Germanium on seamless graphene carbon nanotube hybrids for lithium ion anodes

Abstract Germanium is a promising anode for lithium ion batteries (LIB) because of its potential rate capability and high theoretical specific capacity. Here we demonstrate a seamlessly connected graphene and carbon nanotube (GCNT) hybrid that serves as an integral current collector for a Ge anode. A vertically aligned CNT (VA-CNT) forest grown on graphene provides a high surface area for Ge deposition. The seamless connection between graphene and VA-CNT facilitates electron transport from the Ge to the Cu current collector. Graphene serves to alleviate mechanical strain between the electrode and current collector. The mechanical resilience of the GCNT lessens Ge pulverization on charge/discharge of the LIB. As a result, the Ge/GCNT anode has a high specific capacity of 1315 mAh/g after 200 cycles at 0.5 A/g and a high rate performance of 803 mAh/g at 40 A/g.