Abstract
The components of the active thin-film battery are a lithium intercalation cathode, e.g, V2O5、LiCoO2、or LiMn2O4, and a lithium metal separated by lithium phosphorus oxynitride electrolyte. Among the material, batteries with crystalline LiCoO2 cathodes have highest energy and power densities, and the performance of batteries is affected by crystallization of LiCoO2 cathodes. Studies for microstructure of LiCoO2 cathodes play an important role in development of the thin-film battery.LiCoO2 films composed of 0.15μm-to-0.2μm columnar structure was observed by scanning electron microscope and atomic force microscope, and the columnar structure consisting of 30nm-to-50nm grains was observed by transmission electron microscope. In each grain, there were many discontinuous nanocrystals with similar crystalline direction. After annealing at 400℃，the nanocrystals started to grow and combined with another nanocrystals. Decreasing of the quantity of amorphous phase came along with increasing annealing temperature. The 30nm-to-50nm grains was formed in LiCoO2 films without amorphous phase, and the capacity density of LiCoO2 cathodes could reach theoretical values 69μAh/cm2-μm.