Mno₂and Its Modified Material Electrodeposited Under Supergravity Field For Supercapacitors And Its Electrochemical Properties

Supercapacitors have been recognized as unique energy storage devices for a broadapplication prospects. It is well known that manganese dioxide is a promising electrodematerial for electrochemical capacitors due to its low cost, environmentally friendly natureand high theoretical capacitance.The electrodeposition device under supergravity field is independently designed,produced, and used in the experimental study. MnO₂electrode material is successfullyelectrodeposited under supergravity field. The capacity of MnO₂electrode material isaffected by current density, electrolyte concentration, reaction temperature, and they areall investigated in our paper. The structure and pattern of samples are studied by X-raydiffraction （XRD）, field emission scanning electron microscope （FE-SEM）, and thesurface area （BET）. The electrochemical performance of material is analyzed byelectrodes cyclic voltammetry method （CV）, AC impedance （EIS）, and galvanostaticcharge/discharge testing.The optimum parameters in the electrodeposition under supergravity field process areobtained. Rotational speed is3000r/min; current density,15mA/cm²; electrolyteconcentration,0.2mol/L; and deposition temperature,25℃.XRD result shows that thecrystallographic structure of electrodeposition is γ-MnO₂. The SEM shows that the surfaceof MnO₂is consisted of irregular sheets-like nanostructure. According to the result of BET,the prepared material is mesoporous material, whose pore size range is around3.6nm andspecific surface area is125.39m²/g. The discharge capacity of the samples is285.45F/g.MnO₂electrode materials prepared under optimum parameters are modified by CNTs,graphite and Co2+, and their influences are researched and discussed in our paper. Thecrystal structures of MnO₂materials are hardly affected by modification, while capacitiveproperties take a great change. The discharge capacity of electrode material is increased to297.15F/g, when the CNTs concentration in electrolyte is20mg/L. Composite graphiteimproves the electronic conductivity of MnO₂, as well as the electrochemical properties.The discharge capacity of MnO₂is up to360.31F/g after graphite modification and the appropriate content is41.88wt.%. Co doped more obvious effects for electrode material,when the electrolyte is nCo2+:nMn2+=1.5:100, the prepared electrode materials dischargecapacity is efficiently enhanced by Co-ion doping, which is341.91F/g when the molarratio of Co2+:Mn2+is1.5:100.