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| A capacitor is an electric energy storage device, often constructed with two layers of conducting foil separated by a paper-thin layer of insulator. The capacity is proportional to the area A and inversely proportional to the insulator thickness t, C~A/t. A supercapacitor has a atomic scale insulator thickness given by the solvation layer surrounding an ion in an electrolyte, and a large surface area. Supercapacitor values of 1-1000 F are now available commercially (see https://www.sparkfun.com/products/746) and approach the energy density of batteries while offering fast charge and discharge rates (high power density). For an introduction to graphene based supercapacitors, see http://vimeo.com/51873011. -duncan | |
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| The electronic devices we use in our everyday life utilize two different types of electrical sources in order to operate: batteries and capacitors. A battery stores a fair amount of energy but is slow to charge and discharge (low power density). A capacitor can charge and discharge very rapidly (high power density) but stores a very small amount of energy. A supercapacitor combines the best of both by storing a large amount of energy while also being able to charge and discharge very rapidly. A capacitor is often constructed with two layers of conducting foil separated by a paper-thin layer of insulator. The capacity of such a device is proportional to the area of the foil A and inversely proportional to the insulator thickness t, C∝A/t. A supercapacitor has an atomic scale insulator thickness given by the solvation layer surrounding an ion in an electrolyte, and a large surface area. Supercapacitor on the order of {{http://latex.codecogs.com/gif.latex?\tiny%20\dpi{120}%20\bg_white%2010^{0}-10^{3} }} Farads are now [[https://www.sparkfun.com/products/746|commercially available]] and approach the energy density of batteries while still offering fast charge and discharge rates. El-Kady and Kaner have provided a [[http://vimeo.com/51873011|video introduction]] to graphene based supercapacitors. {{http://i.imgur.com/fJd0bZS.jpg|Fabrication of Microsupercapacitors|width=1000}} |
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Graphene Micro-Supercapacitors
Co-I Garrett Frankson and Austin Jeffries
Current Status: Building Project Page
Project Overview
The electronic devices we use in our everyday life utilize two different types of electrical sources in order to operate: batteries and capacitors. A battery stores a fair amount of energy but is slow to charge and discharge (low power density). A capacitor can charge and discharge very rapidly (high power density) but stores a very small amount of energy. A supercapacitor combines the best of both by storing a large amount of energy while also being able to charge and discharge very rapidly.
A capacitor is often constructed with two layers of conducting foil separated by a paper-thin layer of insulator. The capacity of such a device is proportional to the area of the foil A and inversely proportional to the insulator thickness t, C∝A/t. A supercapacitor has an atomic scale insulator thickness given by the solvation layer surrounding an ion in an electrolyte, and a large surface area. Supercapacitor on the order of Farads are now commercially available and approach the energy density of batteries while still offering fast charge and discharge rates.
El-Kady and Kaner have provided a video introduction to graphene based supercapacitors.
Project Goals
Short Term Goals
- Create graphene micro-supercapacitor material using the methods outlined by El-Kady and Kaner.
- Conduct a series of tests on how to maximize the amount of charge stored within each graphene micro-supercapacitor.
Long Term Goals
- Design an apparatus that can hold many graphene micro-supercapcitors in an efficient and usable way for use in application.
- Experiment with powering small mobile devices (ie. a flash light, a watch, a cellphone).
Relevant Publications
Maher F. El-Kady & Richard B. Kaner
El-Kady and Kaner demonstrate a scalable fabrication of graphene micro-supercapacitors over large areas by direct laser writing on graphite oxide films. More than 100 micro-supercapacitors can be produced on a single disc in 30 min or less. The devices are built on flexible substrates for flexible electronics and on-chip uses. Remarkably, miniaturizing the devices to the microscale results in enhanced charge-storage capacity and rate capability. These microsupercapacitors demonstrate a power density of ~200 W cm-3, which is among the highest values achieved for any supercapacitor.
Preparation of Graphitic Oxide
William S. Hummers & Richard E. Offema
- The conventional method for the preparation of graphitic oxide is time consuming and hazardous. Hummers and Offema have developed a rapid, relatively safe method for preparing graphitic oxide from graphite in what is essentially an anhydrous mixture of sulfuric acid, sodium nitrate and potassium permanganate.
- Nina I. Kovtyukhova et al.
- For the synthesis of graphitic oxide, El-Kady and Kaner used a modified Hummers' method developed by Nina I. Kovtyukhova et al.
Finance