A method for joining a ceramic component to a metallic component is described. At least one initial layer of an active metal is applied to one of the joining surfaces, by a cold spray technique. At least one second layer of a nickel-based braze composition is then applied over the initial layer by cold-spraying. The braze composition and components are then heated, so as to form an active braze joint between them. A method of sealing an open region of a sodium metal halide-based battery is also disclosed, using the brazing technique described herein to form braze joints that seal various components in the battery cells, such as metallic rings and ceramic collar structures.