Preparation method and application of sodium ion battery positive electrode material sodium ferric borate

Abstract

The invention belongs to the technical field of sodium-ion battery positive electrode materials, and particularly discloses a preparation method and application of a sodium-ion battery positive electrode material sodium ferric borate, and the preparation method comprises the following steps: (1) preparation of a precursor solution or suspension: respectively adding a boron source, a sodium source and a ferric iron source into water, and uniformly stirring; sequentially adding into a carbon source aqueous solution, and continuously stirring to obtain a mixed solution; stirring and carrying out a coprecipitation reaction to obtain a precipitate; (2) preparing a ferric sodium borate precursor: drying the precipitate obtained in the step (1) to obtain the ferric sodium borate precursor; and (3) preparing the ferric sodium borate: pre-treating and calcining the ferric sodium borate precursor obtained in the step (2) under the protection of inert atmosphere to obtain the sodium ion battery positive electrode material ferric sodium borate. The positive electrode material prepared by the invention belongs to a sodium-rich phase material, and has excellent air stability, which is very beneficial to subsequent processing and application in batteries.

Description

Technical Field

[0001] The invention belongs to the technical field of sodium ion battery positive electrode materials, and specifically relates to a preparation method and application of sodium ferric borate, a positive electrode material for sodium ion batteries. Background Art

[0002] Lithium-ion batteries have occupied the main market of secondary batteries due to their high energy density and long cycle life. At present, most advanced energy storage systems use lithium-ion battery technology. However, with the fluctuation of lithium-ion battery prices, especially the consumption of lithium resources and the shortage in the future, the development of lithium-ion batteries also has certain limitations. Sodium has become the main candidate to replace lithium because it is in the same main group as lithium, and it has the advantages of abundant sodium sources and low cost. Sodium-ion batteries are expected to become a new generation of energy storage products.

[0003] At present, the main research direction of sodium-ion batteries is to develop cathode materials with higher energy density. Existing cathode materials mainly include three categories: layered metal oxides, polyanion compounds and Prussian blue. Among them, layered metal oxides are divided into O3 and P2 types, with slightly higher capacity and average cycle performance. Polyanions have a slightly lower gram capacity and excellent cycle performance. However, the disadvantage is that they contain vanadium and are relatively expensive. Prussian blue has a relatively low gram capacity, poor cycle performance, and very low material cost. The disadvantage is that the material contains water of crystallization and has problems with processing performance. At the same time, because the material contains cyanide compounds, there are some safety hazards during preparation and use.

[0004] Therefore, it is urgent to continue to develop positive electrode materials with better performance. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the prior art, provide a preparation method and application of sodium ferric borate, a positive electrode material for sodium ion batteries, and solve the problems in the above-mentioned background technology.

[0006] In order to achieve the above purpose, one of the technical solutions of the present invention is: a method for preparing sodium iron borate, a positive electrode material for a sodium ion battery, comprising the following steps:

[0007] (1) Preparation of a precursor solution or suspension: Add a boron source, a sodium source, and a trivalent iron source to water respectively, and then add them to a carbon source aqueous solution in sequence and continuously stir to obtain a mixed solution; after stirring and coprecipitation reaction, obtain a precipitate;

[0008] (2) Preparation of sodium iron borate precursor: drying the precipitate obtained in step (1) to obtain a sodium iron borate precursor;

[0009] (3) Preparation of sodium iron borate: The sodium iron borate precursor obtained in step (2) is pretreated and calcined under an inert atmosphere to obtain sodium iron borate, a positive electrode material for a sodium ion battery.

[0010] In a preferred embodiment of the present invention, the molar ratio of the boron source, the sodium source and the ferric iron source in step (1) is (1.1-1.15):(1-1.05):1.

[0011] In a preferred embodiment of the present invention, the molar ratio of the ferric iron source compound to the carbon source compound in step (1) is 1:(0.5-2);

[0012] In a preferred embodiment of the present invention, the boron source in step (1) is selected from one of boric acid, ammonium borate and boron trioxide.

[0013] In a preferred embodiment of the present invention, the sodium source in step (1) is selected from one of sodium carbonate, sodium hydroxide, sodium oxalate, sodium acetate and sodium nitrate.

[0014] In a preferred embodiment of the present invention, the ferric iron source in step (1) is selected from one of ferric oxide, ferric nitrate, ferric oxalate and ferric citrate.

[0015] In a preferred embodiment of the present invention, the carbon source in step (1) is selected from one or more of glucose, citric acid, sucrose, glycolic acid, tartaric acid and ascorbic acid.

[0016] In a preferred embodiment of the present invention, the rotation speed of the agitator in step (1) is 1800-3000 rpm.

[0017] More preferably, the drying temperature may be 80-180°C, and more preferably 100°C.

[0018] Further preferably, the drying time may be 4-18 hours;

[0019] More preferably, the drying may be performed in an air atmosphere.

[0020] In a preferred embodiment of the present invention, the drying temperature in step (2) is 80-180° C. and the drying time is 4-18 hours.

[0021] In a preferred embodiment of the present invention, the step (2) further comprises crushing and screening the sodium iron borate precursor.

[0022] In a preferred embodiment of the present invention, in step (3), the pretreatment temperature is 300-800° C., the pretreatment time is 2-5 h, the calcination temperature is 600-1000° C., and the calcination time is 10-24 h.

[0023] In order to achieve the above objectives, the second technical solution of the present invention is: a sodium iron borate positive electrode material for a sodium ion battery prepared by the above preparation method.

[0024] In order to achieve the above objectives, the third technical solution of the present invention is: application of sodium iron borate, a positive electrode material of a sodium ion battery, in a battery.

[0025] Unless otherwise specified, the equipment, reagents, processes, parameters, etc. involved in the present invention are conventional equipment, reagents, processes, parameters, etc. and are not given as embodiments.

[0026] All ranges recited herein include all point values ​​within the range.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The present invention utilizes a simple co-precipitation method to prepare a sodium ion battery positive electrode material with large specific capacity and good cycle stability, further filling the gap in the development of sodium ion battery positive electrode materials. Boron source and iron source are used as raw materials, which are widely distributed, low in price, simple to operate, good in controllability and high in repeatability, and are conducive to mass production in factories.

[0029] 2. The positive electrode material prepared by the present invention is a sodium-rich phase material and has excellent air stability, which is very beneficial for its subsequent processing and application in batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The present invention is a process flow chart for preparing the sodium iron borate material. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is described in more detail below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited to these embodiments.

[0032] A method for preparing sodium ferric borate, a positive electrode material for a sodium ion battery, comprises the following steps:

[0033] (1) Preparation of a precursor solution or suspension: Add a boron source, a sodium source, and a trivalent iron source to water respectively, and then add them to a carbon source aqueous solution in sequence and continuously stir to obtain a mixed solution; after stirring and coprecipitation reaction, obtain a precipitate;

[0034] (2) Preparation of sodium iron borate precursor: drying the precipitate obtained in step (1) to obtain a sodium iron borate precursor;

[0035] (3) Preparation of sodium iron borate: The sodium iron borate precursor obtained in step (2) is pretreated and calcined under an inert atmosphere to obtain sodium iron borate, a positive electrode material for a sodium ion battery.

[0036] The molar ratio of the boron source, the sodium source and the ferric iron source in the step (1) is (1.1-1.15):(1-1.05):1.

[0037] In the step (1), the molar ratio of the ferric iron source compound to the carbon source compound is 1:(0.5-2);

[0038] In the step (1), the boron source is selected from one of boric acid, ammonium borate and boron trioxide.

[0039] In the step (1), the sodium source is selected from one of sodium carbonate, sodium hydroxide, sodium oxalate, sodium acetate and sodium nitrate.

[0040] In the step (1), the ferric iron source is selected from one of ferric oxide, ferric nitrate, ferric oxalate and ferric citrate.

[0041] In step (1), the carbon source is selected from one or more of glucose, citric acid, sucrose, glycolic acid, tartaric acid and ascorbic acid.

[0042] In the step (1), the rotation speed of the stirrer is 1800-3000 rpm.

[0043] The drying temperature may be 80-180°C, more preferably 100°C.

[0044] The drying time may be 4-18 hours;

[0045] The drying may be performed under an air atmosphere.

[0046] The drying temperature in step (2) is 80-180° C. and the drying time is 4-18 hours.

[0047] The step (2) further comprises crushing and screening the sodium iron borate precursor.

[0048] In the step (3), the pretreatment temperature is 300-800° C., the pretreatment time is 2-5 hours, the calcination temperature is 600-1000° C., and the calcination time is 10-24 hours.

[0049] A sodium ferric borate positive electrode material for a sodium ion battery prepared by the above preparation method.

[0050] The invention discloses an application of sodium iron borate, a positive electrode material of a sodium ion battery, in the battery.

[0051] Example 1

[0052] A preparation method and application of sodium iron borate, a positive electrode material for sodium ion batteries, comprising:

[0053] (1) Preparation of precursor solution: 0.3 mol of boric acid, 0.2 mol of ferrous oxalate and 0.1 mol of sodium carbonate were dissolved in 20 mL of water respectively, and 0.1 mol of citric acid and 0.09 mol of glucose were dissolved in 20 mL of water together. Under stirring at a speed of 2000 r / min, the boric acid solution, ferrous oxalate solution and sodium carbonate solution were added to the citric acid and glucose solutions in sequence, and the mixed solution was stirred for 8 h to obtain a clear and transparent mixed solution; stirring was continued for coprecipitation to obtain a precipitate;

[0054] (2) Preparation of precursor: The precipitate obtained in step (1) was dried at 90° C. for 16 h, crushed and sieved to obtain a sodium iron borate precursor;

[0055] (3) Preparation of sodium iron borate: The sodium iron borate precursor obtained in step (2) is moved into a high-temperature furnace, pretreated at 500°C for 3 h under argon protection, and then calcined at 850°C for 12 h. The furnace is cooled to room temperature to obtain sodium iron borate (NaFeBO3), a positive electrode material for sodium ion batteries.

[0056] Example 2

[0057] A preparation method and application of sodium iron borate, a positive electrode material for sodium ion batteries, comprising:

[0058] (1) Preparation of precursor solution: 0.6 mol of boric acid, 0.4 mol of ferrous oxalate and 0.2 mol of sodium carbonate were dissolved in 20 mL of water respectively, and 0.2 mol of citric acid and 0.18 mol of glucose were dissolved in 20 mL of water together. Under stirring at a speed of 2000 r / min, the boric acid solution, ferrous oxalate solution and sodium carbonate solution were added to the citric acid and glucose solutions in sequence, and the mixed solution was stirred for 8 h to obtain a clear and transparent mixed solution; stirring was continued for coprecipitation to obtain a precipitate;

[0059] (2) Preparation of precursor: The precipitate obtained in step (1) was dried at 90° C. for 16 h, crushed and sieved to obtain a sodium iron borate precursor;

[0060] (3) Preparation of sodium iron borate: The sodium iron borate precursor obtained in step (2) is moved into a high-temperature furnace, pretreated at 500°C for 3 h under argon protection, and then calcined at 850°C for 12 h. The furnace is cooled to room temperature to obtain sodium iron borate (NaFeBO3), a positive electrode material for sodium ion batteries.

[0061] Example 3

[0062] A preparation method and application of sodium iron borate, a positive electrode material for sodium ion batteries, comprising:

[0063] (1) Preparation of precursor solution: 0.3 mol of boric acid, 0.2 mol of ferrous oxalate and 0.1 mol of sodium carbonate were dissolved in 20 mL of water respectively, and 0.1 mol of citric acid and 0.09 mol of glucose were dissolved in 20 mL of water together. Under stirring at a speed of 2200 r / min, the boric acid solution, ferrous oxalate solution and sodium carbonate solution were added to the citric acid and glucose solutions in sequence, and the mixed solution was stirred for 8 h to obtain a clear and transparent mixed solution; stirring was continued for coprecipitation to obtain a precipitate;

[0064] (2) Preparation of precursor: The precipitate obtained in step (1) was dried at 90° C. for 16 h, crushed and sieved to obtain a sodium iron borate precursor;

[0065] (3) Preparation of sodium iron borate: The sodium iron borate precursor obtained in step (2) is moved into a high-temperature furnace, pretreated at 500°C for 3 h under argon protection, and then calcined at 950°C for 12 h. The furnace is cooled to room temperature to obtain sodium iron borate (NaFeBO3), a positive electrode material for sodium ion batteries.

[0066] Example 4

[0067] A preparation method and application of sodium iron borate, a positive electrode material for sodium ion batteries, comprising:

[0068] (1) Preparation of precursor solution: 0.3 mol of boron trioxide, 0.2 mol of ferric citrate and 0.1 mol of sodium acetate were dissolved in 40 mL of water respectively, and 0.1 mol of citric acid and 0.09 mol of glucose were dissolved in 50 mL of water together. Under stirring at a speed of 2200 r / min, the boric acid solution, ferric oxalate solution and sodium carbonate solution were added to the citric acid and glucose solutions in sequence, and the mixed solution was stirred for 8 h to obtain a clear and transparent mixed solution; stirring was continued for coprecipitation to obtain a precipitate;

[0069] (2) Preparation of precursor: The precipitate obtained in step (1) was dried at 90° C. for 16 h, crushed and sieved to obtain a sodium iron borate precursor;

[0070] (3) Preparation of sodium iron borate: The sodium iron borate precursor obtained in step (2) is moved into a high-temperature furnace, pretreated at 500°C for 3 h under argon protection, and then calcined at 850°C for 12 h. The furnace is cooled to room temperature to obtain sodium iron borate (NaFeBO3), a positive electrode material for sodium ion batteries.

[0071] Example 5

[0072] A preparation method and application of sodium iron borate, a positive electrode material for sodium ion batteries, comprising:

[0073] (1) Preparation of precursor solution: 0.3 mol of boric acid, 0.2 mol of ferric oxalate and 0.1 mol of sodium carbonate were dissolved in 30 mL of water respectively, and 0.1 mol of citric acid and 0.09 mol of glucose were dissolved in 25 mL of water together. Under stirring at a speed of 2000 r / min, the boric acid solution, ferric oxalate solution and sodium carbonate solution were added to the citric acid and glucose solutions in sequence, and the mixed solution was stirred for 8 h to obtain a clear and transparent mixed solution; stirring was continued for coprecipitation to obtain a precipitate;

[0074] (2) Preparation of precursor: The precipitate obtained in step (1) was dried at 90° C. for 16 h, crushed and sieved to obtain a sodium iron borate precursor;

[0075] (3) Preparation of sodium iron borate: The sodium iron borate precursor obtained in step (2) is moved into a high-temperature furnace, pretreated at 500°C for 3 h under argon protection, and then calcined at 900°C for 12 h. The furnace is cooled to room temperature to obtain sodium iron borate (NaFeBO3), a positive electrode material for sodium ion batteries.

[0076] Example 6

[0077] A preparation method and application of sodium iron borate, a positive electrode material for sodium ion batteries, comprising:

[0078] (1) Preparation of precursor solution: 0.3 mol of boric acid, 0.2 mol of ferric oxalate and 0.1 mol of sodium carbonate were each dissolved in 10 mL of water, and 0.1 mol of citric acid and 0.09 mol of glucose were dissolved in 20 mL of water. Under stirring at a speed of 2800 r / min, the boric acid solution, ferric oxalate solution and sodium carbonate solution were added to the citric acid and glucose solutions in sequence, and the mixed solution was stirred for 8 h to obtain a clear and transparent mixed solution; stirring was continued to co-precipitate to obtain a precipitate;

[0079] (2) Preparation of precursor: The precipitate obtained in step (1) was dried at 90° C. for 16 h, crushed and sieved to obtain a sodium iron borate precursor;

[0080] (3) Preparation of sodium iron borate: The sodium iron borate precursor obtained in step (2) is moved into a high-temperature furnace, pretreated at 500°C for 3 h under argon protection, and then calcined at 950°C for 12 h. The furnace is cooled to room temperature to obtain sodium iron borate (NaFeBO3), a positive electrode material for sodium ion batteries.

[0081] Example 7

[0082] A preparation method and application of sodium iron borate, a positive electrode material for sodium ion batteries, comprising:

[0083] (1) Preparation of precursor solution: 0.3 mol of ammonium borate, 0.2 mol of ferric nitrate and 0.1 mol of sodium nitrate were each dissolved in 20 mL of water, and 0.1 mol of citric acid and 0.09 mol of glucose were dissolved in 20 mL of water. Under stirring at a speed of 2000 r / min, the boric acid solution, ferric oxalate solution and sodium carbonate solution were added to the citric acid and glucose solutions in sequence, and the mixed solution was stirred for 8 h to obtain a clear and transparent mixed solution; stirring was continued to co-precipitate to obtain a precipitate;

[0084] (2) Preparation of precursor: The precipitate obtained in step (1) was dried at 90° C. for 16 h, crushed and sieved to obtain a sodium iron borate precursor;

[0085] (3) Preparation of sodium iron borate: The sodium iron borate precursor obtained in step (2) is moved into a high-temperature furnace, pretreated at 500°C for 3 h under argon protection, and then calcined at 850°C for 12 h. The furnace is cooled to room temperature to obtain sodium iron borate (NaFeBO3), a positive electrode material for sodium ion batteries.

[0086] Example 8

[0087] A preparation method and application of sodium iron borate, a positive electrode material for sodium ion batteries, comprising:

[0088] (1) Preparation of precursor solution: 0.3 mol of boric acid, 0.2 mol of ferric oxalate and 0.1 mol of sodium nitrate were dissolved in 20 mL of water respectively, and 0.1 mol of glycolic acid and 0.09 mol of sucrose were dissolved in 20 mL of water together. Under stirring at a speed of 2000 r / min, the boric acid solution, ferric oxalate solution and sodium carbonate solution were added to the citric acid and glucose solutions in sequence, and the mixed solution was stirred for 8 h to obtain a clear and transparent mixed solution; stirring was continued to co-precipitate to obtain a precipitate;

[0089] (2) Preparation of precursor: The precipitate obtained in step (1) was dried at 90° C. for 16 h, crushed and sieved to obtain a sodium iron borate precursor;

[0090] (3) Preparation of sodium iron borate: The sodium iron borate precursor obtained in step (2) is moved into a high-temperature furnace, pretreated at 500°C for 3 h under argon protection, and then calcined at 850°C for 12 h. The furnace is cooled to room temperature to obtain sodium iron borate (NaFeBO3), a positive electrode material for sodium ion batteries.

[0091] Example 9

[0092] (1) Preparation of precursor solution: 0.3 mol of ammonium borate, 0.2 mol of ferric nitrate and 0.1 mol of sodium nitrate were each dissolved in 30 mL of water, 0.1 mol of citric acid and 0.09 mol of glucose were dissolved in 25 mL of water, and the boric acid solution, ferric oxalate solution and sodium carbonate solution were added to the citric acid and glucose solutions in sequence under stirring at a speed of 2200 r / min. The mixed solution was stirred for 8 h to obtain a clear and transparent mixed solution; stirring was continued for coprecipitation to obtain a precipitate;

[0093] (2) Preparation of precursor: The precipitate obtained in step (1) was dried at 90° C. for 16 h, crushed and sieved to obtain a sodium iron borate precursor;

[0094] (3) Preparation of sodium iron borate: The sodium iron borate precursor obtained in step (2) is moved into a high-temperature furnace, pretreated at 500°C for 3 h under argon protection, and then calcined at 850°C for 12 h. The furnace is cooled to room temperature to obtain sodium iron borate (NaFeBO3), a positive electrode material for sodium ion batteries.

[0095] Example 10

[0096] (1) Preparation of precursor solution: 0.3 mol of ammonium borate, 0.2 mol of ferric nitrate and 0.1 mol of sodium nitrate were each dissolved in 10 mL of water, 0.1 mol of citric acid and 0.09 mol of glucose were dissolved in 20 mL of water, and the boric acid solution, ferric oxalate solution and sodium carbonate solution were added to the citric acid and glucose solutions in sequence under stirring at a speed of 2800 r / min. The mixed solution was stirred for 8 h to obtain a clear and transparent mixed solution; stirring was continued for coprecipitation to obtain a precipitate;

[0097] (2) Preparation of precursor: The precipitate obtained in step (1) was dried at 90° C. for 16 h, crushed and sieved to obtain a sodium iron borate precursor;

[0098] (3) Preparation of sodium iron borate: The sodium iron borate precursor obtained in step (2) is moved into a high-temperature furnace, pretreated at 500°C for 3 h under argon protection, and then calcined at 900°C for 12 h. The furnace is cooled to room temperature to obtain sodium iron borate (NaFeBO3), a positive electrode material for sodium ion batteries.

[0099] Embodiment 11

[0100] A preparation method and application of sodium iron borate, a positive electrode material for sodium ion batteries, comprising:

[0101] (1) Preparation of precursor suspension: 0.3 mol of boric acid, 0.2 mol of ferric oxalate and 0.1 mol of sodium carbonate were dissolved in 20 mL of water respectively, and 0.1 mol of citric acid and 0.09 mol of glucose were dissolved in 20 mL of water together. Under stirring at a speed of 2000 r / min, the boric acid solution, ferric oxalate solution and sodium carbonate solution were added to the citric acid and glucose solutions in sequence, and stirring was continued for 8 h to obtain a suspension; stirring was continued to co-precipitate to obtain a precipitate;

[0102] (2) Preparation of precursor: The precipitate obtained in step (1) was dried at 90° C. for 16 h, crushed and sieved to obtain a sodium iron borate precursor;

[0103] (3) Preparation of sodium iron borate: The sodium iron borate precursor obtained in step (2) is moved into a high-temperature furnace, pretreated at 500°C for 3 h under argon protection, and then calcined at 850°C for 12 h. The furnace is cooled to room temperature to obtain sodium iron borate (NaFeBO3), a positive electrode material for sodium ion batteries.

[0104] Comparative Example 1

[0105] Sodium ferric borate was prepared according to the method of Example 1, except that boric acid, ferrous oxalate, sodium carbonate, citric acid and glucose were dissolved in 60 ml of water at the same time to prepare sodium ferric borate.

[0106] Comparative Example 2

[0107] Sodium ferric borate was prepared according to the method of Example 1, except that boric acid, ferric oxalate and sodium carbonate were dissolved in 60 ml of water at the same time to prepare sodium ferric borate.

[0108] The properties of the sodium iron borate obtained in Example 1-2 and Comparative Example 1-2 were tested, and the results are shown in Table 1 below.

[0109] Table 1 Performance test results of sodium iron borate obtained in Example 1-2 and Comparative Example 1-2

[0110]

[0111] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing sodium iron borate as a positive electrode material for sodium ion batteries, characterized in that: The steps include: (1) Preparation of a precursor solution or suspension: Add a boron source, a sodium source, and a trivalent iron source to water respectively, and then add them to a carbon source aqueous solution in sequence and continuously stir to obtain a mixed solution; after stirring and coprecipitation reaction, obtain a precipitate; (2) Preparation of sodium iron borate precursor: drying the precipitate obtained in step (1) to obtain a sodium iron borate precursor; (3) Preparation of sodium iron borate: The sodium iron borate precursor obtained in step (2) is pretreated and calcined under an inert atmosphere to obtain sodium iron borate, a positive electrode material for a sodium ion battery.

2. The method for preparing sodium ferric borate as a positive electrode material for sodium ion batteries according to claim 1, characterized in that: In the step (1), the molar ratio of the boron source, the sodium source and the ferric iron source is (1.1-1.15):(1-1.05):

1.

3. The method for preparing sodium ferric borate as a positive electrode material for sodium ion batteries according to claim 1, characterized in that: In the step (1), the molar ratio of the ferric iron source compound to the carbon source compound is 1:(0.5-2).

4. The method for preparing sodium ferric borate as a positive electrode material for sodium ion batteries according to claim 1, characterized in that: In the step (1), the boron source is selected from one of boric acid, ammonium borate and boron trioxide, the sodium source is selected from one of sodium carbonate, sodium hydroxide, sodium oxalate, sodium acetate and sodium nitrate, the ferric iron source is selected from one of ferric oxide, ferric nitrate, ferric oxalate and ferric citrate, and the carbon source is selected from one or more of glucose, citric acid, sucrose, glycolic acid, tartaric acid and ascorbic acid.

5. The method for preparing sodium ferric borate as a positive electrode material for sodium ion batteries according to claim 1, characterized in that: In the step (1), the rotation speed of the stirrer is 1800-3000 rpm.

6. The method for preparing sodium ferric borate as a positive electrode material for sodium ion batteries according to claim 1, characterized in that: The drying temperature in step (2) is 80-180° C. and the drying time is 4-18 hours.

7. The method for preparing sodium ferric borate as a positive electrode material for sodium ion batteries according to claim 1, characterized in that: The step (2) further comprises crushing and screening the sodium iron borate precursor.

8. The method for preparing sodium ferric borate as a positive electrode material for sodium ion batteries according to claim 1, characterized in that: In the step (3), the pretreatment temperature is 300-800° C., the pretreatment time is 2-5 hours, the calcination temperature is 600-1000° C., and the calcination time is 10-24 hours.

9. Sodium ferric borate, a positive electrode material for a sodium ion battery, obtained by the method for preparing sodium ferric borate, a positive electrode material for a sodium ion battery, according to any one of claims 1 to 8.

10. Use of sodium iron borate, a positive electrode material for sodium ion batteries as claimed in claim 9, in batteries.

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