Assemblyand Performance Study Of N-Ti₃C₂T_X@NiCo₂S₄/RGO Symmetric Supercapacitor

Clean natural resources such as wind and solar energy cannot be readily utilized due to natural conditions,and the emergence of supercapacitors（SCs）can solve this dilemma.SCs,with the advantages of fast charging and discharging,power density and cycling stability above the average,are provoking much attention.Ti₃C₂T_X,with its large layer spacing,excellent electrical conductivity,good chemical stability and hydrophilicity,perfectly meets the needs of SCs electrode materials,but it has the flaws with low specific capacity and self-stacking phenomenon due to the van der Waals force and hydrogen bonding between layers.To compensate for these deficiencies we took some measures,such as heteroatom doping,compounding with pseudocapacitive materials,and constructing three-dimensional structures.Specific methods are as follows:（1）A flake of nitrogen-doped titanium carbide（N-Ti₃C₂T_X）was prepared by mildly doping it with nitrogen,using Ti₃C₂T_Xas a substrate.The successful doping with nitrogen was demonstrated by TEM and XPS characterization,and the significantly increased stripe spacing could be obtained in the HRTEM image;the retention of the hexagonal lattice structure of Ti₃C₂T_Xwas evident in the SAED image.Its performance was proved to be superior to that of Ti₃C₂T_Xby electrochemical characterization means such as CV,GCD,EIS and cycling.（2）Tubular hollow NiCo₂S₄was synthesized by secondary hydrothermal method,and its excellent pseudocapacitive properties and high electrical conductivity were used to compound with N-Ti₃C₂T_Xby electrostatic adsorption to form N-Ti₃C₂T_X@NiCo₂S₄heterostructure.The morphological characterization by SEM and TEM,and XRD and XPS characterization proved the successful composite of Ti₃C₂T_X@NiCo₂S₄heterostructure.（3）The N-Ti₃C₂T_X@NiCo₂S₄heterostructure was formed into a three-dimensional hydrogel structure with RGO using the self-fusion of RGO,and the nitrogen adsorption analysis showed that the hydrogel has a larger surface area and abundant mesopores than the heterostructure,which is beneficial to ion transport.It is demonstrated by comparison that the prepared N-Ti₃C₂T_X@NiCo₂S₄/RGO has high specific capacitance,excellent multiplicative performance and cycling stability(517.11 F g^-1at 1 A g^-1,and can retain92.6%after 10,000 cycles at 10 A g^-1,possess a high energy density 27.78 Wh kg^-1while power density 596 W kg^-1).