Enthalpy-Entropy Molecular Design of Gel Polymer Electrolytes for Regulating Solvation Chemistry in Lithium-Sulfur...

Gel polymer electrolytes (GPEs) show great promise in lithium-sulfur (Li-S) batteries, but their practical application is limited by the high enthalpy of Li⁺ desolvation and the slow conversion rate of polysulfides, which disrupt the redox pathway and accelerate capacity decay. Here, we propose an enthalpy-entropy molecular design strategy to integrate these processes into a unified electrolyte system. By regulating the solvation structures of Li⁺ and polysulfides, we can both restrict available reaction pathways and control the coordination environment of polysulfides within the solvation structure. By modulating the solvation structure, we reduce the desolvation enthalpy of both Li⁺ and polysulfides, thereby promoting uniform nucleation of Li₂S. This pioneering design enables the resulting GPE with an ionic conductivity of up to 1.21 mS cm^-1 at 22°C and a Li⁺ transference number of 0.82, the resulting Li||Li symmetric cell can cycle stably for over 2250 h. Consequently, the cell exhibits an ultralow capacity fading rate of 0.043% per cycle over 1000 cycles at 2C and remained functional when assembled into a 1.8 Ah pouch-cell (403.7 Wh kg^-1). This study highlights the crucial role of enthalpy-entropy molecular design strategies in GPEs.