PEGDA-SN as Both Solid-State Electrolyte and Solid-Solid Interface Material for Li-O₂ Battery

The solid-state batteries have received widespread attention due to their excellent stability and safety, however, the low ionic conductivity and weak interface contact always restricted its performance. In this work, we propose an in situ thermally cross-linked and solidified polymer electrolyte with polyethylene glycol diacrylate (PEGDA) as scaffold in which succinonitrile (SN) and lithium bis-trifluoromethanesulfonimide (LiTFSI) were further introduced to improve the ionic conductivity. Herein, the composite gel was served as not only solid-solid interface material but also solid-state electrolyte. Different with conventional polymer gels, the solvent evaporation could not happen for this composite material during the solidification process, and therefore resulting in good interface contact without inside bubbles. We further present the investigation on transport principle of Li+ in the solid-state electrolyte and the effect of molecular chain on ionic conductivity. The conductivity of the solid-state electrolyte can reach 1.76 × 10−4 S cm−1 at room temperature without any assistance of liquid electrolytes, which is attributed to the short molecular chain of PEGDA. Electrochemical window of the solid-state electrolyte can reach 5.2 V after cross-linking treatment. And the lithium-oxygen battery using this solid-state electrolyte can stably cycle for more than 1100 cycles with a current density of 200 mA g−1 and a limit capacity of 200 mAh g−1 at room temperature.