We investigated the formation of LiMn 2O 4 phases by calcinating a stoichiometric mixture of Li 2CO 3 and various manganese compounds with high temperature X-ray diffraction (HT-XRD) technique to understand the influence of starting materials on the electrochemical performance. XRD measurements were carried out during heating processes from room temperature to 700 °C. In case of Li 2CO 3/electrolytic manganese dioxide and Li 2CO 3/MnCO 3 mixtures used as starting materials, Li 0.33MnO 2 phase and low crystalline phase, respectively, appeared as intermediate products during heating process followed by the crystallization into the spinel. HT-XRD observation confirmed that the LiMn 2O 4 phase was directly formed from starting Li 2CO 3/Mn 2O 3 and Li 2CO 3/Mn 3O 4 mixtures. The reactivity of the mixture, meant by the lower reaction temperature between Li and Mn compounds and the faster evolution of Li-Mn-O phase, depended on manganese compounds. The purity and stoichiometry of spinel type LiMn 2O 4 was not achieved only by the higher reactivity. From these results, the dependence of reversible capacities and cycleability of synthesized LiMn 2O 4s on the formation process which varied with the starting materials was discussed.