Surface phase heterogeneity within a fully charged LiCoO2 (LCO) composite electrode before and after thermal decomposition has been shown to strongly depend on the distribution of the binder and carbon additives, but be independent of the crystalline facet and size of LCO, as revealed by X-ray photoemission electron microscopy (X-PEEM). The obtained new insights deepen the understanding of thermal stability in a real composite electrode, which would be valuable for further development of long-life and safe cathodes for lithium-ion batteries.