Preparation of battery-grade LiFePO4 by the precipitation method: a review of specific features

The precipitation method is an efficient, economically feasible, and reproducible synthetic route to cathode materials for lithium-ion batteries with attractive performance characteristics, in particular, lithium iron phosphate (LiFePO4). This paper reviews the mechanisms of the key steps of the synthesis, namely, precipitation of iron phosphate FePO(4 )followed by its sintering with a lithium-containing raw material to give the LiFePO4 phase. The most probable interactions determining the kinetics of the precipitation process are considered using the data on the dissociation degree of the reacting components. The influence of the nature and concentrations of the commonly used sources of iron (FeSO4, FeCl3, Fe(NO3)(3)) and phosphorus (H3PO4, NH4H2PO4, (NH4)(2)HPO4), as well as the precipitation conditions (pH, temperature) on the precipitation efficiency of FePO4 is analyzed. The effect of the nature of the lithium-containing raw material (LiOH, Li2CO3, LiNO3) and the sintering (calcination) temperature on the morphology, phase composition, and electrochemical properties of the resulting LiFePO4 is discussed. The possibility is considered of obtaining spherical particles with high bulk density, which provides high specific and volumetric energy density of electrochemical cells. Based on the relationships established, optimal parameters for the synthesis of LiFePO(4 )with preliminary FePO4 precipitation step are proposed.