[font face=Serif][font size=5]New Foam Batteries Promise Fast Charging, Higher Capacity[/font]

[font size=4]Affordable, lightweight, and versatile, batteries made of porous materials could soon transform energy storage.[/font]

By Richard Martin on October 26, 2015

[font size=3]Despite billions of dollars in investment and the launch of several high-profile startups, the energy sector still faces a fundamental and seemingly insoluble challenge: it’s very hard to store lots of power in a way that’s compact, long-lasting, and low-cost. A growing number of researchers are hoping to solve that with what are known as three-dimensional batteries, which can take several forms but tend to have porous, sponge-like structures, as opposed to the traditional “2-D” form: thin layers of metal in a liquid electrolyte solution inside a box (see “A Stretchable, Bendable and More Powerful Smart Watch Battery” and “Batteries: Cheapest Form of Grid Power?”).

Over the last several months, a startup called Prieto Battery, spun out of Colorado State University in Fort Collins, has succeeded in producing what founder Amy Prieto calls “the first true 3-D battery that can be charged and discharged, and that will hold a charge”—in other words, that fills the basic requirements of a conventional battery. 3-D batteries could be cheaper to make, faster to charge, safer, smaller, and less environmentally toxic than conventional batteries. What’s more, because they can be made lightweight, flexible, and in an almost limitless variety of shapes, they could offer energy storage applications previously unimaginable.

Prieto’s 3-D solid-state battery represents two radical departures from today’s batteries: what they’re made of and how they’re made. In the Prieto lab, just below the Rocky Mountain foothills, a series of eight shallow water-filled bins sit in a recessed table. Next to the line is a rack with rolls of copper foam of varying densities. The foam is the raw material for the batteries, onto which the anode—made of copper antimonide (copper blended with antimony)—is electroplated. The foam is so porous it’s mostly air, but a small fragment could contain an enormous surface area. Increasing the surface area reduces the distance that the ions have to travel, thus increasing both power and energy density.

Once the foam is coated with the anode, it’s layered with a polymer electrolyte that provides a physical barrier across which ions (but not electrons) can move. Finally, the cathode is applied in the form of a dark, inky slurry. The final product is a foam battery a couple of inches across and the thickness of a sheet of paper. Sealed in a plastic pouch, the Prieto batteries can charge quickly, store up to twice as much energy per unit of volume as conventional batteries, and lack lithium-ion batteries’ unfortunate propensity to overheat.

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