Local Structural Variations of Li[sub 2.6]Co[sub 0.4]N during the First Charge and Discharge

Abstract

The reaction characteristics and the local structural changes of Li 2 . 6 Co 0 . 4 N anode material for lithium secondary batteries were investigated by electrochemical methods and extended X-ray absorption fine structure (EXAFS) analysis. The main reaction during the initial discharge corresponded to Li insertion into Li vacant sites in synthetic Li 2 . 6 Co 0 . 4 N. The variation of Fourier transform magnitude for focused multiple scattering in EXAFS spectrum disclosed the change of local structure around cobalt ions during Li insertion/extraction. Local fine structure around Co ions lost linear symmetry of its own with excess Li extraction during the initial charge. However, the linear symmetric bond was recovered by Li reinsertion during the subsequent discharge, and local structural change during the first cycle can be considered as a reversible process.