Thin films of LiCoOx were deposited by r.f. sputtering, from a LiCoO2 target and in an O2/Ar atmosphere. The structural properties were studied by XRD and IR, the morphology by AFM and the electrochemical properties by cyclic voltammetry and galvanostatic charge/discharge techniques in 1 M LiClO4/PC + EC electrolyte. As-grown films were amorphous and presented compact grain morphology. Annealing promotes a melt of the film at 300°C, followed by crystallisation at higher temperatures. The IR and XRD spectrum of films annealed in air showed the same structural reordering above 300°C. The crystalline film has been identified as a mixed LiCoO2 + Li1.47Co3O4 phase. The open circuit potential for both films is 3.45 V. The films can be cycled till ∼4.2 V, but the crystalline structure presents irreversible phase changes, which limits the cyclability of the material. The films are interesting potential materials to be used at cathodes in lithium batteries. © 1999 Elsevier Science S.A. All rights reserved.