This invention relates to interelectrode separators for secondary electrochemical cells. Batteries of such electrochemical cells are contemplated for use as power sources for electric automobiles, storage of electric energy generated during intervals of off-peak power consumption and various other applications. The separator of this development is particularly applicable to electrochemical cells that operate at high temperatures and therefore require the use of high temperature insulators and materials.
A substantial amount of work has been done in the development of these types of electrochemical cells and their electrodes. Examples of such high temperature cells and their various components are disclosed in U.S. Pat. Nos. 3,915,742 to Battles and Mrazek entitled "Interelectrode Separator for Electrochemical Cell", Oct. 28, 1975; 3,947,291 to Yao and Walsh entitled "Electrochemical Cell Assembled in Discharge State", Mar. 30, 1976; U.S. Pat. No. 4,011,374 to Kaun entitled "Porous Carbonaceous Electrode Structure and Method for Secondary Electrochemical Cell", and copending patent application Ser. No. 771,131 to Mathers et al. entitled "Powdered Electrically Insulative Material as a Separator in an Electrochemical Cell," filed Feb. 23, 1977, and identified as U.S. ERDA Case No. S-47,593.
Previous electrochemical cells which operate at high temperatures, e.g. 300.degree.-600.degree. C, have required the use of suitable high temperature materials. Refractory, electrically insulative materials such as boron nitride, and yttrium oxide have been fabricated into cloth, netting, felt, paper, other fabrics, etc., in attempts to provide suitable interelectrode separators. Although these efforts have been successful to some extent, they involve difficult and expensive fabrication, processes and sometimes provide separator components, that are not sufficiently tough and durable. Also, other oxides and nitrides of metals and metaloids such s magnesium oxide, calcium oxide, silicon nitride and aluminum nitride are unavailable or are difficult to provide in a fibrous form that can be fabricated readily into integral separator components.
Therefore, in view of these disadvantages of prior art separator materials, it is an object of the present invention to provide an improved method of preparing an interelectrode separator for an electrochemical cell.
It is a further object to provide a method of preparing an interelectrode separator during electrode preparation.
It is also an object to provide a method of preparing an interelectrode separator for an electrochemical cell that can employ readily available forms of refractory, electrically insulative material.