Freeze-Drying-Assisted Preparation of High-Compaction-Density LiMn0.69Co0.01Fe0.3PO4 Cathode Materials with High-Capacity and Long Life-Cycle for Lithium Ion Batteries

Abstract

As a successor to LiFePO4, the research interest in LiMn1−yFeyPO4 has been sustained due to its higher working voltage and safety features. However, its further application is limited by the low compaction density caused by uncontrolled particle size. In this study, the high-quality LiMn0.69Co0.01Fe0.3PO4 (LMFP) materials were prepared using the freeze-drying method to process the LMFP precursor synthesized through a solvothermal crystallization method followed by a calcination process at different temperatures (400–550 °C). The results demonstrate that the obtained particles exhibit a spheroidal shape with a low specific surface area after secondary crystallization calcination at 700 °C. The compaction density increased from 1.96 g/cm3 for LMFP precursor (LMFP-M1) to 2.18, 2.27, 2.34, and 2.43 g/cm3 for samples calcined at 400, 450, 500 and 550 °C, respectively, achieving a maximum increase of 24%. The full cell constructed with the high-compaction-density material calcined at 500 °C displayed discharge capacities of 144.1, 143.8, and 142.6 mAh/g at 0.5, 1, and 3 C rates, respectively, with a retention rate of 99% at 3 C rate. After undergoing charging and discharging cycles at a rate of 1 C for up to 800 cycles, the capacity retention rate was found to be 90%, indicating an expected full cell life span exceeding 2500 cycles.