Nano-GeTe Embedded in a Three-Dimensional Carbon Sponge for Flexible Li-Ion and Na-Ion Battery Anodes.

Among the germanium-based compounds, GeTe is a promising anode candidate that exhibits high theoretical capacity (856 mAh g vs Li/Li and 401 mAh g vs Na/Na) and low volume expansion during an ion intercalation/deintercalation process. Nevertheless, achieving good dispersion of metal-like GeTe in anode materials remains a significant challenge. Herein, hybrid GeTe/graphene (GeTe/G) is proposed as a highly efficient anode for LiBs and SiBs by facile ball milling. Pulverized GeTe is effectively anchored on peeled graphene sheets that can accelerate Li transport in electrodes as predicted by theoretical calculations and thus result in improved overall electrochemical performance. For instance, GeTe/G possesses a high reversible capacity of 478 mAh g under 0.1 A g in the 300th cycle. Moreover, by further cross-linking the GeTe/G using carbon nanotube (CNT) and carbon nanofiber pyrolysis from cotton cellulose, the as-prepared three-dimensional (3D) flexible anode possesses macropores that acted as positive channels favorably for ion transport. Remarkably, the as-prepared flexible 3D GeTe/G/CNT electrode with a thickness of 1050 μm exhibits a high reversible capacity of 451.4 mAh g (4.38 mAh cm) vs Li/Li and 372.5 mAh g (2.08 mAh cm) vs Na/Na, respectively, in the second cycle under 0.1 A g. These results shed some light on the direct application of 3D flexible carbon sponge electrodes in high-performance LiBs/SiBs.