This present invention reports a method for drastically improving sodium (Na) wettability on the surface of solid-state electrolytes, such as beta"-alumina solid-state electrolyte (BASE), to augment the performance of Na batteries at lower temperatures. This method describes modify the BASE surface by adding a thin composite layer consisting of carbon black and metal oxide/metal submicron particles. The overall surface treatment process is simple and easy for scaling up. Initially, the BASE surface is simply brushed with thick aqueous ink made of carbon black and metal compound precursors, and then followed by a heat treatment under an inert or a reducing environment.