MnO₂/CNTs Electrodeposited Under Supergravity Field As Anode Material For Supercapacitors

The composites of MnO2and carbon nanotubes have much space to be researchedand applied. However, the significant drawback of pure MnO2is its serious capacitancedecline in preliminary stage of charge-discharge test and bad circling stability, which haverestricted its further development. The bad dispersion capability of carbon nanotubes alsolimits the performances of the composites.MnO2/CNTs composites are electrodeposited under supergravity field conditions inorder to make the properties of the composites better. To improve the dispersion capabilityof carbon nanotubes, hydrothermal method and ball milling in solution are used in thispaper. The effects of deposition time, current density and other factors on the morphologyand electrochemical performances of the composites electrodeposited under supergravityfield were studied. Test methods such as galvanostatic charge-discharge, TGA-DTA, BET,field emission-scanning electron microscopy (FE-SEM) were applied.The results were as follows: the best hydrothermal temperature was100℃, underwhich temperature the performances and the coating conditions were the best amongdifferent temperatures. Carbon nanotubes were coated with well-distributed flocky-likeMnO2. The best parameters of depositing composites were: the rotating speed was3000r/min, the concentration of the solution was0.2mol/L and the deposition time was50min.The TGA-DTA test of the best sample showed that the carbon nanotubes possessed theweight amount of9%in the composite. According to the BET test, the specific area of thecomposite was104.072m2/g. The specific capacitance of the best sample was277.34F/g,and the capacitance could still retain91.04%of the initial specific capacitance after1000cycles.When carbon nanotubes were ball milled in Mn(CH3COO)2solution, the morphologyand electrochemical performances differed from the weight ratio of carbon nanotubes.The weight ratio of3%was the best, in which condition carbon nanotubes were coatedwith well-distributed MnO2. The best parameters of depositing composites undersupergravity field were: the current density was5mA/cm2and the deposition time was50 min. The TGA-DTA test of the best sample showed that the carbon nanotubes possessedthe weight amount of40%in the composite. According to the BET test, the specific areaof the composite was124.63m2/g. The specific capacitance of the best sample was287.27F/g.