Synthesis and investigation of layered GeS as a promising large capacity anode with low voltage and high efficiency in full-cell Li-ion batteries

GeS with a layered structure is expected to be a promising anode material for lithium ion batteries by the theoretical prediction of its excellent ion intercalation response. However, its experimental investigation is limited because of its low yield and complicated synthesis procedure. In this work, we successfully synthesize pure GeS and its carbon composite on a large scale by a simple and facile ball milling method. When serving as a novel anode material, GeS/C delivers a high reversible capacity of 1768 mA h g(-1) with a high initial coulombic efficiency of 94% for lithium-ion batteries. The ex situ XRD patterns and CV tests confirm that GeS undergoes firstly a conversion reaction followed by an alloying type of lithium storage mechanism, in which the electrochemical performance controlled within the alloying reaction region is very stable and highly reversible, with a low and safe potential of 0.35 V vs. Li+/Li. When further applied in a full cell by coupling commercial LiCoO2 as the cathode, the assembled LiCoO2//GeS full cell can offer a high capacity of 736 mA h g(-1), with a high flat discharge plateau of 3.4 V, showing a high utilization efficiency of the GeS anode. These results demonstrate that the layered GeS is a potential anode for high-energy lithium-ion batteries.