In this work, non-graphitized carbon black and graphitized carbon blacks were analyzed with regard to their performance as conductive additives in high voltage spinel Cr-doped LiNi0.5Mn1.5O4 composite cathode electrodes. The degree of graphitization was investigated by X-ray diffraction. X-ray photoelectron spectroscopy was used to investigate the carbon black surface species and their alteration upon graphitization, as well as to the post mortem analysis of the composite cathodes. It was found that the cells with graphitized carbon blacks showed much longer cycling life. The depletion of the functional groups at the carbon black surface by graphitization apparently reduced the side reactions in the composite electrodes. Due to their superior performance, graphitized carbon black should be considered as substitute for the standard carbon black additives in the high voltage cathode electrodes. (C) 2014 The Electrochemical Society. All rights reserved.