“Holey” graphene improves battery electrodes – May be ‘The Holy Grail’ of Next Generation Batteries 

May 12, 2017

Electrodes containing porous graphene and a niobia composite could help improve electrochemical energy storage in batteries. This is the new finding from researchers at the University of California at Los Angeles who say that the nanopores in the carbon material facilitate charge transport in a battery.

By fine tuning the size of these pores, they can not only optimize this charge transport but also increase the amount of active material in the device, which is an important step forward towards practical applications.

Niobia and holey graphene composite with tailored nanopores

Batteries and supercapacitors are two complementary electrochemical energy-storage technologies. They typically contain positive and negative electrodes with the active electrode materials coated on a metal current collector (normally copper or aluminium foil), a separator between the two electrodes, and an electrolyte that facilitates ion transport.

The electrode materials actively participate in charge (energy) storage, whereas the other components are passive but nevertheless compulsory for making the device work.

Batteries offer high energy density but low power density while supercapacitors provide high power density with low energy density.

Although lithium-ion batteries are the most widely employed batteries today for powering consumer electronics, there is a growing demand for more rapid energy storage (high power) and higher energy density. Researchers are thus looking to create materials that combine the high-energy density of battery materials with the short charging times and long cycle life of supercapacitors.

Such materials need to store a large number of charges (such as Li ions) and have an electrode architecture that can quickly deliver charges (electrons and ions) during a given charge/discharge cycle.

Increasing the mass loading of niobia in electrodes

Nanostructured materials fit the bill here, but unfortunately only for electrodes with low areal mass loading of the active materials (around 1 mg/cm2). “This is much lower than the mass of the passive components (around 10 mg/cm2 or greater),” explains team leader Xiangfeng Duan. “As a result, in spite of the high intrinsic capacity or rate capability of these new nanostructured materials, the scaled area capacity or areal current density of nanostructured electrodes rarely exceeds those of today’s Li-ion batteries.

Thus, these electrodes have not been able to deliver their extraordinary promise in practical commercial devices.

“To take full advantage of these new materials, we must increase the mass loading to a level comparable to or higher than the mass of the passive components. To satisfy the energy storage requirement of an electrode with 10 times higher mass loading requires the rapid delivery of 10 times more charge over a distance that is 10 times greater within a given time. This is a rather challenging task and has proven to be a critical roadblock for new electrode materials.

“We have now addressed this very issue of how we can increase the mass loading of niobia (Nb2O5) in electrode structures without compromising its merit for ultrahigh-rate energy storage,” he continues. “Electrodes with intrinsically high capacity or high rate capability in practical devices require a new architecture that can efficiently deliver sufficient electrons or ions.

We have designed a 3D holey-graphene-Nb2O5 composite with excellent electron and ion transport properties for ultrahigh-rate energy storage at practical levels of mass loading (greater than 10 mg/cm2).”

Porous structure facilitates rapid ion transport

“The highly interconnected graphene network in the 3D architecture provides excellent electron transport properties and its hierarchical porous structure facilitates rapid ion transport,” he adds. “What is more, by systematically tailoring the porosity in the holey graphene backbone, we optimize charge transport in the composite architecture to simultaneously deliver areal capacity and high-rate capability at practical levels of mass loading – something that is a critical step forward towards commercial applications.”

The researchers made their mechanically strong 3D porous composites in a two-step synthesis technique. “We uniformly decorate Nb2O5

Decreasing the fraction of inactive materials

The in-plane pores in the holey graphene sheet function as ion transport “shortcuts” in the hierarchical porous structure to facilitate rapid ion transport throughout the entire 3D electrode and so greatly improve ion transport kinetics and access to ions on the surface of the electrode, Duan tells nanotechweb.org.

Spurred on by these results, the researchers say they will now try to incorporate high-capacity active materials such as silicon and tin oxide to further increase output energy levels in electrochemical cells. “Extremely high mass-loaded electrodes (for example, five times that of practical mass loading, or 50 mg/cm2) could also help decrease the fraction of inactive materials in a device and so simplify the process to make these cells.”

So What’s Next?

Team GNT writes: For the Researchers to take ‘the next step’ further exploration of best outcome and integration of new structured  materials must be completed. And then …

  • Proof of Concept
  • Proof of Scalability 
  • Competitive Market Integration Analysis
  • Manufacturing Platform and Market Distribution 

A lot of hard work! But work that will be well worth the effort if the emerging technology can meet all of the required. Milestones! The current rechargeable battery market is a $112 Billion Market!

The research is detailed in Science DOI: 10.1126/science.aam5852.
Belle Dumé is contributing editor at nanotechweb.org

New Research: Nanotechnology in Oil and Natural Gas Production

QDOTS imagesCAKXSY1K 8(Nanowerk News) Flotek Industries, Inc. announced today  sponsorship of applied research at Texas A&M University to investigate the  impact of nanotechnology on oil and natural gas production in emerging,  unconventional resource plays.
“With the acceleration of activity in oil and gas producing  shales, a better understanding of the impact of various completion chemistries  on tight formations with low porosity and permeability will be key to developing  optimal completion techniques in the future,” said John Chisholm, Flotek’s  Chairman, President and Chief Executive Officer. “While we know Flotek’s Complex  nano-Fluid chemistries have been successful in enhancing production in tight  resource formations, we believe a more complete understanding of the interaction  between our chemistries and geologic formations as well as a more precise  comprehension of the physical properties and impact of our nanofluids in the  completion process will significantly enhance the efficacy of the unconventional  hydrocarbon completion process. This research continues our relationship with  Texas A&M where we also are conducting research into acidizing applications  in Enhanced Oil Recovery.”
Specifically, the research will focus its investigation on the  oil recovery potential of complex nanofluids and select surfactants under  subsurface pressure and temperature conditions of liquids-rich shales.
Dr. I. Yucel Akkutlu, Associate Professor of Petroleum  Engineering in the Harold Vance Department of Petroleum Engineering at Texas  A&M University will serve as the principal investigator for the project. Dr.  Akkutlu received his Masters and PhD in Petroleum Engineering from the  University of Southern California. He has over a decade of postgraduate  theoretical and experimental research experience in unconventional oil and gas  recovery, enhanced oil recovery and reactive flow and transport in heterogeneous  porous media. He has recently participated in industry-sponsored research on  resource shales including analysis of microscopic data to better understand  fluid storage and transport properties of organic-rich shales.
“As unconventional resource opportunities continue to grow in  importance to hydrocarbon production, understanding ways to maximize recovery  will be key to improving the efficacy of these projects,” said Dr. Akkutlu. “The  key to enhancing recovery will be to best understand robust, new technologies  and their impact on the completion process. Research into complex nanofluid  chemistries to understand the physical properties and formation interactions  will play an integral role in the future of completion design to optimize  recovery from unconventional hydrocarbon resources.”
Source: Flotek Industries

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