Unveiling the Relationship Between Micropore Forming/Closing Behaviors During Carbonization and Sodium Storage Capability of Hard Carbons

Tuning the nanotextures of hard carbons is of prime concern with a view to developing high‐capacity anodes for Na‐ion batteries. Inasmuch as the evolution of the amorphous carbon nanostructure upon carbonization depends on the nature of the carbon source, a plausible approach is the molecular design of an organic precursor, which is, however, underexplored. In this study, we have prepared a series of porous carbon monoliths from macroporous phenolic resins with similar pore properties but varied macromolecular structures. The almost identical porous morphology can be tailored by the sol‐gel process accompanied by spinodal decomposition, while the reaction between poly(4‐vinylphenol) (PVPh) and formaldehyde yields different types of crosslinked polymer networks when the macromolecular property of PVPh is purposely changed. The respective phenolic resins with varied crosslinking degrees exhibit different carbonization behaviors in terms of micropore evolution and occlusion to generate nanovoids for Na clustering. Comparative investigation of the correlation between carbon nanotextures and electrochemical Na + ‐storage capability reveals that Na clustering can occur in small “open” pores and not in all “closed” pores. It also provides an insight into the favorable micropore formation/closing behaviors for yielding hard carbons enriched in nanovoids, which is conducive to developing high‐capacity anode materials.