Amorphous V2O5(-P2O5) is recognized to be a good cathode active material in lithium secondary cells with nonaqueous liquid electrolyte, because of its long cycling stability (over 3000 cycles) and high specific capacity (150 m Ah/g, at 2 to 3.5 V and 0.5 mA/cm2). To study the cathode characteristic of amorphous V2O5(-P2O5) at elevated temperature, secondary solid-state cells with lithium anodes, a polymer electrolyte (PEO)8CF3SO3, and amorphous V2O5(-P2O5) composite cathodes were prepared. The electrochemical behavior of these cells was determined at 100-degrees-C. Amorphous V2O5(-P2O5) functioned as the cathode active material at 100-degrees-C. The Li/polymer electrolyte/amorphous V2O5(-P2O5) cell exhibited a high specific capacity for the cathode (over 200 mAh/g) to over 80 cycles at 100-degrees-C, under the best condition of a voltage range of 3.5 to 1.8 V, a discharge current of 100 muA/cm2, and a charge current of 50 muA/cm2. These results indicate that amorphous V2O5(-P2O5) is a good candidate for the cathode in a solid-state cell at elevated temperature.