Sandwich-structural graphene-based metal oxides as anode materials for lithium-ion batteries

Graphene-based metal oxides commonly show outstanding electrochemical performance due to the superior properties of graphene. However, the as-formed metal oxides decorated on graphene prefer to disintegrate or aggregate together, and the graphene-metal oxide hybrids also randomly aggregate themselves, resulting in capacity fading and poor cycling stability. Herein, the graphene-based metal oxides are further protected by graphene nanosheets through a stepwise heterocoagulation method, producing a layered sandwich structure. Compared to the normal graphene-based metal oxides, the sandwich-like graphene-based composites exhibit higher reversible capacities, better cycle performances, and higher rate capabilities. Such sandwich structure can avoid the aggregation of the composites and also act as an ideal strain buffer to alleviate the volume change of metal oxides during cycles. Moreover, the electronic conductivity of the electrode can be further enhanced by the introduction of additional graphene nanosheets. This double layer protection strategy is very effective and may be extended to prepare other high-capacity electrode materials for lithium-ion batteries.