ELECTROCHEMICAL SYNTHESIS, TRANSFORMATION, AND CHARACTERIZATION OF MnO2 NANOWIRE ARRAYS FOR SUPERCAPACITOR ELECTRODES
Abstract
The utilization of MnO<sub>2</sub> nanowire arrays for future light weight energy storage devices is investigated here. One of the more specific questions this work looks to answer is: Can ultra high density arrays of MnO<sub>2</sub> nanowires really be used to create future flexible micro-supercapacitors with high energy density, high power density, and long cycle lives? This research investigates the energy storage properties of dense arrays of solely MnO<sub>2</sub> nanowires and synergistic MnO<sub>2</sub> nanowire composites consisting of two or more materials/architectures, where the composite materials are able to offset some of the detrimental intrinsic properties of the MnO<sub>2</sub> nanowires. Accordingly, a complete flexible supercapacitor device was prepared utilizing a coaxial MnO2/poly (3, 4-ethylenedioxythiophene) (PEDOT) core/shell nanowire array cathode with a PEDOT nanowire array anode. This material demonstrated metrics considerably better than current devices even while being flexed. In addition, a hierarchical MnO<sub>2</sub> nanofibril/nanowire array was synthesized by transformation of a bare MnO<sub>2</sub> nanowire array. This material was investigated for its supercapacitor properties while altering the parameters of its nanowire and nanofibril architectures. Finally, MnO<sub>2</sub> nanowires were investigated for their charge storage mechanism using ICP-AES to detect Li ion to Mn ion ratios during the charging and discharging process. Their charge storage process was found to differ depending on whether the electrolyte solvent used was aqueous or organic. These projects all help advance energy storage devices well beyond their current status as bulky, heavy energy sources toward their prospective use as light weight, flexible, micro- power sources.