Atomistic Mechanism in Sodium-Ion Storage Revealed by Experiment and Simulation

Unlike lithium-ion batteries (LIBs), sodium-ion battery (SIB) technology is still in an early stage of development, where the pursuit of cost-effective and sustainable active materials is critical. Hard carbon (HC) is the most extensively studied anode material thanks to its compatibility with sodium-ion insertion. In this study, several cellulose-derived HCs were further evaluated as potential SIB anodes by using experimental and computational methods. Among them, the HC prepared from cellulose nanofibers delivers outstanding rate capability and cycling stability (∼210 mAh g–1 at 1000 mA g–1), exceeding the performance of its commercial counterpart. The excellent electrochemical performance is attributed to multiple merits: enlarged interplanar spacing, a hierarchical porous architecture, abundant defective sites, and enhanced conductivity arising from graphitic ribbon-like networks throughout the carbon matrix. Atomistic simulations using machine learning interatomic potentials further support these findings. Overall, this work offers new insights into the fundamental sodium-ion storage mechanisms in high-performance HC electrodes and highlights a sustainable route to next-generation SIB anodes.