Supercapacitor
Since capacitors' energy content increases with the square of the voltage, researchers were looking for a way to increase the electrolyte's breakdown voltage. In 1994 using the anode of a 200V high voltage tantalum electrolytic capacitor, David A. Evans developed an "Electrolytic-Hybrid Electrochemical Capacitor". These capacitors combine features of electrolytic and electrochemical capacitors. They combine the high dielectric strength of an anode from an electrolytic capacitor with the high capacitance of a pseudocapacitive metal oxide (ruthenium (IV) oxide) cathode from an electrochemical capacitor, yielding a hybrid electrochemical capacitor. Evans' capacitors, coined Capattery, had an energy content about a factor of 5 higher than a comparable tantalum electrolytic capacitor of the same size. Their high costs limited them to specific military applications.
William Dubilier
William Dubilier (July 25, 1888 – July 25, 1969) was an American inventor in the field of radio and electronics. He demonstrated radio communication at Seattle's Alaska-Yukon-Pacific Exposition on June 21, 1909; ten years before the first commercial station operated. A graduate of Cooper Union, he was the first to use sheets of naturally occurring mica as the dielectric in a capacitor. Mica capacitors were widely used in early radio oscillator and tuning circuits because the temperature coefficient of expansion of mica was low, resulting in very stable capacitance – mica capacitors are still used where exceptional temperature stability is needed.