Investigating discharge performance and Mg interphase properties of an Ionic Liquid electrolyte based Mg-air battery

Organic Electrolyte Design for Rechargeable Batteries: From Lithium to Magnesium

Rechargeable magnesium batteries (RMBs) have been considered as one of the most viable battery chemistries amongst the "post" lithium-ion battery (LIB) technologies owing to their high volumetric capacity and the natural abundance of their key elements. The fundamental properties of Mg-ion conducting electrolytes are of essence to regulate the overall performance of RMBs. In this Review, the basic electrochemistry of Mg-ion conducting electrolytes batteries is discussed and compared to that of the Li-ion conducting electrolytes, and a comprehensive overview of the development of different Mg-ion conducting electrolytes is provided. In addition, the remaining challenges and possible solutions for future research are intensively discussed. The present work is expected to give an impetus to inspire the discovery of key electrolytes and thereby improve the electrochemical performances of RMBs and other related emerging battery technologies.

The Discharge Performance of Mg-3In-xCa Alloy Anodes for Mg–Air Batteries

Considering the advantage of safety and cost, designing a Mg–air battery with high capacity has been highly sought in recent years. However, self-corrosion and passivation of Mg anode critically reduce discharge performance, hindering the large-scale application of Mg–air batteries. In this study, a series of as-cast and extruded Mg-3In-xCa alloys were successfully fabricated. Microstructures, chemical composition, and discharge performance were investigated to optimize the content of Ca (x). The selected Mg–air battery with Mg-3In-3Ca alloy as anode represented the best battery performance, including 0.738 V of discharge voltage, 1323.92 mAh g−1 of specific capacity, and 61.74% of anodic efficiency at discharge current density of 30 mA cm−2. All of its parameters were vastly superior to pure Mg–air battery. In addition, the synergistic effects of In and Ca on promoting electrode properties were evaluated in detail, using SEM and electrochemical analysis, which is expected to trigger follow-up research in designing high-performance Mg–air batteries.

O2 reduction on a Au film electrode in an ionic liquid in the absence and presence of Mg2+ ions: Product formation and adlayer dynamics

Aiming at a detailed understanding of the interaction between an ionic liquid, O₂, and electrodes in Mg-air batteries, we performed a combined differential electrochemical mass spectrometry and in situ infrared spectroscopy model study on the interaction between the ionic liquid (IL) 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide (BMP-TFSI) and a gold film electrode in the presence and absence of O₂ and Mg²⁺ ions in the potential range relevant for the oxygen reduction reaction (ORR) and evolution reaction. Detailed information on the dynamic exchange of adsorbed ions, on the stability/decomposition of the ionic liquid, and on the activity/selectivity/reversibility of the ORR is derived from measurements performed under potentiodynamic and potentiostatic conditions. In neat BMP-TFSI, we find the dynamics of the potential induced exchange of adsorbed ions to depend significantly on the exchange direction. In the presence of O₂, the anions formed in the ORR distinctly affect the adsorption characteristics of the IL ions and the exchange dynamics. Furthermore, the ORR changes from reduction to superoxide anions at moderate potentials to reduction to peroxide anion at more negative potentials. In the additional presence of Mg²⁺ ions, dominant magnesium peroxide and oxide formation result in an irreversible ORR, in contrast to the requirements of an efficient re-chargeable Mg-air battery. In addition, these ions result in the increasing formation of a blocking adlayer, reducing the coverage of adsorbed IL species.

Variations and applications of the oxygen reduction reaction in ionic liquids

Increasing energy demands call for new energy storage technologies with high energy density to meet current and future needs. Metal-air batteries are especially attractive due to their superior specific energy, which is as much as 8 times that of today's best Li-ion batteries. However, the practical values achieved to date are far from the theoretical one and require further research to enhance the battery performance. The electrolyte plays an important role in the performance of the battery whose properties can be tuned by varying the chemical composition and through the use of additives. That is the case of ionic liquids which offer a wide variety of anion-cation combinations to realise maximum performance. This feature article overviews recent developments in ionic liquids as electrolytes for both magnesium-air and sodium-air batteries.

An Electrochemical Wind Velocity Sensor

Electrochemical interfaces invariably generate unipolar electromotive force because of the unidirectional nature of electrochemical double layers. Herein we show an unprecedented generation of a time varying bipolar electric field between identical half-cell electrodes induced by tailored interfacial migration of magnetic particles. The periodic oscillation of a bipolar electric field is monotonically correlated with velocity-dependent torque, opening new electrochemical pathways targeting velocity monitoring systems.