Poly(methyl methacrylate)-Based Gel Polymer Electrolyte for High-Performance Solid State Li–O₂ Battery with Enhanced Cycling Stability

The lithium oxygen (Li–O2) battery is considered as one of the promising next-generation energy storage devices due to its high theoretic specific energy. However, some critical problems such as solvent evaporation, lithium dendrites, liquid electrolyte leakage, and liquid electrolyte decomposition under high voltage seriously hinder its application. To address these issues, a well-designed poly(methyl methacrylate) (PMMA) and SiO2 composite gel polymer electrolyte (PMMA/SiO2/PP@GPE) is prepared by a phase inversion method followed by a gelation process. Benefitting from this unique architecture, the PMMA/SiO2/PP@GPE exhibits high liquid electrolyte uptake ability and adequate gelation degree, which result in well-enhanced electrochemical performances and interfacial stability. Compared with traditional polypropylene (PP) separator and liquid electrolyte systems, the electrochemical window of a solid state Li–O2 battery was widened to 4.9 V, and the lithium-ion transference number increased to 0.54. A lithium symmetrical battery displays an enhanced cycling stability due to improved interface compatibility. As a consequence, the solid state Li–O2 battery employing PMMA/SiO2/PP@GPE delivers the high first charge–discharge capacity of 6.8 mAh cm–2 and a stable cyclic performance of 116 cycles with 0.5 mAh cm–2.