Radical Regulation of Bamboo Pyrolysis by Low-Density Polyethylene Enables High-Efficiency Hard Carbon Anodes for Sodium-Ion Batteries

Hard carbon has emerged as a highly promising anode material for sodium-ion batteries. However, rational regulation of its microstructure to achieve synergistic enhancement in electrochemical performance remains a critical challenge. In this work, we demonstrate a scalable co-pyrolysis strategy that integrates bamboo biomass with low-density polyethylene (LDPE) to regulate free-radical evolution and interactions during pyrolysis, thereby enabling the tailored formation of pseudo-graphitic domains and closed-pore architectures in biomass-derived hard carbon. Through systematic structural, spectroscopic, and electrochemical analyses, including in situ Raman spectroscopy and the galvanostatic intermittent titration technique (GITT), we establish multiscale correlations among preparation parameters, structural evolution, sodium-ion storage behavior, and overall electrochemical performance. The optimized hard carbon delivers a reversible capacity of 367.4 mAh g⁻¹, with an initial Coulombic efficiency of 89.6%, and retains 92.5% of its capacity after 500 cycles at 0.1 A g⁻¹. This work provides a novel precursor-modulation strategy to facilitate the practical commercialization of hard carbon for high-performance sodium-ion batteries.