Article ID: ISIJINT-2024-207
The usage of LiFePO4 (LFP) battery cathodes for electric vehicles (EVs) has increased in recent years. Phosphorus for LFP will be required for a comparable amount of fertilizer. However, the economically minable phosphate rock mines are decreasing, and the market for phosphorus is already tight. Thus, it is urgently necessary to promote the production of LFP based on secondary phosphorus resources. In this study, the production of LFP using phosphorus recovered from steelmaking slag was investigated. After selective leaching of steelmaking slag, the phosphorus in the extract is precipitated as FePO4 by titration with FeCl3 at pH=3. The FePO4 was mixed with LiOH·H2O and glucose (C6H12O6) and heat treated at 700°C to prepare LFP. The FeCl3 titration amount should be controlled within 0.6 stoichiometric mole ratio of Fe3+ to phosphorus to avoid the Fe3PO7 generation. The glucose should be mixed at the mole ratio of FePO4/C =1.0 to prevent the Fe3+ from being over-reduced to Fe. The other elements, Ca, Si, Mg, Al, and Mn in the slag extract, did not affect the crystallization process and the structure of FePO4 and LFP. The present study confirmed the feasibility of using steelmaking slag as a source of phosphorus for the preparation of LFP.