Available on-demand - *S.EN08.02.01
Development of Magnesium Electrolytes—From Chloride Mixtures to Weakly Dissociated Anions
Chen Liao1,2
Argonne National Laboratory1,Joint Center of Energy Storage Research2
Show Abstract
The fossil fuel energy crisis causes significant geopolitical stress, and renewable energy such and wind, tide and solar is a green solution to this problem. Energy storage is required for any renewable energy utilization as they are of intermittent nature with usually high production during off-peak hours and low production in peak hours.
Lithium ion battery is the main workhorse for portable electronics and portable tools and start adopting the market of electric vehicles, as well as electrochemical energy storage. However, they are reaching their maximum performance and a new breakthrough in electrochemical energy storage is necessary for a wide adaption of renewable energy. Multivalent ion batteries, particularly Mg and Ca, are of high interest because of their very electropositive electrochemical potentials: Mg has a reduction potential of -2.4 V vs NHE, while Ca has a reduction potential of -2.9 V vs NHE. Other favorable properties include high volumetric energy density and high crustal abundance.
The development of Mg has been mostly impeded by both the cathode and electrolyte developments, unlike its counterpart Li ion, Mg is notoriously famous for formation of a strong bond with oxygen and does not move easily in the lattice of MgO. A premise for a working Mg ion battery is that the surface of the Mg metal cannot be passivated in order to facilitate reversible Mg dissolution/deposition. A classical way of conditioning or preparing the Mg metal surface is either to provide a Cl- in a Mg solution.(1,2) The limited anodic stability of the Cl- would be problematic for Mg ion batteries because of corrosion issue with current collector. Using high-purity Mg salts with weakly associated anion (WCA) such as trifluorosulfonylimide (TFSI) (3) and carborane (4) has been a standard practice in the field since 2015. In 2019, our group introduced a new WCA group for the MV salts, the t-butylperfluoroaluminate ([TPFA]− = [Al{OC(CF3)3}4]−) anion for Mg salts,(5) and demonstrated the highly reversibility of deposition/dissolution, unprecedented anodic stability, and lack of passivation layer formation during the high potentiostatic hold. The favorable properties of the salt make it a friendly anion for the quest of cathode development, especially the transition metal oxide spinels for Mg ion batteries.
We will cover the brief history of the development of Cl- containing electrolyte in our group since 2014 and will present the detailed electrochemical performance, and collaborated work on the decomposition mechanism understanding, solvation behavior in O-donor solvents, and expansion of these research
(1) Liao, C.; Sa, N.; Key, B.; Burrell, A. K.; Cheng, L.; Curtiss, L. A.; Vaughey, J. T.; Woo, J.-J.; Hu, L.; Pan, B. The unexpected discovery of the Mg (HMDS) 2/MgCl 2 complex as a magnesium electrolyte for rechargeable magnesium batteries. Journal of Materials Chemistry A 2015, 3 (11), 6082.
(2) Aurbach, D.; Lu, Z.; Schechter, A.; Gofer, Y.; Gizbar, H.; Turgeman, R.; Cohen, Y.; Moshkovich, M.; Levi, E. Prototype systems for rechargeable magnesium batteries. Nature 2000, 407 (6805), 724.
(3) Ha, S.-Y.; Lee, Y.-W.; Woo, S. W.; Koo, B.; Kim, J.-S.; Cho, J.; Lee, K. T.; Choi, N.-S. Magnesium(II) Bis(trifluoromethane sulfonyl) Imide-Based Electrolytes with Wide Electrochemical Windows for Rechargeable Magnesium Batteries. ACS Applied Materials & Interfaces 2014, 6 (6), 4063.
(4) Carter, T. J.; Mohtadi, R.; Arthur, T. S.; Mizuno, F.; Zhang, R.; Shirai, S.; Kampf, J. W. Boron Clusters as Highly Stable Magnesium-Battery Electrolytes. 2014, 53 (12), 3173.
(5) Lau, K.-C.; Seguin, T. J.; Carino, E. V.; Hahn, N. T.; Connell, J. G.; Ingram, B. J.; Persson, K. A.; Zavadil, K. R.; Liao, C. Widening Electrochemical Window of Mg Salt by Weakly Coordinating Perfluoroalkoxyaluminate Anion for Mg Battery Electrolyte. J. Electrochem. Soc. 2019, 166 (8), A1510.