electrolyte with 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide salt (EMIFSI).

[0163] Example 17

[0164] In this embodiment, a sodium-ion battery without a negative electrode is assembled as a test sample.

[0165] Electrolyte: The electrolyte was prepared in an argon-protected glove box with water and oxygen content below 2 ppm. 1.20 g of urea (CH4N2O) and 3.47 g of AlCl3 were weighed and mixed to prepare a mixed solution. AlCl3 was added in small amounts multiple times and stirred slowly to avoid violent heating. 1 g of the mixed solution was added to 0.06 g of NaCl and stirred for 24 hours. The supernatant was collected, and 5 vol% of thionyl chloride (SOCl2) was added to the supernatant. Stirring was continued for 4 hours to prepare the electrolyte.

[0166] Example 17 adopts a similar implementation method to Example 2, but uses the electrolyte described above.

[0167] Example 18

[0168] In this embodiment, a sodium-ion battery without a negative electrode is assembled as a test sample.

[0169] Electrolyte: The electrolyte was prepared in an argon-protected glove box with water and oxygen content below 2 ppm. 3.49 g of 1-butyl-3-methylimidazolium chloride (BMImCl) and 3.47 g of AlCl3 were weighed and mixed to prepare a mixed solution. AlCl3 was added in small amounts multiple times and stirred slowly to avoid violent heating. 1 g of the mixed solution was added to 0.06 g of NaCl and stirred for 24 hours. The supernatant was collected, and 5 vol% of thionyl chloride (SOCl2) was added to the supernatant. Stirring was continued for 4 hours to prepare the electrolyte.

[0170] Example 18 adopts a similar implementation method to Example 1, but uses the electrolyte described above.

[0171] Example 19

[0172] In this embodiment, a sodium-ion battery without a negative electrode is assembled as a test sample.

[0173] Electrolyte: Prepare the electrolyte in an argon-protected glove box with water and oxygen content below 2 ppm; weigh 3.27 g of N-propyl-N-methylpyrrolidine chloride (Py 13 A mixture of 3.47 g of AlCl3 and 3.47 g of NaCl was prepared. The mixture was prepared by adding small amounts of AlCl3 multiple times and stirring slowly to avoid violent heating. 1 g of the mixture was added to 0.06 g of NaCl and stirred for 24 hours. The supernatant was collected and 5 vol% of thionyl chloride (SOCl2) was added to the supernatant. The mixture was stirred for another 4 hours to prepare the electrolyte.

[0174] Example 19 adopts a similar implementation method to Example 1, but uses the electrolyte described above.

[0175] Example 20

[0176] In this embodiment, a sodium-ion battery without a negative electrode is assembled as a test sample.

[0177] Example 20 adopts a similar implementation method to Example 1, but S is replaced with elemental iodine (I2) in the positive electrode.

[0178] Example 21

[0179] In this embodiment, a sodium-ion battery without a negative electrode is assembled as a test sample.

[0180] Example 21 adopts a similar implementation method to Example 1, but S is replaced with tellurium (Te) in the positive electrode.

[0181] Comparative Example 1

[0182] This comparative assembly of a sodium-ion battery without a negative electrode serves as the test sample.

[0183] Positive electrode: 0.2 g Ketjen black was mixed with 8 g anhydrous ethanol, ball-milled at 500 rpm for 5 hours, dried at 80 ℃, and then ball-milled again at 500 rpm for 2 hours. Then, it was mixed with polytetrafluoroethylene (PTFE, aqueous dispersion, solids content 0.83 g / mL). –1 The two components were mixed at a mass ratio of 9.5:0.5 and dispersed in ethanol by ultrasonic treatment. The resulting slurry was coated onto Ni foam (12 mm in diameter) and dried at 90 °C to remove the ethanol, thus preparing an unloaded NaCl cathode.

[0184] Comparative Example 1 adopts a similar implementation method to Example 1, but the positive electrode adopts the above-mentioned unloaded NaCl positive electrode.

[0185] Comparative Example 2

[0186] This comparative assembly of a sodium-ion battery without a negative electrode serves as the test sample.

[0187] Electrolyte: A conventional electrolyte is used, 1 M sodium perchlorate (NaClO4) in ethylene carbonate (EC) / diethyl carbonate (DEC) / dimethyl carbonate (DMC) (volume ratio 1:1:1), denoted as 1 M NaClO4 in EC / DEC / DMC (1:1:1 volume).

[0188] Comparative Example 2 adopts a similar implementation method to Example 2, but uses the electrolyte described above.

[0189] Comparative Example 3

[0190] This comparative assembly of a sodium-ion battery without a negative electrode serves as the test sample.

[0191] Electrolyte: A conventional electrolyte is used, 1 M sodium trifluoromethanesulfonate (NaOTF) in 1,3-dioxolane (DOL) / 1,2-dimethoxyethane (DME) (volume ratio 1:1), denoted as 1 M NaOTF in DOL / DME (1:1 in volume).

[0192] Comparative Example 3 adopted a similar implementation method to Example 2, but used the electrolyte described above.

[0193] Comparative Example 4

[0194] This comparative assembly of a sodium-ion battery without a negative electrode serves as the test sample.

[0195] Electrolyte: A conventional electrolyte is used, 1 M sodium hexafluorophosphate (NaPF6) in diethylene glycol dimethyl ether electrolyte, denoted as 1 M NaPF6 in diglyme (1:1 in volume).

[0196] Comparative Example 4 adopts a similar implementation method to Example 2, but uses the electrolyte described above.

[0197] All electrochemical measurements were performed in a Neware MHW-200 constant-temperature test chamber at 25 °C unless otherwise specified. Battery electrochemical performance was tested using a Neware battery testing system (CT-4008-5V50mA-164-U). Measurements were taken at a frequency range of 10... -2 Up to 10 6 Electrochemical impedance spectroscopy (EIS) was performed on a CHI660E electrochemical workstation with a frequency of Hz and an amplitude of 5 mV. High-temperature and low-temperature measurements were performed in a blast furnace (DHG-9030) and a refrigerator (Haier BC / BD-307HEM), respectively.

[0198] Raman spectroscopy of the electrolyte was performed on a Horiba LabRAM Solei Raman spectrometer with an excitation laser wavelength of 532 nm. The electrolyte sample was sealed in a capillary prepared in an argon-filled glove box. Scanning electron microscopy (SEM) imaging was performed on a ZEISS Gemini 300 field emission scanning electron microscope. The accelerating voltage was set to 3 kV to prevent structural damage to NaCl. Transmission electron microscopy (TEM) imaging was performed at 200 kV on a FE Talos F200X G2 transmission electron microscope equipped with a liquid nitrogen-cooled sample rack. The button cell was removed in an argon-filled glove box, and residual electrolyte on the TEM grid was removed with anhydrous diethylene glycol dimethyl ether and dried under vacuum. The TEM grid was then carefully mounted on a cryogenic rack and transferred to the TEM chamber, away from air exposure. The chamber pressure was below 1.1 × 10⁻⁶. -9 Data were acquired from an ion-time-of-flight mass spectrometer at a mbar ION-TOF 5-100. Bi0 was used at 30 keV. 3+ bundle and 80×80 μm 2 Depth analysis was performed on the scanned area. A Cs2O3 wavelength of 2 keV was used. + bundle and 250×250 μm 2 Sputtering was performed in the sputtering region. XPS spectra were obtained using a Thermo Fisher Scientific K-Alpha+ X-ray photoelectron spectrometer with a current and voltage of 6 mA and 12 kV. The binding energy was calibrated with a C 1s peak of 284.8 eV. Nuclear magnetic resonance (NMR) analysis was performed at 25 °C on a Bruker Avance III 500 MHz liquid NMR spectrometer. A coaxial NMR tube (Bruker, NI5CCI-B 5mm) was used to acquire the spectra. In a glove box, 400 μL of electrolyte was transferred to the outer tube, and 150 μL of deuterated chloroform was filled into the NMR tube inserted into the coaxial outer tube. Both tubes were tightly sealed with caps and Parafilm tape before characterization. XRD patterns were obtained using a Rigaku Mini Flex600 X-ray diffractometer with Cu Kα radiation. The negative electrode inside the glass container was sealed with Kapton tape to isolate oxygen. X-ray absorption near-edge structure (XANES) spectral data were collected at station 4B7A of the Beijing Synchrotron Radiation Facility (BSRF, operating at 2.5 GeV with a maximum current of 250 mA). All XANES spectral data were obtained in fluorescence mode using a silicon drift detector (SDD).

[0199] like Figure 1As shown, Example 1 uses a chloroaluminate-based ionic liquid electrolyte composed of NaCl / AlCl3 / 1-ethyl-3-methylimidazolium chloride (EMImCl), with a small amount of thionyl chloride (SOCl2) as an auxiliary agent and medium.

[0200] like Figure 17 As shown, the electrode reactions of the negative electrode-free sodium battery provided in Example 1 during cycling are described.

[0201] The choice of electrolyte is crucial for the construction of a negative electrode-free sodium battery, which requires efficient simultaneous Na deposition / stripping and Cl-removal. – / Cl2 redox. Due to the lack of free Cl... – Based on traditional electrolytes ( Figure 6 Anode-free batteries (such as those without negative electrodes) struggle to oxidize NaCl. In contrast, the solvation environment of high-concentration Cl-based ions in chloroaluminate-based ionic liquids promotes the oxidation of Cl. – / Cl2 redox. Furthermore, there is no reactive Al2Cl7 in fully buffered chloroaluminate-based ionic liquids. – This greatly reduces the corrosion of Na metal and helps to achieve reversible deposition / stripping. Figure 7 ).

[0202] We first ruled out the dissolution of the NaCl cathode in the NEAS electrolyte, because after soaking in the NEAS electrolyte for 12 hours, its mass loading remained highly consistent. Figure 2 a) This is because the NaCl in the NEAS electrolyte has reached saturation. At the fully charged positive electrode, the original NaCl salt disappears and is regenerated in the fully discharged state, with a smaller particle size. Figure 2 b). This phenomenon was confirmed by the change in the characteristic diffraction peak at 31.8° of the NaCl(200) crystal plane obtained by in-situ XRD. Figure 2 c). We further based our analysis on Cl 2p X-ray photoelectron spectroscopy ( Figure 2 (d) and (e) verified the formation of NaCl at the discharge-state positive electrode and the formation of Cl2 at the charge-state positive electrode. Simultaneously, in-situ differential electrochemical mass spectrometry also confirmed the formation and consumption of Cl2 (mass-to-charge ratio m / z = 70) during charging and discharging processes, respectively. Figure 2 f). The non-in-situ X-ray absorption near-edge structure spectrum further indicates that, at areal capacities of 1 and 2 mAh / cm², 2 NaCl (~2826.7 eV) was generated on the positive electrode in the discharge state, while Cl2 (~2822.5 eV) was generated on the corresponding positive electrode in the charge state. Figure 2 g). When using time-of-flight secondary ion mass spectrometry to quantitatively analyze the cathode products, we observed NaCl in both the charged and discharged states.– and Cl2 – The signal intensity of ion fragments changed significantly. Figure 2 (h, i), thus verifying the conversion reaction between NaCl and Cl2.

[0203] We investigated the electrochemical reversibility of Na deposition / stripping in Na / Al batteries. Figure 3 a). Batteries using NEAS electrolyte at 3 mA cm⁻¹ –2 and 0.3 mAh cm –2 Under these conditions, after 100 cycles, the average coulombic efficiency is approximately 93.3%. This represents a significant improvement compared to batteries using NEA and SOCl2-based electrolytes, which exhibit poor reversibility and coulombic efficiency below 10%. Figure 3 b). This can be attributed to the formation of a dense and uniform Na deposition layer on the Al current collector in the NEAS electrolyte. Figure 3 c), while the NEA electrolyte showed very little Na deposition ( Figure 3 d). XPS surface analysis revealed the formation of Al metal (72.5 eV), AlCl3 (75.2 eV), and NaCl in the NEA electrolyte, indicating severe side reactions such as Al metal deposition and chlorination. In contrast, the NEAS electrolyte significantly suppressed these reactions, with NaCl becoming the main component of the passivation layer at the negative electrode-electrolyte interface. Figure 3 e). Cryo-transmission electron microscopy further confirmed the formation of a uniform passivation layer on the deposited Na metal, indicating that the side reactions with the electrolyte were mitigated. Figure 3 f–h). Furthermore, XRD patterns show that the characteristic peaks of NaCl remain consistent during Na metal deposition and stripping. Figure 3 i). The robust passivation layer derived from the NEAS electrolyte enables the Na / Al battery to operate at 0.5 mAh cm⁻¹. –2 At the deposition capacity, the critical current density reaches 12 mA cm⁻¹. –2 And the deposition / stripping overpotential is stable ( Figure 3 j and k) highlight the rapid kinetic characteristics of negative electrode chemistry.

[0204] We further investigated the electrochemical performance of the NaCl cathode in the Na / NaCl half-cell, focusing on the electrolyte formulation. Compared to the battery using NEAS electrolyte, it exhibited high electrochemical reversibility (at approximately 458 mAh g⁻¹ in 50 cycles). -1 In stark contrast, batteries using NEA electrolyte exhibit poor charging performance (with an average coulombic efficiency of approximately 99.7% at their capacity). Figure 4 a, b). It is worth noting that the introduction of SOCl2 can make the battery operate at 2 mA cm⁻¹. –2After more than 100 stable runs, we further determined that 5 wt% SOCl2 was the optimal formulation. Figure 8 Our NaCl cathode boasts an exceptional energy density (1374 Wh kg). -1 It even surpasses the most advanced sodium cathode materials. Figure 4 c). Density functional theory simulations show that the negatively charged oxygen atoms in SOCl2 can promote the breaking of the Na–Cl bond in NaCl and stabilize the intermediate species Na2Cl2 and NaCl2, thereby lowering the corresponding reaction energy barriers by 0.63 eV and 2.45 eV, respectively. Figure 4 d). Differential charge density analysis further revealed enhanced electron transfer from the carbon cathode to the SOCl2–NaCl2 intermediate in the NEAS electrolyte. Figure 4 e), promoting the breaking of Na–Cl bonds. Furthermore, the introduction of SOCl2 significantly broadened the electrochemical stability window of the NEA electrolyte from 3.97 V to 4.49 V, which was verified by linear scanning voltammetry of the Na / Ni battery at a scan rate of 1 mV / s. Figure 4 f). Our negative electrode-free sodium battery operates under lean electrolyte conditions (1.5 μL mg). –1 It can run reliably under ( ) Figure 9 Furthermore, it exhibits excellent cycle performance even after long-term storage of over 1000 hours. These attractive characteristics further demonstrate the enormous practical potential of our anode-free sodium battery.

[0205] Kinetically favorable NaCl cathodes can be further applied to sodium-free anode batteries, thus avoiding the use of metallic sodium in the anode. (The last sentence appears to be incomplete and possibly refers to a charging capacity of 459 mAh g.) -1 Current density from 1 A g -1 Increased to 3 A g -1 Under these conditions, the negative electrode-free battery exhibits a high discharge voltage of ~3.1 V and a capacity of 408~426 mAh g⁻¹. -1 High discharge capacity ( Figure 4 Based on the total mass of the positive and negative electrodes, our electrodeless sodium battery exhibits a high energy density (780 Wh kg). -1 ) and power density (5,346 W kg) -1 This makes it highly competitive among current lithium-ion batteries, sodium-ion batteries, and negative electrode-free lithium and sodium metal batteries. Figure 4 We further correlated the superior battery performance with the NaCl salt on the positive electrode. This is reflected in the fact that when the positive electrode is unloaded with NaCl, the charging plateau increases significantly from about 4.1 V to about 4.5 V, resulting in a sharp drop in coulombic efficiency to only 21.8% (h). Figure 4i). When the charging capacity exceeds the theoretical capacity of NaCl (459 mAh g). -1 Reaching 500 and 600 mAh g -1 At that time, a higher charging platform of approximately 4.5 V was observed. Figure 4 j). This is attributed to the oxidation of the NEAS electrolyte, such as... Figure 4 This was verified by f. The irreversible reaction resulted in a coulombic efficiency decrease from 459 mAh g⁻¹. -1 The percentage dropped from 92.7% to 600 mAh g -1 The battery achieved a charge capacity of 74.1%, further confirming that the NaCl salt on the positive electrode is the main contributor to electrochemical performance, rather than the NaCl in the NEAS electrolyte. Based on an optimized NaCl positive electrode composed of nitrogen-doped porous carbon and Nafion binder, the electrodeless battery fabricated achieved a charge capacity of 459 mAh g⁻¹. -1 Under conditions of 100% depth of charge, it exhibits enhanced cycle performance after 50 cycles. Figure 4 k).

[0206] We fabricated a 135 mAh negative electrode-free NaCl pouch battery ( Figure 5 a), the battery is at approximately 2 mA cm -2 It exhibits good cycling performance of 150 cycles at current density. Figure 5 a, b). Non-flammable properties of NEAS ionic liquid electrolyte ( Figure 5 (b. Illustration) contributes to high battery safety, as evidenced by the absence of fire or explosion issues during the nail penetration test. Figure 5 c). We have therefore created a device integrating photovoltaic conversion and electrochemical storage, consisting of commercial solar panels and our negative electrode-free sodium battery. This device can collect solar energy and store it in our battery to power various electrical appliances. Figure 5 d). To further verify its practical potential, we fabricated a 1.10 Ah negative electrode-free sodium battery using a homemade module. Figure 5 e), this battery exhibits good coulombic efficiency and overpotential at 1 C rate, and a reversible capacity of 1.06 Ah after 50 cycles (e). Figure 5 f). To facilitate practical applications, we further developed a low-cost battery prototype using a sea salt cathode and a urea-based electrolyte, which exhibited good electrochemical performance at a cost as low as $7.19 per kilowatt-hour (f). Figure 5 g), significantly lower than the most advanced batteries, such as commercial lithium-ion batteries, which cost $77.12 per kilowatt-hour (g). Figure 5 h).

[0207] Figures 10-16 This demonstrates the feasibility of preparing batteries under different electrode and electrolyte configurations according to embodiments of the present invention.

[0208] Figure 4 The relevant comparative literature involved includes:

[0209] 1. Guo, D. et al. Electrolytes with solvating inner sheathengineering for practical Na–S batteries. Adv. Mater. 35, 2300841 (2023). 2. Jiang, Y. et al. Single-atom vanadium catalyst boosting reactionkinetics of polysulfides in Na–S batteries. Adv. Mater. 35, 2208873 (20). 3. Zhang, E. et al. Single-atom yttrium engineering janus electrodefor rechargeable Na–S batteries. J. Am. Chem. Soc. 144, 18995-19007 (2022). 4. Zhang, Y. et al. Chemical and spatial dual-confinement engineeringfor stable Na-S batteries with approximately 100% capacity retention. Proc.Natl. Acad. Sci. 120, e2314408120 (2023). 5. Guo, C. et al. Hydrogen-bonded organic framework for high-performance lithium / sodium–iodine organic batteries. Angew. Chem. Int. Ed.61, e202213276 (2022). It should be noted that there is a typo in the original text where "2023" in item 8 is written as "20" in the translation. It should be corrected to "2023" in the translation for accuracy.6. Xiang, L. et al. Porous polymer cubosomes with ordered singleprimitive bicontinuous architecture and their sodium–iodine batteries. J. Am.Chem. Soc. 144, 15497-15508 (2022). 7. Sun, H. et al. A safe and non-flammable sodium metal battery basedon an ionic liquid electrolyte. Nat. Commun. 10, 3302 (2019). 8. Liu, Y. et al. Na-rich Na3V2(PO4)3cathodes for long cyclingrechargeable sodium full cells. Adv. Energy Mater. 13, 2203283 (2023). 9. Yu, X. et al. Ambient-temperature all-solid-state sodium batterieswith a laminated composite electrolyte. Adv. Funct. Mater. 31, 2002144(2021). 10. Zhang, H. et al. Prussian blue analogues with optimized crystalplane orientation and low crystal defects toward 450 Wh kg −1 alkali-ionbatteries. Angew. Chem. Int. Ed. 62, e202303953 (2023). 11. Hong, N. et al. An in situ dual-modification strategy for O3-NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3O2 towards high-performance sodium-ion batteries. J. Mater.Chem. A 11, 18872-18880 (2023). 12. Feng, S. et al. Surface engineering through in situ constructionof Co x B-spinel dual coating layers for high-voltage stable sodium-ionbatteries. Adv. Energy Mater. 14, 2303773 (2024). 13. Moeez, I. et al. Enhanced cycle stability of low-cost Na-richmetallic NaCl electrode for advanced Na-ion batteries. Adv. Funct. Mater. 33,2210370 (2023). 14. Moeez, I. et al. Electrochemically induced metallization of NaCl:use of the main component of salt as a cost-effective electrode material forsodium-ion batteries. ACS Energy Lett. 4, 2060-2068 (2019).

[0210] Figure 4 The references cited in Ref. 11 - 21 are as follows:

[0211] 11. Li, M. et al. 30 years of lithium-ion batteries. Adv. Mater. 30,1800561 (2018). 12. Simon, P. & Gogotsi, Y. Perspectives for electrochemical capacitorsand related devices. Nat. Mater. 19, 1151-1163 (2020). 13. Li, Y. et al. Interfacial engineering to achieve an energydensity of over 200 Wh kg −1 in sodium batteries. Nat. Energy 7, 511-519 (2022). 14. Lee, K. et al. A 3D hierarchical host with enhancedsodiophilicity enabling anode-free sodium-metal batteries. Adv. Mater. 34,2109767 (2022). 15. Li, H. et al. Sodiophilic current collectors based on MOF-derivednanocomposites for anode-less Na-metal batteries. Adv. Energy Mater. 12,2202293 (2022). 16. Lu, Z. et al. Building a beyond concentrated electrolyte forhigh-voltage anode-free rechargeable sodium batteries. Angew. Chem. Int. Ed.61, e202200410 (2022). 17. Ma, B. et al. Dynamic interfacial stability confirmed bymicroscopic optical operando experiments enables high-retention-rate anode-free Na metal full cells. Adv. Sci. 8, 2005006 (2021). 18. Cai, Z. et al. A multifunctional super‐sodiophilic coating on aluminum current collector for high-performance anode-free Na-metal batteries. Nano Energy 116, 108814 (2023). 19. Li, S. et al. Space-confined guest synthesis to fabricate Sn-monodispersed N-doped mesoporous host toward anode-free Na batteries. Adv. Mater. 35, 2301967 (2023). 20. Wang, Y. et al. Anode-free lithium metal batteries based on an ultrathin and respirable interphase layer. Angew. Chem. Int. Ed. 62, e202304978 (2023). 21. Ouyang, Z. et al. Programmable DNA interphase layers for high-performance anode-free lithium metal batteries. Adv. Mater. 36, 2401114 (2024).

[0212] Figure 5 The relevant comparative literature includes:

[0213] 1. Li, Z. et al. Air-breathing aqueous sulfur flow battery for ultralow-cost long-duration electrical storage. Joule 1, 306-327 (2017). 2. Vaalma, C. et al. A cost and resource analysis of sodium-ionbatteries. Nat. Rev. Mater. 3, 18013 (2018). 3. Pang, Q. et al. Fast-charging aluminum–chalcogen batteries resistant to dendritic shorting. Nature 608, 704-711 (2022).

[0214] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A sodium battery based on a sodium chloride positive electrode active material, characterized in that: Its positive electrode is composed of a positive electrode current collector and a NaCl-containing conductive coating on its surface, or directly composed of a NaCl-containing composite conductive material; the NaCl content in the NaCl-containing conductive coating and the NaCl-containing composite conductive material is 45~90 wt%. Its electrolyte is a chloroaluminate-based electrolyte prepared by using NaCl and AlCl3 as electrolytes; wherein the molar ratio of NaCl to AlCl3 is 0.1~1.1:1.1~2; The AlCl3 in the electrolyte is used to form a chloroaluminate complex system. This chloroaluminate complex system causes the NaCl on the positive electrode to be oxidized to generate chlorine gas during the charging process. It also causes the chlorine gas to be reduced to NaCl and deposited on the positive electrode during the discharging process, thereby achieving a reversible relationship between NaCl and chlorine gas on the positive electrode.

2. The sodium battery according to claim 1, characterized in that: The NaCl-containing conductive coating is formed by adding NaCl to a conventional conductive coating; the NaCl-containing composite conductive material is formed by adding NaCl to a conventional conductive coating and then drying it.

3. The sodium battery according to claim 1, characterized in that: The positive electrode also includes functional additives that can be used in sodium-based batteries.

4. The sodium battery according to claim 1, characterized in that: The NaCl-containing conductive coating and the NaCl-containing composite conductive material also contain halogens and / or chalcogens as functional additives, wherein the amount of halogens and / or chalcogens added is 0 to 50 wt% of the NaCl content.

5. The sodium battery according to claim 4, characterized in that: The NaCl-containing conductive coating and the NaCl-containing composite conductive material also contain elemental sulfur as a functional additive, wherein the amount of elemental sulfur added is 0 to 50 wt% of the NaCl content.

6. The sodium battery according to claim 1, characterized in that: It also includes a negative electrode current collector to form a negative electrode-free sodium battery.

7. The sodium battery according to claim 1, characterized in that: The solvent of the electrolyte includes at least one of imidazole ionic liquids, pyrrolidine ionic liquids, hydrogen bond donors constituting deep eutectic solvents, and solvents for chlorine-based electrolytes.

8. The sodium battery according to claim 7, characterized in that: The imidazole ionic liquid includes any one of 1-ethyl-3-methylimidazolium chloride, 1-propyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, and 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide salt; The pyrrolidine ionic liquid includes either N-ethyl-N-methylpyrrolidine chloride or N-propyl-N-methylpyrrolidine chloride. The hydrogen bond donors constituting the deep eutectic solvent include either urea or acetamide. The solvent used in the chlorine-based electrolyte includes any one of thionyl chloride, sulfonyl chloride, and chloroacetyl chloride.

9. The sodium battery according to claim 8, characterized in that: When the electrolyte contains two or more solvents, one of the solvents is added as an additive, and the amount added is 2 to 10% of the volume percentage of the electrolyte.

10. The sodium battery according to claim 1, characterized in that: The concentration of NaCl in the electrolyte reached saturation.

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