Unveiling the potential of lithium fluoride phosphate (Li2MPO4F, M = Fe, V, Mn) for the next generation of lithium-ion batteries: A comparative study based on first principles and molecular dynamic simulations

Abstract

LiFePO₄ (LFP) cathode with olivine crystal structure has been a key player in safe and affordable energy storage, owing to its low-cost iron and high electrochemical stability within a voltage range of commercial electrolytes (2.8–3.4 V). To maintain these benefits while enhancing its energy density, Li₂MPO₄F was developed by introducing fluorine (F) and replacing iron with other transition metals (M). However, previous studies on these materials primarily measured performance within a limited voltage window (e.g., 2.5–4.5 V), making it challenging to analyze their performance under advanced electrolytes with a broader voltage range. In this study, we took a novel approach by utilizing first principles and molecular dynamic calculations to investigate the electrochemical performance of Li₂MPO₄F with three types of transition metals (M = V, Fe, Mn). This unique methodology, which includes calculations on theoretical voltages, atomic structures, and diffusion coefficient after structural optimization, allowed us to predict the impact of transition metals on cathode performance. By closely comparing the expected results, this study discusses the pros and cons of each cation substitution and suggests suitable cathode materials for batteries with high energy density and superior rate capability.