A Co3O4@MnO2/Ni nanocomposite as a carbon- and binder-free cathode for rechargeable Li–O2 batteries

Abstract

Rational design and synthesis of cathode catalysts are crucial for enhancing the performance of rechargeable Li–O₂ batteries. Here, we report a controlled synthesis of the nanocomposite, Co₃O₄ nanohorns coated with MnO₂ nanosheets on a Ni foam (Co₃O₄@MnO₂/Ni). It integrates the catalytic activities of oxygen reduction and oxygen evolution reactions and functions as a carbon- and binder-free cathode catalyst for rechargeable Li–O₂ batteries. This nanocomposite catalyst presents a small discharge/charge voltage gap of 0.76 V (a low polarization) and a long cycle life of 170 cycles at 300 mA g⁻¹, coupled with an ionic liquid-based electrolyte, 0.5 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMITFSI), which are much better than those based on the individual Co₃O₄ and MnO₂ cathodes. The enhanced electrochemical performance is ascribed to the integrated bifunctional catalytic activities and the porous micro/nanostructure of the Co₃O₄@MnO₂/Ni nanocomposite, as well as the ionic liquid-based electrolyte, indicating its promising application in rechargeable Li–O₂ batteries.