Synthesis of high-density olivine LiFePO4 from paleozoic siderite FeCO3 and its electrochemical performance in lithium batteries

The lithium-ion cathode material olivine LiFePO4 (LFP) has been synthesized for the first time from natural paleozoic iron carbonate (FeCO3). The ferrous carbonate starting material consists of the mineral siderite at about 92 wt. % purity. Because FeCO3 has divalent iron, the reaction with lithium dihydrogen phosphate (LiH2PO4) provides a unique method to develop iron-(II) containing LFP in an inert atmosphere. Since siderite FeCO3 is a common mineral that can be directly mined, it may, therefore, provide an inexpensive route for the production of LFP. After carbon-coating, the LFP yields a capacity in the range of 80–110 mAh g−1LFP (in one chosen specimen sample), which is lower than commercially available LiFePO4 (150–160 mAh g−1LFP). However, the tap density of LFP derived from siderite is noticeably high at 1.65 g cm−3. The material is likely to be improved with powder purification, nanosized processing, and more complete carbon-coating coverage with increased optimization.