Cluster-type lithium polysulfides regulator for high performance lithium-sulfur batteries

Lithium polysulfide intermediates suffer from serious shuttle effect and slow redox kinetics, resulting in limited rate performance, low discharge capacity and rapid capacity decay of lithium-sulfur (Li-S) batteries. Here, we propose a concept of cluster-type lithium polysulfides (LiPSs) regulator to address the above-mentioned problems. Dipyridyl disulfide (DpyDS) is introduced to be an electrolyte additive to form low solubility macromolecular lithium pyridine-2-thiolate (LiPyS) clusters in electrolyte by in-situ lithiation and Li bond network. The LiPyS monomer in the clusters form complexes (LiPyS-LiPSs) with LiPSs through bi-directional Li center dot center dot center dot S bonds, so as to restrict LiPSs to the clusters on the cathode side, preventing the parasitic reaction between LiPSs and Li metal. At the same time, LiPyS-LiPSs have higher HOMO energy levels and lower LUMO energy levels than that of single LiPSs. As a result, LiPSs can achieve an enhanced redox activity, and the Li-S battery regulated with DpyDS provides a capacity as high as 900 mA h g(-1) at 2 C rate.

Automated summary

This study proposes a concept of cluster-type lithium polysulfides regulator to address the performance and capacity decay issues in lithium-sulfur batteries. By introducing dipyridyl disulfide, the formation of macromolecular lithium pyridine-2-thiolate clusters restricts the polysulfides to the cathode side and enhances the redox activity of lithium polysulfides. The regulated Li-S battery exhibits a high capacity at a high C rate.