Preparation method of titanium sodium phosphate coated carbon composite manganese-based Prussian blue material and battery

Abstract

The invention discloses a titanium sodium phosphate coated carbon composite manganese-based Prussian blue material and a preparation method thereof, as a positive electrode material, a carbon material is added into a manganese-based Prussian blue slurry subjected to primary aging, and then secondary aging is performed, so that the electronic conductivity of the Prussian blue material is increased, and the conductivity of the Prussian blue material is improved; then adding the sodium titanium phosphate slurry with fixed particle size and concentration at a certain speed, heating and stirring, and then carrying out third aging; by controlling the time and temperature of three times of aging, the sodium titanium phosphate / carbon coated manganese-based Prussian blue positive electrode material with a stable structure and a uniform phase can be obtained. The invention also discloses a sodium ion battery, a positive electrode adopts the titanium sodium phosphate / carbon coated manganese-based Prussian blue positive electrode material, a negative electrode adopts the same titanium sodium phosphate, and the capacity and cycle performance of the battery are tested. The result shows that the battery assembled by using the titanium sodium phosphate coated carbon composite manganese-based Prussian blue material as the positive electrode has excellent specific capacity and better cycle performance.

Description

Technical Field

[0001] The present invention relates to a preparation method of a sodium titanate phosphate-coated carbon composite manganese-based Prussian blue material and a sodium-ion battery using this material as a positive electrode. Background Art

[0002] As one of the preferred materials for positive electrode materials of sodium-ion batteries, Prussian blue and its analogs have many synthesis methods and relatively easy synthesis conditions. Compared with transition metal oxides and polyanion compounds, anions with high electronegativity in their frameworks increase the ion conduction ability and enhance the electrochemical kinetics of the materials, showing great advantages in the application to sodium-ion batteries.

[0003] The theoretical discharge specific capacity of manganese-based Prussian blue is 170 mAh / g, and its energy density is higher than that of Fe-Fe Prussian blue. However, there are many variable valence states of Mn in manganese-based Prussian blue (Mn 2+ 、Mn 3+ 、Mn 4+ ), and the Taylor effect is likely to occur during charge and discharge, resulting in unstable material structure, and even manganese dissolution leading to the collapse of the material structure, thus affecting the battery cycle performance. Therefore, it is of great significance to invent a manganese-based Prussian blue material with a stable structure. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a preparation method of a sodium titanate phosphate-coated carbon composite manganese-based Prussian blue material. On the basis of the manganese-based Prussian blue structure, carbon materials are introduced to increase the electronic conductivity of the Prussian blue material, and a polyanion-type sodium titanate phosphate material with a stable structure is introduced to coat the surface of the original manganese-based Prussian blue material with sodium titanate phosphate, obtaining a manganese-based Prussian blue material with a stable structure, combining the advantages of polyanions and Prussian blue materials, and greatly improving the battery cycle performance.

[0005] Another purpose of the present invention is to provide a sodium-ion battery, with a positive electrode using a sodium titanate phosphate-coated carbon composite manganese-based Prussian blue material and a negative electrode using a sodium titanate phosphate material.

[0006] One technical solution to achieve the above purpose is: a preparation method of a sodium titanate phosphate-coated carbon composite manganese-based Prussian blue material, with the carbon composite amount being 0.2-0.5% of the manganese-based Prussian blue material, and the sodium titanate phosphate coating amount being 0.5-1% of the manganese-based Prussian blue material. The preparation steps are as follows:

[0007] S1. Prepare manganese-based Prussian blue. The specific process is as follows:

[0008] S11. Prepare a divalent manganese salt solution, a sodium citrate solution, and a sodium ferrocyanide solution. Under the protection of an inert atmosphere, the above three solutions are uniformly dropped into a stirring kettle and heated and stirred.

[0009] S12. After the dropping is completed, add a pH regulator to the stirring kettle, adjust the pH to 6 - 8, and continue heating and stirring for 2 - 5 h;

[0010] S13. Place the mixture after heating and stirring in an aging kettle, introduce an inert gas into the aging kettle for protection, and conduct the first aging. Heat during the aging process. The heating temperature for the first aging is 30 - 50 °C, the aging time is 0 - 2 h, and a manganese-based Prussian blue suspension is obtained after the first aging;

[0011] S2. Prepare a carbon composite manganese-based Prussian blue material. The specific process is as follows:

[0012] S21. Dissolve the carbon material in a solvent, and after mixing evenly, form a carbon slurry. The solid content of the carbon slurry is 1 - 5%;

[0013] S22. Add the carbon slurry to the manganese-based Prussian blue suspension obtained in step S13 for the second mixing and the second aging; the temperature for the second mixing is 50 - 70 °C, the heating and stirring speed is 300 - 500 r / min, the time is 10 - 60 min, the temperature for the second aging is 50 - 70 °C, the aging time is 2 - 6 h, and a carbon composite manganese-based Prussian blue suspension is obtained after the second aging;

[0014] S3. Prepare a sodium titanium phosphate slurry. The specific process is as follows:

[0015] S31. Shear and crush sodium titanium phosphate until the particle size of the material D50 = 200 - 800 nm;

[0016] S32. Add the sodium titanium phosphate material that has reached the target particle size after crushing and a dispersant together to deionized water, stir and disperse, and mix evenly to prepare a sodium titanium phosphate slurry. The solid content of the sodium titanium phosphate slurry is 10 - 30%;

[0017] S4. Add the sodium titanium phosphate slurry obtained in step S32 to the carbon composite manganese-based Prussian blue suspension obtained in step S22 for the third mixing and the third aging. The temperature for the third mixing is 20 - 30 °C, the heating and stirring speed is 300 - 500 r / min, the time is 10 - 60 min, the temperature for the third aging is 20 - 30 °C, the aging time is 2 - 6 h, and a sodium titanium phosphate-coated carbon composite manganese-based Prussian blue slurry is obtained after the third aging;

[0018] S5. Conduct vacuum filtration on the sodium titanium phosphate-coated carbon composite manganese-based Prussian blue slurry, wash it twice with a solvent, and finally place the washed filter cake in a vacuum drying oven for drying to obtain the target product, sodium titanium phosphate-coated carbon composite manganese-based Prussian blue material.

[0019] In the preparation method of the above-mentioned sodium titanium phosphate-coated carbon composite manganese-based Prussian blue material, in step S11, the concentrations of the divalent manganese salt solution and the sodium ferrocyanide solution are 0.5-2 mol / L.

[0020] In the preparation method of the above-mentioned sodium titanium phosphate-coated carbon composite manganese-based Prussian blue material, in step S12, the pH regulator uses at least one of ammonia water and sodium hydroxide.

[0021] In the preparation method of the above-mentioned sodium titanium phosphate-coated carbon composite manganese-based Prussian blue material, in step S11, during the solution dropping process, the heating and stirring temperature is 70-90 °C, and the heating and stirring speed is 800-1500 r / min;

[0022] In step S12, after the dropping is completed, the heating and stirring temperature is 50-70 °C, and the heating and stirring speed is 300-500 r / min.

[0023] In the preparation method of the above-mentioned sodium titanium phosphate-coated carbon composite manganese-based Prussian blue material, after the first aging, the particle size D90 of the manganese-based Prussian blue material in the manganese-based Prussian blue suspension is 3-5 microns.

[0024] In the preparation method of the above-mentioned sodium titanium phosphate-coated carbon composite manganese-based Prussian blue material, in step S21, the solvent uses at least one of ethanol, methanol, acetone, acetic acid, ethylene glycol, and glycerol;

[0025] The carbon material uses at least one of graphite, acetylene black, carbon nanotube oil-based slurry, carbon nanotube water-based slurry, graphene oil-based slurry, graphene water-based slurry, and Ketjen black. The particle size D90 of all carbon materials is less than 2 microns.

[0026] In the preparation method of the above-mentioned sodium titanium phosphate-coated carbon composite manganese-based Prussian blue material, in step S32, the dispersant uses at least one of polyvinylpyrrolidone, N-methyl-2-pyrrolidone, polyacrylic acid, ethylene glycol, polyethylene glycol, and other polyols. The general formula of other polyols is C n H 2n+2-x (OH) x , where x≥2.

[0027] In the preparation method of the above-mentioned sodium titanium phosphate-coated carbon composite manganese-based Prussian blue material, in step S5, the vacuum drying temperature is 80-200 °C, and the drying time is 5-15 h.

[0028] The present invention also provides a sodium-ion battery. The positive electrode of the sodium-ion battery uses the sodium titanium phosphate-coated carbon composite manganese-based Prussian blue material prepared by the preparation method described in any one of the above, and the negative electrode of the sodium-ion battery uses the sodium titanium phosphate material used in the sodium titanium phosphate-coated carbon composite manganese-based Prussian blue material.

[0029] The above sodium-ion battery, wherein the electrolyte of the sodium-ion battery is an aqueous or mixed electrolyte.

[0030] The preparation method of the sodium titanate phosphate-coated carbon composite manganese-based Prussian blue material of the present invention, and the technical solution of the sodium-ion battery using the sodium titanate phosphate-coated carbon composite manganese-based Prussian blue material as the positive electrode have the following beneficial effects:

[0031] (1) By controlling the three aging times and temperatures, the uniformity and stability of the main manganese-based Prussian blue phase of the material are improved;

[0032] (2) By adding the carbon material and the sodium titanate phosphate coating material in batches, the electronic conductivity and cycle stability of the Prussian blue material are greatly improved;

[0033] (3) Using the sodium titanate phosphate-coated carbon composite manganese-based Prussian blue material as the positive electrode material improves the structural stability of the manganese-based Prussian blue material during the charge and discharge process of the battery, effectively preventing structural changes or even collapse caused by manganese dissolution, thereby improving the cycle performance of the battery;

[0034] (4) Using the sodium titanate phosphate-coated carbon composite manganese-based Prussian blue material as the positive electrode and sodium titanate phosphate as the negative electrode promotes sodium ion transport and enables long-term cycling of the battery;

[0035] (5) Using the sodium titanate phosphate material as both the coating material and the negative electrode material of the positive electrode gives full play to the stability structure of this polyanion material of sodium titanate phosphate. Description of the Drawings

[0036] Figure 1 It is a flowchart of the preparation method of the sodium titanate phosphate-coated carbon composite manganese-based Prussian blue material of the present invention;

[0037] Figure 2 It is a schematic structural diagram of the sodium titanate phosphate-coated carbon composite manganese-based Prussian blue material;

[0038] Figure 3 It is a charge and discharge curve graph of Example 1;

[0039] Figure 4 It is a cycle curve graph of Example 1. Detailed Embodiments

[0040] In order to enable those skilled in the art of the present technology to better understand the technical solution of the present invention, the following describes its detailed embodiments in conjunction with the drawings:

[0041] Table 1, Table of carbon composite content and sodium titanate phosphate coating layer content in each embodiment:

[0042] Carbon composite content Content of sodium titanate phosphate coating layer Example 1 0.3 0.8 Example 2 0.2 1 Example 3 0.5 0.5 Example 4 0 1 Example 5 0.8 0.8 Example 6 0.3 0 Example 7 0.3 1.5

[0043] In the sodium titanium phosphate-coated carbon composite manganese-based Prussian blue material, the carbon composite content is 0.2-0.5% of the manganese-based Prussian blue material, and the sodium titanium phosphate coating content is 0.5-1% of the manganese-based Prussian blue material.

[0044] Please refer to Figure 1 and Figure 2 , and referring to the carbon composite content and sodium titanium phosphate coating layer content in Table 1, the sodium titanium phosphate-coated carbon composite manganese-based Prussian blue materials of Examples 1-7 are prepared by the following preparation steps:

[0045] S1. Prepare manganese-based Prussian blue. The specific process is as follows:

[0046] S11. Select manganese sulfate tetrahydrate as the divalent manganese salt, ascorbic acid as the pH regulator, and sodium citrate solution as the buffer. Prepare 1 mol / L manganese sulfate tetrahydrate solution, sodium ferrocyanide solution, and citric acid solution respectively, and drop the three solutions into the stirring kettle at a speed of 0.5 L / min. During the dropping process, nitrogen is introduced for protection, and heating and stirring are carried out. The heating and stirring temperature is 80 °C, and the heating and stirring speed is 1200 r / min;

[0047] S12. After the dropping is completed, add ascorbic acid (pH regulator) to the stirring kettle, adjust the pH to 7, and continue heating and stirring for 2 h. The heating and stirring temperature is 60 °C, and the heating and stirring speed is 400 r / min;

[0048] S13. Place the heated and stirred mixture in an aging kettle, introduce nitrogen (inert gas) into the aging kettle for protection, and carry out the first aging. The heating temperature during the aging process is 40 °C, and the aging time is 1 h. After the first aging, a manganese-based Prussian blue suspension is obtained;

[0049] S2. Prepare the carbon composite manganese-based Prussian blue material. The specific process is as follows:

[0050] S21. Dissolve the carbon nanotube oil-based slurry (carbon material) in ethanol (solvent), and after mixing evenly, form a carbon slurry. The solid content of the carbon slurry is 1-52%;

[0051] S22. Add the carbon slurry to the manganese-based Prussian blue suspension obtained in step S13 according to the ratio in Table 1, so that the final carbon content is the carbon composite content corresponding to each example in Table 1, and carry out the second mixing and the second aging; the second mixing temperature is 60 °C, the heating and stirring speed is 400 r / min, and the time is 30 min. The second aging temperature is 60 °C, and the aging time is 3 h. After the second aging, a carbon composite manganese-based Prussian blue suspension is obtained;

[0052] S3. Prepare the sodium titanium phosphate slurry. The specific process is as follows:

[0053] S31, shear and crush sodium titanium phosphate to a material particle size D50 = 300 nm;

[0054] S32, add the crushed sodium titanium phosphate material reaching the target particle size and a dispersant (polyacrylic acid, 0.5%) into deionized water, stir and disperse, and mix evenly to prepare a sodium titanium phosphate slurry, with the solid content of the sodium titanium phosphate slurry being 15%;

[0055] S4, add the sodium titanium phosphate slurry obtained in step S32 into the carbon composite manganese-based Prussian blue suspension obtained in step S22 according to the proportions in Table 1, so that the final sodium titanium phosphate coating amount is the sodium titanium phosphate coating layer content corresponding to each example in Table 1, perform the third mixing and aging, with the third mixing temperature being 25 °C, the heating and stirring speed being 400 r / min, the time being 30 min, the third aging temperature being 25 °C, and the aging time being 3 h. After the third aging, a sodium titanium phosphate-coated carbon composite manganese-based Prussian blue slurry is obtained;

[0056] S5, perform vacuum filtration on the sodium titanium phosphate-coated carbon composite manganese-based Prussian blue slurry, wash it twice with a solvent, and finally place the washed filter cake in a vacuum drying oven for drying. The vacuum drying temperature is 120 °C, and the drying time is 10 h to obtain the target product, the sodium titanium phosphate-coated carbon composite manganese-based Prussian blue material.

[0057] A sodium-ion battery uses a sodium titanium phosphate-coated carbon composite manganese-based Prussian blue material as the positive electrode active material and a sodium titanium phosphate material as the negative electrode active material. The preparation method of the sodium-ion battery includes the following steps:

[0058] A, Slurry preparation: Respectively use the sodium titanium phosphate-coated carbon composite manganese-based Prussian blue materials prepared in Examples 1-7 as the positive electrode active material, and the sodium titanium phosphate used in step S3 as the negative electrode active material. Weigh 92.0 g of the positive and negative electrode active materials, 4.0 g of the conductive agent conductive carbon black, 1 g of the conductive agent carbon nanotube dry powder, and 3.0 g of the binder PVDF dry powder, add 150 g of the solvent NMP, and put them into a ball mill tank to ball mill at a speed of 400 rpm for 180 min to obtain the positive and negative electrode slurries respectively;

[0059] B, Preparation of positive and negative electrode sheets: Pour the positive and negative electrode slurries into the trough of a transfer coater, control the transfer die head to coat on an aluminum foil with a thickness of 12 μm, dry it in an oven at 130 °C, coat the front side first and then the back side to obtain the positive and negative electrode rolls respectively; Pass the positive and negative electrode rolls through a roll press with a roll pressure of 4.0 MPa to obtain the compacted positive and negative electrode rolls respectively. Then respectively perform die cutting on the compacted positive and negative electrode rolls to obtain a positive electrode sheet with a size of 56 mm * 43 mm and a negative electrode sheet with a size of 58 mm * 45 mm;

[0060] C, Sodium-ion battery assembly: Stack the sheets in a zigzag pattern in the order of "positive electrode sheet, separator, negative electrode sheet, separator". The number of stacked sheets is 4 layers of positive electrode sheets and 5 layers of negative electrode sheets. After making and welding the electrode tabs, encapsulate the top and bottom edges with a pre-punched aluminum-plastic film. Place the dry battery cell in a vacuum oven with a vacuum degree of -0.095 MPa and a temperature of 120 °C and bake for 12 h to obtain a dry battery cell. Take out the dry battery cell and put it into a glove box. After injecting an electrolyte with a concentration of 1 mol / L, complete the side encapsulation to obtain a sodium-ion battery to be formed. Among them, the electrolyte is prepared by dissolving sodium perchlorate in ethylene carbonate.

[0061] Please refer to Figure 3 and Figure 4 , use the sodium titanate phosphate-coated carbon composite manganese-based Prussian blue material of Examples 1-7 as the positive electrode, and conduct the following performance tests on the finally obtained sodium-ion batteries:

[0062] Battery activation: Send the assembled sodium-ion battery into an incubator at 45 °C and activate the battery using a Blue Power charge and discharge instrument. The activation voltage range is 0.5-2 V, and the charge and discharge rate is 0.1 C for 3 weeks of charge and discharge.

[0063] Battery cycle stability test: Conduct a 2C, 5000-cycle stability test on the activated sodium-ion battery, and the charge and discharge voltage range is 0.5-2 V. During the test, the instrument automatically records the charge and discharge data and related curves. The cycle curve of Example 1 is shown in Figure 4 .

[0064] Battery rate performance test: Conduct constant current charge and discharge tests on the activated battery at 0.1C, 0.5C, 2C, and 10C, and the charge and discharge voltage range is 0.5-2 V. During the test, the instrument automatically records the charge and discharge data and related curves. The charge and discharge curve of Example 1 is shown in Figure 3 .

[0065] The performance test results are shown in Table 2.

[0066] Table 2, Performance test results table of sodium-ion batteries assembled in each example:

[0067]

[0068] It can be seen from the results in Table 2 that within the scope protected by the present invention, in Examples 1-3, the carbon composite content is 0.2-0.5%, the sodium titanate phosphate coating amount is 0.5-1%, and there is not much difference in the rate performance and cycle stability of the battery. After testing the battery capacity and cycle performance, the results show that the battery assembled with the sodium titanate phosphate-coated carbon composite manganese-based Prussian blue material as the positive electrode has excellent specific capacity and better cycle performance.

[0069] According to the test results of Example 4, when the carbon composite content is zero, even if the coating amount of sodium titanium phosphate is 10%, its rate performance drops significantly (especially at high rates, the drop is even greater), mainly because the battery transmission is restricted. In the absence of carbon materials, the growth defects of the Prussian blue material are exposed, and with the progress of cycling, it causes the corrosion of the material, resulting in the decline of the cycling performance.

[0070] According to the test results of Example 5, when the carbon content is too high, due to the relatively low density of the carbon material, the loose bulk density of the obtained powder is very low, resulting in a relatively low solid content of the slurry. Although the battery rate performance is relatively good, the cycle performance decreases by 10%. This is mainly because too much carbon material will cause side reactions during cycling, leading to the decomposition of the electrolyte.

[0071] According to the test results of Examples 6 and 7, without the sodium titanium phosphate coating layer, the cycle stability drops sharply. However, when the content of the sodium titanium phosphate coating layer is too high, since it does not provide the positive electrode capacity, the capacity of the battery decreases. Excessive sodium titanium phosphate may produce a catalytic effect on Ti ions at the positive electrode voltage, resulting in the decline of the cycle stability.

[0072] The sodium titanium phosphate-coated carbon composite manganese-based Prussian blue material of the present invention is prepared by adding carbon materials to the manganese-based Prussian blue slurry after the first aging, followed by secondary aging to increase the electronic conductivity of the Prussian blue material. Then, a sodium titanium phosphate slurry with a fixed particle size and concentration is added at a certain speed, and heating and stirring are carried out, followed by the third aging. The parameter conditions for the three aging processes are shown in Table 3.

[0073] Table 3, Parameter Table for Three Aging Processes:

[0074] Aging times Purpose Stirring temperature Aging temperature Aging time The first time Growth of primary particle size of Prussian blue for the first time 50～70℃ 30～50℃ 0-2h The second time Carbon composite 50～70℃ 50～70℃ 2-6h The third time Sodium titanate phosphate coating 20-30℃ 20-30℃ 2-6h

[0075] The purpose of the first aging is to grow the primary particle size of Prussian blue. The aging temperature should be reduced and the aging time should be shortened to avoid the primary particle size growing too large and affecting the ion transport rate.

[0076] During the second aging, the purpose of stirring is to form a uniformly mixed complex of carbon materials and Prussian blue materials. During the aging stage, due to the combined action of the defects generated during the crystallization process of the Prussian blue material and the unsaturated functional groups of the carbon materials, the two will attract each other and agglomerate together to form carbon composite Prussian blue secondary particles.

[0077] The purpose of the third aging is to coat the outer surface of the carbon composite Prussian blue secondary particles with nanoscale sodium titanium phosphate powder. The key points are the dispersibility and particle distribution of the sodium titanium phosphate slurry, and the stirring temperature and aging temperature can be selected at room temperature.

[0078] By controlling the time and temperature of the three - stage aging, a sodium titanium phosphate / carbon - coated manganese - based Prussian blue cathode material with stable structure and uniform phase can be obtained.

[0079] In summary, for the sodium titanium phosphate - coated carbon composite manganese - based Prussian blue material prepared by the preparation method of the present invention, as a cathode material, it improves the structural stability of the manganese - based Prussian blue material during the charge - discharge process of the battery, effectively prevents the structural changes or even collapse caused by manganese dissolution, and thus improves the cycle performance of the battery.

[0080] Those of ordinary skill in the art should recognize that the above embodiments are only used to illustrate the present invention, rather than to limit the present invention. As long as within the scope of the spirit of the present invention, changes and modifications to the above - described embodiments will fall within the scope of the claims of the present invention.

Claims

1. A method for preparing a sodium titanium phosphate-coated carbon composite manganese-based Prussian blue material, characterized in that: The carbon compounding amount is 0.2-0.5% of the manganese-based Prussian blue material, and the sodium titanium phosphate coating amount is 0.5-1% of the manganese-based Prussian blue material. The preparation steps are as follows: S1, preparing manganese-based Prussian blue, the specific steps are: S11, preparing a divalent manganese salt solution, a sodium citrate solution and a sodium ferrocyanide solution, and adding the three solutions dropwise into a stirring kettle at a uniform speed under the protection of an inert atmosphere, and heating and stirring; S12, after the dropwise addition is completed, a pH adjuster is added to the stirring tank, and the pH is adjusted to 6 to 8, and heating and stirring are continued for 2 to 5 hours; S13, placing the heated and stirred mixture in an aging kettle, introducing an inert gas into the aging kettle for protection, performing a first aging, heating the aging process, the first aging heating temperature is 30 to 50° C., the aging time is 0 to 2 h, and after the first aging, a manganese-based Prussian blue suspension is obtained; S2, preparing carbon composite manganese-based Prussian blue material, the specific process is as follows: S21, dissolving the carbon material in a solvent, and mixing them evenly to form a carbon slurry, wherein the solid content of the carbon slurry is 1 to 5%; S22, adding the carbon slurry to the manganese-based Prussian blue suspension obtained in step S13, performing a second mixing and a second aging; the second mixing temperature is 50-70°C, the heating and stirring speed is 300-500r / min, the time is 10-60min, the second aging temperature is 50-70°C, the aging time is 2-6h, and a carbon composite manganese-based Prussian blue suspension is obtained after the second aging; S3, preparing sodium titanium phosphate slurry, the specific steps are: S31, shearing and crushing the sodium titanium phosphate to a material particle size D50 = 200-800 nm; S32, adding the sodium titanium phosphate material that has reached the target particle size after crushing and a dispersant into deionized water, stirring and dispersing, and mixing evenly to prepare a sodium titanium phosphate slurry, wherein the solid content of the sodium titanium phosphate slurry is 10 to 30%; S4, adding the sodium titanium phosphate slurry obtained in step S32 to the carbon-composite manganese-based Prussian blue suspension obtained in step S22, and performing a third mixing and aging, wherein the third mixing temperature is 20-30°C, the heating stirring speed is 300-500r / min, the time is 10-60min, the third aging temperature is 20-30°C, the aging time is 2-6h, and after the third aging, a sodium titanium phosphate-coated carbon-composite manganese-based Prussian blue slurry is obtained; S5, vacuum filter the sodium titanium phosphate-coated carbon composite manganese-based Prussian blue slurry, wash it twice with a solvent, and finally place the washed filter cake in a vacuum drying oven to obtain the target product, sodium titanium phosphate-coated carbon composite manganese-based Prussian blue material.

2. The method for preparing a sodium titanium phosphate-coated carbon composite manganese-based Prussian blue material according to claim 1, characterized in that: In step S11, the concentrations of the divalent manganese salt solution and the sodium ferrocyanide solution are 0.5-2 mol / L.

3. The method for preparing a sodium titanium phosphate-coated carbon composite manganese-based Prussian blue material according to claim 1, characterized in that: In step S12, the pH adjuster is at least one of ammonia water and sodium hydroxide.

4. The method for preparing a sodium titanium phosphate-coated carbon composite manganese-based Prussian blue material according to claim 1, characterized in that: In step S11, during the solution dropwise addition process, the heating and stirring temperature is 70-90°C, and the heating and stirring speed is 800-1500 r / min; In step S12, after the dropwise addition is completed, the heating and stirring temperature is 50-70°C, and the heating and stirring speed is 300-500 r / min.

5. The method for preparing a sodium titanium phosphate-coated carbon composite manganese-based Prussian blue material according to claim 1, characterized in that: After the first aging, the particle size D90 of the manganese-based Prussian blue material in the manganese-based Prussian blue suspension is 3-5 microns.

6. The method for preparing a sodium titanium phosphate-coated carbon composite manganese-based Prussian blue material according to claim 1, characterized in that: In step S21, the solvent is at least one of ethanol, methanol, acetone, acetic acid, ethylene glycol and glycerol; The carbon material is at least one of graphite, acetylene black, carbon nanotube oily slurry, carbon nanotube aqueous slurry, graphene oily slurry, graphene aqueous slurry and Ketjen black, and the particle size D90 of all carbon materials is less than 2 microns.

7. The method for preparing a sodium titanium phosphate-coated carbon composite manganese-based Prussian blue material according to claim 1, characterized in that: In step S32, the dispersant is at least one of polyvinyl pyrrolidone, N-methyl-2-pyrrolidone, polyacrylic acid, ethylene glycol, polyethylene glycol and other polyols, and the general formula of the other polyols is C n H 2n+2-x (OH) x , where x ≥ 2.

8. The method for preparing a sodium titanium phosphate-coated carbon composite manganese-based Prussian blue material according to claim 1, characterized in that: In step S5, the vacuum drying temperature is 80 to 200° C., and the drying time is 5 to 15 hours.

9. A sodium ion battery, characterized in that: The positive electrode of the sodium ion battery adopts the sodium titanium phosphate-coated carbon composite manganese-based Prussian blue material prepared by the preparation method according to any one of claims 1 to 8, and the negative electrode of the sodium ion battery adopts the sodium titanium phosphate material used in the sodium titanium phosphate-coated carbon composite manganese-based Prussian blue material.

10. The sodium ion battery according to claim 9, characterized in that: The electrolyte of sodium ion battery is aqueous or mixed electrolyte.

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