LiFe0.2Mn0.8PO4 has been prepared by a solid state reaction process in combination with a ball-milling with carbon black and sucrose as carbon sources. The effects of the ratio of carbon precursors, the total carbon content, and ball-milling time on the physico-chemical and electrochemical properties of C-LiFe0.2Mn0.8PO4 are extensively studied. Under the optimal condition, the as-prepared Li Fe0.2Mn0.8PO4 gives a capacity of 150mAhg−1 at 1/20C and 110mAhg−1 at 1C. A novel lithium-ion battery consisting of LiFe0.2Mn0.8PO4 cathode, Li4Ti5O12 anode delivers a capacity of 70mAhg−1 and a specific energy of 170Whkg−1 with an output voltage of 2.45V based on the total weight of both active electrode materials. The cell also exhibits an excellent cycling stability with a capacity retention of 92% over 200 charge/discharge cycles.