Tailored PPy-coated CeO2/Co3O4 yolk-shell nanostructures: engineering sulfur hosts for high-performance lithium-sulfur batteries

Abstract

Lithium-sulfur (LiS) batteries encounter several challenges as a leading competitor in advanced energy storage technology, including the low conductivity of elemental sulfur, volumetric expansion during charge-discharge cycles, and the substantial shuttle effect of lithium polysulfides. These problems significantly impede the practical adoption of LiS batteries. To tackle these issues, polypyrrole (PPy)-coated CeO₂/Co₃O₄ yolk-shell structured hollow nanospheres (PHNS) with a unique structure are prepared as a cathode host material. The unique hollow yolk-shell nanostructure of PHNS, rich in active sites, facilitates high sulfur utilization and optimizes polysulfide physical-chemical encapsulation. At the same time, the effective coating of PPy enhances conductivity and mitigates the volumetric expansion of sulfur. Consequently, LiS batteries with PHNS cathode demonstrate remarkable discharge performance, delivering an initial discharge capacity of 829 mAh g⁻¹ at 2C, with an average capacity decay rate of a mere 0.051 % per cycle after 500 cycles. Additionally, at a high sulfur loading of 6.5 mg cm⁻², a reversible areal capacity of 5.7 mAh cm⁻² remains achievable. The conductive polymer and unique structural characteristics of the host material exhibit low overpotentials and rapid electrochemical kinetics, highlighting the significance and value of this innovative design for advancing high-energy-density energy storage systems.