Abstract
Metal-air batteries hold great promises for future energy storage, driven by their impressive energy density. However, practical applications encounter challenges due to the sluggish kinetics of oxygen reduction and evolution reactions taking place at cathode interface, particularly in demanding conditions such as high-current density and open-air scenarios. Addressing these challenges requires cathodes with high reactivity and optimized structure to efficiently facilitate electrochemical reactions. This necessitates the development of self-supporting cathodes that eliminate the current electrode fabrication process, which can lead to binder-induced blockage of reactive sites and reduce energy density due to heavy current collectors. Here, we propose an effective strategy to design freestanding cathodes with high reactivity and a well-designed hierarchical pore structure. This cathode significantly enhances battery reaction kinetics while accommodating insoluble discharge products and preserving air and electrolyte transport pathways for high-performance Mg-air batteries. The freestanding flexible metal-free carbon fiber cathode (E-CNFs) enables a Mg-air battery operating in an open-air condition to exhibit an ultralow overvoltage of 0.4 V as well as delivered a long-term lifetime of 280 h. As a result, an impressive full discharge capacity of 5772 mAh/g under a current density of 800 mA g−1 is achieved, surpassing those in all previously reported Mg-O2/air batteries.
Published Version
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