Review: Phase transition mechanism and supercritical hydrothermal synthesis of nano lithium iron phosphate

Lithium iron phosphate (LiFePO₄) is one of the most important cathode materials for high-performance lithium-ion batteries in the future, due to its incomparable cheapness, stability and cycle life. However, low Li-ion diffusion and electronic conductivity, which are related to the charging rate and low-temperature performance, have become the bottleneck problem. This review begins with the introduction and comment of and phase transition mechanism in lithium iron phosphate particles, followed by the analysis the application potential of nanotechnology in high performance batteries. Nanoscale LiFePO₄ has been prepared easily in the laboratory, but few were prepared on a macroscopic scale, and it is more difficult to enter the industrial production stage. Supercritical hydrothermal synthesis is a nano-preparation technology with great potential for industrial application. This article reviews the key parameters (temperature, pressure, concentration, etc.) and core equipment (mixer/reactor) of supercritical hydrothermal synthesis from the perspective of crystallization mechanism, and then point out the structural optimization design of mixer and development of micro-reactors may be the core work for industrialization of supercritical hydrothermal synthesis.