Transition Metal Oxide Electrode Materials for Supercapacitors: A Review of Recent Developments

Abstract

In the past decades, the energy consumption of nonrenewable fossil fuels has been increasing, which severely threatens human life. Thus, it is very urgent to develop renewable and reliable energy storage devices with features of environmental harmlessness and low cost. High power density, excellent cycle stability, and a fast charge/discharge process make supercapacitors a promising energy device. However, the energy density of supercapacitors is still less than that of ordinary batteries. As is known to all, the electrochemical performance of supercapacitors is largely dependent on electrode materials. In this review, we firstly introduced six typical transition metal oxides (TMOs) for supercapacitor electrodes, including RuO2, Co3O4, MnO2, ZnO, XCo2O4 (X = Mn, Cu, Ni), and AMoO4 (A = Co, Mn, Ni, Zn). Secondly, the problems of these TMOs in practical application are presented and the corresponding feasible solutions are clarified. Then, we summarize the latest developments of the six TMOs for supercapacitor electrodes. Finally, we discuss the developing trend of supercapacitors and give some recommendations for the future of supercapacitors.

N-Dopant-Mediated Growth of Metal Oxide Nanoparticles on Carbon Nanotubes

“…The voltammograms of the NCNTs in Figure S7A show a nearly rectangular shape, indicating charge storage by the adsorption–desorption mechanism forming electrical double layers (EDLs) [ 34 ]. In contrast, MnO x /NCNT and RuO x /NCNT exhibit pseudo-capacitive behaviors, represented by Faradaic redox peaks in the voltammograms ( Figure S7B,C ) [ 35 ]. Owing to the additional energy storage by the redox reactions on the surfaces of metal oxide nanoparticles [ 36 ], MnO x /NCNT and RuO x /NCNT show an enhanced charge storage capacity of 141.1 F/g and 208.2 F/g at a scan rate of 25 mV/s, respectively, compared to 116.6 F/g for the NCNT electrode ( Figure 5 A).…”

Synthesis and Characterization of Supercapacitor Materials from Soy

“…They are optimal because they have the capability to store energy both electrostatically via electrochemical double layer (EDL) formation, as well as electrochemically via redox reactions of electrolyte ions adsorbed onto the surface of the active supercapacitor material [8,9]. Today's commercial supercapacitors utilize expensive active materials made from metals and metal oxides that show dull cycling stability [10] and require timely synthesis protocols [11][12][13][14][15]. Thus, it is imperative to find more economical materials that can be easily utilized as supercapacitor materials.…”

Preparation of Network-Structured Carbon Nanofiber Mats Based on PAN Blends Using Electrospinning and Hot-Pressing Methods for Supercapacitor Applications

“…The development of advanced electrode materials with excellent energy storage properties is the major task for the fabrication of supercapacitor devices in real-world applications. Hence, the development of new electrode materials with improved electrochemical performance through a simple, cost-effective, and green approach is highly desirable [ 7 , 8 ]. So far, tremendous research efforts have been made to increase the energy density of supercapacitors without sacrificing their high power capability, rate capability, etc.…”

“…So far, tremendous research efforts have been made to increase the energy density of supercapacitors without sacrificing their high power capability, rate capability, etc. Carbon nanomaterials, transition metal oxides/hydroxides, and conducting polymers are the most commonly used electrode materials for supercapacitors [ 8 , 9 , 10 , 11 ]. Among them, carbon-based materials are considered possible candidates for flexible energy storage applications owing to their large specific surface area, high electrical conductivity, light weight, flexibility, and fast ion response for reduced ion transport path, etc.…”