Aluminum Anode Research Articles

Synergistic Reductive Electrolysis Mixture Additive-Based Dual-Cell Configuration: An Effective Approach for High-Performance Aqueous Aluminum–Air Battery

Neutral aqueous electrolyte-based aluminum–air (Al–air) batteries have managed to gather significant attention because of their characteristic safety and cost effectiveness. However, the formation of the passivation layer [Al(OH)3] on the aluminum anode inhibits the long-term shelf life of the battery. Herein, a novel strategy to overturn the passivation by altering the aluminum/electrolyte interface is proposed. Incorporation of synergistic reductive electrolysis mixture additives (Tiron + NaNO3) can significantly reduce the passivation of the aluminum anode. The efficacy of the Tiron + NaNO3 synergistic mixture additive has been systematically examined using half-cell and full-cell with different concentrations of the additives in 0.5% NaCl. Furthermore, dual cell performance was investigated with optimum concentration (0.005 M Tiron + 0.005 M NaNO3) of the additive in 0.5% NaCl as the anolyte and different concentrations of H2SO4 as the catholyte. It is found that the resulting pumpless dual cell battery comprising neutral electrolyte with 0.005 M Tiron + 0.005 M NaNO3 mixture additive as the anolyte and 1 M H2SO4 as the catholyte demonstrated a remarkable cell potential of 1.14 V at a current density of 1 mA g–1, which is closer to the theoretical value. Morphological investigations using optical microscopy studies and X-ray photoelectron spectroscopic investigations also confirmed that the Tiron + NaNO3 additive is effective in preventing the discharge product on both anode and cathode surfaces and thus resulting in enhanced battery performance.

Hydrogen-bonds reconstructing electrolyte enabling low-temperature aluminum-air batteries

Aqueous aluminum-air batteries are promising candidates for the next generation of energy storage/conversion systems with high safety and low cost. However, the inevitable hydrogen evolution reaction on the metal aluminum anode and the freeze of aqueous electrolytes hinder the practical application of aluminum-air batteries at both room temperatures and subzero temperatures. Herein, we report a hydrogen-bonds reconstructing electrolyte strategy to boost aluminum-air batteries through the dipole of glycerol molecule, thus suppressing the self-corrosion of aluminum anode and lowering down the freezing point of electrolyte. This glycerol-based electrolyte endows a flow aluminum-air full battery with an outstanding specific capacity of 1886 mAh g−1 and a low operating temperature of −60 °C. This finding provides a synthetic design strategy to mitigate metal corrosion and expand the application range of temperature adaptation of aqueous batteries.

Combined electrocoagulation and electrooxidation treatment system for real effluents from the fishing industry

Fishing industries are characterized by high water consumption and a considerable content of organic matter and salt in their wastewater. In this work, a combined electrochemical process was studied at laboratory scale for the treatment of real wastewater from the processing of mackerel from an industrial facility located in the province of Buenos Aires that discharges to the sewer, which the plant is currently using and does not produce an effluent in discharge conditions. Taking advantage of the high conductivity of these effluents, in the electrocoagulation stage with aluminum anodes, it was possible to remove the coarsest fraction of suspended matter, achieving a Chemical Oxygen Demand (COD) removal of about 60%, at pH 7.5, showing a higher efficiency over the conventional treatment. Despite this superiority, the necessary removal was still not achieved; therefore, the wastewater treated by electrocoagulation was then subjected to electrooxidation, using a graphite anode and a titanium cathode, and with a first-order oxidation kinetics, achieving a final COD value lower than the discharge limit, after 7.5 min of processing at pH 6, obtaining an efficient treatment for removal of high concentrations dissolved organic matter and colloidal/suspended particles in this kind of effluent. All treatments were performed in batches.The removal of pollutants in the wastewater was verified by means of spectroscopic and voltammetric techniques; at the same time, these techniques, together with SEM-EDX analysis, proved the superiority of electrocoagulation over chemical coagulation. This study laid the groundwork for the design of modifications to the plant to achieve discharge parameters in accordance with current legislation.

Upscaling an electro-bioreactor with rectangular electrodes for single-stage simultaneous removal of ammonia, nitrate and phosphorous from wastewater

The objective of this research was to create simultaneous nitrification-denitrification (SND) conditions in a continuously aerated membrane bioreactor equipped with rectangular electrodes by electrically controlling the oxidation-reduction potential (ORP) in order to remove ammonium and nitrate in a single stage. A membrane electro-bioreactor (MEBR) fitted with rectangular aluminum anodes and iron cathodes was tested in bench and pilot scales. At bench scale, it was found that a minimum total current/reactor volume ratio (TC/V) of 43 A/m3 is needed to regulate the redox potential of the MEBR between aerobic and anoxic conditions and thus remove 91 % of total nitrogen. In the pilot MEBR, the minimum TC/V ratio required was 21 A/m3, while the influent concentration of COD was 160 mg/L compared to 930 mg/L in the bench scale tests. These design parameters could be employed to build up a full scale electrobioreactor.

Precipitation-free aluminum-air batteries with high capacity and durable service life

Aluminum-air batteries are potential candidates for future large-scale energy storage/conversion due to their high safety and energy density. However, aluminum-air batteries face the challenges of continuously accumulated discharge by-products and undesired parasitic hydrogen evolution reaction (HER), which induce inferior performance and service life. Here, HER-suppressing and precipitation-free molecular crowding electrolytes are developed using sodium polyacrylate (PANa) as the crowding agent by taking advantage of its molecular crowding effect and scale inhibition property. The introduced PANa reconfigures the hydrogen-bond networks of electrolyte to suppress the HER by molecular crowding effect. A more uniform electric field distribution can be found on the surface of aluminum anode in the electrolyte containing PANa by employing Comsol multiphysics simulation. In addition, the anion long chains of PANa are electrostatically adsorbed on the surface of Al(OH)3 by-products micro-crystal, resulting in the same negative charge on the surface of the micro-crystal to prevent further aggregation and precipitation. The fabricated flow-based aluminum-air battery exhibits an outstanding specific capacity of 2096 mAh g−1, demonstrating the remarkable positive effect of PANa-based molecular crowding electrolyte in aluminum-air batteries. This work provides new light on aqueous electrolyte design for high capacity and precipitation-free aluminum-air batteries.

Ionic Liquid Electrolytes with Mixed Organic Cations for Low-Temperature Rechargeable Aluminum–Graphite Batteries

Recently, aluminum–graphite batteries using chloroaluminate ionic liquid electrolytes have been shown to store charge with significant pseudocapacitive contributions, features attractive for energy storage systems that must function with high capacity retention and high specific power at low temperatures. Herein, we present results toward rechargeable aluminum–graphite batteries designed specifically for low-temperature applications, focusing on electrolyte design to reduce the melting point and enhance ion transport properties down to −40 °C. Chloroaluminate ionic liquid electrolytes with mixtures of organic cations, particularly imidazolium cations with different asymmetric functional groups, were used to impart disorder, disrupt ion clustering, and enhance low-temperature ion mobilities. Graphite cathodes with higher pseudocapacitive contributions showed improved specific capacity retention at lower temperatures, while aluminum anodes with higher surface roughness reduced the nucleation energy for aluminum electrodeposition. An aluminum–natural graphite battery with mixed imidazolium cations was shown to exhibit 87% specific capacity retention at −20 °C and 10 mA g–1. Overall, the results demonstrate multiple approaches to improve low-temperature aluminum battery performance and illustrate electrochemical methods that quantify electrolyte properties relevant to ion transport and clustering, which can be universally translated into other battery systems.

A Mechanistic Overview of the Current Status and Future Challenges of Aluminum Anode and Electrolyte in Aluminum-Air Batteries.

Aluminum-air batteries (AABs) are regarded as attractive candidates for usage as an electric vehicle power source due to their high theoretical energy density (8100 Wh kg-1 ), which is considerably higher than that of lithium-ion batteries. However, AABs have several issues with commercial applications. In this review, we outline the difficulties and most recent developments in AABs technology, including electrolytes and aluminum anodes, as well as their mechanistic understanding. First, the impact of the Al anode and alloying on battery performance is discussed. Then we focus on the impact of electrolytes on battery performances. The possibility of enhancing electrochemical performances by adding inhibitors to electrolytes is also investigated. Additionally, the use of aqueous and non-aqueous electrolytes in AABs is also discussed. Finally, the challenges and potential future research areas for the advancement of AABs are suggested.

Utilization of Li-Rich Phases in Aluminum Anodes for Improved Cycling Performance through Strategic Thermal Control

Lithium-ion batteries with aluminum anodes had appeared to resolve critical dendrite issues of lithium metal cells in the 1970s. However, the poor cycling performance attributed to aluminum anodes would lead to their obsolescence. In this work, we demonstrate how strategic thermal control in cycling aluminum anodes circumvents the problematic α/β phase transformations that yield poor cycling life. Instead, electrochemical formation of the Li3Al2 and Li2–xAl phases necessitates temperatures slightly above ambient, as the Li3Al2 and Li2–xAl phases are key enablers for high capacity and stable cycling. While delivering a competitive capacity level (ca. 1 Ah kg–1-Al), cycling among those higher-order phases is found to be significantly improved, from several cycles to 100 cycles with ca. 67% capacity retention. Importantly, because modern battery charging is likely to occur above room temperature due to ohmic heating, the thermal conditions explored here are expected to be realized in a variety of applications. Furthermore, we show that elevated temperature is not necessary for aluminum anode delithiation, thus creating additional synergies with many practical scenarios.

Secondary phase precipitate-induced localized corrosion of pure aluminum anode for aluminum—air battery

Secondary phase precipitate-induced localized corrosion of pure aluminum anode for aluminum—air battery

Aluminum Alloy Anode with Various Iron Content Influencing the Performance of Aluminum-Ion Batteries.

Considerable research has been devoted to the development of cathode materials for Al-ion batteries, but challenges remain regarding the behavior of aluminum anodes. Inert oxide (Al2O3) film on Al surfaces presents a barrier to electrochemical activity. The structure of the oxide film needs to be weakened to facilitate ion transfer during electrochemical activity. This study addresses oxide film challenges by studying Al alloy anodes with different iron content. The results reveal that using an anode of 99% Al 1% Fe in a cell increases the cycling lifetime by 48%, compared to a 99.99% Al anode. The improvement observed with the 99% Al 1% Fe anode is attributed to its fractional surface area corrosion being about 12% larger than that of a 99.99% Al anode. This is coupled to precipitation of a higher number of Al3Fe particles, which are evenly scattered in the Al matrix of 99% Al 1% Fe. These Al3Fe particles constitute weak spots in the oxide film for the electrolyte to attack, and access to fresh Al. The addition of iron to an Al anode thus offers a cheap and easy route for targeting the oxide passivating film challenge in Al-ion batteries.

Synthesis of Ye’elimite from Anthropogenic Waste

Calcium sulphoaluminate cement (CSA) is characterized by a different chemical and mineralogical composition than common cements based mainly on Portland clinker. Its main component is ye’elimite—Ca4(AlO2)6SO4. This cement is characterized by a shorter setting time and a dynamic increase in strength in the early aging process. Currently, CSA cements are gaining more and more popularity due to their favorable ecological aspects, including a reduction in carbon dioxide emissions and negative impacts on the environment. The aim of the study was to determine the possibility of obtaining ye’elimite from waste materials of anthropogenic origin, which in this case were by-products from the aluminum anodizing process and cement–asbestos waste. The results of this preliminary research indicated the possibility of obtaining ye’elimite from secondary raw materials of anthropogenic origin. In each material, the phase of ye’elimite was identified to be the main mineral component, and the obtained materials displayed binding properties after mixing with water.

Designing porous photonic crystals for MIR spectral region—a deeper insight into the anodic alumina layer thickness versus charge density relation

The mid-infrared region (MIR) is crucial for many applications in security and industry, in chemical and biomolecular sensing, since it contains strong characteristic vibrational transitions of many important molecules and gases (e.g. CO2, CH4, CO). Despite its great potential, the optical systems operating in this spectral domain are still under development. The situation is caused mainly by the lack of inexpensive and adequate optical materials which show no absorption in the MIR. In this work, we present an easy and affordable way to develop 1D photonic crystals (PCs) based on porous anodic alumina for MIR region. The porous PCs were produced by the pulse anodization of aluminum using charge-controlled mode. The first order photonic stopbands (λ 1) were located within ca. 3.5–6.5 μm. Annealing of the material at 1100 °C for an hour has allowed to recover the wavelength range from around 5.8 to 7.5 μm owing to the decomposition of the absorption centers (oxalate anions) present in the anodic oxide framework while maintaining the PC structural stability. The spectral position and the shape of the resonances were regulated by the charge passing under high (U H) and low (U L) voltage pulses, porosity of the corresponding d H and d L segments, and dura tion of the process (t tot). The thickness of the d H and d L layers was proportional to the charge passing under respective pulses, with the proportionality coefficient increasing with the applied voltage. Despite the constant charge (2500 mC cm−2) applied during the anodization, the thickness of anodic alumina (d) increased with applied voltage (10–60 V) and anodizing temperature (5 °C–30 °C). This behavior was ascribed to the different kinetics of the anodic alumina formation prompted by the variable electrochemical conditions. The photonic material can be used in portable nondispersive gas sensors as an enhancement layer operating up to around 9 μm.

Recent Progress of Fabrication, Characterization, and Applications of Anodic Aluminum Oxide (AAO) Membrane: A Review

The progress of membrane technology with the development of membranes with controlled parameters led to porous membranes. These membranes can be formed using different methods and have numerous applications in science and technology. Anodization of aluminum in this aspect is an electro-synthetic process that changes the surface of the metal through oxidation to deliver an anodic oxide layer. This process results in a self-coordinated, exceptional cluster of round and hollow formed pores with controllable pore widths, periodicity, and thickness. After the initial introduction, the paper proceeds with a brief overview of anodizing process. That engages anodic aluminum oxide (AAO) layers to be used as formats in various nanotechnology applications without the necessity for expensive lithographical systems. This review article surveys the current status of the investigation on AAO membranes. A comprehensive analysis is performed on AAO membranes in applications; filtration, sensors, drug delivery, template-assisted growth of various nanostructures. Their multiple usages in nanotechnology have also been discussed to gather nanomaterials and devices or unite them into specific applications, such as nano-electronic gadgets, channel layers, and clinical platforms tissue designing. From this review, the fact that the specified enhancement of properties of AAO can be done by varying geometric parameters of AAO has been highlighted. No review paper focused on a detailed discussion of applications of AAO with prospects and challenges. This review paper represents the formation, properties, applications with objective consideration of the prospects and challenges of AAO applications. The prospects may appeal to researchers to promote the development of unique membranes with functionalization and controlled geometric parameters and check the feasibility of the AAO membranes in nano-devices.

Aluminum Anodizing in an Aqueous Solution of Formic Acid with Ammonium Heptamolybdate Additive

Morphology, composition, and fluorescence properties of anodic alumina/carbon composites formed in an aqueous solution of formic acid with ammonium heptamolybdate additive at 60–80 V were studied concerning the amount and state of carbon embedded in the alumina structure. According to scanning electron microscopy studies, the composites possess a hierarchical structure with multi-branched pores with a dense, cracked cover layer on the film surface. On the reverse side (i.e., anodizing front), hexagonal-shaped cells with an average diameter of about 180 nm were formed. Linear sweep voltammetry and study of current transient curves demonstrated that the anodizing process is non-steady, which led to the generation of non-uniform current pathways and resulted in the formation of the multi-brunched porous structure. Thermogravimetry/differential thermal analysis and infrared spectroscopy showed that the average carbon content is ca. 5.5 mass%, and the carbon embedded in the alumina is in the form of CO2, CO, carboxylate ions, and a-C:H. X-ray-induced Auger electron spectroscopy of the surface and reverse sides of the films proved that carbon is not only on the surface but also is homogeneously distributed through the oxide layer. According to fluorescence studies, alumina/carbon composites have a wide blue fluorescence in the wavelength range of 350–700 nm with a maximum at around 455 and 460 nm for surface and reverse sides, respectively. Our findings imply that the fluorescence spectrum dynamics is non-exponential and can be described as a superposition of several decay components. These can be different carbon-containing compounds and functional groups, such as OH, C=O, and COOH.

Electrochemical harvesting of Chlorella sp.: Electrolyte concentration and interelectrode distance

Two modes of electrochemical harvesting for microalgae were investigated in the current work. A sacrificial anode (aluminum) was used to study the electrocoagulation-flotation process, and a nonsacrificial anode (graphite) was used to investigate the electroflotation process. The study inspected the effect of chloride ions concentration and the interelectrode distance on the performance of the electrochemical harvesting processes. The results demonstrated that both electrodes achieved maximum harvesting efficiency with a 2 g/L NaCl concentration. Interestingly, by increasing the NaCl concentration to 5 g/L, the harvesting efficiency reduced dramatically to its lowest value. Generally, the energy consumption decreased with increasing of NaCl concentration. Moreover, the energy consumption achieved with aluminum anodes is lower than that achieved with graphite. However, by increasing the gap between the electrodes from 15 mm to 30 mm, the time required to achieve the maximum efficiency doubled, and energy consumption increased consequently.

Regulating solvation and interface chemistry enables advanced aluminum-air batteries.

The main challenge for developing aqueous aluminum-air batteries with high mass-specific capacity depends on the inhibition of the parasitic hydrogen evolution reaction. Herein, a regulation strategy of solvation and interface chemistry has been proposed by introducing organic methylurea (MU) and inorganic stannous chloride (SnCl2) to the alkaline electrolyte, which can modulate the solvent structure and electrode/electrolyte interface and endow the aqueous aluminum-air battery with an outstanding mass-specific capacity of 2625 mA h g-1 at 50 mA cm-2.

Corrosion of Passive Aluminum Anodes in a Chloroaluminate Deep Eutectic Solvent for Secondary Batteries: The Bad, the Good, and the Ugly.

The passivity of aluminum is detrimental to its performance as an anode in batteries. Soaking of native oxide-covered aluminum in a chloroaluminate deep eutectic solvent gradually activates the electrode surface, which is reflected in a continuously decreasing open circuit potential. The underlying processes were studied by analyzing the 3 to 7 nm thick layer of native oxide after increasing periods of soaking with secondary neutral mass spectrometry, X-ray photoelectron spectroscopy, and energy-dispersive spectroscopy in a transmission electron microscope. They consistently show permeation of electrolyte species into the layer associated with gradual swelling. After extended periods of soaking at open circuit potentials, local deposits of a range of foreign metals have been found in scanning electron microscopy images of the electrode surface. The pitting corrosion is caused by trace metal ion impurities present in the electrolyte and results in highly nonuniform current density distribution during discharge/charge cycling of battery cells as shown by local deposits of aluminum. The processes during soaking at open circuit potentials have been monitored by electrochemical impedance spectroscopy and could be analyzed by fitting an equivalent circuit model for pitting corrosion.

Corrosion of Passive Aluminum Anodes in a Chloroaluminate Deep Eutectic Solvent for Secondary Batteries: The Bad, the Good, and the Ugly

Corrosion of Passive Aluminum Anodes in a Chloroaluminate Deep Eutectic Solvent for Secondary Batteries: The Bad, the Good, and the Ugly

Techno-economically feasible beverage can as superior anode in rechargeable Al-air batteries

Porous Fe nitrogen-doped carbon (Fe-NC) with a polyhedron structure, derived from zeolitic imidazolate framework 8 (ZIF8), was synthesized as an efficient electrocatalyst in Al-air batteries, complemented by a low-cost aluminium anode based on beverage cans. The highly-loaded porous Fe-NC demonstrated efficient catalytic activity towards the oxygen reduction reaction (ORR). This was linked to the good conductivity and the large surface area originating from the observed 3D porous architecture. The RDE test confirmed that the favourable 4-electron pathway for porous Fe-NC was higher than that of the 20 wt% Pt/carbon. Besides the high ORR activity, the Al-air battery demonstrated a maximum power density of 46 mW/cm2 at a current density of 80 mA/cm2. The galvanostatic discharge studies showed a stable voltage discharge plateau (>1.1 V) for current densities between 5 and 20 mA/cm2. The Al-air battery with porous Fe/NC catalyst exhibited a remarkably increased discharge capacity of 1920 mAh/g for the pure Al foil and 1173 mAh/g for the commercial Al can foil at a current density of 20 mA/cm2. The finding indicates that both anode and cathode in this work are techno-economically feasible materials. In addition, the Al-air battery showed large charge-discharge cycles (i.e., 180 cycles, 31 h) at 10 mA/cm2 with a low voltage gap using a beverage can.

Enhanced electrical conductivity and stretchability of ionic-liquid PEDOT:PSS air-cathodes for aluminium-air batteries with long lifetime and high specific energy

A hydrogel film, poly-3,4-ethylenedioxythiophene (PEDOT):polystyrenesulfonate (PSS), containing an ionic liquid, is used as an air–cathode for a metal-air battery and its performance is investigated. This work presents the development of the air–cathode and the characterization of its physical, chemical and mechanical properties. Moreover, in view of wearable batteries, these air-cathodes are implemented within a flexible aluminium-air battery. It contains an aluminium anode, an electrolyte made of cellulose paper imbibed with an aqueous sodium chloride solution and the PEDOT:PSS air–cathode. Characterisation tests showed that the ionic liquid did not change the air–cathode chemically, while the electric conductivity increased considerably. The anode has an acceptable purity and was found to be resistant against self-corrosion. Discharge tests showed operating voltages up to 0.65 V, whereas two batteries in series could deliver up to 1.3 V at a current density of 0.9 mA cm−2 for almost a day, sufficient for monitoring and medical devices. Several discharge tests with current densities from 0.25 up to 2.5 mA cm−2 have presented operating lifetimes from 10 h up until over a day. At a current density of 2.8 mA cm−2, the operating voltage and lifetime dropped considerably, explained by approaching the limiting current density of about 3 mA cm−2, as evidenced by linear sweep voltammetry. The batteries showed high specific energies up to about 3140 Wh kg−1. Mechanical tests revealed a sufficient stretchability of the air–cathode, even after battery discharge, implying an acceptable degree of wearability. Together with the reusability of the air–cathode, the battery is a promising route towards a low-cost viable way for wearable power supply for monitoring medical devices with long lifetimes and high specific energies. Optimization of the air–cathode could even lead to higher power applications.