In our work, we aimed to probe the electrochemical activity of anionic oxygen in Li-rich layered oxides from material perspective via tackling the effect of transition metal species. We have successfully synthesized a series of Li-rich layered oxides, Li2-x-yNixTmyO2 (TM is transition metal). Compounds with designed transition metals possess a similar crystal structure and enable a similar amount of Li removal and uptake during charge-discharge processes, but with a significantly different charge profile, characterized by the voltage plateau around 4.55 V. We performed a systematic study to capture the oxygen activity ranging from O2- in the lattice to O0 in gaseous phase in the as-produced compounds by combining a suite of advanced characterization techniques with in-situ differential electrochemical spectrometry (DEMS). We have observed completely different oxygen behaviors in such compounds with varied transition metals. We will present our experimental evidence on a reversible participation of electrons from oxygen in Li-, Mn-rich layered oxide. We hope these findings will provide additional insights into the complex mechanism of oxygen redox and the development of advanced high-capacity Li-ion cathodes.
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