Nanostructured materials prepared by atomic layer deposition for catalysis and lithium-ion battery applications

Atomic/molecular layer deposition (ALD/MLD) has emerged as an important technique for depositing thin films in both scientific research and industrial applications. In this dissertation, ALD/MLD was used to create novel nanostructures for two different applications, catalysis and lithium-ion batteries. MLD was used to prepare ultra-thin dense hybrid organic/inorganic polymer films. Oxidizing the hybrid films removed the organic components and produced the desired nanoporous films. Both porous alumina and titania films can be prepared by such a way. A novel nanostructured catalyst (Pt/SiO2) with an ultra-thin porous alumina shell obtained from the thermal decomposition of an aluminium alkoxide film deposited by MLD for size-selective reactions was developed. The molecular sieving capability of the porous metal oxide films was verified by examining the liquid-phase hydrogenation of n-hexene versus cis-cyclooctene. For lithium-ion battery cathodes, two different approaches are presented. Firstly, ultrathin and highly-conformal conductive CeO2 films were coated on LiMn2O4 particles using ALD process. The initial capacity of the 3 nm CeO2-coated sample showed 24% increment compared to the capacity of the uncoated one, and 96% and 95% of the initial capacity was retained after 1,000 cycles with 1C rate at room temperature (RT) and 55 ⁰C, respectively. The study of ionic and electronic conductivities of the coated and uncoated materials helped explain the improved performance of CeO2 coated materials. Secondly, iron oxide films were deposited using ALD on LiMn1.5Ni0.5O4 particles for the synergetic effect of performance enhancing by iron doping and conformal iron oxide film coating. With an optimal film thickness of ~0.6 nm, the initial capacity improved by 25% at RT and by ~26% at 55 ⁰C at 1C cycling rate. The synergy of doping of LiMn1.5Ni0.5O4 with Fe near surface combined with the conductive and protective nature of the optimal iron oxide film led to high capacity retention (~93% at RT and ~91% at 55 ⁰C) even after 1,000 cycles at 1C cycling rate --Abstract, page iv