A Lithium-Sulfur Cell Based on Reversible Lithium Deposition from a Li2S Cathode Host onto a Hostless-Anode Substrate

The development of lithium-sulfur batteries necessitates a thorough understanding of the lithium-deposition process. A novel full-cell configuration comprising an Li2S cathode and a bare copper foil on the anode side is presented here. The absence of excess lithium allows for the realization of a truly lithium-limited Li-S battery, which operates by reversible plating and stripping of lithium on the hostless-anode substrate (copper foil). Its performance is closely tied to the efficiency of lithium deposition, generating valuable insights on the role and dynamic behavior of lithium anode. The Li2S full cell shows reasonable capacity retention with a Coulombic efficiency of 96% over 100 cycles, which is a tremendous improvement over that of a similar lithium-plating-based full cell with LiFePO4 cathodes. The exceptional robustness of the Li2S system is attributed to an intrinsic stabilization of the lithium-deposition process, which is mediated by polysulfide intermediates that form protective Li2S and Li2S2 regions on the deposited lithium. Combined with the large improvements in energy density and safety by the elimination of a metallic lithium anode, the stability and electrochemical performance of the lithium-plating-based Li2S full cell establish it as an important trajectory for Li-S battery research, focusing on practical realization of reversible lithium anodes.