A sodium polyacrylate supported sodium vanadium phosphate positive electrode material, a preparation method and application thereof

Abstract

The application relates to the technical field of sodium-ion batteries, in particular to a sodium polyacrylate supported sodium vanadium phosphate positive electrode material and a preparation method and application thereof, which comprises the following steps: S1: polyacrylate sodium is added into deionized water I to obtain a polyacrylate sodium dispersion liquid; S2: a vanadium source is added into deionized water II to be stirred until the vanadium source is dissolved to obtain a vanadium source solution; S3: a reducing agent is added into the vanadium source solution to be reduced, then a sodium source and a phosphorus source are added and uniformly mixed to carry out a sol-gel reaction, so that a precursor solution is obtained; S4: the polyacrylate sodium dispersion liquid obtained in S1 is added into the precursor solution obtained in S3, and the solution is stirred to be adjusted to be weakly alkaline; S5: the obtained weakly alkaline precursor solution is dried to obtain a dried precursor; S6: the obtained dried precursor is placed into an inert atmosphere to be calcined at high temperature, so that the target product is obtained; the problems that the existing sodium vanadium phosphate material is limited in rate performance due to low electronic conductivity and low ionic conductivity are solved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of sodium ion batteries, in particular to a sodium polyacrylate supported sodium vanadium phosphate positive electrode material and a preparation method and application thereof. BACKGROUND

[0002] Under the background of accelerating transformation of global energy structure and large-scale grid connection of renewable energy, energy storage technology, as a core link to support stable operation of new power systems, is facing unprecedented development opportunities and challenges. The uneven geographical distribution of lithium resources and the rising cost make it difficult to meet the economic needs of future large-scale energy storage systems. Therefore, due to the earth abundance and cost advantage of sodium resources, sodium ion batteries are regarded as a strategic choice for the next generation of energy storage technology.

[0003] Sodium vanadium phosphate, namely Na3V2(PO4)3, as a typical representative of NASICON type polyanion positive electrode material, has a three-dimensional open framework structure, which endows the material with excellent sodium ion diffusion dynamics, i.e. the diffusion coefficient is 10 -12 ~10 -11 cm 2 s -1 at room temperature, and structural stability, i.e. volume change rate <8%. However, the intrinsic electronic conductivity of sodium vanadium phosphate is about 10 S / cm, and the ion diffusion path is about 20-50 nm, which limits its rate performance and cycle life, especially at a high rate of 10 C or more, the capacity retention rate significantly decreases.

[0004] Therefore, it is necessary to invent a sodium polyacrylate supported sodium vanadium phosphate positive electrode material and a preparation method and application thereof to solve the above problems. SUMMARY

[0005] The application provides a sodium polyacrylate supported sodium vanadium phosphate positive electrode material and a preparation method and application thereof to solve the problem that the existing sodium vanadium phosphate material has low electronic conductivity and low ionic conductivity, thereby limiting its rate performance.

[0006] The application is implemented by adopting the following technical scheme:

[0007] A preparation method of a sodium polyacrylate supported sodium vanadium phosphate positive electrode material, comprising the following steps:

[0008] S1: 0.5g of sodium polyacrylate is added to 25-50mL of deionized water I for soaking to obtain a sodium polyacrylate dispersion liquid;

[0009] S2: a vanadium source is added to 60-90mL of deionized water II for stirring until dissolved to obtain a vanadium source solution;

[0010] S3: Add a reducing agent to the vanadium source solution for reduction, then add sodium and phosphorus sources and mix evenly. Carry out the sol-gel reaction at a temperature of 60-90℃, stir and concentrate to 30mL to obtain the precursor solution.

[0011] S4: Add the sodium polyacrylate dispersion obtained in S1 to the precursor solution obtained in S3, and stir to adjust the solution to weak alkalinity to obtain a weak alkaline precursor solution.

[0012] S5: The obtained weakly alkaline precursor solution is placed in a forced-air drying oven for drying to obtain a dried precursor;

[0013] S6: The obtained dry precursor is placed in an inert atmosphere and calcined at high temperature to obtain the target product.

[0014] Furthermore, the molar ratio of the vanadium source to the reducing agent is 2:(2-3).

[0015] Furthermore, in step S1, the soaking time is 30-60 minutes.

[0016] Furthermore, in step S3, the sol-gel reaction time is 1-2 hours.

[0017] Furthermore, in step S5: the drying temperature of the blower drying oven is 80-120℃, and the drying time is 8-12h.

[0018] Furthermore, in step S6: the inert atmosphere is an argon atmosphere.

[0019] Further, in step S6: the high-temperature calcination treatment conditions are as follows: first, the temperature is increased to 350-550℃ at a heating rate of 3-6℃ / min for 3-6 hours, and then increased to 600-850℃ at a heating rate of 3-6℃ / min for 5-8 hours.

[0020] A sodium vanadium phosphate cathode material supported by sodium polyacrylate is prepared by the preparation method described in this invention, and has a wrinkled, tangerine peel-like sodium polyacrylate support structure.

[0021] The present invention relates to the application of a sodium polyacrylate-supported sodium vanadium phosphate cathode material, which is used as a cathode material for sodium-ion batteries.

[0022] This invention provides a sodium polyacrylate-supported sodium vanadium phosphate cathode material, its preparation method, and its application. By adding sodium polyacrylate to the sodium source, vanadium source, phosphorus source, and reducing agent in the preparation of the sodium vanadium phosphate cathode material, a layered supporting structure resembling dried tangerine peel is generated, effectively increasing the specific surface area, reducing the sodium ion diffusion resistance, and inhibiting the undirected growth of particles. Simultaneously, this invention utilizes the reducing agent as a carbon source to coat the sodium vanadium phosphate surface with a carbon layer, forming an effective conductive layer. This accelerates the rapid transport of electrons, improving the electronic and ionic conductivity of the sodium vanadium phosphate cathode material. Therefore, when applied to sodium-ion batteries, this sodium vanadium phosphate cathode material exhibits excellent cycle stability and rate performance, making it a highly promising cathode material for sodium-ion batteries. Furthermore, the preparation of sodium vanadium phosphate solid powder with a wrinkled, layered structure resembling dried tangerine peel via the sol-gel method, followed by an external carbon coating layer, offers advantages such as simple operation, low production cost, and the ability to achieve mass production. Attached Figure Description

[0023] Figure 1 This is an XRD Rietveld refinement result diagram of the sodium vanadium phosphate cathode material obtained in Example 1 of the present invention.

[0024] Figure 2 This is a 200nm scanning electron microscope image of the sodium vanadium phosphate cathode material obtained in Example 1 of this invention.

[0025] Figure 3 This is a 2μm scanning electron microscope image of the sodium vanadium phosphate cathode material obtained in Example 1 of this invention.

[0026] Figure 4 This is a particle size distribution diagram of the sodium vanadium phosphate cathode material obtained in Example 1 of the present invention.

[0027] Figure 5 This is the Raman spectrum of the sodium vanadium phosphate cathode material obtained in Example 1 of this invention.

[0028] Figure 6 This is the EIS equivalent circuit diagram of a sodium metal half-cell assembled from a cathode sheet made of sodium vanadium phosphate cathode material obtained in Embodiments 1, 2, 3, 4 and Comparative Example 1 of the present invention.

[0029] Figure 7 This is a cyclic voltammetry curve of a sodium metal half-cell assembled from a positive electrode made of sodium vanadium phosphate material obtained in Example 1 of this invention.

[0030] Figure 8 This is a graph showing the first constant current charge-discharge curve of a sodium metal half-cell assembled from a cathode material made of sodium vanadium phosphate obtained in Example 3 of the present invention at a current density of 0.5 C. Detailed Implementation

[0031] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0032] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0033] Unless otherwise specified, the production processes, experimental methods, or testing methods involved in the embodiments of this invention are all conventional operating methods in the prior art, and their names and / or abbreviations are all conventional names in the field, which are very clear and distinct in the relevant application areas. Those skilled in the art can understand the conventional process steps based on the names and apply the corresponding equipment, and implement them according to conventional conditions or the conditions recommended by the manufacturer.

[0034] The various instruments, equipment, raw materials or reagents used in the embodiments of this invention are not subject to any special restrictions on their source. They are all conventional products that can be purchased through regular commercial channels and can be prepared according to conventional methods known to those skilled in the art. Example 1

[0035] This embodiment prepares a sodium polyacrylate-supported sodium vanadium phosphate cathode material. The preparation method of this sodium polyacrylate-supported sodium vanadium phosphate cathode material includes the following steps:

[0036] S1: Add 0.5g of sodium polyacrylate to 30mL of deionized water I and soak for 30min to obtain a sodium polyacrylate dispersion;

[0037] S2: Add 0.002 mmol of ammonium metavanadate to 70 mL of deionized water II, stir in an 80°C water bath until fully dissolved, and obtain a stable yellow transparent solution;

[0038] S3: Add 0.002 mmol of citric acid to the yellow transparent solution and stir to fully reduce it to obtain a stable dark blue solution. Then add 0.003 mmol of anhydrous sodium carbonate and 0.003 mmol of ammonium dihydrogen phosphate to the dark blue solution and mix well. Stir continuously for 1 hour in an 80°C water bath until the solution is concentrated to 30 mL to obtain the precursor solution.

[0039] S4: Add the sodium polyacrylate dispersion obtained in S1 to the precursor solution obtained in S3, and stir to adjust the solution to weak alkalinity to obtain a weak alkaline precursor solution.

[0040] S5: The obtained weakly alkaline precursor solution was placed in an 80°C forced-air drying oven and dried for 12 hours to obtain the dried precursor.

[0041] S6: The obtained dried precursor was placed in a ceramic boat and then placed in a tube furnace. Under an argon atmosphere, the temperature was first increased to 350°C at a rate of 5°C / min and calcined for 6 hours, and then increased to 750°C at a rate of 5°C / min and calcined for 7 hours to obtain the target product. Example 2

[0042] This embodiment prepares a sodium polyacrylate-supported sodium vanadium phosphate cathode material. The preparation method of this sodium polyacrylate-supported sodium vanadium phosphate cathode material includes the following steps:

[0043] S1: Add 0.5g of sodium polyacrylate to 40mL of deionized water I and soak for 40min to obtain a sodium polyacrylate dispersion;

[0044] S2: Add 0.002 mmol of ammonium metavanadate to 80 mL of deionized water II, stir in an 85°C water bath until fully dissolved, and obtain a stable yellow transparent solution;

[0045] S3: Add 0.0025 mmol of glucose to the yellow transparent solution and stir to fully reduce it to obtain a stable dark blue solution. Then add 0.003 mmol of anhydrous sodium carbonate and 0.003 mmol of phosphoric acid to the dark blue solution and mix well. Stir continuously for 1.5 h in an 85°C water bath until the solution is concentrated to 30 mL to obtain the precursor solution.

[0046] S4: Add the sodium polyacrylate dispersion obtained in S1 to the precursor solution obtained in S3, and stir to adjust the solution to weak alkalinity to obtain a weak alkaline precursor solution.

[0047] S5: Place the obtained weakly alkaline precursor solution in a 100°C forced-air drying oven and dry for 10 hours to obtain the dried precursor.

[0048] S6: The obtained dried precursor was placed in a ceramic boat and then placed in a tube furnace. Under an argon atmosphere, the temperature was first increased to 400℃ for 5 hours at a heating rate of 4℃ / min, and then increased to 800℃ for 6 hours at a heating rate of 4℃ / min to obtain the target product. Example 3

[0049] This embodiment prepares a sodium polyacrylate-supported sodium vanadium phosphate cathode material. The preparation method of this sodium polyacrylate-supported sodium vanadium phosphate cathode material includes the following steps:

[0050] S1: Add 0.5g of sodium polyacrylate to 50mL of deionized water I and soak for 50min to obtain a sodium polyacrylate dispersion;

[0051] S2: Add 0.002 mmol of ammonium metavanadate to 90 mL of deionized water II, stir in a 90 °C water bath until fully dissolved, and obtain a stable yellow transparent solution;

[0052] S3: Add 0.003 mmol of oxalic acid to the yellow transparent solution and stir to fully reduce it to obtain a stable dark blue solution. Then add 0.003 mmol of sodium hydroxide and 0.003 mmol of phosphoric acid to the dark blue solution and mix well. Stir continuously for 2 hours under 90°C water bath conditions until the solution is concentrated to 30 mL to obtain the precursor solution.

[0053] S4: Add the sodium polyacrylate dispersion obtained in S1 to the precursor solution obtained in S3, and stir to adjust the solution to weak alkalinity to obtain a weak alkaline precursor solution.

[0054] S5: The obtained weakly alkaline precursor solution was placed in a 120°C forced-air drying oven and dried for 8 hours to obtain the dried precursor.

[0055] S6: The obtained dried precursor was placed in a ceramic boat and then placed in a tube furnace. Under an argon atmosphere, the temperature was first increased to 450°C at a rate of 3°C / min and calcined for 4 hours, and then increased to 850°C at a rate of 3°C / min and calcined for 5 hours to obtain the target product. Example 4

[0056] This embodiment prepared a sodium polyacrylate-supported sodium vanadium phosphate cathode material. The preparation method of this sodium polyacrylate-supported sodium vanadium phosphate cathode material differs from that of Example 1 in the following steps: S1: 0.5 g of sodium polyacrylate was added to 25 mL of deionized water I and soaked for 60 min to obtain a sodium polyacrylate dispersion; S2: 0.002 mmol of ammonium metavanadate was added to 60 mL of deionized water II and stirred in an 80°C water bath to fully dissolve it, obtaining a stable yellow transparent solution; S6: The obtained dried precursor was placed in a ceramic boat and placed in a tube furnace. Under an argon atmosphere, the temperature was first increased to 550°C at a rate of 6°C / min for 3 h, and then increased to 600°C at a rate of 6°C / min for 8 h to obtain the target product. The remaining preparation steps are the same as in Example 1. Comparative Example 1

[0057] This comparative example prepared a sodium vanadium phosphate cathode material, and the preparation method of the sodium vanadium phosphate cathode material includes the following steps:

[0058] S1: Prepare 30mL of deionized water I;

[0059] S2: Add 0.002 mmol of ammonium metavanadate to 70 mL of deionized water II, stir in an 80°C water bath until fully dissolved, and obtain a stable yellow transparent solution;

[0060] S3: Add 0.002 mmol of citric acid to the yellow transparent solution and stir to fully reduce it to obtain a stable dark blue solution. Then add 0.003 mmol of anhydrous sodium carbonate and 0.003 mmol of ammonium dihydrogen phosphate to the dark blue solution and mix well. Stir continuously for 1 hour in an 80°C water bath until the solution is concentrated to 30 mL to obtain the precursor solution.

[0061] S4: Add 30 mL of deionized water I prepared in S1 to the precursor solution obtained in S3, stir and adjust the solution to weak alkalinity to obtain a weak alkaline precursor solution.

[0062] S5: The obtained weakly alkaline precursor solution was placed in an 80°C forced-air drying oven and dried for 12 hours to obtain the dried precursor.

[0063] S6: The obtained dried precursor was placed in a ceramic boat and then placed in a tube furnace. Under an argon atmosphere, the temperature was first increased to 350°C at a rate of 5°C / min and calcined for 6 hours, and then increased to 750°C at a rate of 5°C / min and calcined for 7 hours to obtain the target product.

[0064] The sodium vanadium phosphate cathode materials prepared in Example 1 and Comparative Example 1 were applied to the cathodes of sodium-ion batteries, respectively. Their electrochemical performance was tested using a CR2032 button half-cell. The specific steps are as follows:

[0065] First, the electrode was prepared. The sodium vanadium phosphate positive electrode material prepared in Example 1 and Comparative Example 1 was used as the active material, acetylene black as the conductive agent, and polyvinylidene fluoride (PVDF) as the binder. The active material, acetylene black and PVDF were uniformly mixed in N-methyl-2-pyrrolidone (NMP) solvent at a mass ratio of 8:1:1. After magnetic stirring, a positive electrode slurry was obtained. The positive electrode slurry was then uniformly coated on aluminum foil, dried at 40°C for 4 hours, and vacuum dried at 120°C for 6 hours. The foil was then cut into 12 mm diameter discs using a cutting machine and accurately weighed to prepare positive electrode sheets for sodium-ion batteries with different active materials.

[0066] Then, the battery is assembled. The positive electrode is transferred into an argon-protected glove box. The counter electrode, which also serves as the reference electrode, is made of sodium metal. The electrolyte is 1.0 mol / L sodium perchlorate (NaClO4) dissolved in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) (EC:DEC volume ratio = 1:1), with 5% by mass of fluoroethylene carbonate (FEC) added. The separator is made of glass fiber membrane. After assembly, the battery is allowed to stand for 24 hours to allow the electrolyte to fully impregnate it before battery testing.

[0067] Finally, performance tests were conducted, and the results are as follows: At room temperature, the sodium metal half-cell assembled using the sodium vanadium phosphate cathode material supported by sodium polyacrylate prepared in Example 1 exhibited an initial discharge capacity of 101.52 mAh / g at a current density of 0.5 C, with an initial coulombic efficiency of 94.87%. After 100 cycles at a current density of 1 C, the capacity retention was 98.16%, while the rate capacity retention at a current density of 40 C was 66.4%. The sodium metal half-cell assembled using the sodium vanadium phosphate cathode material prepared in Comparative Example 1 exhibited an initial discharge capacity of 84.09 mAh / g at a current density of 0.5 C, with an initial coulombic efficiency of 99.29%. After 100 cycles at a current density of 1 C, the capacity retention was 99.61%, while the rate capacity retention at a current density of 40 C was 58.33%. Test results show that the sodium polyacrylate-supported sodium vanadium phosphate cathode material of the present invention can significantly reduce the sodium ion diffusion distance and increase electronic conductivity and ionic conductivity, which is attributed to its porous, wrinkled, layered tangerine peel structure.

[0068] Appendix Figure 1 The image shows the XRD Rietveld refinement result of the sodium vanadium phosphate cathode material obtained in Example 1 of this invention. As can be seen from the image, the refinement result R... wp The result of the sample refinement is 6.21%, which is less than 10%, indicating that the result is reliable.

[0069] Appendix Figure 2 The image shows a 200 nm scanning electron microscope image of the sodium vanadium phosphate cathode material obtained in Example 1 of this invention. As can be seen from the image, sodium vanadium phosphate (NVP) primary particles with an average particle size of about 200 nm are attached to the sodium polyacrylate (PAAS) layered structure. The PAAS layer is about 30 nm thick. This structure effectively inhibits the agglomeration of NVP particles during high-temperature calcination.

[0070] Appendix Figure 3 The image shows a 2μm scanning electron microscope image of the sodium vanadium phosphate cathode material obtained in Example 1 of this invention. As can be seen from the image, the sodium vanadium phosphate (NVP) particles are anchored on the layered sodium polyacrylate (PAAs) structure, which significantly increases the specific surface area. This structural design promotes electrolyte permeation and accelerates the diffusion of sodium ions.

[0071] Appendix Figure 4 The figure shows the particle size distribution of the sodium vanadium phosphate cathode material obtained in Example 1 of the present invention. As can be seen from the figure, the particle size range of the sodium vanadium phosphate cathode material of the present invention is 150nm-200nm. The particle size is small, easy to diffuse, and there is no large particle agglomeration.

[0072] Appendix Figure 5The image shows the Raman spectrum of the sodium vanadium phosphate cathode material obtained in Example 1 of this invention. As can be seen from the image, there are two peaks located at 1348 cm⁻¹. -1 and 1591 cm -1 They belong to the D band and the G band respectively, I D / I G The value is approximately 0.85, indicating that the carbon component of the sodium vanadium phosphate cathode material of the present invention has a high degree of graphitization.

[0073] Appendix Figure 6 The diagram shows the EIS equivalent circuit of a sodium metal half-cell assembled from the sodium vanadium phosphate cathode material obtained in Examples 1, 2, 3, 4, and Comparative Example 1 of this invention. As shown in the diagram, Rs (solution resistance) is connected in series with CPE1 (capacitor), and then Rct (charge transfer impedance) and Wo (Warburg impedance) are connected in series and then in parallel with it. The impedance spectrum obtained by EIS testing can be used to quantitatively analyze the interfacial properties and reaction kinetics of the cathode in the electrochemical system by fitting these circuit parameters.

[0074] Appendix Figure 7 The figure shows the cyclic voltammetry curves of a sodium metal half-cell assembled from a cathode material made of sodium vanadium phosphate obtained in Example 1 of this invention. As can be seen from the figure, at scan rates from 0.1 mV / s to 1.0 mV / s, a voltammetry curve with V0.0 can be observed. 4+ and V 3+ The half-cell exhibits a pair of redox peaks corresponding to the electrochemical oxidation / reduction processes. The voltage polarization of this half-cell increases significantly with increasing scan rate, with the oxidation peak shifting to higher voltage and the reduction peak shifting to lower voltage, indicating increased electrochemical irreversibility. At a current density of 0.1 mA s⁻¹, the voltage polarization of this half-cell is only 0.21 V.

[0075] Appendix Figure 8 The figure shows the first constant current charge-discharge curve of a sodium metal half-cell assembled with a cathode material made of sodium vanadium phosphate obtained in Example 3 of this invention at a current density of 0.5 C. As can be seen from the figure, a pair of potential plateaus can be clearly observed at 3.4 V, corresponding to the presence of two Na... + V of the extraction / insertion reaction 3+ / V 4+ Redox pairs. During the electrochemical reaction, a series of reversible phase transitions occurred between Na3V2(PO4)3 and NaV2(PO4)3. This half-cell exhibits a long charge-discharge plateau, indicating that it has a high charge-discharge specific capacity.

[0076] In summary, the sodium polyacrylate-supported sodium vanadium phosphate cathode material of the present invention effectively increases the specific surface area and reduces the sodium ion diffusion resistance by using sodium polyacrylate to form a wrinkled, layered structure, thus inhibiting the undirected growth of particles. Simultaneously, the present invention also utilizes a reducing agent as a carbon source to coat the sodium vanadium phosphate surface with a carbon layer, forming an effective conductive layer that accelerates the rapid transport of electrons and ions, thereby improving the electronic and ionic conductivity of the sodium vanadium phosphate cathode material. Furthermore, the preparation method of the sodium polyacrylate-supported sodium vanadium phosphate cathode material of the present invention is simple and has low raw material costs.

[0077] In the specific implementation of the embodiments and comparative examples of the present invention, the sodium source can be one or more inorganic sodium salts capable of providing sodium ions. The present invention does not particularly limit its use, including but not limited to any one or more of sodium dihydrogen phosphate, disodium hydrogen phosphate, anhydrous sodium carbonate, sodium hydroxide, anhydrous sodium sulfate, sodium chloride, sodium acetate, and sodium metavanadate. The vanadium source can be a vanadium source conventionally used in various sodium vanadium phosphate preparation methods in existing research. The present invention does not particularly limit its use, including but not limited to any one of ammonium metavanadate, sodium metavanadate, and vanadium pentoxide. The phosphorus source can be one or more inorganic compounds capable of providing phosphate ions. The present invention also does not particularly limit its use, including but not limited to any one or more of sodium dihydrogen phosphate, ammonium dihydrogen phosphate, phosphoric acid, sodium phosphate, and sodium metaphosphate. The reducing agent is also a reducing agent conventionally used in various sodium vanadium phosphate preparation methods in existing research to reduce high-valent vanadium sources to trivalent vanadium sources. The present invention also does not particularly limit its use, including but not limited to any one of citric acid, glucose, and oxalic acid.

[0078] It should be noted that in this invention, the sodium source and phosphorus source can be the same substance, that is, one substance can be used as both a sodium source and a phosphorus source. For example, sodium dihydrogen phosphate, when the molar ratio is met, i.e., Na:PO4=1:1, only one material needs to be added to meet the requirement. The sodium source and phosphorus source can be the same substance. When using only one substance cannot meet the molar ratio requirement, a single element source substance needs to be added to make up the ratio and meet the basic usage ratio.

[0079] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A method for preparing a sodium polyacrylate-supported sodium vanadium phosphate cathode material, characterized in that: Includes the following steps: S1: Add 0.5g of sodium polyacrylate to 25-50mL of deionized water I and soak for 30-60 minutes to obtain a sodium polyacrylate dispersion; S2: Add the vanadium source to 60-90 mL of deionized water II and stir until dissolved to obtain a vanadium source solution; S3: Add a reducing agent to the vanadium source solution for reduction, wherein the molar ratio of vanadium source to reducing agent is 2:(2-3), then add sodium source and phosphorus source and mix evenly, and carry out sol-gel reaction at a temperature of 60-90℃ for 1-2 h, and stir and concentrate to 30 mL to obtain precursor solution. S4: Add the sodium polyacrylate dispersion obtained in S1 to the precursor solution obtained in S3, and stir to adjust the solution to weak alkalinity to obtain a weak alkaline precursor solution. S5: The obtained weakly alkaline precursor solution is placed in a forced-air drying oven for drying to obtain a dried precursor; S6: The obtained dried precursor is placed in an inert atmosphere and calcined at high temperature. The high-temperature calcination conditions are as follows: first, the temperature is increased to 350-550℃ at a heating rate of 3-6℃ / min for 3-6 hours, and then increased to 600-850℃ at a heating rate of 3-6℃ / min for 5-8 hours to obtain the target product.

2. The method for preparing a sodium polyacrylate-supported sodium vanadium phosphate cathode material according to claim 1, characterized in that: In step S5: the drying temperature of the blower drying oven is 80-120℃, and the drying time is 8-12h.

3. The method for preparing a sodium polyacrylate-supported sodium vanadium phosphate cathode material according to claim 1, characterized in that: In step S6: the inert atmosphere is an argon atmosphere.

4. A sodium polyacrylate-supported sodium vanadium phosphate cathode material, characterized in that, It is prepared by any one of the preparation methods described in claims 1-3, and it has a wrinkled, layered sodium polyacrylate support structure.

5. The application of the sodium polyacrylate-supported sodium vanadium phosphate cathode material according to claim 4, characterized in that: This material is used as the positive electrode material for sodium-ion batteries.

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