A Collaboratively Polar Conductive Interface for Accelerating Polysulfide Redox Conversion.

Abstract

In order to alleviate the inferior cycle stability of the sulfur cathode, a self-assembled SnO2-doped manganese silicate nanobubble (SMN) is designed as a sulfur/polysulfide host to immobilize the intermediate Li2S x, and nitrogen-doped carbon (N-C) is coated on SMN (SMN@C). The exquisite N-C conductive network not only provides sufficient free space for the volume expansion during the phase transition of solid sulfur into lithium sulfide but also reduces Rct of SMN. During cycling, the soluble polysulfide could be fastened by the silicate with an oxygen-rich functional group and heteronitrogen atoms through chemical bonding, enabling a confined shuttle effect. The synergistic effect between N-C and SMN could also effectively facilitate the interconversion between lithium polysulfides and Li2S, reducing the potential barrier and accelerating the redox kinetics. With an areal sulfur loading of 2 mg/cm2, the S-SMN@C cathodes demonstrate a high initial capacity of 1204 mA·h/g at 0.1 C, and an outstanding cycle stability with a capacity fading rate of 0.0277%, ranging from the 2nd cycle to the 1000th cycle at 2 C.