14 February 2010

A Quantum Leap in Battery Design?

A Quantum Leap in Battery Design
Digital quantum batteries could exceed lithium-ion performance by orders of magnitude.
A "digital quantum battery" concept proposed by a physicist at the University of Illinois at Urbana-Champaign could provide a dramatic boost in energy storage capacity--if it meets its theoretical potential once built.
The concept calls for billions of nanoscale capacitors and would rely on quantum effects--the weird phenomena that occur at atomic size scales--to boost energy storage. Conventional capacitors consist of one pair of macroscale conducting plates, or electrodes, separated by an insulating material. Applying a voltage creates an electric field in the insulating material, storing energy. But all such devices can only hold so much charge, beyond which arcing occurs between the electrodes, wasting the stored power.
If capacitors were instead built as nanoscale arrays--crucially, with electrodes spaced at about 10 nanometers (or 100 atoms) apart--quantum effects ought to suppress such arcing. For years researchers have recognized that nanoscale capacitors exhibit unusually large electric fields, suggesting that the tiny scale of the devices was responsible for preventing energy loss. But "people didn't realize that a large electric field means a large energy density, and could be used for energy storage that would far surpass anything we have today," says Alfred Hubler, the Illinois physicist and lead author of a paper outlining the concept, to be published in the journal Complexity.

That's all quite interesting, and heaven knows the world needs to finally advance beyond battery technology that Volta could understand. Going directly to Hubler's paper yields the following explanation, spanning pgs. 3 and 4:

Nano plasma tubes are generally forward-biased and if the residual gas emits visible light, they can be used for flat-panel plasma lamps and flat panel monitors... The energy density density in reverse-biased nano plasma tubes is small, because gas becomes a partically ionized, conducting plasma at comparatively small electric fields... In this paper, we investitage energy storage in arrays of reverse-biased nano vacuum tubes, which are similar in design to nano plasma tubes, but contain little or no gas... Since there are only residual gases between the electrodes in vacuum junctions, there is no Zener breakdown, no avalanche breakdown, and no material that could be ionized. Electrical breakdown is triggered by quantum mechanical tunneling of electrode material: electron field emission on the cathode and ion field emission on the anode. Because the energy barrier for electron field emission is large and the barrier for ion field emission even larger, the average energy density in reversed-biased nano vacuum tubes can exceed the energy density in solid state tunnel junctions and electrolytic capacitors. Since the inductance of the tubes is very small, the charge-discharge rates exceed batteries and conventional capacitors by orders of magnitude. Charging and discharging involves no faradaic reactions so the lifetime of nano vacuum tubes is virtually unlimited. The volumetric energy density is independent from the materials used as long as they can sustain the mechanical load, the electrodes are good conductors, and the mechanical supports are good insulators. Therefore, nano vacuum tubes can be built from environmentally friendly, non-noxious materials. Materials with a low density are preferable, since the gravimetric density is the ratio between the volumetric energy density and the average density of the electrodes and supports. Leakage currents are small, since the residual gases contain very few charged particles.
The thing is is, I think something much like this has been tried, though not for energy storage: The technology Hubler describes seems very similar to the notion of field-emission displays and surface-conduction electron-emitter displays, two closely-related technologies in which nanoscale vacuum tubes are fabricated microlithograhically and arrayed to stimulate phosphors.

One of Silicon Valley's largest failed ventures was Candescent, a company devoted to developing such displays, which burned through (IIRC) something like $600 million in funding from some stellar sources. As Daniel den Engelsen notes in his article, "The Temptation of Field Emission Displays,"
...Manufacturing of FEDs is too difficult, and thus too expensive; moreover, the recent success of LCDs and PDPs as Flat Panel Displays (FPDs) for TV is now discouraging (large) investments in FED manufacturing facilities. The two main challenges for designing and making FEDs, viz. high voltage breakdown and luminance non-uniformity, are described in this paper. Besides improvements in the field of emitter and spacer technology, a new architecture of FEDs, notably HOPFED, has been proposed recently to solve these two persistent hurdles for manufacturing FEDs.
But energy storage wouldn't care much about luminance non-uniformity, and Hubler seems to have determined that high-voltage breakdown is manageable in his configuration. Hubler and Canon, which acquired the ashes of Candescent from receivership, might want to talk. Sony, a major battery manufacturer as well as a former FED developer, might be another interested party.

1 comment:

HP Notebook Battery said...

Nano-technology has been revealing something new everyday. Each day our entire perception of the future is completely changed, and the Eco-friendly decision is usually the most cost efficient and productive. I can't even begin to imagine what nano-technology holds for our future in 10 years.