New processing technology converts packing peanuts to battery components.

Researchers have shown how to convert waste packing peanuts
into high-performance carbon electrodes for rechargeable
lithium-ion batteries that outperform conventional graphite
electrodes, representing an environmentally friendly approach to
reuse the waste.
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," recalled postdoctoral research associate Vinodkumar
Etacheri. "Professor Vilas Pol suggested a pathway to do
something useful with these peanuts."
This simple suggestion led to a potential new eco-friendly
application for the packaging waste. Research findings indicate
that the new anodes can charge faster and deliver higher
"specific capacity" compared to commercially available graphite
anodes, Pol said.
The new findings are being presented during the 249th American
Chemical Society National Meeting & Exposition in Denver on
March 22-26. The work was performed by Etacheri, Pol and
undergraduate chemical engineering student Chulgi Nathan
Hong.
"Although packing peanuts are used worldwide as a perfect
solution for shipping, they are notoriously difficult to break
down, and only about 10 percent 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."
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, he 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."
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."
Commercial anode particles are about 10 times thicker than the
new anodes and have higher electrical resistance, which
increase charging time.
"In our case, if we are lithiating this material during the charging
of a battery it has to travel only 1 micrometer distance, so you
can charge and discharge a battery faster than your
commercially available material," Pol said.
Because the sheets are thin and porous, they allow better
contact with the liquid electrolyte in batteries.
"These electrodes exhibited notably higher lithium-ion storage
performance compared to the commercially available graphite
anodes," he said.
Packing-peanut-derived carbon anodes demonstrated a
maximum specific capacity of 420 mAh/g (milliamp hours per
gram), which is higher than the theoretical capacity of graphite
(372 mAh/g), Etacheri said.
"Long-term electrochemical performances of these carbon
electrodes are very stable," he said. "We cycled it 300 times
without significant capacity loss. These carbonaceous
electrodes are also promising for rechargeable sodium-ion
batteries. Future work will include steps to potentially improve
performance by further activation to increase the surface area
and pore size to improve the electrochemical performance."
Source: Purdue