SnO₂/Reduced Graphene Oxide Interlayer Mitigating the Shuttle Effect of Li-S Batteries

The short cycle life of lithium-sulfur batteries (LSBs) plagues its practical application. In this study, a uniform SnO₂/reduced graphene oxide (denoted as SnO₂/rGO) composite is successfully designed onto the commercial polypropylene separator for use of interlayer of LSBs to decrease the charge-transfer resistance and trap the soluble lithium polysulfides (LPSs). As a result, the assembled devices using the separator modified with the functional interlayer (SnO₂/rGO) exhibit improved cycle performance; for instance, over 200 cycles at 1C, the discharge capacity of the cells reaches 734 mAh g^-1. The cells also display high rate capability, with the average discharge capacity of 541.9 mAh g^-1 at 5C. Additionally, the mechanism of anchoring behavior of the SnO₂/rGO interlayer was systematically investigated using density functional theory calculations. The results demonstrate that the improved performance is related to the ability of SnO₂/rGO to effectively absorb S₈ cluster and LPS. The strong Li-O/Sn-S/O-S bonds and tight chemical adsorption between LPS and SnO₂ mitigate the shuttle effect of LSBs. This study demonstrates that engineering the functional interlayer of metal oxide and carbon materials in LSBs may be an easy way to improve their rate capacity and cycling life.