Hao Liu, Fiona Strobridge and Prof Clare Grey, and coworkers from Argonne National Laboratory have used in situ synchrotron X-ray diffraction methods to investigate how Li ion battery electrode materials function at fast charge and discharge rates.
In work published recently in the journal Science, they showed that nanoparticles of LiFePO4 transform at via a non-equilibrium solid-solution process, rather than via an abrupt structural transformation (a two-phase reaction) of LiFePO4 to form FePO4.
This mechanism results in more gradual structural rearrangements during cycling and allows lithiation and delithiation to occur throughout the whole nanoparticle, rather than at an interface between LiFePO4 and FePO4, both contributing to the high-rate performance of this material. This finding highlights the importance of non-equilibrium process during battery cycling and suggests alternative strategies for designing electrodes that can be charged and discharged more rapidly for use in portable electronics, electric vehicles and for storage on the grid.