Complementary Ion Beam Analysis and Raman Studies for Investigation of the Carbon Coating Impact on Li Insertion/Deinsertion Process at LiFePO 4 /C Electrodes

Electrode materials were prepared using two commercial C-LiFePO$_4$ powders (called hereafter LFP-A and LFP-B). The nature and the thickness of carbon coating have been characterized by Raman spectroscopy and Transmission Electron Microscopy. The carbon coating of the LFP-B is more graphitized than LFP-A, which appears amorphous. The lithium distribution of these electrodes is investigated using ion beam techniques as a function of its state of charge (SOC). The nuclear microanalyses reveal the presence of different dopings in the active materials (Ti or V). A layer richer in carbon (in addition to the composite electrode) is systematically observed on LFP-A pristine and cycled electrodes. In both materials, immobilization of lithium is visible. Higher content of lithium was observed for the LFP-B electrode.