Nanocellulose-Derived Hard Carbons for Sodium-Ion Batteries: Structure–Function Relationships from Experiment and Molecular Augmented Dynamics Simulations

Sodium-ion batteries (SIBs) are emerging as one of the most promising alternatives to lithium-ion batteries (LIBs) for next-generation energy storage owing to their numerous advantages. Similar to the commercial graphite anodes used in LIBs, carbon materials─particularly hard carbon (HC)─are widely regarded as the leading candidates for the first commercial SIB anode. Cellulose, the world’s most abundant natural polymer, offers an attractive, renewable, and tunable precursor for HC production. In this paper, we report the synthesis of a range of HC materials derived from different types of cellulose. Our findings highlight the strong correlation between the structure of the resulting HCs and the properties of their precursors, which can be further tailored through pre- and post-treatments during synthesis. Notably, the HC obtained from TEMPO-oxidized cellulose nanofibrils (TCNFs) exhibits a combination of desirable structural characteristics, including hierarchical porosity and a balanced degree of order and disorder─features critical for achieving durable, high-performance SIB anodes. Furthermore, the atomic-scale architectures of all HCs were successfully reconstructed through computational simulations based on experimental X-ray diffraction data. The integration of experimental analyses with computational modeling offers a powerful framework for better understanding and optimizing the microstructure of hard carbons.