A new synthesis method using molten carbonate flux was investigated in order to enhance the performance of the lithium ion battery cathode material Li2FeSiO4. The synthesis conditions of temperature, atmosphere, iron source and the amount of carbonate flux were examined. Fine powder with a mean particle size of about 1 mu m and a phase purity of 99% Li2FeSiO4 was obtained from iron and Li2SiO3 using molten (Li0.435Na0.315K0.25)(2)CO3 flux under a CO2-H-2 atmosphere at 773 K. The Li2FeSiO4 cathode showed discharge capacity of 162 mAh g(-1) at the C/10 rate with good cyclability. Through the synthesis method, cathode material with good capacity and cyclability was obtained, utilizing low-cost iron powder at a lower temperature than that of the solid state reaction. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.047112jes] All rights reserved.