omegaLi/V2O5 spirally wound polymer (POE) batteries functioning at 90 degreesC presented an important capacity fading ca. 20th cycle. This, behavior could arise from the cathode material itself, including its in situ formation during the first reduction step from alphaLi/V2O5, or from a technical problem linked either to the composite cathode or one of the other cell components. In this paper, after rejection of the two first hypothesis. we clearly demonstrate the negative role of the nickel foil used as cathodic collector.