Materials For Energy

Hybrid Nanoparticle-Ionic Liquid Electrolyte for Better Batteries

(Chemistry World)

Batteries containing lithium as the ion source can store the highest known density of energy, but the most commonly used electrolytes do not work well in these batteries as they are unstable in typical operating conditions and may break down disastrously. 

Other electrolytes, including polymers and ionic liquids (ILs), have been explored. While polymer electrolytes generally have low conductivity at room temperature, ILs are salts in a liquid state and thus have good conductivity and stability under the battery operating conditions. They are, however, unable to prevent the formation of lithium networks called dendrites, which degrade battery performance. 

A research team has now developed a new family of solventless electrolytes made of hard zirconium oxide nanostructures linked to softer IL species, using a simple one-pot procedure. The electrolytes, which are a gel-like fluid at room temperature, are temperature- and redox-stable which makes them suitable for use in batteries, they transport lithium ions well and they also prevent the growth of dendrites.

Credit: Angew. Chem. Int. Ed. 

Ionic Liquid Tethered Nanoparticle Hybrid Electrolytes
Angewandte Chemie International Edition, 2010. DOI: 10.1002/anie.201004551

 

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Gopal R. Rao, Ph.D.
Web Science Editor
Materials Research Society (MRS)

Molecular Solar–Thermal Energy Storage

(Massachusetts Institute of Technology)

For capturing the sun’s energy, a thermo-chemical approach, in which solar energy is captured in the configuration of certain molecules which can then release the energy on demand to produce usable heat has been explored only to a limited extent. Unlike conventional solar-thermal systems, which require very effective insulation and even then gradually let the heat leak away, the heat-storing chemicals can remain stable for years. Researchers explored this type of solar thermal fuel in the 1970s, but there were big challenges: Nobody could find a chemical that could reliably and reversibly switch between two states. Such a compound was discovered in 1996, but it included ruthenium, a rare and expensive element, so it was impractical for widespread energy storage. Moreover, no one understood how the compound worked, which hindered efforts to find a cheaper variant.

Credit: Jeffrey Grossman, MIT

Researchers at MIT have discovered a molecule, fulvalene dirutheniumovercome, that is able to store thermal energy and release it. A combination of theoretical and experimental work has also revealed exactly how the molecule accomplishes this. Essentially, the molecule undergoes a structural transformation when it absorbs sunlight, putting the molecule into a higher-energy state where it can remain stable indefinitely. Then, triggered by a small addition of heat or a catalyst, it snaps back to its original shape, releasing heat in the process. The process is a somewhat more complicated than that. The researchers discovered an intermediate step that plays a major role. In this intermediate step, the molecule forms a semistable configuration partway between the two previously known states. The two-step process helps explain why the molecule is so stable, why the process is easily reversible and also why substituting other elements for ruthenium has not worked so far.

The problem of ruthenium’s rarity and cost still remains an issue, but since the fundamental mechanism of how the molecule works is understood, it should be easier to find other materials that exhibit the same behavior. The next step, according to the authors, is to use a combination of simulation, chemical intuition, and databases of tens of millions of known molecules to look for other candidates that have structural similarities and might exhibit the same behavior.

Mechanism of Thermal Reversal of the (Fulvalene)tetracarbonyldiruthenium Photoisomerization: Toward Molecular Solar–Thermal Energy Storage
Angewandte Chemie, Article first published online: 14 OCT 2010, DOI: 10.1002/anie.201002994

 

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Gopal R. Rao, Ph.D.
Web Science Editor
Materials Research Society (MRS)

Oil Spill Update

By Russell Chianelli

As discussed here earlier this year, the Macondo Gulf of Mexico oil spill was not the disaster that was predicted. Now that the relief well has been drilled and the spill is contained, we can look back at the event. For example, the use of dispersants was fully justified as the following news story describes: http://news.yahoo.com/s/ap/20100907/ap_on_sc/us_sci_gulf_spill_where_s_the_oil

“Government scientists studying the BP disaster are reporting the best possible outcome: Microbes are consuming the oil in the Gulf without depleting the oxygen in the water and creating “dead zones” where fish cannot survive. Outside scientists said this so far vindicates the difficult and much-debated decision by BP and the government to use massive amounts of chemical dispersants deep underwater to break up the oil before it reached the surface”. ……… Has it hit the sweet spot? Yes. Was it by design? Partly, said Steve Murawski, the National Oceanic and Atmospheric Administration senior scientist who headed the federal team of researchers.” ¹

“The use of dispersants has been a source of fierce debate because it involves an environmental trade-off: protecting the shoreline from oil at the risk of causing unknown problems in the deep. While dispersants make it easier for bacteria to degrade the oil, they tend to hide oil below the surface. There have also been concerns about the chemicals’ toxicity and the long-term effects on marine life.^”1

In May, the federal government convened about 50 scientists for advice on whether to continue using the dispersants. Though the researchers were divided before the meeting, they unanimously recommended continuing with the chemicals, said University of California Davis oil spill scientist Ron Tjeerdema. “The best of two options, neither of which were great, was to continue dispersing,” Tjeerdema said.¹

Further, Dr. Larry McKinney, director of a Gulf of Mexico research center at Texas A&M University in Corpus Christi, said the new federal data showed that it was a “nearly perfect” outcome. “They hit it on the head, which is good,” said McKinney, who was one of the original scientists reporting on the Ixtoc 1979 oil spill. He reported that the Ixtoc spill, which was probably larger than the Macondo spill, had little impact on the beaches and seafood industry because of the widespread use of dispersants by Pemex, Mexico’s government-owned oil company.¹

A recent C&EN article² reported the same results of beaches and seafood quickly coming “back to normal.” These reports are reminiscent of comments made after the Ixtoc oil spill, “where did the oil go?” Similar comments are being made today. “Those who cannot remember the past are condemned to repeat it.”³

1. S. Borenstein. Microbes are eating BP oil without using up oxygen. Associated Press. (2010)
2. C. Hogue, Restricting Dioxide in Dirt. Chem. Eng. News, 88, 22 (2010).
3. G. Santayana, Reason in Common Sense, The Life of Reason, Vol. 1 (1905).
4. Download JAG_Oxygen_Report (FINAL 090410)

For more background and discussion on the science of oil spills and cleanup, see two interviews from KDKA News Radio 1020 (Pittsburgh, PA) from June 8, 2010: KDKA_060810_DrRussChianelli.mp3 Interview by KDKA host Mike Pintek of Russell Chianelli (University of Texas El Paso), "Natural Organisms Fight Oil Spill." KDKA_060810_DrRitaColwell.mp3 Interview by KDKA host Robert Mangino of Rita Colwell (University of Maryland and Johns Hopkins University) commenting on the earlier interview with Russ Chianelli.

KDKA_060810_DrRitaColwell 32 Minutes

KDKA_060810_DrRussChianelli 16 Minutes