Electrochemical characterization of novel layered Cu2MS 4 materials for Li-ion batteries (M = Mo)

Electrochemical performance of Cu₂MoS₄ was evaluated. When the cutoff potential is limited between 1.6 and 3.0 V, the material can give stable cycle performance of up to 100 mA h g^-1. However, the material shows slow kinetics within this region. The material can give a discharge capacity of up to 653 mA h g^-1 when discharged to 0.6 V vs. Li/Li⁺, with a first cycle efficiency of 61.3%. This corresponds to an insertion of 8.5 Li and an extraction of 5.2 Li from the material. XRD and XPS measurements both suggest Cu displacement from the material during discharge and charge, which is a possible reason for the poor cycle stability of the material. A reaction mechanism is proposed based on the XPS analysis. Better cycle performance is observed for Cu₂MoS₄/GO composite. © 2013 Elsevier Ltd.