Metal–organic framework microdomains in 3D conductive host as polysulfide inhibitor for fast, long-cycle Li–S batteries

Abstract

The practical implementation of Li–S batteries is largely hindered by their low Coulombic efficiency (CE), rapid capacity decay, and poor rate capability, due to the poor electrical conductivity of sulfur and notorious “shuttle effect” of lithium polysulfides. Designing multifunctional separators is expected to increase the utilization of active materials and the electrochemical performance of Li–S batteries. Here, we synthesized a hybrid nanostructure with microporous ZIF-8 (dpore = 0.34 nm) microdomains embedded in chemically integrated 3D conductive hosts (ZIF-8@3DC) via a facile hydrothermal approach as modified separators to enable long-life and high-rate Li–S batteries. Specifically, the ZIF-8@3DC-modified separator not only helps block, trap, and efficiently reutilize the polysulfides, but also provides channels allowing smooth Li-ion (d = 0.152 nm) transfer. Results indicate that the ZIF-8@3DC-modified separator, compared with the bare PP one, exhibits significant improvements in suppressing the polysulfide shuttling. Galvanostatic cycling using the ZIF-8@3DC-modified separator shows a high capacity of 992.2 mAh g−1 at 1 C rate for 200 cycles and 587.9 mAh g−1 at 3 C rate for 800 cycles with CE of 96.7%. Notably, the cells with the ZIF-8@3DC-modified separator also overperform those with the pristine separators at higher rates.