In situ grown graphene-encapsulated germanium nanowires for superior lithium-ion storage properties

Alloying anode materials (Si, Ge, Sn etc.) in lithium-ion batteries usually suffer from a remarkable loss of capacity during the charge–discharge cycling. Herein, homogeneous in situ-grown graphene-encapsulated Ge nanowires are successfully achieved by a simple, completely catalyst-free route via arc-discharge. The Ge@G composite is composed of a graphene sheath and a metallic Ge nanowire core. This unique composite of graphene-encapsulated Ge nanowires is an ideal anode material for lithium ion storage. It can exhibit excellent electrochemical performance with a reversible specific capacity of 1400 mA h g−1 after 50 cycles at a current density of 1600 mA g−1 (the theoretical specific capacity of Ge is 1624 mA h g−1). These encouraging results demonstrate that arc-discharge synthesis provides efficient graphene encapsulation of Ge nanowires, and graphene encapsulation is a feasible solution to protect electrode materials for lithium-ion storage.