The Study Of The Capacitive Properties Of The Zr(Hf)-based Active Oxides And The Relationship Between Properties And Structure

In this paper, the low-temperature thermal decomposition method was employed to prepare RuO2-ZrO2 and RuO2-ZrO2 binary oxide electrode materials. The capacitive properties of these binary oxides were investigated by cyclic voltammetry, galvanostatic charge-discharge, and cyclic lifetime tests. The phases, microstructure and phases transition process were in-depth study, using XRD, SEM, HRTEM and extended x-ray absorption fine structure (EXAFS), combined with ab initio first-principles theoretical calculations, trying to reveals the inherent relationship between high specific capacitance of the binary oxides and its structure.The results showed that the optimum content of the second element of the non-noble metal oxide is about 50 mol%, and the critical crystallization temperature of the binary oxides is the optimum temperature point. The RuO2-ZrO2 binary prepared at the optimum composition and critical crystallization temperature, has disordered microcrystalline amorphous solid solution structure. This special structure make it has very high electrocatalytic active sites density and electrochemical roughness, as a supercapacitor electrode shows a specific capacitance as high as 949 F/g, at a constant current of 5 mA/cm2 in 0.5M H2SO4, an excellent specific energy of 118Wh/kg, and a specific power of 8.85KW/kg as well as long-term cyclic stability. Even discharged at ultra-high specific power of 60.7 KW/kg, the corresponding energy density is still as high as 40.5Wh/kg. which still far higher that that of the commercial carbon-based electrochemical double-layer capacitors (about 3～4Wh/kg).Similarly, in the preferred composition and prepared in the optimum temperature, for RuO2-HfO2 binary oxide electrode material, its organizational structure also belong disordered microcrystalline amorphous solid solution oxide. And showing the surplus conventional capacitive performance. A specific capacitance as high as 949 F/g was obtained at a constant current of 5 mA/cm2 in 0.5M H2SO4The reasons why disordered microcrystallines amorphous solution oxides can obtained such high specific capacitance as high as the theoretical specific capacitance of hydrated ruthenium oxide. We believe that the amorphous solid solution structure is a very important factor. Amorphous solid solution structure can get a very high active, because this material has high "outer active surface" and high active sites density result of "synergistic catalytic" of cations interaction. If the effects of "outer surface active" factor and "synergistic catalytic" factor are superimposed, such that the amorphous solid solution will be given an exceptionally high specific capacitance.The thermal decomposition technique is a method of a process for obtaining an oxide or oxides compounds. In this way, some metal chloride salts, sulfate, nitrate or other metal slats were heated, decomposed and then oxidized at 200～600 ℃, to formed oxides. Due to its easy processing, the thermal decomposition technique widely has been used in industrial. In critic crystallization temperature, an amorphous solid solution microstructure active oxides can be made by thermal decomposition technique, this specific structural materials has very high specific capacitance. This finding has a guiding significance for both theoretical research and production practice...