Delocalized electron engineering in metal-air batteries: formation mechanisms, regulation strategies, and applications

Abstract

Metal-air batteries (MABs) are promising next-generation energy storage technologies with high theoretical energy density, environmental friendliness, and abundant material sources. However, the low oxygen kinetic, serious polarizations and short cycle life greatly restrict its widespread application. In recent years, delocalized electron regulation has proven to be a significant strategy for optimizing the intrinsic electronic structure of electrode materials, providing novel perspectives into enhancing charge transport, catalytic oxygen redox kinetics, and structural stability. This review systematically summarizes the fundamental concepts, formation mechanisms, and classification of delocalized electrons in energy storage materials, including π-electron delocalization, d-orbital coupling, intermetallic long-range coupling, and oxygen 2p hole delocalization systems. The regulatory strategies, including local coordination and lattice structure modulation, heteroatom doping, defect and vacancy engineering, interface coupling and heterojunction design, and external field excitation engineering, are discussed in detail, with emphasis on their impact on electronic structure and electrochemical performance. Furthermore, the application of delocalized electronic regulation in typical MABs (especially lithium‑oxygen batteries, zinc-air batteries, and aluminum-air batteries) is reviewed through case studies, and the mechanism of this strategy in promoting reversible oxygen reactions, reducing overpotential, and prolonging cycle stability is revealed. Finally, main challenges and upcoming directions in the precise modulation and practical integration of delocalized electrons are proposed. This overview tries to fill the current gap in summarizing delocalized electron engineering in MABs, providing theoretical guidance and design strategies for high-performance energy storage systems.