A new method for observing the outermost surface morphology and the thickness of solid electrolyte interphase (SEI) are presented. Low acceleration voltage in extreme high resolution scanning electron microscopy (XHR-SEM) provides detailed information on the SEI surface morphology due to secondary electron contrast mechanism. Also, XHR-SEM under low acceleration voltage with low energy induced ion etching in x-ray photoelectron spectroscopy (XPS) studies provides valuable information on the SEI layer thickness. More detailed properties of the SEI layer were investigated by transmission electron microscopy (TEM). (C) 2013 Elsevier B.V. All rights reserved.