Beneficial Impact of Selenate/Selenide Additives on the Performance and Longevity of the Alkaline Iron Electrode

The alkaline iron electrode is an inexpensive and robust negative electrode particularly suited for long-life large-scale energy storage batteries. The longevity of a high-performance iron electrode is limited by the amount of added metal sulfide additive in the electrode. Over years of operation, all the sulfide ion is gradually lost from the electrode by slow dissolution and irreversible oxidation to sulfate ions at the positive electrode. We show that iron selenide (FeSe) additive or an electrolyte containing 0.1 w v −1 % sodium selenate (2.7 mM) can provide the same benefits of sulfides but without irreversible losses. The selenates are electro-reduced in situ to regenerate the selenides and preserve the performance. Through our studies of the electrochemistry of selenate/selenide in the alkaline electrolyte, and with repeated cycling of battery electrodes, we have demonstrated the performance benefits of selenate/selenide additives over the traditional sulfides for the alkaline iron electrode.