Wood-Based Thick Electrodes for High-Energy-Density Electrochemical Storage: Structural Engineering, Transport Regulation, and Device Integration

Thick electrodes boost device-level energy density but suffer from depth-direction ion-electron decoupling: ionic diffusion scales quadratically with electrode thickness, while electronic resistance increases linearly, causing poor interior utilization. Wood offers low-tortuosity axial channels and conductive carbonized walls, yet structural proximity does not guarantee kinetic compatibility. This review reorients the design from passive “structural synergy” to active “trade-off engineering”, establishing a closed-loop structure–transport–performance framework. We analyze how channel orientation, cross-scale pore connectivity, wettability, and gradient conductive networks cooperatively modulate coupled ion-electron transport. Unlike synthetic scaffolds, wood’s advantage lies in functionalizable surfaces (including −OH, −COOH and lignin redox moieties) that actively regulate ion desolvation, nucleation, and intermediate confinement. Representative data: an 850 μm cross-cut wood-carbon anode with a mass loading of 55 mg·cm−2 achieves ~13.5 mAh·cm−2. An 800 μm basswood electrode with a mass loading of ~40 mg·cm−2 achieves an areal capacitance of 6.54 F·cm−2 at 2 mA·cm−2. Through comparative analysis of supercapacitors (mass-transfer-limited), Li/Na-ion batteries (solid-diffusion-limited), and aqueous Zn batteries (interface-limited), we stress device-specific customization. Performance boundaries are not determined by the independent porosity or conductivity maximization, but by spatiotemporal matching between electrolyte residence time and interfacial reaction kinetics. We propose that AI-assisted precursor screening and gradient structure engineering can address the challenges of batch-to-batch variability and thickness limitation, transforming natural wood into a predictively engineerable platform for sustainable high-energy-density energy storage.