Our Ultracapacitor Technology

What is an ultracapacitor?

Capacitors, which used to be known as “condensers,” are devices that store energy electric charges and release them when they are needed.

They are very similar to batteries, except that they are better at releasing power, but not as good at storing energy. Researchers at the University of Wisconsin have separated capacitor development into the following categories:

Generation 1: Traditional Electrolytic Capacitors

Figure 1: Diagram of a simple, traditional electrolytic capacitor.

Traditional electrolytic capacitors (first generation) work by utilizing two conducting plates (usually made of metals that are capable of being charged) and a thin film dielectric (insulating material) as a separator in an electrolyte (see figure 1). The amount of capacitance that can be achieved is described in this simple equation:

Capacitance = [(dielectric constant of medium) x (area of the plate)] / distance between the plates

Generation 2: EDL Capacitors

The first ultracapacitors (also known as “supercapacitors”) were probably developed in the late 1950s. These came to be known as Electric Double Layer (or EDL) capacitors (second generation). They had the ability to store more energy than standard capacitors but still suffer (in terms of energy) when compared to batteries. These devices also employ two conducting plates and a separator. Both plates have a certain geometric size (thickness and surface area). However, they are usually made of a conducting carbon which generally has a much greater surface area than a metal. When one of the plates is charged, the ions, which compensate for the charge on the carbon, are stored in the electrical double layer near the surface of the pores of the carbon. This distance is on the order of angstroms. Therefore, distance goes way down in the formula and capacitance goes way up. Now both pieces of carbon are effectively each capacitors as one is storing charge with cations and the other with anions (see figure 2).

Generation 3: Pseudocapacitors

Figure 2: Diagram of an EDL capacitor.

Pseudocapacitors (third generation) work by EDL means but also take advantage of oxidation/reduction reactions at an interface. These oxidation reduction reactions are like those of batteries. Most pseudocapacitors have been constructed of two transition metal oxides such as RuOx, NiOx, etc. (the “x” here is meant to imply that the system can be either oxidized or reduces). These oxides are conductive.

Generation 4: EDL Ultracapacitor with Nanoparticle Coating

The UW/SolRayo/Enable IPC ultracapacitor is a fourth generation system, combining EDL and an insulating oxide on top of the carbon. We have some EDL capacity developed because of the porous carbon supports as well as the potential that is developed on the insulating oxide. The difference here is that most of our charge is stored by the insulating film of nanoparticulate insulating oxides. Here the charge on the oxide is developed by a potential determining ion, such as the proton.

Figure 3: The laser beam goes through the vial of water, but reflects off the nanoparticles in our solution.

The insulating oxide consists of nanoparticles suspended in a solution (see figure 3). We apply the solution to an uncoated carbon sheet (see figures 4 and 5). The results have been very impressive. When we have applied the solution, we have seen the capacitance of the carbon material increase by 60% to over 400%, depending on the material.

Ultracapacitor Products

There are three basic market areas where ultracapacitors are used: consumer electronics, industrial applications and transportation.

Consumer electronics. Applications in the consumer electronics area include:

Figure 4: A microscopic picture of a carbon sheet (one of the capacitor's plates) before our solution is applied . . .
  • household appliances
  • computers
  • cellular phones with added features
  • and many others.

Industrial. Applications in this area include:

  • power supplies
  • energy (including renewables)
  • industrial automation equipment
  • to name a few

Figure 5: ... and after our solution is applied. Depending on the type of carbon, we have seen improvement in capacitance from 60% to over 400% after applying our coating.

Transportation. Applications in transportation include:

  • hybrid automobiles
  • aircraft door actuators
  • rail systems
  • and more

Will ultracapacitors replace batteries?

Batteries utilize a chemical reaction to create power. Ultracapacitors do not do this; they simply store electricity and have the ability to charge and discharge very quickly. In many applications, where charging can come from another source, they possibly could replace batteries. But, unless there are some leaps in technology, they would not replace batteries where higher energy densities are required.

The information on this page was supplied by Professor Marc Anderson of the University of Wisconsin - Madison and Kevin Leonard, CTO of Enable IPC's subsidiary, SolRayo. They are co-inventors of Enable IPC's ultracapacitor technology.


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