When it comes to alternative battery architectures that might offer improved performance, there are many exciting possibilities and one very common roadblock. Needle-like growths called dendrites form on the electrode to hamper the performance of many promising experimental batteries, but a team at the University of Texas (UT) at Austin is putting forward a solution for a particularly eco-friendly one, by leveraging a novel fabrication technique likened to layering pastries.
The technology at the center of this research is what's known as a sodium battery, and is an attractive proposition because they eschew the heavy metals like lithium and cobalt used in today's batteries. Mining of these materials is linked to environmental impacts such as pollution of water supplies and soil degradation, in addition to human rights issues associated with child labor.
Sodium, in contrast, is cheap and abundant, and promises a more environmentally friendly solution for energy storage. But efforts to bring their performance up to that of today's lithium-ion batteries have been plagued by a few issues, with the problem of dendrite formation chief among them. These tend to grow on the anode, the electrode that stores the ions in a charged battery, as the device is cycled, and can cause it to short-circuit, overheat or catch fire.
The aim is to deposit the anode material as evenly as possible, with even slight imperfections in the surface giving the dendrites the start they need to bring the whole device undone. The UT Austin researchers believe they have come up with a solution to this problem, through a composite material called sodium antimony telluride intermetallic, which serves as the anode.
This is formed by thin sheets of sodium metal, which are rolled onto an antimony telluride powder and folded over on themselves. This process is repeated over and over to form the anode material, and leads to a highly uniform distribution of sodium atoms to lessen the likelihood of dendrite formation.
“Think of making a kind of layered pastry, like spanakopita,” says study author David Mitlin, who designed the material.
The composite material does more than just prevent dendrite formation and improve the stability of the sodium battery. The scientists note that it has a higher theoretical energy density than any existing sodium-ion anode and could therefore lead to greater storage capacity, and also enables it to charge at the same rate as a lithium-ion battery.
“We’re essentially solving two problems at once,” says Mitlin. “Typically, the faster you charge, the more of these dendrites you grow. So if you suppress dendrite growth, you can charge and discharge faster, because all of a sudden it’s safe.”
The scientists have filed a patent for the technology, and published their research in the journal Advanced Materials.
Source: University of Texas at Austin
