Combining insights from the local structure characterization and DFT calculations presented here with our previous operando SAXS, XAS, Raman spectroscopy, and other studies in the literature, we propose a new 3-stage general mechanism for sodium storage in HC anodes: (1) surface adsorption, (2) defect-assisted intercalation, and (3) simultaneous intercalation/pore filling. This mechanism, shown schematically in Figure , clarifies the sequence of storage processes, the coexistence of mechanisms within capacity regimes, the influence of microstructure on sodium cluster size, and the role of defect-assisted intercalation versus conventional intercalation.