A method for preparing a sulfur-phosphorus co-doped nickel-iron-based hydrotalcite cathode material for chloride ion batteries

Abstract

This invention provides a method for preparing a sulfur-phosphorus co-doped nickel-iron-based layered double hydroxide (TLH) cathode material for chloride-ion batteries. The method first prepares a sulfur-doped carbonate LDH precursor; then, the precursor is acid-exchanged using hydrochloric acid in a sodium chloride solution of a certain concentration to obtain chloride-intercalated LDH powder; the LDH powder and a phosphorus source are then calcined in a tube furnace using a temperature difference method. The sulfur-phosphorus co-doped nickel-iron-based LDH cathode material prepared by this method can introduce abundant oxygen vacancy defects under the synergistic effect of the two non-metallic elements, thereby improving the electronic configuration, optimizing electron transfer and anion adsorption capabilities, increasing the material's conductivity and redox kinetics, improving the material's structural stability, and ultimately increasing the initial capacity of the nickel-iron-based LDH and enhancing the battery's long-cycle stability.

Description

Technical Field

[0001] This invention belongs to the field of secondary battery materials and energy; in particular, it relates to a method for preparing a sulfur-phosphorus co-doped nickel-iron-based hydrotalcite chloride-ion battery cathode material. Background Technology

[0002] With the rapid development of the social industrial system, society's demand for energy is increasing daily. The massive consumption of traditional fossil fuels (such as coal, oil, and natural gas) has led to the rapid depletion of their reserves and further exacerbated environmental pollution. Therefore, utilizing renewable and cleaner green energy sources such as solar, wind, and tidal energy has become urgent. Chloride-ion batteries use chloride ions, the second most electronegative form of electrolyte, as the transport medium. They exhibit good stability in the electrolyte and are abundant on Earth; the theoretical capacity of a chloride-ion battery is 2500 Wh / L. -1 Its dendrite-free characteristics make the sustainable development of chloride-ion batteries possible.

[0003] Layered bimetallic hydroxides (LDHs) are a rare class of anion-intercalated two-dimensional materials. Due to the high tunability of the metal elements in the LDH layers and the anions between the layers, the two-dimensional ion channels with variable interlayer spacing, and the unique topological transition characteristics, LDHs can theoretically be used as cathode materials for anion batteries.

[0004] Incorporating heteroatoms (such as nitrogen, boron, phosphorus, and sulfur) into electrode materials is an effective structural modification engineering strategy. Creating oxygen vacancy defects and promoting efficient ion transport and rapid charge transfer can significantly improve electronic properties and regulate the surface chemistry of LDHs. Transition metals and phosphorus possess favorable electronic structures and can exhibit excellent electrocatalytic activity. Sulfur doping can significantly improve the electronic conductivity of bimetallic layered oxide materials. Anion doping can maintain the layered structure of LDHs materials, providing favorable ion diffusion channels for chloride ions. The stable presence / release of chloride ions in the interlayer space of LDHs, along with the favorable electron distribution resulting from the interaction of different cations and heteroatoms, promotes chloride ion diffusion. Simultaneously incorporating multiple heteroatoms (such as nitrogen, boron, phosphorus, and sulfur) into electrode materials represents a technological innovation. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a sulfur-phosphorus co-doped nickel-iron-based hydrotalcite cathode material for chloride ion batteries.

[0006] This invention is achieved through the following technical solution:

[0007] This invention relates to a method for preparing a sulfur-phosphorus co-doped nickel-iron-based hydrotalcite cathode material for chloride ion batteries, comprising the following steps:

[0008] Step 1: Prepare sulfur-doped nickel-iron-based bimetallic hydroxide precursor using a one-step co-precipitation method: Dissolve soluble inorganic salts M1 and M2 with a sulfur source in deionized water to prepare a mixed salt solution; place the mixed salt solution in a beaker and stir thoroughly until homogenized; dissolve sodium hydroxide in deionized water, and after complete dissolution, place it in a constant pressure dropping funnel and slowly add it dropwise to the mixed salt solution while stirring. Adjust the pH of the solution to 8-10, place it in a polytetrafluoroethylene reactor, and keep it at 80-150℃ for 12-36 hours. After the reaction, centrifuge to collect the precipitate and wash it 3-5 times with deionized water and anhydrous ethanol until the impurity ions are completely washed away; place the product in a forced-air drying oven to dry until all moisture is removed, obtaining dried product A;

[0009] Step 2: Pour the dried product A into a sodium chloride solution and stir vigorously to mix it thoroughly. The concentration of the sodium chloride solution is 0.5-5 mol / L. Add a trace amount of hydrochloric acid, stir vigorously at room temperature and under a nitrogen atmosphere, centrifuge, and dry to obtain product B.

[0010] Step 3: Transfer product B and phosphorus source to a tube furnace filled with inert gas and heat to 100-500°C at a heating rate of 1-5°C / min. Keep the temperature under sealed conditions for 1-24 hours to obtain the product. After the product cools to room temperature with the furnace, it is taken out to obtain sulfur-phosphorus co-doped nickel-iron-based hydrotalcite chloride-ion battery cathode material.

[0011] Preferably, in step 1, the concentration of the soluble inorganic salt M1 is 0.01 to 0.5 mol / L, the molar concentration ratio of M1 to M2 is 1 to 3, and the molar concentration of the sulfur source is 0.1 to 0.5 times the total metal molar concentration.

[0012] Preferably, in step 1, the sulfur source is thioacetamide, thiourea, or sodium sulfide.

[0013] Preferably, in step 1, M1 in the soluble inorganic salt M1 is Ni. 2+ Mg 2+ Fe 2+ or Zn 2+ The soluble inorganic salt M2 in the text is Fe. 3+ Co 3+ Ti 3+ Mn 3+ V 3+ Or Al 3+ .

[0014] Preferably, in step 1, the drying temperature is 60°C and the drying time is 24 hours.

[0015] Preferably, in step 2, the sodium chloride solution is prepared from decarbonated deionized water containing sodium chloride, wherein the decarbonated deionized water is prepared by a boiling process.

[0016] Preferably, in step 2, the stirring time is 12 to 36 hours, and the drying temperature is 60°C for 24 hours.

[0017] Preferably, in step 3, the mass ratio of product B to phosphorus source is 1:10.

[0018] Preferably, in step 3, the phosphorus source is sodium hypophosphite monohydrate, sodium hypophosphite pentahydrate, or sodium metaphosphate.

[0019] Preferably, in step 3, the heat preservation time is 1 to 24 hours.

[0020] This invention also relates to the preparation of battery electrode sheets, specifically...

[0021] The sulfur-phosphorus co-doped nickel-iron-based hydrotalcite chloride-ion battery cathode material prepared above, polytetrafluoroethylene and acetylene black are mixed in a certain proportion (mass ratio of the three is 5-8:4-1:1), and after thorough grinding, the slurry is evenly coated on the current collector and placed in a vacuum drying oven at 60-180℃ for 12-36 hours. It is then cut into 12mm or 15mm circular electrode sheets or square soft-pack battery electrode sheets as needed. The current collector is stainless steel foil, nickel foam, aluminum foil, copper foil and graphite paper, etc.

[0022] This invention also relates to assembling a chloride-ion battery using the sulfur-phosphorus co-doped nickel-iron-based layered double hydroxide cathode material prepared above, specifically:

[0023] This invention utilizes acid exchange technology to alter the intercalation ions between the layers to obtain a chloride-intercalated hydrotalcite positive electrode material; lithium foil is selected as the negative electrode material; the electrolyte is 1-butyl-1-methylpiperidinium chloride dissolved in PC with a solubility of 0.05 mol / L; a chloride-ion battery is constructed using a sulfur-phosphorus co-doped nickel-iron-based hydrotalcite electrode material as the positive electrode.

[0024] The principle of this invention: This invention employs a simple co-precipitation method. Two soluble inorganic salts and a sulfur source are thoroughly mixed with deionized water in a certain proportion. The pH is adjusted to between 8 and 10 by titration with a sodium hydroxide solution of a certain molar concentration. The precipitate is placed in a polytetrafluoroethylene reactor and aged in a variable-temperature forced-air drying oven at 80–150°C for 12–24 hours to obtain a sulfur-doped carbonate nickel-iron LDH precursor. The precursor is then subjected to acid exchange treatment with hydrochloric acid in a sodium chloride solution of a certain concentration to replace the carbonate and nitrate anions in the interlayer of the hydrotalcite, resulting in chloride-intercalated hydrotalcite powder. The hydrotalcite powder and a phosphorus source are placed in a tube furnace in a certain proportion and calcined using a temperature difference method to finally obtain a sulfur-phosphorus co-doped nickel-iron based hydrotalcite (LDHs) chloride ion cathode material.

[0025] The present invention has the following advantages:

[0026] (1) The sulfur-phosphorus co-doped nickel-iron-based layered double hydroxides (LDHs) chloride ion cathode material prepared by the method of the present invention can introduce abundant oxygen vacancy defects under the joint coordination of the two non-metallic elements, thereby improving the electronic configuration, optimizing the electron transfer ability and ion adsorption ability, improving the conductivity and redox kinetics of the material, improving the structural stability of the material, and thus improving the initial capacity of nickel-iron-based layered double hydroxides (LDHs) and improving the long-cycle stability of the battery.

[0027] (2) This invention uses two-dimensional layered materials of transition metal LDHs doped with sulfur and phosphorus as positive electrode materials for chloride-ion batteries. By utilizing the electrochemical activity, high anion conductivity, topological transformation characteristics, interlayer two-dimensional ion transport channels, and tunable structure and composition of LDHs, the two inorganic non-metallic elements work together to introduce abundant oxygen vacancy defects to improve the electronic configuration, thus preparing a type of chloride-ion battery with high specific capacity, high safety, and high efficiency. Attached Figure Description

[0028] Figure 1 This is an X-ray diffraction pattern from Embodiment 1 of the present invention;

[0029] Figure 2 This is a scanning electron microscope image from Embodiment 1 of the present invention;

[0030] Figure 3 This is a charging cycle diagram from Embodiment 1 of the present invention. Detailed Implementation

[0031] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are merely further illustrations of the present invention, but the scope of protection of the present invention is not limited to the following embodiments.

[0032] Example

[0033] This embodiment relates to a method for preparing a sulfur-phosphorus co-doped nickel-iron-based hydrotalcite chloride-ion battery cathode material, including the following steps:

[0034] Step 1: Prepare sulfur-doped nickel-iron-based bimetallic hydroxide precursor by one-step co-precipitation method: Dissolve soluble inorganic salts Ni(NO3)2·6H2O and Fe(NO3)3·9H2O with thioacetamide in deionized water to prepare a mixed salt solution;

[0035] The concentrations of Ni(NO3)2·6H2O and Fe(NO3)3·9H2O were 0.15 mol / L, respectively, and the molar concentration of thioacetamide was 0.1 times the total molar concentration of the metals. The mixed salt solution was placed in a beaker and stirred thoroughly to ensure homogenization. Sodium hydroxide was dissolved in deionized water and, after complete dissolution, placed in a constant-pressure dropping funnel and slowly added to the mixed salt solution while stirring. The pH of the solution was adjusted to 9. The mixed solution was then placed in a polytetrafluoroethylene reactor and kept at 130°C for 24 hours. After the reaction, the precipitate was collected by centrifugation and washed 3-5 times with deionized water and anhydrous ethanol to ensure complete removal of impurity ions. The product was placed in a forced-air drying oven and dried at 60°C for 24 hours to completely remove moisture, yielding dried product A.

[0036] Step 2: Pour 0.4 g of the obtained dried product A into 400 mL of decarbonized deionized water containing sodium chloride and stir vigorously to ensure thorough mixing (the decarbonized deionized water is prepared by boiling). The sodium chloride solution concentration is 0.5 mol / L. Then, add a trace amount of 1-5 M hydrochloric acid and stir vigorously at room temperature under a nitrogen atmosphere for 12-36 h. Centrifuge the product and dry it at 60 °C for 24 h to obtain product B.

[0037] Step 3: Mix product B with phosphorus source at a mass ratio of 1:10 and transfer to a tube furnace filled with inert gas. Heat to 120-300℃ at a heating rate of 2℃ / min and hold for 2 hours to obtain the product. After the product cools to room temperature with the furnace, it is taken out. The reaction is completed under sealed conditions to obtain sulfur-phosphorus co-doped nickel-iron-based hydrotalcite chloride-ion battery cathode material.

[0038] This embodiment also relates to the preparation of the positive electrode sheet for a chloride-ion battery, and the specific steps are as follows:

[0039] Take 40 mg of the prepared sulfur-phosphorus co-doped nickel-iron-based hydrotalcite chloride-ion battery positive electrode material sample, add conductive agent acetylene black and binder PVDF (mass ratio of the three is 5-8:4-1:1), and drop in solvent NMP for thorough grinding and mixing to obtain a positive electrode slurry. Use a four-sided coater to uniformly coat the positive electrode slurry onto graphite paper, and quickly place it in a vacuum oven at 90-120℃ for vacuum drying for 24-48 hours. Cut it into a circular electrode sheet with a diameter of 12 mm to obtain the positive electrode sheet of the chloride-ion battery.

[0040] This embodiment also relates to the assembly of a chloride-ion battery:

[0041] Using the positive electrode sheet cut from the example, a high-purity lithium metal sheet was used as the negative electrode, glass fiber paper (GF / D, Whatman) was used as the separator, and 0.5M 1-butyl-1-methylpiperidinium chloride was used as the electrolyte to assemble a chloride-ion battery.

[0042] See Figures 1-3 As shown, X-ray diffraction and scanning electron microscopy were used to study the crystal structure and microstructure of the hydrotalcite cathode material. Figure 1 The diffraction peaks of the (003) and (006) crystal planes belonging to LDHs can be clearly seen, and no extra impurity peaks appear, proving the successful preparation of sulfur-phosphorus co-doped nickel-iron LDHs. Figure 2 The prepared sulfur-phosphorus co-doped nickel-iron LDH exhibits a standard nanosheet structure with an average size of approximately 100 nm. The battery evaluation system was tested at 299 K to assess its electrochemical performance, including constant current charge-discharge behavior, cycle stability, and cyclic voltammetry. Figure 3 The study demonstrated the charge-discharge performance of the sulfur-phosphorus co-doped nickel-iron LDH cathode material after 100 cycles at a current density of 300 mA g. Compared with traditional nickel-iron LDH, its maximum specific capacity and cycle life were greatly improved.

[0043] This invention employs a simple co-precipitation method. Two soluble inorganic salts and a sulfur source are thoroughly mixed with deionized water in a specific ratio. The pH is adjusted to between 8 and 10 by titration with a sodium hydroxide solution of a specific molar concentration. The precipitate is then placed in a polytetrafluoroethylene reactor and aged in a variable-temperature drying oven at 80–150°C for 12–24 hours to obtain a carbonate LDH precursor. The precursor is then subjected to acid exchange treatment with hydrochloric acid in a sodium chloride solution of a specific concentration to replace the carbonate and nitrate anions in the interlayer of the hydrotalcite, resulting in chloride-intercalated hydrotalcite powder. The hydrotalcite powder and a phosphorus source are then placed in a tube furnace in a specific ratio and calcined using a temperature difference method to obtain a sulfur-phosphorus co-doped nickel-iron-based hydrotalcite (LDHs) chloride ion cathode material.

[0044] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a sulfur and phosphorus co-doped nickel-iron based hydrotalcite chloride-ion battery cathode material, characterized in that, The method comprises the following steps: Step 1, a step co-precipitation method is used to prepare a sulfur-doped nickel-iron-based double-metal hydroxide precursor: soluble inorganic salts M1, M2 and a sulfur source are dissolved in deionized water to prepare a mixed salt solution; The mixed salt solution is placed in a beaker and stirred until the solution is homogenized; sodium hydroxide is dissolved in deionized water, fully dissolved, and then placed in a constant-pressure dropping funnel, which is slowly added to the mixed salt solution and stirred, the pH of the solution is adjusted to 8-10, and the solution is placed in a polytetrafluoroethylene reaction kettle and heated at 80-150°C for 12-36 hours; after the reaction is completed, the precipitate is collected by centrifugation and washed with deionized water and anhydrous ethanol for 3-5 times until the impurity ions are completely washed out; the product is placed in a blast drying oven and dried until the water is completely removed, obtaining a dry product A; Step 2, the dry product A is poured into a sodium chloride solution and stirred to mix thoroughly, the concentration of the sodium chloride solution is 0.5-5 mol / L, a small amount of hydrochloric acid is added, and the mixture is stirred at room temperature under a nitrogen atmosphere, centrifuged, and dried to obtain product B; Step 3, product B and a phosphorus source are transferred to a tube furnace filled with inert gas, heated to 100-500°C at a heating rate of 1-5°C / min, and kept at a sealed condition for 1-24h to obtain a product, which is taken out after the product is cooled to room temperature with the furnace body; M1 in the soluble inorganic salt M1 in step 1 is Ni 2+ M2 in the soluble inorganic salt M2 is Fe 3+ The concentration of the soluble inorganic salt M1 is 0.01-0.5 mol / L, the molar concentration ratio of M1 to M2 is 1-3, and the molar concentration of the sulfur source is 0.1-0.5 times of the total metal molar concentration; the sulfur source is thioacetamide, thiourea or sodium sulfide; the drying temperature is 60℃, and the time is 24 h. In step 2, the sodium chloride solution is prepared by using decarburized deionized water containing sodium chloride, wherein the decarburized deionized water is prepared by a boiling process; the stirring time is 12-36h, the drying temperature is 60°C, and the drying time is 24h; the mass ratio of product B to the phosphorus source is 1:10; the phosphorus source is sodium hypophosphite monohydrate, sodium phosphite pentahydrate, or sodium metaphosphate; and the heat preservation time is 1-24h.

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