INVESTIGATION OF ORDERED POROUS MATERIALS FOR LITHIUM AND MAGNESIUM IONS ELECTROCHEMICAL ENERGY STORAGE
Henry, Hakeem Kimani
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As portable electronics and electric vehicles become a more integral part of everyday life, rechargeable electrical energy storage devices (batteries) capable of providing greater energy and power densities will soon be necessary. Lithium-ion batteries (LIBs) have dominated this area of rechargeable energy storage devices since their commercialization in 1990. However, as electronic devices continue to advance, battery technology will have to go beyond conventional lithium-ion battery systems to power these devices. Among the many possible alternatives to lithium, magnesium is a promising candidate. In comparison to lithium, magnesium is more abundant, lower in cost, and more environmentally friendly. Magnesium batteries can also utilize a Mg metal anode which offers a high volumetric capacity and low standard reduction potential. Despite the potential benefits, Mg batteries suffer from several drawbacks. The three main issuesplaguing Mg batteries are (1) a lack of practical cathodes due to slow insertion kinetics of the divalent Mg2+ ion, (2) incompatibility between Mg electrolytes and high voltage cathodes, (3) and parasitic and passivating reactions occurring at the Mg metal anode surface. The work of this dissertation aims to address the Mg2+ insertion issue by developing modified cathodes with enhanced electrochemical performance. In the first study, the effect of structure and hydration on Mg2+ intercalation into amorphous and crystalline V2O5 films was systematically investigated by electrochemical methods. It was determined that the high water content of electrodeposited V2O5 films was the primary factor impacting Mg2+ intercalation, while the crystal structure played a secondary role. In the second study, an ordered mesoporous carbon (OMC) structure was grown on the surface of carbon nanotubes (CNT) to achieve a novel electrode architecture. The hybrid carbon structure allowed for fast ion diffusion and high electronic conductivity. The porous structure also served as an excellent host for the deposition of high-capacity cathode materials for an all-in-one electrode design. In the final study, the OMC synthesis method was paired with electrodeposited V2O5 protocol to further investigate the OMC electrochemical performance. Overall, the work of this dissertation contributes to the development and commercialization of rechargeable Mg batteries by elucidating a portion of this complex chemistry.