For the first time peculiarities of the hydrothermal synthesis of phosphate-based cathode material are studied using in situ Calvet calorimetry. Process staging, temperature intervals and heat effect values of the reactions are determined as a function of concentration of the initial reagents. Obtained results show a distinct correlation between observed heat absorption behavior and lattice parameters and morphology of the LiFePO4 phase. Lower temperatures of the first precursor dehydration stage lead to better Li/Fe ordering and smaller particle size of LiFePO4 samples.
