LiNi0.6Co0.2Mn0.2O2, an α-NaFeO2 type layered lithium transition metal oxide, is deemed as one of the most promising cathode materials for lithium-ion batteries. To ascertain the structural evolution and formation mechanism of this compound during high-temperature solid-state synthesis, thermal and structural analysis methods were performed, confirmed with the characterization of morphology and lithium residue. LiOH, used as the lithium source, showed both a lower initial temperature and a lower degree of lithium intercalation compared to Li2CO3 when reacting with the precursor. A higher temperature for Li2CO3 and a longer reaction time for LiOH during sintering would be beneficial to the material synthesis. Furthermore, a pre-heat treatment process in the temperature range of 400–600°C is beneficial for the lithium intercalation reaction.