Preparation And Electrochemical Performance Researches Of Three-dimensional Porous Ti₃C₂T_x Based Supercapacitor Electrode Materials

In recent decades,the use of low-cost,renewable and advanced green energy sources has been greatly and rapidly developed to meet the growing demand for hybrid vehicles and portable electronic devices.Supercapacitors have attracted a research boom with their advantages of high power density,stable cycling performance and wide operating voltage range.Electrode material is one of the important factors affecting the electrochemical capability of supercapacitors.Among many electrode materials,Ti₃C₂T_x,as one of the typical representatives of MXenes,has received much interest due to its prominent advantages such as strong conductivity,large layer spacing and high capacity.However,the layer stacking between Ti₃C₂T_xsheets caused by van der Waals forces leads to a significant loss of specific surface area and hinders the penetration of electrolyte,which limits its application in energy storage.In this paper,three-dimensional porous structures were obtained by ice template method and unidirectional freeze-drying method to solve the above problems.In this thesis,nitrogen-doped 3D-Ti₃C₂T_x/N film were firstly synthesized using the ice template method for high-performance supercapacitor electrodes.The 3D porous structure of the composite 3D-Ti₃C₂T_x/N has the great advantage of not only reducing the electrolyte diffusion path but also providing more electrochemically active sites and unique multi-dimensional surface contacts,which ultimately prevents nanosheet stacking and capacitance loss.In addition,the nitrogen doping can introduce additional pseudocapacitance and reduce the charge transfer resistance.The superposition of the two methods results in excellent supercapacitor electrochemical performance of3D-Ti₃C₂T_x/N electrodes:In 1 M H₂SO₄electrolyte,the mass specific capacitance of3D-Ti₃C₂T_x/N electrode is 387.5 F g^-1when the scan rate is 2 m V s^-1.In addition,the capacitance retention rate of 3D-Ti₃C₂T_x/N electrode was 96.8%after 40,000 cycles,demonstrating excellent cycling stability.3D Ti₃C₂T_x/SA aerogels with unidirectional channels were successfully prepared by the unidirectional freeze-drying method on the basis of ice template.This Ti₃C₂T_xaerogel with a special three-dimensional porous structure can effectively improve the obvious interlayer stacking phenomenon of Ti₃C₂T_xand apply it to a high mass loading electrode(loading of 14.2 mg cm^-2).The Ti₃C₂T_x/SA-5 electrode has good supercapacitor electrochemical performance in 1 M H₂SO₄electrolyte aqueous solution with a capacitance of 284.5 F g^-1at 2 m V s^-1,and its corresponding area capacitance is calculated to be 4030.4 m F cm^-2.The Ti₃C₂T_x/SA-5 electrode also shows good cycling stability with almost no capacitance decay after 20,000 cycles.The Ti₃C₂T_x/SA-5prepared by setting a specific unidirectional structure and adjusting part of chemical properties can be used as a high-performance MXene-based supercapacitor electrode material,while this high mass loading electrode promotes the practical application in daily energy storage equipment.In this paper,a simple and effective template method is used to solve the layer stacking problem of Ti₃C₂T_x,and improve the electrochemical properties of Ti₃C₂T_xelectrode material,which provides a feasible solution for solving the layer stacking problem of MXene materials.