Pseudocapacitive Co‐Free Trimetallic Ni‐Zn‐Mn Perovskite Fluorides Enable Fast‐Rechargeable Zn‐Based Aqueous Batteries

Abstract The Zn‐ion batteries (ZIBs) have been largely confined by the sluggish diffusion kinetics of the cathode, and to develop the Co‐free electrode materials for Zn‐based aqueous batteries (ZABs) is of great importance for practical applications. Herein, a novel fast‐rechargeable ZAB constructed using a new type of pseudocapacitive Co‐free trimetallic Ni‐Zn‐Mn perovskite fluorides (ABF 3 , KNZMF) cathode is demonstrated. A deep study on the charge storage mechanisms of the KNZMF electrode materials has been conducted by various ex situ techniques, showing a typical conversion mechanism in the alkaline media along with the redox‐active or inert property for Ni/Mn or Zn species and the largely bulk phase transitions of ABF 3 perovskite nanocrystals into amorphous metal oxides/(oxy)hydroxides nanosheets. Interestingly, the Co‐free KNZMF and Zn//KNZMF ZAB exhibit superior performance to the Co‐rich trimetallic Ni‐Co‐Mn ABF 3 (KNCMF) and Zn//KNCMF ZAB, which is largely owing to the superior redox potential, OH − adsorption, deprotonation process, and surface electroactive sites of redox‐active Ni/Mn species confirmed by ex situ characterizations and density functional theory. The findings shed lights on developing advanced electrode materials for high performance electrochemical energy storage.