Lithium-Manganese-Oxide Thin-Film Cathodes Prepared by Plasma-Enhanced Chemical Vapor Deposition

Lithium-manganese-oxide thin-film electrodes have been fabricated using the plasma-enhanced chemical vapor deposition technique. Process parameters such as flow rates of the reactants, deposition temperature, and RF power have been systematically varied to optimize the charge and discharge properties. The thin films are amorphous as found by X-ray diffraction spectrometry and can be cycled reversibly in the range from 4.5 to 3 V or 4.5 to 2.5 V with maximum capacities of 30 and 39 μAh/cm² μm, respectively. The capacity fade of the films is ca. 0.04% per cycle over more than 700 cycles when tested in liquid electrolytes. Films which are optimized for cycling between 4.5 and 3 V demonstrate a near-perfect balance between the charge and discharge capacities during the initial cycle and also show very small capacity fade in the subsequent cycles. Our results indicate that these lithium manganese oxide thin films are good candidates for use as cathodes in thin-film lithium-ion batteries.