Few-Layered Reduced Siloxene Nanosheets for Lithium-Ion Batteries

Increasing the capacity of lithium-ion batteries is always one of the main drives of research and development of battery technology. Two-dimensional silicene is a candidate anode material for lithium-ion batteries due to its enormous theoretical lithium storage capacity. However, its preparation and application conditions are rigorous, hindering its practical applications. This work reports a simple preparation strategy for reduced siloxene nanosheets in atmosphere. The reduced siloxene is produced by liquid-phase exfoliation of Zintl phase CaSi2 in HCl/acetonitrile solution, followed by reduction in a vitamin C solution. This study carried out a systematic investigation on the preparation conditions to understand the effect of the exfoliation temperature, exfoliation time, and concentration of HCl/acetonitrile solution on the resulting siloxene thickness, exfoliation degree, and oxidation degree. The thinnest siloxene nanosheet produced reaches an average of 1.3 nm, a two-layered Weiss siloxene. When tested as an anode for lithium storage, the reduced siloxene shows a storage capacity almost twice that of its as-prepared counterpart, reaching 400 mAh·g–1. The study shows that the best lithium storage requires a synergistic combination of achieving thin thickness and high electrical conductivity of the reduced siloxene. This preparation strategy greatly simplifies the preparation of reduced siloxene and thus facilitates its practical application significantly.