Novel Ultracapacitor Materials

Many commercial ultracapacitors are made using high surface area carbon as the electrode material.  This material provides good capacitance, but is expensive.

We have developed a new method of fabricating ultracapacitors.  We utilize less expensive carbon cloths or papers as our electrode backing material.  We then coat these materials with nanoparticles that are able to improve the performance at a lower cost.

Ultracapacitor Research

The performance of electrical energy storage devices, such as engines and fuel cells, is often shown using Ragone Plots which display specific power (W/kg) and specific energy (Wh/kg) for many devices.   A standard Ragone Plot is shown below.

We are currently evaluating several backing materials including carbon papers and carbon cloths on which we coat our nanoparticles.  As one would expect, different backing materials yield different results.  Results for two nanoparticle-coated backing materials are shown by the blue and green squares in the figure below.  We see that our materials have better energy storage and power delivery compared to typical ultracapacitors (electrochemical capacitors). 

Lifetime

Ultracapacitors can provide one to two orders of magnitude more charge/discharge cycles than rechargeable batteries.  The plot below shows the performance of one of our electrochemical capacitors over 3 million cycles. 

Typical commercial ultracapacitors are rated to have a 20% loss in 500,000 - 1,000,000 cycles.  Our experiments show that we do not reach 20% loss in performance until 1.6 million cycles, and only have a 24% loss after 3 million cycles.  This is a dramatic increase in lifetime compared to other commercial ultracapacitors.

Charge/Discharge Cycle Testing

Summary

We have developed a new type of high-performance ultracapacitor.  We are able to utilize inexpensive carbon cloths and papers as backing materials for our electrodes. Our nano-particulate coatings are low-cost and our manufacturing process is simple and inexpensive.

By using different backing materials, particle sizes, coating processes and differing electrolytes we can tailor performance of these electrochemical capacitors for specific application needs.