We studied the effect of carbon treatment on improving the electrochemical properties (capacity and cyclability) of NASICON-type iron sulfate (Fe-2(SO4)(3)) for the cathodes of lithium ion batteries (LIBs). An optimized ball milling technique that was applied to a mixture of as-synthesized iron sulfate and conductive carbon ketjen black EC-600JD (KB) resulted a high capacity of 117 mA h g(-1), which is close to its theoretical capacity of 134 mA h g(-1). Moreover, the cyclability of coin-type test cell was doubled to 58 cycles by adding a polymer followed by heat treatment to the mixture of conductive carbon and Fe-2(SO4)(3). The smaller particle size and more uniform distribution in the mixture of conductive carbon and Fe-2(SO4)(3) particles accounted for the improved electrochemical properties after treatment, as confirmed by FE-SEM observations. (C) 2013 Elsevier B.V. All rights reserved.