LaF3@SiO2 yolk-shell heterostructure nanofiber-modified separator enhances the long-cycling performance of lithium-sulfur batteries.

Abstract

High-energy-density lithium-sulfur (Li-S) cells are identified as one of the most prospective next-generation energy storage appliances owing to their numerous advantages. Nonetheless, their widespread applications are restricted by the unwanted shuttling effect and tardy conversion reaction kinetics of lithium polysulfides (LiPSs). To address these puzzles, we present an innovative strategy for the one-pot synthesis of LaF₃@SiO₂ yolk-shell heterostructure nanofibers (YSHNFs) through a straightforward uniaxial electrospinning process coupled with fluorination, avoiding the complexities of traditional methods. The specially designed LaF₃@SiO₂ YSHNFs are utilized as an interlayer to modify a polypropylene (PP) film, creating a LaF₃@SiO₂/PP separator for long-cycle Li-S batteries. Peculiar "3 + 1" mode anchoring (quadruplex anchoring) and "3 + 1" mode catalysis (quadruplex catalysis) are present in the LaF₃@SiO₂ YSHNFs, effectively inhibiting the LiPSs shuttling and enhancing their conversion reaction kinetics. Furthermore, the yolk-shell cavity acts as a nanoreactor, advancing the conversion of LiPSs on the LaF₃@SiO₂ heterostructure. Owing to the strategic design of components and the distinctive structure of LaF₃@SiO₂ YSHNFs, the combination of the quadruplex anchoring, the quadruplex catalysis, and the nanoreactor collectively contributes to a long-cyclic Li-S battery with high performances. The bare sulfur cathode using the LaF₃@SiO₂/PP separator exhibits an impressive incipient discharge capacity of 1514 mAh g^-1 at 0.2 C and displays a decay rate of only 0.034 % per cycle at 2 C over 600 cycles with a distinguished stability. Density functional theory calculations offer insights into the mechanisms of quadruplex anchoring and catalytic conversion reactions involving the LaF₃@SiO₂ heterostructure for LiPSs redox process. The strategies for interlayer design, concepts and techniques proposed in this study provide valuable guidance for developing yolk-shell structured materials for advanced long-cyclic Li-S batteries.