Preparation method and application of sodium aluminum vanadium phosphate material

Abstract

The invention relates to the technical field of electrode materials, in particular to a preparation method and application of a sodium aluminum vanadium phosphate material. Comprising the following steps: 1) dissolving an aluminum source and a vanadium source in deionized water to obtain a solution A; 2) dissolving an alkaline substance in deionized water to obtain a solution B, dropwise adding the solution B into the solution A, stirring until the pH value of the mixed solution is 5-9, and centrifugally filtering to obtain a precursor; 3) dissolving fluoride and phosphate in deionized water to obtain a solution C, dispersing the precursor obtained in the step 2) in the solution C, stirring, standing at room temperature for crystallization, and then filtering, washing and drying; and 4) carrying out heat treatment on the product obtained in the step 3) in a nitrogen atmosphere to obtain the sodium aluminum vanadium phosphate material. According to the invention, cost reduction and efficiency increase of the sodium aluminum vanadium phosphate material are realized, the vanadium utilization rate can be effectively improved, the electronic structure of the sodium aluminum vanadium phosphate is changed, and the electrochemical performance of the sodium aluminum vanadium phosphate material is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrode materials, and in particular, to a preparation method and application of a sodium aluminum vanadium phosphate material. Background Art

[0002] As a sodium superionic conductor (NASICON) material, sodium vanadium phosphate has a special sodium ion channel structure, showing excellent sodium ion migration efficiency and high theoretical discharge capacity. However, its poor electronic conductivity makes its actual specific capacity often lower than the theoretical specific capacity. At the same time, the relatively high price of vanadium also increases the preparation cost of sodium vanadium phosphate, greatly limiting the practical application prospects of sodium vanadium phosphate.

[0003] To solve the bottleneck in the application and popularization of sodium vanadium phosphate, the members of this project team proposed a method for the nanometer preparation of sodium vanadium phosphate-based materials by ion exchange and nucleation crystallization isolation in Chinese invention patents with application numbers 202210162593.6 and 202210249477.8. By reducing the microscopic particle size and shortening the electron transport within sodium vanadium phosphate particles, the electron / ion conduction rate is improved, and good electrochemical performance is achieved.

[0004] In addition, in terms of cost control, the goal of cost reduction and efficiency improvement of sodium vanadium phosphate-based materials is expected to be achieved through a metal ion doping strategy. Teng et al. replaced part of the V element with inexpensive Fe element to reduce the proportion of V element and improve the electron-ion transport efficiency of sodium vanadium phosphate (Iron Steel Vanadium Titanium, 2024, 45, 7-12). However, transition metals such as Fe have an obvious John-teller effect and will participate in the electrochemical reaction itself, affecting the cycle life of the material.

[0005] Based on this, it is necessary to propose a new solution that can take into account multiple factors such as particle size, cost, and electrochemical performance, and effectively promote the application process of sodium vanadium phosphate-based materials. Summary of the Invention

[0006] The purpose of the present invention is to provide a preparation method and application of a sodium aluminum vanadium phosphate material. By introducing Al element, the efficient preparation of sodium aluminum vanadium phosphate material is realized. The microscopic morphology of the sodium aluminum vanadium phosphate material is nanoparticle-like, and the nanoparticle size distribution of the particles is concentrated, about 50 nm, with a relatively high specific surface area. This material has good electrochemical performance and can be used as an electrode material for secondary batteries of alkali metals such as lithium, sodium, and potassium.

[0007] To achieve the above purpose, the technical solution of the present invention is as follows:

[0008] On the one hand, the present invention provides a preparation method of a sodium aluminum vanadium phosphate material, and the method includes the following steps:

[0009] 1) Dissolve an aluminum source and a vanadium source in deionized water to obtain solution A;

[0010] 2) Dissolve an alkaline substance in deionized water to obtain solution B, add solution B dropwise to solution A, stir until the pH of the mixed solution is 5 - 9, centrifuge and filter to obtain a precursor;

[0011] 3) Dissolve a fluoride and a phosphate in deionized water to obtain solution C, disperse the precursor obtained in step 2) in solution C, stir, stand for crystallization at room temperature, then filter, wash, and dry;

[0012] 4) Heat - treat the product obtained in step 3) under a nitrogen atmosphere to obtain the sodium aluminum vanadium phosphate material.

[0013] In the above - mentioned technical solution, further, in step (1), the vanadium source is one or more of inorganic metal salts of tetravalent vanadium and organometallic salts of tetravalent vanadium, preferably one or two of vanadyl sulfate and oxalovanadyl; the aluminum source is one or two of aluminum sulfate and aluminum chloride; the molar ratio of vanadium element to aluminum element is 1:1 - 20:1.

[0014] In the above - mentioned technical solution, further, in step (1), in solution A, the concentration of the vanadium source is 0.1 - 5.0 mol / L.

[0015] In the above - mentioned technical solution, further, in step (2), the alkaline substance is one or more of sodium hydroxide, potassium hydroxide, and ammonia water.

[0016] In the above - mentioned technical solution, further, in step (2), the concentration of solution B is 0.5 - 5.0 mol / L.

[0017] In the above - mentioned technical solution, further, in step (3), the fluoride is sodium fluoride; the phosphate is one or more of sodium dihydrogen phosphate, disodium hydrogen phosphate, and sodium phosphate.

[0018] In the above - mentioned technical solution, further, in step (3), in solution C, the molar concentration ratio of the fluoride to the phosphate is 1:2 - 1:10; the ratio of the total molar amount of the vanadium source and the aluminum source to the molar amount of the phosphate is 1:1 - 1:3.

[0019] In the above - mentioned technical solution, further, in step (3), the stirring time is 1 - 3 h, preferably 2 h; the temperature for standing crystallization is 20 - 40 °C, the time is 12 - 48 h, preferably 24 h; the washing is first with an aqueous solution of sodium hydroxide, potassium hydroxide, or ammonia water with pH = 12 - 13, and then with deionized water until neutral; the drying is vacuum drying at a temperature of 80 - 120 °C.

[0020] In the above technical solution, further, in the step (4), the heat treatment temperature is 200-400 °C, and the heat treatment time is 1-3 h.

[0021] The beneficial effects of the present invention are as follows:

[0022] 1. By means of Al doping, anion exchange and other methods, the present invention prepares a sodium aluminum vanadium phosphate material with uniform particle size and an average particle size of about 50 nm.

[0023] 2. The present invention realizes the efficient and low-cost preparation of the sodium aluminum vanadium phosphate material by introducing green, inexpensive and electrochemically inert Al element, realizes the cost reduction and efficiency increase of the sodium aluminum vanadium phosphate material, and at the same time can effectively improve the utilization rate of vanadium, change the electronic structure of the sodium aluminum vanadium phosphate, and enhance the electrochemical performance of the sodium aluminum vanadium phosphate material. Specifically, by using inexpensive aluminum element to partially replace expensive vanadium element, the preparation cost is reduced; based on the chemical inertness of aluminum ions, they do not participate in the redox reaction process of sodium deintercalation and insertion, which helps to realize the transformation of some tetravalent vanadium ions to higher valence states, and maximally maintains the stability of the crystal structure of sodium vanadium phosphate, thus enhancing the electrochemical cycle life of the sodium aluminum vanadium phosphate material; by utilizing the 3+ co-precipitation effect of Al - and OH, the rapid nucleation and static crystallization growth of sodium vanadium phosphate-based materials are controlled, the nano-preparation of sodium aluminum vanadium phosphate is realized, and at the same time, the efficient utilization of vanadium ions can be maximally achieved, so that the utilization rate of vanadium reaches more than 99%.

[0024] 3. The preparation method of the present invention has the advantages of simple operation, convenience, high efficiency, easy scale-up production, etc. Due to the structural and performance advantages of the products prepared by this method, it is expected to improve the limitations of sodium vanadium phosphate-based materials in the application in the energy storage field, and has a certain application prospect in the electrode materials of alkali metal secondary batteries such as lithium, sodium and potassium.

[0025] In summary, the preparation method of the present invention can not only effectively control the vanadium proportion in sodium aluminum vanadium phosphate, realize the regulation of the preparation cost of sodium vanadium phosphate-based materials, but also effectively improve the vanadium utilization rate, change the electronic structure of sodium aluminum vanadium phosphate, and enhance the electrochemical performance of sodium aluminum vanadium phosphate materials. Description of the Drawings

[0026] Figure 1 XRD pattern of the sodium aluminum vanadium phosphate material prepared in Example 1;

[0027] Figure 2 SEM image of the sodium aluminum vanadium phosphate material prepared in Example 1;

[0028] Figure 3 EDS of the sodium aluminum vanadium phosphate material prepared in Example 2;

[0029] Figure 4 Particle size distribution test of the sodium aluminum vanadium phosphate material prepared in Example 2. Specific implementation mode

[0030] The following is a further explanatory description of the present invention in combination with specific embodiments. The protection scope of the present invention should include all the contents of the claims and specific embodiments, but the present invention is not limited thereto.

[0031] Unless otherwise specified, the materials used in the embodiments of the present invention can be obtained through commercial channels or prepared by conventional methods well known to those skilled in the art.

[0032] Example 1

[0033] 1) Weigh 1.6 g of VOSO4 and 0.34 g of Al2(SO4)3, dissolve them in 50 mL of deionized water to obtain solution A;

[0034] 2) Weigh 2.8 g of sodium hydroxide, dissolve it in 50 mL of deionized water to obtain solution B, drop solution B into solution A at a rate of one drop per second, continuously stir until the solution pH = 6, centrifuge and filter to obtain a precursor;

[0035] 3) Weigh 1.2 g of sodium fluoride and 9.0 g of sodium dihydrogen phosphate, dissolve them in 50 ml of deionized water to obtain solution C, disperse the precursor obtained in step 2) in solution C, stir for 2 h, then stand and crystallize at 24 °C for 24 h, filter, then wash once with a sodium hydroxide solution with pH = 12 - 13, and then wash 3 times with deionized water until neutral, and dry in vacuum at 100 °C.

[0036] 4) Heat-treat the product obtained in step 3) at 350 °C for 2 h in a nitrogen atmosphere, with a heating rate of 5 °C / min to obtain the sodium aluminum vanadium phosphate material.

[0037] Example 2

[0038] 1) Weigh 1.6 g of VOSO4 and 0.13 g of AlCl3, dissolve them in 50 mL of deionized water to obtain solution A;

[0039] 2) Weigh 2.4 g of sodium hydroxide, dissolve it in 50 mL of deionized water to obtain solution B, drop solution B into solution A at a rate of one drop per second, continuously stir until the solution pH = 6, centrifuge and filter to obtain a precursor;

[0040] 3) Weigh 1.2 g of sodium fluoride and 10.6 g of disodium hydrogen phosphate, dissolve them in 50 ml of deionized water to obtain solution C. Disperse the precursor obtained in step 2) in solution C, stir for 2 h, then statically crystallize at 24 °C for 24 h, filter, then wash once with an ammonia water solution with pH = 12 - 13, and then wash three times with deionized water until neutral, and then dry in vacuum at 100 °C;

[0041] 4) Heat-treat the product obtained in step 3) at 200 °C for 1 h in a nitrogen atmosphere with a heating rate of 5 °C / min to obtain the sodium aluminum vanadium phosphate material.

[0042] Example 3

[0043] 1) Weigh 2.45 g of VOC2O4·5H2O and 3.42 g of Al2(SO4)3, dissolve them in 50 mL of deionized water to obtain solution A;

[0044] 2) Weigh 50 mL of 2 mol / L ammonia water as solution B, and dropwise add solution B to solution A at a rate of one drop per second, continuously stir until the solution pH = 6, centrifuge and filter to obtain the precursor;

[0045] 3) Weigh 1.2 g of sodium fluoride and 10.0 g of sodium phosphate, dissolve them in 50 ml of deionized water to obtain solution C. Disperse the precursor obtained in step 2) in solution C, stir for 2 h, then statically crystallize at 24 °C for 24 h, filter, then wash once with a sodium hydroxide solution with pH = 12 - 13, and then wash three times with deionized water until neutral, and then dry in vacuum at 100 °C;

[0046] 4) Heat-treat the product obtained in step 3) at 400 °C for 3 h in a nitrogen atmosphere with a heating rate of 5 °C / min to obtain the sodium aluminum vanadium phosphate material.

[0047] Comparative Example 1

[0048] 1) Weigh 1.6 g of VOSO4 and dissolve it in 50 mL of deionized water to obtain solution A;

[0049] 2) Weigh 2.4 g of sodium hydroxide, dissolve it in 50 mL of deionized water to obtain solution B, and dropwise add solution B to solution A at a rate of one drop per second, continuously stir until the solution pH = 6, centrifuge and filter to obtain the precursor;

[0050] 3) Weigh 1.2 g of sodium fluoride and 10.6 g of disodium hydrogen phosphate, dissolve them in 50 ml of deionized water to obtain solution C. Disperse the precursor obtained in step 2) in solution C, stir for 2 h, then crystallize at 24 °C for 24 h, filter, then wash once with an ammonia water solution with pH = 12 - 13, and then wash three times with deionized water until neutral, and then dry in vacuum at 100 °C;

[0051] 4) Heat-treat the product obtained in step 3) at 200 °C for 1 h under a nitrogen atmosphere with a heating rate of 5 °C / min to obtain a sodium vanadium phosphate material.

[0052] Figure 1 XRD pattern of the sodium aluminum vanadium phosphate prepared in Example 1, from Figure 1 It can be seen that the XRD curve of the sodium aluminum vanadium phosphate material prepared in Example 1 has a relatively high intensity and no impurity peaks appear, indicating that the obtained sample product has good purity and crystallinity.

[0053] Figure 2 SEM image of the sodium aluminum vanadium phosphate material prepared in Example 1, from Figure 2 It can be seen that the microscopic morphology of the prepared sodium aluminum vanadium phosphate is in the form of nanoparticles, and the particle size distribution of the nanoparticles is relatively concentrated, about 50 nm.

[0054] Figure 3 EDS of the sodium aluminum vanadium phosphate material prepared in Example 2, from Figure 3 It can be seen that in the sodium vanadium phosphate material prepared in Example 2, the proportion of aluminum and vanadium elements is close to 1:20, which is consistent with the molar ratio of the reaction raw material dosage.

[0055] Figure 4 Particle size distribution test of the sodium aluminum vanadium phosphate material prepared in Example 2, from Figure 4 It can be seen that the average particle size distribution of the prepared sodium aluminum vanadium phosphate is relatively concentrated, mainly distributed around 20 - 50 nm.

[0056] Table 1 shows the specific surface area comparison between the sodium aluminum vanadium phosphate material prepared in Example 2 and the sodium vanadium phosphate material prepared in Comparative Example 1.

[0057] Table 1

[0058] Group Specific surface area Example 2 <![CDATA[46.5m 2 / g]]> Comparative Example 1 <![CDATA[16.3m 2 / g]]>

[0059] From Table 1, it can be obtained that the specific surface area of the sodium aluminum vanadium phosphate material prepared in Example 2 is 46.5 m 2 / g. In contrast, the specific surface area of the sodium vanadium phosphate material prepared in Comparative Example 1 is only 16.3 m 2 / g.

[0060] Application Example 1

[0061] The sodium vanadium aluminum phosphate and sodium vanadium phosphate materials prepared in Example 2 and Comparative Example 1 were used as the sodium-ion battery cathode active materials, respectively, and were ground with a conductive agent and a binder in a ratio of 7:2:1. The conductive agent was Super-Li, and the binder was sodium alginate. Deionized water was used as the solvent. The ground coating was coated on carbon black-coated aluminum foil, and then transferred to a vacuum drying oven to be dried at 110 °C for 12 h, and then cut into circular pieces with a diameter of 12 mm to obtain the positive electrode sheets. CR2032 button cells were used, with sodium sheets as the negative electrode material, 1 m NaClO4 in EC:PC = 1:1 (2% FEC) as the electrolyte, and Whatman as the separator. The button cells were assembled in a glove box with water and oxygen content below 0.1 ppm. After the assembled button cells were left standing for 12 hours, a constant current charge-discharge test was carried out using a BlueTEC battery test system, and the charge-discharge voltage range was 2.5 - 4.2 V.

[0062] Table 2 shows the comparison of the specific capacity and cycle life between the sodium vanadium aluminum phosphate prepared in Example 2 and the sodium vanadium phosphate prepared in Comparative Example 1.

[0063] Table 2

[0064] Group Current density Cycle life % @ 1000 Example 2 104 mAh / g 94％ Comparative Example 1 98 mAh / g 86％

[0065] As can be seen from Table 2, under the charge-discharge current density condition of 0.1C, the specific capacity of the sodium vanadium aluminum phosphate prepared in Example 2 was 104 mAh / g. In contrast, the specific capacity of the sodium vanadium phosphate material prepared in Comparative Example 1 was only 98 mAh / g. In addition, after 1000 cycles, the capacity retention rate of the sodium vanadium aluminum phosphate material was 94%, which was better than 86% of the sodium vanadium phosphate in Comparative Example 1, indicating that the prepared sodium vanadium aluminum phosphate material had better electrochemical performance and could be applied to the electrode materials of sodium-ion secondary batteries.

[0066] It should be understood that the application of the present invention is not limited to the above examples. For those of ordinary skill in the art, improvements or transformations can be made according to the above description, and all such improvements and changes should fall within the protection scope of the appended claims of the present invention.

Claims

1. A preparation method of sodium aluminum vanadium phosphate material, characterized in that, The method includes the following steps: 1) Dissolve an aluminum source and a vanadium source in deionized water to obtain solution A; 2) Dissolve an alkaline substance in deionized water to obtain solution B, add solution B dropwise to solution A, stir until the pH of the mixed solution is 5-9, centrifuge and filter to obtain a precursor; 3) Dissolve a fluoride and a phosphate in deionized water to obtain solution C, disperse the precursor obtained in step 2) in solution C, stir, stand for crystallization at room temperature, then filter, wash, and dry; 4) Heat-treat the product obtained in step 3) under a nitrogen atmosphere to obtain the sodium aluminum vanadium phosphate material.

2. The preparation method according to claim 1, characterized in that, In step 1), the vanadium source is one or more of inorganic metal salts of tetravalent vanadium and organometallic salts of tetravalent vanadium; The aluminum source is one or both of aluminum sulfate and aluminum chloride; The molar ratio of vanadium element to aluminum element is 1:1 to 20:

1.

3. The preparation method according to claim 1, characterized in that, In step 1), in solution A, the concentration of the vanadium source is 0.1-5.0 mol / L.

4. The preparation method according to claim 1, wherein, In step 2), the alkaline substance is one or more of sodium hydroxide, potassium hydroxide, and ammonia water; 5. The preparation method according to claim 1, wherein In step 2), the concentration of solution B is 0.5-5.0 mol / L.

6. The preparation method according to claim 1, characterized in that, In step 3), the fluoride is sodium fluoride; The phosphate is one or more of sodium dihydrogen phosphate, disodium hydrogen phosphate, and sodium phosphate; 7. The preparation method according to claim 1, wherein In step 3), in solution C, the molar concentration ratio of the fluoride to the phosphate is 1:2 to 1:10; The ratio of the total molar amount of the vanadium source and the aluminum source to the molar amount of the phosphate is 1:1 to 1:

3.

8. The preparation method according to claim 1, characterized in that, In step 3), the stirring time is 1-3 h; The standing crystallization time is 12-48 h; Washing is first performed with an aqueous solution of sodium hydroxide, potassium hydroxide, or ammonia water with a pH of 12-13, and then washed with deionized water until neutral; Drying is vacuum drying at a temperature of 80-120 °C.

9. The preparation method according to claim 1, wherein In step 4), the heat treatment temperature is 200-400 °C, and the heat treatment time is 1-3 h.

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