ZnO@MnO₂ Core–Shell Nanofiber Cathodes for High Performance Asymmetric Supercapacitors

Abstract

Asymmetric supercapacitors (ASCs) with aqueous electrolyte medium have recently become the focus of increasing research. For high performance ASCs, selection of cathode materials play a crucial role, and core-shell nanostructures are found to be a good choice. We successfully synthesized, ZnO@MnO core-shell nanofibers (NFs) by modification of high-aspect-ratio-electrospun ZnO NFs hydrothermally with MnO nanoflakes. High conductivity of the ZnO NFs and the exceptionally high pseudocapacitive nature of MnO nanoflakes coating delivered a specific capacitance of 907 Fg at 0.6 Ag for the core-shell NFs. A simple and cost-effective ASC construction was demonstrated with ZnO@MnO NFs as a battery-type cathode material and a commercial-quality activated carbon as a capacitor-type anode material. The fabricated device functioned very well in a voltage window of 0-2.0 V, and a red-LED was illuminated using a single-celled fabricated ASC device. It was found to deliver a maximum energy density of 17 Whkg and a power density of 6.5 kWkg with capacitance retention of 94% and Coulombic efficiency of 100%. The novel architecture of the ZnO@MnO core-shell nanofibrous material implies the importance of using simple design of fiber-based electrode material by mere changes of core and shell counterparts.

One-Pot Hydrothermal Synthesis of Novel Cu-MnS with PVP Cabbage-Like Nanostructures for High-Performance Supercapacitors

“…Moreover, previous results suggested that micropores and mesopores with sizes less than ~5 nm have lower activity at high scan rate/current densities. As shown in Figures 7c and S3 (CV curves of Cu-MnS, Cu-MnS with 1PVP and 3PVP with different scan rates), the positive and negative shifts observed at higher scan rates, which replicate the imperfect redox reaction and the loss of a few peaks, indicate partial loss of the redox reaction [38]. Figure 8a shows the GCD measurements for the resulting electrodes tested at a current density of 1 A g −1 in a 2 M KOH solution.…”

PVA assisted ZnO based mesoporous ternary metal oxides nanomaterials: synthesis, optimization, and evaluation of antibacterial activity

“…Within its melting point range of 220°C-400°C; the degradation of its amorphous part at ∼300°C, and the intermolecular decomposition at about 385°C were found to occur [14,15]. The crystalline part of PVA decays at 398°C [16,17], and complete decomposition to yield the carbon and hydrocarbons that led to the liberation of CO 2 gas and resulting in pure ZnO phase occurred in the temperature range of 400°C-500°C [17][18][19].…”

Facile Synthesis and Electrochemical Properties of Perovskite‐type CeMnO3 Nanofibers

“…[19] Moreover, electrospinning is a common technique for energy storage and delivery technology, like supercapacitors, fuel cells, and lithium-ion batteries. [12] In this study, an effective method for synthesizing perovskite-type CeMnO 3 NFs by combining electrospinning and subsequent calcination process was demonstrated. The merits of this method are (i) simple and available synthetic technique that a great variety of materials can be effectively synthesized, (ii) controllable composition for composites that a large diversity of materials can be fabricated, and (iii) cost-effective synthetic process.…”

“…However, poor electron conductivity limits its application into supercapacitors due to the low specific capacitance . As a typical semiconductor, manganese oxide has gained specific attention in electronic devices and supercapacitors thanks to its high bandgap, low cost, abundance, low toxicity, high theoretical capacitance (1370 F g −1 ), variable valence states, and stable chemical properties . As a typical rare earth based‐perovskite, the electrochemical behaviors of LaMnO 3 have been widely investigated owing to its stable thermal and structural properties.…”

“…[10] As a typical semiconductor, manganese oxide has gained specific attention in electronic devices and supercapacitors thanks to its high bandgap, low cost, abundance, low toxicity, high theoretical capacitance (1370 F g À 1 ), variable valence states, and stable chemical properties. [11][12][13][14] As a typical rare earth based-perovskite, the electrochemical behaviors of LaMnO 3 have been widely investigated owing to its stable thermal and structural properties. In addition, LaMnO 3 possesses charge storage ability both in anion and cation vacancies with intercalation and reversible Faradic reactions.…”