Preparation method and application of manganese-based prussian blue / reduced graphene oxide composite material

Abstract

The application discloses a preparation method and application of a manganese-based Prussian blue / reduced graphene oxide composite material, and the method comprises the following steps: uniformly stirring manganese sulfate monohydrate in a polyvinylpyrrolidone aqueous solution, adding a potassium ferricyanide aqueous solution while stirring, and then standing, centrifuging, washing and drying to prepare manganese-based Prussian blue; adding the manganese-based Prussian blue and ascorbic acid into a dispersion solution of reduced graphene oxide, stirring, transferring into a high-pressure reaction kettle for hydrothermal reaction, cooling to room temperature, centrifuging, washing and drying to obtain the manganese-based Prussian blue / reduced graphene oxide composite material with a three-dimensional framework structure. The manganese-based Prussian blue / reduced graphene oxide composite material is used for preparing a positive electrode material of a water-based zinc ion battery. The conductivity of the material and the contact area of the material are significantly improved, the diffusion rate of ions is promoted, and the storage sites of zinc ions are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of new energy materials and devices, specifically to a method for preparing and applying a manganese-based Prussian blue / reduced graphene oxide composite material. Background Technology

[0002] With the massive burning of fossil fuels, non-renewable energy sources may face shortages, and environmental pollution is worsening. Developing efficient and clean renewable energy sources and exploring newer energy storage devices are urgently needed. Among various energy storage systems, economical, green, safe, and reliable rechargeable batteries have pioneered entirely new energy storage methods. The development of rechargeable batteries plays a crucial and indispensable role in the current energy storage industry. Lithium-ion batteries have high energy density and a more mature market, leading to their widespread use in the electronics industry. However, the limited lithium resources and high cost of lithium-ion batteries, coupled with the flammability and safety issues of their internal organic electrolytes, limit their large-scale application in daily life. Therefore, developing alternative rechargeable batteries is particularly important, and more and more researchers are beginning to study other rechargeable batteries.

[0003] Aqueous zinc-ion batteries (AZIBs) possess advantages such as abundant zinc resources, high capacity (theoretical capacity 819 mAh / g), low manufacturing cost, high safety performance, and environmental friendliness, making them suitable for widespread application in large-scale energy storage. Common cathode materials include manganese-based oxides, vanadium-based oxides, Prussian blue analogs, and organic compounds. Among these, Prussian blue analogs (PBAs) are mixed-valence complexes with abundant redox active sites. Furthermore, their open three-dimensional framework structure and large ion channels in the crystal lattice are highly suitable for Zn. 2+ Due to its rapid migration and advantages such as simple preparation process, low cost, high voltage, and environmental friendliness, PBAs have become a promising cathode material for AZIBs. Theoretically, PBAs possess excellent electrochemical zinc storage performance; however, in actual charge-discharge processes, they generally suffer from low efficiency, poor rate capability, and unstable cycling. The reasons for this are generally believed to be related to excessively rapid precipitation and incomplete reaction during PBA preparation, as well as the presence of numerous defects and water of crystallization in the crystal structure. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing manganese-based Prussian blue / reduced graphene oxide composite material and its application, which improves the specific capacity of the battery, enhances its rate performance, and increases its resilience.

[0005] In one aspect of the present invention, a method for preparing a manganese-based Prussian blue / reduced graphene oxide composite material is provided. According to an embodiment of the present invention, the method includes the following steps:

[0006] (1) Dissolve manganese sulfate monohydrate in polyvinylpyrrolidone aqueous solution and stir until homogeneous. Control the dropping rate and add potassium ferricyanide aqueous solution while stirring. Then let stand, centrifuge, wash and dry to prepare manganese-based Prussian blue.

[0007] (2) Manganese-based Prussian blue and ascorbic acid were added to the dispersion of reduced graphene oxide, stirred and transferred to a high-pressure reactor for hydrothermal reaction. After cooling to room temperature, the mixture was centrifuged, washed and dried to obtain a manganese-based Prussian blue / reduced graphene oxide composite material with a three-dimensional framework structure.

[0008] In addition, the preparation method of the manganese-based Prussian blue / reduced graphene oxide composite material according to the above embodiments of the present invention may also have the following additional technical features:

[0009] In some embodiments of the present invention, the molar ratio of polyvinylpyrrolidone, manganese sulfate monohydrate, potassium ferricyanide, and reduced graphene oxide is 0.037:4.81:4.81:(5-12.5).

[0010] In some embodiments of the present invention, in step (1): a peristaltic pump is used to control the drip rate, and the drip rate controlled by the peristaltic pump is 1-3 mL / min; the centrifugation speed is 8000-9500 rpm, and the centrifugation time is 3-6 minutes; the washing is performed by alternating washing with anhydrous ethanol and deionized water 3-5 times; the drying temperature is 80-120℃, and the drying time is 8-12 hours.

[0011] In some embodiments of the present invention, in step (2): the hydrothermal reaction is carried out at 120-150°C for 6-8 hours; the centrifugation speed is 8000-9500 rpm and the centrifugation time is 3-6 minutes; the washing is carried out by alternating washing with anhydrous ethanol and deionized water, and washing is carried out 3-5 times; the drying is carried out by freeze drying or vacuum drying, the freeze drying temperature is -70-100°C and the freezing time is 24-48 hours; the vacuum drying temperature is 70-90°C and the drying time is 8-12 hours.

[0012] In another aspect of the present invention, the present invention provides a manganese-based Prussian blue / reduced graphene oxide composite material prepared according to the preparation method of the aforementioned manganese-based Prussian blue / reduced graphene oxide composite material.

[0013] In another aspect of the invention, a cathode material is proposed. According to an embodiment of the invention, it is prepared using the aforementioned manganese-based Prussian blue / reduced graphene oxide composite material.

[0014] In another aspect, the present invention provides a method for preparing a cathode material. According to an embodiment of the present invention, the method includes the following steps:

[0015] The manganese-based Prussian blue / reduced graphene oxide composite material is ground evenly with a binder and a conductive agent, N-methylpyrrolidone solvent is added dropwise, and the mixture is ground and mixed evenly. The mixture is then coated onto a stainless steel foil, vacuum dried, and cut to obtain the MnHCF-RGO electrode sheet, which is the positive electrode material.

[0016] In addition, the method for preparing a positive electrode material according to the above embodiments of the present invention may also have the following additional technical features:

[0017] In some embodiments of the present invention, the mass ratio of the manganese-based Prussian blue / reduced graphene oxide composite material, the conductive agent, and the binder is (7-8):(2-1):1, the binder used is polyvinylidene fluoride, and the conductive agent is Ketjen Black.

[0018] In another aspect, the present invention proposes an aqueous zinc-ion battery. According to an embodiment of the invention, the aforementioned positive electrode material is used as the positive electrode.

[0019] In addition, an aqueous zinc-ion battery according to the above embodiments of the present invention may also have the following additional technical features:

[0020] In some embodiments of the present invention, the negative electrode material is a zinc electrode sheet, the electrolyte is a mixture of zinc sulfate and manganese sulfate, and the battery separator is glass fiber.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] 1) The addition of graphene oxide in this invention significantly enhances the conductivity of manganese-based Prussian blue, greatly increases the charge transfer rate of the material, and accelerates the electrochemical reaction rate. Simultaneously, graphene oxide also acts as a buffer matrix, mitigating the structural collapse that may occur during the charge-discharge process of manganese-based Prussian blue. This composite strategy not only effectively improves electrochemical performance but also significantly extends the battery's lifespan, enhancing its reliability and safety. Furthermore, graphene oxide also acts as a structural stabilizer, solidifying the material's structure and thus effectively improving its electrochemical performance.

[0023] 2) This invention utilizes the advantages of reduced graphene oxide, such as good conductivity, low resistance, and fast electron transport speed, to enable the manganese-based Prussian blue composite with a three-dimensional framework structure to form a large network structure, which significantly improves the conductivity and contact area of ​​the material, promotes the diffusion rate of ions, and effectively improves the storage sites of zinc ions.

[0024] 3) This invention employs freeze-drying and vacuum drying technologies. SEM images show that manganese-based Prussian blue cubic blocks are distributed within the layered reduced graphene oxide, effectively preventing particle agglomeration. The overall structure is relatively uniform, resulting in a higher specific surface area. This contributes to the material's good stability and high specific capacity during charge and discharge. After composite graphene, the initial specific capacity is 104 mAh / g at a current density of 0.1 A / g. Upon retesting at a rate of 0.1 A / g, the discharge specific capacity recovery rate reaches 110.9%, indicating a certain degree of improvement in battery specific capacity, better rate performance, and higher recovery.

[0025] 4) The preparation process of this invention is simple, the reaction conditions are mild, the environment is friendly, and the cost is low. It has great application value and is also applicable to other Prussian blue analog cathode materials.

[0026] 5) This invention uses a peristaltic pump to precisely control the flow rate and employs a slow crystallization method to prepare structurally complete manganese-based Prussian blue. Then, a high-temperature hydrothermal method is used to composite reduced graphene oxide, which solves the problem of excessively fast precipitation and incomplete reaction during the preparation of PBAs. Finally, a manganese-based Prussian blue / reduced graphene oxide composite material with superior electrochemical performance is obtained. Attached Figure Description

[0027] Figure 1 The XRD patterns (b) are those of manganese-based Prussian blue (a) prepared in step 1 of Example 1 of this invention and manganese-based Prussian blue / reduced graphene oxide with a three-dimensional framework structure prepared in Examples 1 and 2.

[0028] Figure 2 SEM images (b) of manganese-based Prussian blue (a) and manganese-based Prussian blue / reduced graphene oxide with a three-dimensional framework structure prepared in Example 1 of this invention;

[0029] Figure 3 The AC impedance spectra of manganese-based Prussian blue prepared in Example 1 of this invention and manganese-based Prussian blue / reduced graphene oxide with a three-dimensional framework structure prepared in Examples 1 and 2 are shown.

[0030] Figure 4 This is a cycle diagram of manganese-based Prussian blue (a) prepared in Example 1 of the present invention and manganese-based Prussian blue / reduced graphene oxide with a three-dimensional framework structure prepared in Examples 1 (b) and 2 (c);

[0031] Figure 5 This is a scale diagram of the manganese-based Prussian blue prepared in Example 1 of this invention and the manganese-based Prussian blue / reduced graphene oxide with a three-dimensional framework structure prepared in Examples 1 and 2. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1

[0034] A method for preparing a manganese-based Prussian blue / reduced graphene oxide composite material includes the following steps:

[0035] (1) Weigh 2.221g of polyvinylpyrrolidone and dissolve it completely in 120mL of deionized water. Then weigh 0.813g of manganese sulfate monohydrate and dissolve it in the polyvinylpyrrolidone aqueous solution. Stir thoroughly to prepare solution A. Weigh 1.584g of potassium ferricyanide and dissolve it in 60mL of deionized water. Stir thoroughly to prepare orange-red solution B. Use a peristaltic pump to slowly add solution B to solution A at a rate of 1mL / min while stirring. The solution after the reaction is brown. After the reaction is complete, let it stand for 12h, then centrifuge at 8000 rpm for 5 minutes. Wash the solution three times alternately with anhydrous ethanol and deionized water. Place the obtained sample in a forced-air drying oven and dry at 80℃ for 8 hours. Finally, a brown powder is obtained, which is the prepared manganese-based Prussian blue (MnHCF).

[0036] (2) Weigh 60 mg of reduced graphene oxide and disperse it in 30 mL of deionized water. Sonicate for 3 h to obtain a uniformly dispersed graphene dispersion of 2 mg / mL. Weigh 100 mg of manganese-based Prussian blue prepared in step (1) and 50 mg of ascorbic acid and add them to the 30 mL dispersion of reduced graphene oxide. Sonicate for 1 h and then stir magnetically for 12 h. Then transfer the suspension to a 100 mL high-pressure reactor and keep it in an oven at 120 °C for 6 h. After cooling to room temperature, centrifuge at 8000 rpm for 5 minutes. Wash the mixture three times with alternating washing with anhydrous ethanol and deionized water. Finally, freeze it in a freeze dryer at -70 °C for 24 hours to obtain a manganese-based Prussian blue / reduced graphene oxide (MnHCF-RGO) composite material with a three-dimensional framework structure.

[0037] like Figure 1As shown, the manganese-based Prussian blue sample prepared in step (1) corresponds to PDF card #00-052-1907, indicating that the composition of the sample prepared in step (1) is Mn3[Fe(CN)6]2. All diffraction peaks of the sample prepared in step (2) correspond to the two standard cards Mn3[Fe(CN)6]2 (PDF#00-052-1907) and C (PDF#41-1487). The sharp diffraction peak at 26.3° corresponds to the (002) crystal plane of C, indicating that the manganese-based Prussian blue / reduced graphene oxide (MnHCF-RGO) composite material was successfully prepared by freeze drying.

[0038] like Figure 2 As shown, the manganese-based Prussian blue sample prepared in step (1) is a uniform cubic block, while the sample prepared in step (2) contains MnHCF cubic blocks distributed in layered graphene. This indicates that the introduction of graphene did not change the original morphological characteristics of MnHCF, and the overall structure is relatively uniform. The graphene and manganese-based Prussian blue were well composited by the hydrothermal method.

[0039] Example 2

[0040] A method for preparing a manganese-based Prussian blue / reduced graphene oxide composite material includes the following steps:

[0041] (1) Weigh 2.221g of polyvinylpyrrolidone and dissolve it completely in 120mL of deionized water. Then weigh 0.813g of manganese sulfate monohydrate and dissolve it in the polyvinylpyrrolidone aqueous solution. Stir thoroughly to prepare solution A. Weigh 1.584g of potassium ferricyanide and dissolve it in 60mL of deionized water. Stir thoroughly to prepare orange-red solution B. Use a peristaltic pump to slowly add solution B to solution A at a rate of 1mL / min while stirring. The solution after the reaction is brown. After the reaction is complete, let it stand for 12h, then centrifuge at 8000 rpm for 5 minutes. Wash the solution three times alternately with anhydrous ethanol and deionized water. Place the obtained sample in a forced-air drying oven and dry at 80℃ for 8 hours. Finally, a brown powder is obtained, which is the prepared manganese-based Prussian blue (MnHCF).

[0042] (2) Weigh 60 mg of reduced graphene oxide and disperse it in 30 mL of deionized water. Sonicate the solution for 3 hours to obtain 2 mg / mL of uniformly dispersed graphene oxide. -1100 mg of manganese-based Prussian blue and 50 mg of ascorbic acid prepared in step (1) were weighed and added to 30 mL of reduced graphene oxide dispersion. The mixture was ultrasonically dispersed for 1 h and then magnetically stirred for 12 h. The suspension was then transferred to a 100 mL high-pressure reactor and kept at 120 °C for 6 h. After cooling to room temperature, the mixture was centrifuged at 8000 rpm for 5 minutes. It was washed three times with alternating anhydrous ethanol and deionized water. Finally, it was placed in a vacuum drying oven for vacuum drying at 80 °C for 12 h. This yielded the prepared manganese-based Prussian blue / reduced graphene oxide (MnHCF-RGO) composite material with a three-dimensional framework structure.

[0043] Example 3

[0044] A method for preparing a manganese-based Prussian blue / reduced graphene oxide composite material includes the following steps:

[0045] (1) Weigh 2.221g of polyvinylpyrrolidone and dissolve it completely in 120mL of deionized water. Then weigh 0.813g of manganese sulfate monohydrate and dissolve it in the polyvinylpyrrolidone aqueous solution. Stir thoroughly to prepare solution A. Weigh 1.584g of potassium ferricyanide and dissolve it in 60mL of deionized water. Stir thoroughly to prepare orange-red solution B. Use a peristaltic pump to slowly add solution B to solution A at a rate of 1mL / min while stirring. The solution after the reaction is brown. After the reaction is complete, let it stand for 12h, then centrifuge at 8000 rpm for 5 minutes. Wash the solution three times alternately with anhydrous ethanol and deionized water. Place the obtained sample in a forced-air drying oven and dry at 80℃ for 8 hours. Finally, a brown powder is obtained, which is the prepared manganese-based Prussian blue (MnHCF).

[0046] (2) Weigh 90 mg of reduced graphene oxide and disperse it in 30 mL of deionized water. Sonicate the solution for 3 h to obtain a uniformly dispersed 3 mg / mL solution. -1 100 mg of manganese-based Prussian blue and 50 mg of ascorbic acid prepared in step (1) were weighed and added to 30 mL of reduced graphene oxide dispersion. The mixture was ultrasonically dispersed for 1 h and then magnetically stirred for 12 h. The suspension was then transferred to a 100 mL high-pressure reactor and kept at 120 °C for 6 h. After cooling to room temperature, the mixture was centrifuged at 8000 rpm for 5 minutes. The mixture was washed three times with alternating anhydrous ethanol and deionized water. Finally, it was placed in a freeze dryer for freeze drying at -70 °C for 24 hours. This yielded the prepared manganese-based Prussian blue / reduced graphene oxide (MnHCF-RGO) composite material with a three-dimensional framework structure.

[0047] Example 4

[0048] A method for preparing a manganese-based Prussian blue / reduced graphene oxide composite material includes the following steps:

[0049] (1) Weigh 2.221g of polyvinylpyrrolidone and dissolve it completely in 120mL of deionized water. Then weigh 0.813g of manganese sulfate monohydrate and dissolve it in the polyvinylpyrrolidone aqueous solution. Stir thoroughly to prepare solution A. Weigh 1.584g of potassium ferricyanide and dissolve it in 60mL of deionized water. Stir thoroughly to prepare orange-red solution B. Use a peristaltic pump to slowly add solution B to solution A at a rate of 1mL / min while stirring. The solution after the reaction is brown. After the reaction is complete, let it stand for 12h, then centrifuge at 8000 rpm for 5 minutes. Wash the solution three times alternately with anhydrous ethanol and deionized water. Place the obtained sample in a forced-air drying oven and dry at 80℃ for 8 hours. Finally, a brown powder is obtained, which is the prepared manganese-based Prussian blue (MnHCF).

[0050] (2) Weigh 90 mg of reduced graphene oxide and disperse it in 30 mL of deionized water. Sonicate the solution for 3 h to obtain a uniformly dispersed 3 mg / mL solution. -1 100 mg of manganese-based Prussian blue and 50 mg of ascorbic acid prepared in step (1) were weighed and added to 30 mL of reduced graphene oxide dispersion. The mixture was ultrasonically dispersed for 1 h and then magnetically stirred for 12 h. The suspension was then transferred to a 100 mL high-pressure reactor and kept at 120 °C for 6 h. After cooling to room temperature, the mixture was centrifuged at 8000 rpm for 5 minutes. It was washed three times with alternating anhydrous ethanol and deionized water. Finally, it was placed in a vacuum drying oven for vacuum drying at 80 °C for 12 h. This yielded the prepared manganese-based Prussian blue / reduced graphene oxide (MnHCF-RGO) composite material with a three-dimensional framework structure.

[0051] Example 5

[0052] A method for preparing a manganese-based Prussian blue / reduced graphene oxide composite material includes the following steps:

[0053] (1) Weigh 2.221g of polyvinylpyrrolidone and dissolve it completely in 120mL of deionized water. Then weigh 0.813g of manganese sulfate monohydrate and dissolve it in the polyvinylpyrrolidone aqueous solution. Stir thoroughly to prepare solution A. Weigh 1.584g of potassium ferricyanide and dissolve it in 60mL of deionized water. Stir thoroughly to prepare orange-red solution B. Use a peristaltic pump to slowly add solution B to solution A at a rate of 1mL / min while stirring. The solution after the reaction is brown. After the reaction is complete, let it stand for 12h, then centrifuge at 8000 rpm for 5 minutes. Wash the solution three times alternately with anhydrous ethanol and deionized water. Place the obtained sample in a forced-air drying oven and dry at 80℃ for 8 hours. Finally, a brown powder is obtained, which is the prepared manganese-based Prussian blue (MnHCF).

[0054] (2) Weigh 120 mg of reduced graphene oxide and disperse it in 30 mL of deionized water. Sonicate the solution for 3 hours to obtain 4 mg / mL of uniformly dispersed graphene oxide. -1 100 mg of manganese-based Prussian blue and 50 mg of ascorbic acid prepared in step (1) were weighed and added to 30 mL of reduced graphene oxide dispersion. The mixture was ultrasonically dispersed for 1 h and then magnetically stirred for 12 h. The suspension was then transferred to a 100 mL high-pressure reactor and kept at 120 °C for 6 h. After cooling to room temperature, the mixture was centrifuged at 8000 rpm for 5 minutes. The mixture was washed three times with alternating anhydrous ethanol and deionized water. Finally, it was placed in a freeze dryer for freeze drying at -70 °C for 24 hours. This yielded the prepared manganese-based Prussian blue / reduced graphene oxide (MnHCF-RGO) composite material with a three-dimensional framework structure.

[0055] Example 6

[0056] A method for preparing a manganese-based Prussian blue / reduced graphene oxide composite material includes the following steps:

[0057] (1) Weigh 2.221g of polyvinylpyrrolidone and dissolve it completely in 120mL of deionized water. Then weigh 0.813g of manganese sulfate monohydrate and dissolve it in the polyvinylpyrrolidone aqueous solution. Stir thoroughly to prepare solution A. Weigh 1.584g of potassium ferricyanide and dissolve it in 60mL of deionized water. Stir thoroughly to prepare orange-red solution B. Use a peristaltic pump to slowly add solution B to solution A at a rate of 1mL / min while stirring. The solution after the reaction is brown. After the reaction is complete, let it stand for 12h, then centrifuge at 8000 rpm for 5 minutes. Wash the solution three times alternately with anhydrous ethanol and deionized water. Place the obtained sample in a forced-air drying oven and dry at 80℃ for 8 hours. Finally, a brown powder is obtained, which is the prepared manganese-based Prussian blue (MnHCF).

[0058] (2) Weigh 120 mg of reduced graphene oxide and disperse it in 30 mL of deionized water. Sonicate the solution for 3 hours to obtain 4 mg / mL of uniformly dispersed graphene oxide. -1 100 mg of manganese-based Prussian blue and 50 mg of ascorbic acid prepared in step (1) were weighed and added to 30 mL of reduced graphene oxide dispersion. The mixture was ultrasonically dispersed for 1 h and then magnetically stirred for 12 h. The suspension was then transferred to a 100 mL high-pressure reactor and kept at 120 °C for 6 h. After cooling to room temperature, the mixture was centrifuged at 8000 rpm for 5 minutes. It was washed three times with alternating anhydrous ethanol and deionized water. Finally, it was placed in a vacuum drying oven for vacuum drying at 80 °C for 12 h. This yielded the prepared manganese-based Prussian blue / reduced graphene oxide (MnHCF-RGO) composite material with a three-dimensional framework structure.

[0059] Example 7

[0060] A method for preparing a manganese-based Prussian blue / reduced graphene oxide composite material includes the following steps:

[0061] (1) Weigh 2.221g of polyvinylpyrrolidone and dissolve it completely in 120mL of deionized water. Then weigh 0.813g of manganese sulfate monohydrate and dissolve it in the polyvinylpyrrolidone aqueous solution. Stir thoroughly to prepare solution A. Weigh 1.584g of potassium ferricyanide and dissolve it in 60mL of deionized water. Stir thoroughly to prepare orange-red solution B. Use a peristaltic pump to slowly add solution B to solution A at a rate of 1mL / min while stirring. The solution after the reaction is brown. After the reaction is complete, let it stand for 12h, then centrifuge at 8000 rpm for 5 minutes. Wash the solution three times alternately with anhydrous ethanol and deionized water. Place the obtained sample in a forced-air drying oven and dry at 80℃ for 8 hours. Finally, a brown powder is obtained, which is the prepared manganese-based Prussian blue (MnHCF).

[0062] (2) Weigh 150 mg of reduced graphene oxide and disperse it in 30 mL of deionized water. Sonicate the solution for 3 hours to obtain 5 mg / mL of uniformly dispersed graphene oxide. -1 100 mg of manganese-based Prussian blue and 50 mg of ascorbic acid prepared in step (1) were weighed and added to 30 mL of reduced graphene oxide dispersion. The mixture was ultrasonically dispersed for 1 h and then magnetically stirred for 12 h. The suspension was then transferred to a 100 mL high-pressure reactor and kept at 120 °C for 6 h. After cooling to room temperature, the mixture was centrifuged at 8000 rpm for 5 minutes. The mixture was washed three times with alternating anhydrous ethanol and deionized water. Finally, it was placed in a freeze dryer for freeze drying at -70 °C for 24 hours. This yielded the prepared manganese-based Prussian blue / reduced graphene oxide (MnHCF-RGO) composite material with a three-dimensional framework structure.

[0063] Example 8

[0064] A method for preparing a manganese-based Prussian blue / reduced graphene oxide composite material includes the following steps:

[0065] (1) Weigh 2.221g of polyvinylpyrrolidone and dissolve it completely in 120mL of deionized water. Then weigh 0.813g of manganese sulfate monohydrate and dissolve it in the polyvinylpyrrolidone aqueous solution. Stir thoroughly to prepare solution A. Weigh 1.584g of potassium ferricyanide and dissolve it in 60mL of deionized water. Stir thoroughly to prepare orange-red solution B. Use a peristaltic pump to slowly add solution B to solution A at a rate of 1mL / min while stirring. The solution after the reaction is brown. After the reaction is complete, let it stand for 12h, then centrifuge at 8000 rpm for 5 minutes. Wash the solution three times alternately with anhydrous ethanol and deionized water. Place the obtained sample in a forced-air drying oven and dry at 80℃ for 8 hours. Finally, a brown powder is obtained, which is the prepared manganese-based Prussian blue (MnHCF).

[0066] (2) Weigh 150 mg of reduced graphene oxide and disperse it in 30 mL of deionized water. Sonicate the solution for 3 hours to obtain 5 mg / mL of uniformly dispersed graphene oxide. -1 100 mg of manganese-based Prussian blue and 50 mg of ascorbic acid prepared in step (1) were weighed and added to 30 mL of reduced graphene oxide dispersion. The mixture was ultrasonically dispersed for 1 h and then magnetically stirred for 12 h. The suspension was then transferred to a 100 mL high-pressure reactor and kept at 120 °C for 6 h. After cooling to room temperature, the mixture was centrifuged at 8000 rpm for 5 minutes. It was washed three times with alternating anhydrous ethanol and deionized water. Finally, it was placed in a vacuum drying oven for vacuum drying at 80 °C for 12 h. This yielded the prepared manganese-based Prussian blue / reduced graphene oxide (MnHCF-RGO) composite material with a three-dimensional framework structure.

[0067] Application Example 1

[0068] A method for preparing a positive electrode material includes the following steps:

[0069] The MnHCF prepared in Example 1 and the MnHCF-RGO prepared in Examples 1 and 2 were mixed with Ketjen Black and PVDF at a mass ratio of 7:2:1. A small amount of NMP solvent was added, and the mixture was ground and mixed evenly. The slurry was coated on a stainless steel bowl and dried under vacuum at 80°C for 12 hours. The slurry was then cut into electrode sheets with a diameter of 12 mm using a slicer to obtain the electrode sheets, which are the positive electrode materials.

[0070] Application Example 2

[0071] The preparation method of an aqueous zinc-ion battery includes the following steps:

[0072] A zinc mortar with a thickness of 0.02 mm and a purity of 99.9% was sanded to remove the oxide film, and then cut into zinc electrode sheets with a diameter of 12 mm as negative electrodes. The electrode sheet prepared in Application Example 1 was used as the positive electrode material, a mixture of 3M zinc sulfate and 0.5M manganese sulfate was used as the electrolyte, and glass fiber with a diameter of 16 mm was used as the battery separator to assemble a button-type CR2025 aqueous zinc-ion battery.

[0073] like Figure 3 As shown, the MnHCF-RGO prepared by freeze-drying in Example 1 and by vacuum drying in Example 2 exhibit the following characteristics in the high-frequency region: the MnHCF-RGO prepared by freeze-drying in Example 1 has the smallest semi-circle radius, indicating that the charge transfer resistance Rct at the electrode / electrolyte interface is minimized after the graphene is composited by freeze-drying. Meanwhile, in the low-frequency region, the slope of the oblique line of the MnHCF-RGO sample prepared by freeze-drying in Example 1 is the largest, indicating that the ion diffusion is faster after the graphene is composited by freeze-drying, which increases the charge transfer rate of the material and accelerates the electrochemical reaction rate.

[0074] like Figure 4 As shown, the MnHFC-RGO prepared by freeze-drying in Example 1 had an initial specific capacity of 104 mAh / g at a current density of 0.1 A / g. Compared with the manganese-based Prussian blue sample prepared in step (1) of Example 1, the composite graphene significantly improved the specific capacity of MnHFC. After 50 cycles, the battery specific capacity decreased to 75 mAh / g, and after 200 cycles, the battery specific capacity became 68 mAh / g. After 50 cycles, the capacity retention rate reached 91%.

[0075] like Figure 5 As shown, when the freeze-dried MnHCF-RGO sample was retested with a current density of 0.1 A / g after rate testing, the discharge specific capacity recovery rate reached 110.9%, indicating a certain degree of improvement in battery specific capacity, better rate performance, and higher recovery.

[0076] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the present invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A method for preparing a manganese-based Prussian blue / reduced graphene oxide composite cathode material, characterized in that, Includes the following steps: (1) Dissolve manganese sulfate monohydrate in polyvinylpyrrolidone aqueous solution and stir until uniform. Control the dropping rate and add potassium ferricyanide aqueous solution while stirring. Then let stand, centrifuge, wash and dry to prepare manganese-based Prussian blue. (2) Manganese-based Prussian blue and ascorbic acid were added to the dispersion of reduced graphene oxide, stirred and transferred to a high-pressure reactor for hydrothermal reaction. After cooling to room temperature, the mixture was centrifuged, washed and dried to obtain a composite cathode material of manganese-based Prussian blue / reduced graphene oxide with a three-dimensional framework structure. The hydrothermal reaction was carried out at 120-150℃ for 6-8 hours. The drying was carried out by freeze drying or vacuum drying. The freeze drying temperature was -(70-100)℃ and the freezing time was 24-48 hours. The vacuum drying temperature was 70-90℃ and the drying time was 8-12 hours. Manganese-based Prussian blue cubic blocks were distributed in the layered reduced graphene oxide.

2. The preparation method of a manganese-based Prussian blue / reduced graphene oxide composite cathode material according to claim 1, characterized in that: The molar ratio of polyvinylpyrrolidone, manganese sulfate monohydrate, potassium ferricyanide, and reduced graphene oxide is 0.037:4.81:4.81:(5-12.5).

3. The preparation method of a manganese-based Prussian blue / reduced graphene oxide composite cathode material according to claim 1, characterized in that, In step (1): The drip rate is 1-3 mL / min; The centrifuge speed is 8000-9500 rpm, and the centrifugation time is 3-6 minutes; The washing process involves alternating between anhydrous ethanol and deionized water, and washing 3-5 times. The drying temperature is 80-120℃, and the drying time is 8-12 hours.

4. The preparation method of a manganese-based Prussian blue / reduced graphene oxide composite cathode material according to claim 1, characterized in that, In step (2): The centrifugation speed is 8000-9500 rpm, and the centrifugation time is 3-6 minutes; The washing process involves alternating between anhydrous ethanol and deionized water, repeating the process 3-5 times.

5. A manganese-based Prussian blue / reduced graphene oxide composite cathode material prepared by the preparation method of the manganese-based Prussian blue / reduced graphene oxide composite cathode material according to any one of claims 1-4.

6. An electrode sheet, characterized in that: The composite cathode material is prepared using the manganese-based Prussian blue / reduced graphene oxide composite material as described in claim 5.

7. A method for preparing the electrode sheet according to claim 6, characterized in that, Includes the following steps: Manganese-based Prussian blue / reduced graphene oxide composite cathode material was ground evenly with binder and conductive agent, N-methylpyrrolidone solvent was added dropwise, and grinding and mixing were continued until uniform. The mixture was then coated onto stainless steel foil, vacuum dried, and cut to obtain MnHCF-RGO electrode sheet.

8. The method for preparing an electrode sheet according to claim 7, characterized in that: The mass ratio of the manganese-based Prussian blue / reduced graphene oxide composite cathode material, the conductive agent, and the binder is (7-8):(2-1):

1. The binder used is polyvinylidene fluoride, and the conductive agent is Ketjen Black.

9. An aqueous zinc-ion battery, characterized in that: The electrode sheet described in claim 6 is used as the positive electrode.

10. An aqueous zinc-ion battery according to claim 9, characterized in that: The negative electrode material is a zinc electrode sheet, the electrolyte is a mixture of zinc sulfate and manganese sulfate, and the battery separator is glass fiber.

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