Freeze-thaw synergistic salt template prepared self-supporting MXene/wood-derived porous carbon electrode for supercapacitors

Abstract

Supercapacitors are anticipated to be utilized in the upcoming generation of emerging energy storage devices. The electrode stands out as the most crucial component of the supercapacitor, and a bulk electrode containing sufficient electrochemically active substances is beneficial for enhancing the energy density of the energy storage device. Furthermore, the pore structure and wettability regulation of the electrode are pivotal factors that determine its electrochemical performance. In this study, we propose a monolithic electrode which was created by impregnating different concentrations of MXene dispersions into wood-based carbon materials co-treated with freeze-thaw/LiCl salt template, assisted by freezing treatment. The integration of MXene and freeze-thaw/LiCl salt template wood results in a layered porous structure that enhances both wettability and conductivity of the electrode. Freeze-thaw/LiCl salt template carbonized wood@MXene-4 (FCW@MXene-4) demonstrates an impressive electrochemical performance reaching 7.7 F cm⁻² (184.5 F g⁻¹) at a current density of 1 mA cm⁻². Additionally, when assembled into a symmetric supercapacitor (SSC), it exhibits high specific capacitance at 3.4 F cm⁻² (34.1 F g⁻¹/17 F cm⁻³) and high energy density at 0.478 mWh cm⁻² (6 Wh kg⁻¹/2.39 mWh cm⁻³) at 1 mA cm⁻², with a capacity retention rate of 88 % after 10,000 cycles. This research introduces an innovative self-supporting thick electrode design strategy for high-performance energy storage devices.