High temperature electrochemical cell structures, and methods for making

A sodium metal halide thermal battery, comprising a plurality of electrochemical cells that are in electrical communication with each other, wherein each electrochemical cell comprises:

• (a) an anodic chamber for containing an anodic material;
• and a cathodic chamber for containing a cathodic material, separated from each other by an electrolyte separator tube, all contained within a case for the cell;
• (b) an electrically insulating ceramic collar positioned at an opening of the cathodic chamber, and defining an aperture in communication with the opening;
• (c) a cathode current collector assembly disposed within the cathode chamber;
• (d) at least one ring comprising a metal or metal alloy that has a coefficient of thermal expansion (CTE) in the range of about 3 to about 7.5 ppm/° C. over a temperature range of about 30° C. to about 450° C., contacting at least a portion of a metallic component within the cell, and an adjacent portion of the ceramic collar;
• and
• (e) a braze alloy composition attaching and hermetically sealing the ring to the metallic component and the collar, wherein the braze alloy composition comprises
• (I) nickel;
• an active metal element;
• and at least one of (i) germanium;
• (ii) niobium and chromium;
• and (iii) silicon and boron;
• or
• (II) copper, nickel, and an active metal element.