α-MoO3 spheres as effective polysulfides adsorbent for high sulfur content cathode in lithium-sulfur batteries

Abstract

The practical applications of lithium-sulfur (LiS) batteries remains remote because of low utilization of sulfur and short cycle life caused by low conductivity of sulfur, shuttle effect of lithium polysulfides and severe volume expansion. It is therefore exigent to rationally design an effective sulfur host. Here a novel sulfur host material--alpha molybdenum trioxide (α-MoO3) spheres are introduced into LiS battery cathode acting as lithium polysulfides absorbent and efficient matric of sulfur. The abundant oxygen atoms on the surface of α-MoO3, making it form chemical binding interactions with lithium polysulfides, which can effectively alleviate the dissolution of lithium polysulfides. Moreover, α-MoO3 as the matric of sulfur alleviates volume expansion of active sulfur and enhanced the utilization of sulfur, which results in improving the battery performances. As a result, S/α-MoO3 electrode with the sulfur content of 68 wt.% shows an initial discharge capacity of 1086.2 mAh g−1 and good capacity retention is obtained with 912.8 mAh g−1 after 400 cycles at 0.5 C. After 50 cycles at rates ranging from 0.1 to 2 C, the cell still returns a high specific capacity of 916.5 mAh g−1 at 0.5 C. The results demonstrate α-MoO3 was a promising sulfur host material for promoting the performances of LiS batteries with high sulfur content cathode.