Vanadium manganese sodium phosphate positive electrode material with sodium-position high-entropy structure and preparation method of vanadium manganese sodium phosphate positive electrode material

Abstract

The invention discloses a vanadium manganese sodium phosphate positive electrode material with a sodium-site high-entropy structure and a preparation method, and belongs to the technical field of sodium ion batteries, the chemical general formula of the positive electrode material is Na (4-x-y) MxNyVMn (PO4) 3, M is at least three of Li < + >, K < + >, Rb < + > and Cs < + >, and N is at least two of Be < 2 + >, Mg < 2 + >, Ca < 2 + >, Sr < 2 + > and Ba < 2 + >; according to the method, Na < + > / vacancy ordered and charge ordered structures formed by the crystal during charging and discharging are inhibited through disordered distribution of multiple element atoms at sodium ion sites, structural changes caused by Na < + > intercalation and deintercalation are reduced, meanwhile, the high-entropy elements occupying the sodium sites also play a role of supporting columns on the crystal structure, and all the elements are beneficial to stabilizing the crystal structure; on the other hand, due to the high-entropy elements, lattices are locally distorted, local disorder is caused, an electronic band gap and a sodium ion diffusion barrier can be reduced, the conductivity and ion diffusion kinetics of the material are improved, more importantly, Na (1)-O bonds are effectively weakened by the high-entropy elements at the sodium site, the electrochemical activity of sodium ions at the Na (1) site is activated, and the electrochemical activity of the sodium ions at the Na (1) site is improved. Sodium ion diffusion kinetics and specific capacity are promoted.

Description

Technical Field

[0001] The invention belongs to the technical field of sodium ion batteries, and in particular relates to a sodium vanadium manganese phosphate positive electrode material with a sodium-site high entropy structure and a preparation method thereof. Background Art

[0002] Sodium ion batteries work in a similar way to lithium ion batteries, but the larger radius and relative atomic mass of sodium ions make Na + Insertion and extraction are difficult and slow, and can easily cause large lattice distortion in the host material, leading to structural damage, which greatly limits the theoretical capacity, cycle stability and kinetic performance of the battery, becoming a bottleneck for the commercialization of sodium-ion batteries. Designing and developing positive electrode materials with small lattice distortion, long cycle stability and fast reaction kinetics is a key technology to break through the bottleneck of sodium-ion batteries.

[0003] Sodium superionic conductors (NAS I CON) have become highly anticipated positive electrode materials for sodium-ion batteries due to their high ionic conductivity and excellent chemical and thermodynamic stability. Among them, sodium vanadium manganese phosphate materials with stable structure, high voltage platform and good thermal stability have attracted much attention.

[0004] However, the material still has problems such as poor rate performance and cycle stability that needs to be improved. It also has the common disadvantage of low electronic conductivity of polyanion materials. In particular, the Na(1) position has a stronger Na-O bond and electrochemical inertness, which leads to obstructed sodium ion migration and lower specific capacity. Therefore, how to regulate the coordination environment of the sodium position to improve the ion diffusion kinetics of the vanadium manganese phosphate positive electrode material is the key to improving its sodium storage performance. Summary of the invention

[0005] The purpose of the present invention is to solve the above-mentioned problems and to propose a sodium vanadium manganese phosphate positive electrode material with a sodium-site high entropy structure and a preparation method.

[0006] On the one hand, in order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a sodium vanadium manganese phosphate positive electrode material having a sodium-site high entropy structure, wherein the chemical formula of the positive electrode material is Na (4-x-y) M x N y VMn(PO 4 ) 3 , where M is Li + , K + , Rb + , Cs + At least 3 of the following, N is Be 2+ Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+At least two of the above, x and y are respectively the molar ratios of the alkali metal element and the alkaline earth metal element doped at the sodium ion site in the sodium manganese vanadium phosphate crystal, 0<x≤0.5, 0<y≤0.5.

[0007] As a further description of the above technical solution:

[0008] The particle size of the positive electrode material is 50nm-1μm.

[0009] On the other hand, in order to achieve the above-mentioned object, the present invention adopts the following method: a method for preparing a sodium vanadium manganese phosphate positive electrode material having a sodium-site high entropy structure, characterized in that it comprises the following steps:

[0010] 1) using water and an organic solvent to form a mixed solvent, dissolving an organic complexing agent in the mixed solvent system to form a uniform solution, and then sequentially adding a vanadium source, a manganese source, a sodium source, and a phosphorus source to the mixed solution to form a clear solution, wherein the organic solvent constituting the mixed solvent is at least two of methanol, ethanol, ethylene glycol, tetrahydrofuran, propanol, isopropanol, hexafluoroisopropanol, acetone, N,N'-dimethylformamide, dimethyl sulfoxide, and dioxane, and the organic complexing agent is one or more of ethylenediaminetetraacetic acid, diethanolamine, triethanolamine, 8-hydroxyquinoline, o-phenanthroline, potassium tartrate, citric acid, ammonium citrate, ascorbic acid, etc., wherein the organic complexing agent is also used as a carbon source to form a carbon coating layer on the surface of the synthesized material particles;

[0011] 2) adding an alkali metal / alkaline earth metal / light rare earth metal salt or oxide to the above solution and stirring until a clear solution is formed, wherein the alkali metal / alkaline earth metal / light rare earth metal salt is at least one of their nitrates, phosphates, carbonates, acetates, acetylacetonates, chlorides, etc.;

[0012] 3) heating the above solution to 60-90° C., magnetically stirring for 0.5-4 h, and then placing it in a forced air drying oven at 60-120° C. for 10-48 h to evaporate the solvent and form a gel precursor;

[0013] 4) After grinding the gel precursor, the gel precursor is placed in a tubular furnace under an inert atmosphere at 200-400° C. for 2-6 hours for pre-baking treatment, and then at 700-900° C. for 5-12 hours for high-temperature sintering treatment. After the calcination, the gel precursor is naturally cooled to room temperature to obtain sodium-based high-entropy sodium vanadium manganese phosphate as a positive electrode material for a sodium ion battery.

[0014] As a further description of the above technical solution:

[0015] The vanadium source includes at least one of vanadyl triisopropoxide, vanadium acetylacetonate, ammonium metavanadate, sodium metavanadate, sodium vanadate, vanadium pentoxide, vanadium trioxide, vanadium dioxide, vanadyl sulfate, orthovanadic acid, and vanadium trichloride.

[0016] As a further description of the above technical solution:

[0017] The vanadium source is at least one of vanadyl triisopropoxide, vanadium acetylacetonate, ammonium metavanadate, sodium metavanadate, sodium vanadate, and vanadium pentoxide.

[0018] As a further description of the above technical solution:

[0019] The sodium source includes at least one of sodium carbonate, sodium bicarbonate, sodium acetate, sodium oxalate, sodium phosphate, sodium citrate, sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium nitrate and sodium chloride.

[0020] As a further description of the above technical solution:

[0021] The sodium source is at least one of sodium acetate, sodium carbonate, sodium bicarbonate, sodium hydroxide and sodium dihydrogen phosphate.

[0022] As a further description of the above technical solution:

[0023] The manganese source includes at least one of manganese nitrate, manganese dioxide, manganese carbonate, manganese acetate, manganese sulfate and manganese hydroxide.

[0024] As a further description of the above technical solution:

[0025] The phosphorus source is at least one of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, and metaphosphoric acid.

[0026] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0027] 1. In the present invention, the disordered distribution of high entropy atoms at the sodium ion sites is used to suppress the formation of Na + / Vacancy ordered and charge ordered structures, reducing Na + The structural changes caused by embedding and extraction, and the high entropy elements at the sodium position can effectively regulate the coordination environment of Na(1), weaken the Na(1)-O bond, increase the electrochemically active sodium ions, and enhance their diffusion kinetics. At the same time, these high entropy elements occupying the sodium position also play a "pillar" role in the crystal structure, which helps to stabilize the crystal structure. On the other hand, high entropy elements distort the local crystal structure, resulting in local disorder, which can reduce the electronic band gap and the sodium ion diffusion barrier, thereby improving the material's electrical conductivity and ion diffusion kinetics.

[0028] 2. In the present invention, the preparation process of sodium manganese vanadium phosphate with sodium-position high entropy is simple, the raw materials are cheap and easily available, the purity and yield of the synthetic material are high and the repeatability is good, it is suitable for large-scale production, and has a good industrial application prospect.

[0029] 3. In the present invention, when sodium-site high-entropy sodium manganese vanadium phosphate is used as the positive electrode material of the sodium ion battery, it exhibits high operating voltage, high specific capacity, excellent rate performance and cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The present invention is a flow chart of a method for preparing a sodium manganese vanadium phosphate positive electrode material having a sodium-site high entropy structure.

[0031] Figure 2 This is the XRD diagram of the sodium vanadium manganese phosphate positive electrode material with a high entropy structure at the sodium site.

[0032] Figure 3 This is the constant current charge and discharge curve of the sodium vanadium manganese phosphate positive electrode material with a high entropy structure at the sodium site.

[0033] Figure 4 This is a rate performance comparison curve of sodium vanadium manganese phosphate positive electrode materials with sodium-site high entropy structure.

[0034] Figure 5 This is a comparison curve of the cycling performance of sodium vanadium manganese phosphate positive electrode materials with sodium-site high entropy structure. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] See also Figure 1-5 The present invention provides a technical solution: a sodium vanadium manganese phosphate positive electrode material with a sodium-position high entropy structure, the chemical formula of the positive electrode material is Na (4-x-y) M x N y VMn(PO 4 ) 3 , where M is Li + , K + , Rb + , Cs + At least 3 of the following, N is Be 2+ Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ At least two of the above, x and y are respectively the molar ratios of the alkali metal element, alkaline earth metal element and vanadium element doped at the sodium ion site in the sodium manganese vanadium phosphate crystal, 0<x≤0.5, 0<y≤0.5;

[0037] The particle size of the positive electrode material is 50nm-1μm;

[0038] Working principle: Sodium vanadium manganese phosphate has shown its great potential as a positive electrode material for sodium ion batteries. However, the material still has problems such as low electronic / ionic conductivity, unstable structure during charge and discharge, and ion diffusion kinetics that need to be improved, which seriously restrict its core performance such as discharge capacity, cycle life and rate performance. The present invention designs a sodium-site high-entropy structure for the sodium ion site of the sodium vanadium manganese phosphate crystal, and uses multiple element atoms to share the sodium ion site in the lattice to coordinately regulate the sodium site coordination environment, weaken the strong Na(1)-O bond, increase the electrochemically active sodium ions, and enhance the sodium ion migration kinetics. On the one hand, the disordered distribution of multiple elements at the sodium site disrupts the occupancy of the sodium site, which can effectively stabilize the main lattice and slow down the Na + The structural changes caused by embedding and extraction obtain the "entropy stabilization" effect; on the other hand, the doping of high entropy elements causes local distortion of the material lattice, forming a local disordered structure, which can reduce the electronic band gap and sodium ion diffusion barrier, thereby improving the material's electrical conductivity and ion diffusion rate, and preparing sodium ion battery positive electrode materials with high energy density, long cycle life and excellent rate performance.

[0039] Example 1

[0040] S1. Vanadyl triisopropoxide, manganese acetate, sodium carbonate, ammonium dihydrogen phosphate and ammonium citrate in a molar ratio of 1:1:1.94:3:2 were added to a mixed solvent formed by mixing water, ethanol and acetone in a volume ratio of 1:1:1, and magnetic stirring was performed to form a clear solution;

[0041] S2. Add a high entropy doping element to the above solution, namely lithium hydroxide, potassium nitrate, cesium nitrate, magnesium nitrate, and calcium nitrate in a molar ratio of 0.025:1, 0.015:1, 0.01:1, 0.01:1, and 0.01:1 to the vanadium element, respectively, and stir until a clear solution is formed;

[0042] S3. The mixed solution was heated to 80°C, stirred at this temperature for 4 hours, and then placed in an oven at 80°C for 12 hours to evaporate the solvent to form a gel, thereby obtaining a sodium-based high entropy sodium manganese vanadium phosphate precursor;

[0043] S4. After grinding the precursor, place it in a tubular furnace under a nitrogen atmosphere for calcination, heat it to 300°C at a heating rate of 5°C / min, keep it warm for 5 hours, and then further heat it to 800°C at a rate of 5°C / min, keep it warm for 6 hours. After the calcination, naturally cool it to room temperature to obtain a sodium vanadium manganese phosphate material with a sodium-site high entropy structure.

[0044] Example 2

[0045] S1. ammonium metavanadate, manganese acetate, sodium bicarbonate, phosphoric acid and ammonium tartrate in a molar ratio of 1:1:3.58:3:2 were added to a mixed solvent formed by mixing water, ethanol and acetone in a volume ratio of 1.5:1:1, and magnetic stirring was performed to form a clear solution;

[0046] S2. Add a high entropy doping element to the above solution, namely lithium carbonate, potassium acetate, magnesium nitrate, calcium nitrate, and barium nitrate in molar ratios of 0.025:1, 0.04:1, 0.05:1, 0.05:1, and 0.05:1 to the vanadium element, respectively, and stir until a clear solution is formed;

[0047] S3. The mixed solution was heated to 60°C, stirred for 5 hours, and then placed in an oven at 65°C for 48 hours to evaporate the solvent to obtain a sodium-based high entropy sodium manganese vanadium phosphate precursor;

[0048] S4. After grinding the precursor, place it in a tubular furnace under a nitrogen atmosphere for calcination, heat it to 350°C at a heating rate of 5°C / min, keep it warm for 4 hours, and then further heat it to 750°C at a rate of 5°C / min, keep it warm for 8 hours. After the calcination, naturally cool it to room temperature to obtain a sodium vanadium manganese phosphate material with a sodium-site high entropy structure.

[0049] Example 3

[0050] S1. Vanadium pentoxide, manganese acetate, sodium acetate, ammonium dihydrogen phosphate and citric acid in a molar ratio of 0.5:1:3.82:3:2 are added to a mixed solvent formed by mixing water, ethanol and tetrahydrofuran in a volume ratio of 2:1:1, and magnetic stirring is performed to form a clear solution;

[0051] S2. Add a high entropy doping element to the above solution, namely, lithium hydroxide, potassium nitrate, rubidium nitrate, cesium nitrate, magnesium nitrate, and calcium nitrate in a molar ratio of 0.02:1, 0.015:1, 0.015:1, 0.01:1, 0.025:1, and 0.02:1 to the vanadium element, respectively, and stir until a clear solution is formed;

[0052] S3. The mixed solution was heated to 60°C, stirred for 5 hours, and then placed in an oven at 60°C for 48 hours to evaporate the solvent to obtain a sodium-based high entropy sodium manganese vanadium phosphate precursor;

[0053] S4. After grinding the precursor, place it in a tubular furnace under a nitrogen atmosphere for calcination, heat it to 400°C at a heating rate of 5°C / min, keep it warm for 3 hours, and then further heat it to 700°C at a rate of 5°C / min, keep it warm for 12 hours. After the calcination, naturally cool it to room temperature to obtain a sodium vanadium manganese phosphate material with a sodium-site high entropy structure.

[0054] Example 4

[0055] S1. Vanadium acetylacetonate, manganese nitrate, sodium acetate, phosphoric acid and triethanolamine in a molar ratio of 1:1:3.42:3:2 are added to a mixed solvent formed by mixing water, acetone and propanol in a volume ratio of 1:1:1, and magnetic stirring is performed to form a clear solution;

[0056] S2. Add a high entropy doping element to the above solution, namely potassium nitrate, rubidium nitrate, cesium nitrate, and magnesium nitrate in molar ratios of 0.14:1, 0.12:1, 0.1:1, and 0.05:1 to the vanadium element, respectively, and stir until a clear solution is formed;

[0057] S3. The mixed solution was heated to 60°C, stirred for 4 hours, and then placed in an oven at 60°C for 36 hours to evaporate the solvent to obtain a sodium-based high entropy sodium manganese vanadium phosphate precursor;

[0058] S4. After grinding the precursor, place it in a tubular furnace under a nitrogen atmosphere for calcination, heat it to 250°C at a heating rate of 5°C / min, keep it warm for 6 hours, and then further heat it to 850°C at a rate of 5°C / min, keep it warm for 5 hours. After the calcination, naturally cool it to room temperature to obtain a sodium vanadium manganese phosphate material with a sodium-site high entropy structure.

[0059] Example 5

[0060] S1. ammonium metavanadate, manganese nitrate, sodium carbonate, ammonium dihydrogen phosphate and ascorbic acid in a molar ratio of 1:1:1.79:3:4 were added to a mixed solvent formed by mixing water, ethylene glycol and isopropanol in a volume ratio of 2:1:1, and magnetic stirring was performed to form a clear solution;

[0061] S2. Add a high entropy doping element to the above solution, namely, lithium hydroxide, rubidium nitrate, cesium nitrate, calcium nitrate, and barium nitrate in molar ratios of 0.08:1, 0.06:1, 0.05:1, 0.05:1, and 0.05:1 to the vanadium element, respectively, and stir until a clear solution is formed;

[0062] S3. The mixed solution was heated to 85°C, stirred for 2h, and then placed in a 110°C forced air oven for 48h to evaporate the solvent to obtain a sodium-based high entropy sodium manganese vanadium phosphate precursor;

[0063] S4. After grinding the precursor, place it in a tubular furnace under a nitrogen atmosphere for calcination, heat it to 380°C at a heating rate of 5°C / min, keep it warm for 2 hours, and then further heat it to 800°C at a rate of 5°C / min, keep it warm for 6 hours. After the calcination, naturally cool it to room temperature to obtain a sodium vanadium manganese phosphate material with a sodium-site high entropy structure.

[0064] Comparative Example 1

[0065] S1. Vanadyl triisopropoxide, manganese acetate, sodium carbonate, ammonium dihydrogen phosphate and ammonium citrate in a molar ratio of 1:1:2:3:2 are added to a mixed solvent formed by mixing water, ethanol and acetone in a volume ratio of 1:1:1, and magnetic stirring is performed to form a clear solution;

[0066] S2. The mixed solution was heated to 80°C, stirred at this temperature for 4h, and then placed in an oven at 80°C for 12h to evaporate the solvent to form a gel to obtain a sodium manganese vanadium phosphate precursor;

[0067] S3. After grinding the precursor, place it in a tubular furnace under a nitrogen atmosphere for calcination, heat it to 300°C at a heating rate of 5°C / min, keep it warm for 5 hours, then further heat it to 800°C at a heating rate of 5°C / min, keep it warm for 6 hours, heat it to 800°C at a heating rate of 5°C / min, keep it warm for 10 hours, and after calcination, naturally cool it to room temperature to obtain sodium vanadium manganese phosphate material.

[0068] Comparative Example 2

[0069] S1. ammonium metavanadate, manganese acetate, sodium bicarbonate, phosphoric acid and ammonium tartrate in a molar ratio of 1:1:3.71:3:2 were added to a mixed solvent formed by mixing water, ethanol and acetone in a volume ratio of 1.5:1:1, and magnetic stirring was performed to form a clear solution;

[0070] S2. Add a high entropy doping element to the above solution, namely lithium carbonate, potassium acetate, magnesium nitrate, and calcium nitrate in molar ratios of 0.025:1, 0.04:1, 0.05:1, and 0.05:1 to the vanadium element, respectively, and stir until a clear solution is formed;

[0071] S3. The mixed solution was heated to 60°C, stirred for 5 hours, and then placed in an oven at 65°C for 48 hours to evaporate the solvent to obtain a sodium-based high entropy sodium manganese vanadium phosphate precursor;

[0072] S4. After grinding the precursor, place it in a tubular furnace under a nitrogen atmosphere for calcination, heat it to 350°C at a heating rate of 5°C / min, keep it warm for 4 hours, and then further heat it to 750°C at a rate of 5°C / min, keep it warm for 8 hours. After the calcination, naturally cool it to room temperature to obtain a sodium vanadium manganese phosphate material with a sodium-site high entropy structure.

[0073] From the comparison of the electrochemical performance data of Examples 1-5 with Comparative Example 1, it can be seen that the present invention introduces a strategy for constructing a sodium-site high-entropy structure, and the specific capacity, rate performance and cycle stability of the modified materials are greatly improved, and the electrochemical performance is significantly improved.

[0074] From the comparison of the performance data of Examples 1-5 and Comparative Example 2, it can be seen that the precise construction of the sodium-site high entropy structure of the sodium manganese vanadium phosphate material by the strategy proposed in the present invention has a direct impact on its electrochemical performance. By precisely controlling the configuration entropy of the sodium ion site, the Na + The structural changes caused by insertion and extraction regulate the electronic band gap and sodium ion diffusion barrier, which greatly improves the material conductivity and ion diffusion kinetics, and obtains sodium-site high-entropy positive electrode materials with excellent electrochemical properties.

[0075] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A sodium manganese vanadium phosphate positive electrode material having a sodium-site high entropy structure, characterized in that: The chemical formula of the positive electrode material is Na (4-x-y) M x N y VMn(PO4)3, where M is Li + , K + , Rb + , Cs + At least 3 of the following, N is Be 2+ Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ At least two of the above, x and y are respectively the molar ratios of the alkali metal element and the alkaline earth metal element doped at the sodium ion site in the sodium manganese vanadium phosphate crystal, 0<x≤0.5, 0<y≤0.

5.

2. The sodium vanadium manganese phosphate positive electrode material having a sodium-site high entropy structure according to claim 1, characterized in that: The particle size of the positive electrode material is 50nm-1μm.

3. A method for preparing the sodium vanadium manganese phosphate positive electrode material having a sodium-site high entropy structure as claimed in any one of claims 1 to 2, characterized in that: The steps include: 1) using water and an organic solvent to form a mixed solvent, dissolving an organic complexing agent in the mixed solvent system to form a uniform solution, and then sequentially adding a vanadium source, a manganese source, a sodium source, and a phosphorus source to the mixed solution to form a clear solution, wherein the organic solvent constituting the mixed solvent is at least two of methanol, ethanol, ethylene glycol, tetrahydrofuran, propanol, isopropanol, hexafluoroisopropanol, acetone, N,N'-dimethylformamide, dimethyl sulfoxide, and dioxane, and the organic complexing agent is one or more of ethylenediaminetetraacetic acid, diethanolamine, triethanolamine, 8-hydroxyquinoline, o-phenanthroline, potassium tartrate, citric acid, ammonium citrate, ascorbic acid, etc., wherein the organic complexing agent is also used as a carbon source to form a carbon coating layer on the surface of the synthesized material particles; 2) adding an alkali metal / alkaline earth metal salt or oxide to the above solution and stirring until a clear solution is formed, wherein the alkali metal / alkaline earth metal salt is at least one of their nitrates, phosphates, carbonates, acetates, acetylacetonates, chlorides, etc.; 3) heating the above solution to 60-90° C., magnetically stirring for 0.5-4 h, and then placing it in a forced air drying oven at 60-120° C. for 10-48 h to evaporate the solvent and form a gel precursor; 4) After grinding the gel precursor, placing it in a tubular furnace under an inert atmosphere at 200-400° C. for 2-6 hours for pre-baking treatment, and then keeping it at 700-900° C. for 5-12 hours for high-temperature sintering treatment. After the calcination is completed, it is naturally cooled to room temperature to obtain a sodium-site high-entropy sodium vanadium manganese phosphate positive electrode material for sodium ion batteries.

4. The method for preparing a sodium vanadium manganese phosphate positive electrode material having a sodium-site high entropy structure according to claim 3, characterized in that: The vanadium source includes at least one of vanadyl triisopropoxide, vanadium acetylacetonate, ammonium metavanadate, sodium metavanadate, sodium vanadate, vanadium pentoxide, vanadium trioxide, vanadium dioxide, vanadyl sulfate, orthovanadic acid, and vanadium trichloride.

5. The method for preparing a sodium vanadium manganese phosphate positive electrode material having a sodium-site high entropy structure according to claim 4, characterized in that: The vanadium source is at least one of vanadyl triisopropoxide, vanadium acetylacetonate, ammonium metavanadate, sodium metavanadate, sodium vanadate, and vanadium pentoxide.

6. The method for preparing a sodium vanadium manganese phosphate positive electrode material having a sodium-site high entropy structure according to claim 5, characterized in that: The sodium source includes at least one of sodium carbonate, sodium bicarbonate, sodium acetate, sodium oxalate, sodium phosphate, sodium citrate, sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium nitrate and sodium chloride.

7. The method for preparing a sodium vanadium manganese phosphate positive electrode material having a sodium-site high entropy structure according to claim 6, characterized in that: The sodium source is at least one of sodium acetate, sodium carbonate, sodium bicarbonate, sodium hydroxide and sodium dihydrogen phosphate.

8. The method for preparing a sodium vanadium manganese phosphate positive electrode material having a sodium-site high entropy structure according to claim 7, characterized in that: The manganese source includes at least one of manganese nitrate, manganese dioxide, manganese monoxide, manganese tetraoxide, manganese carbonate, manganese acetate, manganese sulfate and manganese hydroxide.

9. The method for preparing a sodium vanadium manganese phosphate positive electrode material having a sodium-site high entropy structure according to claim 8, characterized in that: The phosphorus source is at least one of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, and metaphosphoric acid.

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