Enhancing reaction kinetics and stabilizing lithium deposition in lithium-sulfur batteries with an FeBr2DME additive

Lithium-sulfur (Li-S) batteries, with their high theoretical specific capacity and energy density, hold the promise of transforming energy storage. However, challenges such as polysulfide shuttling and lithium anode instability hinder their commercialization. This study introduces an innovative electrolyte additive, iron bromide dimethoxyethane (FeBr₂DME), which catalyzes polysulfide conversion, enhances reaction kinetics, and stabilizes lithium deposition. In Li-Li symmetric cells, FeBr₂DME enabled stable cycling for 1000 h at 1 mA cm⁻². Li-Cu cells maintained high coulombic efficiencies (∼99 %) over 200 cycles. Adding 0.5 mM FeBr₂DME to the electrolyte resulted in a specific discharge capacity of 519.3 mAh g⁻¹ at 4C, with 90.3 % capacity retention after 100 cycles at 0.2C. Even with high sulfur loading (3.1 mg cm⁻²) and a low electrolyte/sulfur ratio (5 μL mg⁻¹), the batteries achieved a discharge specific capacity of 425.8 mAh g⁻¹ after 100 cycles at 0.2C, showcasing exceptional cycling stability. These findings highlight FeBr₂DME’s potential as a dual-function electrolyte additive, offering a viable solution to key challenges in Li-S batteries and paving the way for their commercial viability.