LiF-dominant SEI optimized by Isomerism effect for regulation of Li deposition and LiPS-induced corrosion on the Li anode

Abstract

Severe corrosion of lithium metal anodes under high sulfur (S) loading conditions is a major contributor to the dissolution-deposition imbalance in lithium-sulfur (Li-S) batteries, ultimately accelerating cell degradation. To address this challenge, a LiF-rich solid electrolyte interphase (SEI) is in situ constructed on the lithium surface by introducing fluoropyridine as a functional electrolyte additive, enabling precise and effective anode protection. The resulting LiF-dominant SEI combines high compactness, favorable Li⁺ conductivity, and strong chemical stability, and operates through two synergistic mechanisms. On one hand, the SEI simultaneously provides physical separation and chemical passivation, effectively isolating the lithium metal from lithium polysulfides (LiPSs) and suppressing corrosion reactions at their origin.On the other hand, the high ionic selectivity of LiF regulates Li⁺ transport, guiding uniform lithium deposition and improving the reversibility of lithium plating/stripping, thereby mitigating localized lithium depletion and deposition heterogeneity.Leveraging these advantages, the lithium-sulfur battery delivers exceptional electrochemical stability even under stringent operating conditions, such as a high sulfur areal loading of 5.0 mg cm -2 and a lean electrolyte regime (E/S = 8.0 μL mg -1 ), achieving an ultralow average capacity fading rate of only 0.07% per cycle. Moreover, a consistently high Coulombic efficiency above 98% is sustained at a current density of 1 C. Collectively, these findings confirm that the deliberate formation of a LiFenriched solid electrolyte interphase effectively stabilizes the lithium metal anode, mitigates key degradation mechanisms, and markedly improves the long-term cycling performance of lithium-sulfur batteries.