Single-atom scale metal vacancy engineering in heteroatom-doped carbon for rechargeable zinc-air battery with reduced overpotential

Metal-air batteries have drawn great attention in the past decade due to their high energy density and low cost. However, several challenges remain in the development of such promising devices, including slow kinetics of the cathodic reaction and undesirable deposition of metal oxide on air cathode. Herein, as a proof of concept, we show single-atom scale metal vacancy engineering in heteroatom-doped carbon cathode to enable high-performance zinc-air battery with reduced overpotential. Density functional theory calculations indicate that metal vacancy-induced pyridinic-N can tailor the electronic structure and thus facilitate the catalytic reaction. The single-atom dispersed Fe-N-C catalyst with optimized Fe vacancies shows improved reactivity and the facilitated chemisorption of oxygen intermediates in the actual battery operation is directly observed by in-situ X-ray diffraction characterization. Moreover, the in-situ observation also indicates the absence of zinc oxide, which can be ascribed to strong Lewis basicity created by pyridinic-N that effectively prevents the access of zincate ions with negative charge and thus enables non-deposition of zinc oxide. Applying this strategy, the rechargeable zinc-air battery shows high reversibility and stability over 1000 cycles with negligible voltage gap change of only 0.04 V. This work not only affords valuable insights but also opens up new perspectives to develop high-performance metal-air batteries.