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.
Sprague Electric
Sprague used $25,000 of his savings to open Sprague Specialties Company at his home in Quincy, MA, in 1926. One of his first products was the mini condenser (an old name for capacitor). Mini condensers were commonly used in radio applications for noise filtering, signal coupling and tone controls. Early capacitors were two pieces of metal foil wrapped between wax paper or any other type of suitable insulation material. The type of insulating material determined the capacitor's capacitance and maximum voltage. Capacitors are also useful in high power applications like motors, and soon Sprague turned his attention those areas as well.