Preparation And Improvement On Electrochemical Performances Of Silicon Based Composite Anodes For Lithium Ion Batteries And NiO, Co（OH）₂Electrodes Of Supercapacitors

As the application of electric vehicles and increasing needs of storage of solar-energy and wind energy, developing high energy density and high power density energy storages have attracted wide attention. And Li-ion battery and supercapacitor both are the most promising energy storage instruments. They are both known for their high reversible capacity, good cycle performance, high energy density and no memory effect. However, they don’t meet the requirement in applications at the aspects of energy density and power density. The main content of the present research is to improve their performance in the two aspects.In order to improve the energy density and power density,3D porous nano Ni/Si film and graphene/Si composite film are prepared by combining magnetron sputtering and electrodeposition. The3D porous structure is able to release the inner tensity effectively and suppress the pulverization, resulting in improved cycle performance. After100cycles at the rate of0.2C, the specific capacity still maintains2025mAh g1, which retains88.3%of that in the2nd cycle. Besides, the3D nano Ni dentrite greatly improves the conductivity of the composite film and increases the interface between Si and the electrolyte, which makes the electrode shows lower polarization. At the rate of2C after100cycles, the specific remains1273mAh g-1, and the coulombic efficiency is as high as99.3%.The layer graphene between the Cu substrate and the amorphous silicon not only improves the cohesion between the layers but also effectively releases the inner tensity during the charge/discharge procedure. The graphene/Si composite film electrode shows very good cycle performance. After150cycles at the rate of0.2C, the specific capacity still maintains1932mAh g-1, which retains87.7%of that in the2nd cycle.Self-assembled hierarchical porous-structured NiO film directly grown on nickel foam substrate is prepared by a facile ammonia-evaporation method. The as-prepared film possesses a structure consisting of NiO triangular prisms and randomly porous NiO nanoflakes. The self-assembled hierarchical porous-structured NiO film exhibits a high discharge capacitance and excellent rate capability with232F g-1,229F g-213F g-1and200F g-1at2,4,10, and20A g-1, respectively. The specific capacitance of87%is maintained from2A g-1to20A g-1. The NiO film also shows rather good cycling stability and exhibits a specific capacitance of348F g-1after4000cycles.Porous α-Co(OH)2film directly grown on nickel foam is prepared by a facile hydrothermal method. The as-prepared α-Co(OH)2film possesses a structure consisting of randomly porous nanoflakes with thicknesses of20～30nm. The porous α-Co(OH)2film exhibits a high discharge capacitance of935F g-1at a current density of2A g-1and excellent rate capability. The specific capacitance keeps a capacitance of589F g-1when the current density increases to40A g-1. The specific capacitance of82.6%is maintained after1500cycles at2A g-1.