Chemical engineers don’t like waste. We are always looking for ways to use and reuse items that would otherwise be discarded (see my blog ‘Ionic fluids pack a punch for biofuels‘).
At a first glance, some products only have one function. For example, the loose-fill packing peanuts that make shipping fragile items easier.
Packing peanuts normally end up in landfill sites where they remain intact for decades and as they’re difficult to breakdown, only around 10 per cent are recycled in the US.
So, researchers from Purdue University, US, did some clever thinking and found a way to convert packing peanuts into carbon electrodes that can outperform the conventional graphite electrodes found in lithium ion batteries.
It all started when Professor Vilas Pol, an associate professor of chemical engineering, and his postdoctoral researcher, Vinodkumar Etacheri, were unpacking boxes filled with instruments for Vilas’ new lab. After emptying the boxes, they had great new lab full of instruments and a surplus of packing peanuts.
Instead of throwing the packing peanuts away, Pol and Etacheri decided to find another use for them – by manufacturing carbon-nanoparticle and micro sheet anodes from polystyrene and starch-based packing peanuts respectively.
Batteries have two electrodes: an anode (usually made from graphite); and a cathode. As a battery charges and discharges, the graphite absorbs and releases lithium ions.
To turn the packing peanuts into material suitable for making anodes, Vilas and his team heated them for a couple of hours in a furnace at temperatures exceeding 500°C in an inert argon gas atmosphere. They also introduced a transition metal catalyst to tweak the process.
The resultant carbonaceous material was ground into fine particles and subsequently formed into micro sheets suitable for manufacturing the new anodes. It sounds simple, but it really worked as this short YouTube clip reveals.
Tests showed that lithium batteries with anodes that started life as packing peanuts charged faster than their conventional counterparts. That’s because the new anodes are composed of particles that are around 10 times thinner than graphite, with a lower electrical resistance. Hence, faster charging.
As well as supporting faster charging, the microsheets’ large porous surface area permits better absorption of lithium ions. This increases their storage capacity by around 13 per cent compared to commercially available graphite anodes – 420mAh/g (milliamp hours per gram) compared to 372 mAh/g.
There’s huge potential for upcycling here. The team, including chemical engineering student Chulgi Nathan Hong, presented their work at the national meeting of the American Chemical Society in Denver, US, last month.
Sherine Obare, an associate professor of chemistry at Western Michigan University, who chaired the session, pointed out that this carbonisation method would probably work with any material containing polystyrene.
Vilas said: “Long-term electrochemical performance 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.”
Vilas and his team are now looking for funding to scale up the process.
Of course, this is not the first time I’ve blogged about Vilas and his team at Purdue University (see my blog ‘Tiny carbon spheres reduce engine wear and tear’). It just goes to show that chemical engineers can work with materials that have a diverse range of applications.
So, once again, I wish Vilas and his team every success with their research.
*Title may induce snack cravings.
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