Highly Conductive and Thermostable Grafted Polyrotaxane/Ceramic Hybrid Polymer Electrolyte for Solid-State Lithium-Metal Batteries

Although polymer electrolytes have been regarded as potential separator materials for high energy density solid-state lithium-based batteries, their applications were significantly restricted by the low ionic conductivity, poor mechanical strength, and thermostability. Herein, a highly conductive and thermostable hybrid polymer electrolyte was developed by combining poly(vinylidene fluoride-co-hexafluoropropylene)-grafted polyrotaxane and nano-Al2O3 particles. In this unique hybrid, not only the Lewis acid-type Al2O3 and the fluorine groups of polyrotaxane branches exhibited strong integration with ionic species to accelerate the dissociation of lithium salt, improving the Li ionic conductivity, but also the abundant hydroxy functional groups on the surface of Al2O3 hydrogen-bonded with fluorine-containing branches, enhancing the mechanical strength. More importantly, the hybrid electrolyte exhibited superior thermal stability due to the heat resistance of the ceramic filler and the unique bead string structure of polyrotaxane. Consequently, a polymer electrolyte with a comprehensively improved performance was obtained, including high ionic conductivity and Li+ transfer number and superior tensile strength and thermostability. The hybrid electrolyte provided a dendrite-free lithium anode with a long life up to 1800 h and stable solid-state lithium-metal batteries at a high temperature of 80 °C.