China
Africa
Explore chapters and articles related to this topic
Types of Energy Devices and Working Principles
Published in Ram K. Gupta, 2D Nanomaterials, 2022
Yuyan Wang, Yang Liu, Linrui Hou, Changzhou Yuan
Commonly, the pseudocapacitors are classified into three types: (a) underpotential deposition, (b) redox pseudocapacitance (such as MnO2, RuO2, V2O5, or conductive polymer), and (c) intercalation pseudocapacitance (Nb2O5), corresponding processes are illustrated in Figure 5.4b [50]. The mechanism of pseudocapacitors can be summarized as a reversible redox reaction at the interface of the electrode/electrolyte, which is accompanied by the charge transfer, thus achieving the charge storage. During the energy storage process of the pseudocapacitor, a rapid redox reversible reaction will occur on the surface of the electrode active substance, and a large amount of charge or ion transfer can be carried out in a short time [51]. Different physical processes and with different types of materials determine these three different mechanisms, detailed processes are as below:
Emerging Materials for High-Performance Supercapacitors
Published in Anurag Gaur, A.L. Sharma, Anil Arya, Energy Storage and Conversion Devices, 2021
Pseudocapacitor materials include metal oxides, hydroxides, nitrides, intercalating materials, and polymers. These materials exhibit high capacitance due to the redox reaction. Every molecule participates in the faradaic charge transfer, and thus these materials exhibit high energy density. However, compared to EDLC materials, they exhibit low power density and low-rate capability due to kinetic limitations on the charge transfer reaction. However, pseudocapacitive materials suffer from a low electrochemically active surface area (ESA) that gravely impedes the capacitance obtained from these materials [Graves and Inman, 1965; Conway and Pell 2003]. Pseudocapacitive materials have a high theoretical capacitance ranging from 200 to 3000 Fg−1, owing to their redox behavior. Such high capacitance can lead to high energy density as E = 1/2CV2. However, the practical capacitance or the realizable capacitance remains low; this reduced practical capacitance results from the low and inefficient ESA and high resistance [Silva et al. 2019]. Also, since the electrochemical processes are the surface processes occurring only at the electrode–electrolyte interface, the material inaccessible to the electrolyte remains dead that decreases the gravimetric capacitance of pseudocapacitive material [Radhakrishnan et al. 2011]. Thus, it is necessary to increase the ESA, improve the electrolyte accessibility, and reduce dead volume for increasing or improving the performance of the pseudocapacitive material for wide-scale applications.
Three Dimensional Porous Binary Metal Oxide Networks for High Performance Supercapacitor Electrodes
Published in Ranjusha Rajagopalan, Avinash Balakrishnan, Innovations in Engineered Porous Materials for Energy Generation and Storage Applications, 2018
Balasubramaniam Saravanakumar, Tae-Hoon Ko, Santhana Sivabalan Jayaseelan, Jiyoung Park, Min-Kang Seo, Byoung-Suhk Kim
Based on the energy storage mechanism, supercapacitors can be classified as electrochemical double layer capacitor (EDLC), pseudocapacitor and hybrid capacitor. In EDLC device, the charges are stored by the formation of electrostatic double layer at the interface between electroactive material and electrolyte by adsorption/desorption process. Mostly, carbon materials with higher surface area are utilised for EDLC devices, which are symmetric devices. The performances of the EDLC highly rely on the active surface area and nature of pore structure in the electrode materials. The higher active surface area and hierarchal pore nature of the electrode allows ions to move freely to the inner parts the electrode and facilitates the formation of electric double layer on the pore walls. This results in higher charge/discharge capability due to faster ion movement and shorter diffusion path length. The pseudocapacitor is another class of supercapacitor device, which stores the charge through fast, reversible faradic reactions.
KOH-assisted synthesis of oxygen-rich activated carbon derived from biomass sugar palm midrib as performance electrode cell supercapacitor
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Rakhmawati Farma, Haliza Putri, Irma Apriyani
Biomass is an organic material in the form of waste from primary products and is repeatedly produced to provide a sustainable source of energy (Wang et al. 2019). Biomass as a carbon precursor has economic value, which is renewable, environmentally friendly with abundant availability, sustainable, and nontoxic (Farma, Winalda, and Apriyani 2023). Biomass contains cellulose, hemicellulose, lignin, and carbon elements, hence it can be processed into activated carbon (AC) which is applied as energy storage system such as supercapacitors (Naseri et al. 2022). The supercapacitors are energy storage devices separated by a permeable ion membrane and an ionic solution connected by two conductors. Furthermore, the supercapacitor performance is related to the energy storage mechanism which is divided into two, namely double layer electrochemical capacitor and pseudocapacitor (redox supercapacitor) (Saikia et al. 2020). Advantages of the supercapacitor as energy storage devices namely a fast charge-discharge, long-life cycle, simple working principle, and safety (Vinayagam et al. 2020). The supercapacitor consists of four important components, namely the separator, current collector, electrolyte, and electrode. In the component, the electrode is the most important in determining the specific capacitance of the cell and can be made of metal oxides, polymers, and activated carbon (De et al. 2020).
Preparation of bulk doped NiCo2O4 bimetallic oxide supercapacitor materials by in situ growth method
Published in Inorganic and Nano-Metal Chemistry, 2022
Ling Li, Baozhong Liu, Shaogang Hou, Qiming Yang, Zichuang Zhu
Because the introduction of another metal element into the single metal active material can regulate the surface reaction, which can largely improve the utilization rate of pseudocapacitor material, bimetallic compounds are more and more used in the recent preparation of supercapacitor electrodes. The common bimetallic compounds are: iron manganese compounds, nickel zinc compounds, cobalt zinc compounds, cobalt copper compounds, cobalt molybdenum compounds, and nickel cobalt compounds. Among them, cobalt nickel compounds are the most common because of their high capacitance, low price, and low requirement for preparation. Therefore, compared with other bimetallic compounds, nickel cobalt bimetallic compounds are more suitable for supercapacitor active electrode materials. Transition metal oxides can be used not only in supercapacitors, but also in batteries.[26–28]. Among the Ni-Co bimetallic compounds, NiCo2O4 has become the key research object in the field of materials because of its easy preparation, low cost, and environmental friendliness.[29–31] The electrode made of NiCo2O4 has the characteristics of long cycle life, stable chemical properties, many oxidation states, and high electrochemical activity, so it has broad prospects. However, NiCo2O4 also has some disadvantages like small specific surface area, low utilization of active substances, poor conductivity, and poor cycle stability. Therefore, it is necessary to modify NiCo2O4 with other materials.
Recent progress in the conversion of biomass wastes into functional materials for value-added applications
Published in Science and Technology of Advanced Materials, 2020
EDLC and pseudocapacitors are two device schemes of supercapacitors. However, the applications of pseudocapacitor are limited because of their poor cycle stability and low electrical conductivity [138]. Due to the high-power density and superior charge-discharge stability of EDLC, more studies are focusing on them. Generally, different forms of carbon-based electrode materials include AC [135], biochar-based AC [16], graphitic carbon [119], microporous carbons [136], and so on. Gao et al. [135] transformed rice husk into AC through KOH activation. Because SiO2 nanocrystals were encompassed by a carbon matrix in the rice husk, the AC kept the size and shape, and had an increased ordering degree of carbon which showed great high-power solving performance and electrochemical cycle capacity. Moreover, He et al. [16] recycled loblolly pine chips to fabricate biochar-based ACs by NaOH activation and then assembled it into EDLCs as electrode materials due to its high surface area and huge pore volume.