Abstract: A miniature electrochemical cell of a secondary chemistry having a total volume that is less than 0.5 cc is described. Before the present invention, miniature secondary electrochemical cells have been known to experience undesirable open circuit voltage discharge during their initial 21-day aging period. It is believed that electrolyte permeating through the cathode active material and an intermediate carbonaceous coating contacting the titanium base plate of the casing is the source of the undesirable discharge. To ameliorate this, aluminum is contacted to the inner surface of the base plate inside the casing. While aluminum is resistant to the corrosion reaction that is believed to be the mechanism for degraded open circuit voltage in miniature secondary electrochemical cells containing lithium, it is not biocompatible. This means that titanium is still a preferred material for the casing parts including the base plate that might be exposed to body fluids, and the like.

Abstract: A miniature electrochemical cell of a primary or secondary chemistry with a total volume that is less than 0.5 cc is described. The cell casing comprises an annular sidewall connected to a base plate opposite an upper lid. A sealing glass forms a hermetic glass-to-ceramic seal with a dielectric material contacting a lower portion of the annular sidewall and a glass-to-metal seal with the base plate. Since the glass seals against three surfaces of the annular sidewall, which are the inner and outer sidewall surfaces adjacent to the lower edge, the glass seal is robust enough to withstand the heat generated when the lid is welded to the upper edge of the annular sidewall. The lid has a sealed electrolyte fill port that is axially aligned with an annulus residing between the inner surface of the annular sidewall and the electrode assembly.