Optimization of Fluorinated Ether-Based Quasi-Solid Electrolyte Systems for Lithium-Sulfur Batteries

Although quasi-solid-state lithium-sulfur (Li-S) batteries show great promise for safe and high-energy storage systems, optimizing electrolyte formulations remains challenging due to the complex interplay of factors such as ion transport, stability, and sulfur utilization. In this study, seven quasi-solid electrolyte formulations were systematically investigated based on a ternary electrolyte component system of 1,3-dioxolane (DOL), 1H,1H,5H-octafluoropentyl 1,1,2,2-tetrafluoroethyl ether (OTE), and 1,2-dimethoxyethane (DME). The seven electrolyte formulations were designed based on a modified mixture design adapted from the design of experiments (DoE) principles. A Gaussian process regression (GPR) model was then used to statistically map the relationship between electrolyte composition and performance responses. Here, GPR is used as a data-driven approximation to capture composition-performance trends and guide electrolyte optimization within the ternary design space. The electrolytes were formed via in situ polymerization to ensure mechanical stability and maintain favorable interfacial contact with the electrodes. The model, trained on experimental data, identified an optimized composition (DOL:OTE:DME = 0.273:0.505:0.222) with improved predicted performance compared to the initial set. The optimized electrolyte delivered a high initial discharge capacity of 861 mAh g^-1 at 0.3 C with only 9.2% capacity loss over 100 cycles showing markedly improved cycling stability compared to the baseline electrolyte. The statistical modeling provides a powerful framework for electrolyte development and offers valuable insights into the composition-performance relationships in multicomponent electrolyte systems.