Encapsulation of sulfur inside micro-nano carbon/molybdenum carbide by in-situ chemical transformation for high-performance Li-S batteries

In lithium-sulfur (Li-S) batteries, the electrochemical properties of the sulfur cathode are determined by the sulfur host, and this controls the shuttle effect and the kinetics, two of the major problems in these batteries. We confined the S in hollow thin-wall C/Mo2C particles smaller than 7 nm across that clustered together to form micrometer-size particles. The conducting network of C/Mo2C shells facilitates lithium-ion and electron transport while acting as a barrier to the outward diffusion of polysulfides. They also improve the redox kinetics because of the catalytic conversion of polysulfides to sulfur. As a result of these features the material achieved a high reversible capacity of 1 210 mAh g−1 at 0.5 C with a low capacity fade rate of 0.127% per cycle over 300 cycles and a high rate performance (780 mAh g−1 at 3.0 C). It is expected that this work will help in the design of sulfur hosts for Li-S batteries with a high rate performance and high cycling stability.