Alpha-MnO2 positive electrode material reconstructed by electrolytic manganese dioxide crystal form and preparation method and application thereof

Abstract

The invention discloses a positive electrode material reconstructed from an electrolytic manganese dioxide crystal form and a preparation method and application thereof. On the basis of an electrolytic manganese dioxide (EMD)-oxalic acid-potassium persulfate reaction system, cheap EMD is taken as a manganese source, directional preparation is realized by regulating and controlling process parameters, a product with high purity and excellent electrochemical performance is obtained, and meanwhile, the preparation cost and the environmental protection pressure are reduced. And the prepared zinc oxide has a large specific surface area and a smooth zinc ion diffusion path, and shows high first discharge specific capacity and good cycle stability when being applied to an aqueous zinc ion battery positive electrode material.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery materials, specifically to materials reconstructed from the crystal form of electrolytic manganese dioxide. Cathode materials, their preparation methods, and applications. Background Technology

[0002] With the increasing severity of the global energy crisis and environmental problems, developing clean, efficient, and sustainable energy storage systems has become an important direction for technological development. Among numerous electrochemical energy storage technologies, lithium-ion batteries have achieved dominance, but their application in large-scale energy storage is limited by safety hazards such as scarce lithium resources, high costs, and the flammability and explosiveness of organic electrolytes. Therefore, seeking low-cost, high-safety alternative battery systems is urgent. Aqueous zinc-ion batteries have attracted much attention due to their unique advantages. Zinc resources are abundant and inexpensive, and they possess a high theoretical capacity (…). It features a low redox potential (-0.76 V vs. SHE). More importantly, the use of an aqueous electrolyte instead of a flammable organic electrolyte fundamentally improves battery safety and simplifies battery manufacturing and packaging processes, making it a highly promising candidate for large-scale grid energy storage.

[0003] In aqueous zinc-ion battery systems, the cathode material is a key factor determining the overall battery performance (such as capacity, rate performance, and cycle life). Manganese dioxide (…) With its abundant reserves, environmental friendliness, and high theoretical specific capacity, With its advantages such as [missing information], it is considered one of the most promising cathode materials for aqueous zinc-ion batteries. There are multiple crystal configurations (α, β, γ, δ, etc.), among which, It is highly favored for its unique [2×2] tunnel structure. The tunnel size (approximately 4.6 Å) is related to zinc ions ( The size of the ) matches that of the ) (approximately 0.74 Å), for The fast embedding / extraction provides an ideal transmission channel, which is conducive to achieving high capacity and excellent rate performance.

[0004] at present, The main preparation methods include potassium permanganate-manganese sulfate precipitation (Journal of Physics and Chemistry of Solids 73(2012)1487-1491), hydrothermal method (Journal of Alloys and Compounds 992 (2024) 174528), sol-gel method, etc. Among them, the precipitation method has a fast reaction rate and simple operation, but it has obvious defects: on the one hand, the reaction process is easily affected by concentration and temperature fluctuations, and the crystal form of the product is prone to change. On the other hand, the system contains residual... , It easily adsorbs onto the product surface, requiring multiple washing and purification processes, increasing process steps and costs, and generating large amounts of sulfate wastewater. Residual permanganate ions require additional reduction treatment, placing significant environmental pressure on the process. While hydrothermal and sol-gel methods can prepare high-purity... However, the hydrothermal method requires high-temperature and high-pressure equipment, resulting in high energy consumption and significant challenges in industrial scale-up; the sol-gel method has high raw material costs, and the gel drying and calcination processes can easily lead to product structural collapse, affecting electrochemical performance. Therefore, there is an urgent need to develop a novel method. Methods for preparing cathode materials. Summary of the Invention

[0005] In response to the existing The existing preparation methods suffer from problems such as high raw material costs, poor crystal form controllability, significant environmental pressure, and difficulty in industrialization. This invention provides a method based on an electrolytic manganese dioxide (EMD)-oxalic acid-potassium persulfate reaction system. The preparation method uses inexpensive EMD as the manganese source and achieves the desired result by adjusting process parameters. The targeted preparation method yields products with high purity and excellent electrochemical performance, while reducing preparation costs and environmental impact.

[0006] This invention provides a method for reconstructing the crystal structure of electrolytic manganese dioxide. A method for preparing cathode materials, based on the electrolytic reaction system of manganese dioxide-oxalic acid-potassium persulfate to prepare pure phase. The pH of the system was adjusted to 0.8-1.5, and the reaction was carried out in a constant temperature water bath. After the reaction was completed, the mixture was washed and dried to obtain the desired product. Positive electrode material.

[0007] Furthermore, in the raw material preparation stage: the molar ratio of electrolytic manganese dioxide, oxalic acid and potassium persulfate is 1:(0.43~0.63):(1.03~1.29), wherein the concentration of oxalic acid solution is controlled at 0.2~1 mol / L and the concentration of potassium persulfate solution is controlled at 0.15~0.5 mol / L.

[0008] Furthermore, the electrolytic manganese dioxide is... The main phase is ≥90%.

[0009] Furthermore, concentrated sulfuric acid is used as a pH adjuster.

[0010] Furthermore, when the reaction is carried out in a constant temperature water bath, the reaction is stirred at a speed of 250-600 r / min for 4-10 hours at 50-80℃.

[0011] Furthermore, the specific preparation process is as follows: S1. Raw material preparation and batching: Electrolytic manganese dioxide is used as the manganese source, oxalic acid is used as the crystal plane guiding agent, potassium persulfate is used as the oxidant, and concentrated sulfuric acid is used as the pH adjuster; S2. Isothermal reaction: Add EMD and a certain amount of deionized water to the reaction vessel, place the reaction vessel in a constant temperature water bath at 50~80℃, stir to disperse the solid raw materials evenly, and obtain a mixed suspension; at the same time, slowly add the prepared potassium persulfate solution and oxalic acid solution; add concentrated sulfuric acid dropwise to adjust the pH value of the system to 0.8~1.5, and stir the reaction at a speed of 250~600 r / min for 4~10 h; S3. Post-processing: After the reaction is complete, cool the reaction solution to room temperature and filter to separate the product; wash the filter cake with deionized water until neutral, then wash with anhydrous ethanol 1-3 times; place the washed product in a vacuum drying oven and dry at 60-100℃ for 6-15 hours to obtain... product.

[0012] This invention provides a method for reconstructing the crystal structure of electrolytic manganese dioxide. The positive electrode material is made using the method described above.

[0013] This invention also provides an aqueous zinc-ion battery, wherein the positive electrode material is composed of the above-mentioned... Made of positive electrode material.

[0014] Compared with the prior art, the present invention has the following advantages: 1. Low raw material cost: Industrial-grade EMD is used as the manganese source, which is only 1 / 5 to 1 / 8 the price of potassium permanganate, significantly reducing raw material costs; oxalic acid and potassium persulfate are both conventional chemical raw materials, which are convenient to purchase and have stable costs.

[0015] 2. Good controllability of crystal form: By adjusting the molar ratio of EMD, oxalic acid and potassium persulfate, the reaction pH, reaction temperature and time, the crystal form can be directionally induced. The 2×2 tunnel structure was grown, and the product was a pure phase. .

[0016] 3. The process is mild and easy to scale up: the reaction is carried out in a water bath at room temperature to 80°C, without the need for high temperature and high pressure equipment; the process steps are simple, and stirring, filtration and drying are all routine operations, which are suitable for industrial mass production. Furthermore, the excessive loss of raw materials can be reduced by optimizing parameters during large-scale production.

[0017] 4. Environmentally friendly: The main byproducts of the reaction are potassium sulfate and carbon dioxide, with no toxic or harmful substances generated; the wastewater can be discharged in compliance with standards after simple neutralization treatment, or the byproduct potassium sulfate can be purified and recycled as potassium fertilizer, further reducing environmental costs and resource waste.

[0018] 5. Excellent electrochemical performance of the product: The prepared product With its large specific surface area and unobstructed zinc ion diffusion path, it exhibits high initial discharge specific capacity and good cycle stability when applied as a cathode material for aqueous zinc-ion batteries. Attached Figure Description

[0019] Figure 1 XRD patterns of the cathode materials corresponding to Example 1 and Comparative Examples 1-3. Figure 2 SEM images of the cathode materials corresponding to Example 1 and Comparative Examples 1-3: (a) Example 1, (b) Comparative Example 1, (c) Comparative Example 2, (d) Comparative Example 3 Detailed Implementation

[0020] The present invention will now be described in detail with reference to embodiments and comparative examples. Example 1

[0021] Accurately weigh 10.0 g of EMD and 100 mL of deionized water and add them to a reaction vessel placed in a 60°C constant temperature water bath. Turn on the mechanical stirrer (500 r / min) and stir for 5 min to disperse the EMD evenly. Slowly add the prepared potassium persulfate solution (0.35 mol / L) and oxalic acid solution (0.6 mol / L) to make the molar ratio of EMD, oxalic acid and potassium persulfate 1:0.49:1.11. At the same time, add concentrated sulfuric acid dropwise to adjust the pH of the system to 1.0 and continue stirring for 8 h. Cool the reaction solution to room temperature, filter it, wash the filter cake with deionized water until the pH of the washing solution is neutral, and then wash it three times with anhydrous ethanol to remove residual water. Place the washed product in a vacuum drying oven and dry it at 60°C for 12 h to obtain a black powder product.

[0022] Comparative Example 1: Potassium permanganate-manganese sulfate precipitation method (current mainstream process) Prepare 100 mL of 0.15 M solution respectively. Solution and 0.15 M The solution will The solution was gradually added to The reaction mixture was stirred at 500 rpm for 8 hours at 60 °C. The reaction mixture was cooled to room temperature, filtered, washed with deionized water, and then washed three times with anhydrous ethanol. The washed product was placed in a vacuum drying oven and dried at 60 °C for 12 hours to obtain a black powder.

[0023] Comparative Example 2: EMD-oxalic acid-potassium persulfate system (pH value deviates from the range of this invention) Add concentrated sulfuric acid to adjust the pH to 2.0 (higher than the range of 0.8 to 1.2 of this invention), and the rest is the same as in Example 1.

[0024] Comparative Example 3: EMD-oxalic acid-ammonium persulfate system (replacing the oxidant of this invention) The potassium persulfate of this invention is replaced with ammonium persulfate, and everything else is the same as in Example 1. Example 2

[0025] Accurately weigh 10.0 g of EMD and 100 mL of deionized water and add them to a reaction vessel placed in a 70°C constant temperature water bath. Turn on the mechanical stirrer (600 r / min) and stir for 5 min to disperse the EMD evenly. Slowly add the prepared potassium persulfate solution (0.5 mol / L) and oxalic acid solution (1 mol / L) to make the molar ratio of EMD, oxalic acid and potassium persulfate 1:0.58:1.20. At the same time, add concentrated sulfuric acid dropwise to adjust the pH of the system to 1.2 and continue stirring for 6 h. Cool the reaction solution to room temperature, filter it, wash the filter cake with deionized water until the pH of the washing solution is neutral, and then wash it three times with anhydrous ethanol to remove residual water. Place the washed product in a vacuum drying oven and dry it at 80°C for 8 h to obtain a black powder product. Example 3

[0026] Accurately weigh 10.0 g of EMD and 100 mL of deionized water and add them to a reaction vessel placed in a 50 °C constant temperature water bath. Turn on the mechanical stirrer (250 r / min) and stir for 5 min to disperse the EMD evenly. Slowly add the prepared potassium persulfate solution (0.15 mol / L) and oxalic acid solution (0.2 mol / L) to make the molar ratio of EMD, oxalic acid and potassium persulfate 1:0.43:1.03. At the same time, add concentrated sulfuric acid dropwise to adjust the pH of the system to 1.0 and continue stirring for 10 h. Cool the reaction solution to room temperature, filter it, wash the filter cake with deionized water until the pH of the washing solution is neutral, and then wash it three times with anhydrous ethanol to remove residual water. Place the washed product in a vacuum drying oven and dry it at 60 °C for 15 h to obtain a black powder product. Example 4

[0027] Accurately weigh 10.0 g of EMD and 100 mL of deionized water and add them to a reaction vessel placed in an 80°C constant temperature water bath. Turn on the mechanical stirrer (400 r / min) and stir for 5 min to disperse the EMD evenly. Slowly add the prepared potassium persulfate solution (0.25 mol / L) and oxalic acid solution (0.5 mol / L) to make the molar ratio of EMD, oxalic acid and potassium persulfate 1:0.63:1.29. At the same time, add concentrated sulfuric acid dropwise to adjust the pH of the system to 0.8 and continue stirring for 4 h. Cool the reaction solution to room temperature, filter it, wash the filter cake with deionized water until the pH of the washing solution is neutral, and then wash it three times with anhydrous ethanol to remove residual water. Place the washed product in a vacuum drying oven and dry it at 100°C for 6 h to obtain a black powder product. Example 5

[0028] Accurately weigh 10.0 g of EMD and 100 mL of deionized water and add them to a reaction vessel placed in a 65°C constant temperature water bath. Turn on the mechanical stirrer (300 r / min) and stir for 5 min to disperse the EMD evenly. Slowly add the prepared potassium persulfate solution (0.2 mol / L) and oxalic acid solution (0.4 mol / L) to make the molar ratio of EMD, oxalic acid and potassium persulfate 1:0.53:1.11. At the same time, add concentrated sulfuric acid dropwise to adjust the pH of the system to 1.2 and continue stirring for 7 h. Cool the reaction solution to room temperature, filter it, wash the filter cake with deionized water until the pH of the washing solution is neutral, and then wash it three times with anhydrous ethanol to remove residual water. Place the washed product in a vacuum drying oven and dry it at 70°C for 10 h to obtain a black powder product.

[0029] Weigh 0.7g of the prepared positive electrode material, 0.2g of acetylene black, and 0.1g of polyvinylidene fluoride. Add an appropriate amount of N-N'-dimethylpyrrolidone, mix thoroughly, and coat onto a stainless steel foil (99.9%, 2 mm). The mass loading of the positive electrode is 1.0–1.1. After the above positive electrode is dried in an oven, a zinc sheet is used as the counter electrode and glass fiber is used as the diaphragm. A 2 mol / L solution is then applied. and 0.2 M The mixed solution was used as the electrolyte and assembled into a CR2016 coin cell. The battery performance was tested on a LAND CT2001 battery testing system, and the results are shown in Table 1.

[0030] As shown in Table 1, the cathode material in this technical solution exhibits improved discharge specific capacity and cycle stability under different currents compared to the existing mainstream precipitation process. In addition, the type of oxidant and the pH control of the reaction solution have a significant impact on the material performance in this technical solution.

[0031] As can be seen from the attached figures, the product of Example 1 is pure. Phase SEM showed that the product consisted of relatively uniform spherical particles without obvious agglomeration; the product of Comparative Example 1 was pure. The phase was relatively stable, but the crystallinity was significantly poor. SEM showed that the product was mostly composed of spherical particles with a small amount of lumps, uneven particle size, and obvious agglomeration. Comparative Example 2's product was... and The product was a miscible phase; SEM analysis showed it to be a mixture of spherical and rod-shaped particles with uneven particle size and obvious agglomeration. The product of Comparative Example 3 was... and The product was found to be rod-shaped and exhibited obvious aggregation under SEM analysis.

[0032] Table 1 Performance test results of cathode materials

[0033]

Claims

1. A method for reconstructing the crystal form of electrolytic manganese dioxide The method for preparing the positive electrode material is characterized by, Pure phase was prepared based on the electrolytic manganese dioxide-oxalic acid-potassium persulfate reaction system. The pH of the system was adjusted to 0.8-1.2, and the reaction was carried out in a constant temperature water bath. After the reaction was completed, the mixture was washed and dried to obtain the desired product. Positive electrode material.

2. The method described in claim 1, which is a reconstruction of the crystal form of electrolytic manganese dioxide. The method for preparing the positive electrode material is characterized by, Raw material preparation stage: The molar ratio of electrolytic manganese dioxide, oxalic acid and potassium persulfate is 1:(0.43~0.63):(1.03~1.29), wherein the concentration of oxalic acid solution is controlled at 0.2~1mol / L and the concentration of potassium persulfate solution is controlled at 0.15~0.5mol / L.

3. The method described in claim 2, which is a reconstruction of the crystal form of electrolytic manganese dioxide. The method for preparing the positive electrode material is characterized by, The electrolytic manganese dioxide The main phase is ≥90%.

4. The method described in claim 1, which is a reconstruction of the crystal form of electrolytic manganese dioxide. The method for preparing the positive electrode material is characterized by, Concentrated sulfuric acid is used as a pH adjuster.

5. The method of reconstructing the crystal form of electrolytic manganese dioxide as described in claim 1. The method for preparing the positive electrode material is characterized by, When the reaction is carried out in a constant temperature water bath, the mixture is stirred at 250-600 r / min for 4-10 hours at 50-80℃.

6. The method described in claim 3, which is a reconstruction of the crystal form of electrolytic manganese dioxide. The method for preparing the positive electrode material is characterized by, The specific preparation process is as follows: S1. Raw material preparation and batching: Electrolytic manganese dioxide is used as the manganese source, oxalic acid is used as the crystal plane guiding agent, potassium persulfate is used as the oxidant, and concentrated sulfuric acid is used as the pH adjuster; S2. Isothermal reaction: Add EMD and a certain amount of deionized water to the reaction vessel, place the reaction vessel in a constant temperature water bath at 50~80℃, stir to disperse the solid raw materials evenly, and obtain a mixed suspension; at the same time, slowly add the prepared potassium persulfate solution and oxalic acid solution; add concentrated sulfuric acid dropwise to adjust the pH value of the system to 0.8~1.2, and stir the reaction at a speed of 250~600 r / min for 4~10 h; S3. Post-processing: After the reaction is complete, cool the reaction solution to room temperature and filter to separate the product; wash the filter cake with deionized water until neutral, then wash with anhydrous ethanol 1-3 times; place the washed product in a vacuum drying oven and dry at 60-100℃ for 6-15 hours to obtain... product.

7. A method for reconstructing the crystal form of electrolytic manganese dioxide The cathode material is characterized by, It is prepared by the method described in any one of claims 1-6.

8. An aqueous zinc-ion battery, characterized in that, The cathode material is as described in claim 6 Made of positive electrode material.

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