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The reversible and irreversible cationic and anionic charge compensation mechanisms occurring along the first charge and discharge cycle of Li- and Mn-rich Li[Li0.2Ni0.16Mn0.56Co0.08]O2 cathode material at (dis)charge rates of 0.1C and 5C have been identified and quantified by X-ray absorption and emission spectroscopy. The analysis provided the oxidation states of the transition metals, the Mn local coordination, and the lattice elastic constants. Lattice softening occurs along the first charge, while a minor spinel phase forms irreversibly at the expense of the layered phase. Higher charge rate increases the spinel formation and induces an increased softening in the delithiated lattice, which is expected to correspond to a reduced reversible anionic redox. The results evidence a comparable cationic and anionic oxidation since the beginning of the charge, while only anions are contributing towards its end, equivalent to roughly 10% of structural oxygen irreversibly lost. Higher charge rates resulted in a decreased reversible anionic redox, anticipating the cationic oxidation. The reported results provide a reliable experimental approach to characterize the key parameters controlling the reversible and irreversible cationic and anionic contributions to the charge compensation mechanism., This research was funded by the Spanish Government, through the “Severo Ochoa” Programme for Centers of Excellence in R&D (FUNFUTURE, CEX2019-000917-S), the projects RTI2018-097753-B-I00, MAT2017-91404-EXP, with FEDER co-funding, the CSIC program for the Spanish Recovery, Transformation and Resilience Plan “Plataforma Temática Interdisciplinar Transición Energética Sostenible+ (PTI-TRANSENER+)” funded by the Recovery and Resilience Facility of the European Union, established by the Regulation (EU) 2020/2094. A.K., H.C., M.K., D.B. and S.P. would like to acknowledge financial support from the German Federal Ministry of Education and Research (BMBF) within the ExcellBattUlm project (03XP0257D), the European Commission within the Si-DRIVE project (Horizon 2020, 814464), and the Helmholtz Association., With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).