Influence of Strong Ionic Interaction on the Kinetics of Graphite Intercalation Compound Formation.

Graphite intercalation compounds (GICs) of anions have attracted much attention as a positive electrode for use in dual-ion batteries. In this study, GICs of bis(trifluoromethanesulfonyl)amide (TFSA) anions were electrochemically synthesized in ionic liquids with lithium or magnesium salts to investigate the kinetics of GICs formation. By varying the concentrations of LiTFSA or Mg(TFSA) 2 , the activation energy of interfacial anion transfer resistance was discovered to be correlated with the viscosity of the ionic liquid electrolytes. Such a change in activation energy is unique to ionic liquids and not seen in common molecular solvent electrolytes. In addition, ionic liquids with nearly identical viscosities exhibited similar resistances and activation energies. The relationship between the viscosity of ionic liquids and the kinetic parameters of interfacial anion transfer found in this study provides important insights for the construction of dual-ion batteries that aim for both high capacity and high rate capability.