Molecular Insights into Carbon Supercapacitors Based on Room-Temperature Ionic Liquids

Abstract

The performance of supercapacitors is determined by the electrical double layers (EDLs) formed at electrolyte/electrode interfaces. To understand the energy storage mechanism underlying supercapacitors, molecular dynamics (MD) simulations were used to study the capacitive behavior of carbon-based supercapacitors with room-temperature ionic liquid (RTIL) electrolytes. The performance of porous supercapacitors was found to be correlated with the ion/pore size and applied voltage. Supercapacitors composed of RTILs on the outer, positively curved surfaces of onionlike carbons (OLCs) or carbon nanotubes (CNTs) exhibited significant effects on capacitance and the distinctive feature that differential capacitance varies only weakly with voltage. Investigations of temperature influence revealed a positive temperature dependence of capacitance for OLC-based supercapacitors and a weak dependence of capacitance on temperature for CNT-based supercapacitors, in line with experimental observations. Molecular insights into RTIL-based supercapacitors, reviewed in this Perspective, could facilitate the design and development of a new generation of energy storage devices.

Classical Density Functional Study on Interfacial Structure and Differential Capacitance of Ionic Liquids near Charged Surfaces

“…We notice that for the same type of ionic liquids, Vatamanu et al 35 observed camel-shaped DC curve instead of bell shape presented in this work and simulations. 33 The discrepancy is believed to be mainly caused by neglect of image charges in latter studies. In the future, we hope to explore image charge's effect on electric double layer structures and differential capacitance of RTILs.…”

“…To match the surface conditions in simulation, 33 DFT models electrode as a single sheet of graphene in planar, cylindrical and spherical shapes respectively. The surface is composed of uniform distribution of carbon atoms with a density of roughly 2 atom per σ 2 , i.e.…”

“…Screening factor is defined as the minus of ratio of electrolyte charges within certain distance from surface over over surface charge. 16,33 Its dependence on curvature rises from planar surface (Eq.20) to cylindrical (Eq.21) and spherical surface (Eq.22). …”

“…This trend qualitatively agrees with MD simulations. 16,17,33 we focused on. The enhanced screening effect can be explained in the first place, by a lower potential drop across more curved space of EDL at same surface charge density.…”

İndi̇rgenmi̇ş Grafen Oksi̇t-Çi̇nko Oksi̇t-Ti̇tanyum Di̇oksi̇t Kompozi̇t Malzeme Üreti̇mi̇ Ve Uygulamasi

“…Depolama kapasitesini daha da arttırmak için çeşitli malzemeler kullanılmaktadır. Literatürde kapasite arttırmak için farklı iyonik sıvı elektrolitler de kullanılmıştır [1,2]. Elektrokimyasal kapasitörlerden olan pseudokondansatörler geçiş metali oksitleri ve iletken polimerler gibi şarj depolayabilir, yüzeyde veya yüzeye yakın olarak Faradaysal reaksiyon yoluyla yüksek enerji uygulamalarında kapasiteyi artırmak için geliştirilmiştir [2].…”