A novel melt infiltration method promoting porosity development of low-rank coal derived activated carbon as supercapacitor electrode materials

Highly Porous Graphitic Activated Carbons from Lignite via Microwave Pretreatment and Iron-Catalyzed Graphitization at Low-Temperature for Supercapacitor Electrode Materials

“…The CV curves of AC-2FeHLH-5-41.4(H) electrode always presented a quasi-rectangular shape with the increase in scan rate from 20 mV s −1 to 200 mV s −1 , as seen in Figure 7a, but distorted CV curves of the AC electrode and the smaller current density for PGBC and MI-AC-2 were found in previous publications [40,41], indicating a fast charge transport in AC-2FeHLH-5-41.4(H). In addition, compared with the AC electrode [41], the perfect isosceles triangle shapes of AC-2FeHLH-5-41.4(H) at different current densities can be seen in Figure 7b, indicating excellent charge and discharge qualities in terms of an electric double layer capacitor (EDLC). As shown in Figure 7c, the AC-2FeHLH-5-41.4(H) electrode had much higher specific capacitances (224 F g −1 at 1 A g −1 ) than that of PGBC (40 F g −1 at 1 A g −1 ), MI-AC-2(211 F g −1 at 1 A g −1 ), and AC (115 F g −1 at 1 A g −1 ).…”

“…The result of the Nyquist plots for the AC-2FeHLH-5-41.4(H) electrode, in the frequency range from 10 mHz to 100 KHz, is given in Figure 7d. There were clear impedance loops for AC-2FeHLH-5-41.4(H) with a relatively small semicircle radius in the high frequency region relative to a lower slope of AC in the previous publications [41], indicating a small charge transfer resistance. Then, the fitting equivalent circuit model was obtained by the coupled nonlinear Schrodinger equation (CNLS) method, as shown in Figure 7d.…”

“…The result of the cycling stability test for AC-2FeHLH-5-41.4(H) electrode at a current density of 5 A g −1 is shown in Figure 7e. The AC-2FeHLH-5-41.4(H) electrode kept about 96% of the capacitance after 10,000 cycles at a current density of 5 A g −1 , rather than an obvious reduction of PGBC (84%) [40] at 5000 cycles and AC (85%) at 10,000 cycles [41]. Therefore, AC-2FeHLH-5-41.4(H) presented an even greater cycling stability.…”

“…As shown in Figure 7c, the AC-2FeHLH-5-41.4(H) electrode had much higher specific capacitances (224 F g −1 at 1 A g −1 ) than that of PGBC (40 F g −1 at 1 A g −1 ), MI-AC-2(211 F g −1 at 1 A g −1 ), and AC (115 F g −1 at 1 A g −1 ). [40,41] With the increase of current densities, AC-2FeHLH-5-41.4(H) always retained high values (170 F g −1 at 30 A g −1 ), rather than an obvious capacitance decay for PGBC (25 F g −1 at 30 A g −1 ), MI-AC-2 (160 F g −1 at 30 A g −1 ), and AC (45 F g −1 at 30 A g −1 ). [40,41] This result also showed an excellent charge-discharge capability performance for the AC-2FeHLH-5-41.4(H) electrode.…”

“…[40,41] With the increase of current densities, AC-2FeHLH-5-41.4(H) always retained high values (170 F g −1 at 30 A g −1 ), rather than an obvious capacitance decay for PGBC (25 F g −1 at 30 A g −1 ), MI-AC-2 (160 F g −1 at 30 A g −1 ), and AC (45 F g −1 at 30 A g −1 ). [40,41] This result also showed an excellent charge-discharge capability performance for the AC-2FeHLH-5-41.4(H) electrode. Furthermore, the kinetics of the electrochemical reaction was studied by EIS.…”