Local electronic structure of LiFePO₄ nanoparticles in aged Li-ion batteries

The advanced LiFePO₄ cathode based Li-ion batteries have shown potential for applications in electrification of automobiles. The rate capabilities of these batteries have been improved by the development of LiFePO₄ nanoparticles. Here the effect of aging of Li-ion batteries on the local electronic structure of these LiFePO₄ nanoparticles has been investigated with high resolution scanning transmission electron microscopy imaging. The local compositional changes within particles from unaged and aged batteries have been measured from electron energy loss spectroscopy (EELS) on these LiFePO₄ nanoparticles. Further, the Z + 1 approximation within the density functional theory (DFT) framework has been employed to theoretically compute the energy loss near edge structure of LiFePO₄. The measured EELS spectra are compared with the computed O K edge and Fe L_2,3 edge to understand the loss of active Li from the host LiFePO₄ structure in the aged battery, which corresponds to loss of capacity of the battery.