Preparation method of S / P co-doped delta-MnO2 material and application of S / P co-doped delta-MnO2 material in aqueous zinc ion battery

Abstract

The invention belongs to the field of zinc ion batteries, and relates to a preparation method of an S / P co-doped delta-MnO2 material and application of the S / P co-doped delta-MnO2 material in an aqueous zinc ion battery. The method comprises the following steps: carrying out hydrothermal reaction on a uniform potassium permanganate solution, drying to obtain a delta-MnO2 material, adding an S source and a P source, putting into a tubular furnace, and carrying out constant-temperature treatment under Ar gas to prepare the S / P co-doped delta-MnO2 material. According to the S / P co-doped delta-MnO2 material disclosed by the invention, S and P elements are co-doped on the basis of a delta-MnO2 structure, and the obtained S / P co-doped delta-MnO2 material improves the ion diffusion rate, accelerates the battery reaction kinetics and improves the structural stability, so that the reversible capacity, the rate capability and the cycling stability of the material are greatly improved.

Description

Technical Field

[0001] The present invention belongs to the field of zinc-ion batteries, and relates to a preparation method of S / P co-doped δ-MnO2 material and its application in aqueous zinc-ion batteries. Background Art

[0002] Among many energy storage systems, lithium-ion batteries are widely used in transportation, electronic devices, energy storage systems and other fields due to their high energy and power density. However, due to problems such as lithium resource shortage, high cost and charging / discharging safety hazards, the development of battery systems with low cost, safety and environmental friendliness has broad market prospects. Among them, aqueous zinc-ion batteries, as a promising emerging energy storage system, have received extensive attention in recent years. Metallic zinc (Zn) has advantages such as rich reserves, high theoretical specific capacity (820 mAh g -1 ), and low redox potential (-0.76 V vs. SHE). At the same time, aqueous electrolytes have low cost and exhibit high ionic conductivity, safety and environmental friendliness, and are expected to become an ideal choice in the field of large-scale energy storage, providing new ideas and ways to solve the problem of energy storage.

[0003] Designing and selecting suitable electrode materials can support the reversible insertion and extraction behavior of Zn 2+ during charge and discharge, which plays a key role in enhancing the commercial potential of aqueous zinc-ion batteries. Among many cathode materials, manganese dioxide with a typical layered structure (δ-MnO2) has attracted much attention due to its advantages such as rich resources, cheap raw materials and relatively high redox potential. At the same time, the tunability of the layer spacing is beneficial to the rapid insertion and extraction of Zn 2+ and exhibits good electrochemical behavior. However, in practical applications, δ-MnO2 has problems such as unstable structure, manganese dissolution and poor conductivity, which seriously affect the charge-discharge capacity and cycling performance of aqueous zinc-ion batteries. Therefore, how to modify and optimize δ-MnO2 has important theoretical significance and guiding value.

[0004] Element doping can effectively regulate the structure, layer spacing and chemical stability of δ-MnO2. For example, [CN112299493A] discloses a synthesis method of nickel (Ni) atom-doped δ-MnO2 material, and Ni-doped δ-MnO2 nanosheet arrays are prepared by adjusting the pH value and hydrothermal treatment. In addition, in patent CN111653766A, metal salts, lignin, reducing agents and potassium permanganate are mixed, dissolved in deionized water, and placed in a reaction kettle for constant temperature treatment to prepare a MnO2 material co-doped with lignin and metal atoms. However, due to the complexity of the hydrothermal reaction, it is difficult to control the doping uniformity of elements and there are uncontrollable side reactions, which in turn affect the modification efficiency of the cathode material.

[0005] Based on the synergistic regulation of sulfur (S) / phosphorus (P) double anion doping, the electronic structure, lattice stability, and active site distribution of δ-MnO2 can be optimized. Among them, the S element induces the formation of oxygen vacancies, improves the electronic conductivity, the P element constructs reaction sites, and promotes the electro-chemical reaction activity; the difference in electronegativity between the two complements each other, effectively regulating the surface chemistry and multi-electron reactions, while maintaining the stability of the layered structure of δ-MnO2, forming a dynamically adaptable ion transport path, and enhancing the diffusion kinetics of Zn 2 ⁺. Therefore, improving the δ-MnO2 cathode material through the S / P co-doping strategy can significantly enhance the energy density, rate performance, and cycle life of aqueous zinc-ion batteries. Summary of the Invention

[0006] Aiming at the problems of poor stability and low capacity of the δ-MnO2 cathode material during charge and discharge, the purpose of the present invention is to provide an S / P co-doped δ-MnO2 material, its preparation method, and its application in aqueous zinc-ion batteries.

[0007] The technical solution of the present invention is as follows: A preparation method of an S / P co-doped δ-MnO2 material, comprising the following steps: (1) Dissolve potassium permanganate in deionized water and stir at room temperature to form a homogeneous solution A; (2) Pour the solution A prepared in step (1) into a polytetrafluoroethylene reaction kettle, seal it, place it in an oven for hydrothermal reaction, after cooling to room temperature, wash it repeatedly with deionized water, and then place it in a vacuum box for drying to obtain a δ-MnO2 material; (3) Put the S source and P source together with the δ-MnO2 material prepared in step (2) into a tube furnace and react at a constant temperature under Ar gas to obtain an S / P co-doped δ-MnO2 material.

[0008] Preferably, the molar ratio of KMnO4 to deionized water in step (1) is 1:260 - 290.

[0009] Preferably, the stirring time in step (1) is 20 - 30 min.

[0010] Preferably, the hydrothermal reaction temperature in step (2) is 150 - 180 °C, and the reaction time is 10 - 15 h.

[0011] Preferably, the drying temperature in step (2) is 50 - 100 °C, and the drying time is 6 h.

[0012] Preferably, the S source in step (3) is sublimed sulfur, the P source is sodium hypophosphite monohydrate, the molar ratio of the S source to the P source is 1:3 - 7, and further preferably 1:5; the molar ratio of the S source to δ-MnO2 is 1:18 - 20.

[0013] Preferably, the constant temperature reaction temperature in step (3) is 200 - 500 °C, and the reaction time is 2 - 4 h.

[0014] The present invention also provides the application of the S / P co-doped δ-MnO2 material obtained by the above preparation method in an aqueous zinc ion battery.

[0015] The present invention has the following advantages and beneficial effects compared with the prior art: Based on the structure of δ-MnO2, the present invention conducts co-doping of S and P elements, which improves the ion diffusion rate, accelerates the battery reaction kinetics, enhances the structural stability, and significantly improves the reversible capacity, rate performance, and cycle stability of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 XRD pattern of the S / P co-doped δ-MnO2 material prepared in Example 1; Figure 2 SEM image of the S / P co-doped δ-MnO2 material prepared in Example 1; Figure 3 XRD pattern of the pure δ-MnO2 material prepared in Comparative Example 1; Figure 4 SEM image of the pure δ-MnO2 material prepared in Comparative Example 1; Figure 5 Charge-discharge cycle diagram of the S / P co-doped δ-MnO2 material prepared in Example 1 at a current density of 3 A g -1 in the potential range of 0.8 V - 1.9 V; Figure 6 Charge-discharge cycle diagram of the S / P co-doped δ-MnO2 material prepared in Example 2 at a current density of 3 A g -1 in the potential range of 0.8 V - 1.9 V; Figure 7 Charge-discharge cycle diagram of the S / P co-doped δ-MnO2 material prepared in Example 3 at a current density of 3 A g -1 in the potential range of 0.8 V - 1.9 V; Figure 8 Charge-discharge cycle diagram of the S / P co-doped δ-MnO2 material prepared in Example 4 at a current density of 3 A g -1 in the potential range of 0.8 V - 1.9 V; Figure 9 Charge-discharge cycle diagram of the S / P co-doped δ-MnO2 material prepared in Comparative Example 5 at a current density of 3 A g -1 in the potential range of 0.8 V - 1.9 V; Figure 10 is the charge-discharge cycle diagram of the pure δ-MnO2 material prepared in Comparative Example 1 at a current density of 3 A g in the potential range of 0.8 V to 1.9 V; -1 current density; Figure 11 is the charge-discharge cycle diagram of the P-doped δ-MnO2 material prepared in Comparative Example 2 at a current density of 3 A g in the potential range of 0.8 V to 1.9 V; -1 current density; Figure 12 is the XRD pattern of the S / P co-doped δ-MnO2 material prepared in Comparative Example 3; Figure 13 is the SEM image of the S / P co-doped δ-MnO2 material prepared in Comparative Example 3; Figure 14 is the charge-discharge cycle diagram of the S / P co-doped δ-MnO2 material prepared in Comparative Example 3 at a current density of 3 A g in the potential range of 0.8 V to 1.9 V; -1 current density. Detailed implementation manners

[0017] The present invention will be further described below in conjunction with specific embodiments, and the advantages and features of the present invention will become clearer with the description. However, the embodiments are only exemplary and do not constitute any limitation to the scope of the present invention. Those skilled in the art should understand that the details and forms of the technical solutions of the present invention can be modified or replaced without departing from the spirit and scope of the present invention, but these modifications and replacements all fall within the protection scope of the present invention.

[0018] Example 1 A preparation method of an S / P co-doped δ-MnO2 material Weigh 2.5280 g of potassium permanganate, dissolve it in 80 mL of deionized water, stir at room temperature for 20 min, pour the formed homogeneous solution into a 100 mL polytetrafluoroethylene reaction kettle, seal it, put it into an oven, set the temperature to 160 °C, and keep the temperature for 12 h. After cooling to room temperature, filter the sample, wash it repeatedly with deionized water, and put the collected sample into a vacuum drying oven at 80 °C to dry for 6 h to obtain δ-MnO2. Weigh 0.003 g of sublimed sulfur, 0.03 g of sodium hypophosphite monohydrate, and 0.15 g of δ-MnO2, put them into a tube furnace, heat them to 350 °C at a rate of 5 °C / min under an Ar atmosphere, keep the temperature for 30 min, then heat them to 450 °C at a rate of 5 °C / min, keep the temperature for 30 min, and cool naturally to obtain the S / P co-doped δ-MnO2 material.

[0019] Figure 1XRD test results of S / P co-doped δ-MnO2 prepared by the preparation method of the present invention. The slight shift of the peaks in XRD indicates the successful doping of S and P.

[0020] SEM test results of S / P co-doped δ-MnO2 are as Figure 2 shown. The structure of S / P co-doped δ-MnO2 prepared by the preparation method of the present invention is consistent with that of pure δ-MnO2.

[0021] Figure 5 Shows the charge-discharge cycles of the S / P-doped δ-MnO2 material prepared in Example 1 at a current density of 3 A g -1 in the potential range of 0.8 V to 1.9 V. At a current density of 3 A g -1 , the highest capacity can reach 292 mAh g -1 and can be stably cycled 200 times.

[0022] Example 2 A preparation method of S / P co-doped δ-MnO2 material Weigh 2.5280 g of potassium permanganate, dissolve it in 80 mL of deionized water, stir at room temperature for 20 min, pour the formed homogeneous solution into a 100 mL polytetrafluoroethylene reaction kettle, seal it, put it into an oven, set the temperature to 160 °C, and keep the temperature for 12 h. After cooling to room temperature, filter the sample by suction, wash it repeatedly with deionized water, put the collected sample into a vacuum drying oven at 80 °C and dry it for 6 h to obtain δ-MnO2. Weigh 0.002 g of sublimed sulfur, 0.04 g of sodium hypophosphite monohydrate and 0.15 g of δ-MnO2, put them into a tubular furnace, heat them to 350 °C at a rate of 5 °C / min under Ar atmosphere, keep the temperature for 30 min, then heat them to 450 °C at a rate of 5 °C / min, keep the temperature for 30 min, and cool naturally to obtain the S / P co-doped δ-MnO2 material.

[0023] Figure 6 Shows the charge-discharge cycles of the S / P-doped δ-MnO2 material prepared in Example 2 at a current density of 3 A g -1 in the potential range of 0.8 V to 1.9 V. At a current density of 3 A g -1 , the initial capacity is 210 mAh g -1 , which is 30% higher than that of the original material.

[0024] Example 3 A preparation method of S / P co-doped δ-MnO2 material Weigh 2.5280 g of potassium permanganate, dissolve it in 80 mL of deionized water, stir at room temperature for 20 min, pour the formed homogeneous solution into a 100 mL polytetrafluoroethylene reaction kettle, seal it, put it into an oven, set the temperature to 160 °C, and keep the temperature for 12 h. After cooling to room temperature, filter the sample by suction and wash it repeatedly with deionized water. Put the collected sample into a vacuum drying oven at 80 °C and dry it for 6 h to obtain δ-MnO₂. Weigh 0.003 g of sublimed sulfur, 0.05 g of sodium hypophosphite monohydrate and 0.15 g of δ-MnO₂, put them into a tube furnace, heat it to 350 °C at a rate of 5 °C / min under an Ar atmosphere, keep the temperature for 30 min, then heat it to 450 °C at a rate of 5 °C / min, keep the temperature for 30 min, and let it cool naturally to obtain the S / P co-doped δ-MnO₂ material.

[0025] Figure 7 Figure shows the charge-discharge cycles of the S / P-doped δ-MnO₂ material prepared in Example 3 at a current density of 3 A g⁻¹ in the potential range of 0.8 V - 1.9 V. -1 At a current density of 3 A g⁻¹, -1 after 200 cycles, the capacity retention rate is 92%, and the cycling stability is significantly improved compared with the original material.

[0026] Example 4 A preparation method of S / P co-doped δ-MnO₂ material Weigh 2.5280 g of potassium permanganate, dissolve it in 80 mL of deionized water, stir at room temperature for 20 min, pour the formed homogeneous solution into a 100 mL polytetrafluoroethylene reaction kettle, seal it, put it into an oven, set the temperature to 180 °C, and keep the temperature for 10 h. After cooling to room temperature, filter the sample by suction and wash it repeatedly with deionized water. Put the collected sample into a vacuum drying oven at 80 °C and dry it for 6 h to obtain δ-MnO₂. Weigh 0.002 g of sublimed sulfur, 0.03 g of sodium hypophosphite monohydrate and 0.15 g of δ-MnO₂, put them into a tube furnace, heat it to 350 °C at a rate of 5 °C / min under an Ar atmosphere, keep the temperature for 30 min, then heat it to 450 °C at a rate of 5 °C / min, keep the temperature for 30 min, and let it cool naturally to obtain the S / P co-doped δ-MnO₂ material.

[0027] Figure 8 Figure shows the charge-discharge cycles of the S / P-doped δ-MnO₂ material prepared in Example 4 at a current density of 3 A g⁻¹ in the potential range of 0.8 V - 1.9 V. -1 At a current density of 3 A g⁻¹, -1 the highest capacity can reach 225 mAh g⁻¹. -1 .

[0028] Example 5 Preparation method of S / P co-doped δ-MnO2 material Weigh 2.5280 g of potassium permanganate, dissolve it in 80 mL of deionized water, stir at room temperature for 20 min, pour the formed homogeneous solution into a 100 mL polytetrafluoroethylene reaction kettle, seal it, put it into an oven, set the temperature at 160 °C, and keep the temperature for 12 h. After cooling to room temperature, filter the sample by suction, wash it repeatedly with deionized water, put the collected sample into a vacuum drying oven at 80 °C and dry it for 6 h to obtain δ-MnO2. Weigh 0.003 g of sublimed sulfur, 0.06 g of sodium hypophosphite monohydrate and 0.15 g of δ-MnO2, put them into a tubular furnace, heat up to 300 °C at a rate of 5 °C / min under Ar atmosphere, keep the temperature for 30 min, then heat up to 400 °C at a rate of 5 °C / min, keep the temperature for 30 min, and cool down naturally to obtain S / P co-doped δ-MnO2 material.

[0029] Figure 9 The charge-discharge cycle of the S / P-doped δ-MnO2 material prepared in Example 5 is shown at a current density of 3 A g -1 at a current density of 3 A g -1 The highest capacity can reach 300 mAh g -1 .

[0030] Comparative Example 1 Preparation method of a δ-MnO2 material Weigh 2.5280 g of potassium permanganate, dissolve it in 80 mL of deionized water, stir at room temperature for 20 min, pour the formed homogeneous solution into a 100 mL polytetrafluoroethylene reaction kettle, seal it, put it into an oven, set the temperature at 160 °C, and keep the temperature for 12 h. After cooling to room temperature, filter the sample by suction, wash it repeatedly with deionized water, put the collected sample into a vacuum drying oven at 80 °C and dry it for 6 h to obtain δ-MnO2. Weigh 0.15 g of δ-MnO2, put it into a tubular furnace, heat up to 250 °C at a rate of 5 °C / min under Ar atmosphere, keep the temperature for 100 min, and then cool down naturally to obtain δ-MnO2 material.

[0031] Figure 3 The XRD test result of δ-MnO2 prepared by the preparation method of the present invention is completely consistent with the standard card No. 86-0666 in the database, indicating that the crystal phase of the product is δ-MnO2.

[0032] Figure 4SEM image of δ-MnO2 prepared by the preparation method of the present invention. It can be seen that the original δ-MnO2 presents a flower-like morphology and is composed of thin nanosheets with a thickness of about 200 nm.

[0033] Figure 10 Shows the charge-discharge cycles of the pure δ-MnO2 material prepared in Comparative Example 1 at a current density of 3 A g -1 in the potential range of 0.8 V to 1.9 V. At a current density of 3 A g -1 the highest capacity can reach 130 mAh g -1 , and the capacity retention rate after 50 cycles is 65%.

[0034] Comparative Example 2 A preparation method of P-doped δ-MnO2 material Weigh 2.5280 g of potassium permanganate, dissolve it in 80 mL of deionized water, stir at room temperature for 20 min, pour the formed homogeneous solution into a 100 mL polytetrafluoroethylene reaction kettle, seal it, put it into an oven, set the temperature to 160 °C, and keep the temperature for 12 h. After cooling to room temperature, perform suction filtration on the sample, wash it repeatedly with deionized water, and put the collected sample into a vacuum drying oven at 80 °C to dry for 6 h to obtain δ-MnO2. Weigh 0.05 g of sodium hypophosphite monohydrate and 0.15 g of δ-MnO2, put them into a tubular furnace, heat it to 350 °C at a rate of 5 °C / min under an Ar atmosphere, keep the temperature for 80 min, and then cool it naturally to obtain the S / P co-doped δ-MnO2 material.

[0035] Figure 11 Shows the charge-discharge cycles of the P-MnO2 material prepared in Comparative Example 2 at a current density of 3 A g -1 in the potential range of 0.8 V to 1.9 V. As shown in the figure, the capacity reaches stability after 110 cycles at a current density of 3 A g -1 , and the highest capacity can reach 150 mAh g -1 .

[0036] Comparative Example 3 A preparation method of S / P co-doped δ-MnO2 material Weigh 2.5280 g of potassium permanganate, dissolve it in 80 mL of deionized water, stir at room temperature for 20 min, pour the formed homogeneous solution into a 100 mL polytetrafluoroethylene reaction kettle, seal it, put it into an oven, set the temperature at 160 °C, and keep the temperature for 12 h. After cooling to room temperature, filter the sample by suction and wash it repeatedly with deionized water. Put the collected sample into a vacuum drying oven at 80 °C and dry it for 6 h to obtain δ-MnO2. Weigh 0.003 g of sublimed sulfur, 0.10 g of sodium hypophosphite monohydrate and 0.15 g of δ-MnO2, put them into a tubular furnace, heat up to 350 °C at a rate of 5 °C / min under an Ar atmosphere, keep the temperature for 30 min, then heat up to 450 °C at a rate of 5 °C / min, keep the temperature for 30 min, and cool down naturally to obtain the S / P co-doped δ-MnO2 material.

[0037] Figure 12 XRD test results of S / P co-doped δ-MnO2 prepared in Comparative Example 3. The characteristic peak intensity of δ-MnO2 in XRD weakens, and the characteristic peak of Mn3O4 appears, indicating that excessive doping leads to phase transformation of the sample and the formation of Mn3O4.

[0038] Figure 13 SEM test results of S / P co-doped δ-MnO2 material prepared in Comparative Example 3 are shown. Different morphologies from the original δ-MnO2 are shown in the figure, and a large number of fillers appear in the middle of the nanosheets. According to XRD, the fillers are Mn3O4 formed by phase transformation.

[0039] Figure 14 Charge-discharge cycles of S / P co-doped δ-MnO2 material prepared in Comparative Example 3 in the potential range of 0.8 V - 1.9 V at a current density of 3 A g -1 At a current density of 3 A g -1 The highest capacity can reach 344 mAh g -1 , but the cycle stability is poor. The capacity begins to decrease after about 60 cycles and drops to 50 mAh g -1 .

Claims

1. A preparation method of S / P co-doped δ-MnO2 material, characterized in that The preparation method comprises the following steps: (1) Dissolve potassium permanganate in deionized water and stir at room temperature to form a homogeneous solution A; (2) Pour the solution A prepared in step (1) into a polytetrafluoroethylene reaction kettle, seal it, and place it in an oven for hydrothermal reaction. After cooling to room temperature, wash it repeatedly with deionized water, and then place it in a vacuum box for drying to obtain the δ-MnO2 material; (3) Put the S source and P source together with the δ-MnO2 material prepared in step (2) into a tubular furnace and carry out a constant-temperature reaction under Ar gas to obtain the S / P co-doped δ-MnO2 material.

2. The preparation method according to claim 1, wherein The molar ratio of KMnO4 to deionized water in step (1) is 1:260 - 290.

3. The preparation method according to claim 1, wherein The stirring time in step (1) is 20 - 30 min.

4. The preparation method according to claim 1, characterized in that, The hydrothermal reaction temperature in step (2) is 150 - 180 °C, and the reaction time is 10 - 15 h.

5. The preparation method according to claim 1, characterized in that, The drying temperature in step (2) is 50 - 100 °C, and the drying time is 6 h.

6. The preparation method according to claim 1, wherein, The S source in step (3) is sublimed sulfur, the P source is sodium hypophosphite monohydrate, and the molar ratio of the S source to the P source is 1:3 - 7; the molar ratio of the S source to δ-MnO2 is 1:18 - 20.

7. The preparation method according to claim 6, wherein, The molar ratio of the S source to the P source in step (3) is 1:

5.

8. The preparation method according to claim 1, wherein The constant-temperature reaction temperature in step (3) is 200 - 500 °C, and the reaction time is 2 - 4 h.

9. The S / P co-doped δ-MnO2 material obtained by the preparation method according to any one of claims 1 - 8.

10. Application of the S / P co-doped δ-MnO2 material according to claim 9 in an aqueous zinc-ion battery.

Images