Ultrahigh rate capability of 1D/2D polyaniline/titanium carbide(MXene)nanohybrid for advanced asymmetric supercapacitors

High energy density and enhanced rate capability are highly sought-after for supercapacitors in today's mobile world.In this work,polyaniline/titanium carbide(MXene)(PANI/Ti3C2Tx)nanohybrid is synthesized through a facile and cost-effective self-assembly of one-dimensional(1D)PANI nanofibers and two-dimensional(2D)Ti3C2Tx nanosheets.PANI/Ti3C2Tx delivers greatly improved specific capacitance,ultrahigh rate capability(67％capacitance retention from 1 to 100 A·g-1)as well as good cycle stability.Electrochemical kinetic analysis reveals that PANI/Ti3C2Tx is featured with surface capacitance-dominated process and has a quasi-reversible kinetics at high scan rates,giving rise to an ultrahigh rate capability.By using PANI/Ti3C2Txas positive electrode,an 1.8 V aqueous asymmetric supercapacitor(ASC)is successfully assembled,showing a maximum energy density of 50.8 Wh·kg-1(at 0.9 kW·kg-1)and a power density of 18 kW·kg-1(at 26 Wh·kg-1).Moreover,an 3.0 V organic ASC is also elaborately fabricated by using PANI/Ti3C2Tx,achieving an ultrahigh energy density of 67.2 Wh·kg-1(at 1.5 kW·kg-1)and a power density of 30 kW·kg-1(at 26.8 Wh·kg-1).The present work not only improves fundamental understanding of the structure-property relationship towards ultrahigh rate capability electrode materials,but also provides valuable guideline for the rational design of high-performance energy storage devices with both high energy and power densities.