Preparation Of MXene/VS₄ Composite Material And Its Application In Zinc-ion Flexible Supercapacitors

In recent years,the wearable electronic devices has become an irreversible trend.This trend has put forward new requirements for the performance of supercapacitors,which is to meet the electrochemical characteristics of high energy density,high power density,long life,large capacitance,and good mechanical properties to adapt to the actual application scenarios of electronic devices.Zinc-ion flexible supercapacitors have gradually attracted widespread attention as a low-cost,safe and stable energy storage system.Flexible electrodes and electrolytes are the key factors that affect the performance of zinc-ion flexible supercapacitors.By selecting and designing the materials and structures of flexible electrodes reasonably and using suitable electrolytes,the performance of zinc-ion flexible supercapacitors can be maximally improved.Therefore,this study adopts a composite material strategy to use nanosheet-like VS₄ as a spacer combined with MXene to form a composite material to improve the performance of flexible supercapacitors.In addition,the performance of the composite material electrode in different electrolytes was studied.Finally,a high-performance aqueous zinc-ion flexible supercapacitor based on MXene/VS₄ composite film electrode was prepared.The specific research contents are as follows:（1）Nanosheet-like VS₄ was synthesized by solvothermal method and successfully introduced into the layers of MXene by vacuum filtration to obtain MXene/VS₄composite thin film electrodes.The resulting thin film electrode exhibited high flexibility,high specific capacitance,and excellent cycling stability,which was attributed to the high mechanical property of MXene,the high theoretical capacity of VS₄,and the structural improvement achieved by introducing the spacer.Four different mass ratios of MXene/VS₄ electrodes were tested,and the optimized mass ratio was determined to be4:2.The MV-42 electrode showed a specific capacitance of 322.1F g^-1 at a current density of 1 A g^-1.（2）Based on the high-performance MV-42 electrode mentioned above,further research was conducted on its performance in three aqueous zinc ion electrolytes:Zn（CF₃SO₃）₂,Zn Cl₂,and Zn SO₄.The p H value,ionic conductivity and contact angle of the three electrolytes were examined,followed by studying the electrochemical performance and energy storage mechanism of the MV-42 electrode.The results showed that the MV-42 electrode exhibited the highest specific capacitance in the Zn（CF₃SO₃）₂electrolyte,According to electrochemical analysis,it is believed that the reason for the enhanced performance of MXene/VS₄ electrodes in Zn（CF₃SO₃）₂ electrolyte is that MXene/VS₄ electrodes are more conducive to VS₄ or MXene undergoing redox reactions to obtain high diffusion-controlled capacitance.（3）A symmetric zinc-ion flexible supercapacitor was assembled with the MV-42electrode.The flexible supercapacitor exhibits excellent electrochemical performance and flexibility,with a maximum power density of 13.33 W cm^-3 and an energy density of39.88 m Wh cm^-3.After 10000 cycles of charge and discharge,the capacity retention rate is 88.5%.After bending the flexible supercapacitor to 150°,the capacity retention rate remains at 79%.