Mössbauer Spectroscopy and Magnetic Measurements As Complementary Techniques for the Phase Analysis of FeP Electrodes Cycling in Li-Ion Batteries

Iron phosphide (FeP) anodes react with lithium through a conversion reaction FeP + 3Li = Li 3 P + Fe°, leading to nanosized Fe° particles embedded in a Li 3 P matrix. Electrochemical tests coupled to 57 Fe Mössbauer spectroscopy and magnetic measurements confirm the previously proposed reaction mechanism and complete the investigation of the electrodes by gaining information on the Fe nanoparticles size and surface state from magnetic measurements. More importantly, combining Mössbauer spectroscopy and magnetic measurements appears to be a powerful tool to characterize electrode materials and to give better insights into the complex lithiation−delithiation processes.