A Li₂S‐Based Sacrificial Layer for Stable Operation of Lithium‐Sulfur Batteries

Abstract

The polysulfide shuttle effect forms a formidable barrier for lithium‐sulfur (Li−S) battery technology, as it results in serious side reactions on the anode surface and shortens the battery's cyclability. In this work, we propose a facile yet effective preparation of the Li2S‐based sacrificial layer (LSL) as the separator to retard polysulfide crossover. On one hand, before polysulfides (PS) reach the anode surface and react with Li metal, low‐order Li2S prefilled inside the porous separator can chemically interact with PS and sterically physically block PS diffusion. On the other hand, the loss of Li2S in LSL can be replenished by the chemical disproportion of polysulfides, rendering the LSL with excellent endurance over cycling. With the optimized LSL, the Li/polysulfide battery achieves a stabilized discharge capacity at 25 °C (>950 mAh g−1 for 300 cycles, 0.5 C) and demonstrates an excellent thermal stability even at 55 °C (>870 mAh g−1 for 150 cycles, 1 C). The strategy is further generalized to other sulfur based batteries (i. e. Na−S battery), offering new opportunities to improve high‐energy sulfur‐based energy storage technologies.

Mechanistic understanding of the role separators playing in advanced lithium‐sulfur batteries

“…Composites of heat‐resistant materials can significantly reduce the thermal shrinkage in polyolefin‐based separators by providing additional mechanical supports . Based on this principle, several PP/PE‐based composite separators with low thermal shrinkage were prepared . For example, BTO nanoparticles were used as the thermally resistant material, and the PE/BTO separator exhibits a low thermal deformation rate of 45% compared to the PE separator (91.8%) after annealing at 150°C for 1 hour .…”