MnMoO4 nanorods-encapsulated carbon nanofibers hybrid mat as binder-free electrode for flexible asymmetric supercapacitors

In this work, the in-situ formation of MnMoO4 nanoparticles and simultaneous encapsulation within the porous carbon nanofiber (CNF) matrix through electrospinning-carbonization-thermal annealing processes were carried out. The results of various spectroscopic and morphological analyses confirmed the successful formation of rectangular-shaped MnMoO4 nanorods within the CNF matrix. The MnMoO4@CNF hybrid yielded a maximum specific capacitance of 389.7 F/g at 0.1 A/g, which is 3-folds more than that of CNF (123.4 F/g). The MnMoO4@CNF symmetric cell with an aqueous KOH electrolyte possessed a maximum energy density of 54.12 Wh/kg at a power density of 10 W/kg. The excellent capacitive performances of as-prepared MnMoO4@CNF nanofibers could be ascribed to their high specific surface area (229.35 m2/g) with wide mesoporous distribution (3-13 nm) and enhanced reactivity of the nano-sized MnMoO4 nanoparticles. The hybrid electrode demonstrated excellent cyclic stability with capacitance retention of 92.1% after 5000 cycles, suggesting restricted extrication of metal oxide from the CNF matrix during the charge-discharge process. A flexible solid-state asymmetric supercapacitor was assembled by using MnMoO4@CNF hybrid mat as a positive electrode and activated carbon cloth as a negative electrode. The polymer gel electrolyte (PVA + KOH) was used as electrolyte-cum-separator. The as-prepared MnMoO4@CNF//AC cell yielded a highest energy density of 37.46 Wh/kg and an equivalent power density of 278 W/kg. The present investigation could open new horizons in developing next-generation flexible solid-state supercapacitors for wearable electronics.