Li+ transport properties of sulfolane-based gel polymer electrolyte and effective suppression of lithium polysulfide dissolution in lithium–sulfur batteries

Abstract

Sulfolane (SL)-based gel polymer electrolytes composed of a polyether-based host polymer were investigated for long-lifecycle lithium–sulfur batteries. The proposed electrolytes were expected to cause chemical and physical suppression of Li₂S_n dissolution and diffusion owing to the low Li₂S_n solubility, derived from the highly concentrated SL-based electrolytes, and low Li₂S_n diffusion, derived from the host polymer, respectively. The Li⁺ transport properties, and Li⁺–SL and Li⁺–anion interactions, were analyzed by alternating current impedance measurements and Raman spectroscopy, respectively. The relationships between gel polymer electrolyte composition and Li⁺ coordination structure/Li⁺ transport properties were also investigated. The Li–S cells containing gel polymer electrolytes exhibited a sufficient discharge capacity in the first cycle (approx. 1150 mA h g⁻¹) and stable charge discharge operation for 100 cycles. Application of the proposed electrolytes resulted in high battery performance owing to chemical and physical control of Li₂S_n dissolution and diffusion, and favorable electrolyte/Li metal interface formation.