Anodes and Anode/Electrolyte Interfaces for Rechargeable Magnesium Batteries

Abstract

Multivalent battery systems like rechargeable magnesium (Mg) batteries are garnering more interest as candidate post-lithium (Li) battery systems, for eventual applications in electric vehicles (EVs) and plug-in hybrid vehicles (PHVs). Mg, being divalent and denser, is theoretically capable of delivering a higher volumetric energy density (3833 mAh cm⁻³) than Li (2061 mAh cm⁻³), making it a viable battery system for addressing current range and space concerns in vehicles. To date, various low-voltage electrolytes have been utilized in Mg battery systems, due to the incompatibility of high-voltage conventional battery electrolytes (TFSI⁻, ClO₄ ⁻, PF₆ ⁻) with Mg metal anodes. It is however possible to use conventional battery electrolytes for Mg battery systems, by changing the type of anode, from a Mg metal anode to a Mg-ion insertion-type anode (e.g., Bi and Sn), as recently reported. This fact has produced two primary avenues of research for anodes in Mg batteries: the first being to utilize insertion-type anodes via their engineering as effective nanomaterials and the second focused on fundamental studies of the anode/electrolyte interface.

Here, we report the recent progress in electrochemical transport properties and in situ/operando X-ray absorption measurements for Mg deposition and the use of insertion-type anodes for rechargeable Mg-ion batteries. Results from such recent fundamental analyses, focused on studying and understanding these various insertion-type anodes and anode/electrolyte interfaces, are presented and discussed. Further, the authors’ perspective on both research avenues (i.e., insertion-type anodes and nanomaterials, as well as fundamental studies and anode/electrolyte interfaces) for anodes in Mg batteries is presented, via critically examining the importance of both avenues toward the overall advancement of Mg batteries.