Lithium Magic...

Drive for innovation: Electric vehicles are a major target for R&D on novel battery materials. (Image courtesy: imec)

Topics: Battery, Chemical Physics, Green Tech

The batteries we depend on for our mobile phones and computers are based on a technology that is more than a quarter-century old. Rechargeable lithium-ion (Li-ion) batteries were first introduced in 1991, and their appearance heralded a revolution in consumer electronics. From then on, we could pack enough energy in a small volume to start engineering a whole panoply of portable electronic devices – devices that have given us much more flexibility and comfort in our lives and jobs.

In recent years, Li-ion batteries have also become a staple solution in efforts to solve the interlinked conundrums of climate change and renewable energy. Increasingly, they are being used to power electric vehicles and as the principal components of home-based devices that store energy generated from renewable sources, helping to balance an increasingly diverse and smart electrical grid. The technology has improved too: over the past two and a half decades, battery experts have succeeded in making Li-ion batteries 5–10% more efficient each year, just by further optimizing the existing architecture.

Ultimately, though, getting from where we are now to a truly carbon-free economy will require better-performing batteries than today’s (or even tomorrow’s) Li-ion technology can deliver. In electric vehicles, for example, a key consideration is for batteries to be as small and lightweight as possible. Achieving that goal calls for energy densities that are much higher than the 300 Wh/kg and 800 Wh/L which are seen as the practical limits for today’s Li-ion technology. Another issue holding back the adoption of electric vehicles is cost, which is currently still around 300–200 $/kWh, although that is widely projected to go below 100 $/kWh by 2025 or even earlier. The time required to recharge a battery pack – still in the range of a few hours – will also have to come down, and as batteries move into economically critical applications such as grid storage and grid balancing, very long lifetimes (a decade or more) will become a key consideration too.

There is still some room left to improve existing Li-ion technology, but not enough to meet future requirements. Instead, the process of battery innovation needs a step change: materials-science breakthroughs, new electrode chemistries and architectures that have much higher energy densities, new electrolytes that can deliver the necessary high conductivity – all in a battery that remains safe and is long-lasting as well as economical and sustainable to produce.

Beyond the lithium-ion battery, Jan Provoost, imec/Physics World

Grace Under Pressure...

The sample appears as a dark area near the center of this micrograph of the diamond-anvil cell.
Credit: X. Dong et al. Nat. Chem. 2017

Topics: Chemistry, Chemical Physics, Materials Science

Helium doesn’t play well with others. Beyond its noble gas designation on the periodic table, it has the lowest electron affinity—zero—among the elements, and the highest ionization energy. Scientists have managed to mechanically pack He atoms with other elements, but the He has little effect on those compounds’ characteristics.

Now an international team has presented evidence for a compound whose electronic structure and thus its physical properties are influenced by its He components. Researchers led by Artem Oganov ran a crystal structure prediction algorithm to play matchmaker for He and found that the compound Na₂He should form at high pressures. The researchers shared their prediction with Alexander Goncharov and colleagues, who loaded He gas and solid sodium into a diamond-anvil cell at the Carnegie Institution for Science. After increasing the pressure to 140 GPa and heating the sample, Goncharov’s team noticed a marked shift in material properties. New peaks appeared in x-ray diffraction patterns, and the sample’s melting point rose to more than 1500 K; pure Na melts at about 550 K.

Scientific American: Helium compound may form under pressure, Andrew Grant

Microfluidic Self-Assembly

Technology Review

TECHNOLOGY REVIEW: When it comes to building microscopic devices, one of the most promising ideas is to exploit the process of self-assembly. In this way, complex structures can be created by combining building blocks under natural circumstances.

This kind of self-assembly mechanism dominates at the molecular scale, where it is responsible for the construction of most biomolecules. At the heart of this mechanism is Brownian motion which effectively mixes and jiggles molecules so that they rapidly find their place in incipient structures. This is a powerful process that can form hugely complex machines such as the ribosome, a molecular device for synthesizing proteins.

One recent idea is to use colloids rather than molecules as the building blocks for even more advanced structures. Colloids are insoluble, nanometre-scale particles mixed in water. These particles can be chemically engineered to bind together to form specific structures.

But as the building blocks become bigger, it takes longer for Brownian motion to jiggle the blocks into the appropriate locations. So self-assembly take significantly longer. In fact, it can take thousands of seconds to synthesise a single colloidal molecule. At that rate, a millimetre cube containing 1 billion colloidal molecules would take 30 years to form.

Clearly, that is far too slow for any kind of industrial process, so chemists have been looking for ways to speed up colloidal self-assembly. Today, Bingqing Shen at ESPCI (the Paris Institute of Technology) in France and a few buddies say they’ve found an entirely new way to assemble structures on this scale that should reduce manufacturing time by orders of magnitude.

Physics arXiv:
Self-Assembly Driven By Hydrodynamic Interactions In Microfluidic Devices
Bingqing Shen, Joshua Ricouvier, Mathilde Reyssat, Florent Malloggi, Patrick Tabeling

Tadias...

Tadias is an online magazine for the Ethiopian-American community. It means "hi," "what's up," or "how are you?"

This is about a professor at my alma mater. The text and link will speak for itself:

"WASHINGTON, DC (TADIAS) – When Physicist Solomon Bililign was a young teacher imprisoned in Ethiopia during the “Red Terror” era, he never imagined that he would one day receive a Presidential Award in the United States.

Now a professor at North Carolina Agricultural and Technical State University, Dr. Bililign is one of nine individuals whom President Obama this week named recipients of the Presidential Award for Excellence in Science, Mathematics, and Engineering Mentoring. The honorees will receive their awards at a White House ceremony later this year. The award recognizes the role that mentoring plays in the academic and personal development of students studying science and engineering. According to the White House, candidates are nominated by colleagues, administrators, and students at their home institutions.

“Through their commitment to education and innovation, these individuals are playing a crucial role in the development of our 21st century workforce,” President Obama said. “Our nation owes them a debt of gratitude for helping ensure that America remains the global leader in science and engineering for years to come.”

Dr. Bililign said that success in science, engineering or math is not as glamorous as success in performing arts or sports in the U.S., but the economic competitiveness of the nation, depends on a solid foundation in the sciences. “Young people need to be encouraged, pushed, persuaded to do it,” he said. “Not for the money or fame but for the love of discovery and innovation. I believe every one has a gift, and a mentor’s role is to identify the gift and nurture it.”

TADIAS: Obama Honors Physicist Solomon Bililign With Presidential Award for Excellence