First-principles study of the electronic structure and elastic property of Lix FePO4

Based on density functional theory of the first-principle, the electronic structures of LiFexPO4(x = 0. 0, 0. 75, 1.0) are calculated. The calculated results show that Fe3d states restrained by crystalline field cannot contribute to free electrons even though Fe3d states cross the Fermi level. Meanwhile, Fe-O bond is beneficial to stabilize the alloy structure due to the p-d hybrid orbital. With lithium ion extraction, the enhanced covalent bonds appear. In LixFePO4 system, the strength of covalent bond is in the order of P-O > Fe-O > Li-O. LixFePO4 system displays brittleness of material characteristic, and the LixFePO4 (x = 1. 0, 0.75) with lithium intercalation have stronger average bonding strength than that of FePO4.