Lithium batteries have been the king of the battery market for quite a few years now and rightfully so. Lithium-ion batteries pretty much outperform all other commercially-available batteries in key areas such as energy storage and the ability to charge and discharge many times without losing much capacity.
However, these batteries are not without their drawbacks. The cobalt and lithium used in them aren’t particularly abundant and there is a risk of fire or explosion because lithium batteries contain a flammable organic electrolyte. Scientists have even created lithium batteries with a built-in flame retardant. In an effort to resolve these issues, scientists have been conducting research to find a different element that could replace lithium. One of the frontrunners is zinc.
Zinc as a Replacement for Lithium
There is a myriad of different battery chemistries that could potentially fit the role. However, it's very difficult to bring them to their theoretical potential. Of all the possible replacements, it seems that zinc has had the most advances in testing.
Zinc is surprisingly old-school; it has been used in most standard alkaline batteries as an anode. While zinc is fairly abundant, it unfortunately doesn’t perform so well as a rechargeable battery—though it is fairly safe as it uses a water-based electrolyte compared to the flammable organic electrolytes in lithium batteries.
Zinc battery anodes are commonly created by adhering zinc particles together. If the battery goes through multiple periods of recharging, it will typically start forming a coat of zinc oxide, which is less effective at conducting and encases some of the zinc. Dendrites can form due to the difference in charge distribution and, due to this, the battery poses a risk of short circuiting as these dendrites can perforate the anode barrier.
Zinc dendrites forming in water. Image courtesy of Corno, Stout, Yang, and Gole from Diffusion-Controlled Self-Assembly and Dendrite Formation in Silver-Seeded Anatase Titania Nanospheres
A New Zinc Battery
Now a group of researchers led by Debra Rolison from the United States Naval Research Laboratory has potentially created a safe version of a zinc battery that can suppress the formation of zinc dendrites.
The dendrite formation issue was resolved by redesigning the zinc electrode. The initial problem resulting in dendrite formation was due to the behavior of zinc during cycling. The zinc electrodes are typically made by binding together and drying zinc emulsions to create a powder, which lacks the surface area and capability to distribute charge uniformly enough to prevent dendrite formation.
The redesign came in the form of a 3-D sponge-like structure that is capable of distributing charge uniformly during charge cycles.
“Electric currents are more uniformly distributed within the sponge, making it physically difficult to form dendrites,” said Joseph Parker, a researcher from the United States Naval Research laboratory.
From left to right: now-acting Secretary of the Navy Sean J. Stackley, Debra R. Rolison, Jeffrey W. Long, Joseph F. Parker, and Delores Etter. The NRL team were presented with Dr. Delores M. Etter Awards for their work on zinc batteries this year. Image courtesy of the NRL.
How Did It Perform?
The redesigned battery was tested in combination with a nickel electrode and yielded some promising results. The researchers demonstrated the battery by charging and discharging a 12-volt version more than 50,000 times, all the while retaining its porous architecture.
On top of the remarkable charge cycle results, the researcher did some math and showed that the battery was capable of holding more charge, was lighter, and smaller than a typical lead-acid battery. Additional calculations were made showing that the battery could even potentially outperform Li-ion batteries in electric cars in terms of space and weight.
The researchers are currently focused on zinc configuration and further development as the zinc batteries are less expensive to produce than our current lithium-ion batteries containing cobalt.
Rolison and her colleagues have given an exclusive research license to a company called EnZinc, which includes research pertaining to electronic, wheeled vehicles. However, there are still licenses for other research applications and cathodes available.
Read more about the study in Science.