Asymmetry of the nucleation barrier during electrochemically induced phase transitions in LiFePO4 cathode material

In this study, we present a unified and comprehensive investigation into the asymmetry of deintercalation and intercalation kinetics in LiFePO 4 materials, focusing on the previously unexplored asymmetry in nucleation kinetics. Through experimental studies of de/intercalation kinetics in LiFePO 4 using an aqueous electrolyte, we identified three key factors contributing to the faster rate of deintercalation compared to intercalation. To elucidate the origins of the asymmetry in nucleation kinetics, we estimated the parameters of Classical Nucleation Theory using Density Functional Theory and Finite Element Method. The theory revealed that differences in strain energy are the primary driver of slower lithiation compared to delithiation. While other factors, such as differences in diffusion coefficients and molar volumes, also favor faster delithiation, their influence is less significant. Our findings provide valuable insights into the experimentally observed de/intercalation kinetics asymmetry and contribute to a deeper understanding of the processes in phase-transforming materials. • Lithiation is slower than delithiation for LiFePO 4 cathode materials. • Asymmetry is observed in diffusion, charge transfer and nucleation steps. • Strain energy is the key parameter provoking nucleation kinetics asymmetry.