Redox Electrolytes‐Assisting Aqueous Zn‐Based Batteries by Pseudocapacitive Multiple Perovskite Fluorides Cathode and Charge Storage Mechanisms

Abstract Aqueous Zn‐based batteries (AZBs) have attracted intensive attention. However, to explore advanced cathode materials with in‐depth elucidation of their charge storage mechanisms, improve energy storage capacity, and construct novel cell systems remain a great challenge. Herein, a new pseudocapacitive multiple perovskite fluorides (ABF₃) cathode is designed, represented by KMF‐(IV, V, and VI; M = NiCoMnZn/‐Mg/‐MgFe), and constructed Zn//KMF‐(IV, V, and VI) AZBs and their flexible devices. Ex situ tests have revealed a typical bulk phase conversion mechanism of KMF‐VI electrode for charge storage in alkaline media dominated by redox‐active Ni/Co/Mn species, with transformation of ABF₃ nanocrystals into amorphous metal oxide/(oxy)hydroxide nanosheets. By employing single or bipolar redox electrolyte strategies of 20 mm [Fe(CN)₆]³⁻ or/and 10 mm SO₃²⁻/Cu[(NH₃)₄]²⁺ acting on KMF‐(IV, V, and VI) cathode and Zn anode, the AZBs show an improved energy storage owing to additional capacity contribution of redox electrolytes. The as‐designed Zn//polyvinyl alcohol (PVA)‐KOH‐K₃[Fe(CN)₆]//KMF‐(IV, V, and VI) redox gel electrolytes‐assisting flexible AZBs (RGE‐FAZBs) exhibit remarkable performance under different bending angles because of slight dissolution corrosion of zinc anode compared with liquid electrolytes. Overall, the work demonstrates the novel idea of conversion‐type multiple ABF₃ cathode for redox electrolytes‐assisting AZBs (RE‐AZBs) and their flexible systems, showing great significance on electrochemical energy storage.