Additive‐Induced Low‐Coordination Solvation and Interphase Regulation for Stable Zn Anodes in Ester‐Based Calcium Electrolytes

ABSTRACT Ester electrolytes are promising for calcium batteries; however, severe interfacial instability and sluggish redox kinetics limit anodes’ operating current density to the sub‐milliampere range, severely restricting their practical application. Herein, a phenyl iodine bis(trifluoroacetate) (PIFA) additive is developed to reconstruct solvation structures in pure calcium tetrafluoroborate‐based ester electrolytes, forming low‐coordination solvates with reduced desolvation barriers. Preferential adsorption of additive species onto the Zn (002) facet further induces an ultrathin, conductive CaI 2 ‐rich interphase layer. Such dual regulation of solvation and interfacial chemistry enables ordered lateral Zn deposition and accelerated redox kinetics. Consequently, the PIFA‐optimized electrolyte enables stable Zn plating/stripping for over 3200 h and low deposition overpotentials below 0.1 V at 1 mA cm −2 . The corresponding full cells deliver durable cycling of nearly 6000 cycles at 1 A g −1 with 100% capacity retention. This work provides a feasible solvation/interphase co‐regulation strategy for high‐rate, durable metal anodes for calcium electrolytes.