We describe a novel synchronous surface tailoring to form thin and uniform carbon coating layers and simultaneously induce an in-situ phase transition from a layered to spinel-like phase on the surfaces of Li-rich layered oxide (LLOs) particles by the thermal decomposition of 2,3-dihydroxynaphthalene (DN). The Li2MnO3 component in pristine LLO is not affected during carbon coating, but the coordination numbers of the Co ions and the CoO bonds in the LiTMO2 phase are diminished during carbon coating, implying that the formation of a spinel-like phase in LLO after carbon coating begins at the LiTMO2 with little variation in the Li2MnO3. As a result, the optimized DN (0.2 wt%)-coated LLO cathode material shows superb electrochemical properties owing to the formation of uniform carbon coating layers and the layered-to spinel-phase transition on the surfaces of the LLO particles, which improves the surface stability, electronic conductivity, and Li-ion kinetics in the LLO.