Finding unusual performance in unconventional battery materials

Even as our electronic devices become ever more sophisticated and versatile, battery technology remains a stubborn bottleneck, preventing the full realization of promising applications such as electric vehicles and power-grid solar energy storage.  Among the limitations of current materials are poor ionic and electron transport qualities. While strategies exist to improve these properties, and hence reduce charging times and enhance storage capacity, they are often expensive, difficult to implement on a large scale, and of only limited effectiveness.  An alternative solution is the search for new materials with the desired atomic structures and characteristics.  This is the strategy of a group of researchers who, utilizing ultra-bright x-rays from the U.S. Department of Energy’s Advanced Photon Source (APS), identified and characterized two niobium tungsten oxide materials that demonstrate much faster charging rates and power output than conventional lithium electrodes.  Their work appeared in the journal Nature.

Currently, the usual approach for wringing extra capacity and performance from lithium-ion batteries involves the creation of electrode materials with nanoscale structures, which reduces the diffusion distances for lithium ions.  However, this also tends to increase the practical volume of the material and can introduce unwanted additional chemical reactions. Further, when graphite electrodes are pushed to achieve high charging rates, irregular dendrites of lithium can form and grow, leading to short circuits, overheating, and even fires.  Measures to prevent these dendrites generally cause a decrease in energy density.  These issues seriously limit the use of graphite electrodes for high-rate applications.

>Read more on the Advanced Photon Source website

Image: Artist’s impression of rapidly flowing lithium through the niobium tungsten oxide structure. This is a detail of the image, please see here for the entire art work.
Credit: Ella Maru Studio

A super-relaxed myosin state to offset hypertrophic cardiomyopathy

At its most basic level, the proper functioning of the heart depends upon the intricate interaction of proteins that trigger, maintain, and control the muscular contractions and relaxations of this vital organ. Disruption of those interactions can cause serious pathologies such as hypertrophic cardiomyopathy (HCM). Such disruptions can originate with mutations in the primary motor protein involved in heart contraction, ß-cardiac myosin, which can alter the rate of ATP hydrolysis and have been hypothesized to destabilize its super-relaxed state (SRX). Researchers investigated the stabilizing action of mavacamten, a cardiac drug currently in phase 3 clinical trials, on the ß-cardiac myosin super-relaxed state and its possible therapeutic effects on HCM. Their work, which included electron microscopy and low-angle x-ray diffraction at the U.S. Department of Energy’s Advanced Photon Source (APS), was published in Proceedings of the National Academies of Sciences of the United States of America.

Previous work had hinted that a folded state of the myosin protein, seen both in purified form and in isolated filaments and known as the interacting-heads motif or IHM, could be analogous to the SRX state, although this has not yet been demonstrated experimentally. It has been proposed that mutations causing HCM disrupt this state, resulting in a higher percentage of myosin heads being available for interaction with actin and leading to the hypercontractility of cardiac tissue seen in HCM. These investigators, from  MyoKardia, Inc., the Stanford University School of Medicine, the Illinois Institute of Technology, Exemplar Genetics, the Harvard Medical School, and the University of California, San Francisco, first studied this possibility using three separate purified ß-cardiac myosin constructs (25-heptad heavy meromysin [HMM], two-heptad HMM, and short S1), finding that a fraction of their basal ATPase rates were within the range of 0.002-0.004 s-1 which defines the SRX state.

>Read more on the Advanced Photon Source at Argonne National Laboratory

Image: The figure (a) shows a diffraction pattern from untreated muscle compared to treated muscle on the right. Intensification of the x-ray reflections from the treated muscle indicate a highly ordered “super-relaxed” state of myosin motors. Figure (b) shows the myosin heads in the compact “interacting head motif” which the heads adopt in the super-relaxed state allowing them to be packed closely and tightly on the surface of muscle thick filaments.

 

Topological excitations emerge from a vibrating crystal lattice

It has long been known that the properties of materials are crucially dependent on the arrangement of the atoms that make up the material. For example, atoms that are further apart will tend to vibrate more slowly and propagate sound waves more slowly. Now, researchers from Brookhaven National Laboratory have used Sector 30 at the Advanced Photon Source (APS) to discover “topological” vibrations in iron silicide (FeSi). These topological vibration arise from a special symmetrical arrangement of the atoms in FeSi and endow the atomic vibrations with novel properties such as the potential to transmit sound waves along the edge of the materials without scattering and dissipation. Looking to the future one might envisage using these modes to transfer energy or information within technological devices.

In quantum mechanics, atomic motions in crystals are described in terms of vibrational modes called phonons. Similar to electrons moving in metals, phonons can also propagate through materials. The detailed properties of these excitations determine many of the thermal, mechanical and electronic properties of the material. In 2017, part of the current collaborative team from the Chinese Academy of Science, theoretically predicted the existence of the topological phonons in transition metal monosilicides. As shown in Fig.1, these topological phonons are formed by two Dirac-cones with different slopes and are protected by symmetry. Since the mathematical description of each Dirac-cone is intimately related to the famous Weyl-equation that was originally proposed in high-energy physics, these topological phonons are consequently called double-Weyl excitations.

>Read more on the Advanced Photon Source website

Image: (extract) Schematic view of the double-Weyl phonon dispersion. Full image here.
Credit: Brookhaven National Laboratory

Demonstrating a new approach to lithium-ion batteries

A team of researchers from the University of Cambridge, Diamond Light Source and Argonne National Laboratory in the US have demonstrated a new approach that could fast-track the development of lithium-ion batteries that are both high-powered and fast-charging.

In a bid to tackle rising air pollution, the UK government has banned the sale of new diesel and petrol vehicles from 2040, and the race is on to develop high performance batteries for electric vehicles that can be charged in minutes, not hours. The rechargeable battery technology of choice is currently lithium-ion (Li-ion), and the power output and recharging time of Li-ion batteries are dependent on how ions and electrons move between the battery electrodes and electrolyte. In particular, the Li-ion diffusion rate provides a fundamental limitation to the rate at which a battery can be charged and discharged.

>Read more on the Diamond Light Source website

Molecular Anvils Trigger Chemical Reactions

Spin and charge frozen by strain

In the development of next-generation microelectronics, a great deal of attention has been given to the use of epitaxy (the deposition of a crystalline overlayer on a crystalline substrate) to tailor the properties of materials to suit particular applications. Correlated electron systems provide an excellent platform for the development of new microelectronic devices due to the presence of multiple competing ground states of similar energy. In some cases, strain can drive these systems between two or more such states, resulting in phase transitions and dramatic changes in the properties of the material. Often, the specific mechanism by which strain accomplishes such a feat is unknown. This was precisely the case in lanthanum cobaltite, LaCoO3, which undergoes a strain-induced transition from paramagnet to ferromagnet, until a recent study carried out at the U.S. Department of Energy’s Advanced Photon Source (APS) revealed the intriguing microscopic phenomena at work in this system. These phenomena may play a role in spin-state and magnetic-phase transitions, regardless of stimulus, in many other correlated systems.

Lanthanum cobaltite is a perovskite, which means the structure can be thought of as made up of distorted cubes with cobalt at the cube centers, oxygen at the cube faces, and lanthanum at the cube corners. The cobalt ions have a nominal 3+ valence, meaning they lose three electrons to the neighboring oxygen ions. Bulk LaCoO3 is paramagnetic (that is, having a net magnetization only in the presence of an externally applied magnetic field) above 110 Kelvin, and non-magnetic below that temperature. In its ground state, all the electrons on a given cobalt ion are paired, meaning their magnetic spins cancel each other out. These are so-called low-spin (LS) Co3+ ions, and when all of the cobalt ions are in this form, LaCoO3 is non-magnetic.

>Read more on the Advanced Photon Source website

Image: Upper left: Resonant x-ray scattering at the cobalt K-edge. Inversion of the spectra at the reflections shown indicates the presence of charge order. Upper right: X-ray diffraction reciprocal space maps at the (002) and (003) reflection indicating the high epitaxial quality of the films. The satellite peaks result from lattice modulations associated with the reduced symmetry in the film. Lower left: Schematic crystal structure of epitaxial LaCoO3 showing the arrangement of cobalt sites with different charge and spin. The circulated charge transfer from oxygen to the different cobalt sites is also shown. Lower right: Calculated total energy as a function of the difference between the in-plane Co-O bond lengths of HS and LS cobalt ions (∆rCo-O).

Freeze-framing nanosecond movements of nanoparticles

New method allows to monitor fast movements at hard X-ray lasers.

A team of scientists from DESY, the Advanced Photon Source APS and National Accelerator Laboratory SLAC, both in the USA, have developed and integrated a new method for monitoring ultrafast movements of nanoscopic systems. With the light of the X-ray laser LCLS at the research center SLAC in California, they took images of the movements of nanoparticles taking only the billionth of a second (0,000 000 001 s). In their experiments now published in the journal Nature Communications they overcame the slowness of present-day two-dimensional X-ray detectors by splitting individual laser flashes of LCLS, delaying one half of it by a nanosecond and recording a single picture of the nanoparticle with these pairs of X-ray pulses. The tunable light splitter for hard X-rays which the scientists developed for these experiments enables this new technique to monitor movements of nanometer size fluctuations down to femtoseconds and at atomic resolution. For comparison: modern synchrotron radiation light sources like PETRA III at DESY can typically measure movements on millisecond timescales.

The intense light flashes of X-ray lasers are coherent which means that the waves of the monochromatic laser light propagate in phase to each other. Diffracting coherent light by a sample usually results in a so-called speckle diffraction pattern showing apparently randomly ordered light spots. However, this speckle is also a map of the sample arrangement, and movements of the sample constituents result in a different speckle pattern.

>Read more on the DESY website

Image: Scheme of the experiment: An autocorrelator developed at DESY splits the ultrashort X-ray laser pulses into two equal intensity pulses which arrive with a tunable delay at the sample. The speckle pattern of the sample is collected in a single exposure of the 2-D detector
Credit: W. Roseker/DESY

Sending electrons on a rollercoaster ride

A first-of-its-kind x-ray instrument for frontier research with high-brightness x-rays is now in operation at Argonne National Laboratory. The new device utilizes a unique superconducting technology that speeds electrons on a path much like that of a rollercoaster.

The insertion device (ID), called a Helical Superconducting Undulator (HSCU), was designed at the Advanced Photon Source (APS), a U.S. Department of Energy (DOE) Office of Science User Facility at DOE’s Argonne National Laboratory. The device has three primary advantages over other types of IDs for producing high-brightness x-rays: (1) it generates a stronger magnetic field than other IDs; (2) it allows researchers to select a single energy from the x-ray beam without using any x-ray optics; and (3) it produces an x-ray beam with circular polarization. Argonne developed the helical undulator with $2 million in funding from the DOE Office of Science.

>Read more on the Advanced Photon Source website

Image: Matthew Kasa and Susan Bettenhausen of the Advanced Photon Source (APS) Accelerator Division Magnetic Devices Group put the finishing touches on installation of the Helical Superconducting Undulator in Sector 7 of the APS storage ring.

Scientists have a new way to gauge the growth of nanowires

In a new study, researchers from the U.S. Department of Energy’s Argonne and Brookhaven National Laboratories observed the formation of two kinds of defects in individual nanowires, which are smaller in diameter than a human hair.

These nanowires, made of indium gallium arsenide, could be useful for a wide range of applications in a field scientists have termed optoelectronics, which encompasses devices that work by converting light energy into electrical impulses. Fiber optic relays are a good example.

The effectiveness of these devices, however, can be affected by tiny defects in their components. These defects, which can change both the optical and electronic properties of these materials, interest scientists who seek to tailor them to boost the functionality of future optoelectronics, including materials that will be able to manipulate quantum information.

>Read more on the NSLS-II website and the Advanced Photon Source website

Image: Argonne and Brookhaven researchers observed two kinds of defects forming in individual nanowires, depicted here. These nanowires are smaller in diameter than a human hair.
Credit: Megan Hill/Northwestern University

Study suggests water may exist in Earth’s lower mantle

Water on Earth runs deep – very deep. The oceans have been measured to a maximum depth of 7 miles, though water is known to exist well below the oceans. Just how deep this hidden water reaches, and how much of it exists, are the subjects of ongoing research.

Now a new study suggests that water may be more common than expected at extreme depths approaching 400 miles and possibly beyond – within Earth’s lower mantle. The study, which appeared March 8 in the journal Science, explored microscopic pockets of a trapped form of crystallized water molecules in a sampling of diamonds from around the world.

Diamond samples from locations in Africa and China were studied through a variety of techniques, including a method using infrared light at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab). Researchers used Berkeley Lab’s Advanced Light Source (ALS), and Argonne National Laboratory’s Advanced Photon Source, which are research centers known as synchrotron facilities.

>Read more on the Advanced Light Source website

Photo: Oliver Tschauner, professor of research in the Department of Geoscience at the University of Nevada, Las Vegas, holds a diamond sample during a recent round of experiments at Berkeley Lab’s Advanced Light Source.
Credit: Marilyn Chung/Berkeley Lab

Stressing over new materials

Titanium is a workhorse metal of the modern age. Alloyed with small amounts of aluminum and vanadium, it is used in aircraft, premium sports equipment, race cars, space craft, high-end bicycles, and medical devices because of its light weight, ability to withstand extreme temperatures, and excellent corrosion resistance. But titanium is also expensive. Metallurgists would love to understand exactly what makes it so strong so that they could design other materials with similarly desirable properties out of more common, less expensive elements. Now, researchers utilizing the U.S. Department of Energy’s Advanced Photon Source (APS) have used high-intensity x-rays to show how titanium alloy responds to stress in its (until now) hidden interior. Eventually, the researchers believe they will be able to predict how strong a titanium part such as an aircraft engine will be, just by knowing how the crystals are arranged inside of it. And materials scientists may be able to use such a computational model to swap in atoms from different metals to see how their crystalline structures compare to that of titanium.

>Read more on the Advanced Photon Source website

Figure: (extract) (A) A computational model of crystals inside a block of titanium, (B) includes effects noticed during the experiment to place permanent deformations (the darkened areas,) [not visible here, entire picture here]  while (C) models permanent deformations without incorporating the diversity of load seen in the experiment.

X-ray imaging of gigahertz ferroelectric domain dynamics

A team of researchers has made an important advance in broadening our understanding of light-induced mesoscale dynamics using the U.S. Department of Energy’s Advanced Photon Source (APS) at Argonne National Laboratory. Time-resolved x-ray diffraction microscopy, aided by a newly developed dynamical phase-field method (DPFM), revealed how lattice waves can be excited by light pulses and the resulting local structural changes among mesoscopic domains in ferroelectrics, a widely utilized material for sensors, nanoscale positioners, and information storage devices.

Light interaction with matter offers a new way of controlling material properties by harnessing energy transport and conversion in functional materials without contact on ultrafast time scales. However, the desired dynamical control is complicated by the inhomogeneous response of real materials. The ultrafast dynamics depend not only on the intrinsic properties of the compound but also, strongly, on mesoscale structures such as surfaces, domains, interfaces, and defects that govern the coupling between various degrees of freedom.

>Read more on the Advanced Photon Source website

Figure: Schematic illustration of spatially-resolved pump-probe experiment and domain configuration of a BaTiO3 single crystal sample. The inset shows a unit cell of BaTiO3.

Precise layer growth in a superlattice controls electron coupling and magnetism

Two-dimensional (2-D) crystalline films often exhibit interesting physical characteristics, such as unusual magnetic or electric properties. By layering together distinct crystalline thin films, a so-called “superlattice” is formed. Due to their close proximity, the distinct layers of a superlattice may significantly affect the properties of other layers. In this research, single 2-D layers of strontium iridium oxide were sandwiched between either one, two, or three layers of strontium titanium oxide to form three distinct superlattices. Researchers then used x-ray scattering at the U.S. Department of Energy’s Advanced Photon Source (APS) to probe the magnetic structure of each superlattice. The x-ray data revealed that the number of layers of the titanium-based material produced a dramatic difference in the magnetic behavior of the iridium-based layer. These findings are especially significant because the iridium compound is one of the perovskites, a class of materials known for their unique electric, magnetic, optical, and other properties that have proven useful in sensor and energy-related devices, and which are being intensively investigated for their application towards improved electronics and other technologies.

>Read more on the Advance Photon Source website
Image: Fig. 1. Illustration of superlattices. Panel (a) shows the Sr2IrO4 crystalline superlattice, with alternating layers of SrIrO3 and SrO. The SrIrO3 layers are perovskites, depicted as diamond-like shapes formed by six oxygen atoms; inside each diamond is a gold-colored iridium ion (cation), while pink strontium ions lay near the diamond’s ends. The SrIrO3 layers are separated by non-perovskite (inert) SrO layers, depicted as pink bars. Panel (b) shows the more-recently developed SrIrO3/SrTiO3 superlattice used for this research. Three distinct SrIrO3/SrTiO3 superlattices were created, having 1, 2, or 3 layers of inert SrTiO3 layers (colored green) separating the active SrIrO3 layers. Bold green boxes highlight the number of inert SrTiO3 layers in the three distinct lattices. While both SrIrO3 (gold diamonds) and SrTiO3 (green diamonds) are perovskites, the green-colored SrTiO3 layers buffer the active SrIrO3 layers. (The entire image is visible here)

An energy-resolution record for resonant inelastic x-ray scattering

Resonant inelastic x-ray scattering (RIXS) is a powerful technique for studying electronic excitations in a wide variety of new and complex materials, offering momentum- and energy-resolution and potentially even analysis of scattered polarization. Since its inception in the 1990s, the development of RIXS instrumentation and scientific subjects have benefited from a closely intertwined evolution; improvements in energy resolution and throughput, spurred by specific scientific cases, have in turn made new subjects of study feasible. In the continued quest for substantially improved energy resolution, a novel prototype RIXS flat-crystal spectrometer was recently tested at X-ray Science Division beamline 27-ID-B at the U.S. Department of Energy’s Advanced Photon Source (APS). The spectrometer established a new record resolution for RIXS below 10 meV, together with a promise to do even better soon.

Early RIXS work was aimed at the study of charge transfer excitations in transition metal oxides (TMO), including the high-Tc superconducting Cuprates, where electronic excitations could be observed at a few eV. As the understanding of strongly correlated electron systems progressed, orbital degrees of freedom came into focus: in many Mott insulators, transitions between the active d-orbitals, the “dd excitations”, were hot topics and could reliably be observed with the then state-of-the-art resolution of 100-200 meV. Magnetism and magnetic ordering are central questions in the study of correlated electron systems. For example, the layered perovskite Iridates showing strikingly similar magnetic exchange interactions as the Cuprates, implying that unconventional superconductivity might be found here, to the intriguing assertion that magnetic properties of honeycomb Iridates might point to a quantum spin liquid as ground state of this material, the spectrum of novel, exotic properties uncovered or anticipated promise a treasure trove of scientific discoveries. In the late 2000s, RIXS was established as a probe of magnetic excitations. However, spectral features associated with magnetic excitations (“magnons”) lie at a fraction of an eV or even in the sub-10meV regime. A significant advance in energy resolution is needed to attack such subjects with RIXS.

>Read more on the Advanced Photon Source website

Figure: Schematic rendering of the new flat-crystal RIXS spectrometer.

X-ray detector for studying characteristics of materials

Sol M. Gruner’s group, Physics, has been a leader in the development of x-ray detectors for scientific synchrotron applications, and the team’s technology is used around the world. Their detectors utilize pixelated integrated circuit silicon layers to absorb x-rays to produce electrical signals. The wide dynamic range, high sensitivity, and rapid image frame rate of the detectors enable many time-resolved x-ray experiments that have been difficult to perform until now.

The detectors are limited by the silicon layer. Low atomic number materials such as silicon become increasingly transparent to x-rays as the energy of the x-rays rises. Gruner’s group is now developing a variant of their detector that will use semiconductors comprised of high atomic weight elements to absorb the x-rays and produce the resultant electrical signals. The Detector Group, led by Antonio Miceli, at the United States Department of Energy’s Advanced Photon Source (APS) will simultaneously develop the ancillary electronics and interfacing required to produce fully functional prototypes suitable for high x-ray energy experiments at the APS and CHESS.

>Read more on the CHESS website

Image: Sol M. Gruner, Physics, College of Arts and Sciences
Credit: Jesse Winter