Interplay of crystal and electronic structure in battery and strongly correlated electron materials

Alkali and alkaline earth metal batteries, especially lithium-ion batteries, have had increased interest in the last decade. They offer higher energy density storage and quick discharge rates compared to other battery technologies. They power most of our portable electronics including phones and laptops. They have also been recently used more in consumer electric vehicles. Some of the other suggested applications include short term grid relief and storage for renewable energies from solar and wind sources. However, many lithium-ion batteries have poor thermal stability and are made from less abundant materials. Other derivatives of lithium-ion batteries based on magnesium and sodium have gained interest due to the potential increase in capacitance of bivalent magnesium and increased abundance of sodium. Even though sodium and magnesium-ion batteries could address some of the issues of lithium-ion batteries, they have their own issues to be considered.;Many of the lithium-ion cathode materials are transition metal oxides or transition metal polyoxoanions. The electronic structure of these materials typically has strongly correlated electron metal centers. The prospective compound of ordered SrFeO2F has a similar two-dimension transition metal oxide layer to that of many copper oxyfluoride high temperature superconductors. The synthesis of SrFeO2F for this study was compared to the synthetic method of Berry et al. in 2005 and 2008. While neither method produced the ordered SrFeO2F, different magnetic data from each method suggests different localized order around the metal center. Density functional theory studies have predicted different bonding interactions between iron-oxygen bonds and iron-fluorine bonds in terms of both length and spin density. The studies also have suggested that a disordered SrFeO2F structure would be the more thermodynamic stable structure. Future studies could involve looking at magnesium derivatives for potentially new battery materials as the strontium cavities and the oxygen fluorine disorder could introduce large ion conduction pathways.;There are many LiFeO2 polymorphs that have been explored as potential lithium ion batteries. The one polymorph that has been the least studied has been that of the T-LiFeO2 structure. It was notable because it is synthesized from the beta-NaFeO2 structure through ion exchange. The large cavities of beta-NaFeO2 were hypothesized to allow for the intercalation of extra lithium for a multi-redox battery material, T-Li1+xFeO2. While the intercalation of extra lithium has been achieved, only the electrochemical cycling of iron II/III redox couple has been possible through cobalt doping. Room temperature ionic liquids were explored as alternative electrolytes to resist the high-voltage iron III/IV redox, but it proved ineffective. The electronic density of states for the T-Li0.5