Ge Nanoparticles Encapsulated in Nitrogen-Doped Reduced Graphene Oxide as an Advanced Anode Material for Lithium-ion Batteries

Ge nanoparticles/C composites are desirable electrode materials for high energy and power density lithium-ion batteries. However, the production of well-dispersed Ge nanoparticles in a carbon network remains a challenge because of rapid grain growth during high-temperature thermal reduction. Herein, we report a PVP-assisted hydrolysis approach for fabricating a Ge nanoparticles/reduced graphene oxide composite (denoted as Ge/RGO) made of similar to 5 nm Ge nanoparticles that are uniformly distributed within a nitrogen-doped RGO carbon matrix. The Ge/RGO composite exhibits an initial discharge capacity of 1475 mA h g(-1) and a reversible capacity of 700 mA h g(-1) after 200 cycles at a current density of 0.5 A g(-1). Moreover, Ge/RGO shows a capacity of 210 mA h g(-1) even at a high current density of 10 A g(-1). The excellent performance of the Ge/RGO composite is attributed to its unique nanostructure, including Ge nanoparticles, homogeneous particle distribution, and highly conductive RGO carbon matrix. These properties alleviate the pulverization problem, prevent Ge particle aggregation, and facilitate electron and lithium-ion transportation.