Water Evaporation Triggered Self-Assembly of MXene on Non-Carbonized Wood with Well-Aligned Channels as Size-Customizable Free-Standing Electrode for Supercapacitors

Herein, non-carbonized wood-based electrodes and separators with well-aligned channels and excellent mechanical properties are developed for supercapacitors. To enhance the conductivity and boost the capacitance, Ti₃C₂ (MXene) nanosheets with high electrical conductivity and excellent electrochemical activity are loaded into the wood cells via self-assembly triggered by fast evaporating water in Ti₃C₂ suspension. By the assistance of positive charged polydopamine microspheres with large surface area, the self-restacking of Ti₃C₂ nanosheets can be avoided and the high mass loading (50 wt%) can be achieved due to the extra driving force for Ti₃C₂ absorption. Benefiting from the conductive Ti₃C₂ nanosheets with massive active sites and the multiple well-aligned channels in wood with efficient transportation pathways for charge carriers, the as-designed free-standing electrode shows a large areal capacitance of 1060 mF cm⁻² at 0.5 mA cm⁻² and high capacitance retention of 67% at 10 mA cm⁻². Also, this electrode is highly size-customizable, showing a good ability to be industrially processed into various shapes and dimensions. Furthermore, an all-wood based supercapacitor with Ti₃C₂/wood composites as two layers of electrodes and a wood slice as the separator is fabricated, presenting a high energy density of 10.5 μW h cm⁻² at 389.9 μW cm⁻².