g-C3N4/MoO3 composite with optimized crystal face: A synergistic adsorption-catalysis for boosting cathode performance of lithium-sulfur batteries

The commercial application of lithium-sulfur batteries (LSBs) has been seriously hindered by the shuttle effect of lithium polysulfides (LiPSs) and their slow redox kinetics. In this work, g-C3N4/MoO3 composed of graphite carbon nitride (g-C3N4) nanoflake and MoO3 nanosheet is designed and applied to modify the separator. The polar MoO3 can form chemical bond with LiPSs, effectively slowing down the dissolution of LiPSs. And based on the principle of "Goldilocks", LiPSs will be oxidized by MoO3 to thiosulfate, which will promote the rapid conversion from long-chain LiPSs to Li2S. Moreover, g-C3N4 can promote the electron transportation, and its high specific surface area can facilitate the deposition and decomposition of Li2S. What's more, the g-C3N4 promotes the preferential orientation on the MoO3(0 2 1) and MoO3(0 4 0) crystal planes, which optimizes the adsorption capacity of g-C3N4/MoO3 for LiPSs. As a result, the LSBs with g-C3N4/MoO3 modified separator with a synergistic adsorption-catalysis, can achieve an initial capacity of 542 mAh g−1 at 4C with capacity decay rate of 0.0053% per cycle for 700 cycles. This work achieves the synergy of adsorption and catalysis of LiPSs through the combination of two materials, providing a material design strategy for advanced LSBs.