Carbon cage encapsulating nano-cluster Li₂S by ionic liquid polymerization and pyrolysis for high performance Li-S batteries

The reversibility and stability of Li₂S electrode can be improved by carbon coating on nano sized Li₂S. However, how to uniformly coat a dense layer of carbon on nano sized Li₂S is still challenge so far. Here, we utilized a novel flowable ionic liquid (1-Ethyl-3-methylimidazolium dicyanamide) as a carbon precursor to uniformly coat a dense carbon on Li₂S nano-clusters. The carbon coated nano-Li₂S cathode displays not only much high active material utilization (826mAh/g at 0.1C) due to short lithium ion diffusion distance and low charge transfer resistance, but also long cycling stability (82% of capacity retention after 500 cycles at 1C) with near 100% Coulombic efficiency due to encapsulation of the lithium polysulfide within the carbon cage.