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.

Hubler claims the resulting power density (the speed at which energy can be stored or released) could be orders of magnitude greater, and the energy density (the amount of energy that can be stored) two to 10 times greater than possible with today's best lithium-ion and other battery technologies.

What's more, digital quantum batteries could be fabricated using existing lithographic chip-manufacturing technologies using cheap, nontoxic materials, such as iron and tungsten, atop a silicon substrate, he says. The resulting devices would, in principal, waste little or no energy as they absorbed and released electrons. Hubler says it may be possible to build a benchtop prototype in one year.

Today, however, digital quantum batteries are merely a patent-pending research concept. Hubler has applied for Defense Advanced Research Projects Agency funding to develop such a prototype, but the concept presents significant challenges. It's not clear that the nanofabricated materials wouldn't break down once loaded with energy, says Joel Schindall, a professor of electrical engineering at MIT.