Publication News

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Oxygen Loss

6th June 2019

What Triggers Oxygen Loss in Oxygen Redox Cathode Materials?

Research by the Peter Bruce Group and collaborators at Uppsala University, the University of Kent and  Paul Scherrer Institut as reported in Chemistry of Materials clarifies It is possible to increase the charge capacity of transitionmetal (TM) oxide cathodes in alkali-ion batteries by invoking redox reactions on the oxygen. However, oxygen loss often occurs. To explore what affects oxygen loss in oxygen redox materials, they compared two analogous Na-ion cathodes, P2-Na0.67Mg0.28Mn0.72O2 and P2- Na0.78Li0.25Mn0.75O2. On charging to 4.5 V, >0.4e − are removed from the oxide ions of these materials, but neither compound exhibits oxygen loss. Li is retained in P2-Na0.78Li0.25Mn0.75O2 but displaced from the TM to the alkali metal layers, showing that vacancies in the TM layers, which also occur in other oxygen redox compounds that exhibit oxygen loss such as Li[Li0.2Ni0.2Mn0.6]O2, are not a trigger for oxygen loss. On charging at 5 V, P2-Na0.78Li0.25Mn0.75O2 exhibits oxygen loss, whereas P2-Na0.67Mg0.28Mn0.72O2 does not. Under these conditions, both Na+ and Li+ are removed from P2-Na0.78Li0.25Mn0.75O2, resulting in underbonded oxygen (fewer than 3 cations coordinating oxygen) and surface-localized O loss. In contrast, for P2-Na0.67Mg0.28Mn0.72O2, oxygen remains coordinated by at least 2 Mn4+ and 1 Mg2+ ions, stabilizing the oxygen and avoiding oxygen loss.

Li short-circuit

6th June 2019

Microstructural Growth of Lithium in All-Solid-State Batteries

Research by the Peter Bruce Group and collaborators at the University of Cambridge as reported in Chemistry of Materials explains All-solid-state batteries potentially offer safe, high-energy-density electrochemical energy storage, yet are plagued with issues surrounding Li microstructural growth and subsequent cell death. The researchers use 7Li NMR chemical shift imaging and electron microscopy to track Li microstructural growth in the garnet-type solid electrolyte, Li6.5La3Zr1.5Ta0.5O12. They follow the early stages of Li microstructural growth during galvanostatic cycling, from the formation of Li on the electrode surface to dendritic Li connecting both electrodes in symmetrical cells, and correlate these changes with alterations observed in the voltage profiles during cycling and impedance measurements. During these experiments, they observe transformations at both the stripping and plating interfaces, indicating heterogeneities in both Li removal and deposition. At low current densities, 7Li magnetic resonance imaging detects the formation of Li microstructures in cells before short-circuits are observed and allows changes in the electrochemical profiles to be rationalized

Anisotopic Fracture

31st May 2019

Anisotropic Fracture Dynamics Due to Local Lattice Distortions

A brittle material under loading fails by the nucleation and propagation of a sharp crack. Combining annular dark-field scanning transmission electron microscopy and empirical molecular dynamics that are validated by first-principles calculations, researchers at MIT, Oxford and ePSIC have shown in ACS Nano that local atomic distortions from different types of atoms causes a propagation anisotropy.  Conventional  conditions for brittle failure such as surface energy, elasticity, and crack geometry cannot account for this anisotropy because this kind of anisotropy has not been considered as a parameter in traditional theories.

Writing NV Qubits in Diamond

18th May 2019

Laser writing of individual nitrogen-vacancy defects in diamond with near-unity yield

Professor Jason Smith and his fellow NQIT colleagues based in Engineering Science and at the University of Warwick demonstrate, in a paper published in Optica, the success of the new method to create particular defects in diamonds known as nitrogen-vacancy (NV) colour centres. These comprise a nitrogen impurity in the diamond (carbon) lattice located adjacent to an empty lattice site or vacancy. The ability to write NV centres into diamond with a high degree of control is an essential first step towards being able to engineer atomic defect structures for the development of a new generation of quantum information technologies.  Further news articles are available on the Oxford News and EurekAlert.

Nanosims of Se in CdTe

16th May 2019

Understanding the role of selenium in defect passivation for highly efficient selenium-alloyed cadmium telluride solar cells

Electricity produced by cadmium telluride (CdTe) photovoltaic modules has one of the lowest-costs in the solar industry, and is now much cheaper than fossil fuel-based sources in many regions of the world. Recent substantial efficiency gains have been achieved by alloying selenium into the CdTe absorber, improving efficiency from 19.5% to the current record value of 22.1%. This paper in Nature Energy reports directly correlated cathodoluminescence and NanoSIMS results showing that selenium passivates critical defects in the bulk of the absorber layer, and this understanding provides promising directions for further efficiency improvements.


9th May 2019

All-optical spiking neurosynaptic networks with self-learning capabilities

Researchers from University of Munster, University of Oxford and University of Exeter report in Nature an all-optical version of a neurosynaptic system, capable of supervised and unsupervised learning. They exploit wavelength division multiplexing techniques to implement a scalable circuit architecture for photonic neural networks, successfully demonstrating pattern recognition directly in the optical domain. Such photonic neurosynaptic networks promise access to the high speed and high bandwidth inherent to optical systems, thus enabling the direct processing of optical telecommunication and visual data. This report is also discussed further in a Nature news article highlighting the potential future impact should photonic neural accelerators offering high energy efficiencies eventually emerge. This paper also featured in MPLS news.


30th April 2019

Oxide Analogs of Halide Perovskites and the New Semiconductor Ba2AgIO6

The past few years witnessed the rise of halide perovskites as prominent materials for a wide range of optoelectronic applications. George Volonakis and Feliciano Giustino  from the Materials Modelling and Design Group report in The Journal of Physical Chemistry Letters a novel concept of perovskite analogs, which has led to identifying a new semiconductor, Ba2AgIO6, which is a cubic oxide double perovskite with a direct low gap in the visible range at 1.9 eV, opening new opportunities in perovskite-based electronics optoelectronics and energy applications. This paper has been selected to feature on the front cover of the journal.

Li2O2 deposit layers

30th April 2019

Enhanced Li-O2 Battery Performance

Research by the Peter Bruce Group and collaborators at the Technion – Israel Institute of Technology as reported in Advanced Materials Technologies explains that Low capacity, poor rechargeability, and premature cell death are major setbacks in the operation of Li‐O2 battery, hindering its practical application. A promising approach of meeting those challenges is via the use of redox mediators (RMs), promoting Li2O2 solution phase formation upon cell discharge and an efficient oxidation on charging. The use of dual RMs decouples the electrochemical reactions at the cathode with formation/decomposition of Li2O2, resulting in improved discharge capacity, lower charge overpotential, and cycle stability. Although Li‐O2 cell performance is no longer mitigated by an insulating Li2O2, a major inherent barrier to implement viable and functioning Li‐air batteries lies in both limited O2 mass transport and pores clogging. A record discharge capacity of 6 mAh cm−2 (60% increase), by combining dual RMs with “liquid Teflon” type perfluorocarbons binary system, is demonstrated. The combination of the two materials in the cell contributes to the enhanced cell performance manifested also in lower charge overpotential values throughout dozens of cycles. This is also attributed to the unique compact and an exceptionally smooth morphology of the Li2O2 deposit layers at both ends of the air cathode.


29th November 2018

Interfaces Between Graphene‐Related Materials and MAPbI3: Insights from First‐Principles 

George Volonakis and Feliciano Giustino  from the Materials Modelling and Design Group report in Advanced Materials Interfaces the latest advances on the computational exploration of the interactions between graphene and graphene oxide with lead halide perovskites. They also show how recent calculations from first principles have been employed towards understanding the benefits of combining these ‘wonder materials’.  The paper was selected as cover image of the special section on "Interfacial engineering of perovskite solar cells for improved performance and stability".  


26th November 2018

Tailored homo- and hetero- lanthanide porphyrin dimers: a synthetic strategy for integrating multiple spintronic functionalities into a single molecule

Jennifer Le Roy's recent publication in Chemical Science has been selected as front cover article and classed as a hot article. Researchers from Professor Bogani's group in Materials in collaboration with researchers from Professor Anderson's group in Chemistry report the design, synthesis and magnetic properties of molecular magnetic systems that contain all elements necessary for spin-valve control in molecular spintronic devices in a single molecule.

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