Phase transformation of nanocrystalline LiCoO2 cathode after high-temperature cycling

The microstructures of nanocrystalline LiCoO2 cathodes in lithium thin-film batteries resulting from high-temperature cycling have been characterized by transmission electron microscopy. Results show the evolution of the LiCoO2 spinel phase from trigonal to cubic. This irreversible secondary phase is found homogeneously distributed in the LiCoO2 thin film and contributes to capacity loss of thin-film batteries during cycling. (c) 2008 The Electrochemical Society.