New polyurethane acrylate (PUA)-based nanoceramic-polymer electrolytes in a high ceramic filler content were examined in all-solid-state lithium-polymer cells (Li/PUA-SiO2/Li0.33MnO2) and at 60 degrees C. The composite electrolyte containing more than 20 wt % hydrophilic nano-SiO2 enhanced its mechanical strength 600% compared to the ceramic-free electrolyte. The additions of nano-SiO2 powders in a high concentration protected the electrode surfaces, improved greatly the interfacial stability between composite cathode and the electrolyte, and gave rise to a further reversible lithium stripping-deposition process. The cells showed good rate capacity and excellent cyclability. The discharge capacity kept 65% of initial capacity after 300 cycles with a coulombic efficiency approaching 100%. Capacity fading upon cycling was believed to be due to the increase of cell resistance during charge-discharge cycling. The cell self-charge loss at 60 degrees C was extremely low about 0.05% per day. (c) 2005 The Electrochemical Society.