Construction Of Nickel-cobalt Phosphate (Sulfur) Based Self-supporting Electrodes And Their Supercapacitor Performance

As an advanced energy storage technology,supercapacitors have gained the continuous attention and research from academia integrates the characteristics of rapid charge-discharging,long-term cyclic lifespan,safety and reliability compared with secondary batteries.Nonetheless,the lower energy density hampers its practical application.To improve the energy density of supercapacitors from the perspective of electrode materials and structures,which is a practical and feasible approach.Nickel-cobalt phosphate(sulfur)have received extensive research attention in virtue of their high conductivity,high electrochemical activity and abundant redox reactions,while the heart of the matter in practical application are unsatisfactory rate performance and long cycle life.Therefore,this paper focuses on bimetallic nickel-cobalt phosphate(sulfur),and constructs a highly conductive core with strong interface bonding and an active material with high electrochemical utilization rate through the in-situ growth strategy,so that the constructed hierarchical structure self-supported electrode can not only improve the effective utilization of active materials,but also maintain the stability of electrode structure.The double promotion of rate ability and cycle life of electrode material is realized.In this paper,the structure,properties and structure-activity relationship of electrode materials are systematically investigated,and the practical application of the asymmetric supercapacitor(ASC)is explored.The research content and results are as follows:(1)Porous NiO nanoarray structure was constructed on nickel foam via in-situ oxidation strategy,and NiCoP with high-performance was grown on its surface by electrodeposition.Therefore,the NiCoP/NiO self-supported composite electrode with hierarchical porous structure was synthesized.The unique electrode structure and the synergistic interaction between NiO and NiCoP have significantly improved the electrochemical properties of NiCoP/NiO electrode.In detail,the areal capacitance of NiCoP/NiO is 1860 mF cm-2 at 5 mA cm-2,which exhibits goodrate performance(78%capacitance can be maintained until increasing current density to 30 mA cm-2)as well as the initial capacitance retention rate is 89%over 10000 cycles.In addition,the assembled ASC NiCoP/NiO//PAC affords an energy density of 173.7 μWh cm-2 at power density of 1.6 mW cm-2.(2)The CuxO/Cu/NiCoS,CuO/NiCoS and Cu/NiCoS self-supported composite electrodes with different core structures were constructed on copper foam with high conductivity via in-situ redox strategy followed by electrodeposition.It was found that CuxO/Cu/NiCoS-10C shown the better electrochemical performance by adjusting the core structure and the surface load of active material.Specifically,the high areal capacitance of 3305 mF cm-2 was achieved at the current density of 5 mA cm-2.When the current density was increased by 12 times(60 mA cm-2),the rate performance remained at about 68.3%,and appears outstanding cyclic stability(capacity attenuation is only 5.8%after 10000 cycles).At the same time,the assembled asymmetric supercapacitor CuxO/Cu/NiCoS-10C//PAC delivers high energy density of 263.3 μWh cm-2 and retains 88.7%of the initial capacitance after 10000 cycles of charge-discharge at the high current density of 50 mA cm-2 time and again,showing excellent long cycle characteristics.In addition,both LED lights and digital timer can be drived by two devices in series.