Preparation Of Ti₃C₂T_x/Conductive Polymers Composites And Their Electrochemical Properties

Ti₃C₂T_x-Mxene is a member of the layered transition metal carbon/nitride family with structural and chemical performance advantages that have shown potential for application in the field of high-performance supercapacitor electrode materials.However,the layer-to-layer stacking problem and oxidation problem make the specific capacity of pure Ti₃C₂T_x-Mxene low.Conductive polymers have high specific capacitance based on their high electrical conductivity and cheap and easy synthesis,but the expansion and contraction that accompanies redox reactions can affect its stability.In this paper,Ti₃C₂T_x-MXene was compounded with polypyrrole（PPy）and polyaniline（PANI）respectively to prepare supercapacitor electrode materials with high performance by in situ polymerization method using the synergistic effect of Ti₃C₂T_x-MXene and conducting polymers.After investigating the microstructure and electrochemical properties of the composite,it was assembled into a supercapacitor to study its potential for practical applications.The main research contents are as follows:（1）Ti₃C₂T_x/PPy composites were prepared by in situ polymerization for application in symmetric supercapacitor and asymmetric supercapacitor negative electrodes.The research indicate that the monolayer Ti₃C₂T_x-MXene nanosheets（d-Ti₃C₂T_x）prepared by ultrasonic peeling are used as the substrate,and pyrrole monomers are polymerized into nanowires on the surface of d-Ti₃C₂T_x under the guidance of hexadecyltrimethylammonium bromide.The composite material prepared by controlling the mass ratio of d-Ti3C2Tx to pyrrole monomer（Py）to 2:1,synthesis time of 8 hours,and template addition of 0.2 g exhibited excellent electrochemical performance.The specific capacitance of d MPy-21-8-0.2 reached 272.5 F·g^-1at a current density of 1 A·g^-1 in 1 mol/L H₂SO₄ electrolyte,which was 72.94%and 52.92%higher than that of Ti₃C₂T_x-Mxene(157.57 F·g^-1)and PPy(178.2 F·g^-1),respectively.Its capacitance retention rate was 93.63%after 300 charge/discharge cycles at a current density of1 A·g^-1.The symmetric supercapacitor assembled with d MPy-21-8-0.2 composite maintained a specific energy of 2.5 Wh·kg^-1 at a power density of 5000 W·kg^-1,and the SSC device had a capacitance retention rate of 70.1%for 4000 charge/discharge cycles at 1 A·g^-1.The asymmetric supercapacitor assembled with activated carbon（AC）and d MPy-21-8-0.2composite has a voltage window of 1.1 V and an energy density of 5.775 Wh·kg^-1 at a power density of 550 W·kg^-1.84.07%capacity retention was achieved after 4000 cycles at a current density of 1 A·g^-1.The intercalation of polypyrrole not only increased the active sites on the surface of Ti₃C₂T_x-MXene,but also the combination of polypyrrole nanowires and Ti₃C₂T_x-MXene formed abundant pores,which constituted a conductive network to effectively increase the charge transfer rate.（2）Ti₃C₂T_x/PANI composites were prepared by in situ polymerization for application in supercapacitor electrodes.The results showed that the composite MPANI-1.2-1-0.3 obtained with a 1:1 ratio of Ti₃C₂T_x-MXene to aniline,1.2 g of ammonium persulfate and 0.3 g of hexadecyltrimethylammonium bromide had the best electrochemical performance.The specific capacitance reached 398.625 F·g^-1 at a current density of 1 A·g^-1,and the capacitance retention was 90.91%after 4000 charge/discharge cycles.The highest energy density of the assembled symmetric supercapacitor is 7.76 Wh·kg^-1,corresponding to a power density of 500 W·kg^-1,and the capacitance retention rate is 81.44%after 4000 cycles at 1 A·g^-1.The assembled asymmetric supercapacitor has an energy density of 6.11 Wh·kg^-1 at a high power density of5500 W·kg^-1 and a capacity retention of 77.19%after 4000 cycles of charge and discharge.The in situ grown polyaniline effectively improves the specific capacitance and cycling stability of the electrode due to its unique structure and the synergistic effect with Ti₃C₂T_x-MXene material.Ti₃C₂T_x-MXene provides more nucleophilic active sites,and the intercalation of PANI not only hinders the agglomeration and interlayer stacking of Ti₃C₂T_x-MXene,but also inhibits the expansion and contraction of PANI during charging and discharging to a certain extent,which makes the Ti₃C₂T_x/PANI composite have excellent electrochemical properties.