Enhanced performance of Fe₂O₃/MXene based supercapacitors with redox-electrolyte strategy

MXene-based supercapacitors are regarded as advanced energy storage devices owing to their high power density and extended cycle life. However, re-stacking of MXene significantly restricts its electrochemical performance while limited capacitance degrades the energy density. To address these limitations, we propose a dual-optimization strategy which integrates Fe₂O₃/MXene composite electrode design with redox-active electrolyte engineering, and thus achieves a high-performance Fe₂O₃/MXene-based asymmetric supercapacitor. Fe₂O₃ nanoparticles anchored on MXene nanosheets via filtration and annealing mitigate re-stacking and provide redox-active sites, while their interfacial charge synergy with a Cu²⁺-rich electrolyte accelerates Cu²⁺/Cu⁺ redox kinetics. The optimized composite electrode achieves a specific capacitance of 643.8 F g⁻¹ at 2 A g⁻¹ in 3 M H₂SO₄ + 30 mM CuSO₄ redox electrolyte. Moreover, the assembled asymmetric supercapacitor exhibits a high energy density of 20.1 Wh kg⁻¹ at a power density of 1292.5 W kg⁻¹, outperforming most reported MXene-based devices. This work demonstrates a feasible strategy for designing high-performance supercapacitors with hybrid redox electrolytes.