Supercapacitor with electrodes based on high-purity single-walled carbon nanotubes

We studied a supercapacitor with high purity carbon paper electrodes [1] with a specific gravity of 20 g/m2. The specific capacitance of the electrode during assembly in a coin cell housing with an aqueous 6M KOH electrolyte, at a scan rate of 1 mV/s, is 52 F/g. The specific power is 195.42 W/kg and the specific energy is 0.19 W⋅h/kg at a scan rate of 100 mV/s, which is included in the region of supercapacitors in the Ragone plot.

AlO6 clusters’ electric storage effect in amorphous alumina supercapacitors

In this study, the electric storage effect of AlO6 clusters in amorphous alumina (AAO) supercapacitors was investigated in terms of cluster morphologies under electron-beam irradiation. Based on first-principles density functional calculation, the optimised structure of AlO6 clusters around an O-vacancy is characterised by a large vacant space created by the absence of an O atom and its neighbouring Al atom. The localised electrons present near the two-atomic vacancies induce positive charges on the inside of the insulating oxide surface, ensuring the adsorption of many electrons on the surface. Electron-beam irradiation (adsorption) from 100 to 180 keV causes the lengths of the Al–O bonds of the cluster to shrink, but then return to the original length with decreasing voltage energy, indicating a rocking-chair-type charge-breathing effect accompanied by a volume expansion of approximately 4%. The I–V and I–R characteristics depicted Coulomb blockade for the switching effect of both the negative and positive potentials. The Ragone plot of the AAO supercapacitor is located at capability area of the second cell.

One-pot formation of ultra-thin Ni/Co hydroxides with a sheet-like structure for enhanced asymmetric supercapacitors

Ragone plot of the Ni/Co hydroxides (Ni1Co2)//AC device.

CDI ragone plot as a functional tool to evaluate desalination performance in capacitive deionization

A novel concept to evaluate desalination performance in capacitive deionization (CDI) is proposed called the CDI Ragone plot.

A method to obtain a Ragone plot for evaluation of carbon nanotube supercapacitor electrodes

Electrochemical double layer capacitors, also referred to as supercapacitors, are a promising technology in the field of energy storage. Carbon nanotube (CNT)-based supercapacitors are particularly interesting because of CNTs' high surface area and conductivity. CNT supercapacitors can potentially be used in hybrid electric vehicles due to their higher power density. Comparing energy storage systems that store energy in different ways, such as batteries, fuel cells, supercapacitors, and flywheels, requires that an appropriate set of performance data be collected. A Ragone plot is a log-log plot of a device's energy density versus power density, giving insight into its operational range. A method to obtain Ragone plots for CNT-based supercapacitors in a three-terminal electrochemical cell was adapted from a technique to test commercial capacitors for electric vehicles. Ragone plots for different types of as-grown CNT electrodes in different electrolytes are presented, along with the procedural details of this new method to obtain electrode-specific energy and power densities. Additionally, a theoretical weight calculation for a carbon nanotube film was derived and validated with a direct weight measurement of a CNT film. This weight was used in the specific energy and power densities for the Ragone plot.