Tunable structure and chemistry of novel layered metal oxide cathodes for nonaqueous intercalation batteries

Rechargeable batteries are essential electrochemical energy storage technologies for consumer electronics, electrification of transportation, and grid storage. Commercial lithium-ion batteries have been broadly deployed due to their high energy density, high power density, and long cycle life. However, further advances in battery performance require the exploration of novel cathode chemistries with improved specific capacities, structural stability, and structural and compositional tunability. Layered metal oxides are promising cathode candidates because their two-dimensional ion transport channels enable rapid diffusion and efficient redox reactions with transition-metal centers. Bilayered vanadium oxide (BVO, [delta]-V₂O₅·nH₂O) is a particularly attractive cathode material due to its spacious interlayer region, which can be tuned by chemically preintercalating diverse foreign species, including inorganic metal ions and organic molecules. The goal of this dissertation is to demonstrate the highly tunable structure and chemistry of layered metal oxides governed by preintercalants and synthesis precursors to advance charge storage properties in nonaqueous intercalation batteries. This dissertation also provides detailed mechanistic insights by correlating synthesis, structure, chemical composition, and electrochemical properties. To achieve this goal, chemically preintercalated BVOs were used as model layered oxides to investigate two major strategies: tuning interlayer chemistry beyond single inorganic metal-ion preintercalation, and resolving preintercalant- and precursor-governed structural characteristics using advanced characterization and structural modeling techniques. The first objective focuses on the tunability of interlayer chemistry. A novel synthesis route was developed to simultaneously introduce Li⁺ and Mg²⁺ ions into the interlayer regions of BVO, producing dual metal-ion preintercalated [delta]-Li_xMg_yV₂O₅·nH₂O. This work demonstrates that electrochemically active Li⁺ ions and structurally stabilizing Mg²⁺ ions can work synergistically to improve capacity and cycling stability in nonaqueous Li-ion cells. In addition, organic interlayer redox sites were introduced into hybrid BVO electrodes by chemically preintercalating redox-active 2,6-diaminoanthraquinone (DAAQ) molecules. The redox centers in hybrid BVOs were further activated through a dopamine carbonization strategy, leading to notable improvements in specific capacity and rate capability in nonaqueous Li-ion cells. The second objective utilizes two advanced structural characterization techniques, atomic pair distribution function analysis and solid-state nuclear magnetic resonance, to gain structural insights into metal-ion preintercalated BVOs derived from [alpha]-V₂O₅ and V₂CT_x MXene, denoted as AD and MD, respectively. Small-box structural models for metal-ion preintercalated polymorphs were modified based on material characterization results and refined against atomic PDFs obtained from X-ray and neutron total scattering experiments, revealing preintercalant-dependent interlayer metal-H₂O coordination. Magic-angle spinning ²³Na solid-state NMR identified two distinct interlayer Na environments in MD-NVO, including a less hydrated pillaring site that stabilized the layered structure during nonaqueous Na-ion cycling. In contrast, AD-NVO contained a single, more hydrated Na site. Overall, this dissertation provides mechanistic insights into how chemical preintercalation alters the structure and chemistry of layered metal oxides and demonstrates that understanding the interplay among synthesis, structure, and chemistry is critical for designing advanced cathode materials for next-generation nonaqueous batteries.