Synthesis Of Hybrids Based On MXene For High Performance Supercapacitors

MXene,two-dimensional transition metal carbides,carbonitrides and nitrides material,have a multilayer structure similar to an accordion.MXene have been receiving significant research interests from researchers all around the world because of excellent electrochemical energy storage possessions,surface hydrophilicity,good electrical conductivity,and superior stability.However,like other two-dimensional layered materials,aggregation and restacking of MXene sheets limit material's electrochemical performance.Structural design and surface modification can prevent MXene sheets from restacking and accelerate the transfer of charge,which can enlarge the application of MXene in supercapacitors.In this paper,surface modification of MXene by intercalation and loading other materials were studied,and the electrochemical performance of obtained hybrids were also investigated.The main contents were as following:?1?We report a new and effective approach to prevent restacking of MXene sheets and significantly improved electrochemical capability of Ti₃C₂T_x by intercalating with N-doped carbon introduced from ZIF-8.Benefited from lager interlayer distance,higher specific surface area and electron conductivity,the obtained NC-Ti₃C₂T_x hybrid showed quick charge/discharge rate up to 3.0 V s^-1,little IR drop at 50.0 A g^-1,higher specific capacitance of 82.8 F g^-11 at 1.0 A g^-1?about 210%of the origin?,and 100%retention in capacitance after 5000 cycles,which showed excellent stable cyclability.?2?We prepared MnO₂@Ti₃C₂T_x hybrid for supercapacitor by corporating MnO₂,a high-capacity oxide material,with Ti₃C₂T_x as the substrate.We studied the effects of different raw material ratios on the electrochemical performance to find the optimum ratio in the experimental conditions.The results show that the specific capacitance of MnO₂@Ti₃C₂T_x hybrid prepared at the optimum ratio reached 196 F g^-11 at 0.5 A g^-1 and 112 F g^-11 at 10 A g^-1.The specific capacitance of MnO₂@Ti₃C₂T_x hybrid still maintain 76%after 10000 cycles at the current density of 2 A g^-1,which showed good cycle performance.?3?Ti₃C₂T_x was intercalated with three metal ions,Li,Na and K.The introduction of metal ions can increase the interlayer distance of Ti₃C₂T_x and remove part of the negatively charged groups on the surface of Ti₃C₂T_x,which can make more Ti atoms exposed and increase the specific capacitance.The specific capacitances of Ti₃C₂T_x after intercalation of metal ions were all improved.And the specific capacitance of Na-Ti₃C₂T_x hybrid reached 139 F g^-1 at the current density of 1 A g^-1.After 10,000 cycles of charge and discharge,the capacitance of Na-Ti₃C₂T_x hybrid still maintained 93%,which showed good cycle stability.?4?In this chapter,a new material noted PANI@Na-Ti₃C₂T_x hybrid was prepared by electrochemical in-situ polymerization method.The introduction of polyaniline improved the conductivity of Na-Ti₃C₂T_x and promoted the transport of ions,which were benefical for the rate and specific capacitance performance.The substrate of Na-Ti₃C₂T_x can slow the structural change of polyaniline.The obtained PANI@Na-Ti₃C₂T_x hybrid exhibited higher specific capacitance of 237 F g^-1 at the current density of 1 A g^-1,and 102 F g^-1 at 10 A g^-1.After 3000cycles at a current density of 2 A g^-1,the specific capacitance of the hybrid still remained 86%,which showed excellent cycle stability.