Preparation And Electrochemical Performance Of MXene-based Composite Membrane

In recent years,wearable electronic devices have gradually entered people's lives,and there has been an increasing demand for flexible energy storage devices.Good design stability,high power density,and environment-friendly flexible electrode materials are important goals of current research.MXene is a new 2D type material discovered in recent years.It can be used in many application fields including batteries,sensors,photocatalysts and heavy metal adsorbents.As a two-dimensional sheet material,it usually contains surface functional groups such as O,F,and OH.MXene has the characteristics of large specific surface area and abundant surface functional groups,and can be used as an energy storage electrode material.In this thesis,MXene based films were prepared by two kinds of electrochemical deposition of polymer and ultrasonic dispersion.The main research contents and results are as follows:(1)The polypyrrole were deposited on the MXene film by electrochemical deposition.According to the deposition time and voltage,the morphology and structure of the composite film are changed with the various deposition time and voltages.According to the scanning electron microscope,we can obviously find that the changes of polypyrrole content on the surface of Mxene flim.Through X-ray,FTIR,Raman and XPS analysis,it can be shown that the polypyrrole is loaded on the surface of the MXene film.The surface of the obtained MXene/PPy composite film is covered with dense and uniform polypyrrole at 1.2 V deposition voltage with 100 s deposition time.At a current density of 1 A/g,the specific capacitance of the MXene/PPy-1.2 V(100 s)composite film is 286.7 F/g.Moreover,the specific capacitance maintains about 66.2% at a current density of 10 A/g.The results indicate that the electrode material has a good magnification performance.(2)The two-dimensional sheet material GO were introduced to MXene nanosheets by the ultrasonic dispersion method,the morphology and properties of the prepared MXene/GO composites are different at different contents of MXene and GO in the composites.The staggered stacking between MXene nanosheets and GO sheets can not only increase the interlayer spacing of the MXene film,but also improve the electrochemical performance.the specific capacitance of MXene/GO composite film at a current density of 1 A/g is 387.5 F/g in the ratio of MXene nanosheets and GO sheets is 1:1.In addition,even at a current density of 5 A/g,the specific capacitance can reach 286.6 F/g.The results proves that the materials have good rate properties.The energy density of assembled MXene/GO//Mn O2 asymmetric supercapacitor device is 10.1 Wh/kg and power density is 89.6 W/kg.the capacitance retention rate was 87% after 3500 cycles,indicating that the supercapacitor device has good cycle stability.(3)The performance of MXene based materials are studied by introducing different content of CNTs and CNTs@Ni on to the MXene nanosheets.Carbon nanotubes are irregularly embedded in MXene nanosheets.The surface and cross section morphologies of MXENE /CNTs composite films and MXENE /CNTs@Ni composite films were observed by scanning electron microscopy.With their content increaseing,the distance between MXene sheets has been gradually expanded.CNTs@Ni are embedded into MXene nanosheets making the surface of the film divergent,which provides active sites while expanding the diatence of interlayer.At a scan rate of 20 m V/s,the MXene/CNTs@Ni-3:2 composite film exhibits 90.2% capacitance contribution,much higher than the 41.4% capacitance contribution of the MXene/CNTs-1:1 composite film.At a current density of 1A/g,the specific capacitance of MXene/CNTs@Ni-3:2 composite film is 363.3 F/g.Assemble a flexible supercapacitor device by wrapping MXene/CNTs@Ni-3:2 with PVA/H2SO4 gel electrolyte has an energy density of 14 Wh/kg and a power density of 350 W/kg.The flexible supercapacitor device shows a wide range of practical application significance.