(a) Fe K-edge XANES spectra of pristine LiFePO₄and after 120 seconds of chemical delithiation; (b) the evolution and (c) linear combination fitting of Fe K-edge XANES spectra. (d) Comparison of fast delithiation of LiFePO₄betweenin situchemical delithiation and 4.3 V constant voltage charging; solid square symbols represent the FePO₄content, the red solid line is the charge capacity of 4.3 V constant voltage charging. Inset: determination of the Avrami exponent with the Johnson–Mehl–Avrami–Kolmogorov equation; (e) charge curve of LiFePO₄at different C rates.^[60]