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Abstract
Li-Sulfur (Li-S) batteries stand promising as the next-generation energy storage technology but are hindered by sluggish sulfur redox reaction kinetics and sulfur shuttling effect. Many studies tried to address these issues by adopting polycaprolactone (PCL) based gel polymer electrolytes (GPEs), but often overlooked solvent properties, including dielectric constant (ϵ), donor and acceptor numbers (DN and AN), impact performance and prevent the full implementation of GPE-based Li-S batteries. This work compares three distinct electrolytes paired with PCL, namely, dimethoxyethane (DME), dimethyl sulfoxide (DMSO), and tetraethylene glycol dimethyl ether (TEGDME), due to their varied solvent properties, to evaluate their effects on the physical properties of the GPE, Li⁺ transport and solvation, and polysulfide's confinement. The DME-based GPE, with an intermediate DN, exhibited the lowest crystallinity (2.31%), highest ionic conductivity (7.49 mS/cm), and high Li⁺ transference number (0.77), achieving a specific capacity of 795 mAh/g sulfur and an average coulombic efficiency of 97.5% after 120 cycles at C/5, outperforming its competitors. Moreover, operando Raman and UV-Vis spectroscopy confirmed that PCL effectively confines long-chain polysulfides within its network, mitigating the shuttle effect and facilitating reversible polysulfide conversion. These findings highlight that GPEs with moderate DN values and balanced ϵ enhance stability, extend cycle life, and improve rate performance for Li-S batteries, providing unique insights for designing advanced electrolyte systems for practical applications.
Supplementary materials
Title
Comprehensive Study on Solvent Dynamics in Gel Polymer Electrolytes for Lithium-Sulfur Battery
Description
Materials details and fabrication procedures, thermal gravimetric and differential scanning calorimetry experiments procedure, illustration of co-axial NMR tube, specific cyclic voltammetry calculations steps, additional SEM images and photographs of GPEs, additional NMR spectra, CV plots of different GPEs, additional linear fitting of Randles-Sevcik plots, rate capability performance of different liquid electrolyte containing GPEs, additional charge/discharge profile of different liquid electrolyte containing GPEs, cycling performance of different liquid electrolytes, additional DFT and HUMO-LUMO plot between solvent and Li2S4 and Li2S6, EIS spectra of different liquid electrolyte containing GPEs as a function of DoD or SoC, operando Raman of different liquid electrolyte containing GPEs as a function of DoD or SoC, additional UV-Vis spectra of pouch cell in S8 catholyte.
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