Preparation of FePO4?2H2O from LiFePo4 mixed with LiNixCoyMn1-x-yO2 waste material

摘要

A method for preparing battery grade FePO4?2H2O from LiFePO4 and LiNixCoyMn1-x-yO2 mixed waste is proposed. The optimum leaching conditions included: temperature of 50°C, 3:1 liquid–solid mass ratio, 3.6 HCl/FePO4?2H2O mole ratio, 0.75 H2O2/FePO42H2O mole ratio, and 2 h reaction time. The solution obtained from the leaching waste material was diluted to a 1.0 M Fe concentration, then transferred to an 1 L beaker, where temperature, pH, complexing agent, ammonia addition rate and feeding mode were studied in order to determine their effects on the precipitation, particle size and morphology of FePO4?2H2O. High precipitation rate of Fe with low percentages of Al, Ni, Co, Mn in the FePO4?2H2O is achievable when precipitation is performed at a temperature of 85°C, pH of 2.0, and 20 g L-1 complexing agent. Furthermore, it was observed that a slow addition of ammonia and a flow feeding method contributed to the production of FePO4?2H2O, with small particle sizes and a flake morphology.