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Supercapacitors have higher power density than lithium-ion batteries and higher energy density than conventional double-layer capacitors, which have caused widespread research interest in recent years and have achieved commercial applications in related fields. Among many electrode materials, manganese oxide has become one of the most potential supercapacitor electrode materials because of its theoretically higher specific capacitance, environmental friendliness, and low price. However, the disadvantages of low specific surface area, poor electron and ion conductivity, easy dissolution of electrode materials in the electrolyte during cycling, and other limitations have limited the use of manganese oxide electrode materials in supercapacitors.
Wang Dan, a researcher at the Institute of Process Engineering of the Chinese Academy of Sciences, and his collaborators used multishell Mn2O3 hollow spheres with a porous shell structure as electrode materials for supercapacitors, significantly improving the specific capacitance, cycling stability, and large current charging of supercapacitors. Discharge capacity. The related results were published on the recent Advanced Science.
The results of the study indicate that the use of such multi-shell hollow micro-nanostructures as a substitute for solid structures is one of the most effective methods for improving the capacitance performance of manganese oxide electrode materials. (1) The hollow structure has a higher specific surface area, can provide more Faraday reactive sites, and thus can significantly increase the specific capacitance of the supercapacitor; (2) the porous structure is conducive to the diffusion of the electrolyte inside the electrode material. The transmission paths of electrons and ions are shortened, and the high current charging and discharging capacity of the supercapacitor is improved; (3) This special multi-shell structure can support each other between different shells, and the outer shell can be protected to a certain degree. The inner shell is protected from electrochemical dissolution during the cycle, so its cycle stability is also significantly improved.
In order to take full advantage of the advantages of multi-shell hollow structures, the team used carbon spheres as a template to regulate the electrical properties of the surface of metal hydration ions and carbon sphere templates by regulating the pH of the precursor solution during the adsorption process. Shell, double shell, three shells and four shells of Mn2O3 hollow spheres were used to control the structural parameters such as the shell thickness and shell pore size. When the synthesized multi-shell Mn2O3 hollow spheres were used as supercapacitor electrode materials, their capacity, cycling performance, and large current charge and discharge capacity were significantly improved compared with Mn2O3 nanoparticles. At a discharge current density of 0.5 A/g, the specific capacitance of the three shell Mn2O3 hollow spheres reached a record high of 1651 F/g, and after a continuous cycle of 2000 times, the specific capacitance was still as high as 1517 F/g. The synthesis method is simple and controllable, the raw materials used are inexpensive, and the product performance is superior, and the direction for the development of high-performance supercapacitor electrode materials is expanded.
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