3rd May, 2017
Not only could rechargeable zinc-based batteries possibly store as much energy as lithium-ion batteries, they could also be safer, cheaper, smaller and lighter, new research finds. The results suggest zinc batteries could find use in mild hybrids (microhybrids), electric vehicles, electric bicycles, and eventually, perhaps smartphones and power grid storage.
The researchers are now aggressively testing these batteries and exploring scaling up this technology. “We feel we can have a battery ready for the market by the end of 2019,” says Michael Burz, CEO of energy technology firm EnZinc in San Anselmo, Calif., which helped engineer the new batteries.
When it comes to electric vehicles, the new batteries will “be 30 to 50 percent cheaper than comparable lithium-ion systems,” Burz says.
Lithium-ion batteries have become notorious for safety incidents resulting from overheating, at times bursting into flames and even exploding. The U.S. Navy was researching alternative technologies because “there's a Navy and a broader military concern with the safety of lithium-ion batteries—on soldiers, on sailors, on platforms,” says Debra Rolison, head of the advanced electrochemical materials section at the U.S. Naval Research Laboratory in Washington, D.C., and one of the researchers involved in the zinc breakthrough.
Zinc-based batteries do not pose the same fire risk linked with lithium-ion batteries, and can in principle match or surpass them in terms of specific energy (energy per unit mass), as well as energy density (energy per unit volume). Moreover, zinc is cheap and widely available. All these features help explain why zinc-based batteries “are the go-to global battery for single-use applications,” Rolison says.
However, zinc-based batteries “are not considered rechargeable in practice due to their tendency to grow conductive whiskers—dendrites—inside the battery, which can grow long enough to cause short circuits,” Rolison says. As such, zinc-based batteries typically die after several cycles of discharging and recharging, she explains.
Now Rolison, Burz and their colleagues have developed a zinc-based battery whose internal structure can suppress dendrite formation. The zinc anode has a porous, sponge-like architecture that helps charge move uniformly across the entire structure when the battery discharges and recharges. “Electric currents are more uniformly distributed within the sponge, making it physically difficult to form dendrites,” says Joseph Parker, a research chemist at the U.S. Naval Research Laboratory.