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