Multilayer Zn-doped SnO2 hollow nanospheres encapsulated in covalently interconnected three-dimensional graphene foams for high performance lithium-ion batteries

Multilayer Zn-doped SnO2 nanospheres are successfully synthesized by using Sn/Zn bimetal-organic nanoparticles as precursor. These multilayer spheres are found to be very suitable for solving the critical volume expansion problem and mass transfer property due to its high surface area, small crystal size and hollow structure, which is critical for high capacity metal oxide electrodes for lithium-ion batteries. Moreover, the covalently interconnected three-dimensional graphene foams encapsulated these multi layer spheres are successfully obtained through self-assembly effect and chemical cross-linking of graphene oxide nanosheets. The graphene network could further greatly improve the cycling stability and rate capability of the Zn-doped SnO2 spheres electrode due to its flexible buffering matrix and high electric conduction. As a result, the graphene encapsulating multilayer Zn-doped SnO2 spheres anodes exhibit excellent rate capacity and a high reversible capacity of 446 mA hg(-1) even after 1000 cycles at the current density of 1 A g(-1). These excellent electrochemical performances are ascribed to its large specific surface area, fast electron/ion transfer, and stable electrode structure. Furthermore, this strategy using covalently interconnected 3D graphene foams encapsulate the Zn-doped SnO2 spheres not only develops a high performance anode material with long cycle life but also holds great promise for binder-free lithium ion batteries. (C) 2017 Elsevier B.V. All rights reserved.