Thin films of LiCoO2 prepared by the electron cyclotron resonance (ECR) sputtering method are investigated under various deposition conditions. Well-crystallized LiCoO2 films were obtained without a post-annealing process in a high microwave and RF power range with a low O2 to Ar ratio. All-solid-state thin-film lithium batteries using the LiCoO2 films (thickness: 6.2μm) provided a discharge capacity of about 250μAhcm−2 with good cyclability.