LiFePO_4 - Activated Carbon Composite Electrode as Symmetrical Electrochemical Capacitor in Mild Aqueous Electrolyte

摘要

In this study, a symmetric electrochemical capacitor has been fabricated by adopting the lithiated compound (LiFePO_4)-activated carbon (AC) composite as the core electrode materials. The electrochemical performances of the prepared supercapacitor were studied using cyclic voltammetry (CV) in 1.0 M Na_2SO_3 solution. Experimental results reveal that the maximum specific capacitance of 112.41 F/g is obtained in 40 wt% LiFePO_4 loading on AC electrode in comparison to that of pure AC electrode (76.24 F/g) in 1 M Na_2SO_3. The enhanced capacitive performance of the 40 wt% LiFeO_4 –AC composite electrode is believed attributed to the contribution of synergistic effect of electric double layer capacitance (EDLC) on the surface of AC as well as pseudocapacitance via intercalation/extraction of Na~+, (SO_3)~(2-) and Li~+ ions in LiFePO_4 lattices. The composite electrodes can sustain a stable capacitive performance at least 1000 cycles with only ～5% specific capacitance loss after 1000 cycles. Based on the findings above, 40 wt% LiFeO_4 –AC composite electrodes which utilise low cost materials and environmental friendly electrolyte is worth being investigated in more details.