This study investigated the effect of a specific adsorption ion, copper (II) ion, on the kinetics of the charge transfer reaction at a LiMn2O4 thin film electrode/aqueous solution (1 mol dm(-3) LiNO3) interface. The zeta potential of LiMn2O4 particles showed a negative value in 1 x 10(-2) mol dm(-3) LiNO3 aqueous solution. while it was measured as positive in the presence of 1 x 10(-2) mol dm(-3) Cu(NO3)(2) in the solution. The presence of copper (II) ions in the solution increased the charge transfer resistance, and CV measurement revealed that the lithium insertion/extraction reaction was retarded by the presence of small amount of copper (II) ions. The activation energy for the charge transfer reaction in the solution with Cu(NO3)(2) was estimated to be 35 kJ mol(-1), which was ca. 10 kJ mol(-1) larger than that observed in the solution without Cu(NO3)(2). These results suggest that the interaction between the lithium ion and electrode surface is a factor in the kinetics of charge transfer reaction. (C) 2009 Elsevier Ltd. All rights reserved.