A study conducted by Takeshi Uyama et al. was published in the Inorganic Chemistry.
Lithium iron phosphate batteries are now widely used because their positive electrode material, LiFePO4, is composed of earth-abundant elements, particularly Fe. During the charge and discharge reactions, LiFePO4 is known to undergo a two-phase phase transformation accompanied by anisotropic lattice changes and asymmetric behavior between charging and discharging. However, these phase transformation behaviors have not yet been evaluated in a unified and quantitative manner.
In the present study, we defined the difference in lattice parameters between charging and discharging for each phase as the δ parameter. Using simultaneous X-ray diffraction and absorption measurements, we determined the δ parameters and revisited the phase transformation behavior of LiFePO4. Consequently, the δ parameters revealed slight lattice strains (approximately 0.1%) were generated anisotropically and asymmetrically in only one of the two phases. These results suggest that the lattice strain facilitates the phase transformation and contributes to the high-rate charge and discharge performance of LiFePO4.
The proposed δ-parameter-based analysis provides a new framework for evaluating phase transformation behavior not only in LiFePO4 but also in other electrode materials, contributing to the development of high-performance and durable rechargeable batteries.
Title: Rate-Dependent Anisotropic Lattice Strain in LiFePO4 Verified by Simultaneous Operando X‑ray Diffraction and Absorption Measurements
Authors: Uyama, T., Nonaka, T., Mukai, K.
Journal Name: Inorganic Chemistry
Published: May 15, 2026