Enabling Magnesium Anodes by Tuning the Electrode/Electrolyte Interfacial Structure

Synthesis and characterization of divalent metal-betaine-bistriflimide complexes: a property comparison with metal bistriflimide salts

A panel of metal-betaine-bistriflimide complexes (with minimum formula M[Bet]2[Tf2N]2, where M = Mg, Ca, Zn, Cu and Ni) has been prepared in high purity and a quantitative yield. In parallel, a series of metal bistriflimide salts (sharing the same metal cations) has been synthesized and characterized though the same set of techniques. The current work presents a first comprehensive investigation of the physical-chemical properties of these two classes of metal systems, whose importance in a variety of applicative fields was not yet matched, to the best of our knowledge, by an adequate study of their characteristics. All the considered compounds have been spectroscopically, thermally and electrochemically characterized, and their solubility characteristics assessed, gaining insights into the role of metal cations in the definition of their properties. On the other hand, the evident effect of the betaine coordination on the prepared complexes' solubility, thermal stability, melting point, glass and solid-solid transitions, redox behaviour and electrochemical window was ascertained, providing results which would allow a more informed use and application of these classes of divalent metal complexes.

Interfacial Engineering of Magnesiophilic Coordination Layer Stabilizes Mg Metal Anode

Rechargeable magnesium batteries (RMBs) are seriously plagued by the direct exposure of the Mg anode to the electrolyte components, leading to spontaneous and electrochemical side reactions and interfacial passivation. Herein, a benign coordination layer is constructed at the Mg/electrolyte interface where aniline with a strong magnesiophilic amine group and high stability to Mg is chosen as representative, which has higher adsorption energy than DME (1,2-dimethoxyethane) and trace water. This Mg coordination environment mitigates side reactions, forming a non-passivating interface consisting of aniline and much fewer by-products after several cycles. Therefore, the Mg symmetrical cell operates with a low overpotential and uniform Mg0 deposition. This interfacial coordination can also be adopted for Mg anode protection in various electrolyte cases of Mg(TFSI)2 electrolyte systems.

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.

Applying Classical, Ab Initio, and Machine-Learning Molecular Dynamics Simulations to the Liquid Electrolyte for Rechargeable Batteries

Rechargeable batteries have become indispensable implements in our daily life and are considered a promising technology to construct sustainable energy systems in the future. The liquid electrolyte is one of the most important parts of a battery and is extremely critical in stabilizing the electrode-electrolyte interfaces and constructing safe and long-life-span batteries. Tremendous efforts have been devoted to developing new electrolyte solvents, salts, additives, and recipes, where molecular dynamics (MD) simulations play an increasingly important role in exploring electrolyte structures, physicochemical properties such as ionic conductivity, and interfacial reaction mechanisms. This review affords an overview of applying MD simulations in the study of liquid electrolytes for rechargeable batteries. First, the fundamentals and recent theoretical progress in three-class MD simulations are summarized, including classical, ab initio, and machine-learning MD simulations (section 2). Next, the application of MD simulations to the exploration of liquid electrolytes, including probing bulk and interfacial structures (section 3), deriving macroscopic properties such as ionic conductivity and dielectric constant of electrolytes (section 4), and revealing the electrode-electrolyte interfacial reaction mechanisms (section 5), are sequentially presented. Finally, a general conclusion and an insightful perspective on current challenges and future directions in applying MD simulations to liquid electrolytes are provided. Machine-learning technologies are highlighted to figure out these challenging issues facing MD simulations and electrolyte research and promote the rational design of advanced electrolytes for next-generation rechargeable batteries.

Facile and Economic Synthesis of Robust Non-Nucleophilic Electrolyte for High-Performance Rechargeable Magnesium Batteries

A cost-effective and highly efficient electrolyte with a wide electrochemical window, high reversibility of Mg plating/stripping, non-/low-corrosivity, good compatibility with cathode materials, and tolerance of trace water and impurity is crucial for the commercialization of rechargeable magnesium batteries. In this work, a novel boron-centered non-nucleophilic electrolyte that meets all the above requirements is prepared via a facile and economic approach from the raw materials B(TFE)₃/MgCl₂/CrCl₃/Mg (BMCM). The as-prepared BMCM electrolyte is mainly composed of tetracoordinated anions [B(TFE)₄]^- and solvated cations [Mg₂(μ-Cl)₂(DME)₄]²⁺. The BMCM electrolyte demonstrates attractive electrochemical performance, with a low overpotential (∼139 mV), a high Coulombic efficiency (∼97%), a high anodic stability (∼3.5 V vs Mg/Mg²⁺), and a long-term (more than 500 h) cycling stability. Moreover, BMCM shows good compatibility with the CuS cathode material. The CuS|BMCM|Mg full cell delivers a discharge specific capacity of 231 mAh g^-1 (at 56 mA g^-1), which can retain ∼88% even after 100 cycles. Importantly, the BMCM electrolyte is cost-effective and tolerant of trace impurity and water, which has great potential to be commercialized. This work is expected to promote the development of practical rechargeable magnesium batteries.