Radical‐Mediated Pyrolysis Engineering Multi‐Precursor Hard Carbons with Hierarchical Sodium Storage Architectures

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.