Polysulfides\nCapture-Copper Additive for Long Cycle Life Lithium Sulfur Batteries

Abstract

Copper powder was\nintroduced into the lithium sulfur battery system to capture intermediate\npolysulfides and Cu_<i>x</i>S (<i>x</i> = 1 or 2) species was generated depending on the chain length of\npolysulfides. This phenomenon was verified by X-ray absorption near\nedge structure technique. The results indicated that copper can be\noxidized to CuS by Li₂S_<i>x</i> (<i>x</i> ≥ 6), and a mixture of Cu₂S and CuS\nwas obtained when <i>x</i> ranges from 3 to 6. While Cu₂S is eventually formed in the presence of Li₂S₃. After several cycles activation, the polysulfide-shuttle\neffect and self-discharge phenomenon which hinder the application\nof lithium sulfur batteries are found nearly eliminated Further experiments\ndemonstrated that in the case of Cu₂S generation, a high\nspecific sulfur capacity of 1300 mAh g^–1 could be\ndelivered, corresponding to 77.6% sulfur utilization, while the Coulombic\nefficiency approximates around 100%. Self-discharge experiment further\ndemonstrated that polysulfides almost disappear in the electrolyte,\nwhich verified the polysulfide-capture capability of copper.