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/Ti₃C₂T_x) nanohybrid is synthesized through a facile and cost-effective self-assembly of one-dimensional (1D) PANI nanofibers and two-dimensional (2D) Ti₃C₂T_x nanosheets. PANI/Ti₃C₂T_x 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/Ti₃C₂T_x 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/Ti₃C₂T_x as 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/Ti₃C₂T_x, 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.