Poly(acrylonitrile)-based (PAN) electrolytes were prepared by dissolving PAN (0-17 wt.%) in a propylene carbonate-ethylene carbonate mixed solvent (50:50 wt.%) containing LiClO4 (1 M) at 120-140 degrees C, followed by cooling at -15 degrees C for 16 h. The lithium \ electrolyte interface was observed after electro-reductive deposition of lithium (1 mA cm(-2), 1 h). Although lithium dendrites are formed in liquid electrolytes containing 0-3 wt.% PAN, dendrite formation was suppressed in gel electrolytes containing 5-17 wt.% PAN. Considering this effect together with the bulk resistance and liquefaction temperature of the electrolyte and resistance at the lithium \ electrolyte interface, the optimal PAN concentration was 5-10 wt.%.