Optimized electron/ion transport by constructing radially oriented channels in MXene hybrid fiber electrodes for high-performance supercapacitors at low temperatures

Abstract

Although flexible fiber supercapacitors with two-dimensional active nanomaterials are promising for powering miniaturized wearable electronics, there is difficulty in establishing full contact between fiber electrodes and electrolytes, which causes extremely tortuous ion pathways and sluggish ion kinetics, seriously limiting their electrochemical performances. In this study, numerous radially oriented channels were constructed in MXene/reduced graphene oxide/PEDOT:PSS hybrid fiber electrodes by hydrothermal assembly and subsequent radial-freezing to create the shortest ion diffusion pathways and significantly increase the kinetics of the surface electrochemical reactions. The optimal fiber electrode delivers a high capacitance of up to 475 F g⁻¹ at 5 mV s⁻¹ and a competitive rate performance of 366 F g⁻¹ at 1000 mV s⁻¹. The flexible fiber supercapacitor assembled with the fiber electrodes and the anti-freezing electrolyte with an ionic liquid not only exhibits a high energy density of 10.11 W h kg⁻¹ at 80 W kg⁻¹ but also possesses excellent cold resistance with a capacitance retention of 70.5% at an ultralow temperature of −40 °C. Constructing radially oriented channels in fiber electrodes offers a ground-breaking strategy to ameliorate ion accessibility and provide fast ion migration pathways for efficiently enhancing the electrochemical performances of flexible fiber supercapacitors at ultralow temperatures.