CRAB SHELLS ARE USED TO CREATE A NEW BIODEGRADABLE BATTERY

By Piero Facchin

A new battery made from crab shells and zinc promises to be fully biodegradable and recyclable. The safe and environmentally friendly battery can be recharged at least 1,000 times, making it ideal for storing wind and solar energy for the power grid.

Researchers at the University of Maryland and the University of Houston wanted to make a more sustainable battery. They started with zinc-metal battery chemistry, which scientists have been developing for several years for grid storage. Zinc is much more abundant than lithium in the Earth’s crust, so zinc-ion batteries are cheaper. But traditional batteries—made of zinc anodes, metal oxide cathodes and water-based electrolytes—suffer from uneven zinc deposits on the electrode surface, making them dangerous and short-lived.

So the researchers created a new biodegradable gel electrolyte from chitosan, a compound derived from chitin, the protein that makes up the hard shell of crustaceans such as crabs, lobsters and shrimp. Chitin is usually discarded as a by-product of the food industry.

By combining chitin and zinc, they created a solid gel membrane that served as the electrolyte for the battery. They used zinc for the anode as usual, but replaced the conventional cathode with one made from a biodegradable organic material. The battery, reported in the journal Matter, maintained 99.7% efficiency over 1,000 cycles when operated at high current density.

Two thirds of the battery is biodegradable, making it very environmentally friendly. The chitosan electrolyte and cathode material biodegrade in the soil within months, and the zinc left behind can be recycled.