This schematic depicts a process for converting 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. Credit: (Purdue University image/Vinodkumar Etacheri)
A research team from Purdue University has developed a new eco-friendly technique to reuse the packaging waste by transforming waste packing peanuts into carbon electrodes for use in rechargeable lithium-ion batteries. These high-performance electrodes have been found to be better than standard graphite electrodes.
Batteries include two electrodes: a cathode and an anode. Present generation of lithium-ion batteries contain anodes that are made of graphite material. A liquid called electrolyte holds lithium ions, which are stored in the anode at the time of recharging.
The research team has demonstrated ways for manufacturing microsheet anodes and carbon-nanoparticle from starch-based packing peanuts and polystyrene, 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, informed postdoctoral research associate Vinodkumar Etacheri.
This proposal resulted in the development of an innovative, environmentally friendly application for the packaging waste materials. According to the research findings, the novel anodes are not only able to charge much faster, but also deliver higher specific capacity than that of graphite anodes that are commercially available on the market.
The results of the latest study are being presented at the 249th American Chemical Society National Meeting & Exposition held in Denver from March 22 to 26, 2015. The study was carried out by Professor Vilas Pol, Etacheri, and Chulgi Nathan Hong, an undergraduate chemical engineering student.
"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. 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. The new method "is a very simple, straightforward approach. 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," said Pol.
The ensuing material is subsequently processed into the anodes.
"The process is inexpensive, environmentally benign and potentially practical for large-scale manufacturing,. Microscopic and spectroscopic analyses proved the microstructures and morphologies responsible for superior electrochemical performances are preserved after many charge-discharge cycles," said Etacheri.
Commercially available anode particles are roughly 10x thicker when compared to the novel anodes and also exhibit higher electrical resistance that amplify the charging time. Since the sheets are porous and thin, they promote a better contact with the electrolyte present in batteries.
"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. These electrodes exhibited notably higher lithium-ion storage performance compared to the commercially available graphite anodes," added Pol.
"Packing-peanut-derived carbon anodes demonstrated a maximum specific capacity of 420mAh/g (milliamp hours per gram), which is higher than the theoretical capacity of graphite (372mAh/g). Long-term electrochemical performances of these carbon electrodes are very stable. 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," concluded Etacheri.