Hierarchical Porosity Engineering of Birch‐Derived Carbons via KOH Activation for High‐Performance Aluminum Batteries

Aluminum batteries (ABs) present a cost‐effective, high‐energy alternative to lithium‐ion systems, owing to aluminum's abundance and high theoretical capacity. Here, it reports the synthesis of birch wood derived carbons (CBWs) via carbonization of sawdust followed by KOH activation and their evaluation as AB cathodes. Two samples CBW14 and CBW16 are prepared using biochar‐to‐KOH weight ratios of 1:4 and 1:6, respectively. Both materials are highly disordered, predominantly amorphous carbons, exhibiting Brunauer–Emmett–Teller‐specific surface areas of 3015 m 2 g −1 (CBW14) and 3306 m 2 g −1 (CBW16). When cycled between 0.01 and 2.2 V at 0.1 A g −1 , CBW14 and CBW16 delivered discharge capacities of 120 and 140 mAh g −1 , respectively. Notably, CBW16 sustained 35 mAh g −1 at a high rate of 10 A g −1 and achieved energy densities of 155 Wh kg −1 at 0.1 A g −1 and 95 Wh kg −1 at 1.0 A g −1 . These findings underscore the critical influence of KOH activation parameters on pore architecture and electrochemical performance, pointing the way toward scalable fabrication of efficient carbon cathodes for next‐generation aluminum batteries.