Effect of Interaction among Magnesium Ions, Anion, and Solvent on Kinetics of the Magnesium Deposition Process
Version 2 2020-12-16, 22:33
Version 1 2020-12-15, 13:46
journal contribution
posted on 2020-12-16, 22:33 authored by Feilure Tuerxun, Kentaro Yamamoto, Toshihiko Mandai, Yoshitaka Tateyama, Koji Nakanishi, Tomoki Uchiyama, Toshiki Watanabe, Yusuke Tamenori, Kiyoshi Kanamura, Yoshiharu UchimotoTo
clarify the effects of anion species and solvents on the Coulombic
efficiency and polarization of magnesium deposition/dissolution reactions,
the anode/electrolyte interfacial behavior of magnesium tetrakis(hexafluoroisopropyloxy)
borate (Mg[B(HFIP)4]2) and magnesium bis(trifluoromethanesulfonyl)amide
(Mg(TFSA)2) was investigated and compared in triglyme and
2-methlytetrahydrofuran (2-MeTHF). When using triglyme, which has
strong interaction with magnesium ions, decomposition of [B(HFIP)4]− in Mg[B(HFIP)4]2/triglyme was hard to occur because of the high reduction stability
of the uncoordinated [B(HFIP)4]− anion,
resulting in significantly higher Coulombic efficiency and smaller
polarization than Mg(TFSA)2/triglyme. When 2-MeTHF was
used as the solvent, magnesium deposition/dissolution reactions occurred
in the Mg[B(HFIP)4]2/2-MeTHF electrolyte but
not in the Mg[TFSA]2/2-MeTHF electrolyte. This is because
the coordinated [B(HFIP)4]− anion in
Mg[B(HFIP)4]2/2-MeTHF is stable at the magnesium
deposition potential. However, the reductive stability of the coordinated
[B(HFIP)4]− anion is inferior to that
of the uncoordinated [B(HFIP)4]− anion,
resulting in the Mg[B(HFIP)4]2/2-MeTHF Coulombic
efficiency being lower than that of Mg[B(HFIP)4]2/triglyme. Our results indicate that solvents that could not be used
with Mg(TFSA)2 are suitable in weakly coordinating anion
electrolytes, such as Mg[B(HFIP)4]2. Controlling
the interaction between magnesium ions and anions by selecting suitable
anions and solvents is essential for designing new electrolytes for
magnesium rechargeable batteries.
