A dual-electrolyte system for highly efficient Al-air batteries

Green interface optimization strategy based on allium mongolicum regel extract for enhanced alkaline Al-air battery performance

Aqueous aluminum (Al)-air batteries (AABs) are gaining significant attention due to their excellent theoretical performance. However, the self-corrosion of the aluminum anode reduces anodic efficiency and battery capacity, limiting the broad commercial application of AABs. Herein, we propose the utilizing Allium Mongolicum Regel (AMR) extract as a green electrolyte additive to optimize the Al anode/electrolyte interface in alkaline AABs. Our findings indicate that the incorporation of AMR into NaOH electrolyte offers an effective strategy for preventing the self-corrosion of the Al anode, leading to significant enhancements in battery performance. Electrochemical experiments demonstrate that AMR achieves an inhibition efficiency of 53.9%. Through in-situ optical microscopy and in-situ attenuated total reflection Fourier-transform infrared spectroscopy, it is observed that the introduction of AMR can retard pitting corrosion by adsorbing onto the Al surface. This leads to a significant increase in specific capacity, from 1096 to 1667 mAh g-1, compared with the electrolyte without AMR for AABs. Further analysis utilizing X-ray photoelectron spectroscopy, quantum chemical calculations, and ab-initio molecular dynamics determine that 4-hydroxycinnamamide (4-HCAA) and flavone molecules, which are the most active components of AMR, can bind with Al atoms through the carbonyl O functional group, forming an O-Al-O bond, thus suppressing the self-corrosion of the Al anode. The incorporation of the AMR extract into the electrolyte of AABs represents a sustainable approach for optimizing battery performance. This innovative strategy addresses a critical issue in the development of AABs, potentially creating new opportunities for their commercialization and widespread utilization as a reliable energy storage technology.

Asymmetric Electrolytes Design for Aqueous Multivalent Metal Ion Batteries

With the rapid development of portable electronics and electric road vehicles, high-energy-density batteries have been becoming front-burner issues. Traditionally, homogeneous electrolyte cannot simultaneously meet diametrically opposed demands of high-potential cathode and low-potential anode, which are essential for high-voltage batteries. Meanwhile, homogeneous electrolyte is difficult to achieve bi- or multi-functions to meet different requirements of electrodes. In comparison, the asymmetric electrolyte with bi- or multi-layer disparate components can satisfy distinct requirements by playing different roles of each electrolyte layer and meanwhile compensates weakness of individual electrolyte. Consequently, the asymmetric electrolyte can not only suppress by-product sedimentation and continuous electrolyte decomposition at the anode while preserving active substances at the cathode for high-voltage batteries with long cyclic lifespan. In this review, we comprehensively divide asymmetric electrolytes into three categories: decoupled liquid-state electrolytes, bi-phase solid/liquid electrolytes and decoupled asymmetric solid-state electrolytes. The design principles, reaction mechanism and mutual compatibility are also studied, respectively. Finally, we provide a comprehensive vision for the simplification of structure to reduce costs and increase device energy density, and the optimization of solvation structure at anolyte/catholyte interface to realize fast ion transport kinetics.

Quasi-Solid-State Aluminum-Air Batteries with Ultra-high Energy Density and Uniform Aluminum Stripping Behavior

Aqueous aluminum-air batteries are attracting considerable attention with high theoretical capacity, low-cost and high safety. However, lifespan and safety of the battery are still limited by the inevitable hydrogen evolution reaction on the metal aluminum anode and electrolyte leakage. Herein, for the first time, a clay-based quasi-solid-state electrolyte is proposed to address such issues, which has excellent compatibility and a liquid-like ionic conductivity. The clay with uniform pore channels facilitates aluminum ions uniform stripping and reduces the activity of free H2 O molecules by reconstructing hydrogen bonds network, thus suppressing the self-corrosion of aluminum anode. As a result, the fabricated aluminum-air battery achieves the highest energy density of 4.56 KWh kg-1 with liquid-like operating voltage of 1.65 V and outstanding specific capacity of 2765 mAh g-1 , superior to those reported aluminum-air batteries. The principle of constructing quasi-solid-state electrolyte using low-cost clay may further promote the commercialization of aluminum-air batteries and provide a new insight into electrolyte design for aqueous energy storage system.

Correlation between Redox Potential and Solvation Structure in Biphasic Electrolytes for Li Metal Batteries

The activity of lithium ions in electrolytes depends on their solvation structures. However, the understanding of changes in Li+ activity is still elusive in terms of interactions between lithium ions and solvent molecules. Herein, the chelating effect of lithium ion by forming [Li(15C5)]+ gives rise to a decrease in Li+ activity, leading to the negative potential shift of Li metal anode. Moreover, weakly solvating lithium ions in ionic liquids, such as [Li(TFSI)2 ]- (TFSI = bis(trifluoromethanesulfonyl)imide), increase in Li+ activity, resulting in the positive potential shift of LiFePO4 cathode. This allows the development of innovative high energy density Li metal batteries, such as 3.8 V class Li | LiFePO4 cells, along with introducing stable biphasic electrolytes. In addition, correlation between Li+ activity, cell potential shift, and Li+ solvation structure is investigated by comparing solvated Li+ ions with carbonate solvents, chelated Li+ ions with cyclic and linear ethers, and weakly solvating Li+ ions in ionic liquids. These findings elucidate a broader understanding of the complex origin of Li+ activity and provide an opportunity to achieve high energy density lithium metal batteries.