N, S-Coordinated Co Single Atomic Catalyst Boosting Adsorption and Conversion of Lithium Polysulfides for Lithium-Sulfur Batteries.

Abstract

Boosting reversible solid-liquid phase transformation from lithium polysulfides to Li2 S and suppressing the shuttling of lithium polysulfides from the cathode to the lithium anode are critical challenges in lithium-sulfur batteries. Here, sulfiphilic single atomic cobalt implanted in lithiophilic heteroatoms-dopped carbon (SACo@HC) matrix with a CoN3 S structure for high-performance lithium-sulfur batteries is reported. Density functional theory calculation and in situ experiments demonstrate that the optimal CoN3 S structure in SACo@HC can effectively improve the adsorption and redox conversion efficiency of lithium polysulfides. Consequently, the S-SACo@HC composite with sulfur loading of 80 wt% delivers a high capacity of 1425.1 mAh g-1 at 0.05 C and outstanding rate performance with 745.9 mAh g-1 at 4 C. Furthermore, a capacity of 680.8 mAh g-1 at 0.5 C with a low electrolyte/sulfur ratio (6µL mg-1 ) can be achieved even after 300 cycles. With the harsh conditions of lean electrolyte (E/S = 4µL mg-1 ) and high sulfur loading (5.4mg cm-2 ), a superior area capacity of 5.8 mAh cm-2 can be obtained. This work contributes to building a profound understanding of the adsorption and interface engineering of lithium polysulfides and provides ideas to tackle the long-standing polysulfide shuttle problem of lithium-sulfur batteries.