MnO2 pseudocapacitive material containing cationic vacancy defects, and preparation method and application thereof

Abstract

This invention discloses a MnO2 pseudocapacitive material containing cation vacancy defects, its preparation method, and its applications. In the preparation process, different types and amounts of pre-doped ions are introduced during hydrothermal treatment, followed by etching in acid and alkaline solutions. By optimizing the etching conditions, the pre-doped ions are selectively dissolved, forming cation vacancies in the MnO2 lattice, ultimately yielding the MnO2 pseudocapacitive material containing cation vacancy defects. The preparation method provided by this invention is characterized by its simple process, easily controllable reaction, and low cost, making it suitable for large-scale production of pseudocapacitive materials containing cation vacancy defects.

Description

Technical Field

[0001] This invention belongs to the field of supercapacitor electrode material technology, specifically a MnO2 pseudocapacitive material containing cation vacancy defects, its preparation method, and its application. Background Technology

[0002] Developing novel, efficient, and large-scale energy storage systems is crucial for the utilization of renewable energy. Electroactive materials, as the core determinants of energy storage performance, are key to achieving superior electrochemical storage performance through their selection and structural control. Double-layer capacitors, represented by carbon materials, have been successfully commercialized due to their advantages of long cycle life, low cost, and high power density; however, their energy density is generally low. Therefore, developing supercapacitors that combine high energy density and high power density is imperative.

[0003] Pseudocapacitive materials, represented by transition metal oxides, have attracted widespread attention in recent years due to their potential for both high energy density and high power density. Pseudocapacitors possess significantly higher power densities than lithium-ion batteries and much higher energy densities than double-layer capacitors, showing broad application prospects in energy, communications, transportation, power electronics, and defense. Among them, manganese dioxide (MnO2) is considered a potential pseudocapacitive material for large-scale commercial application due to its advantages such as low cost, abundant reserves, environmental friendliness, and high theoretical capacity (1370 F / g). Current research mainly focuses on the δ- and α-phases, but their ion diffusion is primarily limited to the two-dimensional interlayer and one-dimensional tunnels, severely impacting energy storage performance. Furthermore, the intrinsically low conductivity of MnO2 is also a bottleneck restricting its development. Therefore, optimizing the structure and composition to construct effective ion and electron transport channels is crucial for improving the energy density and power density of MnO2 electrode materials.

[0004] Currently, common methods for improving the ion and electron conduction rates of MnO2 mainly include morphology / particle size control (by increasing the specific surface area of ​​the electrode material and reducing the particle size, the diffusion path of electrolyte ions can be shortened) and compositing with conductive materials (which can improve electronic conductivity). Although these two methods are simple and easy to implement, they have a "ceiling effect" in practical applications, and it has become increasingly difficult to achieve a significant improvement in energy storage performance solely through these two methods. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings and defects of existing technologies and provide a simple and scalable method for preparing MnO2 pseudocapacitive materials containing cation vacancy defects. During preparation, a method based on "ion predoping (template)" + "selective etching" is used to controllably introduce cation vacancies of varying amounts into the MnO2 lattice. By introducing different types and amounts of predoped ions during the hydrothermal process and etching in acidic and alkaline solutions, the predoped ions can be selectively dissolved by optimizing the etching conditions, thereby forming cation vacancies in the MnO2 lattice. The preparation method of this invention is characterized by its simple process, easy reaction control, low cost, and ability to be continuously prepared in large quantities, making it very suitable for large-scale production.

[0006] The prepared material has a large specific capacitance and high capacity retention. Due to the formation of cation vacancies in the MnO2 lattice, its pseudocapacitive properties are effectively improved, making it suitable for application in related fields, such as as an electrode material for supercapacitors.

[0007] To achieve the above-mentioned objectives, the specific technical solution adopted by this invention is as follows: A method for preparing a MnO2 pseudocapacitive material containing cation vacancy defects includes the following steps: introducing pre-doped ions of different types and contents during hydrothermal process, and etching in acid and alkaline solutions. By optimizing the etching conditions, the pre-doped ions can be selectively dissolved and cation vacancies can be formed in the MnO2 lattice.

[0008] Furthermore, the preparation method of the MnO2 pseudocapacitive material containing cation vacancy defects described above includes the following specific steps: (1) Potassium permanganate, manganese sulfate, pre-doped ionic salt and deionized water are mixed to obtain precursor solution A; (2) The precursor solution A obtained in step (1) is subjected to hydrothermal reaction to obtain heteroatom predoped MnO2; (3) The heteroatom-predoped MnO2 obtained in step (2) is immersed in hydrochloric acid or sodium hydroxide solution for etching to obtain etched MnO2; (4) After centrifuging, washing and drying the etched MnO2 obtained in step (3), the MnO2 pseudocapacitor material containing cation vacancy defects is obtained.

[0009] In a preferred embodiment of this application, in step (1) of the method for preparing a MnO2 pseudocapacitor material with cation vacancy defects, the ratio of the mass g of potassium permanganate, the mass g of manganese sulfate, and the volume mL of deionized water is 0.08 ~ 0.2: 0.0285 ~ 0.2: 30.

[0010] In a preferred embodiment of this application, in step (1) of the method for preparing a MnO2 pseudocapacitor material with cation vacancy defects, the pre-doped ionic salt includes any one or more of cobalt salt, magnesium salt, and zinc salt; wherein the molar ratio of cobalt salt to manganese sulfate is 1:10 to 3:1; the molar ratio of magnesium salt to manganese sulfate is 1:2 to 3:1; and the molar ratio of zinc salt to manganese sulfate is 1:2 to 3:1.

[0011] Furthermore, the cobalt salt is at least one of cobalt nitrate and cobalt sulfate; the magnesium salt is at least one of magnesium nitrate and magnesium sulfate; and the zinc salt is at least one of zinc nitrate and zinc sulfate.

[0012] In a preferred embodiment of this application, in step (2) of the method for preparing a MnO2 pseudocapacitive material with cation vacancy defects, the hydrothermal reaction temperature is 120-140 °C (specifically, it can be 120 °C, 125 °C, 130 °C, 135 °C, 140 °C, etc.), and the time is 2-12 hours (specifically, it can be 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, etc.). Preferably, the volume of the hydrothermal reactor is 50 mL.

[0013] In a preferred embodiment of this application, in step (3) of the method for preparing a MnO2 pseudocapacitive material with cation vacancy defects, the concentration of hydrochloric acid is 0.1~1 mol / L (specifically, it can be 0.1mol / L, 0.2mol / L, 0.3mol / L, 0.4mol / L, 0.5mol / L, 0.6mol / L, 0.7mol / L, 0.8mol / L, 0.9mol / L, 1.0mol / L, etc.), the etching time is 8~24 hours (specifically, it can be 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours, 24 hours, etc.); the concentration of sodium hydroxide is 0.1~1 mol / L. The etching concentration can be mol / L (specifically 0.1mol / L, 0.2mol / L, 0.3mol / L, 0.4mol / L, 0.5mol / L, 0.6mol / L, 0.7mol / L, 0.8mol / L, 0.9mol / L, 1.0mol / L, etc.), and the etching time can be 1 to 24 hours (specifically 1 hour, 3 hours, 5 hours, 7 hours, 9 hours, 11 hours, 13 hours, 15 hours, 17 hours, 19 hours, 21 hours, 23 hours, 24 hours, etc.).

[0014] In a preferred embodiment of this application, in step (4) of the method for preparing a MnO2 pseudocapacitive material with cation vacancy defects, the centrifugation speed is 8000-12000 rpm (specifically 8000 rpm, 9000 rpm, 10000 rpm, 11000 rpm, 12000 rpm, etc.), the centrifugation time is 5-15 min (specifically 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, etc.); the drying temperature is 80-100 ℃ (specifically 80 ℃, 85 ℃, 90 ℃, 95 ℃, 100 ℃, etc.), and the drying time is 10-16 h (specifically 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, etc.).

[0015] This application also protects a MnO2 pseudocapacitor material containing cation vacancy defects prepared according to any combination of methods or steps described above.

[0016] Furthermore, the MnO2 pseudocapacitive material with cation vacancy defects described above exhibits improved pseudocapacitive characteristics, higher specific capacitance, and higher capacitance retention, effectively promoting the insertion / extraction of electrolyte ions in α-MnO2 under high current density.

[0017] The MnO2 pseudocapacitive material with cation vacancy defects obtained by the above method can also be used as a supercapacitor electrode material.

[0018] Compared with existing technologies, the present invention has the following advantages: (1) Based on the control strategy of “ion predoping (template)” + “selective etching”, this invention introduces different types and contents of predoped ions during the hydrothermal process. By etching in acid and alkaline solutions and optimizing the etching conditions, the predoped ions can be selectively dissolved, thereby forming cation vacancies in the MnO2 lattice and effectively improving its pseudocapacitive characteristics.

[0019] (2) The preparation method provided by the present invention has the characteristics of simple process, easy reaction control and low cost, and is suitable for mass production of pseudocapacitor materials containing cation vacancy defects. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 The images show the Mn K-edge EXAFS spectra of the products of Example 1 and Comparative Example 1 of this invention.

[0022] Figure 2 The images show the Mn K-edge EXAFS spectra of the products from Examples 2, 3, and Comparative Example 2 of this invention.

[0023] Figure 3 The images show the Mn K-edge EXAFS spectra of the products from Examples 4, 5, and Comparative Example 2 of this invention.

[0024] Figure 4 The images show the Mn K-edge EXAFS spectra of the products from Examples 6, 7, and Comparative Example 3 of this invention.

[0025] Figure 5 The graph shows the specific capacitance of the products of Examples 1-5 and Comparative Examples 1-2 at a current density of 0.2 A / g.

[0026] Figure 6 The graph shows the specific capacitance of the products of Examples 6, 7, and Comparative Example 3 at a current density of 0.2 A / g.

[0027] Figure 7 This is a comparison chart showing the capacity retention of the products of Examples 1-7 and Comparative Examples 1-3 of the present invention when the current density is increased from 0.2 A / g to 10 A / g.

[0028] Figure 8 This is a comparison diagram of the charge transfer impedance of the products of Examples 1-7 and Comparative Examples 1-3 of the present invention. Detailed Implementation

[0029] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0030] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention. The preferred embodiments and materials described herein are for illustrative purposes only, and various modifications and refinements can be made without departing from the principles of the embodiments of the invention; such modifications and refinements are also considered to be within the scope of the invention.

[0031] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0032] Example 1: An α-MnO2 pseudocapacitive material containing cation vacancy defects is prepared by the following steps: (1) Dissolve 0.2 g of potassium permanganate and 0.2 g of manganese sulfate in 30 mL of deionized water and stir thoroughly until no precipitate is formed. Then add cobalt nitrate (the molar ratio of cobalt nitrate to manganese sulfate is 1:2) and continue stirring. Transfer the stirred solution to a 50 mL Teflon hydrothermal reactor, heat to 120 °C and maintain for 12 hours, then cool naturally to room temperature. After centrifugation and washing, cobalt ion predoped α-MnO2 is obtained.

[0033] (2) The cobalt ion predoped α-MnO2 was placed in a 1 mol / L hydrochloric acid solution and allowed to stand for 24 hours. Then, it was centrifuged at 9000 rpm for 5 min. After repeated centrifugation, the obtained material was placed in a vacuum drying oven and dried at 80 ℃ for 12 h to obtain α-MnO2 pseudocapacitive material containing cation vacancies.

[0034] Comparative Example 1 An α-MnO2 without cation vacancy defects is prepared in the same way as in Example 1, except that cobalt nitrate is not added in step (1) and step (2) is not included.

[0035] Specifically, the following steps are included: (1) Dissolve 0.2 g potassium permanganate and 0.2 g manganese sulfate in 30 mL of deionized water and stir thoroughly until no precipitate is formed. Transfer the stirred solution to a 50 mL Teflon hydrothermal reactor, heat to 120 °C and maintain for 12 hours, then cool naturally to room temperature, centrifuge and wash to obtain cobalt ion predoped α-MnO2.

[0036] The α-MnO2 prepared in Example 1 and Comparative Example 1 were characterized and analyzed by EXAFS. Specific results are shown below. Figure 1 .

[0037] like Figure 1 As shown, three distinct peaks can be observed in R-space, corresponding to the Mn-O spacing in the MnO6 octahedron, the adjacent Mn-Mn spacing in the MnO6 octahedron with shared edges, and the peaks corresponding to adjacent Mn-Mn pairs in the MnO6 octahedron with shared edges. edge Spacing, and adjacent Mn-Mn groups in MnO6 octahedra with shared vertices. corner Spacing. It is evident that the intensities of all three peaks in the acid-treated sample are significantly weakened, indicating a gradual decrease in the corresponding bond content, thus directly proving that the dissolution of cobalt ions leads to the generation of cation vacancies.

[0038] Example 2 An α-MnO2 pseudocapacitor material with cation vacancy defects is prepared in the same way as in Example 1, except that: in step (1), cobalt nitrate is replaced with magnesium nitrate (the molar ratio of magnesium nitrate to manganese sulfate is 1:1), the hydrothermal reaction temperature is 140 °C, and in step (2), the standing treatment time in 1 mol / L hydrochloric acid solution is 8 hours.

[0039] The specific preparation steps are as follows: (1) Dissolve 0.2 g of potassium permanganate and 0.2 g of manganese sulfate in 30 mL of deionized water and stir thoroughly until no precipitate is formed. Then add magnesium nitrate (the molar ratio of magnesium nitrate to manganese sulfate is 1:1) and continue stirring. Transfer the stirred solution to a 50 mL Teflon hydrothermal reactor, heat to 140 °C and maintain for 12 hours, then cool naturally to room temperature. After centrifugation and washing, magnesium ion predoped α-MnO2 is obtained.

[0040] (2) Magnesium ion predoped α-MnO2 was placed in 1 mol / L hydrochloric acid solution and allowed to stand for 8 hours. Then it was centrifuged at 9000 rpm for 5 min. After repeated centrifugation, the obtained material was placed in a vacuum drying oven and dried at 80 ℃ for 12 h to obtain α-MnO2 pseudocapacitive material containing cation vacancies.

[0041] Example 3 An α-MnO2 containing cation vacancy defects is prepared in the same way as in Example 2, except that: in step (2), the time for standing in 1 mol / L hydrochloric acid solution is 24 hours.

[0042] The specific preparation steps are as follows: (1) Dissolve 0.2 g of potassium permanganate and 0.2 g of manganese sulfate in 30 mL of deionized water and stir thoroughly until no precipitate is formed. Then add magnesium nitrate (the molar ratio of magnesium nitrate to manganese sulfate is 1:1) and continue stirring. Transfer the stirred solution to a 50 mL Teflon hydrothermal reactor, heat to 140 °C and maintain for 12 hours, then cool naturally to room temperature. After centrifugation and washing, magnesium ion predoped α-MnO2 is obtained.

[0043] (2) Magnesium ion predoped α-MnO2 was placed in 1 mol / L hydrochloric acid solution and allowed to stand for 24 hours. Then, it was centrifuged at 9000 rpm for 5 min. After repeated centrifugation, the obtained material was placed in a vacuum drying oven and dried at 80 ℃ for 12 h to obtain α-MnO2 pseudocapacitive material containing cation vacancies.

[0044] Example 4 An α-MnO2 containing cation vacancy defects is prepared in the same way as in Example 2, except that: in step (1), magnesium nitrate is replaced with zinc sulfate (the molar ratio of zinc sulfate to manganese sulfate is 2:1), and in step (2), 1 mol / L hydrochloric acid solution is replaced with 1 mol / L sodium hydroxide solution.

[0045] The specific preparation steps are as follows: (1) Dissolve 0.2 g of potassium permanganate and 0.2 g of manganese sulfate in 30 mL of deionized water and stir thoroughly until no precipitate is formed. Then add zinc sulfate (the molar ratio of zinc sulfate to manganese sulfate is 2:1) and continue stirring. Transfer the stirred solution to a 50 mL Teflon hydrothermal reactor, heat to 140 °C and maintain for 12 hours, then allow it to cool naturally to room temperature. After centrifugation and washing, zinc ion predoped α-MnO2 is obtained.

[0046] (2) The zinc ion predoped α-MnO2 was placed in a 1 mol / L sodium hydroxide solution and allowed to stand for 8 hours. Then it was centrifuged at 9000 rpm for 5 min. After repeated centrifugation, the obtained material was placed in a vacuum drying oven and dried at 80℃ for 12 h to obtain the α-MnO2 pseudocapacitive material containing cation vacancies.

[0047] Example 5 An α-MnO2 containing cation vacancy defects is prepared in the same way as in Example 4, except that: in step (2), the standing time in 1 mol / L sodium hydroxide solution is 24 hours.

[0048] The specific preparation steps are as follows: (1) Dissolve 0.2 g of potassium permanganate and 0.2 g of manganese sulfate in 30 mL of deionized water and stir thoroughly until no precipitate is formed. Then add zinc sulfate (the molar ratio of zinc sulfate to manganese sulfate is 2:1) and continue stirring. Transfer the stirred solution to a 50 mL Teflon hydrothermal reactor, heat to 140 °C and maintain for 12 hours, then allow it to cool naturally to room temperature. After centrifugation and washing, zinc ion predoped α-MnO2 is obtained.

[0049] (2) The zinc ion predoped α-MnO2 was placed in a 1 mol / L sodium hydroxide solution and allowed to stand for 24 hours. Then, it was centrifuged at 9000 rpm for 5 min. After repeated centrifugation, the obtained material was placed in a vacuum drying oven and dried at 80℃ for 12 h to obtain the α-MnO2 pseudocapacitive material containing cation vacancies.

[0050] Comparative Example 2 An α-MnO2 without cation vacancy defects is prepared in the same way as Comparative Example 1, except that the hydrothermal reaction temperature in step (1) is 140 °C.

[0051] Specifically, the following steps are included: (1) Dissolve 0.2 g potassium permanganate and 0.2 g manganese sulfate in 30 mL of deionized water and stir thoroughly until no precipitate is formed. Transfer the stirred solution to a 50 mL Teflon hydrothermal reactor, heat to 140 °C and maintain for 12 hours, then cool naturally to room temperature, centrifuge and wash to obtain cobalt ion predoped α-MnO2.

[0052] The α-MnO2 prepared in Examples 2, 3, and Comparative Example 2 were characterized and analyzed by EXAFS. Figure 2 As shown, the intensities of the three peaks in the acid-treated sample were significantly reduced, and the reduction was more pronounced with increasing acid treatment time, indicating that the corresponding bond content gradually decreased. This directly proves that magnesium ion dissolution leads to the generation of cation vacancies, and the cation vacancy content gradually increases with increasing acid treatment time.

[0053] The α-MnO2 prepared in Examples 4, 5, and Comparative Example 2 were characterized and analyzed by EXAFS. Figure 3 As shown, the intensities of all three peaks in the alkali-treated sample decreased, indicating a gradual reduction in the corresponding bond content, thus directly proving that zinc ion dissolution leads to the generation of cation vacancies. Notably, when the alkali treatment time increased from 8 h to 24 h, the intensities of the first two peaks did not decrease significantly, while the intensity of the third peak decreased markedly, indicating that excessively long alkali treatment times affect the crystal structure of α-MnO2.

[0054] Example 6 A δ-MnO2 containing cation vacancy defects is prepared in the same way as in Example 2, except that: in step (1), the amount of potassium permanganate added is 0.08 g, the amount of manganese sulfate added is 0.0285 g, and the hydrothermal reaction time is 2 hours.

[0055] The specific preparation steps are as follows: (1) Dissolve 0.08 g of potassium permanganate and 0.0285 g of manganese sulfate in 30 mL of deionized water and stir thoroughly until no precipitate is formed. Then add magnesium nitrate (the molar ratio of magnesium nitrate to manganese sulfate is 1:1) and continue stirring. Transfer the stirred solution to a 50 mL Teflon hydrothermal reactor, heat to 140 °C and maintain for 2 hours, then cool naturally to room temperature. After centrifugation and washing, magnesium ion predoped δ-MnO2 is obtained.

[0056] (2) The magnesium ion predoped δ-MnO2 was placed in a 1 mol / L hydrochloric acid solution and allowed to stand for 8 hours. Then, it was centrifuged at 9000 rpm for 5 min. After repeated centrifugation, the obtained material was placed in a vacuum drying oven and dried at 80 ℃ for 12 h to obtain the δ-MnO2 pseudocapacitive material containing cation vacancies.

[0057] Example 7 A δ-MnO2 containing cation vacancy defects is prepared in the same way as in Example 6, except that: in step (2), the standing time in 1 mol / L hydrochloric acid solution is 24 hours.

[0058] The specific preparation steps are as follows: (1) Dissolve 0.08 g of potassium permanganate and 0.0285 g of manganese sulfate in 30 mL of deionized water and stir thoroughly until no precipitate is formed. Then add magnesium nitrate (the molar ratio of magnesium nitrate to manganese sulfate is 1:1) and continue stirring. Transfer the stirred solution to a 50 mL Teflon hydrothermal reactor, heat to 140 °C and maintain for 2 hours, then cool naturally to room temperature. After centrifugation and washing, magnesium ion predoped δ-MnO2 is obtained.

[0059] (2) The magnesium ion predoped δ-MnO2 was placed in a 1 mol / L hydrochloric acid solution and allowed to stand for 24 hours. Then, it was centrifuged at 9000 rpm for 5 min. After repeated centrifugation, the obtained material was placed in a vacuum drying oven and dried at 80 ℃ for 12 h to obtain the δ-MnO2 pseudocapacitive material containing cation vacancies.

[0060] Comparative Example 3 A δ-MnO2 without cation vacancy defects is prepared in the same way as Comparative Example 2, except that: in step (1), the amount of potassium permanganate added is 0.08 g, the amount of manganese sulfate added is 0.0285 g, and the hydrothermal reaction time is 2 hours.

[0061] Specifically, the following steps are included: (1) Dissolve 0.08 g of potassium permanganate and 0.0285 g of manganese sulfate in 30 mL of deionized water and stir thoroughly until no precipitate is formed. Transfer the stirred solution to a 50 mL Teflon hydrothermal reactor, heat to 140 °C and maintain for 2 hours, then cool naturally to room temperature, centrifuge and wash to obtain cobalt ion predoped δ-MnO2.

[0062] The δ-MnO2 prepared in Examples 6, 7, and Comparative Example 3 were characterized and analyzed by EXAFS. Figure 4As shown, two distinct peaks can be observed in R-space, corresponding to the Mn-O spacing in the MnO6 octahedron and the adjacent Mn-Mn pairs in the MnO6 octahedrons connected by common edges within the nanosheets. edge Spacing. It can be clearly seen that the intensities of both peaks in the acid-treated sample are significantly weakened, and the weakening of peak intensity becomes more pronounced with increasing acid treatment time, indicating that the corresponding bond content gradually decreases. This directly proves that magnesium ion dissolution leads to the generation of cation vacancies, and the cation vacancy content in the δ-MnO2 lattice gradually increases with increasing acid treatment time.

[0063] The specific capacity of α-MnO2 prepared in Examples 1-5 and Comparative Examples 1-2 was tested in a three-electrode system, where the working electrode was α-MnO2, the reference electrode was an Ag / AgCl electrode, the counter electrode was a foil, the electrolyte was a 1 mol / L sodium sulfate solution, the voltage window was 0 ~ 1 V, and the test temperature was 25 ℃. Figure 5 As shown, at a current density of 0.2 A / g, the specific capacitances of Examples 1, 2, 3, 4, 5, Comparative Example 1, and Comparative Example 2 are 146.8, 70.4, 91.6, 132.7, 108.6, 38.0, and 39.2 F / g, respectively.

[0064] The specific capacity of δ-MnO2 prepared in Examples 6, 7, and Comparative Example 3 was tested in a three-electrode system, where the working electrode was δ-MnO2, the reference electrode was an Ag / AgCl electrode, the counter electrode was a foil, the electrolyte was a 1 mol / L sodium sulfate solution, the voltage window was 0 ~ 1 V, and the test temperature was 25 °C. Figure 6 As shown, at a current density of 0.2 A / g, the specific capacitances of Example 6, Example 7, and Comparative Example 3 are 381.6, 491.0, and 179.0 F / g, respectively.

[0065] Rate performance tests were performed on the samples prepared in Examples 1-7 and Comparative Examples 1-3. Figure 7 As shown, when the current density increases from 0.2 A / g to 10 A / g, the capacity retention rates of Examples 1, 2, 3, 4, 5, 6, 7, Comparative Example 1, Comparative Example 2, and Comparative Example 3 are 60.5%, 65.9%, 67.0%, 63.3%, 57.6%, 53.5%, 53.3%, 55.3%, 55.0%, and 73.2%, respectively.

[0066] Impedance tests were performed on the samples prepared in Examples 1-7 and Comparative Examples 1-3, with a frequency range of 0.01 Hz - 100 kHz and a test temperature of 25 ℃. Figure 8As shown, the charge transfer impedances of Examples 1, 2, 3, 4, 5, 6, 7, Comparative Examples 1, 2, and 3 are 1.6, 1.2, 1.3, 1.2, 1.5, 2.6, 1.5, 2.7, 2.6, and 2.9 Ω, respectively.

[0067] In summary, the "ion predoping (template)" + "selective etching" strategy proposed in this invention achieves selective dissolution of predoped ions and the formation of cation vacancies in the material lattice by adding different types and amounts of predoped ions during hydrothermal synthesis followed by etching in acid and alkaline solutions. This method, focusing solely on synthesis, allows for arbitrary control of the cation vacancy defect content within a certain range without increasing experimental costs. The method is simple to operate, low in cost, highly reproducible, and provides strong product controllability. Electrochemical testing and analysis show that, without damaging the crystal structure, the introduction of cation vacancies effectively promotes the charge transfer process between δ-MnO2 and α-MnO2, significantly improving the specific capacity of the electrode material. It also effectively promotes the insertion / extraction of electrolyte ions in α-MnO2 at high current densities, thus contributing to the construction of high-energy, high-power-density capacitors.

[0068] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.

[0069] This background section is provided to generally present the context of the invention. The work of the currently named inventors, the work to the extent described in this background section, and aspects of this section that did not constitute prior art at the time of application are neither expressly nor impliedly acknowledged as prior art to the invention.

Claims

1. A method for preparing a MnO2 pseudocapacitive material containing cation vacancy defects, characterized in that... Includes the following steps: By introducing different types and amounts of pre-doped ions during the hydrothermal process and etching them in acid and alkaline solutions, the pre-doped ions are selectively dissolved by optimizing the etching conditions and forming cation vacancies in the MnO2 lattice, ultimately obtaining a MnO2 pseudocapacitor material with cation vacancy defects.

2. The method for preparing a MnO2 pseudocapacitive material containing cation vacancy defects according to claim 1, characterized in that... The specific steps include the following: (1) Potassium permanganate, manganese sulfate, pre-doped ionic salt and deionized water are mixed to obtain precursor solution A; (2) The precursor solution A obtained in step (1) is subjected to hydrothermal reaction to obtain heteroatom predoped MnO2; (3) The heteroatom-predoped MnO2 obtained in step (2) is immersed in hydrochloric acid or sodium hydroxide solution for etching to obtain etched MnO2; (4) After centrifuging, washing and drying the etched MnO2 obtained in step (3), the MnO2 pseudocapacitor material containing cation vacancy defects is obtained.

3. The method for preparing a MnO2 pseudocapacitive material containing cation vacancy defects according to claim 1, characterized in that: In step (1), the ratio of the mass g of potassium permanganate, the mass g of manganese sulfate, and the volume mL of deionized water is 0.08 ~ 0.2 : 0.0285 ~ 0.2 : 30; the pre-doped ionic salt includes any one or more of cobalt salt, magnesium salt, and zinc salt; wherein the molar ratio of cobalt salt to manganese sulfate is 1:10 ~ 3:1; the molar ratio of magnesium salt to manganese sulfate is 1:2 ~ 3:1; and the molar ratio of zinc salt to manganese sulfate is 1:2 ~ 3:

1.

4. The method for preparing a MnO2 pseudocapacitive material containing cation vacancy defects according to claim 2, characterized in that: In step (2), the hydrothermal reaction temperature is 120 ~ 140 ℃ and the time is 2 ~ 12 hours.

5. A method for preparing a MnO2 pseudocapacitive material containing cation vacancy defects according to claim 2, characterized in that: In step (3), the concentration of hydrochloric acid is 0.1 ~ 1 mol / L, and the etching time is 8 ~ 24 hours; the concentration of sodium hydroxide is 0.1 ~ 1 mol / L, and the etching time is 1 ~ 24 hours.

6. The method for preparing a MnO2 pseudocapacitive material containing cation vacancy defects according to claim 2, characterized in that: In step (4), the centrifugation speed is 8000 ~ 12000 rpm and the centrifugation time is 5 ~ 15 min; the drying temperature is 80 ~ 100 ℃ and the drying time is 10 ~ 16 h.

7. The method for preparing a MnO2 pseudocapacitive material containing cation vacancy defects according to claim 3, characterized in that: The cobalt salt is at least one of cobalt nitrate and cobalt sulfate; the magnesium salt is at least one of magnesium nitrate and magnesium sulfate; and the zinc salt is at least one of zinc nitrate and zinc sulfate.

8. A MnO2 pseudocapacitor material containing cation vacancy defects prepared by the method according to any one of claims 1-7.

9. The MnO2 pseudocapacitive material containing cation vacancy defects according to claim 8, characterized in that: This material exhibits improved pseudocapacitive properties, resulting in a large specific capacitance and high capacity retention, effectively promoting the intercalation / deintercalation of electrolyte ions in α-MnO2 under high current density.

10. The application of the MnO2 pseudocapacitive material with cation vacancy defects according to claim 9 in supercapacitor electrode materials.

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