We observed the alkaline cation intercalation into graphite used as a conducting material in nickel electrodes during a study to clarify the origin of the second low-voltage plateau which appeared in the discharging process of alkaline secondary batteries. The Li-7-NMR results of charged or discharged Ni electrode obtained in a LiOH containing KOH solution show a main peak with spinning side bands, indicating the presence of Li+ in the graphite layer. These results suggest that Li+ ions, and also K+ ions remaining in the NiOOH, intercalate into the graphite in contact with NiOOH during the discharging process. (c) 2005 The Electrochemical Society.