Comparative study on electronic structures of two phases compounds and origin of the structural phase transition in LiFePO₄

LiFePO₄ has normal olivine-structured (α-LFP) and high pressure (β-LFP) phases, with the former being one of the cathode materials for commercial Li-ion batteries. Despite extensive focus on the respective electrochemical properties of the two phases, there is a lack of comparative studies on their electronic and magnetic properties, and the origin of the structural phase transition remains unclear. By combining first-principles calculations with molecular dynamics simulations, we find that the anisotropic compression of Li–O bonds drives the structural phase transition from α-LFP to β-LFP at a critical pressure of 20 GPa, while β-LFP undergoes a transition from semiconductor to metal due to Fe³⁺ generated during delithiation. Their antiferromagnetic (AFM) ground states are predicted to arise from the negative magnetic exchange interactions between nearest and next-nearest neighbor sites, with the corresponding Néel temperature showing significant enhancement under pressure. Furthermore, compared with α-LFP, β-LFP shows increases in bulk, shear, and Young’s moduli of 8%, 13%, and 12%, respectively. These findings enrich the physical property data of LiFePO₄ phase compounds, providing knowledge for expanding the application scenarios of the α-LFP phase under special operating conditions such as high pressure.