Highly crystalline olivine- structured LiMnPO4 was prepared by a simple hydrothermal method in a basic aqueous medium at 200 degrees C for 10h. The particle shape of the as-prepared LiMnPO4 was plate-like with the thickness of 100-200nm. A capacity of 68 mA h g(-1) was reversibly achieved between 3 and 4.5 V vs. Li+/Li.