Investigations of Iron and Titanium Substitution into Nickel-Rich Cathode Materials by All-Dry Synthesis

Abstract

Li(Ni0.6Mn0.2Co0.2)O2 (NMC622) is a common cathode active material for lithium-ion batteries given its desirable balance of reversible capacity, cycle lifetime, and structural stability. Recently, strategies to maximize its cost efficacy have included employing dry syntheses to minimize manufacturing costs, limiting the use of expensive metals (e.g., Co), and using single-crystal (SC) particle morphologies to enhance long-term electrochemical performance. In this thesis, transition metal substitutions were performed in SC-NMC622 using dry synthesis methods to investigate performance-enhancing and cost-reducing mechanisms. The first work presented investigates the isovalent co-substitution of Fe for Co and Ti for Mn (i.e., Li(Ni0.6Mn0.2-yCo0.2-xFexTiy)O2) in NMC622 and its effect on the crystal and electronic structure, as well as the electrochemical performance. The second work focuses on the synthesis optimization of Mn-free, Ti-substituted Li(Ni0.6Ti0.2Co0.2)O2 (NTC622) initially explored in the first work. Overall, this thesis further expands the ability to perform all-dry compositional investigations in NMC622