Ghadir Razaz

Aqueous aluminum batteries (AABs) have emerged as promising next generation batteries owing to their sustainability and high theoretical capacity. However, conventional aqueous electrolytes bring challenges, such as low voltage windows, and corrosion. Therefore, the new subclass of aqueous electrolytes, water-in-salt (WIS) electrolytes, are lately being considered. This study explores in detail aluminum/graphite (Al/G) cells utilizing WIS electrolytes. Parameters such as interelectrode distance, voltage range, and current density were investigated. The results revealed that cells with a 6 mm interelectrode distance, operating in the voltage range of 0.1–1.6 V at a current density of 0.5 Ag-1, demonstrate the highest capacity (80 mAhg-1) in the stabilized cycle stage, compared with other configurations.

The 99.99% Al used for negative Al electrodes in aluminum-based battery studies is expensive. This is primarily due to the complex challenges associated with fabricating 99.99% Al, particularly the removal of Fe impurities from Al melts. Despite the importance of this issue for the future commercialization of Al-based batteries, it has been largely overlooked. This work accordingly studied the plating/stripping behavior of Al containing 1 wt % iron (Al 1% Fe) as an alternative electrode using conventional ([EMIm]Cl and AlCl3) electrolyte. Simultaneously, the impact of the surface microstructure of Al 1% Fe on the plating/stripping behavior was examined. The results indicate that the difference in the plating/stripping cycling of Al 1% Fe alloys and 99.99% Al is negligible. Thus, Al 1% Fe negative electrodes could serve as an efficient and commercially viable alternative to 99.99% Al for plating/stripping in Al-based batteries. This is an essential finding because facile and commercial fabrication of Al 1% Fe electrodes is absolutely feasible. The results are further discussed in terms of the impact of the Al surface microstructure (i.e., grain size, defect density, grain boundary distribution, crystal orientation, and intermetallic phases) on plating/stripping behavior. Moreover, this study provides insights into how the interphase layer formed on Al electrodes influences plating/stripping behavior.

Recently, much research has investigated nanocomposites and their properties for the development of energy storage systems. Supercapacitor performance is usually enhanced by the use of porous electrode structures, which produce a larger surface area for reaction. In this work, a biocompatible polymer of starch medium was used to create the porous nanostructure. Two powders, i.e., Nickel molybdate/reduced graphene oxide (NiMoO₄-rGO) and Nickel molybdate/nitrogen-doped reduced graphene oxide (NiMoO₄-NrGO), were synthesized using the deposition method in a medium containing starch, nickel nitrate salts, sodium molybdate, and graphene oxide powder. In terms of electrochemical performance, the NiMoO₄-NrGO electrode displayed a higher specific capacitance, i.e., 932 Fg⁻¹ (466 Cg⁻¹), than the NiMoO₄-rGO electrode, i.e., 884 Fg⁻¹ (442 Cg⁻¹), at a current density of 1 Ag⁻¹. In fact, graphene oxide sheets could lose more oxygen groups in the presence of ammonia, resulting in increased electrical conductivity. For the asymmetric supercapacitor of NiMoO₄-NrGO//AC, the specific capacitance at 1 Ag⁻¹, energy density, and power density were 101.2 Fg⁻¹ (111.32 Cg⁻¹), 17 Wh kg⁻¹, and 174.4 kW kg⁻¹, respectively. In addition, this supercapacitor material displayed a good cycling stability of over 82%.

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.

Severe hot tearing has been observed during DC casting of modified AA3000 alloys with additions of Cu, Ti, and Zr, although these alloys are regarded as rather easy to cast. Extensive studies have been performed on both synthetic and industrial AA2000, AA6000, and AA7000 alloys, but less data are available for AA3000 alloys. This work was thus initiated to investigate the hot tearing susceptibility of AA3000 alloys with varying alloy element content using constrained rod casting molds. The results showed that the Cu and Fe content have a major impact on hot tearing resistance, while the effects of Zr and Ti are minor. Cu in a range from 0.3 to 1.2 wt pct significantly increased the hot tearing tendency. This is due to the existence of high eutectic fractions at low temperatures, as well as porosity formation associated with bad feeding at the end of solidification. A strong cracking tendency was observed below an Fe content 0.2 wt pct owing to decreased precipitation of the Al₆(Mn, Fe) phase. It was found that primary Al₆(Mn, Fe) phases lead to early bridging between the grains, which reinforces the alloy during the vulnerable temperature range for hot tearing. Zr and Ti additions weakly enhanced or reduced hot tearing severity, respectively.

The dissolution of Mn and Fe in liquid Al presents a challenge due to their high melting points and low diffusivity. A literature review reveals that the existing knowledge of the processes involved in the dissolution of both Fe and Mn in liquid Al is rather ambiguous. Thus, this work aimed to obtain more detailed insights into the dissolution behavior of Mn and Fe in various Al melts. The results of the Mn dissolution tests showed that three intermediate phases were involved in the dissolution process, all of which exhibited a smooth interface between Mn and the liquid. These three phases were identified as the γ₂, Al₁₁Mn₄, and µ phases which grow slowly, penetrating the Mn particles. The results of the Fe dissolution tests showed that in pure Al, the Al₅Fe₂ phase dominates the dissolution process and penetrates the Fe particles. The addition of Ti into the molten Al alters the intermetallic compound formation by replacing Al₅Fe₂ by Al₂Fe. The addition of Si significantly inhibited the Fe dissolution kinetics. A theoretical approach based on Ficks’ law was used to explain the experimentally obtained Mn and Fe dissolution rates. It showed that the surface area and shape of the additives significantly affected the dissolution processes.