Li_6.4La₃Zr_1.4Ta_0.6O₁₂/Star-Shaped Hybrid Polyhedral Oligomeric Cage Silsesquioxane Polymer Composite Electrolytes for All-Solid-State Lithium Metal Batteries

The low ionic conductivity and mechanical strength are important factors impeding the application of solid polymer electrolytes. Herein, we design synthesize an organic/inorganic hybrid star-shaped polymer of octa(poly(methyl methacrylate)-poly(poly(ethylene glycol) methyl ether methacrylate) cage oligomeric silsesquioxanes (POSS-(PMMA-PPEGMEM)8) by one-step free atom transfer radical polymerization (ATRP), and compound with Li6.4La3Zr1.4Ta0.6O12 (LLZTO) to prepare a composite polymer electrolyte membrane (LP-CPEM). The star-shaped structure of the POSS-(PMMA-PPEGMEM)8 induced by octachloropropyl polyhedral cage oligomeric silsesquioxane (OCP-POSS) is beneficial to reduce the crystallinity of polymer and increase the movement of the polymer chain to form a continuous interconnected ion migration channel. The LLZTO fillers in the LP-CPEM could simultaneously hinder the orderly arrangement of polymer chains and provide other ion transport paths to increase the ion conductivity of LP-CPEM. The LP-CPEM with 7.5 wt % LLZTO has higher ionic conductivity of 3.8 × 10-4 S cm-1 at 30 °C and high mechanical strength (5.2 MPa). Additionally, Li/Li symmetric cells demonstrate stable constant current charging/discharging during 1000 h at 0.1 mA cm-2, and the all-solid-state batteries fabricated by the LP-CPEM exhibit good cyclic stability. It is promising for the development of next-generation high-safety all-solid-state lithium metal batteries.