Polysulfides Capture-Copper Additive for Long Cycle Life Lithium Sulfur Batteries

Copper powder was introduced into the lithium sulfur battery system to capture intermediate polysulfides and Cu_xS (x = 1 or 2) species was generated depending on the chain length of polysulfides. This phenomenon was verified by X-ray absorption near edge structure technique. The results indicated that copper can be oxidized to CuS by Li₂S_x (x ≥ 6), and a mixture of Cu₂S and CuS was obtained when x ranges from 3 to 6. While Cu₂S is eventually formed in the presence of Li₂S₃. After several cycles activation, the polysulfide-shuttle effect and self-discharge phenomenon which hinder the application of lithium sulfur batteries are found nearly eliminated Further experiments demonstrated that in the case of Cu₂S generation, a high specific sulfur capacity of 1300 mAh g^-1 could be delivered, corresponding to 77.6% sulfur utilization, while the Coulombic efficiency approximates around 100%. Self-discharge experiment further demonstrated that polysulfides almost disappear in the electrolyte, which verified the polysulfide-capture capability of copper.