Effect of the Electrolyte Solution on the ElectrochemicalBehaviors of Graphene-like Graphite as the Cathode of Dual-Ion Batteries

The charge–discharge measurements of graphene-like graphite (GLG) as a cathode of dual-ion battery were performed in various electrolyte solutions, and the effect of salt concentration and solvents on the first discharge capacity of GLG prepared at 700 °C was discussed. The first discharge capacity increased with the increase in the salt concentration and then decreased. The concentrations where the capacity became maximum were higher for the electrolyte solutions containing ethyl methyl carbonate than propylene carbonate. Based on the results in the electrolyte solutions containing LiBF₄, the influence of the surface film on GLG was negligible. The galvanostatic intermittent titration of the GLG electrodes was performed in various electrolyte solutions to estimate the equilibrium potential and solution resistance. The former decreased linearly as the salt concentration increased above 1 M, and the slope became larger for electrolyte solutions containing propylene carbonate. This is not Nernstian behavior and indicates that solvent molecules have some influence on the intercalation of anions. On the other hand, the solution resistance decreased as the salt concentration increased and then increased. This behavior strongly indicated that it is more important to determine the first discharge capacity of GLG than equilibrium potential.