Crystal habit analysis of LiFePO4 microparticles by AFM and first-principles calculations

LiFePO4 (LFP) microparticles with a faceted crystal habit have been fabricated by hydrothermal synthesis. Three different surfactants were employed to control the crystal habits of the particles, which ranged from cubes over different diamond-shaped platelets to pyramids. Crystallographic models of the particles with the lowest matching Miller indices were determined based on the data acquired by atomic force microscopy (AFM) and gave insight into the synthesis process. The analysis of the crystal facets of the observed particles implied the importance of the (2 1 0) facet, which was previously neglected. First-principles investigations based on density functional theory revealed a surface energy for (2 1 0) of 0.83 J m(-2), contributing 2.5% of the surface area of the equilibrium shape of LFP crystals.