Ultra-Fast Synthesis of Single Atoms for All-Solid-State Lithium-Sulfur Batteries

Abstract

All-solid-state lithium-sulfur (Li-S) battery has attracted the most attention in the past decades due to its high theoretical energy density (2600 Wh kg-1), high safety, low cost, and environmentally friendly feature. However, several issues need to be addressed before commercializing all-solid-state Li-S battery. The insulating nature of charged product sulfur and discharged product lithium sulfide results in low active material utilization. The dissolution of polysulfides intermediate and shuttling effect leads to fast capacity decay. Incorporating catalysts into the cathode or separator has proven to be very effective for promoting the sluggish Li-S reaction kinetics, suppress the shuttling effect of polysulfides, thus achieving superior cycling performance of Li-S battery using the liquid electrolyte. Single atom catalyst with the maximum atom utilization, unique coordination environment attracted particular attention. Whether single atom sites are feasible in the solid-state electrolyte is still unexplored. Herein, we synthesized single atom catalysts using ultra-fast approach. High-angle annular dark-field aberration corrected scanning transmission electron microscopy image and extended X-ray absorption fine spectroscopy verified the presence of single atoms on the support. The optimized absorption sites of single atoms were further studied with density functional theories. Using polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide infiltrated polyimide as the solid polymer electrolyte, we evaluated the cycling performance of all-solid-state Li-S battery. Single atoms incorporated sulfur cathodes exhibits higher cycling performance than the bare sulfur cathodes due to the significantly enhance lithium-sulfur redox reaction kinetics. The fast Li-S redox reaction kinetics were also revealed by calculating the energy barrier from sulfur to lithium sulfide using density functional theories. The formation of lithium sulfide from lithium disulfide was found to be the rate-limiting step for discharging sulfur. With the help of single atoms, the energy barrier of the rate-limiting step is significantly reduced. Our work provides new insights to improve the capacity and cycling life of all-solid-state Li-S batteries for commercializing Li-S technology.