Size and morphology controlled polyol synthesis of LiFePO4 nanoparticles with addition of organic acid combinations

A mutual extension of an increasing demand for LiFePO4 (LFP) is the need for developing a synthesis technique that enables improved particle morphology and size control at different scales. In this study, the polyol method was used for this purpose and modified to allow in-situ interventions, which, in turn, increased flexibility in particle design. Ethylene glycol was used as a reaction medium, and pure, porous, hierarchical LFP nanoparticles were synthesized at the lowest temperature reported in the literature. The primary and secondary particle size and morphology could be altered almost independently by controlling the amount and the addition sequence of the ascorbic acid (AA) and citric acid (CA). It was possible to control the particle features at different scales after the individual and combined effects of the acids were revealed. Particles with equiaxed small primaries (∼20 nm) and a mild aspect ratio in the secondaries (∼1.5) led to tap densities of 1.98 g/cm3, which is the highest value reported in the literature. Even though the heat treatment applied in this work had limitations in inducing a fully graphitized layer of carbon on LFPs, the added boost from the increased tap densities was observable in the high volumetric discharge capacities.