A lithium polymer battery with high-capacity (> 180 mAh g(-1)) LiCoO2 was prepared by the fine-powder coating of highly lithium-ion-conductive ceramic electrolyte [Li1.5Al0.5Ge1.5(PO4)(3)] on LiCoO2 powder. The obtained cell (operated at 333 K) exhibited a good reversibility up to 4.4 V and a good sustainability of 105 mAh g(-)1 at the 200th cycle. The oxidation of the polymer electrolyte was determined by alternating current (ac) impedance analysis, and it was observed that a suitable ceramic electrolyte coating is an effective oxidation barrier at the polymer/cathode interface. (c) 2005 The Electrochemical Society.