Electrochemical N(CF3SO2)2− Intercalation/de-intercalation into Graphite Electrode as the Positive Electrode Reaction for Mg Secondary Batteries

Abstract

The electrochemical N(CF3SO2)2− (TFSA−) anion intercalation into graphite was studied, aiming at the use for Mg secondary batteries. In order to achieve both the Mg plating/stripping reaction and anion intercalation, the electrolyte solution consisting of Mg2+/glyme = 1 (mol) with hydrofluoroether (HFE) as the diluent was used. The Raman spectrum indicated that all glyme solvated Mg2+-ion, which led the improvement of anti-oxidation durability up to 4.5 V (vs. Mg2+/Mg). The TFSA− anion intercalation took place in the solution with almost 100% of coulombic efficiency. Besides, the charge-discharge test exhibited the discharge plateau over 3.4 V (vs. Mg2+/Mg) with the capacity of ca. 70 mA h g−1. The results indicated the anion intercalation into graphite will be the attractive candidate for Mg secondary batteries.

Keywords

• mg secondary batteries
• anion intercalation
• solvate ionic liquid
• mg plating