Xi Zhang, Wenhao Yang, Dan You, Ziyi Zhu, Xue Li
Biomass-derived hard carbon (HC) stands as the leading candidate for the anode in commercial sodium-ion batteries (SIBs). However, the effect of precursor components on the formation of HC at the molecular level breezing, and the evolution mechanism of microcrystalline carbon remains controversial. In this work, the introduction of the concept of "steric hindrance", through reducing the steric hindrance to the growth of linear cellulose chains, which can enable the deliberate design of an ordered microcrystalline structure, resulting in significantly enhanced ion diffusion kinetics. Experimental results and molecular dynamics indicate that reduced steric hindrance can decrease the chain rigidity and internal free volume of the precursor, preventing excessive disorder, and promoting the growth of microcrystalline graphite. Additionally, highly crystalline cellulose encourages the creation of closed pores, whereas lignin and hemicellulose impede the graphitization of the carbon layer. The optimized HC anode reveals a high sodium storage capacity of 309.7 mAh/g with a high initial Coulombic efficiency (ICE) of 93.5% at 20 mA/g, excellent cycling stability over 7000 cycles at 400 mA/g. Even at -20°C, it still has remarkable electrochemical performance. This study offers fresh insights into the regulation of microcrystalline structures via steric hindrance engineering.