Orphaned and/or partially-lithiated TM (oxy)hydroxide precursor particles are not static prior to Li 2 CO 3 melting. They continue to evolve crystallographically with temperature. This is evident from the presence of a rocksalt and a partially-layered phase in ex situ XRD of quenched AR-LMR samples, see Figure and SI Figure . These phases are not present in the SL-LMR case. For the AR-LMR pathway, between 530°C and 700°C, these diffraction peaks disappear. At 700°C and especially 750°C, the AR-LMR case has a stronger superstructure reflection than the SL-LMR case. This suggests that solid-liquid lithiation out of a Li 2 CO 3 melt leads to greater superstructure ordering that direct solid-solid lithiation of the original TM (oxy)hydroxide precusor. Notably, the rocksalt and partiallylayered intermediates present in the AR-LMR pathway are of too low intensity to be visible in the in situ data, and highlight the necessity of combining in situ and ex situ techniques in studies of calcination.