Comparative study on electronic structures of two phases compounds and origin of the structural phase transition in LiFePO ₄

Abstract LiFePO 4 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 Fe 3+ 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 LiFePO 4 phase compounds, providing knowledge for expanding the application scenarios of the α -LFP phase under special operating conditions such as high pressure.