Anhydrous Liquid-Phase Exfoliation of Pristine Electrochemically Active GeS Nanosheets

Germanium sulfide (GeS) is an emerging layered material with high promise in its two-dimensional (2D) exfoliated form for energy storage applications. While liquid-phase exfoliation (LPE) has been utilized for the low-cost, scalable production of related 2D materials, it has not yet been demonstrated for GeS nanosheets due to its chemical instability in ambient conditions. Here, GeS LPE is achieved in anhydrous N-methyl-2-pyrrolidone using a customized sealed-tip sonication system, yielding sub-10 nm thick GeS nanosheets that are structurally pristine with minimal chemical degradation as revealed by atomic force microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. Lithium-ion battery anodes based on these high-quality GeS nanosheets possess superlative electrochemical performance including high cycling stability over 1000 cycles and high rate capability in excess of 10 A g–1. Overall, this work establishes a scalable LPE pathway for the production of pristine electrochemically active GeS nanosheets that are well-suited for high-power lithium-ion battery applications.