Bottom-up, hard template and scalable approaches toward designing nanostructured Li2S for high performance lithium sulfur batteries.

Li2S with a high theoretical capacity of 1166 mA h g(-1) and the capability to pair with lithium free anodes has drawn much attention for lithium sulfur (Li-S) battery applications. However, the fast battery decay and the low capacity retention due to dissolution of intermediate polysulfides in electrolytes limit its development. Designing a nanosized and nanostructured host for Li2S through facile techniques is one of the ways to alleviate the dissolution and improve Li-S battery performance; nevertheless, it is technically difficult to synthesize nanosized and nanostructured hosts for Li2S because Li2S is highly sensitive to moisture and oxygen. Herein, a novel technique, i.e., a bottom-up, hard template and scalable method, is proposed to engineer nanoLi2S composites with core-shell structures as cathodes of Li-S batteries. The size of the as-prepared nanostructured Li2S is around 100 nm. With the assistance of FETEM, HRTEM and EFTEM elemental mapping, an excellent core-shell structure has been confirmed and the outside carbon shell has a thickness of 20-50 nm, effectively retarding polysulfide outflow and dissolution. A high initial capacity of 915 mA h g(-1) at 0.2 C has been achieved upon electrochemical cycling and the battery still has exceptional capacity retention after prolonged 200 cycles with a limited decay of 0.18% per cycle. Also, at 0.5 C the electrode exhibits 60% capacity retention with a long life of 300 cycles. We attribute these good performances to the nano-architecture constructed by the novel and facile method.