Acceleration of selective lithium ion transport of PAES-g-2PEG self-assembled flexible solid-state electrolytes for lithium secondary batteries

The solid-state lithium secondary battery (LiB) is a promising alternative to resolve the drawbacks of conventional LiB, but it still suffers from low ionic conductivity and mechanical instability. Accordingly, the flexible self-assembled solid electrolytes (SEMs) based on poly(arylene ether sulfone) (PAES) grafted with double poly(ethylene glycol) (PEG) (PAES-g-2PEG) is prepared to maximize the ion conductivity by creation of large PEG conducting domains without thermal and mechanical failure via reinforcement of PAES matrix. The addition of ionic liquid (IL) along with ethylene carbonate (EC) results in a significant improvement in a selective lithium ion conductivity because of the improved molecular mobility of PEG segments and formation of [Li⁺(EC)_x, (x = 1–5)] complexes for feasible single-ion transport. Consequently, the PAES-g-2PEG membranes containing IL-EC mixture (7:3, v/v) achieve the ionic conductivity of 1.15 × 10⁻³ S cm⁻¹ and Li-ion transference number of 0.51 at room temperature. The PAES-g-2PEG membranes exhibit excellent mechanical flexibility and thermal stability with the onset degradation temperature of 250 °C. Due to the significant suppression of polysulfide permeation as well as high conductivity, the Li/SEM/S cell assembled with PAES-g-2PEG membranes delivers the discharge capacity of 987 mAh g⁻¹ with 98.6% of coulombic efficiency, retaining 94.7% after 200 cycles at 0.2 C-rate.