A ‘warm path’ for Gulf Stream–troposphere interactions

Warm advection by the Gulf Stream creates a characteristic ‘tongue’ of warm water leaving a strong imprint on the sea surface temperature (SST) distribution in the western North Atlantic. This study aims at quantifying the climatological impact of this feature on cyclones travelling across this region in winter using a combination of reanalysis data and numerical experiments. It is suggested that the Gulf Stream ‘warm tongue’ is conducive to enhanced upward motion in cyclones because (i) it helps maintain a high equivalent potential temperature of air parcels at low levels which favors deep ascent in the warm conveyor belt of cyclones and (ii) because the large SST gradients to the north of the warm tongue drive a thermally direct circulation reinforcing and, possibly, destabilizing, the transverse circulation embedded in cyclones. This hypothesis is confirmed by comparing simulations at 12 km resolution from the Met Office Unified Model forced with realistic SST distribution to simulations with an SST distribution from which the Gulf Stream warm tongue was artificially removed or made colder by . It is also supported by a dynamical diagnostic applied to the ERA interim data-set over the wintertime period (1979–2012). The mechanism of oceanic forcing highlighted in this study is associated with near thermal equilibration of low level air masses with SST in the warm sector of cyclones passing over the Gulf Stream warm tongue, which is in sharp contrast to what occurs in their cold sector. It is suggested that this ‘warm path’ for the climatic impact of the Gulf Stream on the North Atlantic storm-track is not currently represented in climate models because of their coarse horizontal resolution

Batteries and Supercapacitors-Fundamentals, Materials and Devices (E-MRS Spring Meeting 2019): Foreword

International audienceThis special collection contains a selection of research articles corresponding to contributions presented at Symposium C of the European Materials Science Meeting Edition 2019 that was held in Nice, France, from the 26th to the 31st of May 2019

Impact of Sulfide-based Solid Electrolyte Particle Size Distribution on the Electrochemistry of ASSB via Impedance Study

14th International Workshop on Impedance Spectroscopy (IWIS), Chemnitz, GERMANY, SEP 29-OCT 01, 2021International audienceSulfide based solid electrolytes (SE) offer high ionic conductivity and can be processed at a low temperature (cold pressing) and hence have been used extensively by the battery community in their quest for the development of all-solid-state batteries (ASSB). In this study, we try to investigate the impact of Argyrodite (Li6PS5Cl) particle size and its distribution, on the solid electrolyte (SE), cathode composite and in turn on the overall performance of the battery. Electrochemical Impedance Spectroscopy (EIS) provides key insights in the understanding of the behaviour of different SE. EIS in this particular study has been used to extract (i) the ionic conductivity of solid electrolytes (sigma(SE)) with small (< 20 mu m) and large particle size (50-150 mu m) distribution, (ii) the effective ionic conductivity (sigma(cathode.copm)) in their respective cathode composites, (iii) the tortuosity based on ionic conductivity (tau(cond)). The following are the highlights of this study: 1) On Solid Electrolyte itself: Given the same amount and same pressure, the ionic conductivity of large particle size distribution is higher. Consequently, the saturation pressure (Pressure to reach the highest ionic conductivity) is lower for large particle size. 2) On Cathode composite and its cycling: the composites with large particle size show the highest compacity values among all and also is the best performing cell. 3) Ionic conductivity-based tortuosity calculated which varied in the range 1.9-2.5. 1.9 being the lowest for large particles

The Use of Lithium (Poly)Sulfide Species in Li\textendashS Batteries

International audienceEmerging lithium ion (Li-ion) batteries for load levelling and transport is challenging, especially for materials chemistry, and will be a major focus for upcoming years. However, in the longer term, Li-ion batteries (LIBs) cannot deliver high-energy densities and more radical approaches are necessary. There are several options to go beyond this limit and one of the possibilities for achieving longer storage life and high-energy batteries associated with cost and environmental advantages is the lithium\textendash sulfur (Li\textendash S) system which can theoretically offer three to five fold increase in energy density compared with conventional Li-ion cells. Although the Li\textendash S system has interested the battery community for more than five decades, 1 it still faces issues such as poor cycle life, to reach the market place.2 \textcopyright 2017 by World Scientific Publishing Europe Ltd

Lithium-ion battery electrode prepared by confining carbon nanotubes/V2O5 nanoribbons suspension in model aireliquid foams

6 pagesInternational audienceWell-defined macroporous V2O5eCNTs hybrid solid foams are synthesized in the form of monolith by a controlled bubbling process. For the first time, the solid phase results from the co-assembly of two different anisotropic nano-building blocks in the continuous phase of model foams whose bubble size and liquid fraction could be tuned. Their electrochemical properties were examined in view of their application as cathode for Li-ion battery. This first investigation revealed that capacity up to 250 mAh g-1 (i.e. 2 Li per V2O5) can be attain with a good retention under cycles when CNTs are present making these new cellular materials interesting candidate for systems which require the penetration of viscous ionic-liquid/polymer electrolytes

The Use of Lithium (Poly)sulfide Species in Li–S Batteries

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Facile Synthesis of Ge@TiO 2 Nanotube Hybrid Nanostructure Anode Materials for Li-Ion Batteries

Utilizing nanostructures of Li-alloying anode materials (e.g., Si, Ge, Sn, etc.) has been proposed as a key strategy to improve the electrochemical performance. However, the main challenge lies in the costly and complex nanostructure synthesis processes. Notably, the nanostructure growth processes are mainly supported by Li-inactive templates, which later need to be removed, and the template removal process results in the destruction of the desired nanostructures. In this report, we demonstrated the use of a Li-active, self-organized TiO2 nanotube template to fabricate germanium (Ge)-based nanostructured anodes. This has been achieved as follows: first, TiO2 nanotubes are fabricated via electrochemical anodization of titanium foil. Then, the nanotubes are coated with a Ge film in the second step via electrodeposition. Besides the effective nanostructure growth using a Li-active template, the implemented electrochemical synthesis methods are cost-effective, accessible, and scalable. Furthermore, the electrochemical methods allow the fabrication of nanostructures with well-controlled structures, morphology, and compositions. Accordingly, a Ge-coated TiO2 nanotube (Ge@TiO2) nanocomposite anode has been successfully fabricated, and its electrochemical performance has been tested for Li-ion batteries. The study has shown the important roles of TiO2 nanotube arrays in improving the performance by providing strong mechanical support to buffer the volume expansion and offering a high surface area to enhance Ge-active mass loading. Moreover, the direct contact of the nanotubes with a Ti current collector facilitates one-dimensional (1D) electron transport and avoids the need of adding inactive binders or conductive additives

The Use of Lithium (Poly)Sulfide Species in Li\textendashS Batteries

International audienceEmerging lithium ion (Li-ion) batteries for load levelling and transport is challenging, especially for materials chemistry, and will be a major focus for upcoming years. However, in the longer term, Li-ion batteries (LIBs) cannot deliver high-energy densities and more radical approaches are necessary. There are several options to go beyond this limit and one of the possibilities for achieving longer storage life and high-energy batteries associated with cost and environmental advantages is the lithium\textendash sulfur (Li\textendash S) system which can theoretically offer three to five fold increase in energy density compared with conventional Li-ion cells. Although the Li\textendash S system has interested the battery community for more than five decades, 1 it still faces issues such as poor cycle life, to reach the market place.2 \textcopyright 2017 by World Scientific Publishing Europe Ltd

A New Sodium-Based Aqueous Rechargeable Battery System: The Special Case of Na0.44MnO2/Dissolved Sodium Polysulfide

International audienceHerein, the electrochemical performance of a new sodium-based aqueous rechargeable battery is demonstrated consisting of Na0.44MnO2 as cathode and dissolved sodium polysulfide (i.e., Na2S5) as anolyte. Na0.44MnO2 synthesized through a solid-state reaction method and dissolved Na2S5 anolyte are tested separately in a half-cell configuration, both giving rise to stable cycling performances. As the anode side of the desired full-cell configuration is at present dissolved in the electrolyte, the positive and negative electrodes need to be separated with an ion-selective membrane that is permeable to sodium ions and impermeable to polysulfide species. Hence, Nafion is tested as a barrier to prevent the leakage of the dissolved polysulfides. After careful tuning of the osmotic pressure inside the Nafion membrane, leakage of the dissolved polysulfide from the anode to the cathode side is eliminated, resulting in a 0.8V average voltage, low-cost sodium-ion aqueous cell

Sol-gel synthesis and electrochemical properties extracted by phase inflection detection method of NASICON-type solid electrolytes LiZr2(PO4)(3) and Li1.2Zr1.9Ca0.1(PO4)(3)

International audienceThe use of good ionic conductors is a key point in various battery technologies such as Li-air Lithium-Sulfur (Li-S) and All-Solid-State batteries. The determination of the conduction properties as well as the structure in function of temperature and their electrochemical stability are paramount. At the same time, the manufacturing process of these solid electrolytes must be simplified in order to foster the emergence of these technologies. In this context, NASICON-type solid electrolytes LiZr2(PO4)(3) (LZP) and Li1.2Zr1.9Ca0.1(PO4)(3) (LCZP) were synthetized by a new sol-gel method to simplify the synthesis process compared to the solid-state reaction and to reduce the synthesis temperature from 1200 degrees C to 1100 degrees C. The influence of Ca-doping on crystal structure and transport properties was studied in function of temperature and for the first time the electrochemical stability determined. A method, the Phase Inflection Detection (PID), was developed to better determine the transport properties extracted from Electrochemical Impedance Spectroscopy. The ionic conductivity of LCZP is greater than that of LZP by about 2 decades at room temperature due to the stabilization of the high temperature phase at room temperature by Ca-doping, an increase in the number of lithium mobile ions and a better compactness compared with LZP. The impact of sintering temperature and grain boundaries on transport properties is clearly demonstrated and must be taken into account in the future studies of solid electrolytes. The LCZP material is not stable below 0.6 V vs. Li+/Li. It thus presents one of the best electrochemical stabilities, making it a potential candidate for various battery technologies