Nav: Home

New 'blue-green' solution for recycling world's batteries

April 01, 2019

HOUSTON - (April 1, 2019) - Rice University researchers literally have a solution to deal with the glut of used lithium-ion batteries left behind by the ever-increasing demand for electric vehicles, cellphones and other electronic devices.

The Rice lab of materials scientist Pulickel Ajayan used an environmentally friendly deep eutectic solvent to extract valuable elements from the metal oxides commonly used as cathodes in lithium-ion batteries. The goal, researchers said, is to curtail the use of harsh processes to recycle batteries and keep them out of landfills.

The solvent, made of commodity products choline chloride and ethylene glycol, extracted more than 90 percent of cobalt from powdered compounds, and a smaller but still significant amount from used batteries.

"Rechargeable battery waste, particularly from lithium-ion batteries, will become an increasingly menacing environmental challenge in the future as the demand for these through their usage in electric vehicles and other gadgets increases dramatically," Ajayan said.

"It's important to recover strategic metals like cobalt that are limited in supply and are critical for the performance of these energy-storage devices," he said. "Something to learn from our present situation with plastics is that it is the right time to have a comprehensive strategy for recycling the growing volume of battery waste."

The results appear in Nature Energy.

"This has been attempted before with acids," said Rice graduate student and lead author Kimmai Tran. "They're effective, but they're corrosive and not eco-friendly. As a whole, recycling lithium-ion batteries is typically expensive and a risk to workers."

Other processes also have drawbacks, she said. Pyrometallurgy involves crushing and mixing at extreme temperatures, and the harmful fumes require scrubbing. Hydrometallurgy requires caustic chemicals, while other "green" solvents that extract metal ions often require additional agents or high-temperature processes to fully capture them.

"The nice thing about this deep eutectic solvent is that it can dissolve a wide variety of metal oxides," Tran said. "It's literally made of a chicken feed additive and a common plastic precursor that, when mixed together at room temperature, form a clear, relatively nontoxic solution that has effective solvating properties."

A deep eutectic solvent is a mixture of two or more compounds that freezes at temperatures much lower than each of its precursors. In that way, she said, one can literally obtain a liquid from a simple combination of solids.

"The large depression of freezing and melting points is due to the hydrogen bonds formed between the different chemicals," Tran said. "By selecting the right precursors, inexpensive 'green' solvents with interesting properties can be fabricated."

When Tran joined, the Rice group was already testing a eutectic solution as an electrolyte in next-generation high-temperature supercapacitors.

"We tried to use it in metal oxide supercapacitors, and it was dissolving them," said Rice research scientist and co-corresponding author Babu Ganguli. "The color of the solution would change."

The eutectic was pulling ions from the supercapacitor's nickel.

"Our team was discussing this and we soon realized we could use what was thought to be a disadvantage for electrolyte as an advantage for dissolving and recycling spent lithium batteries," Ganguli said.

That became Tran's focus, as she tested deep eutectic solvents on metal oxides at different temperatures and time scales. During tests with lithium cobalt oxide powder, the clear solvent yielded a wide spectrum of blue-green colors that indicated the presence of cobalt dissolved within.

At 180 degrees Celsius (356 degrees Fahrenheit), the solvent extracted nearly 90 percent of lithium ions, and up to 99 percent of cobalt ions from the powder when certain conditions were satisfied.

The researchers built small prototype batteries and cycled them 300 times before exposing the electrodes to the same conditions. The solvent proved adept at dissolving the cobalt and lithium while separating the metal oxides from the other compounds present in the electrode.

They found that cobalt could be recovered from the eutectic solution through precipitation or even electroplating to a steel mesh, as this latter method potentially allowed for the deep eutectic solvent itself to be reused.

"We focused on cobalt," said Rice alumnus Marco Rodrigues, now a postdoctoral researcher at Argonne National Laboratory. "From a resource standpoint, it's the most critical part. The battery in your phone will surely have lots of it. Lithium is very valuable too, but cobalt in particular is not only environmentally scarce but also, from a social standpoint, hard to get."

He noted the Department of Energy is mounting new efforts to advance battery recycling technologies and recently announced a center for Li-ion battery recycling.

The path forward will require continued efforts.

"It's likely we won't be able to recycle and replace mining completely," Tran said. "These technologies are relatively new, and there is a lot of optimization that needs to be done, such as exploring other deep eutectic solvents, but we truly believe in the potential for greener ways to do dirty chemistry. Sustainability is in the heart of the work I do and what I want to do for the rest of my career."
-end-
Graduate student Keiko Kato is a co-author of the paper. Ajayan is the Benjamin M. and Mary Greenwood Anderson Professor in Engineering and a professor of chemistry.

The National Science Foundation supported the research through its Graduate Research Fellowship Program.

Read the abstract at https://doi.org/10.1038/s41560-019-0368-4.

This news release can be found online at https://news.rice.edu/2019/04/01/new-blue-green-solution-for-recycling-worlds-batteries/

Follow Rice News and Media Relations via Twitter @RiceUNews.

Related materials:

Ajayan Research Group: http://ajayan.rice.edu

Department of Materials Science and NanoEngineering: https://msne.rice.edu

George R. Brown School of Engineering: https://engineering.rice.edu

Video:

https://youtu.be/76VdelMJ280

Video produced by Brandon Martin/Rice University

Images for download:

https://news-network.rice.edu/news/files/2019/03/0325_RECYCLING-1-web-1r7wsfm.jpg

Rice University graduate student Kimmai Tran and her colleagues have developed an environmentally friendly solution to remove valuable cobalt and lithium metals from spent lithium-ion batteries. (Photo by Jeff Fitlow/Rice University)

https://news-network.rice.edu/news/files/2019/03/0325_RECYCLING-2-web-26lrxdm.jpg

Rice University research scientist Babu Ganguli and graduate student Kimmai Tran show test tubes with their eutectic solvent and varying concentrations of cobalt drawn into the solution. They are developing the solvent to extract cobalt and lithium from spent lithium-ion batteries. (Photo by Jeff Fitlow/Rice University)

https://news-network.rice.edu/news/files/2019/03/0325_RECYCLING-3-web-20t2b9c.jpg

A solution turns green as it pulls cobalt from a spent lithium-ion cathode. A Rice University laboratory is developing an environmentally friendly method to recover valuable metals from used batteries. (Photo by Jeff Fitlow/Rice University)

https://news-network.rice.edu/news/files/2019/03/0325_RECYCLING-4-web-2ard3y3.jpg

The blue-green color of solutions reveals the presence of cobalt taken from spent lithium-ion batteries through a new process developed at Rice University. (Photo by Jeff Fitlow/Rice University)

https://news-network.rice.edu/news/files/2019/03/0325_RECYCLING-5-web-2eeqpyz.jpg

Experiments at Rice University have led to the development of an environmentally friendly process to recover valuable cobalt and lithium metals from spent batteries. (Photo by Jeff Fitlow/Rice University)

Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,962 undergraduates and 3,027 graduate students, Rice's undergraduate student-to-faculty ratio is just under 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for lots of race/class interaction and No. 2 for quality of life by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger's Personal Finance. David Ruth 713-348-6327 david@rice.edu

Mike Williams 713-348-6728 mikewilliams@rice.edu

Rice University

Related Batteries Articles:

A seaweed derivative could be just what lithium-sulfur batteries need
Lithium-sulfur batteries have great potential as a low-cost, high-energy, energy source for both vehicle and grid applications.
Batteries from scrap metal
Chinese scientists have made good use of waste while finding an innovative solution to a technical problem by transforming rusty stainless steel mesh into electrodes with outstanding electrochemical properties that make them ideal for potassium-ion batteries.
Better cathode materials for lithium-sulphur-batteries
A team at the Helmholtz-Zentrum Berlin (HZB) has for the first time fabricated a nanomaterial made from nanoparticles of a titanium oxide compound (Ti4O7) that is characterized by an extremely large surface area, and tested it as a cathode material in lithium-sulphur batteries.
Bright future for self-charging batteries
Who hasn't lived through the frustrating experience of being without a phone after forgetting to recharge it?
Making batteries from waste glass bottles
Researchers at the University of California, Riverside's Bourns College of Engineering have used waste glass bottles and a low-cost chemical process to create nanosilicon anodes for high-performance lithium-ion batteries.
Batteries -- quick coatings
Scientists at Oak Ridge National Laboratory are using the precision of an electron beam to instantly adhere cathode coatings for lithium-ion batteries -- a leap in efficiency that saves energy, reduces production and capital costs, and eliminates the use of toxic solvents.
Lighter, more efficient, safer lithium-ion batteries
Researchers from Universidad Carlos III de Madrid and the Council for Scientific Research (initialed CSIC in Spanish) have patented a method for making new ceramic electrodes for lithium-ion batteries that are more efficient, cheaper, more resistant and safer than conventional batteries.
Clarifying how lithium ions ferry around in rechargeable batteries
IBS scientists observe the real-time ultrafast bonding of lithium ions with the solvents, in the same process that happens during charging and discharging of lithium batteries, and conclude that a new theory is needed.
A new approach to improving lithium-sulfur batteries
Researchers from the University of Delaware and China's Northwestern Polytechnical University, Shenzhen University and Hong Kong Polytechnic University have demonstrated a new polysulfide entrapping strategy that greatly improves the cycle stability of Li-S batteries.
Looking for the next leap in rechargeable batteries
USC researchers may have just found a solution for one of the biggest stumbling blocks to the next wave of rechargeable batteries -- small enough for cellphones and powerful enough for cars.

Related Batteries Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Digital Manipulation
Technology has reshaped our lives in amazing ways. But at what cost? This hour, TED speakers reveal how what we see, read, believe — even how we vote — can be manipulated by the technology we use. Guests include journalist Carole Cadwalladr, consumer advocate Finn Myrstad, writer and marketing professor Scott Galloway, behavioral designer Nir Eyal, and computer graphics researcher Doug Roble.
Now Playing: Science for the People

#530 Why Aren't We Dead Yet?
We only notice our immune systems when they aren't working properly, or when they're under attack. How does our immune system understand what bits of us are us, and what bits are invading germs and viruses? How different are human immune systems from the immune systems of other creatures? And is the immune system so often the target of sketchy medical advice? Those questions and more, this week in our conversation with author Idan Ben-Barak about his book "Why Aren't We Dead Yet?: The Survivor’s Guide to the Immune System".