Ultrathin polymer-in-ceramic and ceramic-in-polymer bilayer composite solid electrolyte membrane for high-voltage lithium metal batteries

Solid-state electrolyte for solid-state batteries is one of the current hotspots in the research field of high-safety and high energy density lithium metal batteries. This work reports a polymer-in-ceramic and ceramic-in-polymer bilayer ultrathin (∼11 μm) composite solid electrolyte (CSE) membrane by exploiting a spontaneous precipitation of Li7La3Zr2O12 in a polymer-lithium salt matrix. The polymer-in-ceramic layer is toward a high-voltage cathode, which can effectively inhibit oxidative decomposition of electrolytes. The ceramic-in-polymer layer toward the anode can provide good flexibility. Experimental results show that the CSE bilayer membrane has not only high ionic conductivity but also satisfactory Li+ transference number. It also exhibits excellent thermal and mechanical properties. High-voltage Li||LiCoO2 (4.5 V) cell employing this CSE membrane exhibits excellent cycling stability (151.18 mAh g−1 at 1 C after 100 cycles), and superior rate performance (124.31 mAh g−1 10 C). This work guides the improvement of both solid state electrolyte membrane and high-voltage solid-state lithium metal batteries.