Preparing high performance of LiFe(1−x)MxPO4 by using Fe(1−x)MxC2O4 as raw material precipitated from ferrochrome alloy leaching solution

To separate ferrum from chromium in the leaching sulfate solution of ferrochrome alloy, the oxalic acid was employed to precipitate the ferrum as the form of FeC2O4 and Cr was left in the solution. In this route, small amount of nickel, cobalt and manganese exited in ferrochrome alloy were also precipitated simultaneously together with ferrous oxalate. Analysis from ICP shows that the molar percent of Fe in oxalic precipitate is 97.9% and the main doped elements are Ni (1.1%) and Mn (0.4%).The mixed metal oxalate Fe(1−x)MxC2O4 was used as a raw material to prepare doped LiFePO4 cathode material of lithium ion batteries. The obtained LiFe(1−x)MxPO4/C was a single olivine-type phase with higher crystallinity and presents the well-distributed fine particles. It shows an outstanding electrochemical performance with a discharge capacity of 162 mAh/g at the rate of 0.1 C, 136 mAh/g at 1 C and 103 mAh/g at 5 C. When cycled at 1 C for 50 times, the capacity retention is 98.2%.