Studyof Higher Discharge Capacity, Phase Transition,and Relative Structural Stability in Li 2 FeSiO 4 Cathode upon Lithium Extraction Using an Experimental and TheoreticalApproach and Full Cell Prototype Study

We have revisited the study of the nanostructured lithium iron silicate-based cathode for a safe lithium-ion battery and to understand the reaction mechanism from the first cycle to the second cycle. Ex situ Mossbauer and X-ray absorption near edge structure spectroscopy (XANES) measurements have been carried out on electrodes charged at various voltages to investigate the electrochemical activity of the Fe3+/Fe4+ redox couple to confirm the existence of Fe4+ and its role in defining the structural and electrochemical properties. The first charge and discharge lead to a structural change, which results in a potential plateau shift after the first charge. To validate this understanding, ex situ synchrotron X-ray diffraction (SXRD) along with Rietveld refinement results and first-principles density functional theory-based analysis have been performed, which also support the change in the crystal structure of the material with cycling. The in situ electrochemical impedance spectroscopy demonstrates phase tra...