LiMnPO4 is synthesized from a MnPO4 center dot H2O precursor precipitated via a spontaneous reaction. These MnPO4 center dot H2O nanoplates react quickly with the lithium source and form a pure phase of LiMnPO4 that has good electrochemical properties. Thermogravimetric analysis was used to determine the optimum synthesis temperature. The crystallization of LiMnPO4 occurs before 438 degrees C. After full nucleation at 550 degrees C, the samples exhibit a discharge capacity of 115 mAh g(-1) (C/20 rate, 2.5-4.4 V) in the first cycle. The coulomb efficiency is maintained at near 100% after the first few cycles. When the synthesis temperature decreases to 350 degrees C, the particle size of LiMnPO4 is further reduced to 10-50 nm with a reversible capacity of more than 90 mAh g(-1). For the 550 degrees C synthesized LiMnPO4, 73% of the initial capacity was retained at the 60th cycle. After the high rate (5C) discharge, the reversible capacity of LiMnPO4 can be recovered to nearly the original value of 110 mAh g(-1) at the C/20 rate. This precipitation method is a cost-effective approach for manufacturing high performance LiMnPO4 cathode materials.