Highly Reversible and Superior Li-Storage Characteristics of Layered GeS2 and Its Amorphous Composites

A layered GeS2 material was assessed as an electrode material in the fabrication of superior rechargeable Li-ion batteries. The electrochemical Li insertion/extraction behavior of the GeS2 electrode was investigated from extended X-ray absorption measurements as well as by cyclic voltammetry and differential capacity plots to better understand its Li insertion/extraction behavior. Using the Li insertion/extraction reaction mechanism of the GeS2 electrode, an interesting amorphous GeS2-based composite was developed and tested for use as a high-performance electrode. Interestingly, the amorphous GeS2-based composite electrode exhibited highly reversible discharging and charging reactions, which were attributed to a conversion/recombination reaction. The amorphous GeS2-based composite electrode exhibited highly reversible and outstanding electrochemical performances, a highly reversible capacity (first charge capacity: 1298 mAh g–1) with a high first Coulombic efficiency (83.3%), rapid rate capability (ca. 800 mAh g–1 at a high current rate of 700 mA g–1), and long capacity retention over 180 cycles with high capacity (1100 mAh g–1) thanks to its interesting electrochemical reaction mechanism. Overall, this layered GeS2 and its amorphous GeS2/C composite are novel alternative anode materials for the potential mass production of rechargeable Li-ion batteries with excellent performance.