Purdue University researchers have come up with a way to transform discarded peanut-shaped packing materials into components for rechargeable batteries that could outperform existing ones. According to Vinodkumar Etacheri, PhD, who described the research at a presentation made at the 249th National Meeting & Exposition of the American Chemical Society (ACS), the lightweight packing materials are geared for packing and protecting fragile objects.

However, the packing materials pose some challenges when it comes to their disposal. They take up a lot of space in landfills, and their light weight and large size increases the costs of transporting them to a recycling centre. It's not typically cost-effective to recycle them, explained Etacheri, a postdoctoral researcher in the lab of Vilas Pol, PhD.

The packing materials can also be potentially harmful to the environment. They are made from new or recycled polystyrene, the same molecule used in Styrofoam, but they no longer use the ozone-depleting gases called CFCs. They may, however, contain additional chemicals, though the exact constituents can vary.

Outside in a landfill, potentially harmful substances in the packing materials, such as heavy metals, chlorides and phthalates, can easily leach into the environment and deteriorate soil and water quality, said Pol, who is at Purdue University. But new versions that are marketed as being more environmentally friendly aren't benign, either. The starch-based alternatives also contain chemicals and detergents that can contaminate ecosystems.

The researchers were able to convert packing materials into high-tech carbon microsheets and nanoparticles for use in rechargeable batteries using a brand-new process they developed.

Pol and Etacheri then tested the microsheets and nanoparticles as anodes in rechargeable lithium ion batteries. The lithium ions move between the electrodes during charging and discharging. They report that their anode works so well that it outperforms commercial ones, with a storage capacity higher than graphite, a typical anode material.

They both have disordered, porous structures, explained Etacheri. Their disordered crystal structure lets them store more lithium ions than the theoretical limit, and their porous microstructure lets the lithium ions quickly diffuse into the microsheets and creates more surface area for electrochemical interactions.

The relatively low temperature used in the new process is key to producing materials with these advantageous architectures. Pol's team baked the packing materials at about 593°C. In contrast, other researchers make microsheets using much higher temperatures of nearly 2204°C. While those high temperatures create a more layered arrangement of carbon atoms to maximise electrical storage performance, Pol's less-ordered materials actually have about a 15 per cent higher electrical storage capacity. In addition, he pointed out that the high-temperature process is less environmentally-friendly because it is much more energy intensive.

By: DocMemory
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