| Summary: | Batteries have been the technology of choice for energy storage in many applications, because of their high energy density with sustainable power supply. However, in recent times the expanding power markets are calling for alternative pulse batteries with high power density and longer cycle life. Inspired by these urgent and increasing demands, research scientists have been paying more attentions to the electrochemical capacitors, which are also known as supercapacitors, due to their much higher power density and longer cycle life than those of the batteries. The research work presented in this project is concentrated on the exploration of novel nanostructured transition metal oxide/sulfide (Co3O4, NiO and CuS/NiS/Ni3S2) based active materials with porous texture for high-performance supercapacitors. First, various cobalt based precursors (CBP) with one to three dimensional microparticles have been synthesized by a facile solvothermal method, and the as-prepared CBP are converted into corresponding porous Co3O4 nanostructures by calcinations in air. When evaluated as supercapacitive electrodes, capacitances of 44-254.2 F g-1 can be obtained from these Co3O4 products, demonstrating their promising application in supercapacitors. The similar synthetic protocol is also applied to prepare porous nickel oxide (NiO) hierarchical nanospheres for supercapacitive application. Secondly, hierarchical nickel sulfide (NiS) hollow spheres are constructed using silica nanocolloids as hard templates. In this strategy, silica@nickel silicate (SiO2@NiSililcate) core/shell nanostructures are readily prepared, which can be hydrothermally converted into hierarchical nickel NiS hollow spheres assembled from ultrathin nanosheets with effect of Na2S. When served as electrode materials in supercapacitors, the as-derived NiS hollow spheres exhibited high specific capacitance with good cycling stability. Lastly, in order to further improve the cyclic performance of the supercapacitors, carbon nanotubes (CNTs) are introduced as backbones for preparation of CNTs based inorganic nanocomposites because the CNTs can increase the electrical conductivity as well as serving as the cushion structure to alleviate the volume change during the charge-discharge process. Based on this synthetic strategy, CNTs supported copper sulfide (CuS) ultralong nanoneedles and nickel sulfide (Ni3S2) ultrathin nanosheets are constructed by the sulfidation of the corresponding metal silicate precursors. As a result, the as-formed CNTs supported metal sulfide nanocomposites have exhibited excellent stability upon the cycling when tested as supercapacitive electrodes. In brief, this research has tried to explore the great potential of novel metal oxide/sulfide with porous textures as electrodes for high-performance electrochemical capacitors. The electrochemical performance is considered to be affected significantly by the morphology and porous texture of the electrode materials, hence, design and construction of novel and unique nanomaterials with high specific surface areas is essential to develop high-performance supercapacitors.
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