Cathode ‘defects’ improve battery performance

A counterintuitive finding revealed by high-precision powder diffraction analyses suggests a new strategy for building better batteries

UPTON, NY—Engineers strive to design smartphones with longer-lasting batteries, electric vehicles that can drive for hundreds of miles on a single charge, and a reliable power grid that can store renewable energy for future use. Each of these technologies is within reach—that is, if scientists can build better cathode materials.

To date, the typical strategy for enhancing cathode materials has been to alter their chemical composition. But now, chemists at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory have made a new finding about battery performance that points to a different strategy for optimizing cathode materials. Their research, published in Chemistry of Materials and featured in ACS Editors’ Choice, focuses on controlling the amount of structural defects in the cathode material.

“Instead of changing the chemical composition of the cathode, we can alter the arrangement of its atoms,” said corresponding author Peter Khalifah, a chemist at Brookhaven Lab and Stony Brook University.

>Read more on the NSLS-II at Brookhaven Lab website

Image: Corresponding author Peter Khalifah (left) with his students/co-authors Gerard Mattei (center) and Zhuo Li (right) at one of Brookhaven’s chemistry labs.

First light for SESAME’s MS beamline

On Monday, 23rd December 2019, at 13:21, scientists at the SESAME light source successfully delivered the first X-ray monochromatic beam to the experimental station of the Materials Science (MS) beamline, that will be used in applications of the X-ray powder diffraction (XRD) technique in materials science, The beamline will provide a powerful tool for studying microcrystalline or disordered/amorphous material on the atomic scale, the evolution of nano-scale structures and materials in various environmental conditions and for developing and characterising new smart materials.  

To have seen the X-ray signal inside the MS experimental station was very exciting said the MS beamline scientist, Mahmoud Abdellatief. It was the realization of four years of hard work, and has given me added stimulus for the new challenges lying ahead before the beamline may host users in some six months. 

Picture: SESAME scientists just after obtaining the first monochromatic X-ray fluorescence signal (from left to right: Mahmoud Abdellatief, MS beamline scientist, Messaoud Harfouche, XAFS/XRF beamline scientist, and Gihan Kamel, IR beamline scientist)
Credit: SESAME

Synchrotron techniques allow geologists to study the surface of Mars

State-of-the-art imaging uncovers the exciting life history of an unusual Mars meteorite

With human and sample-return missions to Mars still on the drawing board, geologists wishing to study the red planet rely on robotic helpers to collect and analyse samples. Earlier this year we said goodbye to NASA’s Opportunity rover, but Insight landed in November 2018, and several space agencies have Mars rover missions on their books for the next few years. But while we’re working on ways to bring samples back from Mars, geologists can study Martian meteorites that have been delivered to us by the forces at play in the Solar System. Earth is bombarded by tonnes of extraterrestrial material every day. Most of it comes from Jupiter Family Comets and the asteroid belt, and much of it burns up in the atmosphere or lands in the oceans, but meteorites from the Moon and Mars do make it to Earth’s surface. In research published in Geochimica et Cosmochimica Acta, scientists used a battery of synchrotron techniques to investigate a very unusual Martian meteorite, whose eventful life story offers some insights to the geological history of Mars.

>Read more on the Diamond Light Source website

Image: BSE image with locations for XANES/XRD and XRF map.

Ultralow-fluence for phase-change process

Ultrafast active materials with tunable properties are currently investigated for producing successful memory and data-processing devices. Among others, Phase-Change Materials (PCMs) are eligible for this purpose. They can reversibly switch between a high-conductive crystalline state (SET) and a low-conductive amorphous state (RESET), defining a binary code. The transformation is triggered by an electrical or optical pulse of different intensity and time duration. 3D Ge-Sb-Te based alloys, of different stoichiometry, are already employed in DVDs or Blu-Ray Disks, but they are expected to function also in non-volatile memories and RAM. The challenge is to demonstrate that the scalability to 2D, 1D up to 0D of the GST alloys improves the phase-change process in terms of lower power threshold and faster switching time. Nowadays, GST thin films and nanoparticles have been synthetized and have beenshown to function with competitive results.
A team of researchers from the University of Trieste and the MagneDyn beamline at Fermi demonstrated the optical switch from crystalline to amorphous state of Ge2Sb2Te5nanoparticles (GST NPs) with size <10 nm, produced via magnetron sputtering by collaborators from the University of Groeningen. Details were reported in the journal Nanoscale.
This work aims at showing the very low power limit of an optical pulse needed to amorphize crystalline Ge2Sb2Te5 nanoparticles. Particles of 7.8 nm and 10.4 nm diameter size were deposited on Mica and capped with ~200nm of PMMA. Researchers made use of a table-top Ti:Sapphire regenerative amplified system-available at the IDontKerr (IDK) laboratory (MagneDyn beamline support laboratory) to produce pump laser pulses at 400 nm, of ~100 fs and with a repetition rate from 1kHz to single shot.

>Read more on the Elettra Sincrotrone Trieste website

Image (extract): Trasmission Electron Microscopy image of the nanoparticles sample. Ultafast single-shot optical process with fs-pulse at 400 nm. Microscope images of amorphized and amorphized/ablated areas obtained on the nanoparticles sample. Comparison of amorphization threshold fluences between thin films and nanoparticles cases.
Please see here the entire image.

Molecular Anvils Trigger Chemical Reactions