Taiyo Yuden Co. Ltd. developed a capacitor that has a high-current property equivalent to an electric double layer capacitor and has several times as high energy density per volume as it.
At CEATEC, the company demonstrated how the new capacitor works.
Activated carbon is used for the capacitor's positive electrode, and hard carbon is used for the negative electrode. It is a so-called "Li-ion capacitor," whose negative electrode is doped with Lithium ions.
The capacitor's energy density per volume is 15 Wh/L. It will be used for toys, mobile devices and hybrid cars in the future. Taiyo Yusen has already started providing samples of the capacitor for some manufacturers.
90% of the volume remains after 100,000 cycles
The newly-developed Li-ion capacitor has a high output voltage of 3.8 V. LiPF6 is used as battery electrolyte. As for the charge-discharge cycle life, the capacitor retains 90% of the volume after 100,000 cycles. "It's equivalent to general electric double layer capacitors," Taiyo Yuden said.
As for the self-discharge, which is said to be a downside of electric double layer capacitors, "If the capacitor is left for 10 days, its voltage will drop from 3.8V to 3.7V. So, the self-discharge rate is small," the company said. Also, its energy density is equivalent to that of an electric double layer capacitor.
The fundamental technology is a capacitor technology of Shoei Electronics Co. Ltd., which Taiyo Yuden purchased in March 2007. Shoei Electronics has been developing technologies of PAS capacitors, which are made with polyacene, for some time.
Shoei Electronics took over a polyacene capacitor business from Kanebo Cosmetics Inc. in 2004. And it made a licensing agreement concerning pre-doping of Li-ion capacitor with Fuji Heavy Industries Ltd. in June 2006.
Taiyo Yuden created a foothold in the capacitor market by subsidizing Shoei Electronics. In the future, the company will develop new products by combining its own technologies with the technologies it newly acquired.
At the exhibition, Taiyo Yuden staged some demonstrations of a small-sized robot and a model of a car driven by Li-ion capacitors. The robot is named "RoboCap", and it carries two Li-ion capacitors whose nominal volume is 200F on its back.
It can operate for five minutes on about one minute of charge, dancing para para and race-walking controlled by remote control.
At present, the company has three kinds of cylindrical capacitors whose nominal volumes are 40F, 100F and 200F. The capacitor with nominal volume of 200F is 40 mm high, and the diameter of its cylinder is 25 mm. Its inner electrical resistance is 50 mΩ.
The capacitor's operating temperature ranges from -25°C to +60°C. In addition, Taiyo Yuden exhibits RAS capacitors and gives demonstrations of the toys that are mounted with PAS capacitors and will be released at the end of the year.