Multivalent-ion battery technology is gaining interest to meet the increasingly diverse energy storage needs we face today. Magnesium and calcium ion batteries are attractive for their high theoretical energy density, ability to use solid metal anodes, and safety advantages. The field of stable electrolytes that display room temperature electrochemical plating and stripping of calcium remains limited. Of utmost importance is the ability to produce a robust electrolyte with a wide electrochemical window to enable the development of high-potential cathode systems. Currently, a few state-of-the-art Mg-ion and Ca-ion electrolyte systems are prevalent in the electrolyte literature (Mg[TPFA]2, where [TPFA]– = [Al(OC(CF3)3)4]– and M[BHFIP]2, where M = Mg, Ca; [BHFIP]– = [B(OCH(CF3)2)4]–). A common theme among these salts is the use of a weakly coordinating anion (WCA) pairing fluorinated alkoxides with a tetracoordinate Al/B center. What is less understood are the inherent properties explaining their robustness and the potential pathways for failure and decomposition that hinder electrolyte activity. Using computationally informed design, we synthesized and studied the structure-property relationship of a series of analogous calcium alkoxy borates and aluminates with varying bond strengths. The synthetic viability of these salts is reported with their resulting reductive and oxidative stability using structural characterization and electrochemical analyses.

Probing stabilities of weakly coordinating anions for multivalent electrolytes

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ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.