Designing Dense, Robust, and Ion-Diffusion-Effective Electrodes from Natural Wood Material toward High-Volumetric-Performance Supercapacitors.

Assembling active materials into dense electrodes is a promising way to obtain high-volumetric-capacitance supercapacitors, but insufficient ion channels in the dense structure lead to a low rate capability. Herein, a dense and robust wood electrode with a large MXene volumetric mass loading (1.25 g cm) and abundant ion diffusion channels is designed via a facile capillary-force-driven self-densification strategy. Specifically, MXene is assembled onto a wood cell wall, endowing the wood electrode with good electrical conductivity (86 S cm) and high electrochemical activity (5.9 F cm at 1 mA cm). Notably, the oriented channels along with spaces between adjacent microfibrils recast after densification ensure efficient ion transport for the wood electrode, achieving an excellent rate capability with a high capacitance retention of 77% from 1 to 20 mA cm. Meanwhile, the capillary force induces self-densification on the softened wood cell wall, resulting in a highly compact and robust structure for the wood electrode.