Two-Dimensional Germanium Sulfide Nanosheets as an Ultra-Stable and High Capacity Anode for Lithium Ion Batteries.

Lithium ion batteries (LIBs) at present still suffer from low rate capability and poor cycle life during fast ion insertion/extraction processes. Searching for high-capacity and stable anode materials is still an ongoing challenge. Herein, a facile strategy for the synthesis of ultrathin GeS2 nanosheets with the thickness of 1.1 nm is reported. When used as anodes for LIBs, the two-dimensional (2D) structure can effectively increase the electrode/electrolyte interface area, facilitate the ion transport, and buffer the volume expansion. Benefiting from these merits, the as-synthesized GeS2 nanosheets deliver high specific capacity (1335 mAh g-1 at 0.15 A g-1 ), extraordinary rate performance (337 mAh g-1 at 15 A g-1 ) and stable cycling performance (974 mAh g-1 after 200 cycles at 0.5 A g-1 ). Importantly, our fabricated Li-ion full cells manifest an impressive specific capacity of 577 mAh g-1 after 50 cycles at 0.1 A g-1 and a high energy density of 361 Wh kg-1 at a power density of 346 W kg-1 . Furthermore, the electrochemical reaction mechanism is investigated by the means of ex-situ high-resolution transmission electron microscopy. These results suggest that GeS2 can use to be an alternative anode material and encourage more efforts to develop other high-performance LIBs anodes.