In order to shed more light on the phenomena, ex situ XRD was
applied for the crystal structure determination of graphitic
electrodes. Fig. 4 shows the XRD patterns of graphite electrodes
in AC/graphite capacitors charged to 3.5 V. The (0 0 2) diffraction
peak of graphite is located at 26.5 corresponding to a d-spacing of
3.354 Å. Once the voltage of AC/graphite capacitors climbs up to
3.5 V, the splitting of (0 0 2) diffraction peak occurred in the PC- and
GBL-solutions, which is a definite signal for the intercalation of
ClO4
. By the calculation methods as introduced in previous
studies [31,32],