Simultaneous Electrodeposition of Ternary Metal Oxide Nanocomposites for High-Efficiency Supercapacitor Applications.

Complex oxides and hydroxides of Ni, Co, and Mn from a precursor mixture were electrochemically deposited on both a cathode and an anode. On the Ni foam cathode, the complex metal hydroxides precipitated as nanolayers at -0.9 V. Simultaneously, the metal ions were oxidized and deposited as blocks on the Ni foam anode. While the concentrations of Ni(NO 3 ) 2 and Mn(NO 3 ) 2 were constant (80 mM for Ni 2+ and 40 mM for Mn 2+ , respectively), the concentration of Co(NO 3 ) 2 was varied from 20 to 120 mM, which affected the morphology and electrochemical properties of the electrode: a Co:Ni:Mn molar ratio resulted in the highest specific capacitance (at a scan rate of 5 mV s -1 , 1800 F g -1 for the cathode material and 720 F g -1 for the anode material). This cathode material was assembled into symmetric supercapacitors, which demonstrated an excellent energy density of 39 Wh kg -1 at a power density of 1300 W kg -1 and a high capacitance retention of 90% after 3000 charge/discharge cycles. This high electrochemical performance was attributed to the optimized ratio of metal oxides, and this simple preparation strategy can be applied to other nanocomposites of complex metal oxides/hydroxides with desired characteristics for various applications.