Enhancing the Surface Stability of Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ in Organic/Inorganic Composite Solid-State Electrolytes via Reduced Graphene Oxide

Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3, as one of the superionic conductors, has been frequently used as a solid electrolyte alone or as a functional additivity in the organic/inorganic composite solid-state electrolytes. However, the surface Ti 4+ ions of Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 can be electrochemically reduced by lithium foil, which largely hinders the practical application of Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 . In the work, Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 nanoparticles are first coated with reduced graphene oxide sheets, and then blended in poly(ethylene oxide) together with lithium bis((trifluoromethyl)sulfonyl)azanide in the presence of acetonitrile. The suspension is cast within the electrospun polyacrylonitrile nanofiber film by solution casting getting a series of organic/inorganic composite solid electrolytes. The as-coated reduced graphene oxide sheets can serve as a protective barrier to prevent the adverse interface reaction of Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 with lithium, suppressing mainly the Ti 4+ reduction by lithium, and boosting interface stability. The composite solid electrolytes exhibit a satisfactory ionic conductivity of 6.02 × 10 –5 S cm –1 at 25 °C, and a stable lithium stripping/plating over 1000 h. All solid-state batteries assembled with the as-prepared electrolytes show remarkable rate performance and cycling stability at 25 °C without external pressure.