Evaluation of Mg[B(HFIP)4]2‑Based Electrolyte Solutions for Rechargeable Mg Batteries

• Published in: ACS applied materials & interfaces 2021-11, Vol.13 (46), p.54894-54905
• Main Authors: Dlugatch, Ben, Mohankumar, Meera, Attias, Ran, Krishna, Balasubramoniam Murali, Elias, Yuval, Gofer, Yosef, Zitoun, David, Aurbach, Doron
• Format: Article
• Language: English
• Subjects: Energy, Environmental, and Catalysis Applications
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.1c13419

One of the greatest challenges toward rechargeable magnesium batteries is the development of noncorrosive electrolyte solutions with high anodic stability that can support reversible Mg deposition/dissolution. In the last few years, magnesium electrolyte solutions based on Cl-free fluorinated alkoxyborates were investigated for Mg batteries due to their high anodic stability and ionic conductivity and the possibility of reversible deposition/dissolution in ethereal solvents. Here, the electrochemical performance of Mg­[B­(hexafluoroisopropanol)4]2/dimethoxyethane (Mg­[B­(HFIP)4]2/DME) solutions was examined. These electrolyte solutions require a special “conditioning” pretreatment that removes undesirable active moieties. Such a process was developed and explored, and basic scientific issues related to the mechanism by which it affects Mg deposition/dissolution were addressed. The chemical changes that occur during the conditioning process were examined. Mg­[B­(HFIP)4]2/DME solutions were found to enable reversible Mg deposition, albeit with a relatively low Coulombic efficiency of 95% during the first cycles. Prolonged deposition/dissolution cycling tests demonstrate a stable behavior of magnesium electrodes. Overall, this system presents a reasonable electrolyte solution and can serve as a basis for future efforts to develop chlorine-free alternatives for secondary magnesium batteries. It is clear that such a conditioning process is mandatory, as it removes reactive contaminants that lead to unavoidable passivation and deactivation of Mg electrodes from the solution.