Self‐Regulating Sodium‐Ion Battery Materials: From Phase Reconstruction to Functional Activation

ABSTRACT Sodium‐ion batteries are advancing toward practical deployment, yet their long‐term durability is governed not by static material properties but by the coupled evolution of the lattice, interface, and electrolyte environments under operating conditions. However, a systematic consolidation of these dispersed mechanistic insights is still lacking. This review introduces a unified self‐regulation framework in which structural and chemical changes remain confined, reversible, and functionally aligned with electrochemical transport. Evidence is organized along three axes: lattice and phase evolution in layered oxides, where controlled slab glide, moderated Na‐vacancy ordering, and stabilized oxygen participation narrow phase windows; interphase chemistry and mechanics, emphasizing inorganic‐rich, self‐renewing interfacial architectures that sustain ion transport and limit dissolution; and electrolyte‐materials coupling, where solvation structure, concentration regimes, and targeted additives steer interphase reconstruction and near‐surface transport. The scope spans major cathode families and self‐buffering anodes, with electrolytes treated as purposeful enablers. From these insights, we distill design rules linking operando signatures to composition and processing choices and outline opportunities for model‐guided optimization and data‐driven discovery. This framework provides a materials‐first roadmap toward programmable, durable sodium‐ion batteries operating reliably under practical constraints.