Research On The Preparation Of Nickel-cobalt-based Nanocomposites And Their Application In The Field Of Supercapacitors

In recent years,there is a growing interest in the application of supercapacitors in energy storage systems due to their high specific power,fast charge/discharge rates and long cycle stability.Researchers have focused recently on developing nanomaterials to enhance their capacitive performance of supercapacitors.Especially,in developing advanced high-performance energy storage systems,transition metal composite have attracted vast attention as pseudocapacitor electrodes due to their excellent specific energy output and the high theoretical specific capacitance from the faradaic charge transfer process.In this paper,we mainly used transition metal sulfide/oxide as research material and adopted composite and modification methods to prepare new high-performance materials with unique structure,and explored their application potential in supercapacitors.Ternary cobalt nickel sulfide,performing as the promising electrode material for supercapacitors has obtained great interests.The hollow and spinous NiCo2S4 nanotubes are designed and prepared through a simple hydrothermal reaction using the natural silk as the template.The spinous Ni-Co precursors are grown on the natural silk through a facile hydrothermal strategy and the hollow structure is obtained by decomposing the silk via hydrothermal sulfurization.After the calcination treatment,the hollow and spinous NiCo₂S₄ nanotubes are applied as the electrode material and exhibit better electrochemical performance than the solely vulcanized samples.Owing to the unique hollow and spinous structure of NiCo₂S₄ nanotubes,the supercapacitor electrode material shows good specific capacitance(630 F g^-1 at 1 A g^-1),low internal resistance Rs?0.68??and high capacitance retention?91%after 3000 cycles?at 10 A g^-1.Furthermore,an all-solid-state asymmetric supercapacitor is self-assembled with the SC400 composite and exhibits an energy density of 52.34 Wh kg^-1 at the power density of 2206.37Wkg^-1.Additionally,a blue LED indicator can be powered by connecting two ASCs in series.The prepared hollow and spinous NiCo₂S₄ nanotubes with excellent electrochemical properties can envision promising applications in energy storage devices and nanotechnology.Beside,the hierarchical nanostructure hybrids of porous Co₃O₄ nanowires coated NiMn layered double hydroxide nanosheets array on Ni foams?Co₃O₄@NiMn-LDH/Ni?are designed and prepared via the two-step hydrothermal reactions with a combination of annealing process.The Co₃O₄ nanowires can be utilized as backbone to grow the NiMn-layered double hydroxide?NiMn-LDH?nanosheets,which provide a large surface area and leading to the enhanced capacitive performance owing to the effective ion/electron diffusion rates.The areal capacitance of the as-prepared Co₃O₄@NiMn-LDH/Ni electrode reaches 19.7 F cm^-2(5419.7 F g^-1)at 2 mA cm^-2(0.56A g^-1).Moreover,a high capacitance retention?93.25%of capacitance maintained after 6000 cycles?and a low internal resistance Rs?0.62??can be acquired.Additionally,an all-solid-state asymmetric supercapacitor?Co₃O₄@NiMn-LDH/Ni//AC ASC?based on the Co₃O₄@NiMn-LDH/Ni as positive electrode and activated carbon?AC?as negative electrode is successfully obtained.The Co₃O₄@NiMn-LDH/Ni//AC ASC shows a high energy density of 47.15 Wh kg^-1 at 376 W kg^-1.Additionally,a LED can be lit up for 12min when three ASCs are connected in series.Therefore,this novel Co₃O₄@NiMn-LDH/Ni with outstanding electrochemical performance should envision potential practical applications in high energy storage appliances.