rGO-CNT aerogel embedding iron phosphide nanocubes for high-performance Li-polysulfide batteries

Li-polysulfide batteries (LPSBs) involving dissolved polysulfides as the catholyte have been sought as an alternative solution for addressing the problem of inefficient sulfur utilization with conventional lithium-sulfur batteries, but imposes even more stringent requirements on polysulfide immobilization. In this study, a hybrid rGO/CNTs aerogel embedding FeP nanocubes is fabricated by instantly freezing and phosphorizing metal organic frameworks (MOF)-containing precursors, and used as the LPSB cathodes for hosting polysulfides with high affinity. A high specific capacity of 1312.3 mA h g−1 at 0.2 C and prolonged cycling with only 0.037% decay per cycle at 1 C were achieved for over 500 cycles, together with an exceptional high areal capacity up to 8.5 mA h cm−2 at the sulfur loading of 9.6 mg cm−2. This remarkable LPSB performance is ascribed to the strong immobilization of polysulfides by the FeP anchoring material, the conductive and microporous carbon scaffolds in providing adequate interfaces for charge transfer, the homogeneous catholyte distribution for promoting sulfur utilization, as well as a possible catalytic effect of FeP on expediting the redox conversion of polysulfides.