High energy and excellent stability asymmetric supercapacitor derived from sulphur-reduced graphene oxide/manganese dioxide composite and activated carbon from peanut shell

Nanorods/fibers, nanosheet and nano-flower like structure were effectively synthesized from sulphur-reduced graphene oxide (RGO-S) and sulphur-reduced graphene oxide/manganese dioxide (RGO-S/MnO2) composites for supercapacitor applications. Structural, chemical composition and morphological analysis reveal an effective synthesis of the RGO-S and RGO-S/MnO2 composite. Electrochemical mea-surements of the optimized mass loading of MnO2 on RGO-S in a three electrode configurations revealed a specific capacitance of 180.4 F g(-1) compared to 75.2 F g(-1) of the pristine sample at 1 A g(-1) in 2.5 M KNO3 electrolyte. An assembled asymmetric device consists of optimized RGO-S/MnO2 as positive electrode and activated carbon from peanut shell (AC-PS) as a negative electrode delivered a high specific energy of 71.74 Wh kg(-1) with its corresponding specific power of 850 W kg(-1) at 1 A g(-1). It was observed that even at high specific current of 5 A g-1 the device was able to maintain a specific energy of 55.30 Wh kg(-1). An excellent stability with capacitance retention of 94.5% and columbic efficiency of 99.6% up to 10, 000 cycles was recorded for the device at 5 A g(-1). The device demonstrated a very good stability after being subjected to a voltage holding of up to 90 h and an outstanding self-discharge of about 1.45 V was recorded within the first 10 h and 1.00 V after 72 h from its maximum potential of 1.7 V. (C) 2020 Elsevier Ltd. All rights reserved.