Highly Active and Stable Li2S−Cu Nanocomposite Cathodes Enabled by Kinetically Favored Displacement Interconversion between Cu2S and Li2S

Abstract The high activation barrier, inferior rate performance, and short cycling life severely constrain the practical applications of the high‐capacity Li2S cathode. Herein, we fabricate a Li2S−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 S8via troublesome soluble lithium polysulfides, Li2S is thermodynamically and kinetically more favorable to react with Cu by the displacement reaction, which alters the redox couple from Li2S/S to Cu/Cu2S, 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 Li2S cathode materials.