The olivine-type compound LiMnPO4 was prepared via a reaction between Li3PO4 and a MnSO4 aqueous solution under hydrothermal conditions at 190 degrees C. The specific surface area and particle morphology of LiMnPO4 changed depending on the amount of water in the reaction mixtures, and the particle size decreased as the amount of water decreased. It was found that nanosized LiMnPO4 particles of ca. 50 nm can be prepared through the reaction between Li3PO4 and the molten aqua-complex of MnSO4 center dot nH(2)O (n = 4 or 5). Galvanostatic charge and discharge tests revealed that the electrochemical reactivity of LiMnPO4 at 30 degrees C increased as the particle size decreased. The small particle size contributes to the decrease in the overpotential for Mn2+/3+ redox and to the increase in the utilization of LiMnPO4 as an active material in the cathode of lithium batteries. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.015112jes] All rights reserved.