Bilayer NASICON/Polymer Hybrid Electrolyte for Stable Solid-State Li–O2 Batteries

The practical application of lithium–oxygen (Li–O2) batteries is limited by the formation of lithium dendrites and the use of flammable and unstable organic liquid electrolytes, which would cause safety issues and poor cycling stability. Herein, we present a bilayer organic/inorganic hybrid solid-state electrolyte to improve the safety and enhance the electrochemical performance of Li–O2 batteries. Si-doped NASICON-type electrolyte Li1.511Al0.5Ge1.5Si0.01P2.99O12 (LAGP-Si) serves as an inorganic rigid backbone to guarantee high ionic conductivity and provide a barrier between active oxygen and lithium anode. Poly(ethylene glycol) methyl ether methacrylate (PEGMEM) is chosen as a polymer buffer layer due to its compatibility with lithium. Benefiting from the synergistic effect between LAGP-Si and PEGMEM, the obtained hybrid electrolyte exhibits high ionic conductivity and good stability against lithium anode. Consequently, the polarization of the Li symmetric cell is dramatically reduced by replacing pure LAGP-Si with a bilayer hybrid electrolyte. The solid-state Li–O2 batteries employing a PEGMEM@LAGP-Si electrolyte deliver a greater initial discharge–charge capacity of 7.3 mAh cm–2 and enhanced cyclic performance for 39 cycles with a restricted capacity of 0.4 mAh cm–2. The present work delivers a promising category of hybrid solid electrolytes for high-performance solid-state Li–O2 batteries.