Modulating Redox Mechanism in Metal Chalcogenides by Precisely Controlling Phase Transition to Achieve Ultrafast and Ultra‐Stable Sodium‐Ion Batteries

ABSTRACT Metal chalcogenides represent promising anodes for sodium‐ion batteries due to their high theoretical capacities and low material costs. However, their practical applications are hampered by inherently sluggish ion diffusion kinetics and severe volume expansion associated with their conventional conversion reaction mechanism. Here, we design a micro‐nano ZnS/ZnSe heterostructured anode through in situ localized phase transformation strategy. This meticulously engineered architecture effectively modulates the Na + storage mechanism from a typical conversion reaction to the surface redox pseudocapacitive reaction by precisely controlling the phase transition processes. Such structural control substantially increases Na + diffusion sites and reconstructs internal electric fields. Moreover, abundant heterointerfaces and porous microstructure effectively alleviate internal mechanical stresses, provide a large number of Na + storage sites and fast Na + migration channels, collectively ensuring ultrafast reaction kinetics and superior structural stability of the ZnS/ZnSe. As a result, the ZnS/ZnSe exhibits a remarkable specific capacity of 796 mAh g − 1 at 0.1 A g − 1 , stable cycling with no capacity decay over 1800 cycles at 15 A g − 1 , and capacity retention of 89% even at ultrahigh current density of 20 A g − 1 . Furthermore, the practical viability of this material is successfully demonstrated in a NaNi 1/3 Fe 1/3 Mn 1/3 O 2 (NFM)//ZnS/ZnSe full‐cell, which shows outstanding cycling stability without noticeable capacity fading after 600 cycles.