Li-rich layered oxides LRLO composite cathode materials were studied with the goal of improving energy density with three main thrusts computational modeling of cation substitution for stabilize oxygen, 2 exploration of coatings for improved capacity retention, and 3 mesostructural modification to improve cycling performance and rate capability. Computational modelling using density functional theory predicts 4d transition metals Mo and Ru to improve oxygen stability experimental doping results were commensurate with calculation results, with Mo showed improved capacity retention and reduced oxygen evolution. LLTO coating was demonstrated to improve capacity retention by preventing surface reconstruction, as evident by high resolution STEM. Mesostructure modification was explored through varied processing method, showing a high degree of particle tenability through precise processing control such altered nanostructuring of secondary particles was shown to have a notable influence on particle cyclability. Great progress was made to determine causes of structural instability and to mitigate such instabilities in LRLO. Doping of a model layered Li-rich nickel manganese material was investigated via DFT calculations to explore stabilization of oxygen ions in the material, and guided by results, experimental doping and characterization was performed. The theoretical model was validated, as compared to previously published work on the evolution of oxygen vacancies. Of all dopants simulated, Mo and Ru were shown to increase the oxygen vacancy formation energy, EFOv, elucidating the potential to reduce oxygen evolution during cycling and improving overall capacity retention. This improved EFOv was attributed to a delocalization of the Mo electrons to the surrounding anions, serving to stabilize the oxygen ions by creating a larger barrier for charge transfer.