Evolution of the chemical valence of Mn in electrodes based on LiNi_0.5Mn_1.5O₄. (a) The electrodes with different SOC used for sXAS measurements are marked on the voltage profiles. (b) and (c) Mn L-edge sXAS spectra (TEY) collected on the sides of electrodes facing separator (b) and current collector (c). Dotted lines on top of the spectra are simulated results for obtaining the quantitative values of Mn²⁺, Mn³⁺, and Mn⁴⁺concentration. (d)–(f) Evolution of the Mn valence deduced from spectral simulations, with respect to the charge/discharge states.^[69]