Iron electrodes were prepared by hot-pressing iron-polyethylene based formulations on nickel foam stripes. NiFe cells were tested by using commercial nickel electrodes and our iron electrodes. Post-hoc comparisons were used to identify meaningful differences between iron electrode formulations (based upon bismuth, bismuth sulphate, potassium sulphide and iron sulphide as additives). Our results confirm that both bismuth sulphide and iron sulphide favour the process of charge/discharge of a NiFe cell. In addition, we have found that the use of metallic bismuth only marginally influences coulombic efficiency; likewise, the presence of the soluble bisulfide anion is not sufficient to increase coulombic efficiency. Finally, NiFe cells prepared with bismuth sulphide outperformed their iron sulphide counterparts. (C) 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/).