Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Cleaning up hybrid battery electrodes improves capacity and lifespan

22.04.2016

New way of building supercapacitor-battery electrodes eliminates interference from inactive components

Hybrid batteries that charge faster than conventional ones could have significantly better electrical capacity and long-term stability when prepared with a gentle-sounding way of making electrodes.


Ion soft landing distributes negative POM ions (bright spots) evenly onto a supercapacitor, leaving unwanted positive ions behind.

Credit: Venkateshkumar Prabhakaran/PNNL

Called ion soft-landing, the high-precision technique resulted in electrodes that could store a third more energy and had twice the lifespan compared to those prepared by a conventional method, the researchers report today in Nature Communications. Straightforward to set up, the method could eventually lead to cheaper, more powerful, longer-lasting rechargeable batteries.

"This is the first time anyone has been able to put together a functioning battery using ion soft-landing," said chemist and Laboratory Fellow Julia Laskin of the Department of Energy's Pacific Northwest National Laboratory.

The advantages come from soft-landing's ability to build an electrode surface very specifically with only the most desirable molecules out of a complex mixture of raw components.

"It will help us unravel important scientific questions about this energy storage technology, a hybrid between common lithium rechargeable batteries and supercapacitors that have very high energy density," said lead author, PNNL chemist Venkateshkumar Prabhakaran.

A different kind of hybrid

Although lithium ion rechargeable batteries are the go-to technology for small electronic devices, they release their energy slowly, which is why hybrid electric vehicles use gasoline for accelerating, and take a long time to recharge, which makes electric vehicles slower to "fill" than their gas-powered cousins.

One possible solution is a hybrid battery that crosses a lithium battery's ability to hold a lot of charge for its size with a fast-charging supercapacitor. PNNL chemists wanted to know if they could make superior hybrid battery materials with a technology -- called ion soft-landing -- that intricately controls the raw components during preparation.

To find out, Laskin and colleagues created hybrid electrodes by spraying a chemical known as POM, or polyoxometalate, onto supercapacitor electrodes made of microscopically small carbon tubes. Off-the-shelf POM has both positively and negatively charged parts called ions, but only the negative ions are needed in hybrid electrodes.

Limited by its design, the conventional preparation technique sprays both the positive and negative ions onto the carbon nanotubes. Ion soft-landing, however, separates the charged parts and only sets down the negative ions on the electrode surface. The question that Laskin and team had was, do positive ions interfere with the performance of hybrid electrodes?

To find out, the team made centimeter-sized square hybrid batteries out of POM-carbon nanotube electrodes that sandwiched a specially developed ionic liquid membrane between them.

"We had to design a membrane that separated the electrodes and also served as the battery's electrolyte, which allows conduction of ions," said Prabhakaran. "Most people know electrolytes as the liquid sloshing around within a car battery. Ours was a solid gel."

They tested this mini-hybrid battery for how much energy it could hold and how many cycles of charging and discharging it could handle before petering out.

They compared soft-landing with conventionally made hybrid batteries, which were made with a technique called electrospray deposition. They used an off-the-shelf POM containing positively charged sodium ions.

Cheers for the POMs

The team found that the POM hybrid electrodes made with soft-landing had superior energy storage capacity. They could hold a third more energy than the carbon nanotube supercapacitors by themselves, which were included as a minimum performance benchmark. And soft-landing hybrids held about 27 percent more energy than conventionally made electrospray deposited electrodes.

To make sure the team was using the optimal amount of POM, they made hybrid electrodes using different amounts and tested which one resulted in the highest capacity. Soft-landing produced the highest capacity overall using the lowest amount of POM. This indicated the electrodes used the active material extremely efficiently. In comparison, conventional, sodium-based POM electrodes required twice as much POM material to reach their highest capacity.

The conventionally-made devices used more POM, but the team couldn't count them out yet. They might in fact have a longer lifespan than the soft-landing produced electrodes. To test that, the team charged and discharged the hybrids 1,000 times and measured how long they lasted.

As they did in the previous tests, the soft-landing-based devices performed the best, losing only a few percent capacity after 1000 cycles. The naked supercapacitors came in second, and the sodium-based, conventionally made devices lost about double the capacity of the soft-landed devices. This suggests that the soft-landing method has the potential to double the lifespan of these types of hybrid batteries.

Looking good

The team was surprised that it took so little of the POM material to make such a big difference to the carbon nanotube supercapacitors. By weight, the amount of POM was just one-fifth of a percent of the amount of carbon nanotube material.

"The fact that the capacitance reaches a maximum with so little POM, and then drops off with more, is remarkable," said Laskin. "We didn't expect such a small amount of POM to be making such a large contribution to the capacitance."

They decided to examine the structure of the electrodes using powerful microscopes in EMSL, the Environmental Molecular Sciences Laboratory, a DOE Office of Science User Facility at PNNL. They compared soft-landing with the conventionally made, sodium-POM electrodes.

Soft-landing created small discrete clusters of POM dotting the carbon nanotubes, but the conventional method resulted in larger clumps of POM clusters swamping out the nanotubes, aggregates up to ten times the size of those made by soft-landing.

This result suggested to the researchers that removing the positive ions from the POM starting material allowed the negative ions to disperse evenly over the surface. As long as the positive ions such as sodium remained, the POM and sodium appear to reform the crystalline material and aggregate on the surface. This prevented much of the POM from doing its job in the battery, thereby reducing capacity.

When the team zoomed out a little and viewed the nanotubes from above, the conventionally made electrodes were covered in large aggregates of POM. The soft-landed electrodes, however, were remarkably indistinguishable from the naked carbon nanotube supercapacitors.

In future research, the team wants to explore how to get the carbon materials to accept more POM, which might increase capacity and lifespan even further.

###

This work was supported by the Department of Energy Office of Science and the Joint Center for Energy Storage Research, a Department of Energy Innovation Hub.

The Joint Center for Energy Storage Research (JCESR), a DOE Energy Innovation Hub, is a major partnership that integrates researchers from many disciplines to overcome critical scientific and technical barriers and create new breakthrough energy storage technology. Led by the U.S. Department of Energy's Argonne National Laboratory, partners include national leaders in science and engineering from academia, the private sector, and national laboratories. Their combined expertise spans the full range of the technology-development pipeline from basic research to prototype development to product engineering to market delivery.

Reference: Venkateshkumar Prabhakaran, B. Layla Mehdi, Jeffrey J. Ditto, Mark H. Engelhard, Bingbing Wang, K. Don D. Gunaratne, David C. Johnson, Nigel D. Browning, Grant E. Johnson and Julia Laskin. Rational Design of Efficient Electrode-Electrolyte Interfaces for Solid-State Energy Storage Using Ion Soft-Landing , Nature Communications April 21, 2016, DOI:10.1038/NCOMMS11399.

EMSL, the Environmental Molecular Sciences Laboratory, is a national scientific user facility sponsored by the Department of Energy's Office of Science. Located at Pacific Northwest National Laboratory in Richland, Wash., EMSL offers an open, collaborative environment for scientific discovery to researchers around the world. Its integrated computational and experimental resources enable researchers to realize important scientific insights and create new technologies. Follow EMSL on Facebook, LinkedIn and Twitter.

Interdisciplinary teams at Pacific Northwest National Laboratory address many of America's most pressing issues in energy, the environment and national security through advances in basic and applied science. Founded in 1965, PNNL employs 4,400 staff and has an annual budget of nearly $1 billion. It is managed by Battelle for the U.S. Department of Energy's Office of Science. As the single largest supporter of basic research in the physical sciences in the United States, the Office of Science is working to address some of the most pressing challenges of our time. For more information on PNNL, visit the PNNL News Center, or follow PNNL on Facebook, Google+, LinkedIn and Twitter.

Media Contact

Mary Beckman
mary.beckman@pnnl.gov
509-375-3688

 @PNNLab

http://www.pnnl.gov/news 

Mary Beckman | EurekAlert!

Further reports about: Cleaning POM battery battery electrodes electrodes ions rechargeable batteries

More articles from Materials Sciences:

nachricht Nagoya physicists resolve long-standing mystery of structure-less transition
21.08.2017 | Nagoya University

nachricht Scientists from the MSU studied new liquid-crystalline photochrom
21.08.2017 | Lomonosov Moscow State University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

Nagoya physicists resolve long-standing mystery of structure-less transition

21.08.2017 | Materials Sciences

Chronic stress induces fatal organ dysfunctions via a new neural circuit

21.08.2017 | Health and Medicine

Scientists from the MSU studied new liquid-crystalline photochrom

21.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>