Lanthanide-doped Prussian blue positive electrode material and preparation method and application thereof

Abstract

The invention discloses a lanthanide-doped Prussian blue positive electrode material and a preparation method and application thereof, and the preparation method comprises the following steps: mixing and dissolving sodium ferrocyanide and lanthanide metal salt to obtain a mixed solution; and under a protective atmosphere, dropwise adding the mixed solution into a mixed chelating agent salt solution through a peristaltic pump, and reacting to obtain the lanthanide-doped Prussian blue positive electrode material. The lanthanide metal in the lanthanide-doped Prussian blue positive electrode material occupies the Na site, the single iron source coprecipitation method is adopted for synthesis, the process concentration is uniform, the synthesized positive electrode material has fewer defects, the material structure is stable, the rate capability is excellent, the specific capacity is high, and the application prospect is very good.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, specifically to a lanthanide-doped Prussian blue cathode material, its preparation method, and its application. Background Technology

[0002] Sodium-ion batteries (SIBs) offer advantages in resources, cost, and safety. Compared to lithium-ion batteries, sodium-ion batteries can use inexpensive elements such as iron and manganese for the positive electrode, and both the positive and negative electrode current collectors can use low-cost aluminum foil, while lithium-ion batteries must use more expensive copper foil for the negative electrode. These combined advantages result in significant cost reduction potential. In terms of safety, sodium-ion batteries have higher internal resistance and higher thermal runaway temperature, significantly reducing the risk of fire and explosion. Because sodium ions migrate faster in the electrolyte, they support high-current charging; even in harsh environments with temperatures tens of degrees below zero, sodium-ion batteries can maintain high capacity, far exceeding that of lithium batteries. Currently, widely researched positive electrode materials include layered oxides, polyanionic compounds, and Prussian blue analogues (PBAs), among which Prussian blue analogues are a class of promising positive electrode materials for sodium-ion batteries.

[0003] The chemical formula of PBAs is (1) <x<2,0<y<1; (representing vacancy), it inherits the open three-dimensional framework structure of classic Prussian blue. This unique structure allows for rapid and stable insertion and extraction of sodium ions, giving it excellent rate performance. Based on the different redox active sites, PBAs used for SIBs can be classified into single-electron transfer type (M=Cu, Zn, Ni, ~85 mAh g⁻¹). -1 ) and dual-electron transfer type (M=Mn, Fe, Co, ~170mAh g) -1 However, the industrialization of Prussian blue analogues still faces some challenges. The primary challenge lies in the prevalent [Fe(CN)6] vacancies and water of crystallization in their crystal structure. These defects not only reduce the initial coulombic efficiency and actual specific capacity of the material, but the decomposition of water of crystallization under high pressure can also trigger gaseous side reactions, seriously threatening the safety and lifespan of the battery.

[0004] To reduce vacancies and water of crystallization in PBAs, researchers currently employ strategies such as optimizing synthesis processes, designing material structures, and introducing other elements to improve their electrochemical performance. For example, adding chelating agents can slow down crystal nucleation growth, promoting the formation of more ordered crystal structures with fewer defects; thermal dehydration can remove interstitial and coordinated water; and high-entropy strategies can introduce multiple transition metal elements to reduce dependence on a single element and minimize specific defects. However, these methods still suffer from challenges such as complex preparation methods and insufficient material performance. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies by providing a lanthanide-doped Prussian blue cathode material, its preparation method, and its applications. By doping sodium sites with lanthanide metals, the prepared material exhibits excellent performance and good stability. Furthermore, the preparation process is simple, low-cost, environmentally friendly, and suitable for large-scale production.

[0006] To address the aforementioned technical problems, the first aspect of this invention provides a lanthanide-doped Prussian blue cathode material, wherein the molecular formula of the cathode material is Na. x M z Fe[Fe(CN)6] 1-y □ y •nH₂O, where M is a lanthanide metal and the lanthanide metal occupies the Na site, □ is a vacancy, 1≤x<2, 0≤y≤0.1, 0<z≤0.1, 0≤n≤3. Preferably, 1.5≤x<1.9, 0≤y≤0.06.

[0007] This invention utilizes a single-transition metal source co-precipitation method, specifically the single-iron source method, to synthesize Prussian blue cathode materials. This differs from existing technologies that typically employ dual-transition metal source co-precipitation, which can lead to rapid nucleation due to excessively high local concentrations, resulting in higher crystal defects and consequently, poorer material performance. The single-iron source synthesis process of this invention ensures uniform concentration, produces materials with fewer defects, a structure closer to the ideal chemical formula, and superior performance.

[0008] Furthermore, the lanthanide metal is selected from at least one of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

[0009] A second aspect of the present invention provides a method for preparing the lanthanide-doped Prussian blue cathode material described in the first aspect, comprising the following steps:

[0010] S1. Dissolve sodium ferrocyanide and lanthanide metal salts together to obtain a mixed solution;

[0011] S2. Under a protective atmosphere, the mixture is added dropwise to a mixed chelating agent salt solution via a peristaltic pump to react and obtain lanthanide-doped Prussian blue cathode material.

[0012] Furthermore, in S1, the concentration of sodium ferrocyanide in the mixture is 0.01 mol / L to 0.1 mol / L, preferably 0.06 mol / L to 0.08 mol / L;

[0013] The molar ratio of sodium ferrocyanide to lanthanide is 10:0.1 to 5:1.

[0014] Furthermore, in S1, the lanthanide metal salt is selected from at least one of the lanthanide metal nitrates, sulfates, and chlorides.

[0015] Furthermore, in S2, the protective atmosphere is nitrogen and / or argon.

[0016] Furthermore, in S2, the method for preparing the mixed chelating agent salt solution is as follows: sodium chloride, sodium citrate, polyvinylpyrrolidone and ascorbic acid are mixed and dissolved, and the pH is adjusted to 0.5-2 to obtain the mixed chelating agent salt solution.

[0017] Further, in S2, the reaction is specifically carried out at: 5℃~35℃ for 2-12 hours; 35℃~75℃ for 1-8 hours; and 75℃~90℃ for 2-6 hours. Preferably, the reaction is carried out at: 10℃~25℃ for 6-12 hours; 40℃~55℃ for 4-8 hours; and 75℃~85℃ for 3-6 hours.

[0018] Furthermore, in S2, the rotational speed of the peristaltic pump is 0.01 rpm to 20 rpm, preferably 5 rpm to 15 rpm.

[0019] Furthermore, in step S2, the reaction is followed by a settling, washing of the precipitate, and drying steps; preferably, the settling time is 2-6 hours, the washing of the precipitate is specifically multiple water washing followed by ethanol washing, and the drying is carried out under vacuum or a protective atmosphere at a temperature of 80-150°C for 12-36 hours.

[0020] The second aspect of this invention provides the application of the lanthanide-doped Prussian blue cathode material described in the first aspect in sodium-ion batteries.

[0021] The beneficial effects of this invention are:

[0022] In this invention, the lanthanide-doped Prussian blue cathode material occupies Na sites and is synthesized using a single iron source co-precipitation method. The process results in uniform concentration, fewer defects in the synthesized cathode material, stable material structure, excellent rate performance, and high specific capacity, showing great application prospects. Attached Figure Description

[0023] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 These are SEM images of the iron-based Prussian blue cathode materials obtained in Example 1 and Comparative Example 1 of the present invention;

[0025] Figure 2These are the XRD patterns of the iron-based Prussian blue cathode materials obtained in Example 1 and Comparative Example 1 of the present invention;

[0026] Figure 3 These are the TG curves of the iron-based Prussian blue cathode materials obtained in Example 1 and Comparative Example 1 of the present invention;

[0027] Figure 4 These are capacity-voltage curves of batteries assembled with iron-based Prussian blue cathode materials obtained in Embodiment 1 and Comparative Example 1 of the present invention.

[0028] Figure 5 This is a rate curve diagram of the battery assembled with iron-based Prussian blue cathode material obtained in Example 1 and Comparative Examples 1-3 of the present invention;

[0029] Figure 6 These are the long-cycle curves of batteries assembled with iron-based Prussian blue cathode materials obtained in Examples 1 and 6 and Comparative Examples 1 and 3 of the present invention. Detailed Implementation

[0030] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1

[0032] This embodiment relates to a method for preparing a lanthanide-doped Prussian blue cathode material, comprising the following steps:

[0033] (1) Add 14g of sodium chloride, 5.88g of sodium citrate, 3g of polyvinylpyrrolidone K30 and 1.76g of ascorbic acid to 200ml of deionized water, stir thoroughly at 400rpm for 10min at room temperature, adjust the pH to 1, and obtain solution A;

[0034] (2) Add 1.936 g (4 mmol) sodium ferrocyanide decahydrate and 0.04 mmol CeCl3 to 50 ml of deionized water (molar ratio of 100:1), and stir thoroughly at 400 rpm for 10 min at room temperature to obtain solution B;

[0035] (3) Under a protective atmosphere (nitrogen, purging rate of 50 ml / min), solution B was added dropwise to solution A at a rate of 15 rpm using a peristaltic pump, and the stirring speed of the system was 400 rpm. The reaction was carried out at room temperature for 8 h, at 50 °C for 8 h, and at 80 °C for 4 h. After standing overnight, the solid and liquid were separated to obtain a solid product.

[0036] (4) Wash the solid product with water and ethanol 3-4 times each, then dry it to obtain the positive electrode material Na. 1.85 Ce 0.01 Fe[Fe(CN)6] 0.97 □ 0.03 •1.5H2O.

[0037] Example 2

[0038] This embodiment relates to a method for preparing a lanthanide-doped Prussian blue cathode material. The difference from Example 1 is that the molar ratio of sodium ferrocyanide to lanthanide metal salt is adjusted to 50:1. The specific steps include the following:

[0039] (1) Add 14g of sodium chloride, 5.88g of sodium citrate, 3g of polyvinylpyrrolidone K30 and 1.76g of ascorbic acid to 200ml of deionized water, stir thoroughly at 400rpm for 10min at room temperature, adjust the pH to 1, and obtain solution A;

[0040] (2) Add 4 mmol sodium ferrocyanide decahydrate and 0.08 mmol CeCl3 to 50 ml of deionized water (molar ratio of 50:1), and stir thoroughly at 400 rpm for 10 min at room temperature to obtain solution B;

[0041] (3) Under a protective atmosphere (nitrogen, purging rate of 50 ml / min), solution B was added dropwise to solution A at a rate of 15 rpm using a peristaltic pump, and the stirring speed of the system was 400 rpm. The reaction was carried out at room temperature for 8 h, at 50 °C for 8 h, and at 80 °C for 4 h. After standing overnight, the solid and liquid were separated to obtain a solid product.

[0042] (4) Wash the solid product with water and ethanol 3-4 times each, then dry it to obtain the positive electrode material Na. 1.8 Ce 0.02 Fe[Fe(CN)6] 0.965 □ 0.035 •1.5H2O.

[0043] Example 3

[0044] This embodiment relates to a method for preparing a lanthanide-doped Prussian blue cathode material. The difference from Example 1 is that the molar ratio of sodium ferrocyanide to lanthanide metal salt is adjusted to 25:1. The specific steps include the following:

[0045] (1) Add 14g of sodium chloride, 5.88g of sodium citrate, 3g of polyvinylpyrrolidone K30 and 1.76g of ascorbic acid to 200ml of deionized water, stir thoroughly at 400rpm for 10min at room temperature, adjust the pH to 1, and obtain solution A;

[0046] (2) Add 4 mmol sodium ferrocyanide decahydrate and 0.16 mmol CeCl3 to 50 ml of deionized water (molar ratio of 25:1), and stir thoroughly at 400 rpm for 10 min at room temperature to obtain solution B;

[0047] (3) Under a protective atmosphere (nitrogen, purging rate of 50 ml / min), solution B was added dropwise to solution A at a rate of 15 rpm using a peristaltic pump, and the stirring speed of the system was 400 rpm. The reaction was carried out at room temperature for 8 h, at 50 °C for 8 h, and at 80 °C for 4 h. After standing overnight, the solid and liquid were separated to obtain a solid product.

[0048] (4) Wash the solid product with water and ethanol 3-4 times each, then dry it to obtain the positive electrode material Na. 1.72 Ce 0.04 Fe[Fe(CN)6] 0.96 □ 0.04 •1.5H2O.

[0049] Example 4

[0050] This embodiment relates to a method for preparing a lanthanide-doped Prussian blue cathode material. The difference from Example 1 is that the molar ratio of sodium ferrocyanide to lanthanide metal salt is adjusted to 50:3. The specific steps include the following:

[0051] (1) Add 14g of sodium chloride, 5.88g of sodium citrate, 3g of polyvinylpyrrolidone K30 and 1.76g of ascorbic acid to 200ml of deionized water, stir thoroughly at 400rpm for 10min at room temperature, adjust the pH to 1, and obtain solution A;

[0052] (2) Add 4 mmol sodium ferrocyanide decahydrate and 0.24 mmol CeCl3 to 50 ml of deionized water (molar ratio of 50:3), and stir thoroughly at 400 rpm for 10 min at room temperature to obtain solution B;

[0053] (3) Under a protective atmosphere (nitrogen, purging rate of 50 ml / min), solution B was added dropwise to solution A at a rate of 15 rpm using a peristaltic pump, and the stirring speed of the system was 400 rpm. The reaction was carried out at room temperature for 8 h, at 50 °C for 8 h, and at 80 °C for 4 h. After standing overnight, the solid and liquid were separated to obtain a solid product.

[0054] (4) Wash the solid product with water and ethanol 3-4 times each, then dry it to obtain the positive electrode material Na. 1.64 Ce 0.06 Fe[Fe(CN)6] 0.955 □ 0.045 •1.5H2O.

[0055] Example 5

[0056] This embodiment relates to a method for preparing a lanthanide-doped Prussian blue cathode material. The difference from Example 1 is that the molar ratio of sodium ferrocyanide to lanthanide metal salt is adjusted to 25:2. The specific steps include the following:

[0057] (1) Add 14g of sodium chloride, 5.88g of sodium citrate, 3g of polyvinylpyrrolidone K30 and 1.76g of ascorbic acid to 200ml of deionized water, stir thoroughly at 400rpm for 10min at room temperature, adjust the pH to 1, and obtain solution A;

[0058] (2) Add 4 mmol sodium ferrocyanide decahydrate and 0.32 mmol CeCl3 to 50 ml of deionized water (molar ratio of 25:2), and stir thoroughly at 400 rpm for 10 min at room temperature to obtain solution B;

[0059] (3) Under a protective atmosphere (nitrogen, purging rate of 50 ml / min), solution B was added dropwise to solution A at a rate of 15 rpm using a peristaltic pump, and the stirring speed of the system was 400 rpm. The reaction was carried out at room temperature for 8 h, at 50 °C for 8 h, and at 80 °C for 4 h. After standing overnight, the solid and liquid were separated to obtain a solid product.

[0060] (4) Wash the solid product with water and ethanol 3-4 times each, then dry it to obtain the positive electrode material Na. 1.54 Ce 0.08 Fe[Fe(CN)6] 0.945 □ 0.055 •1.5H2O.

[0061] Example 6

[0062] This embodiment relates to a method for preparing a lanthanide-doped Prussian blue cathode material. The difference from Example 1 is that the molar ratio of sodium ferrocyanide to lanthanide metal salt is adjusted to 10:1. The specific steps include the following:

[0063] (1) Add 14g of sodium chloride, 5.88g of sodium citrate, 3g of polyvinylpyrrolidone K30 and 1.76g of ascorbic acid to 200ml of deionized water, stir thoroughly at 400rpm for 10min at room temperature, adjust the pH to 1, and obtain solution A;

[0064] (2) Add 4 mmol sodium ferrocyanide decahydrate and 0.4 mmol CeCl3 to 50 ml of deionized water (molar ratio of 10:1), and stir thoroughly at 400 rpm for 10 min at room temperature to obtain solution B;

[0065] (3) Under a protective atmosphere (nitrogen, purging rate of 50 ml / min), solution B was added dropwise to solution A at a rate of 15 rpm using a peristaltic pump, and the stirring speed of the system was 400 rpm. The reaction was carried out at room temperature for 8 h, at 50 °C for 8 h, and at 80 °C for 4 h. After standing overnight, the solid and liquid were separated to obtain a solid product.

[0066] (4) Wash the solid product with water and ethanol 3-4 times each, then dry it to obtain the positive electrode material Na. 1.46 Ce 0.1 Fe[Fe(CN)6] 0.94 □ 0.06 •1.5H2O.

[0067] Comparative Example 1

[0068] This comparative example relates to a method for preparing a cathode material. The difference from Example 1 is that no lanthanide metal salt is added in step (2). Specifically, it includes the following steps:

[0069] (1) Add 14g of sodium chloride, 5.88g of sodium citrate, 3g of polyvinylpyrrolidone K30 and 1.76g of ascorbic acid to 200ml of deionized water, stir thoroughly at 400rpm for 10min at room temperature, adjust the pH to 1, and obtain solution A;

[0070] (2) Add 1.936g of sodium ferrocyanide decahydrate to 50ml of deionized water and stir thoroughly at 400rpm for 10min at room temperature to obtain solution B;

[0071] (3) Under a protective atmosphere (nitrogen, purging rate of 50 ml / min), solution B was added dropwise to solution A at a rate of 15 rpm using a peristaltic pump, and the stirring speed of the system was 400 rpm. The reaction was carried out at room temperature for 8 h, at 50 °C for 8 h, and at 80 °C for 4 h. After standing overnight, the solid and liquid were separated to obtain a solid product.

[0072] (4) Wash the solid product with water and ethanol 3-4 times each, then dry it to obtain the positive electrode material Na. 1.78 Fe[Fe(CN)6] 0.945 □ 0.055 •1.8H2O.

[0073] Comparative Example 2

[0074] This comparative example relates to a method for preparing a cathode material, specifically including the following steps:

[0075] (1) Add 14g of sodium chloride, 5.88g of sodium citrate, 3g of polyvinylpyrrolidone K30 and 1.76g of ascorbic acid to 200ml of deionized water, stir thoroughly at 400rpm for 10min at room temperature, adjust the pH to 1, and obtain solution A;

[0076] (2) Add 1.936g of sodium ferrocyanide decahydrate to 50ml of deionized water and stir thoroughly at 400rpm for 10min at room temperature to obtain solution B;

[0077] (3) Add 0.556g of ferrous sulfate heptahydrate to 50ml of deionized water and stir thoroughly at 400rpm for 10min at room temperature to obtain solution C;

[0078] (4) Under a protective atmosphere (nitrogen, purging rate of 50 ml / min), solutions B and C were added dropwise to solution A at a rate of 15 rpm using a peristaltic pump, and the system was stirred at a rate of 400 rpm. The reaction was carried out at room temperature for 8 h, at 50 °C for 8 h, and at 80 °C for 4 h. After standing overnight, the solid and liquid were separated to obtain a solid product.

[0079] (5) Wash the solid product with water and ethanol 3-4 times each, then dry it to obtain the positive electrode material Na. 1.64 Fe[Fe(CN)6] 0.89 □ 0.11 •1.95H2O.

[0080] Comparative Example 3

[0081] This comparative example relates to a method for preparing a cathode material, specifically including the following steps:

[0082] (1) Add 14g of sodium chloride, 5.88g of sodium citrate, 3g of polyvinylpyrrolidone K30 and 1.76g of ascorbic acid to 200ml of deionized water, stir thoroughly at 400rpm for 10min at room temperature, adjust the pH to 1, and obtain solution A;

[0083] (2) Add 1.936g of sodium ferrocyanide decahydrate and CeCl3 (molar ratio of 10:1) to 50ml of deionized water and stir thoroughly at 400rpm for 10min at room temperature to obtain solution B;

[0084] (3) Add 0.556g of ferrous sulfate heptahydrate to 50ml of deionized water and stir thoroughly at 400rpm for 10min at room temperature to obtain solution C;

[0085] (4) Under a protective atmosphere (nitrogen, purging rate of 50 ml / min), solutions B and C were added dropwise to solution A at a rate of 15 rpm using a peristaltic pump, and the system was stirred at a rate of 400 rpm. The reaction was carried out at room temperature for 8 h, at 50 °C for 8 h, and at 80 °C for 4 h. After standing overnight, the solid and liquid were separated to obtain a solid product.

[0086] S5. Wash the solid product with water and ethanol 3-4 times each, then dry it to obtain the cathode material Na. 1.55 Ce 0.1 Fe[Fe(CN)6] 0.86 □ 0.14 •2.1H2O.

[0087] Test case

[0088] Figure 1 The images show SEM images of the iron-based Prussian blue cathode materials obtained in Example 1 and Comparative Example 1. It can be seen that the Prussian blue cathode material in Example 1 has uniform particle size and a particle size of about 400-600 nm, which is smaller than the particle size (600-800 nm) in Comparative Example 1. Figure 2 The images show the XRD patterns of the iron-based Prussian blue cathode materials obtained in Example 1 and Comparative Example 1. It can be seen that the materials synthesized in each Example 1 exhibit a cubic phase. However, due to the different sodium contents of the materials, the peak of Example 1 with a higher sodium content shifts to a lower angle. Figure 3 The graphs show the TG curves of the iron-based Prussian blue cathode materials obtained in Example 1 and Comparative Example 1. It can be seen that the crystal in Example 1 has higher thermal stability.

[0089] Application examples

[0090] Using the positive electrode materials obtained in the examples and comparative examples as active materials, Super P (SP) and Ketjen Black (KB) as conductive agents, PVDF as binders, and N-methylpyrrolidone (NMP) as dispersants, a slurry was prepared at a mass ratio of positive electrode material:SP:KB:PVDF = 7:1:1:1, and coated onto aluminum foil to form a positive electrode sheet. Then, using a sodium metal sheet as the negative electrode, a glass fiber filter paper membrane as the separator, and 1.0M NaClO4 in EC:DEC = 1:1 Vol% as the electrolyte, a CR2032 button cell was assembled in an argon-filled glove box; and the assembled battery was subjected to charge-discharge cycle testing at room temperature.

[0091] Figure 4 Capacity-voltage curves of batteries assembled with iron-based Prussian blue cathode materials obtained in Example 1 and Comparative Example 1; Figure 5 Rate curves of batteries assembled with iron-based Prussian blue cathode materials obtained in Example 1 and Comparative Examples 1-3; Figure 6 The images show the long-cycle curves of batteries assembled with the iron-based Prussian blue cathode materials obtained in Examples 1 and 6, and Comparative Examples 1 and 3. These curves demonstrate that the capacity of the Prussian blue material doped with lanthanide metals is improved. Comparing the materials synthesized by the single-iron-source method with those synthesized by the dual-iron-source method, the materials synthesized by the single-iron-source method exhibit significantly better stability and a slower capacity decay rate. In terms of rate capability, the high-rate capacity of the lanthanide-doped material is improved, with better electrochemical reversibility and a more stable structure. Overall, the performance of the single-iron-source lanthanide-doped material of this invention is superior to that of the undoped iron-based Prussian blue material.

[0092] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A lanthanide-doped Prussian blue cathode material, characterized in that, The molecular formula of the positive electrode material is Na. x M z Fe[Fe(CN)6] 1-y □ y •nH2O, where M is a lanthanide metal and the lanthanide metal occupies the Na site, □ is a vacancy, 1≤x<2, 0≤y≤0.1, 0<z≤0.1, 0≤n≤3.

2. The lanthanide-doped Prussian blue cathode material as described in claim 1, characterized in that, The lanthanide metal is selected from at least one of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

3. A method for preparing a lanthanide-doped Prussian blue cathode material according to any one of claims 1-2, characterized in that, Includes the following steps: S1. Dissolve sodium ferrocyanide and lanthanide metal salts together to obtain a mixed solution; S2. Under a protective atmosphere, the mixture is added dropwise to a mixed chelating agent salt solution via a peristaltic pump to react and obtain lanthanide-doped Prussian blue cathode material.

4. The method for preparing lanthanide-doped Prussian blue cathode material as described in claim 3, characterized in that, In S1, the concentration of sodium ferrocyanide in the mixture is 0.01 mol / L to 0.1 mol / L.

5. The method for preparing lanthanide-doped Prussian blue cathode material as described in claim 3, characterized in that, In S1, the lanthanide metal salt is selected from at least one of the nitrates, sulfates and chlorides of lanthanide metals.

6. The method for preparing lanthanide-doped Prussian blue cathode material as described in claim 3, characterized in that, In S2, the mixed chelating agent salt solution is prepared by mixing and dissolving sodium chloride, sodium citrate, polyvinylpyrrolidone and ascorbic acid, adjusting the pH to 0.5-2, and obtaining the mixed chelating agent salt solution.

7. The method for preparing lanthanide-doped Prussian blue cathode material as described in claim 3, characterized in that, In S2, the reaction is specifically carried out at 5℃~35℃ for 2-12 hours; at 35℃~75℃ for 1-8 hours; and at 75℃~90℃ for 2-6 hours.

8. The method for preparing lanthanide-doped Prussian blue cathode material as described in claim 3, characterized in that, In S2, the rotational speed of the peristaltic pump is 0.01 rpm to 20 rpm.

9. The method for preparing lanthanide-doped Prussian blue cathode material as described in claim 3, characterized in that, In S2, the reaction also includes steps of settling, washing the precipitate, and drying.

10. The application of the lanthanide-doped Prussian blue cathode material as described in any one of claims 1-2 in sodium-ion batteries.

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