Enhancing the Performance of the Rechargeable Iron Electrode in Alkaline Batteries with Bismuth Oxide and Iron Sulfide Additives

Abstract

Iron-based alkaline rechargeable batteries have the potential of meeting the needs of large-scale electrical energy storage because of their low-cost, robustness and eco-friendliness. However, the widespread commercial deployment of iron-based batteries has been limited by the low charging efficiency and the poor discharge rate capability of the iron electrode. In this study, we have demonstrated iron electrodes containing bismuth oxide and iron sulfide with a charging efficiency of 92% and capable of being discharged at the 3C rate. Such a high value of charging efficiency combined with the ability to discharge at high rates is being reported for the first time. The bismuth oxide additive led to the in situ formation of elemental bismuth and a consequent increase in the overpotential for the hydrogen evolution reaction leading to an increase in the charging efficiency. We observed that the sulfide ions added to the electrolyte and iron sulfide added to the electrode mitigated electrode passivation and allowed for continuous discharge at high rates. At the 3C discharge rate, a utilization of 0.2 Ah/g was achieved. The performance level of the rechargeable iron electrode demonstrated here is attractive for designing economically-viable large-scale energy storage systems based on alkaline nickel-iron and iron-air batteries.

A High-Performance Sintered Iron Electrode for Rechargeable Alkaline Batteries to Enable Large-Scale Energy Storage

“…This performance represents a significant improvement compared to the charging efficiency of 55-70% and the recommended discharge Journal of The Electrochemical Society, 164 (2) A418-A429 (2017) A419 rate of 0.2 C of commercial nickel-iron batteries. 17,44 As mentioned earlier, these iron electrodes that were demonstrated in our previous studies were the pressed-plate type. While this fabrication method is relatively inexpensive for manufacturing, fabricating electrodes by sintering of iron powders can offer other significant benefits.…”

“…17 Our recent efforts with a "pressed-plate" type iron electrode have led to remarkable advances in charging efficiency and rate capability, achieved through electrode re-design and re-formulation. 17,[43][44][45] Such "pressed-plate" electrodes were prepared by hot-pressing of a mixture of the carbonyl iron particles, sulfide-containing additives, a pore-forming additive and a polymeric binder. However, greater mechanical robustness is projected for a "sintered-type" iron electrode when compared to other types of electrodes.…”

“…[37][38][39][40] In the last five years, under an effort funded by ARPA-E at the University of Southern California, Narayanan et al have demonstrated notable improvements in the charging efficiency and discharge-rate capability of iron electrodes. 17,44 Also, there has been a deeper understanding of the formation process and methods to increase charging efficiency. 17,43 The role of sulfides in increasing discharge capacity and the factors affecting the cycle life of iron electrodes have also become better understood.…”

“…17,43 The role of sulfides in increasing discharge capacity and the factors affecting the cycle life of iron electrodes have also become better understood. 44,45 As a result, iron electrodes with charging efficiencies as high as 96% and with the ability to sustain discharge rates up to 3C, have now been demonstrated. This performance represents a significant improvement compared to the charging efficiency of 55-70% and the recommended discharge Journal of The Electrochemical Society, 164 (2) A418-A429 (2017) A419 rate of 0.2 C of commercial nickel-iron batteries.…”

“…17,44 In these pressed-plate type electrodes elemental bismuth was electrodeposited in situ on the iron electrode during electrode formation. 17 The high overpotential for the hydrogen evolution reaction on bismuth led to the suppression of hydrogen evolution and achievement of high charging efficiency.…”