MSE 298 Seminar: Electrolytes for Rechargeable Aluminum Batteries

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Abstract: Reversible electrochemical reactions of aluminum (Al) is an intriguing topic from both scientific and technological perspectives. The centerpiece of reversible Al electrochemistry is the electrolyte. To date, the overwhelming majority of Al battery research activities utilize Lewis acidic chloroaluminate ionic liquids as the electrolytes. However, the complex nature of these electrolytes, such as corrosiveness, proneness to oxidation and rich coordination, can lead to unintended parasitic reactions. We investigated the chemical compatibility of AlCl3-[EMIm]Cl electrolyte (mixture of aluminum chloride and 1-ethyl-3-methylimidazolium chloride) with V2O5, which is a common cathode material reported in the literature of Al batteries. Our study indicates V2O5 chemically reacts to both Lewis neutral and Lewis acidic AlCl3-[EMIm]Cl. By elucidating the reaction mechanisms, we conclude V2O5 is not a feasible Al storage material in the chloroaluminate ionic liquid electrolytes. To understand the formation mechanism of chloroaluminate anions on organic solvents, we studied the change of coordination structures of AlCl3 in g-butyrolactone (GBL) as a function of molar ratio of AlCl3/GBL. Finally, as an attempt to move beyond chloride-containing electrolytes, we for the first time synthesized and characterized an organic electrolyte based on Al salt with weekly coordinating anions, namely aluminum hexafluorophosphate (Al(PF6)3). These findings could provide guidelines for designing more reliable electrolytes for rechargeable Al batteries.

Bio: Juchen Guo is a professor in the Department of Chemical and Environmental Engineering and the chair of the Materials Science and Engineering Program at UC Riverside. His research interests focus on the interfacial phe-nomena and material properties in electrochemical energy storage systems including lithium metal, lithium-sulfur and multi-valent-ion batteries such as magnesium and aluminum systems. Juchen Guo earned his bachelor's degree in chemical engineering from Zhejiang University in 1999 and his doctorate in chemical engineering from University of Maryland in 2007. He performed postdoctoral studies at University of Maryland from 2007 to 2011 and Cornell University from 2011 to 2012, prior to joining UC Riverside in 2012. He is a recipient of the 2014 Hellman Fellowship and 2018 NSF CAREER Award.