Reversibility of a High-Voltage Mg Metal Battery Enabled by a Water-in-Salt Electrolyte

In a research team led by Prof. Dennis Y.C. Leung, Professor of Department of Mechanical Engineering, Sarah Leong, a PhD student, and her teammates designed a highly reversible aqueous Mg metal battery. The battery exhibits a high voltage plateau of 2.4–2.0 V over 700 cycles, with a Coulombic efficiency of up to 99% at 0.5 A g–1.This research work has been recently published in ACS Energy Letters on July 21, 2022.

Details of the publication:

Reversibility of a High-Voltage, Cl–-Regulated, Aqueous Mg Metal Battery Enabled by a Water-in-Salt Electrolyte

Kee Wah Leong, Wending Pan*, Yifei Wang, Shijing Luo, Xiaolong Zhao, and Dennis Y. C. Leung*

Article in ACS Energy Letters 2022 7, 2657-2666. doi: 10.1021/acsenergylett.2c01255


Rechargeable Mg batteries are a promising post-Li-ion battery technology, but their development has been critically hampered by the passivating nature of Mg, particularly in aqueous solutions. Due to a quick dismissal of its reversibility, the use of Mg anodes in aqueous electrolytes has been overlooked, and most researchers focus on nonaqueous systems instead. In this work, reversible, aqueous Mg battery chemistry has been realized for the first time, via the conversion of its impermeable passivation film to a conductive metallic oxide complex, facilitated by Cl– regulation and the suppression of the hydrogen evolution reaction using a MgCl2 water-in-salt (WIS) electrolyte. When coupled with copper hexacyanoferrate as the cathode, the full battery exhibits an impressive voltage plateau of 2.4–2.0 V and a stability of over 700 cycles with a Coulombic efficiency of up to 99% at 0.5 A g–1. Mg dissolution and deposition have proven reversible in the aqueous MgCl2 WIS electrolyte.