Improve the electrodeposition of sulfur and lithium sulfide in lithium-sulfur batteries with a comb-like ion-conductive organo-polysulfide polymer binder

Abstract

Lithium-sulfur (Li-S) battery is a promising candidate for high-energy storage technologies due to its high energy density and low cost. However, the irreversible and unstable phase transfer between the dissolved lithium polysulfide intermediates and the insoluble charge or discharge products (S or Li2S) severely hampers the energy density and the lifespan of Li-S battery. Herein, a comb-like ion-conductive organo-polysulfide polymer (PSPEG) binder was prepared to solve the phase transfer problem. We found that the organo-polysulfide bonds in PSPEG binder could react with the agglomerated S/Li2S to improve their electrodeposition states. And the unique comb-like structure of PSPEG binder endows PSPEG with good adhesive property and compatibility with active material. Hence, the sulfur electrode with PSPEG binder could demonstrate improved cycling performance and rate capability as compared to the electrode with conventional LA132 binder. More importantly, the electrode with PSPEG can deliver a stable capacity over 500 cycles as the PSPEG content is only 1 wt%. In a word, this work provides a new strategy to address the unstable phase transfer problem utilizing the organo-polysulfide polymer, which may arouse the battery community's interest to explore the novel functional binders for the commercial application of high-energy Li-S batteries.