Eamex Corp. announced that the energy density per unit volume of its capacitor, which is under development, has been enhanced up to 600Wh/L. The value 600Wh/L is said to be equivalent to the energy density of a lithium-ion secondary battery. The company expects that the capacitor will be used for electric vehicles, notebook computers, and other applications.
The main characteristic of Eamex’s capacitor is that the surface of its solid polymer electrolyte membrane is applied with metal plating that serves as electrodes. With the improvement of plating technique, the company says it has succeeded in increasing the specific surface area of the electrodes and enhancing the physical adsorption effect. The hybrid capacitor is said to increase the energy density by the electrochemical effect of lithium ions used as electrolyte salt.
Although Eamex did not unveil the details, the company says that it increased the specific surface area to 20,000 times the existing value through the improvement of plating conditions. This is said to make it possible to significantly enhance the energy density. The company announced a capacitor with an energy density per unit volume of 100Wh/L in December 2008, but the specific surface area was only about 1,000 times larger than that of existing electrodes.
Presently, the capacitor’s high energy density cannot constantly be obtained, as Eamex admits "conditions must be optimized to achieve the 600Wh/L performance." Still, the company claims that the energy density reaches 150Wh/L on average. In addition, it reduced the internal resistance through the adjustment of plating structure and achieved a power density per unit volume of 20,000 W/L, which is said to be much higher than that of the existing electric double layer capacitors.
However, the latest prototype is extremely small, measuring only 0.2 x 0.5cm with a thickness of 31μm. In order to commercialize the capacitor, its size must be increased and a stacked structure needs to be developed for larger capacity. Therefore, the company is promoting joint researches with other manufacturers that possess related technologies. The company says that some of the leading automakers are interested in this capacitor, which is said to outperform Li-ion secondary batteries.
