A novel and accurate analytical method based on X-ray photoelectron spectroscopy for the quantitative detection of the lithium content in LiFePO4

We established a novel and accurate strategy to detect the lithium content in LiFePO4 by X-ray photoelectron spectroscopy (XPS). As-prepared LiFePO4 samples were characterized by X-ray diffraction spectroscopy and XPS. The XPS study results confirmed that in the samples, the oxidation state of Fe is +2 and the oxidation state of Li is +1. Good linearity between the ratio of the theoretical value and the measured value of Li+ and Fe2+ was obtained, with a correlation coefficient of approximately 0.9994 and a relative standard deviation of approximately 0.475. These results suggest that the ratio between the content of Li+ and Fe2+ in LiFePO4 samples can be accurately quantitatively analyzed by the peak separation in the XPS technique. The proposed method also highlights the potential of such an approach in extensive applications for determining the Li+ content in lithium-ion batteries during charging and discharging, which can be used as a new idea to study the electrochemical properties of LiFePO4.