We hypothesize that Li originating within large (> 20 µm) Li 2 CO 3 particles does not insert into the LMR material until after the Li source melts. We consider two specific mechanisms. The first mechanism involves slow but homogeneous lithiation, the rate of which is limited by diffusion of Li species within large precursor particles. This would result in similar average Mn oxidation state between secondary particles. In this case, all particles To shed light on the mechanism, we performed scanning transmission X-ray microscopy (STXM) at the Mn L-edge on ultramicrotomed sections (80 nm -150 nm nominal thickness) of the AR-LMR and SL-LMR calcinations quenched at 530 °C. This temperature was selected because it is near to the point of maximum difference between SL-LMR and AR-LMR in lithiation, oxidation, and surface area, as observed via TGA, ex situ XAS, and BET (Figure ). Details of sample preparation and oxidation state fitting are available in the methods and SI. Figure and show typical nanosale oxidation state maps of the AR-LMR and SL-LMR quenched samples. The quenched SL-LMR is both more oxidized and more uniform in oxidation state than AR-LMR. The quenched AR-LMR nonetheless contains entire secondary particles that appear fully oxidized to Mn 4+ , or nearly so. This sample also contains secondary particles with a relatively uniform but much lower Mn oxidation state, close to 3.6 -only slightly oxidized above the TM (oxy)hydroxide precursor. The oxidation state histograms in Figure and SI Figure and 8 quantitatively support this picture.