Preparation Of Foam Nickel@Graphene@Nickel Cobalt(Hydr) Oxides And Investigation Of Supercapacitor Performance

The energy storage of high-performance supercapacitors mainly depends on electrode materials,Therefore,in order to develop electrode materials more suitable for supercapacitors,this paper designs to prepare foam nickel@graphene@nickel cobalt（hydrogen）oxide composites by hydrothermal method and study their electrochemical properties.First,graphene was grown on foam nickel by hydrothermal method to obtain Ni foam@graphene gel（NF@GH）,and then using cetyltrimethylammonium bromide（CTAB）as the guiding agent,it was obtained by hydrothermal treatment at 120℃NF@GH@Ni Co LDH composite.When the concentration of nickel nitrate hexahydrate is4.85 mg/m L and the reaction time is 10 h,the maximum specific capacitance of the composite is 3578 m F cm^-2at 1 m A cm^-2,and 2470 m F cm^-2at 15 m A cm^-2.The capacitance retention rate after 10000 cycles is 62%(15 m A cm^-2).The asymmetric supercapacitor device was assembled with mixed mesh graphene/carbon nanotube（MG/CNT）as the negative electrode and the composite material prepared by the optimal process as the positive electrode（NF@GH@Ni Co LDH//MG/CNT）,with a specific capacitance of 909 m F cm^-2(at 1 m A cm^-2).After 10000 charge-discharge cycles(at 15m A cm^-2),the capacitance retention rate of the device is 53.5%,and the maximum energy density of the device is 0.25 m Wh cm^-2(power density is 0.7 m W cm^-2).NF@c GH@Ni Co₂O₄were prepared by two-step hydrothermal method.First,carbon nanotubes were added to graphene to obtain foam nickel@carbon nanotubes graphene gel substrate material（NF@c GH）,NF@c GH has a larger specific surface area to NF@c GH.As a base material,it can provide more active sites for composites.The hydroxyl radical was produced by the reaction of ethanol and nitrate to provide a precipitant for hydrothermal reaction.The hydrothermal reaction took place at 120℃for 18 h.At the same time,the load quality was controlled by changing the quantity of foam nickel,and then annealing treatment（300℃,3 h）was carried out to obtain NF@c GH@Ni Co₂O_4.The composite material under the optimal process has a nano-sheet structure,and its specific capacitance is 2533.3 m F cm^-2at 1 m A cm^-2.When the current density is increased to 15m A cm^-2,it can still maintain about 80%of the specific capacity,and the specific capacity remains 40%after 10000 cycles at 20 m A cm^-2.Using MG/CNT as negative electrode material,the composite prepared by the best process was used as positive electrode assembly device（NF@c GH@Ni Co₂O₄//MG/CNT）,the device can provide 778 m F cm^-2a specific capacity of 1 m A cm^-2,and 535 m F cm^-2at 15 m A cm^-2.The capacitance retention rate after 10000 cycles is 82%(15 m A cm^-2).In addition,the maximum power density that the device can output is 10.8 m W cm^-2,with an energy density of 0.16 m Wh cm^-2.