Radical‐Mediated Pyrolysis Engineering Multi‐Precursor Hard Carbons with Hierarchical Sodium Storage Architectures
Chenhao Liu, Yuqi Li, Wanli Wang, Longsen Song, Qi Wei, Bin Wang, Kang Sun, Qiang Li, Mingbo Wu, Han Hu
Abstract
Abstract Hard carbon with optimized sodium storage architecture is synthesized through radical‐mediated pyrolysis of low‐cost lignin/asphalt precursors. Spray‐drying followed by instantaneous low‐temperature crosslinking and anaerobic pyrolysis enables covalent C─O─C bridging between asphalt‐derived carbon radicals and lignin oxygen functionalities, directing hierarchical structure evolution. The resulting composite exhibits expanded interlayer spacing (0.393 nm), turbostratic disorder, and size‐regulated closed pores (<1 nm), synergistically enhancing sodium storage. Electrochemical testing demonstrates a reversible capacity of 330.8 mAh g −1 with 60% plateau contribution, outperforming single‐precursor analogs by 29.8%. Structure‐performance relationship analyses reveal that plateau capacity is synergistically regulated by interlayer spacing and closed‐pore volume, which promotes Na + migration and pore filling, while slope capacity is governed by defect density‐dominated adsorption kinetics. Mechanistic studies further establish that ionic‐state Na + (mediated by slope‐region adsorption) are antecedent to metallic‐state Na + formed through confinement storage (e.g., intercalation/pore‐filling), as the latter requires higher driving voltages and operates at deeper electrode storage sites, resulting in slower kinetics. This work establishes a radical chemistry‐guided paradigm for multi‐precursor carbon design, demonstrating how controlled radical interactions during pyrolysis decouple competing structural requirements to simultaneously achieve high capacity and rate performance, a critical advancement toward commercially viable sodium‐ion battery anodes.