Development of a composite iron-matrix electrode for Nickel-Iron Battery Energy Storage Systems

Abstract

Fe-based alkaline batteries have attracted immense interest as a potential grid stabilizing renewable energy storage technology due to their robustness, long life, non-toxicity, and eco-friendliness. However, a few drawbacks need to be addressed for it to be a commercially viable solution to curtail the intermittency obstacle of renewable energy sources availability. These drawbacks include low coulombic efficiency, low specific energy and cyclic instability. One of the key driving factors for the electrode’s restrained performance is the anodic side reactions, i.e. passivation and hydrogen evolution, transpiring during discharging and charging of the Fe-based electrode respectively. In an attempt to enhance the electrochemical performance of the electrode, iron core-copper shell (Fe-Cu) nano-structuring technique and ferrous sulphur (FeS), and graphite (C) additives were utilised. Distinctly electro-conductive nickel mesh (Ni-mesh) current collector was employed coupled with a less sophisticated and low-cost hot-pressing technique. In this study, FeS and C integrated Fe-Cu core-shell composite electrode was investigated for applications in Fe-based alkaline batteries energy storage. The FeCu0.25/FeS/C composite electrode delivered 420 mAh g−1 at ≈71% coulombic efficiency, successfully cycling for over 40 cycles. The electrode kinetics and performance were assessed by rate capability, galvanostatic, cyclic voltammetry measurements in 6 M potassium hydroxide (KOH)/1M lithium hydroxide (LiOH) electrolyte at ambient temperature. Ex-situ X-ray diffraction (XRD) characterizations and scanning electrode microscopy (SEM) imaging of both the fresh and cycled electrode surfaces revealed that electrode material particles were still intact marked with negligible particle agglomeration in comparison with pure Fe electrode. Energy filtered transmission electrode microscopy (EFTEM) images confirmed the Fe core copper shell particle arrangement. The FeCu0.25/FeS electrode exhibited stable performances marked by high specific capacity coupled with negligible capacity decay and high efficiency. This FeS/C integrated Fe core Cu shell electrode is consequently a conducive negative electrode candidate in alkaline Fe-air and Ni-Fe battery technologies.