Enhanced electrochemical energy storage devices utilizing a one-dimensional (1D) α-MnO2 nanocomposite encased in onion-like carbon

Abstract This work describes the fabrication of a novel one-dimensional (1D) α-MnO 2 nanorods encased in onion-like carbon (or) carbon nano-onions (OLC) via microwave irradiation techniques employing electrolytic manganese dioxide (EMD), which is especially beneficial for rapid ion and electron transfer, and great structural stability. The composite of α-MnO 2 and OLC demonstrates exceptional performance as an electrode across various electrochemical energy storage systems, including zinc-ion batteries (ZIB), sodium-ion batteries (SIB), and supercapacitors (SC) than the pristine α-MnO 2 . In SIB systems, the composite exhibits a specific capacity of 266 mAh g −1 at initial cycle with 50% capacity retention over 500 cycles, whereas the pristine electrode delivers only 39% capacity retention. The rapid yet controlled charge transfer kinetics facilitated by OLC addition in the α-MnO 2 matrix outperforms as the ZIB cathode with an excellent specific capacity of 476 mAh g −1 with 100% capacity retention, while the pristine sample exhibits 77.5% capacity retention. As a SC electrode, the α-MnO 2 /OLC composite exhibits better electrochemical properties such as rectangular behavior, increased specific capacitance (792 F g −1 ), excellent capacity retention at high current densities, and others. The higher surface area that could be offered by the OLC to the α-MnO 2 matrix facilitates the improved electrochemistry in the pristine sample and this kind of modification can be a viable solution to overcome the limitations of α-MnO 2 for electrochemical energy storage applications. It is important to note that the performance outputs of α-MnO 2 /OLC composite are far better than the regular carbon (graphite, graphene) in α-MnO 2 electrodes. Further, OLC provided with high surface area and ordered morphology can play the role of conductivity booster, structural stabilizer, and electrochemical active material in all the energy storage applications which may give a significant research attention in near future.