Effect of excess Li+ in solution on LiFePO4 preparation via wet chemical method

Olivine structure LiFePO4 has attracted much attention as a promising cathode material for lithium ion batteries, and many approaches have been developed to produce electrochemically active LiFePO4 at low cost. Here lithium iron phosphate (LiFePO4) was prepared via co-precipitation method by using FeSO4·7H2O, LiOH·H2O, and o-H3PO4 as the raw materials. The effects of Li:Fe:P molar ratios and solution pH value on the synthesis of LiFePO4 were studied. The results illustrated that besides of the pH value parameter which was reported in many other previous researches, excess Li+ in the solution was another essential condition for pure LiFePO4 preparation. It suggested that excessive LiOH was not only a pH regulator, but also a precipitation promoter. Maintaining a certain excess Li+ ion in solution was an efficient measure to avoid the formation of impurities.