Strategies to Enable Reversible Magnesium Electrochemistry: From Electrolytes to Artificial Solid–Electrolyte Interphases

A Facile Strategy for Constructing High-Performance Polymer Electrolytes via Anion Modification and Click Chemistry for Rechargeable Magnesium Batteries

Polymer electrolytes play a crucial role in advancing rechargeable magnesium batteries (RMBs) owing to their exceptional characteristics, including high flexibility, superior interface compatibility, broad electrochemical stability window, and enhanced safety features. Despite these advantages, research in this domain remains nascent, plagued by single preparation approaches and challenges associated with the compatibility between polymer electrolytes and Mg metal anode. In this study, we present a novel synthesis strategy to fabricate a glycerol α,α'-diallyl ether-3,6-dioxa-1,8-octanedithiol-based composite gel polymer electrolyte supported by glass fiber substrate (GDT@GF CGPE) through anion modification and thiol-ene click chemistry polymerization. The developed route exhibits novelty and high efficiency, leading to the production of GDT@GF CGPEs featuring exceptional mechanical properties, heightened ionic conductivity, elevated Mg2+ transference number, and commendable compatibility with Mg anode. The assembled modified Mo6S8||GDT@GF||Mg cells exhibit outstanding performance across a wide temperature range and address critical safety concerns, showcasing the potential for applications under extreme conditions. Our innovative preparation strategy offers a promising avenue for the advancement of polymer electrolytes in high-performance rechargeable magnesium batteries, while also opens up possibilities for future large-scale applications and the development of flexible electronic devices.

Cathode Electrolyte Interphase (CEI) Endows Mo6 S8 with Fast Interfacial Magnesium-Ion Transfer Kinetics

Magnesium (Mg) metal secondary batteries have attracted much attention for their high safety and high energy density characteristics. However, the significant issues of the cathode/electrolyte interphase (CEI) in Mg batteries are still being ignored. In this work, a significant CEI layer on the typical Mo₆ S₈ cathode surface has been unprecedentedly constructed through the oxidation of the chloride-free magnesium tetrakis(hexafluoroisopropyloxy)borate (Mg[B(hfip)₄ ]₂ ) salt under a proper charge cut-off voltage condition. The CEI has been identified to contain B_x O_y effective species originating from the oxidation of [B(hfip)₄ ]^- anion. It is confirmed that the B_x O_y species is beneficial to the desolvation of solvated Mg²⁺ , speeding up the interfacial Mg²⁺ transfer kinetics, thereby improving the Mg²⁺ -storage capability of Mo₆ S₈ host. The firstly reported CEI in Mg batteries will give deeper insights into the interface issues in multivalent electrochemical 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.

Tailoring Coordination in Conventional Ether-Based Electrolytes for Reversible Magnesium-Metal Anodes

Rechargeable magnesium (Mg) batteries based on conventional electrolytes are seriously plagued by the formation of the ion-blocking passivation layer on the Mg metal anode. By tracking the Mg²⁺ solvation sheath, this work links the passivation components to the Mg²⁺ -solvents (1,2-dimethoxyethane, DME) coordination and the consequent thermodynamically unstable DME molecules. On this basis, we propose a methodology to tailor solvation coordination by introducing the additive solvent with extreme electron richness. Oxygen atoms in phosphorus-oxygen groups compete with that in carbon-oxygen groups of DME for the coordination with Mg²⁺ , thus softening the solvation sheath deformation. Meanwhile, the organophosphorus molecules in the rearranged solvation sheath decompose on the Mg surface, increasing the Mg²⁺ transport and electrical resistance by three and one orders of magnitude, respectively. Consequently, the symmetric cells exhibit superior cycling performance of over 600 cycles with low polarization.