A bipolar battery positive electrode active material and preparation method thereof

Abstract

The present invention relates to a bipolar battery positive electrode active material and its preparation method, belonging to the technical field of sulfur-lithium batteries. The material uses a graphene-coated mesoporous molecular sieve as a substrate, loads elemental sulfur onto the substrate by a deposition method, and uses polypyrrole for encapsulation to reduce the diffusion and dissolution of sulfur and its compounds. Finally, the material is coated with silver in situ reduction. The silver coating has good adsorption properties for sulfides and selective permeability to sulfides in the positive electrode material. Both polypyrrole and silver have good electrical conductivity, ensuring that the positive electrode material has good electrical properties. In tests, the material exhibits high capacity and good cycle stability, with a capacity of 946-982 / mAh·g. ‑1 , 0.2A·g ‑1 After 100 cycles, the capacity retention rate reached 92.7-95.3%.

Description

Technical Field

[0001] The present invention belongs to the technical field of sulfur-lithium batteries, and in particular relates to a bipolar battery positive electrode active material and a preparation method thereof. Background Art

[0002] A bipolar battery consists of two unipolar electrode sheets, several bipolar electrode sheets, a separator, and an electrolyte. A bipolar electrode sheet is an electrode sheet with two polarities after a positive electrode material layer and a negative electrode material layer are respectively provided on both sides of a bipolar current collector. A unipolar unipolar sheet is an electrode sheet with a single polarity after a positive electrode material layer or a negative electrode material layer is provided on one side of a unipolar current collector. Because each battery cell in a bipolar battery, consisting of a bipolar plate, a positive electrode material layer, a separator, a negative electrode material layer, and another bipolar plate, has an independent electrochemical structure, the number of battery cells can be increased by increasing the number of bipolar electrode sheets, thereby increasing the overall voltage of the battery. In addition, the electron flow and ion flow in a bipolar battery are basically perpendicular to the bipolar current collector. Therefore, the resistance between battery cells is small, the electrode current and potential are evenly distributed, and the battery charges and discharges quickly, making it suitable for high-power and high-voltage applications such as electric vehicles and power storage.

[0003] Lithium-sulfur battery is a lithium battery that uses sulfur as the positive electrode and metallic lithium as the negative electrode. Compared with existing mature lithium batteries, elemental sulfur can provide up to 1672mAh·g -1 The specific capacity of sulfur is high, and sulfur is widely present in nature. Compared with existing lithium batteries, it is low-cost and has little environmental pollution, showing great application prospects. However, the biggest problem with sulfur-lithium batteries is the shuttle effect caused by the migration of sulfides between the positive and negative electrodes, which greatly reduces the battery capacity and passivates the negative electrode material, resulting in poor cycle stability. Summary of the Invention

[0004] In order to solve the technical problems mentioned in the background technology, the purpose of the present invention is to provide a bipolar battery positive electrode active material and a preparation method thereof.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for preparing a bipolar battery positive electrode active material specifically comprises the following steps:

[0007] Step S1: dissolving elemental sulfur and carbon disulfide by stirring at room temperature, adding graphene composite micropowder, performing ultrasonic dispersion treatment at 28-33 kHz for 1-1.2 hours, and spray drying the dispersion to prepare a sulfur-attached matrix;

[0008] Furthermore, the usage ratio of graphene composite micropowder, elemental sulfur and carbon disulfide is 1g:0.24-0.3g:25-30mL.

[0009] Step S2: Pyrrole and ethanol solution are mixed, sulfur-attached matrix is ​​added, ultrasonically dispersed into a suspension state, and the pH value is adjusted to 5.8-6.2 with hydrochloric acid. The mixture is placed in an ice-water bath to maintain constant temperature, and the stirring rate is set to 400-500 rpm. Ferric chloride solution is slowly added dropwise and continued to stir and react. The total addition reaction time is controlled to be 2.5-3 hours. The bottom precipitate is collected by centrifugation, washed with deionized water, and dried to prepare a doped matrix;

[0010] Furthermore, the usage ratio of the sulfur-attached matrix, pyrrole, ferric chloride and ethanol solution is 1 g: 0.42-0.48 mL: 16-22 mg: 50-60 mL, the concentration of the ferric chloride solution is 0.1 mol / L, and the concentration of the ethanol solution is 60%.

[0011] Step S3: mixing the doped matrix and the silver ammonia solution, maintaining a constant temperature of 80-90°C, and ultrasonically dispersing at 40kHz. The frequency is then reduced to 20kHz, and the formaldehyde solution is slowly added dropwise. After addition, stirring is continued at 300-400 rpm. The overall addition reaction time is controlled to be 40-60 minutes. The precipitate is removed by centrifugation and dried under nitrogen protection to prepare the positive electrode active material.

[0012] Furthermore, the usage ratio of the doping matrix, the silver ammonia solution and the formaldehyde solution is 1 g: 12-16 mL: 45-55 mL, the concentration of the silver ammonia solution is 0.01 M, and the concentration of the formaldehyde solution is 15%.

[0013] The graphene composite micropowder is prepared by the following method:

[0014] Step A1: Graphene oxide, thionyl chloride, and DMF were mixed and stirred at 180-240 rpm for 30-35 h at room temperature. The thionyl chloride was then removed by rotary evaporation. The mixture was then washed with tetrahydrofuran and dried under nitrogen to a constant weight to prepare graphene chloride.

[0015] Furthermore, the usage ratio of graphene oxide, thionyl chloride and DMF is 1 g: 35-45 mL: 2-4 mL.

[0016] Step A2: Mix the mesoporous molecular sieve and deionized water, adjust the pH to 8-9, and stir at room temperature for 5-6 hours. Then, add the silane coupling agent KH550, ultrasonically disperse at 30 kHz for 2-2.5 hours, centrifuge, remove the bottom precipitate, wash, and vacuum dry to prepare an aminated carrier;

[0017] Furthermore, the usage ratio of the silane coupling agent KH550 and the mesoporous molecular sieve is 1.8-2.5 mL: 1 g.

[0018] Step A3: Graphene acyl chloride, triethylamine, and dioxane are mixed, and an aminated carrier is added and treated under 28 kHz ultrasonic dispersion for 20-30 minutes. The bottom precipitate is collected by centrifugation, hydrazine hydrate solution is added, and stirred for 2-3 hours. The mixture is evaporated to dryness under reduced pressure and dispersed to prepare graphene composite micropowder;

[0019] Furthermore, the usage ratio of the amination carrier, the acyl chloride graphene, triethylamine, dioxane and the hydrazine hydrate solution is 3 g: 1 g: 0.6-0.8 mL: 40-50 mL: 15-20 mL, and the concentration of the hydrazine hydrate solution is 30%.

[0020] Beneficial effects of the present invention:

[0021] The present invention prepares a sulfur-carbon-based positive electrode active material. Graphene composite micropowder is used as a matrix. Elemental sulfur is loaded on the matrix by a deposition method. Polypyrrole is used for encapsulation to reduce the diffusion and dissolution of sulfur and its compounds. Finally, silver is used for in-situ reduction coating. The silver coating has good adsorption properties for sulfides and selective permeability for sulfides in the positive electrode material. In addition, both polypyrrole and silver have good electrical conductivity, ensuring that the positive electrode material has good electrical properties. In tests, it shows good cycle stability, 0.2A·g -1 After 100 cycles, the capacity retention rate reaches 92.7-95.3%.

[0022] The present invention prepares a porous graphene composite micropowder. The mesoporous molecular sieve is used as a matrix. Amino groups are grafted onto the surface through KH550 amination treatment. Graphene oxide is used as a covering layer. The graphene oxide is treated with thionyl chloride chlorination. The acyl chloride and amino groups react and condense. The graphene oxide is then coated using a suspension method. The prepared graphene composite micropowder has large surface pores, which is conducive to increasing the loading of elemental sulfur. In tests, the graphene composite micropowder exhibits a high capacity of 946-982 / mAh·g. -1 . DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0024] Example 1

[0025] This embodiment prepares the positive electrode active material of a bipolar battery, and the specific implementation process is as follows:

[0026] 1. Preparation of graphene composite powder

[0027] a1. Graphene oxide, thionyl chloride, and DMF were added to a reactor and stirred at 240 rpm at room temperature for 30 h. The ratio of graphene oxide, thionyl chloride, and DMF was 1 g:45 mL:4 mL. The thionyl chloride was then removed by rotary evaporation. The rotary evaporation product was then washed with twice the mass of tetrahydrofuran and dried at 80°C under nitrogen to a constant weight to obtain graphene chloride.

[0028] a2. Mix a mesoporous molecular sieve (selected from SBA-15, the same below) and deionized water at a solid-liquid ratio of 1:30, adjust the pH to 9 with sodium hydroxide, stir at 120 rpm at room temperature for 5 h, then add silane coupling agent KH550 at 2.5 mL / g, and then ultrasonically disperse at 30 kHz for 2 h. Then, centrifuge the dispersion, take the bottom precipitate, add deionized water, wash repeatedly twice, and then vacuum dry to obtain an ammoniated carrier;

[0029] a3. Mix acylated graphene chloride, triethylamine, and dioxane, add an aminated carrier, and ultrasonically treat for 20 minutes under 28kHz ultrasonic dispersion. Centrifuge to obtain the bottom precipitate, and then add a 30% hydrazine hydrate solution and stir for 2 hours. The amount ratio of the aminated carrier, acylated graphene chloride, triethylamine, dioxane, and hydrazine hydrate solution is 3g:1g:0.8mL:50mL:20mL. Then evaporate to dryness under reduced pressure, place in a disperser and fully disperse to obtain graphene composite micropowder.

[0030] 2. Preparation of positive electrode active materials

[0031] s1. Dissolve elemental sulfur and carbon disulfide by stirring at room temperature, add graphene composite powder, and perform ultrasonic dispersion treatment at 33 kHz for 1 hour. The ratio of graphene composite powder, elemental sulfur, and carbon disulfide is 1 g:0.3 g:30 mL. The dispersion is then spray-dried to obtain a sulfur-attached matrix.

[0032] s2. Pyrrole and 60% ethanol solution were mixed, and the sulfur-attached matrix was added and ultrasonically dispersed at 30kHz. Hydrochloric acid was added dropwise while ultrasonically dispersing to adjust the pH value to 5.8. The mixture was then placed in an ice-water bath to maintain constant temperature. Ferric chloride was prepared into a 0.1 mol / L ferric chloride solution. The stirring rate was set to 500 rpm. The ferric chloride solution was slowly added dropwise to the dispersion within 1 hour. After the addition, the reaction was continued by stirring. The overall reaction time was controlled to be 2.5 hours. The amount ratio of the sulfur-attached matrix, pyrrole, ferric chloride and ethanol solution was 1 g: 0.48 mL: 22 mg: 60 mL. After the reaction, the bottom precipitate was centrifuged and washed with twice the amount of deionized water. The mixture was then dried in a drying oven to obtain a doped matrix.

[0033] s3. Take the doped matrix and mix it with a silver ammonia solution with a concentration of 0.01M, keep it in a constant temperature of 90℃ in a water bath, apply ultrasonic dispersion at 40kHz, then reduce the frequency to 20kHz, slowly add a 15% formaldehyde solution within 20 minutes, continue stirring at 400rpm after addition, and control the overall addition reaction time to be 40 minutes, wherein the amount ratio of the doped matrix, silver ammonia solution and formaldehyde solution is 1g:16mL:55mL, remove the precipitate by centrifugation and dry it under nitrogen protection to make the positive electrode active material.

[0034] Example 2

[0035] This embodiment prepares the positive electrode active material of a bipolar battery, and the specific implementation process is as follows:

[0036] 1. Preparation of graphene composite powder

[0037] a1. Graphene oxide, thionyl chloride, and DMF were added to a reactor and stirred at 240 rpm at room temperature for 32 h. The ratio of graphene oxide, thionyl chloride, and DMF was 1 g:35 mL:2 mL. The thionyl chloride was then removed by rotary evaporation. The rotary evaporation product was then washed with twice the mass of tetrahydrofuran and dried at 80°C under nitrogen to a constant weight to obtain graphene chloride.

[0038] a2. Mix the mesoporous molecular sieve and deionized water at a solid-liquid ratio of 1:30, adjust the pH to 8 with sodium hydroxide, stir at 120 rpm at room temperature for 5.5 h, then add silane coupling agent KH550 at 2.2 mL / g, and then ultrasonically disperse at 30 kHz for 2.5 h. Then, centrifuge the dispersion, take the bottom precipitate, add deionized water, wash it repeatedly twice, and then vacuum dry to obtain an aminated carrier;

[0039] a3. Mix acylated graphene chloride, triethylamine, and dioxane, add an aminated carrier, and ultrasonically treat for 25 minutes under 28kHz ultrasonic dispersion. Centrifuge to obtain the bottom precipitate, and then add a 30% hydrazine hydrate solution and stir for 2.2 hours. The amount ratio of the aminated carrier, acylated graphene chloride, triethylamine, dioxane, and hydrazine hydrate solution is 3g:1g:0.6mL:50mL:15mL. Then evaporate to dryness under reduced pressure, place in a disperser and fully disperse to obtain graphene composite micropowder.

[0040] 2. Preparation of positive electrode active materials

[0041] s1. Dissolve elemental sulfur and carbon disulfide by stirring at room temperature, add graphene composite powder, and perform ultrasonic dispersion treatment at 28 kHz for 1.2 h. The ratio of graphene composite powder, elemental sulfur, and carbon disulfide is 1 g:0.24 g:30 mL. The dispersion is then spray-dried to obtain a sulfur-attached matrix.

[0042] s2. Pyrrole and 60% ethanol solution were mixed, and the sulfur-attached matrix was added and ultrasonically dispersed at 30kHz. Hydrochloric acid was added dropwise while ultrasonically dispersing to adjust the pH value to 6.0. The mixture was then placed in an ice-water bath to maintain constant temperature. Ferric chloride was prepared into a 0.1 mol / L ferric chloride solution. The stirring rate was set to 500 rpm. The ferric chloride solution was slowly added dropwise to the dispersion within 1.5 hours. The reaction was continued by stirring after the addition. The overall reaction time was controlled to be 2.5 hours. The amount ratio of the sulfur-attached matrix, pyrrole, ferric chloride and ethanol solution was 1 g: 0.42 mL: 16 mg: 55 mL. After the reaction, the bottom precipitate was centrifuged and washed with twice the amount of deionized water. The mixture was then dried in a drying oven to obtain a doped matrix.

[0043] s3. Take the doped matrix and mix it with a silver ammonia solution with a concentration of 0.01M, keep it in a constant temperature of 85℃ in a water bath, apply ultrasonic dispersion at 40kHz, then reduce the frequency to 20kHz, slowly add a 15% formaldehyde solution within 25 minutes, continue stirring at 300rpm after addition, and control the overall addition reaction time to be 50 minutes, wherein the amount ratio of the doped matrix, silver ammonia solution and formaldehyde solution is 1g:14mL:50mL, remove the precipitate by centrifugation and dry it under nitrogen protection to make the positive electrode active material.

[0044] Example 3

[0045] This embodiment prepares the positive electrode active material of a bipolar battery, and the specific implementation process is as follows:

[0046] 1. Preparation of graphene composite powder

[0047] a1. Graphene oxide, thionyl chloride, and DMF were added to a reactor and stirred at 180 rpm for 35 h at room temperature. The ratio of graphene oxide, thionyl chloride, and DMF was 1 g:40 mL:3.2 mL. The thionyl chloride was then removed by rotary evaporation. The rotary evaporation product was then washed with twice the mass of tetrahydrofuran and dried at 80°C under nitrogen to a constant weight to obtain graphene chloride.

[0048] a2. Mix the mesoporous molecular sieve and deionized water at a solid-liquid ratio of 1:30, adjust the pH to 8.5 with sodium hydroxide, stir at 120 rpm at room temperature for 6 h, then add 1.8 / g of silane coupling agent KH550, and then ultrasonically disperse at 30 kHz for 2.5 h. Then centrifuge the dispersion, take the bottom precipitate, add deionized water, wash it repeatedly twice, and then vacuum dry to obtain an aminated carrier;

[0049] a3. Mix acylated graphene chloride, triethylamine and dioxane, add an aminated carrier and ultrasonically treat for 30 minutes under 28kHz ultrasonic dispersion, centrifuge to obtain the bottom precipitate, add 30% hydrazine hydrate solution and stir for 3 hours, wherein the amount ratio of aminated carrier, acylated graphene chloride, triethylamine, dioxane and hydrazine hydrate solution is 3g:1g:0.7mL:40mL:18mL, then evaporate to dryness under reduced pressure, place in a disperser and fully disperse to obtain graphene composite micropowder.

[0050] 2. Preparation of positive electrode active materials

[0051] s1. Elemental sulfur and carbon disulfide were stirred and dissolved at room temperature, and then graphene composite powder was added and dispersed at 28 kHz ultrasonication for 1.2 h. The ratio of graphene composite powder, elemental sulfur, and carbon disulfide was 1 g:0.26 g:25 mL. The dispersion was then spray-dried to obtain a sulfur-attached matrix.

[0052] s2. Pyrrole and 60% ethanol solution were mixed, and the sulfur-attached matrix was added and ultrasonically dispersed at 30kHz. Hydrochloric acid was added dropwise while ultrasonically dispersing to adjust the pH value to 5.8. The mixture was then placed in an ice-water bath to maintain constant temperature. Ferric chloride was prepared into a 0.1 mol / L ferric chloride solution. The stirring rate was set to 400 rpm. The ferric chloride solution was slowly added dropwise to the dispersion within 1.5 hours. After addition, the reaction was continued by stirring. The overall reaction time was controlled to be 3 hours. The amount ratio of the sulfur-attached matrix, pyrrole, ferric chloride and ethanol solution was 1 g: 0.45 mL: 20 mg: 50 mL. After the reaction, the bottom precipitate was centrifuged and washed with twice the amount of deionized water. The mixture was then dried in a drying oven to obtain a doped matrix.

[0053] s3. Take the doped matrix and mix it with a silver ammonia solution with a concentration of 0.01M, keep it in a constant temperature of 80℃ in a water bath, apply ultrasonic dispersion at 40kHz, then reduce the frequency to 20kHz, slowly add a 15% formaldehyde solution within 30 minutes, continue stirring at 300rpm after addition, and control the overall addition reaction time to be 60 minutes, wherein the amount ratio of the doped matrix, silver ammonia solution and formaldehyde solution is 1g:12mL:45mL, remove the precipitate by centrifugation and dry it under nitrogen protection to make the positive electrode active material.

[0054] Example 4

[0055] This embodiment prepares the positive electrode active material of a bipolar battery, and the specific implementation process is as follows:

[0056] 1. Preparation of graphene composite powder

[0057] a1. Graphene oxide, thionyl chloride, and DMF were added to a reactor and stirred at 180 rpm at room temperature for 35 h. The ratio of graphene oxide, thionyl chloride, and DMF was 1 g:45 mL:3 mL. The thionyl chloride was then removed by rotary evaporation. The rotary evaporation product was then washed with twice the mass of tetrahydrofuran and dried at 80°C under nitrogen to a constant weight to obtain graphene chloride.

[0058] a2. Mix the mesoporous molecular sieve and deionized water at a solid-liquid ratio of 1:30, adjust the pH to 8.5 with sodium hydroxide, stir at 120 rpm at room temperature for 5.8 h, then add silane coupling agent KH550 at 2.4 mL / g, and then ultrasonically disperse at 30 kHz for 2.5 h. Then centrifuge the dispersion, take the bottom precipitate, add deionized water, wash it twice, and then vacuum dry to obtain an aminated carrier;

[0059] a3. Mix acylated graphene chloride, triethylamine and dioxane, add an aminated carrier and ultrasonically treat for 22 minutes under 28kHz ultrasonic dispersion, centrifuge to obtain the bottom precipitate, add 30% hydrazine hydrate solution and stir for 2.8 hours, wherein the amount ratio of aminated carrier, acylated graphene chloride, triethylamine, dioxane and hydrazine hydrate solution is 3g:1g:0.8mL:42mL:16mL, then evaporate to dryness under reduced pressure, place in a disperser and fully disperse to obtain graphene composite micropowder.

[0060] 2. Preparation of positive electrode active materials

[0061] s1. Dissolve elemental sulfur and carbon disulfide by stirring at room temperature, add graphene composite powder, and perform ultrasonic dispersion treatment at 30 kHz for 1.1 h. The ratio of graphene composite powder, elemental sulfur, and carbon disulfide is 1 g:0.27 g:28 mL. The dispersion is then spray-dried to obtain a sulfur-attached matrix.

[0062] s2. Pyrrole and 60% ethanol solution were mixed, and the sulfur-attached matrix was added and ultrasonically dispersed at 30kHz. Hydrochloric acid was added dropwise while ultrasonically dispersing to adjust the pH value to 6.0. The mixture was then placed in an ice-water bath to maintain constant temperature. Ferric chloride was prepared into a 0.1 mol / L ferric chloride solution. The stirring rate was set to 400 rpm. The ferric chloride solution was slowly added dropwise to the dispersion within 1.2 hours. After addition, the reaction was continued by stirring. The overall reaction time was controlled to be 2.8 hours. The amount ratio of the sulfur-attached matrix, pyrrole, ferric chloride and ethanol solution was 1 g: 0.46 mL: 20 mg: 58 mL. After the reaction, the bottom precipitate was centrifuged and washed with twice the amount of deionized water. The mixture was then dried in a drying oven to obtain a doped matrix.

[0063] s3. Take the doped matrix and mix it with a silver ammonia solution with a concentration of 0.01M, keep it in a constant temperature of 88°C in a water bath, apply ultrasonic dispersion at 40kHz, then reduce the frequency to 20kHz, slowly add a 15% formaldehyde solution within 22 minutes, continue stirring at 400rpm after addition, and control the overall addition reaction time to be 55 minutes, wherein the amount ratio of the doped matrix, silver ammonia solution and formaldehyde solution is 1g:13mL:55mL, remove the precipitate by centrifugation and dry it under nitrogen protection to make the positive electrode active material.

[0064] Polyvinylidene fluoride and N-methyl pyrrolidone were mixed into a binder with a content of 5%. The positive electrode active materials prepared in Examples 1 to 4 were then taken and stirred into a uniform positive electrode slurry according to the mass ratio of the positive electrode active material, acetylene black and polyvinylidene fluoride of 10:1.2:1. The positive electrode slurry was then heated to 2.8 g / cm 2 The electrode sheet was prepared by scraping it onto the surface of aluminum foil and then drying it in a vacuum drying oven at 60°C for 24 hours. The electrode sheet was then cut into disc samples with a diameter of 15 mm and assembled into button batteries for electrical performance testing. The specific test data are shown in Table 1:

[0065] Table 1

[0066]

[0067]

[0068] From the data in Table 1, it can be seen that the capacity of the positive electrode active material prepared by the present invention reaches 946-982 / mAh·g -1 Compared with existing commercial battery cathode materials, it has a higher capacity at 0.2A·g -1 After 100 cycles, the capacity retention rate reaches 92.7-95.3%, showing excellent stability.

[0069] Throughout the specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0070] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in similar ways. As long as they do not deviate from the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a bipolar battery positive electrode active material, characterized in that: The steps include: Step S1: dissolving elemental sulfur with carbon disulfide, adding graphene composite micropowder, performing ultrasonic dispersion treatment at 28-33 kHz for 1-1.2 hours, and spray drying the dispersion to prepare a sulfur-attached matrix; Step S2: Pyrrole and ethanol solution are mixed, sulfur-attached matrix is ​​added, ultrasonically dispersed into a suspension state, and the pH value is adjusted to 5.8-6.2 with hydrochloric acid. Ferric chloride solution is slowly added dropwise at 400-500 rpm in an ice-water bath at a constant temperature. The total addition reaction time is 2.5-3 hours. The bottom precipitate is collected by centrifugation, washed with deionized water, and dried to prepare a doped matrix; Step S3: mixing the doped matrix and the silver ammonia solution, maintaining a constant temperature of 80-90°C, and ultrasonically dispersing at 40kHz. The frequency is then reduced to 20kHz, and the formaldehyde solution is slowly added dropwise. After addition, stirring is continued at 300-400 rpm. The overall addition reaction time is controlled to be 40-60 minutes. The precipitate is removed by centrifugation and dried under nitrogen protection to prepare the positive electrode active material. The graphene composite micropowder is prepared by the following method: Step A1: Graphene oxide, thionyl chloride, and DMF are mixed and stirred at 180-240 rpm for 30-35 hours at room temperature. The thionyl chloride is then removed by rotary evaporation, and the mixture is washed with tetrahydrofuran and dried under nitrogen to a constant weight to prepare graphene chloride. The ratio of graphene oxide, thionyl chloride, and DMF is 1 g: 35-45 mL: 2-4 mL. Step A2: Mix the mesoporous molecular sieve and deionized water, adjust the pH to 8-9, and stir at room temperature for 5-6 hours. Then, add the silane coupling agent KH550, ultrasonically disperse at 30 kHz for 2-2.5 hours, centrifuge, remove the bottom precipitate, wash, and vacuum dry to prepare an ammonium carrier, wherein the amount ratio of the silane coupling agent KH550 to the mesoporous molecular sieve is 1.8-2.5 mL / 1 g; Step A3: chlorinated graphene, triethylamine, and dioxane are mixed, and an aminated carrier is added under 28 kHz ultrasonic dispersion for 20-30 minutes. The bottom precipitate is collected by centrifugation, and a hydrazine hydrate solution is added and stirred for 2-3 hours. The mixture is evaporated to dryness under reduced pressure and broken up to prepare a graphene composite micropowder, wherein the amount ratio of the aminated carrier, chlorinated graphene, triethylamine, dioxane, and hydrazine hydrate solution is 3 g: 1 g: 0.6-0.8 mL: 40-50 mL: 15-20 mL, and the concentration of the hydrazine hydrate solution is 30%.

2. The method for preparing a bipolar battery positive electrode active material according to claim 1, characterized in that: The usage ratio of graphene composite micropowder, elemental sulfur and carbon disulfide is 1g:0.24-0.3g:25-30mL.

3. The method for preparing a bipolar battery positive electrode active material according to claim 2, characterized in that: The dosage ratio of the sulfur-attached matrix, pyrrole, ferric chloride and ethanol solution is 1 g: 0.42-0.48 mL: 16-22 mg: 50-60 mL, the concentration of the ferric chloride solution is 0.1 mol / L, and the concentration of the ethanol solution is 60%.

4. The method for preparing a bipolar battery positive electrode active material according to claim 3, characterized in that: The dosage ratio of the doping matrix, the silver ammonia solution and the formaldehyde solution is 1 g: 12-16 mL: 45-55 mL, the concentration of the silver ammonia solution is 0.01 M, and the concentration of the formaldehyde solution is 15%.

5. A bipolar battery positive electrode active material, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 4.

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