Mixed Structured Metal Oxides:Construction And Their Electrochemical Performance

Supercapacitors have been a research focus of scientists for their high power density, fast recharge ability and long cycle life. The electrode materials play a vital role in the research of supercapacitors, which determine the performance and cost of the capacitors. Metal oxides have been the next generation ideal electrode materials with their good conductivity and fast reversible redox reaction. Mixed metal oxides, such as NiCo2O4, CUCo2O4, ZnCo2O4 and CoMn2O4 were widely concerned owing to their high specific capacitance and low cost. In the paper, the supercapacitor electrode materials with different morphologies were constructed successfully by simple, low cost strategies including hydrothermal treatment, electrochemical deposition and coprecipitation methods, and showed excellent electrochemical performance. The main innovative results are as follows:(1) Hierarchical multi-villous mesoporous NiCo2O4 nanocyclobenzene arrays supported on nickel foam substrate have been fabricated by a cost effective hydrothermal approach together with a post-annealing treatment. By controlling the reaction time and NH4F concentration, realizes the controllable preparation of NiCo2O4 with different morphologies. Compared with the pure nanowires and nanoflakes, hairy benzenering shape NiCo2O4 nanomaterials with larger specific surface area and faster electrolyte ion transport rate, showing the best electrochemical performance.(2) Hierarchical mesoporous NiCo2O4@NiCo2O4 nanocactus arrays supported on nickel foam by hydrothermal and electrochemical deposition method. When applied as the electrode material for supercapacitors and lithium ion batteries, the electrode is able to deliver high specific capacitance of 1264 F g-1 at a current density of 2 A g-1 and a high reversible capacity of 925 mA h g-1 at a rate of 120 mA g"1. These performances are much higher than mere NiCo2O4 electrode materials.(3) CUCo2O4 nanograssess with a large surface area are hydrothermally grown on copper foam. The as-prepared CUCo2O4 nanograss arrays are applied to supercapacitors, and the sample exhibits excellent performance with a high specific capacitance of 796 F g-1 and a capacitance loss of only 5.3% at current density of 2 A g-1 after 5000 cycles.(4) Homogeneous porous ZnCo2O4 nanoflakes are fabricated directly by a facile hydrothermal approach. The electrode material exhibits an ideal capacitance of 1220 F g-1 and retained 94.2% of the maximum capacitance after 5000 charge-discharge cycles.(5) Close ordered CoMn2O4 microspheres are synthesized by coprecipitation and annealing calcining method. As a pseudocapacitive material, the specific capacitance is up to 788 F g-1 and the electrode shows outstanding electrochemical properties.