In the geeky world of energy storage, there are well-understood limitations to plain old batteries and to ultracapacitors, devices able to store relatively little energy but also deliver big bursts of power.

Energy storage company Ioxus on Monday plans to announce a hybrid storage device that combines the attributes of an ultracapacitor with a lithium-ion battery. In the first quarter of next year, it plans to make available a second generation of the device, which could potentially be used in auto applications, according to Ioxus CEO Mark McGough.

Ultracapacitors: the unsung cousins of batteries in energy storage.

Its first hybrid will store more than twice the energy of traditional ultracapacitors, and charging is done on the order of seconds, rather than hours as in the case of traditional batteries, according to the company.

The device, which is about the size of a C cell battery, won't propel a plug-in electric car. But it could be used for power tools, off-grid lighting, and handheld medical devices, according to McGough.

If used in an ear probe for medical applications, for example, a doctor could fully charge the probe in 90 seconds or partially charge in 20 seconds, McGough said. The company is now providing sample to designers in different industries.

"What we've been able to do is take the fast charge/discharge of ultracapacitors and improve the energy density by designing in a lithium ion electrode and putting it all in the same device," McGough said. The device combines the activated carbon material of an ultracapacitor that stores charge and layers of lithium ion material wrapped in a cylinder form, he explained.

The trade-off to the hybrid design is that it won't have the same cycle life--or charge/discharge cycles-- as ultracapacitors. People can expect 20,000 cycles versus millions of cycles for an ultracapacitor, McGough said.

The long cycle life makes it suitable for use in places where replacing a battery would be difficult, such as off-grid lighting. Within cars, it could be used to run smaller motors, such as the ones that raise and lower power windows, in order to lighten the load and cabling from the main battery.

The company's second-generation hybrid device could be used in hybrid cars for what is called "start-stop" technology, or microhybrids, McGough said. In this case, energy storage is used for regenerative braking to harvest energy and a give small burst of power when starting.