Heat-rate-controlled hydrothermal crystallization of high-performance LiMn0.7Fe0.3PO4 cathode material for lithium-ion batteries

High supersaturation degree can endow hydrothermal products with small size, high crystallinity, designed morphology and orientation. However, adjusting the hydrothermal supersaturation level in organic-free systems is still a great challenge. In this work, high supersaturation degree is feasibly achieved via a green and efficient strategy just by elevating the hydrothermal heating rate, where cubic-like LiMn0.7Fe0.3PO4 cathode material with improved electrochemical kinetics is obtained. Detailed studies reveal that the elevated heating rate could improve the critical dissolved temperature of the precursor and lead to shortened time window for nucleation, and finally give rise to high supersaturation level and fast crystallization kinetics. By this heating-rate-controlled hydrothermal strategy, cuboid-like LiMn0.7Fe0.3PO4 particles with average length of 373 nm are successfully synthesized at the optimal heating rate of 5 °C/min. After coated with conductive carbon, the LiMn0.7Fe0.3PO4/C electrode possesses enhanced conductivity for both electron and Li+, which delivers superior electrochemical properties of 166.5 mAh·g−1 and 87.3 mAh·g−1 at the rates of 0.1 C and 10 C, respectively. We believe this work provides new perspectives for the synthesis of properties-controlled nanocrystals in the hydrothermal system.