A novel process for producing synthetic rutile and LiFePO4 cathode material from ilmenite

Synthetic rutile and LiFePO4 cathode materials are prepared from the titanium hydrolysate and iron-rich lixivium, respectively. The titanium hydrolysate and iron-rich lixivium are obtained from the ilmenite by mechanical activation and leaching. The purity of synthetic rutile and the electrochemical performance of LiFePO4 are mainly determined by the leaching process. The optimal leaching conditions are as follows: HCl concentration 20 wt.%, reaction temperature 100 °C and hydrochloric acid/ilmenite mass ratio of 1.2:1. The synthetic rutile prepared under the optimal conditions contains 90.8% TiO2, 2.21% Fe2O3, 0.052% MnO2 and 0.23% (MgO + CaO), which meet the requirement for the production of titanium dioxide by chlorination. A co-precipitation method is used to synthesize FePO4·xH2O precursor from the iron-rich lixivium. ICP and EDS results show that small amounts of Al and Ti exist in the precursor. XRD results indicate that Al–Ti doping does not obviously change the structure of LiFePO4, and all the LiFePO4 samples are pure triphylite phase. The LiFePO4 sample prepared from the lixivium (leaching with 20 wt.% hydrochloric acid) exhibits a first discharge capacity of 151, 140 and 123 mAh g−1 at 1C, 2C and 5C rate, respectively, and shows excellent cycling performance.

Research highlights▶ A new and inexpensive process for comprehensively utilizing the natural ilmenite is proposed in this study. ▶ The synthetic rutile and LiFePO4 cathode material are prepared from natural ilmenite. The impurity content of the obtained synthetic rutile meets the requirement for the production of titanium dioxide by chlorination. Also, the prepared LiFePO4 cathode materials show excellent electrochemical properties. ▶ Three goals can be achieved through this work, namely the utilization of ilmenite, preparation of high quality synthetic rutile and synthesis of high-performance LiFePO4. As a result, almost all the titanium and iron are effectively utilized, and the ultimate products are high value-added.