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 (826 mAh/g at 0.1 C) 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 1 C) with near 100% Coulombic efficiency due to encapsulation of the lithium polysulfide within the carbon cage.

Graphical abstract•A high fluid ionic liquid is utilized as a novel carbon precursor in lithium-sulfur batteries.•Uniform and dense carbon is formed on nano-cluster Li2S.•The material exhibits excellent electrochemical performance. Figure optionsDownload full-size imageDownload as PowerPoint slide