Public Release: 

Turning packing peanuts into energy-storing battery components (video)

American Chemical Society

DENVER, March 22, 2015 -- One person's trash literally could become another's high-tech treasure, according to researchers who have developed a way to turn discarded packing peanuts into components for rechargeable batteries that could outperform the ones we use currently. They will report on the process for the first time today.

The talk will be one of nearly 11,000 presentations here at the 249th National Meeting & Exposition of the American Chemical Society (ACS), the world's largest scientific society, taking place here through Thursday. A brand-new video on the research is available at http://bit.ly/PackingPeanutsACS.

Vinodkumar Etacheri, Ph.D., explains that packing peanuts are lightweight, which makes them ideal for packing and protecting fragile objects. But these peanuts 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 center. "It's not typically cost-effective to recycle them," says Etacheri, a postdoctoral researcher in the lab of Vilas Pol, Ph.D. "Only about 10 percent of the packing peanuts made in the U.S. are recycled."

In addition, packing peanuts can 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 peanuts, such as heavy metals, chlorides and phthalates, can easily leach into the environment and deteriorate soil and water quality," says 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," he explains.

Pol says the idea to turn these puffy pieces of foam into nanoparticles and microsheets came as he was taking delivery of new equipment for his lab. "I looked at the packing peanuts and thought that while we are exploring 'green' technologies, we should not be harming the environment by throwing them away," he says. That's when he advised Etacheri to find a way to transform them.

The researchers were able to convert packing peanuts 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.

What makes these microsheets and nanoparticles so much better for energy storage than existing versions? "They both have disordered, porous structures," says 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."

And the relatively low temperature used in the new process is key to producing materials with these advantageous architectures. Pol's team baked the packing peanuts at about 1,100 degrees Fahrenheit. In contrast, he notes that other researchers make microsheets using much higher temperatures of nearly 4,000 F. While those high temperatures create a more layered arrangement of carbon atoms to maximize electrical storage performance, Pol's less-ordered materials actually have about a 15 percent higher electrical storage capacity. In addition, he points out that the high-temperature process is less environmentally friendly because it's much more energy intensive. Fossil fuel-derived compounds also are typically used as their starting point, he says, adding to the environmental cost.

Pol hopes his group's new, scalable process could have carbon microsheets and nanoparticles ready for commercial use within two years.

A press conference on this topic will be held Monday, March 23, at 11 a.m. Mountain time in the Colorado Convention Center. Reporters may check-in at Room 104 in person, or watch live on YouTube http://bit.ly/ACSLiveDenver. To ask questions, sign in with a Google account.

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The researchers acknowledge funding from the Purdue University, the Purdue University School of Chemical Engineering and a Kirk Endowment grant from the Birck Nanotechnology Center.

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Title
Upcycling of packing-peanuts into carbon electrodes for electrochemical energy storage

Abstract
Environmental pollution caused by ubiquitous waste packaging materials is a serious global issue that need to be urgently addressed. Millions of tons of plastic waste are generated worldwide every year, and it is critical to find efficient methods for their disposal and recycling. Recent studies verified that plastic containers, bags, bottles and packing peanuts constitute 31 % of the municipal waste created in the U. S. A, and only ~ 40 % of these packaging materials are recycled. Currently, only a very small fraction (~10 %) of the packing peanuts is being recycled. Due to their low density (huge containers are required for transportation), shipment to a recycler is expensive, and does not provide profit on investment. As a result, most often packing peanuts end up in landfills, where they stay intact for generations. Chemical moieties such as heavy metals, chlorides, phthalates etc. present in the packing peanuts can be easily leached into the surrounding media and deteriorate soil/water quality.

We addressed the detrimental environmental impacts caused by polystyrene and starch based packing peanuts by upcycling them to carbon nanoparticles and microsheets, respectively for electrochemical energy storage, especially Li, and Na-ion batteries. State of the art synthesis of carbonaceous materials often involves the use of hydrocarbon precursors such as acetylene or coal. The method described herein does not use pressurized containers, which makes them attractive for the large-scale production of carbonaceous materials for numerous applications. Anodes composed of these microsheets and nanoparticles outperformed the electrochemical properties of commercial carbon anode in Li, and Na-ion batteries. At a current density of 0.1 C, carbon microsheet, and nanoparticle anodes exhibited Li-ion storage specific capacity of 420 mAh/g, which is even superior to the theoretical capacity of graphite (372 mAh/g). Superior electrochemical properties of the carbon electrodes are attributed to their disordered nature, and porous microstructure, which allows improved solid-state and interfacial Li, and Na-ion diffusion kinetics. The synthetic method demonstrated here is inexpensive, environmentally benign, and scalable method for the synthesis of carbonaceous materials for electrochemical energy storage.

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