Ceramic solid electrolytes have high Li-ion conductivity and electrochemical stability but suffer from mechanical instability. Polymers are flexible but have low conductivities and reduced electrochemical stability. It is clear the combination of both materials is attractive for high-performance electrolytes. Currently the main bottleneck is the interfacial resistance between the solid electrolyte and the polymer matrix. We are using orientated LLZO single crystals and chemical modify the surface to improve the interface to lower the interfacial resistance to make composites suitable for future energy-storage devices.