Researchers, including one of Indian-origin, have turned waste packing peanuts into high-performance carbon electrodes for rechargeable lithium-ion batteries.
Foam peanuts, also known as packing peanuts, are a common loose-fill packaging and cushioning material used to prevent damage to fragile objects during shipping.
Batteries have two electrodes, called an anode and a cathode. The anodes in most of today's lithium-ion batteries are made of graphite. Lithium ions are contained in a liquid called an electrolyte, and these ions are stored in the anode during recharging.
Now, researchers at Purdue University have shown how to manufacture carbon-nanoparticle and microsheet anodes from polystyrene and starch-based packing peanuts, respectively.
"We were getting a lot of packing peanuts while setting up our new lab. Professor Vilas Pol suggested a pathway to do something useful with these peanuts," said postdoctoral research associate Vinodkumar Etacheri.
Research findings indicate that the new anodes can charge faster and deliver higher "specific capacity" compared to commercially available graphite anodes, Pol said.
"Although packing peanuts are used worldwide as a perfect solution for shipping, they are notoriously difficult to break down, and only about 10 per cent are recycled," Pol said.
"Due to their low density, huge containers are required for transportation and shipment to a recycler, which is expensive and does not provide much profit on investment," Pol added.
Consequently, packing peanuts often end up in landfills, where they remain intact for decades.
Although the starch-based versions are more environmentally friendly than the polystyrene peanuts, they do contain chemicals and detergents that can contaminate soil and aquatic ecosystems, posing a threat to marine animals, Pol said.
The new method "is a very simple, straightforward approach," Pol said.
"Typically, the peanuts are heated between 500 and 900 degrees Celsius in a furnace under inert atmosphere in the presence or absence of a transition metal salt catalyst," Pol said.
The resulting material is then processed into the anodes.
"The process is inexpensive, environmentally benign and potentially practical for large-scale manufacturing," Etacheri said.
"Microscopic and spectroscopic analyses proved the microstructures and morphologies responsible for superior electrochemical performances are preserved after many charge-discharge cycles," he said.
Commercial anode particles are about 10 times thicker than the new anodes and have higher electrical resistance, which increase charging time, researchers said.
