Open‐Structured Zinc Hydroxide Sulfate Formation via Integrated Cathode Design Enabling Highly Reversible Ah‐Level Zn‐MnO ₂ Batteries

Abstract

ABSTRACT The practical deployment of Ah‐level aqueous Zn‐MnO 2 batteries (AZMBs) is hindered by the rampant deposition of insulating zinc hydroxide sulfate (Zn 4 SO 4 (OH) 6 · x H 2 O, ZHS). Due to the inhomogeneous consumption of additives, conventional strategies for ZHS suppression exhibit limited effectiveness in scaled‐up systems, making the goal of complete ZHS elimination both impractical and unnecessary. Herein, a practical paradigm shift from ZHS inhibition to morphological management is presented. A Bi 2 O 3 ‐modified MnO 2 cathode (20BEMD) is synthesized via a one‐step high‐energy ball milling (HEBM) process. Electrochemically inert Bi 2 O 3 regulates the interfacial environment through weak adsorption of SO 4 2− , promoting a sparse ZHS growth that lowers charge transfer resistance. Simultaneously, Bi 3+ doping is achieved through the HEBM process, resulting in bandgap narrowing and oxygen vacancy generation, which enhances electrical conductivity and ion diffusion kinetics. The optimized 20BEMD cathode delivers a reversible capacity of 338.2 mAh g −1 at 0.1 A g −1 , and maintains 90% capacity retention after 500 cycles at 0.5 A g −1 . An Ah‐level pouch cell demonstrates stable operation over 22 days in deep charge/discharge operation, and exhibits practical applicability in photovoltaic energy storage, supporting the feasibility of this approach for scalable AZMBs.