Preparation method and application of Cu micro-doped CoSe2 positive electrode material for magnesium ion battery

Abstract

The application discloses a preparation method of a Cu micro-doped CoSe2 positive electrode material of a magnesium ion battery, and the method comprises the following steps: firstly, a cobalt source and a copper source are mixed and added into methanol to obtain liquid 1; secondly, a dimethyl imidazole methanol solution is prepared and is denoted as liquid 2; thirdly, liquid 1 and liquid 2 are mixed under stirring and continue to be stirred, and then are left to stand after completion; fourthly, the precipitate in the mixed solution after standing is collected and is centrifuged, washed and dried to obtain a precursor of the positive electrode material; and fifthly, the precursor of the positive electrode material is mixed with selenium powder and is sintered, and then is taken out after cooling and is ground; the application further discloses that the positive electrode material is applied to the magnesium ion battery. The Cu micro-doping into the CoSe2 positive electrode material can improve the capacity of the CoSe2 and has a good capacity retention rate, thereby improving the electrochemical performance of the CoSe2 positive electrode material, and further improving the charge-discharge efficiency and the cycle stability of the magnesium ion battery; the method is simple, low in cost and suitable for the field of the magnesium ion battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery positive electrode materials, and particularly relates to a preparation method and application of a Cu micro-doped CoSe2 positive electrode material for a magnesium ion battery. BACKGROUND

[0002] With the increasing global energy demand and the increasingly serious environmental problems, it is particularly important to develop new and efficient energy storage systems. Among various battery technologies, magnesium ion batteries have attracted much attention due to their unique advantages. Magnesium ion batteries have high theoretical volumetric energy density, low cost, are not prone to dendrite formation, and have abundant magnesium resources, making them a potential candidate for the next generation of energy storage systems.

[0003] However, the development of magnesium ion batteries still faces some key challenges, especially in the selection and optimization of positive electrode materials. An ideal magnesium ion battery positive electrode material should have high specific capacity, good cycle stability, and fast ion diffusion capability. CoSe2 is a conversion-type positive electrode material with a relatively high theoretical capacity. However, pure CoSe2 material has problems such as harsh synthesis conditions, low yield, low electrical conductivity, and poor cycle performance in practical applications, which limit its performance in magnesium ion batteries.

[0004] To solve these problems, researchers have tried various methods to improve the performance of CoSe2. Xu et al. (Nanoscale, 2019, 11, 23173-23181) prepared CoSe2 positive electrode materials with different morphological structures by hydrothermal method, but the preparation process is very complex, the reaction time is long, and the yield is particularly low. In addition, the nano-materials obtained by this method are prone to agglomeration, which limits their application in industrial production. They also reported the research results of Ni-doped CoSe2 (ACSSustainable Chem. Eng. 2020, 8, 2964-297), but also have the disadvantages of complex synthesis process, particularly low yield, and low material capacity, which cannot be applied on a large scale. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a preparation method of a Cu micro-doped CoSe2 positive electrode material for a magnesium ion battery to solve the above-mentioned problems of the prior art. The method combines the control of the doping ratio of Cu and the optimization of the process by micro-doping Cu into the CoSe2 positive electrode material, which quickly activates the CoSe2 positive electrode material, greatly improves the capacity of CoSe2, and has a good capacity retention rate, thereby improving the electrochemical performance of the CoSe2 positive electrode material and solving the problem of poor cycle performance of conversion-type positive electrode materials.

[0006] To solve the above technical problems, the technical scheme adopted by the present application is as follows: a preparation method of a Cu micro-doped CoSe2 positive electrode material for a magnesium ion battery, characterized in that the chemical formula of the positive electrode material is Co 1-x Cu x Se2, x is in the range of 0.01-0.05, and the preparation method of the positive electrode material comprises the following steps:

[0007] Step one: a cobalt source and a copper source are mixed and added to methanol for dissolution to obtain a solution, which is referred to as liquid 1; the total concentration of cobalt ions and copper ions in the liquid 1 is 0.01 mol / L-0.2 mol / L, and the concentration ratio of copper ions to cobalt ions in the liquid 1 is 0.01-0.6;

[0008] Step two: a dimethyl imidazole methanol solution is prepared, which is referred to as liquid 2; the concentration of the liquid 2 is 0.04 mol / L-3.2 mol / L;

[0009] Step three: under stirring, the liquid 1 in step one is added dropwise into the liquid 2 in step two, or the liquid 2 in step two is added dropwise into the liquid 1 in step one to form a mixed solution, and stirring is continued for 0.1 h-2 h, then the stirring is stopped and the mixed solution is left to stand for 2 h-24 h;

[0010] Step four: the precipitate in the mixed solution left to stand in step three is collected, centrifuged and washed for 3 times, and then dried to obtain a precursor of the positive electrode material;

[0011] Step five: the precursor of the positive electrode material obtained in step four is mixed with selenium powder, then put into an atmosphere furnace for sintering, cooled with the furnace, taken out when the temperature drops to room temperature, and then ground uniformly to obtain the Cu micro-doped CoSe2 positive electrode material for the magnesium ion battery.

[0012] The preparation method of the Cu micro-doped CoSe2 positive electrode material for the magnesium ion battery described above is characterized in that, in step one, the cobalt source is cobalt nitrate, cobalt acetate, cobalt sulfate or cobalt chloride, and the copper source is copper nitrate, copper acetate, copper sulfate or copper chloride.

[0013] The preparation method of the Cu micro-doped CoSe2 positive electrode material for the magnesium ion battery described above is characterized in that, in step three, the stirring speed during stirring and the stirring speed during the continued stirring is 300 rpm-1000 rpm, and the dropwise adding speed is 10 mL / min-100 mL / min. By controlling the stirring speed, the solution is prevented from splashing due to too high stirring speed or from being stirred unevenly due to too low stirring speed. By controlling the dropwise adding speed, the efficiency is prevented from being low due to too slow dropwise adding or the nucleation from being too fast due to too fast dropwise adding, which affects the performance of the positive electrode material.

[0014] The preparation method of the Cu micro-doped CoSe2 positive electrode material of the magnesium ion battery has the characteristics that, in the step four, the drying process is: drying at 50 DEG C to 100 DEG C for 2h to 10h.

[0015] The preparation method of the Cu micro-doped CoSe2 positive electrode material of the magnesium ion battery has the characteristics that, in the step five, the mass ratio of the positive electrode material precursor to the selenium powder is 0.5 to 2, and the sintering process is: the heating rate is 1 DEG C / min to 5 DEG C / min, and the sintering is carried out at 300 DEG C to 700 DEG C for 1h to 5h.

[0016] Meanwhile, the application also discloses the application of the Cu micro-doped CoSe2 positive electrode material of the magnesium ion battery prepared by the method.

[0017] Compared with the prior art, the application has the following advantages:

[0018] 1. The Cu micro-doped CoSe2 positive electrode material can be obtained by mixing and dissolving the cobalt source and the copper source into methanol, mixing and stirring the methanol solution of dimethyl imidazole, and then sintering the selenium source after washing, centrifuging and drying.

[0019] 2. The electronic structure of CoSe2 is adjusted by the micro-doping of Cu, the conductivity of CoSe2 is improved, the structure stability of CoSe2 is enhanced by the Cu ions doped into the crystal lattice, the interface charge transfer characteristics of CoSe2 are optimized, the structural change of the electrode material in the charging and discharging process is reduced, and the charging and discharging efficiency and the cycle stability of the battery are improved.

[0020] 3. The Cu is micro-doped into the CoSe2 positive electrode material by the solution mixing method, the doping of Cu is uniform, other impurities are not generated, and the performance of the Cu micro-doped CoSe2 positive electrode material is ensured.

[0021] 4. The preparation process is simple, the equipment requirement is not high, the cost is low, the prepared magnesium ion battery positive electrode material has excellent electrochemical performance, has the prospect of large-scale application, and provides a new possibility for the development of the magnesium ion battery.

[0022] The technical solutions of the application are further described below with reference to the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 XRD patterns of the positive electrode material prepared in Example 1, Example 2 and Comparative Example 1 of the present application.

[0024] Figure 2 SEM images of the positive electrode material prepared in Example 1, Example 2 and Comparative Example 1 of the present application at different magnifications.

[0025] Figure 3 TEM images of the positive electrode material prepared in Example 1 and Comparative Example 1 of the present application at different magnifications.

[0026] Figure 4 Elemental distribution map of the positive electrode material prepared in Example 1 of the present application.

[0027] Figure 5 Cycle performance chart of the positive electrode material prepared in Example 1 and Comparative Example 1 of the present application at a current density of 50mA·g-1. -1

[0028] Cycle performance chart of the positive electrode material prepared in Example 1 and Comparative Example 1 of the present application at a current density of 200mA·g-1. -1 Figure 6 DETAILED DESCRIPTION

[0029] Example 1

[0030] The chemical formula of the Cu micro-doped CoSe2 positive electrode material of the magnesium ion battery in this example is Co 0.98 Cu 0.02 Se2. The preparation method of the positive electrode material comprises the following steps:

[0031] Step one, weigh 2.024g of cobalt nitrate hexahydrate and 0.16g of copper acetate monohydrate, mix and add them into 80mL of methanol to dissolve, and the obtained solution is recorded as liquid 1; the total concentration of cobalt ions and copper ions in the liquid 1 is 0.1mol / L;

[0032] Step two, weigh 2.627g of dimethylimidazole, add it into 80mL of methanol to dissolve, and record as liquid 2; the concentration of the liquid 2 is 0.4mol / L;

[0033] Step three, under the stirring state of a stirring rate of 500rpm, drop the liquid 2 in step two into the liquid 1 in step one at a dropping rate of 50mL / min, form a mixed solution, and continue to maintain the stirring rate at 500rpm for 1h, then stop stirring and stand for 24h;

[0034] ​​Step four, collect the precipitate in the mixed solution after standing in step three, centrifugal wash the precipitate with methanol for 3 times, dry at 80℃ for 10h, to obtain the precursor of the positive electrode material;

[0035] Step five, mix the precursor of the positive electrode material obtained in step four with selenium powder according to the mass ratio of 1:1, then put it into an atmosphere furnace, heat to 500℃ at a heating rate of 2℃ / min under argon atmosphere and sinter for 1h, cool down with the furnace, take it out after the temperature drops to room temperature, grind uniformly to obtain the Cu micro-doped CoSe2 positive electrode material for magnesium ion battery, namely Co 0.98 Cu 0.02 Se2.

[0036] The cobalt source in this embodiment can also be replaced by cobalt acetate, cobalt sulfate or cobalt chloride, and the copper source can also be replaced by copper nitrate, copper sulfate or copper chloride.

[0037] Example 2

[0038] The chemical formula of the Cu micro-doped CoSe2 positive electrode material for magnesium ion battery in this embodiment is Co 0.96 Cu 0.04 Se2, and the preparation method of the positive electrode material comprises the following steps:

[0039] Step one, weigh 1.8g of cobalt nitrate hexahydrate and 0.319g of copper acetate monohydrate, mix and add them into 80mL of methanol to dissolve, and the obtained solution is recorded as liquid 1; the total concentration of cobalt ions and copper ions in the liquid 1 is 0.1mol / L;

[0040] Step two, weigh 2.627g of dimethylimidazole, add it into 80mL of methanol to dissolve, and record it as liquid 2; the concentration of the liquid 2 is 0.4mol / L;

[0041] Step three, under the stirring state of a stirring rate of 500rpm, add the liquid 2 in step two into the liquid 1 in step one at a dropping rate of 50mL / min to form a mixed solution, and continue to maintain the stirring rate at 500rpm for 1h, then stop stirring and stand for 24h;

[0042] Step four, collect the precipitate in the mixed solution after standing in step three, centrifugal wash the precipitate with methanol for 3 times, dry at 80℃ for 10h, to obtain the precursor of the positive electrode material;

[0043] Step five, mix the precursor of the positive electrode material obtained in step four with selenium powder according to the mass ratio of 1:1, then put it into an atmosphere furnace, heat to 500℃ at a heating rate of 2℃ / min under argon atmosphere and sinter for 1h, cool down with the furnace, take it out after the temperature drops to room temperature, grind uniformly to obtain the Cu micro-doped CoSe2 positive electrode material for magnesium ion battery, namely Co 0.96Cu 0.04 Se2.

[0044] The cobalt source in the embodiment can also be replaced by cobalt acetate, cobalt sulfate or cobalt chloride, and the copper source can also be replaced by copper nitrate, copper sulfate or copper chloride.

[0045] Comparative Example 1

[0046] The chemical formula of the magnesium ion battery CoSe2 cathode material in the comparative example is CoSe2, and the preparation method of the cathode material comprises the following steps:

[0047] Step one, weigh 2.328g of cobalt nitrate hexahydrate and add it to 80mL of methanol to dissolve, and the obtained solution is recorded as liquid 1; the concentration of cobalt ions in the liquid 1 is 0.1mol / L;

[0048] Step two, weigh 2.627g of dimethyl imidazole and add it to 80mL of methanol to dissolve, and record it as liquid 2; the concentration of the liquid 2 is 0.4mol / L;

[0049] Step three, under the stirring condition of a stirring rate of 500rpm, the liquid 2 in step two is added to the liquid 1 in step one at a drop rate of 50mL / min, a mixed solution is formed, and the stirring rate is continued to be maintained at 500rpm for 1h, then the stirring is stopped and the solution is left to stand for 24h;

[0050] Step four, collect the precipitate in the mixed solution after standing in step three, centrifugal wash the precipitate with methanol for 3 times, dry at 80℃ for 10h, and obtain the precursor of the cathode material;

[0051] Step five, mix the precursor of the cathode material obtained in step four with selenium powder according to a mass ratio of 1:1, then put it into an atmosphere furnace, heat to 500℃ at a heating rate of 2℃ / min under argon atmosphere and sinter for 1h, cool down with the furnace, take out after the temperature drops to room temperature, grind uniformly, and obtain the magnesium ion battery CoSe2 cathode material CoSe2.

[0052] Example 3

[0053] The chemical formula of the magnesium ion battery Cu micro-doped CoSe2 cathode material in the embodiment is Co 0.95 Cu 0.05 Se2, and the preparation method of the cathode material comprises the following steps:

[0054] Step one, weigh 1.781g of cobalt nitrate hexahydrate and 0.399g of copper acetate monohydrate, mix and add them to 40mL of methanol to dissolve, and the obtained solution is recorded as liquid 1; the total concentration of cobalt ions and copper ions in the liquid 1 is 0.2mol / L;

[0055] Step two, 2.627 g of dimethylimidazole was weighed and dissolved in 10 mL of methanol, and was recorded as liquid 2; the concentration of the liquid 2 was 3.2 mol / L;

[0056] Step three, under the stirring condition of a stirring rate of 1000 rpm, liquid 2 in step two was added dropwise into liquid 1 in step one at a dropwise adding rate of 100 mL / min to form a mixed solution, and the stirring rate was continuously maintained at 1000 rpm for 2 h, then the stirring was stopped and the mixed solution was left to stand for 24 h;

[0057] Step four, the precipitate in the mixed solution left to stand in step three was collected, the precipitate was washed by centrifugation with methanol for 3 times, and was dried at 100℃ for 2 h to obtain a precursor of the positive electrode material;

[0058] Step five, the precursor of the positive electrode material obtained in step four was mixed with selenium powder at a mass ratio of 2:1, and then was put into an atmosphere furnace, was heated to 700℃ at a heating rate of 5℃ / min under an argon atmosphere and was sintered for 1 h, was cooled down with the furnace, was taken out after the temperature decreased to room temperature, was ground uniformly to obtain a magnesium ion battery Cu micro-doped CoSe2 positive electrode material, namely Co 0.95 Cu 0.05 Se2.

[0059] The cobalt source in the embodiment can also be replaced by cobalt acetate, cobalt sulfate or cobalt chloride, and the copper source can also be replaced by copper nitrate, copper sulfate or copper chloride.

[0060] Example 4

[0061] The chemical formula of the magnesium ion battery Cu micro-doped CoSe2 positive electrode material in the embodiment is Co 0.96 Cu 0.04 Se2, and the preparation method of the positive electrode material comprises the following steps:

[0062] Step one, 1.8 g of cobalt nitrate hexahydrate and 0.319 g of copper acetate monohydrate were weighed and mixed and dissolved in 800 mL of methanol to obtain a solution, which was recorded as liquid 1; the total concentration of cobalt ions and copper ions in the liquid 1 was 0.01 mol / L;

[0063] Step two, 2.627 g of dimethylimidazole was weighed and dissolved in 800 mL of methanol, and was recorded as liquid 2; the concentration of the liquid 2 was 0.04 mol / L;

[0064] Step three, under the stirring condition of a stirring rate of 300 rpm, liquid 2 in step two was added dropwise into liquid 1 in step one at a dropwise adding rate of 10 mL / min to form a mixed solution, and the stirring rate was continuously maintained at 300 rpm for 0.1 h, then the stirring was stopped and the mixed solution was left to stand for 2 h;

[0065] Step 4: Collect the precipitate from the mixed solution after standing in Step 3, wash the precipitate three times by centrifugation with methanol, and dry it at 50℃ for 10 hours to obtain the precursor of the positive electrode material.

[0066] Step 5: Mix the cathode material precursor obtained in Step 4 with selenium powder at a mass ratio of 1:2, then place it in an atmosphere furnace and heat it to 300℃ at a heating rate of 1℃ / min under an argon atmosphere, and sinter for 5 hours. Cool it with the furnace, and after the temperature drops to room temperature, remove it, grind it evenly, and obtain the magnesium-ion battery Cu micro-doped CoSe2 cathode material, i.e., Co. 0.96 Cu 0.04 Se2.

[0067] In this embodiment, the cobalt source can also be replaced with cobalt acetate, cobalt sulfate, or cobalt chloride, and the copper source can also be replaced with copper nitrate, copper sulfate, or copper chloride.

[0068] I. The structure and morphology of the cathode materials prepared in Examples 1-4 and Comparative Example 1 of the present invention were characterized.

[0069] (1) XRD characterization

[0070] Figure 1 The XRD patterns of the cathode materials prepared in Examples 1, 2, and Comparative Example 1 of this invention are shown below. Figure 1 It can be seen that, compared with Comparative Example 1, the cathode materials in Examples 1 and 2 did not produce impurity phases after Cu doping, and the XRD patterns of each cathode material perfectly matched the standard diffraction card PDF#53-0449 for CoSe2. Cu doping caused the angle of the (200) peak to increase. Based on the Bragg equation, it is speculated that the interplanar spacing of the cathode materials in Examples 1 and 2 decreased, while Cu... 2+ The radius is smaller than Co 2+ Therefore, Cu is indeed doped into the CoSe2 lattice. The lattice constants of the three cathode materials were obtained by full-spectrum fitting and refinement of their XRD patterns, as shown in Table 1 below.

[0071] Table 1

[0072]

[0073] As can be seen from Table 1, the cell parameters of the cathode material gradually decrease with the increase of Cu doping, indicating that Cu is indeed doped into the CoSe2 lattice, which is beneficial to improving the electrochemical performance of the cathode material.

[0074] (2) SEM and TEM characterization

[0075] Figure 2The scanning electron microscope images of the positive electrode materials prepared in Example 1, Example 2 and Comparative Example 1 under different rates, wherein Figure a represents Comparative Example 1, Figure b represents Example 1, and Figure c represents Example 2, from Figure 2 It can be seen that the Cu-doped positive electrode material particles prepared in Example 1 and Example 2 have a particle size of about 3 μm, the rhombohedron structure of the precursor of the positive electrode material is maintained, and the surface is almost not damaged; the CoSe2 particles prepared in Comparative Example 1 have a smaller particle size of about 1 μm, and the surface of the particles is damaged to a certain extent.

[0076] Figure 3 The transmission electron microscope images of the positive electrode materials prepared in Example 1 and Comparative Example 1 under different rates, wherein Figures a~c represent Example 1, and Figures d~f represent Comparative Example 1, from Figures a~c, it can be seen that the CoSe2 of Example 1 has a polycrystalline diffraction ring, indicating that it has a polycrystalline structure, and further high-resolution transmission electron microscopy shows that the interplanar spacing is 0.256 nm, corresponding to the (111) crystal face; from Figures d~f, it can be seen that the CoSe2 of Comparative Example 1 also has a polycrystalline diffraction ring, and is in a semi-hollow shape, the interplanar spacing is 0.258 nm, corresponding to the (111) crystal face, since the copper ion radius is small, its doping into the CoSe2 lattice will cause the reduction of the interplanar spacing, further proving that the Cu in Example 1 is indeed doped into the CoSe2. 0.98 Cu 0.02 Se2 has a polycrystalline diffraction ring, indicating that it has a polycrystalline structure, and further high-resolution transmission electron microscopy shows that the interplanar spacing is 0.256 nm, corresponding to the (111) crystal face; from Figures d~f, it can be seen that the CoSe2 of Comparative Example 1 also has a polycrystalline diffraction ring, and is in a semi-hollow shape, the interplanar spacing is 0.258 nm, corresponding to the (111) crystal face, since the copper ion radius is small, its doping into the CoSe2 lattice will cause the reduction of the interplanar spacing, further proving that the Cu in Example 1 is indeed doped into the CoSe2.

[0077] Figure 4 The element distribution map of the positive electrode material prepared in Example 1, from Figure 4 It can be seen that the Co 0.98 Cu 0.02 Se2 positive electrode material of Example 1 is very uniform, and no obvious impurity phase appears.

[0078] II. Electrochemical performance test of the positive electrode material

[0079] The positive electrode materials prepared in Example 1 and Comparative Example 1 are mixed with conductive carbon black and polyvinylidene fluoride according to a mass ratio of 8:1:1, N-methyl pyrrolidone is added to adjust the viscosity, and then uniformly coated on a copper foil, dried in a vacuum drying oven at 120℃ for 12 h, and then cut into small round pieces with a diameter of 12 mm as positive electrode sheets, and the active material loading is 0.8 mg / cm 2 ~1.5 mg / cm 2 .

[0080] The electrochemical performance test of the present application adopts the traditional two-electrode system of button cell, uses AZ31 magnesium alloy as the negative electrode, glass fiber as the separator, and 0.4M phenylmagnesium chloride-aluminum chloride-tetrahydrofuran solution as the electrolyte to assemble the magnesium ion battery.

[0081] Figure 5 The positive electrode material prepared in Example 1 and Comparative Example 1 was subjected to charge-discharge test at 0.01V~2V, 50mA·g -1 The cycle performance graph of the charge-discharge test can be seen from Figure 5 It can be seen that the capacity of the undoped CoSe2 positive electrode material in Comparative Example 1 is slowly increasing with the increase of cycle number, and the capacity is increased to 63.5mAh / g after 60 cycles, while after doping 2% Cu in CoSe2 in Example 1, the CoSe2 positive electrode is rapidly activated, and the capacity is rapidly increased, and the highest capacity has reached 141.1mAh / g.

[0082] Figure 6 The positive electrode material prepared in Example 1 and Comparative Example 1 was subjected to charge-discharge test at 0.01V~2V, 200mA·g -1 The cycle performance graph of the charge-discharge test can be seen from Figure 6 It can be seen that under high current, the undoped CoSe2 positive electrode material in Comparative Example 1 has very large polarization due to poor conductivity, and the specific capacity after 210 cycles is only 26.9mAh / g, while the specific capacity of the CoSe2 positive electrode material after 210 cycles in Example 1 reaches 133.8mAh / g, which shows that the band structure of the CoSe2 doped with Cu changes, the conductivity of the material is significantly increased, and the CoSe2 is rapidly activated during the test, thereby releasing a large amount of capacity. 0.98 Cu 0.02 Se2 positive electrode material reaches 133.8mAh / g, which shows that the band structure of the CoSe2 doped with Cu changes, the conductivity of the material is significantly increased, and the CoSe2 is rapidly activated during the test, thereby releasing a large amount of capacity.

[0083] The above is only a preferred embodiment of the present application, not any limitation on the present application. Any simple modification, change and equivalent change according to the technical essence of the application to the above embodiment are still within the protection scope of the technical solution of the present application.

Claims

1. A method for preparing Cu micro-doped CoSe2 cathode material for magnesium-ion batteries, characterized in that, The chemical formula of the cathode material is Co. 1-x Cu x The value of Se2, x ranges from 0.01 to 0.

05. The preparation method of this cathode material includes the following steps: Step 1: Mix the cobalt source and copper source and dissolve them in methanol. The resulting solution is denoted as liquid 1. The total concentration of cobalt ions and copper ions in liquid 1 is 0.01 mol / L to 0.2 mol / L, and the concentration ratio of copper ions to cobalt ions in liquid 1 is 0.01 to 0.

6. Step 2: Prepare a methanol solution of dimethylimidazole, denoted as liquid 2; the concentration of liquid 2 is 0.04 mol / L to 3.2 mol / L; Step 3: While stirring, add liquid 1 from step 1 dropwise to liquid 2 from step 2, or add liquid 2 from step 2 dropwise to liquid 1 from step 1 to form a mixed solution, and continue stirring for 0.1h to 2h, then stop stirring and let stand for 2h to 24h. Step 4: Collect the precipitate from the mixed solution after standing in Step 3, centrifuge and wash 3 times, and dry to obtain the precursor of the positive electrode material; Step 5: Mix the precursor of the cathode material obtained in Step 4 with selenium powder, then place it in an atmosphere furnace for sintering, cool it with the furnace, and take it out after the temperature drops to room temperature. Grind it evenly to obtain the Cu micro-doped CoSe2 cathode material for magnesium ion batteries.

2. The method for preparing Cu micro-doped CoSe2 cathode material for magnesium-ion batteries according to claim 1, characterized in that, The cobalt source mentioned in step one is cobalt nitrate, cobalt acetate, cobalt sulfate, or cobalt chloride, and the copper source is copper nitrate, copper acetate, copper sulfate, or copper chloride.

3. The method for preparing Cu micro-doped CoSe2 cathode material for magnesium-ion batteries according to claim 1, characterized in that, The stirring state and stirring rate to be maintained in step three are 300 rpm to 1000 rpm, and the dropping rate is 10 mL / min to 100 mL / min.

4. The method for preparing Cu micro-doped CoSe2 cathode material for magnesium-ion batteries according to claim 1, characterized in that, The drying process described in step four is as follows: drying at 50℃~100℃ for 2h~10h.

5. The method for preparing Cu micro-doped CoSe2 cathode material for magnesium-ion batteries according to claim 1, characterized in that, In step five, the mass ratio of the precursor of the cathode material to the selenium powder is 0.5 to 2. The sintering process is as follows: the heating rate is 1℃ / min to 5℃ / min, and the temperature is raised to 300℃ to 700℃ for sintering for 1h to 5h.

6. An application of a Cu micro-doped CoSe2 cathode material for magnesium-ion batteries prepared by the method described in any one of claims 1 to 5, characterized in that, The positive electrode sheet prepared using this positive electrode material is applied in magnesium-ion batteries.

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