Preparation And Properties Of Ti₃C₂T_x Based Supercapacitor Electrode Material

MXene,a two-dimensional transition metal carbide,is a new two-dimensional(2D)material.Because of its excellent hydrophilicity,flexibility and conductivity,it has caused extensive research in the field of energy storage.However,MXene's heavy stacking and poor stability have seriously affected their development.As a new type of energy storage device,supercapacitors are positioned between rechargeable batteries and conventional capacitors.They have received extensive attention and research due to their high power density,long cycle life,and good safety.In this paper,a series of studies have been conducted on the preparation of Ti3C2Tx Mxene electrode material and its application in supercapacitors.The main research contents are as follows:(1)Ti3C2Tx was produced by etching Ti3AlC2 with LiF-HCl,and Ti3C2Tx-rGO aerogel was prepared by ascorbic acid-assisted hydrothermal treatment.It can effectively reduce the restacking of Ti3C2Tx and enhance the electrochemical performance of electrode materials.The effects of composite ratio and different hydrothermal conditions on its performance were investigated,and the redox kinetics of electrode materials was analyzed.The electrochemical tests were performed in three-electrode system in 1 M H2SO4.As binder-free electrode materials,it can achieve a special capacitance of 313 F g-1 at 1 A g-1(approximately 1.74 times of Ti3C2Tx).When the current density reaches 10 A g-1,the specific capacitance of Ti3C2Tx/rGO-4 can still maintain a specific capacity of up to 234 F g-1,and possess a good retention of 74.8%.The diffusion-controlled process contributions from Ti3C2Tx/rGO-4 were significantly higher than Ti3C2Tx owing to the more exposed active sites after reduced graphene oxide(rGO)intercalation and increased layer spacing.Moreover,Ti3C2Tx/rGO-4 symmetric supercapacitor demonstrated an outstanding energy density of 7.5 Wh kg-1 at a power density of 500 W kg-1.(2)The Ti3C2Tx-Na2CO3-200 electrode was prepared.The Ti3C2Tx is treated with a saturated sodium carbonate solution,and then calcined in an N2/H2 atmosphere to obtain the Ti3C2Tx-Na2CO3-200 electrode material.The result shows:the removal of surface groups can create more active sites and improve the electrochemical performance.The effects of the performance of supercapacitors were studied by adjusting the preparation conditions,and further assembled into a two-electrode system to test its actual application.The electrochemical tests were performed in three-electrode system in 1 M H2SO4.The specific capacitance of Ti3C2Tx-Na2CO3-200 reached 422 F g-1 at 1A g-1.When the current density reaches 10 A g-1,the specific capacitance of Ti3C2Tx-Na2CO3-200 can still maintain 330 F g-1,and possess a good retention of 78.2%.In addition,Ti3C2Tx-Na2CO3-200 symmetric supercapacitors exhibited a higher energy density of 10.81 Wh kg-1.