Multimodal analysis of structural and electrochemical properties of lithium-rich layered oxidesAbbasi, Rabail Badar (Avtor) Chernyshova, Elena (Mentor) Li-ion batteriesLi-rich layered oxidesoxygen vacanciesstacking faultssol-gel synthesischelating agentsadvanced structural characterizationLithium-rich layered oxides (LRLOs) are promising cathode materials for next-generation high-energy lithium-ion batteries (LIBs) as they can access anionic redox and deliver capacities exceeding those of conventional layered oxides. Their commercial implementation, however, is limited by voltage fade and capacity loss arising from progressive layered-to-spinel/rocksalt phase transformation during cycling. These structural changes are triggered by oxygen redox activity and associated transition-metal (TM) migration, whose reversibility is strongly influenced by crystallographic defects intrinsic to LRLOs. Rational control of defect chemistry during synthesis is therefore essential for stabilizing oxygen redox while suppressing irreversible phase evolution. This thesis explores the influence of synthesis-driven defect chemistry on oxygen redox and cation migration in LRLOs during cycling, and further evaluates targeted dopant substitution as a strategy to enhance structural stability. Using Li$_{1.2}$Mn$_{0.54}$Ni$_{0.13}$Co$_{0.13}$O$_2$ as a model system, complementary structural, spectroscopic, and electrochemical techniques are combined to correlate precursor chemistry, stacking disorder, oxygen-vacancy incorporation, dopant site occupancy, and redox mechanisms with phase stability. The research presented in this thesis is divided into two studies. The first study investigates LRLOs synthesized by sol–gel routes employing chelating agents of contrasting strength. All samples adopt a faulted R3m layered framework on average, yet local structural variations emerge from precursor chemistry: the weaker chelating agent promotes oxygen-vacancy incorporation at high temperature, which later migrate into the bulk during cycling, expand the lattice, suppresses TM migration, and lead to improved electrochemical performance. The second study investigates Zn substitution as a means of regulating oxygen redox and cation migration. Moderate Zn incorporation yields the most favorable balance between capacity retention and structural durability. Electrochemical analysis reveals that dopant effectiveness depends critically on lattice site occupancy, with dual-site occupancy, Li-site and TM-site, stabilizing the oxygen sublattice while preserving Li-ion transport pathways. This work establishes a synthesis–defect–performance framework for LRLOs, demonstrating that high-energy-density cathodes can be achieved through rational defect engineering that enables oxygen redox regulation and cation migration. The mechanistic insights and design principles developed in this thesis provide guidance for the future development of LRLOs for high-energy LIBs. 20262026-06-09 11:10:02Doktorsko delo/naloga183235VisID: 25817COBISS_ID: 286853891sl