Optimization of an Artificial Solid Electrolyte Interphase Formed on an Aluminum Anode and Its Application in Rechargeable Aqueous Aluminum Batteries.

Electrochemical cells that incorporate aluminum (Al) as the active material have become increasingly popular due to the advantages of high energy density, cost-effectiveness, and superior safety features. Despite the progress made by research groups in developing rechargeable Al//MxOy (M = Mn, V, etc.) cells using an aqueous Al trifluoromethanesulfonate-based electrolyte, the reactions occurring at the Al anode are still not fully understood. In this study, we explore the artificial solid electrolyte interphase (ASEI) on the Al anode by soaking it in AlCl3/urea ionic liquid. Surprisingly, our findings reveal that the ASEI actually promotes the corrosion of Al by providing chloride anions rather than facilitating the transport of Al3+ ions during charge/discharge cycles. Importantly, the ASEI significantly enhances the cycling stability and activity of Al cells. The primary reactions occurring at the Al anode during the charge/discharge cycle were determined to be irreversible oxidation and gas evolution. Furthermore, we demonstrate the successful realization of urea-treated Al (UTAl)//AlxMnO2 cells (discharge operating voltage of ∼1.45 V and specific capacity of 280 mAh/g), providing a platform to investigate the underlying mechanisms of these cells further. Overall, our work highlights the importance of ASEI in controlling the corrosion of Al in aqueous electrolytes, emphasizing the need for the further development of electrolytic materials that facilitate the transport of Al3+ ions in rechargeable Al batteries.

Understanding the Oxidation and Reduction Reactions of Sulfur in Rechargeable Aluminum-Sulfur Batteries with Deep Eutectic Solvent and Ionic Liquid Electrolytes.

Al-based batteries are promising next-generation rechargeable batteries owing to the abundance of raw materials and their high potential energy density. The Al-S system has attracted considerable attention because of its high energy density and low cost. However, its low discharge voltage plateau (0.6-1.2 V) hampers its practical application. Herein, eight ionic liquids or deep eutectic solvents were studied as electrolyte candidates for an Al-S cell. This was the first study to demonstrate that an Al-S cell based on an AlCl3 /acetamide electrolyte (1.3 molar ratio) showed high discharge voltage plateaus (1.65-1.95 V) and a charging cut-off voltage of 2.5 V in Al-S cells. An Al-S cell of 0.33 mAh capacity with the AlCl3 /acetamide electrolyte successfully lit up a red LED (forward voltage 1.6-2.0 V) for around 2 h. This work may help in promoting the development of high-performance and low-cost Al-S cells.

Aqueous Aluminum Cells: Mechanisms of Aluminum Anode Reactions and Role of the Artificial Solid Electrolyte Interphase.

Electrochemical cells with aluminum (Al) as the active material offer the benefits of high energy density, low cost, and high safety. Although several research groups have assembled rechargeable Al//MxOy (M = Mn, V, etc) cells with 2 m aqueous Al trifluoromethanesulfonate as an electrolyte and demonstrated the importance of the artificial solid electrolyte interphase (ASEI) on the Al anode for realizing high rechargeable capacity, the reactions of the Al anode in such cells remain underexplored. Herein, we investigate the effects of the ASEI on the charge/discharge cycling stability and activity of Al cells with the abovementioned aqueous electrolyte and reveal that this interphase provides chloride anions to induce the corrosion of Al rather than to support the transportation of Al3+ ions during charge/discharge. Regardless of the ASEI presence/absence, the main reactions at the Al anode during charge/discharge cycling are identified as oxidation and gas evolution, which suggests that the reduction of Al in the employed electrolyte is irreversible. The simple introduction of chloride anions (e.g., 0.15 m NaCl) into the electrolyte is shown to allow the realization of an Al//MnO2 cell with superior performance (discharge working voltage ≈ 1.5 V and specific capacity = 250 mA h/g). Thus, the present work unveils the mechanisms of reactions occurring at the Al anode of aqueous electrolyte Al cells to support their further development.

Electrochemical Performance of Graphitic Multi-walled Carbon Nanotubes with Different Aspect Ratios as Cathode Materials for Aluminum-ion Batteries.

Graphitic multi-walled carbon nanotubes (MWCNTs) can function as high-performance cathode materials for rechargeable Al-ion batteries with well-defined discharging plateaus and reasonable charge/discharge C-rates. However, the main intercalation/deintercalation or adsorption/desorption path of AlCl4- anions into or onto G-MWCNTs has not been elucidated. Herein, we used battery cells comprised of G-MWCNTs with different aspect ratios, Al metal, and AlCl3/1-ethyl-3-methylimidazolium chloride ionic liquid as the cathode, anode, and electrolyte, respectively. The electrochemical performance of the Al||G-MWCNT cell increased as the aspect ratio of the G-MWCNT cathode increased (i. e., longer and thinner). The degree of defects of the G-MWCNTs was similar (0.15-0.22); hence, the results confirm that the main and alternate paths for the AlCl4- intercalation/de-intercalation or adsorption/desorption into/from or onto/from the G-MWCNT are the basal and edge planes, respectively. The step-like structures of defects on the basal plane provide the main reaction site for AlCl4- anions.

para-Sulfonatocalix[6]arene-modified silver nanoparticles electrodeposited on glassy carbon electrode: preparation and electrochemical sensing of methyl parathion.

In this paper, a new electrochemical sensor, based on modified silver nanoparticles, was fabricated using one-step electrodeposition approach. The para-sulfonatocalix[6]arene-modified silver nanoparticles coated on glassy carbon electrode (pSC(6)-Ag NPs/GCE) was characterized by attenuated total reflection IR spectroscopy (ATR-IR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), etc. The pSC(6) as the host are highly efficient to capture organophosphates (OPs), which dramatically facilitates the enrichment of nitroaromatic OPs onto the electrochemical sensor surface. The combination of the host-guest supramolecular structure and the excellent electrochemical catalytic activities of the pSC(6)-Ag NPs/GCE provides a fast, simple, and sensitive electrochemical method for detecting nitroaromatic OPs. In this work, methyl parathion (MP) was used as a nitroaromatic OP model for testing the proposed sensor. In comparison with Ag NPs-modified electrode, the cathodic peak current of MP was amplified significantly. Differential pulse voltammetry was used for the simultaneous determination of MP. Under optimum conditions, the current increased linearly with the increasing concentration of MP in the range of 0.01-80microM, with a detection limit of 4.0nM (S/N=3). The fabrication reproducibility and stability of the sensor is better than that of enzyme-based electrodes. The possible underlying mechanism is discussed.

Selective colorimetric sensing of histidine in aqueous solutions using cysteine modified silver nanoparticles in the presence of Hg2+.

Cysteine modified Ag nanoparticles were prepared in aqueous solution, via one-pot protocol, which were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) and ultraviolet-visible spectroscopy (UV-vis). The nanoparticles provided a simple and rapid strategy to detect histidine (His) visually with the help of Hg(2+) ions in solution. The colorimetric sensor allows a rapidly quantitative assay of histidine down to the concentration of 3 x 10(-5) M. The mechanism by which Hg(2+) ions can bind with both the cysteine modified Ag nanoparticles and His molecule through cooperative metal-ligand interactions is discussed.