“…Finally, cuprous sulfide is easily accessible and inexpensive, which makes it very attractive for commercialization. However, Cu 2 S suffers from a rapid capacity decay during cycling [2,14,15], which is attributed to the high solubility (in organic solvent electrolytes) of the polysulfide ions formed during the charge/discharge processes. The dissolution of the polysulfides resulted in low active material utilization, low coulombic efficiency and poor cycle life of Cu 2 S electrodes, thus the composition and polarity of the electrolyte can affect the cycling stability of Cu 2 S or CuS dramatically [7,16,17].…”