Effect of Cl− and TFSI− anions on dual electrolyte systems in a hybrid Mg/Li4Ti5O12 battery

•Mg stripping and deposition in the presence of Cl− and TFSI− anions.•Increased polarisation when TFSI− is added.•Detrimental effect of TFSI− anions.•Lithium has minor influence on stripping and deposition of Mg.

Dual electrolyte systems based on APC electrolyte mixed with either LiCl or LiTFSI are compared in a hybrid Mg/Li4Ti5O12 battery. Their comparison points to the detrimental effect of TFSI− anions on the battery performance through increase of polarization for Mg stripping and subsequent capacity fade. The effect is further explored through the study of Mg deposition/stripping in a dual electrolyte system and its comparison with conventional Mg electrolyte. Again, the detrimental effect of TFSI− anions is confirmed through the increase of polarization and decrease of the Coulombic efficiency, while Cl− anions have a minor beneficial effect on both. We hypothesize that the passivation of Mg metal in TFSI− anions containing electrolytes is the likely cause.

Graphical abstractDownload high-res image (101KB)Download full-size image