Silicon and Iron as Resource-Efficient Anode Materials for Ambient-Temperature Metal-Air Batteries: A Review

Abstract

Metal-air batteries provide a most promising battery technology given their outstanding potential energy densities, which are desirable for both stationary and mobile applications in a ‘beyond lithium-ion’ battery market. Silicon- and iron-air batteries underwent less research and development compared to lithium- and zinc-air batteries. Nevertheless, in the recent past, the two also-ran battery systems made considerable progress and attracted rising research interest due to the excellent resource-efficiency of silicon and iron. Silicon and iron are among the top five of the most abundant elements in the earth’s crust, which ensures almost infinite material supply of the anode materials, even for large scale applications. Furthermore, primary silicon-air batteries are set to provide one of the highest energy densities among all batteries, while iron-air batteries are frequently considered as a highly rechargeable system with decent performance characteristics. Considering fundamental aspects for the anode materials, i.e., the metal electrodes, in this review, we will first outline the challenges, which explicitly apply to silicon- and iron-air batteries and prevented them from a broad implementation so far. Afterwards, we provide an extensive literature survey regarding state-of-the-art experimental approaches, which are set to resolve the aforementioned challenges and might enable the introduction of silicon- and iron-air batteries into the battery market in the future.

Carbonisation temperature dependence of electrochemical activity of nitrogen-doped carbon fibres from electrospinning as air-cathodes for aqueous-alkaline metal–air batteries

“…Primary Zn-air systems have been commercialised for low-power applications, but recent developments in the energy sector have led to a demand in better performing and rechargeable battery systems. [1][2][3] Recent reports on primary and secondary aqueous-alkaline metal-air battery systems, such as the Zn-air, 1 Fe-air, 4,5 and Siair 5 systems, have stressed the points that currently available anodes are performing well and that the full cell performance is limited mainly by the air cathode. 6 During discharge the overall cell voltage is reduced as a result of the high over-potentials in the cathode, and there is a demand for optimisation of the employed catalyst materials as well as the electrode architecture.…”

In Situ Hydrogen Evolution Monitoring During the Electrochemical Formation and Cycling of Pressed‐Plate Carbonyl Iron Electrodes in Alkaline Electrolyte

“…Among the various types of metal‐air batteries, iron‐air batteries stand out, given the vast abundance of iron, a decent theoretical energy density of 9677 Wh/L Fe (or 1228 Wh/kg Fe , excl. oxygen uptake), a potentially low price [6] and a preeminent environmental friendliness [7–10] . Moreover, iron is less prone to form dendrites upon electrochemical cycling in alkaline media than zinc, [8,11] with all of the aforementioned aspects ever‐sparking research and commercial interest since the times of Thomas Alva Edison [12,13] .…”

“…Moreover, temporarily higher discharge capacities of 400 mAh/g Fe [34] and 550 mAh/g Fe [28] have been reported, too, but for inferior charging efficiencies, e. g., 80 % and 57 %. Two main reasons for the difference in performance of various electrodes lie in i) the choice of active material, which may either consist of iron oxide nanoparticles or macroscopic iron particles, [7] and ii) the applied cycling procedure, which would either seek to exploit the full capacity of both possible oxidation reactions [21,28] (Fe(0)→Fe(II)→Fe(III)) or avoids deep discharge by a discharge potential limitation to the first oxidation reaction (Fe(0)→Fe(II)) [9,23] . In case of macroscopic iron particles such as carbonyl iron (particle size: 3–10 μm) the electrochemical oxidation during the discharge is typically limited to an iron electrode potential of −0.75 V vs. Hg/HgO, which marks the transition from one oxidation reaction to the other and allows for extended electrochemical cycling of the iron electrode [17,22,23] .…”

“…oxygen uptake), a potentially low price [6] and a preeminent environmental friendliness. [7][8][9][10] Moreover, iron is less prone to form dendrites upon electrochemical cycling in alkaline media than zinc, [8,11] with all of the aforementioned aspects eversparking research and commercial interest since the times of Thomas Alva Edison. [12,13] However, after a well advanced attempt of commercialization for automotive purposes in the 1970's, [14,15] iron-air batteries almost disappeared due to several issues such as spontaneous hydrogen evolution due to selfdischarge (corrosion of iron) and water splitting during the recharge (parasitic side reaction) as well as unsatisfactory air electrode performance.…”

“…[33] Moreover, temporarily higher discharge capacities of 400 mAh/g Fe [34] and 550 mAh/ g Fe [28] have been reported, too, but for inferior charging efficiencies, e. g., 80 % and 57 %. Two main reasons for the difference in performance of various electrodes lie in i) the choice of active material, which may either consist of iron oxide nanoparticles or macroscopic iron particles, [7] and ii) the applied cycling procedure, which would either seek to exploit the full capacity of both possible oxidation reactions [21,28] (Fe(0)! Fe(II)!Fe(III)) or avoids deep discharge by a discharge potential limitation to the first oxidation reaction (Fe(0)!Fe(II)).…”