Preparating And Capacitance Characteristics Of Manganese Oxide/Hydroxide Film Electrodes

The super-capacitor is superior to a battery in some areas, the main advantagesbeing a fast charge and discharge, excellent reversibility and a long life-cycle. Inthis thesis，low-cost manganese oxide is the super-capacitor electrode material whichdirectly changes the capacitive behavior of electrode materials by increasing thespecific surface area of manganese oxide. In this thesis I analyze the materialpreparation, the capacitance characteristics and the influencing factors. I usedvarious electrochemical methods and physical tests to determine my findings.The main content of this thesis can be summarized by the following three points:(1)The stainless steel was corrupted by the electro-chemical method using ahexagonal crystalline liquid phase medium as a template, resulting in a porousstainless steel electrode substrate. This method can effectively increase the specificarea on the electrode substrate. There were porous structures on the substrate surfaceof varying sizes, and the pore ranged from tens of nanometers to several hundrednanometers through the SEM. The manganese dioxide electrode has good capacitancecharacteristics and also has a long charge and discharge time. The manganese dioxideelectrode achieved a specific capacitance of400F/g when the deposition of chargewas0.4C. The area specific capacitance remained at320*10-3F/cm~2and the specificcapacitance was200F/g when the deposition charges were between4and5C.(2)The manganese and zinc hydroxide compounds were prepared by a cathodereduction reaction on the titanium electrode substrate in a mixed solution ofmanganese sulfate, zinc sulfate and nitrate ions. Then the zinc hydroxide of thecompounds was selectively dissolved. The maximum capacitance of manganesehydroxide was reached at387F/g; the largest area specific capacitance was150mf/cm~2.Its cycling performance was relatively stable, the decrease in capacitance wasrelatively low when the number of cycles increased. There was only a5.4%reductionin capacitance after1200cycles when compared to the capacitance after400cycles.There were urchin-like particles on the substrate observed by the SEM whichdisplayed a relatively uniform distribution.(3)The porous nickel-titanium-based substrate was prepared by the selectivedissolution of zinc from the nickel-zinc alloy which electro-deposited on the smoothtitanium substrate in a solution of2mol/L KOH. The nickel-titanium-based substratehas the largest surface area when the solution contains zinc ions at a concentration of0.1mol/L. There appeared to be a regular porous structure, and the distribution was relatively uniform in the SEM image. Then the manganese hydroxide electrode wasobtained by the use of the porous nickle-titanium based substrate. Under theseconditions, the manganese hydroxide electrode has a high capacitance of350F/g, astable cycling performance and a long life-cycle.