Highly Active and Stable Li2 S-Cu Nanocomposite Cathodes Enabled by Kinetically Favored Displacement Interconversion between Cu2 S and Li2 S

Abstract

The high activation barrier, inferior rate performance, and short cycling life severely constrain the practical applications of the high-capacity Li₂ S cathode. Herein, we fabricate a Li₂ S-Cu nanocomposite with a drastically reduced activation potential, fast rate capability, and extraordinary cycling stability even under a practically relevant areal capacity of 2.96 mAh cm^-2 . Detailed experimental investigations aided by theoretical calculations indicate that instead of converting to S₈ via troublesome soluble lithium polysulfides, Li₂ S is thermodynamically and kinetically more favorable to react with Cu by the displacement reaction, which alters the redox couple from Li₂ S/S to Cu/Cu₂ S, leading to the excellent electrochemical performance. Moreover, the stability of the composite is demonstrated in the full-cell configuration consisting of commercial graphite anodes. This work provides an innovative and effective approach to realize highly activated and stable Li₂ S cathode materials.

Keywords: Displacement Reactions; Li2S Cathode Materials; Li2S-Graphite Full-Cell; Reduced Activation Potential.