Ab-initio study of olivine cathode material: Structural, magnetic and electronic properties of native and yttrium doped LiFePO4

Experimental studies showed the beneficial influence of Yttrium doping on the electrochemical performance of lithium Iron phosphate (LiFePO 4 ) cathode materials. To understand the origin of such improvement, first-principal calculation with the Full Potential Linear Augmented Plane Wave (FP-LAPW) method have been performed to investigate the stability, electronic structure and magnetic properties of native and Yttrium doped LiFePO 4 . It is found that Yttrium prefers occupying Fe sites and leads to the creation of additional density of states in the conduction band, thus improving the material's conduction properties. The magnetic ground state of native LiFePO 4 is found to be consistent with antiferromagnetic interactions between the two nearest Fe 2+ ions in adjacent layers due to the Fe – O – Fe super exchange interactions. The corresponding exchange parameter is calculated to be J 1 = − 0.574 meV which is in good agreement with the experimental value of J 1 = − 0.662 meV determined from fitting the spin-wave dispersion data of a single-crystal LiFePO 4.