New architecture promises better battery
Instead of storing charge in a main battery—then doling it out to individual devices on demand—a new breed of hybrid capacitor/battery is storing just enough energy for an adjacent device for its exclusive use. Ioxus Inc., (Oneonta, N.Y.) says it is solving the "battery problem" by defining a new distributed-energy architecture.
"We have people using our hybrid ultra-capacitors for all types of applications that were challenging for traditional battery architectures," said Ioxus co-founder and Vice President Chad Hall. "When you need short-term or back-up power, we provide a device that satisfies those needs without all problems associated with traditional batteries."
Applications for the technology range from simple to complex. For instance, a simple flashlight using a hybrid ultra-capacitor can be charged in just 20 seconds, then used for up to two hours, according to Hall. And a complex regenerative braking system on an automobile can instead use a hybrid ultra-capacitor that charges every time you brake and stop, then simply restarts the car when you hit the gas–eliminating all the pollution caused by stop-and-start traffic, he said.
Automotive applications allow hybrid capacitors to be economically distributed around a vehicle, storing short-term energy where it is needed for powering LEDs, on-board computers, power windows, power door-locks and security systems. And in the event of a total failure—or even removal—of the main car battery, all hybrid ultra-capacitor powered systems will still work. Plus Ioxus estimates that electric vehicles making use of distributed hybrid ultra-capacitors rather than relying solely on a centralized battery can cut 20-to-30 pounds off their weight.
A handful of other makers claim to have similar hybrid ultra-capacitors to Ioxus’, but none has duplicated its unique combination of features. For instance, Evans Capacitor Co., (East Providence, R.I.) has a higher-voltage lower-energy hybrid capacitor that is more akin to an ultra-capacitor alone than Ioxus’ hybrid ultra-capacitors. And JM Energy Corp. (Yamanashi, Japan) has a "lithium-ion capacitor" that is more akin to a lithium-ion battery than Ioxus’ hybrid ultra-capacitor. Ioxus, however, claims to have intellectual property that makes its approach work better than Evans’ and be safer than JM Energy’s.
Ioxus’ hybrid ultra-capacitors combine the architecture of a capacitor—charge accumulating on plates separated by an insulator—with the chemical storage of a lithium-ion battery. Using the same chemistry as a lithium-ion battery, the hybrid ultra-capacitor distributes those chemicals onto the surface of a solid electrode, rather than embed the chemicals into a porous electrode where the slow process of intercalation is required to charge and discharge them.
As a result, Ioxus’ hybrid ultra-capacitors can be charged and discharged at nearly any rate—allowing them to swallow-up and discharge-out vast or minuscule currents as required by an application. Their only downside is that they cannot store as much charge volume as a traditional battery, nor store it for as long, but the distributed architecture used by applications compensates for these shortcomings, according to Ioxus.
"Hybrid capacitors can be added to supply energy right where it is needed," said Hall. "They store more energy than an ultracapacitor alone, and can endure nearly unlimited numbers of charge-discharge cycles compared to lithium-ion batteries."
Hybrid ultra-capacitors do not store as much charge as a lithium ion battery, but they do store about 100 percent more charge than an ultra-capacitor alone, plus provide almost unlimited charge/discharge cycling. Most lithium ion batteries can only be charged/discharged a few hundred times, and even special long-term versions are limited to a few thousand cycles. Hybrid ultra-capacitors, on the other hand, typically can be charged and discharged more times than the lifetime of the product in which they are being used—more than 20,000 cycles in tests conducted at Ioxus.
Hybrid ultra-capacitors also offer much more instant-on power than even the strongest battery—up to 5 kiloWatts per kilogram compared with 3kW/kg for even the highest priced batteries, according to Ioxus, which also claims that its hybrid ultra-capacitors are 95 percent energy efficient, compared with 70 percent for the best lithium ion batteries.
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