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Ioxus introduces hybrid ultracapacitors with more than 2x energy density of EDLCs

Ioxus hybrid ultracapacitors. Click to enlarge.

Ioxus, Inc. (earlier post) has developed and is in production with a hybrid capacitor, a combination of an ultracapacitor and a lithium-ion battery, with an energy density 115% higher than standard electric double-layer capacitors (EDLCs). Ioxus is the only US company currently offering this technology commercially. Taiyo Yuden also recently introduced a new hybrid Li-ion capacitor.

Ioxus hybrid capacitors use a lithium-ion product as the anode, and an electrochemical double layer capacitors (EDLC) carbon composite coated electrode on aluminum substrate as the cathode, said Ioxus CEO Mark McGough. Although they offer higher energy density, the hybrid capacitors have a cycle life of around 20,000—an order of magnitude above Li-ion batteries, but significantly less than the million or so cycles for a conventional EDLC product.

We have given the designer another tool for the toolbox. The new product has different attributes than a battery or an ultracapacitor. It is literally a hybrid device: greater cycle life than the Li-ion battery, more than two times the energy of an EDLC. You can charge it quickly and permanently install it where Li-ion may be used as a replacement.

—Mark McGough

Ioxus is targeting the hybrid capacitors for numerous applications, including: flashlights; LED applications; memory back-up; portable hand tools; solar charge applications; off-grid lighting; and automotive subsystems such as power windows and door locks.

Applying the hybrid in such automotive applications offers a weight advantage and a cost advantage, McGough noted, saying that Ioxus is currently in discussions and testing for both automotive and consumer applications and lighting applications with the new device. Ioxus has so far produced about 20,000 units.

The hybrid capacitor has a rated voltage of 2.3V DC, and an operating temperature range of -25 °C to +60 °C (-13 °F to 140 °F). At the low end of the range, the hybrid capacitor loses only 5% of its energy while comparable battery energy loss would by 50% or more. Ioxus hybrid capacitors are 90 to 95% efficient, the company says. The devices currently come in capacitances of 220, 800 and 1000 Farads.

Click to enlarge.

Taiyo Yuden. The Taiyo Yuden Hybrid Lithium Ion Capacitors (LICs) provide an increased maximum rated voltage of 3.8V—about 1.5 times higher than the 2.3-2.7V of conventional capacitors. Taiyo Yuden’s says its “Lithium Pre-Dope” technology is the key to this new device. Lithium pre-doping stores lithium ions at the anode in advance.

Taiyo Yuden’s LIC is available in 3 capacitances: 40F, 100F and 200F. Operating temperatures range from -25ºC - +60ºC.



Rather high impedance on those caps. The 220 F unit has an impedance as high as 45 milliohms. Apply a current of 22 amps and you get 1 volt of resistive loss out of the 2.3 volt rating! If these units were going to be used as e.g. surge power in a hybrid vehicle, they would need to be sized for 30 second or more charge/discharge time and also cooled very well.


The 20000 cycle life is nice but energy density is still crap.

Will S

Yes, the ultra-cap's energy density of 6.x Wh/kg is a far cry from the 90+ Wh/kg of LiFePO4.

Henry Gibson

Williams KERS units. just one moving part. ??? ..HG..

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