Advancements in Rechargeable Zinc-Air Batteries: Strategic Modifications in Mn_xCo_yO₄ Bifunctional Catalysts and Air...

This review critically studies Mn_xCo_yO₄-based spinel materials as bifunctional electrocatalysts for rechargeable zinc-air batteries (ZABs). It focuses on the fundamentals and extends comprehensive insights of the key electrochemical characterization techniques for evaluating bifunctional electrocatalyst. The influence of crystal structure and symmetry, particularly the dominance of the cubic MnCo₂O₄ polymorph on the electrochemical performance, is explored in detail, along with comparisons to underexplored tetragonal and trigonal counter forms. Additionally, various potential synthesis strategies are summarized for tailoring morphology and phase in order to control their catalytic activity. Advanced cathode architectures, such as Janus electrodes and binder-free configurations, are also discussed in relation to their role in enhancing air electrode performance. Furthermore, review discusses the performance-enhancing strategies, like facet engineering, alloying, carbon compositing, and transition metal doping. The review is further supported by the inclusion of the emerging concept of anode-free ZABs. A dedicated section highlights the electrochemical metrics of pristine and composite MnCo₂O₄-based catalysts, offering valuable insight into structure-performance correlations. This focused investigation through this comprehensive review aims to provide guidance in the rational design of high-performance air cathodes for next-generation ZABs and is believed to direct the future research community working in the field of electrocatalysis and air-based rechargeable batteries.