Metal-organic framework-derived metal oxide nanoparticles@reduced graphene oxide composites as cathode materials for rechargeable aluminium-ion batteries.

The use of metal oxides as electrode materials has seen great success in lithium-ion batteries. However, this type of electrode materials has been regarded as an improper option for rechargeable aluminium-ion batteries (AIBs) in comparison with sulfides and selenides, and has, thus, been nearly abandoned. Here, we demonstrate the suitability of metal oxides as cathode materials of AIBs, exhibiting high electrochemical activities toward Al-ion storage. We designed economical metal-oxide cathodes (CoO@reduced graphene oxide (rGO), FeO@rGO, and CoFeO@rGO) for AIBs. The CoO@rGO displayed superior electrochemical properties, regarding both capacity and lifespan, to the current state-of-the-art cathode material reported by scientific literature. Furthermore, the CoFeO@rGO exhibits rational electrochemical capacities and an extremely stable charge/discharge process with an excellent Coulombic efficiency of 99.6%. The proposed study expects to stimulate researchers to focus on the overlooked metal oxides as competitive cathode materials for high performance AIBs.