Electrolyte roadblocks to a magnesium rechargeable battery

TLDR

Magnesium metal offers a low‑cost, non‑dendritic anode, but progress is limited by electrolyte development, with DFT predicting potential windows and high‑voltage (>3 V) electrolytes remaining a major challenge. The paper reviews recent advances in magnesium battery electrolytes and proposes strategies to mitigate challenges, including initial work to reduce the corrosive effect of organohaloaluminates on stainless steel. The authors describe initial work to mitigate organohaloaluminate corrosion on stainless steel, survey insertion and conversion cathodes, and focus on electrophilic sulfur paired with magnesium metal using non‑nucleophilic electrolytes prepared by crystallizing in‑situ generated organohaloaluminates. Non‑nucleophilic electrolytes enable the development of magnesium/sulfur batteries.

Abstract

Low cost, non-dendritic magnesium metal is an ideal anode for a post lithium ion battery. Currently, development of magnesium electrolytes governs the rate of progress in this field, because electrolyte properties determine the class of cathodes utilized. A review of the latest progress in the area of magnesium battery electrolyte and a perspective on mitigating present challenges is presented herein. Firstly, density functional theory has been shown to predict the potential window of magnesium electrolytes on inert electrodes. Secondly, we report initial efforts aimed to overcome the corrosive property of these magnesium organohaloaluminates towards less noble metals such as stainless steel. This is a major challenge in developing high voltage magnesium electrolytes essential for batteries which operate above 3V. We lastly touch on cathode candidates including the insertion and conversion classes. One conversion cathode we pay particular attention to is electrophilic sulfur which can be married with magnesium metal anodes by utilizing non-nucleophilic electrolytes obtained by simple crystallization of in situ generated magnesium organohaloaluminates. Effectively, non-nucleophilic electrolytes open the door to research on magnesium/sulfur batteries.