Photoinduced IR absorption in (La(1-x)Sr(x)Mn)(1-\delta)O3: changes of the anti-Jahn-Teller polaron binding energy with doping

Photoinduced IR absorption was measured in (La(1-x)Sr(x)Mn)(1-\delta)O3. A midinfrared peak centered at ~ 5000 cm$^{-1}$ was observed in the x=0 antiferromagnetic sample. The peak diminishes and softens as hole doping is increased. The origin of the photoinduced absorption peak is atributted to the photon assisted hopping of anti-Jahn-Teller polarons formed by photoexcited charge carriers, whose binding energy decreases with increasing hole doping. The shape of the peak indicates that the polarons are small.Comment: 5 pages, 3 figures, submitted to PR

2021 roadmap on lithium sulfur batteries

Batteries that extend performance beyond the intrinsic limits of Li-ion batteries are among the most important developments required to continue the revolution promised by electrochemical devices. Of these next-generation batteries, lithium sulfur (Li–S) chemistry is among the most commercially mature, with cells offering a substantial increase in gravimetric energy density, reduced costs and improved safety prospects. However, there remain outstanding issues to advance the commercial prospects of the technology and benefit from the economies of scale felt by Li-ion cells, including improving both the rate performance and longevity of cells. To address these challenges, the Faraday Institution, the UK's independent institute for electrochemical energy storage science and technology, launched the Lithium Sulfur Technology Accelerator (LiSTAR) programme in October 2019. This Roadmap, authored by researchers and partners of the LiSTAR programme, is intended to highlight the outstanding issues that must be addressed and provide an insight into the pathways towards solving them adopted by the LiSTAR consortium. In compiling this Roadmap we hope to aid the development of the wider Li–S research community, providing a guide for academia, industry, government and funding agencies in this important and rapidly developing research space

2021 roadmap on lithium sulfur batteries

Abstract: Batteries that extend performance beyond the intrinsic limits of Li-ion batteries are among the most important developments required to continue the revolution promised by electrochemical devices. Of these next-generation batteries, lithium sulfur (Li–S) chemistry is among the most commercially mature, with cells offering a substantial increase in gravimetric energy density, reduced costs and improved safety prospects. However, there remain outstanding issues to advance the commercial prospects of the technology and benefit from the economies of scale felt by Li-ion cells, including improving both the rate performance and longevity of cells. To address these challenges, the Faraday Institution, the UK’s independent institute for electrochemical energy storage science and technology, launched the Lithium Sulfur Technology Accelerator (LiSTAR) programme in October 2019. This Roadmap, authored by researchers and partners of the LiSTAR programme, is intended to highlight the outstanding issues that must be addressed and provide an insight into the pathways towards solving them adopted by the LiSTAR consortium. In compiling this Roadmap we hope to aid the development of the wider Li–S research community, providing a guide for academia, industry, government and funding agencies in this important and rapidly developing research space

The effect of H₂O on O₂ reduction in Li-O₂ batteries

There is significant interest in aprotic lithium-air batteries due to their high theoretical specific energy. During discharge, O2 is reduced at the positive electrode and forms Li2O2. Cells are typically discharged in O2, not air, because CO2 and H2O can interfere with the discharge reaction. However, lithium-air batteries will need to use atmospheric O2 if they are to supplant state-of-the-art lithium-ion cells. Therefore, it is important to establish how detrimental CO2 and H2O are to the battery. The former is well-known to induce the formation of Li2CO3 in Li-O2 batteries, but the recent work has suggested that H2O appears to be beneficial at low concentrations in some solvents (e.g. glyme ethers), increasing discharge capacities and still forming Li2O2, while in other solvents, such as acetonitrile (CH3CN), LiOH is the discharge product. Several mechanisms have been proposed to rationalise these findings, but as yet, there is no consensus on the role of H2O on O2 reduction. The purpose of this work was to understand how H2O affects O2 reduction in electrolytes using acetonitrile (CH3CN), dimethyl sulfoxide (DMSO) and tetraethylene glycol dimethyl ether (TEGDME) solvents, and, why the 4e- reduction appears to be unfavourable at low H2O concentrations. Electrochemical and spectroscopic analysis found that, in CH3CN, 4e- reduction occurred at lower H2O concentrations than in DMSO and TEGDME. A mechanism based on the ability of the H2O/solvent mixture to stabilise OH- was proposed, with mixtures that stabilise OH- promoting 4e- O2 reduction. The mechanism was confirmed by using pressure cells to identify the electrochemical reaction occurring during discharge. Cells using DMSO and TEGDME solvents underwent 2e- O2 reduction, even with 1 M H2O concentrations. Finally, TEGDME cells were discharged in a 13% RH at 25 °C O2 atmosphere, corresponding to 1 M H2O in solution, and Li2O2 was confirmed as the discharge product, demonstrating that it is possible for electrolytes to withstand a near-atmospheric humidity.</p

High capacity surface route discharge at the potassium-O2 electrode

Discharge by a surface route at the cathode of an aprotic metal-O2 battery typically results in surface passivation by the non-conducting oxide product. This leads to low capacity and early cell death. Here we investigate the cathode discharge reaction in the potassium-O2 battery and demonstrate that discharge by a surface route is not limited to growth of thin (&lt;10 nm) metal oxide layers. Electrochemical analysis and in situ Raman spectroscopy confirmed that the product of the cathode reaction is a combination of KO2 and K2O2, depending on the applied potential. Use of the low donor number solvent, acetonitrile, allows us to directly probe the surface route. Rotating ring-disk electrode, electrochemical quartz crystal microbalance and scanning electron microscope characterisations clearly demonstrate the formation of a thick &gt;1 μm product layer, far in excess of that possible in the related lithium-O2 battery. These results demonstrate a high-capacity surface route in a metal-O2 battery for the first time and the insights revealed here have significant implications for the design of the K-O2 battery

Inhibition of polydomain formation in PbTiO3/PbZr0.2Ti0.8O3 superlattices by intercalation of ultra-thin SrTiO3 layers

International audienceWe used pulsed laser deposition to grow a series of PbTiO3/PbZr0.2Ti0.8O3 superlattices on SrTiO3 and SrRuO3/SrTiO3 substrates. An a/c polydomain structure was evidenced by reciprocal space mapping and by transmission electron microscopy. Insertion of ultra-thin layers of SrTiO3 at the interfaces between PbTiO3 and PbZr0.2Ti0.8O3 layers has inhibited this polydomain formation. A strong decrease in the tetragonality indicates clearly that the polarization state in these superlattices has changed due to the insertion of the SrTiO3 layers. A purely elastic mechanism does not seem to explain the determined structural parameter

H-band Quartz-Silicon Leaky-Wave Lens with Air-Bridge Interconnect to GaAs Front-End

Thanks to the large bandwidth availability, millimeter and sub-millimeter wave systems are getting more attractive to be used in a wide range of applications, such as high-resolution radar or high-speed communications. In this contribution, a new lens antenna in-package solution is presented for the H-band (220320 GHz), including a wideband quartz-cavity leaky-wave feed combined with an air-bridge chip interconnect technology, based on spray coating and laser lithography. This interconnection acts as a wideband, low-loss transition between the GaAs front-end and the quartz antenna, avoiding the use of expensive waveguide split-blocks. An antenna prototype including the interconnect has been manufactured and characterized, validating the full-wave simulated results for the integrated H-band leaky-wave with aperture efficiency higher than 74% over 34% bandwidth, and radiation efficiency higher than 70% over 37% of bandwidth.</p

108° domain formation in SrTiO3 stabilized tricolour PbTiO3/SrTiO3/ PbZr0.2Ti0.8O3 superlattices

International audienc