(Invited) Surface Modification Effect on the First Charging Process over 4.5 V and the Enhancement of Energy of LiNi1/3Co1/3Mn1/3O2
Authors have developed the sol-gel based coating procedure to make the thin and uniform layer of Al oxide on the commercially available LiNi1/3Co1/3Mn1/3O2 (NCM), by which the decrease of the initial capacity was suppressed . Using this modified NCM, first charging process was precisely investigated electrochemically varying the charge cut-off voltage up to 4.8 V. Below 4.7 V, discharge capacity increased as the charge cut-off voltage was elevated with/without modification. Coulombic efficiency, average voltage, cycling properties were improved by surface modification.
Comparison of AC impedance spectra and dQ/dVof the galvanostatic charge-discharge curves, with the aid of TEM results of the surface region, for modified/bare NCM revealed that the surface of the bare NCM was damaged to be high-resistant in very early stage of first charge, as was observed by surface analysis using synchrotron facilities . Al-oxide modification suppressed the increasing rate of interfacial resistance of Li+ intercalation/deinercalation at the surface.
 Z. H. Chen, et al., Electrochimica Acta, 49(7), 1079 (2004).
 B. C. Park, et. al., Journal of Power Sources, 178(2), 826 (2008).
 .A. T. Appapillai, et.al., Chemistry of Materials, 19(23),5748 (2007).
 A. Yano, H. Sakaebe, et. al., J. Electrochem. Soc., 162(2), A3137-A3144 (2015).
 D. Takamastu, et. al., Angewandte Chemie, 124(46), 11765–11769 (2012).