EuroWire November 2020

Transatlantic Cable

Image: www.bigstockphoto.com Photographer Adrian Grosu

In-situ magnetometry, the technique employed in this study, is a real-time magnetic monitoring method to investigate the evolution of a material’s internal electronic structure. It is able to quantify the charge capacity by measuring variations in magnetism. In-situ magnetometry can also be used to study charge storage at a very small scale, beyond the capabilities of many conventional characterisation tools. “The most significant results were obtained from a technique commonly used by physicists but very rarely in the battery community,” Mr Yu said, describing it as “a beautiful marriage of physics and electrochemistry”. Researchers from the University of Texas, the Massachusetts Institute of Technology, the University of Waterloo in Canada, Shandong University of China, Qingdao University in China and the Chinese Academy of Sciences all took part in the project. An international research team led by Artem Mishchenko, professor of condensed matter physics at the UK’s University of Manchester, has revealed a nanomaterial that mirrors the “magic angle” effect originally found in a complex man-made structure known as twisted bilayer graphene – a key area of study in physics in recent years. The research, published in the journal Nature , shows that the special topology of rhombohedral graphite effectively provides an inbuilt “twist” and offers an alternative medium to study effects such as superconductivity. “It is an interesting alternative to highly popular studies of magic- angle graphene,”said Professor Sir Andre Geim, a co-author of the study. “Rhombohedral graphite can help to better understand materials in which strong electronic correlations are important – such as heavy-fermion compounds and high temperature superconductors,” added Professor Mishchenko. An earlier advance in two-dimensional materials research was the discovery that stacking two sheets of graphene, and twisting it to a “magic angle“ changed the bilayer’s properties and created a superconductor. Prof Mishchenko and his colleagues have now observed the emergence of strong electron-electron interactions in a weakly stable rhombohedral form of graphite – the form in which graphene layers are stacked slightly differently from the stable hexagonal form. Hexagonal graphite (the form of carbon used in pencils) is composed of neatly stacked graphene layers, Further studies of graphene show a new advance using rhombohedral graphite

Research and development

Research inches closer to ultra-fast battery storage systems

An international research team, co-led by The University of Texas at Austin, has examined the scientific anomaly of metal oxides that appear to store significantly more energy than should be possible. It is hoped that understanding the materials will help make it possible to develop ultra-fast battery energy storage systems. The research team found that the metal oxides possess novel ways to store energy. Their findings, published in NatureMaterials , describe several types of metal compounds with up to three times the energy storage capability of the materials commonly used in commercially available lithium-ion batteries. The result could be batteries with greater energy capacity – smaller but more powerful batteries rapidly delivering charge to any device, from smartphones to electric vehicles. “For nearly two decades, the research community has been perplexed by these materials’ anomalously high capacities beyond their theoretical limits,” said Guihua Yu, an associate professor in theWalker Department of Mechanical Engineering at the University of Texas at Austin’s Cockrell School of Engineering, and a leader on the project. “This work demonstrates the very first experimental evidence to show the extra charge is stored physically inside these materials via a space charge storage mechanism.” Researchers found a way to monitor and measure how the elements change over time. Central to the discovery are transition- metal oxides – compounds that include oxygen bonded with transition metals such as iron, nickel and zinc. Energy can be stored inside the metal oxides, as opposed to methods where lithium ions move through materials or convert their crystal structures for energy storage. Studies have also shown that additional charge capacity can be stored on the surface of iron nanoparticles formed during conventional electrochemical processes. According to the researchers, a broad range of transition metals can unlock this extra capacity, and all have the ability to collect a high density of electrons. Further work is needed, but the researchers believe these new findings will shed light on the potential of these materials.

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November 2020