Polygonal WS2-decorated-graphene multilayer films with microcavities prepared from a cheap precursor as anode materials for lithium-ion batteries.

• Inexpensive ammonium metatungstate for synthesis of WS 2 is used. • Composite film with microcavity and nanofilm inside is formed. • The graphene-WS 2 composite presented fast lithium insertation/deinsertation. • The structure of the composite can be modified by the ratio of graphene to WS 2. In this study, the water-evaporation-induced assembly of a graphene oxide-ammonium metatungstate hydrate multilayer film was developed. After chemical reduction and high-temperature sulfurization, a graphene-WS 2 composite nanofilm with microcavities was obtained. When evaluated as an anode material in a lithium-ion battery, the graphene-WS 2 sample (precursor graphene oxide/WS 2 mass ratio of 1:4) exhibited high initial specific capacity (∼980 mAh g−1 at 0.1 A g−1), optimal cycling performance (∼450 mAh g−1 after 100 cycles at 0.1 A g−1), and superior rate capability (∼300 mAh g−1 at 2 A g−1). The graphene/WS 2 mass ratio influenced the contact between WS 2 and graphene and the porous nanofilm structure facilitated the kinetics of lithium-ion diffusion. [ABSTRACT FROM AUTHOR]