Influence of electrochemically deposited polypyrrole layers on NiCo ₂ O ₄ -decorated carbon fiber paper electrodes for high-performance hybrid supercapacitor applications

Abstract

Recently, as environmentally clean and sustainable energy sources, high-performance electrochemical energy storage devices, such as secondary batteries and supercapacitors have received great attention [1-3]. In particular, supercapacitors have received huge interest due to the high power density, long-term cycle stability, fast charging/discharging process, safety and low maintenance cost [4], and therefore are widely used for different applications such as consumer electronics, portable devices, electric vehicles, memory backup devices and public transportation etc [5][6][7]. In order to fulfill the growing energy density demands for next generation supercapacitors, a dramatic improvement of energy density (E = (CV 2 )/2) of supercapacitors is still one of the great challenges, which can be generally accomplished by increasing the specific capacitance (C) and operation potential window (V) [8,9]. Accordingly, the development of high-performance pseudo-capacitors and hybrid supercapacitors involves compounding the high surface area carbon materials with transition metal oxides and/or conducting polymers [10][11][12][13][14][15]. However, poor electrical conductivity (mostly due to inferior conductivity of transition metal oxides) and serious charge transfer resistance (R CT ) (due to poor interface contact/ adhesion between active materials and current collectors) have been limited to improve the performance of the supercapacitor electrodes in view of energy density, power density, cycle stability, rate capability and charge/

A Facile Fabrication of Ordered Mesoporous Carbons Derived from Phenolic Resin and Mesophase Pitch via a Self-Assembly Method

“…Figure 6 shows the CV responses of MC-meso-10 ( Figure 6 a), OMC-meso-10 ( Figure 6 b) and OMC-meso-20 ( Figure 6 c), respectively. The pseudo-rectangular behavior of CV curves was observed for all the MC-modified electrodes at different scan rates, confirming the electric double-layer capacitive (EDLC) nature of as-prepared carbon materials [ 42 , 43 ]. That is, the charge storage occurs via a double-layer formation between the interface of the electrode and electrolytes without any faradic process.…”

Engineering the Hierarchical Heterostructures of Zn–Ni–Co Nanoneedles Arrays@Co–Ni-LDH Nanosheets Core–Sheath Electrodes for a Hybrid Asymmetric Supercapacitor with High Energy Density and Excellent Cyclic Stability

“…Figure S6 shows the CV (a), GCD (b), rate capability curves (c), and Nyquist plot (d) for NGH. As depicted in Figure S6a, all CV curves showed a quasirectangular shape in the sweep rate 5–200 mV s –1 , suggesting the typical electric double-layer capacitance (EDLC) characteristics . The shape of the CV curves did distort as the scan rate increased from lower (5 mV s –1 ) to higher (200 mV s –1 ), indicating the excellent rate capability and noticeable electrochemical reversibility of the NGH electrode.…”

“…As depicted in Figure S6a, all CV curves showed a quasirectangular shape in the sweep rate 5−200 mV s −1 , suggesting the typical electric double-layer capacitance (EDLC) characteristics. 51 The shape of the CV curves did distort as the scan rate increased from lower (5 mV s −1 ) to higher (200 mV s −1 ), indicating the excellent rate capability and noticeable electrochemical reversibility of the NGH electrode. Figure S6b shows the GCD curves of NGH at different current densities from 1 to 10 A g −1 within the potential window from −1.0 to 0 V. The maximum specific capacitance of the NGH electrode was evaluated to be 268, 222, 203, 176, and 132 F g −1 at the current densities of 1, 2, 3, 5, and 10 A g −1 (Figure S6c), respectively, indicating a rate capability of 49.25%.…”

Hybrid Electrodes Based on Zn–Ni–Co Ternary Oxide Nanowires and Nanosheets for Ultra-High-Rate Asymmetric Supercapacitors

“…in the modern society. However, most of these new inventions require energy storage devices with an altitudinous performance featuring high energy and power densities. − Despite the availability of various energy storage devices, batteries and electrochemical capacitors/supercapacitors (SCs) have sparked extensive research interest to meet the mushrooming demand for energy storage applications due to their high energy density and high power density, respectively. − SCs with excellent power density also offer a fast charging time and long life span but have relatively low energy density compared to batteries (about 200 Wh kg –1 ), which hinder their practical applications in the modern electronics industry. − To overcome these shortcomings, the concept of an asymmetric supercapacitor (ASC) has been introduced, presenting the dual advantages of an SC and a battery in a single device. − Nowadays, the research on and investigation into ASCs have earned foremost attention owing to their flaming energy and power densities, fast charge/discharge rates, and high cyclic stability, which bridge the gap between the batteries and SCs. , Generally, ASCs are composed of a combination of pseudocapacitor/battery-like (operating through a faradic reaction) and capacitive-like (storing the charges via an electrochemical double-layer mechanism) materials as positive and negative electrodes for higher energy and power sources. , Therefore, the overall performance of the device is expected to be significantly improved in terms of capacity and driving potential window, thereby increasing the energy density of the ASC in agreement with the equation E = 1/2 CV 2 , where C represents the specific capacitance value and V is the operating voltage . Nevertheless, potential applications of ASC have been still limited by a lack of suitable electrode materials with better electrochemical performance in terms of nonstatic capacity, rate capability, and cyclic stability.…”

“…Until now, diverse materials such as carbon nanomaterials, conductive polymers, and various transition-metal oxides have been considered as promising pseudocapacitive electrode materials. − Principally, the mixed transition-metal oxides (MTMOs) comprising two or three transition-metal cations in their various nanostructures are growing as auspicious ASC electrode materials due to numerous advantages, such as improved electronic conductivity and higher electrochemical activities as offered by multiple oxidation states for an efficient reversible faradic reaction. , The increment in the electrochemical performance primarily initiated with the chemical composition of MTMOs, which exhibits a synergistic effect as induced by different valence states of metal ions on redox reactions. , For instance, the electrical conductivity and capacitive performance of the Zn–Ni–Co ternary oxide (ZNCO) electrodes can be intensified by zinc (Zn) with favorable electrical conductivity, nickel (Ni) with different oxidation states, and cobalt (Co) with an extended potential window, providing enhanced electrical conductivity and higher capacity. − In addition, the affiliation of multiple metal ions may create polyphase metal oxides, creating plentiful structural defects. These unique features of MTMOs are expected to provide a proper ion diffusion pathway and more electroactive sites for pseudocapacitive reactions during repeated charge–discharge cycles.…”