The effects of 3d-transition-metal ions in the electrolyte on the intercalation/de-intercalation reactions of Li+ at graphite negative-electrodes were investigated. The edge plane of highly oriented pyrolytic graphite (HOPG) was used as a model electrode, and electrochemical properties were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. A drastic decrease in redox current due to intercalation/de-intercalation reactions of Li+ was observed in electrolyte solutions containing Fe, Co, Ni, and Mn ions. In addition, interfacial resistance between the edge plane HOPG electrode and the electrolyte increased significantly. The effects of cyclic ethers, such as crown ether, aza crown ether, and cryptand, as electrolyte additives were applied to suppress the degradation of graphite negative-electrodes. As a result, specific cyclic ethers greatly suppressed the degradation of edge plane HOPG negative-electrodes in electrolyte solutions containing the above transition-metal ions. (C) 2016 The Electrochemical Society. All rights reserved.