AAWSAP DIRD, Ultracapacitors as Energy and Power Storage Devices, November 2010

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Figure 3. Ragone Plot. The graph illustrates the areas where ultracaps and batteries dominate in the power
density versus energy density relationship.
HISTORY
The concept of storing electrical energy in the electric double layer that is formed at the
interface between an electrolyte and a solid has been known since the late 1800s. In
1966, Standard Oil Company of Ohio (SOHIO) invented the device in the format now
commonly used, which forms the basis for hundreds of patents and thousands of
journal articles. Figure 4 shows a drawing from the electrochemical double-layer device
invented by SOHIO. NEC introduced the SuperCapacitor™ in 1978 under license from
SOHIO.
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Figure 4. Electrolytic Capacitor as Designed and Patented by SOHIO.
From this point on, ultracaps have rapidly evolved through several generations of
designs. In the 1980s, Matsushita Electric Company developed a method of
manufacturing ultracapacitors with improved electrodes. Initially, they were used as
backup power devices for volatile clock chips and complementary metal-oxide­
semiconductor (CMOS) computer memories. As the technology became more
understood, more and more applications were developed for ultracaps. Many other
applications have emerged over the past 30 years, including wireless communication,
power quality, and improved energy efficiency through regenerative energy capture
processes, as found in hybrid electric vehicles.10
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