Regenerating High-Performance Lithium Iron Phosphate through Establishing a Stable Structure via Designing a Reaction Path with Easy-Transformed Intermediates

Abstract Regenerating lithium iron phosphate (LFP) from recovered lithium carbonate and iron phosphate by conventional hydrometallurgy process is challenged by high wastewater treatment cost and the unsatisfying performance of regenerated LFPs. Herein, a nanoscale LFP with enhanced performances was regenerated via new synthesis path. Iron and phosphorus in leaching solution precipitated to form (NH4)Fe2(PO4)2OH, which was then reduced to Fe3(PO4)2 followed by lithium insertion reaction to form LiFePO4. The synthesis path can help avoid the generation of Li3Fe2(PO4)3 and obtain LFP with low Li-Fe antisite defects and short average lengths of Fe–O and P–O bonds. The regenerated LFP has impressive reversibility (94.4% capacity retention after 500 cycles at 5 C) and rate performance (146.9, 135.8, and 124.8 mAh g–1 for 2, 5, and 10 C, respectively; 113 mAh g–1 at –5 °C and 148.5 mAh g–1 at 35 °C for 0.5 C). Moreover, the synthesis process enjoys advantages in economy and environmental protection due to less wastewater discharge.