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, Ti 3 C 2 (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 Ti 3 C 2 suspension. By the assistance of positive charged polydopamine microspheres with large surface area, the self‐restacking of Ti 3 C 2 nanosheets can be avoided and the high mass loading (50 wt%) can be achieved due to the extra driving force for Ti 3 C 2 absorption. Benefiting from the conductive Ti 3 C 2 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 Ti 3 C 2 /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 .