UC San Diego

Li-rich oxides have generated widespread interest for their use as next generation high energy density Li-ion battery cathodes. Among Li-rich candidates, cation disordered phases are novel lithium intercalation compounds that warrant further fundamental characterization. Here, we compare Li1.3Nb0.3Mn0.4O2 and Li1.3Nb0.3Fe0.4O2 system to explore differences in charge compensation and electrochemical performance. Using Operando XANES/EXAFS measurements examine how the Mn/Fe/Nb local environments and oxidation states change and their effect on electrochemistry. Li1.3Nb0.3Mn0.4O2 displays capacities beyond the traditional transition metal redox (Mn3+/4+), which is considered accessible through oxygen redox. Li1.3Nb0.3Fe0.4O2 exhibits charge capacities at similar potentials to that of anionic redox but our investigations suggest the charge compensation mechanism displays more Fe3+/4+ redox in origin. By using a suite of characterization techniques, we explore the capacity contributions of cation and anionic components in these systems.