Synergistic Effects of Thermally Engineered Defect-Rich Structures in Renewable Nanocarbons for Enhanced Electrochemical Performance

The electrochemical performance of conventional hard carbons remains constrained by their limited surface activity and insufficient interlayer spacing for efficient sodium storage. Here, we report a microstructurally engineered carbon derived from waste passenger tyres, exhibiting tunable defect density, interlayer spacing, and pore distribution through controlled carbonization between 700 and 1500 °C. The thermally driven reconstruction of sp2/sp3 domains induces a hierarchical framework featuring short-range ordered graphene nanodomains embedded within disordered carbon matrices, generating abundant closed and open pores that synergistically facilitate ion transport and adsorption. The optimized carbon produced at 1300 °C delivers a first-cycle reversible capacity of approximately 282.1 mAhg–1, retains approximately 278.5 mAh g–1 after 100 cycles at 10 mA g–1, and exhibits sustained high-current cycling stability over 500 cycles. Detailed micromechanistic analysis reveals that the enhanced sodium storage originates from the coupling of enlarged interlayer spacing (≈0.38–0.40 nm) and optimized Raman-active disorder with the internal pore architecture, enabling coexisting diffusion-controlled intercalation and surface-induced capacitive processes. This work establishes a framework for defect-controlled microstructural engineering of tyre-derived carbons, providing mechanistic insight into the pore–defect–graphite interplay and offering a sustainable pathway for converting end-of-life rubber waste into high-performance anode materials for next-generation sodium-ion batteries.