Atomic layer deposition of spinel lithium manganese oxide by film-body-controlled lithium incorporation for thin-film lithium-ion batteries

Lithium manganese oxide spinels are promising candidate materials for thin-film lithium-ion batteries owing to their high voltage, high specific capacity for storage of electrochemical energy, and minimal structural changes during battery operation. Atomic layer deposition (ALD) offers many benefits for preparing all-solid-state thin-film batteries, including excellent conformity and thickness control of the films. Yet, the number of available lithium-containing electrode materials obtained by ALD is limited. In this article, we demonstrate the ALD of lithium manganese oxide, LixMn2O4, from Mn(thd)3, Li(thd), and ozone. Films were polycrystalline in their as-deposited state and contained less than 0.5 at. % impurities. The chemical reactions between the lithium precursor and the film were found not to be purely surface-limited but to include a bulk component as well, contrary to what is usually found for ALD processes. In addition, we show a process for using Li(thd)/ozone and LiOtBu/water treatments to transform ALD-MnO2 and ALD-V2O5 into LixMn2O4 and LixV2O5, respectively. The formed LixMn2O4 films were characterized electrochemically and found to show high electrochemical capacities and high cycling stabilities.