Marine Snail’s Teeth Hold Secret to Nanomaterials for Li-Ion Batteries, Solar Cells

Lithium-ion battery makers could begin working at a snail’s pace after a breakthrough discovery at the University of California, Riverside.

Assistant Professor David Kisailus of the university’s Bourns College of Engineering is using the teeth of the chiton, a marine snail found off the U.S. West Coast, to create less costly and more efficient nanoscale materials to improve Li-ion batteries and solar cells.

The gumboot chiton, the largest of its type, can grow up to a foot and is found along the shores of the Pacific Ocean from central California to Alaska. The critter has leathery upper skin, which is usually reddish-brown and occasionally orange, leading some to give it the nickname “wandering meatloaf.”

Chitons have evolved to eat algae growing on and within rocks using a specialized rasping organ called a radula, a conveyer belt-like structure in the mouth that contains 70 to 80 parallel rows of teeth.

During the feeding process, the first few rows of the teeth are used to grind rock to get to the algae. They become worn, but new teeth are continuously produced and enter the “wear zone” at the same rate as teeth are shed.

Kisailus began studying chitons five years ago because of his interest in abrasion and impact-resistant materials. He previously found that the chiton teeth contain magnetite, the hardest biomineral known on Earth. The key mineral not only makes the tooth hard, but also magnetic.

Kisailus says he has uncovered how the hard and magnetic outer region of the tooth forms, details of which he reports in a paper in the journal Advanced Functional Materials.

He says the discovery is the result of shared research with colleagues at Harvard University in Cambridge MA; Chapman University in Orange, CA; and Brookhaven National Laboratory in Upton, NY.

According to the study, hydrated iron-oxide (ferrihydrite) crystals first nucleate on a fiber-like chitinous (complex sugar) organic template. These nanocrystalline ferrihydrite particles convert to a magnetic iron oxide (magnetite) through a solid-state transformation.

Finally, the magnetite particles grow along these organic fibers, yielding parallel rods within the chiton’s mature teeth that make them so hard and tough.

“Incredibly, all of this occurs at room temperature and under environmentally benign conditions,” Kisailus says in a statement. This means similar strategies can be used to make nanomaterials in a cost-effective manner.

Kisailus presently is using the snail’s biomineralization pathway to grow minerals used in Li-ion batteries and solar cells. By controlling the crystal size, shape and orientation of engineering nanomaterials, he believes he can build materials that will allow the batteries and solar cells to operate more efficiently.

The solar cells will be able to capture a greater percentage of sunlight and convert it to electricity more efficiently, and the Li-Ion batteries could require significantly less time to recharge.

Using the chiton teeth model has another advantage – engineering nanocrystals can be grown at significantly lower temperatures, and this means significantly lower production costs.

Kisailus says the same techniques could be used to develop everything from materials for car and airplane frames to abrasion-resistant clothing.