A carbon-coated magnesium titanium phosphate electrode material and a preparation method thereof, and a carbon-coated magnesium titanium phosphate composite electrode

Abstract

The present invention belongs to the technical field of electrode materials, and provides a carbon-coated magnesium titanium phosphate electrode material and a preparation method thereof, and a carbon-coated magnesium titanium phosphate composite electrode. The present invention uses a solvent thermal method with a short reaction time and a low temperature to synthesize a magnesium titanium phosphate precursor with uniform morphology, and synthesizes a magnesium titanium phosphate with high purity through secondary sintering; after being compounded with glucose, it is sintered once to form a carbon-coated magnesium titanium phosphate. Its morphology is a three-dimensional tunnel structure, and the thickness of the carbon layer compounded on the surface of the magnesium titanium phosphate is 3 to 5 nm. The present invention improves the rate performance of the magnesium titanium phosphate electrode material and extends its cycle life by improving the conductivity of the magnesium titanium phosphate.

Description

Technical Field

[0001] The invention relates to the technical field of electrode materials, and in particular to a carbon-coated magnesium titanium phosphate electrode material and a preparation method thereof, and a carbon-coated magnesium titanium phosphate composite electrode. Background Art

[0002] Magnesium-ion batteries have shown great advantages as a substitute for lithium-ion batteries and have become the next generation of electrochemical energy storage technology. Compared with lithium, magnesium is abundant in the earth, evenly distributed, and easy to mine, which has an inherent cost advantage. 2+ The divalent nature of magnesium has a volume capacity of 3833 mAh / cm 3 , than lithium (2046mAh / cm 3 Most importantly, unlike lithium and sodium metal anodes, magnesium metal can be safely handled in ambient environments and does not grow dendrites when deposited, suggesting greater safety in practical applications.

[0003] The sodium superion structure NASICON is very attractive for use in batteries due to its high safety and long life. NASICON structural materials have an open framework structure with fast ion diffusion capabilities, which allows them to not undergo major structural changes when alkali metal ions or alkaline earth metal ions are inserted and removed, causing structural collapse and affecting cycle life. Titanium-based phosphate framework materials have high structural stability, easy production and rich structural diversity. Magnesium has a smaller atomic radius and a higher specific surface charge density than sodium in the same period, so the polarization effect of magnesium ions is also stronger than that of sodium ions. Magnesium titanium phosphate also exhibits different characteristics from sodium titanium phosphate in electrochemical properties, and it also has certain potential as a substitute for lithium-ion batteries.

[0004] Magnesium titanium phosphate has the excellent properties of NASICON structural materials, but it also inevitably performs poorly in terms of conductivity, resulting in poor rate performance and large cycle attenuation. Common improvement methods include preparing nano-sized materials, metal doping, highly conductive material modification, and carbon layer coating. Compared with other improvement methods, carbon layer coating has the advantages of simple operation and abundant carbon sources.

[0005] Therefore, by improving magnesium titanium phosphate, researching and developing a magnesium titanium phosphate electrode material with excellent conductivity, rate performance and long cycle life, it undoubtedly has great potential as a candidate material for the next generation of large-scale energy storage. Summary of the invention

[0006] The purpose of the present invention is to provide a carbon-coated magnesium titanium phosphate electrode material and a preparation method thereof and a carbon-coated magnesium titanium phosphate composite electrode in order to overcome the deficiencies of the prior art. The present invention uses a solvent thermal method with a short reaction time and a low temperature to synthesize a magnesium titanium phosphate precursor with uniform morphology, and synthesizes a magnesium titanium phosphate with high purity through secondary sintering; after being compounded with glucose, it is sintered once to form a carbon-coated magnesium titanium phosphate. Its morphology is a three-dimensional tunnel structure, and the thickness of the carbon layer compounded on the surface of the magnesium titanium phosphate is 3 to 5 nm. The present invention improves the rate performance of the magnesium titanium phosphate electrode material and extends its cycle life by improving the conductivity of the magnesium titanium phosphate.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a method for preparing a carbon-coated magnesium titanium phosphate electrode material, comprising the following steps:

[0009] 1) mixing a mixed solution of magnesium acetate dihydrate and ammonium dihydrogen phosphate with a n-butyl titanate solution and reacting the mixture to obtain a precursor;

[0010] 2) The precursor is subjected to a first grinding, a first sintering, a second grinding, and a second sintering under a protective atmosphere in sequence to obtain magnesium titanium phosphate;

[0011] 3) Mixing magnesium titanium phosphate, glucose and ethanol solution, drying, refining and sintering in sequence to obtain a carbon-coated magnesium titanium phosphate electrode material.

[0012] Preferably, in step 1), the mass volume ratio of magnesium acetate dihydrate, ammonium dihydrogen phosphate and n-butyl titanate is 0.4-0.7 g: 1.5-2.5 g: 2-5 mL; the solvent in the mixed solution is water; the mass volume ratio of magnesium acetate dihydrate and water is 0.4-0.7 g: 10-30 mL; the solvent in the n-butyl titanate solution is anhydrous ethanol; the volume ratio of n-butyl titanate and anhydrous ethanol is 2-5: 50-70.

[0013] Preferably, the mixing time in step 1) is 2 to 4 hours; the reaction temperature is 140 to 180° C., and the reaction time is 2 to 4 hours.

[0014] Preferably, in step 2), the temperature of the first sintering is 300-500°C, and the time of the first sintering is 2-4 hours; the temperature of the second sintering is 700-900°C, and the time of the second sintering is 3-5 hours; the heating rate to the second sintering temperature is 3-7°C / min.

[0015] Preferably, in step 3), the volume ratio of anhydrous ethanol to water in the ethanol solution is 1-2:1-2; the mass volume ratio of the magnesium titanium phosphate, glucose and ethanol solution is 0.9-1.2 g: 0.1-0.3 g: 20-40 mL.

[0016] Preferably, in step 3), the mixing time is 5 to 7 hours; the drying temperature is 60 to 100°C, and the drying time is 10 to 12 hours; the sintering temperature is 600 to 1000°C, and the sintering time is 4 to 6 hours; and the heating rate to the sintering temperature is 8 to 12°C / min.

[0017] The present invention also provides a carbon-coated magnesium titanium phosphate electrode material obtained by the preparation method.

[0018] The present invention also provides a carbon-coated magnesium titanium phosphate composite electrode comprising the carbon-coated magnesium titanium phosphate electrode material, wherein the carbon-coated magnesium titanium phosphate composite electrode comprises the carbon-coated magnesium titanium phosphate electrode material, acetylene black and polyvinylidene fluoride;

[0019] The mass ratio of the carbon-coated magnesium titanium phosphate electrode material, acetylene black and polyvinylidene fluoride is 6-8:1-3:1-2.

[0020] Beneficial effects of the present invention:

[0021] The present invention prepares the precursor by a solvothermal method, and the synthesis temperature is low, the time is short, and the synthesized magnesium titanium phosphate has high purity. Cheap glucose is used as a carbon source to coat the magnesium titanium phosphate, which not only improves the conductivity but also forms a protective layer for the magnesium titanium phosphate to extend the cycle life. After the secondary sintering, the magnesium titanium phosphate is coated with glucose. The third sintering is to form a carbon layer on the surface of the magnesium titanium phosphate. The introduction of other substances into the carbon layer does not change the NASICON structure of the magnesium titanium phosphate, which provides the possibility of doping other substances. The carbon-coated magnesium titanium phosphate electrode material prepared by the present invention can be used not only in organic electrolytes, but also in aqueous electrolytes. Aqueous batteries can be constructed using suitable positive electrode materials without affecting the environment. Therefore, it has great potential as a candidate material for the next generation of large-scale energy storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a scanning electron microscope image of the magnesium titanium phosphate electrode material of Example 1;

[0023] Figure 2 This is a scanning electron microscope image of the carbon-coated magnesium titanium phosphate electrode material of Example 2;

[0024] Figure 3 is an X-ray diffraction pattern of the carbon-coated magnesium titanium phosphate electrode material of Example 2;

[0025] Figure 4This is a cycle stability curve of the carbon-coated magnesium titanium phosphate composite electrode of Example 6 at a discharge rate of 1C. DETAILED DESCRIPTION

[0026] The present invention provides a method for preparing a carbon-coated magnesium titanium phosphate electrode material, comprising the following steps:

[0027] 1) mixing a mixed solution of magnesium acetate dihydrate and ammonium dihydrogen phosphate with a n-butyl titanate solution and reacting the mixture to obtain a precursor;

[0028] 2) The precursor is subjected to a first grinding, a first sintering, a second grinding, and a second sintering under a protective atmosphere in sequence to obtain magnesium titanium phosphate;

[0029] 3) Mixing magnesium titanium phosphate, glucose and ethanol solution, drying, refining and sintering in sequence to obtain a carbon-coated magnesium titanium phosphate electrode material.

[0030] In step 1) of the present invention, the mass volume ratio of magnesium acetate dihydrate, ammonium dihydrogen phosphate and n-butyl titanate is preferably 0.4-0.7 g: 1.5-2.5 g: 2-5 mL, and more preferably 0.5-0.6 g: 1.7-2.2 g: 3-4 mL; the solvent in the mixed solution is preferably water, and more preferably ultrapure water; the mass volume ratio of magnesium acetate dihydrate and water is preferably 0.4-0.7 g: 10-30 mL, and more preferably 0.5-0.6 g: 15-25 mL; the solvent in the n-butyl titanate solution is preferably anhydrous ethanol; the volume ratio of n-butyl titanate and anhydrous ethanol is preferably 2-5: 50-70, and more preferably 3-4: 55-65.

[0031] The mixing time of step 1) of the present invention is preferably 2 to 4 hours, more preferably 2 to 3 hours; the reaction temperature is preferably 140 to 180° C., more preferably 150 to 170° C.; the reaction time is preferably 2 to 4 hours, more preferably 2 to 3 hours.

[0032] After the reaction in step 1) of the present invention is completed, it is preferred that the process further includes cooling, centrifugation, washing and drying. The cooling is preferably to room temperature. The washing reagents are preferably ultrapure water and anhydrous ethanol. The ultrapure water and anhydrous ethanol are washed 2 to 4 times respectively. The drying temperature is preferably 60 to 100° C., and the time is preferably 10 to 14 hours.

[0033] The temperature of the first sintering in step 2) of the present invention is preferably 300-500°C, more preferably 350-450°C; the time of the first sintering is preferably 2-4h, more preferably 2-3h; the temperature of the second sintering is preferably 700-900°C, more preferably 750-850°C; the time of the second sintering is preferably 3-5h, more preferably 4-5h; the heating rate to the second sintering temperature is preferably 3-7°C / min, more preferably 4-6°C / min.

[0034] In step 3) of the present invention, the volume ratio of anhydrous ethanol and water in the ethanol solution is preferably 1-2:1-2, and more preferably 1:1; the mass volume ratio of the magnesium titanium phosphate, glucose and ethanol solution is preferably 0.9-1.2g:0.1-0.3g:20-40mL, and more preferably 1.0-1.1g:0.2-0.3g:20-30mL.

[0035] The mixing time in step 3) of the present invention is preferably 5 to 7 hours, and more preferably 6 to 7 hours; the drying temperature is preferably 60 to 100°C, and more preferably 80 to 90°C; the drying time is preferably 10 to 12 hours, and more preferably 10 to 11 hours; the sintering temperature is preferably 600 to 1000°C, and more preferably 700 to 900°C; the sintering time is preferably 4 to 6 hours, and more preferably 4 to 5 hours; the heating rate to the sintering temperature is preferably 8 to 12°C / min, and more preferably 9 to 11°C / min.

[0036] The present invention also provides a carbon-coated magnesium titanium phosphate electrode material obtained by the preparation method.

[0037] The present invention also provides a carbon-coated magnesium titanium phosphate composite electrode comprising the carbon-coated magnesium titanium phosphate electrode material, wherein the carbon-coated magnesium titanium phosphate composite electrode comprises the carbon-coated magnesium titanium phosphate electrode material, acetylene black and polyvinylidene fluoride;

[0038] The mass ratio of the carbon-coated magnesium titanium phosphate electrode material, acetylene black and polyvinylidene fluoride is preferably 6-8:1-3:1-2, and more preferably 7:2:1.

[0039] The present invention also provides a method for preparing the carbon-coated magnesium titanium phosphate composite electrode, wherein the carbon-coated magnesium titanium phosphate electrode material, acetylene black, polyvinylidene fluoride and 1-methylpyrrolidone are mixed and then coated on a copper foil and dried to obtain a carbon-coated magnesium titanium phosphate composite electrode.

[0040] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0041] Example 1

[0042] Dissolve 0.55g of magnesium acetate dihydrate and 1.74g of ammonium dihydrogen phosphate in 20mL of ultrapure water to obtain a mixed solution, and dissolve 3.4mL of n-butyl titanate in 60mL of anhydrous ethanol to obtain an n-butyl titanate solution. Add the mixed solution drop by drop into the n-butyl titanate solution under strong stirring, mix at room temperature for 3h after the dripping, transfer to a high-pressure reactor, and react at 160℃ for 3h. After the reaction is completed, cool to room temperature and take out the precursor, wash it with ultrapure water and anhydrous ethanol respectively by centrifugation for 3 times, and then dry it in an oven at 80℃ for 12h.

[0043] After the above precursor is ground for the first time, it is sintered for the first time at 350°C for 3 hours. After cooling to room temperature, it is ground for the second time. It is sintered for the second time in an argon atmosphere at a heating rate of 5°C / min to 800°C and sintered for 4 hours. After cooling to room temperature, it is taken out and ground to obtain a magnesium titanium phosphate electrode material.

[0044] The magnesium titanium phosphate electrode material, acetylene black and polyvinylidene fluoride were mixed in a mass ratio of 7:2:1, dispersed in 0.25g of 1-methylpyrrolidone and stirred at room temperature for 6h to prepare a slurry, which was coated on a copper foil and dried in an oven at 80°C for 12h. After cooling, the magnesium titanium phosphate composite electrode was obtained by cutting it into small discs with a diameter of 14mm using a slicer.

[0045] The magnesium titanium phosphate electrode material obtained in Example 1 was characterized. The results are as follows Figure 1 As shown:

[0046] Figure 1 This is a scanning electron microscope image of the sintered magnesium titanium phosphate electrode material. As can be seen from the figure, the surface morphology of the material is a three-dimensional structure with three-dimensional holes stacked on top of each other. These holes can facilitate the infiltration of the electrolyte into the electrode active material, facilitate the insertion and removal of sodium ions, and ensure the cycle stability of the magnesium titanium phosphate electrode material.

[0047] Example 2

[0048] Dissolve 0.55g of magnesium acetate dihydrate and 1.74g of ammonium dihydrogen phosphate in 20mL of ultrapure water to obtain a mixed solution, and dissolve 3.4mL of n-butyl titanate in 60mL of anhydrous ethanol to obtain an n-butyl titanate solution. Add the mixed solution drop by drop into the n-butyl titanate solution under strong stirring, mix at room temperature for 3h after the dripping, transfer to a high-pressure reactor, and react at 160℃ for 3h. After the reaction is completed, cool to room temperature and take out the precursor, wash it with ultrapure water and anhydrous ethanol respectively by centrifugation for 3 times, and then dry it in an oven at 80℃ for 12h.

[0049] After the above precursor is ground for the first time, it is sintered for the first time at 350°C for 3 hours, and then ground for the second time after cooling to room temperature. It is sintered for the second time in an argon atmosphere, and the temperature is increased to 800°C at a heating rate of 5°C / min and sintered for 4 hours. It is cooled to room temperature, taken out and ground to obtain magnesium titanium phosphate.

[0050] 1g of magnesium titanium phosphate and 0.20g of glucose were added to 20mL of ethanol solution (the volume ratio of water to anhydrous ethanol in the ethanol solution was 1:1), and then magnetically stirred for 6h and dried in an oven at 100°C for 12h. After cooling to room temperature, the mixture was taken out and ground, heated to 800°C at a heating rate of 10°C / min, sintered for 4h, and cooled to room temperature to obtain a carbon-coated magnesium titanium phosphate electrode material.

[0051] The carbon-coated magnesium titanium phosphate electrode material, acetylene black and polyvinylidene fluoride were mixed in a mass ratio of 7:2:1, dispersed in 2.5g of 1-methylpyrrolidone and stirred at room temperature for 6h to prepare a slurry, which was coated on a copper foil and dried in an oven at 80°C for 12h. After cooling, the carbon-coated magnesium titanium phosphate composite electrode was obtained by cutting it into small discs with a diameter of 14mm using a slicer.

[0052] The carbon-coated magnesium titanium phosphate electrode material prepared in Example 2 was characterized. The results are as follows Figures 2-3 As shown:

[0053] Figure 2 This is a scanning electron microscope image of a carbon-coated magnesium titanium phosphate electrode material. As can be seen from the figure, the surface morphology of the electrode is still a three-dimensional structure with three-dimensional pores stacked on each other. This shows that glucose as a carbon source coating does not affect its basic structure, and can even increase its pores and pore size, making it easier for the electrolyte to infiltrate, thereby increasing the conductivity.

[0054] Figure 3 This is the X-ray diffraction diagram of the carbon-coated magnesium titanium phosphate electrode material. As can be seen from the figure, there is no carbon peak, indicating that the added carbon-coated material glucose has no effect on it.

[0055] Example 3

[0056] Dissolve 0.62g of magnesium acetate dihydrate and 1.84g of ammonium dihydrogen phosphate in 30mL of ultrapure water to obtain a mixed solution, and dissolve 4.1mL of n-butyl titanate in 60mL of anhydrous ethanol to obtain an n-butyl titanate solution. Add the mixed solution drop by drop into the n-butyl titanate solution under strong stirring, mix at room temperature for 3h after the dripping, transfer to a high-pressure reactor, and react at 170℃ for 3h. After the reaction is completed, cool to room temperature and take out the precursor, wash it with ultrapure water and anhydrous ethanol respectively by centrifugation for 3 times, and then dry it in an oven at 90℃ for 10h.

[0057] After the above precursor is ground for the first time, it is sintered for the first time at 400°C for 3 hours, and then ground for the second time after cooling to room temperature. It is sintered for the second time in an argon atmosphere, and the temperature is increased to 900°C at a heating rate of 6°C / min and sintered for 3 hours. It is cooled to room temperature, taken out and ground to obtain magnesium titanium phosphate.

[0058] 1g of magnesium titanium phosphate and 0.10g of glucose were added to 20mL of ethanol solution (the volume ratio of water to anhydrous ethanol in the ethanol solution was 1:1), and then placed in an oven for drying at 80°C for 11h after magnetic stirring for 5h. After cooling to room temperature, the mixture was taken out and ground, and heated to 600°C at a heating rate of 8°C / min and sintered for 4h, and cooled to room temperature to obtain a carbon-coated magnesium titanium phosphate electrode material.

[0059] Example 4

[0060] Dissolve 0.43g of magnesium acetate dihydrate and 1.94g of ammonium dihydrogen phosphate in 30mL of ultrapure water to obtain a mixed solution, and dissolve 3.16mL of n-butyl titanate in 50mL of anhydrous ethanol to obtain an n-butyl titanate solution. Add the mixed solution drop by drop into the n-butyl titanate solution under strong stirring, mix at room temperature for 3h after the dripping, transfer to a high-pressure reactor, and react at 160℃ for 3.5h. After the reaction is completed, cool to room temperature and take out the precursor, wash it twice with ultrapure water and anhydrous ethanol respectively, and then dry it in an oven at 100℃ for 10h.

[0061] After the above precursor is ground for the first time, it is sintered for the first time at 450°C for 2 hours, and then ground for the second time after cooling to room temperature. It is sintered for the second time in an argon atmosphere, and the temperature is increased to 800°C at a heating rate of 4°C / min and sintered for 4 hours. It is cooled to room temperature, taken out and ground to obtain magnesium titanium phosphate.

[0062] 0.9 g of magnesium titanium phosphate and 0.30 g of glucose were added to 30 mL of ethanol solution (the volume ratio of water to anhydrous ethanol in the ethanol solution was 1:1), and then placed in an oven for drying at 90 ° C for 10 h after magnetic stirring for 6 h. After cooling to room temperature, the mixture was taken out and ground, heated to 1000 ° C at a heating rate of 10 ° C / min, sintered for 5 h, and cooled to room temperature to obtain a carbon-coated magnesium titanium phosphate electrode material.

[0063] Example 5

[0064] Dissolve 0.68g of magnesium acetate dihydrate and 2.3g of ammonium dihydrogen phosphate in 30mL of ultrapure water to obtain a mixed solution, and dissolve 4.3mL of n-butyl titanate in 60mL of anhydrous ethanol to obtain an n-butyl titanate solution. Add the mixed solution drop by drop into the n-butyl titanate solution under strong stirring, mix at room temperature for 4h after the dripping, transfer to a high-pressure reactor, and react at 180℃ for 3h. After the reaction is completed, cool to room temperature and take out the precursor, wash it with ultrapure water and anhydrous ethanol respectively by centrifugation 4 times, and then dry it in an oven at 100℃ for 10h.

[0065] After the above precursor is ground for the first time, it is sintered for the first time at 500°C for 3 hours, and then ground for the second time after cooling to room temperature. It is sintered for the second time in an argon atmosphere, and the temperature is increased to 900°C at a heating rate of 6°C / min and sintered for 4 hours. It is cooled to room temperature and ground to obtain magnesium titanium phosphate.

[0066] 1.1g of magnesium titanium phosphate and 0.30g of glucose were added to 30mL of ethanol solution (the volume ratio of water to anhydrous ethanol in the ethanol solution was 1:2), and then placed in an oven for drying at 90°C for 12h after magnetic stirring for 7h. After cooling to room temperature, the mixture was taken out and ground, heated to 900°C at a heating rate of 11°C / min, sintered for 6h, and cooled to room temperature to obtain a carbon-coated magnesium titanium phosphate electrode material.

[0067] Example 6

[0068] The carbon-coated magnesium titanium phosphate composite electrode prepared in Example 2, Whatman GF / C separator, sodium sheet and 1 mol / L NaClO4 electrolyte (in the electrolyte, the solvent is dimethyl carbonate and ethylene carbonate in a volume ratio of 1:1), springs, gaskets, positive electrode shells and negative electrode shells were assembled into button batteries for electrochemical performance testing. The testing equipment was the Blue Electric Battery Testing System (3002A).

[0069] In the voltage range of 0.01 to 3.00 V, the cycle stability of the carbon-coated magnesium titanium phosphate electrode was tested at a charge and discharge rate of 1C. The cycle stability curve is shown in Figure 4 As shown in the figure, after 100 charge and discharge cycles, the charge and discharge capacity of the carbon-coated magnesium titanium phosphate composite electrode is still very stable without significant attenuation, which indicates that the carbon-coated magnesium titanium phosphate composite electrode prepared by the present invention has good cycle stability.

[0070] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a carbon-coated magnesium titanium phosphate electrode material, characterized in that: The following steps are involved: 1) Mixing a mixed solution of magnesium acetate dihydrate and ammonium dihydrogen phosphate with a solution of n-butyl titanate and transferring the mixture to a high-pressure reactor for reaction at a temperature of 140 to 180° C. for 2 to 4 hours to obtain a precursor; 2) The precursor is subjected to a first grinding, a first sintering, a second grinding, and a second sintering under a protective atmosphere in sequence to obtain magnesium titanium phosphate; 3) Mixing magnesium titanium phosphate, glucose and ethanol solution, drying, refining and sintering in sequence, to obtain a carbon-coated magnesium titanium phosphate electrode material, the morphology of which is a three-dimensional tunnel structure, and the thickness of the carbon layer composited on the surface of the magnesium titanium phosphate is 3-5nm; Step 2) The temperature of the first sintering is 300-500°C, and the time of the first sintering is 2-4 hours; the temperature of the second sintering is 700-900°C, and the time of the second sintering is 3-5 hours; the heating rate to the second sintering temperature is 3-7°C / min; Step 3) The volume ratio of anhydrous ethanol to water in the ethanol solution is (1-2): (1-2); the mass volume ratio of the magnesium titanium phosphate, glucose and ethanol solution is (0.9-1.2 g): (0.1-0.3 g): (20-40 mL); Step 3) The mixing time is 5 to 7 hours; the drying temperature is 60 to 100°C, and the drying time is 10 to 12 hours; the sintering temperature is 600 to 1000°C, and the sintering time is 4 to 6 hours; the heating rate to the sintering temperature is 8 to 12°C / min; Step 1) The mass volume ratio of magnesium acetate dihydrate, ammonium dihydrogen phosphate, and n-butyl titanate is (0.4-0.7 g): (1.5-2.5 g): (2-5 mL); The solvent in the mixed solution is water; the mass volume ratio of the magnesium acetate dihydrate and water is (0.4-0.7 g): (10-30 mL); The solvent in the n-butyl titanate solution is anhydrous ethanol; the volume ratio of n-butyl titanate to anhydrous ethanol is (2-5): (50-70).

2. The preparation method according to claim 1, characterized in that: The mixing time in step 1) is 2 to 4 hours.

3. The carbon-coated magnesium titanium phosphate electrode material obtained by the preparation method of the carbon-coated magnesium titanium phosphate electrode material according to any one of claims 1 to 2.

4. A carbon-coated magnesium titanium phosphate composite electrode comprising the carbon-coated magnesium titanium phosphate electrode material according to claim 3, characterized in that: The carbon-coated magnesium titanium phosphate composite electrode comprises a carbon-coated magnesium titanium phosphate electrode material, acetylene black and polyvinylidene fluoride; the mass ratio of the carbon-coated magnesium titanium phosphate electrode material, acetylene black and polyvinylidene fluoride is (6-8): (1-3): (1-2).

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