a film of linear organosilsesquioxane polymer , or &# 34 ; ladder &# 34 ; organosiloxane , coated upon the surface of a limn 2 o 4 secondary battery electrode 19 and cured to a glassy layer is subjected to plasma oxidation to remove pendant organic groups comprising the coated polymer . the resulting ultrathin silica separator layer 17 is replete with minute pores which take up and retain by capillarity a typical liclo 4 electrolyte solution . a counter - electrode 15 placed in intimate contact with the silica electrolyte element completes a secondary battery structure 10 in which lithium ions readily migrate through the electrolyte during repeated discharge / charge cycles without loss of element integrity or efficacy .