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

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.