The redox couples M/M+ of the Group I alkali metals Lithium, Sodium, Potassium, Rubidium and Caesium have been extensively investigated in a room temperature ionic liquid (IL) and compared for the first time. Cyclic voltammetric experiments in the IL N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl) imide ([C(4)mpyrr][NTf2]) and subsequent simulation of the data has allowed the determination of the formal potential (E-f(0) vs. ferrocene/ferrocenium), standard electrochemical rate constant (k(0)) and transfer coefficient (alpha) for each couple in the group. The trend in E-f(0) in [C(4)mpyrr][NTf2] is remarkably similar to the established trend in the common battery electrolyte, propylene carbonate. (C) 2010 Elsevier B.V. All rights reserved.