Wood template-assisted construction of ultrathick lignin-derived carbon electrodes with low tortuosity and hierarchical porosity for advanced energy storage

Fabricate directional micro-nano hierarchical pore to accelerate ion migration • Adopt natural wood as sacrificial template to prepare self-supported electrodes • Achieve ultrahigh mass loading and competitive energy storage capability To develop next-generation high-energy-density storage devices, boosting electrode active mass loading is a critical strategy. Nevertheless, it remains extremely difficult to construct freestanding carbon electrodes with high areal mass loadings and to expedite ion diffusion through straightforward, green fabrication routes. Inspired by the rapid water transport in natural wood, herein we employ industrial lignin as carbonaceous source and natural wood as sacrificial template, thereby constructing a directional micro-nano hierarchical pore structure and endowing the as-synthesized self-supporting carbon electrode with superior electrochemical behaviors. The fabricated self-supporting carbon electrode achieves a high areal mass loading of 61.5 mg/cm 2 and an excellent compressive strength of 5.1 MPa, while delivering an impressive capacitance of 20.3 F/cm 2 (321 F/g) at 1 mA/cm 2 . Furthermore, the fabricated symmetric supercapacitors (SSCs) and Zn-ion hybrid capacitors (ZICs) exhibited remarkable energy densities of 1.1 mWh/cm 2 and 8.4 mWh/cm 2 at a power density of 0.5 mW/cm 2 and 3.8 mW/cm 2 , respectively. This work presents an efficient and sustainable route to address the critical challenges in ultra-thick carbon electrode design, offering new opportunities for developing high-performance energy storage.