Cathode Calcination In article number 2207076, Sugeun Jo, Keeyoung Jung, Jongwoo Lim, and co-workers show how solid-state reaction heterogeneity affects the high-temperature calcination of Li-ion battery particles. Various parallel and serial combinations of the thermal (an)aerobic decomposition and Li2–O insertion/diffusion are chemically imaged during the calcination reaction. The cover image features the calcination intermediates that facilitate the surface Li2–O incorporation, which is impeded by the anaerobically decomposed phase in the particle core.