Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Quantum dots made from fool's gold boost battery performance

12.11.2015

If you add quantum dots - nanocrystals 10,000 times smaller than the width of a human hair - to a smartphone battery it will charge in 30 seconds, but the effect only lasts for a few recharge cycles.

However, a group of researchers at Vanderbilt University report in the Nov. 11 issue of the journal ACS Nano that they have found a way to overcome this problem: Making the quantum dots out of iron pyrite, commonly known as fool's gold, can produce batteries that charge quickly and work for dozens of cycles.


Vanderbilt graduate student Anna Douglas holding one of the batteries that she has modified by adding millions of quantum dots made from iron pyrite, fool's gold.

Credit: John Russell, Vanderbilt University

The research team headed by Assistant Professor of Mechanical Engineering Cary Pint and led by graduate student Anna Douglas became interested in iron pyrite because it is one of the most abundant materials in the earth's surface. It is produced in raw form as a byproduct of coal production and is so cheap that it is used in lithium batteries that are bought in the store and thrown away after a single use.

Despite all their promise, researchers have had trouble getting nanoparticles to improve battery performance.

"Researchers have demonstrated that nanoscale materials can significantly improve batteries, but there is a limit," Pint said. "When the particles get very small, generally meaning below 10 nanometers (40 to 50 atoms wide), the nanoparticles begin to chemically react with the electrolytes and so can only charge and discharge a few times. So this size regime is forbidden In commercial lithium-ion batteries."

Aided by Douglas' expertise in synthesizing nanoparticles, the team set out to explore this "ultrasmall" regime. They did so by adding millions of iron pyrite quantum dots of different sizes to standard lithium button batteries like those that are used to power watches, automobile key remotes and LED flashlights. They got the most bang for their buck when they added ultrasmall nanocrystals that were about 4.5 nanometers in size. These substantially improved both the batteries' cycling and rate capabilities.

The researchers discovered that they got this result because iron pyrite has a unique way of changing form into an iron and a lithium-sulfur (or sodium sulfur) compound to store energy. "This is a different mechanism from how commercial lithium-ion batteries store charge, where lithium inserts into a material during charging and is extracted while discharging - all the while leaving the material that stores the lithium mostly unchanged," Douglas explained.

According to Pint, "You can think of it like vanilla cake. Storing lithium or sodium in conventional battery materials is like pushing chocolate chips into the cake and then pulling the intact chips back out. With the interesting materials we're studying, you put chocolate chips into vanilla cake and it changes into a chocolate cake with vanilla chips."

As a result, the rules that forbid the use of ultrasmall nanoparticles in batteries no longer apply. In fact, the scales are tipped in favor of very small nanoparticles.

"Instead of just inserting lithium or sodium ions in or out of the nanoparticles, storage in iron pyrite requires the diffusion of iron atoms as well. Unfortunately, iron diffuses slowly, requiring that the size be smaller than the iron diffusion length - something that is only possible with ultrasmall nanoparticles," Douglas explained.

A key observation of the team's study was that these ultrasmall nanoparticles are equipped with dimensions that allow the iron to move to the surface while the sodium or lithium reacts with the sulfurs in the iron pyrite. They demonstrated that this isn't the case for larger particles, where the inability of the iron to move through the iron pyrite materials limits their storage capability.

Pint believes that understanding of chemical storage mechanisms and how they depend on nanoscale dimensions is critical to enable the evolution of battery performance at a pace that stands up to Moore's law and can support the transition to electric vehicles.

"The batteries of tomorrow that can charge in seconds and discharge in days will not just use nanotechnology, they will benefit from the development of new tools that will allow us to design nanostructures that can stand up to tens of thousands of cycles and possess energy storage capacities rivaling that of gasoline," said Pint. "Our research is a major step in this direction."

###

Coauthors of the paper with Pint and Douglas include mechanical engineering graduate students Rachel Carter and Adam Cohn and interdisciplinary materials science graduate students Keith Share and Landon Oakes. The research was funded in part by National Science Foundation grant EPS 1004083 and NSF's graduate research fellowship program grant 1445197.

David F. Salisbury | Vanderbilt University

More articles from Information Technology:

nachricht Single-photon detector can count to 4
18.12.2017 | Duke University

nachricht New epidemic management system combats monkeypox outbreak in Nigeria
15.12.2017 | Helmholtz-Zentrum für Infektionsforschung

All articles from Information Technology >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Error-free into the Quantum Computer Age

A study carried out by an international team of researchers and published in the journal Physical Review X shows that ion-trap technologies available today are suitable for building large-scale quantum computers. The scientists introduce trapped-ion quantum error correction protocols that detect and correct processing errors.

In order to reach their full potential, today’s quantum computer prototypes have to meet specific criteria: First, they have to be made bigger, which means...

Im Focus: Search for planets with Carmenes successful

German and Spanish researchers plan, build and use modern spectrograph

Since 2016, German and Spanish researchers, among them scientists from the University of Göttingen, have been hunting for exoplanets with the “Carmenes”...

Im Focus: First-of-its-kind chemical oscillator offers new level of molecular control

DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.

Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Single-photon detector can count to 4

18.12.2017 | Information Technology

Quantum memory with record-breaking capacity based on laser-cooled atoms

18.12.2017 | Physics and Astronomy

How much soil goes down the drain -- New data on soil lost due to water

18.12.2017 | Agricultural and Forestry Science

VideoLinks
B2B-VideoLinks
More VideoLinks >>>