A method for preparing and applying a spindle-shaped Prussian white material

Abstract

This invention discloses a method for preparing and applying a spindle-shaped Prussian white material. The method includes the following steps: dissolving anhydrous ferric chloride, terephthalic acid, and polyvinylpyrrolidone in N,N-dimethylformamide to obtain the precursor MIL-88B(Fe); reacting the obtained MIL-88B(Fe) with potassium ferrocyanide to obtain a spindle-shaped Prussian blue material; and dispersing the obtained spindle-shaped Prussian blue material in a methanol solvent containing KI for a solvothermal reaction to reduce the iron in the raw materials and insert more potassium ions into the structure to obtain the spindle-shaped Prussian white material. Compared with existing technologies, this invention is simple, uses environmentally friendly raw materials, is suitable for mass production, and the obtained material has excellent electrochemical performance, making it a promising cathode material for potassium-ion batteries.

Description

Technical Field

[0001] This invention belongs to the technical field of electrode materials, specifically relating to the preparation method and application of spindle-shaped Prussian white material. Background Technology

[0002] Despite the advantages of lithium-ion batteries, such as high energy density, long cycle life, and high operating voltage, the relative scarcity and high price of lithium resources significantly limit their application in large-scale energy storage systems. In recent years, potassium-ion batteries have attracted considerable attention from researchers due to their similar electrochemical mechanisms to lithium-ion batteries. Potassium is more abundant in nature and cheaper than lithium. Furthermore, potassium has a lower redox potential (K / K). + :–2.93 V) with lithium (Li / Li + The energy density (V) is very similar to that of sodium-ion batteries (–3.04 V). Furthermore, compared to sodium-ion batteries, which cannot use commercially available graphite as the anode, potassium-ion batteries exhibit superior capacity when using graphite anodes, giving them a significant advantage for commercialization. Solvated potassium ions have a smaller radius, potentially leading to higher energy density and rate performance in potassium-ion batteries. However, the relatively large ionic radius of potassium ions (1.38 Å) makes it difficult to achieve good performance with many electrode materials used in lithium-ion batteries. Therefore, developing novel electrode materials for potassium-ion batteries is crucial.

[0003] Prussian blue and its analogues are considered excellent cathode materials for potassium-ion batteries due to their three-dimensional open-frame structure, which facilitates the insertion and extraction of larger potassium ions. Among them, Prussian white has attracted widespread attention because its high potassium content allows it to exhibit high capacity during the first discharge. Its relatively low manufacturing cost and high operating voltage are also significant advantages.

[0004] However, traditional Prussian white is synthesized using ferrous salts and potassium ferrocyanide as raw materials via a co-precipitation method. However, ferrous iron is easily oxidized during synthesis, leading to a decrease in potassium content and the introduction of defects. Therefore, providing an inert atmosphere is essential for synthesizing high-potassium Prussian white. However, considering the synthesis cost, this method is not suitable for large-scale synthetic applications. Summary of the Invention

[0005] To address the aforementioned problems, this invention discloses a novel preparation method and application of a spindle-shaped Prussian white material with high specific capacity, excellent cycle performance, and superior rate performance.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] This invention discloses a method for preparing spindle-shaped Prussian blue material. The synthesis process employs a simple template method, where an inorganic iron salt reacts with terephthalic acid to obtain MIL-88B(Fe) with a spindle-shaped morphology. Subsequently, MIL-88B(Fe) undergoes an ion exchange reaction with potassium ferrocyanide trihydrate to yield potassium-deficient Prussian blue material. In the subsequent solvothermal reaction, potassium iodide in the solvent acts as a reducing agent to reduce ferric iron, while also providing more potassium ions to the structure. This method is simple in its synthesis process and provides a new approach for synthesizing potassium-rich Prussian blue materials.

[0008] Specifically, the following steps are included:

[0009] (1) Ferric chloride, terephthalic acid and polyvinylpyrrolidone were dissolved in N,N-dimethylformamide and stirred at 145°C for 1.5 h. After centrifugation and washing, the precursor MIL-88B(Fe) was obtained.

[0010] (2) Disperse the MIL-88B(Fe) obtained in step (1) in ethanol to obtain solution A;

[0011] (3) Dissolve potassium ferrocyanide trihydrate in deionized water to obtain solution B;

[0012] (4) Add solution B dropwise into solution A and stir. The resulting precipitate is centrifuged and washed to obtain spindle-shaped Prussian blue.

[0013] (5) Disperse the spindle-shaped Prussian blue obtained in step (4) in a methanol solution containing potassium iodide and carry out a solvothermal reaction. Centrifuge and wash the precipitate to obtain spindle-shaped Prussian white material.

[0014] Further, in step (1), the mass ratio of ferric chloride, terephthalic acid, and polyvinylpyrrolidone is 2.8~3.2:2:1, and the mass-volume ratio of ferric chloride to N,N-dimethylformamide is 24.5~25.5:1.

[0015] Furthermore, in step (2), the mass-to-volume ratio of MIL-88B(Fe) to ethanol is 0.6~1:1.

[0016] Furthermore, in step (3), the mass-to-volume ratio of potassium ferrocyanide trihydrate to deionized water is 20~30:0.8~1.

[0017] Furthermore, in step (4), the volume ratio of ethanol in solution A to deionized water in solution B is 1:0.8~1.2.

[0018] Furthermore, in step (4), the dropping rate of solution B is 0.8~1.2 mL / min. −1The stirring time is 5 to 7 hours.

[0019] Furthermore, in step (5), the concentration of the methanol solution containing potassium iodide is 0.016~0.024 mol / L. −1 .

[0020] Furthermore, in step (5), the mass-to-volume ratio of spindle-shaped Prussian blue to methanol solution containing potassium iodide is 0.92 to 1.08:1.

[0021] Furthermore, in step (5), the temperature of the solvothermal reaction is 90~110℃, and the time of the solvothermal reaction is 10~14h.

[0022] The method of this invention can produce Prussian white material with a spindle-shaped porous structure. This material has a larger specific surface area, providing more active sites in electrochemical reactions, greatly promoting the utilization of the material's potassium storage capacity, and improving the cycling stability and rate performance of the Prussian white material. Furthermore, the Prussian white material synthesized by this reduction method has less lattice water and defect content, significantly improving its electrochemical performance.

[0023] Therefore, the present invention also provides an application of the spindle-shaped Prussian white material prepared by the preparation method described above in the cathode material of potassium-ion batteries.

[0024] The beneficial effects of this invention are as follows:

[0025] Compared with existing technologies, this invention achieves the following significant advantages: the Prussian white material prepared by the method of this invention exhibits excellent electrochemical performance, making it suitable as a positive electrode material for potassium-ion batteries at 20 mA g / L. −1 At a current density, it provides 124.2 mAh g⁻¹. −1 Reversible capacity. At 500 mA g −1 It can still provide 82.7 mAh g even under high current. −1 Reversible capacity, at 200 mA g −1 It exhibits good cycle stability after 500 cycles at a current density, with a capacity retention of 89.2%. Therefore, this high-potassium-content spindle-shaped Prussian white material has great application potential as a high-performance, low-cost cathode material.

[0026] This invention utilizes low-cost metal salts as raw materials in its synthesis process, employing a potassium iodide-assisted solvothermal reduction method to obtain spindle-shaped Prussian white material. This method offers a simple synthesis process, significantly reducing experimental costs while maintaining superior performance compared to traditional Prussian white material synthesis methods. Experiments have demonstrated that spindle-shaped Prussian white exhibits excellent potassium storage performance and can be used as a high-performance potassium-ion battery cathode material in large-scale energy storage systems. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the synthesis of spindle-shaped Prussian white in Example 1 of the present invention;

[0028] Figure 2 XRD patterns of spindle-shaped Prussian white and its precursor spindle-shaped Prussian blue in Embodiment 1 of the present invention.

[0029] Figure 3 The FTIR spectra of spindle-shaped Prussian white and its precursor MIL-88B(Fe) in Example 1 of this invention are shown.

[0030] Figure 4 The XPS spectra of spindle-shaped Prussian white, precursor spindle-shaped Prussian blue, and irregularly shaped Prussian white of Comparative Example 1 are shown in Example 1 of the present invention, where (a) is the XPS spectrum of the corresponding Fe and (b) is the corresponding full spectrum.

[0031] Figure 5 The images shown are SEM and TEM images of spindle-shaped Prussian white in Embodiment 1 of the present invention. (a) is the SEM image of spindle-shaped Prussian white, and (b) and (c) are the TEM images of spindle-shaped Prussian white.

[0032] Figure 6 The N2 adsorption / desorption isotherms and corresponding pore size distribution diagrams are shown for spindle-shaped Prussian white in Example 1 and irregularly shaped Prussian white in Comparative Example 1. (a) is the N2 adsorption / desorption isotherm, and (b) is the corresponding pore size distribution diagram.

[0033] Figure 7 This is a cyclic voltammetry curve of the spindle-shaped Prussian white electrode of Embodiment 1 of the present invention;

[0034] Figure 8 This is a charge / discharge curve of the spindle-shaped Prussian white electrode of Embodiment 1 of the present invention;

[0035] Figure 9 The rate performance diagrams of the spindle-shaped Prussian white electrode of Embodiment 1 and the irregularly shaped Prussian white electrode of Comparative Example 1 at different current densities are shown.

[0036] Figure 10 This is a charge / discharge curve of the spindle-shaped Prussian white electrode of Embodiment 1 of the present invention under different current densities;

[0037] Figure 11 The cycling performance diagrams are of the spindle-shaped Prussian white electrode of Embodiment 1 and the irregularly shaped Prussian white electrode of Comparative Example 1.

[0038] Figure 12The image shows the XRD pattern of Prussian white with an irregular morphology, as shown in Comparative Example 1 of this invention. Detailed Implementation

[0039] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Example 1

[0040] Preparation of spindle-shaped Prussian white material:

[0041] (1) Dissolve 300 mg ferric chloride, 200 mg terephthalic acid and 100 mg polyvinylpyrrolidone in 12 mL N,N-dimethylformamide and stir and reflux at 145 °C for 1.5 h. Centrifuge and wash to obtain the precursor MIL-88B(Fe).

[0042] (2) Disperse the 40 mg MIL-88B(Fe) obtained in step (1) in 50 mL of ethanol to obtain solution A;

[0043] (3) Dissolve 1.35g of potassium ferrocyanide in 50mL of deionized water to obtain solution B;

[0044] (4) Stirring solution B at 1 mL / min −1 The solution was added dropwise to solution A at a rate of 1, stirred for 6 hours, and allowed to stand at room temperature for 8 hours. The resulting precipitate was centrifuged and washed to obtain spindle-like Prussian blue (PB).

[0045] (5) Take 50 mg of the spindle-shaped Prussian blue obtained in step (4) and disperse it in a solution containing 50 mL of potassium iodide with a concentration of 0.02 mol / L. −1 The mixture was placed in a methanol solution and then transferred to a stainless steel autoclave lined with polytetrafluoroethylene. The reaction was carried out at 100°C for 12 hours. The resulting precipitate was centrifuged and washed to obtain spindle-like Prussian white material.

[0046] Characterization of spindle-shaped Prussian white material:

[0047] Figure 1 This is a schematic diagram of the synthesis of spindle-shaped Prussian white. Figure 2 The XRD patterns of the spindle-shaped Prussian white synthesized by this method and its precursor, spindle-shaped Prussian blue, show that both materials exhibit a monoclinic crystal structure. However, the peak positions in the XRD pattern of spindle-shaped Prussian white are shifted at higher angles compared to those in the XRD pattern of spindle-shaped Prussian blue. This suggests that potassium incorporation results in smaller lattice parameters. Figure 3In the infrared spectrum, it can be seen that the peaks caused by the vibrations of carboxyl groups, carbon-nitrogen bonds, and carbon-hydrogen bonds in the precursor MIL-88B(Fe) are not found in the infrared spectrum of the synthesized spindle-shaped Prussian white material. Instead, the characteristic peaks of the Prussian white material are present. It can be concluded that the precursor MIL-88(B) was completely converted into Prussian white during the synthesis process. Figure 4 This is the XPS spectrum of the spindle-shaped Prussian white material. As can be seen from the image, the iron in the synthesized spindle-shaped Prussian white mainly exists in the +2 form.

[0048] The size, morphology and microstructure of the obtained spindle-shaped Prussian white were analyzed using SEM and TEM images. Figure 5 In the image 'a', we see a SEM image of spindle-shaped Prussian white nanoparticles. The nanoparticles are 170 nm wide and approximately 240 nm long, and their surface is composed of a large number of tiny nanoparticles. Figure 5 Images b and c in the image are TEM images of spindle-shaped Prussian white, showing that the spindle-shaped Prussian white is composed of a large number of extremely small nanoparticles stacked together to form a hierarchical porous structure. Figure 6 The nitrogen adsorption / desorption analysis, including its specific surface area and pore size distribution, further confirms this viewpoint.

[0049] Electrochemical performance testing:

[0050] Using NMP as a solvent, the spindle-shaped Prussian white prepared in Example 1 was ground and mixed with carbon black and polyvinylidene fluoride at a mass ratio of 70:20:10 until homogeneous. The resulting homogeneous slurry was coated onto Al foil and vacuum dried at 120 °C for 12 h. Using 5 mol L... −1 A potassium bis(fluorosulfonyl)imide solution in diethylene glycol dimethyl ether was used as the electrolyte for the potassium-ion battery. Glass fiber and metallic potassium were used as the separator and counter electrode, respectively. Electrochemical performance was tested using CR2032 batteries. Battery assembly was conducted in a glove box filled with argon atmosphere, with water and oxygen concentrations both less than 0.1 ppm. Constant current charge-discharge tests were performed at room temperature using a Blue Electric CT2001A multichannel battery testing system at 2.0–4.5 V (vs. K). + Cyclic voltammetry (CV) was performed within a fixed voltage range ( / K). CV was measured using a PARSTAT 4000 electrochemical workstation at 0.1 mV / s. −1 The scan was performed at a specific speed. For detailed performance specifications, please refer to [link / reference]. Figures 7 to 11 .

[0051] Figure 7 For spindle-shaped Prussian white at 2.0–4.5 V (vs. K) + / K) voltage range, scan rate of 0.1mVs −1The first five cycles of cyclic voltammetry curves show two sets of symmetrical peaks, corresponding to the redox behavior of high-spin iron coordinated with N and low-spin iron coordinated with C, respectively. The curves of the first five cycles are basically overlapping, indicating the good reversibility of the material. Figure 8 For spindle-shaped Prussian white at 2.0–4.5 V (vs. K) + Charge / discharge curves over a voltage range of / K, with a current density of 20 mAg. −1 The reversible specific capacity reaches 124.2 mAh g. −1 ; Figure 9 The graphs show the rate performance of spindle-shaped Prussian white and the irregularly shaped Prussian white material of Comparative Example 1 at different current densities, even at 500 mAg. −1 Even at high current densities, the capacity of the spindle-shaped Prussian white protein can still reach 82.7 mAh g. −1 In contrast, Comparative Example 1, at the same current density, had a capacity of only 43.9 mAh g⁻¹. −1 . Figure 10 The charge-discharge curves of spindle-shaped Prussian white at different current densities; Figure 11 The spindle-shaped Prussian white and the irregularly shaped Prussian white at 200 mAg −1 The graph shows the cycling performance at current density. It indicates that after 500 cycles, the capacity retention of the spindle-shaped Prussian white is 89.2%, while the capacity of the irregularly shaped Prussian white decreases rapidly during cycling. Example 2

[0052] (1) Dissolve 300 mg ferric chloride, 200 mg terephthalic acid and 100 mg polyvinylpyrrolidone in 12 mL N,N-dimethylformamide and stir and reflux at 145 °C for 1.5 h. Centrifuge and wash to obtain the precursor MIL-88B(Fe);

[0053] (2) Disperse the 30 mg MIL-88B(Fe) obtained in step (1) in 50 mL of ethanol to obtain solution A;

[0054] (3) Dissolve 1.35g of potassium ferrocyanide trihydrate in 50mL of deionized water to obtain solution B;

[0055] (4) Stirring solution B at 1 mL / min −1 The solution was added dropwise to solution A at a rate of 1, stirred for 6 hours, and allowed to stand at room temperature for 8 hours. The resulting precipitate was then centrifuged and washed to obtain spindle-shaped Prussian blue.

[0056] (5) Take 50 mg of the spindle-shaped Prussian blue obtained in step (4) and disperse it in 50 mL of potassium iodide with a concentration of 0.02 mol / L. −1The mixture was placed in a methanol solution and then transferred to a polytetrafluoroethylene-lined stainless steel autoclave. The reaction was carried out at 100°C for 12 hours. The resulting precipitate was centrifuged and washed to obtain spindle-shaped Prussian white material.

[0057] The obtained spindle-shaped Prussian white material was characterized and its electrochemical performance was tested using the same method as in Example 1. The results were basically the same as in Example 1, and are shown in Table 1. Example 3

[0058] (1) Dissolve 300 mg ferric chloride, 200 mg terephthalic acid and 100 mg polyvinylpyrrolidone in 12 mL N,N-dimethylformamide and stir and reflux at 145 °C for 1.5 h. Centrifuge and wash to obtain the precursor MIL-88B(Fe);

[0059] (2) Disperse the 40 mg MIL-88B(Fe) obtained in step (1) in 50 mL of ethanol to obtain solution A;

[0060] (3) Dissolve 1.35g of potassium ferrocyanide trihydrate in 40mL of deionized water to obtain solution B;

[0061] (4) Stirring solution B at 1 mL / min −1 The solution was added dropwise to solution A at a rate of 1, stirred for 6 hours, and allowed to stand at room temperature for 8 hours. The resulting precipitate was then centrifuged and washed to obtain spindle-shaped Prussian blue.

[0062] (5) Take 50 mg of the spindle-shaped Prussian blue obtained in step (4) and disperse it in 50 mL of potassium iodide with a concentration of 0.02 mol / L. −1 The mixture was placed in a methanol solution and then transferred to a polytetrafluoroethylene-lined stainless steel autoclave. The reaction was carried out at 100°C for 12 hours. The resulting precipitate was centrifuged and washed to obtain spindle-shaped Prussian white material.

[0063] The obtained spindle-shaped Prussian white material was characterized and its electrochemical performance was tested using the same method as in Example 1. The results were basically the same as in Example 1, and are shown in Table 1. Example 4

[0064] (1) Dissolve 300 mg ferric chloride, 200 mg terephthalic acid and 100 mg polyvinylpyrrolidone in 12 mL N,N-dimethylformamide and stir and reflux at 145 °C for 1.5 h. Centrifuge and wash to obtain the precursor MIL-88B(Fe);

[0065] (2) Disperse the 40 mg MIL-88B(Fe) obtained in step (1) in 50 mL of ethanol to obtain solution A;

[0066] (3) Dissolve 1.35g of potassium ferrocyanide trihydrate in 50mL of deionized water to obtain solution B;

[0067] (4) Stirring solution B at 1 mL / min −1 The solution was added dropwise to solution A at a rate of 1, stirred for 6 hours, and allowed to stand at room temperature for 8 hours. The resulting precipitate was then centrifuged and washed to obtain spindle-shaped Prussian blue.

[0068] (5) Take 50 mg of the spindle-shaped Prussian blue obtained in step (4) and disperse it in 50 mL of potassium iodide with a concentration of 0.016 mol / L. −1 The mixture was placed in a methanol solution and then transferred to a polytetrafluoroethylene-lined stainless steel autoclave. The reaction was carried out at 100°C for 12 hours. The resulting precipitate was centrifuged and washed to obtain spindle-shaped Prussian white material.

[0069] The obtained spindle-shaped Prussian white material was characterized and its electrochemical performance was tested using the same method as in Example 1. The results were basically the same as in Example 1, and are shown in Table 1. Example 5

[0070] (1) Dissolve 300 mg ferric chloride, 200 mg terephthalic acid and 100 mg polyvinylpyrrolidone in 12 mL N,N-dimethylformamide and stir and reflux at 145 °C for 1.5 h. Centrifuge and wash to obtain the precursor MIL-88B(Fe);

[0071] (2) Disperse the 40 mg MIL-88B(Fe) obtained in step (1) in 50 mL of ethanol to obtain solution A;

[0072] (3) Dissolve 1.35g of potassium ferrocyanide trihydrate in 50mL of deionized water to obtain solution B;

[0073] (4) Stirring solution B at 1 mL / min −1 The solution was added dropwise to solution A at a rate of 1, stirred for 6 hours, and allowed to stand at room temperature for 8 hours. The resulting precipitate was then centrifuged and washed to obtain spindle-shaped Prussian blue.

[0074] (5) Take 46 mg of the spindle-shaped Prussian blue obtained in step (4) and disperse it in 50 mL of potassium iodide with a concentration of 0.02 mol / L. −1 The mixture was placed in a methanol solution and then transferred to a polytetrafluoroethylene-lined stainless steel autoclave. The reaction was carried out at 100°C for 12 hours. The resulting precipitate was centrifuged and washed to obtain spindle-shaped Prussian white material.

[0075] The obtained spindle-shaped Prussian white material was characterized and its electrochemical performance was tested using the same method as in Example 1. The results were basically the same as in Example 1, and are shown in Table 1. Example 6

[0076] 1) Dissolve 300 mg ferric chloride, 200 mg terephthalic acid and 100 mg polyvinylpyrrolidone in 12 mL N,N-dimethylformamide and stir under reflux at 145 °C for 1.5 h. Centrifuge and wash to obtain the precursor MIL-88B(Fe).

[0077] (2) Disperse the 40 mg MIL-88B(Fe) obtained in step (1) in 50 mL of ethanol to obtain solution A;

[0078] (3) Dissolve 1.35g of potassium ferrocyanide trihydrate in 50mL of deionized water to obtain solution B;

[0079] (4) Stirring solution B at 1 mL / min −1 The solution was added dropwise to solution A at a certain rate, stirred for 6 hours, and aged for 8 hours. The resulting precipitate was centrifuged and washed to obtain Prussian blue.

[0080] (5) Take 50 mg of the Prussian blue obtained in step (4) and disperse it in 50 mL of potassium iodide with a concentration of 0.02 mol / L. −1 The mixture was placed in a methanol solution and then transferred to a polytetrafluoroethylene-lined stainless steel autoclave. The reaction was carried out at 100°C for 14 hours. The resulting precipitate was centrifuged and washed to obtain spindle-shaped Prussian white material.

[0081] The obtained spindle-shaped Prussian white material was characterized and its electrochemical performance was tested using the same method as in Example 1. The results were basically the same as in Example 1, and are shown in Table 1. Comparative Example 1

[0082] Preparation of Prussian white with irregular morphology:

[0083] (1) Dissolve 2 mmol of potassium ferrocyanide trihydrate in 40 mL of saturated potassium chloride solution to obtain solution A;

[0084] (2) Dissolve 4 mmol of ferric chloride tetrahydrate in 80 mL of saturated potassium chloride solution to obtain solution B;

[0085] (3) Solution A is slowly added dropwise to solution B under a nitrogen atmosphere and stirred at 60°C for 4 hours. The resulting precipitate is centrifuged, washed and dried to obtain irregular Prussian white material (Irregular PW).

[0086] The electrochemical performance of the irregularly shaped Prussian white material was tested using the same method as in Example 1. Figure 6 It can be concluded that the irregularly shaped Prussian white has a smaller specific surface area and fewer pores. Figure 9The figures show the rate performance of spindle-shaped Prussian white electrode and irregularly shaped Prussian white electrode at different current densities. The discharge capacity of spindle-shaped Prussian white electrode is higher than that of irregularly shaped Prussian white electrode at different current densities. Figure 11 The figure shows the cycling performance of the spindle-shaped Prussian white electrode and the irregularly shaped Prussian white electrode. The figure shows that the cycling stability of the irregularly shaped Prussian white electrode is far inferior to that of the spindle-shaped Prussian white electrode. The above tests show that the spindle-shaped Prussian white electrode has superior electrochemical performance. Figure 12 The XRD pattern of the irregularly shaped Prussian white material shows that it has the same monoclinic phase structure as the spindle-shaped Prussian white material.

[0087] Table 1 Electrochemical performance data

[0088]

[0089] It should be noted that the above content merely illustrates the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, various improvements and modifications can be made without departing from the principle of the present invention, and all such improvements and modifications fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a spindle-shaped Prussian white material, characterized in that, Includes the following steps: (1) Ferric chloride, terephthalic acid and polyvinylpyrrolidone were dissolved in N,N-dimethylformamide and stirred at 145°C for 1.5 h. After centrifugation and washing, the precursor MIL-88B(Fe) was obtained. (2) Disperse the MIL-88B(Fe) obtained in step (1) in ethanol to obtain solution A; (3) Dissolve potassium ferrocyanide trihydrate in deionized water to obtain solution B; (4) Add solution B dropwise into solution A and stir. The resulting precipitate is centrifuged and washed to obtain spindle-shaped Prussian blue. (5) Disperse the spindle-shaped Prussian blue obtained in step (4) in a methanol solution containing potassium iodide and carry out a solvothermal reaction. Centrifuge and wash the precipitate to obtain spindle-shaped Prussian white material. In step (5), the concentration of the methanol solution containing potassium iodide is 0.016~0.024 mol / L. −1 ; In step (5), the mass-to-volume ratio of spindle-shaped Prussian blue to methanol solution containing potassium iodide is 0.92~1.08:1; In step (5), the temperature of the solvothermal reaction is 90~110℃ and the time of the solvothermal reaction is 10~14h.

2. The method for preparing a spindle-shaped Prussian white material according to claim 1, characterized in that, In step (1), the mass ratio of ferric chloride, terephthalic acid, and polyvinylpyrrolidone is 2.8~3.2:2:1, and the mass-volume ratio of ferric chloride to N,N-dimethylformamide is 24.5~25.5:

1.

3. The method for preparing a spindle-shaped Prussian white material according to claim 1, characterized in that, In step (2), the mass-volume ratio of MIL-88B(Fe) to ethanol is 0.6~1:

1.

4. The method for preparing a spindle-shaped Prussian white material according to claim 1, characterized in that, In step (3), the mass-volume ratio of potassium ferrocyanide trihydrate to deionized water is 20~30:0.8~1.

5. The method for preparing a spindle-shaped Prussian white material according to claim 1, characterized in that, In step (4), the volume ratio of ethanol in solution A to deionized water in solution B is 1:0.8~1.

2.

6. The method for preparing a spindle-shaped Prussian white material according to claim 1, characterized in that, In step (4), the dropping rate of solution B is 0.8~1.2 mL / min. −1 The stirring time is 5 to 7 hours.

7. The application of a spindle-shaped Prussian white material prepared by the preparation method according to any one of claims 1-6 in the cathode material of a potassium-ion battery.

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