Synthesis Of Hierarchically Metallic Oxide Nanostructure For Applications In Supercapacitors

Motivated by the increasing demand in energy consumption and environmental protection,sustainable and renewable energy resources and the related energy generation,storage,and conservation technologies have attracted intense attention in recent years.Supercapacitor is considered as a preferable candidate energy storage device due to its high power density,long cycle life and rapid charge/discharge rate.Recently,the hotspot of research around is largely concentrated on the exploration of anode materials with higher specific capacity and better cycling performance.Especially,due toits high theoretical capacity,the metal oxide electrode materialsreceive much concern.However,the defects of poor electrical conductivity and short cycle life are still a big obstacle restricting the development of metal oxide materials.In this paper,we preparedseveral different structures of nickel and cobalt oxide electrode materials by optimizing the electrode materials of nanostructures,and discussed the morphology and structure of the impact on the electrochemical performance of electrode materials.The main results obtained from this paper are as follows:1.We have successfully fabricated NiCo₂O₄@NiMoO₄ Core/shell Arrays on Ni foam by a simple hydrothermal processing.The optimized NiCo₂O₄@NiMoO₄ electrode?4h?delivers 6.91 F cm-2 and 1974 F g-1 at5 mA cm-2,the capacitance maintains 76% after 5000 cycles at 40 mA cm-2,which is much better than that of the pure NiCo₂O₄ electrode.Moreover,an asymmetric supercapacitor was assembled by utilizing NiCo₂O₄@NiMoO₄ electrode?4h?and activated carbon?AC?as the positive and negative electrodes,and it's energy density can reach 47 Wh kg-1 at the power density of 0.4 kW kg-1.In addition,the asymmetric supercapacitor shows outstanding cycling stability.2.We have successfully fabricated NiCo₂O₄@NiMoO₄ Core/shell Arrays by a same method.The intriguing core/shell structure provides unique protective mechanism to help the active materials avoid the rapid property deterioration.Thus the hybrid electrode exhibits greatly improved electrochemical performance with high area specific capacitance?5.4 F·cm-2 at 5mA·cm-2?,good rate capability and excellent cycling stability.Furthermore,the asymmetric supercapacitor based on NiCo₂O₄@CoMoO₄ arrays and AC/graphene as positive and negative electrodes,respectively,in 2 M KOH aqueous electrolyte delivers a high energy density of 42.75 Wh·kg-1 at a power density of 593.5 W·kg-1.The device can easily sustain 10000 charge/discharge cycles with ¹00% retention of its initial capacitance.3.We have successfully fabricated Ni-Al LDH@CoMoO₄ Core/shell Arrays on Ni foam by two steps of hydrothermal processing,and discussed the hydrothermal time impact on the electrochemical performance of electrode materials.