Thin film positive electrodes of lithium-rich manganese oxide spinels were prepared by radiofrequency magnetron sputtering from a LiMn2O4 ceramic target at a total pressure close to 2Pa. Post-annealing treatments were necessary to get well-crystallized thin films displaying interesting electrochemical performances. Raman spectrum exhibiting several well-defined bands between 296 and 635cm−1 is typical for the lithium-rich spinel. Based on ICP, RBS and XRD analyses, the thin films composition is close to Li1.2Mn1.8O4. The latter is also in accordance with a Mn3+/Mn4+ ratio close to 0.1 deduced from XPS measurements. Best electrochemical performance (capacity value, cycling life) between 2V and 3.5V vs Li+/Li was obtained for thin films annealed at 600°C. A volumetric capacity of 52μAhcm−2 μm−1 (close to about 90% of the theoretical value) was obtained at the first cycle at a C/100 regime. Contrary to most studies carried out on spinel thin films cycled in the 3V range, no appreciable degradation of the discharge capacity was observed after few tens of cycles at room temperature, highlighting the beneficial effect of substituting 20% of Mn ions by Li ions and the presence of microvoids in thin films that limits the effect of strain generated from volume variation during the Li insertion/deinsertion process.