Self-assembled carbon wrapped manganese cobaltite nano-composite with promising electrochemical performance for symmetric and asymmetric supercapacitor device

Abstract

The growing energy requirements of modern society have led to an intensive search for advanced supercapacitor (SC) electrode materials. Binary transition metal oxides with excellent supercapacitive performance are among the most promising materials. However, the phase transformation of these metal oxides during repeated charging/discharging is a major concern, which depletes their cyclic performance. Coating metal oxides with carbon can provide structural stability to the metal oxide, thereby increasing their cyclic life. In addition, the highly conductive carbon enhances the capacitance of metal oxides by allowing the effective transfer of charges from MnCo2O4 to the current collector. In this study, self-assembled carbon-wrapped MnCo2O4 composite has been prepared through a two-step process involving hydrothermal and solution-mixing processes. The structural/electrochemical performances of the composites have been investigated. The optimized composite offered a maximum capacitance of 626.8 Fg−1 withholding 98 % of capacitance for 6000 cycles. Furthermore, the electrochemical performance of the composite has also been tested in an all-redox symmetric SC (SSC) as well asymmetric (ASC) configuration. In the symmetric cell, 30.2 Whkg−1 of energy is reported for 1.6 kWkg−1 of power. The asymmetric cell with the optimized composite as a cathode and MnO2/Activated carbon as an anode was fabricated. The ASC displayed 45.5 Whkg−1 of energy corresponding to 10 kWkg−1. Three SSCs/ASCs in series illuminated a panel of 39 red-LEDs for 9 and 15 min, respectively. The results suggest the promising performance of such composites for hybrid supercapacitors. Thus, the fabrication of all-redox-type SSCs/ASCs can be a futuristic approach for hybrid storage systems.