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

Back to the future with emerging iron technologies

Here is a comprehensive overview of iron's potential in low-carbon energy technologies, exploring applications like metal fuel combustion, iron-based batteries, and energy-carrier cycles, as well as sustainable approaches for production and recycling with a focus on reducing environmental impact. Iron, with its abundance, safety, and electrochemical characteristics, is a promising material to contribute to a decarbonized future. This paper discusses the advancements and challenges in iron-based energy storage technologies and sustainable iron production methods. Various innovative approaches are explored as energy storage solutions based on iron, like advancements in thermochemical Fe-Cl cycles highlight the potential of iron chloride electrochemical cycles for long-term high-capacity energy storage technology. Additionally, the utilization of iron as a circular fuel in industrial processes demonstrates its potential in large-scale thermal energy generation. Sustainable iron production methods, such as electrolysis of iron chloride or oxide and deep eutectic solvent extraction, are investigated to reduce the carbon footprint in the iron and steel industry. These findings also show the importance of policy and technology improvements that are vital for the widespread use and recycling of iron-based tech, stressing the need for collaboration toward a sustainable future.

Metal-Air Batteries—A Review

Metal–air batteries are a promising technology that could be used in several applications, from portable devices to large-scale energy storage applications. This work is a comprehensive review of the recent progress made in metal-air batteries MABs. It covers the theoretical considerations and mechanisms of MABs, electrochemical performance, and the progress made in the development of different structures of MABs. The operational concepts and recent developments in MABs are thoroughly discussed, with a particular focus on innovative materials design and cell structures. The classical research on traditional MABs was chosen and contrasted with metal–air flow systems, demonstrating the merits associated with the latter in terms of achieving higher energy density and efficiency, along with stability. Furthermore, the recent applications of MABs were discussed. Finally, a broad overview of challenges/opportunities and potential directions for commercializing this technology is carefully discussed. The primary focus of this investigation is to present a concise summary and to establish future directions in the development of MABs from traditional static to advanced flow technologies. A systematic analysis of this subject from a material and chemistry standpoint is presented as well.

The effect of cobalt on morphology, structure, and ORR activity of electrospun carbon fibre mats in aqueous alkaline environments

An innovative approach for the design of air electrodes for metal-air batteries are free-standing scaffolds made of electrospun polyacrylonitrile fibres. In this study, cobalt-decorated fibres are prepared, and the influence of carbonisation temperature on the resulting particle decoration, as well as on fibre structure and morphology is discussed. Scanning electron microscopy, Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, elemental analysis, and inductively coupled plasma optical emission spectrometry are used for characterisation. The modified fibre system is compared to a benchmark system without cobalt additives. Cobalt is known to catalyse the formation of graphite in carbonaceous materials at elevated temperatures. As a result of cobalt migration in the material the resulting overall morphology is that of turbostratic carbon. Nitrogen removal and nitrogen-type distribution are enhanced by the cobalt additives. At lower carbonisation temperatures cobalt is distributed over the surface of the fibres, whereas at high carbonisation temperatures it forms particles with diameters up to 300 nm. Free-standing, current-collector-free electrodes assembled from carbonised cobalt-decorated fibre mats display promising performance for the oxygen reduction reaction in aqueous alkaline media. High current densities at an overpotential of 100 mV and low overpotentials at current densities of 333 μA·cm-2 were found for all electrodes made from cobalt-decorated fibre mats carbonised at temperatures between 800 and 1000 °C.

Three-Dimensional Fibrous Iron as Anode Current Collector for Rechargeable Zinc–Air Batteries

A three-dimensional (3D) fibrous structure with a high active surface and conductive pathway proved to be an excellent anode current collector for rechargeable zinc–air batteries (ZABs). Herein, a cost-effective and highly stable zinc (Zn) electrode, based on Zn electrodeposited on iron fibers (Zn/IF), is duly examined. Electrochemical characteristics of the proposed electrode are seen to compete with a conventional zinc/nickel foam (Zn/NF) electrode, implying that it can be a suitable alternative for use in ZABs. Results show that the Zn/IF electrode exhibits an almost similar trend as Zn/NF in cyclic voltammetry (CV). Moreover, by using a Zn/IF electrode, electrochemical impedance spectroscopy (EIS) demonstrates lower charge transfer resistance. In the application of a rechargeable ZAB, the fibrous Zn/IF electrode exhibits a high coulombic efficiency (CE) of 78%, close to the conventional Zn/NF (80%), with almost similar capacity and lower charge transfer resistance, after 200 charge/discharge cycles. It is evident that all the positive features of Zn/IF, especially its low cost, shows that it can be a valuable anode for ZABs.

Analysis on discharge behavior and performance of As- and B-doped silicon anodes in non-aqueous Si–air batteries under pulsed discharge operation

Abstract

Very high theoretical specific energies and abundant resource availability have emerged interest in primary Si–air batteries during the last decade. When operated with highly doped Si anodes and EMIm(HF)2.3F ionic liquid electrolyte, specific energies up to 1660 Wh kgSi−1 can be realized. Owing to their high-discharge voltage, the most investigated anode materials are $$\langle 100\rangle$$⟨100⟩ oriented highly As-doped Si wafers. As there is substantial OCV corrosion for these anodes, the most favorable mode of operation is continuous discharge. The objective of the present work is, therefore, to investigate the discharge behavior of cells with $$\langle 100\rangle$$⟨100⟩ As-doped Si anodes and to compare their performance to cells with $$\langle 100\rangle$$⟨100⟩ B-doped Si anodes under pulsed discharge conditions with current densities of 0.1 and 0.3 mA cm−2. Nine cells for both anode materials were operated for 200 h each, whereby current pulse time related to total operating time ranging from zero (OCV) to one (continuous discharge), are considered. The corrosion and discharge behavior of the cells were analyzed and anode surface morphologies after discharge were characterized. The performance is evaluated in terms of specific energy, specific capacity, and anode mass conversion efficiency. While for high-current pulse time fractions, the specific energies are higher for cells with As-doped Si anodes, along with low-current pulse fractions the cells with B-doped Si anodes are more favorable. It is demonstrated, that calculations for the specific energy under pulsed discharge conditions based on only two measurements—the OCV and the continuous discharge—match very well with the experimental data.

Graphic abstract

Influence of Al Alloying on the Electrochemical Behavior of Zn Electrodes for Zn-Air Batteries With Neutral Sodium Chloride Electrolyte

Zn alloy electrodes containing 10 wt. % Al were prepared to examine the applicability as anodes in primary Zn-air batteries with neutral 2M NaCl electrolyte. These electrodes were investigated by electrochemical measurements and microscopic techniques (SEM, LSM, AFM). Based on the cyclic voltammetry and intermediate term (24 h) discharge experiments, the only active element in the as-prepared alloy was found to be Zn. It was further confirmed by LSM that Zn rich areas dissolved while Al remained passive during discharge. The passive state of Al was also demonstrated by conductive AFM investigations on the as-cast alloy surfaces. The results on potentiodynamic polarization and weight loss measurements indicated that the alloy electrode was less prone to corrosion than pure Zn electrode. The electrochemical behavior of the electrodes was modified under certain cathodic polarization previous to measurements. Accordingly, originating from Al activation due to application of cathodic potentials, potentiodynamic polarization studies showed a clear shift on the corrosion potentials of the alloy toward more negative values. On the basis of these results, with the precondition of Al activation prior to discharge experiments, the effect of Al alloying on the Zn electrodes was revealed as temporarily enhanced potentials on the discharge profiles in comparison to pure Zn electrodes.

Recent Advances in Isolated Single-Atom Catalysts for Zinc Air Batteries: A Focus Review

Recently, zinc–air batteries (ZABs) have been receiving attention due to their theoretically high energy density, excellent safety, and the abundance of zinc resources. Typically, the performance of the zinc air batteries is determined by two catalytic reactions on the cathode—the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Therefore, intensive effort has been devoted to explore high performance electrocatalysts with desired morphology, size, and composition. Among them, single-atom catalysts (SACs) have emerged as attractive and unique systems because of their high electrocatalytic activity, good durability, and 100% active atom utilization. In this review, we mainly focus on the advance application of SACs in zinc air batteries in recent years. Firstly, SACs are briefly compared with catalysts in other scales (i.e., micro- and nano-materials). A main emphasis is then focused on synthesis and electrocatalytic activity as well as the underlying mechanisms for mono- and dual-metal-based SACs in zinc air batteries catalysis. Finally, a prospect is provided that is expected to guide the rational design and synthesis of SACs for zinc air batteries.

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

Poly-acrylonitrile (PAN)-derived carbon fibres were characterised as air electrode frameworks for aqueous-alkaline metal–air batteries, focussing on the influence of the carbonisation temperature on the structure and electrochemical properties. Elemental composition, (atomic) structure, electrical conductivity, and electrochemical performance related to the oxygen reduction were investigated for electrodes carbonised in the range from 300 °C to 1400 °C. Chemical and structural properties were analysed using elemental analysis, XPS, SEM, and Raman spectroscopy; electrical conductivities of the fibre networks were examined by four-point probe measurements. Electrochemical properties were evaluated using linear sweep voltammetry in 6 M KOH by the open circuit potentials, the cathodic current densities at given overpotentials, and required overpotentials at given current densities. The highest current density was obtained from fibres carbonised at 850 °C. The connection between the fibre characteristics and electrochemical properties are discussed, highlighting the importance of the nitrogen bonding state. The results provide a base for thedevelopment of high performance air electrodes.

Nitrogen-doped carbon fibres derived from electrospun poly-acrylonitrile display an optimum catalytic activity towards the oxygen reduction reaction in aqueous-alkaline metal–air batteries, when carbonised under argon at 850 °C.