Study On Preparation And Performance Of Two-dimensional Electrode Materials In Large-capacity Supercapacitors

Two-dimensional materials such as graphene and MXene are expected to become ideal electrode materials for high-energy-density supercapacitors due to their high electrical conductivity and high specific surface area.In this paper,graphene and MXene were used as substrates to prepare three kinds of electrode materials:N,P co-doped carbon microspheres/graphene,hydroquinone/graphene and N-doped MXene,and their electrochemical performance were studied.N,P co-doped carbon microspheres/reduced graphene oxide nanocomposites are obtained by hydrothermal treatment of graphene oxide and Nitrogen and phosphorus co-doped carbon microsphere.The as-prepared nanocomposites display a high specific surface area of 604.3 m²/g,and hiearchical pore structure combination composed of micropore,mesopore and macropores.When N,P co-doped carbon microspheres/reduced graphene oxide are used as electrode materials in the redox electrolyte of H₂SO₄ and KI aquesous solution,exhibiting a excellent capacitance performence of up to?654 F/g at 2 A/g,corresponding to the energy density of 14.5 Wh/kg at power density of 402 W/kg.Even at a high current of 20 A/g,the electrode can keep a capacitance of 318 F/g,and the energy density as 7 Wh/kg at power density of 3984 W/kg.This study indicates the potential of nitrogen and phosphorus co-doped carbon microspheres/reduced graphene oxide in high energy density supercapacitor.Hydroquinone modified graphene xerogel as cathode and N-doped MXene as anode are first applied in all-solid-state asymmetric supercapacitors with a wide voltage window.The hydroquinone modified binder-free graphene xerogels are chosen as the cathode material because of their high potential,high pseudo capacitance,and high conductivity,whereas the N-doped MXene are selected as the anode materials due to their low potential,high specific capacitance,and high conductivity.The as-fabricated asymmetric device shows a potential window of 1.7 V in H2SO4 gel electrolyte,and an excellent adaptability in a wide temperature range from room temperatures to-20°C.It is found that an excellent energy density of 33.9 Wh/kg for the asymmetric supercapacitor is achieved at-20°C.Furthermore,the operation of the asymmetric supercapacitor in a wide temperature range greatly increases the practical application potential of supercapacitors.