Dual Li-ion migration channels in an ester-rich copolymer/ionic liquid quasi-solid-state electrolyte for high-performance Li–S batteries

Solid-state polymer electrolytes are expected to fundamentally solve the instability and safety problems of liquid electrolytes for lithium–sulfur batteries. Herein, ionic liquids were introduced on the basis of constructing ester-rich copolymers, and dual Li-ion migration channels were built in an ester-rich copolymer/ionic liquid quasi-solid-state electrolyte (SPE-IL). “Association–disassociation” with the carbonyl groups and rapid ion exchange with the ionic liquids are the two migration modes that synergistically increase the room temperature ionic conductivity of the SPE-IL. In addition, the abundant ester groups provide strong chemisorption on lithium polysulfides and successfully inhibit the sulfur shuttle. More importantly, ionic liquids realize the “soft contact” between the electrode and the electrolyte, which is conducive to the construction of stable interfaces. Together with the GPa-level high modulus brought by vinyl carbonate, the formation of lithium dendrites is inhibited. As a result, the assembled lithium–sulfur battery displayed a high initial discharge capacity of 1106 mA h g−1, good cycling stability (80.2% capacity retention after 300 cycles at 0.1 C) and superior rate performance.