Reversible and Irreversible Redox Processes in Li-Rich Layered Oxides

Reversible and irreversible charge exchange reactions
of Li- and Mn-rich layered oxides (Li1.15Ni0.2Co0.1Mn0.55O2,
LLO) are investigated with bulk and surface-sensitive near-edge Xray
absorption fine structure spectroscopy (NEXAFS) at the Ni
L2,3, Co L2,3, Mn L2,3, and O K edges; mass spectrometry (MS);
and operando synchrotron X-ray powder diffraction (SXPD). The
present work shows the relation between O−O formation in the
bulk and Ni, Co, and Mn reduction/oxidation processes, which in
turn deliver outstanding capacities of Li-rich layered oxides (LLO).
Moreover, the reversibility of charge compensation reactions is
discussed and differences between O−O formation and oxygen
release, both occurring mainly upon the first charge (so-called
activation), are identified.